| // 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 macho implements access to Mach-O object files, as defined by |
| // http://developer.apple.com/mac/library/documentation/DeveloperTools/Conceptual/MachORuntime/Reference/reference.html. |
| package macho |
| |
| // High level access to low level data structures. |
| |
| import ( |
| "bytes" |
| "debug/dwarf" |
| "encoding/binary" |
| "fmt" |
| "io" |
| "os" |
| ) |
| |
| // A File represents an open Mach-O file. |
| type File struct { |
| FileHeader |
| ByteOrder binary.ByteOrder |
| Loads []Load |
| Sections []*Section |
| |
| closer io.Closer |
| } |
| |
| // A Load represents any Mach-O load command. |
| type Load interface { |
| Raw() []byte |
| } |
| |
| // A LoadBytes is the uninterpreted bytes of a Mach-O load command. |
| type LoadBytes []byte |
| |
| func (b LoadBytes) Raw() []byte { return b } |
| |
| // A SegmentHeader is the header for a Mach-O 32-bit or 64-bit load segment command. |
| type SegmentHeader struct { |
| Cmd LoadCmd |
| Len uint32 |
| Name string |
| Addr uint64 |
| Memsz uint64 |
| Offset uint64 |
| Filesz uint64 |
| Maxprot uint32 |
| Prot uint32 |
| Nsect uint32 |
| Flag uint32 |
| } |
| |
| // A Segment represents a Mach-O 32-bit or 64-bit load segment command. |
| type Segment struct { |
| LoadBytes |
| SegmentHeader |
| |
| // 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 segment. |
| func (s *Segment) Data() ([]byte, os.Error) { |
| dat := make([]byte, s.sr.Size()) |
| n, err := s.sr.ReadAt(dat, 0) |
| return dat[0:n], err |
| } |
| |
| // Open returns a new ReadSeeker reading the segment. |
| func (s *Segment) Open() io.ReadSeeker { return io.NewSectionReader(s.sr, 0, 1<<63-1) } |
| |
| type SectionHeader struct { |
| Name string |
| Seg string |
| Addr uint64 |
| Size uint64 |
| Offset uint32 |
| Align uint32 |
| Reloff uint32 |
| Nreloc uint32 |
| Flags uint32 |
| } |
| |
| 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 Mach-O section. |
| func (s *Section) Data() ([]byte, os.Error) { |
| dat := make([]byte, s.sr.Size()) |
| n, err := s.sr.ReadAt(dat, 0) |
| return dat[0:n], err |
| } |
| |
| // Open returns a new ReadSeeker reading the Mach-O section. |
| func (s *Section) Open() io.ReadSeeker { return io.NewSectionReader(s.sr, 0, 1<<63-1) } |
| |
| |
| /* |
| * Mach-O reader |
| */ |
| |
| type FormatError struct { |
| off int64 |
| msg string |
| val interface{} |
| } |
| |
| func (e *FormatError) String() 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 a Mach-O binary. |
| func Open(name string) (*File, os.Error) { |
| f, err := os.Open(name, os.O_RDONLY, 0) |
| 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() os.Error { |
| var err os.Error |
| if f.closer != nil { |
| err = f.closer.Close() |
| f.closer = nil |
| } |
| return err |
| } |
| |
| // NewFile creates a new File for acecssing a Mach-O binary in an underlying reader. |
| // The Mach-O binary is expected to start at position 0 in the ReaderAt. |
| func NewFile(r io.ReaderAt) (*File, os.Error) { |
| f := new(File) |
| sr := io.NewSectionReader(r, 0, 1<<63-1) |
| |
| // Read and decode Mach magic to determine byte order, size. |
| // Magic32 and Magic64 differ only in the bottom bit. |
| var ident [4]byte |
| if _, err := r.ReadAt(ident[0:], 0); err != nil { |
| return nil, err |
| } |
| be := binary.BigEndian.Uint32(ident[0:]) |
| le := binary.LittleEndian.Uint32(ident[0:]) |
| switch Magic32 &^ 1 { |
| case be &^ 1: |
| f.ByteOrder = binary.BigEndian |
| f.Magic = be |
| case le &^ 1: |
| f.ByteOrder = binary.LittleEndian |
| f.Magic = le |
| default: |
| return nil, &FormatError{0, "invalid magic number", nil} |
| } |
| |
| // Read entire file header. |
| if err := binary.Read(sr, f.ByteOrder, &f.FileHeader); err != nil { |
| return nil, err |
| } |
| |
| // Then load commands. |
| offset := int64(fileHeaderSize32) |
| if f.Magic == Magic64 { |
| offset = fileHeaderSize64 |
| } |
| dat := make([]byte, f.Cmdsz) |
| if _, err := r.ReadAt(dat, offset); err != nil { |
| return nil, err |
| } |
| f.Loads = make([]Load, f.Ncmd) |
| bo := f.ByteOrder |
| for i := range f.Loads { |
| // Each load command begins with uint32 command and length. |
| if len(dat) < 8 { |
| return nil, &FormatError{offset, "command block too small", nil} |
