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"
36 void sigaddset_blockable(sigset_t
*s
)
40 sigaddset(s
, SIGQUIT
);
41 sigaddset(s
, SIGPIPE
);
42 sigaddset(s
, SIGALRM
);
45 sigaddset(s
, SIGTSTP
);
46 sigaddset(s
, SIGCHLD
);
48 sigaddset(s
, SIGXCPU
);
49 sigaddset(s
, SIGXFSZ
);
50 sigaddset(s
, SIGVTALRM
);
51 sigaddset(s
, SIGPROF
);
52 sigaddset(s
, SIGWINCH
);
53 sigaddset(s
, SIGUSR1
);
54 sigaddset(s
, SIGUSR2
);
57 /* When we catch an internal error, should we pass it back to Lisp to
58 * be handled in a high-level way? (Early in cold init, the answer is
59 * 'no', because Lisp is still too brain-dead to handle anything.
60 * After sufficient initialization has been completed, the answer
62 boolean internal_errors_enabled
= 0;
64 os_context_t
*lisp_interrupt_contexts
[MAX_INTERRUPTS
];
66 /* As far as I can tell, what's going on here is:
68 * In the case of most signals, when Lisp asks us to handle the
69 * signal, the outermost handler (the one actually passed to UNIX) is
70 * either interrupt_handle_now(..) or interrupt_handle_later(..).
71 * In that case, the Lisp-level handler is stored in interrupt_handlers[..]
72 * and interrupt_low_level_handlers[..] is cleared.
74 * However, some signals need special handling, e.g.
76 * o the SIGSEGV (for e.g. Linux) or SIGBUS (for e.g. FreeBSD) used by the
77 * garbage collector to detect violations of write protection,
78 * because some cases of such signals (e.g. GC-related violations of
79 * write protection) are handled at C level and never passed on to
80 * Lisp. For such signals, we still store any Lisp-level handler
81 * in interrupt_handlers[..], but for the outermost handle we use
82 * the value from interrupt_low_level_handlers[..], instead of the
83 * ordinary interrupt_handle_now(..) or interrupt_handle_later(..).
85 * o the SIGTRAP (Linux/Alpha) which Lisp code uses to handle breakpoints,
86 * pseudo-atomic sections, and some classes of error (e.g. "function
87 * not defined"). This never goes anywhere near the Lisp handlers at all.
88 * See runtime/alpha-arch.c and code/signal.lisp
90 * - WHN 20000728, dan 20010128 */
93 void (*interrupt_low_level_handlers
[NSIG
]) (int, siginfo_t
*, void*) = {0};
94 union interrupt_handler interrupt_handlers
[NSIG
];
96 /* signal number, siginfo_t, and old mask information for pending signal
98 * pending_signal=0 when there is no pending signal. */
99 static int pending_signal
= 0;
100 static siginfo_t pending_info
;
101 static sigset_t pending_mask
;
103 static boolean maybe_gc_pending
= 0;
106 * utility routines used by various signal handlers
110 fake_foreign_function_call(os_context_t
*context
)
117 /* Get current Lisp state from context. */
119 dynamic_space_free_pointer
=
120 (lispobj
*)(*os_context_register_addr(context
, reg_ALLOC
));
122 if ((long)dynamic_space_free_pointer
& 1) {
123 lose("dead in fake_foreign_function_call, context = %x", context
);
128 current_binding_stack_pointer
=
129 (lispobj
*)(*os_context_register_addr(context
, reg_BSP
));
133 /* Build a fake stack frame. */
134 current_control_frame_pointer
=
135 (lispobj
*)(*os_context_register_addr(context
, reg_CSP
));
136 if ((lispobj
*)(*os_context_register_addr(context
, reg_CFP
))
137 == current_control_frame_pointer
) {
138 /* There is a small window during call where the callee's
139 * frame isn't built yet. */
140 if (lowtag_of(*os_context_register_addr(context
, reg_CODE
))
141 == FUN_POINTER_LOWTAG
) {
142 /* We have called, but not built the new frame, so
143 * build it for them. */
144 current_control_frame_pointer
[0] =
145 *os_context_register_addr(context
, reg_OCFP
);
146 current_control_frame_pointer
[1] =
147 *os_context_register_addr(context
, reg_LRA
);
