1/*-
2 * SPDX-License-Identifier: BSD-2-Clause
3 *
4 * Copyright (c) 2004 The FreeBSD Project
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 *
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29#include <sys/cdefs.h>
30#include "opt_kdb.h"
31#include "opt_stack.h"
32
33#include <sys/param.h>
34#include <sys/systm.h>
35#include <sys/cons.h>
36#include <sys/kdb.h>
37#include <sys/kernel.h>
38#include <sys/malloc.h>
39#include <sys/lock.h>
40#include <sys/pcpu.h>
41#include <sys/priv.h>
42#include <sys/proc.h>
43#include <sys/sbuf.h>
44#include <sys/smp.h>
45#include <sys/stack.h>
46#include <sys/sysctl.h>
47#include <sys/tslog.h>
48
49#include <machine/kdb.h>
50#include <machine/pcb.h>
51
52#ifdef SMP
53#include <machine/smp.h>
54#endif
55
56#include <security/mac/mac_framework.h>
57
58u_char __read_frequently kdb_active = 0;
59static void *kdb_jmpbufp = NULL;
60struct kdb_dbbe *kdb_dbbe = NULL;
61static struct pcb kdb_pcb;
62struct pcb *kdb_thrctx = NULL;
63struct thread *kdb_thread = NULL;
64struct trapframe *kdb_frame = NULL;
65
66#ifdef BREAK_TO_DEBUGGER
67#define	KDB_BREAK_TO_DEBUGGER	1
68#else
69#define	KDB_BREAK_TO_DEBUGGER	0
70#endif
71
72#ifdef ALT_BREAK_TO_DEBUGGER
73#define	KDB_ALT_BREAK_TO_DEBUGGER	1
74#else
75#define	KDB_ALT_BREAK_TO_DEBUGGER	0
76#endif
77
78static int	kdb_break_to_debugger = KDB_BREAK_TO_DEBUGGER;
79static int	kdb_alt_break_to_debugger = KDB_ALT_BREAK_TO_DEBUGGER;
80static int	kdb_enter_securelevel = 0;
81
82KDB_BACKEND(null, NULL, NULL, NULL, NULL);
83
84static int kdb_sysctl_available(SYSCTL_HANDLER_ARGS);
85static int kdb_sysctl_current(SYSCTL_HANDLER_ARGS);
86static int kdb_sysctl_enter(SYSCTL_HANDLER_ARGS);
87static int kdb_sysctl_panic(SYSCTL_HANDLER_ARGS);
88static int kdb_sysctl_panic_str(SYSCTL_HANDLER_ARGS);
89static int kdb_sysctl_trap(SYSCTL_HANDLER_ARGS);
90static int kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS);
91static int kdb_sysctl_stack_overflow(SYSCTL_HANDLER_ARGS);
92
93static SYSCTL_NODE(_debug, OID_AUTO, kdb, CTLFLAG_RW | CTLFLAG_MPSAFE, NULL,
94    "KDB nodes");
95
96SYSCTL_PROC(_debug_kdb, OID_AUTO, available,
97    CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 0,
98    kdb_sysctl_available, "A",
99    "list of available KDB backends");
100
101SYSCTL_PROC(_debug_kdb, OID_AUTO, current,
102    CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE, NULL, 0,
103    kdb_sysctl_current, "A",
104    "currently selected KDB backend");
105
106SYSCTL_PROC(_debug_kdb, OID_AUTO, enter,
107    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE, NULL, 0,
108    kdb_sysctl_enter, "I",
109    "set to enter the debugger");
110
111SYSCTL_PROC(_debug_kdb, OID_AUTO, panic,
112    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
113    kdb_sysctl_panic, "I",
114    "set to panic the kernel");
115
116SYSCTL_PROC(_debug_kdb, OID_AUTO, panic_str,
117    CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
118    kdb_sysctl_panic_str, "A",
119    "trigger a kernel panic, using the provided string as the panic message");
120
121SYSCTL_PROC(_debug_kdb, OID_AUTO, trap,
122    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
123    kdb_sysctl_trap, "I",
124    "set to cause a page fault via data access");
125
126SYSCTL_PROC(_debug_kdb, OID_AUTO, trap_code,
127    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
128    kdb_sysctl_trap_code, "I",
129    "set to cause a page fault via code access");
130
131SYSCTL_PROC(_debug_kdb, OID_AUTO, stack_overflow,
132    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
133    kdb_sysctl_stack_overflow, "I",
134    "set to cause a stack overflow");
135
136SYSCTL_INT(_debug_kdb, OID_AUTO, break_to_debugger,
137    CTLFLAG_RWTUN,
138    &kdb_break_to_debugger, 0, "Enable break to debugger");
139
140SYSCTL_INT(_debug_kdb, OID_AUTO, alt_break_to_debugger,
141    CTLFLAG_RWTUN,
142    &kdb_alt_break_to_debugger, 0, "Enable alternative break to debugger");
143
144SYSCTL_INT(_debug_kdb, OID_AUTO, enter_securelevel,
145    CTLFLAG_RWTUN | CTLFLAG_SECURE,
146    &kdb_enter_securelevel, 0,
147    "Maximum securelevel to enter a KDB backend");
148
149/*
150 * Flag to indicate to debuggers why the debugger was entered.
