2 * interrupt-handling magic
6 * This software is part of the SBCL system. See the README file for
9 * This software is derived from the CMU CL system, which was
10 * written at Carnegie Mellon University and released into the
11 * public domain. The software is in the public domain and is
12 * provided with absolutely no warranty. See the COPYING and CREDITS
13 * files for more information.
25 #include "interrupt.h"
35 void sigaddset_blockable(sigset_t *s)
39 sigaddset(s, SIGQUIT);
40 sigaddset(s, SIGPIPE);
41 sigaddset(s, SIGALRM);
44 sigaddset(s, SIGTSTP);
45 sigaddset(s, SIGCHLD);
47 sigaddset(s, SIGXCPU);
48 sigaddset(s, SIGXFSZ);
49 sigaddset(s, SIGVTALRM);
50 sigaddset(s, SIGPROF);
51 sigaddset(s, SIGWINCH);
52 sigaddset(s, SIGUSR1);
53 sigaddset(s, SIGUSR2);
56 /* When we catch an internal error, should we pass it back to Lisp to
57 * be handled in a high-level way? (Early in cold init, the answer is
58 * 'no', because Lisp is still too brain-dead to handle anything.
59 * After sufficient initialization has been completed, the answer
61 boolean internal_errors_enabled = 0;
63 os_context_t *lisp_interrupt_contexts[MAX_INTERRUPTS];
65 /* As far as I can tell, what's going on here is:
67 * In the case of most signals, when Lisp asks us to handle the
68 * signal, the outermost handler (the one actually passed to UNIX) is
69 * either interrupt_handle_now(..) or interrupt_handle_later(..).
70 * In that case, the Lisp-level handler is stored in interrupt_handlers[..]
71 * and interrupt_low_level_handlers[..] is cleared.
73 * However, some signals need special handling, e.g.
75 * o the SIGSEGV (for e.g. Linux) or SIGBUS (for e.g. FreeBSD) used by the
76 * garbage collector to detect violations of write protection,
77 * because some cases of such signals (e.g. GC-related violations of
78 * write protection) are handled at C level and never passed on to
79 * Lisp. For such signals, we still store any Lisp-level handler
80 * in interrupt_handlers[..], but for the outermost handle we use
81 * the value from interrupt_low_level_handlers[..], instead of the
82 * ordinary interrupt_handle_now(..) or interrupt_handle_later(..).
84 * o the SIGTRAP (Linux/Alpha) which Lisp code uses to handle breakpoints,
85 * pseudo-atomic sections, and some classes of error (e.g. "function
86 * not defined"). This never goes anywhere near the Lisp handlers at all.
87 * See runtime/alpha-arch.c and code/signal.lisp
89 * - WHN 20000728, dan 20010128 */
92 void (*interrupt_low_level_handlers[NSIG]) (int, siginfo_t*, void*) = {0};
93 union interrupt_handler interrupt_handlers[NSIG];
95 /* signal number, siginfo_t, and old mask information for pending signal
97 * pending_signal=0 when there is no pending signal. */
98 static int pending_signal = 0;
99 static siginfo_t pending_info;
100 static sigset_t pending_mask;
102 static boolean maybe_gc_pending = 0;
105 * utility routines used by various signal handlers
109 fake_foreign_function_call(os_context_t *context)
116 /* Get current Lisp state from context. */
118 dynamic_space_free_pointer =
119 (lispobj *)(*os_context_register_addr(context, reg_ALLOC));
121 if ((long)dynamic_space_free_pointer & 1) {
122 lose("dead in fake_foreign_function_call, context = %x", context);
127 current_binding_stack_pointer =
128 (lispobj *)(*os_context_register_addr(context, reg_BSP));
132 /* Build a fake stack frame. */
133 current_control_frame_pointer =
134 (lispobj *)(*os_context_register_addr(context, reg_CSP));
135 if ((lispobj *)(*os_context_register_addr(context, reg_CFP))
136 == current_control_frame_pointer) {
137 /* There is a small window during call where the callee's
138 * frame isn't built yet. */
139 if (lowtag_of(*os_context_register_addr(context, reg_CODE))
140 == FUN_POINTER_LOWTAG) {
141 /* We have called, but not built the new frame, so
142 * build it for them. */
143 current_control_frame_pointer[0] =
144 *os_context_register_addr(context, reg_OCFP);
145 current_control_frame_pointer[1] =
146 *os_context_register_addr(context, reg_LRA);
147 current_control_frame_pointer += 8;
148 /* Build our frame on top of it. */
149 oldcont = (lispobj)(*os_context_register_addr(context, reg_CFP));
