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 #include <elf.h>
  11 #include <endian.h>
  12
  13 /**
  14  * Generic ELF macros for the target system
  15  */
  16 #ifdef __LP64__
  17 #  define Elf_(type) Elf64_##type
  18 #  define ELFCLASS ELFCLASS64
  19 #  define ELF_R_TYPE ELF64_R_TYPE
  20 #  define ELF_R_SYM ELF64_R_SYM
  21 #  ifndef ELF_ST_BIND
  22 #    define ELF_ST_BIND ELF64_ST_BIND
  23 #  endif
  24 #else
  25 #  define Elf_(type) Elf32_##type
  26 #  define ELFCLASS ELFCLASS32
  27 #  define ELF_R_TYPE ELF32_R_TYPE
  28 #  define ELF_R_SYM ELF32_R_SYM
  29 #  ifndef ELF_ST_BIND
  30 #    define ELF_ST_BIND ELF32_ST_BIND
  31 #  endif
  32 #endif
  33
  34 #ifndef __BYTE_ORDER
  35 #  error Cannot find endianness
  36 #endif
  37
  38 #if __BYTE_ORDER == __LITTLE_ENDIAN
  39 #  define ELFDATA ELFDATA2LSB
  40 #elif __BYTE_ORDER == __BIG_ENDIAN
  41 #  define ELFDATA ELFDATA2MSB
  42 #endif
  43
  44 #ifdef __linux__
  45 #  define ELFOSABI ELFOSABI_LINUX
  46 #  ifdef EI_ABIVERSION
  47 #    define ELFABIVERSION 0
  48 #  endif
  49 #else
  50 #  error Unknown ELF OSABI
  51 #endif
  52
  53 #if defined(__i386__)
  54 #  define ELFMACHINE EM_386
  55
  56 // Doing this way probably doesn't scale to other architectures
  57 #  define R_ABS R_386_32
  58 #  define R_GLOB_DAT R_386_GLOB_DAT
  59 #  define R_JMP_SLOT R_386_JMP_SLOT
  60 #  define R_RELATIVE R_386_RELATIVE
  61 #  define RELOC(n) DT_REL##n
  62 #  define UNSUPPORTED_RELOC(n) DT_RELA##n
  63 #  define STR_RELOC(n) "DT_REL" #n
  64 #  define Reloc Rel
  65
  66 #elif defined(__x86_64__)
  67 #  define ELFMACHINE EM_X86_64
  68
  69 #  define R_ABS R_X86_64_64
  70 #  define R_GLOB_DAT R_X86_64_GLOB_DAT
  71 #  define R_JMP_SLOT R_X86_64_JUMP_SLOT
  72 #  define R_RELATIVE R_X86_64_RELATIVE
  73 #  define RELOC(n) DT_RELA##n
  74 #  define UNSUPPORTED_RELOC(n) DT_REL##n
  75 #  define STR_RELOC(n) "DT_RELA" #n
  76 #  define Reloc Rela
  77
  78 #elif defined(__arm__)
  79 #  define ELFMACHINE EM_ARM
  80
  81 #  ifndef R_ARM_ABS32
  82 #    define R_ARM_ABS32 2
  83 #  endif
  84 #  ifndef R_ARM_GLOB_DAT
  85 #    define R_ARM_GLOB_DAT 21
  86 #  endif
  87 #  ifndef R_ARM_JUMP_SLOT
  88 #    define R_ARM_JUMP_SLOT 22
  89 #  endif
  90 #  ifndef R_ARM_RELATIVE
  91 #    define R_ARM_RELATIVE 23
  92 #  endif
  93
  94 #  define R_ABS R_ARM_ABS32
  95 #  define R_GLOB_DAT R_ARM_GLOB_DAT
  96 #  define R_JMP_SLOT R_ARM_JUMP_SLOT
  97 #  define R_RELATIVE R_ARM_RELATIVE
  98 #  define RELOC(n) DT_REL##n
  99 #  define UNSUPPORTED_RELOC(n) DT_RELA##n
 100 #  define STR_RELOC(n) "DT_REL" #n
 101 #  define Reloc Rel
 102
 103 #elif defined(__aarch64__)
 104 #  define ELFMACHINE EM_AARCH64
 105
 106 #  define R_ABS R_AARCH64_ABS64
 107 #  define R_GLOB_DAT R_AARCH64_GLOB_DAT
 108 #  define R_JMP_SLOT R_AARCH64_JUMP_SLOT
 109 #  define R_RELATIVE R_AARCH64_RELATIVE
 110 #  define RELOC(n) DT_RELA##n
 111 #  define UNSUPPORTED_RELOC(n) DT_REL##n
 112 #  define STR_RELOC(n) "DT_RELA" #n
 113 #  define Reloc Rela
 114
 115 #else
 116 #  error Unknown ELF machine type
 117 #endif
 118
 119 namespace Elf {
 120
 121 /**
 122  * Define a few basic Elf Types
 123  */
 124 typedef Elf_(Phdr) Phdr;
 125 typedef Elf_(Dyn) Dyn;
 126 typedef Elf_(Sym) Sym;
 127 typedef Elf_(Addr) Addr;
 128 typedef Elf_(Word) Word;
 129 typedef Elf_(Half) Half;
 130
 131 /**
 132  * Helper class around the standard Elf header struct
 133  */
 134 struct Ehdr : public Elf_(Ehdr) {
 135   /**
 136    * Equivalent to reinterpret_cast<const Ehdr *>(buf), but additionally
 137    * checking that this is indeed an Elf header and that the Elf type
 138    * corresponds to that of the system
 139    */
 140   static const Ehdr* validate(const void* buf);
 141 };
 142
 143 /**
 144  * Elf String table
 145  */
 146 class Strtab : public UnsizedArray<const char> {
 147  public:
 148   /**
 149    * Returns the string at the given index in the table
 150    */
 151   const char* GetStringAt(off_t index) const {
 152     return &UnsizedArray<const char>::operator[](index);
 153   }
 154 };
 155
 156 /**
 157  * Helper class around Elf relocation.
 158  */
 159 struct Rel
 160     : public Elf_(Rel){/**
 161                         * Returns the addend for the relocation, which is the
 162                         * value stored at r_offset.
 163                         */
 164                        Addr GetAddend(void* base)
 165                            const {return *(reinterpret_cast<const Addr*>(
 166                                reinterpret_cast<const char*>(base) + r_offset));
 167 }  // namespace Elf
 168 }
 169 ;
 170
 171 /**
 172  * Helper class around Elf relocation with addend.
 173  */
 174 struct Rela
 175     : public Elf_(Rela){/**
 176                          * Returns the addend for the relocation.
 177                          */
 178                         Addr GetAddend(void* base) const {return r_addend;
 179 }
 180 }
 181 ;
 182
 183 } /* namespace Elf */
 184
 185 #endif /* Elfxx_h */