// 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 loadelf implements an ELF file reader.
package loadelf
import (
"bytes"
"cmd/internal/bio"
"cmd/internal/objabi"
"cmd/internal/sys"
"cmd/link/internal/sym"
"debug/elf"
"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
ElfSymTypeCommon = 5
ElfSymTypeTLS = 6
)
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
)
// TODO(crawshaw): de-duplicate with cmd/link/internal/ld/elf.go.
const (
ELF64SYMSIZE = 24
ELF32SYMSIZE = 16
SHT_ARM_ATTRIBUTES = 0x70000003
)
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 *sym.Symbol
}
type ElfObj struct {
f *bio.Reader
base int64 // offset in f where ELF begins
length int64 // length of ELF
is64 int
name string
e binary.ByteOrder
sect []ElfSect
nsect uint
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 *sym.Symbol
}
var ElfMagic = [4]uint8{0x7F, 'E', 'L', 'F'}
const (
TagFile = 1
TagCPUName = 4
TagCPURawName = 5
TagCompatibility = 32
TagNoDefaults = 64
TagAlsoCompatibleWith = 65
TagABIVFPArgs = 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 == TagCompatibility:
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 == TagCPUName || attr.tag == TagCPURawName || (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) (found bool, ehdrFlags uint32, err error) {
found = false
if data[0] != 'A' {
return false, 0, fmt.Errorf(".ARM.attributes has unexpected format %c\n", data[0])
}
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 {
return false, 0, fmt.Errorf("corrupt .ARM.attributes (section name not NUL-terminated)\n")
}
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 != TagFile {
continue
}
attrList := elfAttributeList{data: subsectiondata}
for !attrList.done() {
attr := attrList.armAttr()
if attr.tag == TagABIVFPArgs && attr.ival == 1 {
found = true
ehdrFlags = 0x5000402 // has entry point, Version5 EABI, hard-float ABI
}
}
if attrList.err != nil {
return false, 0, fmt.Errorf("could not parse .ARM.attributes\n")
}
}
}
return found, ehdrFlags, nil
}
// Load loads the ELF file pn from f.
// Symbols are written into syms, and a slice of the text symbols is returned.
//
// On ARM systems, Load will attempt to determine what ELF header flags to
// emit by scanning the attributes in the ELF file being loaded. The
// parameter initEhdrFlags contains the current header flags for the output
// object, and the returnd ehdrFlags contains what this Load function computes.
// TODO: find a better place for this logic.
func Load(arch *sys.Arch, syms *sym.Symbols, f *bio.Reader, pkg string, length int64, pn string, initEhdrFlags uint32) (textp []*sym.Symbol, ehdrFlags uint32, err error) {
errorf := func(str string, args ...interface{}) ([]*sym.Symbol, uint32, error) {
return nil, 0, fmt.Errorf("loadelf: %s: %v", pn, fmt.Sprintf(str, args...))
}
localSymVersion := syms.IncVersion()
base := f.Offset()
var hdrbuf [64]uint8
if _, err := io.ReadFull(f, hdrbuf[:]); err != nil {
return errorf("malformed elf file: %v", err)
}
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" {
return errorf("malformed elf file, bad header")
}
var e binary.ByteOrder
switch hdr.Ident[5] {
case ElfDataLsb:
e = binary.LittleEndian
case ElfDataMsb:
e = binary.BigEndian
default:
return errorf("malformed elf file, unknown header")
}
// read header
elfobj := new(ElfObj)
elfobj.e = e
elfobj.f = f
elfobj.base = 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 v := uint32(hdr.Ident[6]); v != elfobj.version {
return errorf("malformed elf version: got %d, want %d", v, elfobj.version)
}
if e.Uint16(hdr.Type[:]) != ElfTypeRelocatable {
return errorf("elf but not elf relocatable object")
}
switch arch.Family {
default:
return errorf("elf %s unimplemented", arch.Name)
case sys.MIPS:
if elfobj.machine != ElfMachMips || hdr.Ident[4] != ElfClass32 {
return errorf("elf object but not mips")
}
case sys.MIPS64:
if elfobj.machine != ElfMachMips || hdr.Ident[4] != ElfClass64 {
return errorf("elf object but not mips64")
}
case sys.ARM:
if e != binary.LittleEndian || elfobj.machine != ElfMachArm || hdr.Ident[4] != ElfClass32 {
return errorf("elf object but not arm")
}
case sys.AMD64:
if e != binary.LittleEndian || elfobj.machine != ElfMachAmd64 || hdr.Ident[4] != ElfClass64 {
