/
ldelf.go
1172 lines (1036 loc) · 26.9 KB
/
ldelf.go
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package ld
import (
"bytes"
"cmd/internal/obj"
"encoding/binary"
"fmt"
"io"
"log"
"sort"
"strings"
)
/*
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.
*/
const (
ElfClassNone = 0
ElfClass32 = 1
ElfClass64 = 2
)
const (
ElfDataNone = 0
ElfDataLsb = 1
ElfDataMsb = 2
)
const (
ElfTypeNone = 0
ElfTypeRelocatable = 1
ElfTypeExecutable = 2
ElfTypeSharedObject = 3
ElfTypeCore = 4
)
const (
ElfMachNone = 0
ElfMach32100 = 1
ElfMachSparc = 2
ElfMach386 = 3
ElfMach68000 = 4
ElfMach88000 = 5
ElfMach486 = 6
ElfMach860 = 7
ElfMachMips = 8
ElfMachS370 = 9
ElfMachMipsLe = 10
ElfMachParisc = 15
ElfMachVpp500 = 17
ElfMachSparc32Plus = 18
ElfMach960 = 19
ElfMachPower = 20
ElfMachPower64 = 21
ElfMachS390 = 22
ElfMachV800 = 36
ElfMachFr20 = 37
ElfMachRh32 = 38
ElfMachRce = 39
ElfMachArm = 40
ElfMachAlpha = 41
ElfMachSH = 42
ElfMachSparc9 = 43
ElfMachAmd64 = 62
ElfMachArm64 = 183
)
const (
ElfAbiNone = 0
ElfAbiSystemV = 0
ElfAbiHPUX = 1
ElfAbiNetBSD = 2
ElfAbiLinux = 3
ElfAbiSolaris = 6
ElfAbiAix = 7
ElfAbiIrix = 8
ElfAbiFreeBSD = 9
ElfAbiTru64 = 10
ElfAbiModesto = 11
ElfAbiOpenBSD = 12
ElfAbiARM = 97
ElfAbiEmbedded = 255
)
const (
ElfSectNone = 0
ElfSectProgbits = 1
ElfSectSymtab = 2
ElfSectStrtab = 3
ElfSectRela = 4
ElfSectHash = 5
ElfSectDynamic = 6
ElfSectNote = 7
ElfSectNobits = 8
ElfSectRel = 9
ElfSectShlib = 10
ElfSectDynsym = 11
ElfSectFlagWrite = 0x1
ElfSectFlagAlloc = 0x2
ElfSectFlagExec = 0x4
)
const (
ElfSymBindLocal = 0
ElfSymBindGlobal = 1
ElfSymBindWeak = 2
)
const (
ElfSymTypeNone = 0
ElfSymTypeObject = 1
ElfSymTypeFunc = 2
ElfSymTypeSection = 3
ElfSymTypeFile = 4
)
const (
ElfSymShnNone = 0
ElfSymShnAbs = 0xFFF1
ElfSymShnCommon = 0xFFF2
)
const (
ElfProgNone = 0
ElfProgLoad = 1
ElfProgDynamic = 2
ElfProgInterp = 3
ElfProgNote = 4
ElfProgShlib = 5
ElfProgPhdr = 6
ElfProgFlagExec = 0x1
ElfProgFlagWrite = 0x2
ElfProgFlagRead = 0x4
)
const (
ElfNotePrStatus = 1
ElfNotePrFpreg = 2
ElfNotePrPsinfo = 3
ElfNotePrTaskstruct = 4
ElfNotePrAuxv = 6
ElfNotePrXfpreg = 0x46e62b7f
)
type ElfHdrBytes struct {
Ident [16]uint8
Type [2]uint8
Machine [2]uint8
Version [4]uint8
Entry [4]uint8
Phoff [4]uint8
Shoff [4]uint8
Flags [4]uint8
Ehsize [2]uint8
Phentsize [2]uint8
Phnum [2]uint8
Shentsize [2]uint8
Shnum [2]uint8
Shstrndx [2]uint8
}
type ElfSectBytes struct {
Name [4]uint8
Type [4]uint8
Flags [4]uint8
Addr [4]uint8
Off [4]uint8
Size [4]uint8
Link [4]uint8
Info [4]uint8
Align [4]uint8
Entsize [4]uint8
}
type ElfProgBytes struct {
}
type ElfSymBytes struct {
