[dev.link] cmd/link: convert Asmb2 path to loader APIs for Elf/AMD64

This patch converts the linker's Asmb2 phase to use loader APIs
for AMD64 (other architectures to be converted in a subsequent
patch).

Change-Id: I5a9aa9b03769cabc1a22b982f48fd113213d7bcf
Reviewed-on: https://go-review.googlesource.com/c/go/+/233338
Run-TryBot: Than McIntosh <thanm@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

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

@@ -396,9 +396,9 @@ func adddynrel2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s load
 func elfreloc2(ctxt *ld.Link, ldr *loader.Loader, s loader.Sym, r loader.ExtRelocView, sectoff int64) bool {
 	ctxt.Out.Write64(uint64(sectoff))
 
-	xsym := ldr.Syms[r.Xsym]
+	elfsym := ld.ElfSymForReloc2(ctxt, r.Xsym)
-	elfsym := ld.ElfSymForReloc(ctxt, xsym)
 	siz := r.Siz()
+	xst := ldr.SymType(r.Xsym)
 	switch r.Type() {
 	default:
 		return false
@@ -424,7 +424,7 @@ func elfreloc2(ctxt *ld.Link, ldr *loader.Loader, s loader.Sym, r loader.ExtRelo
 		}
 	case objabi.R_CALL:
 		if siz == 4 {
-			if xsym.Type == sym.SDYNIMPORT {
+			if xst == sym.SDYNIMPORT {
 				if ctxt.DynlinkingGo() {
 					ctxt.Out.Write64(uint64(elf.R_X86_64_PLT32) | uint64(elfsym)<<32)
 				} else {
@@ -438,7 +438,7 @@ func elfreloc2(ctxt *ld.Link, ldr *loader.Loader, s loader.Sym, r loader.ExtRelo
 		}
 	case objabi.R_PCREL:
 		if siz == 4 {
-			if xsym.Type == sym.SDYNIMPORT && xsym.ElfType() == elf.STT_FUNC {
+			if xst == sym.SDYNIMPORT && ldr.SymElfType(r.Xsym) == 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)

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

@@ -2104,6 +2104,11 @@ func (ctxt *Link) buildinfo() {
 	ldr := ctxt.loader
 	s := ldr.CreateSymForUpdate(".go.buildinfo", 0)
 	s.SetReachable(true)
+	if !ctxt.IsAIX() {
+		// On AIX, .go.buildinfo must be in the symbol table as
+		// it has relocations.
+		s.SetNotInSymbolTable(true)
+	}
 	s.SetType(sym.SBUILDINFO)
 	s.SetAlign(16)
 	// The \xff is invalid UTF-8, meant to make it less likely

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

@@ -2112,12 +2112,6 @@ func (d *dwctxt2) dwarfaddshstrings(ctxt *Link, shstrtab loader.Sym) {
 	panic("not yet implemented")
 }
 
-// Add section symbols for DWARF debug info.  This is called before
-// dwarfaddelfheaders.
-func (d *dwctxt2) dwarfaddelfsectionsyms(ctxt *Link) {
-	panic("not yet implemented")
-}
-
 // dwarfcompress compresses the DWARF sections. Relocations are applied
 // on the fly. After this, dwarfp will contain a different (new) set of
 // symbols, and sections may have been replaced.
@@ -2152,3 +2146,19 @@ func saveDwsectCUSize(sname string, pkgname string, size uint64) {
 func addDwsectCUSize(sname string, pkgname string, size uint64) {
 	dwsectCUSize[sname+"."+pkgname] += size
 }
+
+func dwarfaddelfsectionsyms(ctxt *Link) {
+	if *FlagW { // disable dwarf
+		return
+	}
+	if ctxt.LinkMode != LinkExternal {
+		return
+	}
+
+	ldr := ctxt.loader
+	for _, si := range dwarfp2 {
+		s := si.secSym()
+		sect := ldr.SymSect(si.secSym())
+		putelfsectionsym(ctxt, ctxt.Out, s, sect.Elfsect.(*ElfShdr).shnum)
+	}
+}

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

@@ -67,7 +67,7 @@ func dwarfaddshstrings(ctxt *Link, shstrtab *loader.SymbolBuilder) {
 
 // Add section symbols for DWARF debug info.  This is called before
 // dwarfaddelfheaders.
-func dwarfaddelfsectionsyms(ctxt *Link) {
+func dwarfaddelfsectionsyms2(ctxt *Link) {
 	if *FlagW { // disable dwarf
 		return
 	}
@@ -76,20 +76,20 @@ func dwarfaddelfsectionsyms(ctxt *Link) {
 	}
 
 	s := ctxt.Syms.Lookup(".debug_info", 0)
-	putelfsectionsym(ctxt, ctxt.Out, s, s.Sect.Elfsect.(*ElfShdr).shnum)
+	putelfsectionsym2(ctxt, ctxt.Out, s, s.Sect.Elfsect.(*ElfShdr).shnum)
 	s = ctxt.Syms.Lookup(".debug_abbrev", 0)
-	putelfsectionsym(ctxt, ctxt.Out, s, s.Sect.Elfsect.(*ElfShdr).shnum)
+	putelfsectionsym2(ctxt, ctxt.Out, s, s.Sect.Elfsect.(*ElfShdr).shnum)
 	s = ctxt.Syms.Lookup(".debug_line", 0)
-	putelfsectionsym(ctxt, ctxt.Out, s, s.Sect.Elfsect.(*ElfShdr).shnum)
+	putelfsectionsym2(ctxt, ctxt.Out, s, s.Sect.Elfsect.(*ElfShdr).shnum)
 	s = ctxt.Syms.Lookup(".debug_frame", 0)
-	putelfsectionsym(ctxt, ctxt.Out, s, s.Sect.Elfsect.(*ElfShdr).shnum)
+	putelfsectionsym2(ctxt, ctxt.Out, s, s.Sect.Elfsect.(*ElfShdr).shnum)
 	s = ctxt.Syms.Lookup(".debug_loc", 0)
 	if s.Sect != nil {
-		putelfsectionsym(ctxt, ctxt.Out, s, s.Sect.Elfsect.(*ElfShdr).shnum)
+		putelfsectionsym2(ctxt, ctxt.Out, s, s.Sect.Elfsect.(*ElfShdr).shnum)
 	}
 	s = ctxt.Syms.Lookup(".debug_ranges", 0)
 	if s.Sect != nil {
-		putelfsectionsym(ctxt, ctxt.Out, s, s.Sect.Elfsect.(*ElfShdr).shnum)
+		putelfsectionsym2(ctxt, ctxt.Out, s, s.Sect.Elfsect.(*ElfShdr).shnum)
 	}
 }
 

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

@@ -1344,12 +1344,7 @@ func elfshreloc(arch *sys.Arch, sect *sym.Section) *ElfShdr {
 	return sh
 }
 
-func elfrelocsect(ctxt *Link, sect *sym.Section, syms []*sym.Symbol) {
+func elfrelocsect(ctxt *Link, sect *sym.Section, syms []loader.Sym) {
-	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 {
@@ -1359,43 +1354,43 @@ func elfrelocsect(ctxt *Link, sect *sym.Section, syms []*sym.Symbol) {
 		return
 	}
 
+	ldr := ctxt.loader
 	sect.Reloff = uint64(ctxt.Out.Offset())
 	for i, s := range syms {
-		if !s.Attr.Reachable() {
+		if !ldr.AttrReachable(s) {
-			continue
+			panic("should never happen")
 		}
-		if uint64(s.Value) >= sect.Vaddr {
+		if uint64(ldr.SymValue(s)) >= sect.Vaddr {
 			syms = syms[i:]
 			break
 		}
 	}
 
