// Copyright 2017 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 loadmacho implements a Mach-O file reader.
package loadmacho
import (
"bytes"
"cmd/internal/bio"
"cmd/internal/objabi"
"cmd/internal/sys"
"cmd/link/internal/sym"
"encoding/binary"
"fmt"
"io"
"sort"
)
/*
Derived from Plan 9 from User Space's src/libmach/elf.h, elf.c
http://code.swtch.com/plan9port/src/tip/src/libmach/
Copyright © 2004 Russ Cox.
Portions Copyright © 2008-2010 Google Inc.
Portions Copyright © 2010 The Go Authors.
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/
// TODO(crawshaw): de-duplicate these symbols with cmd/internal/ld
const (
MACHO_X86_64_RELOC_UNSIGNED = 0
MACHO_X86_64_RELOC_SIGNED = 1
MACHO_FAKE_GOTPCREL = 100
)
type ldMachoObj struct {
f *bio.Reader
base int64 // off in f where Mach-O begins
length int64 // length of Mach-O
is64 bool
name string
e binary.ByteOrder
cputype uint
subcputype uint
filetype uint32
flags uint32
cmd []ldMachoCmd
ncmd uint
}
type ldMachoCmd struct {
type_ int
off uint32
size uint32
seg ldMachoSeg
sym ldMachoSymtab
dsym ldMachoDysymtab
}
type ldMachoSeg struct {
name string
vmaddr uint64
vmsize uint64
fileoff uint32
filesz uint32
maxprot uint32
initprot uint32
nsect uint32
flags uint32
sect []ldMachoSect
}
type ldMachoSect struct {
name string
segname string
addr uint64
size uint64
off uint32
align uint32
reloff uint32
nreloc uint32
flags uint32
res1 uint32
res2 uint32
sym *sym.Symbol
rel []ldMachoRel
}
type ldMachoRel struct {
addr uint32
symnum uint32
pcrel uint8
length uint8
extrn uint8
type_ uint8
scattered uint8
value uint32
}
type ldMachoSymtab struct {
symoff uint32
nsym uint32
stroff uint32
strsize uint32
str []byte
sym []ldMachoSym
}
type ldMachoSym struct {
name string
type_ uint8
sectnum uint8
desc uint16
kind int8
value uint64
sym *sym.Symbol
}
type ldMachoDysymtab struct {
ilocalsym uint32
nlocalsym uint32
iextdefsym uint32
nextdefsym uint32
iundefsym uint32
nundefsym uint32
tocoff uint32
ntoc uint32
modtaboff uint32
nmodtab uint32
extrefsymoff uint32
nextrefsyms uint32
indirectsymoff uint32
nindirectsyms uint32
extreloff uint32
nextrel uint32
locreloff uint32
nlocrel uint32
indir []uint32
}
// ldMachoSym.type_
const (
N_EXT = 0x01
N_TYPE = 0x1e
N_STAB = 0xe0
)
// ldMachoSym.desc
const (
N_WEAK_REF = 0x40
N_WEAK_DEF = 0x80
)
const (
LdMachoCpuVax = 1
LdMachoCpu68000 = 6
LdMachoCpu386 = 7
LdMachoCpuAmd64 = 0x1000007
LdMachoCpuMips = 8
LdMachoCpu98000 = 10
LdMachoCpuHppa = 11
LdMachoCpuArm = 12
LdMachoCpu88000 = 13
LdMachoCpuSparc = 14
LdMachoCpu860 = 15
LdMachoCpuAlpha = 16
LdMachoCpuPower = 18
LdMachoCmdSegment = 1
LdMachoCmdSymtab = 2
LdMachoCmdSymseg = 3
LdMachoCmdThread = 4
LdMachoCmdDysymtab = 11
LdMachoCmdSegment64 = 25
LdMachoFileObject = 1
LdMachoFileExecutable = 2
LdMachoFileFvmlib = 3
LdMachoFileCore = 4
LdMachoFilePreload = 5
)
func unpackcmd(p []byte, m *ldMachoObj, c *ldMachoCmd, type_ uint, sz uint) int {