152 /* We haven't yet called, build our frame as if the
153 * partial frame wasn't there. */
154 oldcont = (lispobj)(*os_context_register_addr(context, reg_OCFP));
157 /* ### We can't tell whether we are still in the caller if it had
158 * to reg_ALLOCate the stack frame due to stack arguments. */
159 /* ### Can anything strange happen during return? */
162 oldcont = (lispobj)(*os_context_register_addr(context, reg_CFP));
165 current_control_stack_pointer = current_control_frame_pointer + 8;
167 current_control_frame_pointer[0] = oldcont;
168 current_control_frame_pointer[1] = NIL;
169 current_control_frame_pointer[2] =
170 (lispobj)(*os_context_register_addr(context, reg_CODE));
173 /* Do dynamic binding of the active interrupt context index
174 * and save the context in the context array. */
175 context_index = SymbolValue(FREE_INTERRUPT_CONTEXT_INDEX)>>2;
176 /* FIXME: Ick! Why use abstract "make_fixnum" in some places if
177 * you're going to convert from fixnum by bare >>2 in other
178 * places? Use fixnum_value(..) here, and look for other places
179 * which do bare >> and << for fixnum_value and make_fixnum. */
181 if (context_index >= MAX_INTERRUPTS) {
182 lose("maximum interrupt nesting depth (%d) exceeded",
186 bind_variable(FREE_INTERRUPT_CONTEXT_INDEX,
187 make_fixnum(context_index + 1));
189 lisp_interrupt_contexts[context_index] = context;
191 /* no longer in Lisp now */
192 foreign_function_call_active = 1;
196 undo_fake_foreign_function_call(os_context_t *context)
198 /* Block all blockable signals. */
201 sigaddset_blockable(&block);
202 sigprocmask(SIG_BLOCK, &block, 0);
204 /* going back into Lisp */
205 foreign_function_call_active = 0;
207 /* Undo dynamic binding. */
208 /* ### Do I really need to unbind_to_here()? */
209 /* FIXME: Is this to undo the binding of
210 * FREE_INTERRUPT_CONTEXT_INDEX? If so, we should say so. And
211 * perhaps yes, unbind_to_here() really would be clearer and less
213 /* dan (2001.08.10) thinks the above supposition is probably correct */
217 /* Put the dynamic space free pointer back into the context. */
218 *os_context_register_addr(context, reg_ALLOC) =
219 (unsigned long) dynamic_space_free_pointer;
223 /* a handler for the signal caused by execution of a trap opcode
224 * signalling an internal error */
226 interrupt_internal_error(int signal, siginfo_t *info, os_context_t *context,
229 lispobj context_sap = 0;
231 fake_foreign_function_call(context);
233 /* Allocate the SAP object while the interrupts are still
235 if (internal_errors_enabled) {
236 context_sap = alloc_sap(context);
239 sigprocmask(SIG_SETMASK, os_context_sigmask_addr(context), 0);
241 if (internal_errors_enabled) {
242 SHOW("in interrupt_internal_error");
244 /* Display some rudimentary debugging information about the
245 * error, so that even if the Lisp error handler gets badly
246 * confused, we have a chance to determine what's going on. */
247 describe_internal_error(context);
249 funcall2(SymbolFunction(INTERNAL_ERROR), context_sap,
250 continuable ? T : NIL);
252 describe_internal_error(context);
253 /* There's no good way to recover from an internal error
254 * before the Lisp error handling mechanism is set up. */
255 lose("internal error too early in init, can't recover");
257 undo_fake_foreign_function_call(context);
259 arch_skip_instruction(context);
263 /* This function handles pending interrupts. Note that in C/kernel
264 * terms we dealt with the signal already; we just haven't decided
265 * whether to call a Lisp handler or do a GC or something like that.
266 * If it helps, you can think of pending_{signal,mask,info} as a
267 * one-element queue of signals that we have acknowledged but not
271 interrupt_handle_pending(os_context_t *context)
274 boolean were_in_lisp = !foreign_function_call_active;
277 SetSymbolValue(INTERRUPT_PENDING, NIL);
279 if (maybe_gc_pending) {
280 maybe_gc_pending = 0;
285 fake_foreign_function_call(context);
287 funcall0(SymbolFunction(MAYBE_GC));
292 undo_fake_foreign_function_call(context);
296 /* FIXME: This isn't very clear. It would be good to reverse
297 * engineer it and rewrite the code more clearly, or write a clear
298 * explanation of what's going on in the comments, or both.