-	ldr := ctxt.loader
 	eaddr := int32(sect.Vaddr + sect.Length)
 	for _, s := range syms {
-		if !s.Attr.Reachable() {
+		if !ldr.AttrReachable(s) {
 			continue
 		}
-		if s.Value >= int64(eaddr) {
+		if ldr.SymValue(s) >= int64(eaddr) {
 			break
 		}
-		i := loader.Sym(s.SymIdx)
+
-		relocs := ldr.ExtRelocs(i)
+		relocs := ldr.ExtRelocs(s)
 		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()))
+				ldr.Errorf(s, "missing xsym in relocation")
 				continue
 			}
-			esr := ElfSymForReloc(ctxt, ldr.Syms[r.Xsym])
+			esr := ElfSymForReloc2(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()), ldr.Syms[r.Sym()].Name, ldr.Syms[r.Xsym].Name, ldr.Syms[r.Sym()].Type, ldr.Syms[r.Sym()].Type)
+				ldr.Errorf(s, "reloc %d (%s) to non-elf symbol %s (outer=%s) %d (%s)", r.Type(), sym.RelocName(ctxt.Arch, r.Type()), ldr.SymName(r.Sym()), ldr.SymName(r.Xsym), ldr.SymType(r.Sym()), ldr.SymType(r.Sym()).String())
 			}
 			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)
+				ldr.Errorf(s, "unreachable reloc %d (%s) target %v", r.Type(), sym.RelocName(ctxt.Arch, r.Type()), ldr.SymName(r.Xsym))
 			}
-			if !thearch.Elfreloc2(ctxt, ldr, i, r, int64(uint64(s.Value+int64(r.Off()))-sect.Vaddr)) {
+			if !thearch.Elfreloc2(ctxt, ldr, s, r, int64(uint64(ldr.SymValue(s)+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)
+				ldr.Errorf(s, "unsupported obj reloc %d (%s)/%d to %s", r.Type, sym.RelocName(ctxt.Arch, r.Type()), r.Siz(), ldr.SymName(r.Sym()))
 			}
 		}
 	}
@@ -1404,32 +1399,37 @@ func elfrelocsect(ctxt *Link, sect *sym.Section, syms []*sym.Symbol) {
 }
 
 func Elfemitreloc(ctxt *Link) {
+	if !ctxt.IsAMD64() {
+		Elfemitreloc2(ctxt)
+		return
+	}
+
 	for ctxt.Out.Offset()&7 != 0 {
 		ctxt.Out.Write8(0)
 	}
 
 	for _, sect := range Segtext.Sections {
 		if sect.Name == ".text" {
-			elfrelocsect(ctxt, sect, ctxt.Textp)
+			elfrelocsect(ctxt, sect, ctxt.Textp2)
 		} else {
-			elfrelocsect(ctxt, sect, ctxt.datap)
+			elfrelocsect(ctxt, sect, ctxt.datap2)
 		}
 	}
 
 	for _, sect := range Segrodata.Sections {
-		elfrelocsect(ctxt, sect, ctxt.datap)
+		elfrelocsect(ctxt, sect, ctxt.datap2)
 	}
 	for _, sect := range Segrelrodata.Sections {
-		elfrelocsect(ctxt, sect, ctxt.datap)
+		elfrelocsect(ctxt, sect, ctxt.datap2)
 	}
 	for _, sect := range Segdata.Sections {
-		elfrelocsect(ctxt, sect, ctxt.datap)
+		elfrelocsect(ctxt, sect, ctxt.datap2)
 	}
 	for i := 0; i < len(Segdwarf.Sections); i++ {
 		sect := Segdwarf.Sections[i]
-		si := dwarfp[i]
+		si := dwarfp2[i]
-		if si.secSym() != sect.Sym ||
+		if si.secSym() != loader.Sym(sect.Sym2) ||
-			si.secSym().Sect != sect {
+			ctxt.loader.SymSect(si.secSym()) != sect {
 			panic("inconsistency between dwarfp and Segdwarf")
 		}
 		elfrelocsect(ctxt, sect, si.syms)
@@ -1734,13 +1734,16 @@ func (ctxt *Link) doelf() {
 }
 
 // Do not write DT_NULL.  elfdynhash will finish it.
-func shsym(sh *ElfShdr, s *sym.Symbol) {
+func shsym2(sh *ElfShdr, ldr *loader.Loader, s loader.Sym) {
-	addr := Symaddr(s)
+	if s == 0 {
+		panic("bad symbol in shsym2")
+	}
+	addr := ldr.SymValue(s)
 	if sh.flags&SHF_ALLOC != 0 {
 		sh.addr = uint64(addr)
 	}
-	sh.off = uint64(datoff(s, addr))
+	sh.off = uint64(datoff(ldr, s, addr))
-	sh.size = uint64(s.Size)
+	sh.size = uint64(ldr.SymSize(s))
 }
 
 func phsh(ph *ElfPhdr, sh *ElfShdr) {
@@ -1782,6 +1785,12 @@ func Asmbelfsetup() {
 }
 
 func Asmbelf(ctxt *Link, symo int64) {
+	if !ctxt.IsAMD64() {
+		Asmbelf2(ctxt, symo)
+		return
+	}
+
+	ldr := ctxt.loader
 	eh := getElfEhdr()
 	switch ctxt.Arch.Family {
 	default:
@@ -2000,22 +2009,22 @@ func Asmbelf(ctxt *Link, symo int64) {
 		sh.link = uint32(elfshname(".dynstr").shnum)
 
 		// sh.info is the index of first non-local symbol (number of local symbols)
-		s := ctxt.Syms.Lookup(".dynsym", 0)
+		s := ldr.Lookup(".dynsym", 0)
 		i := uint32(0)
-		for sub := s; sub != nil; sub = symSub(ctxt, sub) {
+		for sub := s; sub != 0; sub = ldr.SubSym(sub) {
 			i++
-			if !sub.Attr.Local() {
+			if !ldr.AttrLocal(sub) {
 				break
 			}
 		}
 		sh.info = i
-		shsym(sh, s)
+		shsym2(sh, ldr, s)
 
 		sh = elfshname(".dynstr")
 		sh.type_ = SHT_STRTAB
 		sh.flags = SHF_ALLOC
 		sh.addralign = 1
-		shsym(sh, ctxt.Syms.Lookup(".dynstr", 0))
+		shsym2(sh, ldr, ldr.Lookup(".dynstr", 0))
 
 		if elfverneed != 0 {
 			sh := elfshname(".gnu.version")
@@ -2024,7 +2033,7 @@ func Asmbelf(ctxt *Link, symo int64) {
 			sh.addralign = 2
 			sh.link = uint32(elfshname(".dynsym").shnum)
 			sh.entsize = 2
-			shsym(sh, ctxt.Syms.Lookup(".gnu.version", 0))
+			shsym2(sh, ldr, ldr.Lookup(".gnu.version", 0))
 
 			sh = elfshname(".gnu.version_r")
 			sh.type_ = SHT_GNU_VERNEED
@@ -2032,7 +2041,7 @@ func Asmbelf(ctxt *Link, symo int64) {
 			sh.addralign = uint64(ctxt.Arch.RegSize)
 			sh.info = uint32(elfverneed)
 			sh.link = uint32(elfshname(".dynstr").shnum)
-			shsym(sh, ctxt.Syms.Lookup(".gnu.version_r", 0))
+			shsym2(sh, ldr, ldr.Lookup(".gnu.version_r", 0))
 		}
 
 		if elfRelType == ".rela" {
@@ -2043,7 +2052,7 @@ func Asmbelf(ctxt *Link, symo int64) {
 			sh.addralign = uint64(ctxt.Arch.RegSize)
 			sh.link = uint32(elfshname(".dynsym").shnum)
 			sh.info = uint32(elfshname(".plt").shnum)
-			shsym(sh, ctxt.Syms.Lookup(".rela.plt", 0))
+			shsym2(sh, ldr, ldr.Lookup(".rela.plt", 0))
 
 			sh = elfshname(".rela")
 			sh.type_ = SHT_RELA
@@ -2051,7 +2060,7 @@ func Asmbelf(ctxt *Link, symo int64) {
 			sh.entsize = ELF64RELASIZE
 			sh.addralign = 8
 			sh.link = uint32(elfshname(".dynsym").shnum)
-			shsym(sh, ctxt.Syms.Lookup(".rela", 0))
+			shsym2(sh, ldr, ldr.Lookup(".rela", 0))
 		} else {
 			sh := elfshname(".rel.plt")
 			sh.type_ = SHT_REL
@@ -2059,7 +2068,7 @@ func Asmbelf(ctxt *Link, symo int64) {
 			sh.entsize = ELF32RELSIZE
 			sh.addralign = 4
 			sh.link = uint32(elfshname(".dynsym").shnum)
-			shsym(sh, ctxt.Syms.Lookup(".rel.plt", 0))
+			shsym2(sh, ldr, ldr.Lookup(".rel.plt", 0))
 
 			sh = elfshname(".rel")
 			sh.type_ = SHT_REL
@@ -2067,7 +2076,7 @@ func Asmbelf(ctxt *Link, symo int64) {
 			sh.entsize = ELF32RELSIZE
 			sh.addralign = 4
 			sh.link = uint32(elfshname(".dynsym").shnum)
-			shsym(sh, ctxt.Syms.Lookup(".rel", 0))
+			shsym2(sh, ldr, ldr.Lookup(".rel", 0))
 		}
 
 		if eh.machine == EM_PPC64 {
@@ -2075,7 +2084,7 @@ func Asmbelf(ctxt *Link, symo int64) {
 			sh.type_ = SHT_PROGBITS
 			sh.flags = SHF_ALLOC + SHF_EXECINSTR
 			sh.addralign = 4
-			shsym(sh, ctxt.Syms.Lookup(".glink", 0))
+			shsym2(sh, ldr, ldr.Lookup(".glink", 0))
 		}
 
 		sh = elfshname(".plt")
@@ -2096,7 +2105,7 @@ func Asmbelf(ctxt *Link, symo int64) {
 			sh.entsize = 4
 		}
 		sh.addralign = sh.entsize
-		shsym(sh, ctxt.Syms.Lookup(".plt", 0))
+		shsym2(sh, ldr, ldr.Lookup(".plt", 0))
 
