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[dev.link] cmd/link: directly use loader.ExtReloc in ELF relocation generation

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Convert the part that uses relocations to use loader.ExtReloc
directly. It still uses sym.Symbols for now, but not sym.Relocs.

This reduces some memory usage: linking cmd/compile with external
linking,

name             old allocs/op  new allocs/op  delta
Loadlibfull_GC     52.2MB ± 0%    13.9MB ± 0%  -73.40%  (p=0.008 n=5+5)

name             old live-B     new live-B     delta
Loadlibfull_GC      75.5M ± 0%     61.9M ± 0%  -18.02%  (p=0.008 n=5+5)

Change-Id: I317ecbf516063c42b255b2caba310ea6281342d7
Reviewed-on: https://go-review.googlesource.com/c/go/+/231319
Reviewed-by: Jeremy Faller <jeremy@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
This commit is contained in:
Cherry Zhang 2020-04-30 21:15:54 -04:00
parent 7aa6e0faf2
commit 1667b35740
7 changed files with 144 additions and 47 deletions
Download patch file Download diff file Expand all files Collapse all files

26
src/cmd/link/internal/amd64/asm.go
View file

@ -393,36 +393,38 @@ func adddynrel2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s load
return false
}
func elfreloc1(ctxt *ld.Link, r *sym.Reloc, sectoff int64) bool {
func elfreloc2(ctxt *ld.Link, ldr *loader.Loader, s loader.Sym, r loader.ExtRelocView, sectoff int64) bool {
ctxt.Out.Write64(uint64(sectoff))
elfsym := ld.ElfSymForReloc(ctxt, r.Xsym)
switch r.Type {
xsym := ldr.Syms[r.Xsym]
elfsym := ld.ElfSymForReloc(ctxt, xsym)
siz := r.Siz()
switch r.Type() {
default:
return false
case objabi.R_ADDR, objabi.R_DWARFSECREF:
if r.Siz == 4 {
if siz == 4 {
ctxt.Out.Write64(uint64(elf.R_X86_64_32) | uint64(elfsym)<<32)
} else if r.Siz == 8 {
} else if siz == 8 {
ctxt.Out.Write64(uint64(elf.R_X86_64_64) | uint64(elfsym)<<32)
} else {
return false
}
case objabi.R_TLS_LE:
if r.Siz == 4 {
if siz == 4 {
ctxt.Out.Write64(uint64(elf.R_X86_64_TPOFF32) | uint64(elfsym)<<32)
} else {
return false
}
case objabi.R_TLS_IE:
if r.Siz == 4 {
if siz == 4 {
ctxt.Out.Write64(uint64(elf.R_X86_64_GOTTPOFF) | uint64(elfsym)<<32)
} else {
return false
}
case objabi.R_CALL:
if r.Siz == 4 {
if r.Xsym.Type == sym.SDYNIMPORT {
if siz == 4 {
if xsym.Type == sym.SDYNIMPORT {
if ctxt.DynlinkingGo() {
ctxt.Out.Write64(uint64(elf.R_X86_64_PLT32) | uint64(elfsym)<<32)
} else {
@ -435,8 +437,8 @@ func elfreloc1(ctxt *ld.Link, r *sym.Reloc, sectoff int64) bool {
return false
}
case objabi.R_PCREL:
if r.Siz == 4 {
if r.Xsym.Type == sym.SDYNIMPORT && r.Xsym.ElfType() == elf.STT_FUNC {
if siz == 4 {
if xsym.Type == sym.SDYNIMPORT && xsym.ElfType() == elf.STT_FUNC {
ctxt.Out.Write64(uint64(elf.R_X86_64_PLT32) | uint64(elfsym)<<32)
} else {
ctxt.Out.Write64(uint64(elf.R_X86_64_PC32) | uint64(elfsym)<<32)
@ -445,7 +447,7 @@ func elfreloc1(ctxt *ld.Link, r *sym.Reloc, sectoff int64) bool {
return false
}
case objabi.R_GOTPCREL:
if r.Siz == 4 {
if siz == 4 {
ctxt.Out.Write64(uint64(elf.R_X86_64_GOTPCREL) | uint64(elfsym)<<32)
} else {
return false

2
src/cmd/link/internal/amd64/obj.go
View file

@ -52,7 +52,7 @@ func Init() (*sys.Arch, ld.Arch) {
Archrelocvariant: archrelocvariant,
Asmb: asmb,
Asmb2: asmb2,
Elfreloc1: elfreloc1,
Elfreloc2: elfreloc2,
Elfsetupplt: elfsetupplt,
Gentext2: gentext2,
Machoreloc1: machoreloc1,