Name [4]uint8
Value [4]uint8
Size [4]uint8
Info uint8
Other uint8
Shndx [2]uint8
}
type ElfHdrBytes64 struct {
Ident [16]uint8
Type [2]uint8
Machine [2]uint8
Version [4]uint8
Entry [8]uint8
Phoff [8]uint8
Shoff [8]uint8
Flags [4]uint8
Ehsize [2]uint8
Phentsize [2]uint8
Phnum [2]uint8
Shentsize [2]uint8
Shnum [2]uint8
Shstrndx [2]uint8
}
type ElfSectBytes64 struct {
Name [4]uint8
Type [4]uint8
Flags [8]uint8
Addr [8]uint8
Off [8]uint8
Size [8]uint8
Link [4]uint8
Info [4]uint8
Align [8]uint8
Entsize [8]uint8
}
type ElfProgBytes64 struct {
}
type ElfSymBytes64 struct {
Name [4]uint8
Info uint8
Other uint8
Shndx [2]uint8
Value [8]uint8
Size [8]uint8
}
type ElfSect struct {
name string
nameoff uint32
type_ uint32
flags uint64
addr uint64
off uint64
size uint64
link uint32
info uint32
align uint64
entsize uint64
base []byte
sym *LSym
}
type ElfObj struct {
f *obj.Biobuf
base int64 // offset in f where ELF begins
length int64 // length of ELF
is64 int
name string
e binary.ByteOrder
sect []ElfSect
nsect uint
shstrtab string
nsymtab int
symtab *ElfSect
symstr *ElfSect
type_ uint32
machine uint32
version uint32
entry uint64
phoff uint64
shoff uint64
flags uint32
ehsize uint32
phentsize uint32
phnum uint32
shentsize uint32
shnum uint32
shstrndx uint32
}
type ElfSym struct {
name string
value uint64
size uint64
bind uint8
type_ uint8
other uint8
shndx uint16
sym *LSym
}
var ElfMagic = [4]uint8{0x7F, 'E', 'L', 'F'}
func valuecmp(a *LSym, b *LSym) int {
if a.Value < b.Value {
return -1
}
if a.Value > b.Value {
return +1
}
return 0
}
const (
Tag_file = 1
Tag_CPU_name = 4
Tag_CPU_raw_name = 5
Tag_compatibility = 32
Tag_nodefaults = 64
Tag_also_compatible_with = 65
Tag_ABI_VFP_args = 28
)
type elfAttribute struct {
tag uint64
sval string
ival uint64
}
type elfAttributeList struct {
data []byte
err error
}
func (a *elfAttributeList) string() string {
if a.err != nil {
return ""
}
nul := bytes.IndexByte(a.data, 0)
if nul < 0 {
a.err = io.EOF
return ""
}
s := string(a.data[:nul])
a.data = a.data[nul+1:]
return s
}
func (a *elfAttributeList) uleb128() uint64 {
if a.err != nil {
return 0
}
v, size := binary.Uvarint(a.data)
a.data = a.data[size:]
return v
}
// Read an elfAttribute from the list following the rules used on ARM systems.
func (a *elfAttributeList) armAttr() elfAttribute {
attr := elfAttribute{tag: a.uleb128()}
switch {
case attr.tag == Tag_compatibility:
attr.ival = a.uleb128()
attr.sval = a.string()
case attr.tag == 64: // Tag_nodefaults has no argument
case attr.tag == 65: // Tag_also_compatible_with
// Not really, but we don't actually care about this tag.