 		// On ppc64, .got comes from the input files, so don't
 		// create it here, and .got.plt is not used.
@@ -2106,14 +2115,14 @@ func Asmbelf(ctxt *Link, symo int64) {
 			sh.flags = SHF_ALLOC + SHF_WRITE
 			sh.entsize = uint64(ctxt.Arch.RegSize)
 			sh.addralign = uint64(ctxt.Arch.RegSize)
-			shsym(sh, ctxt.Syms.Lookup(".got", 0))
+			shsym2(sh, ldr, ldr.Lookup(".got", 0))
 
 			sh = elfshname(".got.plt")
 			sh.type_ = SHT_PROGBITS
 			sh.flags = SHF_ALLOC + SHF_WRITE
 			sh.entsize = uint64(ctxt.Arch.RegSize)
 			sh.addralign = uint64(ctxt.Arch.RegSize)
-			shsym(sh, ctxt.Syms.Lookup(".got.plt", 0))
+			shsym2(sh, ldr, ldr.Lookup(".got.plt", 0))
 		}
 
 		sh = elfshname(".hash")
@@ -2122,7 +2131,7 @@ func Asmbelf(ctxt *Link, symo int64) {
 		sh.entsize = 4
 		sh.addralign = uint64(ctxt.Arch.RegSize)
 		sh.link = uint32(elfshname(".dynsym").shnum)
-		shsym(sh, ctxt.Syms.Lookup(".hash", 0))
+		shsym2(sh, ldr, ldr.Lookup(".hash", 0))
 
 		/* sh and PT_DYNAMIC for .dynamic section */
 		sh = elfshname(".dynamic")
@@ -2132,7 +2141,7 @@ func Asmbelf(ctxt *Link, symo int64) {
 		sh.entsize = 2 * uint64(ctxt.Arch.RegSize)
 		sh.addralign = uint64(ctxt.Arch.RegSize)
 		sh.link = uint32(elfshname(".dynstr").shnum)
-		shsym(sh, ctxt.Syms.Lookup(".dynamic", 0))
+		shsym2(sh, ldr, ldr.Lookup(".dynamic", 0))
 		ph := newElfPhdr()
 		ph.type_ = PT_DYNAMIC
 		ph.flags = PF_R + PF_W
@@ -2176,7 +2185,7 @@ elfobj:
 	sh := elfshname(".shstrtab")
 	sh.type_ = SHT_STRTAB
 	sh.addralign = 1
-	shsym(sh, ctxt.Syms.Lookup(".shstrtab", 0))
+	shsym2(sh, ldr, ldr.Lookup(".shstrtab", 0))
 	eh.shstrndx = uint16(sh.shnum)
 
 	// put these sections early in the list
@@ -2214,9 +2223,9 @@ elfobj:
 		for _, sect := range Segdata.Sections {
 			elfshreloc(ctxt.Arch, sect)
 		}
-		for _, si := range dwarfp {
+		for _, si := range dwarfp2 {
-			s := si.secSym()
+			sect := ldr.SymSect(si.secSym())
-			elfshreloc(ctxt.Arch, s.Sect)
+			elfshreloc(ctxt.Arch, sect)
 		}
 		// add a .note.GNU-stack section to mark the stack as non-executable
 		sh := elfshname(".note.GNU-stack")
@@ -2279,7 +2288,7 @@ elfobj:
 	}
 
 	if ctxt.LinkMode != LinkExternal {
-		eh.entry = uint64(Entryvalue(ctxt))
+		eh.entry = uint64(Entryvalue2(ctxt))
 	}
 
 	eh.version = EV_CURRENT

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

@@ -5,7 +5,10 @@
 package ld
 
 import (
+	"cmd/internal/objabi"
+	"cmd/internal/sys"
 	"cmd/link/internal/sym"
+	"encoding/binary"
 )
 
 // Temporary dumping around for sym.Symbol version of helper
@@ -24,6 +27,588 @@ func elfsetstring(s *sym.Symbol, str string, off int) {
 	nelfstr++
 }
 