e4 := m.e.Uint32
e8 := m.e.Uint64
c.type_ = int(type_)
c.size = uint32(sz)
switch type_ {
default:
return -1
case LdMachoCmdSegment:
if sz < 56 {
return -1
}
c.seg.name = cstring(p[8:24])
c.seg.vmaddr = uint64(e4(p[24:]))
c.seg.vmsize = uint64(e4(p[28:]))
c.seg.fileoff = e4(p[32:])
c.seg.filesz = e4(p[36:])
c.seg.maxprot = e4(p[40:])
c.seg.initprot = e4(p[44:])
c.seg.nsect = e4(p[48:])
c.seg.flags = e4(p[52:])
c.seg.sect = make([]ldMachoSect, c.seg.nsect)
if uint32(sz) < 56+c.seg.nsect*68 {
return -1
}
p = p[56:]
var s *ldMachoSect
for i := 0; uint32(i) < c.seg.nsect; i++ {
s = &c.seg.sect[i]
s.name = cstring(p[0:16])
s.segname = cstring(p[16:32])
s.addr = uint64(e4(p[32:]))
s.size = uint64(e4(p[36:]))
s.off = e4(p[40:])
s.align = e4(p[44:])
s.reloff = e4(p[48:])
s.nreloc = e4(p[52:])
s.flags = e4(p[56:])
s.res1 = e4(p[60:])
s.res2 = e4(p[64:])
p = p[68:]
}
case LdMachoCmdSegment64:
if sz < 72 {
return -1
}
c.seg.name = cstring(p[8:24])
c.seg.vmaddr = e8(p[24:])
c.seg.vmsize = e8(p[32:])
c.seg.fileoff = uint32(e8(p[40:]))
c.seg.filesz = uint32(e8(p[48:]))
c.seg.maxprot = e4(p[56:])
c.seg.initprot = e4(p[60:])
c.seg.nsect = e4(p[64:])
c.seg.flags = e4(p[68:])
c.seg.sect = make([]ldMachoSect, c.seg.nsect)
if uint32(sz) < 72+c.seg.nsect*80 {
return -1
}
p = p[72:]
var s *ldMachoSect
for i := 0; uint32(i) < c.seg.nsect; i++ {
s = &c.seg.sect[i]
s.name = cstring(p[0:16])
s.segname = cstring(p[16:32])
s.addr = e8(p[32:])
s.size = e8(p[40:])
s.off = e4(p[48:])
s.align = e4(p[52:])
s.reloff = e4(p[56:])
s.nreloc = e4(p[60:])
s.flags = e4(p[64:])
s.res1 = e4(p[68:])
s.res2 = e4(p[72:])
// p+76 is reserved
p = p[80:]
}
case LdMachoCmdSymtab:
if sz < 24 {
return -1
}
c.sym.symoff = e4(p[8:])
c.sym.nsym = e4(p[12:])
c.sym.stroff = e4(p[16:])
c.sym.strsize = e4(p[20:])
case LdMachoCmdDysymtab:
if sz < 80 {
return -1
}
c.dsym.ilocalsym = e4(p[8:])
c.dsym.nlocalsym = e4(p[12:])
c.dsym.iextdefsym = e4(p[16:])
c.dsym.nextdefsym = e4(p[20:])
c.dsym.iundefsym = e4(p[24:])
c.dsym.nundefsym = e4(p[28:])
c.dsym.tocoff = e4(p[32:])
c.dsym.ntoc = e4(p[36:])
c.dsym.modtaboff = e4(p[40:])
c.dsym.nmodtab = e4(p[44:])
c.dsym.extrefsymoff = e4(p[48:])
c.dsym.nextrefsyms = e4(p[52:])
c.dsym.indirectsymoff = e4(p[56:])
c.dsym.nindirectsyms = e4(p[60:])
c.dsym.extreloff = e4(p[64:])
c.dsym.nextrel = e4(p[68:])
c.dsym.locreloff = e4(p[72:])
c.dsym.nlocrel = e4(p[76:])
}
return 0
}
func macholoadrel(m *ldMachoObj, sect *ldMachoSect) int {
if sect.rel != nil || sect.nreloc == 0 {
return 0
}
rel := make([]ldMachoRel, sect.nreloc)
n := int(sect.nreloc * 8)
buf := make([]byte, n)
m.f.MustSeek(m.base+int64(sect.reloff), 0)
if _, err := io.ReadFull(m.f, buf); err != nil {
return -1
}
for i := uint32(0); i < sect.nreloc; i++ {
r := &rel[i]
p := buf[i*8:]
r.addr = m.e.Uint32(p)
// TODO(rsc): Wrong interpretation for big-endian bitfields?
