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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 elf implements access to ELF object files.
package elf
import (
"bytes"
"debug/dwarf"
"encoding/binary"
"errors"
"fmt"
"io"
"os"
"strings"
)
// TODO: error reporting detail
/*
* Internal ELF representation
*/
// A FileHeader represents an ELF file header.
type FileHeader struct {
Class Class
Data Data
Version Version
OSABI OSABI
ABIVersion uint8
ByteOrder binary.ByteOrder
Type Type
Machine Machine
Entry uint64
}
// A File represents an open ELF file.
type File struct {
FileHeader
Sections []*Section
Progs []*Prog
closer io.Closer
gnuNeed []verneed
gnuVersym []byte
}
// A SectionHeader represents a single ELF section header.
type SectionHeader struct {
Name string
Type SectionType
Flags SectionFlag
Addr uint64
Offset uint64
Size uint64
Link uint32
Info uint32
Addralign uint64
Entsize uint64
}
// A Section represents a single section in an ELF file.
type Section struct {
SectionHeader
// Embed ReaderAt for ReadAt method.
// Do not embed SectionReader directly
// to avoid having Read and Seek.
// If a client wants Read and Seek it must use
// Open() to avoid fighting over the seek offset
// with other clients.
io.ReaderAt
sr *io.SectionReader
}
// Data reads and returns the contents of the ELF section.
func (s *Section) Data() ([]byte, error) {
dat := make([]byte, s.sr.Size())
n, err := s.sr.ReadAt(dat, 0)
if n == len(dat) {
err = nil
}
return dat[0:n], err
}
// stringTable reads and returns the string table given by the
// specified link value.
func (f *File) stringTable(link uint32) ([]byte, error) {
if link <= 0 || link >= uint32(len(f.Sections)) {
return nil, errors.New("section has invalid string table link")
}
return f.Sections[link].Data()
}
// Open returns a new ReadSeeker reading the ELF section.
func (s *Section) Open() io.ReadSeeker { return io.NewSectionReader(s.sr, 0, 1<<63-1) }
// A ProgHeader represents a single ELF program header.
type ProgHeader struct {
Type ProgType
Flags ProgFlag
Off uint64
Vaddr uint64
Paddr uint64
Filesz uint64
Memsz uint64
Align uint64
}
// A Prog represents a single ELF program header in an ELF binary.
type Prog struct {
ProgHeader
// Embed ReaderAt for ReadAt method.
// Do not embed SectionReader directly
// to avoid having Read and Seek.
// If a client wants Read and Seek it must use
// Open() to avoid fighting over the seek offset
// with other clients.
io.ReaderAt
sr *io.SectionReader
}
// Open returns a new ReadSeeker reading the ELF program body.
func (p *Prog) Open() io.ReadSeeker { return io.NewSectionReader(p.sr, 0, 1<<63-1) }
// A Symbol represents an entry in an ELF symbol table section.
type Symbol struct {
Name string
Info, Other byte
Section SectionIndex
Value, Size uint64
}
/*
* ELF reader
*/
type FormatError struct {
off int64
msg string
val interface{}
}
func (e *FormatError) Error() string {
msg := e.msg
if e.val != nil {
msg += fmt.Sprintf(" '%v' ", e.val)
}
msg += fmt.Sprintf("in record at byte %#x", e.off)
return msg
}
// Open opens the named file using os.Open and prepares it for use as an ELF binary.
func Open(name string) (*File, error) {
f, err := os.Open(name)
if err != nil {
return nil, err
}
ff, err := NewFile(f)
if err != nil {
f.Close()
return nil, err
}
ff.closer = f
return ff, nil
}
// Close closes the File.
// If the File was created using NewFile directly instead of Open,
// Close has no effect.
func (f *File) Close() error {
var err error
if f.closer != nil {
err = f.closer.Close()
f.closer = nil
}
return err
}
// SectionByType returns the first section in f with the
// given type, or nil if there is no such section.
func (f *File) SectionByType(typ SectionType) *Section {
for _, s := range f.Sections {
if s.Type == typ {
return s
}
}
return nil
}
// NewFile creates a new File for accessing an ELF binary in an underlying reader.