300 * WHN's question 1a: How come we unconditionally copy from
301 * pending_mask into the context, and then test whether
302 * pending_signal is set?
304 * WHN's question 1b: If pending_signal wasn't set, how could
305 * pending_mask be valid?
307 * Dan Barlow's reply (sbcl-devel 2001-03-13): And the answer is -
308 * or appears to be - because interrupt_maybe_gc set it that way
309 * (look in the #ifndef __i386__ bit). We can't GC during a
310 * pseudo-atomic, so we set maybe_gc_pending=1 and
311 * arch_set_pseudo_atomic_interrupted(..) When we come out of
312 * pseudo_atomic we're marked as interrupted, so we call
313 * interrupt_handle_pending, which does the GC using the pending
314 * context (it needs a context so that it has registers to use as
315 * GC roots) then notices there's no actual interrupt handler to
316 * call, so doesn't. That's the second question [1b] answered,
317 * anyway. Why we still need to copy the pending_mask into the
318 * context given that we're now done with the context anyway, I
321 memcpy(os_context_sigmask_addr(context), &pending_mask,
322 4 /* sizeof(sigset_t) */ );
324 sigemptyset(&pending_mask);
325 if (pending_signal) {
326 int signal = pending_signal;
328 memcpy(&info, &pending_info, sizeof(siginfo_t));
330 interrupt_handle_now(signal, &info, context);
335 * the two main signal handlers:
336 * interrupt_handle_now(..)
337 * maybe_now_maybe_later(..)
341 interrupt_handle_now(int signal, siginfo_t *info, void *void_context)
343 os_context_t *context = (os_context_t*)void_context;
345 boolean were_in_lisp;
347 union interrupt_handler handler;
349 /* FIXME: The CMU CL we forked off of had this Linux-only
350 * operation here. Newer CMU CLs (e.g. 18c) have hairier
351 * Linux/i386-only logic here. SBCL seems to be more reliable
352 * without anything here. However, if we start supporting code
353 * which sets the rounding mode, then we may want to do something
354 * special to force the rounding mode back to some standard value
355 * here, so that ISRs can have a standard environment. (OTOH, if
356 * rounding modes are under user control, then perhaps we should
357 * leave this up to the user.)
359 * In the absence of a test case to show that this is really a
360 * problem, we just suppress this code completely (just like the
361 * parallel code in maybe_now_maybe_later).
363 * SET_FPU_CONTROL_WORD(context->__fpregs_mem.cw);
366 handler = interrupt_handlers[signal];
368 if (ARE_SAME_HANDLER(handler.c, SIG_IGN)) {
373 were_in_lisp = !foreign_function_call_active;
377 fake_foreign_function_call(context);
382 "/entering interrupt_handle_now(%d, info, context)\n",
386 if (ARE_SAME_HANDLER(handler.c, SIG_DFL)) {
388 /* This can happen if someone tries to ignore or default one
389 * of the signals we need for runtime support, and the runtime
390 * support decides to pass on it. */
391 lose("no handler for signal %d in interrupt_handle_now(..)", signal);
393 } else if (lowtag_of(handler.lisp) == FUN_POINTER_LOWTAG) {
395 /* Allocate the SAPs while the interrupts are still disabled.
396 * (FIXME: Why? This is the way it was done in CMU CL, and it
397 * even had the comment noting that this is the way it was
398 * done, but no motivation..) */
399 lispobj info_sap,context_sap = alloc_sap(context);
400 info_sap = alloc_sap(info);
401 /* Allow signals again. */
402 sigprocmask(SIG_SETMASK, os_context_sigmask_addr(context), 0);
405 SHOW("calling Lisp-level handler");
408 funcall3(handler.lisp,
415 SHOW("calling C-level handler");
418 /* Allow signals again. */
419 sigprocmask(SIG_SETMASK, os_context_sigmask_addr(context), 0);
421 (*handler.c)(signal, info, void_context);
428 undo_fake_foreign_function_call(context);
433 "/returning from interrupt_handle_now(%d, info, context)\n",
439 maybe_now_maybe_later(int signal, siginfo_t *info, void *void_context)
441 os_context_t *context = (os_context_t*)void_context;
443 /* FIXME: See Debian cmucl 2.4.17, and mail from DTC on the CMU CL
444 * mailing list 23 Oct 1999, for changes in FPU handling at
445 * interrupt time which should be ported into SBCL. Also see the
446 * analogous logic at the head of interrupt_handle_now for
447 * more related FIXME stuff.
