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cmd/link: clean up some comments to Go standards

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Also drop a couple of unused names.

Change-Id: I0f09775a276c34ece7809cf5d3f7c6b8cd1fa487
Reviewed-on: https://go-review.googlesource.com/c/go/+/718580
Auto-Submit: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
This commit is contained in:
Ian Lance Taylor 2025-11-06 14:03:59 -08:00 • committed by Gopher Robot
parent 5cd1b73772
commit de84ac55c6
1 changed files with 71 additions and 147 deletions
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218
src/cmd/link/internal/ld/elf.go
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@ -61,80 +61,24 @@ import (
*
*/
/*
* ELF definitions that are independent of architecture or word size.
*/
// ELF definitions that are independent of architecture or word size.
/*
* Note header. The ".note" section contains an array of notes. Each
* begins with this header, aligned to a word boundary. Immediately
* following the note header is n_namesz bytes of name, padded to the
* next word boundary. Then comes n_descsz bytes of descriptor, again
* padded to a word boundary. The values of n_namesz and n_descsz do
* not include the padding.
*/
type elfNote struct {
nNamesz uint32
nDescsz uint32
nType uint32
}
// We use the 64-bit data structures on both 32- and 64-bit machines
// in order to write the code just once. The 64-bit data structure is
// written in the 32-bit format on the 32-bit machines.
/* For accessing the fields of r_info. */
/* For constructing r_info from field values. */
/*
* Relocation types.
*/
const (
ARM_MAGIC_TRAMP_NUMBER = 0x5c000003
)
/*
* Symbol table entries.
*/
/* For accessing the fields of st_info. */
/* For constructing st_info from field values. */
/* For accessing the fields of st_other. */
/*
* ELF header.
*/
// ElfEhdr is the ELF file header.
type ElfEhdr elf.Header64
/*
* Section header.
*/
// ElfShdr is an ELF section entry, plus the section index.
type ElfShdr struct {
elf.Section64
shnum elf.SectionIndex
}
/*
* Program header.
*/
// ElfPhdr is the ELF program, or segment, header.
type ElfPhdr elf.ProgHeader
/* For accessing the fields of r_info. */
/* For constructing r_info from field values. */
/*
* Symbol table entries.
*/
/* For accessing the fields of st_info. */
/* For constructing st_info from field values. */
/* For accessing the fields of st_other. */
/*
* Go linker interface
*/
const (
ELF64HDRSIZE = 64
ELF64PHDRSIZE = 56
@ -149,29 +93,14 @@ const (
ELF32RELSIZE = 8
)
/*
* The interface uses the 64-bit structures always,
* to avoid code duplication. The writers know how to
* marshal a 32-bit representation from the 64-bit structure.
*/
var elfstrdat, elfshstrdat []byte
/*
* Total amount of space to reserve at the start of the file
* for Header, PHeaders, SHeaders, and interp.
* May waste some.
* On FreeBSD, cannot be larger than a page.
*/
const (
ELFRESERVE = 4096
)
// ELFRESERVE is the total amount of space to reserve at the
// start of the file for Header, PHeaders, SHeaders, and interp.
// May waste some space.
// On FreeBSD, cannot be larger than a page.
const ELFRESERVE = 4096
/*
* We use the 64-bit data structures on both 32- and 64-bit machines
* in order to write the code just once. The 64-bit data structure is
* written in the 32-bit format on the 32-bit machines.
*/
const (
NSECT = 400
)
@ -227,10 +156,8 @@ var nelfstr int
var buildinfo []byte
/*
Initialize the global variable that describes the ELF header. It will be updated as
we write section and prog headers.
*/
// Elfinit initializes the global ehdr variable that holds the ELF header.
// It will be updated as write section and program headers.