// The ELF binary is expected to start at position 0 in the ReaderAt.
func NewFile(r io.ReaderAt) (*File, error) {
sr := io.NewSectionReader(r, 0, 1<<63-1)
// Read and decode ELF identifier
var ident [16]uint8
if _, err := r.ReadAt(ident[0:], 0); err != nil {
return nil, err
}
if ident[0] != '\x7f' || ident[1] != 'E' || ident[2] != 'L' || ident[3] != 'F' {
return nil, &FormatError{0, "bad magic number", ident[0:4]}
}
f := new(File)
f.Class = Class(ident[EI_CLASS])
switch f.Class {
case ELFCLASS32:
case ELFCLASS64:
// ok
default:
return nil, &FormatError{0, "unknown ELF class", f.Class}
}
f.Data = Data(ident[EI_DATA])
switch f.Data {
case ELFDATA2LSB:
f.ByteOrder = binary.LittleEndian
case ELFDATA2MSB:
f.ByteOrder = binary.BigEndian
default:
return nil, &FormatError{0, "unknown ELF data encoding", f.Data}
}
f.Version = Version(ident[EI_VERSION])
if f.Version != EV_CURRENT {
return nil, &FormatError{0, "unknown ELF version", f.Version}
}
f.OSABI = OSABI(ident[EI_OSABI])
f.ABIVersion = ident[EI_ABIVERSION]
// Read ELF file header
var phoff int64
var phentsize, phnum int
var shoff int64
var shentsize, shnum, shstrndx int
shstrndx = -1
switch f.Class {
case ELFCLASS32:
hdr := new(Header32)
sr.Seek(0, os.SEEK_SET)
if err := binary.Read(sr, f.ByteOrder, hdr); err != nil {
return nil, err
}
f.Type = Type(hdr.Type)
f.Machine = Machine(hdr.Machine)
f.Entry = uint64(hdr.Entry)
if v := Version(hdr.Version); v != f.Version {
return nil, &FormatError{0, "mismatched ELF version", v}
}
phoff = int64(hdr.Phoff)
phentsize = int(hdr.Phentsize)
phnum = int(hdr.Phnum)
shoff = int64(hdr.Shoff)
shentsize = int(hdr.Shentsize)
shnum = int(hdr.Shnum)
shstrndx = int(hdr.Shstrndx)
case ELFCLASS64:
hdr := new(Header64)
sr.Seek(0, os.SEEK_SET)
if err := binary.Read(sr, f.ByteOrder, hdr); err != nil {
return nil, err
}
f.Type = Type(hdr.Type)
f.Machine = Machine(hdr.Machine)
f.Entry = uint64(hdr.Entry)
if v := Version(hdr.Version); v != f.Version {
return nil, &FormatError{0, "mismatched ELF version", v}
}
phoff = int64(hdr.Phoff)
phentsize = int(hdr.Phentsize)
phnum = int(hdr.Phnum)
shoff = int64(hdr.Shoff)
shentsize = int(hdr.Shentsize)
shnum = int(hdr.Shnum)
shstrndx = int(hdr.Shstrndx)
}
if shnum > 0 && shoff > 0 && (shstrndx < 0 || shstrndx >= shnum) {
return nil, &FormatError{0, "invalid ELF shstrndx", shstrndx}
}
// Read program headers
f.Progs = make([]*Prog, phnum)
for i := 0; i < phnum; i++ {
off := phoff + int64(i)*int64(phentsize)
sr.Seek(off, os.SEEK_SET)
p := new(Prog)
switch f.Class {
case ELFCLASS32:
ph := new(Prog32)
if err := binary.Read(sr, f.ByteOrder, ph); err != nil {
return nil, err
}
p.ProgHeader = ProgHeader{
Type: ProgType(ph.Type),
Flags: ProgFlag(ph.Flags),
Off: uint64(ph.Off),
Vaddr: uint64(ph.Vaddr),
Paddr: uint64(ph.Paddr),
Filesz: uint64(ph.Filesz),
Memsz: uint64(ph.Memsz),
Align: uint64(ph.Align),
}
case ELFCLASS64:
ph := new(Prog64)
if err := binary.Read(sr, f.ByteOrder, ph); err != nil {
return nil, err
}
p.ProgHeader = ProgHeader{
Type: ProgType(ph.Type),
Flags: ProgFlag(ph.Flags),
Off: uint64(ph.Off),
Vaddr: uint64(ph.Vaddr),
Paddr: uint64(ph.Paddr),
Filesz: uint64(ph.Filesz),
Memsz: uint64(ph.Memsz),
Align: uint64(ph.Align),
}
}
p.sr = io.NewSectionReader(r, int64(p.Off), int64(p.Filesz))
p.ReaderAt = p.sr
f.Progs[i] = p
}
// Read section headers
f.Sections = make([]*Section, shnum)
names := make([]uint32, shnum)
for i := 0; i < shnum; i++ {
off := shoff + int64(i)*int64(shentsize)
sr.Seek(off, os.SEEK_SET)
