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go/src/cmd/link/internal/ppc64/asm.go
Cherry Zhang cdfff4d25a [dev.link] cmd/link: use more compact representation for external relocations 
Currently, for external relocations, the ExtReloc structure
contains all the fields of the relocation. In fact, many of the
fields are the same with the original relocation. So, instead, we
can just use an index to reference the original relocation and
not expand the fields.

There is one place where we modify relocation type: changing
R_DWARFSECTREF to R_ADDR. Get away with it by changing
downstreams.

It also makes it easier to retrieve the reloc variant.

This reduces some allocation. Linking cmd/compile with external
linking,

name           old alloc/op   new alloc/op   delta
Reloc_GC         34.1MB ± 0%    22.7MB ± 0%  -33.30%  (p=0.000 n=5+4)

Change-Id: Id08a89ed2aee705296886d3b95014b806a0d55cf
Reviewed-on: https://go-review.googlesource.com/c/go/+/231217
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Jeremy Faller <jeremy@golang.org>
2020-04-30 21:30:02 +00:00

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// Inferno utils/5l/asm.c
// https://bitbucket.org/inferno-os/inferno-os/src/default/utils/5l/asm.c
//
// Copyright © 1994-1999 Lucent Technologies Inc. All rights reserved.
// Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
// Portions Copyright © 1997-1999 Vita Nuova Limited
// Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
// Portions Copyright © 2004,2006 Bruce Ellis
// Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
// Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
// Portions Copyright © 2009 The Go Authors. All rights reserved.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package ppc64
import (
"cmd/internal/objabi"
"cmd/internal/sys"
"cmd/link/internal/ld"
"cmd/link/internal/loader"
"cmd/link/internal/sym"
"debug/elf"
"encoding/binary"
"fmt"
"log"
"strings"
"sync"
)
func genplt2(ctxt *ld.Link, ldr *loader.Loader) {
// The ppc64 ABI PLT has similar concepts to other
// architectures, but is laid out quite differently. When we
// see an R_PPC64_REL24 relocation to a dynamic symbol
// (indicating that the call needs to go through the PLT), we
// generate up to three stubs and reserve a PLT slot.
//
// 1) The call site will be bl x; nop (where the relocation
// applies to the bl). We rewrite this to bl x_stub; ld
// r2,24(r1). The ld is necessary because x_stub will save
// r2 (the TOC pointer) at 24(r1) (the "TOC save slot").
//
// 2) We reserve space for a pointer in the .plt section (once
// per referenced dynamic function). .plt is a data
// section filled solely by the dynamic linker (more like
// .plt.got on other architectures). Initially, the
// dynamic linker will fill each slot with a pointer to the
// corresponding x@plt entry point.
//
// 3) We generate the "call stub" x_stub (once per dynamic
// function/object file pair). This saves the TOC in the
// TOC save slot, reads the function pointer from x's .plt
// slot and calls it like any other global entry point
// (including setting r12 to the function address).
//
// 4) We generate the "symbol resolver stub" x@plt (once per
// dynamic function). This is solely a branch to the glink
// resolver stub.
//
// 5) We generate the glink resolver stub (only once). This
// computes which symbol resolver stub we came through and
// invokes the dynamic resolver via a pointer provided by
// the dynamic linker. This will patch up the .plt slot to
// point directly at the function so future calls go
// straight from the call stub to the real function, and
// then call the function.
// NOTE: It's possible we could make ppc64 closer to other
// architectures: ppc64's .plt is like .plt.got on other
// platforms and ppc64's .glink is like .plt on other
// platforms.
// Find all R_PPC64_REL24 relocations that reference dynamic
// imports. Reserve PLT entries for these symbols and
// generate call stubs. The call stubs need to live in .text,
// which is why we need to do this pass this early.
//
// This assumes "case 1" from the ABI, where the caller needs
// us to save and restore the TOC pointer.
var stubs []loader.Sym
for _, s := range ctxt.Textp2 {
relocs := ldr.Relocs(s)
for i := 0; i < relocs.Count(); i++ {
r := relocs.At2(i)
if r.Type() != objabi.ElfRelocOffset+objabi.RelocType(elf.R_PPC64_REL24) || ldr.SymType(r.Sym()) != sym.SDYNIMPORT {
continue
}
// Reserve PLT entry and generate symbol
// resolver
addpltsym2(ctxt, ldr, r.Sym())
// Generate call stub. Important to note that we're looking
// up the stub using the same version as the parent symbol (s),
// needed so that symtoc() will select the right .TOC. symbol
// when processing the stub. In older versions of the linker
// this was done by setting stub.Outer to the parent, but
// if the stub has the right version initially this is not needed.
n := fmt.Sprintf("%s.%s", ldr.SymName(s), ldr.SymName(r.Sym()))
stub := ldr.CreateSymForUpdate(n, ldr.SymVersion(s))
if stub.Size() == 0 {
stubs = append(stubs, stub.Sym())
gencallstub2(ctxt, ldr, 1, stub, r.Sym())
}
// Update the relocation to use the call stub
r.SetSym(stub.Sym())
// make sure the data is writeable
if ldr.AttrReadOnly(s) {
panic("can't write to read-only sym data")
}
// Restore TOC after bl. The compiler put a
// nop here for us to overwrite.
sp := ldr.Data(s)
const o1 = 0xe8410018 // ld r2,24(r1)
ctxt.Arch.ByteOrder.PutUint32(sp[r.Off()+4:], o1)
}
}
// Put call stubs at the beginning (instead of the end).
// So when resolving the relocations to calls to the stubs,
// the addresses are known and trampolines can be inserted
// when necessary.
ctxt.Textp2 = append(stubs, ctxt.Textp2...)
