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[dev.link] cmd/link: create symbol updated lazily in amd64 adddynrel

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Tweak the code in the amd64 version of adddynrel to avoid creating a
symbol updated for the symbol being processed until it's clear we need
to alter its relocations. This should help performance for the
PIE+internal linking scenario.

Reviewed-on: https://go-review.googlesource.com/c/go/+/229866
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

Change-Id: Id25adfd81a5bbd2dde0f80a83b976397ba6abfb5
Reviewed-on: https://go-review.googlesource.com/c/go/+/230026
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
This commit is contained in:
Than McIntosh 2020-04-24 11:07:17 -04:00 committed by Cherry Zhang
parent 027055240f
commit 42cca1a7fe
2 changed files with 11 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
src/cmd/link/internal/amd64/asm.go
View File

@ -85,7 +85,6 @@ func adddynrel2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s load
targType = ldr.SymType(targ)
}
su := ldr.MakeSymbolUpdater(s)
switch r.Type() {
default:
if r.Type() >= objabi.ElfRelocOffset {
@ -103,6 +102,7 @@ func adddynrel2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s load
if (targType == 0 || targType == sym.SXREF) && !ldr.AttrVisibilityHidden(targ) {
ldr.Errorf(s, "unknown symbol %s in pcrel", ldr.SymName(targ))
}
su := ldr.MakeSymbolUpdater(s)
su.SetRelocType(rIdx, objabi.R_PCREL)
su.SetRelocAdd(rIdx, r.Add()+4)
return true
@ -114,11 +114,13 @@ func adddynrel2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s load
if targType == 0 || targType == sym.SXREF {
ldr.Errorf(s, "unknown symbol %s in pcrel", ldr.SymName(targ))
}
su := ldr.MakeSymbolUpdater(s)
su.SetRelocType(rIdx, objabi.R_PCREL)
su.SetRelocAdd(rIdx, r.Add()+8)
return true
case objabi.ElfRelocOffset + objabi.RelocType(elf.R_X86_64_PLT32):
su := ldr.MakeSymbolUpdater(s)
su.SetRelocType(rIdx, objabi.R_PCREL)
su.SetRelocAdd(rIdx, r.Add()+4)
if targType == sym.SDYNIMPORT {
@ -132,11 +134,11 @@ func adddynrel2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s load
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):
su := ldr.MakeSymbolUpdater(s)
if targType != sym.SDYNIMPORT {
// have symbol
sData := ldr.Data(s)
if r.Off() >= 2 && sData[r.Off()-2] == 0x8b {
su := ldr.MakeSymbolUpdater(s)
su.MakeWritable()
// turn MOVQ of GOT entry into LEAQ of symbol itself
writeableData := su.Data()
@ -160,6 +162,7 @@ func adddynrel2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s load
if targType == sym.SDYNIMPORT {
ldr.Errorf(s, "unexpected R_X86_64_64 relocation for dynamic symbol %s", ldr.SymName(targ))
}
su := ldr.MakeSymbolUpdater(s)
su.SetRelocType(rIdx, objabi.R_ADDR)
if target.IsPIE() && target.IsInternal() {
// For internal linking PIE, this R_ADDR relocation cannot
@ -174,6 +177,7 @@ func adddynrel2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s load
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?
su := ldr.MakeSymbolUpdater(s)
su.SetRelocType(rIdx, objabi.R_ADDR)
if targType == sym.SDYNIMPORT {
@ -184,6 +188,7 @@ func adddynrel2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s load
case objabi.MachoRelocOffset + ld.MACHO_X86_64_RELOC_BRANCH*2 + 1:
if targType == sym.SDYNIMPORT {
addpltsym2(target, ldr, syms, targ)
su := ldr.MakeSymbolUpdater(s)
su.SetRelocSym(rIdx, syms.PLT2)
su.SetRelocType(rIdx, objabi.R_PCREL)
su.SetRelocAdd(rIdx, int64(ldr.SymPlt(targ)))
@ -196,6 +201,7 @@ func adddynrel2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s load
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:
su := ldr.MakeSymbolUpdater(s)
su.SetRelocType(rIdx, objabi.R_PCREL)
if targType == sym.SDYNIMPORT {
@ -227,6 +233,7 @@ func adddynrel2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s load
ldr.Errorf(s, "unexpected GOT reloc for non-dynamic symbol %s", ldr.SymName(targ))
}
addgotsym2(target, ldr, syms, targ)
su := ldr.MakeSymbolUpdater(s)
su.SetRelocType(rIdx, objabi.R_PCREL)
su.SetRelocSym(rIdx, syms.GOT2)
su.SetRelocAdd(rIdx, r.Add()+int64(ldr.SymGot(targ)))
@ -251,12 +258,14 @@ func adddynrel2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s load
// Internal linking, for both ELF and Mach-O.
// Build a PLT entry and change the relocation target to that entry.
addpltsym2(target, ldr, syms, targ)
su := ldr.MakeSymbolUpdater(s)
su.SetRelocSym(rIdx, syms.PLT2)
su.SetRelocAdd(rIdx, int64(ldr.SymPlt(targ)))
return true
case objabi.R_ADDR:
if ldr.SymType(s) == sym.STEXT && target.IsElf() {
su := ldr.MakeSymbolUpdater(s)
if target.IsSolaris() {
addpltsym2(target, ldr, syms, targ)
su.SetRelocSym(rIdx, syms.PLT2)

4
src/cmd/link/internal/ld/data.go
View File

@ -684,10 +684,6 @@ func dynrelocsym2(ctxt *Link, s loader.Sym) {
relocs := ldr.Relocs(s)
for ri := 0; ri < relocs.Count(); ri++ {
r := relocs.At2(ri)
// FIXME: the call to Adddynrel2 below is going to wind up
// eagerly promoting the symbol to external, which is not great--
// it would improve things for internal/PIE if we could
// create the symbol updater lazily.
if ctxt.BuildMode == BuildModePIE && ctxt.LinkMode == LinkInternal {
// It's expected that some relocations will be done
// later by relocsym (R_TLS_LE, R_ADDROFF), so