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 Linux) or SIGBUS (for 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");
247 /* Display some rudimentary debugging information about the
248 * error, so that even if the Lisp error handler gets badly
249 * confused, we have a chance to determine what's going on. */
250 describe_internal_error(context);
252 funcall2(SymbolFunction(INTERNAL_ERROR), context_sap,
253 continuable ? T : NIL);
255 describe_internal_error(context);
256 /* There's no good way to recover from an internal error
257 * before the Lisp error handling mechanism is set up. */
258 lose("internal error too early in init, can't recover");
260 undo_fake_foreign_function_call(context);
262 arch_skip_instruction(context);
266 /* This function handles pending interrupts. Note that in C/kernel
267 * terms we dealt with the signal already; we just haven't decided
268 * whether to call a Lisp handler or do a GC or something like that.
269 * If it helps, you can think of pending_{signal,mask,info} as a
270 * one-element queue of signals that we have acknowledged but not
274 interrupt_handle_pending(os_context_t *context)
277 boolean were_in_lisp = !foreign_function_call_active;
280 SetSymbolValue(INTERRUPT_PENDING, NIL);
282 if (maybe_gc_pending) {
283 maybe_gc_pending = 0;
288 fake_foreign_function_call(context);
290 funcall0(SymbolFunction(MAYBE_GC));
295 undo_fake_foreign_function_call(context);
299 /* FIXME: This isn't very clear. It would be good to reverse
300 * engineer it and rewrite the code more clearly, or write a clear
301 * explanation of what's going on in the comments, or both.
303 * WHN's question 1a: How come we unconditionally copy from
304 * pending_mask into the context, and then test whether
305 * pending_signal is set?
307 * WHN's question 1b: If pending_signal wasn't set, how could
308 * pending_mask be valid?
310 * Dan Barlow's reply (sbcl-devel 2001-03-13): And the answer is -
311 * or appears to be - because interrupt_maybe_gc set it that way
312 * (look in the #ifndef __i386__ bit). We can't GC during a
313 * pseudo-atomic, so we set maybe_gc_pending=1 and
314 * arch_set_pseudo_atomic_interrupted(..) When we come out of
315 * pseudo_atomic we're marked as interrupted, so we call
316 * interrupt_handle_pending, which does the GC using the pending
317 * context (it needs a context so that it has registers to use as
318 * GC roots) then notices there's no actual interrupt handler to
319 * call, so doesn't. That's the second question [1b] answered,
320 * anyway. Why we still need to copy the pending_mask into the
321 * context given that we're now done with the context anyway, I
323 memcpy(os_context_sigmask_addr(context), &pending_mask, 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);
381 FSHOW((stderr, "in interrupt_handle_now(%d, info, context)\n", signal));
384 if (ARE_SAME_HANDLER(handler.c, SIG_DFL)) {
386 /* This can happen if someone tries to ignore or default one
387 * of the signals we need for runtime support, and the runtime
388 * support decides to pass on it. */
389 lose("no handler for signal %d in interrupt_handle_now(..)", signal);
391 } else if (LowtagOf(handler.lisp) == type_FunctionPointer) {
393 /* Allocate the SAPs while the interrupts are still disabled.
394 * (FIXME: Why? This is the way it was done in CMU CL, and it
395 * even had the comment noting that this is the way it was
396 * done, but no motivation..) */
397 lispobj info_sap,context_sap = alloc_sap(context);
398 info_sap = alloc_sap(info);
399 /* Allow signals again. */
400 sigprocmask(SIG_SETMASK, os_context_sigmask_addr(context), 0);
403 SHOW("calling Lisp-level handler");
406 funcall3(handler.lisp,
413 SHOW("calling C-level handler");
416 /* Allow signals again. */
417 sigprocmask(SIG_SETMASK, os_context_sigmask_addr(context), 0);
419 (*handler.c)(signal, info, void_context);
426 undo_fake_foreign_function_call(context);
431 maybe_now_maybe_later(int signal, siginfo_t *info, void *void_context)
433 os_context_t *context = (os_context_t*)void_context;
435 /* FIXME: See Debian cmucl 2.4.17, and mail from DTC on the CMU CL
436 * mailing list 23 Oct 1999, for changes in FPU handling at
437 * interrupt time which should be ported into SBCL. Also see the
438 * analogous logic at the head of interrupt_handle_now for
439 * more related FIXME stuff.
441 * For now, we just suppress this code completely.
