uclibc-ng/libc/sysdeps/linux/x86_64/sigaction.c

/* POSIX.1 `sigaction' call for Linux/x86-64.
   Copyright (C) 2001, 2002, 2003 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 Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <http://www.gnu.org/licenses/>.  */


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

#include <sys/syscall.h>

#include <bits/kernel_sigaction.h>

/* We do not globally define the SA_RESTORER flag so do it here.  */
#define SA_RESTORER 0x04000000

#ifdef __NR_rt_sigaction

/* Using the hidden attribute here does not change the code but it
   helps to avoid warnings.  */
extern void restore_rt(void) __asm__ ("__restore_rt") attribute_hidden;
extern void restore(void) __asm__ ("__restore") attribute_hidden;

/* 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
__libc_sigaction(int sig, const struct sigaction *act, struct sigaction *oact)
{
	struct sigaction kact;

	if (act) {
		memcpy(&kact, act, sizeof(kact));
		kact.sa_flags |= SA_RESTORER;
		kact.sa_restorer = &restore_rt;
		act = &kact;
	}
	/* NB: kernel (as of 2.6.25) will return EINVAL
	 * if sizeof(act->sa_mask) does not match kernel's sizeof(sigset_t) */
	return INLINE_SYSCALL(rt_sigaction, 4, sig, act, oact, sizeof(act->sa_mask));
}

#else

extern void restore(void) __asm__ ("__restore") attribute_hidden;

/* 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
__libc_sigaction(int sig, const struct sigaction *act, struct sigaction *oact)
{
	int result;
	struct old_kernel_sigaction kact, koact;

	if (act) {
		kact.k_sa_handler = act->sa_handler;
		kact.sa_mask = act->sa_mask.__val[0];
		kact.sa_flags = act->sa_flags | SA_RESTORER;
		kact.sa_restorer = &restore;
	}
	__asm__ __volatile__ (
		"syscall\n"
		: "=a" (result)
		: "0" (__NR_sigaction), "mr" (sig),
		  "c" (act ? &kact : NULL),
		  "d" (oact ? &koact : NULL));
	if (result < 0) {
		__set_errno(-result);
		return -1;
	}
	if (oact) {
		oact->sa_handler = koact.k_sa_handler;
		oact->sa_mask.__val[0] = koact.sa_mask;
		oact->sa_flags = koact.sa_flags;
		oact->sa_restorer = koact.sa_restorer;
	}
	return result;
}

#endif


#ifndef LIBC_SIGACTION
# ifndef __UCLIBC_HAS_THREADS__
strong_alias(__libc_sigaction,sigaction)
libc_hidden_def(sigaction)
# else
weak_alias(__libc_sigaction,sigaction)
libc_hidden_weak(sigaction)
# endif
#endif


/* NOTE: Please think twice before making any changes to the bits of
   code below.  GDB needs some intimate knowledge about it to
   recognize them as signal trampolines, and make backtraces through
   signal handlers work right.  Important are both the names
   (__restore_rt) and the exact instruction sequence.
   If you ever feel the need to make any changes, please notify the
   appropriate GDB maintainer.

   The unwind information starts a byte before __restore_rt, so that
   it is found when unwinding, to get an address the unwinder assumes
   will be in the middle of a call instruction.  See the Linux kernel
   (the i386 vsyscall, in particular) for an explanation of the complex
   unwind information used here in order to get the traditional CFA.
 */

#define RESTORE(name, syscall) RESTORE2(name, syscall)
#define RESTORE2(name, syscall) \
__asm__ (						\
	"nop\n"						\
	".text\n"					\
	"__" #name ":\n"				\
	"	movq	$" #syscall ", %rax\n"		\
	"	syscall\n"				\
);

#ifdef __NR_rt_sigaction
/* The return code for realtime-signals.  */
RESTORE(restore_rt, __NR_rt_sigreturn)
#endif
#ifdef __NR_sigreturn
RESTORE(restore, __NR_sigreturn)
#endif