31
src/cmd/link/internal/ld/elf.go
View file

@ -1374,6 +1374,11 @@ func elfshreloc(arch *sys.Arch, sect *sym.Section) *ElfShdr {
}
func elfrelocsect(ctxt *Link, sect *sym.Section, syms []*sym.Symbol) {
if !ctxt.IsAMD64() {
elfrelocsect2(ctxt, sect, syms)
return
}
// If main section is SHT_NOBITS, nothing to relocate.
// Also nothing to relocate in .shstrtab.
if sect.Vaddr >= sect.Seg.Vaddr+sect.Seg.Filelen {
@ -1394,6 +1399,7 @@ func elfrelocsect(ctxt *Link, sect *sym.Section, syms []*sym.Symbol) {
}
}
ldr := ctxt.loader
eaddr := int32(sect.Vaddr + sect.Length)
for _, s := range syms {
if !s.Attr.Reachable() {
@ -1402,24 +1408,23 @@ func elfrelocsect(ctxt *Link, sect *sym.Section, syms []*sym.Symbol) {
if s.Value >= int64(eaddr) {
break
}
for ri := range s.R {
r := &s.R[ri]
if r.Done {
i := loader.Sym(s.SymIdx)
relocs := ldr.ExtRelocs(i)
for ri := 0; ri < relocs.Count(); ri++ {
r := relocs.At(ri)
if r.Xsym == 0 {
Errorf(s, "missing xsym in relocation %v", ldr.SymName(r.Sym()))
continue
}
if r.Xsym == nil {
Errorf(s, "missing xsym in relocation %#v %#v", r.Sym.Name, s)
continue
}
esr := ElfSymForReloc(ctxt, r.Xsym)
esr := ElfSymForReloc(ctxt, ldr.Syms[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)
Errorf(s, "reloc %d (%s) to non-elf symbol %s (outer=%s) %d (%s)", r.Type(), sym.RelocName(ctxt.Arch, r.Type()), ldr.Syms[r.Sym()].Name, ldr.Syms[r.Xsym].Name, ldr.Syms[r.Sym()].Type, ldr.Syms[r.Sym()].Type)
}
if !r.Xsym.Attr.Reachable() {
Errorf(s, "unreachable reloc %d (%s) target %v", r.Type, sym.RelocName(ctxt.Arch, r.Type), r.Xsym.Name)
if !ldr.AttrReachable(r.Xsym) {
Errorf(s, "unreachable reloc %d (%s) target %v", r.Type(), sym.RelocName(ctxt.Arch, r.Type()), ldr.Syms[r.Xsym].Name)
}
if !thearch.Elfreloc1(ctxt, r, int64(uint64(s.Value+int64(r.Off))-sect.Vaddr)) {
Errorf(s, "unsupported obj reloc %d (%s)/%d to %s", r.Type, sym.RelocName(ctxt.Arch, r.Type), r.Siz, r.Sym.Name)
if !thearch.Elfreloc2(ctxt, ldr, i, r, int64(uint64(s.Value+int64(r.Off()))-sect.Vaddr)) {
Errorf(s, "unsupported obj reloc %d (%s)/%d to %s", r.Type(), sym.RelocName(ctxt.Arch, r.Type()), r.Siz(), ldr.Syms[r.Sym()].Name)
}
}
}

54
src/cmd/link/internal/ld/elf2.go
View file

@ -23,3 +23,57 @@ func elfsetstring(s *sym.Symbol, str string, off int) {
elfstr[nelfstr].off = off
nelfstr++
}
func elfrelocsect2(ctxt *Link, sect *sym.Section, syms []*sym.Symbol) {
// If main section is SHT_NOBITS, nothing to relocate.
// Also nothing to relocate in .shstrtab.
if sect.Vaddr >= sect.Seg.Vaddr+sect.Seg.Filelen {
return
}
if sect.Name == ".shstrtab" {
return
}
sect.Reloff = uint64(ctxt.Out.Offset())
for i, s := range syms {
if !s.Attr.Reachable() {
continue
}
if uint64(s.Value) >= sect.Vaddr {
syms = syms[i:]
break
}
}
eaddr := int32(sect.Vaddr + sect.Length)
for _, s := range syms {
if !s.Attr.Reachable() {
continue
}
if s.Value >= int64(eaddr) {
break
}
for ri := range s.R {
r := &s.R[ri]
if r.Done {
continue
}
if r.Xsym == nil {
Errorf(s, "missing xsym in relocation %#v %#v", r.Sym.Name, s)
continue
}
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() {
Errorf(s, "unreachable reloc %d (%s) target %v", r.Type, sym.RelocName(ctxt.Arch, r.Type), r.Xsym.Name)
}
if !thearch.Elfreloc1(ctxt, r, int64(uint64(s.Value+int64(r.Off))-sect.Vaddr)) {
Errorf(s, "unsupported obj reloc %d (%s)/%d to %s", r.Type, sym.RelocName(ctxt.Arch, r.Type), r.Siz, r.Sym.Name)
}
}
}
sect.Rellen = uint64(ctxt.Out.Offset()) - sect.Reloff
}

