subr_kdb.c revision 222531 
1/*-
2 * Copyright (c) 2004 The FreeBSD Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 *
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27#include <sys/cdefs.h>
28__FBSDID("$FreeBSD: head/sys/kern/subr_kdb.c 222531 2011-05-31 15:11:43Z nwhitehorn $");
29
30#include "opt_kdb.h"
31#include "opt_stack.h"
32
33#include <sys/param.h>
34#include <sys/systm.h>
35#include <sys/kdb.h>
36#include <sys/kernel.h>
37#include <sys/malloc.h>
38#include <sys/pcpu.h>
39#include <sys/proc.h>
40#include <sys/sbuf.h>
41#include <sys/smp.h>
42#include <sys/stack.h>
43#include <sys/sysctl.h>
44
45#include <machine/kdb.h>
46#include <machine/pcb.h>
47
48#ifdef SMP
49#include <machine/smp.h>
50#endif
51
52int kdb_active = 0;
53static void *kdb_jmpbufp = NULL;
54struct kdb_dbbe *kdb_dbbe = NULL;
55static struct pcb kdb_pcb;
56struct pcb *kdb_thrctx = NULL;
57struct thread *kdb_thread = NULL;
58struct trapframe *kdb_frame = NULL;
59
60KDB_BACKEND(null, NULL, NULL, NULL);
61SET_DECLARE(kdb_dbbe_set, struct kdb_dbbe);
62
63static int kdb_sysctl_available(SYSCTL_HANDLER_ARGS);
64static int kdb_sysctl_current(SYSCTL_HANDLER_ARGS);
65static int kdb_sysctl_enter(SYSCTL_HANDLER_ARGS);
66static int kdb_sysctl_panic(SYSCTL_HANDLER_ARGS);
67static int kdb_sysctl_trap(SYSCTL_HANDLER_ARGS);
68static int kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS);
69
70SYSCTL_NODE(_debug, OID_AUTO, kdb, CTLFLAG_RW, NULL, "KDB nodes");
71
72SYSCTL_PROC(_debug_kdb, OID_AUTO, available, CTLTYPE_STRING | CTLFLAG_RD, NULL,
73    0, kdb_sysctl_available, "A", "list of available KDB backends");
74
75SYSCTL_PROC(_debug_kdb, OID_AUTO, current, CTLTYPE_STRING | CTLFLAG_RW, NULL,
76    0, kdb_sysctl_current, "A", "currently selected KDB backend");
77
78SYSCTL_PROC(_debug_kdb, OID_AUTO, enter, CTLTYPE_INT | CTLFLAG_RW, NULL, 0,
79    kdb_sysctl_enter, "I", "set to enter the debugger");
80
81SYSCTL_PROC(_debug_kdb, OID_AUTO, panic, CTLTYPE_INT | CTLFLAG_RW, NULL, 0,
82    kdb_sysctl_panic, "I", "set to panic the kernel");
83
84SYSCTL_PROC(_debug_kdb, OID_AUTO, trap, CTLTYPE_INT | CTLFLAG_RW, NULL, 0,
85    kdb_sysctl_trap, "I", "set to cause a page fault via data access");
86
87SYSCTL_PROC(_debug_kdb, OID_AUTO, trap_code, CTLTYPE_INT | CTLFLAG_RW, NULL, 0,
88    kdb_sysctl_trap_code, "I", "set to cause a page fault via code access");
89
90/*
91 * Flag indicating whether or not to IPI the other CPUs to stop them on
92 * entering the debugger.  Sometimes, this will result in a deadlock as
93 * stop_cpus() waits for the other cpus to stop, so we allow it to be
94 * disabled.  In order to maximize the chances of success, use a hard
95 * stop for that.
96 */
97#ifdef SMP
98static int kdb_stop_cpus = 1;
99SYSCTL_INT(_debug_kdb, OID_AUTO, stop_cpus, CTLFLAG_RW | CTLFLAG_TUN,
100    &kdb_stop_cpus, 0, "stop other CPUs when entering the debugger");
101TUNABLE_INT("debug.kdb.stop_cpus", &kdb_stop_cpus);
102#endif
103
104/*
105 * Flag to indicate to debuggers why the debugger was entered.