func Elfinit(ctxt *Link) {
ctxt.IsELF = true
@ -244,28 +171,28 @@ func Elfinit(ctxt *Link) {
// 64-bit architectures
case sys.PPC64, sys.S390X:
if ctxt.Arch.ByteOrder == binary.BigEndian && ctxt.HeadType != objabi.Hopenbsd {
ehdr.Flags = 1 /* Version 1 ABI */
ehdr.Flags = 1 // Version 1 ABI
} else {
ehdr.Flags = 2 /* Version 2 ABI */
ehdr.Flags = 2 // Version 2 ABI
}
fallthrough
case sys.AMD64, sys.ARM64, sys.Loong64, sys.MIPS64, sys.RISCV64:
if ctxt.Arch.Family == sys.MIPS64 {
ehdr.Flags = 0x20000004 /* MIPS 3 CPIC */
ehdr.Flags = 0x20000004 // MIPS 3 CPIC
}
if ctxt.Arch.Family == sys.Loong64 {
ehdr.Flags = 0x43 /* DOUBLE_FLOAT, OBJABI_V1 */
ehdr.Flags = 0x43 // DOUBLE_FLOAT, OBJABI_V1
}
if ctxt.Arch.Family == sys.RISCV64 {
ehdr.Flags = 0x4 /* RISCV Float ABI Double */
ehdr.Flags = 0x4 // RISCV Float ABI Double
}
elf64 = true
ehdr.Phoff = ELF64HDRSIZE /* Must be ELF64HDRSIZE: first PHdr must follow ELF header */
ehdr.Shoff = ELF64HDRSIZE /* Will move as we add PHeaders */
ehdr.Ehsize = ELF64HDRSIZE /* Must be ELF64HDRSIZE */
ehdr.Phentsize = ELF64PHDRSIZE /* Must be ELF64PHDRSIZE */
ehdr.Shentsize = ELF64SHDRSIZE /* Must be ELF64SHDRSIZE */
ehdr.Phoff = ELF64HDRSIZE // Must be ELF64HDRSIZE: first PHdr must follow ELF header
ehdr.Shoff = ELF64HDRSIZE // Will move as we add PHeaders
ehdr.Ehsize = ELF64HDRSIZE // Must be ELF64HDRSIZE
ehdr.Phentsize = ELF64PHDRSIZE // Must be ELF64PHDRSIZE
ehdr.Shentsize = ELF64SHDRSIZE // Must be ELF64SHDRSIZE
// 32-bit architectures
case sys.ARM, sys.MIPS:
@ -283,22 +210,21 @@ func Elfinit(ctxt *Link) {
ehdr.Flags = 0x5000002 // has entry point, Version5 EABI
}
} else if ctxt.Arch.Family == sys.MIPS {
ehdr.Flags = 0x50001004 /* MIPS 32 CPIC O32*/
ehdr.Flags = 0x50001004 // MIPS 32 CPIC O32
}
fallthrough
default:
ehdr.Phoff = ELF32HDRSIZE
/* Must be ELF32HDRSIZE: first PHdr must follow ELF header */
ehdr.Shoff = ELF32HDRSIZE /* Will move as we add PHeaders */
ehdr.Ehsize = ELF32HDRSIZE /* Must be ELF32HDRSIZE */
ehdr.Phentsize = ELF32PHDRSIZE /* Must be ELF32PHDRSIZE */
ehdr.Shentsize = ELF32SHDRSIZE /* Must be ELF32SHDRSIZE */
// Must be ELF32HDRSIZE: first PHdr must follow ELF header
ehdr.Shoff = ELF32HDRSIZE // Will move as we add PHeaders
ehdr.Ehsize = ELF32HDRSIZE // Must be ELF32HDRSIZE
ehdr.Phentsize = ELF32PHDRSIZE // Must be ELF32PHDRSIZE
ehdr.Shentsize = ELF32SHDRSIZE // Must be ELF32SHDRSIZE
}
}
// Make sure PT_LOAD is aligned properly and
// that there is no gap,
// correct ELF loaders will do this implicitly,
// fixElfPhdr makes sure PT_LOAD is aligned properly and that there is no gap.
// Correct ELF loaders will do this implicitly,
// but buggy ELF loaders like the one in some
// versions of QEMU and UPX won't.
func fixElfPhdr(e *ElfPhdr) {
@ -483,7 +409,10 @@ func elfwritehdr(out *OutBuf) uint32 {
return elf32writehdr(out)
}
/* Taken directly from the definition document for ELF64. */
// elfhash is the dynamic symbol hash function .
// This is taken directly from the definition document for ELF,
// except that instead of finishing with "h &^= g" we just write
// "h &= 0xfffffff", which results in the same value.
func elfhash(name string) uint32 {
var h uint32
for i := 0; i < len(name); i++ {
@ -578,6 +507,8 @@ func elfMipsAbiFlags(sh *ElfShdr, startva uint64, resoff uint64) int {
return n
}
// elfWriteMipsAbiFlags writes the .MIPS.abiflags section.
