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/9.0/sys/kern/subr_kdb.c 225797 2011-09-27 14:00:32Z attilio $");
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/sbuf.h>
41 #include <sys/smp.h>
42 #include <sys/stack.h>
43 #include <sys/sysctl.h>
44
45 #include <machine/kdb.h>
46 #include <machine/pcb.h>
47
48 #ifdef SMP
49 #include <machine/smp.h>
50 #endif
51
52 int kdb_active = 0;
53 static void *kdb_jmpbufp = NULL;
54 struct kdb_dbbe *kdb_dbbe = NULL;
55 static struct pcb kdb_pcb;
56 struct pcb *kdb_thrctx = NULL;
57 struct thread *kdb_thread = NULL;
58 struct trapframe *kdb_frame = NULL;
59
60 #ifdef BREAK_TO_DEBUGGER
61 #define KDB_BREAK_TO_DEBUGGER 1
62 #else
63 #define KDB_BREAK_TO_DEBUGGER 0
64 #endif
65
66 #ifdef ALT_BREAK_TO_DEBUGGER
67 #define KDB_ALT_BREAK_TO_DEBUGGER 1
68 #else
69 #define KDB_ALT_BREAK_TO_DEBUGGER 0
70 #endif
71
72 static int kdb_break_to_debugger = KDB_BREAK_TO_DEBUGGER;
73 static int kdb_alt_break_to_debugger = KDB_ALT_BREAK_TO_DEBUGGER;
74
75 KDB_BACKEND(null, NULL, NULL, NULL);
76 SET_DECLARE(kdb_dbbe_set, struct kdb_dbbe);
77
78 static int kdb_sysctl_available(SYSCTL_HANDLER_ARGS);
79 static int kdb_sysctl_current(SYSCTL_HANDLER_ARGS);
80 static int kdb_sysctl_enter(SYSCTL_HANDLER_ARGS);
81 static int kdb_sysctl_panic(SYSCTL_HANDLER_ARGS);
82 static int kdb_sysctl_trap(SYSCTL_HANDLER_ARGS);
83 static int kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS);
84
85 SYSCTL_NODE(_debug, OID_AUTO, kdb, CTLFLAG_RW, NULL, "KDB nodes");
86
87 SYSCTL_PROC(_debug_kdb, OID_AUTO, available, CTLTYPE_STRING | CTLFLAG_RD, NULL,
88 0, kdb_sysctl_available, "A", "list of available KDB backends");
89
90 SYSCTL_PROC(_debug_kdb, OID_AUTO, current, CTLTYPE_STRING | CTLFLAG_RW, NULL,
91 0, kdb_sysctl_current, "A", "currently selected KDB backend");
92
93 SYSCTL_PROC(_debug_kdb, OID_AUTO, enter, CTLTYPE_INT | CTLFLAG_RW, NULL, 0,
94 kdb_sysctl_enter, "I", "set to enter the debugger");
95
96 SYSCTL_PROC(_debug_kdb, OID_AUTO, panic, CTLTYPE_INT | CTLFLAG_RW, NULL, 0,
97 kdb_sysctl_panic, "I", "set to panic the kernel");
98
99 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap, CTLTYPE_INT | CTLFLAG_RW, NULL, 0,
100 kdb_sysctl_trap, "I", "set to cause a page fault via data access");
101
102 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap_code, CTLTYPE_INT | CTLFLAG_RW, NULL, 0,
103 kdb_sysctl_trap_code, "I", "set to cause a page fault via code access");
104
105 SYSCTL_INT(_debug_kdb, OID_AUTO, break_to_debugger, CTLTYPE_INT | CTLFLAG_RW |
106 CTLFLAG_TUN, &kdb_break_to_debugger, 0, "Enable break to debugger");
107 TUNABLE_INT("debug.kdb.break_to_debugger", &kdb_break_to_debugger);
108
109 SYSCTL_INT(_debug_kdb, OID_AUTO, alt_break_to_debugger, CTLTYPE_INT |
110 CTLFLAG_RW | CTLFLAG_TUN, &kdb_alt_break_to_debugger, 0,
111 "Enable alternative break to debugger");
112 TUNABLE_INT("debug.kdb.alt_break_to_debugger", &kdb_alt_break_to_debugger);
113
114 /*
115 * Flag to indicate to debuggers why the debugger was entered.