attr.sval = a.string()
// Tag with string argument
case attr.tag == Tag_CPU_name || attr.tag == Tag_CPU_raw_name || (attr.tag >= 32 && attr.tag&1 != 0):
attr.sval = a.string()
default: // Tag with integer argument
attr.ival = a.uleb128()
}
return attr
}
func (a *elfAttributeList) done() bool {
if a.err != nil || len(a.data) == 0 {
return true
}
return false
}
// Look for the attribute that indicates the object uses the hard-float ABI (a
// file-level attribute with tag Tag_VFP_arch and value 1). Unfortunately the
// format used means that we have to parse all of the file-level attributes to
// find the one we are looking for. This format is slightly documented in "ELF
// for the ARM Architecture" but mostly this is derived from reading the source
// to gold and readelf.
func parseArmAttributes(e binary.ByteOrder, data []byte) {
// We assume the soft-float ABI unless we see a tag indicating otherwise.
if ehdr.flags == 0x5000002 {
ehdr.flags = 0x5000202
}
if data[0] != 'A' {
fmt.Fprintf(&Bso, ".ARM.attributes has unexpected format %c\n", data[0])
return
}
data = data[1:]
for len(data) != 0 {
sectionlength := e.Uint32(data)
sectiondata := data[4:sectionlength]
data = data[sectionlength:]
nulIndex := bytes.IndexByte(sectiondata, 0)
if nulIndex < 0 {
fmt.Fprintf(&Bso, "corrupt .ARM.attributes (section name not NUL-terminated)\n")
return
}
name := string(sectiondata[:nulIndex])
sectiondata = sectiondata[nulIndex+1:]
if name != "aeabi" {
continue
}
for len(sectiondata) != 0 {
subsectiontag, sz := binary.Uvarint(sectiondata)
subsectionsize := e.Uint32(sectiondata[sz:])
subsectiondata := sectiondata[sz+4 : subsectionsize]
sectiondata = sectiondata[subsectionsize:]
if subsectiontag == Tag_file {
attrList := elfAttributeList{data: subsectiondata}
for !attrList.done() {
attr := attrList.armAttr()
if attr.tag == Tag_ABI_VFP_args && attr.ival == 1 {
ehdr.flags = 0x5000402 // has entry point, Version5 EABI, hard-float ABI
}
}
if attrList.err != nil {
fmt.Fprintf(&Bso, "could not parse .ARM.attributes\n")
}
}
}
}
}
func ldelf(f *obj.Biobuf, pkg string, length int64, pn string) {
if Debug['v'] != 0 {
fmt.Fprintf(&Bso, "%5.2f ldelf %s\n", obj.Cputime(), pn)
}
Ctxt.Version++
base := int32(obj.Boffset(f))
var add uint64
var e binary.ByteOrder
var elfobj *ElfObj
var err error
var flag int
var hdr *ElfHdrBytes
var hdrbuf [64]uint8
var info uint64
var is64 int
var j int
var n int
var name string
var p []byte
var r []Reloc
var rela int
var rp *Reloc
var rsect *ElfSect
var s *LSym
var sect *ElfSect
var sym ElfSym
var symbols []*LSym
if obj.Bread(f, hdrbuf[:]) != len(hdrbuf) {
goto bad
}
hdr = new(ElfHdrBytes)
binary.Read(bytes.NewReader(hdrbuf[:]), binary.BigEndian, hdr) // only byte arrays; byte order doesn't matter
if string(hdr.Ident[:4]) != "\x7FELF" {
