Magic.cpp revision 341825 
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#include "llvm/Support/MemoryBuffer.h"
18
19#if !defined(_MSC_VER) && !defined(__MINGW32__)
20#include <unistd.h>
21#else
22#include <io.h>
23#endif
24
25using namespace llvm;
26using namespace llvm::support::endian;
27using namespace llvm::sys::fs;
28
29template <size_t N>
30static bool startswith(StringRef Magic, const char (&S)[N]) {
31  return Magic.startswith(StringRef(S, N - 1));
32}
33
34/// Identify the magic in magic.
35file_magic llvm::identify_magic(StringRef Magic) {
36  if (Magic.size() < 4)
37    return file_magic::unknown;
38  switch ((unsigned char)Magic[0]) {
39  case 0x00: {
40    // COFF bigobj, CL.exe's LTO object file, or short import library file
41    if (startswith(Magic, "\0\0\xFF\xFF")) {
42      size_t MinSize =
43          offsetof(COFF::BigObjHeader, UUID) + sizeof(COFF::BigObjMagic);
44      if (Magic.size() < MinSize)
45        return file_magic::coff_import_library;
46
47      const char *Start = Magic.data() + offsetof(COFF::BigObjHeader, UUID);
48      if (memcmp(Start, COFF::BigObjMagic, sizeof(COFF::BigObjMagic)) == 0)
49        return file_magic::coff_object;
50      if (memcmp(Start, COFF::ClGlObjMagic, sizeof(COFF::BigObjMagic)) == 0)
51        return file_magic::coff_cl_gl_object;
52      return file_magic::coff_import_library;
53    }
54    // Windows resource file
55    if (Magic.size() >= sizeof(COFF::WinResMagic) &&
56        memcmp(Magic.data(), COFF::WinResMagic, sizeof(COFF::WinResMagic)) == 0)
57      return file_magic::windows_resource;
58    // 0x0000 = COFF unknown machine type
59    if (Magic[1] == 0)
60      return file_magic::coff_object;
61    if (startswith(Magic, "\0asm"))
62      return file_magic::wasm_object;
63    break;
64  }
65  case 0xDE: // 0x0B17C0DE = BC wraper
66    if (startswith(Magic, "\xDE\xC0\x17\x0B"))
67      return file_magic::bitcode;
68    break;
69  case 'B':
70    if (startswith(Magic, "BC\xC0\xDE"))
71      return file_magic::bitcode;
72    break;
73  case '!':
74    if (startswith(Magic, "!<arch>\n") || startswith(Magic, "!<thin>\n"))
75      return file_magic::archive;
76    break;
77
78  case '\177':
79    if (startswith(Magic, "\177ELF") && Magic.size() >= 18) {
80      bool Data2MSB = Magic[5] == 2;
81      unsigned high = Data2MSB ? 16 : 17;
82      unsigned low = Data2MSB ? 17 : 16;
83      if (Magic[high] == 0) {
84        switch (Magic[low]) {
85        default:
86          return file_magic::elf;
87        case 1:
88          return file_magic::elf_relocatable;
89        case 2:
90          return file_magic::elf_executable;
91        case 3:
92          return file_magic::elf_shared_object;
93        case 4:
94          return file_magic::elf_core;
95        }
96      }
97      // It's still some type of ELF file.
98      return file_magic::elf;
99    }
100    break;
101
102  case 0xCA:
103    if (startswith(Magic, "\xCA\xFE\xBA\xBE") ||
104        startswith(Magic, "\xCA\xFE\xBA\xBF")) {
105      // This is complicated by an overlap with Java class files.
106      // See the Mach-O section in /usr/share/file/magic for details.