116 */
117 const char * volatile kdb_why = KDB_WHY_UNSET;
118
119 static int
120 kdb_sysctl_available(SYSCTL_HANDLER_ARGS)
121 {
122 struct kdb_dbbe **iter;
123 struct sbuf sbuf;
124 int error;
125
126 sbuf_new_for_sysctl(&sbuf, NULL, 64, req);
127 SET_FOREACH(iter, kdb_dbbe_set) {
128 if ((*iter)->dbbe_active == 0)
129 sbuf_printf(&sbuf, "%s ", (*iter)->dbbe_name);
130 }
131 error = sbuf_finish(&sbuf);
132 sbuf_delete(&sbuf);
133 return (error);
134 }
135
136 static int
137 kdb_sysctl_current(SYSCTL_HANDLER_ARGS)
138 {
139 char buf[16];
140 int error;
141
142 if (kdb_dbbe != NULL)
143 strlcpy(buf, kdb_dbbe->dbbe_name, sizeof(buf));
144 else
145 *buf = '\0';
146 error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
147 if (error != 0 || req->newptr == NULL)
148 return (error);
149 if (kdb_active)
150 return (EBUSY);
151 return (kdb_dbbe_select(buf));
152 }
153
154 static int
155 kdb_sysctl_enter(SYSCTL_HANDLER_ARGS)
156 {
157 int error, i;
158
159 error = sysctl_wire_old_buffer(req, sizeof(int));
160 if (error == 0) {
161 i = 0;
162 error = sysctl_handle_int(oidp, &i, 0, req);
163 }
164 if (error != 0 || req->newptr == NULL)
165 return (error);
166 if (kdb_active)
167 return (EBUSY);
168 kdb_enter(KDB_WHY_SYSCTL, "sysctl debug.kdb.enter");
169 return (0);
170 }
171
172 static int
173 kdb_sysctl_panic(SYSCTL_HANDLER_ARGS)
174 {
175 int error, i;
176
177 error = sysctl_wire_old_buffer(req, sizeof(int));
178 if (error == 0) {
179 i = 0;
180 error = sysctl_handle_int(oidp, &i, 0, req);
181 }
182 if (error != 0 || req->newptr == NULL)
183 return (error);
184 panic("kdb_sysctl_panic");
185 return (0);
186 }
187
188 static int
189 kdb_sysctl_trap(SYSCTL_HANDLER_ARGS)
190 {
191 int error, i;
192 int *addr = (int *)0x10;
193
194 error = sysctl_wire_old_buffer(req, sizeof(int));
195 if (error == 0) {
196 i = 0;
197 error = sysctl_handle_int(oidp, &i, 0, req);
198 }
199 if (error != 0 || req->newptr == NULL)
200 return (error);
201 return (*addr);
202 }
203
204 static int
205 kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS)
206 {
207 int error, i;
208 void (*fp)(u_int, u_int, u_int) = (void *)0xdeadc0de;
209
210 error = sysctl_wire_old_buffer(req, sizeof(int));
211 if (error == 0) {
212 i = 0;
213 error = sysctl_handle_int(oidp, &i, 0, req);
214 }
215 if (error != 0 || req->newptr == NULL)
216 return (error);
217 (*fp)(0x11111111, 0x22222222, 0x33333333);
218 return (0);
219 }
220
221 void
222 kdb_panic(const char *msg)
223 {
224 #ifdef SMP
225 cpuset_t other_cpus;
226
227 other_cpus = all_cpus;
228 CPU_CLR(PCPU_GET(cpuid), &other_cpus);
229 stop_cpus_hard(other_cpus);
230 #endif
231 printf("KDB: panic\n");
232 panic("%s", msg);
233 }
234
235 void
236 kdb_reboot(void)
237 {
238
239 printf("KDB: reboot requested\n");
240 shutdown_nice(0);
241 }
242
243 /*
244 * Solaris implements a new BREAK which is initiated by a character sequence
245 * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the
246 * Remote Console.
