elf/dl-addr-obj.c

   1 /* Determine if address is inside object load segments.
   2    Copyright (C) 1996-2019 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 <link.h>
  20 #include <elf.h>
  21
  22 /* Return non-zero if ADDR lies within one of L's loadable segments.
  23    We have three cases we care about.
  24
  25    Case 1: addr is above a segment.
  26    +==================+<- l_map_end
  27    |                  |<- addr
  28    |------------------|<- l_addr + p_vaddr + p_memsz
  29    |                  |
  30    |                  |
  31    |------------------|<- l_addr + p_vaddr
  32    |------------------|<- l_addr
  33    |                  |
  34    +==================+<- l_map_start
  35
  36    Case 2: addr is within a segments.
  37    +==================+<- l_map_end
  38    |                  |
  39    |------------------|<- l_addr + p_vaddr + p_memsz
  40    |                  |<- addr
  41    |                  |
  42    |------------------|<- l_addr + p_vaddr
  43    |------------------|<- l_addr
  44    |                  |
  45    +==================+<- l_map_start
  46
  47    Case 3: addr is below a segments.
  48    +==================+<- l_map_end
  49    |                  |
  50    |------------------|<- l_addr + p_vaddr + p_memsz
  51    |                  |
  52    |                  |
  53    |------------------|<- l_addr + p_vaddr
  54    |------------------|<- l_addr
  55    |                  |<- addr
  56    +==================+<- l_map_start
  57
  58    All the arithmetic is unsigned and we shift all the values down by
  59    l_addr + p_vaddr and then compare the normalized addr to the range
  60    of interest i.e. 0 <= addr < p_memsz.
  61
  62 */
  63 int
  64 _dl_addr_inside_object (struct link_map *l, const ElfW(Addr) addr)
  65 {
  66   int n = l->l_phnum;
  67   const ElfW(Addr) reladdr = addr - l->l_addr;
  68
  69   while (--n >= 0)
  70     if (l->l_phdr[n].p_type == PT_LOAD
  71         && reladdr - l->l_phdr[n].p_vaddr < l->l_phdr[n].p_memsz)
  72       return 1;
  73   return 0;
  74 }