//
// Layout is given by this C definition:
//
// typedef struct
@ -668,7 +599,7 @@ const (
ELF_NOTE_NETBSD_NAMESZ = 7
ELF_NOTE_NETBSD_DESCSZ = 4
ELF_NOTE_NETBSD_TAG = 1
ELF_NOTE_NETBSD_VERSION = 700000000 /* NetBSD 7.0 */
ELF_NOTE_NETBSD_VERSION = 700000000 // NetBSD 7.0
)
var ELF_NOTE_NETBSD_NAME = []byte("NetBSD\x00")
@ -1416,7 +1347,7 @@ func addgonote(ctxt *Link, sectionName string, tag uint32, desc []byte) {
func (ctxt *Link) doelf() {
ldr := ctxt.loader
/* predefine strings we need for section headers */
// Predefine strings we need for section headers.
addshstr := func(s string) int {
off := len(elfshstrdat)
@ -1511,7 +1442,7 @@ func (ctxt *Link) doelf() {
hasinitarr := ctxt.linkShared
/* shared library initializer */
// Shared library initializer.
switch ctxt.BuildMode {
case BuildModeCArchive, BuildModeCShared, BuildModeShared, BuildModePlugin:
hasinitarr = true
@ -1532,7 +1463,7 @@ func (ctxt *Link) doelf() {
shstrtabAddstring(".shstrtab")
if !*FlagD { /* -d suppresses dynamic loader format */
if !*FlagD { // -d suppresses dynamic loader format
shstrtabAddstring(".interp")
shstrtabAddstring(".hash")
shstrtabAddstring(".got")
@ -1550,7 +1481,7 @@ func (ctxt *Link) doelf() {
shstrtabAddstring(".gnu.version")
shstrtabAddstring(".gnu.version_r")
/* dynamic symbol table - first entry all zeros */
// dynamic symbol table - first entry all zeros
dynsym := ldr.CreateSymForUpdate(".dynsym", 0)
dynsym.SetType(sym.SELFROSECT)
@ -1560,7 +1491,7 @@ func (ctxt *Link) doelf() {
dynsym.SetSize(dynsym.Size() + ELF32SYMSIZE)
}
/* dynamic string table */
// dynamic string table
dynstr := ldr.CreateSymForUpdate(".dynstr", 0)
dynstr.SetType(sym.SELFROSECT)
@ -1568,11 +1499,11 @@ func (ctxt *Link) doelf() {
dynstr.Addstring("")
}
/* relocation table */
// relocation table
s := ldr.CreateSymForUpdate(elfRelType, 0)
s.SetType(sym.SELFROSECT)
/* global offset table */
// global offset table
got := ldr.CreateSymForUpdate(".got", 0)
if ctxt.UseRelro() {
got.SetType(sym.SELFRELROSECT)
@ -1580,13 +1511,13 @@ func (ctxt *Link) doelf() {
got.SetType(sym.SELFGOT) // writable
}
/* ppc64 glink resolver */
// ppc64 glink resolver
if ctxt.IsPPC64() {
s := ldr.CreateSymForUpdate(".glink", 0)
s.SetType(sym.SELFRXSECT)
}
/* hash */
// hash
hash := ldr.CreateSymForUpdate(".hash", 0)
hash.SetType(sym.SELFROSECT)
@ -1615,7 +1546,7 @@ func (ctxt *Link) doelf() {
s = ldr.CreateSymForUpdate(".gnu.version_r", 0)
s.SetType(sym.SELFROSECT)
/* define dynamic elf table */
// define dynamic elf table
dynamic := ldr.CreateSymForUpdate(".dynamic", 0)
switch {
case thearch.ELF.DynamicReadOnly:
@ -1632,9 +1563,7 @@ func (ctxt *Link) doelf() {
}
thearch.ELF.SetupPLT(ctxt, ctxt.loader, plt, gotplt, dynamic.Sym())
/*
* .dynamic table
*/
// .dynamic table
elfWriteDynEntSym(ctxt, dynamic, elf.DT_HASH, hash.Sym())
elfWriteDynEntSym(ctxt, dynamic, elf.DT_SYMTAB, dynsym.Sym())
@ -1739,7 +1668,7 @@ func (ctxt *Link) doelf() {
}
}
// Do not write DT_NULL. elfdynhash will finish it.