+func Asmbelf2(ctxt *Link, symo int64) {
+	eh := getElfEhdr()
+	switch ctxt.Arch.Family {
+	default:
+		Exitf("unknown architecture in asmbelf: %v", ctxt.Arch.Family)
+	case sys.MIPS, sys.MIPS64:
+		eh.machine = EM_MIPS
+	case sys.ARM:
+		eh.machine = EM_ARM
+	case sys.AMD64:
+		eh.machine = EM_X86_64
+	case sys.ARM64:
+		eh.machine = EM_AARCH64
+	case sys.I386:
+		eh.machine = EM_386
+	case sys.PPC64:
+		eh.machine = EM_PPC64
+	case sys.RISCV64:
+		eh.machine = EM_RISCV
+	case sys.S390X:
+		eh.machine = EM_S390
+	}
+
+	elfreserve := int64(ELFRESERVE)
+
+	numtext := int64(0)
+	for _, sect := range Segtext.Sections {
+		if sect.Name == ".text" {
+			numtext++
+		}
+	}
+
+	// If there are multiple text sections, extra space is needed
+	// in the elfreserve for the additional .text and .rela.text
+	// section headers.  It can handle 4 extra now. Headers are
+	// 64 bytes.
+
+	if numtext > 4 {
+		elfreserve += elfreserve + numtext*64*2
+	}
+
+	startva := *FlagTextAddr - int64(HEADR)
+	resoff := elfreserve
+
+	var pph *ElfPhdr
+	var pnote *ElfPhdr
+	if *flagRace && ctxt.IsNetbsd() {
+		sh := elfshname(".note.netbsd.pax")
+		resoff -= int64(elfnetbsdpax(sh, uint64(startva), uint64(resoff)))
+		pnote = newElfPhdr()
+		pnote.type_ = PT_NOTE
+		pnote.flags = PF_R
+		phsh(pnote, sh)
+	}
+	if ctxt.LinkMode == LinkExternal {
+		/* skip program headers */
+		eh.phoff = 0
+
+		eh.phentsize = 0
+
+		if ctxt.BuildMode == BuildModeShared {
+			sh := elfshname(".note.go.pkg-list")
+			sh.type_ = SHT_NOTE
+			sh = elfshname(".note.go.abihash")
+			sh.type_ = SHT_NOTE
+			sh.flags = SHF_ALLOC
+			sh = elfshname(".note.go.deps")
+			sh.type_ = SHT_NOTE
+		}
+
+		if *flagBuildid != "" {
+			sh := elfshname(".note.go.buildid")
+			sh.type_ = SHT_NOTE
+			sh.flags = SHF_ALLOC
+		}
+
+		goto elfobj
+	}
+
+	/* program header info */
+	pph = newElfPhdr()
+
+	pph.type_ = PT_PHDR
+	pph.flags = PF_R
+	pph.off = uint64(eh.ehsize)
+	pph.vaddr = uint64(*FlagTextAddr) - uint64(HEADR) + pph.off
+	pph.paddr = uint64(*FlagTextAddr) - uint64(HEADR) + pph.off
+	pph.align = uint64(*FlagRound)
+
+	/*
+	 * PHDR must be in a loaded segment. Adjust the text
+	 * segment boundaries downwards to include it.
+	 */
+	{
+		o := int64(Segtext.Vaddr - pph.vaddr)
+		Segtext.Vaddr -= uint64(o)
+		Segtext.Length += uint64(o)
+		o = int64(Segtext.Fileoff - pph.off)
+		Segtext.Fileoff -= uint64(o)
+		Segtext.Filelen += uint64(o)
+	}
+
+	if !*FlagD { /* -d suppresses dynamic loader format */
+		/* interpreter */
+		sh := elfshname(".interp")
+
+		sh.type_ = SHT_PROGBITS
+		sh.flags = SHF_ALLOC
+		sh.addralign = 1
+
+		if interpreter == "" && objabi.GO_LDSO != "" {
+			interpreter = objabi.GO_LDSO
+		}
+
+		if interpreter == "" {
+			switch ctxt.HeadType {
+			case objabi.Hlinux:
+				if objabi.GOOS == "android" {
+					interpreter = thearch.Androiddynld
+					if interpreter == "" {
+						Exitf("ELF interpreter not set")
+					}
+				} else {
+					interpreter = thearch.Linuxdynld
+				}
+
+			case objabi.Hfreebsd:
+				interpreter = thearch.Freebsddynld
+
+			case objabi.Hnetbsd:
+				interpreter = thearch.Netbsddynld
+
+			case objabi.Hopenbsd:
+				interpreter = thearch.Openbsddynld
+
+			case objabi.Hdragonfly:
+				interpreter = thearch.Dragonflydynld
+
+			case objabi.Hsolaris:
+				interpreter = thearch.Solarisdynld
+			}
+		}
+
+		resoff -= int64(elfinterp(sh, uint64(startva), uint64(resoff), interpreter))
+
+		ph := newElfPhdr()
+		ph.type_ = PT_INTERP
+		ph.flags = PF_R
+		phsh(ph, sh)
+	}
+
+	pnote = nil
+	if ctxt.HeadType == objabi.Hnetbsd || ctxt.HeadType == objabi.Hopenbsd {
+		var sh *ElfShdr
+		switch ctxt.HeadType {
+		case objabi.Hnetbsd:
+			sh = elfshname(".note.netbsd.ident")
+			resoff -= int64(elfnetbsdsig(sh, uint64(startva), uint64(resoff)))
+
+		case objabi.Hopenbsd:
+			sh = elfshname(".note.openbsd.ident")
+			resoff -= int64(elfopenbsdsig(sh, uint64(startva), uint64(resoff)))
+		}
+
+		pnote = newElfPhdr()
+		pnote.type_ = PT_NOTE
+		pnote.flags = PF_R
+		phsh(pnote, sh)
+	}
+
+	if len(buildinfo) > 0 {
+		sh := elfshname(".note.gnu.build-id")
+		resoff -= int64(elfbuildinfo(sh, uint64(startva), uint64(resoff)))
+
+		if pnote == nil {
+			pnote = newElfPhdr()
+			pnote.type_ = PT_NOTE
+			pnote.flags = PF_R
+		}
+
+		phsh(pnote, sh)
+	}
+
+	if *flagBuildid != "" {
+		sh := elfshname(".note.go.buildid")
+		resoff -= int64(elfgobuildid(sh, uint64(startva), uint64(resoff)))
+
+		pnote := newElfPhdr()
+		pnote.type_ = PT_NOTE
+		pnote.flags = PF_R
+		phsh(pnote, sh)
+	}
+
+	// Additions to the reserved area must be above this line.
+
+	elfphload(&Segtext)
+	if len(Segrodata.Sections) > 0 {
+		elfphload(&Segrodata)
+	}
+	if len(Segrelrodata.Sections) > 0 {
+		elfphload(&Segrelrodata)
+		elfphrelro(&Segrelrodata)
+	}
+	elfphload(&Segdata)
+
+	/* Dynamic linking sections */
+	if !*FlagD {
+		sh := elfshname(".dynsym")
+		sh.type_ = SHT_DYNSYM
+		sh.flags = SHF_ALLOC
+		if elf64 {
+			sh.entsize = ELF64SYMSIZE
+		} else {
+			sh.entsize = ELF32SYMSIZE
+		}
+		sh.addralign = uint64(ctxt.Arch.RegSize)
+		sh.link = uint32(elfshname(".dynstr").shnum)
+
+		// sh.info is the index of first non-local symbol (number of local symbols)
+		s := ctxt.Syms.Lookup(".dynsym", 0)
+		i := uint32(0)
+		for sub := s; sub != nil; sub = symSub(ctxt, sub) {
+			i++
+			if !sub.Attr.Local() {
+				break
+			}
+		}
+		sh.info = i
+		shsym(sh, s)
+
+		sh = elfshname(".dynstr")
+		sh.type_ = SHT_STRTAB
+		sh.flags = SHF_ALLOC
+		sh.addralign = 1
+		shsym(sh, ctxt.Syms.Lookup(".dynstr", 0))
+
+		if elfverneed != 0 {
+			sh := elfshname(".gnu.version")
+			sh.type_ = SHT_GNU_VERSYM
+			sh.flags = SHF_ALLOC
+			sh.addralign = 2
+			sh.link = uint32(elfshname(".dynsym").shnum)
+			sh.entsize = 2
+			shsym(sh, ctxt.Syms.Lookup(".gnu.version", 0))
+
+			sh = elfshname(".gnu.version_r")
+			sh.type_ = SHT_GNU_VERNEED
+			sh.flags = SHF_ALLOC
+			sh.addralign = uint64(ctxt.Arch.RegSize)
+			sh.info = uint32(elfverneed)
+			sh.link = uint32(elfshname(".dynstr").shnum)
+			shsym(sh, ctxt.Syms.Lookup(".gnu.version_r", 0))
+		}
+
+		if elfRelType == ".rela" {
+			sh := elfshname(".rela.plt")
+			sh.type_ = SHT_RELA
+			sh.flags = SHF_ALLOC
+			sh.entsize = ELF64RELASIZE
+			sh.addralign = uint64(ctxt.Arch.RegSize)
+			sh.link = uint32(elfshname(".dynsym").shnum)
+			sh.info = uint32(elfshname(".plt").shnum)
+			shsym(sh, ctxt.Syms.Lookup(".rela.plt", 0))
+
+			sh = elfshname(".rela")
+			sh.type_ = SHT_RELA
+			sh.flags = SHF_ALLOC
+			sh.entsize = ELF64RELASIZE
+			sh.addralign = 8
+			sh.link = uint32(elfshname(".dynsym").shnum)
+			shsym(sh, ctxt.Syms.Lookup(".rela", 0))
+		} else {
+			sh := elfshname(".rel.plt")
+			sh.type_ = SHT_REL
+			sh.flags = SHF_ALLOC
+			sh.entsize = ELF32RELSIZE
+			sh.addralign = 4
+			sh.link = uint32(elfshname(".dynsym").shnum)
+			shsym(sh, ctxt.Syms.Lookup(".rel.plt", 0))
+
+			sh = elfshname(".rel")
+			sh.type_ = SHT_REL
+			sh.flags = SHF_ALLOC
+			sh.entsize = ELF32RELSIZE
+			sh.addralign = 4
+			sh.link = uint32(elfshname(".dynsym").shnum)
+			shsym(sh, ctxt.Syms.Lookup(".rel", 0))
+		}
+
+		if eh.machine == EM_PPC64 {
+			sh := elfshname(".glink")
+			sh.type_ = SHT_PROGBITS
+			sh.flags = SHF_ALLOC + SHF_EXECINSTR
+			sh.addralign = 4
+			shsym(sh, ctxt.Syms.Lookup(".glink", 0))
+		}
+
+		sh = elfshname(".plt")
+		sh.type_ = SHT_PROGBITS
