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.
19 #ifdef mach /* KLUDGE: #ifdef on lowercase symbols? Ick. -- WHN 19990904 */
29 #include "interrupt.h"
39 void sigaddset_blockable(sigset_t *s)
43 sigaddset(s, SIGQUIT);
44 sigaddset(s, SIGPIPE);
45 sigaddset(s, SIGALRM);
47 sigaddset(s, SIGTSTP);
48 sigaddset(s, SIGCHLD);
50 sigaddset(s, SIGXCPU);
51 sigaddset(s, SIGXFSZ);
52 sigaddset(s, SIGVTALRM);
53 sigaddset(s, SIGPROF);
54 sigaddset(s, SIGWINCH);
55 sigaddset(s, SIGUSR1);
56 sigaddset(s, SIGUSR2);
59 /* When we catch an internal error, should we pass it back to Lisp to
60 * be handled in a high-level way? (Early in cold init, the answer is
61 * 'no', because Lisp is still too brain-dead to handle anything.
62 * After sufficient initialization has been completed, the answer
64 boolean internal_errors_enabled = 0;
66 os_context_t *lisp_interrupt_contexts[MAX_INTERRUPTS];
68 /* As far as I can tell, what's going on here is:
70 * In the case of most signals, when Lisp asks us to handle the
71 * signal, the outermost handler (the one actually passed to UNIX) is
72 * either interrupt_handle_now(..) or interrupt_handle_later(..).
73 * In that case, the Lisp-level handler is stored in interrupt_handlers[..]
74 * and interrupt_low_level_handlers[..] is cleared.
76 * However, some signals need special handling, e.g.
78 * o the SIGSEGV (for e.g. Linux) or SIGBUS (for e.g. FreeBSD) used by the
79 * garbage collector to detect violations of write protection,
80 * because some cases of such signals (e.g. GC-related violations of
81 * write protection) are handled at C level and never passed on to
82 * Lisp. For such signals, we still store any Lisp-level handler
83 * in interrupt_handlers[..], but for the outermost handle we use
84 * the value from interrupt_low_level_handlers[..], instead of the
85 * ordinary interrupt_handle_now(..) or interrupt_handle_later(..).
87 * o the SIGTRAP (Linux/Alpha) which Lisp code uses to handle breakpoints,
88 * pseudo-atomic sections, and some classes of error (e.g. "function
89 * not defined"). This never goes anywhere near the Lisp handlers at all.
90 * See runtime/alpha-arch.c and code/signal.lisp
92 * - WHN 20000728, dan 20010128 */
95 void (*interrupt_low_level_handlers[NSIG]) (int, siginfo_t*, void*) = {0};
96 union interrupt_handler interrupt_handlers[NSIG];
98 /* signal number, siginfo_t, and old mask information for pending signal
100 * pending_signal=0 when there is no pending signal. */
101 static int pending_signal = 0;
102 static siginfo_t pending_info;
103 static sigset_t pending_mask;
105 static boolean maybe_gc_pending = 0;
108 * utility routines used by various signal handlers
112 fake_foreign_function_call(os_context_t *context)
119 /* Get current Lisp state from context. */
121 dynamic_space_free_pointer =
122 (lispobj *)(*os_context_register_addr(context, reg_ALLOC));
124 if ((long)dynamic_space_free_pointer & 1) {
125 lose("dead in fake_foreign_function_call, context = %x", context);
130 current_binding_stack_pointer =
131 (lispobj *)(*os_context_register_addr(context, reg_BSP));
135 /* Build a fake stack frame. */
136 current_control_frame_pointer =
137 (lispobj *)(*os_context_register_addr(context, reg_CSP));
138 if ((lispobj *)(*os_context_register_addr(context, reg_CFP))
139 == current_control_frame_pointer) {
140 /* There is a small window during call where the callee's
141 * frame isn't built yet. */
142 if (LowtagOf(*os_context_register_addr(context, reg_CODE))
143 == type_FunctionPointer) {
144 /* We have called, but not built the new frame, so
145 * build it for them. */
146 current_control_frame_pointer[0] =
147 *os_context_register_addr(context, reg_OCFP);
148 current_control_frame_pointer[1] =
149 *os_context_register_addr(context, reg_LRA);
150 current_control_frame_pointer += 8;
151 /* Build our frame on top of it. */
152 oldcont = (lispobj)(*os_context_register_addr(context, reg_CFP));
155 /* We haven't yet called, build our frame as if the
156 * partial frame wasn't there. */