goto bad
}
switch hdr.Ident[5] {
case ElfDataLsb:
e = binary.LittleEndian
case ElfDataMsb:
e = binary.BigEndian
default:
goto bad
}
// read header
elfobj = new(ElfObj)
elfobj.e = e
elfobj.f = f
elfobj.base = int64(base)
elfobj.length = length
elfobj.name = pn
is64 = 0
if hdr.Ident[4] == ElfClass64 {
is64 = 1
hdr := new(ElfHdrBytes64)
binary.Read(bytes.NewReader(hdrbuf[:]), binary.BigEndian, hdr) // only byte arrays; byte order doesn't matter
elfobj.type_ = uint32(e.Uint16(hdr.Type[:]))
elfobj.machine = uint32(e.Uint16(hdr.Machine[:]))
elfobj.version = e.Uint32(hdr.Version[:])
elfobj.phoff = e.Uint64(hdr.Phoff[:])
elfobj.shoff = e.Uint64(hdr.Shoff[:])
elfobj.flags = e.Uint32(hdr.Flags[:])
elfobj.ehsize = uint32(e.Uint16(hdr.Ehsize[:]))
elfobj.phentsize = uint32(e.Uint16(hdr.Phentsize[:]))
elfobj.phnum = uint32(e.Uint16(hdr.Phnum[:]))
elfobj.shentsize = uint32(e.Uint16(hdr.Shentsize[:]))
elfobj.shnum = uint32(e.Uint16(hdr.Shnum[:]))
elfobj.shstrndx = uint32(e.Uint16(hdr.Shstrndx[:]))
} else {
elfobj.type_ = uint32(e.Uint16(hdr.Type[:]))
elfobj.machine = uint32(e.Uint16(hdr.Machine[:]))
elfobj.version = e.Uint32(hdr.Version[:])
elfobj.entry = uint64(e.Uint32(hdr.Entry[:]))
elfobj.phoff = uint64(e.Uint32(hdr.Phoff[:]))
elfobj.shoff = uint64(e.Uint32(hdr.Shoff[:]))
elfobj.flags = e.Uint32(hdr.Flags[:])
elfobj.ehsize = uint32(e.Uint16(hdr.Ehsize[:]))
elfobj.phentsize = uint32(e.Uint16(hdr.Phentsize[:]))
elfobj.phnum = uint32(e.Uint16(hdr.Phnum[:]))
elfobj.shentsize = uint32(e.Uint16(hdr.Shentsize[:]))
elfobj.shnum = uint32(e.Uint16(hdr.Shnum[:]))
elfobj.shstrndx = uint32(e.Uint16(hdr.Shstrndx[:]))
}
elfobj.is64 = is64
if uint32(hdr.Ident[6]) != elfobj.version {
goto bad
}
if e.Uint16(hdr.Type[:]) != ElfTypeRelocatable {
Diag("%s: elf but not elf relocatable object", pn)
return
}
switch Thearch.Thechar {
default:
Diag("%s: elf %s unimplemented", pn, Thestring)
return
case '0':
if elfobj.machine != ElfMachMips || hdr.Ident[4] != ElfClass64 {
Diag("%s: elf object but not mips64", pn)
return
}
case '5':
if e != binary.LittleEndian || elfobj.machine != ElfMachArm || hdr.Ident[4] != ElfClass32 {
Diag("%s: elf object but not arm", pn)
return
}
case '6':
if e != binary.LittleEndian || elfobj.machine != ElfMachAmd64 || hdr.Ident[4] != ElfClass64 {
Diag("%s: elf object but not amd64", pn)
return
}
case '7':
if e != binary.LittleEndian || elfobj.machine != ElfMachArm64 || hdr.Ident[4] != ElfClass64 {
Diag("%s: elf object but not arm64", pn)
return
}
case '8':
if e != binary.LittleEndian || elfobj.machine != ElfMach386 || hdr.Ident[4] != ElfClass32 {
Diag("%s: elf object but not 386", pn)
return
}
case '9':
if elfobj.machine != ElfMachPower64 || hdr.Ident[4] != ElfClass64 {
Diag("%s: elf object but not ppc64", pn)
return
}
}
// load section list into memory.