+		sh.flags = SHF_ALLOC + SHF_EXECINSTR
+		if eh.machine == EM_X86_64 {
+			sh.entsize = 16
+		} else if eh.machine == EM_S390 {
+			sh.entsize = 32
+		} else if eh.machine == EM_PPC64 {
+			// On ppc64, this is just a table of addresses
+			// filled by the dynamic linker
+			sh.type_ = SHT_NOBITS
+
+			sh.flags = SHF_ALLOC + SHF_WRITE
+			sh.entsize = 8
+		} else {
+			sh.entsize = 4
+		}
+		sh.addralign = sh.entsize
+		shsym(sh, ctxt.Syms.Lookup(".plt", 0))
+
+		// On ppc64, .got comes from the input files, so don't
+		// create it here, and .got.plt is not used.
+		if eh.machine != EM_PPC64 {
+			sh := elfshname(".got")
+			sh.type_ = SHT_PROGBITS
+			sh.flags = SHF_ALLOC + SHF_WRITE
+			sh.entsize = uint64(ctxt.Arch.RegSize)
+			sh.addralign = uint64(ctxt.Arch.RegSize)
+			shsym(sh, ctxt.Syms.Lookup(".got", 0))
+
+			sh = elfshname(".got.plt")
+			sh.type_ = SHT_PROGBITS
+			sh.flags = SHF_ALLOC + SHF_WRITE
+			sh.entsize = uint64(ctxt.Arch.RegSize)
+			sh.addralign = uint64(ctxt.Arch.RegSize)
+			shsym(sh, ctxt.Syms.Lookup(".got.plt", 0))
+		}
+
+		sh = elfshname(".hash")
+		sh.type_ = SHT_HASH
+		sh.flags = SHF_ALLOC
+		sh.entsize = 4
+		sh.addralign = uint64(ctxt.Arch.RegSize)
+		sh.link = uint32(elfshname(".dynsym").shnum)
+		shsym(sh, ctxt.Syms.Lookup(".hash", 0))
+
+		/* sh and PT_DYNAMIC for .dynamic section */
+		sh = elfshname(".dynamic")
+
+		sh.type_ = SHT_DYNAMIC
+		sh.flags = SHF_ALLOC + SHF_WRITE
+		sh.entsize = 2 * uint64(ctxt.Arch.RegSize)
+		sh.addralign = uint64(ctxt.Arch.RegSize)
+		sh.link = uint32(elfshname(".dynstr").shnum)
+		shsym(sh, ctxt.Syms.Lookup(".dynamic", 0))
+		ph := newElfPhdr()
+		ph.type_ = PT_DYNAMIC
+		ph.flags = PF_R + PF_W
+		phsh(ph, sh)
+
+		/*
+		 * Thread-local storage segment (really just size).
+		 */
+		tlssize := uint64(0)
+		for _, sect := range Segdata.Sections {
+			if sect.Name == ".tbss" {
+				tlssize = sect.Length
+			}
+		}
+		if tlssize != 0 {
+			ph := newElfPhdr()
+			ph.type_ = PT_TLS
+			ph.flags = PF_R
+			ph.memsz = tlssize
+			ph.align = uint64(ctxt.Arch.RegSize)
+		}
+	}
+
+	if ctxt.HeadType == objabi.Hlinux {
+		ph := newElfPhdr()
+		ph.type_ = PT_GNU_STACK
+		ph.flags = PF_W + PF_R
+		ph.align = uint64(ctxt.Arch.RegSize)
+
+		ph = newElfPhdr()
+		ph.type_ = PT_PAX_FLAGS
+		ph.flags = 0x2a00 // mprotect, randexec, emutramp disabled
+		ph.align = uint64(ctxt.Arch.RegSize)
+	} else if ctxt.HeadType == objabi.Hsolaris {
+		ph := newElfPhdr()
+		ph.type_ = PT_SUNWSTACK
+		ph.flags = PF_W + PF_R
+	}
+
+elfobj:
+	sh := elfshname(".shstrtab")
+	sh.type_ = SHT_STRTAB
+	sh.addralign = 1
+	shsym(sh, ctxt.Syms.Lookup(".shstrtab", 0))
+	eh.shstrndx = uint16(sh.shnum)
+
+	// put these sections early in the list
+	if !*FlagS {
+		elfshname(".symtab")
+		elfshname(".strtab")
+	}
+
+	for _, sect := range Segtext.Sections {
+		elfshbits(ctxt.LinkMode, sect)
+	}
+	for _, sect := range Segrodata.Sections {
+		elfshbits(ctxt.LinkMode, sect)
+	}
+	for _, sect := range Segrelrodata.Sections {
+		elfshbits(ctxt.LinkMode, sect)
+	}
+	for _, sect := range Segdata.Sections {
+		elfshbits(ctxt.LinkMode, sect)
+	}
+	for _, sect := range Segdwarf.Sections {
+		elfshbits(ctxt.LinkMode, sect)
+	}
+
+	if ctxt.LinkMode == LinkExternal {
+		for _, sect := range Segtext.Sections {
+			elfshreloc(ctxt.Arch, sect)
+		}
+		for _, sect := range Segrodata.Sections {
+			elfshreloc(ctxt.Arch, sect)
+		}
+		for _, sect := range Segrelrodata.Sections {
+			elfshreloc(ctxt.Arch, sect)
+		}
+		for _, sect := range Segdata.Sections {
+			elfshreloc(ctxt.Arch, sect)
+		}
+		for _, si := range dwarfp {
+			s := si.secSym()
+			elfshreloc(ctxt.Arch, s.Sect)
+		}
+		// add a .note.GNU-stack section to mark the stack as non-executable
+		sh := elfshname(".note.GNU-stack")
+
+		sh.type_ = SHT_PROGBITS
+		sh.addralign = 1
+		sh.flags = 0
+	}
+
+	if !*FlagS {
+		sh := elfshname(".symtab")
+		sh.type_ = SHT_SYMTAB
+		sh.off = uint64(symo)
+		sh.size = uint64(Symsize)
+		sh.addralign = uint64(ctxt.Arch.RegSize)
+		sh.entsize = 8 + 2*uint64(ctxt.Arch.RegSize)
+		sh.link = uint32(elfshname(".strtab").shnum)
+		sh.info = uint32(elfglobalsymndx)
+
+		sh = elfshname(".strtab")
+		sh.type_ = SHT_STRTAB
+		sh.off = uint64(symo) + uint64(Symsize)
+		sh.size = uint64(len(Elfstrdat))
+		sh.addralign = 1
+	}
+
+	/* Main header */
+	eh.ident[EI_MAG0] = '\177'
+
+	eh.ident[EI_MAG1] = 'E'
+	eh.ident[EI_MAG2] = 'L'
+	eh.ident[EI_MAG3] = 'F'
+	if ctxt.HeadType == objabi.Hfreebsd {
+		eh.ident[EI_OSABI] = ELFOSABI_FREEBSD
+	} else if ctxt.HeadType == objabi.Hnetbsd {
+		eh.ident[EI_OSABI] = ELFOSABI_NETBSD
+	} else if ctxt.HeadType == objabi.Hopenbsd {
+		eh.ident[EI_OSABI] = ELFOSABI_OPENBSD
+	} else if ctxt.HeadType == objabi.Hdragonfly {
+		eh.ident[EI_OSABI] = ELFOSABI_NONE
+	}
+	if elf64 {
+		eh.ident[EI_CLASS] = ELFCLASS64
+	} else {
+		eh.ident[EI_CLASS] = ELFCLASS32
+	}
+	if ctxt.Arch.ByteOrder == binary.BigEndian {
+		eh.ident[EI_DATA] = ELFDATA2MSB
+	} else {
+		eh.ident[EI_DATA] = ELFDATA2LSB
+	}
+	eh.ident[EI_VERSION] = EV_CURRENT
+
+	if ctxt.LinkMode == LinkExternal {
+		eh.type_ = ET_REL
+	} else if ctxt.BuildMode == BuildModePIE {
+		eh.type_ = ET_DYN
+	} else {
+		eh.type_ = ET_EXEC
+	}
+
+	if ctxt.LinkMode != LinkExternal {
+		eh.entry = uint64(Entryvalue(ctxt))
+	}
+
+	eh.version = EV_CURRENT
+
+	if pph != nil {
+		pph.filesz = uint64(eh.phnum) * uint64(eh.phentsize)
+		pph.memsz = pph.filesz
+	}
+
+	ctxt.Out.SeekSet(0)
+	a := int64(0)
+	a += int64(elfwritehdr(ctxt.Out))
+	a += int64(elfwritephdrs(ctxt.Out))
+	a += int64(elfwriteshdrs(ctxt.Out))
+	if !*FlagD {
+		a += int64(elfwriteinterp(ctxt.Out))
+	}
+	if ctxt.LinkMode != LinkExternal {
+		if ctxt.HeadType == objabi.Hnetbsd {
+			a += int64(elfwritenetbsdsig(ctxt.Out))
+		}
+		if ctxt.HeadType == objabi.Hopenbsd {
+			a += int64(elfwriteopenbsdsig(ctxt.Out))
+		}
+		if len(buildinfo) > 0 {
+			a += int64(elfwritebuildinfo(ctxt.Out))
+		}
+		if *flagBuildid != "" {
+			a += int64(elfwritegobuildid(ctxt.Out))
+		}
+	}
+	if *flagRace && ctxt.IsNetbsd() {
+		a += int64(elfwritenetbsdpax(ctxt.Out))
+	}
+
+	if a > elfreserve {
+		Errorf(nil, "ELFRESERVE too small: %d > %d with %d text sections", a, elfreserve, numtext)
+	}
+}
+
+// Do not write DT_NULL.  elfdynhash will finish it.
+func shsym(sh *ElfShdr, s *sym.Symbol) {
+	addr := Symaddr(s)
+	if sh.flags&SHF_ALLOC != 0 {
+		sh.addr = uint64(addr)
+	}
+	sh.off = uint64(datoff2(s, addr))
+	sh.size = uint64(s.Size)
+}
+
+func Elfemitreloc2(ctxt *Link) {
+	for ctxt.Out.Offset()&7 != 0 {
+		ctxt.Out.Write8(0)
+	}
+
+	for _, sect := range Segtext.Sections {
+		if sect.Name == ".text" {
+			elfrelocsect2(ctxt, sect, ctxt.Textp)
+		} else {
+			elfrelocsect2(ctxt, sect, ctxt.datap)
+		}
+	}
+
+	for _, sect := range Segrodata.Sections {
+		elfrelocsect2(ctxt, sect, ctxt.datap)
+	}
+	for _, sect := range Segrelrodata.Sections {
+		elfrelocsect2(ctxt, sect, ctxt.datap)
+	}
+	for _, sect := range Segdata.Sections {
+		elfrelocsect2(ctxt, sect, ctxt.datap)
+	}
+	for i := 0; i < len(Segdwarf.Sections); i++ {
+		sect := Segdwarf.Sections[i]
+		si := dwarfp[i]
+		if si.secSym() != sect.Sym ||
+			si.secSym().Sect != sect {
+			panic("inconsistency between dwarfp and Segdwarf")
+		}
+		elfrelocsect2(ctxt, sect, si.syms)
+	}
+}
+
 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.

