cmd: merge branch 'dev.link' into master

In the dev.link branch we continued developing the new object
file format support and the linker improvements described in
https://golang.org/s/better-linker . Since the last merge, more
progress has been made to improve the new linker.

This is a clean merge.

Change-Id: Ide5ad6fcec9cede99e9b21c4548929b4ba1f4185

src/cmd/compile/internal/gc/iexport.go

@@ -35,6 +35,8 @@
 //         }
 //     }
 //
+//     Fingerprint [8]byte
+//
 // uvarint means a uint64 written out using uvarint encoding.
 //
 // []T means a uvarint followed by that many T objects. In other
@@ -296,6 +298,10 @@ func iexport(out *bufio.Writer) {
 	io.Copy(out, &hdr)
 	io.Copy(out, &p.strings)
 	io.Copy(out, &p.data0)
+
+	// Add fingerprint (used by linker object file).
+	// Attach this to the end, so tools (e.g. gcimporter) don't care.
+	out.Write(Ctxt.Fingerprint[:])
 }
 
 // writeIndex writes out an object index. mainIndex indicates whether

src/cmd/compile/internal/gc/iimport.go

@@ -10,6 +10,7 @@ package gc
 import (
 	"cmd/compile/internal/types"
 	"cmd/internal/bio"
+	"cmd/internal/goobj2"
 	"cmd/internal/obj"
 	"cmd/internal/src"
 	"encoding/binary"
@@ -95,7 +96,7 @@ func (r *intReader) uint64() uint64 {
 	return i
 }
 
-func iimport(pkg *types.Pkg, in *bio.Reader) {
+func iimport(pkg *types.Pkg, in *bio.Reader) (fingerprint goobj2.FingerprintType) {
 	ir := &intReader{in, pkg}
 
 	version := ir.uint64()
@@ -188,6 +189,14 @@ func iimport(pkg *types.Pkg, in *bio.Reader) {
 			inlineImporter[s] = iimporterAndOffset{p, off}
 		}
 	}
+
+	// Fingerprint
+	n, err := in.Read(fingerprint[:])
+	if err != nil || n != len(fingerprint) {
+		yyerror("import %s: error reading fingerprint", pkg.Path)
+		errorexit()
+	}
+	return fingerprint
 }
 
 type iimporter struct {

src/cmd/compile/internal/gc/main.go

@@ -14,6 +14,7 @@ import (
 	"cmd/compile/internal/types"
 	"cmd/internal/bio"
 	"cmd/internal/dwarf"
+	"cmd/internal/goobj2"
 	"cmd/internal/obj"
 	"cmd/internal/objabi"
 	"cmd/internal/src"
@@ -1254,15 +1255,6 @@ func importfile(f *Val) *types.Pkg {
 		}
 	}
 
-	// assume files move (get installed) so don't record the full path
-	if packageFile != nil {
-		// If using a packageFile map, assume path_ can be recorded directly.
-		Ctxt.AddImport(path_)
-	} else {
-		// For file "/Users/foo/go/pkg/darwin_amd64/math.a" record "math.a".
-		Ctxt.AddImport(file[len(file)-len(path_)-len(".a"):])
-	}
-
 	// In the importfile, if we find:
 	// $$\n  (textual format): not supported anymore
 	// $$B\n (binary format) : import directly, then feed the lexer a dummy statement
@@ -1287,6 +1279,7 @@ func importfile(f *Val) *types.Pkg {
 		c, _ = imp.ReadByte()
 	}
 
+	var fingerprint goobj2.FingerprintType
 	switch c {
 	case '\n':
 		yyerror("cannot import %s: old export format no longer supported (recompile library)", path_)
@@ -1310,13 +1303,22 @@ func importfile(f *Val) *types.Pkg {
 			yyerror("import %s: unexpected package format byte: %v", file, c)
 			errorexit()
 		}
-		iimport(importpkg, imp)
+		fingerprint = iimport(importpkg, imp)
 
 	default:
 		yyerror("no import in %q", path_)
 		errorexit()
 	}
 
+	// assume files move (get installed) so don't record the full path
+	if packageFile != nil {
+		// If using a packageFile map, assume path_ can be recorded directly.
+		Ctxt.AddImport(path_, fingerprint)
+	} else {
+		// For file "/Users/foo/go/pkg/darwin_amd64/math.a" record "math.a".
+		Ctxt.AddImport(file[len(file)-len(path_)-len(".a"):], fingerprint)
+	}
+
 	if importpkg.Height >= myheight {
 		myheight = importpkg.Height + 1
 	}

src/cmd/internal/goobj/readnew.go

@@ -25,7 +25,11 @@ func (r *objReader) readNew() {
 	}
 
 	// Imports
-	r.p.Imports = rr.Autolib()
+	autolib := rr.Autolib()
+	for _, p := range autolib {
+		r.p.Imports = append(r.p.Imports, p.Pkg)
+		// Ignore fingerprint (for tools like objdump which only reads one object).
+	}
 
 	pkglist := rr.Pkglist()
 

src/cmd/internal/goobj2/objfile.go

@@ -20,8 +20,8 @@ import (
 //
 //    Header struct {
 //       Magic       [...]byte   // "\x00go115ld"
+//       Fingerprint [8]byte
 //       Flags       uint32
-//       // TODO: Fingerprint
 //       Offsets     [...]uint32 // byte offset of each block below
 //    }
 //
@@ -29,7 +29,11 @@ import (
 //       Data [...]byte
 //    }
 //
-//    Autolib  [...]string // imported packages (for file loading) // TODO: add fingerprints
+//    Autolib  [...]struct { // imported packages (for file loading)
+//       Pkg         string
+//       Fingerprint [8]byte
+//    }
+//
 //    PkgIndex [...]string // referenced packages by index
 //
 //    DwarfFiles [...]string
@@ -119,6 +123,10 @@ import (
 
 const stringRefSize = 8 // two uint32s
 
+type FingerprintType [8]byte
+
+func (fp FingerprintType) IsZero() bool { return fp == FingerprintType{} }
+
 // Package Index.
 const (
 	PkgIdxNone    = (1<<31 - 1) - iota // Non-package symbols
@@ -150,6 +158,7 @@ const (
 // TODO: probably no need to export this.
 type Header struct {
 	Magic       string
+	Fingerprint FingerprintType
 	Flags       uint32
 	Offsets     [NBlk]uint32
 }
@@ -158,6 +167,7 @@ const Magic = "\x00go115ld"
 
 func (h *Header) Write(w *Writer) {
 	w.RawString(h.Magic)
+	w.Bytes(h.Fingerprint[:])
 	w.Uint32(h.Flags)
 	for _, x := range h.Offsets {
 		w.Uint32(x)
@@ -171,6 +181,8 @@ func (h *Header) Read(r *Reader) error {
 		return errors.New("wrong magic, not a Go object file")
 	}
 	off := uint32(len(h.Magic))
+	copy(h.Fingerprint[:], r.BytesAt(off, len(h.Fingerprint)))
+	off += 8
 	h.Flags = r.uint32At(off)
 	off += 4
 	for i := range h.Offsets {
@@ -184,6 +196,19 @@ func (h *Header) Size() int {
 	return len(h.Magic) + 4 + 4*len(h.Offsets)
 }
 
+// Autolib
+type ImportedPkg struct {
+	Pkg         string
+	Fingerprint FingerprintType
+}
+
+const importedPkgSize = stringRefSize + 8
+
+func (p *ImportedPkg) Write(w *Writer) {
+	w.StringRef(p.Pkg)
+	w.Bytes(p.Fingerprint[:])
+}
+
 // Symbol definition.
 //
 // Serialized format:
@@ -495,12 +520,18 @@ func (r *Reader) StringRef(off uint32) string {
 	return r.StringAt(r.uint32At(off+4), l)
 }
 
-func (r *Reader) Autolib() []string {
+func (r *Reader) Fingerprint() FingerprintType {
-	n := (r.h.Offsets[BlkAutolib+1] - r.h.Offsets[BlkAutolib]) / stringRefSize
+	return r.h.Fingerprint
-	s := make([]string, n)
+}
+
+func (r *Reader) Autolib() []ImportedPkg {
+	n := (r.h.Offsets[BlkAutolib+1] - r.h.Offsets[BlkAutolib]) / importedPkgSize
+	s := make([]ImportedPkg, n)
+	off := r.h.Offsets[BlkAutolib]
 	for i := range s {
-		off := r.h.Offsets[BlkAutolib] + uint32(i)*stringRefSize
+		s[i].Pkg = r.StringRef(off)
-		s[i] = r.StringRef(off)
+		copy(s[i].Fingerprint[:], r.BytesAt(off+stringRefSize, len(s[i].Fingerprint)))
+		off += importedPkgSize
 	}
 	return s
 }
@@ -508,9 +539,10 @@ func (r *Reader) Autolib() []string {
 func (r *Reader) Pkglist() []string {
 	n := (r.h.Offsets[BlkPkgIdx+1] - r.h.Offsets[BlkPkgIdx]) / stringRefSize
 	s := make([]string, n)
+	off := r.h.Offsets[BlkPkgIdx]
 	for i := range s {
-		off := r.h.Offsets[BlkPkgIdx] + uint32(i)*stringRefSize
 		s[i] = r.StringRef(off)
+		off += stringRefSize
 	}
 	return s
 }

src/cmd/internal/obj/line.go

@@ -5,12 +5,13 @@
 package obj
 
 import (
+	"cmd/internal/goobj2"
 	"cmd/internal/src"
 )
 
 // AddImport adds a package to the list of imported packages.
-func (ctxt *Link) AddImport(pkg string) {
+func (ctxt *Link) AddImport(pkg string, fingerprint goobj2.FingerprintType) {
-	ctxt.Imports = append(ctxt.Imports, pkg)
+	ctxt.Imports = append(ctxt.Imports, goobj2.ImportedPkg{Pkg: pkg, Fingerprint: fingerprint})
 }
 
 func linkgetlineFromPos(ctxt *Link, xpos src.XPos) (f string, l int32) {

src/cmd/internal/obj/link.go

@@ -33,6 +33,7 @@ package obj
 import (
 	"bufio"
 	"cmd/internal/dwarf"
+	"cmd/internal/goobj2"
 	"cmd/internal/objabi"
 	"cmd/internal/src"
 	"cmd/internal/sys"
@@ -666,7 +667,7 @@ type Link struct {
 	PosTable           src.PosTable
 	InlTree            InlTree // global inlining tree used by gc/inl.go
 	DwFixups           *DwarfFixupTable
-	Imports            []string
+	Imports            []goobj2.ImportedPkg
 	DiagFunc           func(string, ...interface{})
 	DiagFlush          func()
 	DebugInfo          func(fn *LSym, info *LSym, curfn interface{}) ([]dwarf.Scope, dwarf.InlCalls) // if non-nil, curfn is a *gc.Node
@@ -699,6 +700,8 @@ type Link struct {
 	defs       []*LSym // list of defined symbols in the current package
 	nonpkgdefs []*LSym // list of defined non-package symbols
 	nonpkgrefs []*LSym // list of referenced non-package symbols
+
+	Fingerprint goobj2.FingerprintType // fingerprint of symbol indices, to catch index mismatch
 }
 
 func (ctxt *Link) Diag(format string, args ...interface{}) {

src/cmd/internal/obj/objfile.go

@@ -98,8 +98,9 @@ func WriteObjFile(ctxt *Link, bout *bio.Writer, pkgpath string) {
 	w.wr.WriteByte(1)
 
 	// Autolib
-	for _, pkg := range ctxt.Imports {
+	for _, p := range ctxt.Imports {
-		w.writeString(pkg)
+		w.writeString(p.Pkg)
+		// This object format ignores p.Fingerprint.
 	}
 	w.writeString("")
 

src/cmd/internal/obj/objfile2.go

@@ -38,7 +38,11 @@ func WriteObjFile2(ctxt *Link, b *bio.Writer, pkgpath string) {
 	if ctxt.Flag_shared {
 		flags |= goobj2.ObjFlagShared
 	}
-	h := goobj2.Header{Magic: goobj2.Magic, Flags: flags}
+	h := goobj2.Header{
+		Magic:       goobj2.Magic,
+		Fingerprint: ctxt.Fingerprint,
+		Flags:       flags,
+	}
 	h.Write(w.Writer)
 
 	// String table
@@ -46,8 +50,8 @@ func WriteObjFile2(ctxt *Link, b *bio.Writer, pkgpath string) {
 
 	// Autolib
 	h.Offsets[goobj2.BlkAutolib] = w.Offset()
-	for _, pkg := range ctxt.Imports {
+	for i := range ctxt.Imports {
-		w.StringRef(pkg)
+		ctxt.Imports[i].Write(w.Writer)
 	}
 
 	// Package references
@@ -180,8 +184,8 @@ func (w *writer) init() {
 
 func (w *writer) StringTable() {
 	w.AddString("")
-	for _, pkg := range w.ctxt.Imports {
+	for _, p := range w.ctxt.Imports {
-		w.AddString(pkg)
+		w.AddString(p.Pkg)
 	}
 	for _, pkg := range w.pkglist {
 		w.AddString(pkg)

src/cmd/internal/obj/sym.go

@@ -34,6 +34,7 @@ package obj
 import (
 	"cmd/internal/goobj2"
 	"cmd/internal/objabi"
+	"crypto/md5"
 	"fmt"
 	"log"
 	"math"
@@ -241,6 +242,15 @@ func (ctxt *Link) NumberSyms(asm bool) {
 		ctxt.pkgIdx[pkg] = ipkg
 		ipkg++
 	})
+
+	// Compute a fingerprint of the indices, for exporting.
+	if !asm {
+		h := md5.New()
+		for _, s := range ctxt.defs {
+			h.Write([]byte(s.Name))
+		}
+		copy(ctxt.Fingerprint[:], h.Sum(nil)[:])
+	}
 }
 
 // Returns whether s is a non-package symbol, which needs to be referenced

src/cmd/link/internal/amd64/asm.go

@@ -78,48 +78,55 @@ func makeWritable(s *sym.Symbol) {
 	}
 }
 
-func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s *sym.Symbol, r *sym.Reloc) bool {
+func adddynrel2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loader.Sym, r *loader.Reloc2, rIdx int) bool {
-	targ := r.Sym
+	targ := r.Sym()
+	var targType sym.SymKind
+	if targ != 0 {
+		targType = ldr.SymType(targ)
+	}
 
-	switch r.Type {
+	switch r.Type() {
 	default:
-		if r.Type >= objabi.ElfRelocOffset {
+		if r.Type() >= objabi.ElfRelocOffset {
-			ld.Errorf(s, "unexpected relocation type %d (%s)", r.Type, sym.RelocName(target.Arch, r.Type))
+			ldr.Errorf(s, "unexpected relocation type %d (%s)", r.Type(), sym.RelocName(target.Arch, r.Type()))
 			return false
 		}
 
 		// Handle relocations found in ELF object files.
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_X86_64_PC32):
-		if targ.Type == sym.SDYNIMPORT {
+		if targType == sym.SDYNIMPORT {
-			ld.Errorf(s, "unexpected R_X86_64_PC32 relocation for dynamic symbol %s", targ.Name)
+			ldr.Errorf(s, "unexpected R_X86_64_PC32 relocation for dynamic symbol %s", ldr.SymName(targ))
 		}
 		// TODO(mwhudson): the test of VisibilityHidden here probably doesn't make
 		// sense and should be removed when someone has thought about it properly.
-		if (targ.Type == 0 || targ.Type == sym.SXREF) && !targ.Attr.VisibilityHidden() {
+		if (targType == 0 || targType == sym.SXREF) && !ldr.AttrVisibilityHidden(targ) {
-			ld.Errorf(s, "unknown symbol %s in pcrel", targ.Name)
+			ldr.Errorf(s, "unknown symbol %s in pcrel", ldr.SymName(targ))
 		}
-		r.Type = objabi.R_PCREL
+		su := ldr.MakeSymbolUpdater(s)
-		r.Add += 4
+		su.SetRelocType(rIdx, objabi.R_PCREL)
+		su.SetRelocAdd(rIdx, r.Add()+4)
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_X86_64_PC64):
-		if targ.Type == sym.SDYNIMPORT {
+		if targType == sym.SDYNIMPORT {
-			ld.Errorf(s, "unexpected R_X86_64_PC64 relocation for dynamic symbol %s", targ.Name)
+			ldr.Errorf(s, "unexpected R_X86_64_PC64 relocation for dynamic symbol %s", ldr.SymName(targ))
 		}
-		if targ.Type == 0 || targ.Type == sym.SXREF {
+		if targType == 0 || targType == sym.SXREF {
-			ld.Errorf(s, "unknown symbol %s in pcrel", targ.Name)
+			ldr.Errorf(s, "unknown symbol %s in pcrel", ldr.SymName(targ))
 		}
-		r.Type = objabi.R_PCREL
+		su := ldr.MakeSymbolUpdater(s)
-		r.Add += 8
+		su.SetRelocType(rIdx, objabi.R_PCREL)
+		su.SetRelocAdd(rIdx, r.Add()+8)
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_X86_64_PLT32):
-		r.Type = objabi.R_PCREL
+		su := ldr.MakeSymbolUpdater(s)
-		r.Add += 4
+		su.SetRelocType(rIdx, objabi.R_PCREL)
-		if targ.Type == sym.SDYNIMPORT {
+		su.SetRelocAdd(rIdx, r.Add()+4)
-			addpltsym(target, syms, targ)
+		if targType == sym.SDYNIMPORT {
-			r.Sym = syms.PLT
+			addpltsym2(target, ldr, syms, targ)
-			r.Add += int64(targ.Plt())
+			su.SetRelocSym(rIdx, syms.PLT2)
+			su.SetRelocAdd(rIdx, r.Add()+int64(ldr.SymPlt(targ)))
 		}
 
 		return true
@@ -127,34 +134,36 @@ func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s *sym.
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_X86_64_GOTPCREL),
 		objabi.ElfRelocOffset + objabi.RelocType(elf.R_X86_64_GOTPCRELX),
 		objabi.ElfRelocOffset + objabi.RelocType(elf.R_X86_64_REX_GOTPCRELX):
-		if targ.Type != sym.SDYNIMPORT {
+		su := ldr.MakeSymbolUpdater(s)
+		if targType != sym.SDYNIMPORT {
 			// have symbol
-			if r.Off >= 2 && s.P[r.Off-2] == 0x8b {
+			sData := ldr.Data(s)
-				makeWritable(s)
+			if r.Off() >= 2 && sData[r.Off()-2] == 0x8b {
+				su.MakeWritable()
 				// turn MOVQ of GOT entry into LEAQ of symbol itself
-				s.P[r.Off-2] = 0x8d
+				writeableData := su.Data()
-
+				writeableData[r.Off()-2] = 0x8d
-				r.Type = objabi.R_PCREL
+				su.SetRelocType(rIdx, objabi.R_PCREL)
-				r.Add += 4
+				su.SetRelocAdd(rIdx, r.Add()+4)
 				return true
 			}
 		}
 
 		// fall back to using GOT and hope for the best (CMOV*)
 		// TODO: just needs relocation, no need to put in .dynsym
-		addgotsym(target, syms, targ)
+		addgotsym2(target, ldr, syms, targ)
 
-		r.Type = objabi.R_PCREL
+		su.SetRelocType(rIdx, objabi.R_PCREL)
-		r.Sym = syms.GOT
+		su.SetRelocSym(rIdx, syms.GOT2)
-		r.Add += 4
+		su.SetRelocAdd(rIdx, r.Add()+4+int64(ldr.SymGot(targ)))
-		r.Add += int64(targ.Got())
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_X86_64_64):
-		if targ.Type == sym.SDYNIMPORT {
+		if targType == sym.SDYNIMPORT {
-			ld.Errorf(s, "unexpected R_X86_64_64 relocation for dynamic symbol %s", targ.Name)
+			ldr.Errorf(s, "unexpected R_X86_64_64 relocation for dynamic symbol %s", ldr.SymName(targ))
 		}
-		r.Type = objabi.R_ADDR
+		su := ldr.MakeSymbolUpdater(s)
+		su.SetRelocType(rIdx, objabi.R_ADDR)
 		if target.IsPIE() && target.IsInternal() {
 			// For internal linking PIE, this R_ADDR relocation cannot
 			// be resolved statically. We need to generate a dynamic
@@ -168,19 +177,21 @@ func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s *sym.
 		objabi.MachoRelocOffset + ld.MACHO_X86_64_RELOC_SIGNED*2 + 0,
 		objabi.MachoRelocOffset + ld.MACHO_X86_64_RELOC_BRANCH*2 + 0:
 		// TODO: What is the difference between all these?
-		r.Type = objabi.R_ADDR
+		su := ldr.MakeSymbolUpdater(s)
+		su.SetRelocType(rIdx, objabi.R_ADDR)
 
-		if targ.Type == sym.SDYNIMPORT {
+		if targType == sym.SDYNIMPORT {
-			ld.Errorf(s, "unexpected reloc for dynamic symbol %s", targ.Name)
+			ldr.Errorf(s, "unexpected reloc for dynamic symbol %s", ldr.SymName(targ))
 		}
 		return true
 
 	case objabi.MachoRelocOffset + ld.MACHO_X86_64_RELOC_BRANCH*2 + 1:
-		if targ.Type == sym.SDYNIMPORT {
+		if targType == sym.SDYNIMPORT {
-			addpltsym(target, syms, targ)
+			addpltsym2(target, ldr, syms, targ)
-			r.Sym = syms.PLT
+			su := ldr.MakeSymbolUpdater(s)
-			r.Add = int64(targ.Plt())
+			su.SetRelocSym(rIdx, syms.PLT2)
-			r.Type = objabi.R_PCREL
+			su.SetRelocType(rIdx, objabi.R_PCREL)
+			su.SetRelocAdd(rIdx, int64(ldr.SymPlt(targ)))
 			return true
 		}
 		fallthrough
@@ -190,44 +201,53 @@ func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s *sym.
 		objabi.MachoRelocOffset + ld.MACHO_X86_64_RELOC_SIGNED_1*2 + 1,
 		objabi.MachoRelocOffset + ld.MACHO_X86_64_RELOC_SIGNED_2*2 + 1,
 		objabi.MachoRelocOffset + ld.MACHO_X86_64_RELOC_SIGNED_4*2 + 1:
-		r.Type = objabi.R_PCREL
+		su := ldr.MakeSymbolUpdater(s)
+		su.SetRelocType(rIdx, objabi.R_PCREL)
 
-		if targ.Type == sym.SDYNIMPORT {
+		if targType == sym.SDYNIMPORT {
-			ld.Errorf(s, "unexpected pc-relative reloc for dynamic symbol %s", targ.Name)
+			ldr.Errorf(s, "unexpected pc-relative reloc for dynamic symbol %s", ldr.SymName(targ))
 		}
 		return true
 
 	case objabi.MachoRelocOffset + ld.MACHO_X86_64_RELOC_GOT_LOAD*2 + 1:
-		if targ.Type != sym.SDYNIMPORT {
+		if targType != sym.SDYNIMPORT {
 			// have symbol
 			// turn MOVQ of GOT entry into LEAQ of symbol itself
-			if r.Off < 2 || s.P[r.Off-2] != 0x8b {
+			sdata := ldr.Data(s)
-				ld.Errorf(s, "unexpected GOT_LOAD reloc for non-dynamic symbol %s", targ.Name)
+			if r.Off() < 2 || sdata[r.Off()-2] != 0x8b {
+				ldr.Errorf(s, "unexpected GOT_LOAD reloc for non-dynamic symbol %s", ldr.SymName(targ))
 				return false
 			}
 
-			makeWritable(s)
+			su := ldr.MakeSymbolUpdater(s)
-			s.P[r.Off-2] = 0x8d
+			su.MakeWritable()
-			r.Type = objabi.R_PCREL
+			sdata = su.Data()
+			sdata[r.Off()-2] = 0x8d
+			su.SetRelocType(rIdx, objabi.R_PCREL)
 			return true
 		}
 		fallthrough
 
 	case objabi.MachoRelocOffset + ld.MACHO_X86_64_RELOC_GOT*2 + 1:
-		if targ.Type != sym.SDYNIMPORT {
+		if targType != sym.SDYNIMPORT {
-			ld.Errorf(s, "unexpected GOT reloc for non-dynamic symbol %s", targ.Name)
+			ldr.Errorf(s, "unexpected GOT reloc for non-dynamic symbol %s", ldr.SymName(targ))
 		}
-		addgotsym(target, syms, targ)
+		addgotsym2(target, ldr, syms, targ)
-		r.Type = objabi.R_PCREL
+		su := ldr.MakeSymbolUpdater(s)
-		r.Sym = syms.GOT
+		su.SetRelocType(rIdx, objabi.R_PCREL)
-		r.Add += int64(targ.Got())
+		su.SetRelocSym(rIdx, syms.GOT2)
+		su.SetRelocAdd(rIdx, r.Add()+int64(ldr.SymGot(targ)))
 		return true
 	}
 
-	switch r.Type {
+	// Reread the reloc to incorporate any changes in type above.
+	relocs := ldr.Relocs(s)
+	*r = relocs.At2(rIdx)
+
+	switch r.Type() {
 	case objabi.R_CALL,
 		objabi.R_PCREL:
-		if targ.Type != sym.SDYNIMPORT {
+		if targType != sym.SDYNIMPORT {
 			// nothing to do, the relocation will be laid out in reloc
 			return true
 		}
@@ -237,26 +257,28 @@ func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s *sym.
 		}
 		// Internal linking, for both ELF and Mach-O.
 		// Build a PLT entry and change the relocation target to that entry.
-		addpltsym(target, syms, targ)
+		addpltsym2(target, ldr, syms, targ)
-		r.Sym = syms.PLT
+		su := ldr.MakeSymbolUpdater(s)
-		r.Add = int64(targ.Plt())
+		su.SetRelocSym(rIdx, syms.PLT2)
+		su.SetRelocAdd(rIdx, int64(ldr.SymPlt(targ)))
 		return true
 
 	case objabi.R_ADDR:
-		if s.Type == sym.STEXT && target.IsElf() {
+		if ldr.SymType(s) == sym.STEXT && target.IsElf() {
+			su := ldr.MakeSymbolUpdater(s)
 			if target.IsSolaris() {
-				addpltsym(target, syms, targ)
+				addpltsym2(target, ldr, syms, targ)
-				r.Sym = syms.PLT
+				su.SetRelocSym(rIdx, syms.PLT2)
-				r.Add += int64(targ.Plt())
+				su.SetRelocAdd(rIdx, r.Add()+int64(ldr.SymPlt(targ)))
 				return true
 			}
 			// The code is asking for the address of an external
 			// function. We provide it with the address of the
 			// correspondent GOT symbol.
-			addgotsym(target, syms, targ)
+			addgotsym2(target, ldr, syms, targ)
 
-			r.Sym = syms.GOT
+			su.SetRelocSym(rIdx, syms.GOT2)
-			r.Add += int64(targ.Got())
+			su.SetRelocAdd(rIdx, r.Add()+int64(ldr.SymGot(targ)))
 			return true
 		}
 
@@ -293,7 +315,7 @@ func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s *sym.
 			// symbol offset as determined by reloc(), not the
 			// final dynamically linked address as a dynamic
 			// relocation would provide.
-			switch s.Name {
+			switch ldr.SymName(s) {
 			case ".dynsym", ".rela", ".rela.plt", ".got.plt", ".dynamic":
 				return false
 			}
@@ -304,7 +326,7 @@ func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s *sym.
 			// linking, in which case the relocation will be
 			// prepared in the 'reloc' phase and passed to the
 			// external linker in the 'asmb' phase.
-			if s.Type != sym.SDATA && s.Type != sym.SRODATA {
+			if ldr.SymType(s) != sym.SDATA && ldr.SymType(s) != sym.SRODATA {
 				break
 			}
 		}
@@ -327,14 +349,14 @@ func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s *sym.
 			// AddAddrPlus is used for r_offset and r_addend to
 			// generate new R_ADDR relocations that will update
 			// these fields in the 'reloc' phase.
-			rela := syms.Rela
+			rela := ldr.MakeSymbolUpdater(syms.Rela2)
-			rela.AddAddrPlus(target.Arch, s, int64(r.Off))
+			rela.AddAddrPlus(target.Arch, s, int64(r.Off()))
-			if r.Siz == 8 {
+			if r.Siz() == 8 {
 				rela.AddUint64(target.Arch, ld.ELF64_R_INFO(0, uint32(elf.R_X86_64_RELATIVE)))
 			} else {
-				ld.Errorf(s, "unexpected relocation for dynamic symbol %s", targ.Name)
+				ldr.Errorf(s, "unexpected relocation for dynamic symbol %s", ldr.SymName(targ))
 			}
-			rela.AddAddrPlus(target.Arch, targ, int64(r.Add))
+			rela.AddAddrPlus(target.Arch, targ, int64(r.Add()))
 			// Not mark r done here. So we still apply it statically,
 			// so in the file content we'll also have the right offset
 			// to the relocation target. So it can be examined statically
@@ -342,7 +364,7 @@ func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s *sym.
 			return true
 		}
 
-		if target.IsDarwin() && s.Size == int64(target.Arch.PtrSize) && r.Off == 0 {
+		if target.IsDarwin() && ldr.SymSize(s) == int64(target.Arch.PtrSize) && r.Off() == 0 {
 			// Mach-O relocations are a royal pain to lay out.
 			// They use a compact stateful bytecode representation
 			// that is too much bother to deal with.
@@ -353,18 +375,17 @@ func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s *sym.
 			// just in case the C code assigns to the variable,
 			// and of course it only works for single pointers,
 			// but we only need to support cgo and that's all it needs.
-			ld.Adddynsym(target, syms, targ)
+			ld.Adddynsym2(ldr, target, syms, targ)
 
-			got := syms.GOT
+			got := ldr.MakeSymbolUpdater(syms.GOT2)
-			s.Type = got.Type
+			su := ldr.MakeSymbolUpdater(s)
-			s.Attr |= sym.AttrSubSymbol
+			su.SetType(got.Type())
-			s.Outer = got
+			got.PrependSub(s)
-			s.Sub = got.Sub
+			su.SetValue(got.Size())
-			got.Sub = s
-			s.Value = got.Size
 			got.AddUint64(target.Arch, 0)
-			syms.LinkEditGOT.AddUint32(target.Arch, uint32(targ.Dynid))
+			leg := ldr.MakeSymbolUpdater(syms.LinkEditGOT2)
-			r.Type = objabi.ElfRelocOffset // ignore during relocsym
+			leg.AddUint32(target.Arch, uint32(ldr.SymDynid(targ)))
+			su.SetRelocType(rIdx, objabi.ElfRelocOffset) // ignore during relocsym
 			return true
 		}
 	}
@@ -375,7 +396,7 @@ func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s *sym.
 func elfreloc1(ctxt *ld.Link, r *sym.Reloc, sectoff int64) bool {
 	ctxt.Out.Write64(uint64(sectoff))
 
-	elfsym := r.Xsym.ElfsymForReloc()
+	elfsym := ld.ElfSymForReloc(ctxt, r.Xsym)
 	switch r.Type {
 	default:
 		return false
@@ -569,18 +590,18 @@ func elfsetupplt(ctxt *ld.Link, plt, got *loader.SymbolBuilder, dynamic loader.S
 	}
 }
 
-func addpltsym(target *ld.Target, syms *ld.ArchSyms, s *sym.Symbol) {
+func addpltsym2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loader.Sym) {
-	if s.Plt() >= 0 {
+	if ldr.SymPlt(s) >= 0 {
 		return
 	}
 
-	ld.Adddynsym(target, syms, s)
+	ld.Adddynsym2(ldr, target, syms, s)
 
 	if target.IsElf() {
-		plt := syms.PLT
+		plt := ldr.MakeSymbolUpdater(syms.PLT2)
-		got := syms.GOTPLT
+		got := ldr.MakeSymbolUpdater(syms.GOTPLT2)
-		rela := syms.RelaPLT
+		rela := ldr.MakeSymbolUpdater(syms.RelaPLT2)
-		if plt.Size == 0 {
+		if plt.Size() == 0 {
 			panic("plt is not set up")
 		}
 
@@ -588,28 +609,29 @@ func addpltsym(target *ld.Target, syms *ld.ArchSyms, s *sym.Symbol) {
 		plt.AddUint8(0xff)
 
 		plt.AddUint8(0x25)
-		plt.AddPCRelPlus(target.Arch, got, got.Size)
+		plt.AddPCRelPlus(target.Arch, got.Sym(), got.Size())
 
 		// add to got: pointer to current pos in plt
-		got.AddAddrPlus(target.Arch, plt, plt.Size)
+		got.AddAddrPlus(target.Arch, plt.Sym(), plt.Size())
 
 		// pushq $x
 		plt.AddUint8(0x68)
 
-		plt.AddUint32(target.Arch, uint32((got.Size-24-8)/8))
+		plt.AddUint32(target.Arch, uint32((got.Size()-24-8)/8))
 
 		// jmpq .plt
 		plt.AddUint8(0xe9)
 
-		plt.AddUint32(target.Arch, uint32(-(plt.Size + 4)))
+		plt.AddUint32(target.Arch, uint32(-(plt.Size() + 4)))
 
 		// rela
-		rela.AddAddrPlus(target.Arch, got, got.Size-8)
+		rela.AddAddrPlus(target.Arch, got.Sym(), got.Size()-8)
 
-		rela.AddUint64(target.Arch, ld.ELF64_R_INFO(uint32(s.Dynid), uint32(elf.R_X86_64_JMP_SLOT)))
+		sDynid := ldr.SymDynid(s)
+		rela.AddUint64(target.Arch, ld.ELF64_R_INFO(uint32(sDynid), uint32(elf.R_X86_64_JMP_SLOT)))
 		rela.AddUint64(target.Arch, 0)
 
-		s.SetPlt(int32(plt.Size - 16))
+		ldr.SetPlt(s, int32(plt.Size()-16))
 	} else if target.IsDarwin() {
 		// To do lazy symbol lookup right, we're supposed
 		// to tell the dynamic loader which library each
@@ -621,45 +643,48 @@ func addpltsym(target *ld.Target, syms *ld.ArchSyms, s *sym.Symbol) {
 		// https://networkpx.blogspot.com/2009/09/about-lcdyldinfoonly-command.html
 		// has details about what we're avoiding.
 
