subr_kdb.c revision 145727 
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 145727 2005-04-30 20:01:00Z dwhite $");
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
43#ifdef KDB_STOP_NMI
44#include <machine/smp.h>
45#endif
46
47/*
48 * KDB_STOP_NMI requires SMP to pick up the right dependencies
49 * (And isn't useful on UP anyway)
50 */
51#if defined(KDB_STOP_NMI) && !defined(SMP)
52#error "options KDB_STOP_NMI" requires "options SMP"
53#endif
54
55int kdb_active = 0;
56void *kdb_jmpbufp = NULL;
57struct kdb_dbbe *kdb_dbbe = NULL;
58struct pcb kdb_pcb;
59struct pcb *kdb_thrctx = NULL;
60struct thread *kdb_thread = NULL;
61struct trapframe *kdb_frame = NULL;
62
63KDB_BACKEND(null, NULL, NULL, NULL);
64SET_DECLARE(kdb_dbbe_set, struct kdb_dbbe);
65
66static int kdb_sysctl_available(SYSCTL_HANDLER_ARGS);
67static int kdb_sysctl_current(SYSCTL_HANDLER_ARGS);
68static int kdb_sysctl_enter(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, 0, 0,
73    kdb_sysctl_available, "A", "list of available KDB backends");
74
75SYSCTL_PROC(_debug_kdb, OID_AUTO, current, CTLTYPE_STRING | CTLFLAG_RW, 0, 0,
76    kdb_sysctl_current, "A", "currently selected KDB backend");
77
78SYSCTL_PROC(_debug_kdb, OID_AUTO, enter, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
79    kdb_sysctl_enter, "I", "set to enter the debugger");
80
81/*
82 * Flag indicating whether or not to IPI the other CPUs to stop them on
83 * entering the debugger.  Sometimes, this will result in a deadlock as
84 * stop_cpus() waits for the other cpus to stop, so we allow it to be
85 * disabled.
86 */
87#ifdef SMP
88static int kdb_stop_cpus = 1;
89SYSCTL_INT(_debug_kdb, OID_AUTO, stop_cpus, CTLTYPE_INT | CTLFLAG_RW,
90    &kdb_stop_cpus, 0, "");
91TUNABLE_INT("debug.kdb.stop_cpus", &kdb_stop_cpus);
92
93#ifdef KDB_STOP_NMI
94/*
95 * Provide an alternate method of stopping other CPUs. If another CPU has
96 * disabled interrupts the conventional STOP IPI will be blocked. This
97 * NMI-based stop should get through in that case.
98 */
99static int kdb_stop_cpus_with_nmi = 0;
100SYSCTL_INT(_debug_kdb, OID_AUTO, stop_cpus_with_nmi, CTLTYPE_INT | CTLFLAG_RW,
101    &kdb_stop_cpus_with_nmi, 0, "");
102TUNABLE_INT("debug.kdb.stop_cpus_with_nmi", &kdb_stop_cpus_with_nmi);
103#endif /* KDB_STOP_NMI */
104
105#endif
106
107static int
108kdb_sysctl_available(SYSCTL_HANDLER_ARGS)
109{
110	struct kdb_dbbe *be, **iter;
111	char *avail, *p;
112	ssize_t len, sz;
113	int error;
114
115	sz = 0;
116	SET_FOREACH(iter, kdb_dbbe_set) {
117		be = *iter;
118		if (be->dbbe_active == 0)
119			sz += strlen(be->dbbe_name) + 1;
120	}
121	sz++;
122	avail = malloc(sz, M_TEMP, M_WAITOK);
123	p = avail;
124	*p = '\0';
125
126	SET_FOREACH(iter, kdb_dbbe_set) {
127		be = *iter;
128		if (be->dbbe_active == 0) {
129			len = snprintf(p, sz, "%s ", be->dbbe_name);
130			p += len;
131			sz -= len;
132		}
133	}
134	KASSERT(sz >= 0, ("%s", __func__));
135	error = sysctl_handle_string(oidp, avail, 0, req);
136	free(avail, M_TEMP);
137	return (error);
138}
139
140static int
141kdb_sysctl_current(SYSCTL_HANDLER_ARGS)
142{
143	char buf[16];
144	int error;
145
146	if (kdb_dbbe != NULL) {
147		strncpy(buf, kdb_dbbe->dbbe_name, sizeof(buf));
148		buf[sizeof(buf) - 1] = '\0';
149	} else
150		*buf = '\0';
151	error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
152	if (error != 0 || req->newptr == NULL)
153		return (error);
154	if (kdb_active)
155		return (EBUSY);
156	return (kdb_dbbe_select(buf));
157}
158
159static int
160kdb_sysctl_enter(SYSCTL_HANDLER_ARGS)
161{
162	int error, i;
163
164	error = sysctl_wire_old_buffer(req, sizeof(int));
165	if (error == 0) {
166		i = 0;
167		error = sysctl_handle_int(oidp, &i, 0, req);
168	}
169	if (error != 0 || req->newptr == NULL)
170		return (error);
171	if (kdb_active)
172		return (EBUSY);
173	kdb_enter("sysctl debug.kdb.enter");
174	return (0);
175}
176
177/*
178 * Solaris implements a new BREAK which is initiated by a character sequence
179 * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the
180 * Remote Console.
