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("$FreeBSD$");
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/cons.h>
36 #include <sys/kdb.h>
37 #include <sys/kernel.h>
38 #include <sys/malloc.h>
39 #include <sys/pcpu.h>
40 #include <sys/proc.h>
41 #include <sys/sbuf.h>
42 #include <sys/smp.h>
43 #include <sys/stack.h>
44 #include <sys/sysctl.h>
45
46 #include <machine/kdb.h>
47 #include <machine/pcb.h>
48
49 #ifdef SMP
50 #include <machine/smp.h>
51 #endif
52
53 int kdb_active = 0;
54 static void *kdb_jmpbufp = NULL;
55 struct kdb_dbbe *kdb_dbbe = NULL;
56 static struct pcb kdb_pcb;
57 struct pcb *kdb_thrctx = NULL;
58 struct thread *kdb_thread = NULL;
59 struct trapframe *kdb_frame = NULL;
60
61 #ifdef BREAK_TO_DEBUGGER
62 #define KDB_BREAK_TO_DEBUGGER 1
63 #else
64 #define KDB_BREAK_TO_DEBUGGER 0
65 #endif
66
67 #ifdef ALT_BREAK_TO_DEBUGGER
68 #define KDB_ALT_BREAK_TO_DEBUGGER 1
69 #else
70 #define KDB_ALT_BREAK_TO_DEBUGGER 0
71 #endif
72
73 static int kdb_break_to_debugger = KDB_BREAK_TO_DEBUGGER;
74 static int kdb_alt_break_to_debugger = KDB_ALT_BREAK_TO_DEBUGGER;
75
76 KDB_BACKEND(null, NULL, NULL, NULL, NULL);
77 SET_DECLARE(kdb_dbbe_set, struct kdb_dbbe);
78
79 static int kdb_sysctl_available(SYSCTL_HANDLER_ARGS);
80 static int kdb_sysctl_current(SYSCTL_HANDLER_ARGS);
81 static int kdb_sysctl_enter(SYSCTL_HANDLER_ARGS);
82 static int kdb_sysctl_panic(SYSCTL_HANDLER_ARGS);
83 static int kdb_sysctl_trap(SYSCTL_HANDLER_ARGS);
84 static int kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS);
85
86 static SYSCTL_NODE(_debug, OID_AUTO, kdb, CTLFLAG_RW, NULL, "KDB nodes");
87
88 SYSCTL_PROC(_debug_kdb, OID_AUTO, available, CTLTYPE_STRING | CTLFLAG_RD, NULL,
89 0, kdb_sysctl_available, "A", "list of available KDB backends");
90
91 SYSCTL_PROC(_debug_kdb, OID_AUTO, current, CTLTYPE_STRING | CTLFLAG_RW, NULL,
92 0, kdb_sysctl_current, "A", "currently selected KDB backend");
93
94 SYSCTL_PROC(_debug_kdb, OID_AUTO, enter,
95 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE, NULL, 0,
96 kdb_sysctl_enter, "I", "set to enter the debugger");
97
98 SYSCTL_PROC(_debug_kdb, OID_AUTO, panic,
99 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE, NULL, 0,
100 kdb_sysctl_panic, "I", "set to panic the kernel");
101
102 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap,
103 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE, NULL, 0,
104 kdb_sysctl_trap, "I", "set to cause a page fault via data access");
105
106 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap_code,
107 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE, NULL, 0,
108 kdb_sysctl_trap_code, "I", "set to cause a page fault via code access");
109
110 SYSCTL_INT(_debug_kdb, OID_AUTO, break_to_debugger,
111 CTLFLAG_RWTUN | CTLFLAG_SECURE,
112 &kdb_break_to_debugger, 0, "Enable break to debugger");
113 TUNABLE_INT("debug.kdb.break_to_debugger", &kdb_break_to_debugger);
114
115 SYSCTL_INT(_debug_kdb, OID_AUTO, alt_break_to_debugger,
116 CTLFLAG_RWTUN | CTLFLAG_SECURE,
117 &kdb_alt_break_to_debugger, 0, "Enable alternative break to debugger");
118 TUNABLE_INT("debug.kdb.alt_break_to_debugger", &kdb_alt_break_to_debugger);
119
120 /*
121 * Flag to indicate to debuggers why the debugger was entered.