-		addgotsym(target, syms, s)
+		addgotsym2(target, ldr, syms, s)
-		plt := syms.PLT
+		plt := ldr.MakeSymbolUpdater(syms.PLT2)
 
-		syms.LinkEditPLT.AddUint32(target.Arch, uint32(s.Dynid))
+		sDynid := ldr.SymDynid(s)
+		lep := ldr.MakeSymbolUpdater(syms.LinkEditPLT2)
+		lep.AddUint32(target.Arch, uint32(sDynid))
 
 		// jmpq *got+size(IP)
-		s.SetPlt(int32(plt.Size))
+		ldr.SetPlt(s, int32(plt.Size()))
 
 		plt.AddUint8(0xff)
 		plt.AddUint8(0x25)
-		plt.AddPCRelPlus(target.Arch, syms.GOT, int64(s.Got()))
+		plt.AddPCRelPlus(target.Arch, syms.GOT2, int64(ldr.SymGot(s)))
 	} else {
-		ld.Errorf(s, "addpltsym: unsupported binary format")
+		ldr.Errorf(s, "addpltsym: unsupported binary format")
 	}
 }
 
-func addgotsym(target *ld.Target, syms *ld.ArchSyms, s *sym.Symbol) {
+func addgotsym2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loader.Sym) {
-	if s.Got() >= 0 {
+	if ldr.SymGot(s) >= 0 {
 		return
 	}
 
-	ld.Adddynsym(target, syms, s)
+	ld.Adddynsym2(ldr, target, syms, s)
-	got := syms.GOT
+	got := ldr.MakeSymbolUpdater(syms.GOT2)
-	s.SetGot(int32(got.Size))
+	ldr.SetGot(s, int32(got.Size()))
 	got.AddUint64(target.Arch, 0)
 
 	if target.IsElf() {
-		rela := syms.Rela
+		rela := ldr.MakeSymbolUpdater(syms.Rela2)
-		rela.AddAddrPlus(target.Arch, got, int64(s.Got()))
+		rela.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
-		rela.AddUint64(target.Arch, ld.ELF64_R_INFO(uint32(s.Dynid), uint32(elf.R_X86_64_GLOB_DAT)))
+		rela.AddUint64(target.Arch, ld.ELF64_R_INFO(uint32(ldr.SymDynid(s)), uint32(elf.R_X86_64_GLOB_DAT)))
 		rela.AddUint64(target.Arch, 0)
 	} else if target.IsDarwin() {
-		syms.LinkEditGOT.AddUint32(target.Arch, uint32(s.Dynid))
+		leg := ldr.MakeSymbolUpdater(syms.LinkEditGOT2)
+		leg.AddUint32(target.Arch, uint32(ldr.SymDynid(s)))
 	} else {
-		ld.Errorf(s, "addgotsym: unsupported binary format")
+		ldr.Errorf(s, "addgotsym: unsupported binary format")
 	}
 }
 
-func asmb(ctxt *ld.Link) {
+func asmb(ctxt *ld.Link, _ *loader.Loader) {
 	if ctxt.IsELF {
 		ld.Asmbelfsetup()
 	}
@@ -816,7 +841,7 @@ func asmb2(ctxt *ld.Link) {
 	}
 }
 
-func tlsIEtoLE(s *sym.Symbol, off, size int) {
+func tlsIEtoLE(P []byte, off, size int) {
 	// Transform the PC-relative instruction into a constant load.
 	// That is,
 	//
@@ -827,7 +852,7 @@ func tlsIEtoLE(s *sym.Symbol, off, size int) {
 	if off < 3 {
 		log.Fatal("R_X86_64_GOTTPOFF reloc not preceded by MOVQ or ADDQ instruction")
 	}
-	op := s.P[off-3 : off]
+	op := P[off-3 : off]
 	reg := op[2] >> 3
 
 	if op[1] == 0x8b || reg == 4 {

src/cmd/link/internal/amd64/obj.go

@@ -46,7 +46,7 @@ func Init() (*sys.Arch, ld.Arch) {
 		Dwarfregsp: dwarfRegSP,
 		Dwarfreglr: dwarfRegLR,
 
-		Adddynrel:        adddynrel,
+		Adddynrel2:       adddynrel2,
 		Archinit:         archinit,
 		Archreloc:        archreloc,
 		Archrelocvariant: archrelocvariant,

src/cmd/link/internal/arm/asm.go

@@ -103,24 +103,30 @@ func braddoff(a int32, b int32) int32 {
 	return int32((uint32(a))&0xff000000 | 0x00ffffff&uint32(a+b))
 }
 
-func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s *sym.Symbol, r *sym.Reloc) bool {
+func adddynrel2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loader.Sym, r *loader.Reloc2, rIdx int) bool {
-	targ := r.Sym
 
-	switch r.Type {
+	targ := r.Sym()
+	var targType sym.SymKind
+	if targ != 0 {
+		targType = ldr.SymType(targ)
+	}
+
+	switch r.Type() {
 	default:
-		if r.Type >= objabi.ElfRelocOffset {
+		if r.Type() >= objabi.ElfRelocOffset {
-			ld.Errorf(s, "unexpected relocation type %d (%s)", r.Type, sym.RelocName(target.Arch, r.Type))
+			ldr.Errorf(s, "unexpected relocation type %d (%s)", r.Type(), sym.RelocName(target.Arch, r.Type()))
 			return false
 		}
 
 		// Handle relocations found in ELF object files.
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_PLT32):
-		r.Type = objabi.R_CALLARM
+		su := ldr.MakeSymbolUpdater(s)
+		su.SetRelocType(rIdx, objabi.R_CALLARM)
 
-		if targ.Type == sym.SDYNIMPORT {
+		if targType == sym.SDYNIMPORT {
-			addpltsym(target, syms, targ)
+			addpltsym2(target, ldr, syms, targ)
-			r.Sym = syms.PLT
+			su.SetRelocSym(rIdx, syms.PLT2)
-			r.Add = int64(braddoff(int32(r.Add), targ.Plt()/4))
+			su.SetRelocAdd(rIdx, int64(braddoff(int32(r.Add()), ldr.SymPlt(targ)/4)))
 		}
 
 		return true
@@ -130,113 +136,112 @@ func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s *sym.
 		return false
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_GOT32): // R_ARM_GOT_BREL
-		if targ.Type != sym.SDYNIMPORT {
+		if targType != sym.SDYNIMPORT {
-			addgotsyminternal(target, syms, targ)
+			addgotsyminternal2(target, ldr, syms, targ)
 		} else {
-			addgotsym(target, syms, targ)
+			addgotsym2(target, ldr, syms, targ)
 		}
 
-		r.Type = objabi.R_CONST // write r->add during relocsym
+		su := ldr.MakeSymbolUpdater(s)
-		r.Sym = nil
+		su.SetRelocType(rIdx, objabi.R_CONST) // write r->add during relocsym
-		r.Add += int64(targ.Got())
+		su.SetRelocSym(rIdx, 0)
+		su.SetRelocAdd(rIdx, r.Add()+int64(ldr.SymGot(targ)))
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_GOT_PREL): // GOT(nil) + A - nil
-		if targ.Type != sym.SDYNIMPORT {
+		if targType != sym.SDYNIMPORT {
-			addgotsyminternal(target, syms, targ)
+			addgotsyminternal2(target, ldr, syms, targ)
 		} else {
-			addgotsym(target, syms, targ)
+			addgotsym2(target, ldr, syms, targ)
 		}
-
+		su := ldr.MakeSymbolUpdater(s)
-		r.Type = objabi.R_PCREL
+		su.SetRelocType(rIdx, objabi.R_PCREL)
-		r.Sym = syms.GOT
+		su.SetRelocSym(rIdx, syms.GOT2)
-		r.Add += int64(targ.Got()) + 4
+		su.SetRelocAdd(rIdx, r.Add()+4+int64(ldr.SymGot(targ)))
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_GOTOFF): // R_ARM_GOTOFF32
-		r.Type = objabi.R_GOTOFF
+		su := ldr.MakeSymbolUpdater(s)
-
+		su.SetRelocType(rIdx, objabi.R_GOTOFF)
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_GOTPC): // R_ARM_BASE_PREL
-		r.Type = objabi.R_PCREL
+		su := ldr.MakeSymbolUpdater(s)
-
+		su.SetRelocType(rIdx, objabi.R_PCREL)
-		r.Sym = syms.GOT
+		su.SetRelocSym(rIdx, syms.GOT2)
-		r.Add += 4
+		su.SetRelocAdd(rIdx, r.Add()+4)
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_CALL):
-		r.Type = objabi.R_CALLARM
+		su := ldr.MakeSymbolUpdater(s)
-		if targ.Type == sym.SDYNIMPORT {
+		su.SetRelocType(rIdx, objabi.R_CALLARM)
-			addpltsym(target, syms, targ)
+		if targType == sym.SDYNIMPORT {
-			r.Sym = syms.PLT
+			addpltsym2(target, ldr, syms, targ)
-			r.Add = int64(braddoff(int32(r.Add), targ.Plt()/4))
+			su.SetRelocSym(rIdx, syms.PLT2)
+			su.SetRelocAdd(rIdx, int64(braddoff(int32(r.Add()), ldr.SymPlt(targ)/4)))
 		}
-
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_REL32): // R_ARM_REL32
-		r.Type = objabi.R_PCREL
+		su := ldr.MakeSymbolUpdater(s)
-
+		su.SetRelocType(rIdx, objabi.R_PCREL)
-		r.Add += 4
+		su.SetRelocAdd(rIdx, r.Add()+4)
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_ABS32):
-		if targ.Type == sym.SDYNIMPORT {
+		if targType == sym.SDYNIMPORT {
-			ld.Errorf(s, "unexpected R_ARM_ABS32 relocation for dynamic symbol %s", targ.Name)
+			ldr.Errorf(s, "unexpected R_ARM_ABS32 relocation for dynamic symbol %s", ldr.SymName(targ))
 		}
-		r.Type = objabi.R_ADDR
+		su := ldr.MakeSymbolUpdater(s)
-		return true
+		su.SetRelocType(rIdx, objabi.R_ADDR)
-
-		// we can just ignore this, because we are targeting ARM V5+ anyway
-	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_V4BX):
-		if r.Sym != nil {
-			// R_ARM_V4BX is ABS relocation, so this symbol is a dummy symbol, ignore it
-			r.Sym.Type = 0
-		}
-
-		r.Sym = nil
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_PC24),
 		objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_JUMP24):
-		r.Type = objabi.R_CALLARM
+		su := ldr.MakeSymbolUpdater(s)
-		if targ.Type == sym.SDYNIMPORT {
+		su.SetRelocType(rIdx, objabi.R_CALLARM)
-			addpltsym(target, syms, targ)
+		if targType == sym.SDYNIMPORT {
-			r.Sym = syms.PLT
+			addpltsym2(target, ldr, syms, targ)
-			r.Add = int64(braddoff(int32(r.Add), targ.Plt()/4))
+			su.SetRelocSym(rIdx, syms.PLT2)
+			su.SetRelocAdd(rIdx, int64(braddoff(int32(r.Add()), ldr.SymPlt(targ)/4)))
 		}
 
 		return true
 	}
 
 	// Handle references to ELF symbols from our own object files.
-	if targ.Type != sym.SDYNIMPORT {
+	if targType != sym.SDYNIMPORT {
 		return true
 	}
 
-	switch r.Type {
+	// Reread the reloc to incorporate any changes in type above.
+	relocs := ldr.Relocs(s)
+	*r = relocs.At2(rIdx)
+
+	switch r.Type() {
 	case objabi.R_CALLARM:
 		if target.IsExternal() {
 			// External linker will do this relocation.
 			return true
 		}
-		addpltsym(target, syms, targ)
+		addpltsym2(target, ldr, syms, targ)
-		r.Sym = syms.PLT
+		su := ldr.MakeSymbolUpdater(s)
-		r.Add = int64(targ.Plt())
+		su.SetRelocSym(rIdx, syms.PLT2)
+		su.SetRelocAdd(rIdx, int64(ldr.SymPlt(targ)))
 		return true
 
 	case objabi.R_ADDR:
-		if s.Type != sym.SDATA {
+		if ldr.SymType(s) != sym.SDATA {
 			break
 		}
 		if target.IsElf() {
-			ld.Adddynsym(target, syms, targ)
+			ld.Adddynsym2(ldr, target, syms, targ)
-			rel := syms.Rel
+			rel := ldr.MakeSymbolUpdater(syms.Rel2)
-			rel.AddAddrPlus(target.Arch, s, int64(r.Off))
+			rel.AddAddrPlus(target.Arch, s, int64(r.Off()))
-			rel.AddUint32(target.Arch, ld.ELF32_R_INFO(uint32(targ.Dynid), uint32(elf.R_ARM_GLOB_DAT))) // we need a nil + A dynamic reloc
+			rel.AddUint32(target.Arch, ld.ELF32_R_INFO(uint32(ldr.SymDynid(targ)), uint32(elf.R_ARM_GLOB_DAT))) // we need a nil + A dynamic reloc
-			r.Type = objabi.R_CONST                                                                     // write r->add during relocsym
+			su := ldr.MakeSymbolUpdater(s)
-			r.Sym = nil
+			su.SetRelocType(rIdx, objabi.R_CONST) // write r->add during relocsym
+			su.SetRelocSym(rIdx, 0)
 			return true
 		}
 	}
@@ -247,7 +252,7 @@ func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s *sym.
 func elfreloc1(ctxt *ld.Link, r *sym.Reloc, sectoff int64) bool {
 	ctxt.Out.Write32(uint32(sectoff))
 
-	elfsym := r.Xsym.ElfsymForReloc()
+	elfsym := ld.ElfSymForReloc(ctxt, r.Xsym)
 	switch r.Type {
 	default:
 		return false
@@ -592,94 +597,92 @@ func archrelocvariant(target *ld.Target, syms *ld.ArchSyms, r *sym.Reloc, s *sym
 	return t
 }
 
-func addpltreloc(plt *sym.Symbol, got *sym.Symbol, s *sym.Symbol, typ objabi.RelocType) {
+func addpltreloc2(ldr *loader.Loader, plt *loader.SymbolBuilder, got *loader.SymbolBuilder, s loader.Sym, typ objabi.RelocType) {
-	r := plt.AddRel()
+	r, _ := plt.AddRel(typ)
-	r.Sym = got
+	r.SetSym(got.Sym())
-	r.Off = int32(plt.Size)
+	r.SetOff(int32(plt.Size()))
-	r.Siz = 4
+	r.SetSiz(4)
-	r.Type = typ
+	r.SetAdd(int64(ldr.SymGot(s)) - 8)
-	r.Add = int64(s.Got()) - 8
 
-	plt.Attr |= sym.AttrReachable
+	plt.SetReachable(true)
-	plt.Size += 4
+	plt.SetSize(plt.Size() + 4)
-	plt.Grow(plt.Size)
+	plt.Grow(plt.Size())
 }
 
-func addpltsym(target *ld.Target, syms *ld.ArchSyms, s *sym.Symbol) {
+func addpltsym2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loader.Sym) {
-	if s.Plt() >= 0 {
+	if ldr.SymPlt(s) >= 0 {
 		return
 	}
 
-	ld.Adddynsym(target, syms, s)
+	ld.Adddynsym2(ldr, target, syms, s)
 
 	if target.IsElf() {
-		plt := syms.PLT
+		plt := ldr.MakeSymbolUpdater(syms.PLT2)
-		got := syms.GOTPLT
+		got := ldr.MakeSymbolUpdater(syms.GOTPLT2)
-		rel := syms.RelPLT
+		rel := ldr.MakeSymbolUpdater(syms.RelPLT2)
-		if plt.Size == 0 {
+		if plt.Size() == 0 {
 			panic("plt is not set up")
 		}
 
 		// .got entry
-		s.SetGot(int32(got.Size))
+		ldr.SetGot(s, int32(got.Size()))
 
 		// In theory, all GOT should point to the first PLT entry,
 		// Linux/ARM's dynamic linker will do that for us, but FreeBSD/ARM's
 		// dynamic linker won't, so we'd better do it ourselves.
-		got.AddAddrPlus(target.Arch, plt, 0)
+		got.AddAddrPlus(target.Arch, plt.Sym(), 0)
 
 		// .plt entry, this depends on the .got entry
-		s.SetPlt(int32(plt.Size))
+		ldr.SetPlt(s, int32(plt.Size()))
 
-		addpltreloc(plt, got, s, objabi.R_PLT0) // add lr, pc, #0xXX00000
+		addpltreloc2(ldr, plt, got, s, objabi.R_PLT0) // add lr, pc, #0xXX00000
-		addpltreloc(plt, got, s, objabi.R_PLT1) // add lr, lr, #0xYY000
+		addpltreloc2(ldr, plt, got, s, objabi.R_PLT1) // add lr, lr, #0xYY000
-		addpltreloc(plt, got, s, objabi.R_PLT2) // ldr pc, [lr, #0xZZZ]!
+		addpltreloc2(ldr, plt, got, s, objabi.R_PLT2) // ldr pc, [lr, #0xZZZ]!
 
 		// rel
-		rel.AddAddrPlus(target.Arch, got, int64(s.Got()))
+		rel.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
 
-		rel.AddUint32(target.Arch, ld.ELF32_R_INFO(uint32(s.Dynid), uint32(elf.R_ARM_JUMP_SLOT)))
+		rel.AddUint32(target.Arch, ld.ELF32_R_INFO(uint32(ldr.SymDynid(s)), uint32(elf.R_ARM_JUMP_SLOT)))
 	} else {
-		ld.Errorf(s, "addpltsym: unsupported binary format")
+		ldr.Errorf(s, "addpltsym: unsupported binary format")
 	}
 }
 
-func addgotsyminternal(target *ld.Target, syms *ld.ArchSyms, s *sym.Symbol) {
+func addgotsyminternal2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loader.Sym) {
-	if s.Got() >= 0 {
+	if ldr.SymGot(s) >= 0 {
 		return
 	}
 
-	got := syms.GOT
+	got := ldr.MakeSymbolUpdater(syms.GOT2)
-	s.SetGot(int32(got.Size))
+	ldr.SetGot(s, int32(got.Size()))
-
 	got.AddAddrPlus(target.Arch, s, 0)
 
 	if target.IsElf() {
 	} else {
-		ld.Errorf(s, "addgotsyminternal: unsupported binary format")
+		ldr.Errorf(s, "addgotsyminternal: unsupported binary format")
 	}
 }
 
-func addgotsym(target *ld.Target, syms *ld.ArchSyms, s *sym.Symbol) {
+func addgotsym2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loader.Sym) {
-	if s.Got() >= 0 {
+	if ldr.SymGot(s) >= 0 {
 		return
 	}
 
-	ld.Adddynsym(target, syms, s)
+	ld.Adddynsym2(ldr, target, syms, s)
-	got := syms.GOT
+	got := ldr.MakeSymbolUpdater(syms.GOT2)
-	s.SetGot(int32(got.Size))
+	ldr.SetGot(s, int32(got.Size()))
-	got.AddUint32(target.Arch, 0)
+	got.AddUint64(target.Arch, 0)
 
 	if target.IsElf() {
-		rel := syms.Rel
+		rel := ldr.MakeSymbolUpdater(syms.Rel2)
-		rel.AddAddrPlus(target.Arch, got, int64(s.Got()))
+		rel.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
-		rel.AddUint32(target.Arch, ld.ELF32_R_INFO(uint32(s.Dynid), uint32(elf.R_ARM_GLOB_DAT)))
+		rel.AddUint32(target.Arch, ld.ELF32_R_INFO(uint32(ldr.SymDynid(s)), uint32(elf.R_ARM_GLOB_DAT)))
 	} else {
-		ld.Errorf(s, "addgotsym: unsupported binary format")
+		ldr.Errorf(s, "addgotsym: unsupported binary format")
 	}
 }
 
-func asmb(ctxt *ld.Link) {
+func asmb(ctxt *ld.Link, _ *loader.Loader) {
 	if ctxt.IsELF {
 		ld.Asmbelfsetup()
 	}

src/cmd/link/internal/arm/obj.go

@@ -46,7 +46,7 @@ func Init() (*sys.Arch, ld.Arch) {
 		Dwarfregsp: dwarfRegSP,
 		Dwarfreglr: dwarfRegLR,
 
-		Adddynrel:        adddynrel,
+		Adddynrel2:       adddynrel2,
 		Archinit:         archinit,
 		Archreloc:        archreloc,
 		Archrelocvariant: archrelocvariant,

src/cmd/link/internal/arm64/asm.go

@@ -78,86 +78,97 @@ func gentext2(ctxt *ld.Link, ldr *loader.Loader) {
 	initfunc.AddReloc(rel2)
 }
 
-func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s *sym.Symbol, r *sym.Reloc) bool {
+func adddynrel2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loader.Sym, r *loader.Reloc2, rIdx int) bool {
-	targ := r.Sym
 
-	switch r.Type {
+	targ := r.Sym()
+	var targType sym.SymKind
+	if targ != 0 {
+		targType = ldr.SymType(targ)
+	}
+
+	switch r.Type() {
 	default:
-		if r.Type >= objabi.ElfRelocOffset {
+		if r.Type() >= objabi.ElfRelocOffset {
-			ld.Errorf(s, "unexpected relocation type %d (%s)", r.Type, sym.RelocName(target.Arch, r.Type))
+			ldr.Errorf(s, "unexpected relocation type %d (%s)", r.Type(), sym.RelocName(target.Arch, r.Type()))
 			return false
 		}
 
 	// Handle relocations found in ELF object files.
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_AARCH64_PREL32):
-		if targ.Type == sym.SDYNIMPORT {
+		if targType == sym.SDYNIMPORT {
-			ld.Errorf(s, "unexpected R_AARCH64_PREL32 relocation for dynamic symbol %s", targ.Name)
+			ldr.Errorf(s, "unexpected R_AARCH64_PREL32 relocation for dynamic symbol %s", ldr.SymName(targ))
 		}
 		// TODO(mwhudson): the test of VisibilityHidden here probably doesn't make
 		// sense and should be removed when someone has thought about it properly.
-		if (targ.Type == 0 || targ.Type == sym.SXREF) && !targ.Attr.VisibilityHidden() {
+		if (targType == 0 || targType == sym.SXREF) && !ldr.AttrVisibilityHidden(targ) {
-			ld.Errorf(s, "unknown symbol %s in pcrel", targ.Name)
+			ldr.Errorf(s, "unknown symbol %s in pcrel", ldr.SymName(targ))
 		}
-		r.Type = objabi.R_PCREL
+		su := ldr.MakeSymbolUpdater(s)
-		r.Add += 4
+		su.SetRelocType(rIdx, objabi.R_PCREL)
+		su.SetRelocAdd(rIdx, r.Add()+4)
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_AARCH64_PREL64):
-		if targ.Type == sym.SDYNIMPORT {
+		if targType == sym.SDYNIMPORT {
-			ld.Errorf(s, "unexpected R_AARCH64_PREL64 relocation for dynamic symbol %s", targ.Name)
+			ldr.Errorf(s, "unexpected R_AARCH64_PREL64 relocation for dynamic symbol %s", ldr.SymName(targ))
 		}
-		if targ.Type == 0 || targ.Type == sym.SXREF {
+		if targType == 0 || targType == sym.SXREF {
-			ld.Errorf(s, "unknown symbol %s in pcrel", targ.Name)
+			ldr.Errorf(s, "unknown symbol %s in pcrel", ldr.SymName(targ))
 		}
-		r.Type = objabi.R_PCREL
+		su := ldr.MakeSymbolUpdater(s)
-		r.Add += 8
+		su.SetRelocType(rIdx, objabi.R_PCREL)
+		su.SetRelocAdd(rIdx, r.Add()+8)
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_AARCH64_CALL26),
 		objabi.ElfRelocOffset + objabi.RelocType(elf.R_AARCH64_JUMP26):
-		if targ.Type == sym.SDYNIMPORT {
+		if targType == sym.SDYNIMPORT {
-			addpltsym(target, syms, targ)
+			addpltsym2(target, ldr, syms, targ)
-			r.Sym = syms.PLT
+			su := ldr.MakeSymbolUpdater(s)
-			r.Add += int64(targ.Plt())
+			su.SetRelocSym(rIdx, syms.PLT2)
+			su.SetRelocAdd(rIdx, r.Add()+int64(ldr.SymPlt(targ)))
 		}
-		if (targ.Type == 0 || targ.Type == sym.SXREF) && !targ.Attr.VisibilityHidden() {
+		if (targType == 0 || targType == sym.SXREF) && !ldr.AttrVisibilityHidden(targ) {
-			ld.Errorf(s, "unknown symbol %s in callarm64", targ.Name)
+			ldr.Errorf(s, "unknown symbol %s in callarm64", ldr.SymName(targ))
 		}
-		r.Type = objabi.R_CALLARM64
+		su := ldr.MakeSymbolUpdater(s)
+		su.SetRelocType(rIdx, objabi.R_CALLARM64)
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_AARCH64_ADR_GOT_PAGE),
 		objabi.ElfRelocOffset + objabi.RelocType(elf.R_AARCH64_LD64_GOT_LO12_NC):
-		if targ.Type != sym.SDYNIMPORT {
+		if targType != sym.SDYNIMPORT {
 			// have symbol
 			// TODO: turn LDR of GOT entry into ADR of symbol itself
 		}
 
 		// fall back to using GOT
 		// TODO: just needs relocation, no need to put in .dynsym
-		addgotsym(target, syms, targ)
+		addgotsym2(target, ldr, syms, targ)
-
+		su := ldr.MakeSymbolUpdater(s)
-		r.Type = objabi.R_ARM64_GOT
+		su.SetRelocType(rIdx, objabi.R_ARM64_GOT)
-		r.Sym = syms.GOT
+		su.SetRelocSym(rIdx, syms.GOT2)
-		r.Add += int64(targ.Got())
+		su.SetRelocAdd(rIdx, r.Add()+int64(ldr.SymGot(targ)))
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_AARCH64_ADR_PREL_PG_HI21),
 		objabi.ElfRelocOffset + objabi.RelocType(elf.R_AARCH64_ADD_ABS_LO12_NC):
-		if targ.Type == sym.SDYNIMPORT {
+		if targType == sym.SDYNIMPORT {
-			ld.Errorf(s, "unexpected relocation for dynamic symbol %s", targ.Name)
+			ldr.Errorf(s, "unexpected relocation for dynamic symbol %s", ldr.SymName(targ))
 		}
-		if targ.Type == 0 || targ.Type == sym.SXREF {
+		if targType == 0 || targType == sym.SXREF {
-			ld.Errorf(s, "unknown symbol %s", targ.Name)
+			ldr.Errorf(s, "unknown symbol %s", ldr.SymName(targ))
 		}
-		r.Type = objabi.R_ARM64_PCREL
+		su := ldr.MakeSymbolUpdater(s)
+		su.SetRelocType(rIdx, objabi.R_ARM64_PCREL)
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_AARCH64_ABS64):
-		if targ.Type == sym.SDYNIMPORT {
+		if targType == sym.SDYNIMPORT {
-			ld.Errorf(s, "unexpected R_AARCH64_ABS64 relocation for dynamic symbol %s", targ.Name)
+			ldr.Errorf(s, "unexpected R_AARCH64_ABS64 relocation for dynamic symbol %s", ldr.SymName(targ))
 		}
-		r.Type = objabi.R_ADDR
+		su := ldr.MakeSymbolUpdater(s)
+		su.SetRelocType(rIdx, objabi.R_ADDR)
 		if target.IsPIE() && target.IsInternal() {
 			// For internal linking PIE, this R_ADDR relocation cannot
 			// be resolved statically. We need to generate a dynamic
@@ -167,39 +178,48 @@ func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s *sym.
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_AARCH64_LDST8_ABS_LO12_NC):
-		if targ.Type == sym.SDYNIMPORT {
+		if targType == sym.SDYNIMPORT {
-			ld.Errorf(s, "unexpected relocation for dynamic symbol %s", targ.Name)
+			ldr.Errorf(s, "unexpected relocation for dynamic symbol %s", ldr.SymName(targ))
 		}
-		r.Type = objabi.R_ARM64_LDST8
+		su := ldr.MakeSymbolUpdater(s)
+		su.SetRelocType(rIdx, objabi.R_ARM64_LDST8)
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_AARCH64_LDST32_ABS_LO12_NC):
-		if targ.Type == sym.SDYNIMPORT {
+		if targType == sym.SDYNIMPORT {
-			ld.Errorf(s, "unexpected relocation for dynamic symbol %s", targ.Name)
+			ldr.Errorf(s, "unexpected relocation for dynamic symbol %s", ldr.SymName(targ))
 		}
-		r.Type = objabi.R_ARM64_LDST32
+		su := ldr.MakeSymbolUpdater(s)
+		su.SetRelocType(rIdx, objabi.R_ARM64_LDST32)
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_AARCH64_LDST64_ABS_LO12_NC):
-		if targ.Type == sym.SDYNIMPORT {
+		if targType == sym.SDYNIMPORT {
-			ld.Errorf(s, "unexpected relocation for dynamic symbol %s", targ.Name)
+			ldr.Errorf(s, "unexpected relocation for dynamic symbol %s", ldr.SymName(targ))
 		}
-		r.Type = objabi.R_ARM64_LDST64
+		su := ldr.MakeSymbolUpdater(s)
+		su.SetRelocType(rIdx, objabi.R_ARM64_LDST64)
+
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_AARCH64_LDST128_ABS_LO12_NC):
-		if targ.Type == sym.SDYNIMPORT {
+		if targType == sym.SDYNIMPORT {
-			ld.Errorf(s, "unexpected relocation for dynamic symbol %s", targ.Name)
+			ldr.Errorf(s, "unexpected relocation for dynamic symbol %s", ldr.SymName(targ))
 		}
-		r.Type = objabi.R_ARM64_LDST128
+		su := ldr.MakeSymbolUpdater(s)
+		su.SetRelocType(rIdx, objabi.R_ARM64_LDST128)
 		return true
 	}
 
-	switch r.Type {
+	// Reread the reloc to incorporate any changes in type above.
+	relocs := ldr.Relocs(s)
+	*r = relocs.At2(rIdx)
+
+	switch r.Type() {
 	case objabi.R_CALL,
 		objabi.R_PCREL,
 		objabi.R_CALLARM64:
-		if targ.Type != sym.SDYNIMPORT {
+		if targType != sym.SDYNIMPORT {
 			// nothing to do, the relocation will be laid out in reloc
 			return true
 		}
@@ -209,14 +229,14 @@ func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s *sym.
 		}
 
 	case objabi.R_ADDR:
-		if s.Type == sym.STEXT && target.IsElf() {
+		if ldr.SymType(s) == sym.STEXT && target.IsElf() {
 			// The code is asking for the address of an external
 			// function. We provide it with the address of the
 			// correspondent GOT symbol.
-			addgotsym(target, syms, targ)
+			addgotsym2(target, ldr, syms, targ)
-
+			su := ldr.MakeSymbolUpdater(s)
-			r.Sym = syms.GOT
+			su.SetRelocSym(rIdx, syms.GOT2)
-			r.Add += int64(targ.Got())
+			su.SetRelocAdd(rIdx, r.Add()+int64(ldr.SymGot(targ)))
 			return true
 		}
 
@@ -253,7 +273,7 @@ func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s *sym.
 			// symbol offset as determined by reloc(), not the
 			// final dynamically linked address as a dynamic
 			// relocation would provide.
-			switch s.Name {
+			switch ldr.SymName(s) {
 			case ".dynsym", ".rela", ".rela.plt", ".got.plt", ".dynamic":
 				return false
 			}
@@ -264,7 +284,7 @@ func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s *sym.
 			// linking, in which case the relocation will be
 			// prepared in the 'reloc' phase and passed to the
 			// external linker in the 'asmb' phase.
-			if s.Type != sym.SDATA && s.Type != sym.SRODATA {
+			if ldr.SymType(s) != sym.SDATA && ldr.SymType(s) != sym.SRODATA {
 				break
 			}
 		}
@@ -287,14 +307,14 @@ func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s *sym.
 			// AddAddrPlus is used for r_offset and r_addend to
 			// generate new R_ADDR relocations that will update
 			// these fields in the 'reloc' phase.
-			rela := syms.Rela
+			rela := ldr.MakeSymbolUpdater(syms.Rela2)
-			rela.AddAddrPlus(target.Arch, s, int64(r.Off))
+			rela.AddAddrPlus(target.Arch, s, int64(r.Off()))
-			if r.Siz == 8 {
+			if r.Siz() == 8 {
 				rela.AddUint64(target.Arch, ld.ELF64_R_INFO(0, uint32(elf.R_AARCH64_RELATIVE)))
 			} else {
-				ld.Errorf(s, "unexpected relocation for dynamic symbol %s", targ.Name)
+				ldr.Errorf(s, "unexpected relocation for dynamic symbol %s", ldr.SymName(targ))
 			}
-			rela.AddAddrPlus(target.Arch, targ, int64(r.Add))
+			rela.AddAddrPlus(target.Arch, targ, int64(r.Add()))
 			// Not mark r done here. So we still apply it statically,
 			// so in the file content we'll also have the right offset
 			// to the relocation target. So it can be examined statically
@@ -308,7 +328,7 @@ func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s *sym.
 func elfreloc1(ctxt *ld.Link, r *sym.Reloc, sectoff int64) bool {
 	ctxt.Out.Write64(uint64(sectoff))
 
