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// Copyright 2009 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 (
"bytes"
"cmd/internal/objabi"
"cmd/internal/sys"
"cmd/link/internal/loader"
"cmd/link/internal/sym"
"debug/macho"
"encoding/binary"
"fmt"
"io"
"os"
"sort"
"strings"
)
type MachoHdr struct {
cpu uint32
subcpu uint32
}
type MachoSect struct {
name string
segname string
addr uint64
size uint64
off uint32
align uint32
reloc uint32
nreloc uint32
flag uint32
res1 uint32
res2 uint32
}
type MachoSeg struct {
name string
vsize uint64
vaddr uint64
fileoffset uint64
filesize uint64
prot1 uint32
prot2 uint32
nsect uint32
msect uint32
sect []MachoSect
flag uint32
}
// MachoPlatformLoad represents a LC_VERSION_MIN_* or
// LC_BUILD_VERSION load command.
type MachoPlatformLoad struct {
platform MachoPlatform // One of PLATFORM_* constants.
cmd MachoLoad
}
type MachoLoad struct {
type_ uint32
data []uint32
}
type MachoPlatform int
/*
* Total amount of space to reserve at the start of the file
* for Header, PHeaders, and SHeaders.
* May waste some.
*/
const (
INITIAL_MACHO_HEADR = 4 * 1024
)
const (
MACHO_CPU_AMD64 = 1<<24 | 7
MACHO_CPU_386 = 7
MACHO_SUBCPU_X86 = 3
MACHO_CPU_ARM = 12
MACHO_SUBCPU_ARM = 0
MACHO_SUBCPU_ARMV7 = 9
MACHO_CPU_ARM64 = 1<<24 | 12
MACHO_SUBCPU_ARM64_ALL = 0
MACHO32SYMSIZE = 12
MACHO64SYMSIZE = 16
MACHO_X86_64_RELOC_UNSIGNED = 0
MACHO_X86_64_RELOC_SIGNED = 1
MACHO_X86_64_RELOC_BRANCH = 2
MACHO_X86_64_RELOC_GOT_LOAD = 3
MACHO_X86_64_RELOC_GOT = 4
MACHO_X86_64_RELOC_SUBTRACTOR = 5
MACHO_X86_64_RELOC_SIGNED_1 = 6
MACHO_X86_64_RELOC_SIGNED_2 = 7
MACHO_X86_64_RELOC_SIGNED_4 = 8
MACHO_ARM_RELOC_VANILLA = 0
MACHO_ARM_RELOC_PAIR = 1
MACHO_ARM_RELOC_SECTDIFF = 2
MACHO_ARM_RELOC_BR24 = 5
MACHO_ARM64_RELOC_UNSIGNED = 0
MACHO_ARM64_RELOC_BRANCH26 = 2
MACHO_ARM64_RELOC_PAGE21 = 3
MACHO_ARM64_RELOC_PAGEOFF12 = 4
MACHO_ARM64_RELOC_ADDEND = 10
MACHO_GENERIC_RELOC_VANILLA = 0
MACHO_FAKE_GOTPCREL = 100
)
const (
MH_MAGIC = 0xfeedface
MH_MAGIC_64 = 0xfeedfacf
MH_OBJECT = 0x1
MH_EXECUTE = 0x2
MH_NOUNDEFS = 0x1
)
const (
LC_SEGMENT = 0x1
LC_SYMTAB = 0x2
LC_SYMSEG = 0x3
LC_THREAD = 0x4
LC_UNIXTHREAD = 0x5
LC_LOADFVMLIB = 0x6
LC_IDFVMLIB = 0x7
LC_IDENT = 0x8
LC_FVMFILE = 0x9
LC_PREPAGE = 0xa
LC_DYSYMTAB = 0xb
LC_LOAD_DYLIB = 0xc
LC_ID_DYLIB = 0xd
LC_LOAD_DYLINKER = 0xe
LC_ID_DYLINKER = 0xf
LC_PREBOUND_DYLIB = 0x10
LC_ROUTINES = 0x11
LC_SUB_FRAMEWORK = 0x12
LC_SUB_UMBRELLA = 0x13
LC_SUB_CLIENT = 0x14
LC_SUB_LIBRARY = 0x15
LC_TWOLEVEL_HINTS = 0x16
LC_PREBIND_CKSUM = 0x17
LC_LOAD_WEAK_DYLIB = 0x80000018
LC_SEGMENT_64 = 0x19
LC_ROUTINES_64 = 0x1a
LC_UUID = 0x1b
LC_RPATH = 0x8000001c
LC_CODE_SIGNATURE = 0x1d
LC_SEGMENT_SPLIT_INFO = 0x1e
LC_REEXPORT_DYLIB = 0x8000001f
LC_LAZY_LOAD_DYLIB = 0x20
LC_ENCRYPTION_INFO = 0x21
LC_DYLD_INFO = 0x22
LC_DYLD_INFO_ONLY = 0x80000022
LC_LOAD_UPWARD_DYLIB = 0x80000023
LC_VERSION_MIN_MACOSX = 0x24
LC_VERSION_MIN_IPHONEOS = 0x25
LC_FUNCTION_STARTS = 0x26
LC_DYLD_ENVIRONMENT = 0x27
LC_MAIN = 0x80000028
LC_DATA_IN_CODE = 0x29
LC_SOURCE_VERSION = 0x2A
LC_DYLIB_CODE_SIGN_DRS = 0x2B
LC_ENCRYPTION_INFO_64 = 0x2C
LC_LINKER_OPTION = 0x2D
LC_LINKER_OPTIMIZATION_HINT = 0x2E
LC_VERSION_MIN_TVOS = 0x2F
LC_VERSION_MIN_WATCHOS = 0x30
LC_VERSION_NOTE = 0x31
LC_BUILD_VERSION = 0x32
)
const (
S_REGULAR = 0x0