157 oldcont = (lispobj)(*os_context_register_addr(context, reg_OCFP));
160 /* ### We can't tell whether we are still in the caller if it had
161 * to reg_ALLOCate the stack frame due to stack arguments. */
162 /* ### Can anything strange happen during return? */
165 oldcont = (lispobj)(*os_context_register_addr(context, reg_CFP));
168 current_control_stack_pointer = current_control_frame_pointer + 8;
170 current_control_frame_pointer[0] = oldcont;
171 current_control_frame_pointer[1] = NIL;
172 current_control_frame_pointer[2] =
173 (lispobj)(*os_context_register_addr(context, reg_CODE));
176 /* Do dynamic binding of the active interrupt context index
177 * and save the context in the context array. */
178 context_index = SymbolValue(FREE_INTERRUPT_CONTEXT_INDEX)>>2;
179 /* FIXME: Ick! Why use abstract "make_fixnum" in some places if
180 * you're going to convert from fixnum by bare >>2 in other
181 * places? Use fixnum_value(..) here, and look for other places
182 * which do bare >> and << for fixnum_value and make_fixnum. */
184 if (context_index >= MAX_INTERRUPTS) {
185 lose("maximum interrupt nesting depth (%d) exceeded",
189 bind_variable(FREE_INTERRUPT_CONTEXT_INDEX,
190 make_fixnum(context_index + 1));
192 lisp_interrupt_contexts[context_index] = context;
194 /* no longer in Lisp now */
195 foreign_function_call_active = 1;
199 undo_fake_foreign_function_call(os_context_t *context)
201 /* Block all blockable signals. */
204 sigaddset_blockable(&block);
205 sigprocmask(SIG_BLOCK, &block, 0);
207 /* going back into Lisp */
208 foreign_function_call_active = 0;
210 /* Undo dynamic binding. */
211 /* ### Do I really need to unbind_to_here()? */
212 /* FIXME: Is this to undo the binding of
213 * FREE_INTERRUPT_CONTEXT_INDEX? If so, we should say so. And
214 * perhaps yes, unbind_to_here() really would be clearer and less
219 /* Put the dynamic space free pointer back into the context. */
220 *os_context_register_addr(context, reg_ALLOC) =
221 (unsigned long) dynamic_space_free_pointer;
225 /* a handler for the signal caused by execution of a trap opcode
226 * signalling an internal error */
228 interrupt_internal_error(int signal, siginfo_t *info, os_context_t *context,
231 lispobj context_sap = 0;
233 fake_foreign_function_call(context);
235 /* Allocate the SAP object while the interrupts are still
237 if (internal_errors_enabled) {
238 context_sap = alloc_sap(context);
241 sigprocmask(SIG_SETMASK, os_context_sigmask_addr(context), 0);
243 if (internal_errors_enabled) {
244 SHOW("in interrupt_internal_error");
246 /* Display some rudimentary debugging information about the
247 * error, so that even if the Lisp error handler gets badly
248 * confused, we have a chance to determine what's going on. */
249 describe_internal_error(context);
251 funcall2(SymbolFunction(INTERNAL_ERROR), context_sap,
252 continuable ? T : NIL);
254 describe_internal_error(context);
255 /* There's no good way to recover from an internal error
256 * before the Lisp error handling mechanism is set up. */
257 lose("internal error too early in init, can't recover");
259 undo_fake_foreign_function_call(context);
261 arch_skip_instruction(context);
265 /* This function handles pending interrupts. Note that in C/kernel
266 * terms we dealt with the signal already; we just haven't decided
267 * whether to call a Lisp handler or do a GC or something like that.
268 * If it helps, you can think of pending_{signal,mask,info} as a
269 * one-element queue of signals that we have acknowledged but not
273 interrupt_handle_pending(os_context_t *context)
276 boolean were_in_lisp = !foreign_function_call_active;
279 SetSymbolValue(INTERRUPT_PENDING, NIL);
281 if (maybe_gc_pending) {
282 maybe_gc_pending = 0;
287 fake_foreign_function_call(context);
289 funcall0(SymbolFunction(MAYBE_GC));
294 undo_fake_foreign_function_call(context);
298 /* FIXME: This isn't very clear. It would be good to reverse
299 * engineer it and rewrite the code more clearly, or write a clear
300 * explanation of what's going on in the comments, or both.
