subr_kdb.c revision 132481 
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 132481 2004-07-21 04:49:48Z 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
69static int
70kdb_sysctl_available(SYSCTL_HANDLER_ARGS)
71{
72	struct kdb_dbbe *be, **iter;
73	char *avail, *p;
74	ssize_t len, sz;
75	int error;
76
77	sz = 0;
78	SET_FOREACH(iter, kdb_dbbe_set) {
79		be = *iter;
80		if (be->dbbe_active == 0)
81			sz += strlen(be->dbbe_name) + 1;
82	}
83	sz++;
84	avail = malloc(sz, M_TEMP, M_WAITOK);
85	p = avail;
86	SET_FOREACH(iter, kdb_dbbe_set) {
87		be = *iter;
88		if (be->dbbe_active == 0) {
89			len = snprintf(p, sz, "%s ", be->dbbe_name);
90			p += len;
91			sz -= len;
92		}
93	}
94	KASSERT(sz >= 0, ("%s", __func__));
95	error = sysctl_handle_string(oidp, avail, 0, req);
96	free(avail, M_TEMP);
97	return (error);
98}
99
100static int
101kdb_sysctl_current(SYSCTL_HANDLER_ARGS)
102{
103	char buf[16];
104	int error;
105
106	if (kdb_dbbe != NULL) {
107		strncpy(buf, kdb_dbbe->dbbe_name, sizeof(buf));
108		buf[sizeof(buf) - 1] = '\0';
109	} else
110		*buf = '\0';
111	error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
112	if (error != 0 || req->newptr == NULL)
113		return (error);
114	if (kdb_active)
115		return (EBUSY);
116	return (kdb_dbbe_select(buf));
117}
118
119static int
120kdb_sysctl_enter(SYSCTL_HANDLER_ARGS)
121{
122	int error, i;
123
124	error = sysctl_wire_old_buffer(req, sizeof(int));
125	if (error == 0) {
126		i = 0;
127		error = sysctl_handle_int(oidp, &i, 0, req);
128	}
129	if (error != 0 || req->newptr == NULL)
130		return (error);
131	if (kdb_active)
132		return (EBUSY);
133	kdb_enter("sysctl debug.kdb.enter");
134	return (0);
135}
136
137/*
138 * Solaris implements a new BREAK which is initiated by a character sequence
139 * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the
140 * Remote Console.
141 *
142 * Note that this function may be called from almost anywhere, with interrupts
143 * disabled and with unknown locks held, so it must not access data other than
144 * its arguments.  Its up to the caller to ensure that the state variable is
145 * consistent.
146 */
147
148#define	KEY_CR		13	/* CR '\r' */
149#define	KEY_TILDE	126	/* ~ */
150#define	KEY_CRTLB	2	/* ^B */
151
152int
153kdb_alt_break(int key, int *state)
154{
155	int brk;
156
157	brk = 0;
158	switch (key) {
159	case KEY_CR:
160		*state = KEY_TILDE;
161		break;
162	case KEY_TILDE:
163		*state = (*state == KEY_TILDE) ? KEY_CRTLB : 0;
164		break;
165	case KEY_CRTLB:
166		if (*state == KEY_CRTLB)
167			brk = 1;
168		/* FALLTHROUGH */
169	default:
170		*state = 0;
171		break;
172	}
173	return (brk);
174}
175
176/*
177 * Print a backtrace of the calling thread. The backtrace is generated by
178 * the selected debugger, provided it supports backtraces. If no debugger
179 * is selected or the current debugger does not support backtraces, this
180 * function silently returns.
181 */
182
183void
184kdb_backtrace()
185{
186
187	if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) {
188		printf("KDB: stack backtrace:\n");
189		kdb_dbbe->dbbe_trace();
190	}
191}
192
193/*
194 * Set/change the current backend.
195 */
196
197int
198kdb_dbbe_select(const char *name)
199{
200	struct kdb_dbbe *be, **iter;
201
202	SET_FOREACH(iter, kdb_dbbe_set) {
203		be = *iter;
204		if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) {
205			kdb_dbbe = be;
206			return (0);
207		}
208	}
209	return (EINVAL);
210}
211
212/*
213 * Enter the currently selected debugger. If a message has been provided,
214 * it is printed first. If the debugger does not support the enter method,
215 * it is entered by using breakpoint(), which enters the debugger through
216 * kdb_trap().
217 */
218
219void
220kdb_enter(const char *msg)
221{
222
223	if (kdb_dbbe != NULL && kdb_active == 0) {
224		if (msg != NULL)
225			printf("KDB: enter: %s\n", msg);
226		breakpoint();
227	}
228}
229
230/*
231 * Initialize the kernel debugger interface.