S_ZEROFILL = 0x1
S_NON_LAZY_SYMBOL_POINTERS = 0x6
S_SYMBOL_STUBS = 0x8
S_MOD_INIT_FUNC_POINTERS = 0x9
S_ATTR_PURE_INSTRUCTIONS = 0x80000000
S_ATTR_DEBUG = 0x02000000
S_ATTR_SOME_INSTRUCTIONS = 0x00000400
)
const (
PLATFORM_MACOS MachoPlatform = 1
PLATFORM_IOS MachoPlatform = 2
PLATFORM_TVOS MachoPlatform = 3
PLATFORM_WATCHOS MachoPlatform = 4
PLATFORM_BRIDGEOS MachoPlatform = 5
)
// Mach-O file writing
// https://developer.apple.com/mac/library/DOCUMENTATION/DeveloperTools/Conceptual/MachORuntime/Reference/reference.html
var machohdr MachoHdr
var load []MachoLoad
var machoPlatform MachoPlatform
var seg [16]MachoSeg
var nseg int
var ndebug int
var nsect int
const (
SymKindLocal = 0 + iota
SymKindExtdef
SymKindUndef
NumSymKind
)
var nkind [NumSymKind]int
var sortsym []loader.Sym
var nsortsym int
// Amount of space left for adding load commands
// that refer to dynamic libraries. Because these have
// to go in the Mach-O header, we can't just pick a
// "big enough" header size. The initial header is
// one page, the non-dynamic library stuff takes
// up about 1300 bytes; we overestimate that as 2k.
var loadBudget = INITIAL_MACHO_HEADR - 2*1024
func getMachoHdr() *MachoHdr {
return &machohdr
}
func newMachoLoad(arch *sys.Arch, type_ uint32, ndata uint32) *MachoLoad {
if arch.PtrSize == 8 && (ndata&1 != 0) {
ndata++
}
load = append(load, MachoLoad{})
l := &load[len(load)-1]
l.type_ = type_
l.data = make([]uint32, ndata)
return l
}
func newMachoSeg(name string, msect int) *MachoSeg {
if nseg >= len(seg) {
Exitf("too many segs")
}
s := &seg[nseg]
nseg++
s.name = name
s.msect = uint32(msect)
s.sect = make([]MachoSect, msect)
return s
}
func newMachoSect(seg *MachoSeg, name string, segname string) *MachoSect {
if seg.nsect >= seg.msect {
Exitf("too many sects in segment %s", seg.name)
}
s := &seg.sect[seg.nsect]
seg.nsect++
s.name = name
s.segname = segname
nsect++
return s
}
// Generic linking code.
var dylib []string
var linkoff int64
func machowrite(arch *sys.Arch, out *OutBuf, linkmode LinkMode) int {
o1 := out.Offset()
loadsize := 4 * 4 * ndebug
for i := range load {
loadsize += 4 * (len(load[i].data) + 2)
}
if arch.PtrSize == 8 {
loadsize += 18 * 4 * nseg
loadsize += 20 * 4 * nsect
} else {
loadsize += 14 * 4 * nseg
loadsize += 17 * 4 * nsect
}
if arch.PtrSize == 8 {
out.Write32(MH_MAGIC_64)
} else {
out.Write32(MH_MAGIC)
}
out.Write32(machohdr.cpu)
out.Write32(machohdr.subcpu)
if linkmode == LinkExternal {
out.Write32(MH_OBJECT) /* file type - mach object */
} else {
out.Write32(MH_EXECUTE) /* file type - mach executable */
}
out.Write32(uint32(len(load)) + uint32(nseg) + uint32(ndebug))
out.Write32(uint32(loadsize))
if nkind[SymKindUndef] == 0 {
out.Write32(MH_NOUNDEFS) /* flags - no undefines */
} else {
out.Write32(0) /* flags */
}
if arch.PtrSize == 8 {
out.Write32(0) /* reserved */
}
for i := 0; i < nseg; i++ {
s := &seg[i]
if arch.PtrSize == 8 {
out.Write32(LC_SEGMENT_64)
out.Write32(72 + 80*s.nsect)
out.WriteStringN(s.name, 16)
out.Write64(s.vaddr)
out.Write64(s.vsize)
out.Write64(s.fileoffset)
out.Write64(s.filesize)
out.Write32(s.prot1)
out.Write32(s.prot2)
out.Write32(s.nsect)
out.Write32(s.flag)
} else {
out.Write32(LC_SEGMENT)
out.Write32(56 + 68*s.nsect)
out.WriteStringN(s.name, 16)
out.Write32(uint32(s.vaddr))