151 */
152const char * volatile kdb_why = KDB_WHY_UNSET;
153
154static int
155kdb_sysctl_available(SYSCTL_HANDLER_ARGS)
156{
157	struct kdb_dbbe **iter;
158	struct sbuf sbuf;
159	int error;
160
161	sbuf_new_for_sysctl(&sbuf, NULL, 64, req);
162	SET_FOREACH(iter, kdb_dbbe_set) {
163		if ((*iter)->dbbe_active == 0)
164			sbuf_printf(&sbuf, "%s ", (*iter)->dbbe_name);
165	}
166	error = sbuf_finish(&sbuf);
167	sbuf_delete(&sbuf);
168	return (error);
169}
170
171static int
172kdb_sysctl_current(SYSCTL_HANDLER_ARGS)
173{
174	char buf[16];
175	int error;
176
177	if (kdb_dbbe != NULL)
178		strlcpy(buf, kdb_dbbe->dbbe_name, sizeof(buf));
179	else
180		*buf = '\0';
181	error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
182	if (error != 0 || req->newptr == NULL)
183		return (error);
184	if (kdb_active)
185		return (EBUSY);
186	return (kdb_dbbe_select(buf));
187}
188
189static int
190kdb_sysctl_enter(SYSCTL_HANDLER_ARGS)
191{
192	int error, i;
193
194	error = sysctl_wire_old_buffer(req, sizeof(int));
195	if (error == 0) {
196		i = 0;
197		error = sysctl_handle_int(oidp, &i, 0, req);
198	}
199	if (error != 0 || req->newptr == NULL)
200		return (error);
201	if (kdb_active)
202		return (EBUSY);
203	kdb_enter(KDB_WHY_SYSCTL, "sysctl debug.kdb.enter");
204	return (0);
205}
206
207static int
208kdb_sysctl_panic(SYSCTL_HANDLER_ARGS)
209{
210	int error, i;
211
212	error = sysctl_wire_old_buffer(req, sizeof(int));
213	if (error == 0) {
214		i = 0;
215		error = sysctl_handle_int(oidp, &i, 0, req);
216	}
217	if (error != 0 || req->newptr == NULL)
218		return (error);
219	panic("kdb_sysctl_panic");
220	return (0);
221}
222
223static int
224kdb_sysctl_panic_str(SYSCTL_HANDLER_ARGS)
225{
226	int error;
227	static char buf[256]; /* static buffer to limit mallocs when panicing */
228
229	*buf = '\0';
230	error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
231	if (error != 0 || req->newptr == NULL)
232		return (error);
233	panic("kdb_sysctl_panic: %s", buf);
234	return (0);
235}
236
237static int
238kdb_sysctl_trap(SYSCTL_HANDLER_ARGS)
239{
240	int error, i;
241	int *addr = (int *)0x10;
242
243	error = sysctl_wire_old_buffer(req, sizeof(int));
244	if (error == 0) {
245		i = 0;
246		error = sysctl_handle_int(oidp, &i, 0, req);
247	}
248	if (error != 0 || req->newptr == NULL)
249		return (error);
250	return (*addr);
251}
252
253static int
254kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS)
255{
256	int error, i;
257	void (*fp)(u_int, u_int, u_int) = (void *)0xdeadc0de;
258
259	error = sysctl_wire_old_buffer(req, sizeof(int));
260	if (error == 0) {
261		i = 0;
262		error = sysctl_handle_int(oidp, &i, 0, req);
263	}
264	if (error != 0 || req->newptr == NULL)
265		return (error);
266	(*fp)(0x11111111, 0x22222222, 0x33333333);
267	return (0);
268}
269
270static void kdb_stack_overflow(volatile int *x)  __noinline;
271static void
272kdb_stack_overflow(volatile int *x)
