// 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.
# Security
This package is not designed to be hardened against adversarial inputs, and is
outside the scope of https://go.dev/security/policy. In particular, only basic
validation is done when parsing object files. As such, care should be taken when
parsing untrusted inputs, as parsing malformed files may consume significant
resources, or cause panics.
*/
package elf
import (
"bytes"
"compress/zlib"
"debug/dwarf"
"encoding/binary"
"errors"
"fmt"
"internal/saferio"
"internal/zstd"
"io"
"os"
"strings"
"unsafe"
)
// 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
dynVers []DynamicVersion
dynVerNeeds []DynamicVersionNeed
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
// FileSize is the size of this section in the file in bytes.
// If a section is compressed, FileSize is the size of the
// compressed data, while Size (above) is the size of the
// uncompressed data.
FileSize 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.
//
// ReaderAt may be nil if the section is not easily available
// in a random-access form. For example, a compressed section
// may have a nil ReaderAt.
io.ReaderAt
sr *io.SectionReader
compressionType CompressionType
compressionOffset int64
}
// Data reads and returns the contents of the ELF section.
// Even if the section is stored compressed in the ELF file,
// Data returns uncompressed data.
//
// For an [SHT_NOBITS] section, Data always returns a non-nil error.
func (s *Section) Data() ([]byte, error) {
return saferio.ReadData(s.Open(), s.Size)
}
// 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.
// Even if the section is stored compressed in the ELF file,
// the ReadSeeker reads uncompressed data.
//
// For an [SHT_NOBITS] section, all calls to the opened reader
// will return a non-nil error.
func (s *Section) Open() io.ReadSeeker {
if s.Type == SHT_NOBITS {
return io.NewSectionReader(&nobitsSectionReader{}, 0, int64(s.Size))
}
var zrd func(io.Reader) (io.ReadCloser, error)
if s.Flags&SHF_COMPRESSED == 0 {
if !strings.HasPrefix(s.Name, ".zdebug") {
return io.NewSectionReader(s.sr, 0, 1<<63-1)
}
b := make([]byte, 12)
n, _ := s.sr.ReadAt(b, 0)
if n != 12 || string(b[:4]) != "ZLIB" {
return io.NewSectionReader(s.sr, 0, 1<<63-1)
}
s.compressionOffset = 12
s.compressionType = COMPRESS_ZLIB
s.Size = binary.BigEndian.Uint64(b[4:12])
zrd = zlib.NewReader
} else if s.Flags&SHF_ALLOC != 0 {
return errorReader{&FormatError{int64(s.Offset),
"SHF_COMPRESSED applies only to non-allocable sections", s.compressionType}}
}
switch s.compressionType {
case COMPRESS_ZLIB:
zrd = zlib.NewReader
case COMPRESS_ZSTD:
zrd = func(r io.Reader) (io.ReadCloser, error) {
return io.NopCloser(zstd.NewReader(r)), nil
}
}
if zrd == nil {
return errorReader{&FormatError{int64(s.Offset), "unknown compression type", s.compressionType}}
}
return &readSeekerFromReader{
reset: func() (io.Reader, error) {
fr := io.NewSectionReader(s.sr, s.compressionOffset, int64(s.FileSize)-s.compressionOffset)
return zrd(fr)
},
size: int64(s.Size),
}
}
// 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
// HasVersion reports whether the symbol has any version information.
// This will only be true for the dynamic symbol table.
HasVersion bool
// VersionIndex is the symbol's version index.
// Use the methods of the [VersionIndex] type to access it.
// This field is only meaningful if HasVersion is true.
VersionIndex VersionIndex
Section SectionIndex
Value, Size uint64
// These fields are present only for the dynamic symbol table.
