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/* -*-comment-start: "//";comment-end:""-*-
* GNU Mes --- Maxwell Equations of Software
* Copyright © 2018,2019,2022,2023 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
*
* This file is part of GNU Mes.
*
* GNU Mes is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3 of the License, or (at
* your option) any later version.
*
* GNU Mes 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GNU Mes. If not, see <http://www.gnu.org/licenses/>.
*/
#include <linux/syscall.h>
#include <arch/syscall.h>
#include <unistd.h>
#include <signal.h>
#if __i386__
#else
void
_restorer_for_siginfo (void)
{
_sys_call (SYS_rt_sigreturn);
}
#endif
sighandler_t
signal (int signum, sighandler_t action)
{
#if __i386__
return (sighandler_t) _sys_call2 (SYS_signal, signum, (long) action);
#else
static struct sigaction setup_action = { 0 };
static struct sigaction old = { 0 };
unsigned short bitindex;
unsigned short itembitcount;
setup_action.sa_handler = action;
/* The sa_restorer is not used. Reason:
* The kernel uses its own restorer anyway by pretending we gave one on
our side (no, really).
glibc still has a custom restorer because they want to be able to
backtrace. gdb has a second part that detects a specific instruction
sequence and then fixes up the backtrace. Since we don't use that
specific instruction sequence and also the non-siginfo restorer
is complicated (pops foreign item off the stack--so needs inline
assembly) and we don't support great debuggability in other places,
I've decided to take the easy way out for now. */
/*setup_action.sa_restorer = _restorer_for_siginfo;*/
bitindex = signum - 1;
itembitcount = 8 * sizeof (setup_action.sa_mask.items[0]);
setup_action.sa_mask.items[bitindex / itembitcount] = 1UL << (bitindex % itembitcount);
old.sa_handler = SIG_DFL;
setup_action.sa_flags = SA_RESTART;
#if __x86_64__
/* Tell kernel that we use a restorer, on penalty of segfault. */
setup_action.sa_flags |= SA_RESTORER;
#endif
int r = _sys_call4 (SYS_rt_sigaction, signum, (long) &setup_action, (long) &old, sizeof (sigset_t));
if (r)
return 0;
return old.sa_handler;
#endif
}
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