FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_kdb.c
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: releng/8.4/sys/kern/subr_kdb.c 235742 2012-05-21 21:16:08Z jhb $");
29
30 #include "opt_kdb.h"
31 #include "opt_stack.h"
32
33 #include <sys/param.h>
34 #include <sys/systm.h>
35 #include <sys/kdb.h>
36 #include <sys/kernel.h>
37 #include <sys/malloc.h>
38 #include <sys/pcpu.h>
39 #include <sys/proc.h>
40 #include <sys/smp.h>
41 #include <sys/stack.h>
42 #include <sys/sysctl.h>
43
44 #include <machine/kdb.h>
45 #include <machine/pcb.h>
46
47 #ifdef SMP
48 #include <machine/smp.h>
49 #endif
50
51 int kdb_active = 0;
52 static void *kdb_jmpbufp = NULL;
53 struct kdb_dbbe *kdb_dbbe = NULL;
54 static struct pcb kdb_pcb;
55 struct pcb *kdb_thrctx = NULL;
56 struct thread *kdb_thread = NULL;
57 struct trapframe *kdb_frame = NULL;
58
59 #ifdef BREAK_TO_DEBUGGER
60 #define KDB_BREAK_TO_DEBUGGER 1
61 #else
62 #define KDB_BREAK_TO_DEBUGGER 0
63 #endif
64
65 #ifdef ALT_BREAK_TO_DEBUGGER
66 #define KDB_ALT_BREAK_TO_DEBUGGER 1
67 #else
68 #define KDB_ALT_BREAK_TO_DEBUGGER 0
69 #endif
70
71 static int kdb_break_to_debugger = KDB_BREAK_TO_DEBUGGER;
72 static int kdb_alt_break_to_debugger = KDB_ALT_BREAK_TO_DEBUGGER;
73
74 KDB_BACKEND(null, NULL, NULL, NULL, NULL);
75 SET_DECLARE(kdb_dbbe_set, struct kdb_dbbe);
76
77 static int kdb_sysctl_available(SYSCTL_HANDLER_ARGS);
78 static int kdb_sysctl_current(SYSCTL_HANDLER_ARGS);
79 static int kdb_sysctl_enter(SYSCTL_HANDLER_ARGS);
80 static int kdb_sysctl_panic(SYSCTL_HANDLER_ARGS);
81 static int kdb_sysctl_trap(SYSCTL_HANDLER_ARGS);
82 static int kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS);
83
84 SYSCTL_NODE(_debug, OID_AUTO, kdb, CTLFLAG_RW, NULL, "KDB nodes");
85
86 SYSCTL_PROC(_debug_kdb, OID_AUTO, available, CTLTYPE_STRING | CTLFLAG_RD, NULL,
87 0, kdb_sysctl_available, "A", "list of available KDB backends");
88
89 SYSCTL_PROC(_debug_kdb, OID_AUTO, current, CTLTYPE_STRING | CTLFLAG_RW, NULL,
90 0, kdb_sysctl_current, "A", "currently selected KDB backend");
91
92 SYSCTL_PROC(_debug_kdb, OID_AUTO, enter, CTLTYPE_INT | CTLFLAG_RW, NULL, 0,
93 kdb_sysctl_enter, "I", "set to enter the debugger");
94
95 SYSCTL_PROC(_debug_kdb, OID_AUTO, panic, CTLTYPE_INT | CTLFLAG_RW, NULL, 0,
96 kdb_sysctl_panic, "I", "set to panic the kernel");
97
98 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap, CTLTYPE_INT | CTLFLAG_RW, NULL, 0,
99 kdb_sysctl_trap, "I", "set to cause a page fault via data access");
100
101 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap_code, CTLTYPE_INT | CTLFLAG_RW, NULL, 0,
102 kdb_sysctl_trap_code, "I", "set to cause a page fault via code access");
103
104 SYSCTL_INT(_debug_kdb, OID_AUTO, break_to_debugger, CTLTYPE_INT | CTLFLAG_RW |
105 CTLFLAG_TUN, &kdb_break_to_debugger, 0, "Enable break to debugger");
106 TUNABLE_INT("debug.kdb.break_to_debugger", &kdb_break_to_debugger);
107
108 SYSCTL_INT(_debug_kdb, OID_AUTO, alt_break_to_debugger, CTLTYPE_INT |
109 CTLFLAG_RW | CTLFLAG_TUN, &kdb_alt_break_to_debugger, 0,
110 "Enable alternative break to debugger");
111 TUNABLE_INT("debug.kdb.alt_break_to_debugger", &kdb_alt_break_to_debugger);
112
113 /*
114 * Flag indicating whether or not to IPI the other CPUs to stop them on
115 * entering the debugger. Sometimes, this will result in a deadlock as
116 * stop_cpus() waits for the other cpus to stop, so we allow it to be
117 * disabled. In order to maximize the chances of success, use a hard
118 * stop for that.
