sysdeps/unix/sysv/linux/sigstack.c

   1 /* Emulate sigstack function using sigaltstack.
   2    Copyright (C) 1998-2017 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <signal.h>
  21 #include <stddef.h>
  22 #include <sys/syscall.h>
  23
  24
  25 #ifdef __NR_sigaltstack
  26 int
  27 sigstack (struct sigstack *ss, struct sigstack *oss)
  28 {
  29   stack_t sas;
  30   stack_t *sasp = NULL;
  31   stack_t osas;
  32   stack_t *osasp = oss == NULL ? NULL : &osas;
  33   int result;
  34
  35   if (ss != NULL)
  36     {
  37       /* We have to convert the information.  */
  38       sas.ss_sp = ss->ss_sp;
  39       sas.ss_flags = ss->ss_onstack ? SS_ONSTACK : 0;
  40
  41       /* For the size of the stack we have no value we can pass to the
  42          kernel.  This is why this function should not be used.  We simply
  43          assume that all the memory down to address zero (in case the stack
  44          grows down) is available.  */
  45       sas.ss_size = ss->ss_sp - NULL;
  46
  47       sasp = &sas;
  48     }
  49
  50   /* Call the kernel.  */
  51   result = __sigaltstack (sasp, osasp);
  52
  53   /* Convert the result, if wanted and possible.  */
  54   if (result == 0 && oss != NULL)
  55     {
  56       oss->ss_sp = osas.ss_sp;
  57       oss->ss_onstack = (osas.ss_flags & SS_ONSTACK) != 0;
  58     }
  59
  60   return result;
  61 }
  62
  63 link_warning (sigstack, "the `sigstack' function is dangerous.  `sigaltstack' should be used instead.")
  64 #else
  65 # include <signal/sigstack.c>
  66 #endif