5
src/cmd/link/internal/ld/lib.go
View file

@ -270,6 +270,7 @@ type Arch struct {
Asmb2 func(*Link)
Elfreloc1 func(*Link, *sym.Reloc, int64) bool
Elfreloc2 func(*Link, *loader.Loader, loader.Sym, loader.ExtRelocView, int64) bool
Elfsetupplt func(ctxt *Link, plt, gotplt *loader.SymbolBuilder, dynamic loader.Sym)
Gentext func(*Link)
Gentext2 func(*Link, *loader.Loader)
@ -2825,9 +2826,9 @@ func addToTextp(ctxt *Link) {
ctxt.Textp = textp
}
func (ctxt *Link) loadlibfull(symGroupType []sym.SymKind, needReloc bool) {
func (ctxt *Link) loadlibfull(symGroupType []sym.SymKind, needReloc, needExtReloc bool) {
// Load full symbol contents, resolve indexed references.
ctxt.loader.LoadFull(ctxt.Arch, ctxt.Syms, needReloc)
ctxt.loader.LoadFull(ctxt.Arch, ctxt.Syms, needReloc, needExtReloc)
// Convert ctxt.Moduledata2 to ctxt.Moduledata, etc
if ctxt.Moduledata2 != 0 {

7
src/cmd/link/internal/ld/main.go
View file

@ -335,10 +335,13 @@ func Main(arch *sys.Arch, theArch Arch) {
// An exception is internal linking on Windows, see pe.go:addPEBaseRelocSym
// Wasm is another exception, where it applies text relocations in Asmb2.
needReloc := (ctxt.IsWindows() && ctxt.IsInternal()) || ctxt.IsWasm()
ctxt.loadlibfull(symGroupType, needReloc) // XXX do it here for now
// On AMD64 ELF, we directly use the loader's ExtRelocs, so we don't
// need conversion. Otherwise we do.
needExtReloc := ctxt.IsExternal() && !(ctxt.IsAMD64() && ctxt.IsELF)
ctxt.loadlibfull(symGroupType, needReloc, needExtReloc) // XXX do it here for now
} else {
bench.Start("loadlibfull")
ctxt.loadlibfull(symGroupType, true) // XXX do it here for now
ctxt.loadlibfull(symGroupType, true, false) // XXX do it here for now
bench.Start("reloc")
ctxt.reloc2()
}