s := new(Section)
switch f.Class {
case ELFCLASS32:
sh := new(Section32)
if err := binary.Read(sr, f.ByteOrder, sh); err != nil {
return nil, err
}
names[i] = sh.Name
s.SectionHeader = SectionHeader{
Type: SectionType(sh.Type),
Flags: SectionFlag(sh.Flags),
Addr: uint64(sh.Addr),
Offset: uint64(sh.Off),
Size: uint64(sh.Size),
Link: uint32(sh.Link),
Info: uint32(sh.Info),
Addralign: uint64(sh.Addralign),
Entsize: uint64(sh.Entsize),
}
case ELFCLASS64:
sh := new(Section64)
if err := binary.Read(sr, f.ByteOrder, sh); err != nil {
return nil, err
}
names[i] = sh.Name
s.SectionHeader = SectionHeader{
Type: SectionType(sh.Type),
Flags: SectionFlag(sh.Flags),
Offset: uint64(sh.Off),
Size: uint64(sh.Size),
Addr: uint64(sh.Addr),
Link: uint32(sh.Link),
Info: uint32(sh.Info),
Addralign: uint64(sh.Addralign),
Entsize: uint64(sh.Entsize),
}
}
s.sr = io.NewSectionReader(r, int64(s.Offset), int64(s.Size))
s.ReaderAt = s.sr
f.Sections[i] = s
}
if len(f.Sections) == 0 {
return f, nil
}
// Load section header string table.
shstrtab, err := f.Sections[shstrndx].Data()
if err != nil {
return nil, err
}
for i, s := range f.Sections {
var ok bool
s.Name, ok = getString(shstrtab, int(names[i]))
if !ok {
return nil, &FormatError{shoff + int64(i*shentsize), "bad section name index", names[i]}
}
}
return f, nil
}
// getSymbols returns a slice of Symbols from parsing the symbol table
// with the given type, along with the associated string table.
func (f *File) getSymbols(typ SectionType) ([]Symbol, []byte, error) {
switch f.Class {
case ELFCLASS64:
return f.getSymbols64(typ)
case ELFCLASS32:
return f.getSymbols32(typ)
}
return nil, nil, errors.New("not implemented")
}
// ErrNoSymbols is returned by File.Symbols and File.DynamicSymbols
// if there is no such section in the File.
var ErrNoSymbols = errors.New("no symbol section")
func (f *File) getSymbols32(typ SectionType) ([]Symbol, []byte, error) {
symtabSection := f.SectionByType(typ)
if symtabSection == nil {
return nil, nil, ErrNoSymbols
}
data, err := symtabSection.Data()
if err != nil {
return nil, nil, errors.New("cannot load symbol section")
}
symtab := bytes.NewReader(data)
if symtab.Len()%Sym32Size != 0 {
return nil, nil, errors.New("length of symbol section is not a multiple of SymSize")
}
strdata, err := f.stringTable(symtabSection.Link)
if err != nil {
return nil, nil, errors.New("cannot load string table section")
}
// The first entry is all zeros.
var skip [Sym32Size]byte
symtab.Read(skip[:])
symbols := make([]Symbol, symtab.Len()/Sym32Size)
i := 0
var sym Sym32
for symtab.Len() > 0 {
binary.Read(symtab, f.ByteOrder, &sym)
str, _ := getString(strdata, int(sym.Name))
symbols[i].Name = str
symbols[i].Info = sym.Info
symbols[i].Other = sym.Other
symbols[i].Section = SectionIndex(sym.Shndx)
symbols[i].Value = uint64(sym.Value)
symbols[i].Size = uint64(sym.Size)
i++
}
return symbols, strdata, nil
}
func (f *File) getSymbols64(typ SectionType) ([]Symbol, []byte, error) {
symtabSection := f.SectionByType(typ)
if symtabSection == nil {
return nil, nil, ErrNoSymbols
}
data, err := symtabSection.Data()
if err != nil {
return nil, nil, errors.New("cannot load symbol section")
}
symtab := bytes.NewReader(data)
if symtab.Len()%Sym64Size != 0 {
return nil, nil, errors.New("length of symbol section is not a multiple of Sym64Size")
}
strdata, err := f.stringTable(symtabSection.Link)
if err != nil {
return nil, nil, errors.New("cannot load string table section")
}
// The first entry is all zeros.