}
func genaddmoduledata2(ctxt *ld.Link, ldr *loader.Loader) {
initfunc, addmoduledata := ld.PrepareAddmoduledata(ctxt)
if initfunc == nil {
return
}
o := func(op uint32) {
initfunc.AddUint32(ctxt.Arch, op)
}
// addis r2, r12, .TOC.-func@ha
toc := ctxt.DotTOC2[0]
rel1 := loader.Reloc{
Off: 0,
Size: 8,
Type: objabi.R_ADDRPOWER_PCREL,
Sym: toc,
}
initfunc.AddReloc(rel1)
o(0x3c4c0000)
// addi r2, r2, .TOC.-func@l
o(0x38420000)
// mflr r31
o(0x7c0802a6)
// stdu r31, -32(r1)
o(0xf801ffe1)
// addis r3, r2, local.moduledata@got@ha
var tgt loader.Sym
if s := ldr.Lookup("local.moduledata", 0); s != 0 {
tgt = s
} else if s := ldr.Lookup("local.pluginmoduledata", 0); s != 0 {
tgt = s
} else {
tgt = ldr.LookupOrCreateSym("runtime.firstmoduledata", 0)
}
rel2 := loader.Reloc{
Off: int32(initfunc.Size()),
Size: 8,
Type: objabi.R_ADDRPOWER_GOT,
Sym: tgt,
}
initfunc.AddReloc(rel2)
o(0x3c620000)
// ld r3, local.moduledata@got@l(r3)
o(0xe8630000)
// bl runtime.addmoduledata
rel3 := loader.Reloc{
Off: int32(initfunc.Size()),
Size: 4,
Type: objabi.R_CALLPOWER,
Sym: addmoduledata,
}
initfunc.AddReloc(rel3)
o(0x48000001)
// nop
o(0x60000000)
// ld r31, 0(r1)
o(0xe8010000)
// mtlr r31
o(0x7c0803a6)
// addi r1,r1,32
o(0x38210020)
// blr
o(0x4e800020)
}
func gentext2(ctxt *ld.Link, ldr *loader.Loader) {
if ctxt.DynlinkingGo() {
genaddmoduledata2(ctxt, ldr)
}
if ctxt.LinkMode == ld.LinkInternal {
genplt2(ctxt, ldr)
}
}
// Construct a call stub in stub that calls symbol targ via its PLT
// entry.
func gencallstub2(ctxt *ld.Link, ldr *loader.Loader, abicase int, stub *loader.SymbolBuilder, targ loader.Sym) {
if abicase != 1 {
// If we see R_PPC64_TOCSAVE or R_PPC64_REL24_NOTOC
// relocations, we'll need to implement cases 2 and 3.
log.Fatalf("gencallstub only implements case 1 calls")
}
plt := ctxt.PLT2
stub.SetType(sym.STEXT)
// Save TOC pointer in TOC save slot
stub.AddUint32(ctxt.Arch, 0xf8410018) // std r2,24(r1)
// Load the function pointer from the PLT.
rel := loader.Reloc{
Off: int32(stub.Size()),
Size: 2,
Add: int64(ldr.SymPlt(targ)),
Type: objabi.R_POWER_TOC,
Sym: plt,
}
if ctxt.Arch.ByteOrder == binary.BigEndian {
rel.Off += int32(rel.Size)
}
ri1 := stub.AddReloc(rel)
ldr.SetRelocVariant(stub.Sym(), int(ri1), sym.RV_POWER_HA)
stub.AddUint32(ctxt.Arch, 0x3d820000) // addis r12,r2,targ@plt@toc@ha
rel2 := loader.Reloc{
Off: int32(stub.Size()),
Size: 2,
Add: int64(ldr.SymPlt(targ)),
Type: objabi.R_POWER_TOC,
Sym: plt,
}
if ctxt.Arch.ByteOrder == binary.BigEndian {
rel2.Off += int32(rel.Size)
}
ri2 := stub.AddReloc(rel2)
ldr.SetRelocVariant(stub.Sym(), int(ri2), sym.RV_POWER_LO)
stub.AddUint32(ctxt.Arch, 0xe98c0000) // ld r12,targ@plt@toc@l(r12)
// Jump to the loaded pointer
stub.AddUint32(ctxt.Arch, 0x7d8903a6) // mtctr r12
stub.AddUint32(ctxt.Arch, 0x4e800420) // bctr
}
func adddynrel2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loader.Sym, r loader.Reloc2, rIdx int) bool {
if target.IsElf() {
return addelfdynrel2(target, ldr, syms, s, r, rIdx)
} else if target.IsAIX() {
return ld.Xcoffadddynrel2(target, ldr, syms, s, r, rIdx)
}
return false
}
func addelfdynrel2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loader.Sym, r loader.Reloc2, rIdx int) bool {
targ := r.Sym()
var targType sym.SymKind
if targ != 0 {
targType = ldr.SymType(targ)
}
switch r.Type() {
default:
if r.Type() >= objabi.ElfRelocOffset {
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):
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.)
