subr_kdb.c revision 157442 
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 157442 2006-04-03 20:55:52Z marcel $");
29
30#include "opt_kdb.h"
31
32#include <sys/param.h>
33#include <sys/systm.h>
34#include <sys/kdb.h>
35#include <sys/kernel.h>
36#include <sys/malloc.h>
37#include <sys/pcpu.h>
38#include <sys/proc.h>
39#include <sys/smp.h>
40#include <sys/sysctl.h>
41
42#include <machine/kdb.h>
43#include <machine/pcb.h>
44
45#ifdef SMP
46#if defined (__i386__) || defined(__amd64__) || defined(__sparc64__) || defined(__alpha__)
47#define	HAVE_STOPPEDPCBS
48#include <machine/smp.h>
49#endif
50#endif
51
52int kdb_active = 0;
53void *kdb_jmpbufp = NULL;
54struct kdb_dbbe *kdb_dbbe = NULL;
55struct 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);
68
69SYSCTL_NODE(_debug, OID_AUTO, kdb, CTLFLAG_RW, NULL, "KDB nodes");
70
71SYSCTL_PROC(_debug_kdb, OID_AUTO, available, CTLTYPE_STRING | CTLFLAG_RD, 0, 0,
72    kdb_sysctl_available, "A", "list of available KDB backends");
73
74SYSCTL_PROC(_debug_kdb, OID_AUTO, current, CTLTYPE_STRING | CTLFLAG_RW, 0, 0,
75    kdb_sysctl_current, "A", "currently selected KDB backend");
76
77SYSCTL_PROC(_debug_kdb, OID_AUTO, enter, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
78    kdb_sysctl_enter, "I", "set to enter the debugger");
79
80SYSCTL_PROC(_debug_kdb, OID_AUTO, panic, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
81    kdb_sysctl_panic, "I", "set to panic the kernel");
82
83SYSCTL_PROC(_debug_kdb, OID_AUTO, trap, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
84    kdb_sysctl_trap, "I", "set cause a page fault");
85
86/*
87 * Flag indicating whether or not to IPI the other CPUs to stop them on
88 * entering the debugger.  Sometimes, this will result in a deadlock as
89 * stop_cpus() waits for the other cpus to stop, so we allow it to be
90 * disabled.
91 */
92#ifdef SMP
93static int kdb_stop_cpus = 1;
94SYSCTL_INT(_debug_kdb, OID_AUTO, stop_cpus, CTLTYPE_INT | CTLFLAG_RW,
95    &kdb_stop_cpus, 0, "");
96TUNABLE_INT("debug.kdb.stop_cpus", &kdb_stop_cpus);
97#endif
98
99static int
100kdb_sysctl_available(SYSCTL_HANDLER_ARGS)
101{
102	struct kdb_dbbe *be, **iter;
103	char *avail, *p;
104	ssize_t len, sz;
105	int error;
106
107	sz = 0;
108	SET_FOREACH(iter, kdb_dbbe_set) {
109		be = *iter;
110		if (be->dbbe_active == 0)
111			sz += strlen(be->dbbe_name) + 1;
112	}
113	sz++;
114	avail = malloc(sz, M_TEMP, M_WAITOK);
115	p = avail;
116	*p = '\0';
117
118	SET_FOREACH(iter, kdb_dbbe_set) {
119		be = *iter;
120		if (be->dbbe_active == 0) {
121			len = snprintf(p, sz, "%s ", be->dbbe_name);
122			p += len;
123			sz -= len;
124		}
125	}
126	KASSERT(sz >= 0, ("%s", __func__));
127	error = sysctl_handle_string(oidp, avail, 0, req);
128	free(avail, M_TEMP);
129	return (error);
130}
131
132static int
133kdb_sysctl_current(SYSCTL_HANDLER_ARGS)
134{
135	char buf[16];
136	int error;
137
138	if (kdb_dbbe != NULL) {
139		strncpy(buf, kdb_dbbe->dbbe_name, sizeof(buf));
140		buf[sizeof(buf) - 1] = '\0';
141	} else
142		*buf = '\0';
143	error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
144	if (error != 0 || req->newptr == NULL)
145		return (error);
146	if (kdb_active)
147		return (EBUSY);
148	return (kdb_dbbe_select(buf));
149}
150
151static int
152kdb_sysctl_enter(SYSCTL_HANDLER_ARGS)
153{
154	int error, i;
155
156	error = sysctl_wire_old_buffer(req, sizeof(int));
157	if (error == 0) {
158		i = 0;
159		error = sysctl_handle_int(oidp, &i, 0, req);
160	}
161	if (error != 0 || req->newptr == NULL)
162		return (error);
163	if (kdb_active)
164		return (EBUSY);
165	kdb_enter("sysctl debug.kdb.enter");
166	return (0);
167}
168
169static int
170kdb_sysctl_panic(SYSCTL_HANDLER_ARGS)
171{
172	int error, i;
173
174	error = sysctl_wire_old_buffer(req, sizeof(int));
175	if (error == 0) {
176		i = 0;
177		error = sysctl_handle_int(oidp, &i, 0, req);
178	}
179	if (error != 0 || req->newptr == NULL)
180		return (error);
181	panic("kdb_sysctl_panic");
182	return (0);
183}
184
185static int
186kdb_sysctl_trap(SYSCTL_HANDLER_ARGS)
187{
188	int error, i;
189	int *addr = (int *)0x10;
190
191	error = sysctl_wire_old_buffer(req, sizeof(int));
192	if (error == 0) {
193		i = 0;
194		error = sysctl_handle_int(oidp, &i, 0, req);
195	}
196	if (error != 0 || req->newptr == NULL)
197		return (error);
198	return (*addr);
199}
200
201/*
202 * Solaris implements a new BREAK which is initiated by a character sequence
203 * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the
204 * Remote Console.
