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// Copyright 2019 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 version
import (
"bytes"
"debug/elf"
"debug/macho"
"debug/pe"
"fmt"
"internal/xcoff"
"io"
"os"
)
// An exe is a generic interface to an OS executable (ELF, Mach-O, PE, XCOFF).
type exe interface {
// Close closes the underlying file.
Close() error
// ReadData reads and returns up to size byte starting at virtual address addr.
ReadData(addr, size uint64) ([]byte, error)
// DataStart returns the writable data segment start address.
DataStart() uint64
}
// openExe opens file and returns it as an exe.
func openExe(file string) (exe, error) {
f, err := os.Open(file)
if err != nil {
return nil, err
}
data := make([]byte, 16)
if _, err := io.ReadFull(f, data); err != nil {
return nil, err
}
f.Seek(0, 0)
if bytes.HasPrefix(data, []byte("\x7FELF")) {
e, err := elf.NewFile(f)
if err != nil {
f.Close()
return nil, err
}
return &elfExe{f, e}, nil
}
if bytes.HasPrefix(data, []byte("MZ")) {
e, err := pe.NewFile(f)
if err != nil {
f.Close()
return nil, err
}
return &peExe{f, e}, nil
}
if bytes.HasPrefix(data, []byte("\xFE\xED\xFA")) || bytes.HasPrefix(data[1:], []byte("\xFA\xED\xFE")) {
e, err := macho.NewFile(f)
if err != nil {
f.Close()
return nil, err
}
return &machoExe{f, e}, nil
}
if bytes.HasPrefix(data, []byte{0x01, 0xDF}) || bytes.HasPrefix(data, []byte{0x01, 0xF7}) {
e, err := xcoff.NewFile(f)
if err != nil {
f.Close()
return nil, err
}
return &xcoffExe{f, e}, nil
}
return nil, fmt.Errorf("unrecognized executable format")
}
// elfExe is the ELF implementation of the exe interface.
type elfExe struct {
os *os.File
f *elf.File
}
func (x *elfExe) Close() error {
return x.os.Close()
}
func (x *elfExe) ReadData(addr, size uint64) ([]byte, error) {
for _, prog := range x.f.Progs {
if prog.Vaddr <= addr && addr <= prog.Vaddr+prog.Filesz-1 {
n := prog.Vaddr + prog.Filesz - addr
if n > size {
n = size
}
data := make([]byte, n)
_, err := prog.ReadAt(data, int64(addr-prog.Vaddr))
if err != nil {
return nil, err
}
return data, nil
}
}
return nil, fmt.Errorf("address not mapped")
}
func (x *elfExe) DataStart() uint64 {
for _, s := range x.f.Sections {
if s.Name == ".go.buildinfo" {
return s.Addr
}
}
for _, p := range x.f.Progs {
if p.Type == elf.PT_LOAD && p.Flags&(elf.PF_X|elf.PF_W) == elf.PF_W {
return p.Vaddr
}
}
return 0
}
// peExe is the PE (Windows Portable Executable) implementation of the exe interface.
type peExe struct {
os *os.File
f *pe.File
}
func (x *peExe) Close() error {
return x.os.Close()
}
func (x *peExe) imageBase() uint64 {
switch oh := x.f.OptionalHeader.(type) {
case *pe.OptionalHeader32:
return uint64(oh.ImageBase)
case *pe.OptionalHeader64:
return oh.ImageBase
}
return 0
}
func (x *peExe) ReadData(addr, size uint64) ([]byte, error) {
addr -= x.imageBase()
for _, sect := range x.f.Sections {
if uint64(sect.VirtualAddress) <= addr && addr <= uint64(sect.VirtualAddress+sect.Size-1) {
n := uint64(sect.VirtualAddress+sect.Size) - addr
if n > size {
n = size
}
data := make([]byte, n)
_, err := sect.ReadAt(data, int64(addr-uint64(sect.VirtualAddress)))
if err != nil {
return nil, err
}
return data, nil
}
}
return nil, fmt.Errorf("address not mapped")
}
func (x *peExe) DataStart() uint64 {
// Assume data is first writable section.
const (
IMAGE_SCN_CNT_CODE = 0x00000020
IMAGE_SCN_CNT_INITIALIZED_DATA = 0x00000040
IMAGE_SCN_CNT_UNINITIALIZED_DATA = 0x00000080
IMAGE_SCN_MEM_EXECUTE = 0x20000000
IMAGE_SCN_MEM_READ = 0x40000000
IMAGE_SCN_MEM_WRITE = 0x80000000
IMAGE_SCN_MEM_DISCARDABLE = 0x2000000
IMAGE_SCN_LNK_NRELOC_OVFL = 0x1000000
IMAGE_SCN_ALIGN_32BYTES = 0x600000
)
for _, sect := range x.f.Sections {
if sect.VirtualAddress != 0 && sect.Size != 0 &&
sect.Characteristics&^IMAGE_SCN_ALIGN_32BYTES == IMAGE_SCN_CNT_INITIALIZED_DATA|IMAGE_SCN_MEM_READ|IMAGE_SCN_MEM_WRITE {
return uint64(sect.VirtualAddress) + x.imageBase()
}
}
return 0
}
// machoExe is the Mach-O (Apple macOS/iOS) implementation of the exe interface.
type machoExe struct {
os *os.File
f *macho.File
}
func (x *machoExe) Close() error {
return x.os.Close()
}
func (x *machoExe) ReadData(addr, size uint64) ([]byte, error) {
for _, load := range x.f.Loads {
seg, ok := load.(*macho.Segment)
if !ok {
continue
}
if seg.Addr <= addr && addr <= seg.Addr+seg.Filesz-1 {
if seg.Name == "__PAGEZERO" {
continue
}
n := seg.Addr + seg.Filesz - addr
if n > size {
n = size
}
data := make([]byte, n)
_, err := seg.ReadAt(data, int64(addr-seg.Addr))
if err != nil {
return nil, err
}
return data, nil
}
}
return nil, fmt.Errorf("address not mapped")
}
func (x *machoExe) DataStart() uint64 {
// Look for section named "__go_buildinfo".
for _, sec := range x.f.Sections {
if sec.Name == "__go_buildinfo" {
return sec.Addr
}
}
// Try the first non-empty writable segment.
const RW = 3
for _, load := range x.f.Loads {
seg, ok := load.(*macho.Segment)
if ok && seg.Addr != 0 && seg.Filesz != 0 && seg.Prot == RW && seg.Maxprot == RW {
return seg.Addr
}
}
return 0
}
// xcoffExe is the XCOFF (AIX eXtended COFF) implementation of the exe interface.
type xcoffExe struct {
os *os.File
f *xcoff.File
}
func (x *xcoffExe) Close() error {
return x.os.Close()
}
func (x *xcoffExe) ReadData(addr, size uint64) ([]byte, error) {
for _, sect := range x.f.Sections {
if uint64(sect.VirtualAddress) <= addr && addr <= uint64(sect.VirtualAddress+sect.Size-1) {
n := uint64(sect.VirtualAddress+sect.Size) - addr
if n > size {
n = size
}
data := make([]byte, n)
_, err := sect.ReadAt(data, int64(addr-uint64(sect.VirtualAddress)))
if err != nil {
return nil, err
}
return data, nil
}
}
return nil, fmt.Errorf("address not mapped")
}
func (x *xcoffExe) DataStart() uint64 {
return x.f.SectionByType(xcoff.STYP_DATA).VirtualAddress
}
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