273{
274
275	if (*x > 10000000)
276		return;
277	kdb_stack_overflow(x);
278	*x += PCPU_GET(cpuid) / 1000000;
279}
280
281static int
282kdb_sysctl_stack_overflow(SYSCTL_HANDLER_ARGS)
283{
284	int error, i;
285	volatile int x;
286
287	error = sysctl_wire_old_buffer(req, sizeof(int));
288	if (error == 0) {
289		i = 0;
290		error = sysctl_handle_int(oidp, &i, 0, req);
291	}
292	if (error != 0 || req->newptr == NULL)
293		return (error);
294	x = 0;
295	kdb_stack_overflow(&x);
296	return (0);
297}
298
299void
300kdb_panic(const char *msg)
301{
302
303	kdb_why = KDB_WHY_PANIC;
304	printf("KDB: panic\n");
305	panic("%s", msg);
306}
307
308void
309kdb_reboot(void)
310{
311
312	kdb_why = KDB_WHY_REBOOT;
313	printf("KDB: reboot requested\n");
314	shutdown_nice(0);
315}
316
317/*
318 * Solaris implements a new BREAK which is initiated by a character sequence
319 * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the
320 * Remote Console.
321 *
322 * Note that this function may be called from almost anywhere, with interrupts
323 * disabled and with unknown locks held, so it must not access data other than
324 * its arguments.  Its up to the caller to ensure that the state variable is
325 * consistent.
326 */
327#define	KEY_CR		13	/* CR '\r' */
328#define	KEY_TILDE	126	/* ~ */
329#define	KEY_CRTLB	2	/* ^B */
330#define	KEY_CRTLP	16	/* ^P */
331#define	KEY_CRTLR	18	/* ^R */
332
333/* States of th KDB "alternate break sequence" detecting state machine. */
334enum {
335	KDB_ALT_BREAK_SEEN_NONE,
336	KDB_ALT_BREAK_SEEN_CR,
337	KDB_ALT_BREAK_SEEN_CR_TILDE,
338};
339
340int
341kdb_break(void)
342{
343
344	if (!kdb_break_to_debugger)
345		return (0);
346	kdb_enter(KDB_WHY_BREAK, "Break to debugger");
347	return (KDB_REQ_DEBUGGER);
348}
349
350static int
351kdb_alt_break_state(int key, int *state)
352{
353	int brk;
354
355	/* All states transition to KDB_ALT_BREAK_SEEN_CR on a CR. */
356	if (key == KEY_CR) {
357		*state = KDB_ALT_BREAK_SEEN_CR;
358		return (0);
359	}
360
361	brk = 0;
362	switch (*state) {
363	case KDB_ALT_BREAK_SEEN_CR:
364		*state = KDB_ALT_BREAK_SEEN_NONE;
365		if (key == KEY_TILDE)
366			*state = KDB_ALT_BREAK_SEEN_CR_TILDE;
367		break;
368	case KDB_ALT_BREAK_SEEN_CR_TILDE:
369		*state = KDB_ALT_BREAK_SEEN_NONE;
370		if (key == KEY_CRTLB)
371			brk = KDB_REQ_DEBUGGER;
372		else if (key == KEY_CRTLP)
373			brk = KDB_REQ_PANIC;
374		else if (key == KEY_CRTLR)
375			brk = KDB_REQ_REBOOT;
376		break;
377	case KDB_ALT_BREAK_SEEN_NONE:
378	default:
379		*state = KDB_ALT_BREAK_SEEN_NONE;
380		break;
381	}
382	return (brk);
383}
384
385static int
386kdb_alt_break_internal(int key, int *state, int force_gdb)
387{
388	int brk;
389
390	if (!kdb_alt_break_to_debugger)
391		return (0);
392	brk = kdb_alt_break_state(key, state);
393	switch (brk) {
394	case KDB_REQ_DEBUGGER:
395		if (force_gdb)
396			kdb_dbbe_select("gdb");
397		kdb_enter(KDB_WHY_BREAK, "Break to debugger");