return errorf("elf object but not amd64")
}
case sys.ARM64:
if e != binary.LittleEndian || elfobj.machine != ElfMachArm64 || hdr.Ident[4] != ElfClass64 {
return errorf("elf object but not arm64")
}
case sys.I386:
if e != binary.LittleEndian || elfobj.machine != ElfMach386 || hdr.Ident[4] != ElfClass32 {
return errorf("elf object but not 386")
}
case sys.PPC64:
if elfobj.machine != ElfMachPower64 || hdr.Ident[4] != ElfClass64 {
return errorf("elf object but not ppc64")
}
case sys.S390X:
if elfobj.machine != ElfMachS390 || hdr.Ident[4] != ElfClass64 {
return errorf("elf object but not s390x")
}
}
// 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 f.Seek(int64(uint64(base)+elfobj.shoff+uint64(int64(i)*int64(elfobj.shentsize))), 0) < 0 {
return errorf("malformed elf file: negative seek")
}
sect := &elfobj.sect[i]
if is64 != 0 {
var b ElfSectBytes64
if err := binary.Read(f, e, &b); err != nil {
return errorf("malformed elf file: %v", err)
}
sect.nameoff = 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 {
return errorf("malformed elf file: %v", err)
}
sect.nameoff = 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) {
return errorf("malformed elf file: shstrndx out of range %d >= %d", elfobj.shstrndx, elfobj.nsect)
}
sect := &elfobj.sect[elfobj.shstrndx]
if err := elfmap(elfobj, sect); err != nil {
return errorf("malformed elf file: %v", err)
}
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) {
return errorf("elf object has symbol table with invalid string table link")
}
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 {
return errorf("malformed elf file: %v", err)
}
if err := elfmap(elfobj, elfobj.symstr); err != nil {
return errorf("malformed elf file: %v", err)
}
// 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 {
return errorf("%s: malformed elf file: %v", pn, err)
}
// We assume the soft-float ABI unless we see a tag indicating otherwise.
if initEhdrFlags == 0x5000002 {
ehdrFlags = 0x5000202
} else {
ehdrFlags = initEhdrFlags
}
found, newEhdrFlags, err := parseArmAttributes(e, sect.base[:sect.size])
if err != nil {
// TODO(dfc) should this return an error?
log.Printf("%s: %v", pn, err)
}
if found {
ehdrFlags = newEhdrFlags
}
}
if (sect.type_ != ElfSectProgbits && sect.type_ != ElfSectNobits) || sect.flags&ElfSectFlagAlloc == 0 {
continue
}
if sect.type_ != ElfSectNobits {
if err := elfmap(elfobj, sect); err != nil {
return errorf("%s: malformed elf file: %v", pn, err)
}
}
name := fmt.Sprintf("%s(%s)", pkg, sect.name)
s := syms.Lookup(name, localSymVersion)
switch int(sect.flags) & (ElfSectFlagAlloc | ElfSectFlagWrite | ElfSectFlagExec) {
default:
return errorf("%s: unexpected flags for ELF section %s", pn, sect.name)
case ElfSectFlagAlloc:
s.Type = sym.SRODATA
case ElfSectFlagAlloc + ElfSectFlagWrite:
if sect.type_ == ElfSectNobits {
s.Type = sym.SNOPTRBSS
} else {
s.Type = sym.SNOPTRDATA
}
case ElfSectFlagAlloc + ElfSectFlagExec:
s.Type = sym.STEXT
}
if sect.name == ".got" || sect.name == ".toc" {
s.Type = sym.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([]*sym.Symbol, elfobj.nsymtab)
for i := 1; i < elfobj.nsymtab; i++ {
var elfsym ElfSym
if err := readelfsym(arch, syms, elfobj, i, &elfsym, 1, localSymVersion); err != nil {
return errorf("%s: malformed elf file: %v", pn, err)
}
symbols[i] = elfsym.sym
if elfsym.type_ != ElfSymTypeFunc && elfsym.type_ != ElfSymTypeObject && elfsym.type_ != ElfSymTypeNone && elfsym.type_ != ElfSymTypeCommon {
continue
}
if elfsym.shndx == ElfSymShnCommon || elfsym.type_ == ElfSymTypeCommon {
s := elfsym.sym
if uint64(s.Size) < elfsym.size {
s.Size = int64(elfsym.size)
}
if s.Type == 0 || s.Type == sym.SXREF {
s.Type = sym.SNOPTRBSS
}
continue
}
if uint(elfsym.shndx) >= elfobj.nsect || elfsym.shndx == 0 {
continue
}
// even when we pass needSym == 1 to readelfsym, it might still return nil to skip some unwanted symbols
if elfsym.sym == nil {
continue
}
sect = &elfobj.sect[elfsym.shndx]
if sect.sym == nil {
if strings.HasPrefix(elfsym.name, ".Linfo_string") { // clang does this
continue
}
if elfsym.name == "" && elfsym.type_ == 0 && sect.name == ".debug_str" {
// This reportedly happens with clang 3.7 on ARM.