302 * WHN's question 1a: How come we unconditionally copy from
303 * pending_mask into the context, and then test whether
304 * pending_signal is set?
306 * WHN's question 1b: If pending_signal wasn't set, how could
307 * pending_mask be valid?
309 * Dan Barlow's reply (sbcl-devel 2001-03-13): And the answer is -
310 * or appears to be - because interrupt_maybe_gc set it that way
311 * (look in the #ifndef __i386__ bit). We can't GC during a
312 * pseudo-atomic, so we set maybe_gc_pending=1 and
313 * arch_set_pseudo_atomic_interrupted(..) When we come out of
314 * pseudo_atomic we're marked as interrupted, so we call
315 * interrupt_handle_pending, which does the GC using the pending
316 * context (it needs a context so that it has registers to use as
317 * GC roots) then notices there's no actual interrupt handler to
318 * call, so doesn't. That's the second question [1b] answered,
319 * anyway. Why we still need to copy the pending_mask into the
320 * context given that we're now done with the context anyway, I
322 memcpy(os_context_sigmask_addr(context), &pending_mask, sizeof(sigset_t));
323 sigemptyset(&pending_mask);
324 if (pending_signal) {
325 int signal = pending_signal;
327 memcpy(&info, &pending_info, sizeof(siginfo_t));
329 interrupt_handle_now(signal, &info, context);
334 * the two main signal handlers:
335 * interrupt_handle_now(..)
336 * maybe_now_maybe_later(..)
340 interrupt_handle_now(int signal, siginfo_t *info, void *void_context)
342 os_context_t *context = (os_context_t*)void_context;
344 boolean were_in_lisp;
346 union interrupt_handler handler;
348 /* FIXME: The CMU CL we forked off of had this Linux-only
349 * operation here. Newer CMU CLs (e.g. 18c) have hairier
350 * Linux/i386-only logic here. SBCL seems to be more reliable
351 * without anything here. However, if we start supporting code
352 * which sets the rounding mode, then we may want to do something
353 * special to force the rounding mode back to some standard value
354 * here, so that ISRs can have a standard environment. (OTOH, if
355 * rounding modes are under user control, then perhaps we should
356 * leave this up to the user.)
358 * In the absence of a test case to show that this is really a
359 * problem, we just suppress this code completely (just like the
360 * parallel code in maybe_now_maybe_later).
362 * SET_FPU_CONTROL_WORD(context->__fpregs_mem.cw);
365 handler = interrupt_handlers[signal];
367 if (ARE_SAME_HANDLER(handler.c, SIG_IGN)) {
372 were_in_lisp = !foreign_function_call_active;
376 fake_foreign_function_call(context);
381 "/entering interrupt_handle_now(%d, info, context)\n",
385 if (ARE_SAME_HANDLER(handler.c, SIG_DFL)) {
387 /* This can happen if someone tries to ignore or default one
388 * of the signals we need for runtime support, and the runtime
389 * support decides to pass on it. */
390 lose("no handler for signal %d in interrupt_handle_now(..)", signal);
392 } else if (LowtagOf(handler.lisp) == type_FunctionPointer) {
394 /* Allocate the SAPs while the interrupts are still disabled.
395 * (FIXME: Why? This is the way it was done in CMU CL, and it
396 * even had the comment noting that this is the way it was
397 * done, but no motivation..) */
398 lispobj info_sap,context_sap = alloc_sap(context);
399 info_sap = alloc_sap(info);
400 /* Allow signals again. */
401 sigprocmask(SIG_SETMASK, os_context_sigmask_addr(context), 0);
404 SHOW("calling Lisp-level handler");
407 funcall3(handler.lisp,
414 SHOW("calling C-level handler");
417 /* Allow signals again. */
418 sigprocmask(SIG_SETMASK, os_context_sigmask_addr(context), 0);
420 (*handler.c)(signal, info, void_context);
427 undo_fake_foreign_function_call(context);
432 "/returning from interrupt_handle_now(%d, info, context)\n",
438 maybe_now_maybe_later(int signal, siginfo_t *info, void *void_context)
440 os_context_t *context = (os_context_t*)void_context;
442 /* FIXME: See Debian cmucl 2.4.17, and mail from DTC on the CMU CL
443 * mailing list 23 Oct 1999, for changes in FPU handling at
444 * interrupt time which should be ported into SBCL. Also see the
445 * analogous logic at the head of interrupt_handle_now for
446 * more related FIXME stuff.