119 */
120 #ifdef SMP
121 static int kdb_stop_cpus = 1;
122 SYSCTL_INT(_debug_kdb, OID_AUTO, stop_cpus, CTLFLAG_RW | CTLFLAG_TUN,
123 &kdb_stop_cpus, 0, "stop other CPUs when entering the debugger");
124 TUNABLE_INT("debug.kdb.stop_cpus", &kdb_stop_cpus);
125 #endif
126
127 /*
128 * Flag to indicate to debuggers why the debugger was entered.
129 */
130 const char * volatile kdb_why = KDB_WHY_UNSET;
131
132 static int
133 kdb_sysctl_available(SYSCTL_HANDLER_ARGS)
134 {
135 struct kdb_dbbe *be, **iter;
136 char *avail, *p;
137 ssize_t len, sz;
138 int error;
139
140 sz = 0;
141 SET_FOREACH(iter, kdb_dbbe_set) {
142 be = *iter;
143 if (be->dbbe_active == 0)
144 sz += strlen(be->dbbe_name) + 1;
145 }
146 sz++;
147 avail = malloc(sz, M_TEMP, M_WAITOK);
148 p = avail;
149 *p = '\0';
150
151 SET_FOREACH(iter, kdb_dbbe_set) {
152 be = *iter;
153 if (be->dbbe_active == 0) {
154 len = snprintf(p, sz, "%s ", be->dbbe_name);
155 p += len;
156 sz -= len;
157 }
158 }
159 KASSERT(sz >= 0, ("%s", __func__));
160 error = sysctl_handle_string(oidp, avail, 0, req);
161 free(avail, M_TEMP);
162 return (error);
163 }
164
165 static int
166 kdb_sysctl_current(SYSCTL_HANDLER_ARGS)
167 {
168 char buf[16];
169 int error;
170
171 if (kdb_dbbe != NULL)
172 strlcpy(buf, kdb_dbbe->dbbe_name, sizeof(buf));
173 else
174 *buf = '\0';
175 error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
176 if (error != 0 || req->newptr == NULL)
177 return (error);
178 if (kdb_active)
179 return (EBUSY);
180 return (kdb_dbbe_select(buf));
181 }
182
183 static int
184 kdb_sysctl_enter(SYSCTL_HANDLER_ARGS)
185 {
186 int error, i;
187
188 error = sysctl_wire_old_buffer(req, sizeof(int));
189 if (error == 0) {
190 i = 0;
191 error = sysctl_handle_int(oidp, &i, 0, req);
192 }
193 if (error != 0 || req->newptr == NULL)
194 return (error);
195 if (kdb_active)
196 return (EBUSY);
197 kdb_enter(KDB_WHY_SYSCTL, "sysctl debug.kdb.enter");
198 return (0);
199 }
200
201 static int
202 kdb_sysctl_panic(SYSCTL_HANDLER_ARGS)
203 {
204 int error, i;
205
206 error = sysctl_wire_old_buffer(req, sizeof(int));
207 if (error == 0) {
208 i = 0;
209 error = sysctl_handle_int(oidp, &i, 0, req);
210 }
211 if (error != 0 || req->newptr == NULL)
212 return (error);
213 panic("kdb_sysctl_panic");
214 return (0);
215 }
216
217 static int
218 kdb_sysctl_trap(SYSCTL_HANDLER_ARGS)
219 {
220 int error, i;
221 int *addr = (int *)0x10;
222
223 error = sysctl_wire_old_buffer(req, sizeof(int));
224 if (error == 0) {
225 i = 0;
226 error = sysctl_handle_int(oidp, &i, 0, req);
227 }
228 if (error != 0 || req->newptr == NULL)
229 return (error);
230 return (*addr);
231 }
232
233 static int
234 kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS)
235 {
236 int error, i;
237 void (*fp)(u_int, u_int, u_int) = (void *)0xdeadc0de;
238
239 error = sysctl_wire_old_buffer(req, sizeof(int));
240 if (error == 0) {
241 i = 0;
242 error = sysctl_handle_int(oidp, &i, 0, req);
243 }
244 if (error != 0 || req->newptr == NULL)
245 return (error);
246 (*fp)(0x11111111, 0x22222222, 0x33333333);
247 return (0);
248 }
249
250 void
251 kdb_panic(const char *msg)
252 {
253
254 printf("KDB: panic\n");
255 panic("%s", msg);
256 }
257
258 void
259 kdb_reboot(void)
260 {
261
262 printf("KDB: reboot requested\n");
263 shutdown_nice(0);
264 }
265
266 /*
267 * Solaris implements a new BREAK which is initiated by a character sequence
268 * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the
269 * Remote Console.