// See issue 13139.
continue
}
if strings.HasPrefix(elfsym.name, ".LASF") { // gcc on s390x does this
continue
}
return errorf("%v: sym#%d: ignoring symbol in section %d (type %d)", elfsym.sym, i, elfsym.shndx, elfsym.type_)
}
s := elfsym.sym
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.Sub = sect.sym.Sub
sect.sym.Sub = s
s.Type = sect.sym.Type
s.Attr |= sym.AttrSubSymbol
if !s.Attr.CgoExportDynamic() {
s.Dynimplib = "" // satisfy dynimport
}
s.Value = int64(elfsym.value)
s.Size = int64(elfsym.size)
s.Outer = sect.sym
if sect.sym.Type == sym.STEXT {
if s.Attr.External() && !s.Attr.DuplicateOK() {
return errorf("%v: duplicate symbol definition", s)
}
s.Attr |= sym.AttrExternal
}
if elfobj.machine == ElfMachPower64 {
flag := int(elfsym.other) >> 5
if 2 <= flag && flag <= 6 {
s.Localentry = 1 << uint(flag-2)
} else if flag == 7 {
return errorf("%v: invalid sym.other 0x%x", s, elfsym.other)
}
}
}
// Sort outer lists by address, adding to textp.
// This keeps textp in increasing address order.
for i := uint(0); i < elfobj.nsect; i++ {
s := elfobj.sect[i].sym
if s == nil {
continue
}
if s.Sub != nil {
s.Sub = sym.SortSub(s.Sub)
}
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 s = s.Sub; s != nil; s = s.Sub {
if s.Attr.OnList() {
return errorf("symbol %s listed multiple times", s.Name)
}
s.Attr |= sym.AttrOnList
textp = append(textp, s)
}
}
}
// load relocations
for i := uint(0); 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 {
return errorf("malformed elf file: %v", err)
}
rela := 0
if rsect.type_ == ElfSectRela {
rela = 1
}
n := int(rsect.size / uint64(4+4*is64) / uint64(2+rela))
r := make([]sym.Reloc, n)
p := rsect.base
for j := 0; j < n; j++ {
var add uint64
rp := &r[j]
var info uint64
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 {
var elfsym ElfSym
if err := readelfsym(arch, syms, elfobj, int(info>>32), &elfsym, 0, 0); err != nil {
return errorf("malformed elf file: %v", err)
}
elfsym.sym = symbols[info>>32]
if elfsym.sym == nil {
return errorf("malformed elf file: %s#%d: reloc of invalid sym #%d %s shndx=%d type=%d", sect.sym.Name, j, int(info>>32), elfsym.name, elfsym.shndx, elfsym.type_)
}
rp.Sym = elfsym.sym
}
rp.Type = 256 + objabi.RelocType(info)
rp.Siz, err = relSize(arch, pn, uint32(info))
if err != nil {
return nil, 0, err
}
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 {
return errorf("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(sym.RelocByOff(r[:n]))
// just in case
s := sect.sym
s.R = r
s.R = s.R[:n]
}
return textp, ehdrFlags, nil
}
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)
if elfobj.f.Seek(int64(uint64(elfobj.base)+sect.off), 0) < 0 {
return fmt.Errorf("short read: seek not successful")
}
if _, err := io.ReadFull(elfobj.f, sect.base); err != nil {
return fmt.Errorf("short read: %v", err)
}
return nil
}
func readelfsym(arch *sys.Arch, syms *sym.Symbols, elfobj *ElfObj, i int, elfsym *ElfSym, needSym int, localSymVersion int) (err error) {
if i >= elfobj.nsymtab || i < 0 {
err = fmt.Errorf("invalid elf symbol index")
return err
}
if i == 0 {
