1  /* Operating system specific code for generic dynamic loader functions.
       2     Copyright (C) 2009-2023 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 <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  }