subr_kdb.c revision 135808 
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 135808 2004-09-26 06:48:59Z marcel $");
29
30#include <sys/param.h>
31#include <sys/systm.h>
32#include <sys/kdb.h>
33#include <sys/kernel.h>
34#include <sys/malloc.h>
35#include <sys/pcpu.h>
36#include <sys/proc.h>
37#include <sys/smp.h>
38#include <sys/sysctl.h>
39
40#include <machine/kdb.h>
41#include <machine/pcb.h>
42
43int kdb_active = 0;
44void *kdb_jmpbufp = NULL;
45struct kdb_dbbe *kdb_dbbe = NULL;
46struct pcb kdb_pcb;
47struct pcb *kdb_thrctx = NULL;
48struct thread *kdb_thread = NULL;
49struct trapframe *kdb_frame = NULL;
50
51KDB_BACKEND(null, NULL, NULL, NULL);
52SET_DECLARE(kdb_dbbe_set, struct kdb_dbbe);
53
54static int kdb_sysctl_available(SYSCTL_HANDLER_ARGS);
55static int kdb_sysctl_current(SYSCTL_HANDLER_ARGS);
56static int kdb_sysctl_enter(SYSCTL_HANDLER_ARGS);
57
58SYSCTL_NODE(_debug, OID_AUTO, kdb, CTLFLAG_RW, NULL, "KDB nodes");
59
60SYSCTL_PROC(_debug_kdb, OID_AUTO, available, CTLTYPE_STRING | CTLFLAG_RD, 0, 0,
61    kdb_sysctl_available, "A", "list of available KDB backends");
62
63SYSCTL_PROC(_debug_kdb, OID_AUTO, current, CTLTYPE_STRING | CTLFLAG_RW, 0, 0,
64    kdb_sysctl_current, "A", "currently selected KDB backend");
65
66SYSCTL_PROC(_debug_kdb, OID_AUTO, enter, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
67    kdb_sysctl_enter, "I", "set to enter the debugger");
68
69/*
70 * Flag indicating whether or not to IPI the other CPUs to stop them on
71 * entering the debugger.  Sometimes, this will result in a deadlock as
72 * stop_cpus() waits for the other cpus to stop, so we allow it to be
73 * disabled.
74 */
75#ifdef SMP
76static int kdb_stop_cpus = 1;
77SYSCTL_INT(_debug_kdb, OID_AUTO, stop_cpus, CTLTYPE_INT | CTLFLAG_RW,
78    &kdb_stop_cpus, 0, "");
79TUNABLE_INT("debug.kdb.stop_cpus", &kdb_stop_cpus);
80#endif
81
82static int
83kdb_sysctl_available(SYSCTL_HANDLER_ARGS)
84{
85	struct kdb_dbbe *be, **iter;
86	char *avail, *p;
87	ssize_t len, sz;
88	int error;
89
90	sz = 0;
91	SET_FOREACH(iter, kdb_dbbe_set) {
92		be = *iter;
93		if (be->dbbe_active == 0)
94			sz += strlen(be->dbbe_name) + 1;
95	}
96	sz++;
97	avail = malloc(sz, M_TEMP, M_WAITOK);
98	p = avail;
99	SET_FOREACH(iter, kdb_dbbe_set) {
100		be = *iter;
101		if (be->dbbe_active == 0) {
102			len = snprintf(p, sz, "%s ", be->dbbe_name);
103			p += len;
104			sz -= len;
105		}
106	}
107	KASSERT(sz >= 0, ("%s", __func__));
108	error = sysctl_handle_string(oidp, avail, 0, req);
109	free(avail, M_TEMP);
110	return (error);
111}
112
113static int
114kdb_sysctl_current(SYSCTL_HANDLER_ARGS)
115{
116	char buf[16];
117	int error;
118
119	if (kdb_dbbe != NULL) {
120		strncpy(buf, kdb_dbbe->dbbe_name, sizeof(buf));
121		buf[sizeof(buf) - 1] = '\0';
122	} else
123		*buf = '\0';
124	error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
125	if (error != 0 || req->newptr == NULL)
126		return (error);
127	if (kdb_active)
128		return (EBUSY);
129	return (kdb_dbbe_select(buf));
130}
131
132static int
133kdb_sysctl_enter(SYSCTL_HANDLER_ARGS)
134{
135	int error, i;
136
137	error = sysctl_wire_old_buffer(req, sizeof(int));
138	if (error == 0) {
139		i = 0;
140		error = sysctl_handle_int(oidp, &i, 0, req);
141	}
142	if (error != 0 || req->newptr == NULL)
143		return (error);
144	if (kdb_active)
145		return (EBUSY);
146	kdb_enter("sysctl debug.kdb.enter");
147	return (0);
148}
149
150/*
151 * Solaris implements a new BREAK which is initiated by a character sequence
152 * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the
153 * Remote Console.