var skip [Sym64Size]byte
symtab.Read(skip[:])
symbols := make([]Symbol, symtab.Len()/Sym64Size)
i := 0
var sym Sym64
for symtab.Len() > 0 {
binary.Read(symtab, f.ByteOrder, &sym)
str, _ := getString(strdata, int(sym.Name))
symbols[i].Name = str
symbols[i].Info = sym.Info
symbols[i].Other = sym.Other
symbols[i].Section = SectionIndex(sym.Shndx)
symbols[i].Value = sym.Value
symbols[i].Size = sym.Size
i++
}
return symbols, strdata, nil
}
// getString extracts a string from an ELF string table.
func getString(section []byte, start int) (string, bool) {
if start < 0 || start >= len(section) {
return "", false
}
for end := start; end < len(section); end++ {
if section[end] == 0 {
return string(section[start:end]), true
}
}
return "", false
}
// Section returns a section with the given name, or nil if no such
// section exists.
func (f *File) Section(name string) *Section {
for _, s := range f.Sections {
if s.Name == name {
return s
}
}
return nil
}
// applyRelocations applies relocations to dst. rels is a relocations section
// in RELA format.
func (f *File) applyRelocations(dst []byte, rels []byte) error {
switch {
case f.Class == ELFCLASS64 && f.Machine == EM_X86_64:
return f.applyRelocationsAMD64(dst, rels)
case f.Class == ELFCLASS32 && f.Machine == EM_386:
return f.applyRelocations386(dst, rels)
case f.Class == ELFCLASS32 && f.Machine == EM_ARM:
return f.applyRelocationsARM(dst, rels)
case f.Class == ELFCLASS64 && f.Machine == EM_AARCH64:
return f.applyRelocationsARM64(dst, rels)
case f.Class == ELFCLASS32 && f.Machine == EM_PPC:
return f.applyRelocationsPPC(dst, rels)
case f.Class == ELFCLASS64 && f.Machine == EM_PPC64:
return f.applyRelocationsPPC64(dst, rels)
default:
return errors.New("applyRelocations: not implemented")
}
}
func (f *File) applyRelocationsAMD64(dst []byte, rels []byte) error {
// 24 is the size of Rela64.
if len(rels)%24 != 0 {
return errors.New("length of relocation section is not a multiple of 24")
}
symbols, _, err := f.getSymbols(SHT_SYMTAB)
if err != nil {
return err
}
b := bytes.NewReader(rels)
var rela Rela64
for b.Len() > 0 {
binary.Read(b, f.ByteOrder, &rela)
symNo := rela.Info >> 32
t := R_X86_64(rela.Info & 0xffff)
if symNo == 0 || symNo > uint64(len(symbols)) {
continue
}
sym := &symbols[symNo-1]
if SymType(sym.Info&0xf) != STT_SECTION {
// We don't handle non-section relocations for now.
continue
}
// There are relocations, so this must be a normal
// object file, and we only look at section symbols,
// so we assume that the symbol value is 0.
switch t {
case R_X86_64_64:
if rela.Off+8 >= uint64(len(dst)) || rela.Addend < 0 {
continue
}
f.ByteOrder.PutUint64(dst[rela.Off:rela.Off+8], uint64(rela.Addend))
case R_X86_64_32:
if rela.Off+4 >= uint64(len(dst)) || rela.Addend < 0 {
continue
}
f.ByteOrder.PutUint32(dst[rela.Off:rela.Off+4], uint32(rela.Addend))
}
}
return nil
}
func (f *File) applyRelocations386(dst []byte, rels []byte) error {
// 8 is the size of Rel32.