148 current_control_frame_pointer
+= 8;
149 /* Build our frame on top of it. */
150 oldcont
= (lispobj
)(*os_context_register_addr(context
, reg_CFP
));
153 /* We haven't yet called, build our frame as if the
154 * partial frame wasn't there. */
155 oldcont
= (lispobj
)(*os_context_register_addr(context
, reg_OCFP
));
158 /* ### We can't tell whether we are still in the caller if it had
159 * to reg_ALLOCate the stack frame due to stack arguments. */
160 /* ### Can anything strange happen during return? */
163 oldcont
= (lispobj
)(*os_context_register_addr(context
, reg_CFP
));
166 current_control_stack_pointer
= current_control_frame_pointer
+ 8;
168 current_control_frame_pointer
[0] = oldcont
;
169 current_control_frame_pointer
[1] = NIL
;
170 current_control_frame_pointer
[2] =
171 (lispobj
)(*os_context_register_addr(context
, reg_CODE
));
174 /* Do dynamic binding of the active interrupt context index
175 * and save the context in the context array. */
176 context_index
= SymbolValue(FREE_INTERRUPT_CONTEXT_INDEX
)>>2;
177 /* FIXME: Ick! Why use abstract "make_fixnum" in some places if
178 * you're going to convert from fixnum by bare >>2 in other
179 * places? Use fixnum_value(..) here, and look for other places
180 * which do bare >> and << for fixnum_value and make_fixnum. */
182 if (context_index
>= MAX_INTERRUPTS
) {
183 lose("maximum interrupt nesting depth (%d) exceeded",
187 bind_variable(FREE_INTERRUPT_CONTEXT_INDEX
,
188 make_fixnum(context_index
+ 1));
190 lisp_interrupt_contexts
[context_index
] = context
;
192 /* no longer in Lisp now */
193 foreign_function_call_active
= 1;
197 undo_fake_foreign_function_call(os_context_t
*context
)
199 /* Block all blockable signals. */
202 sigaddset_blockable(&block
);
203 sigprocmask(SIG_BLOCK
, &block
, 0);
205 /* going back into Lisp */
206 foreign_function_call_active
= 0;
208 /* Undo dynamic binding. */
209 /* ### Do I really need to unbind_to_here()? */
210 /* FIXME: Is this to undo the binding of
211 * FREE_INTERRUPT_CONTEXT_INDEX? If so, we should say so. And
212 * perhaps yes, unbind_to_here() really would be clearer and less
214 /* dan (2001.08.10) thinks the above supposition is probably correct */
218 /* Put the dynamic space free pointer back into the context. */
219 *os_context_register_addr(context
, reg_ALLOC
) =
220 (unsigned long) dynamic_space_free_pointer
;
224 /* a handler for the signal caused by execution of a trap opcode
225 * signalling an internal error */
227 interrupt_internal_error(int signal
, siginfo_t
*info
, os_context_t
*context
,
230 lispobj context_sap
= 0;
232 fake_foreign_function_call(context
);
234 /* Allocate the SAP object while the interrupts are still
236 if (internal_errors_enabled
) {
237 context_sap
= alloc_sap(context
);
240 sigprocmask(SIG_SETMASK
, os_context_sigmask_addr(context
), 0);
242 if (internal_errors_enabled
) {
243 SHOW("in interrupt_internal_error");
245 /* Display some rudimentary debugging information about the
246 * error, so that even if the Lisp error handler gets badly
247 * confused, we have a chance to determine what's going on. */
248 describe_internal_error(context
);
250 funcall2(SymbolFunction(INTERNAL_ERROR
), context_sap
,
251 continuable
? T
: NIL
);
253 describe_internal_error(context
);
254 /* There's no good way to recover from an internal error
255 * before the Lisp error handling mechanism is set up. */
256 lose("internal error too early in init, can't recover");
258 undo_fake_foreign_function_call(context
);
260 arch_skip_instruction(context
);
264 /* This function handles pending interrupts. Note that in C/kernel
265 * terms we dealt with the signal already; we just haven't decided
266 * whether to call a Lisp handler or do a GC or something like that.