106 */
107const char * volatile kdb_why = KDB_WHY_UNSET;
108
109static int
110kdb_sysctl_available(SYSCTL_HANDLER_ARGS)
111{
112	struct kdb_dbbe **iter;
113	struct sbuf sbuf;
114	int error;
115
116	sbuf_new_for_sysctl(&sbuf, NULL, 64, req);
117	SET_FOREACH(iter, kdb_dbbe_set) {
118		if ((*iter)->dbbe_active == 0)
119			sbuf_printf(&sbuf, "%s ", (*iter)->dbbe_name);
120	}
121	error = sbuf_finish(&sbuf);
122	sbuf_delete(&sbuf);
123	return (error);
124}
125
126static int
127kdb_sysctl_current(SYSCTL_HANDLER_ARGS)
128{
129	char buf[16];
130	int error;
131
132	if (kdb_dbbe != NULL)
133		strlcpy(buf, kdb_dbbe->dbbe_name, sizeof(buf));
134	else
135		*buf = '\0';
136	error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
137	if (error != 0 || req->newptr == NULL)
138		return (error);
139	if (kdb_active)
140		return (EBUSY);
141	return (kdb_dbbe_select(buf));
142}
143
144static int
145kdb_sysctl_enter(SYSCTL_HANDLER_ARGS)
146{
147	int error, i;
148
149	error = sysctl_wire_old_buffer(req, sizeof(int));
150	if (error == 0) {
151		i = 0;
152		error = sysctl_handle_int(oidp, &i, 0, req);
153	}
154	if (error != 0 || req->newptr == NULL)
155		return (error);
156	if (kdb_active)
157		return (EBUSY);
158	kdb_enter(KDB_WHY_SYSCTL, "sysctl debug.kdb.enter");
159	return (0);
160}
161
162static int
163kdb_sysctl_panic(SYSCTL_HANDLER_ARGS)
164{
165	int error, i;
166
167	error = sysctl_wire_old_buffer(req, sizeof(int));
168	if (error == 0) {
169		i = 0;
170		error = sysctl_handle_int(oidp, &i, 0, req);
171	}
172	if (error != 0 || req->newptr == NULL)
173		return (error);
174	panic("kdb_sysctl_panic");
175	return (0);
176}
177
178static int
179kdb_sysctl_trap(SYSCTL_HANDLER_ARGS)
180{
181	int error, i;
182	int *addr = (int *)0x10;
183
184	error = sysctl_wire_old_buffer(req, sizeof(int));
185	if (error == 0) {
186		i = 0;
187		error = sysctl_handle_int(oidp, &i, 0, req);
188	}
189	if (error != 0 || req->newptr == NULL)
190		return (error);
191	return (*addr);
192}
193
194static int
195kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS)
196{
197	int error, i;
198	void (*fp)(u_int, u_int, u_int) = (void *)0xdeadc0de;
199
200	error = sysctl_wire_old_buffer(req, sizeof(int));
201	if (error == 0) {
202		i = 0;
203		error = sysctl_handle_int(oidp, &i, 0, req);
204	}
205	if (error != 0 || req->newptr == NULL)
206		return (error);
207	(*fp)(0x11111111, 0x22222222, 0x33333333);
208	return (0);
209}
210
211void
212kdb_panic(const char *msg)
213{
214
215#ifdef SMP
216	stop_cpus_hard(PCPU_GET(other_cpus));
217#endif
218	printf("KDB: panic\n");
219	panic("%s", msg);
220}
221
222void
223kdb_reboot(void)
224{
225
226	printf("KDB: reboot requested\n");
227	shutdown_nice(0);
228}
229
230/*
231 * Solaris implements a new BREAK which is initiated by a character sequence
232 * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the
233 * Remote Console.
234 *
235 * Note that this function may be called from almost anywhere, with interrupts
236 * disabled and with unknown locks held, so it must not access data other than
237 * its arguments.  Its up to the caller to ensure that the state variable is
238 * consistent.