out.Write32(uint32(s.vsize))
out.Write32(uint32(s.fileoffset))
out.Write32(uint32(s.filesize))
out.Write32(s.prot1)
out.Write32(s.prot2)
out.Write32(s.nsect)
out.Write32(s.flag)
}
for j := uint32(0); j < s.nsect; j++ {
t := &s.sect[j]
if arch.PtrSize == 8 {
out.WriteStringN(t.name, 16)
out.WriteStringN(t.segname, 16)
out.Write64(t.addr)
out.Write64(t.size)
out.Write32(t.off)
out.Write32(t.align)
out.Write32(t.reloc)
out.Write32(t.nreloc)
out.Write32(t.flag)
out.Write32(t.res1) /* reserved */
out.Write32(t.res2) /* reserved */
out.Write32(0) /* reserved */
} else {
out.WriteStringN(t.name, 16)
out.WriteStringN(t.segname, 16)
out.Write32(uint32(t.addr))
out.Write32(uint32(t.size))
out.Write32(t.off)
out.Write32(t.align)
out.Write32(t.reloc)
out.Write32(t.nreloc)
out.Write32(t.flag)
out.Write32(t.res1) /* reserved */
out.Write32(t.res2) /* reserved */
}
}
}
for i := range load {
l := &load[i]
out.Write32(l.type_)
out.Write32(4 * (uint32(len(l.data)) + 2))
for j := 0; j < len(l.data); j++ {
out.Write32(l.data[j])
}
}
return int(out.Offset() - o1)
}
func (ctxt *Link) domacho() {
if *FlagD {
return
}
// Copy platform load command.
for _, h := range hostobj {
load, err := hostobjMachoPlatform(&h)
if err != nil {
Exitf("%v", err)
}
if load != nil {
machoPlatform = load.platform
ml := newMachoLoad(ctxt.Arch, load.cmd.type_, uint32(len(load.cmd.data)))
copy(ml.data, load.cmd.data)
break
}
}
if machoPlatform == 0 {
switch ctxt.Arch.Family {
default:
machoPlatform = PLATFORM_MACOS
if ctxt.LinkMode == LinkInternal {
// For lldb, must say LC_VERSION_MIN_MACOSX or else
// it won't know that this Mach-O binary is from OS X
// (could be iOS or WatchOS instead).
// Go on iOS uses linkmode=external, and linkmode=external
// adds this itself. So we only need this code for linkmode=internal
// and we can assume OS X.
//
// See golang.org/issues/12941.
//
// The version must be at least 10.9; see golang.org/issues/30488.
ml := newMachoLoad(ctxt.Arch, LC_VERSION_MIN_MACOSX, 2)
ml.data[0] = 10<<16 | 9<<8 | 0<<0 // OS X version 10.9.0
ml.data[1] = 10<<16 | 9<<8 | 0<<0 // SDK 10.9.0
}
case sys.ARM, sys.ARM64:
machoPlatform = PLATFORM_IOS
}
}
// empirically, string table must begin with " \x00".
s := ctxt.loader.LookupOrCreateSym(".machosymstr", 0)
sb := ctxt.loader.MakeSymbolUpdater(s)
sb.SetType(sym.SMACHOSYMSTR)
sb.SetReachable(true)
sb.AddUint8(' ')
sb.AddUint8('\x00')
s = ctxt.loader.LookupOrCreateSym(".machosymtab", 0)
sb = ctxt.loader.MakeSymbolUpdater(s)
sb.SetType(sym.SMACHOSYMTAB)
sb.SetReachable(true)
if ctxt.IsInternal() {
s = ctxt.loader.LookupOrCreateSym(".plt", 0) // will be __symbol_stub
sb = ctxt.loader.MakeSymbolUpdater(s)
sb.SetType(sym.SMACHOPLT)
sb.SetReachable(true)
s = ctxt.loader.LookupOrCreateSym(".got", 0) // will be __nl_symbol_ptr
sb = ctxt.loader.MakeSymbolUpdater(s)
sb.SetType(sym.SMACHOGOT)
sb.SetReachable(true)
sb.SetAlign(4)
s = ctxt.loader.LookupOrCreateSym(".linkedit.plt", 0) // indirect table for .plt
sb = ctxt.loader.MakeSymbolUpdater(s)
sb.SetType(sym.SMACHOINDIRECTPLT)
sb.SetReachable(true)
s = ctxt.loader.LookupOrCreateSym(".linkedit.got", 0) // indirect table for .got
sb = ctxt.loader.MakeSymbolUpdater(s)
sb.SetType(sym.SMACHOINDIRECTGOT)
sb.SetReachable(true)
}
// Add a dummy symbol that will become the __asm marker section.