443 * SET_FPU_CONTROL_WORD(context->__fpregs_mem.cw);
446 /* see comments at top of code/signal.lisp for what's going on here
447 * with INTERRUPTS_ENABLED/INTERRUPT_HANDLE_NOW
449 if (SymbolValue(INTERRUPTS_ENABLED) == NIL) {
451 /* FIXME: This code is exactly the same as the code in the
452 * other leg of the if(..), and should be factored out into
453 * a shared function. */
454 pending_signal = signal;
455 memcpy(&pending_info, info, sizeof(siginfo_t));
456 memcpy(&pending_mask,
457 os_context_sigmask_addr(context),
459 sigaddset_blockable(os_context_sigmask_addr(context));
460 SetSymbolValue(INTERRUPT_PENDING, T);
464 (!foreign_function_call_active) &&
466 arch_pseudo_atomic_atomic(context)) {
468 /* FIXME: It would probably be good to replace these bare
469 * memcpy(..) calls with calls to cpy_siginfo_t and
470 * cpy_sigset_t, so that we only have to get the sizeof
471 * expressions right in one place, and after that static type
472 * checking takes over. */
473 pending_signal = signal;
474 memcpy(&pending_info, info, sizeof(siginfo_t));
475 memcpy(&pending_mask,
476 os_context_sigmask_addr(context),
478 sigaddset_blockable(os_context_sigmask_addr(context));
480 arch_set_pseudo_atomic_interrupted(context);
483 interrupt_handle_now(signal, info, context);
488 * stuff to detect and handle hitting the GC trigger
491 #ifndef INTERNAL_GC_TRIGGER
493 gc_trigger_hit(int signal, siginfo_t *info, os_context_t *context)
495 if (current_auto_gc_trigger == NULL)
498 lispobj *badaddr=(lispobj *)arch_get_bad_addr(signal,
502 return (badaddr >= current_auto_gc_trigger &&
503 badaddr < current_dynamic_space + DYNAMIC_SPACE_SIZE);
509 /* This function gets called from the SIGSEGV (Linux) or SIGBUS (BSD)
510 * handler. Here we check whether the signal was due to treading on
511 * the mprotect()ed zone - and if so, arrange for a GC to happen.
514 interrupt_maybe_gc(int signal, siginfo_t *info, void *void_context)
516 os_context_t *context=(os_context_t *) void_context;
518 if (!foreign_function_call_active
519 #ifndef INTERNAL_GC_TRIGGER
520 && gc_trigger_hit(signal, info, context)
523 #ifndef INTERNAL_GC_TRIGGER
524 clear_auto_gc_trigger();
527 if (arch_pseudo_atomic_atomic(context)) {
528 /* don't GC during an atomic operation. Instead, copy the
529 * signal mask somewhere safe. interrupt_handle_pending
530 * will detect pending_signal==0 and know to do a GC with the
531 * signal context instead of calling a Lisp-level handler */
532 maybe_gc_pending = 1;
533 if (pending_signal == 0) {
534 /* FIXME: This copy-pending_mask-then-sigaddset_blockable
535 * idiom occurs over and over. It should be factored out
536 * into a function with a descriptive name. */
537 memcpy(&pending_mask,
538 os_context_sigmask_addr(context),
540 sigaddset_blockable(os_context_sigmask_addr(context));
542 arch_set_pseudo_atomic_interrupted(context);
545 fake_foreign_function_call(context);
546 funcall0(SymbolFunction(MAYBE_GC));
547 undo_fake_foreign_function_call(context);
558 * noise to install handlers
561 /* Install a special low-level handler for signal; or if handler is
562 * SIG_DFL, remove any special handling for signal. */
564 interrupt_install_low_level_handler (int signal,
565 void handler(int, siginfo_t*, void*))
569 sa.sa_sigaction = handler;
570 sigemptyset(&sa.sa_mask);
571 sigaddset_blockable(&sa.sa_mask);
572 sa.sa_flags = SA_SIGINFO | SA_RESTART;
574 sigaction(signal, &sa, NULL);
575 interrupt_low_level_handlers[signal] =
576 (ARE_SAME_HANDLER(handler,SIG_DFL) ? 0 : handler);
579 /* This is called from Lisp. */
581 install_handler(int signal, void handler(int, siginfo_t*, void*))
585 union interrupt_handler oldhandler;
587 FSHOW((stderr, "entering POSIX install_handler(%d, ..)\n", signal));
590 sigaddset(&new, signal);
591 sigprocmask(SIG_BLOCK, &new, &old);
594 sigaddset_blockable(&new);
596 FSHOW((stderr, "interrupt_low_level_handlers[signal]=%d\n",
597 interrupt_low_level_handlers[signal]));
598 if (interrupt_low_level_handlers[signal]==0) {
599 if (ARE_SAME_HANDLER(handler, SIG_DFL) ||
600 ARE_SAME_HANDLER(handler, SIG_IGN)) {
601 sa.sa_sigaction = handler;
602 } else if (sigismember(&new, signal)) {
603 sa.sa_sigaction = maybe_now_maybe_later;
605 sa.sa_sigaction = interrupt_handle_now;
608 sigemptyset(&sa.sa_mask);
609 sigaddset_blockable(&sa.sa_mask);
610 sa.sa_flags = SA_SIGINFO | SA_RESTART;
612 sigaction(signal, &sa, NULL);
615 oldhandler = interrupt_handlers[signal];
616 interrupt_handlers[signal].c = handler;
618 sigprocmask(SIG_SETMASK, &old, 0);
620 FSHOW((stderr, "leaving POSIX install_handler(%d, ..)\n", signal));
622 return (unsigned long)oldhandler.lisp;
630 for (i = 0; i < NSIG; i++) {
631 interrupt_handlers[i].c =
632 /* (The cast here blasts away the distinction between
633 * SA_SIGACTION-style three-argument handlers and
634 * signal(..)-style one-argument handlers, which is OK
635 * because it works to call the 1-argument form where the
636 * 3-argument form is expected.) */
637 (void (*)(int, siginfo_t*, void*))SIG_DFL;