398		break;
399
400	case KDB_REQ_PANIC:
401		if (force_gdb)
402			kdb_dbbe_select("gdb");
403		kdb_panic("Panic sequence on console");
404		break;
405
406	case KDB_REQ_REBOOT:
407		kdb_reboot();
408		break;
409	}
410	return (0);
411}
412
413int
414kdb_alt_break(int key, int *state)
415{
416
417	return (kdb_alt_break_internal(key, state, 0));
418}
419
420/*
421 * This variation on kdb_alt_break() is used only by dcons, which has its own
422 * configuration flag to force GDB use regardless of the global KDB
423 * configuration.
424 */
425int
426kdb_alt_break_gdb(int key, int *state)
427{
428
429	return (kdb_alt_break_internal(key, state, 1));
430}
431
432/*
433 * Print a backtrace of the calling thread. The backtrace is generated by
434 * the selected debugger, provided it supports backtraces. If no debugger
435 * is selected or the current debugger does not support backtraces, this
436 * function silently returns.
437 */
438void
439kdb_backtrace(void)
440{
441
442	if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) {
443		printf("KDB: stack backtrace:\n");
444		kdb_dbbe->dbbe_trace();
445	}
446#ifdef STACK
447	else {
448		struct stack st;
449
450		printf("KDB: stack backtrace:\n");
451		stack_save(&st);
452		stack_print_ddb(&st);
453	}
454#endif
455}
456
457/*
458 * Similar to kdb_backtrace() except that it prints a backtrace of an
459 * arbitrary thread rather than the calling thread.
460 */
461void
462kdb_backtrace_thread(struct thread *td)
463{
464
465	if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace_thread != NULL) {
466		printf("KDB: stack backtrace of thread %d:\n", td->td_tid);
467		kdb_dbbe->dbbe_trace_thread(td);
468	}
469#ifdef STACK
470	else {
471		struct stack st;
472
473		printf("KDB: stack backtrace of thread %d:\n", td->td_tid);
474		if (stack_save_td(&st, td) == 0)
475			stack_print_ddb(&st);
476	}
477#endif
478}
479
480/*
481 * Set/change the current backend.
482 */
483int
484kdb_dbbe_select(const char *name)
485{
486	struct kdb_dbbe *be, **iter;
487	int error;
488
489	error = priv_check(curthread, PRIV_KDB_SET_BACKEND);
490	if (error)
491		return (error);
492
493	SET_FOREACH(iter, kdb_dbbe_set) {
494		be = *iter;
495		if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) {
496			kdb_dbbe = be;
497			return (0);
498		}
499	}
500	return (EINVAL);
501}
502
503static bool
504kdb_backend_permitted(struct kdb_dbbe *be, struct thread *td)
505{
506	struct ucred *cred;
507	int error;
508
509	cred = td->td_ucred;
510	if (cred == NULL) {
511		KASSERT(td == &thread0 && cold,
512		    ("%s: missing cred for %p", __func__, td));
513		error = 0;
514	} else {
515		error = securelevel_gt(cred, kdb_enter_securelevel);
516	}
517#ifdef MAC
518	/*
519	 * Give MAC a chance to weigh in on the policy: if the securelevel is
520	 * not raised, then MAC may veto the backend, otherwise MAC may
521	 * explicitly grant access.