267 * If it helps, you can think of pending_{signal,mask,info} as a
268 * one-element queue of signals that we have acknowledged but not
272 interrupt_handle_pending(os_context_t
*context
)
275 boolean were_in_lisp
= !foreign_function_call_active
;
278 SetSymbolValue(INTERRUPT_PENDING
, NIL
);
280 if (maybe_gc_pending
) {
281 maybe_gc_pending
= 0;
286 fake_foreign_function_call(context
);
288 funcall0(SymbolFunction(MAYBE_GC
));
293 undo_fake_foreign_function_call(context
);
297 /* FIXME: This isn't very clear. It would be good to reverse
298 * engineer it and rewrite the code more clearly, or write a clear
299 * explanation of what's going on in the comments, or both.
301 * WHN's question 1a: How come we unconditionally copy from
302 * pending_mask into the context, and then test whether
303 * pending_signal is set?
305 * WHN's question 1b: If pending_signal wasn't set, how could
306 * pending_mask be valid?
308 * Dan Barlow's reply (sbcl-devel 2001-03-13): And the answer is -
309 * or appears to be - because interrupt_maybe_gc set it that way
310 * (look in the #ifndef __i386__ bit). We can't GC during a
311 * pseudo-atomic, so we set maybe_gc_pending=1 and
312 * arch_set_pseudo_atomic_interrupted(..) When we come out of
313 * pseudo_atomic we're marked as interrupted, so we call
314 * interrupt_handle_pending, which does the GC using the pending
315 * context (it needs a context so that it has registers to use as
316 * GC roots) then notices there's no actual interrupt handler to
317 * call, so doesn't. That's the second question [1b] answered,
318 * anyway. Why we still need to copy the pending_mask into the
319 * context given that we're now done with the context anyway, I
322 memcpy(os_context_sigmask_addr(context
), &pending_mask
,
323 4 /* sizeof(sigset_t) */ );
325 sigemptyset(&pending_mask
);
326 if (pending_signal
) {
327 int signal
= pending_signal
;
329 memcpy(&info
, &pending_info
, sizeof(siginfo_t
));
331 interrupt_handle_now(signal
, &info
, context
);
336 * the two main signal handlers:
337 * interrupt_handle_now(..)
338 * maybe_now_maybe_later(..)
342 interrupt_handle_now(int signal
, siginfo_t
*info
, void *void_context
)
344 os_context_t
*context
= (os_context_t
*)void_context
;
346 boolean were_in_lisp
;
348 union interrupt_handler handler
;
350 #ifdef LISP_FEATURE_LINUX
351 /* Under Linux, we appear to have to restore the fpu control word
352 from the context, as after the signal is delivered we appear to
353 have a null fpu control word. */
354 os_restore_fp_control(context
);
356 handler
= interrupt_handlers
[signal
];
358 if (ARE_SAME_HANDLER(handler
.c
, SIG_IGN
)) {
363 were_in_lisp
= !foreign_function_call_active
;
367 fake_foreign_function_call(context
);
372 "/entering interrupt_handle_now(%d, info, context)\n",
376 if (ARE_SAME_HANDLER(handler
.c
, SIG_DFL
)) {
378 /* This can happen if someone tries to ignore or default one
379 * of the signals we need for runtime support, and the runtime
380 * support decides to pass on it. */
381 lose("no handler for signal %d in interrupt_handle_now(..)", signal
);
383 } else if (lowtag_of(handler
.lisp
) == FUN_POINTER_LOWTAG
) {
385 /* Allocate the SAPs while the interrupts are still disabled.