if ctxt.IsExternal() {
s = ctxt.loader.LookupOrCreateSym(".llvmasm", 0)
sb = ctxt.loader.MakeSymbolUpdater(s)
sb.SetType(sym.SMACHO)
sb.SetReachable(true)
sb.AddUint8(0)
}
}
func machoadddynlib(lib string, linkmode LinkMode) {
if seenlib[lib] || linkmode == LinkExternal {
return
}
seenlib[lib] = true
// Will need to store the library name rounded up
// and 24 bytes of header metadata. If not enough
// space, grab another page of initial space at the
// beginning of the output file.
loadBudget -= (len(lib)+7)/8*8 + 24
if loadBudget < 0 {
HEADR += 4096
*FlagTextAddr += 4096
loadBudget += 4096
}
dylib = append(dylib, lib)
}
func machoshbits(ctxt *Link, mseg *MachoSeg, sect *sym.Section, segname string) {
buf := "__" + strings.Replace(sect.Name[1:], ".", "_", -1)
msect := newMachoSect(mseg, buf, segname)
if sect.Rellen > 0 {
msect.reloc = uint32(sect.Reloff)
msect.nreloc = uint32(sect.Rellen / 8)
}
for 1<<msect.align < sect.Align {
msect.align++
}
msect.addr = sect.Vaddr
msect.size = sect.Length
if sect.Vaddr < sect.Seg.Vaddr+sect.Seg.Filelen {
// data in file
if sect.Length > sect.Seg.Vaddr+sect.Seg.Filelen-sect.Vaddr {
Errorf(nil, "macho cannot represent section %s crossing data and bss", sect.Name)
}
msect.off = uint32(sect.Seg.Fileoff + sect.Vaddr - sect.Seg.Vaddr)
} else {
msect.off = 0
msect.flag |= S_ZEROFILL
}
if sect.Rwx&1 != 0 {
msect.flag |= S_ATTR_SOME_INSTRUCTIONS
}
if sect.Name == ".text" {
msect.flag |= S_ATTR_PURE_INSTRUCTIONS
}
if sect.Name == ".plt" {
msect.name = "__symbol_stub1"
msect.flag = S_ATTR_PURE_INSTRUCTIONS | S_ATTR_SOME_INSTRUCTIONS | S_SYMBOL_STUBS
msect.res1 = 0 //nkind[SymKindLocal];
msect.res2 = 6
}
if sect.Name == ".got" {
msect.name = "__nl_symbol_ptr"
msect.flag = S_NON_LAZY_SYMBOL_POINTERS
msect.res1 = uint32(ctxt.loader.SymSize(ctxt.ArchSyms.LinkEditPLT) / 4) /* offset into indirect symbol table */
}
if sect.Name == ".init_array" {
msect.name = "__mod_init_func"
msect.flag = S_MOD_INIT_FUNC_POINTERS
}
// Some platforms such as watchOS and tvOS require binaries with
// bitcode enabled. The Go toolchain can't output bitcode, so use
// a marker section in the __LLVM segment, "__asm", to tell the Apple
// toolchain that the Go text came from assembler and thus has no
// bitcode. This is not true, but Kotlin/Native, Rust and Flutter
// are also using this trick.
if sect.Name == ".llvmasm" {
msect.name = "__asm"
msect.segname = "__LLVM"
}
if segname == "__DWARF" {
msect.flag |= S_ATTR_DEBUG
}
}
func asmbMacho(ctxt *Link) {
machlink := doMachoLink(ctxt)
if !*FlagS && ctxt.IsExternal() {
symo := int64(Segdwarf.Fileoff + uint64(Rnd(int64(Segdwarf.Filelen), int64(*FlagRound))) + uint64(machlink))
ctxt.Out.SeekSet(symo)
machoEmitReloc(ctxt)
}
ctxt.Out.SeekSet(0)
/* apple MACH */
va := *FlagTextAddr - int64(HEADR)
mh := getMachoHdr()
switch ctxt.Arch.Family {
default:
Exitf("unknown macho architecture: %v", ctxt.Arch.Family)
case sys.AMD64:
mh.cpu = MACHO_CPU_AMD64
mh.subcpu = MACHO_SUBCPU_X86
case sys.ARM64:
mh.cpu = MACHO_CPU_ARM64
mh.subcpu = MACHO_SUBCPU_ARM64_ALL
}
var ms *MachoSeg
if ctxt.LinkMode == LinkExternal {
/* segment for entire file */
ms = newMachoSeg("", 40)
ms.fileoffset = Segtext.Fileoff
ms.filesize = Segdwarf.Fileoff + Segdwarf.Filelen - Segtext.Fileoff
ms.vsize = Segdwarf.Vaddr + Segdwarf.Length - Segtext.Vaddr
}
/* segment for zero page */
if ctxt.LinkMode != LinkExternal {
ms = newMachoSeg("__PAGEZERO", 0)
ms.vsize = uint64(va)
}
/* text */
v := Rnd(int64(uint64(HEADR)+Segtext.Length), int64(*FlagRound))
if ctxt.LinkMode != LinkExternal {
