aboutsummaryrefslogtreecommitdiff
path: root/sys/kern/subr_kdb.c
blob: 8b66a584ec5121c175fb1d590c2f45ecfbd887d3 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
/*-
 * Copyright (c) 2004 The FreeBSD Project
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include "opt_kdb.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kdb.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/pcpu.h>
#include <sys/proc.h>
#include <sys/smp.h>
#include <sys/sysctl.h>

#include <machine/kdb.h>
#include <machine/pcb.h>

#ifdef SMP
#include <machine/smp.h>
#endif

int kdb_active = 0;
void *kdb_jmpbufp = NULL;
struct kdb_dbbe *kdb_dbbe = NULL;
struct pcb kdb_pcb;
struct pcb *kdb_thrctx = NULL;
struct thread *kdb_thread = NULL;
struct trapframe *kdb_frame = NULL;

KDB_BACKEND(null, NULL, NULL, NULL);
SET_DECLARE(kdb_dbbe_set, struct kdb_dbbe);

static int kdb_sysctl_available(SYSCTL_HANDLER_ARGS);
static int kdb_sysctl_current(SYSCTL_HANDLER_ARGS);
static int kdb_sysctl_enter(SYSCTL_HANDLER_ARGS);
static int kdb_sysctl_panic(SYSCTL_HANDLER_ARGS);
static int kdb_sysctl_trap(SYSCTL_HANDLER_ARGS);
static int kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS);

SYSCTL_NODE(_debug, OID_AUTO, kdb, CTLFLAG_RW, NULL, "KDB nodes");

SYSCTL_PROC(_debug_kdb, OID_AUTO, available, CTLTYPE_STRING | CTLFLAG_RD, 0, 0,
    kdb_sysctl_available, "A", "list of available KDB backends");

SYSCTL_PROC(_debug_kdb, OID_AUTO, current, CTLTYPE_STRING | CTLFLAG_RW, 0, 0,
    kdb_sysctl_current, "A", "currently selected KDB backend");

SYSCTL_PROC(_debug_kdb, OID_AUTO, enter, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
    kdb_sysctl_enter, "I", "set to enter the debugger");

SYSCTL_PROC(_debug_kdb, OID_AUTO, panic, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
    kdb_sysctl_panic, "I", "set to panic the kernel");

SYSCTL_PROC(_debug_kdb, OID_AUTO, trap, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
    kdb_sysctl_trap, "I", "set to cause a page fault via data access");

SYSCTL_PROC(_debug_kdb, OID_AUTO, trap_code, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
    kdb_sysctl_trap_code, "I", "set to cause a page fault via code access");

/*
 * Flag indicating whether or not to IPI the other CPUs to stop them on
 * entering the debugger.  Sometimes, this will result in a deadlock as
 * stop_cpus() waits for the other cpus to stop, so we allow it to be
 * disabled.
 */
#ifdef SMP
static int kdb_stop_cpus = 1;
SYSCTL_INT(_debug_kdb, OID_AUTO, stop_cpus, CTLTYPE_INT | CTLFLAG_RW,
    &kdb_stop_cpus, 0, "stop other CPUs when entering the debugger");
TUNABLE_INT("debug.kdb.stop_cpus", &kdb_stop_cpus);
#endif

/*
 * Flag to indicate to debuggers why the debugger was entered.
 */
const char * volatile kdb_why = KDB_WHY_UNSET;

static int
kdb_sysctl_available(SYSCTL_HANDLER_ARGS)
{
	struct kdb_dbbe *be, **iter;
	char *avail, *p;
	ssize_t len, sz;
	int error;

	sz = 0;
	SET_FOREACH(iter, kdb_dbbe_set) {
		be = *iter;
		if (be->dbbe_active == 0)
			sz += strlen(be->dbbe_name) + 1;
	}
	sz++;
	avail = malloc(sz, M_TEMP, M_WAITOK);
	p = avail;
	*p = '\0';

	SET_FOREACH(iter, kdb_dbbe_set) {
		be = *iter;
		if (be->dbbe_active == 0) {
			len = snprintf(p, sz, "%s ", be->dbbe_name);
			p += len;
			sz -= len;
		}
	}
	KASSERT(sz >= 0, ("%s", __func__));
	error = sysctl_handle_string(oidp, avail, 0, req);
	free(avail, M_TEMP);
	return (error);
}

static int
kdb_sysctl_current(SYSCTL_HANDLER_ARGS)
{
	char buf[16];
	int error;