if r.addr&0x80000000 != 0 {
// scatterbrained relocation
r.scattered = 1
v := r.addr >> 24
r.addr &= 0xFFFFFF
r.type_ = uint8(v & 0xF)
v >>= 4
r.length = 1 << (v & 3)
v >>= 2
r.pcrel = uint8(v & 1)
r.value = m.e.Uint32(p[4:])
} else {
v := m.e.Uint32(p[4:])
r.symnum = v & 0xFFFFFF
v >>= 24
r.pcrel = uint8(v & 1)
v >>= 1
r.length = 1 << (v & 3)
v >>= 2
r.extrn = uint8(v & 1)
v >>= 1
r.type_ = uint8(v)
}
}
sect.rel = rel
return 0
}
func macholoaddsym(m *ldMachoObj, d *ldMachoDysymtab) int {
n := int(d.nindirectsyms)
p := make([]byte, n*4)
m.f.MustSeek(m.base+int64(d.indirectsymoff), 0)
if _, err := io.ReadFull(m.f, p); err != nil {
return -1
}
d.indir = make([]uint32, n)
for i := 0; i < n; i++ {
d.indir[i] = m.e.Uint32(p[4*i:])
}
return 0
}
func macholoadsym(m *ldMachoObj, symtab *ldMachoSymtab) int {
if symtab.sym != nil {
return 0
}
strbuf := make([]byte, symtab.strsize)
m.f.MustSeek(m.base+int64(symtab.stroff), 0)
if _, err := io.ReadFull(m.f, strbuf); err != nil {
return -1
}
symsize := 12
if m.is64 {
symsize = 16
}
n := int(symtab.nsym * uint32(symsize))
symbuf := make([]byte, n)
m.f.MustSeek(m.base+int64(symtab.symoff), 0)
if _, err := io.ReadFull(m.f, symbuf); err != nil {
return -1
}
sym := make([]ldMachoSym, symtab.nsym)
p := symbuf
for i := uint32(0); i < symtab.nsym; i++ {
s := &sym[i]
v := m.e.Uint32(p)
if v >= symtab.strsize {
return -1
}
s.name = cstring(strbuf[v:])
s.type_ = p[4]
s.sectnum = p[5]
s.desc = m.e.Uint16(p[6:])
if m.is64 {
s.value = m.e.Uint64(p[8:])
} else {
s.value = uint64(m.e.Uint32(p[8:]))
}
p = p[symsize:]
}
symtab.str = strbuf
symtab.sym = sym
return 0
}
// Load loads the Mach-O file pn from f.
// Symbols are written into syms, and a slice of the text symbols is returned.
func Load(arch *sys.Arch, syms *sym.Symbols, f *bio.Reader, pkg string, length int64, pn string) (textp []*sym.Symbol, err error) {
errorf := func(str string, args ...interface{}) ([]*sym.Symbol, error) {
return nil, fmt.Errorf("loadmacho: %v: %v", pn, fmt.Sprintf(str, args...))
}
localSymVersion := syms.IncVersion()
base := f.Offset()
var hdr [7 * 4]uint8
if _, err := io.ReadFull(f, hdr[:]); err != nil {
return errorf("reading hdr: %v", err)
}
var e binary.ByteOrder
if binary.BigEndian.Uint32(hdr[:])&^1 == 0xFEEDFACE {
e = binary.BigEndian
} else if binary.LittleEndian.Uint32(hdr[:])&^1 == 0xFEEDFACE {
e = binary.LittleEndian
} else {
return errorf("bad magic - not mach-o file")
}
is64 := e.Uint32(hdr[:]) == 0xFEEDFACF
ncmd := e.Uint32(hdr[4*4:])
cmdsz := e.Uint32(hdr[5*4:])
if ncmd > 0x10000 || cmdsz >= 0x01000000 {
return errorf("implausible mach-o header ncmd=%d cmdsz=%d", ncmd, cmdsz)
}
if is64 {
f.MustSeek(4, 1) // skip reserved word in header
}
m := &ldMachoObj{
f: f,
e: e,
cputype: uint(e.Uint32(hdr[1*4:])),
subcputype: uint(e.Uint32(hdr[2*4:])),
filetype: e.Uint32(hdr[3*4:]),
ncmd: uint(ncmd),