154 *
155 * Note that this function may be called from almost anywhere, with interrupts
156 * disabled and with unknown locks held, so it must not access data other than
157 * its arguments.  Its up to the caller to ensure that the state variable is
158 * consistent.
159 */
160
161#define	KEY_CR		13	/* CR '\r' */
162#define	KEY_TILDE	126	/* ~ */
163#define	KEY_CRTLB	2	/* ^B */
164
165int
166kdb_alt_break(int key, int *state)
167{
168	int brk;
169
170	brk = 0;
171	switch (key) {
172	case KEY_CR:
173		*state = KEY_TILDE;
174		break;
175	case KEY_TILDE:
176		*state = (*state == KEY_TILDE) ? KEY_CRTLB : 0;
177		break;
178	case KEY_CRTLB:
179		if (*state == KEY_CRTLB)
180			brk = 1;
181		/* FALLTHROUGH */
182	default:
183		*state = 0;
184		break;
185	}
186	return (brk);
187}
188
189/*
190 * Print a backtrace of the calling thread. The backtrace is generated by
191 * the selected debugger, provided it supports backtraces. If no debugger
192 * is selected or the current debugger does not support backtraces, this
193 * function silently returns.
194 */
195
196void
197kdb_backtrace()
198{
199
200	if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) {
201		printf("KDB: stack backtrace:\n");
202		kdb_dbbe->dbbe_trace();
203	}
204}
205
206/*
207 * Set/change the current backend.
208 */
209
210int
211kdb_dbbe_select(const char *name)
212{
213	struct kdb_dbbe *be, **iter;
214
215	SET_FOREACH(iter, kdb_dbbe_set) {
216		be = *iter;
217		if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) {
218			kdb_dbbe = be;
219			return (0);
220		}
221	}
222	return (EINVAL);
223}
224
225/*
226 * Enter the currently selected debugger. If a message has been provided,
227 * it is printed first. If the debugger does not support the enter method,
228 * it is entered by using breakpoint(), which enters the debugger through
229 * kdb_trap().
230 */
231
232void
233kdb_enter(const char *msg)
234{
235
236	if (kdb_dbbe != NULL && kdb_active == 0) {
237		if (msg != NULL)
238			printf("KDB: enter: %s\n", msg);
239		breakpoint();
240	}
241}
242
243/*
244 * Initialize the kernel debugger interface.
245 */
246
247void
248kdb_init()
249{
250	struct kdb_dbbe *be, **iter;
251	int cur_pri, pri;
252
253	kdb_active = 0;
254	kdb_dbbe = NULL;
255	cur_pri = -1;
256	SET_FOREACH(iter, kdb_dbbe_set) {
257		be = *iter;
258		pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1;
259		be->dbbe_active = (pri >= 0) ? 0 : -1;
260		if (pri > cur_pri) {
261			cur_pri = pri;
262			kdb_dbbe = be;
263		}
264	}
265	if (kdb_dbbe != NULL) {
266		printf("KDB: debugger backends:");
267		SET_FOREACH(iter, kdb_dbbe_set) {
268			be = *iter;
269			if (be->dbbe_active == 0)
270				printf(" %s", be->dbbe_name);
271		}
272		printf("\n");
273		printf("KDB: current backend: %s\n",
274		    kdb_dbbe->dbbe_name);
275	}
276}
277
278/*
279 * Handle contexts.