-	elfsym := r.Xsym.ElfsymForReloc()
+	elfsym := ld.ElfSymForReloc(ctxt, r.Xsym)
 	switch r.Type {
 	default:
 		return false
@@ -737,75 +757,80 @@ func elfsetupplt(ctxt *ld.Link, plt, gotplt *loader.SymbolBuilder, dynamic loade
 	}
 }
 
-func addpltsym(target *ld.Target, syms *ld.ArchSyms, s *sym.Symbol) {
+func addpltsym2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loader.Sym) {
-	if s.Plt() >= 0 {
+	if ldr.SymPlt(s) >= 0 {
 		return
 	}
 
-	ld.Adddynsym(target, syms, s)
+	ld.Adddynsym2(ldr, target, syms, s)
 
 	if target.IsElf() {
-		plt := syms.PLT
+		plt := ldr.MakeSymbolUpdater(syms.PLT2)
-		gotplt := syms.GOTPLT
+		gotplt := ldr.MakeSymbolUpdater(syms.GOTPLT2)
-		rela := syms.RelaPLT
+		rela := ldr.MakeSymbolUpdater(syms.RelaPLT2)
-		if plt.Size == 0 {
+		if plt.Size() == 0 {
 			panic("plt is not set up")
 		}
 
 		// adrp    x16, &got.plt[0]
-		plt.AddAddrPlus4(gotplt, gotplt.Size)
+		plt.AddAddrPlus4(target.Arch, gotplt.Sym(), gotplt.Size())
-		plt.SetUint32(target.Arch, plt.Size-4, 0x90000010)
+		plt.SetUint32(target.Arch, plt.Size()-4, 0x90000010)
-		plt.R[len(plt.R)-1].Type = objabi.R_ARM64_GOT
+		relocs := plt.Relocs()
+		plt.SetRelocType(relocs.Count()-1, objabi.R_ARM64_GOT)
 
 		// <offset> is the offset value of &got.plt[n] to &got.plt[0]
 		// ldr     x17, [x16, <offset>]
-		plt.AddAddrPlus4(gotplt, gotplt.Size)
+		plt.AddAddrPlus4(target.Arch, gotplt.Sym(), gotplt.Size())
-		plt.SetUint32(target.Arch, plt.Size-4, 0xf9400211)
+		plt.SetUint32(target.Arch, plt.Size()-4, 0xf9400211)
-		plt.R[len(plt.R)-1].Type = objabi.R_ARM64_GOT
+		relocs = plt.Relocs()
+		plt.SetRelocType(relocs.Count()-1, objabi.R_ARM64_GOT)
 
 		// add     x16, x16, <offset>
-		plt.AddAddrPlus4(gotplt, gotplt.Size)
+		plt.AddAddrPlus4(target.Arch, gotplt.Sym(), gotplt.Size())
-		plt.SetUint32(target.Arch, plt.Size-4, 0x91000210)
+		plt.SetUint32(target.Arch, plt.Size()-4, 0x91000210)
-		plt.R[len(plt.R)-1].Type = objabi.R_ARM64_PCREL
+		relocs = plt.Relocs()
+		plt.SetRelocType(relocs.Count()-1, objabi.R_ARM64_PCREL)
 
 		// br      x17
 		plt.AddUint32(target.Arch, 0xd61f0220)
 
 		// add to got.plt: pointer to plt[0]
-		gotplt.AddAddrPlus(target.Arch, plt, 0)
+		gotplt.AddAddrPlus(target.Arch, plt.Sym(), 0)
 
 		// rela
-		rela.AddAddrPlus(target.Arch, gotplt, gotplt.Size-8)
+		rela.AddAddrPlus(target.Arch, gotplt.Sym(), gotplt.Size()-8)
-		rela.AddUint64(target.Arch, ld.ELF64_R_INFO(uint32(s.Dynid), uint32(elf.R_AARCH64_JUMP_SLOT)))
+		sDynid := ldr.SymDynid(s)
+
+		rela.AddUint64(target.Arch, ld.ELF64_R_INFO(uint32(sDynid), uint32(elf.R_AARCH64_JUMP_SLOT)))
 		rela.AddUint64(target.Arch, 0)
 
-		s.SetPlt(int32(plt.Size - 16))
+		ldr.SetPlt(s, int32(plt.Size()-16))
 	} else {
-		ld.Errorf(s, "addpltsym: unsupported binary format")
+		ldr.Errorf(s, "addpltsym: unsupported binary format")
 	}
 }
 
-func addgotsym(target *ld.Target, syms *ld.ArchSyms, s *sym.Symbol) {
+func addgotsym2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loader.Sym) {
-	if s.Got() >= 0 {
+	if ldr.SymGot(s) >= 0 {
 		return
 	}
 
-	ld.Adddynsym(target, syms, s)
+	ld.Adddynsym2(ldr, target, syms, s)
-	got := syms.GOT
+	got := ldr.MakeSymbolUpdater(syms.GOT2)
-	s.SetGot(int32(got.Size))
+	ldr.SetGot(s, int32(got.Size()))
 	got.AddUint64(target.Arch, 0)
 
 	if target.IsElf() {
-		rela := syms.Rela
+		rela := ldr.MakeSymbolUpdater(syms.Rela2)
-		rela.AddAddrPlus(target.Arch, got, int64(s.Got()))
+		rela.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
-		rela.AddUint64(target.Arch, ld.ELF64_R_INFO(uint32(s.Dynid), uint32(elf.R_AARCH64_GLOB_DAT)))
+		rela.AddUint64(target.Arch, ld.ELF64_R_INFO(uint32(ldr.SymDynid(s)), uint32(elf.R_AARCH64_GLOB_DAT)))
 		rela.AddUint64(target.Arch, 0)
 	} else {
-		ld.Errorf(s, "addgotsym: unsupported binary format")
+		ldr.Errorf(s, "addgotsym: unsupported binary format")
 	}
 }
 
-func asmb(ctxt *ld.Link) {
+func asmb(ctxt *ld.Link, _ *loader.Loader) {
 	if ctxt.IsELF {
 		ld.Asmbelfsetup()
 	}

src/cmd/link/internal/arm64/obj.go

@@ -46,7 +46,7 @@ func Init() (*sys.Arch, ld.Arch) {
 		Dwarfregsp: dwarfRegSP,
 		Dwarfreglr: dwarfRegLR,
 
-		Adddynrel:        adddynrel,
+		Adddynrel2:       adddynrel2,
 		Archinit:         archinit,
 		Archreloc:        archreloc,
 		Archrelocvariant: archrelocvariant,

src/cmd/link/internal/ld/data2.go

@@ -0,0 +1,518 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ld
+
+import (
+	"cmd/internal/objabi"
+	"cmd/link/internal/loader"
+	"cmd/link/internal/sym"
+	"fmt"
+	"log"
+	"strings"
+	"sync"
+)
+
+// Temporary dumping around for sym.Symbol version of helper
+// functions in dodata(), still being used for some archs/oses.
+// FIXME: get rid of this file when dodata() is completely
+// converted.
+
+func Addstring(s *sym.Symbol, str string) int64 {
+	if s.Type == 0 {
+		s.Type = sym.SNOPTRDATA
+	}
+	s.Attr |= sym.AttrReachable
+	r := s.Size
+	if s.Name == ".shstrtab" {
+		elfsetstring(s, str, int(r))
+	}
+	s.P = append(s.P, str...)
+	s.P = append(s.P, 0)
+	s.Size = int64(len(s.P))
+	return r
+}
+
+// symalign returns the required alignment for the given symbol s.
+func symalign(s *sym.Symbol) int32 {
+	min := int32(thearch.Minalign)
+	if s.Align >= min {
+		return s.Align
+	} else if s.Align != 0 {
+		return min
+	}
+	if strings.HasPrefix(s.Name, "go.string.") || strings.HasPrefix(s.Name, "type..namedata.") {
+		// String data is just bytes.
+		// If we align it, we waste a lot of space to padding.
+		return min
+	}
+	align := int32(thearch.Maxalign)
+	for int64(align) > s.Size && align > min {
+		align >>= 1
+	}
+	s.Align = align
+	return align
+}
+
+func relocsym2(target *Target, ldr *loader.Loader, err *ErrorReporter, syms *ArchSyms, s *sym.Symbol) {
+	if len(s.R) == 0 {
+		return
+	}
+	for ri := int32(0); ri < int32(len(s.R)); ri++ {
+		r := &s.R[ri]
+		if r.Done {
+			// Relocation already processed by an earlier phase.
+			continue
+		}
+		r.Done = true
+		off := r.Off
+		siz := int32(r.Siz)
+		if off < 0 || off+siz > int32(len(s.P)) {
+			rname := ""
+			if r.Sym != nil {
+				rname = r.Sym.Name
+			}
+			Errorf(s, "invalid relocation %s: %d+%d not in [%d,%d)", rname, off, siz, 0, len(s.P))
+			continue
+		}
+
+		if r.Sym != nil && ((r.Sym.Type == sym.Sxxx && !r.Sym.Attr.VisibilityHidden()) || r.Sym.Type == sym.SXREF) {
+			// When putting the runtime but not main into a shared library
+			// these symbols are undefined and that's OK.
+			if target.IsShared() || target.IsPlugin() {
+				if r.Sym.Name == "main.main" || (!target.IsPlugin() && r.Sym.Name == "main..inittask") {
+					r.Sym.Type = sym.SDYNIMPORT
+				} else if strings.HasPrefix(r.Sym.Name, "go.info.") {
+					// Skip go.info symbols. They are only needed to communicate
+					// DWARF info between the compiler and linker.
+					continue
+				}
+			} else {
+				err.errorUnresolved2(s, r)
+				continue
+			}
+		}
+
+		if r.Type >= objabi.ElfRelocOffset {
+			continue
+		}
+		if r.Siz == 0 { // informational relocation - no work to do
+			continue
+		}
+
+		// We need to be able to reference dynimport symbols when linking against
+		// shared libraries, and Solaris, Darwin and AIX need it always
+		if !target.IsSolaris() && !target.IsDarwin() && !target.IsAIX() && r.Sym != nil && r.Sym.Type == sym.SDYNIMPORT && !target.IsDynlinkingGo() && !r.Sym.Attr.SubSymbol() {
+			if !(target.IsPPC64() && target.IsExternal() && r.Sym.Name == ".TOC.") {
+				Errorf(s, "unhandled relocation for %s (type %d (%s) rtype %d (%s))", r.Sym.Name, r.Sym.Type, r.Sym.Type, r.Type, sym.RelocName(target.Arch, r.Type))
+			}
+		}
+		if r.Sym != nil && r.Sym.Type != sym.STLSBSS && r.Type != objabi.R_WEAKADDROFF && !r.Sym.Attr.Reachable() {
+			Errorf(s, "unreachable sym in relocation: %s", r.Sym.Name)
+		}
+
+		if target.IsExternal() {
+			r.InitExt()
+		}
+
+		// TODO(mundaym): remove this special case - see issue 14218.
+		if target.IsS390X() {
+			switch r.Type {
+			case objabi.R_PCRELDBL:
+				r.InitExt()
+				r.Type = objabi.R_PCREL
+				r.Variant = sym.RV_390_DBL
+			case objabi.R_CALL:
+				r.InitExt()
+				r.Variant = sym.RV_390_DBL
+			}
+		}
+
+		var o int64
+		switch r.Type {
+		default:
+			switch siz {
+			default:
+				Errorf(s, "bad reloc size %#x for %s", uint32(siz), r.Sym.Name)
+			case 1:
+				o = int64(s.P[off])
+			case 2:
+				o = int64(target.Arch.ByteOrder.Uint16(s.P[off:]))
+			case 4:
+				o = int64(target.Arch.ByteOrder.Uint32(s.P[off:]))
+			case 8:
+				o = int64(target.Arch.ByteOrder.Uint64(s.P[off:]))
+			}
+			if offset, ok := thearch.Archreloc(target, syms, r, s, o); ok {
+				o = offset
+			} else {
+				Errorf(s, "unknown reloc to %v: %d (%s)", r.Sym.Name, r.Type, sym.RelocName(target.Arch, r.Type))
+			}
+		case objabi.R_TLS_LE:
+			if target.IsExternal() && target.IsElf() {
+				r.Done = false
+				if r.Sym == nil {
+					r.Sym = syms.Tlsg
+				}
+				r.Xsym = r.Sym
+				r.Xadd = r.Add
+				o = 0
+				if !target.IsAMD64() {
+					o = r.Add
+				}
+				break
+			}
+
+			if target.IsElf() && target.IsARM() {
+				// On ELF ARM, the thread pointer is 8 bytes before
+				// the start of the thread-local data block, so add 8
+				// to the actual TLS offset (r->sym->value).
+				// This 8 seems to be a fundamental constant of
+				// ELF on ARM (or maybe Glibc on ARM); it is not
+				// related to the fact that our own TLS storage happens
+				// to take up 8 bytes.
+				o = 8 + r.Sym.Value
+			} else if target.IsElf() || target.IsPlan9() || target.IsDarwin() {
+				o = int64(syms.Tlsoffset) + r.Add
+			} else if target.IsWindows() {
+				o = r.Add
+			} else {
+				log.Fatalf("unexpected R_TLS_LE relocation for %v", target.HeadType)
+			}
+		case objabi.R_TLS_IE:
+			if target.IsExternal() && target.IsElf() {
+				r.Done = false
+				if r.Sym == nil {
+					r.Sym = syms.Tlsg
+				}
+				r.Xsym = r.Sym
+				r.Xadd = r.Add
+				o = 0
+				if !target.IsAMD64() {
+					o = r.Add
+				}
+				break
+			}
+			if target.IsPIE() && target.IsElf() {
+				// We are linking the final executable, so we
+				// can optimize any TLS IE relocation to LE.
+				if thearch.TLSIEtoLE == nil {
+					log.Fatalf("internal linking of TLS IE not supported on %v", target.Arch.Family)
+				}
+				thearch.TLSIEtoLE(s.P, int(off), int(r.Siz))
+				o = int64(syms.Tlsoffset)
+				// TODO: o += r.Add when !target.IsAmd64()?
+				// Why do we treat r.Add differently on AMD64?
+				// Is the external linker using Xadd at all?
+			} else {
+				log.Fatalf("cannot handle R_TLS_IE (sym %s) when linking internally", s.Name)
+			}
+		case objabi.R_ADDR:
+			if target.IsExternal() && r.Sym.Type != sym.SCONST {
+				r.Done = false
+
+				// set up addend for eventual relocation via outer symbol.
+				rs := r.Sym
+
+				r.Xadd = r.Add
+				for rs.Outer != nil {
+					r.Xadd += Symaddr(rs) - Symaddr(rs.Outer)
+					rs = rs.Outer
+				}
+
+				if rs.Type != sym.SHOSTOBJ && rs.Type != sym.SDYNIMPORT && rs.Type != sym.SUNDEFEXT && rs.Sect == nil {
+					Errorf(s, "missing section for relocation target %s", rs.Name)
+				}
+				r.Xsym = rs
+
+				o = r.Xadd
+				if target.IsElf() {
+					if target.IsAMD64() {
+						o = 0
+					}
+				} else if target.IsDarwin() {
+					if rs.Type != sym.SHOSTOBJ {
+						o += Symaddr(rs)
+					}
+				} else if target.IsWindows() {
+					// nothing to do
+				} else if target.IsAIX() {
+					o = Symaddr(r.Sym) + r.Add
+				} else {
+					Errorf(s, "unhandled pcrel relocation to %s on %v", rs.Name, target.HeadType)
+				}
+
+				break
+			}
+
+			// On AIX, a second relocation must be done by the loader,
+			// as section addresses can change once loaded.
+			// The "default" symbol address is still needed by the loader so
+			// the current relocation can't be skipped.
+			if target.IsAIX() && r.Sym.Type != sym.SDYNIMPORT {
+				// It's not possible to make a loader relocation in a
+				// symbol which is not inside .data section.
+				// FIXME: It should be forbidden to have R_ADDR from a
+				// symbol which isn't in .data. However, as .text has the
+				// same address once loaded, this is possible.
+				if s.Sect.Seg == &Segdata {
+					Xcoffadddynrel(target, ldr, s, r)
+				}
+			}
+
+			o = Symaddr(r.Sym) + r.Add
+
+			// On amd64, 4-byte offsets will be sign-extended, so it is impossible to
+			// access more than 2GB of static data; fail at link time is better than
+			// fail at runtime. See https://golang.org/issue/7980.
+			// Instead of special casing only amd64, we treat this as an error on all
+			// 64-bit architectures so as to be future-proof.
+			if int32(o) < 0 && target.Arch.PtrSize > 4 && siz == 4 {
+				Errorf(s, "non-pc-relative relocation address for %s is too big: %#x (%#x + %#x)", r.Sym.Name, uint64(o), Symaddr(r.Sym), r.Add)
+				errorexit()
+			}
+		case objabi.R_DWARFSECREF:
+			if r.Sym.Sect == nil {
+				Errorf(s, "missing DWARF section for relocation target %s", r.Sym.Name)
+			}
+
+			if target.IsExternal() {
+				r.Done = false
+
+				// On most platforms, the external linker needs to adjust DWARF references
+				// as it combines DWARF sections. However, on Darwin, dsymutil does the
+				// DWARF linking, and it understands how to follow section offsets.
+				// Leaving in the relocation records confuses it (see
+				// https://golang.org/issue/22068) so drop them for Darwin.
+				if target.IsDarwin() {
+					r.Done = true
+				}
+
+				// PE code emits IMAGE_REL_I386_SECREL and IMAGE_REL_AMD64_SECREL
+				// for R_DWARFSECREF relocations, while R_ADDR is replaced with
+				// IMAGE_REL_I386_DIR32, IMAGE_REL_AMD64_ADDR64 and IMAGE_REL_AMD64_ADDR32.
+				// Do not replace R_DWARFSECREF with R_ADDR for windows -
+				// let PE code emit correct relocations.
+				if !target.IsWindows() {
+					r.Type = objabi.R_ADDR
+				}
+
+				r.Xsym = r.Sym.Sect.Sym
+				r.Xadd = r.Add + Symaddr(r.Sym) - int64(r.Sym.Sect.Vaddr)
+
+				o = r.Xadd
+				if target.IsElf() && target.IsAMD64() {
+					o = 0
+				}
+				break
+			}
+			o = Symaddr(r.Sym) + r.Add - int64(r.Sym.Sect.Vaddr)
+		case objabi.R_WEAKADDROFF:
+			if !r.Sym.Attr.Reachable() {
+				continue
+			}
+			fallthrough
+		case objabi.R_ADDROFF:
+			// The method offset tables using this relocation expect the offset to be relative
+			// to the start of the first text section, even if there are multiple.
+			if r.Sym.Sect.Name == ".text" {
+				o = Symaddr(r.Sym) - int64(Segtext.Sections[0].Vaddr) + r.Add
+			} else {
+				o = Symaddr(r.Sym) - int64(r.Sym.Sect.Vaddr) + r.Add
+			}
+
+		case objabi.R_ADDRCUOFF:
+			// debug_range and debug_loc elements use this relocation type to get an
+			// offset from the start of the compile unit.
+			u := ldr.SymUnit(loader.Sym(r.Sym.SymIdx))
+			o = Symaddr(r.Sym) + r.Add - Symaddr(ldr.Syms[u.Textp2[0]])
+
+			// r->sym can be null when CALL $(constant) is transformed from absolute PC to relative PC call.
+		case objabi.R_GOTPCREL:
+			if target.IsDynlinkingGo() && target.IsDarwin() && r.Sym != nil && r.Sym.Type != sym.SCONST {
+				r.Done = false
+				r.Xadd = r.Add
+				r.Xadd -= int64(r.Siz) // relative to address after the relocated chunk
+				r.Xsym = r.Sym
+
+				o = r.Xadd
+				o += int64(r.Siz)
+				break
+			}
+			fallthrough
+		case objabi.R_CALL, objabi.R_PCREL:
+			if target.IsExternal() && r.Sym != nil && r.Sym.Type == sym.SUNDEFEXT {
+				// pass through to the external linker.
+				r.Done = false
+				r.Xadd = 0
+				if target.IsElf() {
+					r.Xadd -= int64(r.Siz)
+				}
+				r.Xsym = r.Sym
+				o = 0
+				break
+			}
+			if target.IsExternal() && r.Sym != nil && r.Sym.Type != sym.SCONST && (r.Sym.Sect != s.Sect || r.Type == objabi.R_GOTPCREL) {
+				r.Done = false
+
+				// set up addend for eventual relocation via outer symbol.
+				rs := r.Sym
+
+				r.Xadd = r.Add
+				for rs.Outer != nil {
+					r.Xadd += Symaddr(rs) - Symaddr(rs.Outer)
+					rs = rs.Outer
+				}
+
+				r.Xadd -= int64(r.Siz) // relative to address after the relocated chunk
+				if rs.Type != sym.SHOSTOBJ && rs.Type != sym.SDYNIMPORT && rs.Sect == nil {
+					Errorf(s, "missing section for relocation target %s", rs.Name)
+				}
+				r.Xsym = rs
+
+				o = r.Xadd
+				if target.IsElf() {
+					if target.IsAMD64() {
+						o = 0
+					}
+				} else if target.IsDarwin() {
+					if r.Type == objabi.R_CALL {
+						if target.IsExternal() && rs.Type == sym.SDYNIMPORT {
+							if target.IsAMD64() {
+								// AMD64 dynamic relocations are relative to the end of the relocation.
+								o += int64(r.Siz)
+							}
+						} else {
+							if rs.Type != sym.SHOSTOBJ {
+								o += int64(uint64(Symaddr(rs)) - rs.Sect.Vaddr)
+							}
+							o -= int64(r.Off) // relative to section offset, not symbol
+						}
+					} else {
+						o += int64(r.Siz)
+					}
+				} else if target.IsWindows() && target.IsAMD64() { // only amd64 needs PCREL
+					// PE/COFF's PC32 relocation uses the address after the relocated
+					// bytes as the base. Compensate by skewing the addend.
+					o += int64(r.Siz)
+				} else {
+					Errorf(s, "unhandled pcrel relocation to %s on %v", rs.Name, target.HeadType)
+				}
+
+				break
+			}
+
+			o = 0
+			if r.Sym != nil {
+				o += Symaddr(r.Sym)
+			}
+
+			o += r.Add - (s.Value + int64(r.Off) + int64(r.Siz))
+		case objabi.R_SIZE:
+			o = r.Sym.Size + r.Add
+
+		case objabi.R_XCOFFREF:
+			if !target.IsAIX() {
+				Errorf(s, "find XCOFF R_REF on non-XCOFF files")
+			}
+			if !target.IsExternal() {
+				Errorf(s, "find XCOFF R_REF with internal linking")
+			}
+			r.Xsym = r.Sym
+			r.Xadd = r.Add
+			r.Done = false
+
+			// This isn't a real relocation so it must not update
+			// its offset value.
+			continue
+
+		case objabi.R_DWARFFILEREF:
+			// The final file index is saved in r.Add in dwarf.go:writelines.
+			o = r.Add
+		}
+
+		if target.IsPPC64() || target.IsS390X() {
+			r.InitExt()
+			if r.Variant != sym.RV_NONE {
+				o = thearch.Archrelocvariant(target, syms, r, s, o)
+			}
+		}
+
+		if false {
+			nam := "<nil>"
+			var addr int64
+			if r.Sym != nil {
+				nam = r.Sym.Name
+				addr = Symaddr(r.Sym)
+			}
+			xnam := "<nil>"
+			if r.Xsym != nil {
+				xnam = r.Xsym.Name
+			}
+			fmt.Printf("relocate %s %#x (%#x+%#x, size %d) => %s %#x +%#x (xsym: %s +%#x) [type %d (%s)/%d, %x]\n", s.Name, s.Value+int64(off), s.Value, r.Off, r.Siz, nam, addr, r.Add, xnam, r.Xadd, r.Type, sym.RelocName(target.Arch, r.Type), r.Variant, o)
+		}
+		switch siz {
+		default:
+			Errorf(s, "bad reloc size %#x for %s", uint32(siz), r.Sym.Name)
+			fallthrough
+
+			// TODO(rsc): Remove.
+		case 1:
+			s.P[off] = byte(int8(o))
+		case 2:
+			if o != int64(int16(o)) {
+				Errorf(s, "relocation address for %s is too big: %#x", r.Sym.Name, o)
+			}
+			i16 := int16(o)
+			target.Arch.ByteOrder.PutUint16(s.P[off:], uint16(i16))
+		case 4:
+			if r.Type == objabi.R_PCREL || r.Type == objabi.R_CALL {
+				if o != int64(int32(o)) {
+					Errorf(s, "pc-relative relocation address for %s is too big: %#x", r.Sym.Name, o)
+				}
+			} else {
+				if o != int64(int32(o)) && o != int64(uint32(o)) {
+					Errorf(s, "non-pc-relative relocation address for %s is too big: %#x", r.Sym.Name, uint64(o))
+				}
+			}
+
+			fl := int32(o)
+			target.Arch.ByteOrder.PutUint32(s.P[off:], uint32(fl))
+		case 8:
+			target.Arch.ByteOrder.PutUint64(s.P[off:], uint64(o))
+		}
+	}
+}
+
+func (ctxt *Link) reloc2() {
+	var wg sync.WaitGroup
+	target := &ctxt.Target
+	ldr := ctxt.loader
+	reporter := &ctxt.ErrorReporter
+	syms := &ctxt.ArchSyms
+	wg.Add(3)
+	go func() {
+		if !ctxt.IsWasm() { // On Wasm, text relocations are applied in Asmb2.
+			for _, s := range ctxt.Textp {
+				relocsym2(target, ldr, reporter, syms, s)
+			}
+		}
+		wg.Done()
+	}()
+	go func() {
+		for _, s := range ctxt.datap {
+			relocsym2(target, ldr, reporter, syms, s)
+		}
+		wg.Done()
+	}()
+	go func() {
+		for _, si := range dwarfp {
+			for _, s := range si.syms {
+				relocsym2(target, ldr, reporter, syms, s)
+			}
+		}
+		wg.Done()
+	}()
+	wg.Wait()
+}

src/cmd/link/internal/ld/decodesym.go

@@ -5,12 +5,9 @@
 package ld
 
 import (
-	"bytes"
 	"cmd/internal/objabi"
 	"cmd/internal/sys"
-	"cmd/link/internal/sym"
 	"debug/elf"
-	"fmt"
 )
 
 // Decoding the type.* symbols.	 This has to be in sync with
@@ -29,23 +26,6 @@ const (
 	tflagExtraStar = 1 << 1
 )
 
-func decodeReloc(s *sym.Symbol, off int32) *sym.Reloc {
-	for i := range s.R {
-		if s.R[i].Off == off {
-			return &s.R[i]
-		}
-	}
-	return nil
-}
-
-func decodeRelocSym(s *sym.Symbol, off int32) *sym.Symbol {
-	r := decodeReloc(s, off)
-	if r == nil {
-		return nil
-	}
-	return r.Sym
-}
-
 func decodeInuxi(arch *sys.Arch, p []byte, sz int) uint64 {
 	switch sz {
 	case 2:
@@ -103,26 +83,6 @@ func findShlibSection(ctxt *Link, path string, addr uint64) *elf.Section {
 	return nil
 }
 
-// Type.commonType.gc
-func decodetypeGcprog(ctxt *Link, s *sym.Symbol) []byte {
-	if s.Type == sym.SDYNIMPORT {
-		addr := decodetypeGcprogShlib(ctxt, s.P)
-		sect := findShlibSection(ctxt, s.File, addr)
-		if sect != nil {
-			// A gcprog is a 4-byte uint32 indicating length, followed by
-			// the actual program.
-			progsize := make([]byte, 4)
-			sect.ReadAt(progsize, int64(addr-sect.Addr))
-			progbytes := make([]byte, ctxt.Arch.ByteOrder.Uint32(progsize))
-			sect.ReadAt(progbytes, int64(addr-sect.Addr+4))
-			return append(progsize, progbytes...)
-		}
-		Exitf("cannot find gcprog for %s", s.Name)
-		return nil
-	}
-	return decodeRelocSym(s, 2*int32(ctxt.Arch.PtrSize)+8+1*int32(ctxt.Arch.PtrSize)).P
-}
-
 func decodetypeGcprogShlib(ctxt *Link, data []byte) uint64 {
 	if ctxt.Arch.Family == sys.ARM64 {
 		return 0
@@ -130,51 +90,6 @@ func decodetypeGcprogShlib(ctxt *Link, data []byte) uint64 {
 	return decodeInuxi(ctxt.Arch, data[2*int32(ctxt.Arch.PtrSize)+8+1*int32(ctxt.Arch.PtrSize):], ctxt.Arch.PtrSize)
 }
 
-func decodetypeGcmask(ctxt *Link, s *sym.Symbol) []byte {
-	if s.Type == sym.SDYNIMPORT {
-		addr := decodetypeGcprogShlib(ctxt, s.P)
-		ptrdata := decodetypePtrdata(ctxt.Arch, s.P)
-		sect := findShlibSection(ctxt, s.File, addr)
-		if sect != nil {
-			r := make([]byte, ptrdata/int64(ctxt.Arch.PtrSize))
-			sect.ReadAt(r, int64(addr-sect.Addr))
-			return r
-		}
-		Exitf("cannot find gcmask for %s", s.Name)
-		return nil
-	}
-	mask := decodeRelocSym(s, 2*int32(ctxt.Arch.PtrSize)+8+1*int32(ctxt.Arch.PtrSize))
-	return mask.P
-}
-
-// Type.ArrayType.elem and Type.SliceType.Elem
-func decodetypeArrayElem(arch *sys.Arch, s *sym.Symbol) *sym.Symbol {
-	return decodeRelocSym(s, int32(commonsize(arch))) // 0x1c / 0x30
-}
-
-func decodetypeArrayLen(arch *sys.Arch, s *sym.Symbol) int64 {
-	return int64(decodeInuxi(arch, s.P[commonsize(arch)+2*arch.PtrSize:], arch.PtrSize))
-}
-
-// Type.PtrType.elem
-func decodetypePtrElem(arch *sys.Arch, s *sym.Symbol) *sym.Symbol {
-	return decodeRelocSym(s, int32(commonsize(arch))) // 0x1c / 0x30
-}
-
-// Type.MapType.key, elem
-func decodetypeMapKey(arch *sys.Arch, s *sym.Symbol) *sym.Symbol {
-	return decodeRelocSym(s, int32(commonsize(arch))) // 0x1c / 0x30
-}
-
-func decodetypeMapValue(arch *sys.Arch, s *sym.Symbol) *sym.Symbol {
-	return decodeRelocSym(s, int32(commonsize(arch))+int32(arch.PtrSize)) // 0x20 / 0x38
-}
-
-// Type.ChanType.elem
-func decodetypeChanElem(arch *sys.Arch, s *sym.Symbol) *sym.Symbol {
-	return decodeRelocSym(s, int32(commonsize(arch))) // 0x1c / 0x30
-}
-
 // Type.FuncType.dotdotdot
 func decodetypeFuncDotdotdot(arch *sys.Arch, p []byte) bool {
 	return uint16(decodeInuxi(arch, p[commonsize(arch)+2:], 2))&(1<<15) != 0
@@ -189,75 +104,6 @@ func decodetypeFuncOutCount(arch *sys.Arch, p []byte) int {
 	return int(uint16(decodeInuxi(arch, p[commonsize(arch)+2:], 2)) & (1<<15 - 1))
 }
 
