mozglue/linker/Elfxx.h

   1 /* This Source Code Form is subject to the terms of the Mozilla Public
   2  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
   3  * You can obtain one at http://mozilla.org/MPL/2.0/. */
   4
   5 #ifndef Elfxx_h
   6 #define Elfxx_h
   7
   8 #include "Utils.h"
   9
  10 /**
  11  * Android system headers have two different elf.h file. The one under linux/
  12  * is the most complete on older Android API versions without unified headers.
  13  */
  14 #if defined(ANDROID) && __ANDROID_API__ < 21 && !defined(__ANDROID_API_L__)
  15 #  include <linux/elf.h>
  16 #else
  17 #  include <elf.h>
  18 #endif
  19 #include <endian.h>
  20
  21 #if defined(__ARM_EABI__) && !defined(PT_ARM_EXIDX)
  22 #  define PT_ARM_EXIDX 0x70000001
  23 #endif
  24
  25 /**
  26  * Generic ELF macros for the target system
  27  */
  28 #ifdef __LP64__
  29 #  define Elf_(type) Elf64_##type
  30 #  define ELFCLASS ELFCLASS64
  31 #  define ELF_R_TYPE ELF64_R_TYPE
  32 #  define ELF_R_SYM ELF64_R_SYM
  33 #  ifndef ELF_ST_BIND
  34 #    define ELF_ST_BIND ELF64_ST_BIND
  35 #  endif
  36 #else
  37 #  define Elf_(type) Elf32_##type
  38 #  define ELFCLASS ELFCLASS32
  39 #  define ELF_R_TYPE ELF32_R_TYPE
  40 #  define ELF_R_SYM ELF32_R_SYM
  41 #  ifndef ELF_ST_BIND
  42 #    define ELF_ST_BIND ELF32_ST_BIND
  43 #  endif
  44 #endif
  45
  46 #ifndef __BYTE_ORDER
  47 #  error Cannot find endianness
  48 #endif
  49
  50 #if __BYTE_ORDER == __LITTLE_ENDIAN
  51 #  define ELFDATA ELFDATA2LSB
  52 #elif __BYTE_ORDER == __BIG_ENDIAN
  53 #  define ELFDATA ELFDATA2MSB
  54 #endif
  55
  56 #ifdef __linux__
  57 #  define ELFOSABI ELFOSABI_LINUX
  58 #  ifdef EI_ABIVERSION
  59 #    define ELFABIVERSION 0
  60 #  endif
  61 #else
  62 #  error Unknown ELF OSABI
  63 #endif
  64
  65 #if defined(__i386__)
  66 #  define ELFMACHINE EM_386
  67
  68 // Doing this way probably doesn't scale to other architectures
  69 #  define R_ABS R_386_32
  70 #  define R_GLOB_DAT R_386_GLOB_DAT
  71 #  define R_JMP_SLOT R_386_JMP_SLOT
  72 #  define R_RELATIVE R_386_RELATIVE
  73 #  define RELOC(n) DT_REL##n
  74 #  define UNSUPPORTED_RELOC(n) DT_RELA##n
  75 #  define STR_RELOC(n) "DT_REL" #n
  76 #  define Reloc Rel
  77
  78 #elif defined(__x86_64__)
  79 #  define ELFMACHINE EM_X86_64
  80
  81 #  define R_ABS R_X86_64_64
  82 #  define R_GLOB_DAT R_X86_64_GLOB_DAT
  83 #  define R_JMP_SLOT R_X86_64_JUMP_SLOT
  84 #  define R_RELATIVE R_X86_64_RELATIVE
  85 #  define RELOC(n) DT_RELA##n
  86 #  define UNSUPPORTED_RELOC(n) DT_REL##n
  87 #  define STR_RELOC(n) "DT_RELA" #n
  88 #  define Reloc Rela
  89
  90 #elif defined(__arm__)
  91 #  define ELFMACHINE EM_ARM
  92
  93 #  ifndef R_ARM_ABS32
  94 #    define R_ARM_ABS32 2
  95 #  endif
  96 #  ifndef R_ARM_GLOB_DAT
  97 #    define R_ARM_GLOB_DAT 21
  98 #  endif
  99 #  ifndef R_ARM_JUMP_SLOT
 100 #    define R_ARM_JUMP_SLOT 22
 101 #  endif
 102 #  ifndef R_ARM_RELATIVE
 103 #    define R_ARM_RELATIVE 23
 104 #  endif
 105
 106 #  define R_ABS R_ARM_ABS32
 107 #  define R_GLOB_DAT R_ARM_GLOB_DAT
 108 #  define R_JMP_SLOT R_ARM_JUMP_SLOT
 109 #  define R_RELATIVE R_ARM_RELATIVE
 110 #  define RELOC(n) DT_REL##n
 111 #  define UNSUPPORTED_RELOC(n) DT_RELA##n
 112 #  define STR_RELOC(n) "DT_REL" #n
 113 #  define Reloc Rel
 114
 115 #elif defined(__aarch64__)
 116 #  define ELFMACHINE EM_AARCH64
