Magic.cpp revision 319799 
1//===- llvm/BinaryFormat/Magic.cpp - File magic identification --*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9
10#include "llvm/BinaryFormat/Magic.h"
11
12#include "llvm/BinaryFormat/COFF.h"
13#include "llvm/BinaryFormat/ELF.h"
14#include "llvm/BinaryFormat/MachO.h"
15#include "llvm/Support/Endian.h"
16#include "llvm/Support/FileSystem.h"
17
18#if !defined(_MSC_VER) && !defined(__MINGW32__)
19#include <unistd.h>
20#else
21#include <io.h>
22#endif
23
24using namespace llvm;
25using namespace llvm::support::endian;
26using namespace llvm::sys::fs;
27
28template <size_t N>
29static bool startswith(StringRef Magic, const char (&S)[N]) {
30  return Magic.startswith(StringRef(S, N - 1));
31}
32
33/// @brief Identify the magic in magic.
34file_magic llvm::identify_magic(StringRef Magic) {
35  if (Magic.size() < 4)
36    return file_magic::unknown;
37  switch ((unsigned char)Magic[0]) {
38  case 0x00: {
39    // COFF bigobj, CL.exe's LTO object file, or short import library file
40    if (startswith(Magic, "\0\0\xFF\xFF")) {
41      size_t MinSize =
42          offsetof(COFF::BigObjHeader, UUID) + sizeof(COFF::BigObjMagic);
43      if (Magic.size() < MinSize)
44        return file_magic::coff_import_library;
45
46      const char *Start = Magic.data() + offsetof(COFF::BigObjHeader, UUID);
47      if (memcmp(Start, COFF::BigObjMagic, sizeof(COFF::BigObjMagic)) == 0)
48        return file_magic::coff_object;
49      if (memcmp(Start, COFF::ClGlObjMagic, sizeof(COFF::BigObjMagic)) == 0)
50        return file_magic::coff_cl_gl_object;
51      return file_magic::coff_import_library;
52    }
53    // Windows resource file
54    if (startswith(Magic, "\0\0\0\0\x20\0\0\0\xFF"))
55      return file_magic::windows_resource;
56    // 0x0000 = COFF unknown machine type
57    if (Magic[1] == 0)
58      return file_magic::coff_object;
59    if (startswith(Magic, "\0asm"))
60      return file_magic::wasm_object;
61    break;
62  }
63  case 0xDE: // 0x0B17C0DE = BC wraper
64    if (startswith(Magic, "\xDE\xC0\x17\x0B"))
65      return file_magic::bitcode;
66    break;
67  case 'B':
68    if (startswith(Magic, "BC\xC0\xDE"))
69      return file_magic::bitcode;
70    break;
71  case '!':
72    if (startswith(Magic, "!<arch>\n") || startswith(Magic, "!<thin>\n"))
73      return file_magic::archive;
74    break;
75
76  case '\177':
77    if (startswith(Magic, "\177ELF") && Magic.size() >= 18) {
78      bool Data2MSB = Magic[5] == 2;
79      unsigned high = Data2MSB ? 16 : 17;
80      unsigned low = Data2MSB ? 17 : 16;
81      if (Magic[high] == 0) {
82        switch (Magic[low]) {
83        default:
84          return file_magic::elf;
85        case 1:
86          return file_magic::elf_relocatable;
87        case 2:
88          return file_magic::elf_executable;
89        case 3:
90          return file_magic::elf_shared_object;
91        case 4:
92          return file_magic::elf_core;
93        }
94      }
95      // It's still some type of ELF file.
96      return file_magic::elf;
97    }
98    break;
99
100  case 0xCA:
101    if (startswith(Magic, "\xCA\xFE\xBA\xBE") ||
102        startswith(Magic, "\xCA\xFE\xBA\xBF")) {
103      // This is complicated by an overlap with Java class files.
104      // See the Mach-O section in /usr/share/file/magic for details.
