mozglue/linker/Elfxx.h
author Jim Blandy <jimb@mozilla.com>
Tue, 24 Jun 2014 22:12:07 -0700
changeset 199513 69d61e42d5dfbf4588b72449249ff3e7f2125304
parent 155714 88ac9143dd30ba7eadc72ff28e5ae4288deef9eb
child 225077 f7bcbc2534294cb583937cf3813e26646f08b74a
permissions -rw-r--r--
Bug 914753: Make Emacs file variable header lines correct, or at least consistent. DONTBUILD r=ehsan The -*- file variable lines -*- establish per-file settings that Emacs will pick up. This patch makes the following changes to those lines (and touches nothing else): - Never set the buffer's mode. Years ago, Emacs did not have a good JavaScript mode, so it made sense to use Java or C++ mode in .js files. However, Emacs has had js-mode for years now; it's perfectly serviceable, and is available and enabled by default in all major Emacs packagings. Selecting a mode in the -*- file variable line -*- is almost always the wrong thing to do anyway. It overrides Emacs's default choice, which is (now) reasonable; and even worse, it overrides settings the user might have made in their '.emacs' file for that file extension. It's only useful when there's something specific about that particular file that makes a particular mode appropriate. - Correctly propagate settings that establish the correct indentation level for this file: c-basic-offset and js2-basic-offset should be js-indent-level. Whatever value they're given should be preserved; different parts of our tree use different indentation styles. - We don't use tabs in Mozilla JS code. Always set indent-tabs-mode: nil. Remove tab-width: settings, at least in files that don't contain tab characters. - Remove js2-mode settings that belong in the user's .emacs file, like js2-skip-preprocessor-directives.

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef Elfxx_h
#define Elfxx_h

/**
 * Android system headers have two different elf.h file. The one under linux/
 * is the most complete.
 */
#ifdef ANDROID
#include <linux/elf.h>
#else
#include <elf.h>
#endif
#include <endian.h>

#if defined(__ARM_EABI__) && !defined(PT_ARM_EXIDX)
#define PT_ARM_EXIDX 0x70000001
#endif

/**
 * Generic ELF macros for the target system
 */
#ifdef __LP64__
#define Elf_(type) Elf64_ ## type
#define ELFCLASS ELFCLASS64
#define ELF_R_TYPE ELF64_R_TYPE
#define ELF_R_SYM ELF64_R_SYM
#ifndef ELF_ST_BIND
#define ELF_ST_BIND ELF64_ST_BIND
#endif
#else
#define Elf_(type) Elf32_ ## type
#define ELFCLASS ELFCLASS32
#define ELF_R_TYPE ELF32_R_TYPE
#define ELF_R_SYM ELF32_R_SYM
#ifndef ELF_ST_BIND
#define ELF_ST_BIND ELF32_ST_BIND
#endif
#endif

#ifndef __BYTE_ORDER
#error Cannot find endianness
#endif

#if __BYTE_ORDER == __LITTLE_ENDIAN
#define ELFDATA ELFDATA2LSB
#elif __BYTE_ORDER == __BIG_ENDIAN
#define ELFDATA ELFDATA2MSB
#endif

#ifdef __linux__
#define ELFOSABI ELFOSABI_LINUX
#ifdef EI_ABIVERSION
#define ELFABIVERSION 0
#endif
#else
#error Unknown ELF OSABI
#endif

#if defined(__i386__)
#define ELFMACHINE EM_386

// Doing this way probably doesn't scale to other architectures
#define R_ABS R_386_32
#define R_GLOB_DAT R_386_GLOB_DAT
#define R_JMP_SLOT R_386_JMP_SLOT
#define R_RELATIVE R_386_RELATIVE
#define RELOC(n) DT_REL ## n
#define UNSUPPORTED_RELOC(n) DT_RELA ## n
#define STR_RELOC(n) "DT_REL" # n
#define Reloc Rel

#elif defined(__x86_64__)
#define ELFMACHINE EM_X86_64

#define R_ABS R_X86_64_64
#define R_GLOB_DAT R_X86_64_GLOB_DAT
#define R_JMP_SLOT R_X86_64_JUMP_SLOT
#define R_RELATIVE R_X86_64_RELATIVE
#define RELOC(n) DT_RELA ## n
#define UNSUPPORTED_RELOC(n) DT_REL ## n
#define STR_RELOC(n) "DT_RELA" # n
#define Reloc Rela