Version string
Library string
}
/*
* ELF reader
*/
type FormatError struct {
off int64
msg string
val any
}
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])
var bo binary.ByteOrder
switch f.Data {
case ELFDATA2LSB:
bo = binary.LittleEndian
case ELFDATA2MSB:
bo = binary.BigEndian
default:
return nil, &FormatError{0, "unknown ELF data encoding", f.Data}
}
f.ByteOrder = bo
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
switch f.Class {
case ELFCLASS32:
var hdr Header32
data := make([]byte, unsafe.Sizeof(hdr))
if _, err := sr.ReadAt(data, 0); err != nil {
return nil, err
}
f.Type = Type(bo.Uint16(data[unsafe.Offsetof(hdr.Type):]))
f.Machine = Machine(bo.Uint16(data[unsafe.Offsetof(hdr.Machine):]))
f.Entry = uint64(bo.Uint32(data[unsafe.Offsetof(hdr.Entry):]))
if v := Version(bo.Uint32(data[unsafe.Offsetof(hdr.Version):])); v != f.Version {
return nil, &FormatError{0, "mismatched ELF version", v}
}
phoff = int64(bo.Uint32(data[unsafe.Offsetof(hdr.Phoff):]))
phentsize = int(bo.Uint16(data[unsafe.Offsetof(hdr.Phentsize):]))
phnum = int(bo.Uint16(data[unsafe.Offsetof(hdr.Phnum):]))
shoff = int64(bo.Uint32(data[unsafe.Offsetof(hdr.Shoff):]))
shentsize = int(bo.Uint16(data[unsafe.Offsetof(hdr.Shentsize):]))
shnum = int(bo.Uint16(data[unsafe.Offsetof(hdr.Shnum):]))
shstrndx = int(bo.Uint16(data[unsafe.Offsetof(hdr.Shstrndx):]))
case ELFCLASS64:
var hdr Header64
data := make([]byte, unsafe.Sizeof(hdr))
if _, err := sr.ReadAt(data, 0); err != nil {
return nil, err
}
f.Type = Type(bo.Uint16(data[unsafe.Offsetof(hdr.Type):]))
f.Machine = Machine(bo.Uint16(data[unsafe.Offsetof(hdr.Machine):]))
f.Entry = bo.Uint64(data[unsafe.Offsetof(hdr.Entry):])
if v := Version(bo.Uint32(data[unsafe.Offsetof(hdr.Version):])); v != f.Version {
return nil, &FormatError{0, "mismatched ELF version", v}
}
phoff = int64(bo.Uint64(data[unsafe.Offsetof(hdr.Phoff):]))
phentsize = int(bo.Uint16(data[unsafe.Offsetof(hdr.Phentsize):]))
phnum = int(bo.Uint16(data[unsafe.Offsetof(hdr.Phnum):]))
shoff = int64(bo.Uint64(data[unsafe.Offsetof(hdr.Shoff):]))
shentsize = int(bo.Uint16(data[unsafe.Offsetof(hdr.Shentsize):]))
shnum = int(bo.Uint16(data[unsafe.Offsetof(hdr.Shnum):]))
shstrndx = int(bo.Uint16(data[unsafe.Offsetof(hdr.Shstrndx):]))
}
if shoff < 0 {
return nil, &FormatError{0, "invalid shoff", shoff}
}
if phoff < 0 {
return nil, &FormatError{0, "invalid phoff", phoff}
}
if shoff == 0 && shnum != 0 {
return nil, &FormatError{0, "invalid ELF shnum for shoff=0", shnum}
}
if shnum > 0 && shstrndx >= shnum {
return nil, &FormatError{0, "invalid ELF shstrndx", shstrndx}
}
var wantPhentsize, wantShentsize int
switch f.Class {
case ELFCLASS32:
wantPhentsize = 8 * 4
wantShentsize = 10 * 4
case ELFCLASS64:
wantPhentsize = 2*4 + 6*8
wantShentsize = 4*4 + 6*8
}
if phnum > 0 && phentsize < wantPhentsize {
return nil, &FormatError{0, "invalid ELF phentsize", phentsize}
}
// Read program headers
f.Progs = make([]*Prog, phnum)
phdata, err := saferio.ReadDataAt(sr, uint64(phnum)*uint64(phentsize), phoff)
if err != nil {
return nil, err
}
for i := 0; i < phnum; i++ {
off := uintptr(i) * uintptr(phentsize)
p := new(Prog)
switch f.Class {
case ELFCLASS32:
var ph Prog32
p.ProgHeader = ProgHeader{
Type: ProgType(bo.Uint32(phdata[off+unsafe.Offsetof(ph.Type):])),
Flags: ProgFlag(bo.Uint32(phdata[off+unsafe.Offsetof(ph.Flags):])),
Off: uint64(bo.Uint32(phdata[off+unsafe.Offsetof(ph.Off):])),
Vaddr: uint64(bo.Uint32(phdata[off+unsafe.Offsetof(ph.Vaddr):])),
Paddr: uint64(bo.Uint32(phdata[off+unsafe.Offsetof(ph.Paddr):])),
Filesz: uint64(bo.Uint32(phdata[off+unsafe.Offsetof(ph.Filesz):])),
Memsz: uint64(bo.Uint32(phdata[off+unsafe.Offsetof(ph.Memsz):])),
Align: uint64(bo.Uint32(phdata[off+unsafe.Offsetof(ph.Align):])),
}
case ELFCLASS64:
var ph Prog64
p.ProgHeader = ProgHeader{
Type: ProgType(bo.Uint32(phdata[off+unsafe.Offsetof(ph.Type):])),
Flags: ProgFlag(bo.Uint32(phdata[off+unsafe.Offsetof(ph.Flags):])),
Off: bo.Uint64(phdata[off+unsafe.Offsetof(ph.Off):]),
Vaddr: bo.Uint64(phdata[off+unsafe.Offsetof(ph.Vaddr):]),
Paddr: bo.Uint64(phdata[off+unsafe.Offsetof(ph.Paddr):]),
Filesz: bo.Uint64(phdata[off+unsafe.Offsetof(ph.Filesz):]),
Memsz: bo.Uint64(phdata[off+unsafe.Offsetof(ph.Memsz):]),
Align: bo.Uint64(phdata[off+unsafe.Offsetof(ph.Align):]),
}
}
if int64(p.Off) < 0 {
return nil, &FormatError{phoff + int64(off), "invalid program header offset", p.Off}
}
if int64(p.Filesz) < 0 {
return nil, &FormatError{phoff + int64(off), "invalid program header file size", p.Filesz}
}
p.sr = io.NewSectionReader(r, int64(p.Off), int64(p.Filesz))
p.ReaderAt = p.sr
f.Progs[i] = p
}
// If the number of sections is greater than or equal to SHN_LORESERVE
// (0xff00), shnum has the value zero and the actual number of section
// header table entries is contained in the sh_size field of the section
// header at index 0.