-func decodetypeFuncInType(arch *sys.Arch, s *sym.Symbol, i int) *sym.Symbol {
-	uadd := commonsize(arch) + 4
-	if arch.PtrSize == 8 {
-		uadd += 4
-	}
-	if decodetypeHasUncommon(arch, s.P) {
-		uadd += uncommonSize()
-	}
-	return decodeRelocSym(s, int32(uadd+i*arch.PtrSize))
-}
-
-func decodetypeFuncOutType(arch *sys.Arch, s *sym.Symbol, i int) *sym.Symbol {
-	return decodetypeFuncInType(arch, s, i+decodetypeFuncInCount(arch, s.P))
-}
-
-// Type.StructType.fields.Slice::length
-func decodetypeStructFieldCount(arch *sys.Arch, s *sym.Symbol) int {
-	return int(decodeInuxi(arch, s.P[commonsize(arch)+2*arch.PtrSize:], arch.PtrSize))
-}
-
-func decodetypeStructFieldArrayOff(arch *sys.Arch, s *sym.Symbol, i int) int {
-	off := commonsize(arch) + 4*arch.PtrSize
-	if decodetypeHasUncommon(arch, s.P) {
-		off += uncommonSize()
-	}
-	off += i * structfieldSize(arch)
-	return off
-}
-
-// decodetypeStr returns the contents of an rtype's str field (a nameOff).
-func decodetypeStr(arch *sys.Arch, s *sym.Symbol) string {
-	str := decodetypeName(s, 4*arch.PtrSize+8)
-	if s.P[2*arch.PtrSize+4]&tflagExtraStar != 0 {
-		return str[1:]
-	}
-	return str
-}
-
-// decodetypeName decodes the name from a reflect.name.
-func decodetypeName(s *sym.Symbol, off int) string {
-	r := decodeReloc(s, int32(off))
-	if r == nil {
-		return ""
-	}
-
-	data := r.Sym.P
-	namelen := int(uint16(data[1])<<8 | uint16(data[2]))
-	return string(data[3 : 3+namelen])
-}
-
-func decodetypeStructFieldName(arch *sys.Arch, s *sym.Symbol, i int) string {
-	off := decodetypeStructFieldArrayOff(arch, s, i)
-	return decodetypeName(s, off)
-}
-
-func decodetypeStructFieldType(arch *sys.Arch, s *sym.Symbol, i int) *sym.Symbol {
-	off := decodetypeStructFieldArrayOff(arch, s, i)
-	return decodeRelocSym(s, int32(off+arch.PtrSize))
-}
-
-func decodetypeStructFieldOffs(arch *sys.Arch, s *sym.Symbol, i int) int64 {
-	return decodetypeStructFieldOffsAnon(arch, s, i) >> 1
-}
-
-func decodetypeStructFieldOffsAnon(arch *sys.Arch, s *sym.Symbol, i int) int64 {
-	off := decodetypeStructFieldArrayOff(arch, s, i)
-	return int64(decodeInuxi(arch, s.P[off+2*arch.PtrSize:], arch.PtrSize))
-}
-
 // InterfaceType.methods.length
 func decodetypeIfaceMethodCount(arch *sys.Arch, p []byte) int64 {
 	return int64(decodeInuxi(arch, p[commonsize(arch)+2*arch.PtrSize:], arch.PtrSize))
@@ -279,91 +125,3 @@ const (
 	kindStruct    = 25
 	kindMask      = (1 << 5) - 1
 )
-
-// decodeMethodSig decodes an array of method signature information.
-// Each element of the array is size bytes. The first 4 bytes is a
-// nameOff for the method name, and the next 4 bytes is a typeOff for
-// the function type.
-//
-// Conveniently this is the layout of both runtime.method and runtime.imethod.
-func decodeMethodSig(arch *sys.Arch, s *sym.Symbol, off, size, count int) []methodsig {
-	var buf bytes.Buffer
-	var methods []methodsig
-	for i := 0; i < count; i++ {
-		buf.WriteString(decodetypeName(s, off))
-		mtypSym := decodeRelocSym(s, int32(off+4))
-
-		buf.WriteRune('(')
-		inCount := decodetypeFuncInCount(arch, mtypSym.P)
-		for i := 0; i < inCount; i++ {
-			if i > 0 {
-				buf.WriteString(", ")
-			}
-			buf.WriteString(decodetypeFuncInType(arch, mtypSym, i).Name)
-		}
-		buf.WriteString(") (")
-		outCount := decodetypeFuncOutCount(arch, mtypSym.P)
-		for i := 0; i < outCount; i++ {
-			if i > 0 {
-				buf.WriteString(", ")
-			}
-			buf.WriteString(decodetypeFuncOutType(arch, mtypSym, i).Name)
-		}
-		buf.WriteRune(')')
-
-		off += size
-		methods = append(methods, methodsig(buf.String()))
-		buf.Reset()
-	}
-	return methods
-}
-
-func decodeIfaceMethods(arch *sys.Arch, s *sym.Symbol) []methodsig {
-	if decodetypeKind(arch, s.P)&kindMask != kindInterface {
-		panic(fmt.Sprintf("symbol %q is not an interface", s.Name))
-	}
-	r := decodeReloc(s, int32(commonsize(arch)+arch.PtrSize))
-	if r == nil {
-		return nil
-	}
-	if r.Sym != s {
-		panic(fmt.Sprintf("imethod slice pointer in %q leads to a different symbol", s.Name))
-	}
-	off := int(r.Add) // array of reflect.imethod values
-	numMethods := int(decodetypeIfaceMethodCount(arch, s.P))
-	sizeofIMethod := 4 + 4
-	return decodeMethodSig(arch, s, off, sizeofIMethod, numMethods)
-}
-
-func decodetypeMethods(arch *sys.Arch, s *sym.Symbol) []methodsig {
-	if !decodetypeHasUncommon(arch, s.P) {
-		panic(fmt.Sprintf("no methods on %q", s.Name))
-	}
-	off := commonsize(arch) // reflect.rtype
-	switch decodetypeKind(arch, s.P) & kindMask {
-	case kindStruct: // reflect.structType
-		off += 4 * arch.PtrSize
-	case kindPtr: // reflect.ptrType
-		off += arch.PtrSize
-	case kindFunc: // reflect.funcType
-		off += arch.PtrSize // 4 bytes, pointer aligned
-	case kindSlice: // reflect.sliceType
-		off += arch.PtrSize
-	case kindArray: // reflect.arrayType
-		off += 3 * arch.PtrSize
-	case kindChan: // reflect.chanType
-		off += 2 * arch.PtrSize
-	case kindMap: // reflect.mapType
-		off += 4*arch.PtrSize + 8
-	case kindInterface: // reflect.interfaceType
-		off += 3 * arch.PtrSize
-	default:
-		// just Sizeof(rtype)
-	}
-
-	mcount := int(decodeInuxi(arch, s.P[off+4:], 2))
-	moff := int(decodeInuxi(arch, s.P[off+4+2+2:], 4))
-	off += moff                // offset to array of reflect.method values
-	const sizeofMethod = 4 * 4 // sizeof reflect.method in program
-	return decodeMethodSig(arch, s, off, sizeofMethod, mcount)
-}

src/cmd/link/internal/ld/dwarf2.go

@@ -101,20 +101,20 @@ func dwarfcompress(ctxt *Link) {
 	type compressedSect struct {
 		index      int
 		compressed []byte
-		syms       []*sym.Symbol
+		syms       []loader.Sym
 	}
 
-	supported := ctxt.IsELF || ctxt.HeadType == objabi.Hwindows || ctxt.HeadType == objabi.Hdarwin
+	supported := ctxt.IsELF || ctxt.IsWindows() || ctxt.IsDarwin()
-	if !ctxt.compressDWARF || !supported || ctxt.LinkMode != LinkInternal {
+	if !ctxt.compressDWARF || !supported || ctxt.IsExternal() {
 		return
 	}
 
 	var compressedCount int
 	resChannel := make(chan compressedSect)
-	for i := range dwarfp {
+	for i := range dwarfp2 {
-		go func(resIndex int, syms []*sym.Symbol) {
+		go func(resIndex int, syms []loader.Sym) {
 			resChannel <- compressedSect{resIndex, compressSyms(ctxt, syms), syms}
-		}(compressedCount, dwarfp[i].syms)
+		}(compressedCount, dwarfp2[i].syms)
 		compressedCount++
 	}
 	res := make([]compressedSect, compressedCount)
@@ -123,46 +123,55 @@ func dwarfcompress(ctxt *Link) {
 		res[r.index] = r
 	}
 
-	var newDwarfp []dwarfSecInfo2
+	ldr := ctxt.loader
+	var newDwarfp []dwarfSecInfo
 	Segdwarf.Sections = Segdwarf.Sections[:0]
 	for _, z := range res {
 		s := z.syms[0]
 		if z.compressed == nil {
 			// Compression didn't help.
-			ds := dwarfSecInfo2{syms: z.syms}
+			ds := dwarfSecInfo{syms: z.syms}
 			newDwarfp = append(newDwarfp, ds)
-			Segdwarf.Sections = append(Segdwarf.Sections, s.Sect)
+			Segdwarf.Sections = append(Segdwarf.Sections, ldr.SymSect(s))
 		} else {
-			compressedSegName := ".zdebug_" + s.Sect.Name[len(".debug_"):]
+			compressedSegName := ".zdebug_" + ldr.SymSect(s).Name[len(".debug_"):]
 			sect := addsection(ctxt.loader, ctxt.Arch, &Segdwarf, compressedSegName, 04)
+			sect.Align = 1
 			sect.Length = uint64(len(z.compressed))
-			newSym := ctxt.Syms.Lookup(compressedSegName, 0)
+			newSym := ldr.CreateSymForUpdate(compressedSegName, 0)
-			newSym.P = z.compressed
+			newSym.SetReachable(true)
-			newSym.Size = int64(len(z.compressed))
+			newSym.SetData(z.compressed)
-			newSym.Sect = sect
+			newSym.SetSize(int64(len(z.compressed)))
-			ds := dwarfSecInfo2{syms: []*sym.Symbol{newSym}}
+			ldr.SetSymSect(newSym.Sym(), sect)
+			ds := dwarfSecInfo{syms: []loader.Sym{newSym.Sym()}}
 			newDwarfp = append(newDwarfp, ds)
+
+			// compressed symbols are no longer needed.
+			for _, s := range z.syms {
+				ldr.SetAttrReachable(s, false)
 			}
 		}
-	dwarfp = newDwarfp
+	}
+	dwarfp2 = newDwarfp
 
 	// Re-compute the locations of the compressed DWARF symbols
 	// and sections, since the layout of these within the file is
 	// based on Section.Vaddr and Symbol.Value.
 	pos := Segdwarf.Vaddr
 	var prevSect *sym.Section
-	for _, si := range dwarfp {
+	for _, si := range dwarfp2 {
 		for _, s := range si.syms {
-			s.Value = int64(pos)
+			ldr.SetSymValue(s, int64(pos))
-			if s.Sect != prevSect {
+			sect := ldr.SymSect(s)
-				s.Sect.Vaddr = uint64(s.Value)
+			if sect != prevSect {
-				prevSect = s.Sect
+				sect.Vaddr = uint64(pos)
+				prevSect = sect
 			}
-			if s.Sub != nil {
+			if ldr.SubSym(s) != 0 {
-				log.Fatalf("%s: unexpected sub-symbols", s)
+				log.Fatalf("%s: unexpected sub-symbols", ldr.SymName(s))
 			}
-			pos += uint64(s.Size)
+			pos += uint64(ldr.SymSize(s))
-			if ctxt.HeadType == objabi.Hwindows {
+			if ctxt.IsWindows() {
 				pos = uint64(Rnd(int64(pos), PEFILEALIGN))
 			}
 		}

src/cmd/link/internal/ld/elf.go

@@ -628,9 +628,9 @@ func elfwriteshdrs(out *OutBuf) uint32 {
 	return uint32(ehdr.shnum) * ELF32SHDRSIZE
 }
 
-func elfsetstring(s *sym.Symbol, str string, off int) {
+func elfsetstring2(ctxt *Link, s loader.Sym, str string, off int) {
 	if nelfstr >= len(elfstr) {
-		Errorf(s, "too many elf strings")
+		ctxt.Errorf(s, "too many elf strings")
 		errorexit()
 	}
 
@@ -753,8 +753,8 @@ func elfWriteDynEnt(arch *sys.Arch, s *sym.Symbol, tag int, val uint64) {
 	}
 }
 
-func elfWriteDynEntSym(arch *sys.Arch, s *sym.Symbol, tag int, t *sym.Symbol) {
+func elfWriteDynEntSym2(ctxt *Link, s *loader.SymbolBuilder, tag int, t loader.Sym) {
-	Elfwritedynentsymplus(arch, s, tag, t, 0)
+	Elfwritedynentsymplus2(ctxt, s, tag, t, 0)
 }
 
 func Elfwritedynentsymplus(arch *sys.Arch, s *sym.Symbol, tag int, t *sym.Symbol, add int64) {
@@ -1057,15 +1057,16 @@ havelib:
 	return aux
 }
 
-func elfdynhash(ctxt *Link) {
+func elfdynhash2(ctxt *Link) {
 	if !ctxt.IsELF {
 		return
 	}
 
 	nsym := Nelfsym
-	s := ctxt.Syms.Lookup(".hash", 0)
+	ldr := ctxt.loader
-	s.Type = sym.SELFROSECT
+	s := ldr.CreateSymForUpdate(".hash", 0)
-	s.Attr |= sym.AttrReachable
+	s.SetType(sym.SELFROSECT)
+	s.SetReachable(true)
 
 	i := nsym
 	nbucket := 1
@@ -1079,21 +1080,19 @@ func elfdynhash(ctxt *Link) {
 	chain := make([]uint32, nsym)
 	buckets := make([]uint32, nbucket)
 
-	for _, sy := range ctxt.Syms.Allsym {
+	for _, sy := range ldr.DynidSyms() {
-		if sy.Dynid <= 0 {
+
-			continue
+		dynid := ldr.SymDynid(sy)
+		if ldr.SymDynimpvers(sy) != "" {
+			need[dynid] = addelflib(&needlib, ldr.SymDynimplib(sy), ldr.SymDynimpvers(sy))
 		}
 
-		if sy.Dynimpvers() != "" {
+		name := ldr.SymExtname(sy)
-			need[sy.Dynid] = addelflib(&needlib, sy.Dynimplib(), sy.Dynimpvers())
-		}
-
-		name := sy.Extname()
 		hc := elfhash(name)
 
 		b := hc % uint32(nbucket)
-		chain[sy.Dynid] = buckets[b]
+		chain[dynid] = buckets[b]
-		buckets[b] = uint32(sy.Dynid)
+		buckets[b] = uint32(dynid)
 	}
 
 	// s390x (ELF64) hash table entries are 8 bytes
@@ -1117,10 +1116,11 @@ func elfdynhash(ctxt *Link) {
 		}
 	}
 
-	// version symbols
+	dynstr := ldr.CreateSymForUpdate(".dynstr", 0)
-	dynstr := ctxt.Syms.Lookup(".dynstr", 0)
 
-	s = ctxt.Syms.Lookup(".gnu.version_r", 0)
+	// version symbols
+	gnuVersionR := ldr.CreateSymForUpdate(".gnu.version_r", 0)
+	s = gnuVersionR
 	i = 2
 	nfile := 0
 	for l := needlib; l != nil; l = l.next {
@@ -1133,7 +1133,7 @@ func elfdynhash(ctxt *Link) {
 			j++
 		}
 		s.AddUint16(ctxt.Arch, uint16(j))                        // aux count
-		s.AddUint32(ctxt.Arch, uint32(Addstring(dynstr, l.file))) // file string offset
+		s.AddUint32(ctxt.Arch, uint32(dynstr.Addstring(l.file))) // file string offset
 		s.AddUint32(ctxt.Arch, 16)                               // offset from header to first aux
 		if l.next != nil {
 			s.AddUint32(ctxt.Arch, 16+uint32(j)*16) // offset from this header to next
@@ -1149,7 +1149,7 @@ func elfdynhash(ctxt *Link) {
 			s.AddUint32(ctxt.Arch, elfhash(x.vers))                  // hash
 			s.AddUint16(ctxt.Arch, 0)                                // flags
 			s.AddUint16(ctxt.Arch, uint16(x.num))                    // other - index we refer to this by
-			s.AddUint32(ctxt.Arch, uint32(Addstring(dynstr, x.vers))) // version string offset
+			s.AddUint32(ctxt.Arch, uint32(dynstr.Addstring(x.vers))) // version string offset
 			if x.next != nil {
 				s.AddUint32(ctxt.Arch, 16) // offset from this aux to next
 			} else {
@@ -1159,7 +1159,8 @@ func elfdynhash(ctxt *Link) {
 	}
 
 	// version references
-	s = ctxt.Syms.Lookup(".gnu.version", 0)
+	gnuVersion := ldr.CreateSymForUpdate(".gnu.version", 0)
+	s = gnuVersion
 
 	for i := 0; i < nsym; i++ {
 		if i == 0 {
@@ -1171,26 +1172,26 @@ func elfdynhash(ctxt *Link) {
 		}
 	}
 
-	s = ctxt.Syms.Lookup(".dynamic", 0)
+	s = ldr.CreateSymForUpdate(".dynamic", 0)
 	elfverneed = nfile
 	if elfverneed != 0 {
-		elfWriteDynEntSym(ctxt.Arch, s, DT_VERNEED, ctxt.Syms.Lookup(".gnu.version_r", 0))
+		elfWriteDynEntSym2(ctxt, s, DT_VERNEED, gnuVersionR.Sym())
-		elfWriteDynEnt(ctxt.Arch, s, DT_VERNEEDNUM, uint64(nfile))
+		Elfwritedynent2(ctxt.Arch, s, DT_VERNEEDNUM, uint64(nfile))
-		elfWriteDynEntSym(ctxt.Arch, s, DT_VERSYM, ctxt.Syms.Lookup(".gnu.version", 0))
+		elfWriteDynEntSym2(ctxt, s, DT_VERSYM, gnuVersion.Sym())
 	}
 
-	sy := ctxt.Syms.Lookup(elfRelType+".plt", 0)
+	sy := ldr.CreateSymForUpdate(elfRelType+".plt", 0)
-	if sy.Size > 0 {
+	if sy.Size() > 0 {
 		if elfRelType == ".rela" {
-			elfWriteDynEnt(ctxt.Arch, s, DT_PLTREL, DT_RELA)
+			Elfwritedynent2(ctxt.Arch, s, DT_PLTREL, DT_RELA)
 		} else {
-			elfWriteDynEnt(ctxt.Arch, s, DT_PLTREL, DT_REL)
+			Elfwritedynent2(ctxt.Arch, s, DT_PLTREL, DT_REL)
 		}
-		elfWriteDynEntSymSize(ctxt.Arch, s, DT_PLTRELSZ, sy)
+		elfwritedynentsymsize2(ctxt, s, DT_PLTRELSZ, sy.Sym())
-		elfWriteDynEntSym(ctxt.Arch, s, DT_JMPREL, sy)
+		elfWriteDynEntSym2(ctxt, s, DT_JMPREL, sy.Sym())
 	}
 
-	elfWriteDynEnt(ctxt.Arch, s, DT_NULL, 0)
+	Elfwritedynent2(ctxt.Arch, s, DT_NULL, 0)
 }
 
 func elfphload(seg *sym.Segment) *ElfPhdr {
@@ -1410,7 +1411,8 @@ func elfrelocsect(ctxt *Link, sect *sym.Section, syms []*sym.Symbol) {
 				Errorf(s, "missing xsym in relocation %#v %#v", r.Sym.Name, s)
 				continue
 			}
-			if r.Xsym.ElfsymForReloc() == 0 {
+			esr := ElfSymForReloc(ctxt, r.Xsym)
+			if esr == 0 {
 				Errorf(s, "reloc %d (%s) to non-elf symbol %s (outer=%s) %d (%s)", r.Type, sym.RelocName(ctxt.Arch, r.Type), r.Sym.Name, r.Xsym.Name, r.Sym.Type, r.Sym.Type)
 			}
 			if !r.Xsym.Attr.Reachable() {
@@ -2342,93 +2344,6 @@ elfobj:
 	}
 }
 
-func elfadddynsym(target *Target, syms *ArchSyms, s *sym.Symbol) {
-	if elf64 {
-		s.Dynid = int32(Nelfsym)
-		Nelfsym++
-
-		d := syms.DynSym
-
-		name := s.Extname()
-		d.AddUint32(target.Arch, uint32(Addstring(syms.DynStr, name)))
-
-		/* type */
-		t := STB_GLOBAL << 4
-
-		if s.Attr.CgoExport() && s.Type == sym.STEXT {
-			t |= STT_FUNC
-		} else {
-			t |= STT_OBJECT
-		}
-		d.AddUint8(uint8(t))
-
-		/* reserved */
-		d.AddUint8(0)
-
-		/* section where symbol is defined */
-		if s.Type == sym.SDYNIMPORT {
-			d.AddUint16(target.Arch, SHN_UNDEF)
-		} else {
-			d.AddUint16(target.Arch, 1)
-		}
-
-		/* value */
-		if s.Type == sym.SDYNIMPORT {
-			d.AddUint64(target.Arch, 0)
-		} else {
-			d.AddAddr(target.Arch, s)
-		}
-
-		/* size of object */
-		d.AddUint64(target.Arch, uint64(s.Size))
-
-		if target.Arch.Family == sys.AMD64 && !s.Attr.CgoExportDynamic() && s.Dynimplib() != "" && !seenlib[s.Dynimplib()] {
-			elfWriteDynEnt(target.Arch, syms.Dynamic, DT_NEEDED, uint64(Addstring(syms.DynStr, s.Dynimplib())))
-		}
-	} else {
-		s.Dynid = int32(Nelfsym)
-		Nelfsym++
-
-		d := syms.DynSym
-
-		/* name */
-		name := s.Extname()
-
-		d.AddUint32(target.Arch, uint32(Addstring(syms.DynStr, name)))
-
-		/* value */
-		if s.Type == sym.SDYNIMPORT {
-			d.AddUint32(target.Arch, 0)
-		} else {
-			d.AddAddr(target.Arch, s)
-		}
-
-		/* size of object */
-		d.AddUint32(target.Arch, uint32(s.Size))
-
-		/* type */
-		t := STB_GLOBAL << 4
-
-		// TODO(mwhudson): presumably the behavior should actually be the same on both arm and 386.
-		if target.Arch.Family == sys.I386 && s.Attr.CgoExport() && s.Type == sym.STEXT {
-			t |= STT_FUNC
-		} else if target.Arch.Family == sys.ARM && s.Attr.CgoExportDynamic() && s.Type == sym.STEXT {
-			t |= STT_FUNC
-		} else {
-			t |= STT_OBJECT
-		}
-		d.AddUint8(uint8(t))
-		d.AddUint8(0)
-
-		/* shndx */
-		if s.Type == sym.SDYNIMPORT {
-			d.AddUint16(target.Arch, SHN_UNDEF)
-		} else {
-			d.AddUint16(target.Arch, 1)
-		}
-	}
-}
-
 func elfadddynsym2(ldr *loader.Loader, target *Target, syms *ArchSyms, s loader.Sym) {
 	ldr.SetSymDynid(s, int32(Nelfsym))
 	Nelfsym++

src/cmd/link/internal/ld/elf2.go

@@ -0,0 +1,25 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ld
+
+import (
+	"cmd/link/internal/sym"
+)
+
+// Temporary dumping around for sym.Symbol version of helper
+// functions in elf.go, still being used for some archs/oses.
+// FIXME: get rid of this file when dodata() is completely
+// converted and the sym.Symbol functions are not needed.
+
+func elfsetstring(s *sym.Symbol, str string, off int) {
+	if nelfstr >= len(elfstr) {
+		Errorf(s, "too many elf strings")
+		errorexit()
+	}
+
+	elfstr[nelfstr].s = str
+	elfstr[nelfstr].off = off
+	nelfstr++
+}

src/cmd/link/internal/ld/errors.go

@@ -7,12 +7,15 @@ import (
 	"cmd/internal/obj"
 	"cmd/link/internal/loader"
 	"cmd/link/internal/sym"
-	"fmt"
-	"os"
 	"sync"
 )
 
 type unresolvedSymKey struct {
+	from loader.Sym // Symbol that referenced unresolved "to"
+	to   loader.Sym // Unresolved symbol referenced by "from"
+}
+
+type unresolvedSymKey2 struct {
 	from *sym.Symbol // Symbol that referenced unresolved "to"
 	to   *sym.Symbol // Unresolved symbol referenced by "from"
 }
@@ -22,22 +25,62 @@ type symNameFn func(s loader.Sym) string
 
 // ErrorReporter is used to make error reporting thread safe.
 type ErrorReporter struct {
+	loader.ErrorReporter
 	unresOnce  sync.Once
 	unresSyms  map[unresolvedSymKey]bool
+	unresSyms2 map[unresolvedSymKey2]bool
 	unresMutex sync.Mutex
 	lookup     lookupFn
 	SymName    symNameFn
 }
 
-// errorUnresolved prints unresolved symbol error for r.Sym that is referenced from s.
+// errorUnresolved prints unresolved symbol error for rs that is referenced from s.
-func (reporter *ErrorReporter) errorUnresolved(s *sym.Symbol, r *sym.Reloc) {
+func (reporter *ErrorReporter) errorUnresolved(ldr *loader.Loader, s, rs loader.Sym) {
 	reporter.unresOnce.Do(func() { reporter.unresSyms = make(map[unresolvedSymKey]bool) })
 
-	k := unresolvedSymKey{from: s, to: r.Sym}
+	k := unresolvedSymKey{from: s, to: rs}
 	reporter.unresMutex.Lock()
 	defer reporter.unresMutex.Unlock()
 	if !reporter.unresSyms[k] {
 		reporter.unresSyms[k] = true
+		name := ldr.SymName(rs)
+
+		// Try to find symbol under another ABI.
+		var reqABI, haveABI obj.ABI
+		haveABI = ^obj.ABI(0)
+		reqABI, ok := sym.VersionToABI(ldr.SymVersion(rs))
+		if ok {
+			for abi := obj.ABI(0); abi < obj.ABICount; abi++ {
+				v := sym.ABIToVersion(abi)
+				if v == -1 {
+					continue
+				}
+				if rs1 := ldr.Lookup(name, v); rs1 != 0 && ldr.SymType(rs1) != sym.Sxxx && ldr.SymType(rs1) != sym.SXREF {
+					haveABI = abi
+				}
+			}
+		}
+
+		// Give a special error message for main symbol (see #24809).
+		if name == "main.main" {
+			reporter.Errorf(s, "function main is undeclared in the main package")
+		} else if haveABI != ^obj.ABI(0) {
+			reporter.Errorf(s, "relocation target %s not defined for %s (but is defined for %s)", name, reqABI, haveABI)
+		} else {
+			reporter.Errorf(s, "relocation target %s not defined", name)
+		}
+	}
+}
+
+// errorUnresolved2 prints unresolved symbol error for r.Sym that is referenced from s.
+func (reporter *ErrorReporter) errorUnresolved2(s *sym.Symbol, r *sym.Reloc) {
+	reporter.unresOnce.Do(func() { reporter.unresSyms2 = make(map[unresolvedSymKey2]bool) })
+
+	k := unresolvedSymKey2{from: s, to: r.Sym}
+	reporter.unresMutex.Lock()
+	defer reporter.unresMutex.Unlock()
+	if !reporter.unresSyms2[k] {
+		reporter.unresSyms2[k] = true
 
 		// Try to find symbol under another ABI.
 		var reqABI, haveABI obj.ABI
@@ -65,23 +108,3 @@ func (reporter *ErrorReporter) errorUnresolved(s *sym.Symbol, r *sym.Reloc) {
 		}
 	}
 }
-
-// Errorf method logs an error message.
-//
-// If more than 20 errors have been printed, exit with an error.
-//
-// Logging an error means that on exit cmd/link will delete any
-// output file and return a non-zero error code.
-// TODO: consolidate the various different versions of Errorf (
-// function, Link method, and ErrorReporter method).
-func (reporter *ErrorReporter) Errorf(s loader.Sym, format string, args ...interface{}) {
-	if s != 0 && reporter.SymName != nil {
-		sn := reporter.SymName(s)
-		format = sn + ": " + format
-	} else {
-		format = fmt.Sprintf("sym %d: %s", s, format)
-	}
-	format += "\n"
-	fmt.Fprintf(os.Stderr, format, args...)
-	afterErrorAction()
-}

src/cmd/link/internal/ld/go.go

@@ -331,7 +331,7 @@ func adddynlib(ctxt *Link, lib string) {
 	}
 }
 
-func Adddynsym2(ldr *loader.Loader, reporter *ErrorReporter, target *Target, syms *ArchSyms, s loader.Sym) {
+func Adddynsym2(ldr *loader.Loader, target *Target, syms *ArchSyms, s loader.Sym) {
 	if ldr.SymDynid(s) >= 0 || target.LinkMode == LinkExternal {
 		return
 	}
@@ -339,27 +339,11 @@ func Adddynsym2(ldr *loader.Loader, reporter *ErrorReporter, target *Target, sym
 	if target.IsELF {
 		elfadddynsym2(ldr, target, syms, s)
 	} else if target.HeadType == objabi.Hdarwin {
-		reporter.Errorf(s, "adddynsym: missed symbol (Extname=%s)", ldr.SymExtname(s))
+		ldr.Errorf(s, "adddynsym: missed symbol (Extname=%s)", ldr.SymExtname(s))
 	} else if target.HeadType == objabi.Hwindows {
 		// already taken care of
 	} else {
-		reporter.Errorf(s, "adddynsym: unsupported binary format")
+		ldr.Errorf(s, "adddynsym: unsupported binary format")
-	}
-}
-
-func Adddynsym(target *Target, syms *ArchSyms, s *sym.Symbol) {
-	if s.Dynid >= 0 || target.LinkMode == LinkExternal {
-		return
-	}
-
-	if target.IsELF {
-		elfadddynsym(target, syms, s)
-	} else if target.HeadType == objabi.Hdarwin {
-		Errorf(s, "adddynsym: missed symbol (Extname=%s)", s.Extname())
-	} else if target.HeadType == objabi.Hwindows {
-		// already taken care of
-	} else {
-		Errorf(s, "adddynsym: unsupported binary format")
 	}
 }
 
@@ -425,7 +409,7 @@ func (ctxt *Link) addexport() {
 	}
 
 	for _, exp := range ctxt.dynexp2 {
-		Adddynsym2(ctxt.loader, &ctxt.ErrorReporter, &ctxt.Target, &ctxt.ArchSyms, exp)
+		Adddynsym2(ctxt.loader, &ctxt.Target, &ctxt.ArchSyms, exp)
 	}
 	for _, lib := range dynlib {
 		adddynlib(ctxt, lib)

src/cmd/link/internal/ld/ld.go

@@ -32,6 +32,7 @@
 package ld
 
 import (
+	"cmd/internal/goobj2"
 	"cmd/link/internal/loader"
 	"cmd/link/internal/sym"
 	"io/ioutil"
@@ -155,11 +156,12 @@ func findlib(ctxt *Link, lib string) (string, bool) {
 	return pname, isshlib
 }
 
-func addlib(ctxt *Link, src string, obj string, lib string) *sym.Library {
+func addlib(ctxt *Link, src, obj, lib string, fingerprint goobj2.FingerprintType) *sym.Library {
 	pkg := pkgname(ctxt, lib)
 
 	// already loaded?
 	if l := ctxt.LibraryByPkg[pkg]; l != nil {
+		checkFingerprint(l, l.Fingerprint, src, fingerprint)
 		return l
 	}
 
@@ -170,9 +172,9 @@ func addlib(ctxt *Link, src string, obj string, lib string) *sym.Library {
 	}
 
 	if isshlib {
-		return addlibpath(ctxt, src, obj, "", pkg, pname)
+		return addlibpath(ctxt, src, obj, "", pkg, pname, fingerprint)
 	}
-	return addlibpath(ctxt, src, obj, pname, pkg, "")
+	return addlibpath(ctxt, src, obj, pname, pkg, "", fingerprint)
 }
 
 /*
@@ -182,14 +184,16 @@ func addlib(ctxt *Link, src string, obj string, lib string) *sym.Library {
  *	file: object file, e.g., /home/rsc/go/pkg/container/vector.a
  *	pkg: package import path, e.g. container/vector
  *	shlib: path to shared library, or .shlibname file holding path
+ *	fingerprint: if not 0, expected fingerprint for import from srcref
+ *	             fingerprint is 0 if the library is not imported (e.g. main)
  */
-func addlibpath(ctxt *Link, srcref string, objref string, file string, pkg string, shlib string) *sym.Library {
+func addlibpath(ctxt *Link, srcref, objref, file, pkg, shlib string, fingerprint goobj2.FingerprintType) *sym.Library {
 	if l := ctxt.LibraryByPkg[pkg]; l != nil {
 		return l
 	}
 
 	if ctxt.Debugvlog > 1 {
-		ctxt.Logf("addlibpath: srcref: %s objref: %s file: %s pkg: %s shlib: %s\n", srcref, objref, file, pkg, shlib)
+		ctxt.Logf("addlibpath: srcref: %s objref: %s file: %s pkg: %s shlib: %s fingerprint: %x\n", srcref, objref, file, pkg, shlib, fingerprint)
 	}
 
 	l := &sym.Library{}
@@ -199,6 +203,7 @@ func addlibpath(ctxt *Link, srcref string, objref string, file string, pkg strin
 	l.Srcref = srcref
 	l.File = file
 	l.Pkg = pkg
+	l.Fingerprint = fingerprint
 	if shlib != "" {
 		if strings.HasSuffix(shlib, ".shlibname") {
 			data, err := ioutil.ReadFile(shlib)

src/cmd/link/internal/ld/lib.go

@@ -33,6 +33,7 @@ package ld
 import (
 	"bytes"
 	"cmd/internal/bio"
+	"cmd/internal/goobj2"
 	"cmd/internal/obj"
 	"cmd/internal/objabi"
 	"cmd/internal/sys"
@@ -232,6 +233,7 @@ type Arch struct {
 	Dragonflydynld string
 	Solarisdynld   string
 	Adddynrel      func(*Target, *loader.Loader, *ArchSyms, *sym.Symbol, *sym.Reloc) bool
+	Adddynrel2     func(*Target, *loader.Loader, *ArchSyms, loader.Sym, *loader.Reloc2, int) bool
 	Archinit       func(*Link)
 	// Archreloc is an arch-specific hook that assists in
 	// relocation processing (invoked by 'relocsym'); it handles
@@ -263,7 +265,7 @@ type Arch struct {
 	// file. Typically, Asmb writes most of the content (sections and
 	// segments), for which we have computed the size and offset. Asmb2
 	// writes the rest.
-	Asmb  func(*Link)
+	Asmb  func(*Link, *loader.Loader)
 	Asmb2 func(*Link)
 
 	Elfreloc1   func(*Link, *sym.Reloc, int64) bool
@@ -280,7 +282,7 @@ type Arch struct {
 	// This is possible when a TLS IE relocation refers to a local
 	// symbol in an executable, which is typical when internally
 	// linking PIE binaries.
-	TLSIEtoLE func(s *sym.Symbol, off, size int)
+	TLSIEtoLE func(P []byte, off, size int)
 
 	// optional override for assignAddress
 	AssignAddress func(ldr *loader.Loader, sect *sym.Section, n int, s loader.Sym, va uint64, isTramp bool) (*sym.Section, int, uint64)
@@ -424,14 +426,15 @@ func errorexit() {
 }
 
 func loadinternal(ctxt *Link, name string) *sym.Library {
+	zerofp := goobj2.FingerprintType{}
 	if ctxt.linkShared && ctxt.PackageShlib != nil {
 		if shlib := ctxt.PackageShlib[name]; shlib != "" {
-			return addlibpath(ctxt, "internal", "internal", "", name, shlib)
+			return addlibpath(ctxt, "internal", "internal", "", name, shlib, zerofp)
 		}
 	}
 	if ctxt.PackageFile != nil {
 		if pname := ctxt.PackageFile[name]; pname != "" {
-			return addlibpath(ctxt, "internal", "internal", pname, name, "")
+			return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
 		}
 		ctxt.Logf("loadinternal: cannot find %s\n", name)
 		return nil
@@ -444,7 +447,7 @@ func loadinternal(ctxt *Link, name string) *sym.Library {
 				ctxt.Logf("searching for %s.a in %s\n", name, shlibname)
 			}
 			if _, err := os.Stat(shlibname); err == nil {
-				return addlibpath(ctxt, "internal", "internal", "", name, shlibname)
+				return addlibpath(ctxt, "internal", "internal", "", name, shlibname, zerofp)
 			}
 		}
 		pname := filepath.Join(libdir, name+".a")
@@ -452,7 +455,7 @@ func loadinternal(ctxt *Link, name string) *sym.Library {
 			ctxt.Logf("searching for %s.a in %s\n", name, pname)
 		}
 		if _, err := os.Stat(pname); err == nil {
-			return addlibpath(ctxt, "internal", "internal", pname, name, "")
+			return addlibpath(ctxt, "internal", "internal", pname, name, "", zerofp)
 		}
 	}
 
