/****************************************************************************
* Copyright (c) 1998,1999 Free Software Foundation, Inc. *
* *
* Permission is hereby granted, free of charge, to any person obtaining a *
* copy of this software and associated documentation files (the *
* "Software"), to deal in the Software without restriction, including *
* without limitation the rights to use, copy, modify, merge, publish, *
* distribute, distribute with modifications, sublicense, and/or sell *
* copies of the Software, and to permit persons to whom the Software is *
* furnished to do so, subject to the following conditions: *
* *
* The above copyright notice and this permission notice shall be included *
* in all copies or substantial portions of the Software. *
* *
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS *
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF *
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. *
* IN NO EVENT SHALL THE ABOVE COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, *
* DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR *
* OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR *
* THE USE OR OTHER DEALINGS IN THE SOFTWARE. *
* *
* Except as contained in this notice, the name(s) of the above copyright *
* holders shall not be used in advertising or otherwise to promote the *
* sale, use or other dealings in this Software without prior written *
* authorization. *
****************************************************************************/
/****************************************************************************
* Author: Zeyd M. Ben-Halim <zmbenhal@netcom.com> 1992,1995 *
* and: Eric S. Raymond <esr@snark.thyrsus.com> *
****************************************************************************/
/*
** lib_tstp.c
**
** The routine _nc_signal_handler().
**
*/
#include <curses.priv.h>
#include <signal.h>
#include <SigAction.h>
#if defined(SVR4_ACTION) && !defined(_POSIX_SOURCE)
#define _POSIX_SOURCE
#endif
MODULE_ID("$Id: lib_tstp.c,v 1.20 1999/10/22 23:11:09 tom Exp $")
#if defined(SIGTSTP) && (HAVE_SIGACTION || HAVE_SIGVEC)
#define USE_SIGTSTP 1
#else
#define USE_SIGTSTP 0
#endif
/*
* Note: This code is fragile! Its problem is that different OSs
* handle restart of system calls interrupted by signals differently.
* The ncurses code needs signal-call restart to happen -- otherwise,
* interrupted wgetch() calls will return FAIL, probably making the
* application think the input stream has ended and it should
* terminate. In particular, you know you have this problem if, when
* you suspend an ncurses-using lynx with ^Z and resume, it dies
* immediately.
*
* Default behavior of POSIX sigaction(2) is not to restart
* interrupted system calls, but Linux's sigaction does it anyway (at
* least, on and after the 1.1.47 I (esr) use). Thus this code works
* OK under Linux. The 4.4BSD sigaction(2) supports a (non-portable)
* SA_RESTART flag that forces the right behavior. Thus, this code
* should work OK under BSD/OS, NetBSD, and FreeBSD (let us know if it
* does not).
*
* Stock System Vs (and anything else using a strict-POSIX
* sigaction(2) without SA_RESTART) may have a problem. Possible
* solutions:
*
* sigvec restarts by default (SV_INTERRUPT flag to not restart)
* signal restarts by default in SVr4 (assuming you link with -lucb)
* and BSD, but not SVr3.
* sigset restarts, but is only available under SVr4/Solaris.
*
* The signal(3) call is mandated by the ANSI standard, and its
* interaction with sigaction(2) is described in the POSIX standard
* (3.3.4.2, page 72,line 934). According to section 8.1, page 191,
* however, signal(3) itself is not required by POSIX.1. And POSIX is
* silent on whether it is required to restart signals.
*
* So. The present situation is, we use sigaction(2) with no
* guarantee of restart anywhere but on Linux and BSD. We could
* switch to signal(3) and collar Linux, BSD, and SVr4. Any way
* we slice it, System V UNIXes older than SVr4 will probably lose
* (this may include XENIX).
*
* This implementation will probably be changed to use signal(3) in
* the future. If nothing else, it's simpler...