if shoff > 0 && shnum == 0 {
var typ, link uint32
sr.Seek(shoff, io.SeekStart)
switch f.Class {
case ELFCLASS32:
sh := new(Section32)
if err := binary.Read(sr, bo, sh); err != nil {
return nil, err
}
shnum = int(sh.Size)
typ = sh.Type
link = sh.Link
case ELFCLASS64:
sh := new(Section64)
if err := binary.Read(sr, bo, sh); err != nil {
return nil, err
}
shnum = int(sh.Size)
typ = sh.Type
link = sh.Link
}
if SectionType(typ) != SHT_NULL {
return nil, &FormatError{shoff, "invalid type of the initial section", SectionType(typ)}
}
if shnum < int(SHN_LORESERVE) {
return nil, &FormatError{shoff, "invalid ELF shnum contained in sh_size", shnum}
}
// If the section name string table section index is greater than or
// equal to SHN_LORESERVE (0xff00), this member has the value
// SHN_XINDEX (0xffff) and the actual index of the section name
// string table section is contained in the sh_link field of the
// section header at index 0.
if shstrndx == int(SHN_XINDEX) {
shstrndx = int(link)
if shstrndx < int(SHN_LORESERVE) {
return nil, &FormatError{shoff, "invalid ELF shstrndx contained in sh_link", shstrndx}
}
}
}
if shnum > 0 && shentsize < wantShentsize {
return nil, &FormatError{0, "invalid ELF shentsize", shentsize}
}
// Read section headers
c := saferio.SliceCap[Section](uint64(shnum))
if c < 0 {
return nil, &FormatError{0, "too many sections", shnum}
}
if shnum > 0 && ((1<<64)-1)/uint64(shnum) < uint64(shentsize) {
return nil, &FormatError{0, "section header overflow", shnum}
}
f.Sections = make([]*Section, 0, c)
names := make([]uint32, 0, c)
shdata, err := saferio.ReadDataAt(sr, uint64(shnum)*uint64(shentsize), shoff)
if err != nil {
return nil, err
}
for i := 0; i < shnum; i++ {
off := uintptr(i) * uintptr(shentsize)
s := new(Section)
switch f.Class {
case ELFCLASS32:
var sh Section32
names = append(names, bo.Uint32(shdata[off+unsafe.Offsetof(sh.Name):]))
s.SectionHeader = SectionHeader{
Type: SectionType(bo.Uint32(shdata[off+unsafe.Offsetof(sh.Type):])),
Flags: SectionFlag(bo.Uint32(shdata[off+unsafe.Offsetof(sh.Flags):])),
Addr: uint64(bo.Uint32(shdata[off+unsafe.Offsetof(sh.Addr):])),
Offset: uint64(bo.Uint32(shdata[off+unsafe.Offsetof(sh.Off):])),
FileSize: uint64(bo.Uint32(shdata[off+unsafe.Offsetof(sh.Size):])),
Link: bo.Uint32(shdata[off+unsafe.Offsetof(sh.Link):]),
Info: bo.Uint32(shdata[off+unsafe.Offsetof(sh.Info):]),
Addralign: uint64(bo.Uint32(shdata[off+unsafe.Offsetof(sh.Addralign):])),
Entsize: uint64(bo.Uint32(shdata[off+unsafe.Offsetof(sh.Entsize):])),
}
case ELFCLASS64:
var sh Section64
names = append(names, bo.Uint32(shdata[off+unsafe.Offsetof(sh.Name):]))
s.SectionHeader = SectionHeader{
Type: SectionType(bo.Uint32(shdata[off+unsafe.Offsetof(sh.Type):])),
Flags: SectionFlag(bo.Uint64(shdata[off+unsafe.Offsetof(sh.Flags):])),
Offset: bo.Uint64(shdata[off+unsafe.Offsetof(sh.Off):]),
FileSize: bo.Uint64(shdata[off+unsafe.Offsetof(sh.Size):]),
Addr: bo.Uint64(shdata[off+unsafe.Offsetof(sh.Addr):]),
Link: bo.Uint32(shdata[off+unsafe.Offsetof(sh.Link):]),
Info: bo.Uint32(shdata[off+unsafe.Offsetof(sh.Info):]),
Addralign: bo.Uint64(shdata[off+unsafe.Offsetof(sh.Addralign):]),
Entsize: bo.Uint64(shdata[off+unsafe.Offsetof(sh.Entsize):]),
}
}
if int64(s.Offset) < 0 {
return nil, &FormatError{shoff + int64(off), "invalid section offset", int64(s.Offset)}
}
if int64(s.FileSize) < 0 {
return nil, &FormatError{shoff + int64(off), "invalid section size", int64(s.FileSize)}
}
s.sr = io.NewSectionReader(r, int64(s.Offset), int64(s.FileSize))
if s.Flags&SHF_COMPRESSED == 0 {
s.ReaderAt = s.sr
s.Size = s.FileSize
} else {
// Read the compression header.