448 * For now, we just suppress this code completely.
450 * SET_FPU_CONTROL_WORD(context->__fpregs_mem.cw);
453 /* see comments at top of code/signal.lisp for what's going on here
454 * with INTERRUPTS_ENABLED/INTERRUPT_HANDLE_NOW
456 if (SymbolValue(INTERRUPTS_ENABLED) == NIL) {
458 /* FIXME: This code is exactly the same as the code in the
459 * other leg of the if(..), and should be factored out into
460 * a shared function. */
461 pending_signal = signal;
462 memcpy(&pending_info, info, sizeof(siginfo_t));
463 memcpy(&pending_mask,
464 os_context_sigmask_addr(context),
466 sigaddset_blockable(os_context_sigmask_addr(context));
467 SetSymbolValue(INTERRUPT_PENDING, T);
471 (!foreign_function_call_active) &&
473 arch_pseudo_atomic_atomic(context)) {
475 /* FIXME: It would probably be good to replace these bare
476 * memcpy(..) calls with calls to cpy_siginfo_t and
477 * cpy_sigset_t, so that we only have to get the sizeof
478 * expressions right in one place, and after that static type
479 * checking takes over. */
480 pending_signal = signal;
481 memcpy(&pending_info, info, sizeof(siginfo_t));
482 memcpy(&pending_mask,
483 os_context_sigmask_addr(context),
485 sigaddset_blockable(os_context_sigmask_addr(context));
487 arch_set_pseudo_atomic_interrupted(context);
490 interrupt_handle_now(signal, info, context);
495 * stuff to detect and handle hitting the GC trigger
498 #ifndef INTERNAL_GC_TRIGGER
500 gc_trigger_hit(int signal, siginfo_t *info, os_context_t *context)
502 if (current_auto_gc_trigger == NULL)
505 lispobj *badaddr=(lispobj *)arch_get_bad_addr(signal,
509 return (badaddr >= current_auto_gc_trigger &&
510 badaddr < current_dynamic_space + DYNAMIC_SPACE_SIZE);
516 /* This function gets called from the SIGSEGV (for e.g. Linux or
517 * OpenBSD) or SIGBUS (for e.g. FreeBSD) handler. Here we check
518 * whether the signal was due to treading on the mprotect()ed zone -
519 * and if so, arrange for a GC to happen. */
521 interrupt_maybe_gc(int signal, siginfo_t *info, void *void_context)
523 os_context_t *context=(os_context_t *) void_context;
525 if (!foreign_function_call_active
526 #ifndef INTERNAL_GC_TRIGGER
527 && gc_trigger_hit(signal, info, context)
530 #ifndef INTERNAL_GC_TRIGGER
531 clear_auto_gc_trigger();
534 if (arch_pseudo_atomic_atomic(context)) {
535 /* don't GC during an atomic operation. Instead, copy the
536 * signal mask somewhere safe. interrupt_handle_pending
537 * will detect pending_signal==0 and know to do a GC with the
538 * signal context instead of calling a Lisp-level handler */
539 maybe_gc_pending = 1;
540 if (pending_signal == 0) {
541 /* FIXME: This copy-pending_mask-then-sigaddset_blockable
542 * idiom occurs over and over. It should be factored out
543 * into a function with a descriptive name. */
544 memcpy(&pending_mask,
545 os_context_sigmask_addr(context),
547 sigaddset_blockable(os_context_sigmask_addr(context));
549 arch_set_pseudo_atomic_interrupted(context);
552 fake_foreign_function_call(context);
553 funcall0(SymbolFunction(MAYBE_GC));
554 undo_fake_foreign_function_call(context);
565 * noise to install handlers
569 * what low-level signal handlers looked like before
570 * undoably_install_low_level_interrupt_handler() got involved
572 struct low_level_signal_handler_state {
574 void (*handler)(int, siginfo_t*, void*);
575 } old_low_level_signal_handler_states[NSIG];
578 uninstall_low_level_interrupt_handlers_atexit(void)
581 for (signal = 0; signal < NSIG; ++signal) {
582 struct low_level_signal_handler_state
583 *old_low_level_signal_handler_state =
584 old_low_level_signal_handler_states + signal;
585 if (old_low_level_signal_handler_state->was_modified) {
587 sa.sa_sigaction = old_low_level_signal_handler_state->handler;
588 sigemptyset(&sa.sa_mask);
589 sa.sa_flags = SA_SIGINFO | SA_RESTART;
590 sigaction(signal, &sa, NULL);
595 /* Undoably install a special low-level handler for signal; or if
596 * handler is SIG_DFL, remove any special handling for signal.