flags: e.Uint32(hdr[6*4:]),
is64: is64,
base: base,
length: length,
name: pn,
}
switch arch.Family {
default:
return errorf("mach-o %s unimplemented", arch.Name)
case sys.AMD64:
if e != binary.LittleEndian || m.cputype != LdMachoCpuAmd64 {
return errorf("mach-o object but not amd64")
}
case sys.I386:
if e != binary.LittleEndian || m.cputype != LdMachoCpu386 {
return errorf("mach-o object but not 386")
}
}
m.cmd = make([]ldMachoCmd, ncmd)
cmdp := make([]byte, cmdsz)
if _, err := io.ReadFull(f, cmdp); err != nil {
return errorf("reading cmds: %v", err)
}
// read and parse load commands
var c *ldMachoCmd
var symtab *ldMachoSymtab
var dsymtab *ldMachoDysymtab
off := uint32(len(hdr))
for i := uint32(0); i < ncmd; i++ {
ty := e.Uint32(cmdp)
sz := e.Uint32(cmdp[4:])
m.cmd[i].off = off
unpackcmd(cmdp, m, &m.cmd[i], uint(ty), uint(sz))
cmdp = cmdp[sz:]
off += sz
if ty == LdMachoCmdSymtab {
if symtab != nil {
return errorf("multiple symbol tables")
}
symtab = &m.cmd[i].sym
macholoadsym(m, symtab)
}
if ty == LdMachoCmdDysymtab {
dsymtab = &m.cmd[i].dsym
macholoaddsym(m, dsymtab)
}
if (is64 && ty == LdMachoCmdSegment64) || (!is64 && ty == LdMachoCmdSegment) {
if c != nil {
return errorf("multiple load commands")
}
c = &m.cmd[i]
}
}
// load text and data segments into memory.
// they are not as small as the load commands, but we'll need
// the memory anyway for the symbol images, so we might
// as well use one large chunk.
if c == nil {
return errorf("no load command")
}
if symtab == nil {
// our work is done here - no symbols means nothing can refer to this file
return
}
if int64(c.seg.fileoff+c.seg.filesz) >= length {
return errorf("load segment out of range")
}
f.MustSeek(m.base+int64(c.seg.fileoff), 0)
dat := make([]byte, c.seg.filesz)
if _, err := io.ReadFull(f, dat); err != nil {
return errorf("cannot load object data: %v", err)
}
for i := uint32(0); i < c.seg.nsect; i++ {
sect := &c.seg.sect[i]
if sect.segname != "__TEXT" && sect.segname != "__DATA" {
continue
}
if sect.name == "__eh_frame" {
continue
}
name := fmt.Sprintf("%s(%s/%s)", pkg, sect.segname, sect.name)
s := syms.Lookup(name, localSymVersion)
if s.Type != 0 {
return errorf("duplicate %s/%s", sect.segname, sect.name)
}
if sect.flags&0xff == 1 { // S_ZEROFILL
s.P = make([]byte, sect.size)
} else {
s.P = dat[sect.addr-c.seg.vmaddr:][:sect.size]
}
s.Size = int64(len(s.P))
if sect.segname == "__TEXT" {
if sect.name == "__text" {
s.Type = sym.STEXT
} else {
s.Type = sym.SRODATA
}
} else {
if sect.name == "__bss" {
s.Type = sym.SNOPTRBSS
s.P = s.P[:0]
} else {
s.Type = sym.SNOPTRDATA
}
}
sect.sym = s
}
// enter sub-symbols into symbol table.
// have to guess sizes from next symbol.
for i := uint32(0); i < symtab.nsym; i++ {
machsym := &symtab.sym[i]
if machsym.type_&N_STAB != 0 {
continue
}
// TODO: check sym->type against outer->type.