205 *
206 * Note that this function may be called from almost anywhere, with interrupts
207 * disabled and with unknown locks held, so it must not access data other than
208 * its arguments.  Its up to the caller to ensure that the state variable is
209 * consistent.
210 */
211
212#define	KEY_CR		13	/* CR '\r' */
213#define	KEY_TILDE	126	/* ~ */
214#define	KEY_CRTLB	2	/* ^B */
215
216int
217kdb_alt_break(int key, int *state)
218{
219	int brk;
220
221	brk = 0;
222	switch (key) {
223	case KEY_CR:
224		*state = KEY_TILDE;
225		break;
226	case KEY_TILDE:
227		*state = (*state == KEY_TILDE) ? KEY_CRTLB : 0;
228		break;
229	case KEY_CRTLB:
230		if (*state == KEY_CRTLB)
231			brk = 1;
232		/* FALLTHROUGH */
233	default:
234		*state = 0;
235		break;
236	}
237	return (brk);
238}
239
240/*
241 * Print a backtrace of the calling thread. The backtrace is generated by
242 * the selected debugger, provided it supports backtraces. If no debugger
243 * is selected or the current debugger does not support backtraces, this
244 * function silently returns.
245 */
246
247void
248kdb_backtrace()
249{
250
251	if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) {
252		printf("KDB: stack backtrace:\n");
253		kdb_dbbe->dbbe_trace();
254	}
255}
256
257/*
258 * Set/change the current backend.
259 */
260
261int
262kdb_dbbe_select(const char *name)
263{
264	struct kdb_dbbe *be, **iter;
265
266	SET_FOREACH(iter, kdb_dbbe_set) {
267		be = *iter;
268		if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) {
269			kdb_dbbe = be;
270			return (0);
271		}
272	}
273	return (EINVAL);
274}
275
276/*
277 * Enter the currently selected debugger. If a message has been provided,
278 * it is printed first. If the debugger does not support the enter method,
279 * it is entered by using breakpoint(), which enters the debugger through
280 * kdb_trap().
281 */
282
283void
284kdb_enter(const char *msg)
285{
286
287	if (kdb_dbbe != NULL && kdb_active == 0) {
288		if (msg != NULL)
289			printf("KDB: enter: %s\n", msg);
290		breakpoint();
291	}
292}
293
294/*
295 * Initialize the kernel debugger interface.
296 */
297
298void
299kdb_init()
300{
301	struct kdb_dbbe *be, **iter;
302	int cur_pri, pri;
303
304	kdb_active = 0;
305	kdb_dbbe = NULL;
306	cur_pri = -1;
307	SET_FOREACH(iter, kdb_dbbe_set) {
308		be = *iter;
309		pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1;
310		be->dbbe_active = (pri >= 0) ? 0 : -1;
311		if (pri > cur_pri) {
312			cur_pri = pri;
313			kdb_dbbe = be;
314		}
315	}
316	if (kdb_dbbe != NULL) {
317		printf("KDB: debugger backends:");
318		SET_FOREACH(iter, kdb_dbbe_set) {
319			be = *iter;
320			if (be->dbbe_active == 0)
321				printf(" %s", be->dbbe_name);
322		}
323		printf("\n");
324		printf("KDB: current backend: %s\n",
325		    kdb_dbbe->dbbe_name);
326	}
327}
328
329/*
330 * Handle contexts.