if len(rels)%8 != 0 {
return errors.New("length of relocation section is not a multiple of 8")
}
symbols, _, err := f.getSymbols(SHT_SYMTAB)
if err != nil {
return err
}
b := bytes.NewReader(rels)
var rel Rel32
for b.Len() > 0 {
binary.Read(b, f.ByteOrder, &rel)
symNo := rel.Info >> 8
t := R_386(rel.Info & 0xff)
if symNo == 0 || symNo > uint32(len(symbols)) {
continue
}
sym := &symbols[symNo-1]
if t == R_386_32 {
if rel.Off+4 >= uint32(len(dst)) {
continue
}
val := f.ByteOrder.Uint32(dst[rel.Off : rel.Off+4])
val += uint32(sym.Value)
f.ByteOrder.PutUint32(dst[rel.Off:rel.Off+4], val)
}
}
return nil
}
func (f *File) applyRelocationsARM(dst []byte, rels []byte) error {
// 8 is the size of Rel32.
if len(rels)%8 != 0 {
return errors.New("length of relocation section is not a multiple of 8")
}
symbols, _, err := f.getSymbols(SHT_SYMTAB)
if err != nil {
return err
}
b := bytes.NewReader(rels)
var rel Rel32
for b.Len() > 0 {
binary.Read(b, f.ByteOrder, &rel)
symNo := rel.Info >> 8
t := R_ARM(rel.Info & 0xff)
if symNo == 0 || symNo > uint32(len(symbols)) {
continue
}
sym := &symbols[symNo-1]
switch t {
case R_ARM_ABS32:
if rel.Off+4 >= uint32(len(dst)) {
continue
}
val := f.ByteOrder.Uint32(dst[rel.Off : rel.Off+4])
val += uint32(sym.Value)
f.ByteOrder.PutUint32(dst[rel.Off:rel.Off+4], val)
}
}
return nil
}
func (f *File) applyRelocationsARM64(dst []byte, rels []byte) error {
// 24 is the size of Rela64.
if len(rels)%24 != 0 {
return errors.New("length of relocation section is not a multiple of 24")
}
symbols, _, err := f.getSymbols(SHT_SYMTAB)
if err != nil {
return err
}
b := bytes.NewReader(rels)
var rela Rela64
for b.Len() > 0 {
binary.Read(b, f.ByteOrder, &rela)
symNo := rela.Info >> 32
t := R_AARCH64(rela.Info & 0xffff)
if symNo == 0 || symNo > uint64(len(symbols)) {
continue
}
sym := &symbols[symNo-1]
if SymType(sym.Info&0xf) != STT_SECTION {
// We don't handle non-section relocations for now.
continue
}
// There are relocations, so this must be a normal
// object file, and we only look at section symbols,
// so we assume that the symbol value is 0.
switch t {
case R_AARCH64_ABS64:
if rela.Off+8 >= uint64(len(dst)) || rela.Addend < 0 {
continue
}
f.ByteOrder.PutUint64(dst[rela.Off:rela.Off+8], uint64(rela.Addend))
case R_AARCH64_ABS32:
if rela.Off+4 >= uint64(len(dst)) || rela.Addend < 0 {
continue
}
f.ByteOrder.PutUint32(dst[rela.Off:rela.Off+4], uint32(rela.Addend))
}
}
return nil
}
func (f *File) applyRelocationsPPC(dst []byte, rels []byte) error {
// 12 is the size of Rela32.
if len(rels)%12 != 0 {
return errors.New("length of relocation section is not a multiple of 12")
}
symbols, _, err := f.getSymbols(SHT_SYMTAB)
if err != nil {
return err
}
b := bytes.NewReader(rels)
var rela Rela32
for b.Len() > 0 {
binary.Read(b, f.ByteOrder, &rela)
symNo := rela.Info >> 8
t := R_PPC(rela.Info & 0xff)
if symNo == 0 || symNo > uint32(len(symbols)) {
continue
}
sym := &symbols[symNo-1]
if SymType(sym.Info&0xf) != STT_SECTION {
// We don't handle non-section relocations for now.
continue
}
switch t {
case R_PPC_ADDR32:
if rela.Off+4 >= uint32(len(dst)) || rela.Addend < 0 {
continue
}
f.ByteOrder.PutUint32(dst[rela.Off:rela.Off+4], uint32(rela.Addend))
}
}
return nil
}
func (f *File) applyRelocationsPPC64(dst []byte, rels []byte) error {
// 24 is the size of Rela64.