239 */
240
241#define	KEY_CR		13	/* CR '\r' */
242#define	KEY_TILDE	126	/* ~ */
243#define	KEY_CRTLB	2	/* ^B */
244#define	KEY_CRTLP	16	/* ^P */
245#define	KEY_CRTLR	18	/* ^R */
246
247int
248kdb_alt_break(int key, int *state)
249{
250	int brk;
251
252	brk = 0;
253	switch (*state) {
254	case 0:
255		if (key == KEY_CR)
256			*state = 1;
257		break;
258	case 1:
259		if (key == KEY_TILDE)
260			*state = 2;
261		break;
262	case 2:
263		if (key == KEY_CRTLB)
264			brk = KDB_REQ_DEBUGGER;
265		else if (key == KEY_CRTLP)
266			brk = KDB_REQ_PANIC;
267		else if (key == KEY_CRTLR)
268			brk = KDB_REQ_REBOOT;
269		*state = 0;
270	}
271	return (brk);
272}
273
274/*
275 * Print a backtrace of the calling thread. The backtrace is generated by
276 * the selected debugger, provided it supports backtraces. If no debugger
277 * is selected or the current debugger does not support backtraces, this
278 * function silently returns.
279 */
280
281void
282kdb_backtrace(void)
283{
284
285	if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) {
286		printf("KDB: stack backtrace:\n");
287		kdb_dbbe->dbbe_trace();
288	}
289#ifdef STACK
290	else {
291		struct stack st;
292
293		printf("KDB: stack backtrace:\n");
294		stack_save(&st);
295		stack_print_ddb(&st);
296	}
297#endif
298}
299
300/*
301 * Set/change the current backend.
302 */
303
304int
305kdb_dbbe_select(const char *name)
306{
307	struct kdb_dbbe *be, **iter;
308
309	SET_FOREACH(iter, kdb_dbbe_set) {
310		be = *iter;
311		if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) {
312			kdb_dbbe = be;
313			return (0);
314		}
315	}
316	return (EINVAL);
317}
318
319/*
320 * Enter the currently selected debugger. If a message has been provided,
321 * it is printed first. If the debugger does not support the enter method,
322 * it is entered by using breakpoint(), which enters the debugger through
323 * kdb_trap().  The 'why' argument will contain a more mechanically usable
324 * string than 'msg', and is relied upon by DDB scripting to identify the
325 * reason for entering the debugger so that the right script can be run.
326 */
327void
328kdb_enter(const char *why, const char *msg)
329{
330
331	if (kdb_dbbe != NULL && kdb_active == 0) {
332		if (msg != NULL)
333			printf("KDB: enter: %s\n", msg);
334		kdb_why = why;
335		breakpoint();
336		kdb_why = KDB_WHY_UNSET;
337	}
338}
339
340/*
341 * Initialize the kernel debugger interface.
342 */
343
344void
345kdb_init(void)
346{
347	struct kdb_dbbe *be, **iter;
348	int cur_pri, pri;
349
350	kdb_active = 0;
351	kdb_dbbe = NULL;
352	cur_pri = -1;
353	SET_FOREACH(iter, kdb_dbbe_set) {
354		be = *iter;
355		pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1;
356		be->dbbe_active = (pri >= 0) ? 0 : -1;
357		if (pri > cur_pri) {
358			cur_pri = pri;
359			kdb_dbbe = be;
360		}
361	}
362	if (kdb_dbbe != NULL) {
363		printf("KDB: debugger backends:");
364		SET_FOREACH(iter, kdb_dbbe_set) {
365			be = *iter;
366			if (be->dbbe_active == 0)
367				printf(" %s", be->dbbe_name);
368		}
369		printf("\n");
370		printf("KDB: current backend: %s\n",
371		    kdb_dbbe->dbbe_name);
372	}
373}
374
375/*
376 * Handle contexts.
377 */
378
379void *
380kdb_jmpbuf(jmp_buf new)
381{
382	void *old;
383
384	old = kdb_jmpbufp;
385	kdb_jmpbufp = new;
386	return (old);
387}
388
389void
390kdb_reenter(void)
391{
392
393	if (!kdb_active || kdb_jmpbufp == NULL)
394		return;
395
396	longjmp(kdb_jmpbufp, 1);
397	/* NOTREACHED */
398}
399
400/*
401 * Thread related support functions.