*/
#if USE_SIGTSTP
static void tstp(int dummy GCC_UNUSED)
{
sigset_t mask, omask;
sigaction_t act, oact;
#ifdef SIGTTOU
int sigttou_blocked;
#endif
T(("tstp() called"));
/*
* The user may have changed the prog_mode tty bits, so save them.
*
* But first try to detect whether we still are in the foreground
* process group - if not, an interactive shell may already have
* taken ownership of the tty and modified the settings when our
* parent was stopped before us, and we would likely pick up the
* settings already modified by the shell.
*/
if (SP != 0 && !SP->_endwin) /* don't do this if we're not in curses */
#if HAVE_TCGETPGRP
if (tcgetpgrp(STDIN_FILENO) == getpgrp())
#endif
def_prog_mode();
/*
* Block window change and timer signals. The latter
* is because applications use timers to decide when
* to repaint the screen.
*/
(void)sigemptyset(&mask);
(void)sigaddset(&mask, SIGALRM);
#if USE_SIGWINCH
(void)sigaddset(&mask, SIGWINCH);
#endif
(void)sigprocmask(SIG_BLOCK, &mask, &omask);
#ifdef SIGTTOU
sigttou_blocked = sigismember(&omask, SIGTTOU);
if (!sigttou_blocked) {
(void)sigemptyset(&mask);
(void)sigaddset(&mask, SIGTTOU);
(void)sigprocmask(SIG_BLOCK, &mask, NULL);
}
#endif
/*
* End window mode, which also resets the terminal state to the
* original (pre-curses) modes.
*/
endwin();
/* Unblock SIGTSTP. */
(void)sigemptyset(&mask);
(void)sigaddset(&mask, SIGTSTP);
#ifdef SIGTTOU
if (!sigttou_blocked) {
/* Unblock this too if it wasn't blocked on entry */
(void)sigaddset(&mask, SIGTTOU);
}
#endif
(void)sigprocmask(SIG_UNBLOCK, &mask, NULL);
/* Now we want to resend SIGSTP to this process and suspend it */
act.sa_handler = SIG_DFL;
sigemptyset(&act.sa_mask);
act.sa_flags = 0;
#ifdef SA_RESTART
act.sa_flags |= SA_RESTART;
#endif /* SA_RESTART */
sigaction(SIGTSTP, &act, &oact);
kill(getpid(), SIGTSTP);
/* Process gets suspended...time passes...process resumes */
T(("SIGCONT received"));
sigaction(SIGTSTP, &oact, NULL);
flushinp();
/*
* If the user modified the tty state while suspended, he wants
* those changes to stick. So save the new "default" terminal state.
*/
def_shell_mode();
/*
* This relies on the fact that doupdate() will restore the
* program-mode tty state, and issue enter_ca_mode if need be.
*/
doupdate();
/* Reset the signals. */
(void)sigprocmask(SIG_SETMASK, &omask, NULL);
}
#endif /* USE_SIGTSTP */
static void cleanup(int sig)
{
static int nested;
/*
* Actually, doing any sort of I/O from within an signal handler is
* "unsafe". But we'll _try_ to clean up the screen and terminal
* settings on the way out.
*/
if (!nested++
&& (sig == SIGINT
|| sig == SIGQUIT)) {
#if HAVE_SIGACTION || HAVE_SIGVEC
sigaction_t act;
sigemptyset(&act.sa_mask);
act.sa_flags = 0;
act.sa_handler = SIG_IGN;
if (sigaction(sig, &act, (sigaction_t *)0) == 0)
#else
if (signal(sig, SIG_IGN) != SIG_ERR)
#endif
{
SCREEN *scan = _nc_screen_chain;
while(scan)
{
if (SP != 0
&& SP->_ofp != 0
&& isatty(fileno(SP->_ofp))) {
SP->_cleanup = TRUE;
}
set_term(scan);
endwin();
if (SP)
SP->_endwin = FALSE; /* in case we have an atexit! */
scan = scan->_next_screen;
}
}
}
exit(EXIT_FAILURE);
}
#if USE_SIGWINCH
static void sigwinch(int sig GCC_UNUSED)
{
SCREEN *scan = _nc_screen_chain;
while(scan)
{
scan->_sig_winch = TRUE;
scan = scan->_next_screen;
}
}
#endif /* USE_SIGWINCH */
/*
* If the given signal is still in its default state, set it to the given
* handler.