| } |
| cmd, siz := LoadCmd(bo.Uint32(dat[0:4])), bo.Uint32(dat[4:8]) |
| if siz < 8 || siz > uint32(len(dat)) { |
| return nil, &FormatError{offset, "invalid command block size", nil} |
| } |
| var cmddat []byte |
| cmddat, dat = dat[0:siz], dat[siz:] |
| offset += int64(siz) |
| var s *Segment |
| switch cmd { |
| default: |
| f.Loads[i] = LoadBytes(cmddat) |
| |
| case LoadCmdSegment: |
| var seg32 Segment32 |
| b := bytes.NewBuffer(cmddat) |
| if err := binary.Read(b, bo, &seg32); err != nil { |
| return nil, err |
| } |
| s = new(Segment) |
| s.LoadBytes = cmddat |
| s.Cmd = cmd |
| s.Len = siz |
| s.Name = cstring(seg32.Name[0:]) |
| s.Addr = uint64(seg32.Addr) |
| s.Memsz = uint64(seg32.Memsz) |
| s.Offset = uint64(seg32.Offset) |
| s.Filesz = uint64(seg32.Filesz) |
| s.Maxprot = seg32.Maxprot |
| s.Prot = seg32.Prot |
| s.Nsect = seg32.Nsect |
| s.Flag = seg32.Flag |
| f.Loads[i] = s |
| for i := 0; i < int(s.Nsect); i++ { |
| var sh32 Section32 |
| if err := binary.Read(b, bo, &sh32); err != nil { |
| return nil, err |
| } |
| sh := new(Section) |
| sh.Name = cstring(sh32.Name[0:]) |
| sh.Seg = cstring(sh32.Seg[0:]) |
| sh.Addr = uint64(sh32.Addr) |
| sh.Size = uint64(sh32.Size) |
| sh.Offset = sh32.Offset |
| sh.Align = sh32.Align |
| sh.Reloff = sh32.Reloff |
| sh.Nreloc = sh32.Nreloc |
| sh.Flags = sh32.Flags |
| f.pushSection(sh, r) |
| } |
| |
| case LoadCmdSegment64: |
| var seg64 Segment64 |
| b := bytes.NewBuffer(cmddat) |
| if err := binary.Read(b, bo, &seg64); err != nil { |
| return nil, err |
| } |
| s = new(Segment) |
| s.LoadBytes = cmddat |
| s.Cmd = cmd |
| s.Len = siz |
| s.Name = cstring(seg64.Name[0:]) |
| s.Addr = seg64.Addr |
| s.Memsz = seg64.Memsz |
| s.Offset = seg64.Offset |
| s.Filesz = seg64.Filesz |
| s.Maxprot = seg64.Maxprot |
| s.Prot = seg64.Prot |
| s.Nsect = seg64.Nsect |
| s.Flag = seg64.Flag |
| f.Loads[i] = s |
| for i := 0; i < int(s.Nsect); i++ { |
| var sh64 Section64 |
| if err := binary.Read(b, bo, &sh64); err != nil { |
| return nil, err |
| } |
| sh := new(Section) |
| sh.Name = cstring(sh64.Name[0:]) |
| sh.Seg = cstring(sh64.Seg[0:]) |
| sh.Addr = sh64.Addr |
| sh.Size = sh64.Size |
| sh.Offset = sh64.Offset |
| sh.Align = sh64.Align |
| sh.Reloff = sh64.Reloff |
| sh.Nreloc = sh64.Nreloc |
| sh.Flags = sh64.Flags |
| f.pushSection(sh, r) |
| } |
| } |
| if s != nil { |
| s.sr = io.NewSectionReader(r, int64(s.Offset), int64(s.Filesz)) |
| s.ReaderAt = s.sr |
| } |
| } |
| return f, nil |
| } |
| |
| func (f *File) pushSection(sh *Section, r io.ReaderAt) { |
| n := len(f.Sections) |
| if n >= cap(f.Sections) { |
| m := (n + 1) * 2 |
| new := make([]*Section, n, m) |
| for i, sh := range f.Sections { |
| new[i] = sh |
| } |
| f.Sections = new |
| } |
| f.Sections = f.Sections[0 : n+1] |
| f.Sections[n] = sh |
| sh.sr = io.NewSectionReader(r, int64(sh.Offset), int64(sh.Size)) |
| sh.ReaderAt = sh.sr |
| } |
| |
| func cstring(b []byte) string { |
| var i int |
| for i = 0; i < len(b) && b[i] != 0; i++ { |
| } |
| return string(b[0:i]) |
| } |
| |
| // Segment returns the first Segment with the given name, or nil if no such segment exists. |
| func (f *File) Segment(name string) *Segment { |
| for _, l := range f.Loads { |
| if s, ok := l.(*Segment); ok && s.Name == name { |
| return s |
| } |
| } |
| return nil |
| } |
| |
| // Section returns the first 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 |
| } |
| |
| // DWARF returns the DWARF debug information for the Mach-O file. |
| func (f *File) DWARF() (*dwarf.Data, os.Error) { |
| // There are many other DWARF sections, but these |
| // are the required ones, and the debug/dwarf package |
| // does not use the others, so don't bother loading them. |
| var names = [...]string{"abbrev", "info", "str"} |
| var dat [len(names)][]byte |
| for i, name := range names { |
| name = "__debug_" + name |
| s := f.Section(name) |
| if s == nil { |
| return nil, os.NewError("missing Mach-O section " + name) |
| } |
| b, err := s.Data() |
| if err != nil && uint64(len(b)) < s.Size { |
| return nil, err |
| } |
| dat[i] = b |
| } |
| |
| abbrev, info, str := dat[0], dat[1], dat[2] |
| return dwarf.New(abbrev, nil, nil, info, nil, nil, nil, str) |
| } |