270 *
271 * Note that this function may be called from almost anywhere, with interrupts
272 * disabled and with unknown locks held, so it must not access data other than
273 * its arguments. Its up to the caller to ensure that the state variable is
274 * consistent.
275 */
276
277 #define KEY_CR 13 /* CR '\r' */
278 #define KEY_TILDE 126 /* ~ */
279 #define KEY_CRTLB 2 /* ^B */
280 #define KEY_CRTLP 16 /* ^P */
281 #define KEY_CRTLR 18 /* ^R */
282
283 int
284 kdb_break(void)
285 {
286
287 if (!kdb_break_to_debugger)
288 return (0);
289 kdb_enter(KDB_WHY_BREAK, "Break to debugger");
290 return (KDB_REQ_DEBUGGER);
291 }
292
293 static int
294 kdb_alt_break_state(int key, int *state)
295 {
296 int brk;
297
298 brk = 0;
299 switch (*state) {
300 case 0:
301 if (key == KEY_CR)
302 *state = 1;
303 break;
304 case 1:
305 if (key == KEY_TILDE)
306 *state = 2;
307 break;
308 case 2:
309 if (key == KEY_CRTLB)
310 brk = KDB_REQ_DEBUGGER;
311 else if (key == KEY_CRTLP)
312 brk = KDB_REQ_PANIC;
313 else if (key == KEY_CRTLR)
314 brk = KDB_REQ_REBOOT;
315 *state = 0;
316 }
317 return (brk);
318 }
319
320 static int
321 kdb_alt_break_internal(int key, int *state, int force_gdb)
322 {
323 int brk;
324
325 if (!kdb_alt_break_to_debugger)
326 return (0);
327 brk = kdb_alt_break_state(key, state);
328 switch (brk) {
329 case KDB_REQ_DEBUGGER:
330 if (force_gdb)
331 kdb_dbbe_select("gdb");
332 kdb_enter(KDB_WHY_BREAK, "Break to debugger");
333 break;
334
335 case KDB_REQ_PANIC:
336 if (force_gdb)
337 kdb_dbbe_select("gdb");
338 kdb_panic("Panic sequence on console");
339 break;
340
341 case KDB_REQ_REBOOT:
342 kdb_reboot();
343 break;
344 }
345 return (0);
346 }
347
348 int
349 kdb_alt_break(int key, int *state)
350 {
351
352 return (kdb_alt_break_internal(key, state, 0));
353 }
354
355 /*
356 * This variation on kdb_alt_break() is used only by dcons, which has its own
357 * configuration flag to force GDB use regardless of the global KDB
358 * configuration.
359 */
360 int
361 kdb_alt_break_gdb(int key, int *state)
362 {
363
364 return (kdb_alt_break_internal(key, state, 1));
365 }
366
367 /*
368 * Print a backtrace of the calling thread. The backtrace is generated by
369 * the selected debugger, provided it supports backtraces. If no debugger
370 * is selected or the current debugger does not support backtraces, this
371 * function silently returns.