if len(rels)%24 != 0 {
return errors.New("length of relocation section is not a multiple of 24")
}
symbols, _, err := f.getSymbols(SHT_SYMTAB)
if err != nil {
return err
}
b := bytes.NewReader(rels)
var rela Rela64
for b.Len() > 0 {
binary.Read(b, f.ByteOrder, &rela)
symNo := rela.Info >> 32
t := R_PPC64(rela.Info & 0xffff)
if symNo == 0 || symNo > uint64(len(symbols)) {
continue
}
sym := &symbols[symNo-1]
if SymType(sym.Info&0xf) != STT_SECTION {
// We don't handle non-section relocations for now.
continue
}
switch t {
case R_PPC64_ADDR64:
if rela.Off+8 >= uint64(len(dst)) || rela.Addend < 0 {
continue
}
f.ByteOrder.PutUint64(dst[rela.Off:rela.Off+8], uint64(rela.Addend))
case R_PPC64_ADDR32:
if rela.Off+4 >= uint64(len(dst)) || rela.Addend < 0 {
continue
}
f.ByteOrder.PutUint32(dst[rela.Off:rela.Off+4], uint32(rela.Addend))
}
}
return nil
}
func (f *File) DWARF() (*dwarf.Data, error) {
// sectionData gets the data for s, checks its size, and
// applies any applicable relations.
sectionData := func(i int, s *Section) ([]byte, error) {
b, err := s.Data()
if err != nil && uint64(len(b)) < s.Size {
return nil, err
}
for _, r := range f.Sections {
if r.Type != SHT_RELA && r.Type != SHT_REL {
continue
}
if int(r.Info) != i {
continue
}
rd, err := r.Data()
if err != nil {
return nil, err
}
err = f.applyRelocations(b, rd)
if err != nil {
return nil, err
}
}
return b, nil
}
// There are many other DWARF sections, but these
// are the ones the debug/dwarf package uses.
// Don't bother loading others.
var dat = map[string][]byte{"abbrev": nil, "info": nil, "str": nil, "line": nil}
for i, s := range f.Sections {
if !strings.HasPrefix(s.Name, ".debug_") {
continue
}
if _, ok := dat[s.Name[7:]]; !ok {
continue
}
b, err := sectionData(i, s)
if err != nil {
return nil, err
}
dat[s.Name[7:]] = b
}
d, err := dwarf.New(dat["abbrev"], nil, nil, dat["info"], dat["line"], nil, nil, dat["str"])
if err != nil {
return nil, err
}
// Look for DWARF4 .debug_types sections.
for i, s := range f.Sections {
if s.Name == ".debug_types" {
b, err := sectionData(i, s)
if err != nil {
return nil, err
}
err = d.AddTypes(fmt.Sprintf("types-%d", i), b)
if err != nil {
return nil, err
}
}
}
return d, nil
}
// Symbols returns the symbol table for f. The symbols will be listed in the order
// they appear in f.
//
// For compatibility with Go 1.0, Symbols omits the null symbol at index 0.
// After retrieving the symbols as symtab, an externally supplied index x
// corresponds to symtab[x-1], not symtab[x].
func (f *File) Symbols() ([]Symbol, error) {
sym, _, err := f.getSymbols(SHT_SYMTAB)
return sym, err
}
// DynamicSymbols returns the dynamic symbol table for f. The symbols
// will be listed in the order they appear in f.
//
// For compatibility with Symbols, DynamicSymbols omits the null symbol at index 0.
// After retrieving the symbols as symtab, an externally supplied index x
// corresponds to symtab[x-1], not symtab[x].
func (f *File) DynamicSymbols() ([]Symbol, error) {
sym, _, err := f.getSymbols(SHT_DYNSYM)
return sym, err
}
type ImportedSymbol struct {
Name string
Version string
Library string
}
// ImportedSymbols returns the names of all symbols
// referred to by the binary f that are expected to be
// satisfied by other libraries at dynamic load time.