su.SetRelocAdd(rIdx, r.Add()+int64(ldr.SymLocalentry(targ))*4)
if targType == sym.SDYNIMPORT {
// Should have been handled in elfsetupplt
ldr.Errorf(s, "unexpected R_PPC64_REL24 for dyn import")
}
return true
case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC_REL32):
su := ldr.MakeSymbolUpdater(s)
su.SetRelocType(rIdx, objabi.R_PCREL)
su.SetRelocAdd(rIdx, r.Add()+4)
if targType == sym.SDYNIMPORT {
ldr.Errorf(s, "unexpected R_PPC_REL32 for dyn import")
}
return true
case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_ADDR64):
su := ldr.MakeSymbolUpdater(s)
su.SetRelocType(rIdx, objabi.R_ADDR)
if targType == sym.SDYNIMPORT {
// These happen in .toc sections
ld.Adddynsym2(ldr, target, syms, targ)
rela := ldr.MakeSymbolUpdater(syms.Rela2)
rela.AddAddrPlus(target.Arch, s, int64(r.Off()))
rela.AddUint64(target.Arch, ld.ELF64_R_INFO(uint32(ldr.SymDynid(targ)), uint32(elf.R_PPC64_ADDR64)))
rela.AddUint64(target.Arch, uint64(r.Add()))
su.SetRelocType(rIdx, objabi.ElfRelocOffset) // ignore during relocsym
}
return true
case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_TOC16):
su := ldr.MakeSymbolUpdater(s)
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):
su := ldr.MakeSymbolUpdater(s)
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):
su := ldr.MakeSymbolUpdater(s)
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):
su := ldr.MakeSymbolUpdater(s)
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):
su := ldr.MakeSymbolUpdater(s)
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):
su := ldr.MakeSymbolUpdater(s)
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):
su := ldr.MakeSymbolUpdater(s)
su.SetRelocType(rIdx, objabi.R_PCREL)
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):
su := ldr.MakeSymbolUpdater(s)
su.SetRelocType(rIdx, objabi.R_PCREL)
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):
su := ldr.MakeSymbolUpdater(s)
su.SetRelocType(rIdx, objabi.R_PCREL)
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 targType != sym.SDYNIMPORT {
return true
}
// TODO(austin): Translate our relocations to ELF
return false
}
func xcoffreloc1(arch *sys.Arch, out *ld.OutBuf, s *sym.Symbol, r *sym.Reloc, sectoff int64) bool {
rs := r.Xsym
emitReloc := func(v uint16, off uint64) {
out.Write64(uint64(sectoff) + off)
out.Write32(uint32(rs.Dynid))
out.Write16(v)
}
var v uint16
switch r.Type {
default:
return false
case objabi.R_ADDR:
v = ld.XCOFF_R_POS
if r.Siz == 4 {
v |= 0x1F << 8
} else {
v |= 0x3F << 8
}
emitReloc(v, 0)
case objabi.R_ADDRPOWER_TOCREL:
case objabi.R_ADDRPOWER_TOCREL_DS:
emitReloc(ld.XCOFF_R_TOCU|(0x0F<<8), 2)
emitReloc(ld.XCOFF_R_TOCL|(0x0F<<8), 6)
case objabi.R_POWER_TLS_LE:
emitReloc(ld.XCOFF_R_TLS_LE|0x0F<<8, 2)
case objabi.R_CALLPOWER:
if r.Siz != 4 {
return false
}
emitReloc(ld.XCOFF_R_RBR|0x19<<8, 0)
case objabi.R_XCOFFREF:
emitReloc(ld.XCOFF_R_REF|0x3F<<8, 0)
}
return true
}
func elfreloc1(ctxt *ld.Link, r *sym.Reloc, sectoff int64) bool {
// Beware that bit0~bit15 start from the third byte of a instruction in Big-Endian machines.
if r.Type == objabi.R_ADDR || r.Type == objabi.R_POWER_TLS || r.Type == objabi.R_CALLPOWER {
} else {
if ctxt.Arch.ByteOrder == binary.BigEndian {
sectoff += 2
}
}
ctxt.Out.Write64(uint64(sectoff))
elfsym := ld.ElfSymForReloc(ctxt, r.Xsym)
switch r.Type {
default:
return false
case objabi.R_ADDR, objabi.R_DWARFSECREF:
switch r.Siz {
case 4:
ctxt.Out.Write64(uint64(elf.R_PPC64_ADDR32) | uint64(elfsym)<<32)
case 8:
ctxt.Out.Write64(uint64(elf.R_PPC64_ADDR64) | uint64(elfsym)<<32)
default:
return false
}
case objabi.R_POWER_TLS:
ctxt.Out.Write64(uint64(elf.R_PPC64_TLS) | uint64(elfsym)<<32)
case objabi.R_POWER_TLS_LE:
ctxt.Out.Write64(uint64(elf.R_PPC64_TPREL16) | uint64(elfsym)<<32)
case objabi.R_POWER_TLS_IE:
ctxt.Out.Write64(uint64(elf.R_PPC64_GOT_TPREL16_HA) | uint64(elfsym)<<32)
ctxt.Out.Write64(uint64(r.Xadd))
ctxt.Out.Write64(uint64(sectoff + 4))