#elif defined(__arm__)
#define ELFMACHINE EM_ARM

#ifndef R_ARM_ABS32
#define R_ARM_ABS32 2
#endif
#ifndef R_ARM_GLOB_DAT
#define R_ARM_GLOB_DAT 21
#endif
#ifndef R_ARM_JUMP_SLOT
#define R_ARM_JUMP_SLOT 22
#endif
#ifndef R_ARM_RELATIVE
#define R_ARM_RELATIVE 23
#endif

#define R_ABS R_ARM_ABS32
#define R_GLOB_DAT R_ARM_GLOB_DAT
#define R_JMP_SLOT R_ARM_JUMP_SLOT
#define R_RELATIVE R_ARM_RELATIVE
#define RELOC(n) DT_REL ## n
#define UNSUPPORTED_RELOC(n) DT_RELA ## n
#define STR_RELOC(n) "DT_REL" # n
#define Reloc Rel

#else
#error Unknown ELF machine type
#endif

/**
 * Android system headers don't have all definitions
 */
#ifndef STN_UNDEF
#define STN_UNDEF 0
#endif
#ifndef DT_INIT_ARRAY
#define DT_INIT_ARRAY 25
#endif
#ifndef DT_FINI_ARRAY
#define DT_FINI_ARRAY 26
#endif
#ifndef DT_INIT_ARRAYSZ
#define DT_INIT_ARRAYSZ 27
#endif
#ifndef DT_FINI_ARRAYSZ
#define DT_FINI_ARRAYSZ 28
#endif
#ifndef DT_RELACOUNT
#define DT_RELACOUNT 0x6ffffff9
#endif
#ifndef DT_RELCOUNT
#define DT_RELCOUNT 0x6ffffffa
#endif
#ifndef DT_VERSYM
#define DT_VERSYM 0x6ffffff0
#endif
#ifndef DT_VERDEF
#define DT_VERDEF 0x6ffffffc
#endif
#ifndef DT_VERDEFNUM
#define DT_VERDEFNUM 0x6ffffffd
#endif
#ifndef DT_VERNEED
#define DT_VERNEED 0x6ffffffe
#endif
#ifndef DT_VERNEEDNUM
#define DT_VERNEEDNUM 0x6fffffff
#endif
#ifndef DT_FLAGS_1
#define DT_FLAGS_1 0x6ffffffb
#endif
#ifndef DT_FLAGS
#define DT_FLAGS 30
#endif
#ifndef DF_SYMBOLIC
#define DF_SYMBOLIC 0x00000002
#endif
#ifndef DF_TEXTREL
#define DF_TEXTREL 0x00000004
#endif

namespace Elf {

/**
 * Define a few basic Elf Types
 */
typedef Elf_(Phdr) Phdr;
typedef Elf_(Dyn) Dyn;
typedef Elf_(Sym) Sym;
typedef Elf_(Addr) Addr;
typedef Elf_(Word) Word;
typedef Elf_(Half) Half;

/**
 * Helper class around the standard Elf header struct
 */
struct Ehdr: public Elf_(Ehdr)
{
  /**
   * Equivalent to reinterpret_cast<const Ehdr *>(buf), but additionally
   * checking that this is indeed an Elf header and that the Elf type
   * corresponds to that of the system
   */
  static const Ehdr *validate(const void *buf);
};

/**
 * Elf String table
 */
class Strtab: public UnsizedArray<const char>
{
public:
  /**
   * Returns the string at the given index in the table
   */
  const char *GetStringAt(off_t index) const
  {
    return &UnsizedArray<const char>::operator[](index);
  }
};

/**
 * Helper class around Elf relocation.
 */
struct Rel: public Elf_(Rel)
{
  /**
   * Returns the addend for the relocation, which is the value stored
   * at r_offset.
   */
  Addr GetAddend(void *base) const
  {
    return *(reinterpret_cast<const Addr *>(
                   reinterpret_cast<const char *>(base) + r_offset));
  }
};

/**
 * Helper class around Elf relocation with addend.
 */
struct Rela: public Elf_(Rela)
{
  /**
   * Returns the addend for the relocation.
   */
  Addr GetAddend(void *base) const
  {
    return r_addend;
  }
};

} /* namespace Elf */

#endif /* Elfxx_h */