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

@@ -2662,46 +2662,32 @@ func (ctxt *Link) xdefine2(p string, t sym.SymKind, v int64) {
 	s.SetLocal(true)
 }
 
-func datoff(s *sym.Symbol, addr int64) int64 {
+func datoff(ldr *loader.Loader, s loader.Sym, addr int64) int64 {
 	if uint64(addr) >= Segdata.Vaddr {
 		return int64(uint64(addr) - Segdata.Vaddr + Segdata.Fileoff)
 	}
 	if uint64(addr) >= Segtext.Vaddr {
 		return int64(uint64(addr) - Segtext.Vaddr + Segtext.Fileoff)
 	}
-	Errorf(s, "invalid datoff %#x", addr)
+	ldr.Errorf(s, "invalid datoff %#x", addr)
 	return 0
 }
 
-func Entryvalue(ctxt *Link) int64 {
-	a := *flagEntrySymbol
-	if a[0] >= '0' && a[0] <= '9' {
-		return atolwhex(a)
-	}
-	s := ctxt.Syms.Lookup(a, 0)
-	if s.Type == 0 {
-		return *FlagTextAddr
-	}
-	if ctxt.HeadType != objabi.Haix && s.Type != sym.STEXT {
-		Errorf(s, "entry not text")
-	}
-	return s.Value
-}
-
 func Entryvalue2(ctxt *Link) int64 {
 	a := *flagEntrySymbol
 	if a[0] >= '0' && a[0] <= '9' {
 		return atolwhex(a)
 	}
-	s := ctxt.loader.Lookup(a, 0)
+	ldr := ctxt.loader
-	typ := ctxt.loader.SymType(s)
+	s := ldr.Lookup(a, 0)
-	if typ == 0 {
+	st := ldr.SymType(s)
+	if st == 0 {
 		return *FlagTextAddr
 	}
-	if ctxt.HeadType != objabi.Haix && typ != sym.STEXT {
+	if !ctxt.IsAIX() && st != sym.STEXT {
-		ctxt.Errorf(s, "entry not text")
+		ldr.Errorf(s, "entry not text")
 	}
-	return ctxt.loader.SymValue(s)
+	return ldr.SymValue(s)
 }
 
 func (ctxt *Link) callgraph() {
@@ -2799,6 +2785,7 @@ func addToTextp(ctxt *Link) {
 }
 
 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, needExtReloc)
 
@@ -2891,14 +2878,14 @@ func symPkg(ctxt *Link, s *sym.Symbol) string {
 	return ctxt.loader.SymPkg(loader.Sym(s.SymIdx))
 }
 
-func ElfSymForReloc(ctxt *Link, s *sym.Symbol) int32 {
+func ElfSymForReloc2(ctxt *Link, s loader.Sym) int32 {
 	// If putelfsym created a local version of this symbol, use that in all
 	// relocations.
-	les := ctxt.loader.SymLocalElfSym(loader.Sym(s.SymIdx))
+	les := ctxt.loader.SymLocalElfSym(s)
 	if les != 0 {
 		return les
 	} else {
-		return ctxt.loader.SymElfSym(loader.Sym(s.SymIdx))
+		return ctxt.loader.SymElfSym(s)
 	}
 }
 

src/cmd/link/internal/ld/lib2.go

@@ -0,0 +1,51 @@
+// 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 lib.go, still being used for some archs/oses.
+
+func Entryvalue(ctxt *Link) int64 {
+	a := *flagEntrySymbol
+	if a[0] >= '0' && a[0] <= '9' {
+		return atolwhex(a)
+	}
+	s := ctxt.Syms.Lookup(a, 0)
+	if s.Type == 0 {
+		return *FlagTextAddr
+	}
+	if ctxt.HeadType != objabi.Haix && s.Type != sym.STEXT {
+		Errorf(s, "entry not text")
+	}
+	return s.Value
+}
+
+func datoff2(s *sym.Symbol, addr int64) int64 {
+	if uint64(addr) >= Segdata.Vaddr {
+		return int64(uint64(addr) - Segdata.Vaddr + Segdata.Fileoff)
+	}
+	if uint64(addr) >= Segtext.Vaddr {
+		return int64(uint64(addr) - Segtext.Vaddr + Segtext.Fileoff)
+	}
+	Errorf(s, "invalid datoff %#x", addr)
+	return 0
+}
+
+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))
+	}
+}

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

@@ -320,7 +320,7 @@ func Main(arch *sys.Arch, theArch Arch) {
 	thearch.Asmb(ctxt, ctxt.loader)
 	bench.Start("reloc")
 	ctxt.reloc()
-	newasmb2 := ctxt.IsDarwin() || ctxt.IsWindows() || ctxt.IsWasm() || ctxt.IsPlan9()
+	newasmb2 := ctxt.IsDarwin() || ctxt.IsWindows() || ctxt.IsWasm() || ctxt.IsPlan9() || (ctxt.IsElf() && ctxt.IsAMD64())
 	if !newasmb2 {
 		bench.Start("loadlibfull")
 		// We don't need relocations at this point.