@@ -503,7 +506,7 @@ func (ctxt *Link) loadlib() {
 	default:
 		log.Fatalf("invalid -strictdups flag value %d", *FlagStrictDups)
 	}
-	ctxt.loader = loader.NewLoader(flags, elfsetstring)
+	ctxt.loader = loader.NewLoader(flags, elfsetstring, &ctxt.ErrorReporter.ErrorReporter)
 	ctxt.ErrorReporter.SymName = func(s loader.Sym) string {
 		return ctxt.loader.SymName(s)
 	}
@@ -1984,11 +1987,29 @@ func ldobj(ctxt *Link, f *bio.Reader, lib *sym.Library, length int64, pn string,
 	ldpkg(ctxt, f, lib, import1-import0-2, pn) // -2 for !\n
 	f.MustSeek(import1, 0)
 
-	ctxt.loader.Preload(ctxt.Syms, f, lib, unit, eof-f.Offset(), 0)
+	fingerprint := ctxt.loader.Preload(ctxt.Syms, f, lib, unit, eof-f.Offset())
+	if !fingerprint.IsZero() { // Assembly objects don't have fingerprints. Ignore them.
+		// Check fingerprint, to ensure the importing and imported packages
+		// have consistent view of symbol indices.
+		// Normally the go command should ensure this. But in case something
+		// goes wrong, it could lead to obscure bugs like run-time crash.
+		// Check it here to be sure.
+		if lib.Fingerprint.IsZero() { // Not yet imported. Update its fingerprint.
+			lib.Fingerprint = fingerprint
+		}
+		checkFingerprint(lib, fingerprint, lib.Srcref, lib.Fingerprint)
+	}
+
 	addImports(ctxt, lib, pn)
 	return nil
 }
 
+func checkFingerprint(lib *sym.Library, libfp goobj2.FingerprintType, src string, srcfp goobj2.FingerprintType) {
+	if libfp != srcfp {
+		Exitf("fingerprint mismatch: %s has %x, import from %s expecting %x", lib, libfp, src, srcfp)
+	}
+}
+
 func readelfsymboldata(ctxt *Link, f *elf.File, sym *elf.Symbol) []byte {
 	data := make([]byte, sym.Size)
 	sect := f.Sections[sym.Section]
@@ -2472,7 +2493,7 @@ const (
 	DeletedAutoSym = 'x'
 )
 
-func genasmsym(ctxt *Link, put func(*Link, *sym.Symbol, string, SymbolType, int64, *sym.Symbol)) {
+func genasmsym(ctxt *Link, put func(*Link, *sym.Symbol, string, SymbolType, int64)) {
 	// These symbols won't show up in the first loop below because we
 	// skip sym.STEXT symbols. Normal sym.STEXT symbols are emitted by walking textp.
 	s := ctxt.Syms.Lookup("runtime.text", 0)
@@ -2482,7 +2503,7 @@ func genasmsym(ctxt *Link, put func(*Link, *sym.Symbol, string, SymbolType, int6
 		// on AIX with external linker.
 		// See data.go:/textaddress
 		if !(ctxt.DynlinkingGo() && ctxt.HeadType == objabi.Hdarwin) && !(ctxt.HeadType == objabi.Haix && ctxt.LinkMode == LinkExternal) {
-			put(ctxt, s, s.Name, TextSym, s.Value, nil)
+			put(ctxt, s, s.Name, TextSym, s.Value)
 		}
 	}
 
@@ -2503,7 +2524,7 @@ func genasmsym(ctxt *Link, put func(*Link, *sym.Symbol, string, SymbolType, int6
 			break
 		}
 		if s.Type == sym.STEXT {
-			put(ctxt, s, s.Name, TextSym, s.Value, nil)
+			put(ctxt, s, s.Name, TextSym, s.Value)
 		}
 		n++
 	}
@@ -2515,7 +2536,7 @@ func genasmsym(ctxt *Link, put func(*Link, *sym.Symbol, string, SymbolType, int6
 		// on AIX with external linker.
 		// See data.go:/textaddress
 		if !(ctxt.DynlinkingGo() && ctxt.HeadType == objabi.Hdarwin) && !(ctxt.HeadType == objabi.Haix && ctxt.LinkMode == LinkExternal) {
-			put(ctxt, s, s.Name, TextSym, s.Value, nil)
+			put(ctxt, s, s.Name, TextSym, s.Value)
 		}
 	}
 
@@ -2534,7 +2555,10 @@ func genasmsym(ctxt *Link, put func(*Link, *sym.Symbol, string, SymbolType, int6
 		return true
 	}
 
-	for _, s := range ctxt.Syms.Allsym {
+	for _, s := range ctxt.loader.Syms {
+		if s == nil {
+			continue
+		}
 		if !shouldBeInSymbolTable(s) {
 			continue
 		}
@@ -2565,7 +2589,7 @@ func genasmsym(ctxt *Link, put func(*Link, *sym.Symbol, string, SymbolType, int6
 			if !s.Attr.Reachable() {
 				continue
 			}
-			put(ctxt, s, s.Name, DataSym, Symaddr(s), s.Gotype)
+			put(ctxt, s, s.Name, DataSym, Symaddr(s))
 
 		case sym.SBSS, sym.SNOPTRBSS, sym.SLIBFUZZER_EXTRA_COUNTER:
 			if !s.Attr.Reachable() {
@@ -2574,11 +2598,11 @@ func genasmsym(ctxt *Link, put func(*Link, *sym.Symbol, string, SymbolType, int6
 			if len(s.P) > 0 {
 				Errorf(s, "should not be bss (size=%d type=%v special=%v)", len(s.P), s.Type, s.Attr.Special())
 			}
-			put(ctxt, s, s.Name, BSSSym, Symaddr(s), s.Gotype)
+			put(ctxt, s, s.Name, BSSSym, Symaddr(s))
 
 		case sym.SUNDEFEXT:
 			if ctxt.HeadType == objabi.Hwindows || ctxt.HeadType == objabi.Haix || ctxt.IsELF {
-				put(ctxt, s, s.Name, UndefinedSym, s.Value, nil)
+				put(ctxt, s, s.Name, UndefinedSym, s.Value)
 			}
 
 		case sym.SHOSTOBJ:
@@ -2586,24 +2610,24 @@ func genasmsym(ctxt *Link, put func(*Link, *sym.Symbol, string, SymbolType, int6
 				continue
 			}
 			if ctxt.HeadType == objabi.Hwindows || ctxt.IsELF {
-				put(ctxt, s, s.Name, UndefinedSym, s.Value, nil)
+				put(ctxt, s, s.Name, UndefinedSym, s.Value)
 			}
 
 		case sym.SDYNIMPORT:
 			if !s.Attr.Reachable() {
 				continue
 			}
-			put(ctxt, s, s.Extname(), UndefinedSym, 0, nil)
+			put(ctxt, s, s.Extname(), UndefinedSym, 0)
 
 		case sym.STLSBSS:
 			if ctxt.LinkMode == LinkExternal {
-				put(ctxt, s, s.Name, TLSSym, Symaddr(s), s.Gotype)
+				put(ctxt, s, s.Name, TLSSym, Symaddr(s))
 			}
 		}
 	}
 
 	for _, s := range ctxt.Textp {
-		put(ctxt, s, s.Name, TextSym, s.Value, s.Gotype)
+		put(ctxt, s, s.Name, TextSym, s.Value)
 	}
 
 	if ctxt.Debugvlog != 0 || *flagN {
@@ -2800,10 +2824,9 @@ func addToTextp(ctxt *Link) {
 	ctxt.Textp = textp
 }
 
-func (ctxt *Link) loadlibfull() {
+func (ctxt *Link) loadlibfull(symGroupType []sym.SymKind, needReloc bool) {
-
 	// Load full symbol contents, resolve indexed references.
-	ctxt.loader.LoadFull(ctxt.Arch, ctxt.Syms)
+	ctxt.loader.LoadFull(ctxt.Arch, ctxt.Syms, needReloc)
 
 	// Convert ctxt.Moduledata2 to ctxt.Moduledata, etc
 	if ctxt.Moduledata2 != 0 {
@@ -2841,12 +2864,41 @@ func (ctxt *Link) loadlibfull() {
 		dwarfp = append(dwarfp, dwarfSecInfo2{syms: syms})
 	}
 
+	// Populate datap from datap2
+	ctxt.datap = make([]*sym.Symbol, len(ctxt.datap2))
+	for i, symIdx := range ctxt.datap2 {
+		s := ctxt.loader.Syms[symIdx]
+		if s == nil {
+			panic(fmt.Sprintf("nil sym for datap2 element %d", symIdx))
+		}
+		ctxt.datap[i] = s
+	}
+
+	// Populate the sym.Section 'Sym' fields based on their 'Sym2'
+	// fields.
+	allSegments := []*sym.Segment{&Segtext, &Segrodata, &Segrelrodata, &Segdata, &Segdwarf}
+	for _, seg := range allSegments {
+		for _, sect := range seg.Sections {
+			if sect.Sym2 != 0 {
+				s := ctxt.loader.Syms[sect.Sym2]
+				if s == nil {
+					panic(fmt.Sprintf("nil sym for sect %s sym %d", sect.Name, sect.Sym2))
+				}
+				sect.Sym = s
+			}
+		}
+	}
+
 	// For now, overwrite symbol type with its "group" type, as dodata
 	// expected. Once we converted dodata, this will probably not be
 	// needed.
 	for i, t := range symGroupType {
 		if t != sym.Sxxx {
-			ctxt.loader.Syms[i].Type = t
+			s := ctxt.loader.Syms[i]
+			if s == nil {
+				continue // in dwarfcompress we drop compressed DWARF symbols
+			}
+			s.Type = t
 		}
 	}
 	symGroupType = nil
@@ -2858,8 +2910,29 @@ func (ctxt *Link) loadlibfull() {
 	}
 }
 
+func symPkg(ctxt *Link, s *sym.Symbol) string {
+	if s == nil {
+		return ""
+	}
+	return ctxt.loader.SymPkg(loader.Sym(s.SymIdx))
+}
+
+func ElfSymForReloc(ctxt *Link, s *sym.Symbol) int32 {
+	// If putelfsym created a local version of this symbol, use that in all
+	// relocations.
+	les := ctxt.loader.SymLocalElfSym(loader.Sym(s.SymIdx))
+	if les != 0 {
+		return les
+	} else {
+		return ctxt.loader.SymElfSym(loader.Sym(s.SymIdx))
+	}
+}
+
 func (ctxt *Link) dumpsyms() {
-	for _, s := range ctxt.Syms.Allsym {
+	for _, s := range ctxt.loader.Syms {
+		if s == nil {
+			continue
+		}
 		fmt.Printf("%s %s reachable=%v onlist=%v outer=%v sub=%v\n", s, s.Type, s.Attr.Reachable(), s.Attr.OnList(), s.Outer, s.Sub)
 		for i := range s.R {
 			fmt.Println("\t", s.R[i].Type, s.R[i].Sym)

src/cmd/link/internal/ld/link.go

@@ -66,7 +66,6 @@ type Link struct {
 
 	compressDWARF bool
 
-	Tlsg2        loader.Sym
 	Libdir       []string
 	Library      []*sym.Library
 	LibraryByPkg map[string]*sym.Library
@@ -92,6 +91,7 @@ type Link struct {
 	cgo_export_dynamic map[string]bool
 
 	datap   []*sym.Symbol
+	datap2  []loader.Sym
 	dynexp2 []loader.Sym
 
 	// Elf symtab variables.
@@ -129,11 +129,11 @@ func (ctxt *Link) Logf(format string, args ...interface{}) {
 
 func addImports(ctxt *Link, l *sym.Library, pn string) {
 	pkg := objabi.PathToPrefix(l.Pkg)
-	for _, importStr := range l.ImportStrings {
+	for _, imp := range l.Autolib {
-		lib := addlib(ctxt, pkg, pn, importStr)
+		lib := addlib(ctxt, pkg, pn, imp.Pkg, imp.Fingerprint)
 		if lib != nil {
 			l.Imports = append(l.Imports, lib)
 		}
 	}
-	l.ImportStrings = nil
+	l.Autolib = nil
 }

src/cmd/link/internal/ld/macho.go

@@ -8,6 +8,7 @@ import (
 	"bytes"
 	"cmd/internal/objabi"
 	"cmd/internal/sys"
+	"cmd/link/internal/loader"
 	"cmd/link/internal/sym"
 	"debug/macho"
 	"encoding/binary"
@@ -216,7 +217,7 @@ const (
 
 var nkind [NumSymKind]int
 
-var sortsym []*sym.Symbol
+var sortsym []loader.Sym
 
 var nsortsym int
 
@@ -743,106 +744,125 @@ func Asmbmacho(ctxt *Link) {
 	}
 }
 
-func symkind(s *sym.Symbol) int {
+func symkind(ldr *loader.Loader, s loader.Sym) int {
-	if s.Type == sym.SDYNIMPORT {
+	if ldr.SymType(s) == sym.SDYNIMPORT {
 		return SymKindUndef
 	}
-	if s.Attr.CgoExport() {
+	if ldr.AttrCgoExport(s) {
 		return SymKindExtdef
 	}
 	return SymKindLocal
 }
 
-func addsym(ctxt *Link, s *sym.Symbol, name string, type_ SymbolType, addr int64, gotype *sym.Symbol) {
+func collectmachosyms(ctxt *Link) {
-	if s == nil {
+	ldr := ctxt.loader
-		return
+
+	addsym := func(s loader.Sym) {
+		sortsym = append(sortsym, s)
+		nkind[symkind(ldr, s)]++
 	}
 
-	switch type_ {
+	// Add special runtime.text and runtime.etext symbols.
-	default:
+	// We've already included this symbol in Textp on darwin if ctxt.DynlinkingGo().
-		return
+	// See data.go:/textaddress
-
+	if !ctxt.DynlinkingGo() {
-	case DataSym, BSSSym, TextSym:
+		s := ldr.Lookup("runtime.text", 0)
-		break
+		if ldr.SymType(s) == sym.STEXT {
+			addsym(s)
+		}
+		s = ldr.Lookup("runtime.etext", 0)
+		if ldr.SymType(s) == sym.STEXT {
+			addsym(s)
+		}
 	}
 
-	if sortsym != nil {
+	// Add text symbols.
-		sortsym[nsortsym] = s
+	for _, s := range ctxt.Textp2 {
-		nkind[symkind(s)]++
+		addsym(s)
 	}
 
-	nsortsym++
+	shouldBeInSymbolTable := func(s loader.Sym) bool {
-}
+		if ldr.AttrNotInSymbolTable(s) {
-
+			return false
-type machoscmp []*sym.Symbol
+		}
-
+		name := ldr.RawSymName(s) // TODO: try not to read the name
-func (x machoscmp) Len() int {
+		if name == "" || name[0] == '.' {
-	return len(x)
+			return false
-}
+		}
-
+		return true
-func (x machoscmp) Swap(i, j int) {
-	x[i], x[j] = x[j], x[i]
-}
-
-func (x machoscmp) Less(i, j int) bool {
-	s1 := x[i]
-	s2 := x[j]
-
-	k1 := symkind(s1)
-	k2 := symkind(s2)
-	if k1 != k2 {
-		return k1 < k2
 	}
 
-	return s1.Extname() < s2.Extname()
+	// Add data symbols and external references.
-}
+	for s := loader.Sym(1); s < loader.Sym(ldr.NSym()); s++ {
+		if !ldr.AttrReachable(s) {
+			continue
+		}
+		t := ldr.SymType(s)
+		if t >= sym.SELFRXSECT && t < sym.SXREF { // data sections handled in dodata
+			if t == sym.STLSBSS {
+				// TLSBSS is not used on darwin. See data.go:allocateDataSections
+				continue
+			}
+			if !shouldBeInSymbolTable(s) {
+				continue
+			}
+			addsym(s)
+		}
+
+		switch t {
+		case sym.SDYNIMPORT, sym.SHOSTOBJ, sym.SUNDEFEXT, sym.SCONST:
+			addsym(s)
+		}
 
-func machogenasmsym(ctxt *Link) {
-	genasmsym(ctxt, addsym)
-	for _, s := range ctxt.Syms.Allsym {
 		// Some 64-bit functions have a "$INODE64" or "$INODE64$UNIX2003" suffix.
-		if s.Type == sym.SDYNIMPORT && s.Dynimplib() == "/usr/lib/libSystem.B.dylib" {
+		if t == sym.SDYNIMPORT && ldr.SymDynimplib(s) == "/usr/lib/libSystem.B.dylib" {
 			// But only on macOS.
 			if machoPlatform == PLATFORM_MACOS {
-				switch n := s.Extname(); n {
+				switch n := ldr.SymExtname(s); n {
 				case "fdopendir":
 					switch objabi.GOARCH {
 					case "amd64":
-						s.SetExtname(n + "$INODE64")
+						ldr.SetSymExtname(s, n+"$INODE64")
 					case "386":
-						s.SetExtname(n + "$INODE64$UNIX2003")
+						ldr.SetSymExtname(s, n+"$INODE64$UNIX2003")
 					}
 				case "readdir_r", "getfsstat":
 					switch objabi.GOARCH {
 					case "amd64", "386":
-						s.SetExtname(n + "$INODE64")
+						ldr.SetSymExtname(s, n+"$INODE64")
+					}
 				}
 			}
 		}
 	}
 
-		if s.Type == sym.SDYNIMPORT || s.Type == sym.SHOSTOBJ || s.Type == sym.SUNDEFEXT {
+	nsortsym = len(sortsym)
-			if s.Attr.Reachable() {
-				addsym(ctxt, s, "", DataSym, 0, nil)
-			}
-		}
-	}
 }
 
 func machosymorder(ctxt *Link) {
+	ldr := ctxt.loader
+
 	// On Mac OS X Mountain Lion, we must sort exported symbols
 	// So we sort them here and pre-allocate dynid for them
 	// See https://golang.org/issue/4029
-	for i := range dynexp {
+	for _, s := range ctxt.dynexp2 {
-		dynexp[i].Attr |= sym.AttrReachable
+		if !ldr.AttrReachable(s) {
+			panic("dynexp symbol is not reachable")
 		}
-	machogenasmsym(ctxt)
+	}
-	sortsym = make([]*sym.Symbol, nsortsym)
+	collectmachosyms(ctxt)
-	nsortsym = 0
+	sort.Slice(sortsym[:nsortsym], func(i, j int) bool {
-	machogenasmsym(ctxt)
+		s1 := sortsym[i]
-	sort.Sort(machoscmp(sortsym[:nsortsym]))
+		s2 := sortsym[j]
-	for i := 0; i < nsortsym; i++ {
+		k1 := symkind(ldr, s1)
-		sortsym[i].Dynid = int32(i)
+		k2 := symkind(ldr, s2)
+		if k1 != k2 {
+			return k1 < k2
+		}
+		return ldr.SymExtname(s1) < ldr.SymExtname(s2) // Note: unnamed symbols are not added in collectmachosyms
+	})
+	for i, s := range sortsym {
+		ldr.SetSymDynid(s, int32(i))
 	}
 }
 
@@ -877,7 +897,7 @@ func machosymtab(ctxt *Link) {
 	symstr := ctxt.Syms.Lookup(".machosymstr", 0)
 
 	for i := 0; i < nsortsym; i++ {
-		s := sortsym[i]
+		s := ctxt.loader.Syms[sortsym[i]]
 		symtab.AddUint32(ctxt.Arch, uint32(symstr.Size))
 
 		export := machoShouldExport(ctxt, s)

src/cmd/link/internal/ld/main.go

@@ -32,6 +32,7 @@ package ld
 
 import (
 	"bufio"
+	"cmd/internal/goobj2"
 	"cmd/internal/objabi"
 	"cmd/internal/sys"
 	"cmd/link/internal/benchmark"
@@ -74,7 +75,7 @@ var (
 	flagExtldflags = flag.String("extldflags", "", "pass `flags` to external linker")
 	flagExtar      = flag.String("extar", "", "archive program for buildmode=c-archive")
 
-	flagA           = flag.Bool("a", false, "disassemble output")
+	flagA           = flag.Bool("a", false, "no-op (deprecated)")
 	FlagC           = flag.Bool("c", false, "dump call graph")
 	FlagD           = flag.Bool("d", false, "disable dynamic executable")
 	flagF           = flag.Bool("f", false, "ignore version mismatch")
@@ -154,6 +155,9 @@ func Main(arch *sys.Arch, theArch Arch) {
 			usage()
 		}
 	}
+	if ctxt.HeadType == objabi.Hunknown {
+		ctxt.HeadType.Set(objabi.GOOS)
+	}
 
 	checkStrictDups = *FlagStrictDups
 
@@ -190,11 +194,6 @@ func Main(arch *sys.Arch, theArch Arch) {
 
 	bench.Start("libinit")
 	libinit(ctxt) // creates outfile
-
-	if ctxt.HeadType == objabi.Hunknown {
-		ctxt.HeadType.Set(objabi.GOOS)
-	}
-
 	bench.Start("computeTLSOffset")
 	ctxt.computeTLSOffset()
 	bench.Start("Archinit")
@@ -208,6 +207,7 @@ func Main(arch *sys.Arch, theArch Arch) {
 		ctxt.Logf("HEADER = -H%d -T0x%x -R0x%x\n", ctxt.HeadType, uint64(*FlagTextAddr), uint32(*FlagRound))
 	}
 
+	zerofp := goobj2.FingerprintType{}
 	switch ctxt.BuildMode {
 	case BuildModeShared:
 		for i := 0; i < flag.NArg(); i++ {
@@ -221,12 +221,12 @@ func Main(arch *sys.Arch, theArch Arch) {
 			}
 			pkglistfornote = append(pkglistfornote, pkgpath...)
 			pkglistfornote = append(pkglistfornote, '\n')
-			addlibpath(ctxt, "command line", "command line", file, pkgpath, "")
+			addlibpath(ctxt, "command line", "command line", file, pkgpath, "", zerofp)
 		}
 	case BuildModePlugin:
-		addlibpath(ctxt, "command line", "command line", flag.Arg(0), *flagPluginPath, "")
+		addlibpath(ctxt, "command line", "command line", flag.Arg(0), *flagPluginPath, "", zerofp)
 	default:
-		addlibpath(ctxt, "command line", "command line", flag.Arg(0), "main", "")
+		addlibpath(ctxt, "command line", "command line", flag.Arg(0), "main", "", zerofp)
 	}
 	bench.Start("loadlib")
 	ctxt.loadlib()
@@ -297,11 +297,9 @@ func Main(arch *sys.Arch, theArch Arch) {
 	bench.Start("dwarfGenerateDebugSyms")
 	dwarfGenerateDebugSyms(ctxt)
 	bench.Start("symtab")
-	ctxt.symtab()
+	symGroupType := ctxt.symtab()
-	bench.Start("loadlibfull")
-	ctxt.loadlibfull() // XXX do it here for now
 	bench.Start("dodata")
-	ctxt.dodata()
+	ctxt.dodata2(symGroupType)
 	bench.Start("address")
 	order := ctxt.address()
 	bench.Start("dwarfcompress")
@@ -321,19 +319,27 @@ func Main(arch *sys.Arch, theArch Arch) {
 		if err := ctxt.Out.Mmap(filesize); err != nil {
 			panic(err)
 		}
+	}
 	// Asmb will redirect symbols to the output file mmap, and relocations
 	// will be applied directly there.
 	bench.Start("Asmb")
-		thearch.Asmb(ctxt)
+	ctxt.loader.InitOutData()
+	thearch.Asmb(ctxt, ctxt.loader)
+
+	newreloc := ctxt.IsInternal() && ctxt.IsAMD64()
+	if newreloc {
 		bench.Start("reloc")
 		ctxt.reloc()
+		bench.Start("loadlibfull")
+		// We don't need relocations at this point.
+		// An exception is Windows, see pe.go:addPEBaseRelocSym
+		needReloc := ctxt.IsWindows()
+		ctxt.loadlibfull(symGroupType, needReloc) // XXX do it here for now
 	} else {
-		// If we don't mmap, we need to apply relocations before
+		bench.Start("loadlibfull")
-		// writing out.
+		ctxt.loadlibfull(symGroupType, true) // XXX do it here for now
 		bench.Start("reloc")
-		ctxt.reloc()
+		ctxt.reloc2()
-		bench.Start("Asmb")
-		thearch.Asmb(ctxt)
 	}
 	bench.Start("Asmb2")
 	thearch.Asmb2(ctxt)
@@ -346,7 +352,7 @@ func Main(arch *sys.Arch, theArch Arch) {
 	bench.Start("hostlink")
 	ctxt.hostlink()
 	if ctxt.Debugvlog != 0 {
-		ctxt.Logf("%d symbols\n", len(ctxt.Syms.Allsym))
+		ctxt.Logf("%d symbols, %d reachable\n", len(ctxt.loader.Syms), ctxt.loader.NReachableSym())
 		ctxt.Logf("%d liveness data\n", liveness)
 	}
 	bench.Start("Flush")

src/cmd/link/internal/ld/outbuf.go

@@ -6,7 +6,7 @@ package ld
 
 import (
 	"cmd/internal/sys"
-	"cmd/link/internal/sym"
+	"cmd/link/internal/loader"
 	"encoding/binary"
 	"errors"
 	"log"
@@ -285,11 +285,11 @@ func (out *OutBuf) WriteStringPad(s string, n int, pad []byte) {
 // to point to the output buffer that we just wrote, so we can apply further
 // edit to the symbol content.
 // If the output file is not Mmap'd, just writes the content.
-func (out *OutBuf) WriteSym(s *sym.Symbol) {
+func (out *OutBuf) WriteSym(ldr *loader.Loader, s loader.Sym) {
-	n := int64(len(s.P))
+	P := ldr.Data(s)
+	n := int64(len(P))
 	pos, buf := out.writeLoc(n)
-	copy(buf[pos:], s.P)
+	copy(buf[pos:], P)
 	out.off += n
-	s.P = buf[pos : pos+n]
+	ldr.SetOutData(s, buf[pos:pos+n])
-	s.Attr.Set(sym.AttrReadOnly, false)
 }

src/cmd/link/internal/ld/pe.go

@@ -646,7 +646,7 @@ func (f *peFile) mapToPESection(s *sym.Symbol, linkmode LinkMode) (pesectidx int
 // writeSymbols writes all COFF symbol table records.
 func (f *peFile) writeSymbols(ctxt *Link) {
 
-	put := func(ctxt *Link, s *sym.Symbol, name string, type_ SymbolType, addr int64, gotype *sym.Symbol) {
+	put := func(ctxt *Link, s *sym.Symbol, name string, type_ SymbolType, addr int64) {
 		if s == nil {
 			return
 		}

src/cmd/link/internal/ld/sym.go

@@ -34,12 +34,14 @@ package ld
 import (
 	"cmd/internal/objabi"
 	"cmd/internal/sys"
+	"cmd/link/internal/loader"
 	"cmd/link/internal/sym"
 	"log"
 	"runtime"
 )
 
 func linknew(arch *sys.Arch) *Link {
+	ler := loader.ErrorReporter{AfterErrorAction: afterErrorAction}
 	ctxt := &Link{
 		Target:        Target{Arch: arch},
 		Syms:          sym.NewSymbols(),
@@ -47,6 +49,7 @@ func linknew(arch *sys.Arch) *Link {
 		Out:           NewOutBuf(arch),
 		LibraryByPkg:  make(map[string]*sym.Library),
 		numelfsym:     1,
+		ErrorReporter: ErrorReporter{ErrorReporter: ler},
 	}
 
 	if objabi.GOARCH != arch.Name {

src/cmd/link/internal/ld/symtab.go

@@ -74,7 +74,7 @@ func putelfsyment(out *OutBuf, off int, addr int64, size int64, info int, shndx
 	}
 }
 
-func putelfsym(ctxt *Link, x *sym.Symbol, s string, t SymbolType, addr int64, go_ *sym.Symbol) {
+func putelfsym(ctxt *Link, x *sym.Symbol, s string, t SymbolType, addr int64) {
 	var typ int
 
 	switch t {
@@ -185,7 +185,7 @@ func putelfsym(ctxt *Link, x *sym.Symbol, s string, t SymbolType, addr int64, go
 		// ELF linker -Bsymbolic-functions option, but that is buggy on
 		// several platforms.
 		putelfsyment(ctxt.Out, putelfstr("local."+s), addr, size, STB_LOCAL<<4|typ&0xf, elfshnum, other)
-		x.LocalElfsym = int32(ctxt.numelfsym)
+		ctxt.loader.SetSymLocalElfSym(loader.Sym(x.SymIdx), int32(ctxt.numelfsym))
 		ctxt.numelfsym++
 		return
 	} else if bind != ctxt.elfbind {
@@ -193,13 +193,13 @@ func putelfsym(ctxt *Link, x *sym.Symbol, s string, t SymbolType, addr int64, go
 	}
 
 	putelfsyment(ctxt.Out, putelfstr(s), addr, size, bind<<4|typ&0xf, elfshnum, other)
-	x.Elfsym = int32(ctxt.numelfsym)
+	ctxt.loader.SetSymElfSym(loader.Sym(x.SymIdx), int32(ctxt.numelfsym))
 	ctxt.numelfsym++
 }
 
 func putelfsectionsym(ctxt *Link, out *OutBuf, s *sym.Symbol, shndx int) {
 	putelfsyment(out, 0, 0, 0, STB_LOCAL<<4|STT_SECTION, shndx, 0)
-	s.Elfsym = int32(ctxt.numelfsym)
+	ctxt.loader.SetSymElfSym(loader.Sym(s.SymIdx), int32(ctxt.numelfsym))
 	ctxt.numelfsym++
 }
 
@@ -224,7 +224,7 @@ func Asmelfsym(ctxt *Link) {
 	genasmsym(ctxt, putelfsym)
 }
 
-func putplan9sym(ctxt *Link, x *sym.Symbol, s string, typ SymbolType, addr int64, go_ *sym.Symbol) {
+func putplan9sym(ctxt *Link, x *sym.Symbol, s string, typ SymbolType, addr int64) {
 	t := int(typ)
 	switch typ {
 	case TextSym, DataSym, BSSSym:
@@ -327,9 +327,7 @@ func textsectionmap(ctxt *Link) (loader.Sym, uint32) {
 	return t.Sym(), uint32(n)
 }
 
-var symGroupType []sym.SymKind // temporarily assign a symbol's "group" type
+func (ctxt *Link) symtab() []sym.SymKind {
-
-func (ctxt *Link) symtab() {
 	ldr := ctxt.loader
 
 	if !ctxt.IsAIX() {
@@ -441,7 +439,7 @@ func (ctxt *Link) symtab() {
 	// just defined above will be first.
 	// hide the specific symbols.
 	nsym := loader.Sym(ldr.NSym())
-	symGroupType = make([]sym.SymKind, nsym)
+	symGroupType := make([]sym.SymKind, nsym)
 	for s := loader.Sym(1); s < nsym; s++ {
 		name := ldr.SymName(s)
 		if !ctxt.IsExternal() && isStaticTemp(name) {
@@ -709,6 +707,7 @@ func (ctxt *Link) symtab() {
 		lastmoduledatap.SetData(nil)
 		lastmoduledatap.AddAddr(ctxt.Arch, moduledata.Sym())
 	}
+	return symGroupType
 }
 
 func isStaticTemp(name string) bool {

src/cmd/link/internal/ld/target.go

@@ -61,6 +61,7 @@ func (t *Target) CanUsePlugins() bool {
 }
 
 func (t *Target) IsElf() bool {
+	t.mustSetHeadType()
 	return t.IsELF
 }
 
@@ -91,14 +92,30 @@ func (t *Target) IsARM() bool {
 	return t.Arch.Family == sys.ARM
 }
 
+func (t *Target) IsARM64() bool {
+	return t.Arch.Family == sys.ARM64
+}
+
 func (t *Target) IsAMD64() bool {
 	return t.Arch.Family == sys.AMD64
 }
 
+func (t *Target) IsMIPS() bool {
+	return t.Arch.Family == sys.MIPS
+}
+
+func (t *Target) IsMIPS64() bool {
+	return t.Arch.Family == sys.MIPS64
+}
+
 func (t *Target) IsPPC64() bool {
 	return t.Arch.Family == sys.PPC64
 }
 
+func (t *Target) IsRISCV64() bool {
+	return t.Arch.Family == sys.RISCV64
+}
+
 func (t *Target) IsS390X() bool {
 	return t.Arch.Family == sys.S390X
 }
@@ -112,37 +129,51 @@ func (t *Target) IsWasm() bool {
 //
 
 func (t *Target) IsLinux() bool {
+	t.mustSetHeadType()
 	return t.HeadType == objabi.Hlinux
 }
 
 func (t *Target) IsDarwin() bool {
+	t.mustSetHeadType()
 	return t.HeadType == objabi.Hdarwin
 }
 
 func (t *Target) IsWindows() bool {
+	t.mustSetHeadType()
 	return t.HeadType == objabi.Hwindows
 }
 
 func (t *Target) IsPlan9() bool {
+	t.mustSetHeadType()
 	return t.HeadType == objabi.Hplan9
 }
 
 func (t *Target) IsAIX() bool {
+	t.mustSetHeadType()
 	return t.HeadType == objabi.Haix
 }
 
 func (t *Target) IsSolaris() bool {
+	t.mustSetHeadType()
 	return t.HeadType == objabi.Hsolaris
 }
 
 func (t *Target) IsNetbsd() bool {
+	t.mustSetHeadType()
 	return t.HeadType == objabi.Hnetbsd
 }
 
 func (t *Target) IsOpenbsd() bool {
+	t.mustSetHeadType()
 	return t.HeadType == objabi.Hopenbsd
 }
 