*/
#if HAVE_SIGACTION || HAVE_SIGVEC
static int CatchIfDefault(int sig, sigaction_t *act)
{
sigaction_t old_act;
if (sigaction(sig, (sigaction_t *)0, &old_act) == 0
&& (old_act.sa_handler == SIG_DFL
#if USE_SIGWINCH
|| (sig == SIGWINCH && old_act.sa_handler == SIG_IGN)
#endif
)) {
(void)sigaction(sig, act, (sigaction_t *)0);
return TRUE;
}
return FALSE;
}
#else
static int CatchIfDefault(int sig, RETSIGTYPE (*handler)(int))
{
void (*ohandler)(int);
ohandler = signal(sig, SIG_IGN);
if (ohandler == SIG_DFL
#if USE_SIGWINCH
|| (sig == SIGWINCH && ohandler == SIG_IGN)
#endif
) {
signal(sig, handler);
return TRUE;
} else {
signal(sig, ohandler);
return FALSE;
}
}
#endif
/*
* This is invoked once at the beginning (e.g., from 'initscr()'), to
* initialize the signal catchers, and thereafter when spawning a shell (and
* returning) to disable/enable the SIGTSTP (i.e., ^Z) catcher.
*
* If the application has already set one of the signals, we'll not modify it
* (during initialization).
*
* The XSI document implies that we shouldn't keep the SIGTSTP handler if
* the caller later changes its mind, but that doesn't seem correct.
*/
void _nc_signal_handler(bool enable)
{
#if USE_SIGTSTP /* Xenix 2.x doesn't have SIGTSTP, for example */
static sigaction_t act, oact;
static int ignore;
if (!ignore)
{
if (!enable)
{
act.sa_handler = SIG_IGN;
sigaction(SIGTSTP, &act, &oact);
}
else if (act.sa_handler)
{
sigaction(SIGTSTP, &oact, NULL);
}
else /*initialize */
{
sigemptyset(&act.sa_mask);
act.sa_flags = 0;
#if USE_SIGWINCH
act.sa_handler = sigwinch;
CatchIfDefault(SIGWINCH, &act);
#endif
#ifdef SA_RESTART
act.sa_flags |= SA_RESTART;
#endif /* SA_RESTART */
act.sa_handler = cleanup;
CatchIfDefault(SIGINT, &act);
CatchIfDefault(SIGTERM, &act);
act.sa_handler = tstp;
if (!CatchIfDefault(SIGTSTP, &act))
ignore = TRUE;
}
}
#else /* !USE_SIGTSTP */
if (enable)
{
#if HAVE_SIGACTION || HAVE_SIGVEC
static sigaction_t act;
sigemptyset(&act.sa_mask);
#if USE_SIGWINCH
act.sa_handler = sigwinch;
CatchIfDefault(SIGWINCH, &act);
#endif
#ifdef SA_RESTART
act.sa_flags |= SA_RESTART;
#endif /* SA_RESTART */
act.sa_handler = cleanup;
CatchIfDefault(SIGINT, &act);
CatchIfDefault(SIGTERM, &act);
#else /* !(HAVE_SIGACTION || HAVE_SIGVEC) */
CatchIfDefault(SIGINT, cleanup);
CatchIfDefault(SIGTERM, cleanup);
#if USE_SIGWINCH
CatchIfDefault(SIGWINCH, sigwinch);
#endif
#endif /* !(HAVE_SIGACTION || HAVE_SIGVEC) */
}
#endif /* !USE_SIGTSTP */
}