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

@@ -32,7 +32,6 @@ package ld
 
 import (
 	"cmd/internal/objabi"
-	"cmd/internal/sys"
 	"cmd/link/internal/loader"
 	"cmd/link/internal/sym"
 	"fmt"
@@ -74,58 +73,38 @@ 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) {
+func putelfsym(ctxt *Link, x loader.Sym, typ int, curbind int) {
-	var typ int
+	ldr := ctxt.loader
-
+	addr := ldr.SymValue(x)
-	switch t {
+	size := ldr.SymSize(x)
-	default:
-		return
-
-	case TextSym:
-		typ = STT_FUNC
-
-	case DataSym, BSSSym:
-		typ = STT_OBJECT
-
-	case UndefinedSym:
-		// ElfType is only set for symbols read from Go shared libraries, but
-		// for other symbols it is left as STT_NOTYPE which is fine.
-		typ = int(x.ElfType())
-
-	case TLSSym:
-		typ = STT_TLS
-	}
-
-	size := x.Size
-	if t == UndefinedSym {
-		size = 0
-	}
 
 	xo := x
-	if xo.Outer != nil {
+	if ldr.OuterSym(x) != 0 {
-		xo = xo.Outer
+		xo = ldr.OuterSym(x)
 	}
+	xot := ldr.SymType(xo)
+	xosect := ldr.SymSect(xo)
 
 	var elfshnum int
-	if xo.Type == sym.SDYNIMPORT || xo.Type == sym.SHOSTOBJ || xo.Type == sym.SUNDEFEXT {
+	if xot == sym.SDYNIMPORT || xot == sym.SHOSTOBJ || xot == sym.SUNDEFEXT {
 		elfshnum = SHN_UNDEF
+		size = 0
 	} else {
-		if xo.Sect == nil {
+		if xosect == nil {
-			Errorf(x, "missing section in putelfsym")
+			ldr.Errorf(x, "missing section in putelfsym")
 			return
 		}
-		if xo.Sect.Elfsect == nil {
+		if xosect.Elfsect == nil {
-			Errorf(x, "missing ELF section in putelfsym")
+			ldr.Errorf(x, "missing ELF section in putelfsym")
 			return
 		}
-		elfshnum = xo.Sect.Elfsect.(*ElfShdr).shnum
+		elfshnum = xosect.Elfsect.(*ElfShdr).shnum
 	}
 
 	// One pass for each binding: STB_LOCAL, STB_GLOBAL,
 	// maybe one day STB_WEAK.
 	bind := STB_GLOBAL
-
+	if ldr.IsFileLocal(x) || ldr.AttrVisibilityHidden(x) || ldr.AttrLocal(x) {
-	if x.IsFileLocal() || x.Attr.VisibilityHidden() || x.Attr.Local() {
 		bind = STB_LOCAL
 	}
 
@@ -134,15 +113,15 @@ func putelfsym(ctxt *Link, x *sym.Symbol, s string, t SymbolType, addr int64) {
 	// To avoid filling the dynamic table with lots of unnecessary symbols,
 	// mark all Go symbols local (not global) in the final executable.
 	// But when we're dynamically linking, we need all those global symbols.
-	if !ctxt.DynlinkingGo() && ctxt.LinkMode == LinkExternal && !x.Attr.CgoExportStatic() && elfshnum != SHN_UNDEF {
+	if !ctxt.DynlinkingGo() && ctxt.IsExternal() && !ldr.AttrCgoExportStatic(x) && elfshnum != SHN_UNDEF {
 		bind = STB_LOCAL
 	}
 
 	if ctxt.LinkMode == LinkExternal && elfshnum != SHN_UNDEF {
-		addr -= int64(xo.Sect.Vaddr)
+		addr -= int64(xosect.Vaddr)
 	}
 	other := STV_DEFAULT
-	if x.Attr.VisibilityHidden() {
+	if ldr.AttrVisibilityHidden(x) {
 		// TODO(mwhudson): We only set AttrVisibilityHidden in ldelf, i.e. when
 		// internally linking. But STV_HIDDEN visibility only matters in object
 		// files and shared libraries, and as we are a long way from implementing
@@ -150,7 +129,7 @@ func putelfsym(ctxt *Link, x *sym.Symbol, s string, t SymbolType, addr int64) {
 		// externally linking, I don't think this makes a lot of sense.
 		other = STV_HIDDEN
 	}
-	if ctxt.Arch.Family == sys.PPC64 && typ == STT_FUNC && x.Attr.Shared() && x.Name != "runtime.duffzero" && x.Name != "runtime.duffcopy" {
+	if ctxt.IsPPC64() && typ == STT_FUNC && ldr.AttrShared(x) && ldr.SymName(x) != "runtime.duffzero" && ldr.SymName(x) != "runtime.duffcopy" {
 		// On ppc64 the top three bits of the st_other field indicate how
 		// many instructions separate the global and local entry points. In
 		// our case it is two instructions, indicated by the value 3.
@@ -160,22 +139,17 @@ func putelfsym(ctxt *Link, x *sym.Symbol, s string, t SymbolType, addr int64) {
 		other |= 3 << 5
 	}
 
-	if s == x.Name {
+	sname := ldr.SymExtname(x)
-		// We should use Extname for ELF symbol table.
-		// TODO: maybe genasmsym should have done this. That function is too
-		// overloaded and I would rather not change it for now.
-		s = x.Extname()
-	}
 
 	// When dynamically linking, we create Symbols by reading the names from
 	// the symbol tables of the shared libraries and so the names need to
 	// match exactly. Tools like DTrace will have to wait for now.
 	if !ctxt.DynlinkingGo() {
 		// Rewrite · to . for ASCII-only tools like DTrace (sigh)
-		s = strings.Replace(s, "·", ".", -1)
+		sname = strings.Replace(sname, "·", ".", -1)
 	}
 
-	if ctxt.DynlinkingGo() && bind == STB_GLOBAL && ctxt.elfbind == STB_LOCAL && x.Type == sym.STEXT {
+	if ctxt.DynlinkingGo() && bind == STB_GLOBAL && curbind == STB_LOCAL && ldr.SymType(x) == sym.STEXT {
 		// When dynamically linking, we want references to functions defined
 		// in this module to always be to the function object, not to the
 		// PLT. We force this by writing an additional local symbol for every
@@ -184,26 +158,82 @@ func putelfsym(ctxt *Link, x *sym.Symbol, s string, t SymbolType, addr int64) {
 		// (*sym.Symbol).ElfsymForReloc). This is approximately equivalent to the
 		// 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)
+		putelfsyment(ctxt.Out, putelfstr("local."+sname), addr, size, STB_LOCAL<<4|typ&0xf, elfshnum, other)
-		ctxt.loader.SetSymLocalElfSym(loader.Sym(x.SymIdx), int32(ctxt.numelfsym))
+		ldr.SetSymLocalElfSym(x, int32(ctxt.numelfsym))
 		ctxt.numelfsym++
 		return
-	} else if bind != ctxt.elfbind {
+	} else if bind != curbind {
 		return
 	}
 
-	putelfsyment(ctxt.Out, putelfstr(s), addr, size, bind<<4|typ&0xf, elfshnum, other)
+	putelfsyment(ctxt.Out, putelfstr(sname), addr, size, bind<<4|typ&0xf, elfshnum, other)
-	ctxt.loader.SetSymElfSym(loader.Sym(x.SymIdx), int32(ctxt.numelfsym))
+	ldr.SetSymElfSym(x, int32(ctxt.numelfsym))
 	ctxt.numelfsym++
 }
 
-func putelfsectionsym(ctxt *Link, out *OutBuf, s *sym.Symbol, shndx int) {
+func putelfsectionsym(ctxt *Link, out *OutBuf, s loader.Sym, shndx int) {
 	putelfsyment(out, 0, 0, 0, STB_LOCAL<<4|STT_SECTION, shndx, 0)
-	ctxt.loader.SetSymElfSym(loader.Sym(s.SymIdx), int32(ctxt.numelfsym))
+	ctxt.loader.SetSymElfSym(s, int32(ctxt.numelfsym))
 	ctxt.numelfsym++
 }
 
+func genelfsym(ctxt *Link, elfbind int) {
+	ldr := ctxt.loader
+
+	// Text symbols.
+	s := ldr.Lookup("runtime.text", 0)
+	putelfsym(ctxt, s, STT_FUNC, elfbind)
+	for _, s := range ctxt.Textp2 {
+		putelfsym(ctxt, s, STT_FUNC, elfbind)
+	}
+	s = ldr.Lookup("runtime.etext", 0)
+	if ldr.SymType(s) == sym.STEXT {
+		putelfsym(ctxt, s, STT_FUNC, elfbind)
+	}
+
+	shouldBeInSymbolTable := func(s loader.Sym) bool {
+		if ldr.AttrNotInSymbolTable(s) {
+			return false
+		}
+		// FIXME: avoid having to do name inspections here.
+		sn := ldr.SymName(s)
+		if (sn == "" || sn[0] == '.') && !ldr.IsFileLocal(s) {
+			return false
+		}
+		return true
+	}
+
+	// Data symbols.
+	for s := loader.Sym(1); s < loader.Sym(ldr.NSym()); s++ {
+		if !ldr.AttrReachable(s) {
+			continue
+		}
+		st := ldr.SymType(s)
+		if st >= sym.SELFRXSECT && st < sym.SXREF {
+			typ := STT_OBJECT
+			if st == sym.STLSBSS {
+				if ctxt.IsInternal() {
+					continue
+				}
+				typ = STT_TLS
+			}
+			if !shouldBeInSymbolTable(s) {
+				continue
+			}
+			putelfsym(ctxt, s, typ, elfbind)
+			continue
+		}
+		if st == sym.SHOSTOBJ || st == sym.SDYNIMPORT || st == sym.SUNDEFEXT {
+			putelfsym(ctxt, s, int(ldr.SymElfType(s)), elfbind)
+		}
+	}
+}
+
 func Asmelfsym(ctxt *Link) {
+	if !ctxt.IsAMD64() {
+		Asmelfsym2(ctxt)
+		return
+	}
 	// the first symbol entry is reserved
 	putelfsyment(ctxt.Out, 0, 0, 0, STB_LOCAL<<4|STT_NOTYPE, 0, 0)
 