386 * (FIXME: Why? This is the way it was done in CMU CL, and it
387 * even had the comment noting that this is the way it was
388 * done, but no motivation..) */
389 lispobj info_sap
,context_sap
= alloc_sap(context
);
390 info_sap
= alloc_sap(info
);
391 /* Allow signals again. */
392 sigprocmask(SIG_SETMASK
, os_context_sigmask_addr(context
), 0);
395 SHOW("calling Lisp-level handler");
398 funcall3(handler
.lisp
,
405 SHOW("calling C-level handler");
408 /* Allow signals again. */
409 sigprocmask(SIG_SETMASK
, os_context_sigmask_addr(context
), 0);
411 (*handler
.c
)(signal
, info
, void_context
);
418 undo_fake_foreign_function_call(context
);
423 "/returning from interrupt_handle_now(%d, info, context)\n",
429 maybe_now_maybe_later(int signal
, siginfo_t
*info
, void *void_context
)
431 os_context_t
*context
= (os_context_t
*)void_context
;
433 /* FIXME: See Debian cmucl 2.4.17, and mail from DTC on the CMU CL
434 * mailing list 23 Oct 1999, for changes in FPU handling at
435 * interrupt time which should be ported into SBCL. Also see the
436 * analogous logic at the head of interrupt_handle_now for
437 * more related FIXME stuff.
440 #ifdef LISP_FEATURE_LINUX
441 os_restore_fp_control(context
);
444 /* see comments at top of code/signal.lisp for what's going on here
445 * with INTERRUPTS_ENABLED/INTERRUPT_HANDLE_NOW
447 if (SymbolValue(INTERRUPTS_ENABLED
) == NIL
) {
449 /* FIXME: This code is exactly the same as the code in the
450 * other leg of the if(..), and should be factored out into
451 * a shared function. */
452 pending_signal
= signal
;
453 memcpy(&pending_info
, info
, sizeof(siginfo_t
));
454 memcpy(&pending_mask
,
455 os_context_sigmask_addr(context
),
457 sigaddset_blockable(os_context_sigmask_addr(context
));
458 SetSymbolValue(INTERRUPT_PENDING
, T
);
462 (!foreign_function_call_active
) &&
464 arch_pseudo_atomic_atomic(context
)) {
466 /* FIXME: It would probably be good to replace these bare
467 * memcpy(..) calls with calls to cpy_siginfo_t and
468 * cpy_sigset_t, so that we only have to get the sizeof
469 * expressions right in one place, and after that static type
470 * checking takes over. */
471 pending_signal
= signal
;
472 memcpy(&pending_info
, info
, sizeof(siginfo_t
));
473 memcpy(&pending_mask
,
474 os_context_sigmask_addr(context
),
476 sigaddset_blockable(os_context_sigmask_addr(context
));
478 arch_set_pseudo_atomic_interrupted(context
);
481 interrupt_handle_now(signal
, info
, context
);
486 * stuff to detect and handle hitting the GC trigger
489 #ifndef GENCGC /* since GENCGC has its own way to record trigger */
491 gc_trigger_hit(int signal
, siginfo_t
*info
, os_context_t
*context
)
493 if (current_auto_gc_trigger
== NULL
)
496 lispobj
*badaddr
=(lispobj
*)arch_get_bad_addr(signal
,
500 return (badaddr
>= current_auto_gc_trigger
&&
501 badaddr
< current_dynamic_space
+ DYNAMIC_SPACE_SIZE
);
507 /* This function gets called from the SIGSEGV (for e.g. Linux or
508 * OpenBSD) or SIGBUS (for e.g. FreeBSD) handler. Here we check
509 * whether the signal was due to treading on the mprotect()ed zone -
510 * and if so, arrange for a GC to happen. */
512 interrupt_maybe_gc(int signal
, siginfo_t
*info
, void *void_context
)
514 os_context_t
*context
=(os_context_t
*) void_context
;
516 if (!foreign_function_call_active
517 #ifndef GENCGC /* since GENCGC has its own way to record trigger */
518 && gc_trigger_hit(signal
, info
, context
)
521 #ifndef GENCGC /* since GENCGC has its own way to record trigger */
522 clear_auto_gc_trigger();
525 if (arch_pseudo_atomic_atomic(context
)) {
