sysdeps/posix/sigset.c

   1 /* Copyright (C) 1998-2015 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 (sig, disp)
  28      int sig;
  29      __sighandler_t disp;
  30 {
  31   struct sigaction act;
  32   struct sigaction oact;
  33   sigset_t set;
  34   sigset_t oset;
  35
  36 #ifdef SIG_HOLD
  37   /* Handle SIG_HOLD first.  */
  38   if (disp == SIG_HOLD)
  39     {
  40       /* Create an empty signal set.  */
  41       if (__sigemptyset (&set) < 0)
  42         return SIG_ERR;
  43
  44       /* Add the specified signal.  */
  45       if (__sigaddset (&set, sig) < 0)
  46         return SIG_ERR;
  47
  48       /* Add the signal set to the current signal mask.  */
  49       if (__sigprocmask (SIG_BLOCK, &set, &oset) < 0)
  50         return SIG_ERR;
  51
  52       /* If the signal was already blocked signal this to the caller.  */
  53       if (__sigismember (&oset, sig))
  54         return SIG_HOLD;
  55
  56       /* We need to determine whether a specific handler is installed.  */
  57       if (__sigaction (sig, NULL, &oact) < 0)
  58         return SIG_ERR;
  59
  60       return oact.sa_handler;
  61     }
  62 #endif  /* SIG_HOLD */
  63
  64   /* Check signal extents to protect __sigismember.  */
  65   if (disp == SIG_ERR || sig < 1 || sig >= NSIG)
  66     {
  67       __set_errno (EINVAL);
  68       return SIG_ERR;
  69     }
  70
  71   act.sa_handler = disp;
  72   if (__sigemptyset (&act.sa_mask) < 0)
  73     return SIG_ERR;
  74   act.sa_flags = 0;
  75   if (__sigaction (sig, &act, &oact) < 0)
  76     return SIG_ERR;
  77
  78   /* Create an empty signal set.  */
  79   if (__sigemptyset (&set) < 0)
  80     return SIG_ERR;
  81
  82   /* Add the specified signal.  */
  83   if (__sigaddset (&set, sig) < 0)
  84     return SIG_ERR;
  85
  86   /* Remove the signal set from the current signal mask.  */
  87   if (__sigprocmask (SIG_UNBLOCK, &set, &oset) < 0)
  88     return SIG_ERR;
  89
  90   /* If the signal was already blocked return SIG_HOLD.  */
  91   return __sigismember (&oset, sig) ? SIG_HOLD : oact.sa_handler;
  92 }