	if (kdb_dbbe != NULL) {
		strncpy(buf, kdb_dbbe->dbbe_name, sizeof(buf));
		buf[sizeof(buf) - 1] = '\0';
	} else
		*buf = '\0';
	error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
	if (error != 0 || req->newptr == NULL)
		return (error);
	if (kdb_active)
		return (EBUSY);
	return (kdb_dbbe_select(buf));
}

static int
kdb_sysctl_enter(SYSCTL_HANDLER_ARGS)
{
	int error, i;

	error = sysctl_wire_old_buffer(req, sizeof(int));
	if (error == 0) {
		i = 0;
		error = sysctl_handle_int(oidp, &i, 0, req);
	}
	if (error != 0 || req->newptr == NULL)
		return (error);
	if (kdb_active)
		return (EBUSY);
	kdb_enter(KDB_WHY_SYSCTL, "sysctl debug.kdb.enter");
	return (0);
}

static int
kdb_sysctl_panic(SYSCTL_HANDLER_ARGS)
{
	int error, i;

	error = sysctl_wire_old_buffer(req, sizeof(int));
	if (error == 0) {
		i = 0;
		error = sysctl_handle_int(oidp, &i, 0, req);
	}
	if (error != 0 || req->newptr == NULL)
		return (error);
	panic("kdb_sysctl_panic");
	return (0);
}

static int
kdb_sysctl_trap(SYSCTL_HANDLER_ARGS)
{
	int error, i;
	int *addr = (int *)0x10;

	error = sysctl_wire_old_buffer(req, sizeof(int));
	if (error == 0) {
		i = 0;
		error = sysctl_handle_int(oidp, &i, 0, req);
	}
	if (error != 0 || req->newptr == NULL)
		return (error);
	return (*addr);
}

static int
kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS)
{
	int error, i;
	void (*fp)(u_int, u_int, u_int) = (void *)0xdeadc0de;

	error = sysctl_wire_old_buffer(req, sizeof(int));
	if (error == 0) {
		i = 0;
		error = sysctl_handle_int(oidp, &i, 0, req);
	}
	if (error != 0 || req->newptr == NULL)
		return (error);
	(*fp)(0x11111111, 0x22222222, 0x33333333);
	return (0);
}

/*
 * Solaris implements a new BREAK which is initiated by a character sequence
 * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the
 * Remote Console.
 *
 * Note that this function may be called from almost anywhere, with interrupts
 * disabled and with unknown locks held, so it must not access data other than
 * its arguments.  Its up to the caller to ensure that the state variable is
 * consistent.
 */

#define	KEY_CR		13	/* CR '\r' */
#define	KEY_TILDE	126	/* ~ */
#define	KEY_CRTLB	2	/* ^B */

int
kdb_alt_break(int key, int *state)
{
	int brk;

	brk = 0;
	switch (key) {
	case KEY_CR:
		*state = KEY_TILDE;
		break;
	case KEY_TILDE:
		*state = (*state == KEY_TILDE) ? KEY_CRTLB : 0;
		break;
	case KEY_CRTLB:
		if (*state == KEY_CRTLB)
			brk = 1;
		/* FALLTHROUGH */
	default:
		*state = 0;
		break;
	}
	return (brk);
}

/*
 * Print a backtrace of the calling thread. The backtrace is generated by
 * the selected debugger, provided it supports backtraces. If no debugger
 * is selected or the current debugger does not support backtraces, this
 * function silently returns.
 */

void
kdb_backtrace()
{

	if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) {
		printf("KDB: stack backtrace:\n");
		kdb_dbbe->dbbe_trace();
	}
}

/*
 * Set/change the current backend.
 */

int
kdb_dbbe_select(const char *name)
{
	struct kdb_dbbe *be, **iter;

	SET_FOREACH(iter, kdb_dbbe_set) {
		be = *iter;
		if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) {
			kdb_dbbe = be;
			return (0);
		}
	}
	return (EINVAL);
}

/*
 * Enter the currently selected debugger. If a message has been provided,
 * it is printed first. If the debugger does not support the enter method,
 * it is entered by using breakpoint(), which enters the debugger through
 * kdb_trap().  The 'why' argument will contain a more mechanically usable
 * string than 'msg', and is relied upon by DDB scripting to identify the
 * reason for entering the debugger so that the right script can be run.
 */
void
kdb_enter(const char *why, const char *msg)
{

	if (kdb_dbbe != NULL && kdb_active == 0) {
		if (msg != NULL)
			printf("KDB: enter: %s\n", msg);
		kdb_why = why;
		breakpoint();
		kdb_why = KDB_WHY_UNSET;
	}
}