elfobj.sect = make([]ElfSect, elfobj.shnum)
elfobj.nsect = uint(elfobj.shnum)
for i := 0; uint(i) < elfobj.nsect; i++ {
if obj.Bseek(f, int64(uint64(base)+elfobj.shoff+uint64(int64(i)*int64(elfobj.shentsize))), 0) < 0 {
goto bad
}
sect = &elfobj.sect[i]
if is64 != 0 {
var b ElfSectBytes64
if err = binary.Read(f, e, &b); err != nil {
goto bad
}
sect.nameoff = uint32(e.Uint32(b.Name[:]))
sect.type_ = e.Uint32(b.Type[:])
sect.flags = e.Uint64(b.Flags[:])
sect.addr = e.Uint64(b.Addr[:])
sect.off = e.Uint64(b.Off[:])
sect.size = e.Uint64(b.Size[:])
sect.link = e.Uint32(b.Link[:])
sect.info = e.Uint32(b.Info[:])
sect.align = e.Uint64(b.Align[:])
sect.entsize = e.Uint64(b.Entsize[:])
} else {
var b ElfSectBytes
if err = binary.Read(f, e, &b); err != nil {
goto bad
}
sect.nameoff = uint32(e.Uint32(b.Name[:]))
sect.type_ = e.Uint32(b.Type[:])
sect.flags = uint64(e.Uint32(b.Flags[:]))
sect.addr = uint64(e.Uint32(b.Addr[:]))
sect.off = uint64(e.Uint32(b.Off[:]))
sect.size = uint64(e.Uint32(b.Size[:]))
sect.link = e.Uint32(b.Link[:])
sect.info = e.Uint32(b.Info[:])
sect.align = uint64(e.Uint32(b.Align[:]))
sect.entsize = uint64(e.Uint32(b.Entsize[:]))
}
}
// read section string table and translate names
if elfobj.shstrndx >= uint32(elfobj.nsect) {
err = fmt.Errorf("shstrndx out of range %d >= %d", elfobj.shstrndx, elfobj.nsect)
goto bad
}
sect = &elfobj.sect[elfobj.shstrndx]
if err = elfmap(elfobj, sect); err != nil {
goto bad
}
for i := 0; uint(i) < elfobj.nsect; i++ {
if elfobj.sect[i].nameoff != 0 {
elfobj.sect[i].name = cstring(sect.base[elfobj.sect[i].nameoff:])
}
}
// load string table for symbols into memory.
elfobj.symtab = section(elfobj, ".symtab")
if elfobj.symtab == nil {
// our work is done here - no symbols means nothing can refer to this file
return
}
if elfobj.symtab.link <= 0 || elfobj.symtab.link >= uint32(elfobj.nsect) {
Diag("%s: elf object has symbol table with invalid string table link", pn)
return
}
elfobj.symstr = &elfobj.sect[elfobj.symtab.link]
if is64 != 0 {
elfobj.nsymtab = int(elfobj.symtab.size / ELF64SYMSIZE)
} else {
elfobj.nsymtab = int(elfobj.symtab.size / ELF32SYMSIZE)
}
if err = elfmap(elfobj, elfobj.symtab); err != nil {
goto bad
}
if err = elfmap(elfobj, elfobj.symstr); err != nil {
goto bad
}
// load text and data segments into memory.
// they are not as small as the section lists, but we'll need
// the memory anyway for the symbol images, so we might
// as well use one large chunk.
// create symbols for elfmapped sections
for i := 0; uint(i) < elfobj.nsect; i++ {
sect = &elfobj.sect[i]
if sect.type_ == SHT_ARM_ATTRIBUTES && sect.name == ".ARM.attributes" {
if err = elfmap(elfobj, sect); err != nil {
goto bad
}
parseArmAttributes(e, sect.base[:sect.size])
}
if (sect.type_ != ElfSectProgbits && sect.type_ != ElfSectNobits) || sect.flags&ElfSectFlagAlloc == 0 {
continue
}
if sect.type_ != ElfSectNobits {
if err = elfmap(elfobj, sect); err != nil {
goto bad
}
}
name = fmt.Sprintf("%s(%s)", pkg, sect.name)
s = Linklookup(Ctxt, name, Ctxt.Version)
switch int(sect.flags) & (ElfSectFlagAlloc | ElfSectFlagWrite | ElfSectFlagExec) {
default:
err = fmt.Errorf("unexpected flags for ELF section %s", sect.name)
goto bad
case ElfSectFlagAlloc:
s.Type = obj.SRODATA
case ElfSectFlagAlloc + ElfSectFlagWrite:
if sect.type_ == ElfSectNobits {
s.Type = obj.SNOPTRBSS
} else {
s.Type = obj.SNOPTRDATA
}
case ElfSectFlagAlloc + ElfSectFlagExec:
s.Type = obj.STEXT
}
if sect.name == ".got" || sect.name == ".toc" {
s.Type = obj.SELFGOT
}
if sect.type_ == ElfSectProgbits {
s.P = sect.base
s.P = s.P[:sect.size]
}
s.Size = int64(sect.size)
s.Align = int32(sect.align)
sect.sym = s
}
// enter sub-symbols into symbol table.
