sysdeps/unix/sysv/linux/sigstack.c

   1 /* Emulate sigstack function using sigaltstack.
   2    Copyright (C) 1998-2023 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 <signal.h>
  20 #include <stddef.h>
  21 #include <sys/syscall.h>
  22
  23
  24 int
  25 sigstack (struct sigstack *ss, struct sigstack *oss)
  26 {
  27   stack_t sas;
  28   stack_t *sasp = NULL;
  29   stack_t osas;
  30   stack_t *osasp = oss == NULL ? NULL : &osas;
  31   int result;
  32
  33   if (ss != NULL)
  34     {
  35       /* We have to convert the information.  */
  36       sas.ss_sp = ss->ss_sp;
  37       sas.ss_flags = ss->ss_onstack ? SS_ONSTACK : 0;
  38
  39       /* For the size of the stack we have no value we can pass to the
  40          kernel.  This is why this function should not be used.  We simply
  41          assume that all the memory down to address zero (in case the stack
  42          grows down) is available.  */
  43       sas.ss_size = ss->ss_sp - NULL;
  44
  45       sasp = &sas;
  46     }
  47
  48   /* Call the kernel.  */
  49   result = __sigaltstack (sasp, osasp);
  50
  51   /* Convert the result, if wanted and possible.  */
  52   if (result == 0 && oss != NULL)
  53     {
  54       oss->ss_sp = osas.ss_sp;
  55       oss->ss_onstack = (osas.ss_flags & SS_ONSTACK) != 0;
  56     }
  57
  58   return result;
  59 }
  60
  61 link_warning (sigstack, "the `sigstack' function is dangerous.  `sigaltstack' should be used instead.")