bfd/elf.c

   1 /* ELF executable support for BFD.
   2    Copyright 1993 Free Software Foundation, Inc.
   3
   4 This file is part of BFD, the Binary File Descriptor library.
   5
   6 This program is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2 of the License, or
   9 (at your option) any later version.
  10
  11 This program is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with this program; if not, write to the Free Software
  18 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */
  19
  20 #include "bfd.h"
  21 #include "sysdep.h"
  22 #include "libbfd.h"
  23 #define ARCH_SIZE 0
  24 #include "libelf.h"
  25
  26 #ifndef INLINE
  27 #if __GNUC__ >= 2
  28 #define INLINE __inline__
  29 #else
  30 #define INLINE
  31 #endif
  32 #endif
  33
  34 /* Standard ELF hash function.  Do not change this function; you will
  35    cause invalid hash tables to be generated.  (Well, you would if this
  36    were being used yet.)  */
  37 unsigned long
  38 DEFUN (bfd_elf_hash, (name),
  39        CONST unsigned char *name)
  40 {
  41   unsigned long h = 0;
  42   unsigned long g;
  43   int ch;
  44
  45   while ((ch = *name++) != '\0')
  46     {
  47       h = (h << 4) + ch;
  48       if ((g = (h & 0xf0000000)) != 0)
  49         {
  50           h ^= g >> 24;
  51           h &= ~g;
  52         }
  53     }
  54   return h;
  55 }
  56
  57 /* Read a specified number of bytes at a specified offset in an ELF
  58    file, into a newly allocated buffer, and return a pointer to the
  59    buffer. */
  60
  61 static char *
  62 DEFUN (elf_read, (abfd, offset, size),
  63        bfd * abfd AND
  64        long offset AND
  65        int size)
  66 {
  67   char *buf;
  68
  69   if ((buf = bfd_alloc (abfd, size)) == NULL)
  70     {
  71       bfd_error = no_memory;
  72       return NULL;
  73     }
  74   if (bfd_seek (abfd, offset, SEEK_SET) == -1)
  75     {
  76       bfd_error = system_call_error;
  77       return NULL;
  78     }
  79   if (bfd_read ((PTR) buf, size, 1, abfd) != size)
  80     {
  81       bfd_error = system_call_error;
  82       return NULL;
  83     }
  84   return buf;
  85 }
  86
  87 boolean
  88 DEFUN (elf_mkobject, (abfd), bfd * abfd)
  89 {
  90   /* this just does initialization */
  91   /* coff_mkobject zalloc's space for tdata.coff_obj_data ... */
  92   elf_tdata (abfd) = (struct elf_obj_tdata *)
  93     bfd_zalloc (abfd, sizeof (struct elf_obj_tdata));
  94   if (elf_tdata (abfd) == 0)
  95     {
  96       bfd_error = no_memory;
  97       return false;
  98     }
  99   /* since everything is done at close time, do we need any
 100      initialization? */
 101
 102   return true;
 103 }
 104
 105 char *
 106 DEFUN (elf_get_str_section, (abfd, shindex),
 107        bfd * abfd AND
 108        unsigned int shindex)
 109 {
 110   Elf_Internal_Shdr **i_shdrp;
 111   char *shstrtab = NULL;
 112   unsigned int offset;
 113   unsigned int shstrtabsize;
 114
 115   i_shdrp = elf_elfsections (abfd);
 116   if (i_shdrp == 0 || i_shdrp[shindex] == 0)
 117     return 0;
 118
 119   shstrtab = i_shdrp[shindex]->rawdata;
 120   if (shstrtab == NULL)
 121     {
 122       /* No cached one, attempt to read, and cache what we read. */
 123       offset = i_shdrp[shindex]->sh_offset;
 124       shstrtabsize = i_shdrp[shindex]->sh_size;
 125       shstrtab = elf_read (abfd, offset, shstrtabsize);
 126       i_shdrp[shindex]->rawdata = (void *) shstrtab;
 127     }
 128   return shstrtab;
 129 }
 130
 131 char *
 132 DEFUN (elf_string_from_elf_section, (abfd, shindex, strindex),
 133        bfd * abfd AND
 134        unsigned int shindex AND
 135        unsigned int strindex)
 136 {
 137   Elf_Internal_Shdr *hdr;
 138
 139   if (strindex == 0)
 140     return "";
 141
 142   hdr = elf_elfsections (abfd)[shindex];
 143
 144   if (!hdr->rawdata
 145       && elf_get_str_section (abfd, shindex) == NULL)
 146     return NULL;
 147
 148   return ((char *) hdr->rawdata) + strindex;
 149 }
 150
 151 /*
 152 INTERNAL_FUNCTION
 153         bfd_elf_find_section
 154
 155 SYNOPSIS
 156         struct elf_internal_shdr *bfd_elf_find_section (bfd *abfd, char *name);