return fmt.Errorf("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)
elfsym.name = cstring(elfobj.symstr.base[elfobj.e.Uint32(b.Name[:]):])
elfsym.value = elfobj.e.Uint64(b.Value[:])
elfsym.size = elfobj.e.Uint64(b.Size[:])
elfsym.shndx = elfobj.e.Uint16(b.Shndx[:])
elfsym.bind = b.Info >> 4
elfsym.type_ = b.Info & 0xf
elfsym.other = b.Other
} else {
b := new(ElfSymBytes)
binary.Read(bytes.NewReader(elfobj.symtab.base[i*ELF32SYMSIZE:(i+1)*ELF32SYMSIZE]), elfobj.e, b)
elfsym.name = cstring(elfobj.symstr.base[elfobj.e.Uint32(b.Name[:]):])
elfsym.value = uint64(elfobj.e.Uint32(b.Value[:]))
elfsym.size = uint64(elfobj.e.Uint32(b.Size[:]))
elfsym.shndx = elfobj.e.Uint16(b.Shndx[:])
elfsym.bind = b.Info >> 4
elfsym.type_ = b.Info & 0xf
elfsym.other = b.Other
}
var s *sym.Symbol
if elfsym.name == "_GLOBAL_OFFSET_TABLE_" {
elfsym.name = ".got"
}
if elfsym.name == ".TOC." {
// Magic symbol on ppc64. Will be set to this object
// file's .got+0x8000.
elfsym.bind = ElfSymBindLocal
}
switch elfsym.type_ {
case ElfSymTypeSection:
s = elfobj.sect[elfsym.shndx].sym
case ElfSymTypeObject, ElfSymTypeFunc, ElfSymTypeNone, ElfSymTypeCommon:
switch elfsym.bind {
case ElfSymBindGlobal:
if needSym != 0 {
s = syms.Lookup(elfsym.name, 0)
// for global scoped hidden symbols we should insert it into
// symbol hash table, but mark them as hidden.
// __i686.get_pc_thunk.bx is allowed to be duplicated, to
// workaround that we set dupok.
// TODO(minux): correctly handle __i686.get_pc_thunk.bx without
// set dupok generally. See http://codereview.appspot.com/5823055/
// comment #5 for details.
if s != nil && elfsym.other == 2 {
s.Attr |= sym.AttrDuplicateOK | sym.AttrVisibilityHidden
}
}
case ElfSymBindLocal:
if arch.Family == sys.ARM && (strings.HasPrefix(elfsym.name, "$a") || strings.HasPrefix(elfsym.name, "$d")) {
// binutils for arm generate these mapping
// symbols, ignore these
break
}
if elfsym.name == ".TOC." {
// We need to be able to look this up,
// so put it in the hash table.
if needSym != 0 {
s = syms.Lookup(elfsym.name, localSymVersion)
s.Attr |= sym.AttrVisibilityHidden
}
break
}
if needSym != 0 {
// local names and hidden global names are unique
// and should only be referenced by their index, not name, so we
// don't bother to add them into the hash table
s = syms.Newsym(elfsym.name, localSymVersion)
s.Attr |= sym.AttrVisibilityHidden
}
case ElfSymBindWeak:
if needSym != 0 {
s = syms.Lookup(elfsym.name, 0)
if elfsym.other == 2 {
s.Attr |= sym.AttrVisibilityHidden
}
}
default:
err = fmt.Errorf("%s: invalid symbol binding %d", elfsym.name, elfsym.bind)
return err
}
}
// TODO(mwhudson): the test of VisibilityHidden here probably doesn't make
// sense and should be removed when someone has thought about it properly.
if s != nil && s.Type == 0 && !s.Attr.VisibilityHidden() && elfsym.type_ != ElfSymTypeSection {
s.Type = sym.SXREF
}
elfsym.sym = s
return nil
}
func relSize(arch *sys.Arch, pn string, elftype uint32) (uint8, error) {
// TODO(mdempsky): Replace this with a struct-valued switch statement
// once golang.org/issue/15164 is fixed or found to not impair cmd/link
// performance.