switch f.Class {
case ELFCLASS32:
var ch Chdr32
chdata := make([]byte, unsafe.Sizeof(ch))
if _, err := s.sr.ReadAt(chdata, 0); err != nil {
return nil, err
}
s.compressionType = CompressionType(bo.Uint32(chdata[unsafe.Offsetof(ch.Type):]))
s.Size = uint64(bo.Uint32(chdata[unsafe.Offsetof(ch.Size):]))
s.Addralign = uint64(bo.Uint32(chdata[unsafe.Offsetof(ch.Addralign):]))
s.compressionOffset = int64(unsafe.Sizeof(ch))
case ELFCLASS64:
var ch Chdr64
chdata := make([]byte, unsafe.Sizeof(ch))
if _, err := s.sr.ReadAt(chdata, 0); err != nil {
return nil, err
}
s.compressionType = CompressionType(bo.Uint32(chdata[unsafe.Offsetof(ch.Type):]))
s.Size = bo.Uint64(chdata[unsafe.Offsetof(ch.Size):])
s.Addralign = bo.Uint64(chdata[unsafe.Offsetof(ch.Addralign):])
s.compressionOffset = int64(unsafe.Sizeof(ch))
}
}
f.Sections = append(f.Sections, s)
}
if len(f.Sections) == 0 {
return f, nil
}
// Load section header string table.
if shstrndx == 0 {
// If the file has no section name string table,
// shstrndx holds the value SHN_UNDEF (0).
return f, nil
}
shstr := f.Sections[shstrndx]
if shstr.Type != SHT_STRTAB {
return nil, &FormatError{shoff + int64(shstrndx*shentsize), "invalid ELF section name string table type", shstr.Type}
}
shstrtab, err := shstr.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, fmt.Errorf("cannot load symbol section: %w", err)
}
if len(data) == 0 {
return nil, nil, errors.New("symbol section is empty")
}
if len(data)%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, fmt.Errorf("cannot load string table section: %w", err)
}
// The first entry is all zeros.
data = data[Sym32Size:]
symbols := make([]Symbol, len(data)/Sym32Size)
i := 0
var sym Sym32
for len(data) > 0 {
sym.Name = f.ByteOrder.Uint32(data[0:4])
sym.Value = f.ByteOrder.Uint32(data[4:8])
sym.Size = f.ByteOrder.Uint32(data[8:12])
sym.Info = data[12]
sym.Other = data[13]
sym.Shndx = f.ByteOrder.Uint16(data[14:16])
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++
data = data[Sym32Size:]
}
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, fmt.Errorf("cannot load symbol section: %w", err)
}
if len(data)%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, fmt.Errorf("cannot load string table section: %w", err)
}
// The first entry is all zeros.
data = data[Sym64Size:]
symbols := make([]Symbol, len(data)/Sym64Size)
i := 0
var sym Sym64
for len(data) > 0 {
sym.Name = f.ByteOrder.Uint32(data[0:4])
sym.Info = data[4]
sym.Other = data[5]
sym.Shndx = f.ByteOrder.Uint16(data[6:8])
sym.Value = f.ByteOrder.Uint64(data[8:16])
sym.Size = f.ByteOrder.Uint64(data[16:24])
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++
data = data[Sym64Size:]
}
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 REL or 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)
case f.Class == ELFCLASS32 && f.Machine == EM_MIPS:
return f.applyRelocationsMIPS(dst, rels)
case f.Class == ELFCLASS64 && f.Machine == EM_MIPS:
return f.applyRelocationsMIPS64(dst, rels)
case f.Class == ELFCLASS64 && f.Machine == EM_LOONGARCH:
return f.applyRelocationsLOONG64(dst, rels)
case f.Class == ELFCLASS64 && f.Machine == EM_RISCV:
return f.applyRelocationsRISCV64(dst, rels)
case f.Class == ELFCLASS64 && f.Machine == EM_S390:
return f.applyRelocationss390x(dst, rels)
case f.Class == ELFCLASS64 && f.Machine == EM_SPARCV9:
return f.applyRelocationsSPARC64(dst, rels)
default:
return errors.New("applyRelocations: not implemented")
}
}
// canApplyRelocation reports whether we should try to apply a
// relocation to a DWARF data section, given a pointer to the symbol
// targeted by the relocation.
