sysdeps/posix/sigset.c

   1 /* Copyright (C) 1998-2016 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <errno.h>
  19 #define __need_NULL
  20 #include <stddef.h>
  21 #include <signal.h>
  22 #include <string.h>     /* For the real memset prototype.  */
  23
  24
  25 /* Set the disposition for SIG.  */
  26 __sighandler_t
  27 sigset (int sig, __sighandler_t disp)
  28 {
  29   struct sigaction act;
  30   struct sigaction oact;
  31   sigset_t set;
  32   sigset_t oset;
  33
  34 #ifdef SIG_HOLD
  35   /* Handle SIG_HOLD first.  */
  36   if (disp == SIG_HOLD)
  37     {
  38       /* Create an empty signal set.  */
  39       if (__sigemptyset (&set) < 0)
  40         return SIG_ERR;
  41
  42       /* Add the specified signal.  */
  43       if (__sigaddset (&set, sig) < 0)
  44         return SIG_ERR;
  45
  46       /* Add the signal set to the current signal mask.  */
  47       if (__sigprocmask (SIG_BLOCK, &set, &oset) < 0)
  48         return SIG_ERR;
  49
  50       /* If the signal was already blocked signal this to the caller.  */
  51       if (__sigismember (&oset, sig))
  52         return SIG_HOLD;
  53
  54       /* We need to determine whether a specific handler is installed.  */
  55       if (__sigaction (sig, NULL, &oact) < 0)
  56         return SIG_ERR;
  57
  58       return oact.sa_handler;
  59     }
  60 #endif  /* SIG_HOLD */
  61
  62   /* Check signal extents to protect __sigismember.  */
  63   if (disp == SIG_ERR || sig < 1 || sig >= NSIG)
  64     {
  65       __set_errno (EINVAL);
  66       return SIG_ERR;
  67     }
  68
  69   act.sa_handler = disp;
  70   if (__sigemptyset (&act.sa_mask) < 0)
  71     return SIG_ERR;
  72   act.sa_flags = 0;
  73   if (__sigaction (sig, &act, &oact) < 0)
  74     return SIG_ERR;
  75
  76   /* Create an empty signal set.  */
  77   if (__sigemptyset (&set) < 0)
  78     return SIG_ERR;
  79
  80   /* Add the specified signal.  */
  81   if (__sigaddset (&set, sig) < 0)
  82     return SIG_ERR;
  83
  84   /* Remove the signal set from the current signal mask.  */
  85   if (__sigprocmask (SIG_UNBLOCK, &set, &oset) < 0)
  86     return SIG_ERR;
  87
  88   /* If the signal was already blocked return SIG_HOLD.  */
  89   return __sigismember (&oset, sig) ? SIG_HOLD : oact.sa_handler;
  90 }