280 */
281
282void *
283kdb_jmpbuf(jmp_buf new)
284{
285	void *old;
286
287	old = kdb_jmpbufp;
288	kdb_jmpbufp = new;
289	return (old);
290}
291
292void
293kdb_reenter(void)
294{
295
296	if (!kdb_active || kdb_jmpbufp == NULL)
297		return;
298
299	longjmp(kdb_jmpbufp, 1);
300	/* NOTREACHED */
301}
302
303/*
304 * Thread related support functions.
305 */
306
307struct pcb *
308kdb_thr_ctx(struct thread *thr)
309{
310	return ((thr == curthread) ? &kdb_pcb : thr->td_pcb);
311}
312
313struct thread *
314kdb_thr_first(void)
315{
316	struct proc *p;
317	struct thread *thr;
318
319	p = LIST_FIRST(&allproc);
320	while (p != NULL) {
321		if (p->p_sflag & PS_INMEM) {
322			thr = FIRST_THREAD_IN_PROC(p);
323			if (thr != NULL)
324				return (thr);
325		}
326		p = LIST_NEXT(p, p_list);
327	}
328	return (NULL);
329}
330
331struct thread *
332kdb_thr_from_pid(pid_t pid)
333{
334	struct proc *p;
335
336	p = LIST_FIRST(&allproc);
337	while (p != NULL) {
338		if (p->p_sflag & PS_INMEM && p->p_pid == pid)
339			return (FIRST_THREAD_IN_PROC(p));
340		p = LIST_NEXT(p, p_list);
341	}
342	return (NULL);
343}
344
345struct thread *
346kdb_thr_lookup(lwpid_t tid)
347{
348	struct thread *thr;
349
350	thr = kdb_thr_first();
351	while (thr != NULL && thr->td_tid != tid)
352		thr = kdb_thr_next(thr);
353	return (thr);
354}
355
356struct thread *
357kdb_thr_next(struct thread *thr)
358{
359	struct proc *p;
360
361	p = thr->td_proc;
362	thr = TAILQ_NEXT(thr, td_plist);
363	do {
364		if (thr != NULL)
365			return (thr);
366		p = LIST_NEXT(p, p_list);
367		if (p != NULL && (p->p_sflag & PS_INMEM))
368			thr = FIRST_THREAD_IN_PROC(p);
369	} while (p != NULL);
370	return (NULL);
371}
372
373int
374kdb_thr_select(struct thread *thr)
375{
376	if (thr == NULL)
377		return (EINVAL);
378	kdb_thread = thr;
379	kdb_thrctx = kdb_thr_ctx(thr);
380	return (0);
381}
382
383/*
384 * Enter the debugger due to a trap.
385 */
386
387int
388kdb_trap(int type, int code, struct trapframe *tf)
389{
390#ifdef SMP
391	int did_stop_cpus;
392#endif
393	int handled;
394
395	if (kdb_dbbe == NULL || kdb_dbbe->dbbe_trap == NULL)
396		return (0);
397
398	/* We reenter the debugger through kdb_reenter(). */
399	if (kdb_active)
400		return (0);
401
402	critical_enter();
403
404	kdb_active++;
405
406#ifdef SMP
407	if ((did_stop_cpus = kdb_stop_cpus) != 0)
408		stop_cpus(PCPU_GET(other_cpus));
409#endif
410
411	kdb_frame = tf;
412
413	/* Let MD code do its thing first... */
414	kdb_cpu_trap(type, code);
415
416	makectx(tf, &kdb_pcb);
417	kdb_thr_select(curthread);
418
419	handled = kdb_dbbe->dbbe_trap(type, code);
420
421#ifdef SMP
422	if (did_stop_cpus)
423		restart_cpus(stopped_cpus);
424#endif
425
426	kdb_active--;
427
428	critical_exit();
429
430	return (handled);
431}
432