331 */
332
333void *
334kdb_jmpbuf(jmp_buf new)
335{
336	void *old;
337
338	old = kdb_jmpbufp;
339	kdb_jmpbufp = new;
340	return (old);
341}
342
343void
344kdb_reenter(void)
345{
346
347	if (!kdb_active || kdb_jmpbufp == NULL)
348		return;
349
350	longjmp(kdb_jmpbufp, 1);
351	/* NOTREACHED */
352}
353
354/*
355 * Thread related support functions.
356 */
357
358struct pcb *
359kdb_thr_ctx(struct thread *thr)
360{
361#ifdef HAVE_STOPPEDPCBS
362	struct pcpu *pc;
363	u_int cpuid;
364#endif
365
366	if (thr == curthread)
367		return (&kdb_pcb);
368
369#ifdef HAVE_STOPPEDPCBS
370	SLIST_FOREACH(pc, &cpuhead, pc_allcpu)  {
371		cpuid = pc->pc_cpuid;
372		if (pc->pc_curthread == thr && (stopped_cpus & (1 << cpuid)))
373			return (&stoppcbs[cpuid]);
374	}
375#endif
376	return (thr->td_pcb);
377}
378
379struct thread *
380kdb_thr_first(void)
381{
382	struct proc *p;
383	struct thread *thr;
384
385	p = LIST_FIRST(&allproc);
386	while (p != NULL) {
387		if (p->p_sflag & PS_INMEM) {
388			thr = FIRST_THREAD_IN_PROC(p);
389			if (thr != NULL)
390				return (thr);
391		}
392		p = LIST_NEXT(p, p_list);
393	}
394	return (NULL);
395}
396
397struct thread *
398kdb_thr_from_pid(pid_t pid)
399{
400	struct proc *p;
401
402	p = LIST_FIRST(&allproc);
403	while (p != NULL) {
404		if (p->p_sflag & PS_INMEM && p->p_pid == pid)
405			return (FIRST_THREAD_IN_PROC(p));
406		p = LIST_NEXT(p, p_list);
407	}
408	return (NULL);
409}
410
411struct thread *
412kdb_thr_lookup(lwpid_t tid)
413{
414	struct thread *thr;
415
416	thr = kdb_thr_first();
417	while (thr != NULL && thr->td_tid != tid)
418		thr = kdb_thr_next(thr);
419	return (thr);
420}
421
422struct thread *
423kdb_thr_next(struct thread *thr)
424{
425	struct proc *p;
426
427	p = thr->td_proc;
428	thr = TAILQ_NEXT(thr, td_plist);
429	do {
430		if (thr != NULL)
431			return (thr);
432		p = LIST_NEXT(p, p_list);
433		if (p != NULL && (p->p_sflag & PS_INMEM))
434			thr = FIRST_THREAD_IN_PROC(p);
435	} while (p != NULL);
436	return (NULL);
437}
438
439int
440kdb_thr_select(struct thread *thr)
441{
442	if (thr == NULL)
443		return (EINVAL);
444	kdb_thread = thr;
445	kdb_thrctx = kdb_thr_ctx(thr);
446	return (0);
447}
448
449/*
450 * Enter the debugger due to a trap.
451 */
452
453int
454kdb_trap(int type, int code, struct trapframe *tf)
455{
456	register_t intr;
457#ifdef SMP
458	int did_stop_cpus;
459#endif
460	int handled;
461
462	if (kdb_dbbe == NULL || kdb_dbbe->dbbe_trap == NULL)
463		return (0);
464
465	/* We reenter the debugger through kdb_reenter(). */
466	if (kdb_active)
467		return (0);
468
469	intr = intr_disable();
470
471	kdb_active++;
472
473#ifdef SMP
474	if ((did_stop_cpus = kdb_stop_cpus) != 0)
475		stop_cpus(PCPU_GET(other_cpus));
476#endif
477
478	kdb_frame = tf;
479
480	/* Let MD code do its thing first... */
481	kdb_cpu_trap(type, code);
482
483	makectx(tf, &kdb_pcb);
484	kdb_thr_select(curthread);
485
486	handled = kdb_dbbe->dbbe_trap(type, code);
487
488#ifdef SMP
489	if (did_stop_cpus)
490		restart_cpus(stopped_cpus);
491#endif
492
493	kdb_active--;
494
495	intr_restore(intr);
496
497	return (handled);
498}
499