247 *
248 * Note that this function may be called from almost anywhere, with interrupts
249 * disabled and with unknown locks held, so it must not access data other than
250 * its arguments. Its up to the caller to ensure that the state variable is
251 * consistent.
252 */
253
254 #define KEY_CR 13 /* CR '\r' */
255 #define KEY_TILDE 126 /* ~ */
256 #define KEY_CRTLB 2 /* ^B */
257 #define KEY_CRTLP 16 /* ^P */
258 #define KEY_CRTLR 18 /* ^R */
259
260 /* States of th KDB "alternate break sequence" detecting state machine. */
261 enum {
262 KDB_ALT_BREAK_SEEN_NONE,
263 KDB_ALT_BREAK_SEEN_CR,
264 KDB_ALT_BREAK_SEEN_CR_TILDE,
265 };
266
267 int
268 kdb_break(void)
269 {
270
271 if (!kdb_break_to_debugger)
272 return (0);
273 kdb_enter(KDB_WHY_BREAK, "Break to debugger");
274 return (KDB_REQ_DEBUGGER);
275 }
276
277 static int
278 kdb_alt_break_state(int key, int *state)
279 {
280 int brk;
281
282 /* All states transition to KDB_ALT_BREAK_SEEN_CR on a CR. */
283 if (key == KEY_CR) {
284 *state = KDB_ALT_BREAK_SEEN_CR;
285 return (0);
286 }
287
288 brk = 0;
289 switch (*state) {
290 case KDB_ALT_BREAK_SEEN_CR:
291 *state = KDB_ALT_BREAK_SEEN_NONE;
292 if (key == KEY_TILDE)
293 *state = KDB_ALT_BREAK_SEEN_CR_TILDE;
294 break;
295 case KDB_ALT_BREAK_SEEN_CR_TILDE:
296 *state = KDB_ALT_BREAK_SEEN_NONE;
297 if (key == KEY_CRTLB)
298 brk = KDB_REQ_DEBUGGER;
299 else if (key == KEY_CRTLP)
300 brk = KDB_REQ_PANIC;
301 else if (key == KEY_CRTLR)
302 brk = KDB_REQ_REBOOT;
303 break;
304 case KDB_ALT_BREAK_SEEN_NONE:
305 default:
306 *state = KDB_ALT_BREAK_SEEN_NONE;
307 break;
308 }
309 return (brk);
310 }
311
312 static int
313 kdb_alt_break_internal(int key, int *state, int force_gdb)
314 {
315 int brk;
316
317 if (!kdb_alt_break_to_debugger)
318 return (0);
319 brk = kdb_alt_break_state(key, state);
320 switch (brk) {
321 case KDB_REQ_DEBUGGER:
322 if (force_gdb)
323 kdb_dbbe_select("gdb");
324 kdb_enter(KDB_WHY_BREAK, "Break to debugger");
325 break;
326
327 case KDB_REQ_PANIC:
328 if (force_gdb)
329 kdb_dbbe_select("gdb");
330 kdb_panic("Panic sequence on console");
331 break;
332
333 case KDB_REQ_REBOOT:
334 kdb_reboot();
335 break;
336 }
337 return (0);
338 }
339
340 int
341 kdb_alt_break(int key, int *state)
342 {
343
344 return (kdb_alt_break_internal(key, state, 0));
345 }
346
347 /*
348 * This variation on kdb_alt_break() is used only by dcons, which has its own
349 * configuration flag to force GDB use regardless of the global KDB
350 * configuration.
