glibc/sysdeps/unix/sysv/linux/arm/sigaction.c

/* Copyright (C) 1997, 1998, 1999 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include <errno.h>
#include <signal.h>
#include <string.h>

#include <sysdep.h>
#include <sys/syscall.h>

/* The difference here is that the sigaction structure used in the
   kernel is not the same as we use in the libc.  Therefore we must
   translate it here.  */
#include <kernel_sigaction.h>

extern int __syscall_sigaction (int, const struct old_kernel_sigaction *,
				struct old_kernel_sigaction *);
extern int __syscall_rt_sigaction (int, const struct kernel_sigaction *,
				   struct kernel_sigaction *, size_t);

/* The variable is shared between all wrappers around signal handling
   functions which have RT equivalents.  */
int __libc_missing_rt_sigs;

#define SA_RESTORER	0x04000000

/* When RT signals are in use we need to use a different return stub.  */
#ifdef __NR_rt_sigreturn
#define choose_restorer(flags)					\
  (flags & SA_SIGINFO) ? &&__default_rt_sa_restorer		\
  : &&__default_sa_restorer
#else
#define choose_restorer(flags)					\
  &&__default_sa_restorer
#endif

/* If ACT is not NULL, change the action for SIG to *ACT.
   If OACT is not NULL, put the old action for SIG in *OACT.  */
int
__sigaction (sig, act, oact)
     int sig;
     const struct sigaction *act;
     struct sigaction *oact;
{
  struct old_kernel_sigaction k_sigact, k_osigact;
  int result;

#ifdef __NR_rt_sigaction
  /* First try the RT signals.  */
  if (!__libc_missing_rt_sigs)
    {
      struct kernel_sigaction kact, koact;
      int saved_errno = errno;

      if (act)
	{
	  kact.k_sa_handler = act->sa_handler;
	  memcpy (&kact.sa_mask, &act->sa_mask, sizeof (sigset_t));
	  kact.sa_flags = act->sa_flags;
# ifdef HAVE_SA_RESTORER
	  /* If the user specified SA_ONSTACK this means she is trying to
	     use the old-style stack switching.  Unfortunately this
	     requires the sa_restorer field so we cannot install our own
	     handler.  (In fact the user is likely to be out of luck anyway
	     since the kernel currently only supports stack switching via
	     the X/Open sigaltstack interface, but we allow for the
	     possibility that this might change in the future.)  */
	  if (kact.sa_flags & (SA_RESTORER | SA_ONSTACK))
	    kact.sa_restorer = act->sa_restorer;
	  else
	    {
	      kact.sa_restorer = choose_restorer (kact.sa_flags);
	      kact.sa_flags |= SA_RESTORER;
	    }
# endif
	}

      /* XXX The size argument hopefully will have to be changed to the
	 real size of the user-level sigset_t.  */
      result = INLINE_SYSCALL (rt_sigaction, 4, sig, act ? &kact : NULL,
			       oact ? &koact : NULL, _NSIG / 8);

      if (result >= 0 || errno != ENOSYS)
	{
	  if (oact && result >= 0)
	    {
	      oact->sa_handler = koact.k_sa_handler;
	      memcpy (&oact->sa_mask, &koact.sa_mask, sizeof (sigset_t));
	      oact->sa_flags = koact.sa_flags;
# ifdef HAVE_SA_RESTORER
	      oact->sa_restorer = koact.sa_restorer;
# endif
	    }
	  return result;
	}

      __set_errno (saved_errno);
      __libc_missing_rt_sigs = 1;
    }
#endif

  if (act)
    {
      k_sigact.k_sa_handler = act->sa_handler;
      k_sigact.sa_mask = act->sa_mask.__val[0];
      k_sigact.sa_flags = act->sa_flags;
#ifdef HAVE_SA_RESTORER
      /* See the comments above for why we test SA_ONSTACK.  */
      if (k_sigact.sa_flags & (SA_RESTORER | SA_ONSTACK))
	k_sigact.sa_restorer = act->sa_restorer;
      else
	{
	  k_sigact.sa_restorer = choose_restorer (k_sigact.sa_flags);
	  k_sigact.sa_flags |= SA_RESTORER;
	}
#endif
    }
  result = INLINE_SYSCALL (sigaction, 3, sig, act ? &k_sigact : NULL,
			   oact ? &k_osigact : NULL);
  if (oact && result >= 0)
    {
      oact->sa_handler = k_osigact.k_sa_handler;
      oact->sa_mask.__val[0] = k_osigact.sa_mask;
      oact->sa_flags = k_osigact.sa_flags;
#ifdef HAVE_SA_RESTORER
      oact->sa_restorer = k_osigact.sa_restorer;
#endif
    }
  return result;

  /* If no SA_RESTORER function was specified by the application we use
     this one.  This avoids the need for the kernel to synthesise a return
     instruction on the stack, which would involve expensive cache flushes. */
 __default_sa_restorer:
  asm volatile ("swi %0" : : "i" (__NR_sigreturn));
  
#ifdef __NR_rt_sigreturn
 __default_rt_sa_restorer:
  asm volatile ("swi %0" : : "i" (__NR_rt_sigreturn));
#endif

  /* NOTREACHED */
  return -1;
}

weak_alias (__sigaction, sigaction)