181 *
182 * Note that this function may be called from almost anywhere, with interrupts
183 * disabled and with unknown locks held, so it must not access data other than
184 * its arguments.  Its up to the caller to ensure that the state variable is
185 * consistent.
186 */
187
188#define	KEY_CR		13	/* CR '\r' */
189#define	KEY_TILDE	126	/* ~ */
190#define	KEY_CRTLB	2	/* ^B */
191
192int
193kdb_alt_break(int key, int *state)
194{
195	int brk;
196
197	brk = 0;
198	switch (key) {
199	case KEY_CR:
200		*state = KEY_TILDE;
201		break;
202	case KEY_TILDE:
203		*state = (*state == KEY_TILDE) ? KEY_CRTLB : 0;
204		break;
205	case KEY_CRTLB:
206		if (*state == KEY_CRTLB)
207			brk = 1;
208		/* FALLTHROUGH */
209	default:
210		*state = 0;
211		break;
212	}
213	return (brk);
214}
215
216/*
217 * Print a backtrace of the calling thread. The backtrace is generated by
218 * the selected debugger, provided it supports backtraces. If no debugger
219 * is selected or the current debugger does not support backtraces, this
220 * function silently returns.
221 */
222
223void
224kdb_backtrace()
225{
226
227	if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) {
228		printf("KDB: stack backtrace:\n");
229		kdb_dbbe->dbbe_trace();
230	}
231}
232
233/*
234 * Set/change the current backend.
235 */
236
237int
238kdb_dbbe_select(const char *name)
239{
240	struct kdb_dbbe *be, **iter;
241
242	SET_FOREACH(iter, kdb_dbbe_set) {
243		be = *iter;
244		if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) {
245			kdb_dbbe = be;
246			return (0);
247		}
248	}
249	return (EINVAL);
250}
251
252/*
253 * Enter the currently selected debugger. If a message has been provided,
254 * it is printed first. If the debugger does not support the enter method,
255 * it is entered by using breakpoint(), which enters the debugger through
256 * kdb_trap().
257 */
258
259void
260kdb_enter(const char *msg)
261{
262
263	if (kdb_dbbe != NULL && kdb_active == 0) {
264		if (msg != NULL)
265			printf("KDB: enter: %s\n", msg);
266		breakpoint();
267	}
268}
269
270/*
271 * Initialize the kernel debugger interface.
272 */
273
274void
275kdb_init()
276{
277	struct kdb_dbbe *be, **iter;
278	int cur_pri, pri;
279
280	kdb_active = 0;
281	kdb_dbbe = NULL;
282	cur_pri = -1;
283	SET_FOREACH(iter, kdb_dbbe_set) {
284		be = *iter;
285		pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1;
286		be->dbbe_active = (pri >= 0) ? 0 : -1;
287		if (pri > cur_pri) {
288			cur_pri = pri;
289			kdb_dbbe = be;
290		}
291	}
292	if (kdb_dbbe != NULL) {
293		printf("KDB: debugger backends:");
294		SET_FOREACH(iter, kdb_dbbe_set) {
295			be = *iter;
296			if (be->dbbe_active == 0)
297				printf(" %s", be->dbbe_name);
298		}
299		printf("\n");
300		printf("KDB: current backend: %s\n",
301		    kdb_dbbe->dbbe_name);
302	}
303}
304
305/*
306 * Handle contexts.
307 */
308
309void *
310kdb_jmpbuf(jmp_buf new)
311{
312	void *old;
313
314	old = kdb_jmpbufp;
315	kdb_jmpbufp = new;
316	return (old);
317}
318
319void
320kdb_reenter(void)
321{
322
323	if (!kdb_active || kdb_jmpbufp == NULL)
324		return;
325
326	longjmp(kdb_jmpbufp, 1);
327	/* NOTREACHED */
328}
329
330/*
331 * Thread related support functions.