// It does not return weak symbols.
func (f *File) ImportedSymbols() ([]ImportedSymbol, error) {
sym, str, err := f.getSymbols(SHT_DYNSYM)
if err != nil {
return nil, err
}
f.gnuVersionInit(str)
var all []ImportedSymbol
for i, s := range sym {
if ST_BIND(s.Info) == STB_GLOBAL && s.Section == SHN_UNDEF {
all = append(all, ImportedSymbol{Name: s.Name})
f.gnuVersion(i, &all[len(all)-1])
}
}
return all, nil
}
type verneed struct {
File string
Name string
}
// gnuVersionInit parses the GNU version tables
// for use by calls to gnuVersion.
func (f *File) gnuVersionInit(str []byte) {
// Accumulate verneed information.
vn := f.SectionByType(SHT_GNU_VERNEED)
if vn == nil {
return
}
d, _ := vn.Data()
var need []verneed
i := 0
for {
if i+16 > len(d) {
break
}
vers := f.ByteOrder.Uint16(d[i : i+2])
if vers != 1 {
break
}
cnt := f.ByteOrder.Uint16(d[i+2 : i+4])
fileoff := f.ByteOrder.Uint32(d[i+4 : i+8])
aux := f.ByteOrder.Uint32(d[i+8 : i+12])
next := f.ByteOrder.Uint32(d[i+12 : i+16])
file, _ := getString(str, int(fileoff))
var name string
j := i + int(aux)
for c := 0; c < int(cnt); c++ {
if j+16 > len(d) {
break
}
// hash := f.ByteOrder.Uint32(d[j:j+4])
// flags := f.ByteOrder.Uint16(d[j+4:j+6])
other := f.ByteOrder.Uint16(d[j+6 : j+8])
nameoff := f.ByteOrder.Uint32(d[j+8 : j+12])
next := f.ByteOrder.Uint32(d[j+12 : j+16])
name, _ = getString(str, int(nameoff))
ndx := int(other)
if ndx >= len(need) {
a := make([]verneed, 2*(ndx+1))
copy(a, need)
need = a
}
need[ndx] = verneed{file, name}
if next == 0 {
break
}
j += int(next)
}
if next == 0 {
break
}
i += int(next)
}
// Versym parallels symbol table, indexing into verneed.
vs := f.SectionByType(SHT_GNU_VERSYM)
if vs == nil {
return
}
d, _ = vs.Data()
f.gnuNeed = need
f.gnuVersym = d
}
// gnuVersion adds Library and Version information to sym,
// which came from offset i of the symbol table.
func (f *File) gnuVersion(i int, sym *ImportedSymbol) {
// Each entry is two bytes.
i = (i + 1) * 2
if i >= len(f.gnuVersym) {
return
}
j := int(f.ByteOrder.Uint16(f.gnuVersym[i:]))
if j < 2 || j >= len(f.gnuNeed) {
return
}
n := &f.gnuNeed[j]
sym.Library = n.File
sym.Version = n.Name
}
// ImportedLibraries returns the names of all libraries
// referred to by the binary f that are expected to be
// linked with the binary at dynamic link time.
func (f *File) ImportedLibraries() ([]string, error) {
return f.DynString(DT_NEEDED)
}
// DynString returns the strings listed for the given tag in the file's dynamic
// section.
//
// The tag must be one that takes string values: DT_NEEDED, DT_SONAME, DT_RPATH, or
// DT_RUNPATH.
func (f *File) DynString(tag DynTag) ([]string, error) {
switch tag {
case DT_NEEDED, DT_SONAME, DT_RPATH, DT_RUNPATH:
default:
return nil, fmt.Errorf("non-string-valued tag %v", tag)
}
ds := f.SectionByType(SHT_DYNAMIC)
if ds == nil {
// not dynamic, so no libraries
return nil, nil
}
d, err := ds.Data()
if err != nil {
return nil, err
}
str, err := f.stringTable(ds.Link)
if err != nil {
return nil, err
}
var all []string
for len(d) > 0 {
var t DynTag
var v uint64
switch f.Class {
case ELFCLASS32:
t = DynTag(f.ByteOrder.Uint32(d[0:4]))
v = uint64(f.ByteOrder.Uint32(d[4:8]))
d = d[8:]
case ELFCLASS64:
t = DynTag(f.ByteOrder.Uint64(d[0:8]))
v = f.ByteOrder.Uint64(d[8:16])
d = d[16:]
}
if t == tag {
s, ok := getString(str, int(v))
if ok {
all = append(all, s)
}
}
}
return all, nil
}