ms = newMachoSeg("__TEXT", 20)
ms.vaddr = uint64(va)
ms.vsize = uint64(v)
ms.fileoffset = 0
ms.filesize = uint64(v)
ms.prot1 = 7
ms.prot2 = 5
}
for _, sect := range Segtext.Sections {
machoshbits(ctxt, ms, sect, "__TEXT")
}
/* rodata */
if ctxt.LinkMode != LinkExternal && Segrelrodata.Length > 0 {
ms = newMachoSeg("__DATA_CONST", 20)
ms.vaddr = Segrelrodata.Vaddr
ms.vsize = Segrelrodata.Length
ms.fileoffset = Segrelrodata.Fileoff
ms.filesize = Segrelrodata.Filelen
ms.prot1 = 3
ms.prot2 = 3
ms.flag = 0x10 // SG_READ_ONLY
}
for _, sect := range Segrelrodata.Sections {
machoshbits(ctxt, ms, sect, "__DATA_CONST")
}
/* data */
if ctxt.LinkMode != LinkExternal {
ms = newMachoSeg("__DATA", 20)
ms.vaddr = Segdata.Vaddr
ms.vsize = Segdata.Length
ms.fileoffset = Segdata.Fileoff
ms.filesize = Segdata.Filelen
ms.prot1 = 3
ms.prot2 = 3
}
for _, sect := range Segdata.Sections {
machoshbits(ctxt, ms, sect, "__DATA")
}
/* dwarf */
if !*FlagW {
if ctxt.LinkMode != LinkExternal {
ms = newMachoSeg("__DWARF", 20)
ms.vaddr = Segdwarf.Vaddr
ms.vsize = 0
ms.fileoffset = Segdwarf.Fileoff
ms.filesize = Segdwarf.Filelen
}
for _, sect := range Segdwarf.Sections {
machoshbits(ctxt, ms, sect, "__DWARF")
}
}
if ctxt.LinkMode != LinkExternal {
switch ctxt.Arch.Family {
default:
Exitf("unknown macho architecture: %v", ctxt.Arch.Family)
case sys.AMD64:
ml := newMachoLoad(ctxt.Arch, LC_UNIXTHREAD, 42+2)
ml.data[0] = 4 /* thread type */
ml.data[1] = 42 /* word count */
ml.data[2+32] = uint32(Entryvalue(ctxt)) /* start pc */
ml.data[2+32+1] = uint32(Entryvalue(ctxt) >> 32)
case sys.ARM64:
ml := newMachoLoad(ctxt.Arch, LC_UNIXTHREAD, 68+2)
ml.data[0] = 6 /* thread type */
ml.data[1] = 68 /* word count */
ml.data[2+64] = uint32(Entryvalue(ctxt)) /* start pc */
ml.data[2+64+1] = uint32(Entryvalue(ctxt) >> 32)
}
}
if !*FlagD {
ldr := ctxt.loader
// must match domacholink below
s1 := ldr.SymSize(ldr.Lookup(".machosymtab", 0))
s2 := ldr.SymSize(ctxt.ArchSyms.LinkEditPLT)
s3 := ldr.SymSize(ctxt.ArchSyms.LinkEditGOT)
s4 := ldr.SymSize(ldr.Lookup(".machosymstr", 0))
if ctxt.LinkMode != LinkExternal {
ms := newMachoSeg("__LINKEDIT", 0)
ms.vaddr = uint64(Rnd(int64(Segdata.Vaddr+Segdata.Length), int64(*FlagRound)))
ms.vsize = uint64(s1) + uint64(s2) + uint64(s3) + uint64(s4)
ms.fileoffset = uint64(linkoff)
ms.filesize = ms.vsize
ms.prot1 = 7
ms.prot2 = 3
}
ml := newMachoLoad(ctxt.Arch, LC_SYMTAB, 4)
ml.data[0] = uint32(linkoff) /* symoff */
ml.data[1] = uint32(nsortsym) /* nsyms */
ml.data[2] = uint32(linkoff + s1 + s2 + s3) /* stroff */
ml.data[3] = uint32(s4) /* strsize */
machodysymtab(ctxt)
if ctxt.LinkMode != LinkExternal {
ml := newMachoLoad(ctxt.Arch, LC_LOAD_DYLINKER, 6)
ml.data[0] = 12 /* offset to string */
stringtouint32(ml.data[1:], "/usr/lib/dyld")
for _, lib := range dylib {
ml = newMachoLoad(ctxt.Arch, LC_LOAD_DYLIB, 4+(uint32(len(lib))+1+7)/8*2)
ml.data[0] = 24 /* offset of string from beginning of load */
ml.data[1] = 0 /* time stamp */
ml.data[2] = 0 /* version */
ml.data[3] = 0 /* compatibility version */
stringtouint32(ml.data[4:], lib)
}
}
}
a := machowrite(ctxt.Arch, ctxt.Out, ctxt.LinkMode)
if int32(a) > HEADR {
Exitf("HEADR too small: %d > %d", a, HEADR)
}
}
func symkind(ldr *loader.Loader, s loader.Sym) int {
if ldr.SymType(s) == sym.SDYNIMPORT {
return SymKindUndef
}
if ldr.AttrCgoExport(s) {
return SymKindExtdef
}
return SymKindLocal
}
func collectmachosyms(ctxt *Link) {
ldr := ctxt.loader
addsym := func(s loader.Sym) {
sortsym = append(sortsym, s)
nkind[symkind(ldr, s)]++
}
// Add special runtime.text and runtime.etext symbols.