449 * For now, we just suppress this code completely.
451 * SET_FPU_CONTROL_WORD(context->__fpregs_mem.cw);
454 /* see comments at top of code/signal.lisp for what's going on here
455 * with INTERRUPTS_ENABLED/INTERRUPT_HANDLE_NOW
457 if (SymbolValue(INTERRUPTS_ENABLED) == NIL) {
459 /* FIXME: This code is exactly the same as the code in the
460 * other leg of the if(..), and should be factored out into
461 * a shared function. */
462 pending_signal = signal;
463 memcpy(&pending_info, info, sizeof(siginfo_t));
464 memcpy(&pending_mask,
465 os_context_sigmask_addr(context),
467 sigaddset_blockable(os_context_sigmask_addr(context));
468 SetSymbolValue(INTERRUPT_PENDING, T);
472 (!foreign_function_call_active) &&
474 arch_pseudo_atomic_atomic(context)) {
476 /* FIXME: It would probably be good to replace these bare
477 * memcpy(..) calls with calls to cpy_siginfo_t and
478 * cpy_sigset_t, so that we only have to get the sizeof
479 * expressions right in one place, and after that static type
480 * checking takes over. */
481 pending_signal = signal;
482 memcpy(&pending_info, info, sizeof(siginfo_t));
483 memcpy(&pending_mask,
484 os_context_sigmask_addr(context),
486 sigaddset_blockable(os_context_sigmask_addr(context));
488 arch_set_pseudo_atomic_interrupted(context);
491 interrupt_handle_now(signal, info, context);
496 * stuff to detect and handle hitting the GC trigger
499 #ifndef INTERNAL_GC_TRIGGER
501 gc_trigger_hit(int signal, siginfo_t *info, os_context_t *context)
503 if (current_auto_gc_trigger == NULL)
506 lispobj *badaddr=(lispobj *)arch_get_bad_addr(signal,
510 return (badaddr >= current_auto_gc_trigger &&
511 badaddr < current_dynamic_space + DYNAMIC_SPACE_SIZE);
517 /* This function gets called from the SIGSEGV (for e.g. Linux or
518 * OpenBSD) or SIGBUS (for e.g. FreeBSD) handler. Here we check
519 * whether the signal was due to treading on the mprotect()ed zone -
520 * and if so, arrange for a GC to happen. */
522 interrupt_maybe_gc(int signal, siginfo_t *info, void *void_context)
524 os_context_t *context=(os_context_t *) void_context;
526 if (!foreign_function_call_active
527 #ifndef INTERNAL_GC_TRIGGER
528 && gc_trigger_hit(signal, info, context)
531 #ifndef INTERNAL_GC_TRIGGER
532 clear_auto_gc_trigger();
535 if (arch_pseudo_atomic_atomic(context)) {
536 /* don't GC during an atomic operation. Instead, copy the
537 * signal mask somewhere safe. interrupt_handle_pending
538 * will detect pending_signal==0 and know to do a GC with the
539 * signal context instead of calling a Lisp-level handler */
540 maybe_gc_pending = 1;
541 if (pending_signal == 0) {
542 /* FIXME: This copy-pending_mask-then-sigaddset_blockable
543 * idiom occurs over and over. It should be factored out
544 * into a function with a descriptive name. */
545 memcpy(&pending_mask,
546 os_context_sigmask_addr(context),
548 sigaddset_blockable(os_context_sigmask_addr(context));
550 arch_set_pseudo_atomic_interrupted(context);
553 fake_foreign_function_call(context);
554 funcall0(SymbolFunction(MAYBE_GC));
555 undo_fake_foreign_function_call(context);
566 * noise to install handlers
570 * what low-level signal handlers looked like before
571 * undoably_install_low_level_interrupt_handler() got involved
573 struct low_level_signal_handler_state {
575 void (*handler)(int, siginfo_t*, void*);
576 } old_low_level_signal_handler_states[NSIG];
579 uninstall_low_level_interrupt_handlers_atexit(void)
582 for (signal = 0; signal < NSIG; ++signal) {
583 struct low_level_signal_handler_state
584 *old_low_level_signal_handler_state =
585 old_low_level_signal_handler_states + signal;
586 if (old_low_level_signal_handler_state->was_modified) {
588 sa.sa_sigaction = old_low_level_signal_handler_state->handler;
589 sigemptyset(&sa.sa_mask);
590 sa.sa_flags = SA_SIGINFO | SA_RESTART;
591 sigaction(signal, &sa, NULL);
596 /* Undoably install a special low-level handler for signal; or if
597 * handler is SIG_DFL, remove any special handling for signal.