372 */
373
374 void
375 kdb_backtrace(void)
376 {
377
378 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) {
379 printf("KDB: stack backtrace:\n");
380 kdb_dbbe->dbbe_trace();
381 }
382 #ifdef STACK
383 else {
384 struct stack st;
385
386 printf("KDB: stack backtrace:\n");
387 stack_zero(&st);
388 stack_save(&st);
389 stack_print_ddb(&st);
390 }
391 #endif
392 }
393
394 /*
395 * Similar to kdb_backtrace() except that it prints a backtrace of an
396 * arbitrary thread rather than the calling thread.
397 */
398 void
399 kdb_backtrace_thread(struct thread *td)
400 {
401
402 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace_thread != NULL) {
403 printf("KDB: stack backtrace of thread %d:\n", td->td_tid);
404 kdb_dbbe->dbbe_trace_thread(td);
405 }
406 #ifdef STACK
407 else {
408 struct stack st;
409
410 printf("KDB: stack backtrace of thread %d:\n", td->td_tid);
411 stack_zero(&st);
412 stack_save_td(&st, td);
413 stack_print_ddb(&st);
414 }
415 #endif
416 }
417
418 /*
419 * Set/change the current backend.
420 */
421
422 int
423 kdb_dbbe_select(const char *name)
424 {
425 struct kdb_dbbe *be, **iter;
426
427 SET_FOREACH(iter, kdb_dbbe_set) {
428 be = *iter;
429 if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) {
430 kdb_dbbe = be;
431 return (0);
432 }
433 }
434 return (EINVAL);
435 }
436
437 /*
438 * Enter the currently selected debugger. If a message has been provided,
439 * it is printed first. If the debugger does not support the enter method,
440 * it is entered by using breakpoint(), which enters the debugger through
441 * kdb_trap(). The 'why' argument will contain a more mechanically usable
442 * string than 'msg', and is relied upon by DDB scripting to identify the
443 * reason for entering the debugger so that the right script can be run.
444 */
445 void
446 kdb_enter(const char *why, const char *msg)
447 {
448
449 if (kdb_dbbe != NULL && kdb_active == 0) {
450 if (msg != NULL)
451 printf("KDB: enter: %s\n", msg);
452 kdb_why = why;
453 breakpoint();
454 kdb_why = KDB_WHY_UNSET;
455 }
456 }
457
458 /*
459 * Initialize the kernel debugger interface.
460 */
461
462 void
463 kdb_init(void)
464 {
465 struct kdb_dbbe *be, **iter;
466 int cur_pri, pri;
467
468 kdb_active = 0;
469 kdb_dbbe = NULL;
470 cur_pri = -1;
471 SET_FOREACH(iter, kdb_dbbe_set) {
472 be = *iter;
473 pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1;
474 be->dbbe_active = (pri >= 0) ? 0 : -1;
475 if (pri > cur_pri) {
476 cur_pri = pri;
477 kdb_dbbe = be;
478 }
479 }
480 if (kdb_dbbe != NULL) {
481 printf("KDB: debugger backends:");
482 SET_FOREACH(iter, kdb_dbbe_set) {
483 be = *iter;
484 if (be->dbbe_active == 0)
485 printf(" %s", be->dbbe_name);
486 }
487 printf("\n");
488 printf("KDB: current backend: %s\n",
489 kdb_dbbe->dbbe_name);
490 }
491 }
492
493 /*
494 * Handle contexts.
495 */
496
497 void *
498 kdb_jmpbuf(jmp_buf new)
499 {
500 void *old;
501
502 old = kdb_jmpbufp;
503 kdb_jmpbufp = new;
504 return (old);
505 }
506
507 void
508 kdb_reenter(void)
509 {
510
511 if (!kdb_active || kdb_jmpbufp == NULL)
512 return;
513
514 longjmp(kdb_jmpbufp, 1);
515 /* NOTREACHED */
516 }
517
518 /*
519 * Thread related support functions.