526 /* don't GC during an atomic operation. Instead, copy the
527 * signal mask somewhere safe. interrupt_handle_pending
528 * will detect pending_signal==0 and know to do a GC with the
529 * signal context instead of calling a Lisp-level handler */
530 maybe_gc_pending
= 1;
531 if (pending_signal
== 0) {
532 /* FIXME: This copy-pending_mask-then-sigaddset_blockable
533 * idiom occurs over and over. It should be factored out
534 * into a function with a descriptive name. */
535 memcpy(&pending_mask
,
536 os_context_sigmask_addr(context
),
538 sigaddset_blockable(os_context_sigmask_addr(context
));
540 arch_set_pseudo_atomic_interrupted(context
);
543 lispobj
*old_free_space
=current_dynamic_space
;
544 fake_foreign_function_call(context
);
545 funcall0(SymbolFunction(MAYBE_GC
));
546 undo_fake_foreign_function_call(context
);
547 if(current_dynamic_space
==old_free_space
)
548 /* MAYBE-GC (as the name suggest) might not. If it
549 * doesn't, it won't reset the GC trigger either, so we
550 * have to do it ourselves. Add small amount of space
551 * to tide us over while GC is inhibited
553 set_auto_gc_trigger(DYNAMIC_SPACE_SIZE
554 -(u32
)os_vm_page_size
);
564 * noise to install handlers
568 * what low-level signal handlers looked like before
569 * undoably_install_low_level_interrupt_handler() got involved
571 struct low_level_signal_handler_state
{
573 void (*handler
)(int, siginfo_t
*, void*);
574 } old_low_level_signal_handler_states
[NSIG
];
577 uninstall_low_level_interrupt_handlers_atexit(void)
580 for (signal
= 0; signal
< NSIG
; ++signal
) {
581 struct low_level_signal_handler_state
582 *old_low_level_signal_handler_state
=
583 old_low_level_signal_handler_states
+ signal
;
584 if (old_low_level_signal_handler_state
->was_modified
) {
586 sa
.sa_sigaction
= old_low_level_signal_handler_state
->handler
;
587 sigemptyset(&sa
.sa_mask
);
588 sa
.sa_flags
= SA_SIGINFO
| SA_RESTART
;
589 sigaction(signal
, &sa
, NULL
);
594 /* Undoably install a special low-level handler for signal; or if
595 * handler is SIG_DFL, remove any special handling for signal.
597 * The "undoably" aspect is because we also arrange with atexit() for
598 * the handler to be restored to its old value. This is for tidiness:
599 * it shouldn't matter much ordinarily, but it does remove a window
600 * where e.g. memory fault signals (SIGSEGV or SIGBUS, which in
601 * ordinary operation of SBCL are sent to the generational garbage
602 * collector, then possibly onward to Lisp code) or SIGINT (which is
603 * ordinarily passed to Lisp code) could otherwise be handled
604 * bizarrely/brokenly because the Lisp code would try to deal with
605 * them using machinery (like stream output buffers) which has already
606 * been dismantled. */
608 undoably_install_low_level_interrupt_handler (int signal
,
614 struct low_level_signal_handler_state
*old_low_level_signal_handler_state
=
615 old_low_level_signal_handler_states
+ signal
;
617 if (0 > signal
|| signal
>= NSIG
) {
618 lose("bad signal number %d", signal
);
621 sa
.sa_sigaction
= handler
;
622 sigemptyset(&sa
.sa_mask
);
623 sigaddset_blockable(&sa
.sa_mask
);
624 sa
.sa_flags
= SA_SIGINFO
| SA_RESTART
;
626 /* In the case of interrupt handlers which are modified more than
627 * once, we only save the original unmodified copy. */
628 if (!old_low_level_signal_handler_state
->was_modified
) {
629 struct sigaction
*old_handler
=
630 (struct sigaction
*) &old_low_level_signal_handler_state
->handler
;
631 old_low_level_signal_handler_state
->was_modified
= 1;
632 sigaction(signal
, &sa
, old_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()");