107      if (Magic.size() >= 8 && Magic[7] < 43)
108        return file_magic::macho_universal_binary;
109    }
110    break;
111
112  // The two magic numbers for mach-o are:
113  // 0xfeedface - 32-bit mach-o
114  // 0xfeedfacf - 64-bit mach-o
115  case 0xFE:
116  case 0xCE:
117  case 0xCF: {
118    uint16_t type = 0;
119    if (startswith(Magic, "\xFE\xED\xFA\xCE") ||
120        startswith(Magic, "\xFE\xED\xFA\xCF")) {
121      /* Native endian */
122      size_t MinSize;
123      if (Magic[3] == char(0xCE))
124        MinSize = sizeof(MachO::mach_header);
125      else
126        MinSize = sizeof(MachO::mach_header_64);
127      if (Magic.size() >= MinSize)
128        type = Magic[12] << 24 | Magic[13] << 12 | Magic[14] << 8 | Magic[15];
129    } else if (startswith(Magic, "\xCE\xFA\xED\xFE") ||
130               startswith(Magic, "\xCF\xFA\xED\xFE")) {
131      /* Reverse endian */
132      size_t MinSize;
133      if (Magic[0] == char(0xCE))
134        MinSize = sizeof(MachO::mach_header);
135      else
136        MinSize = sizeof(MachO::mach_header_64);
137      if (Magic.size() >= MinSize)
138        type = Magic[15] << 24 | Magic[14] << 12 | Magic[13] << 8 | Magic[12];
139    }
140    switch (type) {
141    default:
142      break;
143    case 1:
144      return file_magic::macho_object;
145    case 2:
146      return file_magic::macho_executable;
147    case 3:
148      return file_magic::macho_fixed_virtual_memory_shared_lib;
149    case 4:
150      return file_magic::macho_core;
151    case 5:
152      return file_magic::macho_preload_executable;
153    case 6:
154      return file_magic::macho_dynamically_linked_shared_lib;
155    case 7:
156      return file_magic::macho_dynamic_linker;
157    case 8:
158      return file_magic::macho_bundle;
159    case 9:
160      return file_magic::macho_dynamically_linked_shared_lib_stub;
161    case 10:
162      return file_magic::macho_dsym_companion;
163    case 11:
164      return file_magic::macho_kext_bundle;
165    }
166    break;
167  }
168  case 0xF0: // PowerPC Windows
169  case 0x83: // Alpha 32-bit
170  case 0x84: // Alpha 64-bit
171  case 0x66: // MPS R4000 Windows
172  case 0x50: // mc68K
173  case 0x4c: // 80386 Windows
174  case 0xc4: // ARMNT Windows
175    if (Magic[1] == 0x01)
176      return file_magic::coff_object;
177    LLVM_FALLTHROUGH;
178
179  case 0x90: // PA-RISC Windows
180  case 0x68: // mc68K Windows
181    if (Magic[1] == 0x02)
182      return file_magic::coff_object;
183    break;
184
185  case 'M': // Possible MS-DOS stub on Windows PE file or MSF/PDB file.
186    if (startswith(Magic, "MZ") && Magic.size() >= 0x3c + 4) {
187      uint32_t off = read32le(Magic.data() + 0x3c);
188      // PE/COFF file, either EXE or DLL.
189      if (Magic.substr(off).startswith(
190              StringRef(COFF::PEMagic, sizeof(COFF::PEMagic))))
191        return file_magic::pecoff_executable;
192    }
193    if (Magic.startswith("Microsoft C/C++ MSF 7.00\r\n"))
194      return file_magic::pdb;
195    break;
196
197  case 0x64: // x86-64 or ARM64 Windows.
198    if (Magic[1] == char(0x86) || Magic[1] == char(0xaa))
199      return file_magic::coff_object;
200    break;
201
202  default:
203    break;
204  }
205  return file_magic::unknown;
206}
207
208std::error_code llvm::identify_magic(const Twine &Path, file_magic &Result) {
209  auto FileOrError = MemoryBuffer::getFile(Path);
210  if (!FileOrError)
211    return FileOrError.getError();
212
213  std::unique_ptr<MemoryBuffer> FileBuffer = std::move(*FileOrError);
214  Result = identify_magic(FileBuffer->getBuffer());
215
216  return std::error_code();
217}
218