520 */
521
522 struct pcb *
523 kdb_thr_ctx(struct thread *thr)
524 {
525 #if defined(SMP) && defined(KDB_STOPPEDPCB)
526 struct pcpu *pc;
527 #endif
528
529 if (thr == curthread)
530 return (&kdb_pcb);
531
532 #if defined(SMP) && defined(KDB_STOPPEDPCB)
533 SLIST_FOREACH(pc, &cpuhead, pc_allcpu) {
534 if (pc->pc_curthread == thr && (stopped_cpus & pc->pc_cpumask))
535 return (KDB_STOPPEDPCB(pc));
536 }
537 #endif
538 return (thr->td_pcb);
539 }
540
541 struct thread *
542 kdb_thr_first(void)
543 {
544 struct proc *p;
545 struct thread *thr;
546
547 p = LIST_FIRST(&allproc);
548 while (p != NULL) {
549 if (p->p_flag & P_INMEM) {
550 thr = FIRST_THREAD_IN_PROC(p);
551 if (thr != NULL)
552 return (thr);
553 }
554 p = LIST_NEXT(p, p_list);
555 }
556 return (NULL);
557 }
558
559 struct thread *
560 kdb_thr_from_pid(pid_t pid)
561 {
562 struct proc *p;
563
564 p = LIST_FIRST(&allproc);
565 while (p != NULL) {
566 if (p->p_flag & P_INMEM && p->p_pid == pid)
567 return (FIRST_THREAD_IN_PROC(p));
568 p = LIST_NEXT(p, p_list);
569 }
570 return (NULL);
571 }
572
573 struct thread *
574 kdb_thr_lookup(lwpid_t tid)
575 {
576 struct thread *thr;
577
578 thr = kdb_thr_first();
579 while (thr != NULL && thr->td_tid != tid)
580 thr = kdb_thr_next(thr);
581 return (thr);
582 }
583
584 struct thread *
585 kdb_thr_next(struct thread *thr)
586 {
587 struct proc *p;
588
589 p = thr->td_proc;
590 thr = TAILQ_NEXT(thr, td_plist);
591 do {
592 if (thr != NULL)
593 return (thr);
594 p = LIST_NEXT(p, p_list);
595 if (p != NULL && (p->p_flag & P_INMEM))
596 thr = FIRST_THREAD_IN_PROC(p);
597 } while (p != NULL);
598 return (NULL);
599 }
600
601 int
602 kdb_thr_select(struct thread *thr)
603 {
604 if (thr == NULL)
605 return (EINVAL);
606 kdb_thread = thr;
607 kdb_thrctx = kdb_thr_ctx(thr);
608 return (0);
609 }
610
611 /*
612 * Enter the debugger due to a trap.
613 */
614
615 int
616 kdb_trap(int type, int code, struct trapframe *tf)
617 {
618 struct kdb_dbbe *be;
619 register_t intr;
620 #ifdef SMP
621 int did_stop_cpus;
622 #endif
623 int handled;
624
625 be = kdb_dbbe;
626 if (be == NULL || be->dbbe_trap == NULL)
627 return (0);
628
629 /* We reenter the debugger through kdb_reenter(). */
630 if (kdb_active)
631 return (0);
632
633 intr = intr_disable();
634
635 #ifdef SMP
636 if (!SCHEDULER_STOPPED()) {
637 if ((did_stop_cpus = kdb_stop_cpus) != 0)
638 stop_cpus_hard(PCPU_GET(other_cpus));
639 } else
640 did_stop_cpus = 0;
641 #endif
642
643 kdb_active++;
644
645 kdb_frame = tf;
646
647 /* Let MD code do its thing first... */
648 kdb_cpu_trap(type, code);
649
650 makectx(tf, &kdb_pcb);
651 kdb_thr_select(curthread);
652
653 for (;;) {
654 handled = be->dbbe_trap(type, code);
655 if (be == kdb_dbbe)
656 break;
657 be = kdb_dbbe;
658 if (be == NULL || be->dbbe_trap == NULL)
659 break;
660 printf("Switching to %s back-end\n", be->dbbe_name);
661 }
662
663 kdb_active--;
664
665 #ifdef SMP
666 if (did_stop_cpus)
667 restart_cpus(stopped_cpus);
668 #endif
669
670 intr_restore(intr);
671
672 return (handled);
673 }
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