ctxt.Out.Write64(uint64(elf.R_PPC64_GOT_TPREL16_LO_DS) | uint64(elfsym)<<32)
case objabi.R_ADDRPOWER:
ctxt.Out.Write64(uint64(elf.R_PPC64_ADDR16_HA) | uint64(elfsym)<<32)
ctxt.Out.Write64(uint64(r.Xadd))
ctxt.Out.Write64(uint64(sectoff + 4))
ctxt.Out.Write64(uint64(elf.R_PPC64_ADDR16_LO) | uint64(elfsym)<<32)
case objabi.R_ADDRPOWER_DS:
ctxt.Out.Write64(uint64(elf.R_PPC64_ADDR16_HA) | uint64(elfsym)<<32)
ctxt.Out.Write64(uint64(r.Xadd))
ctxt.Out.Write64(uint64(sectoff + 4))
ctxt.Out.Write64(uint64(elf.R_PPC64_ADDR16_LO_DS) | uint64(elfsym)<<32)
case objabi.R_ADDRPOWER_GOT:
ctxt.Out.Write64(uint64(elf.R_PPC64_GOT16_HA) | uint64(elfsym)<<32)
ctxt.Out.Write64(uint64(r.Xadd))
ctxt.Out.Write64(uint64(sectoff + 4))
ctxt.Out.Write64(uint64(elf.R_PPC64_GOT16_LO_DS) | uint64(elfsym)<<32)
case objabi.R_ADDRPOWER_PCREL:
ctxt.Out.Write64(uint64(elf.R_PPC64_REL16_HA) | uint64(elfsym)<<32)
ctxt.Out.Write64(uint64(r.Xadd))
ctxt.Out.Write64(uint64(sectoff + 4))
ctxt.Out.Write64(uint64(elf.R_PPC64_REL16_LO) | uint64(elfsym)<<32)
r.Xadd += 4
case objabi.R_ADDRPOWER_TOCREL:
ctxt.Out.Write64(uint64(elf.R_PPC64_TOC16_HA) | uint64(elfsym)<<32)
ctxt.Out.Write64(uint64(r.Xadd))
ctxt.Out.Write64(uint64(sectoff + 4))
ctxt.Out.Write64(uint64(elf.R_PPC64_TOC16_LO) | uint64(elfsym)<<32)
case objabi.R_ADDRPOWER_TOCREL_DS:
ctxt.Out.Write64(uint64(elf.R_PPC64_TOC16_HA) | uint64(elfsym)<<32)
ctxt.Out.Write64(uint64(r.Xadd))
ctxt.Out.Write64(uint64(sectoff + 4))
ctxt.Out.Write64(uint64(elf.R_PPC64_TOC16_LO_DS) | uint64(elfsym)<<32)
case objabi.R_CALLPOWER:
if r.Siz != 4 {
return false
}
ctxt.Out.Write64(uint64(elf.R_PPC64_REL24) | uint64(elfsym)<<32)
}
ctxt.Out.Write64(uint64(r.Xadd))
return true
}
func elfsetupplt(ctxt *ld.Link, plt, got *loader.SymbolBuilder, dynamic loader.Sym) {
if plt.Size() == 0 {
// The dynamic linker stores the address of the
// dynamic resolver and the DSO identifier in the two
// doublewords at the beginning of the .plt section
// before the PLT array. Reserve space for these.
plt.SetSize(16)
}
}
func machoreloc1(arch *sys.Arch, out *ld.OutBuf, s *sym.Symbol, r *sym.Reloc, sectoff int64) bool {
return false
}
// Return the value of .TOC. for symbol s
func symtoc(syms *ld.ArchSyms, s *sym.Symbol) int64 {
v := s.Version
if s.Outer != nil {
v = s.Outer.Version
}
toc := syms.DotTOC[v]
if toc == nil {
ld.Errorf(s, "TOC-relative relocation in object without .TOC.")
return 0
}
return toc.Value
}
// archreloctoc relocates a TOC relative symbol.
// If the symbol pointed by this TOC relative symbol is in .data or .bss, the
// default load instruction can be changed to an addi instruction and the
// symbol address can be used directly.
// This code is for AIX only.
func archreloctoc(target *ld.Target, syms *ld.ArchSyms, r *sym.Reloc, s *sym.Symbol, val int64) int64 {
if target.IsLinux() {
ld.Errorf(s, "archrelocaddr called for %s relocation\n", r.Sym.Name)
}
var o1, o2 uint32
o1 = uint32(val >> 32)
o2 = uint32(val)
var t int64
useAddi := false
const prefix = "TOC."
var tarSym *sym.Symbol
if strings.HasPrefix(r.Sym.Name, prefix) {
tarSym = r.Sym.R[0].Sym
} else {
ld.Errorf(s, "archreloctoc called for a symbol without TOC anchor")
}
if target.IsInternal() && tarSym != nil && tarSym.Attr.Reachable() && (tarSym.Sect.Seg == &ld.Segdata) {
t = ld.Symaddr(tarSym) + r.Add - syms.TOC.Value
// change ld to addi in the second instruction
o2 = (o2 & 0x03FF0000) | 0xE<<26
useAddi = true
} else {
t = ld.Symaddr(r.Sym) + r.Add - syms.TOC.Value
}
if t != int64(int32(t)) {
ld.Errorf(s, "TOC relocation for %s is too big to relocate %s: 0x%x", s.Name, r.Sym, t)
}
if t&0x8000 != 0 {
t += 0x10000
}
o1 |= uint32((t >> 16) & 0xFFFF)
switch r.Type {
case objabi.R_ADDRPOWER_TOCREL_DS:
if useAddi {
o2 |= uint32(t) & 0xFFFF
} else {
if t&3 != 0 {
ld.Errorf(s, "bad DS reloc for %s: %d", s.Name, ld.Symaddr(r.Sym))
}
o2 |= uint32(t) & 0xFFFC
}
default:
return -1
}
return int64(o1)<<32 | int64(o2)
}
// archrelocaddr relocates a symbol address.
