73 lines
2.5 KiB
C
73 lines
2.5 KiB
C
/* -*-comment-start: "//";comment-end:""-*-
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* GNU Mes --- Maxwell Equations of Software
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* Copyright © 2018,2019 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
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*
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* This file is part of GNU Mes.
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*
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* GNU Mes is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3 of the License, or (at
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* your option) any later version.
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*
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* GNU Mes is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with GNU Mes. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <linux/syscall.h>
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#include <syscall.h>
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#include <unistd.h>
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#include <signal.h>
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#if __i386__
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#else
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void
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_restorer_for_siginfo (void)
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{
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_sys_call (SYS_rt_sigreturn);
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}
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#endif
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sighandler_t
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signal (int signum, sighandler_t action)
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{
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#if __i386__
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return _sys_call2 (SYS_signal, signum, action);
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#else
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static struct sigaction setup_action = { 0 };
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static struct sigaction old = { 0 };
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unsigned short bitindex;
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unsigned short itembitcount;
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setup_action.sa_handler = action;
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/* The sa_restorer is not used. Reason:
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* The kernel uses its own restorer anyway by pretending we gave one on
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our side (no, really).
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glibc still has a custom restorer because they want to be able to
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backtrace. gdb has a second part that detects a specific instruction
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sequence and then fixes up the backtrace. Since we don't use that
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specific instruction sequence and also the non-siginfo restorer
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is complicated (pops foreign item off the stack--so needs inline
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assembly) and we don't support great debuggability in other places,
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I've decided to take the easy way out for now. */
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/*setup_action.sa_restorer = _restorer_for_siginfo;*/
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bitindex = signum - 1;
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itembitcount = 8 * sizeof (setup_action.sa_mask.items[0]);
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setup_action.sa_mask.items[bitindex / itembitcount] = 1UL << (bitindex % itembitcount);
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old.sa_handler = SIG_DFL;
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setup_action.sa_flags = SA_RESTART;
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#if __x86_64__
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/* Tell kernel that we use a restorer, on penalty of segfault. */
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setup_action.sa_flags |= SA_RESTORER;
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#endif
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int r = _sys_call4 (SYS_rt_sigaction, signum, (long) &setup_action, (long) &old, sizeof (sigset_t));
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if (r)
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return 0;
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return old.sa_handler;
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#endif
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}
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