Magic.cpp revision 321369 
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 (Magic.size() >= sizeof(COFF::WinResMagic) &&
55        memcmp(Magic.data(), COFF::WinResMagic, sizeof(COFF::WinResMagic)) == 0)
56      return file_magic::windows_resource;
57    // 0x0000 = COFF unknown machine type
58    if (Magic[1] == 0)
59      return file_magic::coff_object;
60    if (startswith(Magic, "\0asm"))
61      return file_magic::wasm_object;
62    break;
63  }
64  case 0xDE: // 0x0B17C0DE = BC wraper
65    if (startswith(Magic, "\xDE\xC0\x17\x0B"))
66      return file_magic::bitcode;
67    break;
68  case 'B':
69    if (startswith(Magic, "BC\xC0\xDE"))
70      return file_magic::bitcode;
71    break;
72  case '!':
73    if (startswith(Magic, "!<arch>\n") || startswith(Magic, "!<thin>\n"))
74      return file_magic::archive;
75    break;
76
77  case '\177':
78    if (startswith(Magic, "\177ELF") && Magic.size() >= 18) {
79      bool Data2MSB = Magic[5] == 2;
80      unsigned high = Data2MSB ? 16 : 17;
81      unsigned low = Data2MSB ? 17 : 16;
82      if (Magic[high] == 0) {
83        switch (Magic[low]) {
84        default:
85          return file_magic::elf;
86        case 1:
87          return file_magic::elf_relocatable;
88        case 2:
89          return file_magic::elf_executable;
90        case 3:
91          return file_magic::elf_shared_object;
92        case 4:
93          return file_magic::elf_core;
94        }
95      }
96      // It's still some type of ELF file.
97      return file_magic::elf;
98    }
99    break;
100
101  case 0xCA:
102    if (startswith(Magic, "\xCA\xFE\xBA\xBE") ||
103        startswith(Magic, "\xCA\xFE\xBA\xBF")) {
104      // This is complicated by an overlap with Java class files.
105      // See the Mach-O section in /usr/share/file/magic for details.
106      if (Magic.size() >= 8 && Magic[7] < 43)
107        return file_magic::macho_universal_binary;
108    }
109    break;
110
111  // The two magic numbers for mach-o are:
112  // 0xfeedface - 32-bit mach-o
113  // 0xfeedfacf - 64-bit mach-o
114  case 0xFE:
115  case 0xCE:
116  case 0xCF: {
117    uint16_t type = 0;
118    if (startswith(Magic, "\xFE\xED\xFA\xCE") ||
119        startswith(Magic, "\xFE\xED\xFA\xCF")) {
120      /* Native endian */
121      size_t MinSize;
122      if (Magic[3] == char(0xCE))
123        MinSize = sizeof(MachO::mach_header);
124      else
125        MinSize = sizeof(MachO::mach_header_64);
126      if (Magic.size() >= MinSize)
127        type = Magic[12] << 24 | Magic[13] << 12 | Magic[14] << 8 | Magic[15];
128    } else if (startswith(Magic, "\xCE\xFA\xED\xFE") ||
129               startswith(Magic, "\xCF\xFA\xED\xFE")) {
130      /* Reverse endian */
131      size_t MinSize;
132      if (Magic[0] == char(0xCE))
133        MinSize = sizeof(MachO::mach_header);
134      else
135        MinSize = sizeof(MachO::mach_header_64);
136      if (Magic.size() >= MinSize)
137        type = Magic[15] << 24 | Magic[14] << 12 | Magic[13] << 8 | Magic[12];
138    }
139    switch (type) {
140    default:
141      break;
142    case 1:
143      return file_magic::macho_object;
144    case 2:
145      return file_magic::macho_executable;
146    case 3:
147      return file_magic::macho_fixed_virtual_memory_shared_lib;
148    case 4:
149      return file_magic::macho_core;
150    case 5:
151      return file_magic::macho_preload_executable;
152    case 6:
153      return file_magic::macho_dynamically_linked_shared_lib;
154    case 7:
155      return file_magic::macho_dynamic_linker;
156    case 8:
157      return file_magic::macho_bundle;
158    case 9:
159      return file_magic::macho_dynamically_linked_shared_lib_stub;
160    case 10:
161      return file_magic::macho_dsym_companion;
162    case 11:
163      return file_magic::macho_kext_bundle;
164    }
165    break;
166  }
167  case 0xF0: // PowerPC Windows
168  case 0x83: // Alpha 32-bit
169  case 0x84: // Alpha 64-bit
170  case 0x66: // MPS R4000 Windows
171  case 0x50: // mc68K
172  case 0x4c: // 80386 Windows
173  case 0xc4: // ARMNT Windows
174    if (Magic[1] == 0x01)
175      return file_magic::coff_object;
176    LLVM_FALLTHROUGH;
177
178  case 0x90: // PA-RISC Windows
179  case 0x68: // mc68K Windows
180    if (Magic[1] == 0x02)
181      return file_magic::coff_object;
182    break;
183
184  case 'M': // Possible MS-DOS stub on Windows PE file
185    if (startswith(Magic, "MZ")) {
186      uint32_t off = read32le(Magic.data() + 0x3c);
187      // PE/COFF file, either EXE or DLL.
188      if (off < Magic.size() &&
189          memcmp(Magic.data() + off, COFF::PEMagic, sizeof(COFF::PEMagic)) == 0)
190        return file_magic::pecoff_executable;
191    }
192    break;
193
194  case 0x64: // x86-64 or ARM64 Windows.
195    if (Magic[1] == char(0x86) || Magic[1] == char(0xaa))
196      return file_magic::coff_object;
197    break;
198
199  default:
200    break;
201  }
202  return file_magic::unknown;
203}
204
205std::error_code llvm::identify_magic(const Twine &Path, file_magic &Result) {
206  int FD;
207  if (std::error_code EC = openFileForRead(Path, FD))
208    return EC;
209
210  char Buffer[32];
211  int Length = read(FD, Buffer, sizeof(Buffer));
212  if (close(FD) != 0 || Length < 0)
213    return std::error_code(errno, std::generic_category());
214
215  Result = identify_magic(StringRef(Buffer, Length));
216  return std::error_code();
217}
218