// We've already included this symbol in Textp on darwin if ctxt.DynlinkingGo().
// See data.go:/textaddress
if !ctxt.DynlinkingGo() {
s := ldr.Lookup("runtime.text", 0)
if ldr.SymType(s) == sym.STEXT {
addsym(s)
}
s = ldr.Lookup("runtime.etext", 0)
if ldr.SymType(s) == sym.STEXT {
addsym(s)
}
}
// Add text symbols.
for _, s := range ctxt.Textp {
addsym(s)
}
shouldBeInSymbolTable := func(s loader.Sym) bool {
if ldr.AttrNotInSymbolTable(s) {
return false
}
name := ldr.RawSymName(s) // TODO: try not to read the name
if name == "" || name[0] == '.' {
return false
}
return true
}
// Add data symbols and external references.
for s := loader.Sym(1); s < loader.Sym(ldr.NSym()); s++ {
if !ldr.AttrReachable(s) {
continue
}
t := ldr.SymType(s)
if t >= sym.SELFRXSECT && t < sym.SXREF { // data sections handled in dodata
if t == sym.STLSBSS {
// TLSBSS is not used on darwin. See data.go:allocateDataSections
continue
}
if !shouldBeInSymbolTable(s) {
continue
}
addsym(s)
}
switch t {
case sym.SDYNIMPORT, sym.SHOSTOBJ, sym.SUNDEFEXT:
addsym(s)
}
// Some 64-bit functions have a "$INODE64" or "$INODE64$UNIX2003" suffix.
if t == sym.SDYNIMPORT && ldr.SymDynimplib(s) == "/usr/lib/libSystem.B.dylib" {
// But only on macOS.
if machoPlatform == PLATFORM_MACOS {
switch n := ldr.SymExtname(s); n {
case "fdopendir":
switch objabi.GOARCH {
case "amd64":
ldr.SetSymExtname(s, n+"$INODE64")
case "386":
ldr.SetSymExtname(s, n+"$INODE64$UNIX2003")
}
case "readdir_r", "getfsstat":
switch objabi.GOARCH {
case "amd64", "386":
ldr.SetSymExtname(s, n+"$INODE64")
}
}
}
}
}
nsortsym = len(sortsym)
}
func machosymorder(ctxt *Link) {
ldr := ctxt.loader
// On Mac OS X Mountain Lion, we must sort exported symbols
// So we sort them here and pre-allocate dynid for them
// See https://golang.org/issue/4029
for _, s := range ctxt.dynexp {
if !ldr.AttrReachable(s) {
panic("dynexp symbol is not reachable")
}
}
collectmachosyms(ctxt)
sort.Slice(sortsym[:nsortsym], func(i, j int) bool {
s1 := sortsym[i]
s2 := sortsym[j]
k1 := symkind(ldr, s1)
k2 := symkind(ldr, s2)
if k1 != k2 {
return k1 < k2
}
return ldr.SymExtname(s1) < ldr.SymExtname(s2) // Note: unnamed symbols are not added in collectmachosyms
})
for i, s := range sortsym {
ldr.SetSymDynid(s, int32(i))
}
}
// machoShouldExport reports whether a symbol needs to be exported.
//
// When dynamically linking, all non-local variables and plugin-exported
// symbols need to be exported.
func machoShouldExport(ctxt *Link, ldr *loader.Loader, s loader.Sym) bool {
if !ctxt.DynlinkingGo() || ldr.AttrLocal(s) {
return false
}
if ctxt.BuildMode == BuildModePlugin && strings.HasPrefix(ldr.SymExtname(s), objabi.PathToPrefix(*flagPluginPath)) {
return true
}
name := ldr.RawSymName(s)
if strings.HasPrefix(name, "go.itab.") {
return true
}
if strings.HasPrefix(name, "type.") && !strings.HasPrefix(name, "type..") {
// reduce runtime typemap pressure, but do not
// export alg functions (type..*), as these
// appear in pclntable.
return true
}
if strings.HasPrefix(name, "go.link.pkghash") {
return true
}
return ldr.SymType(s) >= sym.SFirstWritable // only writable sections
}
func machosymtab(ctxt *Link) {
ldr := ctxt.loader
symtab := ldr.CreateSymForUpdate(".machosymtab", 0)
symstr := ldr.CreateSymForUpdate(".machosymstr", 0)
for _, s := range sortsym[:nsortsym] {
symtab.AddUint32(ctxt.Arch, uint32(symstr.Size()))
export := machoShouldExport(ctxt, ldr, s)
isGoSymbol := strings.Contains(ldr.SymExtname(s), ".")