// Most relocations in DWARF data tend to be section-relative, but
// some target non-section symbols (for example, low_PC attrs on
// subprogram or compilation unit DIEs that target function symbols).
func canApplyRelocation(sym *Symbol) bool {
return sym.Section != SHN_UNDEF && sym.Section < SHN_LORESERVE
}
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 !canApplyRelocation(sym) {
continue
}
// There are relocations, so this must be a normal
// object file. The code below handles only basic relocations
// of the form S + A (symbol plus addend).
switch t {
case R_X86_64_64:
if rela.Off+8 >= uint64(len(dst)) || rela.Addend < 0 {
continue
}
val64 := sym.Value + uint64(rela.Addend)
f.ByteOrder.PutUint64(dst[rela.Off:rela.Off+8], val64)
case R_X86_64_32:
if rela.Off+4 >= uint64(len(dst)) || rela.Addend < 0 {
continue
}
val32 := uint32(sym.Value) + uint32(rela.Addend)
f.ByteOrder.PutUint32(dst[rela.Off:rela.Off+4], val32)
}
}
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 !canApplyRelocation(sym) {
continue
}
// There are relocations, so this must be a normal
// object file. The code below handles only basic relocations
// of the form S + A (symbol plus addend).
switch t {
case R_AARCH64_ABS64:
if rela.Off+8 >= uint64(len(dst)) || rela.Addend < 0 {
continue
}
val64 := sym.Value + uint64(rela.Addend)
f.ByteOrder.PutUint64(dst[rela.Off:rela.Off+8], val64)
case R_AARCH64_ABS32:
if rela.Off+4 >= uint64(len(dst)) || rela.Addend < 0 {
continue
}
val32 := uint32(sym.Value) + uint32(rela.Addend)
f.ByteOrder.PutUint32(dst[rela.Off:rela.Off+4], val32)
}
}
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 !canApplyRelocation(sym) {
continue
}
switch t {
case R_PPC_ADDR32:
if rela.Off+4 >= uint32(len(dst)) || rela.Addend < 0 {
continue
}
val32 := uint32(sym.Value) + uint32(rela.Addend)
f.ByteOrder.PutUint32(dst[rela.Off:rela.Off+4], val32)
}
}
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 !canApplyRelocation(sym) {
continue
}
switch t {
case R_PPC64_ADDR64:
if rela.Off+8 >= uint64(len(dst)) || rela.Addend < 0 {
continue
}
val64 := sym.Value + uint64(rela.Addend)
f.ByteOrder.PutUint64(dst[rela.Off:rela.Off+8], val64)
case R_PPC64_ADDR32:
if rela.Off+4 >= uint64(len(dst)) || rela.Addend < 0 {
continue
}
val32 := uint32(sym.Value) + uint32(rela.Addend)
f.ByteOrder.PutUint32(dst[rela.Off:rela.Off+4], val32)
}
}
return nil
}
func (f *File) applyRelocationsMIPS(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_MIPS(rel.Info & 0xff)
if symNo == 0 || symNo > uint32(len(symbols)) {
continue
}
sym := &symbols[symNo-1]
switch t {
case R_MIPS_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) applyRelocationsMIPS64(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)
var symNo uint64
var t R_MIPS
if f.ByteOrder == binary.BigEndian {
symNo = rela.Info >> 32
t = R_MIPS(rela.Info & 0xff)
} else {
symNo = rela.Info & 0xffffffff
t = R_MIPS(rela.Info >> 56)
}
if symNo == 0 || symNo > uint64(len(symbols)) {
continue
}
sym := &symbols[symNo-1]
if !canApplyRelocation(sym) {
continue
}
switch t {
case R_MIPS_64:
if rela.Off+8 >= uint64(len(dst)) || rela.Addend < 0 {
continue
}
val64 := sym.Value + uint64(rela.Addend)
f.ByteOrder.PutUint64(dst[rela.Off:rela.Off+8], val64)
case R_MIPS_32:
if rela.Off+4 >= uint64(len(dst)) || rela.Addend < 0 {
continue
}
val32 := uint32(sym.Value) + uint32(rela.Addend)
f.ByteOrder.PutUint32(dst[rela.Off:rela.Off+4], val32)
}
}
return nil
}
func (f *File) applyRelocationsLOONG64(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)
var symNo uint64
var t R_LARCH
symNo = rela.Info >> 32
t = R_LARCH(rela.Info & 0xffff)
if symNo == 0 || symNo > uint64(len(symbols)) {
continue
}
sym := &symbols[symNo-1]
if !canApplyRelocation(sym) {
continue
}
switch t {
case R_LARCH_64:
if rela.Off+8 >= uint64(len(dst)) || rela.Addend < 0 {