// This code is for AIX only.
func archrelocaddr(target *ld.Target, syms *ld.ArchSyms, r *sym.Reloc, s *sym.Symbol, val int64) int64 {
if target.IsAIX() {
ld.Errorf(s, "archrelocaddr called for %s relocation\n", r.Sym.Name)
}
var o1, o2 uint32
if target.IsBigEndian() {
o1 = uint32(val >> 32)
o2 = uint32(val)
} else {
o1 = uint32(val)
o2 = uint32(val >> 32)
}
// We are spreading a 31-bit address across two instructions, putting the
// high (adjusted) part in the low 16 bits of the first instruction and the
// low part in the low 16 bits of the second instruction, or, in the DS case,
// bits 15-2 (inclusive) of the address into bits 15-2 of the second
// instruction (it is an error in this case if the low 2 bits of the address
// are non-zero).
t := ld.Symaddr(r.Sym) + r.Add
if t < 0 || t >= 1<<31 {
ld.Errorf(s, "relocation for %s is too big (>=2G): 0x%x", s.Name, ld.Symaddr(r.Sym))
}
if t&0x8000 != 0 {
t += 0x10000
}
switch r.Type {
case objabi.R_ADDRPOWER:
o1 |= (uint32(t) >> 16) & 0xffff
o2 |= uint32(t) & 0xffff
case objabi.R_ADDRPOWER_DS:
o1 |= (uint32(t) >> 16) & 0xffff
if t&3 != 0 {
ld.Errorf(s, "bad DS reloc for %s: %d", s.Name, ld.Symaddr(r.Sym))
}
o2 |= uint32(t) & 0xfffc
default:
return -1
}
if target.IsBigEndian() {
return int64(o1)<<32 | int64(o2)
}
return int64(o2)<<32 | int64(o1)
}
// resolve direct jump relocation r in s, and add trampoline if necessary
func trampoline(ctxt *ld.Link, ldr *loader.Loader, ri int, rs, s loader.Sym) {
// Trampolines are created if the branch offset is too large and the linker cannot insert a call stub to handle it.
// For internal linking, trampolines are always created for long calls.
// For external linking, the linker can insert a call stub to handle a long call, but depends on having the TOC address in
// r2. For those build modes with external linking where the TOC address is not maintained in r2, trampolines must be created.
if ctxt.IsExternal() && (ctxt.DynlinkingGo() || ctxt.BuildMode == ld.BuildModeCArchive || ctxt.BuildMode == ld.BuildModeCShared || ctxt.BuildMode == ld.BuildModePIE) {
// No trampolines needed since r2 contains the TOC
return
}
relocs := ldr.Relocs(s)
r := relocs.At2(ri)
t := ldr.SymValue(rs) + r.Add() - (ldr.SymValue(s) + int64(r.Off()))
switch r.Type() {
case objabi.R_CALLPOWER:
// If branch offset is too far then create a trampoline.
if (ctxt.IsExternal() && ldr.SymSect(s) != ldr.SymSect(rs)) || (ctxt.IsInternal() && int64(int32(t<<6)>>6) != t) || (*ld.FlagDebugTramp > 1 && ldr.SymPkg(s) != ldr.SymPkg(rs)) {
var tramp loader.Sym
for i := 0; ; i++ {
// Using r.Add as part of the name is significant in functions like duffzero where the call
// target is at some offset within the function. Calls to duff+8 and duff+256 must appear as
// distinct trampolines.
name := ldr.SymName(rs)
if r.Add() == 0 {
name = name + fmt.Sprintf("-tramp%d", i)
} else {
name = name + fmt.Sprintf("%+x-tramp%d", r.Add(), i)
}
// Look up the trampoline in case it already exists
tramp = ldr.LookupOrCreateSym(name, int(ldr.SymVersion(rs)))
if ldr.SymValue(tramp) == 0 {
break
}
t = ldr.SymValue(tramp) + r.Add() - (ldr.SymValue(s) + int64(r.Off()))
// With internal linking, the trampoline can be used if it is not too far.
// With external linking, the trampoline must be in this section for it to be reused.
if (ctxt.IsInternal() && int64(int32(t<<6)>>6) == t) || (ctxt.IsExternal() && ldr.SymSect(s) == ldr.SymSect(tramp)) {
break
}
}
if ldr.SymType(tramp) == 0 {
if ctxt.DynlinkingGo() || ctxt.BuildMode == ld.BuildModeCArchive || ctxt.BuildMode == ld.BuildModeCShared || ctxt.BuildMode == ld.BuildModePIE {
// Should have returned for above cases
ctxt.Errorf(s, "unexpected trampoline for shared or dynamic linking")
} else {
trampb := ldr.MakeSymbolUpdater(tramp)
ctxt.AddTramp(trampb)
gentramp(ctxt, ldr, trampb, rs, r.Add())
}
}
sb := ldr.MakeSymbolUpdater(s)
relocs := sb.Relocs()
r := relocs.At2(ri)
r.SetSym(tramp)
r.SetAdd(0) // This was folded into the trampoline target address
}
default:
ctxt.Errorf(s, "trampoline called with non-jump reloc: %d (%s)", r.Type(), sym.RelocName(ctxt.Arch, r.Type()))
}
}
func gentramp(ctxt *ld.Link, ldr *loader.Loader, tramp *loader.SymbolBuilder, target loader.Sym, offset int64) {
tramp.SetSize(16) // 4 instructions
P := make([]byte, tramp.Size())
t := ldr.SymValue(target) + offset
var o1, o2 uint32
if ctxt.IsAIX() {
// On AIX, the address is retrieved with a TOC symbol.
// For internal linking, the "Linux" way might still be used.
// However, all text symbols are accessed with a TOC symbol as
// text relocations aren't supposed to be possible.
