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 /**
   9  * Android system headers have two different elf.h file. The one under linux/
  10  * is the most complete on older Android API versions without unified headers.
  11  */
  12 #if defined(ANDROID) && __ANDROID_API__ < 21 && !defined(__ANDROID_API_L__)
  13 #include <linux/elf.h>
  14 #else
  15 #include <elf.h>
  16 #endif
  17 #include <endian.h>
  18
  19 #if defined(__ARM_EABI__) && !defined(PT_ARM_EXIDX)
  20 #define PT_ARM_EXIDX 0x70000001
  21 #endif
  22
  23 /**
  24  * Generic ELF macros for the target system
  25  */
  26 #ifdef __LP64__
  27 #define Elf_(type) Elf64_ ## type
  28 #define ELFCLASS ELFCLASS64
  29 #define ELF_R_TYPE ELF64_R_TYPE
  30 #define ELF_R_SYM ELF64_R_SYM
  31 #ifndef ELF_ST_BIND
  32 #define ELF_ST_BIND ELF64_ST_BIND
  33 #endif
  34 #else
  35 #define Elf_(type) Elf32_ ## type
  36 #define ELFCLASS ELFCLASS32
  37 #define ELF_R_TYPE ELF32_R_TYPE
  38 #define ELF_R_SYM ELF32_R_SYM
  39 #ifndef ELF_ST_BIND
  40 #define ELF_ST_BIND ELF32_ST_BIND
  41 #endif
  42 #endif
  43
  44 #ifndef __BYTE_ORDER
  45 #error Cannot find endianness
  46 #endif
  47
  48 #if __BYTE_ORDER == __LITTLE_ENDIAN
  49 #define ELFDATA ELFDATA2LSB
  50 #elif __BYTE_ORDER == __BIG_ENDIAN
  51 #define ELFDATA ELFDATA2MSB
  52 #endif
  53
  54 #ifdef __linux__
  55 #define ELFOSABI ELFOSABI_LINUX
  56 #ifdef EI_ABIVERSION
  57 #define ELFABIVERSION 0
  58 #endif
  59 #else
  60 #error Unknown ELF OSABI
  61 #endif
  62
  63 #if defined(__i386__)
  64 #define ELFMACHINE EM_386
  65
  66 // Doing this way probably doesn't scale to other architectures
  67 #define R_ABS R_386_32
  68 #define R_GLOB_DAT R_386_GLOB_DAT
  69 #define R_JMP_SLOT R_386_JMP_SLOT
  70 #define R_RELATIVE R_386_RELATIVE
  71 #define RELOC(n) DT_REL ## n
  72 #define UNSUPPORTED_RELOC(n) DT_RELA ## n
  73 #define STR_RELOC(n) "DT_REL" # n
  74 #define Reloc Rel
  75
  76 #elif defined(__x86_64__)
  77 #define ELFMACHINE EM_X86_64
  78
  79 #define R_ABS R_X86_64_64
  80 #define R_GLOB_DAT R_X86_64_GLOB_DAT
  81 #define R_JMP_SLOT R_X86_64_JUMP_SLOT
  82 #define R_RELATIVE R_X86_64_RELATIVE
  83 #define RELOC(n) DT_RELA ## n
  84 #define UNSUPPORTED_RELOC(n) DT_REL ## n
  85 #define STR_RELOC(n) "DT_RELA" # n
  86 #define Reloc Rela
  87
  88 #elif defined(__arm__)
  89 #define ELFMACHINE EM_ARM
  90
  91 #ifndef R_ARM_ABS32
  92 #define R_ARM_ABS32 2
  93 #endif
  94 #ifndef R_ARM_GLOB_DAT
  95 #define R_ARM_GLOB_DAT 21
  96 #endif
  97 #ifndef R_ARM_JUMP_SLOT
  98 #define R_ARM_JUMP_SLOT 22
  99 #endif
 100 #ifndef R_ARM_RELATIVE
 101 #define R_ARM_RELATIVE 23
 102 #endif
 103
 104 #define R_ABS R_ARM_ABS32
 105 #define R_GLOB_DAT R_ARM_GLOB_DAT
 106 #define R_JMP_SLOT R_ARM_JUMP_SLOT
 107 #define R_RELATIVE R_ARM_RELATIVE
 108 #define RELOC(n) DT_REL ## n
 109 #define UNSUPPORTED_RELOC(n) DT_RELA ## n
 110 #define STR_RELOC(n) "DT_REL" # n
 111 #define Reloc Rel
 112
 113 #elif defined(__aarch64__)
 114 #define ELFMACHINE EM_AARCH64
 115
 116 #define R_ABS R_AARCH64_ABS64
 117 #define R_GLOB_DAT R_AARCH64_GLOB_DAT
 118 #define R_JMP_SLOT R_AARCH64_JUMP_SLOT
 119 #define R_RELATIVE R_AARCH64_RELATIVE