// shsym fills in fields of sh where s contains the contents of the section.
func shsym(sh *ElfShdr, ldr *loader.Loader, s loader.Sym) {
if s == 0 {
panic("bad symbol in shsym2")
@ -1762,7 +1691,7 @@ func phsh(ph *ElfPhdr, sh *ElfShdr) {
}
func Asmbelfsetup() {
/* This null SHdr must appear before all others */
// This null SHdr must appear before all others.
elfshname("")
for _, sect := range Segtext.Sections {
@ -1870,7 +1799,7 @@ func asmbElf(ctxt *Link) {
phsh(getpnote(), sh)
}
if ctxt.LinkMode == LinkExternal {
/* skip program headers */
// skip program headers
eh.Phoff = 0
eh.Phentsize = 0
@ -1894,7 +1823,7 @@ func asmbElf(ctxt *Link) {
goto elfobj
}
/* program header info */
// program header info
pph = newElfPhdr()
pph.Type = elf.PT_PHDR
@ -1904,10 +1833,8 @@ func asmbElf(ctxt *Link) {
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.
*/
// 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)
@ -1917,8 +1844,8 @@ func asmbElf(ctxt *Link) {
Segtext.Filelen += uint64(o)
}
if !*FlagD { /* -d suppresses dynamic loader format */
/* interpreter */
if !*FlagD { // -d suppresses dynamic loader format
// interpreter
sh := elfshname(".interp")
sh.Type = uint32(elf.SHT_PROGBITS)
@ -2022,7 +1949,7 @@ func asmbElf(ctxt *Link) {
}
elfphload(&Segdata)
/* Dynamic linking sections */
// Dynamic linking sections
if !*FlagD {
sh := elfshname(".dynsym")
sh.Type = uint32(elf.SHT_DYNSYM)
@ -2160,7 +2087,7 @@ func asmbElf(ctxt *Link) {
sh.Link = uint32(elfshname(".dynsym").shnum)
shsym(sh, ldr, ldr.Lookup(".hash", 0))
/* sh and elf.PT_DYNAMIC for .dynamic section */
// sh and elf.PT_DYNAMIC for .dynamic section
sh = elfshname(".dynamic")
sh.Type = uint32(elf.SHT_DYNAMIC)
@ -2174,9 +2101,7 @@ func asmbElf(ctxt *Link) {
ph.Flags = elf.PF_R + elf.PF_W
phsh(ph, sh)
/*
* Thread-local storage segment (really just size).
*/
// Thread-local storage segment (really just size).
tlssize := uint64(0)
for _, sect := range Segdata.Sections {
if sect.Name == ".tbss" {
@ -2305,7 +2230,7 @@ elfobj:
sh.Size = uint64(len(elfshstrdat))
sh.Addralign = 1
/* Main header */
// Main header
copy(eh.Ident[:], elf.ELFMAG)
var osabi elf.OSABI
@ -2410,8 +2335,7 @@ func elfadddynsym(ldr *loader.Loader, target *Target, syms *ArchSyms, s loader.S
d.AddUint32(target.Arch, uint32(dstru.Addstring(name)))
if elf64 {
/* type */
// type
var t uint8
if cgoexp && st.IsText() {
@ -2421,24 +2345,24 @@ func elfadddynsym(ldr *loader.Loader, target *Target, syms *ArchSyms, s loader.S
}
d.AddUint8(t)
/* reserved */
// reserved
d.AddUint8(0)
/* section where symbol is defined */
// section where symbol is defined
if st == sym.SDYNIMPORT {
d.AddUint16(target.Arch, uint16(elf.SHN_UNDEF))
} else {
d.AddUint16(target.Arch, 1)
}
/* value */
// value
if st == sym.SDYNIMPORT {
d.AddUint64(target.Arch, 0)
} else {
d.AddAddrPlus(target.Arch, s, 0)
}
/* size of object */
// size of object
d.AddUint64(target.Arch, uint64(len(ldr.Data(s))))
dil := ldr.SymDynimplib(s)
@ -2450,17 +2374,17 @@ func elfadddynsym(ldr *loader.Loader, target *Target, syms *ArchSyms, s loader.S
}
} else {
/* value */
// value
if st == sym.SDYNIMPORT {
d.AddUint32(target.Arch, 0)
} else {
d.AddAddrPlus(target.Arch, s, 0)
}
/* size of object */
// size of object
d.AddUint32(target.Arch, uint32(len(ldr.Data(s))))
/* type */
// type
var t uint8
// TODO(mwhudson): presumably the behavior should actually be the same on both arm and 386.
@ -2474,7 +2398,7 @@ func elfadddynsym(ldr *loader.Loader, target *Target, syms *ArchSyms, s loader.S
d.AddUint8(t)
d.AddUint8(0)
/* shndx */
// shndx
if st == sym.SDYNIMPORT {
d.AddUint16(target.Arch, uint16(elf.SHN_UNDEF))
} else {