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Centralize signal handling into a single function

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Prior to this diff, fish had different signal handling functions for
different signals. However it was hard to coordinate when a signal needed
to be the default handler, and when it was custom. In #5962 we overwrote
fish's custom WINCH handler with the default_handler when fish script asked
for WINCH to be handled.

Just have a single big signal handler function. That way it can never be
set to the wrong thing.

Fixes #5969
This commit is contained in:
ridiculousfish 2019-06-28 10:47:36 -07:00
parent 8254342339
commit e3f94f4b72
1 changed files with 60 additions and 68 deletions
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128
src/signal.cpp
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@ -198,73 +198,65 @@ static bool reraise_if_forked_child(int sig) {
return true;
}
/// Standard signal handler.
static void default_handler(int signal, siginfo_t *info, void *context) {
/// The single signal handler. By centralizing signal handling we ensure that we can never install
/// the "wrong" signal handler (see #5969).
static void fish_signal_handler(int sig, siginfo_t *info, void *context) {
UNUSED(info);
UNUSED(context);
if (event_is_signal_observed(signal)) {
event_enqueue_signal(signal);
}
}
// Check if we are a forked child.
if (reraise_if_forked_child(sig)) {
return;
}
// Check if fish script cares about this.
const bool observed = event_is_signal_observed(sig);
if (observed) {
event_enqueue_signal(sig);
}
// Do some signal-specific stuff.
switch (sig) {
#ifdef SIGWINCH
/// Respond to a winch signal by checking the terminal size.
static void handle_winch(int sig, siginfo_t *info, void *context) {
UNUSED(info);
UNUSED(context);
if (reraise_if_forked_child(sig)) return;
common_handle_winch(sig);
default_handler(sig, 0, 0);
}
case SIGWINCH:
/// Respond to a winch signal by checking the terminal size.
common_handle_winch(sig);
break;
#endif
/// Respond to a hup signal by exiting, unless it is caught by a shellscript function, in which case
/// we do nothing.
static void handle_hup(int sig, siginfo_t *info, void *context) {
UNUSED(info);
UNUSED(context);
if (reraise_if_forked_child(sig)) return;
if (event_is_signal_observed(SIGHUP)) {
default_handler(sig, 0, 0);
} else {
reader_force_exit();
case SIGHUP:
/// Respond to a hup signal by exiting, unless it is caught by a shellscript function,
/// in which case we do nothing.
if (!observed) {
reader_force_exit();
}
topic_monitor_t::principal().post(topic_t::sighupint);
break;
case SIGTERM:
/// Handle sigterm. The only thing we do is restore the front process ID, then die.
restore_term_foreground_process_group();
signal(SIGTERM, SIG_DFL);
raise(SIGTERM);
break;
case SIGINT:
/// Interactive mode ^C handler. Respond to int signal by setting interrupted-flag and
/// stopping all loops and conditionals.
reader_handle_sigint();
topic_monitor_t::principal().post(topic_t::sighupint);
break;
case SIGCHLD:
// A child process stopped or exited.
topic_monitor_t::principal().post(topic_t::sigchld);
break;
case SIGALRM:
// We have a sigalarm handler that does nothing. This is used in the signal torture
// test, to verify that we behave correctly when receiving lots of irrelevant signals.
break;
}
topic_monitor_t::principal().post(topic_t::sighupint);
}
/// Handle sigterm. The only thing we do is restore the front process ID, then die.
static void handle_sigterm(int sig, siginfo_t *info, void *context) {
UNUSED(info);
UNUSED(context);
if (reraise_if_forked_child(sig)) return;
restore_term_foreground_process_group();
signal(SIGTERM, SIG_DFL);
raise(SIGTERM);
}
/// Interactive mode ^C handler. Respond to int signal by setting interrupted-flag and stopping all
/// loops and conditionals.
static void handle_int(int sig, siginfo_t *info, void *context) {
if (reraise_if_forked_child(sig)) return;
reader_handle_sigint();
default_handler(sig, info, context);
topic_monitor_t::principal().post(topic_t::sighupint);
}
/// sigchld handler. Does notification and calls the handler in proc.c.
static void handle_chld(int sig, siginfo_t *info, void *context) {
if (reraise_if_forked_child(sig)) return;
default_handler(sig, info, context);
topic_monitor_t::principal().post(topic_t::sigchld);
}
// We have a sigalarm handler that does nothing. This is used in the signal torture test, to verify
// that we behave correctly when receiving lots of irrelevant signals.
static void handle_sigalarm(int sig, siginfo_t *info, void *context) {
UNUSED(info);
UNUSED(context);
if (reraise_if_forked_child(sig)) return;
default_handler(sig, info, context);
}
void signal_reset_handlers() {
@ -296,29 +288,29 @@ static void set_interactive_handlers() {
sigaction(SIGTTOU, &act, NULL);
// We don't ignore SIGTTIN because we might send it to ourself.
act.sa_sigaction = &default_handler;
act.sa_sigaction = &fish_signal_handler;
act.sa_flags = SA_SIGINFO;
sigaction(SIGTTIN, &act, NULL);
// SIGTERM restores the terminal controlling process before dying.
act.sa_sigaction = &handle_sigterm;
act.sa_sigaction = &fish_signal_handler;
act.sa_flags = SA_SIGINFO;
sigaction(SIGTERM, &act, NULL);
sigaction(SIGHUP, NULL, &oact);
if (oact.sa_handler == SIG_DFL) {
act.sa_sigaction = &handle_hup;
act.sa_sigaction = &fish_signal_handler;
act.sa_flags = SA_SIGINFO;
sigaction(SIGHUP, &act, NULL);
}
// SIGALARM as part of our signal torture test
act.sa_sigaction = &handle_sigalarm;
act.sa_sigaction = &fish_signal_handler;
act.sa_flags = SA_SIGINFO;
sigaction(SIGALRM, &act, NULL);
#ifdef SIGWINCH
act.sa_sigaction = &handle_winch;
act.sa_sigaction = &fish_signal_handler;
act.sa_flags = SA_SIGINFO;
sigaction(SIGWINCH, &act, NULL);
#endif
@ -341,13 +333,13 @@ void signal_set_handlers() {
sigaction(SIGQUIT, &act, 0);
// Apply our SIGINT handler.
act.sa_sigaction = &handle_int;
act.sa_sigaction = &fish_signal_handler;
act.sa_flags = SA_SIGINFO;
sigaction(SIGINT, &act, NULL);
// Whether or not we're interactive we want SIGCHLD to not interrupt restartable syscalls.
act.sa_flags = SA_SIGINFO;
act.sa_sigaction = &handle_chld;
act.sa_sigaction = &fish_signal_handler;
act.sa_flags = SA_SIGINFO | SA_RESTART;
if (sigaction(SIGCHLD, &act, 0)) {
wperror(L"sigaction");
@ -370,7 +362,7 @@ void signal_handle(int sig) {
act.sa_flags = 0;
sigemptyset(&act.sa_mask);
act.sa_flags = SA_SIGINFO;
act.sa_sigaction = &default_handler;
act.sa_sigaction = &fish_signal_handler;
sigaction(sig, &act, nullptr);
}