// So, keep using the external linking way to be more AIX friendly.
o1 = uint32(0x3fe20000) // lis r2, toctargetaddr hi
o2 = uint32(0xebff0000) // ld r31, toctargetaddr lo
toctramp := ldr.CreateSymForUpdate("TOC."+ldr.SymName(tramp.Sym()), 0)
toctramp.SetType(sym.SXCOFFTOC)
toctramp.SetReachable(true)
toctramp.AddAddrPlus(ctxt.Arch, target, offset)
r := loader.Reloc{
Off: 0,
Type: objabi.R_ADDRPOWER_TOCREL_DS,
Size: 8, // generates 2 relocations: HA + LO
Sym: toctramp.Sym(),
}
tramp.AddReloc(r)
} else {
// Used for default build mode for an executable
// Address of the call target is generated using
// relocation and doesn't depend on r2 (TOC).
o1 = uint32(0x3fe00000) // lis r31,targetaddr hi
o2 = uint32(0x3bff0000) // addi r31,targetaddr lo
// With external linking, the target address must be
// relocated using LO and HA
if ctxt.IsExternal() {
r := loader.Reloc{
Off: 0,
Type: objabi.R_ADDRPOWER,
Size: 8, // generates 2 relocations: HA + LO
Sym: target,
Add: offset,
}
tramp.AddReloc(r)
} else {
// adjustment needed if lo has sign bit set
// when using addi to compute address
val := uint32((t & 0xffff0000) >> 16)
if t&0x8000 != 0 {
val += 1
}
o1 |= val // hi part of addr
o2 |= uint32(t & 0xffff) // lo part of addr
}
}
o3 := uint32(0x7fe903a6) // mtctr r31
o4 := uint32(0x4e800420) // bctr
ctxt.Arch.ByteOrder.PutUint32(P, o1)
ctxt.Arch.ByteOrder.PutUint32(P[4:], o2)
ctxt.Arch.ByteOrder.PutUint32(P[8:], o3)
ctxt.Arch.ByteOrder.PutUint32(P[12:], o4)
tramp.SetData(P)
}
func archreloc(target *ld.Target, syms *ld.ArchSyms, r *sym.Reloc, s *sym.Symbol, val int64) (int64, bool) {
if target.IsExternal() {
// On AIX, relocations (except TLS ones) must be also done to the
// value with the current addresses.
switch r.Type {
default:
if target.IsAIX() {
return val, false
}
case objabi.R_POWER_TLS, objabi.R_POWER_TLS_LE, objabi.R_POWER_TLS_IE:
r.Done = false
// check Outer is nil, Type is TLSBSS?
r.Xadd = r.Add
r.Xsym = r.Sym
return val, true
case objabi.R_ADDRPOWER,
objabi.R_ADDRPOWER_DS,
objabi.R_ADDRPOWER_TOCREL,
objabi.R_ADDRPOWER_TOCREL_DS,
objabi.R_ADDRPOWER_GOT,
objabi.R_ADDRPOWER_PCREL:
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 += ld.Symaddr(rs) - ld.Symaddr(rs.Outer)
rs = rs.Outer
}
if rs.Type != sym.SHOSTOBJ && rs.Type != sym.SDYNIMPORT && rs.Type != sym.SUNDEFEXT && rs.Sect == nil {
ld.Errorf(s, "missing section for %s", rs.Name)
}
r.Xsym = rs
if !target.IsAIX() {
return val, true
}
case objabi.R_CALLPOWER:
r.Done = false
r.Xsym = r.Sym
r.Xadd = r.Add
if !target.IsAIX() {
return val, true
}
}
}
switch r.Type {
case objabi.R_CONST:
return r.Add, true
case objabi.R_GOTOFF:
return ld.Symaddr(r.Sym) + r.Add - ld.Symaddr(syms.GOT), true
case objabi.R_ADDRPOWER_TOCREL, objabi.R_ADDRPOWER_TOCREL_DS:
return archreloctoc(target, syms, r, s, val), true
case objabi.R_ADDRPOWER, objabi.R_ADDRPOWER_DS:
return archrelocaddr(target, syms, r, s, val), true
case objabi.R_CALLPOWER:
// Bits 6 through 29 = (S + A - P) >> 2
t := ld.Symaddr(r.Sym) + r.Add - (s.Value + int64(r.Off))
if t&3 != 0 {
ld.Errorf(s, "relocation for %s+%d is not aligned: %d", r.Sym.Name, r.Off, t)
}
// If branch offset is too far then create a trampoline.
if int64(int32(t<<6)>>6) != t {
ld.Errorf(s, "direct call too far: %s %x", r.Sym.Name, t)
}
return val | int64(uint32(t)&^0xfc000003), true
case objabi.R_POWER_TOC: // S + A - .TOC.
return ld.Symaddr(r.Sym) + r.Add - symtoc(syms, s), true
case objabi.R_POWER_TLS_LE:
// The thread pointer points 0x7000 bytes after the start of the
// thread local storage area as documented in section "3.7.2 TLS
// Runtime Handling" of "Power Architecture 64-Bit ELF V2 ABI
// Specification".
v := r.Sym.Value - 0x7000
if target.IsAIX() {
// On AIX, the thread pointer points 0x7800 bytes after
// the TLS.