// In normal buildmodes, only add _ to C symbols, as
// Go symbols have dot in the name.
//
// Do not export C symbols in plugins, as runtime C
// symbols like crosscall2 are in pclntab and end up
// pointing at the host binary, breaking unwinding.
// See Issue #18190.
cexport := !isGoSymbol && (ctxt.BuildMode != BuildModePlugin || onlycsymbol(ldr.SymName(s)))
if cexport || export || isGoSymbol {
symstr.AddUint8('_')
}
// replace "·" as ".", because DTrace cannot handle it.
symstr.Addstring(strings.Replace(ldr.SymExtname(s), "·", ".", -1))
if t := ldr.SymType(s); t == sym.SDYNIMPORT || t == sym.SHOSTOBJ || t == sym.SUNDEFEXT {
symtab.AddUint8(0x01) // type N_EXT, external symbol
symtab.AddUint8(0) // no section
symtab.AddUint16(ctxt.Arch, 0) // desc
symtab.AddUintXX(ctxt.Arch, 0, ctxt.Arch.PtrSize) // no value
} else {
if ldr.AttrCgoExport(s) || export {
symtab.AddUint8(0x0f)
} else {
symtab.AddUint8(0x0e)
}
o := s
if outer := ldr.OuterSym(o); outer != 0 {
o = outer
}
if ldr.SymSect(o) == nil {
ldr.Errorf(s, "missing section for symbol")
symtab.AddUint8(0)
} else {
symtab.AddUint8(uint8(ldr.SymSect(o).Extnum))
}
symtab.AddUint16(ctxt.Arch, 0) // desc
symtab.AddUintXX(ctxt.Arch, uint64(ldr.SymAddr(s)), ctxt.Arch.PtrSize)
}
}
}
func machodysymtab(ctxt *Link) {
ml := newMachoLoad(ctxt.Arch, LC_DYSYMTAB, 18)
n := 0
ml.data[0] = uint32(n) /* ilocalsym */
ml.data[1] = uint32(nkind[SymKindLocal]) /* nlocalsym */
n += nkind[SymKindLocal]
ml.data[2] = uint32(n) /* iextdefsym */
ml.data[3] = uint32(nkind[SymKindExtdef]) /* nextdefsym */
n += nkind[SymKindExtdef]
ml.data[4] = uint32(n) /* iundefsym */
ml.data[5] = uint32(nkind[SymKindUndef]) /* nundefsym */
ml.data[6] = 0 /* tocoffset */
ml.data[7] = 0 /* ntoc */
ml.data[8] = 0 /* modtaboff */
ml.data[9] = 0 /* nmodtab */
ml.data[10] = 0 /* extrefsymoff */
ml.data[11] = 0 /* nextrefsyms */
ldr := ctxt.loader
// must match domacholink below
s1 := ldr.SymSize(ldr.Lookup(".machosymtab", 0))
s2 := ldr.SymSize(ctxt.ArchSyms.LinkEditPLT)
s3 := ldr.SymSize(ctxt.ArchSyms.LinkEditGOT)
ml.data[12] = uint32(linkoff + s1) /* indirectsymoff */
ml.data[13] = uint32((s2 + s3) / 4) /* nindirectsyms */
ml.data[14] = 0 /* extreloff */
ml.data[15] = 0 /* nextrel */
ml.data[16] = 0 /* locreloff */
ml.data[17] = 0 /* nlocrel */
}
func doMachoLink(ctxt *Link) int64 {
machosymtab(ctxt)
ldr := ctxt.loader
// write data that will be linkedit section
s1 := ldr.Lookup(".machosymtab", 0)
s2 := ctxt.ArchSyms.LinkEditPLT
s3 := ctxt.ArchSyms.LinkEditGOT
s4 := ldr.Lookup(".machosymstr", 0)
// Force the linkedit section to end on a 16-byte
// boundary. This allows pure (non-cgo) Go binaries
// to be code signed correctly.
//
// Apple's codesign_allocate (a helper utility for
// the codesign utility) can do this fine itself if
// it is run on a dynamic Mach-O binary. However,
// when it is run on a pure (non-cgo) Go binary, where
// the linkedit section is mostly empty, it fails to
// account for the extra padding that it itself adds
// when adding the LC_CODE_SIGNATURE load command
// (which must be aligned on a 16-byte boundary).
