| 1 | // Copyright 2014 The Go Authors. All rights reserved. |
|---|---|
| 2 | // Use of this source code is governed by a BSD-style |
| 3 | // license that can be found in the LICENSE file. |
| 4 | |
| 5 | package macho |
| 6 | |
| 7 | import ( |
| 8 | "encoding/binary" |
| 9 | "io" |
| 10 | "os" |
| 11 | ) |
| 12 | |
| 13 | // A FatFile is a Mach-O universal binary that contains at least one architecture. |
| 14 | type FatFile struct { |
| 15 | Magic uint32 |
| 16 | Arches []FatArch |
| 17 | closer io.Closer |
| 18 | } |
| 19 | |
| 20 | // A FatArchHeader represents a fat header for a specific image architecture. |
| 21 | type FatArchHeader struct { |
| 22 | Cpu Cpu |
| 23 | SubCpu uint32 |
| 24 | Offset uint32 |
| 25 | Size uint32 |
| 26 | Align uint32 |
| 27 | } |
| 28 | |
| 29 | const fatArchHeaderSize = 5 * 4 |
| 30 | |
| 31 | // A FatArch is a Mach-O File inside a FatFile. |
| 32 | type FatArch struct { |
| 33 | FatArchHeader |
| 34 | *File |
| 35 | } |
| 36 | |
| 37 | // NewFatFile creates a new FatFile for accessing all the Mach-O images in a |
| 38 | // universal binary. The Mach-O binary is expected to start at position 0 in |
| 39 | // the ReaderAt. |
| 40 | func NewFatFile(r io.ReaderAt) (*FatFile, error) { |
| 41 | var ff FatFile |
| 42 | sr := io.NewSectionReader(r, 0, 1<<63-1) |
| 43 | |
| 44 | // Read the fat_header struct, which is always in big endian. |
| 45 | // Start with the magic number. |
| 46 | err := binary.Read(sr, binary.BigEndian, &ff.Magic) |
| 47 | if err != nil { |
| 48 | return nil, formatError(0, "error reading magic number, %v", err) |
| 49 | } else if ff.Magic != MagicFat { |
| 50 | // See if this is a Mach-O file via its magic number. The magic |
| 51 | // must be converted to little endian first though. |
| 52 | var buf [4]byte |
| 53 | binary.BigEndian.PutUint32(buf[:], ff.Magic) |
| 54 | leMagic := binary.LittleEndian.Uint32(buf[:]) |
| 55 | if leMagic == Magic32 || leMagic == Magic64 { |
| 56 | return nil, formatError(0, "not a fat Mach-O file, leMagic=0x%x", leMagic) |
| 57 | } else { |
| 58 | return nil, formatError(0, "invalid magic number, leMagic=0x%x", leMagic) |
| 59 | } |
| 60 | } |
| 61 | offset := int64(4) |
| 62 | |
| 63 | // Read the number of FatArchHeaders that come after the fat_header. |
| 64 | var narch uint32 |
| 65 | err = binary.Read(sr, binary.BigEndian, &narch) |
| 66 | if err != nil { |
| 67 | return nil, formatError(offset, "invalid fat_header %v", err) |
| 68 | } |
| 69 | offset += 4 |
| 70 | |
| 71 | if narch < 1 { |
| 72 | return nil, formatError(offset, "file contains no images, narch=%d", narch) |
| 73 | } |
| 74 | |
| 75 | // Combine the Cpu and SubCpu (both uint32) into a uint64 to make sure |
| 76 | // there are not duplicate architectures. |
| 77 | seenArches := make(map[uint64]bool, narch) |
| 78 | // Make sure that all images are for the same MH_ type. |
| 79 | var machoType HdrType |
| 80 | |
| 81 | // Following the fat_header comes narch fat_arch structs that index |
| 82 | // Mach-O images further in the file. |
| 83 | ff.Arches = make([]FatArch, narch) |
| 84 | for i := uint32(0); i < narch; i++ { |
| 85 | fa := &ff.Arches[i] |
| 86 | err = binary.Read(sr, binary.BigEndian, &fa.FatArchHeader) |
| 87 | if err != nil { |
| 88 | return nil, formatError(offset, "invalid fat_arch header, %v", err) |
| 89 | } |
| 90 | offset += fatArchHeaderSize |
| 91 | |
| 92 | fr := io.NewSectionReader(r, int64(fa.Offset), int64(fa.Size)) |
| 93 | fa.File, err = NewFile(fr) |
| 94 | if err != nil { |
| 95 | return nil, err |
| 96 | } |
| 97 | |
| 98 | // Make sure the architecture for this image is not duplicate. |
| 99 | seenArch := (uint64(fa.Cpu) << 32) | uint64(fa.SubCpu) |
| 100 | if o, k := seenArches[seenArch]; o || k { |
| 101 | return nil, formatError(offset, "duplicate architecture cpu=%v, subcpu=%#x", fa.Cpu, fa.SubCpu) |
| 102 | } |
| 103 | seenArches[seenArch] = true |
| 104 | |
| 105 | // Make sure the Mach-O type matches that of the first image. |
| 106 | if i == 0 { |
| 107 | machoType = HdrType(fa.Type) |
| 108 | } else { |
| 109 | if HdrType(fa.Type) != machoType { |
| 110 | return nil, formatError(offset, "Mach-O type for architecture #%d (type=%#x) does not match first (type=%#x)", i, fa.Type, machoType) |
| 111 | } |
| 112 | } |
| 113 | } |
| 114 | |
| 115 | return &ff, nil |
| 116 | } |
| 117 | |
| 118 | // OpenFat opens the named file using os.Open and prepares it for use as a Mach-O |
| 119 | // universal binary. |
| 120 | func OpenFat(name string) (*FatFile, error) { |
| 121 | f, err := os.Open(name) |
| 122 | if err != nil { |
| 123 | return nil, err |
| 124 | } |
| 125 | ff, err := NewFatFile(f) |
| 126 | if err != nil { |
| 127 | f.Close() |
| 128 | return nil, err |
| 129 | } |
| 130 | ff.closer = f |
| 131 | return ff, nil |
| 132 | } |
| 133 | |
| 134 | func (ff *FatFile) Close() error { |
| 135 | var err error |
| 136 | if ff.closer != nil { |
| 137 | err = ff.closer.Close() |
| 138 | ff.closer = nil |
| 139 | } |
| 140 | return err |
| 141 | } |
| 142 |
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