v -= 0x800
}
if int64(int16(v)) != v {
ld.Errorf(s, "TLS offset out of range %d", v)
}
return (val &^ 0xffff) | (v & 0xffff), true
}
return val, false
}
func archrelocvariant(target *ld.Target, syms *ld.ArchSyms, r *sym.Reloc, s *sym.Symbol, t int64) int64 {
switch r.Variant & sym.RV_TYPE_MASK {
default:
ld.Errorf(s, "unexpected relocation variant %d", r.Variant)
fallthrough
case sym.RV_NONE:
return t
case sym.RV_POWER_LO:
if r.Variant&sym.RV_CHECK_OVERFLOW != 0 {
// Whether to check for signed or unsigned
// overflow depends on the instruction
var o1 uint32
if target.IsBigEndian() {
o1 = binary.BigEndian.Uint32(s.P[r.Off-2:])
} else {
o1 = binary.LittleEndian.Uint32(s.P[r.Off:])
}
switch o1 >> 26 {
case 24, // ori
26, // xori
28: // andi
if t>>16 != 0 {
goto overflow
}
default:
if int64(int16(t)) != t {
goto overflow
}
}
}
return int64(int16(t))
case sym.RV_POWER_HA:
t += 0x8000
fallthrough
// Fallthrough
case sym.RV_POWER_HI:
t >>= 16
if r.Variant&sym.RV_CHECK_OVERFLOW != 0 {
// Whether to check for signed or unsigned
// overflow depends on the instruction
var o1 uint32
if target.IsBigEndian() {
o1 = binary.BigEndian.Uint32(s.P[r.Off-2:])
} else {
o1 = binary.LittleEndian.Uint32(s.P[r.Off:])
}
switch o1 >> 26 {
case 25, // oris
27, // xoris
29: // andis
if t>>16 != 0 {
goto overflow
}
default:
if int64(int16(t)) != t {
goto overflow
}
}
}
return int64(int16(t))
case sym.RV_POWER_DS:
var o1 uint32
if target.IsBigEndian() {
o1 = uint32(binary.BigEndian.Uint16(s.P[r.Off:]))
} else {
o1 = uint32(binary.LittleEndian.Uint16(s.P[r.Off:]))
}
if t&3 != 0 {
ld.Errorf(s, "relocation for %s+%d is not aligned: %d", r.Sym.Name, r.Off, t)
}
if (r.Variant&sym.RV_CHECK_OVERFLOW != 0) && int64(int16(t)) != t {
goto overflow
}
return int64(o1)&0x3 | int64(int16(t))
}
overflow:
ld.Errorf(s, "relocation for %s+%d is too big: %d", r.Sym.Name, r.Off, t)
return t
}
func addpltsym2(ctxt *ld.Link, ldr *loader.Loader, s loader.Sym) {
if ldr.SymPlt(s) >= 0 {
return
}
ld.Adddynsym2(ldr, &ctxt.Target, &ctxt.ArchSyms, s)
if ctxt.IsELF {
plt := ldr.MakeSymbolUpdater(ctxt.PLT2)
rela := ldr.MakeSymbolUpdater(ctxt.RelaPLT2)
if plt.Size() == 0 {
panic("plt is not set up")
}
// Create the glink resolver if necessary
glink := ensureglinkresolver2(ctxt, ldr)
// Write symbol resolver stub (just a branch to the
// glink resolver stub)
rel := loader.Reloc{
Off: int32(glink.Size()),
Size: 4,
Type: objabi.R_CALLPOWER,
Sym: glink.Sym(),
}
glink.AddReloc(rel)
glink.AddUint32(ctxt.Arch, 0x48000000) // b .glink
// In the ppc64 ABI, the dynamic linker is responsible
// for writing the entire PLT. We just need to
// reserve 8 bytes for each PLT entry and generate a
// JMP_SLOT dynamic relocation for it.
//
// TODO(austin): ABI v1 is different
ldr.SetPlt(s, int32(plt.Size()))
plt.Grow(plt.Size() + 8)
rela.AddAddrPlus(ctxt.Arch, plt.Sym(), int64(ldr.SymPlt(s)))
rela.AddUint64(ctxt.Arch, ld.ELF64_R_INFO(uint32(ldr.SymDynid(s)), uint32(elf.R_PPC64_JMP_SLOT)))
rela.AddUint64(ctxt.Arch, 0)
} else {
ctxt.Errorf(s, "addpltsym: unsupported binary format")
}
}
// Generate the glink resolver stub if necessary and return the .glink section
func ensureglinkresolver2(ctxt *ld.Link, ldr *loader.Loader) *loader.SymbolBuilder {
gs := ldr.LookupOrCreateSym(".glink", 0)
glink := ldr.MakeSymbolUpdater(gs)
if glink.Size() != 0 {
return glink
}
// This is essentially the resolver from the ppc64 ELF ABI.
// At entry, r12 holds the address of the symbol resolver stub
// for the target routine and the argument registers hold the
// arguments for the target routine.
//
// This stub is PIC, so first get the PC of label 1 into r11.
// Other things will be relative to this.
glink.AddUint32(ctxt.Arch, 0x7c0802a6) // mflr r0
glink.AddUint32(ctxt.Arch, 0x429f0005) // bcl 20,31,1f
glink.AddUint32(ctxt.Arch, 0x7d6802a6) // 1: mflr r11
glink.AddUint32(ctxt.Arch, 0x7c0803a6) // mtlf r0
// Compute the .plt array index from the entry point address.
// Because this is PIC, everything is relative to label 1b (in
// r11):
// r0 = ((r12 - r11) - (res_0 - r11)) / 4 = (r12 - res_0) / 4
glink.AddUint32(ctxt.Arch, 0x3800ffd0) // li r0,-(res_0-1b)=-48
glink.AddUint32(ctxt.Arch, 0x7c006214) // add r0,r0,r12
glink.AddUint32(ctxt.Arch, 0x7c0b0050) // sub r0,r0,r11
glink.AddUint32(ctxt.Arch, 0x7800f082) // srdi r0,r0,2
// r11 = address of the first byte of the PLT
glink.AddSymRef(ctxt.Arch, ctxt.PLT2, 0, objabi.R_ADDRPOWER, 8)
glink.AddUint32(ctxt.Arch, 0x3d600000) // addis r11,0,.plt@ha
glink.AddUint32(ctxt.Arch, 0x396b0000) // addi r11,r11,.plt@l
// Load r12 = dynamic resolver address and r11 = DSO
// identifier from the first two doublewords of the PLT.
glink.AddUint32(ctxt.Arch, 0xe98b0000) // ld r12,0(r11)
glink.AddUint32(ctxt.Arch, 0xe96b0008) // ld r11,8(r11)
// Jump to the dynamic resolver
glink.AddUint32(ctxt.Arch, 0x7d8903a6) // mtctr r12
glink.AddUint32(ctxt.Arch, 0x4e800420) // bctr
// The symbol resolvers must immediately follow.