name := machsym.name
if name[0] == '_' && name[1] != '\x00' {
name = name[1:]
}
v := 0
if machsym.type_&N_EXT == 0 {
v = localSymVersion
}
s := syms.Lookup(name, v)
if machsym.type_&N_EXT == 0 {
s.Attr |= sym.AttrDuplicateOK
}
if machsym.desc&(N_WEAK_REF|N_WEAK_DEF) != 0 {
s.Attr |= sym.AttrDuplicateOK
}
machsym.sym = s
if machsym.sectnum == 0 { // undefined
continue
}
if uint32(machsym.sectnum) > c.seg.nsect {
return errorf("reference to invalid section %d", machsym.sectnum)
}
sect := &c.seg.sect[machsym.sectnum-1]
outer := sect.sym
if outer == nil {
continue // ignore reference to invalid section
}
if s.Outer != nil {
if s.Attr.DuplicateOK() {
continue
}
return errorf("duplicate symbol reference: %s in both %s and %s", s.Name, s.Outer.Name, sect.sym.Name)
}
s.Type = outer.Type
s.Attr |= sym.AttrSubSymbol
s.Sub = outer.Sub
outer.Sub = s
s.Outer = outer
s.Value = int64(machsym.value - sect.addr)
if !s.Attr.CgoExportDynamic() {
s.SetDynimplib("") // satisfy dynimport
}
if outer.Type == sym.STEXT {
if s.Attr.External() && !s.Attr.DuplicateOK() {
return errorf("%v: duplicate symbol definition", s)
}
s.Attr |= sym.AttrExternal
}
machsym.sym = s
}
// Sort outer lists by address, adding to textp.
// This keeps textp in increasing address order.
for i := 0; uint32(i) < c.seg.nsect; i++ {
sect := &c.seg.sect[i]
s := sect.sym
if s == nil {
continue
}
if s.Sub != nil {
s.Sub = sym.SortSub(s.Sub)
// assign sizes, now that we know symbols in sorted order.
for s1 := s.Sub; s1 != nil; s1 = s1.Sub {
if s1.Sub != nil {
s1.Size = s1.Sub.Value - s1.Value
} else {
s1.Size = s.Value + s.Size - s1.Value
}
}
}
if s.Type == sym.STEXT {
if s.Attr.OnList() {
return errorf("symbol %s listed multiple times", s.Name)
}
s.Attr |= sym.AttrOnList
textp = append(textp, s)
for s1 := s.Sub; s1 != nil; s1 = s1.Sub {
if s1.Attr.OnList() {
return errorf("symbol %s listed multiple times", s1.Name)
}
s1.Attr |= sym.AttrOnList
textp = append(textp, s1)
}
}
}
// load relocations
for i := 0; uint32(i) < c.seg.nsect; i++ {
sect := &c.seg.sect[i]
s := sect.sym
if s == nil {
continue
}
macholoadrel(m, sect)
if sect.rel == nil {
continue
}
r := make([]sym.Reloc, sect.nreloc)
rpi := 0
Reloc:
for j := uint32(0); j < sect.nreloc; j++ {
rp := &r[rpi]
rel := §.rel[j]
if rel.scattered != 0 {
if arch.Family != sys.I386 {
// mach-o only uses scattered relocation on 32-bit platforms
return errorf("%v: unexpected scattered relocation", s)
}
// on 386, rewrite scattered 4/1 relocation and some
// scattered 2/1 relocation into the pseudo-pc-relative
// reference that it is.
// assume that the second in the pair is in this section
// and use that as the pc-relative base.
if j+1 >= sect.nreloc {
return errorf("unsupported scattered relocation %d", int(rel.type_))
}
if sect.rel[j+1].scattered == 0 || sect.rel[j+1].type_ != 1 || (rel.type_ != 4 && rel.type_ != 2) || uint64(sect.rel[j+1].value) < sect.addr || uint64(sect.rel[j+1].value) >= sect.addr+sect.size {
return errorf("unsupported scattered relocation %d/%d", int(rel.type_), int(sect.rel[j+1].type_))
}
rp.Siz = rel.length
rp.Off = int32(rel.addr)
// NOTE(rsc): I haven't worked out why (really when)
// we should ignore the addend on a
// scattered relocation, but it seems that the
// common case is we ignore it.
// It's likely that this is not strictly correct
// and that the math should look something
// like the non-scattered case below.
rp.Add = 0
// want to make it pc-relative aka relative to rp->off+4
// but the scatter asks for relative to off = sect->rel[j+1].value - sect->addr.
// adjust rp->add accordingly.
rp.Type = objabi.R_PCREL
rp.Add += int64(uint64(int64(rp.Off)+4) - (uint64(sect.rel[j+1].value) - sect.addr))
// now consider the desired symbol.
// find the section where it lives.
for k := 0; uint32(k) < c.seg.nsect; k++ {
ks := &c.seg.sect[k]
if ks.addr <= uint64(rel.value) && uint64(rel.value) < ks.addr+ks.size {
if ks.sym != nil {
rp.Sym = ks.sym
rp.Add += int64(uint64(rel.value) - ks.addr)
} else if ks.segname == "__IMPORT" && ks.name == "__pointers" {
// handle reference to __IMPORT/__pointers.