 117
 118 #  define R_ABS R_AARCH64_ABS64
 119 #  define R_GLOB_DAT R_AARCH64_GLOB_DAT
 120 #  define R_JMP_SLOT R_AARCH64_JUMP_SLOT
 121 #  define R_RELATIVE R_AARCH64_RELATIVE
 122 #  define RELOC(n) DT_RELA##n
 123 #  define UNSUPPORTED_RELOC(n) DT_REL##n
 124 #  define STR_RELOC(n) "DT_RELA" #n
 125 #  define Reloc Rela
 126
 127 #else
 128 #  error Unknown ELF machine type
 129 #endif
 130
 131 /**
 132  * Android system headers don't have all definitions
 133  */
 134 #ifndef STN_UNDEF
 135 #  define STN_UNDEF 0
 136 #endif
 137 #ifndef DT_INIT_ARRAY
 138 #  define DT_INIT_ARRAY 25
 139 #endif
 140 #ifndef DT_FINI_ARRAY
 141 #  define DT_FINI_ARRAY 26
 142 #endif
 143 #ifndef DT_INIT_ARRAYSZ
 144 #  define DT_INIT_ARRAYSZ 27
 145 #endif
 146 #ifndef DT_FINI_ARRAYSZ
 147 #  define DT_FINI_ARRAYSZ 28
 148 #endif
 149 #ifndef DT_RELACOUNT
 150 #  define DT_RELACOUNT 0x6ffffff9
 151 #endif
 152 #ifndef DT_RELCOUNT
 153 #  define DT_RELCOUNT 0x6ffffffa
 154 #endif
 155 #ifndef DT_VERSYM
 156 #  define DT_VERSYM 0x6ffffff0
 157 #endif
 158 #ifndef DT_VERDEF
 159 #  define DT_VERDEF 0x6ffffffc
 160 #endif
 161 #ifndef DT_VERDEFNUM
 162 #  define DT_VERDEFNUM 0x6ffffffd
 163 #endif
 164 #ifndef DT_VERNEED
 165 #  define DT_VERNEED 0x6ffffffe
 166 #endif
 167 #ifndef DT_VERNEEDNUM
 168 #  define DT_VERNEEDNUM 0x6fffffff
 169 #endif
 170 #ifndef DT_FLAGS_1
 171 #  define DT_FLAGS_1 0x6ffffffb
 172 #endif
 173 #ifndef DT_FLAGS
 174 #  define DT_FLAGS 30
 175 #endif
 176 #ifndef DF_SYMBOLIC
 177 #  define DF_SYMBOLIC 0x00000002
 178 #endif
 179 #ifndef DF_TEXTREL
 180 #  define DF_TEXTREL 0x00000004
 181 #endif
 182
 183 namespace Elf {
 184
 185 /**
 186  * Define a few basic Elf Types
 187  */
 188 typedef Elf_(Phdr) Phdr;
 189 typedef Elf_(Dyn) Dyn;
 190 typedef Elf_(Sym) Sym;
 191 typedef Elf_(Addr) Addr;
 192 typedef Elf_(Word) Word;
 193 typedef Elf_(Half) Half;
 194
 195 /**
 196  * Helper class around the standard Elf header struct
 197  */
 198 struct Ehdr : public Elf_(Ehdr) {
 199   /**
 200    * Equivalent to reinterpret_cast<const Ehdr *>(buf), but additionally
 201    * checking that this is indeed an Elf header and that the Elf type
 202    * corresponds to that of the system
 203    */
 204   static const Ehdr* validate(const void* buf);
 205 };
 206
 207 /**
 208  * Elf String table
 209  */
 210 class Strtab : public UnsizedArray<const char> {
 211  public:
 212   /**
 213    * Returns the string at the given index in the table
 214    */
 215   const char* GetStringAt(off_t index) const {
 216     return &UnsizedArray<const char>::operator[](index);
 217   }
 218 };
 219
 220 /**
 221  * Helper class around Elf relocation.
 222  */
 223 struct Rel : public Elf_(Rel) {
 224   /**
 225    * Returns the addend for the relocation, which is the value stored
 226    * at r_offset.
 227    */
 228   Addr GetAddend(void* base) const {
 229     return *(reinterpret_cast<const Addr*>(reinterpret_cast<const char*>(base) +
 230                                            r_offset));
 231   }
 232 };
 233
 234 /**
 235  * Helper class around Elf relocation with addend.
 236  */
 237 struct Rela : public Elf_(Rela) {
 238   /**
 239    * Returns the addend for the relocation.
 240    */
 241   Addr GetAddend(void* base) const { return r_addend; }
 242 };
 243
 244 } /* namespace Elf */
 245
 246 #endif /* Elfxx_h */