522	 */
523	if (error == 0) {
524		error = mac_kdb_check_backend(be);
525		if (error != 0) {
526			printf("MAC prevented execution of KDB backend: %s\n",
527			    be->dbbe_name);
528			return (false);
529		}
530	} else if (mac_kdb_grant_backend(be) == 0) {
531		error = 0;
532	}
533#endif
534	if (error != 0)
535		printf("refusing to enter KDB with elevated securelevel\n");
536	return (error == 0);
537}
538
539/*
540 * Enter the currently selected debugger. If a message has been provided,
541 * it is printed first. If the debugger does not support the enter method,
542 * it is entered by using breakpoint(), which enters the debugger through
543 * kdb_trap().  The 'why' argument will contain a more mechanically usable
544 * string than 'msg', and is relied upon by DDB scripting to identify the
545 * reason for entering the debugger so that the right script can be run.
546 */
547void
548kdb_enter(const char *why, const char *msg)
549{
550
551	if (kdb_dbbe != NULL && kdb_active == 0) {
552		kdb_why = why;
553		if (msg != NULL)
554			printf("KDB: enter: %s\n", msg);
555		breakpoint();
556		kdb_why = KDB_WHY_UNSET;
557	}
558}
559
560/*
561 * Initialize the kernel debugger interface.
562 */
563void
564kdb_init(void)
565{
566	struct kdb_dbbe *be, **iter;
567	int cur_pri, pri;
568
569	TSENTER();
570	kdb_active = 0;
571	kdb_dbbe = NULL;
572	cur_pri = -1;
573	SET_FOREACH(iter, kdb_dbbe_set) {
574		be = *iter;
575		pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1;
576		be->dbbe_active = (pri >= 0) ? 0 : -1;
577		if (pri > cur_pri) {
578			cur_pri = pri;
579			kdb_dbbe = be;
580		}
581	}
582	if (kdb_dbbe != NULL) {
583		printf("KDB: debugger backends:");
584		SET_FOREACH(iter, kdb_dbbe_set) {
585			be = *iter;
586			if (be->dbbe_active == 0)
587				printf(" %s", be->dbbe_name);
588		}
589		printf("\n");
590		printf("KDB: current backend: %s\n",
591		    kdb_dbbe->dbbe_name);
592	}
593	TSEXIT();
594}
595
596/*
597 * Handle contexts.
598 */
599void *
600kdb_jmpbuf(jmp_buf new)
601{
602	void *old;
603
604	old = kdb_jmpbufp;
605	kdb_jmpbufp = new;
606	return (old);
607}
608
609void
610kdb_reenter(void)
611{
612
613	if (!kdb_active || kdb_jmpbufp == NULL)
614		return;
615
616	printf("KDB: reentering\n");
617	kdb_backtrace();
618	longjmp(kdb_jmpbufp, 1);
619	/* NOTREACHED */
620}
621
622void
623kdb_reenter_silent(void)
624{
625
626	if (!kdb_active || kdb_jmpbufp == NULL)
627		return;
628
629	longjmp(kdb_jmpbufp, 1);
630	/* NOTREACHED */
631}
632
633/*
634 * Thread-related support functions.
