sysdeps/unix/sysv/linux/dl-osinfo.h

   1 /* Operating system specific code for generic dynamic loader functions.  Linux.
   2    Copyright (C) 2000-2024 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 <dl-sysdep.h>
  20 #include <endian.h>
  21 #include <fcntl.h>
  22 #include <stdint.h>
  23 #include <not-cancel.h>
  24
  25 static inline uintptr_t __attribute__ ((always_inline))
  26 _dl_setup_stack_chk_guard (void *dl_random)
  27 {
  28   union
  29   {
  30     uintptr_t num;
  31     unsigned char bytes[sizeof (uintptr_t)];
  32   } ret;
  33
  34   /* We need in the moment only 8 bytes on 32-bit platforms and 16
  35      bytes on 64-bit platforms.  Therefore we can use the data
  36      directly and not use the kernel-provided data to seed a PRNG.  */
  37   memcpy (ret.bytes, dl_random, sizeof (ret));
  38 #if BYTE_ORDER == LITTLE_ENDIAN
  39   ret.num &= ~(uintptr_t) 0xff;
  40 #elif BYTE_ORDER == BIG_ENDIAN
  41   ret.num &= ~((uintptr_t) 0xff << (8 * (sizeof (ret) - 1)));
  42 #else
  43 # error "BYTE_ORDER unknown"
  44 #endif
  45   return ret.num;
  46 }
  47
  48 static inline uintptr_t __attribute__ ((always_inline))
  49 _dl_setup_pointer_guard (void *dl_random, uintptr_t stack_chk_guard)
  50 {
  51   uintptr_t ret;
  52   memcpy (&ret, (char *) dl_random + sizeof (ret), sizeof (ret));
  53   return ret;
  54 }