/*
 * Initialize the kernel debugger interface.
 */

void
kdb_init()
{
	struct kdb_dbbe *be, **iter;
	int cur_pri, pri;

	kdb_active = 0;
	kdb_dbbe = NULL;
	cur_pri = -1;
	SET_FOREACH(iter, kdb_dbbe_set) {
		be = *iter;
		pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1;
		be->dbbe_active = (pri >= 0) ? 0 : -1;
		if (pri > cur_pri) {
			cur_pri = pri;
			kdb_dbbe = be;
		}
	}
	if (kdb_dbbe != NULL) {
		printf("KDB: debugger backends:");
		SET_FOREACH(iter, kdb_dbbe_set) {
			be = *iter;
			if (be->dbbe_active == 0)
				printf(" %s", be->dbbe_name);
		}
		printf("\n");
		printf("KDB: current backend: %s\n",
		    kdb_dbbe->dbbe_name);
	}
}

/*
 * Handle contexts.
 */

void *
kdb_jmpbuf(jmp_buf new)
{
	void *old;

	old = kdb_jmpbufp;
	kdb_jmpbufp = new;
	return (old);
}

void
kdb_reenter(void)
{

	if (!kdb_active || kdb_jmpbufp == NULL)
		return;

	longjmp(kdb_jmpbufp, 1);
	/* NOTREACHED */
}

/*
 * Thread related support functions.
 */

struct pcb *
kdb_thr_ctx(struct thread *thr)
{  
#if defined(SMP) && defined(KDB_STOPPEDPCB)
	struct pcpu *pc;
#endif
 
	if (thr == curthread) 
		return (&kdb_pcb);

#if defined(SMP) && defined(KDB_STOPPEDPCB)
	SLIST_FOREACH(pc, &cpuhead, pc_allcpu)  {
		if (pc->pc_curthread == thr && (stopped_cpus & pc->pc_cpumask))
			return (KDB_STOPPEDPCB(pc));
	}
#endif
	return (thr->td_pcb);
}

struct thread *
kdb_thr_first(void)
{
	struct proc *p;
	struct thread *thr;

	p = LIST_FIRST(&allproc);
	while (p != NULL) {
		if (p->p_flag & P_INMEM) {
			thr = FIRST_THREAD_IN_PROC(p);
			if (thr != NULL)
				return (thr);
		}
		p = LIST_NEXT(p, p_list);
	}
	return (NULL);
}

struct thread *
kdb_thr_from_pid(pid_t pid)
{
	struct proc *p;

	p = LIST_FIRST(&allproc);
	while (p != NULL) {
		if (p->p_flag & P_INMEM && p->p_pid == pid)
			return (FIRST_THREAD_IN_PROC(p));
		p = LIST_NEXT(p, p_list);
	}
	return (NULL);
}

struct thread *
kdb_thr_lookup(lwpid_t tid)
{
	struct thread *thr;

	thr = kdb_thr_first();
	while (thr != NULL && thr->td_tid != tid)
		thr = kdb_thr_next(thr);
	return (thr);
}

struct thread *
kdb_thr_next(struct thread *thr)
{
	struct proc *p;

	p = thr->td_proc;
	thr = TAILQ_NEXT(thr, td_plist);
	do {
		if (thr != NULL)
			return (thr);
		p = LIST_NEXT(p, p_list);
		if (p != NULL && (p->p_flag & P_INMEM))
			thr = FIRST_THREAD_IN_PROC(p);
	} while (p != NULL);
	return (NULL);
}

int
kdb_thr_select(struct thread *thr)
{
	if (thr == NULL)
		return (EINVAL);
	kdb_thread = thr;
	kdb_thrctx = kdb_thr_ctx(thr);
	return (0);
}

/*
 * Enter the debugger due to a trap.
 */

int
kdb_trap(int type, int code, struct trapframe *tf)
{
	register_t intr;
#ifdef SMP
	int did_stop_cpus;
#endif
	int handled;

	if (kdb_dbbe == NULL || kdb_dbbe->dbbe_trap == NULL)
		return (0);

	/* We reenter the debugger through kdb_reenter(). */
	if (kdb_active)
		return (0);

	intr = intr_disable();

#ifdef SMP
	if ((did_stop_cpus = kdb_stop_cpus) != 0)
		stop_cpus(PCPU_GET(other_cpus));
#endif

	kdb_active++;

	kdb_frame = tf;

	/* Let MD code do its thing first... */
	kdb_cpu_trap(type, code);

	makectx(tf, &kdb_pcb);
	kdb_thr_select(curthread);

	handled = kdb_dbbe->dbbe_trap(type, code);

	kdb_active--;

#ifdef SMP
	if (did_stop_cpus)
		restart_cpus(stopped_cpus);
#endif

	intr_restore(intr);

	return (handled);
}