402 */
403
404struct pcb *
405kdb_thr_ctx(struct thread *thr)
406{
407#if defined(SMP) && defined(KDB_STOPPEDPCB)
408	struct pcpu *pc;
409#endif
410
411	if (thr == curthread)
412		return (&kdb_pcb);
413
414#if defined(SMP) && defined(KDB_STOPPEDPCB)
415	STAILQ_FOREACH(pc, &cpuhead, pc_allcpu)  {
416		if (pc->pc_curthread == thr && (stopped_cpus & pc->pc_cpumask))
417			return (KDB_STOPPEDPCB(pc));
418	}
419#endif
420	return (thr->td_pcb);
421}
422
423struct thread *
424kdb_thr_first(void)
425{
426	struct proc *p;
427	struct thread *thr;
428
429	p = LIST_FIRST(&allproc);
430	while (p != NULL) {
431		if (p->p_flag & P_INMEM) {
432			thr = FIRST_THREAD_IN_PROC(p);
433			if (thr != NULL)
434				return (thr);
435		}
436		p = LIST_NEXT(p, p_list);
437	}
438	return (NULL);
439}
440
441struct thread *
442kdb_thr_from_pid(pid_t pid)
443{
444	struct proc *p;
445
446	p = LIST_FIRST(&allproc);
447	while (p != NULL) {
448		if (p->p_flag & P_INMEM && p->p_pid == pid)
449			return (FIRST_THREAD_IN_PROC(p));
450		p = LIST_NEXT(p, p_list);
451	}
452	return (NULL);
453}
454
455struct thread *
456kdb_thr_lookup(lwpid_t tid)
457{
458	struct thread *thr;
459
460	thr = kdb_thr_first();
461	while (thr != NULL && thr->td_tid != tid)
462		thr = kdb_thr_next(thr);
463	return (thr);
464}
465
466struct thread *
467kdb_thr_next(struct thread *thr)
468{
469	struct proc *p;
470
471	p = thr->td_proc;
472	thr = TAILQ_NEXT(thr, td_plist);
473	do {
474		if (thr != NULL)
475			return (thr);
476		p = LIST_NEXT(p, p_list);
477		if (p != NULL && (p->p_flag & P_INMEM))
478			thr = FIRST_THREAD_IN_PROC(p);
479	} while (p != NULL);
480	return (NULL);
481}
482
483int
484kdb_thr_select(struct thread *thr)
485{
486	if (thr == NULL)
487		return (EINVAL);
488	kdb_thread = thr;
489	kdb_thrctx = kdb_thr_ctx(thr);
490	return (0);
491}
492
493/*
494 * Enter the debugger due to a trap.
495 */
496
497int
498kdb_trap(int type, int code, struct trapframe *tf)
499{
500	struct kdb_dbbe *be;
501	register_t intr;
502#ifdef SMP
503	int did_stop_cpus;
504#endif
505	int handled;
506
507	be = kdb_dbbe;
508	if (be == NULL || be->dbbe_trap == NULL)
509		return (0);
510
511	/* We reenter the debugger through kdb_reenter(). */
512	if (kdb_active)
513		return (0);
514
515	intr = intr_disable();
516
517#ifdef SMP
518	if ((did_stop_cpus = kdb_stop_cpus) != 0)
519		stop_cpus_hard(PCPU_GET(other_cpus));
520#endif
521
522	kdb_active++;
523
524	kdb_frame = tf;
525
526	/* Let MD code do its thing first... */
527	kdb_cpu_trap(type, code);
528
529	makectx(tf, &kdb_pcb);
530	kdb_thr_select(curthread);
531
532	for (;;) {
533		handled = be->dbbe_trap(type, code);
534		if (be == kdb_dbbe)
535			break;
536		be = kdb_dbbe;
537		if (be == NULL || be->dbbe_trap == NULL)
538			break;
539		printf("Switching to %s back-end\n", be->dbbe_name);
540	}
541
542	kdb_active--;
543
544#ifdef SMP
545	if (did_stop_cpus)
546		restart_cpus(stopped_cpus);
547#endif
548
549	intr_restore(intr);
550
551	return (handled);
552}
553