continue
}
val64 := sym.Value + uint64(rela.Addend)
f.ByteOrder.PutUint64(dst[rela.Off:rela.Off+8], val64)
case R_LARCH_32:
if rela.Off+4 >= uint64(len(dst)) || rela.Addend < 0 {
continue
}
val32 := uint32(sym.Value) + uint32(rela.Addend)
f.ByteOrder.PutUint32(dst[rela.Off:rela.Off+4], val32)
}
}
return nil
}
func (f *File) applyRelocationsRISCV64(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_RISCV(rela.Info & 0xffff)
if symNo == 0 || symNo > uint64(len(symbols)) {
continue
}
sym := &symbols[symNo-1]
if !canApplyRelocation(sym) {
continue
}
switch t {
case R_RISCV_64:
if rela.Off+8 >= uint64(len(dst)) || rela.Addend < 0 {
continue
}
val64 := sym.Value + uint64(rela.Addend)
f.ByteOrder.PutUint64(dst[rela.Off:rela.Off+8], val64)
case R_RISCV_32:
if rela.Off+4 >= uint64(len(dst)) || rela.Addend < 0 {
continue
}
val32 := uint32(sym.Value) + uint32(rela.Addend)
f.ByteOrder.PutUint32(dst[rela.Off:rela.Off+4], val32)
}
}
return nil
}
func (f *File) applyRelocationss390x(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_390(rela.Info & 0xffff)
if symNo == 0 || symNo > uint64(len(symbols)) {
continue
}
sym := &symbols[symNo-1]
if !canApplyRelocation(sym) {
continue
}
switch t {
case R_390_64:
if rela.Off+8 >= uint64(len(dst)) || rela.Addend < 0 {
continue
}
val64 := sym.Value + uint64(rela.Addend)
f.ByteOrder.PutUint64(dst[rela.Off:rela.Off+8], val64)
case R_390_32:
if rela.Off+4 >= uint64(len(dst)) || rela.Addend < 0 {
continue
}
val32 := uint32(sym.Value) + uint32(rela.Addend)
f.ByteOrder.PutUint32(dst[rela.Off:rela.Off+4], val32)
}
}
return nil
}
func (f *File) applyRelocationsSPARC64(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_SPARC(rela.Info & 0xff)
if symNo == 0 || symNo > uint64(len(symbols)) {
continue
}
sym := &symbols[symNo-1]
if !canApplyRelocation(sym) {
continue
}
switch t {
case R_SPARC_64, R_SPARC_UA64:
if rela.Off+8 >= uint64(len(dst)) || rela.Addend < 0 {
continue
}
val64 := sym.Value + uint64(rela.Addend)
f.ByteOrder.PutUint64(dst[rela.Off:rela.Off+8], val64)
case R_SPARC_32, R_SPARC_UA32:
if rela.Off+4 >= uint64(len(dst)) || rela.Addend < 0 {
continue
}
val32 := uint32(sym.Value) + uint32(rela.Addend)
f.ByteOrder.PutUint32(dst[rela.Off:rela.Off+4], val32)
}
}
return nil
}
func (f *File) DWARF() (*dwarf.Data, error) {
dwarfSuffix := func(s *Section) string {
switch {
case strings.HasPrefix(s.Name, ".debug_"):
return s.Name[7:]
case strings.HasPrefix(s.Name, ".zdebug_"):
return s.Name[8:]
default:
return ""
}
}
// 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
}
if f.Type == ET_EXEC {
// Do not apply relocations to DWARF sections for ET_EXEC binaries.
// Relocations should already be applied, and .rela sections may
// contain incorrect data.
return b, nil
}
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 DWARf sections, but these are the ones
// the debug/dwarf package started with.
var dat = map[string][]byte{"abbrev": nil, "info": nil, "str": nil, "line": nil, "ranges": nil}
for i, s := range f.Sections {
suffix := dwarfSuffix(s)
if suffix == "" {
continue
}
if _, ok := dat[suffix]; !ok {
continue
}
b, err := sectionData(i, s)
if err != nil {
return nil, err
}
dat[suffix] = b
}
d, err := dwarf.New(dat["abbrev"], nil, nil, dat["info"], dat["line"], nil, dat["ranges"], dat["str"])
if err != nil {
return nil, err
}
// Look for DWARF4 .debug_types sections and DWARF5 sections.
for i, s := range f.Sections {
suffix := dwarfSuffix(s)
if suffix == "" {
continue
}
if _, ok := dat[suffix]; ok {
// Already handled.
continue
}
b, err := sectionData(i, s)
if err != nil {
return nil, err
}
if suffix == "types" {
if err := d.AddTypes(fmt.Sprintf("types-%d", i), b); err != nil {
return nil, err
}
} else {
if err := d.AddSection(".debug_"+suffix, b); 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.
