elf/dl-setup_hash.c

   1 /* Cache the location of a link map hash table.
   2    Copyright (C) 1995-2022 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <assert.h>
  20 #include <link.h>
  21 #include <ldsodefs.h>
  22
  23 void
  24 _dl_setup_hash (struct link_map *map)
  25 {
  26   Elf_Symndx *hash;
  27
  28   if (__glibc_likely (map->l_info[ELF_MACHINE_GNU_HASH_ADDRIDX] != NULL))
  29     {
  30       Elf32_Word *hash32
  31         = (void *) D_PTR (map, l_info[ELF_MACHINE_GNU_HASH_ADDRIDX]);
  32       map->l_nbuckets = *hash32++;
  33       Elf32_Word symbias = *hash32++;
  34       Elf32_Word bitmask_nwords = *hash32++;
  35       /* Must be a power of two.  */
  36       assert ((bitmask_nwords & (bitmask_nwords - 1)) == 0);
  37       map->l_gnu_bitmask_idxbits = bitmask_nwords - 1;
  38       map->l_gnu_shift = *hash32++;
  39
  40       map->l_gnu_bitmask = (ElfW(Addr) *) hash32;
  41       hash32 += __ELF_NATIVE_CLASS / 32 * bitmask_nwords;
  42
  43       map->l_gnu_buckets = hash32;
  44       hash32 += map->l_nbuckets;
  45       map->l_gnu_chain_zero = hash32 - symbias;
  46
  47       /* Initialize MIPS xhash translation table.  */
  48       ELF_MACHINE_XHASH_SETUP (hash32, symbias, map);
  49
  50       return;
  51     }
  52
  53   if (!map->l_info[DT_HASH])
  54     return;
  55   hash = (void *) D_PTR (map, l_info[DT_HASH]);
  56
  57   map->l_nbuckets = *hash++;
  58   /* Skip nchain.  */
  59   hash++;
  60   map->l_buckets = hash;
  61   hash += map->l_nbuckets;
  62   map->l_chain = hash;
  63 }