// how much worse can this get?
// why are we supporting 386 on the mac anyway?
rp.Type = objabi.MachoRelocOffset + MACHO_FAKE_GOTPCREL
// figure out which pointer this is a reference to.
k = int(uint64(ks.res1) + (uint64(rel.value)-ks.addr)/4)
// load indirect table for __pointers
// fetch symbol number
if dsymtab == nil || k < 0 || uint32(k) >= dsymtab.nindirectsyms || dsymtab.indir == nil {
return errorf("invalid scattered relocation: indirect symbol reference out of range")
}
k = int(dsymtab.indir[k])
if k < 0 || uint32(k) >= symtab.nsym {
return errorf("invalid scattered relocation: symbol reference out of range")
}
rp.Sym = symtab.sym[k].sym
} else {
return errorf("unsupported scattered relocation: reference to %s/%s", ks.segname, ks.name)
}
rpi++
// skip #1 of 2 rel; continue skips #2 of 2.
j++
continue Reloc
}
}
return errorf("unsupported scattered relocation: invalid address %#x", rel.addr)
}
rp.Siz = rel.length
rp.Type = objabi.MachoRelocOffset + (objabi.RelocType(rel.type_) << 1) + objabi.RelocType(rel.pcrel)
rp.Off = int32(rel.addr)
// Handle X86_64_RELOC_SIGNED referencing a section (rel->extrn == 0).
if arch.Family == sys.AMD64 && rel.extrn == 0 && rel.type_ == MACHO_X86_64_RELOC_SIGNED {
// Calculate the addend as the offset into the section.
//
// The rip-relative offset stored in the object file is encoded
// as follows:
//
// movsd 0x00000360(%rip),%xmm0
//
// To get the absolute address of the value this rip-relative address is pointing
// to, we must add the address of the next instruction to it. This is done by
// taking the address of the relocation and adding 4 to it (since the rip-relative
// offset can at most be 32 bits long). To calculate the offset into the section the
// relocation is referencing, we subtract the vaddr of the start of the referenced
// section found in the original object file.
//
// [For future reference, see Darwin's /usr/include/mach-o/x86_64/reloc.h]
secaddr := c.seg.sect[rel.symnum-1].addr
rp.Add = int64(uint64(int64(int32(e.Uint32(s.P[rp.Off:])))+int64(rp.Off)+4) - secaddr)
} else {
rp.Add = int64(int32(e.Uint32(s.P[rp.Off:])))
}
// An unsigned internal relocation has a value offset
// by the section address.
if arch.Family == sys.AMD64 && rel.extrn == 0 && rel.type_ == MACHO_X86_64_RELOC_UNSIGNED {
secaddr := c.seg.sect[rel.symnum-1].addr
rp.Add -= int64(secaddr)
}
// For i386 Mach-O PC-relative, the addend is written such that
// it *is* the PC being subtracted. Use that to make
// it match our version of PC-relative.
if rel.pcrel != 0 && arch.Family == sys.I386 {
rp.Add += int64(rp.Off) + int64(rp.Siz)
}
if rel.extrn == 0 {
if rel.symnum < 1 || rel.symnum > c.seg.nsect {
return errorf("invalid relocation: section reference out of range %d vs %d", rel.symnum, c.seg.nsect)
}
rp.Sym = c.seg.sect[rel.symnum-1].sym
if rp.Sym == nil {
return errorf("invalid relocation: %s", c.seg.sect[rel.symnum-1].name)
}
// References to symbols in other sections
// include that information in the addend.
// We only care about the delta from the
// section base.
if arch.Family == sys.I386 {
rp.Add -= int64(c.seg.sect[rel.symnum-1].addr)
}
} else {
if rel.symnum >= symtab.nsym {
return errorf("invalid relocation: symbol reference out of range")
}
rp.Sym = symtab.sym[rel.symnum].sym
}
rpi++
}
sort.Sort(sym.RelocByOff(r[:rpi]))
s.R = r
s.R = s.R[:rpi]
}
return textp, nil
}
func cstring(x []byte) string {
i := bytes.IndexByte(x, '\x00')
if i >= 0 {
x = x[:i]
}
return string(x)
}
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