//
// If f has a symbol version table, the returned [File.Symbols] will have
// initialized Version and Library fields.
//
// For compatibility with [File.Symbols], [File.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, str, err := f.getSymbols(SHT_DYNSYM)
if err != nil {
return nil, err
}
hasVersions, err := f.gnuVersionInit(str)
if err != nil {
return nil, err
}
if hasVersions {
for i := range sym {
sym[i].HasVersion, sym[i].VersionIndex, sym[i].Version, sym[i].Library = f.gnuVersion(i)
}
}
return sym, nil
}
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
}
if _, err := f.gnuVersionInit(str); err != nil {
return nil, err
}
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})
sym := &all[len(all)-1]
_, _, sym.Version, sym.Library = f.gnuVersion(i)
}
}
return all, nil
}
// VersionIndex is the type of a [Symbol] version index.
type VersionIndex uint16
// IsHidden reports whether the symbol is hidden within the version.
// This means that the symbol can only be seen by specifying the exact version.
func (vi VersionIndex) IsHidden() bool {
return vi&0x8000 != 0
}
// Index returns the version index.
// If this is the value 0, it means that the symbol is local,
// and is not visible externally.
// If this is the value 1, it means that the symbol is in the base version,
// and has no specific version; it may or may not match a
// [DynamicVersion.Index] in the slice returned by [File.DynamicVersions].
// Other values will match either [DynamicVersion.Index]
// in the slice returned by [File.DynamicVersions],
// or [DynamicVersionDep.Index] in the Needs field
// of the elements of the slice returned by [File.DynamicVersionNeeds].
// In general, a defined symbol will have an index referring
// to DynamicVersions, and an undefined symbol will have an index
// referring to some version in DynamicVersionNeeds.
func (vi VersionIndex) Index() uint16 {
return uint16(vi & 0x7fff)
}
// DynamicVersion is a version defined by a dynamic object.
// This describes entries in the ELF SHT_GNU_verdef section.
// We assume that the vd_version field is 1.
// Note that the name of the version appears here;
// it is not in the first Deps entry as it is in the ELF file.
type DynamicVersion struct {
Name string // Name of version defined by this index.
Index uint16 // Version index.
Flags DynamicVersionFlag
Deps []string // Names of versions that this version depends upon.
}
// DynamicVersionNeed describes a shared library needed by a dynamic object,
// with a list of the versions needed from that shared library.
// This describes entries in the ELF SHT_GNU_verneed section.
// We assume that the vn_version field is 1.
type DynamicVersionNeed struct {
Name string // Shared library name.
Needs []DynamicVersionDep // Dependencies.
}
// DynamicVersionDep is a version needed from some shared library.
type DynamicVersionDep struct {
Flags DynamicVersionFlag
Index uint16 // Version index.
Dep string // Name of required version.
}
// dynamicVersions returns version information for a dynamic object.
func (f *File) dynamicVersions(str []byte) error {
if f.dynVers != nil {
// Already initialized.
return nil
}
// Accumulate verdef information.
vd := f.SectionByType(SHT_GNU_VERDEF)
if vd == nil {
return nil
}
d, _ := vd.Data()
var dynVers []DynamicVersion
i := 0
for {
if i+20 > len(d) {
break
}
version := f.ByteOrder.Uint16(d[i : i+2])
if version != 1 {
return &FormatError{int64(vd.Offset + uint64(i)), "unexpected dynamic version", version}
}
flags := DynamicVersionFlag(f.ByteOrder.Uint16(d[i+2 : i+4]))
ndx := f.ByteOrder.Uint16(d[i+4 : i+6])
cnt := f.ByteOrder.Uint16(d[i+6 : i+8])
aux := f.ByteOrder.Uint32(d[i+12 : i+16])
next := f.ByteOrder.Uint32(d[i+16 : i+20])
if cnt == 0 {
return &FormatError{int64(vd.Offset + uint64(i)), "dynamic version has no name", nil}
}
var name string
var depName string
var deps []string
j := i + int(aux)
for c := 0; c < int(cnt); c++ {
if j+8 > len(d) {
break
}
vname := f.ByteOrder.Uint32(d[j : j+4])
vnext := f.ByteOrder.Uint32(d[j+4 : j+8])
depName, _ = getString(str, int(vname))
if c == 0 {
name = depName
} else {
deps = append(deps, depName)
}
j += int(vnext)
}
dynVers = append(dynVers, DynamicVersion{
Name: name,
Index: ndx,
Flags: flags,
Deps: deps,
})
if next == 0 {
break
}
i += int(next)
}
f.dynVers = dynVers
return nil
}
// DynamicVersions returns version information for a dynamic object.