 120 #define RELOC(n) DT_RELA ## n
 121 #define UNSUPPORTED_RELOC(n) DT_REL ## n
 122 #define STR_RELOC(n) "DT_RELA" # n
 123 #define Reloc Rela
 124
 125 #else
 126 #error Unknown ELF machine type
 127 #endif
 128
 129 /**
 130  * Android system headers don't have all definitions
 131  */
 132 #ifndef STN_UNDEF
 133 #define STN_UNDEF 0
 134 #endif
 135 #ifndef DT_INIT_ARRAY
 136 #define DT_INIT_ARRAY 25
 137 #endif
 138 #ifndef DT_FINI_ARRAY
 139 #define DT_FINI_ARRAY 26
 140 #endif
 141 #ifndef DT_INIT_ARRAYSZ
 142 #define DT_INIT_ARRAYSZ 27
 143 #endif
 144 #ifndef DT_FINI_ARRAYSZ
 145 #define DT_FINI_ARRAYSZ 28
 146 #endif
 147 #ifndef DT_RELACOUNT
 148 #define DT_RELACOUNT 0x6ffffff9
 149 #endif
 150 #ifndef DT_RELCOUNT
 151 #define DT_RELCOUNT 0x6ffffffa
 152 #endif
 153 #ifndef DT_VERSYM
 154 #define DT_VERSYM 0x6ffffff0
 155 #endif
 156 #ifndef DT_VERDEF
 157 #define DT_VERDEF 0x6ffffffc
 158 #endif
 159 #ifndef DT_VERDEFNUM
 160 #define DT_VERDEFNUM 0x6ffffffd
 161 #endif
 162 #ifndef DT_VERNEED
 163 #define DT_VERNEED 0x6ffffffe
 164 #endif
 165 #ifndef DT_VERNEEDNUM
 166 #define DT_VERNEEDNUM 0x6fffffff
 167 #endif
 168 #ifndef DT_FLAGS_1
 169 #define DT_FLAGS_1 0x6ffffffb
 170 #endif
 171 #ifndef DT_FLAGS
 172 #define DT_FLAGS 30
 173 #endif
 174 #ifndef DF_SYMBOLIC
 175 #define DF_SYMBOLIC 0x00000002
 176 #endif
 177 #ifndef DF_TEXTREL
 178 #define DF_TEXTREL 0x00000004
 179 #endif
 180
 181 namespace Elf {
 182
 183 /**
 184  * Define a few basic Elf Types
 185  */
 186 typedef Elf_(Phdr) Phdr;
 187 typedef Elf_(Dyn) Dyn;
 188 typedef Elf_(Sym) Sym;
 189 typedef Elf_(Addr) Addr;
 190 typedef Elf_(Word) Word;
 191 typedef Elf_(Half) Half;
 192
 193 /**
 194  * Helper class around the standard Elf header struct
 195  */
 196 struct Ehdr: public Elf_(Ehdr)
 197 {
 198   /**
 199    * Equivalent to reinterpret_cast<const Ehdr *>(buf), but additionally
 200    * checking that this is indeed an Elf header and that the Elf type
 201    * corresponds to that of the system
 202    */
 203   static const Ehdr *validate(const void *buf);
 204 };
 205
 206 /**
 207  * Elf String table
 208  */
 209 class Strtab: public UnsizedArray<const char>
 210 {
 211 public:
 212   /**
 213    * Returns the string at the given index in the table
 214    */
 215   const char *GetStringAt(off_t index) const
 216   {
 217     return &UnsizedArray<const char>::operator[](index);
 218   }
 219 };
 220
 221 /**
 222  * Helper class around Elf relocation.
 223  */
 224 struct Rel: public Elf_(Rel)
 225 {
 226   /**
 227    * Returns the addend for the relocation, which is the value stored
 228    * at r_offset.
 229    */
 230   Addr GetAddend(void *base) const
 231   {
 232     return *(reinterpret_cast<const Addr *>(
 233                    reinterpret_cast<const char *>(base) + r_offset));
 234   }
 235 };
 236
 237 /**
 238  * Helper class around Elf relocation with addend.
 239  */
 240 struct Rela: public Elf_(Rela)
 241 {
 242   /**
 243    * Returns the addend for the relocation.
 244    */
 245   Addr GetAddend(void *base) const
 246   {
 247     return r_addend;
 248   }
 249 };
 250
 251 } /* namespace Elf */
 252
 253 #endif /* Elfxx_h */