105      if (Magic.size() >= 8 && Magic[7] < 43)
106        return file_magic::macho_universal_binary;
107    }
108    break;
109
110  // The two magic numbers for mach-o are:
111  // 0xfeedface - 32-bit mach-o
112  // 0xfeedfacf - 64-bit mach-o
113  case 0xFE:
114  case 0xCE:
115  case 0xCF: {
116    uint16_t type = 0;
117    if (startswith(Magic, "\xFE\xED\xFA\xCE") ||
118        startswith(Magic, "\xFE\xED\xFA\xCF")) {
119      /* Native endian */
120      size_t MinSize;
121      if (Magic[3] == char(0xCE))
122        MinSize = sizeof(MachO::mach_header);
123      else
124        MinSize = sizeof(MachO::mach_header_64);
125      if (Magic.size() >= MinSize)
126        type = Magic[12] << 24 | Magic[13] << 12 | Magic[14] << 8 | Magic[15];
127    } else if (startswith(Magic, "\xCE\xFA\xED\xFE") ||
128               startswith(Magic, "\xCF\xFA\xED\xFE")) {
129      /* Reverse endian */
130      size_t MinSize;
131      if (Magic[0] == char(0xCE))
132        MinSize = sizeof(MachO::mach_header);
133      else
134        MinSize = sizeof(MachO::mach_header_64);
135      if (Magic.size() >= MinSize)
136        type = Magic[15] << 24 | Magic[14] << 12 | Magic[13] << 8 | Magic[12];
137    }
138    switch (type) {
139    default:
140      break;
141    case 1:
142      return file_magic::macho_object;
143    case 2:
144      return file_magic::macho_executable;
145    case 3:
146      return file_magic::macho_fixed_virtual_memory_shared_lib;
147    case 4:
148      return file_magic::macho_core;
149    case 5:
150      return file_magic::macho_preload_executable;
151    case 6:
152      return file_magic::macho_dynamically_linked_shared_lib;
153    case 7:
154      return file_magic::macho_dynamic_linker;
155    case 8:
156      return file_magic::macho_bundle;
157    case 9:
158      return file_magic::macho_dynamically_linked_shared_lib_stub;
159    case 10:
160      return file_magic::macho_dsym_companion;
161    case 11:
162      return file_magic::macho_kext_bundle;
163    }
164    break;
165  }
166  case 0xF0: // PowerPC Windows
167  case 0x83: // Alpha 32-bit
168  case 0x84: // Alpha 64-bit
169  case 0x66: // MPS R4000 Windows
170  case 0x50: // mc68K
171  case 0x4c: // 80386 Windows
172  case 0xc4: // ARMNT Windows
173    if (Magic[1] == 0x01)
174      return file_magic::coff_object;
175    LLVM_FALLTHROUGH;
176
177  case 0x90: // PA-RISC Windows
178  case 0x68: // mc68K Windows
179    if (Magic[1] == 0x02)
180      return file_magic::coff_object;
181    break;
182
183  case 'M': // Possible MS-DOS stub on Windows PE file
184    if (startswith(Magic, "MZ")) {
185      uint32_t off = read32le(Magic.data() + 0x3c);
186      // PE/COFF file, either EXE or DLL.
187      if (off < Magic.size() &&
188          memcmp(Magic.data() + off, COFF::PEMagic, sizeof(COFF::PEMagic)) == 0)
189        return file_magic::pecoff_executable;
190    }
191    break;
192
193  case 0x64: // x86-64 Windows.
194    if (Magic[1] == char(0x86))
195      return file_magic::coff_object;
196    break;
197
198  default:
199    break;
200  }
201  return file_magic::unknown;
202}
203
204std::error_code llvm::identify_magic(const Twine &Path, file_magic &Result) {
205  int FD;
206  if (std::error_code EC = openFileForRead(Path, FD))
207    return EC;
208
209  char Buffer[32];
210  int Length = read(FD, Buffer, sizeof(Buffer));
211  if (close(FD) != 0 || Length < 0)
212    return std::error_code(errno, std::generic_category());
213
214  Result = identify_magic(StringRef(Buffer, Length));
215  return std::error_code();
216}
217