351 */
352 int
353 kdb_alt_break_gdb(int key, int *state)
354 {
355
356 return (kdb_alt_break_internal(key, state, 1));
357 }
358
359 /*
360 * Print a backtrace of the calling thread. The backtrace is generated by
361 * the selected debugger, provided it supports backtraces. If no debugger
362 * is selected or the current debugger does not support backtraces, this
363 * function silently returns.
364 */
365
366 void
367 kdb_backtrace(void)
368 {
369
370 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) {
371 printf("KDB: stack backtrace:\n");
372 kdb_dbbe->dbbe_trace();
373 }
374 #ifdef STACK
375 else {
376 struct stack st;
377
378 printf("KDB: stack backtrace:\n");
379 stack_save(&st);
380 stack_print_ddb(&st);
381 }
382 #endif
383 }
384
385 /*
386 * Set/change the current backend.
387 */
388
389 int
390 kdb_dbbe_select(const char *name)
391 {
392 struct kdb_dbbe *be, **iter;
393
394 SET_FOREACH(iter, kdb_dbbe_set) {
395 be = *iter;
396 if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) {
397 kdb_dbbe = be;
398 return (0);
399 }
400 }
401 return (EINVAL);
402 }
403
404 /*
405 * Enter the currently selected debugger. If a message has been provided,
406 * it is printed first. If the debugger does not support the enter method,
407 * it is entered by using breakpoint(), which enters the debugger through
408 * kdb_trap(). The 'why' argument will contain a more mechanically usable
409 * string than 'msg', and is relied upon by DDB scripting to identify the
410 * reason for entering the debugger so that the right script can be run.
411 */
412 void
413 kdb_enter(const char *why, const char *msg)
414 {
415
416 if (kdb_dbbe != NULL && kdb_active == 0) {
417 if (msg != NULL)
418 printf("KDB: enter: %s\n", msg);
419 kdb_why = why;
420 breakpoint();
421 kdb_why = KDB_WHY_UNSET;
422 }
423 }
424
425 /*
426 * Initialize the kernel debugger interface.
427 */
428
429 void
430 kdb_init(void)
431 {
432 struct kdb_dbbe *be, **iter;
433 int cur_pri, pri;
434
435 kdb_active = 0;
436 kdb_dbbe = NULL;
437 cur_pri = -1;
438 SET_FOREACH(iter, kdb_dbbe_set) {
439 be = *iter;
440 pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1;
441 be->dbbe_active = (pri >= 0) ? 0 : -1;
442 if (pri > cur_pri) {
443 cur_pri = pri;
444 kdb_dbbe = be;
445 }
446 }
447 if (kdb_dbbe != NULL) {
448 printf("KDB: debugger backends:");
449 SET_FOREACH(iter, kdb_dbbe_set) {
450 be = *iter;
451 if (be->dbbe_active == 0)
452 printf(" %s", be->dbbe_name);
453 }
454 printf("\n");
455 printf("KDB: current backend: %s\n",
456 kdb_dbbe->dbbe_name);
457 }
458 }
459
460 /*
461 * Handle contexts.
462 */
463
464 void *
465 kdb_jmpbuf(jmp_buf new)
466 {
467 void *old;
468
469 old = kdb_jmpbufp;
470 kdb_jmpbufp = new;
471 return (old);
472 }
473
474 void
475 kdb_reenter(void)
476 {
477
478 if (!kdb_active || kdb_jmpbufp == NULL)
479 return;
480
481 longjmp(kdb_jmpbufp, 1);
482 /* NOTREACHED */
483 }
484
485 /*
486 * Thread related support functions.
