1  /* longjmp fortify implementation.  Linux version.
       2     Copyright (C) 2011-2023 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 <jmpbuf-offsets.h>
      20  #include <sysdep.h>
      21  #include <setjmp.h>
      22  #include <signal.h>
      23  #include <stdio.h>
      24  #include <stackinfo.h>
      25  
      26  #ifdef _STACK_GROWS_DOWN
      27  #define called_from(this, saved) ((this) < (saved))
      28  #else
      29  #define called_from(this, saved) ((this) > (saved))
      30  #endif
      31  
      32  _Noreturn extern void ____longjmp_chk (__jmp_buf __env, int __val);
      33  
      34  void ____longjmp_chk (__jmp_buf env, int val)
      35  {
      36    void *this_frame = __builtin_frame_address (0);
      37    void *saved_frame = JB_FRAME_ADDRESS (env);
      38    stack_t ss;
      39  
      40    /* If "env" is from a frame that called us, we're all set.  */
      41    if (called_from(this_frame, saved_frame))
      42      __longjmp (env, val);
      43  
      44    /* If we can't get the current stack state, give up and do the longjmp. */
      45    if (INTERNAL_SYSCALL_CALL (sigaltstack, NULL, &ss) != 0)
      46      __longjmp (env, val);
      47  
      48    /* If we we are executing on the alternate stack and within the
      49       bounds, do the longjmp.  */
      50    if (ss.ss_flags == SS_ONSTACK
      51        && (this_frame >= ss.ss_sp && this_frame < (ss.ss_sp + ss.ss_size)))
      52      __longjmp (env, val);
      53  
      54    __fortify_fail ("longjmp causes uninitialized stack frame");
      55  }