//
// By forcing the linkedit section to end on a 16-byte
// boundary, codesign_allocate will not need to apply
// any alignment padding itself, working around the
// issue.
s4b := ldr.MakeSymbolUpdater(s4)
for s4b.Size()%16 != 0 {
s4b.AddUint8(0)
}
size := int(ldr.SymSize(s1) + ldr.SymSize(s2) + ldr.SymSize(s3) + ldr.SymSize(s4))
if size > 0 {
linkoff = Rnd(int64(uint64(HEADR)+Segtext.Length), int64(*FlagRound)) + Rnd(int64(Segrelrodata.Filelen), int64(*FlagRound)) + Rnd(int64(Segdata.Filelen), int64(*FlagRound)) + Rnd(int64(Segdwarf.Filelen), int64(*FlagRound))
ctxt.Out.SeekSet(linkoff)
ctxt.Out.Write(ldr.Data(s1))
ctxt.Out.Write(ldr.Data(s2))
ctxt.Out.Write(ldr.Data(s3))
ctxt.Out.Write(ldr.Data(s4))
}
return Rnd(int64(size), int64(*FlagRound))
}
func machorelocsect(ctxt *Link, out *OutBuf, sect *sym.Section, syms []loader.Sym) {
// If main section has no bits, nothing to relocate.
if sect.Vaddr >= sect.Seg.Vaddr+sect.Seg.Filelen {
return
}
ldr := ctxt.loader
for i, s := range syms {
if !ldr.AttrReachable(s) {
continue
}
if uint64(ldr.SymValue(s)) >= sect.Vaddr {
syms = syms[i:]
break
}
}
eaddr := int32(sect.Vaddr + sect.Length)
for _, s := range syms {
if !ldr.AttrReachable(s) {
continue
}
if ldr.SymValue(s) >= int64(eaddr) {
break
}
// Compute external relocations on the go, and pass to Machoreloc1
// to stream out.
relocs := ldr.Relocs(s)
for ri := 0; ri < relocs.Count(); ri++ {
r := relocs.At(ri)
rr, ok := extreloc(ctxt, ldr, s, r)
if !ok {
continue
}
if rr.Xsym == 0 {
ldr.Errorf(s, "missing xsym in relocation")
continue
}
if !ldr.AttrReachable(rr.Xsym) {
ldr.Errorf(s, "unreachable reloc %d (%s) target %v", r.Type(), sym.RelocName(ctxt.Arch, r.Type()), ldr.SymName(rr.Xsym))
}
if !thearch.Machoreloc1(ctxt.Arch, out, ldr, s, rr, int64(uint64(ldr.SymValue(s)+int64(r.Off()))-sect.Vaddr)) {
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()))
}
}
}
// sanity check
if uint64(out.Offset()) != sect.Reloff+sect.Rellen {
panic("machorelocsect: size mismatch")
}
}
func machoEmitReloc(ctxt *Link) {
for ctxt.Out.Offset()&7 != 0 {
ctxt.Out.Write8(0)
}
sizeExtRelocs(ctxt, thearch.MachorelocSize)
relocSect, wg := relocSectFn(ctxt, machorelocsect)
relocSect(ctxt, Segtext.Sections[0], ctxt.Textp)
for _, sect := range Segtext.Sections[1:] {
relocSect(ctxt, sect, ctxt.datap)
}
for _, sect := range Segrelrodata.Sections {
relocSect(ctxt, sect, ctxt.datap)
}
for _, sect := range Segdata.Sections {
relocSect(ctxt, sect, ctxt.datap)
}
for i := 0; i < len(Segdwarf.Sections); i++ {
sect := Segdwarf.Sections[i]
si := dwarfp[i]
if si.secSym() != loader.Sym(sect.Sym) ||
ctxt.loader.SymSect(si.secSym()) != sect {
panic("inconsistency between dwarfp and Segdwarf")
}
relocSect(ctxt, sect, si.syms)
}
wg.Wait()
}
// hostobjMachoPlatform returns the first platform load command found
// in the host object, if any.
func hostobjMachoPlatform(h *Hostobj) (*MachoPlatformLoad, error) {
f, err := os.Open(h.file)
if err != nil {
return nil, fmt.Errorf("%s: failed to open host object: %v\n", h.file, err)
}
defer f.Close()
sr := io.NewSectionReader(f, h.off, h.length)
m, err := macho.NewFile(sr)
if err != nil {
// Not a valid Mach-O file.
return nil, nil
}
return peekMachoPlatform(m)
}
// peekMachoPlatform returns the first LC_VERSION_MIN_* or LC_BUILD_VERSION
// load command found in the Mach-O file, if any.
func peekMachoPlatform(m *macho.File) (*MachoPlatformLoad, error) {
for _, cmd := range m.Loads {
raw := cmd.Raw()
ml := MachoLoad{
type_: m.ByteOrder.Uint32(raw),
}
// Skip the type and command length.
data := raw[8:]
var p MachoPlatform
switch ml.type_ {
case LC_VERSION_MIN_IPHONEOS:
p = PLATFORM_IOS
case LC_VERSION_MIN_MACOSX:
p = PLATFORM_MACOS
case LC_VERSION_MIN_WATCHOS:
p = PLATFORM_WATCHOS
case LC_VERSION_MIN_TVOS:
p = PLATFORM_TVOS
case LC_BUILD_VERSION:
p = MachoPlatform(m.ByteOrder.Uint32(data))
default:
continue
}
ml.data = make([]uint32, len(data)/4)
r := bytes.NewReader(data)
if err := binary.Read(r, m.ByteOrder, &ml.data); err != nil {
return nil, err
}
return &MachoPlatformLoad{
platform: p,
cmd: ml,
}, nil
}
return nil, nil
}