func (f *File) DynamicVersions() ([]DynamicVersion, error) {
if f.dynVers == nil {
_, str, err := f.getSymbols(SHT_DYNSYM)
if err != nil {
return nil, err
}
hasVersions, err := f.gnuVersionInit(str)
if err != nil {
return nil, err
}
if !hasVersions {
return nil, errors.New("DynamicVersions: missing version table")
}
}
return f.dynVers, nil
}
// dynamicVersionNeeds returns version dependencies for a dynamic object.
func (f *File) dynamicVersionNeeds(str []byte) error {
if f.dynVerNeeds != nil {
// Already initialized.
return nil
}
// Accumulate verneed information.
vn := f.SectionByType(SHT_GNU_VERNEED)
if vn == nil {
return nil
}
d, _ := vn.Data()
var dynVerNeeds []DynamicVersionNeed
i := 0
for {
if i+16 > len(d) {
break
}
vers := f.ByteOrder.Uint16(d[i : i+2])
if vers != 1 {
return &FormatError{int64(vn.Offset + uint64(i)), "unexpected dynamic need version", vers}
}
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 deps []DynamicVersionDep
j := i + int(aux)
for c := 0; c < int(cnt); c++ {
if j+16 > len(d) {
break
}
flags := DynamicVersionFlag(f.ByteOrder.Uint16(d[j+4 : j+6]))
index := 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])
depName, _ := getString(str, int(nameoff))
deps = append(deps, DynamicVersionDep{
Flags: flags,
Index: index,
Dep: depName,
})
if next == 0 {
break
}
j += int(next)
}
dynVerNeeds = append(dynVerNeeds, DynamicVersionNeed{
Name: file,
Needs: deps,
})
if next == 0 {
break
}
i += int(next)
}
f.dynVerNeeds = dynVerNeeds
return nil
}
// DynamicVersionNeeds returns version dependencies for a dynamic object.
func (f *File) DynamicVersionNeeds() ([]DynamicVersionNeed, error) {
if f.dynVerNeeds == nil {
_, str, err := f.getSymbols(SHT_DYNSYM)
if err != nil {
return nil, err
}
hasVersions, err := f.gnuVersionInit(str)
if err != nil {
return nil, err
}
if !hasVersions {
return nil, errors.New("DynamicVersionNeeds: missing version table")
}
}
return f.dynVerNeeds, nil
}
// gnuVersionInit parses the GNU version tables
// for use by calls to gnuVersion.
// It reports whether any version tables were found.
func (f *File) gnuVersionInit(str []byte) (bool, error) {
// Versym parallels symbol table, indexing into verneed.
vs := f.SectionByType(SHT_GNU_VERSYM)
if vs == nil {
return false, nil
}
d, _ := vs.Data()
f.gnuVersym = d
if err := f.dynamicVersions(str); err != nil {
return false, err
}
if err := f.dynamicVersionNeeds(str); err != nil {
return false, err
}
return true, nil
}
// gnuVersion adds Library and Version information to sym,
// which came from offset i of the symbol table.
func (f *File) gnuVersion(i int) (hasVersion bool, versionIndex VersionIndex, version string, library string) {
// Each entry is two bytes; skip undef entry at beginning.
i = (i + 1) * 2
if i >= len(f.gnuVersym) {
return false, 0, "", ""
}
s := f.gnuVersym[i:]
if len(s) < 2 {
return false, 0, "", ""
}
vi := VersionIndex(f.ByteOrder.Uint16(s))
ndx := vi.Index()
if ndx == 0 || ndx == 1 {
return true, vi, "", ""
}
for _, v := range f.dynVerNeeds {
for _, n := range v.Needs {
if ndx == n.Index {
return true, vi, n.Dep, v.Name
}
}
}
for _, v := range f.dynVers {
if ndx == v.Index {
return true, vi, v.Name, ""
}
}
return false, 0, "", ""
}
// 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
}
dynSize := 8
if f.Class == ELFCLASS64 {
dynSize = 16
}
if len(d)%dynSize != 0 {
return nil, errors.New("length of dynamic section is not a multiple of dynamic entry size")
}
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
}
// DynValue returns the values listed for the given tag in the file's dynamic
// section.
func (f *File) DynValue(tag DynTag) ([]uint64, error) {
ds := f.SectionByType(SHT_DYNAMIC)
if ds == nil {
return nil, nil
}
d, err := ds.Data()
if err != nil {
return nil, err
}
dynSize := 8
if f.Class == ELFCLASS64 {
dynSize = 16
}
if len(d)%dynSize != 0 {
return nil, errors.New("length of dynamic section is not a multiple of dynamic entry size")
}
// Parse the .dynamic section as a string of bytes.
var vals []uint64
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 {
vals = append(vals, v)
}
}
return vals, nil
}
type nobitsSectionReader struct{}
func (*nobitsSectionReader) ReadAt(p []byte, off int64) (n int, err error) {
return 0, errors.New("unexpected read from SHT_NOBITS section")
}