// res_0:
// Add DT_PPC64_GLINK .dynamic entry, which points to 32 bytes
// before the first symbol resolver stub.
du := ldr.MakeSymbolUpdater(ctxt.Dynamic2)
ld.Elfwritedynentsymplus2(ctxt, du, ld.DT_PPC64_GLINK, glink.Sym(), glink.Size()-32)
return glink
}
func asmb(ctxt *ld.Link, _ *loader.Loader) {
if ctxt.IsELF {
ld.Asmbelfsetup()
}
var wg sync.WaitGroup
for _, sect := range ld.Segtext.Sections {
offset := sect.Vaddr - ld.Segtext.Vaddr + ld.Segtext.Fileoff
// Handle additional text sections with Codeblk
if sect.Name == ".text" {
ld.WriteParallel(&wg, ld.Codeblk, ctxt, offset, sect.Vaddr, sect.Length)
} else {
ld.WriteParallel(&wg, ld.Datblk, ctxt, offset, sect.Vaddr, sect.Length)
}
}
for _, sect := range ld.Segtext.Sections[1:] {
offset := sect.Vaddr - ld.Segtext.Vaddr + ld.Segtext.Fileoff
ld.WriteParallel(&wg, ld.Datblk, ctxt, offset, sect.Vaddr, sect.Length)
}
if ld.Segrodata.Filelen > 0 {
ld.WriteParallel(&wg, ld.Datblk, ctxt, ld.Segrodata.Fileoff, ld.Segrodata.Vaddr, ld.Segrodata.Filelen)
}
if ld.Segrelrodata.Filelen > 0 {
ld.WriteParallel(&wg, ld.Datblk, ctxt, ld.Segrelrodata.Fileoff, ld.Segrelrodata.Vaddr, ld.Segrelrodata.Filelen)
}
ld.WriteParallel(&wg, ld.Datblk, ctxt, ld.Segdata.Fileoff, ld.Segdata.Vaddr, ld.Segdata.Filelen)
ld.WriteParallel(&wg, ld.Dwarfblk, ctxt, ld.Segdwarf.Fileoff, ld.Segdwarf.Vaddr, ld.Segdwarf.Filelen)
wg.Wait()
}
func asmb2(ctxt *ld.Link) {
/* output symbol table */
ld.Symsize = 0
ld.Lcsize = 0
symo := uint32(0)
if !*ld.FlagS {
// TODO: rationalize
switch ctxt.HeadType {
default:
if ctxt.IsELF {
symo = uint32(ld.Segdwarf.Fileoff + ld.Segdwarf.Filelen)
symo = uint32(ld.Rnd(int64(symo), int64(*ld.FlagRound)))
}
case objabi.Hplan9:
symo = uint32(ld.Segdata.Fileoff + ld.Segdata.Filelen)
case objabi.Haix:
// Nothing to do
}
ctxt.Out.SeekSet(int64(symo))
switch ctxt.HeadType {
default:
if ctxt.IsELF {
ld.Asmelfsym(ctxt)
ctxt.Out.Write(ld.Elfstrdat)
if ctxt.LinkMode == ld.LinkExternal {
ld.Elfemitreloc(ctxt)
}
}
case objabi.Hplan9:
ld.Asmplan9sym(ctxt)
sym := ctxt.Syms.Lookup("pclntab", 0)
if sym != nil {
ld.Lcsize = int32(len(sym.P))
ctxt.Out.Write(sym.P)
}
case objabi.Haix:
// symtab must be added once sections have been created in ld.Asmbxcoff
}
}
ctxt.Out.SeekSet(0)
switch ctxt.HeadType {
default:
case objabi.Hplan9: /* plan 9 */
ctxt.Out.Write32(0x647) /* magic */
ctxt.Out.Write32(uint32(ld.Segtext.Filelen)) /* sizes */
ctxt.Out.Write32(uint32(ld.Segdata.Filelen))
ctxt.Out.Write32(uint32(ld.Segdata.Length - ld.Segdata.Filelen))
ctxt.Out.Write32(uint32(ld.Symsize)) /* nsyms */
ctxt.Out.Write32(uint32(ld.Entryvalue(ctxt))) /* va of entry */
ctxt.Out.Write32(0)
ctxt.Out.Write32(uint32(ld.Lcsize))
case objabi.Hlinux,
objabi.Hfreebsd,
objabi.Hnetbsd,
objabi.Hopenbsd:
ld.Asmbelf(ctxt, int64(symo))
case objabi.Haix:
fileoff := uint32(ld.Segdwarf.Fileoff + ld.Segdwarf.Filelen)
fileoff = uint32(ld.Rnd(int64(fileoff), int64(*ld.FlagRound)))
ld.Asmbxcoff(ctxt, int64(fileoff))
}
if *ld.FlagC {
fmt.Printf("textsize=%d\n", ld.Segtext.Filelen)
fmt.Printf("datsize=%d\n", ld.Segdata.Filelen)
fmt.Printf("bsssize=%d\n", ld.Segdata.Length-ld.Segdata.Filelen)
fmt.Printf("symsize=%d\n", ld.Symsize)
fmt.Printf("lcsize=%d\n", ld.Lcsize)
fmt.Printf("total=%d\n", ld.Segtext.Filelen+ld.Segdata.Length+uint64(ld.Symsize)+uint64(ld.Lcsize))
}
}
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