sysdeps/generic/dl-osinfo.h

   1 /* Operating system specific code for generic dynamic loader functions.
   2    Copyright (C) 2009-2020 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 <endian.h>
  20 #include <stdint.h>
  21
  22 static inline uintptr_t __attribute__ ((always_inline))
  23 _dl_setup_stack_chk_guard (void *dl_random)
  24 {
  25   union
  26   {
  27     uintptr_t num;
  28     unsigned char bytes[sizeof (uintptr_t)];
  29   } ret = { 0 };
  30
  31   if (dl_random == NULL)
  32     {
  33       ret.bytes[sizeof (ret) - 1] = 255;
  34       ret.bytes[sizeof (ret) - 2] = '\n';
  35     }
  36   else
  37     {
  38       memcpy (ret.bytes, dl_random, sizeof (ret));
  39 #if BYTE_ORDER == LITTLE_ENDIAN
  40       ret.num &= ~(uintptr_t) 0xff;
  41 #elif BYTE_ORDER == BIG_ENDIAN
  42       ret.num &= ~((uintptr_t) 0xff << (8 * (sizeof (ret) - 1)));
  43 #else
  44 # error "BYTE_ORDER unknown"
  45 #endif
  46     }
  47   return ret.num;
  48 }
  49
  50 static inline uintptr_t __attribute__ ((always_inline))
  51 _dl_setup_pointer_guard (void *dl_random, uintptr_t stack_chk_guard)
  52 {
  53   uintptr_t ret;
  54   if (dl_random == NULL)
  55     ret = stack_chk_guard;
  56   else
  57     memcpy (&ret, (char *) dl_random + sizeof (ret), sizeof (ret));
  58   return ret;
  59 }