* noise to install handlers
*/
+/*
+ * what low-level signal handlers looked like before
+ * undoably_install_low_level_interrupt_handler() got involved
+ */
+struct low_level_signal_handler_state {
+ int was_modified;
+ void (*handler)(int, siginfo_t*, void*);
+} old_low_level_signal_handler_states[NSIG];
+
+void
+uninstall_low_level_interrupt_handlers_atexit(void)
+{
+ int signal;
+ for (signal = 0; signal < NSIG; ++signal) {
+ struct low_level_signal_handler_state
+ *old_low_level_signal_handler_state =
+ old_low_level_signal_handler_states + signal;
+ if (old_low_level_signal_handler_state->was_modified) {
+ struct sigaction sa;
+ sa.sa_sigaction = old_low_level_signal_handler_state->handler;
+ sigemptyset(&sa.sa_mask);
+ sa.sa_flags = SA_SIGINFO | SA_RESTART;
+ sigaction(signal, &sa, NULL);
+ }
+ }
+}
+
/* Install a special low-level handler for signal; or if handler is
- * SIG_DFL, remove any special handling for signal. */
+ * SIG_DFL, remove any special handling for signal.
+ *
+ * The "undoably_" part is because we also arrange with atexit() for
+ * the handler to be restored to its old value. This is for tidiness,
+ * though it shouldn't really matter in normal operation of the
+ * program, except perhaps that it removes a window when e.g. SIGINT
+ * would be handled bizarrely. The original motivation was that some
+ * memory corruption problems in OpenBSD ca sbcl-0.6.12.12 became
+ * unnecessarily hard to debug when they ended up back in gencgc.c
+ * code (courtesy of the gencgc SIGSEGV handler) after exit() was
+ * called. */
void
-interrupt_install_low_level_handler (int signal,
- void handler(int, siginfo_t*, void*))
+undoably_install_low_level_interrupt_handler (int signal,
+ void handler(int,
+ siginfo_t*,
+ void*))
{
struct sigaction sa;
+ struct low_level_signal_handler_state *old_low_level_signal_handler_state =
+ old_low_level_signal_handler_states + signal;
+
+ if (0 > signal || signal >= NSIG) {
+ lose("bad signal number %d", signal);
+ }
sa.sa_sigaction = handler;
sigemptyset(&sa.sa_mask);
sigaddset_blockable(&sa.sa_mask);
sa.sa_flags = SA_SIGINFO | SA_RESTART;
- sigaction(signal, &sa, NULL);
+ /* In the case of interrupt handlers which are modified
+ * more than once, we only save the original unmodified
+ * copy. */
+ if (!old_low_level_signal_handler_state->was_modified) {
+ old_low_level_signal_handler_state->was_modified = 1;
+ sigaction(signal, &sa, &old_low_level_signal_handler_state->handler);
+ } else {
+ sigaction(signal, &sa, NULL);
+ }
+
interrupt_low_level_handlers[signal] =
(ARE_SAME_HANDLER(handler,SIG_DFL) ? 0 : handler);
}
int i;
SHOW("entering interrupt_init()");
+
+ /* Set up for recovery from any installed low-level handlers. */
+ atexit(&uninstall_low_level_interrupt_handlers_atexit);
+
+ /* Set up high level handler information. */
for (i = 0; i < NSIG; i++) {
interrupt_handlers[i].c =
/* (The cast here blasts away the distinction between
* 3-argument form is expected.) */
(void (*)(int, siginfo_t*, void*))SIG_DFL;
}
+
SHOW("returning from interrupt_init()");
}
projects / sbcl.git / commitdiff