66
src/cmd/link/internal/loader/loader.go
View file

@ -56,6 +56,14 @@ type ExtReloc struct {
Xadd int64
}
// ExtRelocView is a view of an external relocation.
// It is intended to be constructed on the fly, such as ExtRelocs.At.
// It is not the data structure used to store the payload internally.
type ExtRelocView struct {
Reloc2
*ExtReloc
}
// Reloc2 holds a "handle" to access a relocation record from an
// object file.
type Reloc2 struct {
@ -1116,7 +1124,7 @@ func (l *Loader) InitOutData() {
l.outdata = make([][]byte, l.extStart)
}
// SetExtRelocs sets the section of the i-th symbol. i is global index.
// SetExtRelocs sets the external relocations of the i-th symbol. i is global index.
func (l *Loader) SetExtRelocs(i Sym, relocs []ExtReloc) {
l.extRelocs[i] = relocs
}
@ -1699,6 +1707,24 @@ func (l *Loader) relocs(r *oReader, li int) Relocs {
}
}
// ExtRelocs returns the external relocations of the i-th symbol.
func (l *Loader) ExtRelocs(i Sym) ExtRelocs {
return ExtRelocs{l.Relocs(i), l.extRelocs[i]}
}
// ExtRelocs represents the set of external relocations of a symbol.
type ExtRelocs struct {
rs Relocs
es []ExtReloc
}
func (ers ExtRelocs) Count() int { return len(ers.es) }
func (ers ExtRelocs) At(j int) ExtRelocView {
i := ers.es[j].Idx
return ExtRelocView{ers.rs.At2(i), &ers.es[j]}
}
// RelocByOff implements sort.Interface for sorting relocations by offset.
type RelocByOff []Reloc
@ -2033,7 +2059,7 @@ func (l *Loader) preprocess(arch *sys.Arch, s Sym, name string) {
}
// Load full contents.
func (l *Loader) LoadFull(arch *sys.Arch, syms *sym.Symbols, needReloc bool) {
func (l *Loader) LoadFull(arch *sys.Arch, syms *sym.Symbols, needReloc, needExtReloc bool) {
// create all Symbols first.
l.growSyms(l.NSym())
l.growSects(l.NSym())
@ -2047,7 +2073,7 @@ func (l *Loader) LoadFull(arch *sys.Arch, syms *sym.Symbols, needReloc bool) {
nr := 0 // total number of sym.Reloc's we'll need
for _, o := range l.objs[1:] {
nr += loadObjSyms(l, syms, o.r, needReloc)
nr += loadObjSyms(l, syms, o.r, needReloc, needExtReloc)
}
// Make a first pass through the external symbols, making
@ -2063,7 +2089,7 @@ func (l *Loader) LoadFull(arch *sys.Arch, syms *sym.Symbols, needReloc bool) {
if needReloc {
nr += len(pp.relocs)
}
if int(i) < len(l.extRelocs) {
if needExtReloc && int(i) < len(l.extRelocs) {
nr += len(l.extRelocs[i])
}
// create and install the sym.Symbol here so that l.Syms will
@ -2079,7 +2105,7 @@ func (l *Loader) LoadFull(arch *sys.Arch, syms *sym.Symbols, needReloc bool) {
// allocate a single large slab of relocations for all live symbols
if nr != 0 {
l.relocBatch = make([]sym.Reloc, nr)
if len(l.extRelocs) != 0 {
if needExtReloc {
l.relocExtBatch = make([]sym.RelocExt, nr)
}
}
@ -2102,8 +2128,9 @@ func (l *Loader) LoadFull(arch *sys.Arch, syms *sym.Symbols, needReloc bool) {
relocs := l.Relocs(i)
l.convertRelocations(i, &relocs, s, false)
}
l.convertExtRelocs(s, i)
if needExtReloc {
l.convertExtRelocs(s, i)
}
// Copy data
s.P = pp.data
@ -2114,7 +2141,7 @@ func (l *Loader) LoadFull(arch *sys.Arch, syms *sym.Symbols, needReloc bool) {
// load contents of defined symbols
for _, o := range l.objs[1:] {
loadObjFull(l, o.r, needReloc)
loadObjFull(l, o.r, needReloc, needExtReloc)
}
// Sanity check: we should have consumed all batched allocations.
@ -2170,17 +2197,21 @@ func (l *Loader) LoadFull(arch *sys.Arch, syms *sym.Symbols, needReloc bool) {
l.plt = nil
l.got = nil
l.dynid = nil
l.relocVariant = nil
l.extRelocs = nil
if needExtReloc { // converted to sym.Relocs, drop loader references
l.relocVariant = nil
l.extRelocs = nil
}
// Drop fields that are no longer needed.
for _, i := range l.extReader.syms {
pp := l.getPayload(i)
pp.name = ""
pp.relocs = nil
pp.reltypes = nil
pp.auxs = nil
pp.data = nil
if needExtReloc {
pp.relocs = nil
pp.reltypes = nil
}
}
}
@ -2450,7 +2481,7 @@ func topLevelSym(sname string, skind sym.SymKind) bool {
// 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.
func loadObjSyms(l *Loader, syms *sym.Symbols, r *oReader, needReloc bool) int {
func loadObjSyms(l *Loader, syms *sym.Symbols, r *oReader, needReloc, needExtReloc bool) int {
nr := 0
for i, n := 0, r.NSym()+r.NNonpkgdef(); i < n; i++ {
gi := r.syms[i]
@ -2483,7 +2514,7 @@ func loadObjSyms(l *Loader, syms *sym.Symbols, r *oReader, needReloc bool) int {
if needReloc {
nr += r.NReloc(i)
}
if int(gi) < len(l.extRelocs) {
if needExtReloc && int(gi) < len(l.extRelocs) {
nr += len(l.extRelocs[gi])
}
}
@ -2690,7 +2721,7 @@ func (l *Loader) FreeSym(i Sym) {
}
}
func loadObjFull(l *Loader, r *oReader, needReloc bool) {
func loadObjFull(l *Loader, r *oReader, needReloc, needExtReloc bool) {
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
@ -2722,8 +2753,9 @@ func loadObjFull(l *Loader, r *oReader, needReloc bool) {
l.relocBatch = batch[relocs.Count():]
l.convertRelocations(gi, &relocs, s, false)
}
l.convertExtRelocs(s, gi)
if needExtReloc {
l.convertExtRelocs(s, gi)
}
// Aux symbol info
auxs := r.Auxs(i)