487 */
488
489 struct pcb *
490 kdb_thr_ctx(struct thread *thr)
491 {
492 #if defined(SMP) && defined(KDB_STOPPEDPCB)
493 struct pcpu *pc;
494 #endif
495
496 if (thr == curthread)
497 return (&kdb_pcb);
498
499 #if defined(SMP) && defined(KDB_STOPPEDPCB)
500 STAILQ_FOREACH(pc, &cpuhead, pc_allcpu) {
501 if (pc->pc_curthread == thr &&
502 CPU_ISSET(pc->pc_cpuid, &stopped_cpus))
503 return (KDB_STOPPEDPCB(pc));
504 }
505 #endif
506 return (thr->td_pcb);
507 }
508
509 struct thread *
510 kdb_thr_first(void)
511 {
512 struct proc *p;
513 struct thread *thr;
514
515 p = LIST_FIRST(&allproc);
516 while (p != NULL) {
517 if (p->p_flag & P_INMEM) {
518 thr = FIRST_THREAD_IN_PROC(p);
519 if (thr != NULL)
520 return (thr);
521 }
522 p = LIST_NEXT(p, p_list);
523 }
524 return (NULL);
525 }
526
527 struct thread *
528 kdb_thr_from_pid(pid_t pid)
529 {
530 struct proc *p;
531
532 p = LIST_FIRST(&allproc);
533 while (p != NULL) {
534 if (p->p_flag & P_INMEM && p->p_pid == pid)
535 return (FIRST_THREAD_IN_PROC(p));
536 p = LIST_NEXT(p, p_list);
537 }
538 return (NULL);
539 }
540
541 struct thread *
542 kdb_thr_lookup(lwpid_t tid)
543 {
544 struct thread *thr;
545
546 thr = kdb_thr_first();
547 while (thr != NULL && thr->td_tid != tid)
548 thr = kdb_thr_next(thr);
549 return (thr);
550 }
551
552 struct thread *
553 kdb_thr_next(struct thread *thr)
554 {
555 struct proc *p;
556
557 p = thr->td_proc;
558 thr = TAILQ_NEXT(thr, td_plist);
559 do {
560 if (thr != NULL)
561 return (thr);
562 p = LIST_NEXT(p, p_list);
563 if (p != NULL && (p->p_flag & P_INMEM))
564 thr = FIRST_THREAD_IN_PROC(p);
565 } while (p != NULL);
566 return (NULL);
567 }
568
569 int
570 kdb_thr_select(struct thread *thr)
571 {
572 if (thr == NULL)
573 return (EINVAL);
574 kdb_thread = thr;
575 kdb_thrctx = kdb_thr_ctx(thr);
576 return (0);
577 }
578
579 /*
580 * Enter the debugger due to a trap.
581 */
582
583 int
584 kdb_trap(int type, int code, struct trapframe *tf)
585 {
586 #ifdef SMP
587 cpuset_t other_cpus;
588 #endif
589 struct kdb_dbbe *be;
590 register_t intr;
591 int handled;
592
593 be = kdb_dbbe;
594 if (be == NULL || be->dbbe_trap == NULL)
595 return (0);
596
597 /* We reenter the debugger through kdb_reenter(). */
598 if (kdb_active)
599 return (0);
600
601 intr = intr_disable();
602
603 #ifdef SMP
604 other_cpus = all_cpus;
605 CPU_CLR(PCPU_GET(cpuid), &other_cpus);
606 stop_cpus_hard(other_cpus);
607 #endif
608
609 kdb_active++;
610
611 kdb_frame = tf;
612
613 /* Let MD code do its thing first... */
614 kdb_cpu_trap(type, code);
615
616 makectx(tf, &kdb_pcb);
617 kdb_thr_select(curthread);
618
619 for (;;) {
620 handled = be->dbbe_trap(type, code);
621 if (be == kdb_dbbe)
622 break;
623 be = kdb_dbbe;
624 if (be == NULL || be->dbbe_trap == NULL)
625 break;
626 printf("Switching to %s back-end\n", be->dbbe_name);
627 }
628
629 kdb_active--;
630
631 #ifdef SMP
632 restart_cpus(stopped_cpus);
633 #endif
634
635 intr_restore(intr);
636
637 return (handled);
638 }
Cache object: bf7010dc3abfbaa9bfa7b1e975740aab
|