@@ -216,12 +246,13 @@ func Asmelfsym(ctxt *Link) {
 	putelfsyment(ctxt.Out, putelfstr("go.go"), 0, 0, STB_LOCAL<<4|STT_FILE, SHN_ABS, 0)
 	ctxt.numelfsym++
 
-	ctxt.elfbind = STB_LOCAL
+	bindings := []int{STB_LOCAL, STB_GLOBAL}
-	genasmsym(ctxt, putelfsym)
+	for _, elfbind := range bindings {
-
+		if elfbind == STB_GLOBAL {
-	ctxt.elfbind = STB_GLOBAL
 			elfglobalsymndx = ctxt.numelfsym
-	genasmsym(ctxt, putelfsym)
+		}
+		genelfsym(ctxt, elfbind)
+	}
 }
 
 func putplan9sym(ctxt *Link, ldr *loader.Loader, s loader.Sym, char SymbolType) {

src/cmd/link/internal/ld/symtab2.go

@@ -0,0 +1,166 @@
+// 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/sys"
+	"cmd/link/internal/loader"
+	"cmd/link/internal/sym"
+	"strings"
+)
+
+// Temporary dumping around for sym.Symbol version of helper
+// functions in symtab.go, still being used for some archs/oses.
+
+func Asmelfsym2(ctxt *Link) {
+
+	// the first symbol entry is reserved
+	putelfsyment(ctxt.Out, 0, 0, 0, STB_LOCAL<<4|STT_NOTYPE, 0, 0)
+
+	dwarfaddelfsectionsyms2(ctxt)
+
+	// Some linkers will add a FILE sym if one is not present.
+	// Avoid having the working directory inserted into the symbol table.
+	// It is added with a name to avoid problems with external linking
+	// encountered on some versions of Solaris. See issue #14957.
+	putelfsyment(ctxt.Out, putelfstr("go.go"), 0, 0, STB_LOCAL<<4|STT_FILE, SHN_ABS, 0)
+	ctxt.numelfsym++
+
+	ctxt.elfbind = STB_LOCAL
+	genasmsym(ctxt, putelfsym2)
+
+	ctxt.elfbind = STB_GLOBAL
+	elfglobalsymndx = ctxt.numelfsym
+	genasmsym(ctxt, putelfsym2)
+}
+
+func putelfsectionsym2(ctxt *Link, out *OutBuf, s *sym.Symbol, shndx int) {
+	putelfsyment(out, 0, 0, 0, STB_LOCAL<<4|STT_SECTION, shndx, 0)
+	ctxt.loader.SetSymElfSym(loader.Sym(s.SymIdx), int32(ctxt.numelfsym))
+	ctxt.numelfsym++
+}
+
+func putelfsym2(ctxt *Link, x *sym.Symbol, s string, t SymbolType, addr int64) {
+	var typ int
+
+	switch t {
+	default:
+		return
+
+	case TextSym:
+		typ = STT_FUNC
+
+	case DataSym, BSSSym:
+		typ = STT_OBJECT
+
+	case UndefinedSym:
+		// ElfType is only set for symbols read from Go shared libraries, but
+		// for other symbols it is left as STT_NOTYPE which is fine.
+		typ = int(x.ElfType())
+
+	case TLSSym:
+		typ = STT_TLS
+	}
+
+	size := x.Size
+	if t == UndefinedSym {
+		size = 0
+	}
+
+	xo := x
+	if xo.Outer != nil {
+		xo = xo.Outer
+	}
+
+	var elfshnum int
+	if xo.Type == sym.SDYNIMPORT || xo.Type == sym.SHOSTOBJ || xo.Type == sym.SUNDEFEXT {
+		elfshnum = SHN_UNDEF
+	} else {
+		if xo.Sect == nil {
+			Errorf(x, "missing section in putelfsym")
+			return
+		}
+		if xo.Sect.Elfsect == nil {
+			Errorf(x, "missing ELF section in putelfsym")
+			return
+		}
+		elfshnum = xo.Sect.Elfsect.(*ElfShdr).shnum
+	}
+
+	// One pass for each binding: STB_LOCAL, STB_GLOBAL,
+	// maybe one day STB_WEAK.
+	bind := STB_GLOBAL
+
+	if x.IsFileLocal() || x.Attr.VisibilityHidden() || x.Attr.Local() {
+		bind = STB_LOCAL
+	}
+
+	// In external linking mode, we have to invoke gcc with -rdynamic
+	// to get the exported symbols put into the dynamic symbol table.
+	// To avoid filling the dynamic table with lots of unnecessary symbols,
+	// mark all Go symbols local (not global) in the final executable.
+	// But when we're dynamically linking, we need all those global symbols.
+	if !ctxt.DynlinkingGo() && ctxt.LinkMode == LinkExternal && !x.Attr.CgoExportStatic() && elfshnum != SHN_UNDEF {
+		bind = STB_LOCAL
+	}
+
+	if ctxt.LinkMode == LinkExternal && elfshnum != SHN_UNDEF {
+		addr -= int64(xo.Sect.Vaddr)
+	}
+	other := STV_DEFAULT
+	if x.Attr.VisibilityHidden() {
+		// TODO(mwhudson): We only set AttrVisibilityHidden in ldelf, i.e. when
+		// internally linking. But STV_HIDDEN visibility only matters in object
+		// files and shared libraries, and as we are a long way from implementing
+		// internal linking for shared libraries and only create object files when
+		// externally linking, I don't think this makes a lot of sense.
+		other = STV_HIDDEN
+	}
+	if ctxt.Arch.Family == sys.PPC64 && typ == STT_FUNC && x.Attr.Shared() && x.Name != "runtime.duffzero" && x.Name != "runtime.duffcopy" {
+		// On ppc64 the top three bits of the st_other field indicate how
+		// many instructions separate the global and local entry points. In
+		// our case it is two instructions, indicated by the value 3.
+		// The conditions here match those in preprocess in
+		// cmd/internal/obj/ppc64/obj9.go, which is where the
+		// instructions are inserted.
+		other |= 3 << 5
+	}
+
+	if s == x.Name {
+		// We should use Extname for ELF symbol table.
+		// TODO: maybe genasmsym should have done this. That function is too
+		// overloaded and I would rather not change it for now.
+		s = x.Extname()
+	}
+
+	// When dynamically linking, we create Symbols by reading the names from
+	// the symbol tables of the shared libraries and so the names need to
+	// match exactly. Tools like DTrace will have to wait for now.
+	if !ctxt.DynlinkingGo() {
+		// Rewrite · to . for ASCII-only tools like DTrace (sigh)
+		s = strings.Replace(s, "·", ".", -1)
+	}
+
+	if ctxt.DynlinkingGo() && bind == STB_GLOBAL && ctxt.elfbind == STB_LOCAL && x.Type == sym.STEXT {
+		// When dynamically linking, we want references to functions defined
+		// in this module to always be to the function object, not to the
+		// PLT. We force this by writing an additional local symbol for every
+		// global function symbol and making all relocations against the
+		// global symbol refer to this local symbol instead (see
+		// (*sym.Symbol).ElfsymForReloc). This is approximately equivalent to the
+		// 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)
+		ctxt.loader.SetSymLocalElfSym(loader.Sym(x.SymIdx), int32(ctxt.numelfsym))
+		ctxt.numelfsym++
+		return
+	} else if bind != ctxt.elfbind {
+		return
+	}
+
+	putelfsyment(ctxt.Out, putelfstr(s), addr, size, bind<<4|typ&0xf, elfshnum, other)
+	ctxt.loader.SetSymElfSym(loader.Sym(x.SymIdx), int32(ctxt.numelfsym))
+	ctxt.numelfsym++
+}