1  /* Cache the location of a link map hash table.
       2     Copyright (C) 1995-2023 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  }