598 * The "undoably" aspect is because we also arrange with atexit() for
599 * the handler to be restored to its old value. This is for tidiness:
600 * it shouldn't matter much ordinarily, but it does remove a window
601 * where e.g. memory fault signals (SIGSEGV or SIGBUS, which in
602 * ordinary operation of SBCL are sent to the generational garbage
603 * collector, then possibly onward to Lisp code) or SIGINT (which is
604 * ordinarily passed to Lisp code) could otherwise be handled
605 * bizarrely/brokenly because the Lisp code would try to deal with
606 * them using machinery (like stream output buffers) which has already
607 * been dismantled. */
609 undoably_install_low_level_interrupt_handler (int signal,
615 struct low_level_signal_handler_state *old_low_level_signal_handler_state =
616 old_low_level_signal_handler_states + signal;
618 if (0 > signal || signal >= NSIG) {
619 lose("bad signal number %d", signal);
622 sa.sa_sigaction = handler;
623 sigemptyset(&sa.sa_mask);
624 sigaddset_blockable(&sa.sa_mask);
625 sa.sa_flags = SA_SIGINFO | SA_RESTART;
627 /* In the case of interrupt handlers which are modified
628 * more than once, we only save the original unmodified
630 if (!old_low_level_signal_handler_state->was_modified) {
631 old_low_level_signal_handler_state->was_modified = 1;
632 sigaction(signal, &sa, &old_low_level_signal_handler_state->handler);
634 sigaction(signal, &sa, NULL);
637 interrupt_low_level_handlers[signal] =
638 (ARE_SAME_HANDLER(handler, SIG_DFL) ? 0 : handler);
641 /* This is called from Lisp. */
643 install_handler(int signal, void handler(int, siginfo_t*, void*))
647 union interrupt_handler oldhandler;
649 FSHOW((stderr, "/entering POSIX install_handler(%d, ..)\n", signal));
652 sigaddset(&new, signal);
653 sigprocmask(SIG_BLOCK, &new, &old);
656 sigaddset_blockable(&new);
658 FSHOW((stderr, "/interrupt_low_level_handlers[signal]=%d\n",
659 interrupt_low_level_handlers[signal]));
660 if (interrupt_low_level_handlers[signal]==0) {
661 if (ARE_SAME_HANDLER(handler, SIG_DFL) ||
662 ARE_SAME_HANDLER(handler, SIG_IGN)) {
663 sa.sa_sigaction = handler;
664 } else if (sigismember(&new, signal)) {
665 sa.sa_sigaction = maybe_now_maybe_later;
667 sa.sa_sigaction = interrupt_handle_now;
670 sigemptyset(&sa.sa_mask);
671 sigaddset_blockable(&sa.sa_mask);
672 sa.sa_flags = SA_SIGINFO | SA_RESTART;
674 sigaction(signal, &sa, NULL);
677 oldhandler = interrupt_handlers[signal];
678 interrupt_handlers[signal].c = handler;
680 sigprocmask(SIG_SETMASK, &old, 0);
682 FSHOW((stderr, "/leaving POSIX install_handler(%d, ..)\n", signal));
684 return (unsigned long)oldhandler.lisp;
692 SHOW("entering interrupt_init()");
694 /* Set up for recovery from any installed low-level handlers. */
695 atexit(&uninstall_low_level_interrupt_handlers_atexit);
697 /* Set up high level handler information. */
698 for (i = 0; i < NSIG; i++) {
699 interrupt_handlers[i].c =
700 /* (The cast here blasts away the distinction between
701 * SA_SIGACTION-style three-argument handlers and
702 * signal(..)-style one-argument handlers, which is OK
703 * because it works to call the 1-argument form where the
704 * 3-argument form is expected.) */
705 (void (*)(int, siginfo_t*, void*))SIG_DFL;
708 SHOW("returning from interrupt_init()");