// symbol 0 is the null symbol.
symbols = make([]*LSym, elfobj.nsymtab)
for i := 1; i < elfobj.nsymtab; i++ {
if err = readelfsym(elfobj, i, &sym, 1); err != nil {
goto bad
}
symbols[i] = sym.sym
if sym.type_ != ElfSymTypeFunc && sym.type_ != ElfSymTypeObject && sym.type_ != ElfSymTypeNone {
continue
}
if sym.shndx == ElfSymShnCommon {
s = sym.sym
if uint64(s.Size) < sym.size {
s.Size = int64(sym.size)
}
if s.Type == 0 || s.Type == obj.SXREF {
s.Type = obj.SNOPTRBSS
}
continue
}
if uint(sym.shndx) >= elfobj.nsect || sym.shndx == 0 {
continue
}
// even when we pass needSym == 1 to readelfsym, it might still return nil to skip some unwanted symbols
if sym.sym == nil {
continue
}
sect = &elfobj.sect[sym.shndx:][0]
if sect.sym == nil {
if strings.HasPrefix(sym.name, ".Linfo_string") { // clang does this
continue
}
if sym.name == "" && sym.type_ == 0 && sect.name == ".debug_str" {
// This reportedly happens with clang 3.7 on ARM.
// See issue 13139.
continue
}
Diag("%s: sym#%d: ignoring %s in section %d (type %d)", pn, i, sym.name, sym.shndx, sym.type_)
continue
}
s = sym.sym
if s.Outer != nil {
if s.Dupok != 0 {
continue
}
Exitf("%s: duplicate symbol reference: %s in both %s and %s", pn, s.Name, s.Outer.Name, sect.sym.Name)
}
s.Sub = sect.sym.Sub
sect.sym.Sub = s
s.Type = sect.sym.Type | s.Type&^obj.SMASK | obj.SSUB
if s.Cgoexport&CgoExportDynamic == 0 {
s.Dynimplib = "" // satisfy dynimport
}
s.Value = int64(sym.value)
s.Size = int64(sym.size)
s.Outer = sect.sym
if sect.sym.Type == obj.STEXT {
if s.External != 0 && s.Dupok == 0 {
Diag("%s: duplicate definition of %s", pn, s.Name)
}
s.External = 1
}
if elfobj.machine == ElfMachPower64 {
flag = int(sym.other) >> 5
if 2 <= flag && flag <= 6 {
s.Localentry = 1 << uint(flag-2)
} else if flag == 7 {
Diag("%s: invalid sym.other 0x%x for %s", pn, sym.other, s.Name)
}
}
}
// Sort outer lists by address, adding to textp.
// This keeps textp in increasing address order.
for i := 0; uint(i) < elfobj.nsect; i++ {
s = elfobj.sect[i].sym
if s == nil {
continue
}
if s.Sub != nil {
s.Sub = listsort(s.Sub, valuecmp, listsubp)
}
if s.Type == obj.STEXT {
if s.Onlist != 0 {
log.Fatalf("symbol %s listed multiple times", s.Name)
}
s.Onlist = 1
if Ctxt.Etextp != nil {
Ctxt.Etextp.Next = s
} else {
Ctxt.Textp = s
}
Ctxt.Etextp = s
for s = s.Sub; s != nil; s = s.Sub {
if s.Onlist != 0 {
log.Fatalf("symbol %s listed multiple times", s.Name)
}
s.Onlist = 1
Ctxt.Etextp.Next = s
Ctxt.Etextp = s
}
}
}
// load relocations
for i := 0; uint(i) < elfobj.nsect; i++ {
rsect = &elfobj.sect[i]
if rsect.type_ != ElfSectRela && rsect.type_ != ElfSectRel {
continue
}
if rsect.info >= uint32(elfobj.nsect) || elfobj.sect[rsect.info].base == nil {
continue
}
sect = &elfobj.sect[rsect.info]
if err = elfmap(elfobj, rsect); err != nil {
goto bad