599 * The "undoably" aspect is because we also arrange with atexit() for
600 * the handler to be restored to its old value. This is for tidiness:
601 * it shouldn't matter much ordinarily, but it does remove a window
602 * where e.g. memory fault signals (SIGSEGV or SIGBUS, which in
603 * ordinary operation of SBCL are sent to the generational garbage
604 * collector, then possibly onward to Lisp code) or SIGINT (which is
605 * ordinarily passed to Lisp code) could otherwise be handled
606 * bizarrely/brokenly because the Lisp code would try to deal with
607 * them using machinery (like stream output buffers) which has already
608 * been dismantled. */
610 undoably_install_low_level_interrupt_handler (int signal,
616 struct low_level_signal_handler_state *old_low_level_signal_handler_state =
617 old_low_level_signal_handler_states + signal;
619 if (0 > signal || signal >= NSIG) {
620 lose("bad signal number %d", signal);
623 sa.sa_sigaction = handler;
624 sigemptyset(&sa.sa_mask);
625 sigaddset_blockable(&sa.sa_mask);
626 sa.sa_flags = SA_SIGINFO | SA_RESTART;
628 /* In the case of interrupt handlers which are modified more than
629 * once, we only save the original unmodified copy. */
630 if (!old_low_level_signal_handler_state->was_modified) {
631 struct sigaction *old_handler =
632 (struct sigaction*) &old_low_level_signal_handler_state->handler;
633 old_low_level_signal_handler_state->was_modified = 1;
634 sigaction(signal, &sa, old_handler);
636 sigaction(signal, &sa, NULL);
639 interrupt_low_level_handlers[signal] =
640 (ARE_SAME_HANDLER(handler, SIG_DFL) ? 0 : handler);
643 /* This is called from Lisp. */
645 install_handler(int signal, void handler(int, siginfo_t*, void*))
649 union interrupt_handler oldhandler;
651 FSHOW((stderr, "/entering POSIX install_handler(%d, ..)\n", signal));
654 sigaddset(&new, signal);
655 sigprocmask(SIG_BLOCK, &new, &old);
658 sigaddset_blockable(&new);
660 FSHOW((stderr, "/interrupt_low_level_handlers[signal]=%d\n",
661 interrupt_low_level_handlers[signal]));
662 if (interrupt_low_level_handlers[signal]==0) {
663 if (ARE_SAME_HANDLER(handler, SIG_DFL) ||
664 ARE_SAME_HANDLER(handler, SIG_IGN)) {
665 sa.sa_sigaction = handler;
666 } else if (sigismember(&new, signal)) {
667 sa.sa_sigaction = maybe_now_maybe_later;
669 sa.sa_sigaction = interrupt_handle_now;
672 sigemptyset(&sa.sa_mask);
673 sigaddset_blockable(&sa.sa_mask);
674 sa.sa_flags = SA_SIGINFO | SA_RESTART;
676 sigaction(signal, &sa, NULL);
679 oldhandler = interrupt_handlers[signal];
680 interrupt_handlers[signal].c = handler;
682 sigprocmask(SIG_SETMASK, &old, 0);
684 FSHOW((stderr, "/leaving POSIX install_handler(%d, ..)\n", signal));
686 return (unsigned long)oldhandler.lisp;
694 SHOW("entering interrupt_init()");
696 /* Set up for recovery from any installed low-level handlers. */
697 atexit(&uninstall_low_level_interrupt_handlers_atexit);
699 /* Set up high level handler information. */
700 for (i = 0; i < NSIG; i++) {
701 interrupt_handlers[i].c =
702 /* (The cast here blasts away the distinction between
703 * SA_SIGACTION-style three-argument handlers and
704 * signal(..)-style one-argument handlers, which is OK
705 * because it works to call the 1-argument form where the
706 * 3-argument form is expected.) */
707 (void (*)(int, siginfo_t*, void*))SIG_DFL;
710 SHOW("returning from interrupt_init()");