+func (t *Target) mustSetHeadType() {
+	if t.HeadType == objabi.Hunknown {
+		panic("HeadType is not set")
+	}
+}
+
 //
 // MISC
 //

src/cmd/link/internal/ld/util.go

@@ -73,12 +73,12 @@ func Errorf(s *sym.Symbol, format string, args ...interface{}) {
 // Logging an error means that on exit cmd/link will delete any
 // output file and return a non-zero error code.
 func (ctxt *Link) Errorf(s loader.Sym, format string, args ...interface{}) {
-	if s != 0 && ctxt.loader != nil {
+	if ctxt.loader != nil {
-		sn := ctxt.loader.SymName(s)
+		ctxt.loader.Errorf(s, format, args...)
-		format = sn + ": " + format
+		return
-	} else {
-		format = fmt.Sprintf("sym %d: %s", s, format)
 	}
+	// Note: this is not expected to happen very often.
+	format = fmt.Sprintf("sym %d: %s", s, format)
 	format += "\n"
 	fmt.Fprintf(os.Stderr, format, args...)
 	afterErrorAction()

src/cmd/link/internal/ld/xcoff.go

@@ -360,7 +360,8 @@ type XcoffLdRel64 struct {
 // xcoffLoaderReloc holds information about a relocation made by the loader.
 type xcoffLoaderReloc struct {
 	sym    *sym.Symbol
-	rel    *sym.Reloc
+	sym2   loader.Sym
+	roff   int32
 	rtype  uint16
 	symndx int32
 }
@@ -567,11 +568,12 @@ var (
 
 // xcoffUpdateOuterSize stores the size of outer symbols in order to have it
 // in the symbol table.
-func xcoffUpdateOuterSize(ctxt *Link, size int64, stype sym.SymKind) {
+func xcoffUpdateOuterSize2(ctxt *Link, size int64, stype sym.SymKind) {
 	if size == 0 {
 		return
 	}
 
+	ldr := ctxt.loader
 	switch stype {
 	default:
 		Errorf(nil, "unknown XCOFF outer symbol for type %s", stype.String())
@@ -580,14 +582,16 @@ func xcoffUpdateOuterSize(ctxt *Link, size int64, stype sym.SymKind) {
 	case sym.STYPERELRO:
 		if ctxt.UseRelro() && (ctxt.BuildMode == BuildModeCArchive || ctxt.BuildMode == BuildModeCShared || ctxt.BuildMode == BuildModePIE) {
 			// runtime.types size must be removed, as it's a real symbol.
-			outerSymSize["typerel.*"] = size - ctxt.Syms.ROLookup("runtime.types", 0).Size
+			tsize := ldr.SymSize(ldr.Lookup("runtime.types", 0))
+			outerSymSize["typerel.*"] = size - tsize
 			return
 		}
 		fallthrough
 	case sym.STYPE:
 		if !ctxt.DynlinkingGo() {
 			// runtime.types size must be removed, as it's a real symbol.
-			outerSymSize["type.*"] = size - ctxt.Syms.ROLookup("runtime.types", 0).Size
+			tsize := ldr.SymSize(ldr.Lookup("runtime.types", 0))
+			outerSymSize["type.*"] = size - tsize
 		}
 	case sym.SGOSTRING:
 		outerSymSize["go.string.*"] = size
@@ -603,7 +607,6 @@ func xcoffUpdateOuterSize(ctxt *Link, size int64, stype sym.SymKind) {
 		outerSymSize["runtime.itablink"] = size
 
 	}
-
 }
 
 // addSymbol writes a symbol or an auxiliary symbol entry on ctxt.out.
@@ -780,19 +783,19 @@ func (f *xcoffFile) writeSymbolFunc(ctxt *Link, x *sym.Symbol) []xcoffSym {
 		// Trampoline don't have a FILE so there are considered
 		// in the current file.
 		// Same goes for runtime.text.X symbols.
-	} else if x.File == "" { // Undefined global symbol
+	} else if symPkg(ctxt, x) == "" { // Undefined global symbol
 		// If this happens, the algorithm must be redone.
 		if currSymSrcFile.name != "" {
 			Exitf("undefined global symbol found inside another file")
 		}
 	} else {
 		// Current file has changed. New C_FILE, C_DWARF, etc must be generated.
-		if currSymSrcFile.name != x.File {
+		if currSymSrcFile.name != symPkg(ctxt, x) {
 			if ctxt.LinkMode == LinkInternal {
 				// update previous file values
 				xfile.updatePreviousFile(ctxt, false)
-				currSymSrcFile.name = x.File
+				currSymSrcFile.name = symPkg(ctxt, x)
-				f.writeSymbolNewFile(ctxt, x.File, uint64(x.Value), xfile.getXCOFFscnum(x.Sect))
+				f.writeSymbolNewFile(ctxt, symPkg(ctxt, x), uint64(x.Value), xfile.getXCOFFscnum(x.Sect))
 			} else {
 				// With external linking, ld will crash if there is several
 				// .FILE and DWARF debugging enable, somewhere during
@@ -802,7 +805,7 @@ func (f *xcoffFile) writeSymbolFunc(ctxt *Link, x *sym.Symbol) []xcoffSym {
 				// TODO(aix); remove once ld has been fixed or the triggering
 				// relocation has been found and fixed.
 				if currSymSrcFile.name == "" {
-					currSymSrcFile.name = x.File
+					currSymSrcFile.name = symPkg(ctxt, x)
 					f.writeSymbolNewFile(ctxt, "go_functions", uint64(x.Value), xfile.getXCOFFscnum(x.Sect))
 				}
 			}
@@ -852,7 +855,7 @@ func (f *xcoffFile) writeSymbolFunc(ctxt *Link, x *sym.Symbol) []xcoffSym {
 }
 
 // put function used by genasmsym to write symbol table
-func putaixsym(ctxt *Link, x *sym.Symbol, str string, t SymbolType, addr int64, go_ *sym.Symbol) {
+func putaixsym(ctxt *Link, x *sym.Symbol, str string, t SymbolType, addr int64) {
 
 	// All XCOFF symbols generated by this GO symbols
 	// Can be a symbol entry or a auxiliary entry
@@ -863,7 +866,7 @@ func putaixsym(ctxt *Link, x *sym.Symbol, str string, t SymbolType, addr int64,
 		return
 
 	case TextSym:
-		if x.File != "" || strings.Contains(x.Name, "-tramp") || strings.HasPrefix(x.Name, "runtime.text.") {
+		if symPkg(ctxt, x) != "" || strings.Contains(x.Name, "-tramp") || strings.HasPrefix(x.Name, "runtime.text.") {
 			// Function within a file
 			syms = xfile.writeSymbolFunc(ctxt, x)
 		} else {
@@ -1106,51 +1109,55 @@ func (f *xcoffFile) adddynimpsym(ctxt *Link, s loader.Sym) {
 
 // Xcoffadddynrel adds a dynamic relocation in a XCOFF file.
 // This relocation will be made by the loader.
-func Xcoffadddynrel(target *Target, ldr *loader.Loader, s *sym.Symbol, r *sym.Reloc) bool {
+func Xcoffadddynrel2(target *Target, ldr *loader.Loader, syms *ArchSyms, s loader.Sym, r *loader.Reloc2, rIdx int) bool {
 	if target.IsExternal() {
 		return true
 	}
-	if s.Type <= sym.SPCLNTAB {
+	if ldr.SymType(s) <= sym.SPCLNTAB {
-		Errorf(s, "cannot have a relocation to %s in a text section symbol", r.Sym.Name)
+		ldr.Errorf(s, "cannot have a relocation to %s in a text section symbol", ldr.SymName(r.Sym()))
 		return false
 	}
 
 	xldr := &xcoffLoaderReloc{
-		sym: s,
+		sym2: s,
-		rel: r,
+		roff: r.Off(),
+	}
+	targ := r.Sym()
+	var targType sym.SymKind
+	if targ != 0 {
+		targType = ldr.SymType(targ)
 	}
 
-	switch r.Type {
+	switch r.Type() {
 	default:
-		Errorf(s, "unexpected .loader relocation to symbol: %s (type: %s)", r.Sym.Name, r.Type.String())
+		ldr.Errorf(s, "unexpected .loader relocation to symbol: %s (type: %s)", ldr.SymName(targ), r.Type().String())
 		return false
 	case objabi.R_ADDR:
-		if s.Type == sym.SXCOFFTOC && r.Sym.Type == sym.SDYNIMPORT {
+		if ldr.SymType(s) == sym.SXCOFFTOC && targType == sym.SDYNIMPORT {
 			// Imported symbol relocation
 			for i, dynsym := range xfile.loaderSymbols {
-				if ldr.Syms[dynsym.sym].Name == r.Sym.Name {
+				if ldr.SymName(dynsym.sym) == ldr.SymName(targ) {
 					xldr.symndx = int32(i + 3) // +3 because of 3 section symbols
 					break
 				}
 			}
-		} else if s.Type == sym.SDATA {
+		} else if t := ldr.SymType(s); t == sym.SDATA || t == sym.SNOPTRDATA || t == sym.SBUILDINFO || t == sym.SXCOFFTOC {
-			switch r.Sym.Sect.Seg {
+			switch ldr.SymSect(targ).Seg {
 			default:
-				Errorf(s, "unknown segment for .loader relocation with symbol %s", r.Sym.Name)
+				ldr.Errorf(s, "unknown segment for .loader relocation with symbol %s", ldr.SymName(targ))
 			case &Segtext:
 			case &Segrodata:
 				xldr.symndx = 0 // .text
 			case &Segdata:
-				if r.Sym.Type == sym.SBSS || r.Sym.Type == sym.SNOPTRBSS {
+				if targType == sym.SBSS || targType == sym.SNOPTRBSS {
 					xldr.symndx = 2 // .bss
 				} else {
 					xldr.symndx = 1 // .data
 				}
-
 			}
 
 		} else {
-			Errorf(s, "unexpected type for .loader relocation R_ADDR for symbol %s: %s to %s", r.Sym.Name, s.Type, r.Sym.Type)
+			ldr.Errorf(s, "unexpected type for .loader relocation R_ADDR for symbol %s: %s to %s", ldr.SymName(targ), ldr.SymType(s), ldr.SymType(targ))
 			return false
 		}
 
@@ -1301,14 +1308,18 @@ func (f *xcoffFile) writeLdrScn(ctxt *Link, globalOff uint64) {
 
 	off += uint64(16 * len(f.loaderReloc))
 	for _, r := range f.loaderReloc {
+		symp := r.sym
+		if symp == nil {
+			symp = ctxt.loader.Syms[r.sym2]
+		}
 		xldr = &XcoffLdRel64{
-			Lvaddr:  uint64(r.sym.Value + int64(r.rel.Off)),
+			Lvaddr:  uint64(symp.Value + int64(r.roff)),
 			Lrtype:  r.rtype,
 			Lsymndx: r.symndx,
 		}
 
-		if r.sym.Sect != nil {
+		if symp.Sect != nil {
-			xldr.Lrsecnm = f.getXCOFFscnum(r.sym.Sect)
+			xldr.Lrsecnm = f.getXCOFFscnum(symp.Sect)
 		}
 
 		reloctab = append(reloctab, xldr)
@@ -1389,45 +1400,6 @@ func (f *xcoffFile) writeLdrScn(ctxt *Link, globalOff uint64) {
 	}
 
 	f.loaderSize = off + uint64(stlen)
-
-	/* again for printing */
-	if !*flagA {
-		return
-	}
-
-	ctxt.Logf("\n.loader section")
-	// write in buf
-	var buf bytes.Buffer
-
-	binary.Write(&buf, ctxt.Arch.ByteOrder, hdr)
-	for _, s := range symtab {
-		binary.Write(&buf, ctxt.Arch.ByteOrder, s)
-
-	}
-	for _, f := range importtab {
-		buf.WriteString(f.Limpidpath)
-		buf.WriteByte(0)
-		buf.WriteString(f.Limpidbase)
-		buf.WriteByte(0)
-		buf.WriteString(f.Limpidmem)
-		buf.WriteByte(0)
-	}
-	for _, s := range strtab {
-		binary.Write(&buf, ctxt.Arch.ByteOrder, s.size)
-		buf.WriteString(s.name)
-		buf.WriteByte(0) // null terminator
-	}
-
-	// Log buffer
-	ctxt.Logf("\n\t%.8x|", globalOff)
-	for i, b := range buf.Bytes() {
-		if i > 0 && i%16 == 0 {
-			ctxt.Logf("\n\t%.8x|", uint64(globalOff)+uint64(i))
-		}
-		ctxt.Logf(" %.2x", b)
-	}
-	ctxt.Logf("\n")
-
 }
 
 // XCOFF assembling and writing file
@@ -1683,7 +1655,10 @@ func xcoffCreateExportFile(ctxt *Link) (fname string) {
 	fname = filepath.Join(*flagTmpdir, "export_file.exp")
 	var buf bytes.Buffer
 
-	for _, s := range ctxt.Syms.Allsym {
+	for _, s := range ctxt.loader.Syms {
+		if s == nil {
+			continue
+		}
 		if !s.Attr.CgoExport() {
 			continue
 		}

src/cmd/link/internal/ld/xcoff2.go

@@ -0,0 +1,113 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ld
+
+import (
+	"cmd/internal/objabi"
+	"cmd/link/internal/loader"
+	"cmd/link/internal/sym"
+)
+
+// Temporary dumping around for sym.Symbol version of helper
+// functions in xcoff.go, still being used for some archs/oses.
+// FIXME: get rid of this file when dodata() is completely
+// converted.
+
+// xcoffUpdateOuterSize stores the size of outer symbols in order to have it
+// in the symbol table.
+func xcoffUpdateOuterSize(ctxt *Link, size int64, stype sym.SymKind) {
+	if size == 0 {
+		return
+	}
+
+	switch stype {
+	default:
+		Errorf(nil, "unknown XCOFF outer symbol for type %s", stype.String())
+	case sym.SRODATA, sym.SRODATARELRO, sym.SFUNCTAB, sym.SSTRING:
+		// Nothing to do
+	case sym.STYPERELRO:
+		if ctxt.UseRelro() && (ctxt.BuildMode == BuildModeCArchive || ctxt.BuildMode == BuildModeCShared || ctxt.BuildMode == BuildModePIE) {
+			// runtime.types size must be removed, as it's a real symbol.
+			outerSymSize["typerel.*"] = size - ctxt.Syms.ROLookup("runtime.types", 0).Size
+			return
+		}
+		fallthrough
+	case sym.STYPE:
+		if !ctxt.DynlinkingGo() {
+			// runtime.types size must be removed, as it's a real symbol.
+			outerSymSize["type.*"] = size - ctxt.Syms.ROLookup("runtime.types", 0).Size
+		}
+	case sym.SGOSTRING:
+		outerSymSize["go.string.*"] = size
+	case sym.SGOFUNC:
+		if !ctxt.DynlinkingGo() {
+			outerSymSize["go.func.*"] = size
+		}
+	case sym.SGOFUNCRELRO:
+		outerSymSize["go.funcrel.*"] = size
+	case sym.SGCBITS:
+		outerSymSize["runtime.gcbits.*"] = size
+	case sym.SITABLINK:
+		outerSymSize["runtime.itablink"] = size
+
+	}
+}
+
+// Xcoffadddynrel adds a dynamic relocation in a XCOFF file.
+// This relocation will be made by the loader.
+func Xcoffadddynrel(target *Target, ldr *loader.Loader, s *sym.Symbol, r *sym.Reloc) bool {
+	if target.IsExternal() {
+		return true
+	}
+	if s.Type <= sym.SPCLNTAB {
+		Errorf(s, "cannot have a relocation to %s in a text section symbol", r.Sym.Name)
+		return false
+	}
+
+	xldr := &xcoffLoaderReloc{
+		sym:  s,
+		roff: r.Off,
+	}
+
+	switch r.Type {
+	default:
+		Errorf(s, "unexpected .loader relocation to symbol: %s (type: %s)", r.Sym.Name, r.Type.String())
+		return false
+	case objabi.R_ADDR:
+		if s.Type == sym.SXCOFFTOC && r.Sym.Type == sym.SDYNIMPORT {
+			// Imported symbol relocation
+			for i, dynsym := range xfile.loaderSymbols {
+				if ldr.Syms[dynsym.sym].Name == r.Sym.Name {
+					xldr.symndx = int32(i + 3) // +3 because of 3 section symbols
+					break
+				}
+			}
+		} else if s.Type == sym.SDATA || s.Type == sym.SNOPTRDATA || s.Type == sym.SBUILDINFO || s.Type == sym.SXCOFFTOC {
+			switch r.Sym.Sect.Seg {
+			default:
+				Errorf(s, "unknown segment for .loader relocation with symbol %s", r.Sym.Name)
+			case &Segtext:
+			case &Segrodata:
+				xldr.symndx = 0 // .text
+			case &Segdata:
+				if r.Sym.Type == sym.SBSS || r.Sym.Type == sym.SNOPTRBSS {
+					xldr.symndx = 2 // .bss
+				} else {
+					xldr.symndx = 1 // .data
+				}
+
+			}
+
+		} else {
+			Errorf(s, "unexpected type for .loader relocation R_ADDR for symbol %s: %s to %s", r.Sym.Name, s.Type, r.Sym.Type)
+			return false
+		}
+
+		xldr.rtype = 0x3F<<8 + XCOFF_R_POS
+	}
+
+	xfile.loaderReloc = append(xfile.loaderReloc, xldr)
+	return true
+}

src/cmd/link/internal/loader/loader.go

@@ -58,7 +58,7 @@ type Reloc2 struct {
 
 	// External reloc types may not fit into a uint8 which the Go object file uses.
 	// Store it here, instead of in the byte of goobj2.Reloc2.
-	// For Go symbols this will always be 0.
+	// For Go symbols this will always be zero.
 	// goobj2.Reloc2.Type() + typ is always the right type, for both Go and external
 	// symbols.
 	typ objabi.RelocType
@@ -73,6 +73,10 @@ func (rel Reloc2) SetType(t objabi.RelocType) {
 		panic("SetType: type doesn't fit into Reloc2")
 	}
 	rel.Reloc.SetType(uint8(t))
+	if rel.typ != 0 {
+		// should use SymbolBuilder.SetRelocType
+		panic("wrong method to set reloc type")
+	}
 }
 
 // Aux2 holds a "handle" to access an aux symbol record from an
@@ -143,6 +147,16 @@ func (bm Bitmap) Has(i Sym) bool {
 func (bm Bitmap) Len() int {
 	return len(bm) * 32
 }
+
+// return the number of bits set.
+func (bm Bitmap) Count() int {
+	s := 0
+	for _, x := range bm {
+		s += bits.OnesCount32(x)
+	}
+	return s
+}
+
 func MakeBitmap(n int) Bitmap {
 	return make(Bitmap, (n+31)/32)
 }
@@ -202,6 +216,8 @@ type Loader struct {
 	sects    []*sym.Section // sections
 	symSects []uint16       // symbol's section, index to sects array
 
+	outdata [][]byte // symbol's data in the output buffer
+
 	itablink map[Sym]struct{} // itablink[j] defined if j is go.itablink.*
 
 	objByPkg map[string]*oReader // map package path to its Go object reader
@@ -246,6 +262,8 @@ type Loader struct {
 	localentry  map[Sym]uint8       // stores Localentry symbol attribute
 	extname     map[Sym]string      // stores Extname symbol attribute
 	elfType     map[Sym]elf.SymType // stores elf type symbol property
+	elfSym      map[Sym]int32       // stores elf sym symbol property
+	localElfSym map[Sym]int32       // stores "local" elf sym symbol property
 	symPkg      map[Sym]string      // stores package for symbol, or library for shlib-derived syms
 	plt         map[Sym]int32       // stores dynimport for pe objects
 	got         map[Sym]int32       // stores got for pe objects
@@ -266,6 +284,8 @@ type Loader struct {
 
 	elfsetstring elfsetstringFunc
 
+	errorReporter *ErrorReporter
+
 	SymLookup func(name string, ver int) *sym.Symbol
 }
 
@@ -297,9 +317,9 @@ const (
 	FlagStrictDups = 1 << iota
 )
 
-func NewLoader(flags uint32, elfsetstring elfsetstringFunc) *Loader {
+func NewLoader(flags uint32, elfsetstring elfsetstringFunc, reporter *ErrorReporter) *Loader {
 	nbuiltin := goobj2.NBuiltin()
-	return &Loader{
+	ldr := &Loader{
 		start:                make(map[*oReader]Sym),
 		objs:                 []objIdx{{}}, // reserve index 0 for nil symbol
 		objSyms:              []objSym{{}}, // reserve index 0 for nil symbol
@@ -315,6 +335,8 @@ func NewLoader(flags uint32, elfsetstring elfsetstringFunc) *Loader {
 		extname:              make(map[Sym]string),
 		attrReadOnly:         make(map[Sym]bool),
 		elfType:              make(map[Sym]elf.SymType),
+		elfSym:               make(map[Sym]int32),
+		localElfSym:          make(map[Sym]int32),
 		symPkg:               make(map[Sym]string),
 		plt:                  make(map[Sym]int32),
 		got:                  make(map[Sym]int32),
@@ -328,8 +350,11 @@ func NewLoader(flags uint32, elfsetstring elfsetstringFunc) *Loader {
 		builtinSyms:          make([]Sym, nbuiltin),
 		flags:                flags,
 		elfsetstring:         elfsetstring,
+		errorReporter:        reporter,
 		sects:                []*sym.Section{nil}, // reserve index 0 for nil section
 	}
+	reporter.ldr = ldr
+	return ldr
 }
 
 // Add object file r, return the start index.
@@ -616,6 +641,11 @@ func (l *Loader) NDef() int {
 	return int(l.extStart)
 }
 
+// Number of reachable symbols.
+func (l *Loader) NReachableSym() int {
+	return l.attrReachable.Count()
+}
+
 // Returns the raw (unpatched) name of the i-th symbol.
 func (l *Loader) RawSymName(i Sym) string {
 	if l.IsExternal(i) {
@@ -732,6 +762,14 @@ func (l *Loader) SetAttrLocal(i Sym, v bool) {
 	}
 }
 
+// SymAddr checks that a symbol is reachable, and returns its value.
+func (l *Loader) SymAddr(i Sym) int64 {
+	if !l.AttrReachable(i) {
+		panic("unreachable symbol in symaddr")
+	}
+	return l.values[i]
+}
+
 // AttrNotInSymbolTable returns true for symbols that should not be
 // added to the symbol table of the final generated load module.
 func (l *Loader) AttrNotInSymbolTable(i Sym) bool {
@@ -1026,6 +1064,11 @@ func (l *Loader) SetSymValue(i Sym, val int64) {
 	l.values[i] = val
 }
 
+// AddToSymValue adds to the value of the i-th symbol. i is the global index.
+func (l *Loader) AddToSymValue(i Sym, val int64) {
+	l.values[i] += val
+}
+
 // Returns the symbol content of the i-th symbol. i is global index.
 func (l *Loader) Data(i Sym) []byte {
 	if l.IsExternal(i) {
@@ -1039,6 +1082,32 @@ func (l *Loader) Data(i Sym) []byte {
 	return r.Data(li)
 }
 
+// Returns the data of the i-th symbol in the output buffer.
+func (l *Loader) OutData(i Sym) []byte {
+	if int(i) < len(l.outdata) && l.outdata[i] != nil {
+		return l.outdata[i]
+	}
+	return l.Data(i)
+}
+
+// SetOutData sets the position of the data of the i-th symbol in the output buffer.
+// i is global index.
+func (l *Loader) SetOutData(i Sym, data []byte) {
+	if l.IsExternal(i) {
+		pp := l.getPayload(i)
+		if pp != nil {
+			pp.data = data
+			return
+		}
+	}
+	l.outdata[i] = data
+}
+
+// InitOutData initializes the slice used to store symbol output data.
+func (l *Loader) InitOutData() {
+	l.outdata = make([][]byte, l.extStart)
+}
+
 // SymAlign returns the alignment for a symbol.
 func (l *Loader) SymAlign(i Sym) int32 {
 	// If an alignment has been recorded, return that.
@@ -1075,6 +1144,12 @@ func (l *Loader) SetSymAlign(i Sym, align int32) {
 
 // SymValue returns the section of the i-th symbol. i is global index.
 func (l *Loader) SymSect(i Sym) *sym.Section {
+	if int(i) >= len(l.symSects) {
+		// symSects is extended lazily -- it the sym in question is
+		// outside the range of the existing slice, then we assume its
+		// section has not yet been set.
+		return nil
+	}
 	return l.sects[l.symSects[i]]
 }
 
@@ -1192,6 +1267,42 @@ func (l *Loader) SetSymElfType(i Sym, et elf.SymType) {
 	}
 }
 
+// SymElfSym returns the ELF symbol index for a given loader
+// symbol, assigned during ELF symtab generation.
+func (l *Loader) SymElfSym(i Sym) int32 {
+	return l.elfSym[i]
+}
+
+// SetSymElfSym sets the elf symbol index for a symbol.
+func (l *Loader) SetSymElfSym(i Sym, es int32) {
+	if i == 0 {
+		panic("bad sym index")
+	}
+	if es == 0 {
+		delete(l.elfSym, i)
+	} else {
+		l.elfSym[i] = es
+	}
+}
+
+// SymLocalElfSym returns the "local" ELF symbol index for a given loader
+// symbol, assigned during ELF symtab generation.
+func (l *Loader) SymLocalElfSym(i Sym) int32 {
+	return l.localElfSym[i]
+}
+
+// SetSymLocalElfSym sets the "local" elf symbol index for a symbol.
+func (l *Loader) SetSymLocalElfSym(i Sym, es int32) {
+	if i == 0 {
+		panic("bad sym index")
+	}
+	if es == 0 {
+		delete(l.localElfSym, i)
+	} else {
+		l.localElfSym[i] = es
+	}
+}
+
 // SymPlt returns the plt value for pe symbols.
 func (l *Loader) SymPlt(s Sym) int32 {
 	if v, ok := l.plt[s]; ok {
@@ -1253,6 +1364,18 @@ func (l *Loader) SetSymDynid(i Sym, val int32) {
 	}
 }
 
+// DynIdSyms returns the set of symbols for which dynID is set to an
+// interesting (non-default) value. This is expected to be a fairly
+// small set.
+func (l *Loader) DynidSyms() []Sym {
+	sl := make([]Sym, 0, len(l.dynid))
+	for s := range l.dynid {
+		sl = append(sl, s)
+	}
+	sort.Slice(sl, func(i, j int) bool { return sl[i] < sl[j] })
+	return sl
+}
+
 // SymGoType returns the 'Gotype' property for a given symbol (set by
 // the Go compiler for variable symbols). This version relies on
 // reading aux symbols for the target sym -- it could be that a faster
@@ -1734,7 +1857,8 @@ func (l *Loader) FuncInfo(i Sym) FuncInfo {
 // Preload a package: add autolibs, add defined package symbols to the symbol table.
 // Does not add non-package symbols yet, which will be done in LoadNonpkgSyms.
 // Does not read symbol data.
-func (l *Loader) Preload(syms *sym.Symbols, f *bio.Reader, lib *sym.Library, unit *sym.CompilationUnit, length int64, flags int) {
+// Returns the fingerprint of the object.
+func (l *Loader) Preload(syms *sym.Symbols, f *bio.Reader, lib *sym.Library, unit *sym.CompilationUnit, length int64) goobj2.FingerprintType {
 	roObject, readonly, err := f.Slice(uint64(length))
 	if err != nil {
 		log.Fatal("cannot read object file:", err)
@@ -1753,7 +1877,7 @@ func (l *Loader) Preload(syms *sym.Symbols, f *bio.Reader, lib *sym.Library, uni
 	or := &oReader{r, unit, localSymVersion, r.Flags(), pkgprefix, make([]Sym, ndef+nnonpkgdef+r.NNonpkgref()), ndef, uint32(len(l.objs))}
 
 	// Autolib
-	lib.ImportStrings = append(lib.ImportStrings, r.Autolib()...)
+	lib.Autolib = append(lib.Autolib, r.Autolib()...)
 
 	// DWARF file table
 	nfile := r.NDwarfFile()
@@ -1767,6 +1891,8 @@ func (l *Loader) Preload(syms *sym.Symbols, f *bio.Reader, lib *sym.Library, uni
 
 	// The caller expects us consuming all the data
 	f.MustSeek(length, os.SEEK_CUR)
+
+	return r.Fingerprint()
 }
 
 // Preload symbols of given kind from an object.
@@ -1890,7 +2016,7 @@ func (l *Loader) preprocess(arch *sys.Arch, s Sym, name string) {
 }
 
 // Load full contents.
-func (l *Loader) LoadFull(arch *sys.Arch, syms *sym.Symbols) {
+func (l *Loader) LoadFull(arch *sys.Arch, syms *sym.Symbols, needReloc bool) {
 	// create all Symbols first.
 	l.growSyms(l.NSym())
 	l.growSects(l.NSym())
@@ -1923,7 +2049,9 @@ func (l *Loader) LoadFull(arch *sys.Arch, syms *sym.Symbols) {
 	}
 
 	// allocate a single large slab of relocations for all live symbols
+	if needReloc {
 		l.relocBatch = make([]sym.Reloc, nr)
+	}
 
 	// convert payload-based external symbols into sym.Symbol-based
 	for _, i := range toConvert {
@@ -1934,21 +2062,15 @@ func (l *Loader) LoadFull(arch *sys.Arch, syms *sym.Symbols) {
 		s.Version = int16(pp.ver)
 		s.Type = pp.kind
 		s.Size = pp.size
-		if pp.gotype != 0 {
-			s.Gotype = l.Syms[pp.gotype]
-		}
-		if f, ok := l.symPkg[i]; ok {
-			s.File = f
-		} else if pp.objidx != 0 {
-			s.File = l.objs[pp.objidx].r.unit.Lib.Pkg
-		}
 
 		// Copy relocations
+		if needReloc {
 			batch := l.relocBatch
 			s.R = batch[:len(pp.relocs):len(pp.relocs)]
 			l.relocBatch = batch[len(pp.relocs):]
 			relocs := l.Relocs(i)
 			l.convertRelocations(i, &relocs, s, false)
+		}
 
 		// Copy data
 		s.P = pp.data
@@ -1959,7 +2081,7 @@ func (l *Loader) LoadFull(arch *sys.Arch, syms *sym.Symbols) {
 
 	// load contents of defined symbols
 	for _, o := range l.objs[1:] {
-		loadObjFull(l, o.r)
+		loadObjFull(l, o.r, needReloc)
 	}
 
 	// Note: resolution of ABI aliases is now also handled in
@@ -2103,22 +2225,7 @@ func (l *Loader) PropagateLoaderChangesToSymbols(toconvert []Sym, anonVerReplace
 			relfix = true
 		}
 
-		// For 'new' symbols, copy other content (such as Gotype,
+		// For 'new' symbols, copy other content.
-		// sym file, relocations, etc).
-		if isnew {
-			if gt := l.SymGoType(cand); gt != 0 {
-				s.Gotype = l.Syms[gt]
-			}
-			if f, ok := l.symPkg[cand]; ok {
-				s.File = f
-			} else {
-				r, _ := l.toLocal(cand)
-				if r != nil && r != l.extReader {
-					s.File = l.SymPkg(cand)
-				}
-			}
-		}
-
 		if relfix {
 			relocfixup = append(relocfixup, cand)
 		}
@@ -2165,7 +2272,6 @@ func (l *Loader) ExtractSymbols(syms *sym.Symbols) {
 		if s == nil {
 			continue
 		}
-		syms.Allsym = append(syms.Allsym, s) // XXX still add to Allsym for now, as there are code looping through Allsym
 		if s.Version < 0 {
 			s.Version = int16(anonVerReplacement)
 		}
@@ -2179,7 +2285,6 @@ func (l *Loader) ExtractSymbols(syms *sym.Symbols) {
 		}
 		s := l.allocSym(name, ver)
 		l.installSym(i, s)
-		syms.Allsym = append(syms.Allsym, s) // XXX see above
 		return s
 	}
 	syms.Lookup = l.SymLookup
@@ -2191,7 +2296,6 @@ func (l *Loader) ExtractSymbols(syms *sym.Symbols) {
 		i := l.newExtSym(name, ver)
 		s := l.allocSym(name, ver)
 		l.installSym(i, s)
-		syms.Allsym = append(syms.Allsym, s) // XXX see above
 		return s
 	}
 }
@@ -2221,6 +2325,7 @@ func (l *Loader) installSym(i Sym, s *sym.Symbol) {
 		panic("sym already present in installSym")
 	}
 	l.Syms[i] = s
+	s.SymIdx = sym.LoaderSym(i)
 }
 
 // addNewSym adds a new sym.Symbol to the i-th index in the list of symbols.
@@ -2234,12 +2339,35 @@ func (l *Loader) addNewSym(i Sym, name string, ver int, unit *sym.CompilationUni
 		t = s.Type
 	}
 	s.Type = t
-	s.Unit = unit
 	l.growSyms(int(i))
 	l.installSym(i, s)
 	return s
 }
 