 157
 158 DESCRIPTION
 159         Helper functions for GDB to locate the string tables.
 160         Since BFD hides string tables from callers, GDB needs to use an
 161         internal hook to find them.  Sun's .stabstr, in particular,
 162         isn't even pointed to by the .stab section, so ordinary
 163         mechanisms wouldn't work to find it, even if we had some.
 164 */
 165
 166 struct elf_internal_shdr *
 167 DEFUN (bfd_elf_find_section, (abfd, name),
 168        bfd * abfd AND
 169        char *name)
 170 {
 171   Elf_Internal_Shdr **i_shdrp;
 172   char *shstrtab;
 173   unsigned int max;
 174   unsigned int i;
 175
 176   i_shdrp = elf_elfsections (abfd);
 177   if (i_shdrp != NULL)
 178     {
 179       shstrtab = elf_get_str_section (abfd, elf_elfheader (abfd)->e_shstrndx);
 180       if (shstrtab != NULL)
 181         {
 182           max = elf_elfheader (abfd)->e_shnum;
 183           for (i = 1; i < max; i++)
 184             if (!strcmp (&shstrtab[i_shdrp[i]->sh_name], name))
 185               return i_shdrp[i];
 186         }
 187     }
 188   return 0;
 189 }
 190
 191 const struct bfd_elf_arch_map bfd_elf_arch_map[] = {
 192   { bfd_arch_sparc, EM_SPARC },
 193   { bfd_arch_i386, EM_386 },
 194   { bfd_arch_m68k, EM_68K },
 195   { bfd_arch_m88k, EM_88K },
 196   { bfd_arch_i860, EM_860 },
 197   { bfd_arch_mips, EM_MIPS },
 198   { bfd_arch_hppa, EM_HPPA },
 199 };
 200
 201 const int bfd_elf_arch_map_size = sizeof (bfd_elf_arch_map) / sizeof (bfd_elf_arch_map[0]);
 202
 203 const char *const bfd_elf_section_type_names[] = {
 204   "SHT_NULL", "SHT_PROGBITS", "SHT_SYMTAB", "SHT_STRTAB",
 205   "SHT_RELA", "SHT_HASH", "SHT_DYNAMIC", "SHT_NOTE",
 206   "SHT_NOBITS", "SHT_REL", "SHT_SHLIB", "SHT_DYNSYM",
 207 };
 208
 209 /* ELF relocs are against symbols.  If we are producing relocateable
 210    output, and the reloc is against an external symbol, and nothing
 211    has given us any additional addend, the resulting reloc will also
 212    be against the same symbol.  In such a case, we don't want to
 213    change anything about the way the reloc is handled, since it will
 214    all be done at final link time.  Rather than put special case code
 215    into bfd_perform_relocation, all the reloc types use this howto
 216    function.  It just short circuits the reloc if producing
 217    relocateable output against an external symbol.  */
 218
 219 bfd_reloc_status_type
 220 bfd_elf_generic_reloc (abfd,
 221                        reloc_entry,
 222                        symbol,
 223                        data,
 224                        input_section,
 225                        output_bfd)
 226      bfd *abfd;
 227      arelent *reloc_entry;
 228      asymbol *symbol;
 229      PTR data;
 230      asection *input_section;
 231      bfd *output_bfd;
 232 {
 233   if (output_bfd != (bfd *) NULL
 234       && (symbol->flags & BSF_SECTION_SYM) == 0
 235       && reloc_entry->addend == 0)
 236     {
 237       reloc_entry->address += input_section->output_offset;
 238       return bfd_reloc_ok;
 239     }
 240
 241   return bfd_reloc_continue;
 242 }