}
rela = 0
if rsect.type_ == ElfSectRela {
rela = 1
}
n = int(rsect.size / uint64(4+4*is64) / uint64(2+rela))
r = make([]Reloc, n)
p = rsect.base
for j = 0; j < n; j++ {
add = 0
rp = &r[j]
if is64 != 0 {
// 64-bit rel/rela
rp.Off = int32(e.Uint64(p))
p = p[8:]
info = e.Uint64(p)
p = p[8:]
if rela != 0 {
add = e.Uint64(p)
p = p[8:]
}
} else {
// 32-bit rel/rela
rp.Off = int32(e.Uint32(p))
p = p[4:]
info = uint64(e.Uint32(p))
info = info>>8<<32 | info&0xff // convert to 64-bit info
p = p[4:]
if rela != 0 {
add = uint64(e.Uint32(p))
p = p[4:]
}
}
if info&0xffffffff == 0 { // skip R_*_NONE relocation
j--
n--
continue
}
if info>>32 == 0 { // absolute relocation, don't bother reading the null symbol
rp.Sym = nil
} else {
if err = readelfsym(elfobj, int(info>>32), &sym, 0); err != nil {
goto bad
}
sym.sym = symbols[info>>32]
if sym.sym == nil {
err = fmt.Errorf("%s#%d: reloc of invalid sym #%d %s shndx=%d type=%d", sect.sym.Name, j, int(info>>32), sym.name, sym.shndx, sym.type_)
goto bad
}
rp.Sym = sym.sym
}
rp.Type = int32(reltype(pn, int(uint32(info)), &rp.Siz))
if rela != 0 {
rp.Add = int64(add)
} else {
// load addend from image
if rp.Siz == 4 {
rp.Add = int64(e.Uint32(sect.base[rp.Off:]))
} else if rp.Siz == 8 {
rp.Add = int64(e.Uint64(sect.base[rp.Off:]))
} else {
Diag("invalid rela size %d", rp.Siz)
}
}
if rp.Siz == 2 {
rp.Add = int64(int16(rp.Add))
}
if rp.Siz == 4 {
rp.Add = int64(int32(rp.Add))
}
}
//print("rel %s %d %d %s %#llx\n", sect->sym->name, rp->type, rp->siz, rp->sym->name, rp->add);
sort.Sort(rbyoff(r[:n]))
// just in case
s = sect.sym
s.R = r
s.R = s.R[:n]
}
return
bad:
Diag("%s: malformed elf file: %v", pn, err)
}
func section(elfobj *ElfObj, name string) *ElfSect {
for i := 0; uint(i) < elfobj.nsect; i++ {
if elfobj.sect[i].name != "" && name != "" && elfobj.sect[i].name == name {
return &elfobj.sect[i]
}
}
return nil
}
func elfmap(elfobj *ElfObj, sect *ElfSect) (err error) {
if sect.base != nil {
return nil
}
if sect.off+sect.size > uint64(elfobj.length) {
err = fmt.Errorf("elf section past end of file")
return err
}
sect.base = make([]byte, sect.size)
err = fmt.Errorf("short read")
if obj.Bseek(elfobj.f, int64(uint64(elfobj.base)+sect.off), 0) < 0 || obj.Bread(elfobj.f, sect.base) != len(sect.base) {
return err
}
return nil
}
func readelfsym(elfobj *ElfObj, i int, sym *ElfSym, needSym int) (err error) {
if i >= elfobj.nsymtab || i < 0 {
err = fmt.Errorf("invalid elf symbol index")
return err
}
if i == 0 {
Diag("readym: read null symbol!")
}
if elfobj.is64 != 0 {
b := new(ElfSymBytes64)
binary.Read(bytes.NewReader(elfobj.symtab.base[i*ELF64SYMSIZE:(i+1)*ELF64SYMSIZE]), elfobj.e, b)
sym.name = cstring(elfobj.symstr.base[elfobj.e.Uint32(b.Name[:]):])
sym.value = elfobj.e.Uint64(b.Value[:])
sym.size = elfobj.e.Uint64(b.Size[:])