+// TopLevelSym tests a symbol (by name and kind) to determine whether
+// the symbol first class sym (participating in the link) or is an
+// anonymous aux or sub-symbol containing some sub-part or payload of
+// another symbol.
+func (l *Loader) TopLevelSym(s Sym) bool {
+	return topLevelSym(l.RawSymName(s), l.SymType(s))
+}
+
+// topLevelSym tests a symbol name and kind to determine whether
+// the symbol first class sym (participating in the link) or is an
+// anonymous aux or sub-symbol containing some sub-part or payload of
+// another symbol.
+func topLevelSym(sname string, skind sym.SymKind) bool {
+	if sname != "" {
+		return true
+	}
+	switch skind {
+	case sym.SDWARFINFO, sym.SDWARFRANGE, sym.SDWARFLOC, sym.SDWARFLINES, sym.SGOFUNC:
+		return true
+	default:
+		return false
+	}
+}
+
 // loadObjSyms creates sym.Symbol objects for the live Syms in the
 // object corresponding to object reader "r". Return value is the
 // number of sym.Reloc entries required for all the new symbols.
@@ -2253,17 +2381,12 @@ func loadObjSyms(l *Loader, syms *sym.Symbols, r *oReader) int {
 		osym := r.Sym(i)
 		name := strings.Replace(osym.Name(r.Reader), "\"\".", r.pkgprefix, -1)
 		t := sym.AbiSymKindToSymKind[objabi.SymKind(osym.Type())]
-		// NB: for the test below, we can skip most anonymous symbols
+
-		// since they will never be turned into sym.Symbols (eg:
+		// Skip non-dwarf anonymous symbols (e.g. funcdata),
-		// funcdata). DWARF symbols are an exception however -- we
+		// since they will never be turned into sym.Symbols.
-		// want to include all reachable but nameless DWARF symbols.
+		if !topLevelSym(name, t) {
-		if name == "" {
-			switch t {
-			case sym.SDWARFINFO, sym.SDWARFRANGE, sym.SDWARFLOC, sym.SDWARFLINES:
-			default:
 			continue
 		}
-		}
 		ver := abiToVer(osym.ABI(), r.version)
 		if t == sym.SXREF {
 			log.Fatalf("bad sxref")
@@ -2479,12 +2602,7 @@ func (l *Loader) CreateStaticSym(name string) Sym {
 	return l.newExtSym(name, l.anonVersion)
 }
 
-func loadObjFull(l *Loader, r *oReader) {
+func loadObjFull(l *Loader, r *oReader, needReloc bool) {
-	resolveSymRef := func(s goobj2.SymRef) *sym.Symbol {
-		i := l.resolve(r, s)
-		return l.Syms[i]
-	}
-
 	for i, n := 0, r.NSym()+r.NNonpkgdef(); i < n; i++ {
 		// A symbol may be a dup or overwritten. In this case, its
 		// content will actually be provided by a different object
@@ -2506,27 +2624,23 @@ func loadObjFull(l *Loader, r *oReader) {
 		size := osym.Siz()
 
 		// Symbol data
-		s.P = r.Data(i)
+		s.P = l.OutData(gi)
-		s.Attr.Set(sym.AttrReadOnly, r.ReadOnly())
 
 		// Relocs
+		if needReloc {
 			relocs := l.relocs(r, i)
 			batch := l.relocBatch
 			s.R = batch[:relocs.Count():relocs.Count()]
 			l.relocBatch = batch[relocs.Count():]
 			l.convertRelocations(gi, &relocs, s, false)
+		}
 
 		// Aux symbol info
 		auxs := r.Auxs(i)
 		for j := range auxs {
 			a := &auxs[j]
 			switch a.Type() {
-			case goobj2.AuxGotype:
+			case goobj2.AuxFuncInfo, goobj2.AuxFuncdata, goobj2.AuxGotype:
-				typ := resolveSymRef(a.Sym())
-				if typ != nil {
-					s.Gotype = typ
-				}
-			case goobj2.AuxFuncInfo, goobj2.AuxFuncdata:
 				// already handled
 			case goobj2.AuxDwarfInfo, goobj2.AuxDwarfLoc, goobj2.AuxDwarfRanges, goobj2.AuxDwarfLines:
 				// ignored for now
@@ -2535,7 +2649,6 @@ func loadObjFull(l *Loader, r *oReader) {
 			}
 		}
 
-		s.File = r.pkgprefix[:len(r.pkgprefix)-1]
 		if s.Size < int64(size) {
 			s.Size = int64(size)
 		}
@@ -2744,6 +2857,42 @@ func (l *Loader) AssignTextSymbolOrder(libs []*sym.Library, intlibs []bool, exts
 	return textp2
 }
 
+// ErrorReporter is a helper class for reporting errors.
+type ErrorReporter struct {
+	ldr              *Loader
+	AfterErrorAction func()
+}
+
+// Errorf method logs an error message.
+//
+// After each error, the error actions function will be invoked; this
+// will either terminate the link immediately (if -h option given)
+// or it will keep a count and exit if more than 20 errors have been printed.
+//
+// Logging an error means that on exit cmd/link will delete any
+// output file and return a non-zero error code.
+//
+func (reporter *ErrorReporter) Errorf(s Sym, format string, args ...interface{}) {
+	if s != 0 && reporter.ldr.SymName(s) != "" {
+		format = reporter.ldr.SymName(s) + ": " + format
+	} else {
+		format = fmt.Sprintf("sym %d: %s", s, format)
+	}
+	format += "\n"
+	fmt.Fprintf(os.Stderr, format, args...)
+	reporter.AfterErrorAction()
+}
+
+// GetErrorReporter returns the loader's associated error reporter.
+func (l *Loader) GetErrorReporter() *ErrorReporter {
+	return l.errorReporter
+}
+
+// Errorf method logs an error message. See ErrorReporter.Errorf for details.
+func (l *Loader) Errorf(s Sym, format string, args ...interface{}) {
+	l.errorReporter.Errorf(s, format, args...)
+}
+
 // For debugging.
 func (l *Loader) Dump() {
 	fmt.Println("objs")

src/cmd/link/internal/loader/loader_test.go

@@ -27,9 +27,16 @@ func addDummyObjSym(t *testing.T, ldr *Loader, or *oReader, name string) Sym {
 	return s
 }
 
-func TestAddMaterializedSymbol(t *testing.T) {
+func mkLoader() *Loader {
 	edummy := func(s *sym.Symbol, str string, off int) {}
-	ldr := NewLoader(0, edummy)
+	er := ErrorReporter{}
+	ldr := NewLoader(0, edummy, &er)
+	er.ldr = ldr
+	return ldr
+}
+
+func TestAddMaterializedSymbol(t *testing.T) {
+	ldr := mkLoader()
 	dummyOreader := oReader{version: -1, syms: make([]Sym, 100)}
 	or := &dummyOreader
 
@@ -229,8 +236,7 @@ func sameRelocSlice(s1 *Relocs, s2 []Reloc) bool {
 type addFunc func(l *Loader, s Sym, s2 Sym) Sym
 
 func TestAddDataMethods(t *testing.T) {
-	edummy := func(s *sym.Symbol, str string, off int) {}
+	ldr := mkLoader()
-	ldr := NewLoader(0, edummy)
 	dummyOreader := oReader{version: -1, syms: make([]Sym, 100)}
 	or := &dummyOreader
 
@@ -352,8 +358,7 @@ func TestAddDataMethods(t *testing.T) {
 }
 
 func TestOuterSub(t *testing.T) {
-	edummy := func(s *sym.Symbol, str string, off int) {}
+	ldr := mkLoader()
-	ldr := NewLoader(0, edummy)
 	dummyOreader := oReader{version: -1, syms: make([]Sym, 100)}
 	or := &dummyOreader
 

src/cmd/link/internal/loader/symbolbuilder.go

@@ -143,6 +143,22 @@ func (sb *SymbolBuilder) SetRelocs(rslice []Reloc) {
 	}
 }
 
+// SetRelocType sets the type of the 'i'-th relocation on this sym to 't'
+func (sb *SymbolBuilder) SetRelocType(i int, t objabi.RelocType) {
+	sb.relocs[i].SetType(0)
+	sb.reltypes[i] = t
+}
+
+// SetRelocSym sets the target sym of the 'i'-th relocation on this sym to 's'
+func (sb *SymbolBuilder) SetRelocSym(i int, tgt Sym) {
+	sb.relocs[i].SetSym(goobj2.SymRef{PkgIdx: 0, SymIdx: uint32(tgt)})
+}
+
+// SetRelocAdd sets the addend of the 'i'-th relocation on this sym to 'a'
+func (sb *SymbolBuilder) SetRelocAdd(i int, a int64) {
+	sb.relocs[i].SetAdd(a)
+}
+
 // Add n relocations, return a handle to the relocations.
 func (sb *SymbolBuilder) AddRelocs(n int) Relocs {
 	sb.relocs = append(sb.relocs, make([]goobj2.Reloc, n)...)
@@ -431,3 +447,10 @@ func GenAddAddrPlusFunc(internalExec bool) func(s *SymbolBuilder, arch *sys.Arch
 		return (*SymbolBuilder).AddAddrPlus
 	}
 }
+
+func (sb *SymbolBuilder) MakeWritable() {
+	if sb.ReadOnly() {
+		sb.data = append([]byte(nil), sb.data...)
+		sb.l.SetAttrReadOnly(sb.symIdx, false)
+	}
+}

src/cmd/link/internal/mips/asm.go

@@ -54,7 +54,7 @@ func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s *sym.
 func elfreloc1(ctxt *ld.Link, r *sym.Reloc, sectoff int64) bool {
 	ctxt.Out.Write32(uint32(sectoff))
 
-	elfsym := r.Xsym.ElfsymForReloc()
+	elfsym := ld.ElfSymForReloc(ctxt, r.Xsym)
 	switch r.Type {
 	default:
 		return false
@@ -164,7 +164,7 @@ func archrelocvariant(target *ld.Target, syms *ld.ArchSyms, r *sym.Reloc, s *sym
 	return -1
 }
 
-func asmb(ctxt *ld.Link) {
+func asmb(ctxt *ld.Link, _ *loader.Loader) {
 	if ctxt.IsELF {
 		ld.Asmbelfsetup()
 	}

src/cmd/link/internal/mips64/asm.go

@@ -61,7 +61,7 @@ func elfreloc1(ctxt *ld.Link, r *sym.Reloc, sectoff int64) bool {
 
 	ctxt.Out.Write64(uint64(sectoff))
 
-	elfsym := r.Xsym.ElfsymForReloc()
+	elfsym := ld.ElfSymForReloc(ctxt, r.Xsym)
 	ctxt.Out.Write32(uint32(elfsym))
 	ctxt.Out.Write8(0)
 	ctxt.Out.Write8(0)
@@ -170,7 +170,7 @@ func archrelocvariant(target *ld.Target, syms *ld.ArchSyms, r *sym.Reloc, s *sym
 	return -1
 }
 
-func asmb(ctxt *ld.Link) {
+func asmb(ctxt *ld.Link, _ *loader.Loader) {
 	if ctxt.IsELF {
 		ld.Asmbelfsetup()
 	}

src/cmd/link/internal/ppc64/asm.go

@@ -267,120 +267,134 @@ func gencallstub2(ctxt *ld.Link, ldr *loader.Loader, abicase int, stub *loader.S
 	stub.AddUint32(ctxt.Arch, 0x4e800420) // bctr
 }
 
-func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s *sym.Symbol, r *sym.Reloc) bool {
+func adddynrel2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loader.Sym, r *loader.Reloc2, rIdx int) bool {
 	if target.IsElf() {
-		return addelfdynrel(target, syms, s, r)
+		return addelfdynrel2(target, ldr, syms, s, r, rIdx)
 	} else if target.IsAIX() {
-		return ld.Xcoffadddynrel(target, ldr, s, r)
+		return ld.Xcoffadddynrel2(target, ldr, syms, s, r, rIdx)
 	}
 	return false
 }
 
-func addelfdynrel(target *ld.Target, syms *ld.ArchSyms, s *sym.Symbol, r *sym.Reloc) bool {
+func addelfdynrel2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loader.Sym, r *loader.Reloc2, rIdx int) bool {
-	targ := r.Sym
+	targ := r.Sym()
-	r.InitExt()
+	var targType sym.SymKind
+	if targ != 0 {
+		targType = ldr.SymType(targ)
+	}
 
-	switch r.Type {
+	switch r.Type() {
 	default:
-		if r.Type >= objabi.ElfRelocOffset {
+		if r.Type() >= objabi.ElfRelocOffset {
-			ld.Errorf(s, "unexpected relocation type %d (%s)", r.Type, sym.RelocName(target.Arch, r.Type))
+			ldr.Errorf(s, "unexpected relocation type %d (%s)", r.Type(), sym.RelocName(target.Arch, r.Type()))
 			return false
 		}
 
 		// Handle relocations found in ELF object files.
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_REL24):
-		r.Type = objabi.R_CALLPOWER
+		su := ldr.MakeSymbolUpdater(s)
+		su.SetRelocType(rIdx, objabi.R_CALLPOWER)
 
 		// This is a local call, so the caller isn't setting
 		// up r12 and r2 is the same for the caller and
 		// callee. Hence, we need to go to the local entry
 		// point.  (If we don't do this, the callee will try
 		// to use r12 to compute r2.)
-		r.Add += int64(r.Sym.Localentry()) * 4
+		su.SetRelocAdd(rIdx, r.Add()+int64(ldr.SymLocalentry(targ))*4)
 
-		if targ.Type == sym.SDYNIMPORT {
+		if targType == sym.SDYNIMPORT {
 			// Should have been handled in elfsetupplt
-			ld.Errorf(s, "unexpected R_PPC64_REL24 for dyn import")
+			ldr.Errorf(s, "unexpected R_PPC64_REL24 for dyn import")
 		}
 
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC_REL32):
-		r.Type = objabi.R_PCREL
+		su := ldr.MakeSymbolUpdater(s)
-		r.Add += 4
+		su.SetRelocType(rIdx, objabi.R_PCREL)
+		su.SetRelocAdd(rIdx, r.Add()+4)
 
-		if targ.Type == sym.SDYNIMPORT {
+		if targType == sym.SDYNIMPORT {
-			ld.Errorf(s, "unexpected R_PPC_REL32 for dyn import")
+			ldr.Errorf(s, "unexpected R_PPC_REL32 for dyn import")
 		}
 
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_ADDR64):
-		r.Type = objabi.R_ADDR
+		su := ldr.MakeSymbolUpdater(s)
-		if targ.Type == sym.SDYNIMPORT {
+		su.SetRelocType(rIdx, objabi.R_ADDR)
+		if targType == sym.SDYNIMPORT {
 			// These happen in .toc sections
-			ld.Adddynsym(target, syms, targ)
+			ld.Adddynsym2(ldr, target, syms, targ)
 
-			rela := syms.Rela
+			rela := ldr.MakeSymbolUpdater(syms.Rela2)
-			rela.AddAddrPlus(target.Arch, s, int64(r.Off))
+			rela.AddAddrPlus(target.Arch, s, int64(r.Off()))
-			rela.AddUint64(target.Arch, ld.ELF64_R_INFO(uint32(targ.Dynid), uint32(elf.R_PPC64_ADDR64)))
+			rela.AddUint64(target.Arch, ld.ELF64_R_INFO(uint32(ldr.SymDynid(targ)), uint32(elf.R_PPC64_ADDR64)))
-			rela.AddUint64(target.Arch, uint64(r.Add))
+			rela.AddUint64(target.Arch, uint64(r.Add()))
-			r.Type = objabi.ElfRelocOffset // ignore during relocsym
+			su.SetRelocType(rIdx, objabi.ElfRelocOffset) // ignore during relocsym
 		}
-
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_TOC16):
-		r.Type = objabi.R_POWER_TOC
+		su := ldr.MakeSymbolUpdater(s)
-		r.Variant = sym.RV_POWER_LO | sym.RV_CHECK_OVERFLOW
+		su.SetRelocType(rIdx, objabi.R_POWER_TOC)
+		ldr.SetRelocVariant(s, rIdx, sym.RV_POWER_LO|sym.RV_CHECK_OVERFLOW)
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_TOC16_LO):
-		r.Type = objabi.R_POWER_TOC
+		su := ldr.MakeSymbolUpdater(s)
-		r.Variant = sym.RV_POWER_LO
+		su.SetRelocType(rIdx, objabi.R_POWER_TOC)
+		ldr.SetRelocVariant(s, rIdx, sym.RV_POWER_LO)
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_TOC16_HA):
-		r.Type = objabi.R_POWER_TOC
+		su := ldr.MakeSymbolUpdater(s)
-		r.Variant = sym.RV_POWER_HA | sym.RV_CHECK_OVERFLOW
+		su.SetRelocType(rIdx, objabi.R_POWER_TOC)
+		ldr.SetRelocVariant(s, rIdx, sym.RV_POWER_HA|sym.RV_CHECK_OVERFLOW)
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_TOC16_HI):
-		r.Type = objabi.R_POWER_TOC
+		su := ldr.MakeSymbolUpdater(s)
-		r.Variant = sym.RV_POWER_HI | sym.RV_CHECK_OVERFLOW
+		su.SetRelocType(rIdx, objabi.R_POWER_TOC)
+		ldr.SetRelocVariant(s, rIdx, sym.RV_POWER_HI|sym.RV_CHECK_OVERFLOW)
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_TOC16_DS):
-		r.Type = objabi.R_POWER_TOC
+		su := ldr.MakeSymbolUpdater(s)
-		r.Variant = sym.RV_POWER_DS | sym.RV_CHECK_OVERFLOW
+		su.SetRelocType(rIdx, objabi.R_POWER_TOC)
+		ldr.SetRelocVariant(s, rIdx, sym.RV_POWER_DS|sym.RV_CHECK_OVERFLOW)
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_TOC16_LO_DS):
-		r.Type = objabi.R_POWER_TOC
+		su := ldr.MakeSymbolUpdater(s)
-		r.Variant = sym.RV_POWER_DS
+		su.SetRelocType(rIdx, objabi.R_POWER_TOC)
+		ldr.SetRelocVariant(s, rIdx, sym.RV_POWER_DS)
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_REL16_LO):
-		r.Type = objabi.R_PCREL
+		su := ldr.MakeSymbolUpdater(s)
-		r.Variant = sym.RV_POWER_LO
+		su.SetRelocType(rIdx, objabi.R_PCREL)
-		r.Add += 2 // Compensate for relocation size of 2
+		ldr.SetRelocVariant(s, rIdx, sym.RV_POWER_LO)
+		su.SetRelocAdd(rIdx, r.Add()+2) // Compensate for relocation size of 2
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_REL16_HI):
-		r.Type = objabi.R_PCREL
+		su := ldr.MakeSymbolUpdater(s)
-		r.Variant = sym.RV_POWER_HI | sym.RV_CHECK_OVERFLOW
+		su.SetRelocType(rIdx, objabi.R_PCREL)
-		r.Add += 2
+		ldr.SetRelocVariant(s, rIdx, sym.RV_POWER_HI|sym.RV_CHECK_OVERFLOW)
+		su.SetRelocAdd(rIdx, r.Add()+2)
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_REL16_HA):
-		r.Type = objabi.R_PCREL
+		su := ldr.MakeSymbolUpdater(s)
-		r.Variant = sym.RV_POWER_HA | sym.RV_CHECK_OVERFLOW
+		su.SetRelocType(rIdx, objabi.R_PCREL)
-		r.Add += 2
+		ldr.SetRelocVariant(s, rIdx, sym.RV_POWER_HA|sym.RV_CHECK_OVERFLOW)
+		su.SetRelocAdd(rIdx, r.Add()+2)
 		return true
 	}
 
 	// Handle references to ELF symbols from our own object files.
-	if targ.Type != sym.SDYNIMPORT {
+	if targType != sym.SDYNIMPORT {
 		return true
 	}
 
@@ -439,7 +453,7 @@ func elfreloc1(ctxt *ld.Link, r *sym.Reloc, sectoff int64) bool {
 	}
 	ctxt.Out.Write64(uint64(sectoff))
 
-	elfsym := r.Xsym.ElfsymForReloc()
+	elfsym := ld.ElfSymForReloc(ctxt, r.Xsym)
 	switch r.Type {
 	default:
 		return false
@@ -972,7 +986,7 @@ func addpltsym2(ctxt *ld.Link, ldr *loader.Loader, s loader.Sym) {
 		return
 	}
 
-	ld.Adddynsym2(ldr, &ctxt.ErrorReporter, &ctxt.Target, &ctxt.ArchSyms, s)
+	ld.Adddynsym2(ldr, &ctxt.Target, &ctxt.ArchSyms, s)
 
 	if ctxt.IsELF {
 		plt := ldr.MakeSymbolUpdater(ctxt.PLT2)
@@ -1068,7 +1082,7 @@ func ensureglinkresolver2(ctxt *ld.Link, ldr *loader.Loader) *loader.SymbolBuild
 	return glink
 }
 
-func asmb(ctxt *ld.Link) {
+func asmb(ctxt *ld.Link, _ *loader.Loader) {
 	if ctxt.IsELF {
 		ld.Asmbelfsetup()
 	}

src/cmd/link/internal/ppc64/obj.go

@@ -49,7 +49,7 @@ func Init() (*sys.Arch, ld.Arch) {
 		Dwarfregsp: dwarfRegSP,
 		Dwarfreglr: dwarfRegLR,
 
-		Adddynrel:        adddynrel,
+		Adddynrel2:       adddynrel2,
 		Archinit:         archinit,
 		Archreloc:        archreloc,
 		Archrelocvariant: archrelocvariant,

src/cmd/link/internal/riscv64/asm.go

@@ -98,7 +98,7 @@ func archrelocvariant(target *ld.Target, syms *ld.ArchSyms, r *sym.Reloc, s *sym
 	return -1
 }
 
-func asmb(ctxt *ld.Link) {
+func asmb(ctxt *ld.Link, _ *loader.Loader) {
 	if ctxt.IsELF {
 		ld.Asmbelfsetup()
 	}

src/cmd/link/internal/s390x/asm.go

@@ -75,135 +75,146 @@ func gentext2(ctxt *ld.Link, ldr *loader.Loader) {
 	initfunc.AddUint32(ctxt.Arch, 0)
 }
 
-func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s *sym.Symbol, r *sym.Reloc) bool {
+func adddynrel2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loader.Sym, r *loader.Reloc2, rIdx int) bool {
-	targ := r.Sym
+	targ := r.Sym()
-	r.InitExt()
+	var targType sym.SymKind
+	if targ != 0 {
+		targType = ldr.SymType(targ)
+	}
 
-	switch r.Type {
+	switch r.Type() {
 	default:
-		if r.Type >= objabi.ElfRelocOffset {
+		if r.Type() >= objabi.ElfRelocOffset {
-			ld.Errorf(s, "unexpected relocation type %d", r.Type)
+			ldr.Errorf(s, "unexpected relocation type %d", r.Type())
 			return false
 		}
 
 		// Handle relocations found in ELF object files.
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_12),
 		objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_GOT12):
-		ld.Errorf(s, "s390x 12-bit relocations have not been implemented (relocation type %d)", r.Type-objabi.ElfRelocOffset)
+		ldr.Errorf(s, "s390x 12-bit relocations have not been implemented (relocation type %d)", r.Type()-objabi.ElfRelocOffset)
 		return false
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_8),
 		objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_16),
 		objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_32),
 		objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_64):
-		if targ.Type == sym.SDYNIMPORT {
+		if targType == sym.SDYNIMPORT {
-			ld.Errorf(s, "unexpected R_390_nn relocation for dynamic symbol %s", targ.Name)
+			ldr.Errorf(s, "unexpected R_390_nn relocation for dynamic symbol %s", ldr.SymName(targ))
 		}
-		r.Type = objabi.R_ADDR
+
+		su := ldr.MakeSymbolUpdater(s)
+		su.SetRelocType(rIdx, objabi.R_ADDR)
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_PC16),
 		objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_PC32),
 		objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_PC64):
-		if targ.Type == sym.SDYNIMPORT {
+		if targType == sym.SDYNIMPORT {
-			ld.Errorf(s, "unexpected R_390_PCnn relocation for dynamic symbol %s", targ.Name)
+			ldr.Errorf(s, "unexpected R_390_PCnn relocation for dynamic symbol %s", ldr.SymName(targ))
 		}
 		// TODO(mwhudson): the test of VisibilityHidden here probably doesn't make
 		// sense and should be removed when someone has thought about it properly.
-		if (targ.Type == 0 || targ.Type == sym.SXREF) && !targ.Attr.VisibilityHidden() {
+		if (targType == 0 || targType == sym.SXREF) && !ldr.AttrVisibilityHidden(targ) {
-			ld.Errorf(s, "unknown symbol %s in pcrel", targ.Name)
+			ldr.Errorf(s, "unknown symbol %s in pcrel", ldr.SymName(targ))
 		}
-		r.Type = objabi.R_PCREL
+		su := ldr.MakeSymbolUpdater(s)
-		r.Add += int64(r.Siz)
+		su.SetRelocType(rIdx, objabi.R_PCREL)
+		su.SetRelocAdd(rIdx, r.Add()+int64(r.Siz()))
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_GOT16),
 		objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_GOT32),
 		objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_GOT64):
-		ld.Errorf(s, "unimplemented S390x relocation: %v", r.Type-objabi.ElfRelocOffset)
+		ldr.Errorf(s, "unimplemented S390x relocation: %v", r.Type()-objabi.ElfRelocOffset)
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_PLT16DBL),
 		objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_PLT32DBL):
-		r.Type = objabi.R_PCREL
+		su := ldr.MakeSymbolUpdater(s)
-		r.Variant = sym.RV_390_DBL
+		su.SetRelocType(rIdx, objabi.R_PCREL)
-		r.Add += int64(r.Siz)
+		ldr.SetRelocVariant(s, rIdx, sym.RV_390_DBL)
-		if targ.Type == sym.SDYNIMPORT {
+		su.SetRelocAdd(rIdx, r.Add()+int64(r.Siz()))
-			addpltsym(target, syms, targ)
+		if targType == sym.SDYNIMPORT {
-			r.Sym = syms.PLT
+			addpltsym2(target, ldr, syms, targ)
-			r.Add += int64(targ.Plt())
+			r.SetSym(syms.PLT2)
+			su.SetRelocAdd(rIdx, r.Add()+int64(ldr.SymPlt(targ)))
 		}
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_PLT32),
 		objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_PLT64):
-		r.Type = objabi.R_PCREL
+		su := ldr.MakeSymbolUpdater(s)
-		r.Add += int64(r.Siz)
+		su.SetRelocType(rIdx, objabi.R_PCREL)
-		if targ.Type == sym.SDYNIMPORT {
+		su.SetRelocAdd(rIdx, r.Add()+int64(r.Siz()))
-			addpltsym(target, syms, targ)
+		if targType == sym.SDYNIMPORT {
-			r.Sym = syms.PLT
+			addpltsym2(target, ldr, syms, targ)
-			r.Add += int64(targ.Plt())
+			r.SetSym(syms.PLT2)
+			su.SetRelocAdd(rIdx, r.Add()+int64(ldr.SymPlt(targ)))
 		}
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_COPY):
-		ld.Errorf(s, "unimplemented S390x relocation: %v", r.Type-objabi.ElfRelocOffset)
+		ldr.Errorf(s, "unimplemented S390x relocation: %v", r.Type()-objabi.ElfRelocOffset)
 		return false
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_GLOB_DAT):
-		ld.Errorf(s, "unimplemented S390x relocation: %v", r.Type-objabi.ElfRelocOffset)
+		ldr.Errorf(s, "unimplemented S390x relocation: %v", r.Type()-objabi.ElfRelocOffset)
 		return false
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_JMP_SLOT):
-		ld.Errorf(s, "unimplemented S390x relocation: %v", r.Type-objabi.ElfRelocOffset)
+		ldr.Errorf(s, "unimplemented S390x relocation: %v", r.Type()-objabi.ElfRelocOffset)
 		return false
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_RELATIVE):
-		ld.Errorf(s, "unimplemented S390x relocation: %v", r.Type-objabi.ElfRelocOffset)
+		ldr.Errorf(s, "unimplemented S390x relocation: %v", r.Type()-objabi.ElfRelocOffset)
 		return false
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_GOTOFF):
-		if targ.Type == sym.SDYNIMPORT {
+		if targType == sym.SDYNIMPORT {
-			ld.Errorf(s, "unexpected R_390_GOTOFF relocation for dynamic symbol %s", targ.Name)
+			ldr.Errorf(s, "unexpected R_390_GOTOFF relocation for dynamic symbol %s", ldr.SymName(targ))
 		}
-		r.Type = objabi.R_GOTOFF
+		su := ldr.MakeSymbolUpdater(s)
+		su.SetRelocType(rIdx, objabi.R_GOTOFF)
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_GOTPC):
-		r.Type = objabi.R_PCREL
+		su := ldr.MakeSymbolUpdater(s)
-		r.Sym = syms.GOT
+		su.SetRelocType(rIdx, objabi.R_PCREL)
-		r.Add += int64(r.Siz)
+		r.SetSym(syms.GOT2)
+		su.SetRelocAdd(rIdx, r.Add()+int64(r.Siz()))
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_PC16DBL),
 		objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_PC32DBL):
-		r.Type = objabi.R_PCREL
+		su := ldr.MakeSymbolUpdater(s)
-		r.Variant = sym.RV_390_DBL
+		su.SetRelocType(rIdx, objabi.R_PCREL)
-		r.Add += int64(r.Siz)
+		ldr.SetRelocVariant(s, rIdx, sym.RV_390_DBL)
-		if targ.Type == sym.SDYNIMPORT {
+		su.SetRelocAdd(rIdx, r.Add()+int64(r.Siz()))
-			ld.Errorf(s, "unexpected R_390_PCnnDBL relocation for dynamic symbol %s", targ.Name)
+		if targType == sym.SDYNIMPORT {
+			ldr.Errorf(s, "unexpected R_390_PCnnDBL relocation for dynamic symbol %s", ldr.SymName(targ))
 		}
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_GOTPCDBL):
-		r.Type = objabi.R_PCREL
+		su := ldr.MakeSymbolUpdater(s)
-		r.Variant = sym.RV_390_DBL
+		su.SetRelocType(rIdx, objabi.R_PCREL)
-		r.Sym = syms.GOT
+		ldr.SetRelocVariant(s, rIdx, sym.RV_390_DBL)
-		r.Add += int64(r.Siz)
+		r.SetSym(syms.GOT2)
+		su.SetRelocAdd(rIdx, r.Add()+int64(r.Siz()))
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_390_GOTENT):
-		addgotsym(target, syms, targ)
+		addgotsym2(target, ldr, syms, targ)
-
+		su := ldr.MakeSymbolUpdater(s)
-		r.Type = objabi.R_PCREL
+		su.SetRelocType(rIdx, objabi.R_PCREL)
-		r.Variant = sym.RV_390_DBL
+		ldr.SetRelocVariant(s, rIdx, sym.RV_390_DBL)
-		r.Sym = syms.GOT
+		r.SetSym(syms.GOT2)
-		r.Add += int64(targ.Got())
+		su.SetRelocAdd(rIdx, r.Add()+int64(ldr.SymGot(targ))+int64(r.Siz()))
-		r.Add += int64(r.Siz)
 		return true
 	}
 	// Handle references to ELF symbols from our own object files.
-	if targ.Type != sym.SDYNIMPORT {
+	if targType != sym.SDYNIMPORT {
 		return true
 	}
 
@@ -213,7 +224,7 @@ func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s *sym.
 func elfreloc1(ctxt *ld.Link, r *sym.Reloc, sectoff int64) bool {
 	ctxt.Out.Write64(uint64(sectoff))
 
-	elfsym := r.Xsym.ElfsymForReloc()
+	elfsym := ld.ElfSymForReloc(ctxt, r.Xsym)
 	switch r.Type {
 	default:
 		return false
@@ -388,28 +399,30 @@ func archrelocvariant(target *ld.Target, syms *ld.ArchSyms, r *sym.Reloc, s *sym
 	}
 }
 
-func addpltsym(target *ld.Target, syms *ld.ArchSyms, s *sym.Symbol) {
+func addpltsym2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loader.Sym) {
-	if s.Plt() >= 0 {
+	if ldr.SymPlt(s) >= 0 {
 		return
 	}
 
-	ld.Adddynsym(target, syms, s)
+	ld.Adddynsym2(ldr, target, syms, s)
 
 	if target.IsElf() {
-		plt := syms.PLT
+		plt := ldr.MakeSymbolUpdater(syms.PLT2)
-		got := syms.GOT
+		got := ldr.MakeSymbolUpdater(syms.GOT2)
-		rela := syms.RelaPLT
+		rela := ldr.MakeSymbolUpdater(syms.RelaPLT2)
-		if plt.Size == 0 {
+		if plt.Size() == 0 {
 			panic("plt is not set up")
 		}
 		// larl    %r1,_GLOBAL_OFFSET_TABLE_+index
 
 		plt.AddUint8(0xc0)
 		plt.AddUint8(0x10)
-		plt.AddPCRelPlus(target.Arch, got, got.Size+6) // need variant?
+		plt.AddPCRelPlus(target.Arch, got.Sym(), got.Size()+6)
+		pltrelocs := plt.Relocs()
+		ldr.SetRelocVariant(plt.Sym(), pltrelocs.Count()-1, sym.RV_390_DBL)
 
 		// add to got: pointer to current pos in plt
-		got.AddAddrPlus(target.Arch, plt, plt.Size+8) // weird but correct
+		got.AddAddrPlus(target.Arch, plt.Sym(), plt.Size()+8) // weird but correct
 		// lg      %r1,0(%r1)
 		plt.AddUint8(0xe3)
 		plt.AddUint8(0x10)
@@ -434,44 +447,45 @@ func addpltsym(target *ld.Target, syms *ld.ArchSyms, s *sym.Symbol) {
 		plt.AddUint8(0xc0)
 		plt.AddUint8(0xf4)
 
-		plt.AddUint32(target.Arch, uint32(-((plt.Size - 2) >> 1))) // roll-your-own relocation
+		plt.AddUint32(target.Arch, uint32(-((plt.Size() - 2) >> 1))) // roll-your-own relocation
 		//.plt index
-		plt.AddUint32(target.Arch, uint32(rela.Size)) // rela size before current entry
+		plt.AddUint32(target.Arch, uint32(rela.Size())) // rela size before current entry
 