332 */
333
334struct pcb *
335kdb_thr_ctx(struct thread *thr)
336#ifdef KDB_STOP_NMI
337{
338  u_int		cpuid;
339  struct pcpu *pc;
340
341  if (thr == curthread)
342    return &kdb_pcb;
343
344  SLIST_FOREACH(pc, &cpuhead, pc_allcpu)  {
345    cpuid = pc->pc_cpuid;
346    if (pc->pc_curthread == thr && (atomic_load_acq_int(&stopped_cpus) & (1 << cpuid)))
347      return &stoppcbs[cpuid];
348  }
349
350  return  thr->td_pcb;
351}
352#else
353{
354	return ((thr == curthread) ? &kdb_pcb : thr->td_pcb);
355}
356#endif /* KDB_STOP_NMI */
357
358struct thread *
359kdb_thr_first(void)
360{
361	struct proc *p;
362	struct thread *thr;
363
364	p = LIST_FIRST(&allproc);
365	while (p != NULL) {
366		if (p->p_sflag & PS_INMEM) {
367			thr = FIRST_THREAD_IN_PROC(p);
368			if (thr != NULL)
369				return (thr);
370		}
371		p = LIST_NEXT(p, p_list);
372	}
373	return (NULL);
374}
375
376struct thread *
377kdb_thr_from_pid(pid_t pid)
378{
379	struct proc *p;
380
381	p = LIST_FIRST(&allproc);
382	while (p != NULL) {
383		if (p->p_sflag & PS_INMEM && p->p_pid == pid)
384			return (FIRST_THREAD_IN_PROC(p));
385		p = LIST_NEXT(p, p_list);
386	}
387	return (NULL);
388}
389
390struct thread *
391kdb_thr_lookup(lwpid_t tid)
392{
393	struct thread *thr;
394
395	thr = kdb_thr_first();
396	while (thr != NULL && thr->td_tid != tid)
397		thr = kdb_thr_next(thr);
398	return (thr);
399}
400
401struct thread *
402kdb_thr_next(struct thread *thr)
403{
404	struct proc *p;
405
406	p = thr->td_proc;
407	thr = TAILQ_NEXT(thr, td_plist);
408	do {
409		if (thr != NULL)
410			return (thr);
411		p = LIST_NEXT(p, p_list);
412		if (p != NULL && (p->p_sflag & PS_INMEM))
413			thr = FIRST_THREAD_IN_PROC(p);
414	} while (p != NULL);
415	return (NULL);
416}
417
418int
419kdb_thr_select(struct thread *thr)
420{
421	if (thr == NULL)
422		return (EINVAL);
423	kdb_thread = thr;
424	kdb_thrctx = kdb_thr_ctx(thr);
425	return (0);
426}
427
428/*
429 * Enter the debugger due to a trap.
430 */
431
432int
433kdb_trap(int type, int code, struct trapframe *tf)
434{
435#ifdef SMP
436	int did_stop_cpus;
437#endif
438	int handled;
439
440	if (kdb_dbbe == NULL || kdb_dbbe->dbbe_trap == NULL)
441		return (0);
442
443	/* We reenter the debugger through kdb_reenter(). */
444	if (kdb_active)
445		return (0);
446
447	critical_enter();
448
449	kdb_active++;
450
451#ifdef SMP
452	if ((did_stop_cpus = kdb_stop_cpus) != 0)
453	  {
454#ifdef KDB_STOP_NMI
455	    if(kdb_stop_cpus_with_nmi)
456	      stop_cpus_nmi(PCPU_GET(other_cpus));
457	    else
458#endif /* KDB_STOP_NMI */
459		stop_cpus(PCPU_GET(other_cpus));
460	  }
461#endif
462
463	kdb_frame = tf;
464
465	/* Let MD code do its thing first... */
466	kdb_cpu_trap(type, code);
467
468	makectx(tf, &kdb_pcb);
469	kdb_thr_select(curthread);
470
471	handled = kdb_dbbe->dbbe_trap(type, code);
472
473#ifdef SMP
474	if (did_stop_cpus)
475		restart_cpus(stopped_cpus);
476#endif
477
478	kdb_active--;
479
480	critical_exit();
481
482	return (handled);
483}
484