232 */
233
234void
235kdb_init()
236{
237	struct kdb_dbbe *be, **iter;
238	int cur_pri, pri;
239
240	kdb_active = 0;
241	kdb_dbbe = NULL;
242	cur_pri = -1;
243	SET_FOREACH(iter, kdb_dbbe_set) {
244		be = *iter;
245		pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1;
246		be->dbbe_active = (pri >= 0) ? 0 : -1;
247		if (pri > cur_pri) {
248			cur_pri = pri;
249			kdb_dbbe = be;
250		}
251	}
252	if (kdb_dbbe != NULL) {
253		printf("KDB: debugger backends:");
254		SET_FOREACH(iter, kdb_dbbe_set) {
255			be = *iter;
256			if (be->dbbe_active == 0)
257				printf(" %s", be->dbbe_name);
258		}
259		printf("\n");
260		printf("KDB: current backend: %s\n",
261		    kdb_dbbe->dbbe_name);
262	}
263}
264
265/*
266 * Handle contexts.
267 */
268
269void *
270kdb_jmpbuf(jmp_buf new)
271{
272	void *old;
273
274	old = kdb_jmpbufp;
275	kdb_jmpbufp = new;
276	return (old);
277}
278
279void
280kdb_reenter(void)
281{
282
283	if (!kdb_active || kdb_jmpbufp == NULL)
284		return;
285
286	longjmp(kdb_jmpbufp, 1);
287	/* NOTREACHED */
288}
289
290/*
291 * Thread related support functions.
292 */
293
294struct pcb *
295kdb_thr_ctx(struct thread *thr)
296{
297	return ((thr == curthread) ? &kdb_pcb : thr->td_pcb);
298}
299
300struct thread *
301kdb_thr_first(void)
302{
303	struct proc *p;
304	struct thread *thr;
305
306	p = LIST_FIRST(&allproc);
307	while (p != NULL) {
308		if (p->p_sflag & PS_INMEM) {
309			thr = FIRST_THREAD_IN_PROC(p);
310			if (thr != NULL)
311				return (thr);
312		}
313		p = LIST_NEXT(p, p_list);
314	}
315	return (NULL);
316}
317
318struct thread *
319kdb_thr_from_pid(pid_t pid)
320{
321	struct proc *p;
322
323	p = LIST_FIRST(&allproc);
324	while (p != NULL) {
325		if (p->p_sflag & PS_INMEM && p->p_pid == pid)
326			return (FIRST_THREAD_IN_PROC(p));
327		p = LIST_NEXT(p, p_list);
328	}
329	return (NULL);
330}
331
332struct thread *
333kdb_thr_lookup(lwpid_t tid)
334{
335	struct thread *thr;
336
337	thr = kdb_thr_first();
338	while (thr != NULL && thr->td_tid != tid)
339		thr = kdb_thr_next(thr);
340	return (thr);
341}
342
343struct thread *
344kdb_thr_next(struct thread *thr)
345{
346	struct proc *p;
347
348	p = thr->td_proc;
349	thr = TAILQ_NEXT(thr, td_plist);
350	do {
351		if (thr != NULL)
352			return (thr);
353		p = LIST_NEXT(p, p_list);
354		if (p != NULL && (p->p_sflag & PS_INMEM))
355			thr = FIRST_THREAD_IN_PROC(p);
356	} while (p != NULL);
357	return (NULL);
358}
359
360int
361kdb_thr_select(struct thread *thr)
362{
363	if (thr == NULL)
364		return (EINVAL);
365	kdb_thread = thr;
366	kdb_thrctx = kdb_thr_ctx(thr);
367	return (0);
368}
369
370/*
371 * Enter the debugger due to a trap.
372 */
373
374int
375kdb_trap(int type, int code, struct trapframe *tf)
376{
377	int handled;
378
379	if (kdb_dbbe == NULL || kdb_dbbe->dbbe_trap == NULL)
380		return (0);
381
382	/* We reenter the debugger through kdb_reenter(). */
383	if (kdb_active)
384		return (0);
385
386	makectx(tf, &kdb_pcb);
387
388	critical_enter();
389
390	kdb_active++;
391	kdb_frame = tf;
392	kdb_thr_select(curthread);
393
394#ifdef SMP
395	stop_cpus(PCPU_GET(other_cpus));
396#endif
397
398	/* Let MD code do its thing first... */
399	kdb_cpu_trap(type, code);
400
401	handled = kdb_dbbe->dbbe_trap(type, code);
402
403#ifdef SMP
404	restart_cpus(stopped_cpus);
405#endif
406
407	kdb_active--;
408
409	critical_exit();
410
411	return (handled);
412}
413