sysdeps/unix/sysv/sysv4/sigaction.c

   1 /* Copyright (C) 1994, 1995 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 Library General Public License as
   6 published by the Free Software Foundation; either version 2 of the
   7 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 Library General Public License for more details.
  13
  14 You should have received a copy of the GNU Library General Public
  15 License along with the GNU C Library; see the file COPYING.LIB.  If
  16 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  17 Cambridge, MA 02139, USA.  */
  18
  19 #include <ansidecl.h>
  20 #include <errno.h>
  21 #include <signal.h>
  22 #include <stddef.h>
  23
  24 static __sighandler_t user_handlers[NSIG];
  25
  26 extern int __context_syscall (int, struct sigcontext *);
  27 extern int __sigaction_syscall (int,
  28                                 const struct sigaction *, struct sigaction *);
  29
  30 static void
  31 trampoline (int sig, int code, struct sigcontext *context)
  32 {
  33   (*(void (*) (int, int, struct sigcontext *)) user_handlers[sig])
  34     (sig, code, context);
  35   __context_syscall (1, context);
  36 }
  37
  38 /* If ACT is not NULL, change the action for SIG to *ACT.
  39    If OACT is not NULL, put the old action for SIG in *OACT.  */
  40 int
  41 DEFUN(__sigaction, (sig, act, oact),
  42       int sig AND CONST struct sigaction *act AND struct sigaction *oact)
  43 {
  44   struct sigaction myact;
  45   __sighandler_t ohandler;
  46
  47   if (sig <= 0 || sig >= NSIG)
  48     {
  49       errno = EINVAL;
  50       return -1;
  51     }
  52
  53   ohandler = user_handlers[sig];
  54
  55   if (act != NULL)
  56     {
  57       user_handlers[sig] = act->sa_handler;
  58       if (act->sa_handler != SIG_DFL && act->sa_handler != SIG_IGN)
  59         {
  60           myact = *act;
  61           act = &myact;
  62           act->sa_handler = (__sighandler_t) trampoline;
  63         }
  64     }
  65
  66   if (__sigaction_syscall (sig, act, oact) < 0)
  67     {
  68       /* The syscall got an error.  Restore the old handler and return -1.  */
  69       user_handlers[sig] = ohandler;
  70       return -1;
  71     }
  72
  73   if (oact != NULL && oact->sa_handler == (__sighandler_t) trampoline)
  74     oact->sa_handler = ohandler;
  75
  76   return 0;
  77 }
  78
  79 weak_alias (__sigaction, sigaction)