const (
AMD64 = uint32(sys.AMD64)
ARM = uint32(sys.ARM)
I386 = uint32(sys.I386)
PPC64 = uint32(sys.PPC64)
S390X = uint32(sys.S390X)
)
switch uint32(arch.Family) | elftype<<24 {
default:
return 0, fmt.Errorf("%s: unknown relocation type %d; compiled without -fpic?", pn, elftype)
case S390X | uint32(elf.R_390_8)<<24:
return 1, nil
case PPC64 | uint32(elf.R_PPC64_TOC16)<<24,
PPC64 | uint32(elf.R_PPC64_TOC16_LO)<<24,
PPC64 | uint32(elf.R_PPC64_TOC16_HI)<<24,
PPC64 | uint32(elf.R_PPC64_TOC16_HA)<<24,
PPC64 | uint32(elf.R_PPC64_TOC16_DS)<<24,
PPC64 | uint32(elf.R_PPC64_TOC16_LO_DS)<<24,
PPC64 | uint32(elf.R_PPC64_REL16_LO)<<24,
PPC64 | uint32(elf.R_PPC64_REL16_HI)<<24,
PPC64 | uint32(elf.R_PPC64_REL16_HA)<<24,
S390X | uint32(elf.R_390_16)<<24,
S390X | uint32(elf.R_390_GOT16)<<24,
S390X | uint32(elf.R_390_PC16)<<24,
S390X | uint32(elf.R_390_PC16DBL)<<24,
S390X | uint32(elf.R_390_PLT16DBL)<<24:
return 2, nil
case ARM | uint32(elf.R_ARM_ABS32)<<24,
ARM | uint32(elf.R_ARM_GOT32)<<24,
ARM | uint32(elf.R_ARM_PLT32)<<24,
ARM | uint32(elf.R_ARM_GOTOFF)<<24,
ARM | uint32(elf.R_ARM_GOTPC)<<24,
ARM | uint32(elf.R_ARM_THM_PC22)<<24,
ARM | uint32(elf.R_ARM_REL32)<<24,
ARM | uint32(elf.R_ARM_CALL)<<24,
ARM | uint32(elf.R_ARM_V4BX)<<24,
ARM | uint32(elf.R_ARM_GOT_PREL)<<24,
ARM | uint32(elf.R_ARM_PC24)<<24,
ARM | uint32(elf.R_ARM_JUMP24)<<24,
AMD64 | uint32(elf.R_X86_64_PC32)<<24,
AMD64 | uint32(elf.R_X86_64_PLT32)<<24,
AMD64 | uint32(elf.R_X86_64_GOTPCREL)<<24,
AMD64 | uint32(elf.R_X86_64_GOTPCRELX)<<24,
AMD64 | uint32(elf.R_X86_64_REX_GOTPCRELX)<<24,
I386 | uint32(elf.R_386_32)<<24,
I386 | uint32(elf.R_386_PC32)<<24,
I386 | uint32(elf.R_386_GOT32)<<24,
I386 | uint32(elf.R_386_PLT32)<<24,
I386 | uint32(elf.R_386_GOTOFF)<<24,
I386 | uint32(elf.R_386_GOTPC)<<24,
I386 | uint32(elf.R_386_GOT32X)<<24,
PPC64 | uint32(elf.R_PPC64_REL24)<<24,
PPC64 | uint32(elf.R_PPC_REL32)<<24,
S390X | uint32(elf.R_390_32)<<24,
S390X | uint32(elf.R_390_PC32)<<24,
S390X | uint32(elf.R_390_GOT32)<<24,
S390X | uint32(elf.R_390_PLT32)<<24,
S390X | uint32(elf.R_390_PC32DBL)<<24,
S390X | uint32(elf.R_390_PLT32DBL)<<24,
S390X | uint32(elf.R_390_GOTPCDBL)<<24,
S390X | uint32(elf.R_390_GOTENT)<<24:
return 4, nil
case AMD64 | uint32(elf.R_X86_64_64)<<24,
AMD64 | uint32(elf.R_X86_64_PC64)<<24,
PPC64 | uint32(elf.R_PPC64_ADDR64)<<24,
S390X | uint32(elf.R_390_GLOB_DAT)<<24,
S390X | uint32(elf.R_390_RELATIVE)<<24,
S390X | uint32(elf.R_390_GOTOFF)<<24,
S390X | uint32(elf.R_390_GOTPC)<<24,
S390X | uint32(elf.R_390_64)<<24,
S390X | uint32(elf.R_390_PC64)<<24,
S390X | uint32(elf.R_390_GOT64)<<24,
S390X | uint32(elf.R_390_PLT64)<<24:
return 8, nil
}
}
func cstring(x []byte) string {
i := bytes.IndexByte(x, '\x00')
if i >= 0 {
x = x[:i]
}
return string(x)
}