sysdeps/nacl/dl-unmap-segments.h

   1 /* Unmap a shared object's segments.  NaCl version.
   2    Copyright (C) 2015-2016 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    <http://www.gnu.org/licenses/>.  */
  18
  19 #ifndef _DL_UNMAP_SEGMENTS_H
  20 #define _DL_UNMAP_SEGMENTS_H    1
  21
  22 #include <link.h>
  23 #include <sys/mman.h>
  24
  25 /* There is always a big gap between the executable segment and the data
  26    segments.  Other code segments and data pages lie in there.  So we must
  27    unmap each segment individually (except for a codeless module).  */
  28
  29 static void __always_inline
  30 _dl_unmap_segments (struct link_map *l)
  31 {
  32   if (l->l_contiguous)
  33     /* Simple case.  */
  34     __munmap ((void *) l->l_map_start, l->l_map_end - l->l_map_start);
  35   else
  36     {
  37       /* Normally l_phdr points into the RODATA segment, which we will
  38          unmap in one iteration of the loop.  So we cannot use it directly
  39          throughout.  */
  40
  41       struct { ElfW(Addr) start, end; } segments[l->l_phnum], *seg = segments;
  42
  43       for (const ElfW(Phdr) *ph = l->l_phdr; ph < &l->l_phdr[l->l_phnum]; ++ph)
  44         if (ph->p_type == PT_LOAD)
  45           {
  46             seg->start = (l->l_addr + ph->p_vaddr) & -GLRO(dl_pagesize);
  47             seg->end = (l->l_addr + ph->p_vaddr + ph->p_memsz
  48                         + GLRO(dl_pagesize) - 1) & -GLRO(dl_pagesize);
  49             if (seg > segments && seg[-1].end == seg->start)
  50               /* Coalesce two adjacent segments into one munmap call.  */
  51               seg[-1].end = seg->end;
  52             else
  53               ++seg;
  54           }
  55
  56       do
  57         {
  58           --seg;
  59           __munmap ((void *) seg->start, seg->end - seg->start);
  60         }
  61       while (seg > segments);
  62     }
  63 }
  64
  65 #endif  /* dl-unmap-segments.h */