635 */
636struct pcb *
637kdb_thr_ctx(struct thread *thr)
638{
639#ifdef SMP
640	struct pcpu *pc;
641#endif
642
643	if (thr == curthread)
644		return (&kdb_pcb);
645
646#ifdef SMP
647	STAILQ_FOREACH(pc, &cpuhead, pc_allcpu)  {
648		if (pc->pc_curthread == thr &&
649		    CPU_ISSET(pc->pc_cpuid, &stopped_cpus))
650			return (&stoppcbs[pc->pc_cpuid]);
651	}
652#endif
653	return (thr->td_pcb);
654}
655
656struct thread *
657kdb_thr_first(void)
658{
659	struct proc *p;
660	struct thread *thr;
661	u_int i;
662
663	/* This function may be called early. */
664	if (pidhashtbl == NULL)
665		return (&thread0);
666
667	for (i = 0; i <= pidhash; i++) {
668		LIST_FOREACH(p, &pidhashtbl[i], p_hash) {
669			thr = FIRST_THREAD_IN_PROC(p);
670			if (thr != NULL)
671				return (thr);
672		}
673	}
674	return (NULL);
675}
676
677struct thread *
678kdb_thr_from_pid(pid_t pid)
679{
680	struct proc *p;
681
682	LIST_FOREACH(p, PIDHASH(pid), p_hash) {
683		if (p->p_pid == pid)
684			return (FIRST_THREAD_IN_PROC(p));
685	}
686	return (NULL);
687}
688
689struct thread *
690kdb_thr_lookup(lwpid_t tid)
691{
692	struct thread *thr;
693
694	thr = kdb_thr_first();
695	while (thr != NULL && thr->td_tid != tid)
696		thr = kdb_thr_next(thr);
697	return (thr);
698}
699
700struct thread *
701kdb_thr_next(struct thread *thr)
702{
703	struct proc *p;
704	u_int hash;
705
706	p = thr->td_proc;
707	thr = TAILQ_NEXT(thr, td_plist);
708	if (thr != NULL)
709		return (thr);
710	if (pidhashtbl == NULL)
711		return (NULL);
712	hash = p->p_pid & pidhash;
713	for (;;) {
714		p = LIST_NEXT(p, p_hash);
715		while (p == NULL) {
716			if (++hash > pidhash)
717				return (NULL);
718			p = LIST_FIRST(&pidhashtbl[hash]);
719		}
720		thr = FIRST_THREAD_IN_PROC(p);
721		if (thr != NULL)
722			return (thr);
723	}
724}
725
726int
727kdb_thr_select(struct thread *thr)
728{
729	if (thr == NULL)
730		return (EINVAL);
731	kdb_thread = thr;
732	kdb_thrctx = kdb_thr_ctx(thr);
733	return (0);
734}
735
736/*
737 * Enter the debugger due to a trap.
738 */
739int
740kdb_trap(int type, int code, struct trapframe *tf)
741{
742#ifdef SMP
743	cpuset_t other_cpus;
744#endif
745	struct kdb_dbbe *be;
746	register_t intr;
747	int handled;
748	int did_stop_cpus;
749
750	be = kdb_dbbe;
751	if (be == NULL || be->dbbe_trap == NULL)
752		return (0);
753
754	/* We reenter the debugger through kdb_reenter(). */
755	if (kdb_active)
756		return (0);
757
758	intr = intr_disable();
759
760	if (!SCHEDULER_STOPPED()) {
761#ifdef SMP
762		other_cpus = all_cpus;
763		CPU_ANDNOT(&other_cpus, &other_cpus, &stopped_cpus);
764		CPU_CLR(PCPU_GET(cpuid), &other_cpus);
765		stop_cpus_hard(other_cpus);
766#endif
767		scheduler_stopped = true;
768		did_stop_cpus = 1;
769	} else
770		did_stop_cpus = 0;
771
772	kdb_active++;
773
774	kdb_frame = tf;
775
776	/* Let MD code do its thing first... */
777	kdb_cpu_trap(type, code);
778
779	makectx(tf, &kdb_pcb);
780	kdb_thr_select(curthread);
781
782	cngrab();
783
784	for (;;) {
785		if (!kdb_backend_permitted(be, curthread)) {
786			/* Unhandled breakpoint traps are fatal. */
787			handled = 1;
788			break;
789		}
790		handled = be->dbbe_trap(type, code);
791		if (be == kdb_dbbe)
792			break;
793		be = kdb_dbbe;
794		if (be == NULL || be->dbbe_trap == NULL)
795			break;
796		printf("Switching to %s back-end\n", be->dbbe_name);
797	}
798
799	cnungrab();
800
801	kdb_active--;
802
803	if (did_stop_cpus) {
804		scheduler_stopped = false;
805#ifdef SMP
806		CPU_AND(&other_cpus, &other_cpus, &stopped_cpus);
807		restart_cpus(other_cpus);
808#endif
809	}
810
811	intr_restore(intr);
812
813	return (handled);
814}
815