 		// rela
-		rela.AddAddrPlus(target.Arch, got, got.Size-8)
+		rela.AddAddrPlus(target.Arch, got.Sym(), got.Size()-8)
 
-		rela.AddUint64(target.Arch, ld.ELF64_R_INFO(uint32(s.Dynid), uint32(elf.R_390_JMP_SLOT)))
+		sDynid := ldr.SymDynid(s)
+		rela.AddUint64(target.Arch, ld.ELF64_R_INFO(uint32(sDynid), uint32(elf.R_390_JMP_SLOT)))
 		rela.AddUint64(target.Arch, 0)
 
-		s.SetPlt(int32(plt.Size - 32))
+		ldr.SetPlt(s, int32(plt.Size()-32))
 
 	} else {
-		ld.Errorf(s, "addpltsym: unsupported binary format")
+		ldr.Errorf(s, "addpltsym: unsupported binary format")
 	}
 }
 
-func addgotsym(target *ld.Target, syms *ld.ArchSyms, s *sym.Symbol) {
+func addgotsym2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loader.Sym) {
-	if s.Got() >= 0 {
+	if ldr.SymGot(s) >= 0 {
 		return
 	}
 
-	ld.Adddynsym(target, syms, s)
+	ld.Adddynsym2(ldr, target, syms, s)
-	got := syms.GOT
+	got := ldr.MakeSymbolUpdater(syms.GOT2)
-	s.SetGot(int32(got.Size))
+	ldr.SetGot(s, int32(got.Size()))
 	got.AddUint64(target.Arch, 0)
 
 	if target.IsElf() {
-		rela := syms.Rela
+		rela := ldr.MakeSymbolUpdater(syms.Rela2)
-		rela.AddAddrPlus(target.Arch, got, int64(s.Got()))
+		rela.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
-		rela.AddUint64(target.Arch, ld.ELF64_R_INFO(uint32(s.Dynid), uint32(elf.R_390_GLOB_DAT)))
+		rela.AddUint64(target.Arch, ld.ELF64_R_INFO(uint32(ldr.SymDynid(s)), uint32(elf.R_390_GLOB_DAT)))
 		rela.AddUint64(target.Arch, 0)
 	} else {
-		ld.Errorf(s, "addgotsym: unsupported binary format")
+		ldr.Errorf(s, "addgotsym: unsupported binary format")
 	}
 }
 
-func asmb(ctxt *ld.Link) {
+func asmb(ctxt *ld.Link, _ *loader.Loader) {
 	if ctxt.IsELF {
 		ld.Asmbelfsetup()
 	}

src/cmd/link/internal/s390x/obj.go

@@ -46,7 +46,7 @@ func Init() (*sys.Arch, ld.Arch) {
 		Dwarfregsp: dwarfRegSP,
 		Dwarfreglr: dwarfRegLR,
 
-		Adddynrel:        adddynrel,
+		Adddynrel2:       adddynrel2,
 		Archinit:         archinit,
 		Archreloc:        archreloc,
 		Archrelocvariant: archrelocvariant,

src/cmd/link/internal/sym/library.go

@@ -4,6 +4,8 @@
 
 package sym
 
+import "cmd/internal/goobj2"
+
 type Library struct {
 	Objref      string
 	Srcref      string
@@ -11,7 +13,8 @@ type Library struct {
 	Pkg         string
 	Shlib       string
 	Hash        string
-	ImportStrings []string
+	Fingerprint goobj2.FingerprintType
+	Autolib     []goobj2.ImportedPkg
 	Imports     []*Library
 	Main        bool
 	Safe        bool

src/cmd/link/internal/sym/segment.go

@@ -56,5 +56,6 @@ type Section struct {
 	Reloff  uint64
 	Rellen  uint64
 	Sym     *Symbol   // symbol for the section, if any
+	Sym2    LoaderSym // symbol for the section, if any
 	Index   uint16    // each section has a unique index, used internally
 }

src/cmd/link/internal/sym/sizeof_test.go

@@ -21,7 +21,7 @@ func TestSizeof(t *testing.T) {
 		_32bit uintptr     // size on 32bit platforms
 		_64bit uintptr     // size on 64bit platforms
 	}{
-		{Symbol{}, 104, 168},
+		{Symbol{}, 84, 136},
 	}
 
 	for _, tt := range tests {

src/cmd/link/internal/sym/symbol.go

@@ -21,17 +21,13 @@ type Symbol struct {
 	Attr    Attribute
 	Dynid   int32
 	Align   int32
-	Elfsym      int32
-	LocalElfsym int32
 	Value   int64
 	Size    int64
 	Sub     *Symbol
 	Outer   *Symbol
-	Gotype      *Symbol
+	SymIdx  LoaderSym
-	File        string // actually package!
 	auxinfo *AuxSymbol
 	Sect    *Section
-	Unit        *CompilationUnit
 	// P contains the raw symbol data.
 	P []byte
 	R []Reloc
@@ -88,16 +84,6 @@ func (s *Symbol) IsFileLocal() bool {
 	return s.Version >= SymVerStatic
 }
 
-func (s *Symbol) ElfsymForReloc() int32 {
-	// If putelfsym created a local version of this symbol, use that in all
-	// relocations.
-	if s.LocalElfsym != 0 {
-		return s.LocalElfsym
-	} else {
-		return s.Elfsym
-	}
-}
-
 func (s *Symbol) Len() int64 {
 	return s.Size
 }
@@ -444,80 +430,6 @@ func (s *Symbol) SetElfType(val elf.SymType) {
 	s.auxinfo.elftype = val
 }
 
-// SortSub sorts a linked-list (by Sub) of *Symbol by Value.
-// Used for sub-symbols when loading host objects (see e.g. ldelf.go).
-func SortSub(l *Symbol) *Symbol {
-	if l == nil || l.Sub == nil {
-		return l
-	}
-
-	l1 := l
-	l2 := l
-	for {
-		l2 = l2.Sub
-		if l2 == nil {
-			break
-		}
-		l2 = l2.Sub
-		if l2 == nil {
-			break
-		}
-		l1 = l1.Sub
-	}
-
-	l2 = l1.Sub
-	l1.Sub = nil
-	l1 = SortSub(l)
-	l2 = SortSub(l2)
-
-	/* set up lead element */
-	if l1.Value < l2.Value {
-		l = l1
-		l1 = l1.Sub
-	} else {
-		l = l2
-		l2 = l2.Sub
-	}
-
-	le := l
-
-	for {
-		if l1 == nil {
-			for l2 != nil {
-				le.Sub = l2
-				le = l2
-				l2 = l2.Sub
-			}
-
-			le.Sub = nil
-			break
-		}
-
-		if l2 == nil {
-			for l1 != nil {
-				le.Sub = l1
-				le = l1
-				l1 = l1.Sub
-			}
-
-			break
-		}
-
-		if l1.Value < l2.Value {
-			le.Sub = l1
-			le = l1
-			l1 = l1.Sub
-		} else {
-			le.Sub = l2
-			le = l2
-			l2 = l2.Sub
-		}
-	}
-
-	le.Sub = nil
-	return l
-}
-
 type Pcdata struct {
 	P []byte
 }

src/cmd/link/internal/sym/symbols.go

@@ -34,8 +34,6 @@ type Symbols struct {
 	// Symbol lookup based on name and indexed by version.
 	versions int
 
-	Allsym []*Symbol
-
 	// Provided by the loader
 
 	// Look up the symbol with the given name and version, creating the
@@ -55,7 +53,6 @@ type Symbols struct {
 func NewSymbols() *Symbols {
 	return &Symbols{
 		versions: SymVerStatic,
-		Allsym:   make([]*Symbol, 0, 100000),
 	}
 }
 

src/cmd/link/internal/wasm/asm.go

@@ -92,7 +92,30 @@ func assignAddress(ldr *loader.Loader, sect *sym.Section, n int, s loader.Sym, v
 	return sect, n, va
 }
 
-func asmb(ctxt *ld.Link) {} // dummy
+type wasmDataSect struct {
+	sect *sym.Section
+	data []byte
+}
+
+var dataSects []wasmDataSect
+
+func asmb(ctxt *ld.Link, ldr *loader.Loader) {
+	sections := []*sym.Section{
+		ldr.SymSect(ldr.Lookup("runtime.rodata", 0)),
+		ldr.SymSect(ldr.Lookup("runtime.typelink", 0)),
+		ldr.SymSect(ldr.Lookup("runtime.itablink", 0)),
+		ldr.SymSect(ldr.Lookup("runtime.symtab", 0)),
+		ldr.SymSect(ldr.Lookup("runtime.pclntab", 0)),
+		ldr.SymSect(ldr.Lookup("runtime.noptrdata", 0)),
+		ldr.SymSect(ldr.Lookup("runtime.data", 0)),
+	}
+
+	dataSects = make([]wasmDataSect, len(sections))
+	for i, sect := range sections {
+		data := ld.DatblkBytes(ctxt, int64(sect.Vaddr), int64(sect.Length))
+		dataSects[i] = wasmDataSect{sect, data}
+	}
+}
 
 // asmb writes the final WebAssembly module binary.
 // Spec: https://webassembly.github.io/spec/core/binary/modules.html
@@ -396,16 +419,6 @@ func writeCodeSec(ctxt *ld.Link, fns []*wasmFunc) {
 func writeDataSec(ctxt *ld.Link) {
 	sizeOffset := writeSecHeader(ctxt, sectionData)
 
-	sections := []*sym.Section{
-		ctxt.Syms.Lookup("runtime.rodata", 0).Sect,
-		ctxt.Syms.Lookup("runtime.typelink", 0).Sect,
-		ctxt.Syms.Lookup("runtime.itablink", 0).Sect,
-		ctxt.Syms.Lookup("runtime.symtab", 0).Sect,
-		ctxt.Syms.Lookup("runtime.pclntab", 0).Sect,
-		ctxt.Syms.Lookup("runtime.noptrdata", 0).Sect,
-		ctxt.Syms.Lookup("runtime.data", 0).Sect,
-	}
-
 	type dataSegment struct {
 		offset int32
 		data   []byte
@@ -420,9 +433,9 @@ func writeDataSec(ctxt *ld.Link) {
 	const maxNumSegments = 100000
 
 	var segments []*dataSegment
-	for secIndex, sec := range sections {
+	for secIndex, ds := range dataSects {
-		data := ld.DatblkBytes(ctxt, int64(sec.Vaddr), int64(sec.Length))
+		data := ds.data
-		offset := int32(sec.Vaddr)
+		offset := int32(ds.sect.Vaddr)
 
 		// skip leading zeroes
 		for len(data) > 0 && data[0] == 0 {
@@ -433,7 +446,7 @@ func writeDataSec(ctxt *ld.Link) {
 		for len(data) > 0 {
 			dataLen := int32(len(data))
 			var segmentEnd, zeroEnd int32
-			if len(segments)+(len(sections)-secIndex) == maxNumSegments {
+			if len(segments)+(len(dataSects)-secIndex) == maxNumSegments {
 				segmentEnd = dataLen
 				zeroEnd = dataLen
 			} else {

src/cmd/link/internal/x86/asm.go

@@ -129,161 +129,189 @@ func gentext2(ctxt *ld.Link, ldr *loader.Loader) {
 	o(0xc3)
 }
 
-func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s *sym.Symbol, r *sym.Reloc) bool {
+func adddynrel2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loader.Sym, r *loader.Reloc2, rIdx int) bool {
-	targ := r.Sym
+	targ := r.Sym()
+	var targType sym.SymKind
+	if targ != 0 {
+		targType = ldr.SymType(targ)
+	}
 
-	switch r.Type {
+	switch r.Type() {
 	default:
-		if r.Type >= objabi.ElfRelocOffset {
+		if r.Type() >= objabi.ElfRelocOffset {
-			ld.Errorf(s, "unexpected relocation type %d (%s)", r.Type, sym.RelocName(target.Arch, r.Type))
+			ldr.Errorf(s, "unexpected relocation type %d (%s)", r.Type(), sym.RelocName(target.Arch, r.Type()))
 			return false
 		}
 
 		// Handle relocations found in ELF object files.
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_386_PC32):
-		if targ.Type == sym.SDYNIMPORT {
+		if targType == sym.SDYNIMPORT {
-			ld.Errorf(s, "unexpected R_386_PC32 relocation for dynamic symbol %s", targ.Name)
+			ldr.Errorf(s, "unexpected R_386_PC32 relocation for dynamic symbol %s", ldr.SymName(targ))
 		}
 		// TODO(mwhudson): the test of VisibilityHidden here probably doesn't make
 		// sense and should be removed when someone has thought about it properly.
-		if (targ.Type == 0 || targ.Type == sym.SXREF) && !targ.Attr.VisibilityHidden() {
+		if (targType == 0 || targType == sym.SXREF) && !ldr.AttrVisibilityHidden(targ) {
-			ld.Errorf(s, "unknown symbol %s in pcrel", targ.Name)
+			ldr.Errorf(s, "unknown symbol %s in pcrel", ldr.SymName(targ))
 		}
-		r.Type = objabi.R_PCREL
+		su := ldr.MakeSymbolUpdater(s)
-		r.Add += 4
+		su.SetRelocType(rIdx, objabi.R_PCREL)
+		su.SetRelocAdd(rIdx, r.Add()+4)
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_386_PLT32):
-		r.Type = objabi.R_PCREL
+		su := ldr.MakeSymbolUpdater(s)
-		r.Add += 4
+		su.SetRelocType(rIdx, objabi.R_PCREL)
-		if targ.Type == sym.SDYNIMPORT {
+		su.SetRelocAdd(rIdx, r.Add()+4)
-			addpltsym(target, syms, targ)
+		if targType == sym.SDYNIMPORT {
-			r.Sym = syms.PLT
+			addpltsym2(target, ldr, syms, targ)
-			r.Add += int64(targ.Plt())
+			su.SetRelocSym(rIdx, syms.PLT2)
+			su.SetRelocAdd(rIdx, r.Add()+int64(ldr.SymPlt(targ)))
 		}
 
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_386_GOT32),
 		objabi.ElfRelocOffset + objabi.RelocType(elf.R_386_GOT32X):
-		if targ.Type != sym.SDYNIMPORT {
+		su := ldr.MakeSymbolUpdater(s)
+		if targType != sym.SDYNIMPORT {
 			// have symbol
-			if r.Off >= 2 && s.P[r.Off-2] == 0x8b {
+			sData := ldr.Data(s)
-				// turn MOVL of GOT entry into LEAL of symbol address, relative to GOT.
-				s.P[r.Off-2] = 0x8d
 
-				r.Type = objabi.R_GOTOFF
+			if r.Off() >= 2 && sData[r.Off()-2] == 0x8b {
+				su.MakeWritable()
+
+				// turn MOVL of GOT entry into LEAL of symbol address, relative to GOT.
+				writeableData := su.Data()
+				writeableData[r.Off()-2] = 0x8d
+				su.SetRelocType(rIdx, objabi.R_GOTOFF)
 				return true
 			}
 
-			if r.Off >= 2 && s.P[r.Off-2] == 0xff && s.P[r.Off-1] == 0xb3 {
+			if r.Off() >= 2 && sData[r.Off()-2] == 0xff && sData[r.Off()-1] == 0xb3 {
+				su.MakeWritable()
 				// turn PUSHL of GOT entry into PUSHL of symbol itself.
 				// use unnecessary SS prefix to keep instruction same length.
-				s.P[r.Off-2] = 0x36
+				writeableData := su.Data()
-
+				writeableData[r.Off()-2] = 0x36
-				s.P[r.Off-1] = 0x68
+				writeableData[r.Off()-1] = 0x68
-				r.Type = objabi.R_ADDR
+				su.SetRelocType(rIdx, objabi.R_ADDR)
 				return true
 			}
 
-			ld.Errorf(s, "unexpected GOT reloc for non-dynamic symbol %s", targ.Name)
+			ldr.Errorf(s, "unexpected GOT reloc for non-dynamic symbol %s", ldr.SymName(targ))
 			return false
 		}
 
-		addgotsym(target, syms, targ)
+		addgotsym2(target, ldr, syms, targ)
-		r.Type = objabi.R_CONST // write r->add during relocsym
+		su.SetRelocType(rIdx, objabi.R_CONST) // write r->add during relocsym
-		r.Sym = nil
+		su.SetRelocSym(rIdx, 0)
-		r.Add += int64(targ.Got())
+		su.SetRelocAdd(rIdx, r.Add()+int64(ldr.SymGot(targ)))
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_386_GOTOFF):
-		r.Type = objabi.R_GOTOFF
+		su := ldr.MakeSymbolUpdater(s)
+		su.SetRelocType(rIdx, objabi.R_GOTOFF)
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_386_GOTPC):
-		r.Type = objabi.R_PCREL
+		su := ldr.MakeSymbolUpdater(s)
-		r.Sym = syms.GOT
+		su.SetRelocType(rIdx, objabi.R_PCREL)
-		r.Add += 4
+		su.SetRelocSym(rIdx, syms.GOT2)
+		su.SetRelocAdd(rIdx, r.Add()+4)
 		return true
 
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_386_32):
-		if targ.Type == sym.SDYNIMPORT {
+		if targType == sym.SDYNIMPORT {
-			ld.Errorf(s, "unexpected R_386_32 relocation for dynamic symbol %s", targ.Name)
+			ldr.Errorf(s, "unexpected R_386_32 relocation for dynamic symbol %s", ldr.SymName(targ))
 		}
-		r.Type = objabi.R_ADDR
+		su := ldr.MakeSymbolUpdater(s)
+		su.SetRelocType(rIdx, objabi.R_ADDR)
 		return true
 
 	case objabi.MachoRelocOffset + ld.MACHO_GENERIC_RELOC_VANILLA*2 + 0:
-		r.Type = objabi.R_ADDR
+		su := ldr.MakeSymbolUpdater(s)
-		if targ.Type == sym.SDYNIMPORT {
+		su.SetRelocType(rIdx, objabi.R_ADDR)
-			ld.Errorf(s, "unexpected reloc for dynamic symbol %s", targ.Name)
+		if targType == sym.SDYNIMPORT {
+			ldr.Errorf(s, "unexpected reloc for dynamic symbol %s", ldr.SymName(targ))
 		}
 		return true
 
 	case objabi.MachoRelocOffset + ld.MACHO_GENERIC_RELOC_VANILLA*2 + 1:
-		if targ.Type == sym.SDYNIMPORT {
+		su := ldr.MakeSymbolUpdater(s)
-			addpltsym(target, syms, targ)
+		if targType == sym.SDYNIMPORT {
-			r.Sym = syms.PLT
+			addpltsym2(target, ldr, syms, targ)
-			r.Add = int64(targ.Plt())
+			su.SetRelocSym(rIdx, syms.PLT2)
-			r.Type = objabi.R_PCREL
+			su.SetRelocAdd(rIdx, int64(ldr.SymPlt(targ)))
+			su.SetRelocType(rIdx, objabi.R_PCREL)
 			return true
 		}
 
-		r.Type = objabi.R_PCREL
+		su.SetRelocType(rIdx, objabi.R_PCREL)
 		return true
 
 	case objabi.MachoRelocOffset + ld.MACHO_FAKE_GOTPCREL:
-		if targ.Type != sym.SDYNIMPORT {
+		su := ldr.MakeSymbolUpdater(s)
+		if targType != sym.SDYNIMPORT {
 			// have symbol
 			// turn MOVL of GOT entry into LEAL of symbol itself
-			if r.Off < 2 || s.P[r.Off-2] != 0x8b {
+			sData := ldr.Data(s)
-				ld.Errorf(s, "unexpected GOT reloc for non-dynamic symbol %s", targ.Name)
+			if r.Off() < 2 || sData[r.Off()-2] != 0x8b {
+				ldr.Errorf(s, "unexpected GOT reloc for non-dynamic symbol %s", ldr.SymName(targ))
 				return false
 			}
 
-			s.P[r.Off-2] = 0x8d
+			su.MakeWritable()
-			r.Type = objabi.R_PCREL
+			writeableData := su.Data()
+			writeableData[r.Off()-2] = 0x8d
+			su.SetRelocType(rIdx, objabi.R_PCREL)
 			return true
 		}
 
-		addgotsym(target, syms, targ)
+		addgotsym2(target, ldr, syms, targ)
-		r.Sym = syms.GOT
+		su.SetRelocSym(rIdx, syms.GOT2)
-		r.Add += int64(targ.Got())
+		su.SetRelocAdd(rIdx, r.Add()+int64(ldr.SymGot(targ)))
-		r.Type = objabi.R_PCREL
+		su.SetRelocType(rIdx, objabi.R_PCREL)
 		return true
 	}
 
 	// Handle references to ELF symbols from our own object files.
-	if targ.Type != sym.SDYNIMPORT {
+	if targType != sym.SDYNIMPORT {
 		return true
 	}
-	switch r.Type {
+
+	// Reread the reloc to incorporate any changes in type above.
+	relocs := ldr.Relocs(s)
+	*r = relocs.At2(rIdx)
+
+	switch r.Type() {
 	case objabi.R_CALL,
 		objabi.R_PCREL:
 		if target.IsExternal() {
 			// External linker will do this relocation.
 			return true
 		}
-		addpltsym(target, syms, targ)
+		addpltsym2(target, ldr, syms, targ)
-		r.Sym = syms.PLT
+		su := ldr.MakeSymbolUpdater(s)
-		r.Add = int64(targ.Plt())
+		su.SetRelocSym(rIdx, syms.PLT2)
+		su.SetRelocAdd(rIdx, int64(ldr.SymPlt(targ)))
 		return true
 
 	case objabi.R_ADDR:
-		if s.Type != sym.SDATA {
+		if ldr.SymType(s) != sym.SDATA {
 			break
 		}
 		if target.IsElf() {
-			ld.Adddynsym(target, syms, targ)
+			ld.Adddynsym2(ldr, target, syms, targ)
-			rel := syms.Rel
+			rel := ldr.MakeSymbolUpdater(syms.Rel2)
-			rel.AddAddrPlus(target.Arch, s, int64(r.Off))
+			rel.AddAddrPlus(target.Arch, s, int64(r.Off()))
-			rel.AddUint32(target.Arch, ld.ELF32_R_INFO(uint32(targ.Dynid), uint32(elf.R_386_32)))
+			rel.AddUint32(target.Arch, ld.ELF32_R_INFO(uint32(ldr.SymDynid(targ)), uint32(elf.R_386_32)))
-			r.Type = objabi.R_CONST // write r->add during relocsym
+			su := ldr.MakeSymbolUpdater(s)
-			r.Sym = nil
+			su.SetRelocType(rIdx, objabi.R_CONST) // write r->add during relocsym
+			su.SetRelocSym(rIdx, 0)
 			return true
 		}
 
-		if target.IsDarwin() && s.Size == int64(target.Arch.PtrSize) && r.Off == 0 {
+		if target.IsDarwin() && ldr.SymSize(s) == int64(target.Arch.PtrSize) && r.Off() == 0 {
 			// Mach-O relocations are a royal pain to lay out.
 			// They use a compact stateful bytecode representation
 			// that is too much bother to deal with.
@@ -294,18 +322,17 @@ func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s *sym.
 			// just in case the C code assigns to the variable,
 			// and of course it only works for single pointers,
 			// but we only need to support cgo and that's all it needs.
-			ld.Adddynsym(target, syms, targ)
+			ld.Adddynsym2(ldr, target, syms, targ)
 
-			got := syms.GOT
+			got := ldr.MakeSymbolUpdater(syms.GOT2)
-			s.Type = got.Type
+			su := ldr.MakeSymbolUpdater(s)
-			s.Attr |= sym.AttrSubSymbol
+			su.SetType(got.Type())
-			s.Outer = got
+			got.PrependSub(s)
-			s.Sub = got.Sub
+			su.SetValue(got.Size())
-			got.Sub = s
-			s.Value = got.Size
 			got.AddUint32(target.Arch, 0)
-			syms.LinkEditGOT.AddUint32(target.Arch, uint32(targ.Dynid))
+			leg := ldr.MakeSymbolUpdater(syms.LinkEditGOT2)
-			r.Type = objabi.ElfRelocOffset // ignore during relocsym
+			leg.AddUint32(target.Arch, uint32(ldr.SymDynid(targ)))
+			su.SetRelocType(rIdx, objabi.ElfRelocOffset) // ignore during relocsym
 			return true
 		}
 	}
@@ -316,7 +343,7 @@ func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s *sym.
 func elfreloc1(ctxt *ld.Link, r *sym.Reloc, sectoff int64) bool {
 	ctxt.Out.Write32(uint32(sectoff))
 
-	elfsym := r.Xsym.ElfsymForReloc()
+	elfsym := ld.ElfSymForReloc(ctxt, r.Xsym)
 	switch r.Type {
 	default:
 		return false
@@ -452,18 +479,18 @@ func elfsetupplt(ctxt *ld.Link, plt, got *loader.SymbolBuilder, dynamic loader.S
 	}
 }
 
-func addpltsym(target *ld.Target, syms *ld.ArchSyms, s *sym.Symbol) {
+func addpltsym2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loader.Sym) {
-	if s.Plt() >= 0 {
+	if ldr.SymPlt(s) >= 0 {
 		return
 	}
 
-	ld.Adddynsym(target, syms, s)
+	ld.Adddynsym2(ldr, target, syms, s)
 
 	if target.IsElf() {
-		plt := syms.PLT
+		plt := ldr.MakeSymbolUpdater(syms.PLT2)
-		got := syms.GOTPLT
+		got := ldr.MakeSymbolUpdater(syms.GOTPLT2)
-		rel := syms.RelPLT
+		rel := ldr.MakeSymbolUpdater(syms.RelPLT2)
-		if plt.Size == 0 {
+		if plt.Size() == 0 {
 			panic("plt is not set up")
 		}
 
@@ -471,69 +498,73 @@ func addpltsym(target *ld.Target, syms *ld.ArchSyms, s *sym.Symbol) {
 		plt.AddUint8(0xff)
 
 		plt.AddUint8(0x25)
-		plt.AddAddrPlus(target.Arch, got, got.Size)
+		plt.AddAddrPlus(target.Arch, got.Sym(), got.Size())
 
 		// add to got: pointer to current pos in plt
-		got.AddAddrPlus(target.Arch, plt, plt.Size)
+		got.AddAddrPlus(target.Arch, plt.Sym(), plt.Size())
 
 		// pushl $x
 		plt.AddUint8(0x68)
 
-		plt.AddUint32(target.Arch, uint32(rel.Size))
+		plt.AddUint32(target.Arch, uint32(rel.Size()))
 
 		// jmp .plt
 		plt.AddUint8(0xe9)
 
-		plt.AddUint32(target.Arch, uint32(-(plt.Size + 4)))
+		plt.AddUint32(target.Arch, uint32(-(plt.Size() + 4)))
 
 		// rel
-		rel.AddAddrPlus(target.Arch, got, got.Size-4)
+		rel.AddAddrPlus(target.Arch, got.Sym(), got.Size()-4)
 
-		rel.AddUint32(target.Arch, ld.ELF32_R_INFO(uint32(s.Dynid), uint32(elf.R_386_JMP_SLOT)))
+		sDynid := ldr.SymDynid(s)
+		rel.AddUint32(target.Arch, ld.ELF32_R_INFO(uint32(sDynid), uint32(elf.R_386_JMP_SLOT)))
 
-		s.SetPlt(int32(plt.Size - 16))
+		ldr.SetPlt(s, int32(plt.Size()-16))
 	} else if target.IsDarwin() {
 		// Same laziness as in 6l.
 
-		plt := syms.PLT
+		plt := ldr.MakeSymbolUpdater(syms.PLT2)
 
-		addgotsym(target, syms, s)
+		addgotsym2(target, ldr, syms, s)
 
-		syms.LinkEditPLT.AddUint32(target.Arch, uint32(s.Dynid))
+		sDynid := ldr.SymDynid(s)
+		lep := ldr.MakeSymbolUpdater(syms.LinkEditPLT2)
+		lep.AddUint32(target.Arch, uint32(sDynid))
 
 		// jmpq *got+size(IP)
-		s.SetPlt(int32(plt.Size))
+		ldr.SetPlt(s, int32(plt.Size()))
 
 		plt.AddUint8(0xff)
 		plt.AddUint8(0x25)
-		plt.AddAddrPlus(target.Arch, syms.GOT, int64(s.Got()))
+		plt.AddAddrPlus(target.Arch, syms.GOT2, int64(ldr.SymGot(s)))
 	} else {
-		ld.Errorf(s, "addpltsym: unsupported binary format")
+		ldr.Errorf(s, "addpltsym: unsupported binary format")
 	}
 }
 
-func addgotsym(target *ld.Target, syms *ld.ArchSyms, s *sym.Symbol) {
+func addgotsym2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loader.Sym) {
-	if s.Got() >= 0 {
+	if ldr.SymGot(s) >= 0 {
 		return
 	}
 
-	ld.Adddynsym(target, syms, s)
+	ld.Adddynsym2(ldr, target, syms, s)
-	got := syms.GOT
+	got := ldr.MakeSymbolUpdater(syms.GOT2)
-	s.SetGot(int32(got.Size))
+	ldr.SetGot(s, int32(got.Size()))
 	got.AddUint32(target.Arch, 0)
 
 	if target.IsElf() {
-		rel := syms.Rel
+		rel := ldr.MakeSymbolUpdater(syms.Rel2)
-		rel.AddAddrPlus(target.Arch, got, int64(s.Got()))
+		rel.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s)))
-		rel.AddUint32(target.Arch, ld.ELF32_R_INFO(uint32(s.Dynid), uint32(elf.R_386_GLOB_DAT)))
+		rel.AddUint32(target.Arch, ld.ELF32_R_INFO(uint32(ldr.SymDynid(s)), uint32(elf.R_386_GLOB_DAT)))
 	} else if target.IsDarwin() {
-		syms.LinkEditGOT.AddUint32(target.Arch, uint32(s.Dynid))
+		leg := ldr.MakeSymbolUpdater(syms.LinkEditGOT2)
+		leg.AddUint32(target.Arch, uint32(ldr.SymDynid(s)))
 	} else {
-		ld.Errorf(s, "addgotsym: unsupported binary format")
+		ldr.Errorf(s, "addgotsym: unsupported binary format")
 	}
 }
 
-func asmb(ctxt *ld.Link) {
+func asmb(ctxt *ld.Link, _ *loader.Loader) {
 	if ctxt.IsELF {
 		ld.Asmbelfsetup()
 	}

src/cmd/link/internal/x86/obj.go

@@ -46,7 +46,7 @@ func Init() (*sys.Arch, ld.Arch) {
 		Dwarfregsp: dwarfRegSP,
 		Dwarfreglr: dwarfRegLR,
 
-		Adddynrel:        adddynrel,
+		Adddynrel2:       adddynrel2,
 		Archinit:         archinit,
 		Archreloc:        archreloc,
 		Archrelocvariant: archrelocvariant,

src/cmd/link/link_test.go

@@ -675,3 +675,61 @@ func TestTrampoline(t *testing.T) {
 		t.Errorf("unexpected output:\n%s", out)
 	}
 }
+
+func TestIndexMismatch(t *testing.T) {
+	// Test that index mismatch will cause a link-time error (not run-time error).
+	// This shouldn't happen with "go build". We invoke the compiler and the linker
+	// manually, and try to "trick" the linker with an inconsistent object file.
+	testenv.MustHaveGoBuild(t)
+
+	tmpdir, err := ioutil.TempDir("", "TestIndexMismatch")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmpdir)
+
+	aSrc := filepath.Join("testdata", "testIndexMismatch", "a.go")
+	bSrc := filepath.Join("testdata", "testIndexMismatch", "b.go")
+	mSrc := filepath.Join("testdata", "testIndexMismatch", "main.go")
+	aObj := filepath.Join(tmpdir, "a.o")
+	mObj := filepath.Join(tmpdir, "main.o")
+	exe := filepath.Join(tmpdir, "main.exe")
+
+	// Build a program with main package importing package a.
+	cmd := exec.Command(testenv.GoToolPath(t), "tool", "compile", "-o", aObj, aSrc)
+	t.Log(cmd)
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("compiling a.go failed: %v\n%s", err, out)
+	}
+	cmd = exec.Command(testenv.GoToolPath(t), "tool", "compile", "-I", tmpdir, "-o", mObj, mSrc)
+	t.Log(cmd)
+	out, err = cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("compiling main.go failed: %v\n%s", err, out)
+	}
+	cmd = exec.Command(testenv.GoToolPath(t), "tool", "link", "-L", tmpdir, "-o", exe, mObj)
+	t.Log(cmd)
+	out, err = cmd.CombinedOutput()
+	if err != nil {
+		t.Errorf("linking failed: %v\n%s", err, out)
+	}
+
+	// Now, overwrite a.o with the object of b.go. This should
+	// result in an index mismatch.
+	cmd = exec.Command(testenv.GoToolPath(t), "tool", "compile", "-o", aObj, bSrc)
+	t.Log(cmd)
+	out, err = cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("compiling a.go failed: %v\n%s", err, out)
+	}
+	cmd = exec.Command(testenv.GoToolPath(t), "tool", "link", "-L", tmpdir, "-o", exe, mObj)
+	t.Log(cmd)
+	out, err = cmd.CombinedOutput()
+	if err == nil {
+		t.Fatalf("linking didn't fail")
+	}
+	if !bytes.Contains(out, []byte("fingerprint mismatch")) {
+		t.Errorf("did not see expected error message. out:\n%s", out)
+	}
+}

src/cmd/link/testdata/testIndexMismatch/a.go

@@ -0,0 +1,8 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package a
+
+//go:noinline
+func A() { println("A") }

src/cmd/link/testdata/testIndexMismatch/b.go

@@ -0,0 +1,8 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package a
+
+//go:noinline
+func B() { println("B") }

src/cmd/link/testdata/testIndexMismatch/main.go

@@ -0,0 +1,9 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import "a"
+
+func main() { a.A() }