122 */
123 const char * volatile kdb_why = KDB_WHY_UNSET;
124
125 static int
126 kdb_sysctl_available(SYSCTL_HANDLER_ARGS)
127 {
128 struct kdb_dbbe **iter;
129 struct sbuf sbuf;
130 int error;
131
132 sbuf_new_for_sysctl(&sbuf, NULL, 64, req);
133 SET_FOREACH(iter, kdb_dbbe_set) {
134 if ((*iter)->dbbe_active == 0)
135 sbuf_printf(&sbuf, "%s ", (*iter)->dbbe_name);
136 }
137 error = sbuf_finish(&sbuf);
138 sbuf_delete(&sbuf);
139 return (error);
140 }
141
142 static int
143 kdb_sysctl_current(SYSCTL_HANDLER_ARGS)
144 {
145 char buf[16];
146 int error;
147
148 if (kdb_dbbe != NULL)
149 strlcpy(buf, kdb_dbbe->dbbe_name, sizeof(buf));
150 else
151 *buf = '\0';
152 error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
153 if (error != 0 || req->newptr == NULL)
154 return (error);
155 if (kdb_active)
156 return (EBUSY);
157 return (kdb_dbbe_select(buf));
158 }
159
160 static int
161 kdb_sysctl_enter(SYSCTL_HANDLER_ARGS)
162 {
163 int error, i;
164
165 error = sysctl_wire_old_buffer(req, sizeof(int));
166 if (error == 0) {
167 i = 0;
168 error = sysctl_handle_int(oidp, &i, 0, req);
169 }
170 if (error != 0 || req->newptr == NULL)
171 return (error);
172 if (kdb_active)
173 return (EBUSY);
174 kdb_enter(KDB_WHY_SYSCTL, "sysctl debug.kdb.enter");
175 return (0);
176 }
177
178 static int
179 kdb_sysctl_panic(SYSCTL_HANDLER_ARGS)
180 {
181 int error, i;
182
183 error = sysctl_wire_old_buffer(req, sizeof(int));
184 if (error == 0) {
185 i = 0;
186 error = sysctl_handle_int(oidp, &i, 0, req);
187 }
188 if (error != 0 || req->newptr == NULL)
189 return (error);
190 panic("kdb_sysctl_panic");
191 return (0);
192 }
193
194 static int
195 kdb_sysctl_trap(SYSCTL_HANDLER_ARGS)
196 {
197 int error, i;
198 int *addr = (int *)0x10;
199
200 error = sysctl_wire_old_buffer(req, sizeof(int));
201 if (error == 0) {
202 i = 0;
203 error = sysctl_handle_int(oidp, &i, 0, req);
204 }
205 if (error != 0 || req->newptr == NULL)
206 return (error);
207 return (*addr);
208 }
209
210 static int
211 kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS)
212 {
213 int error, i;
214 void (*fp)(u_int, u_int, u_int) = (void *)0xdeadc0de;
215
216 error = sysctl_wire_old_buffer(req, sizeof(int));
217 if (error == 0) {
218 i = 0;
219 error = sysctl_handle_int(oidp, &i, 0, req);
220 }
221 if (error != 0 || req->newptr == NULL)
222 return (error);
223 (*fp)(0x11111111, 0x22222222, 0x33333333);
224 return (0);
225 }
226
227 void
228 kdb_panic(const char *msg)
229 {
230
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_zero(&st);
380 stack_save(&st);
381 stack_print_ddb(&st);
382 }
383 #endif
384 }
385
386 /*
387 * Similar to kdb_backtrace() except that it prints a backtrace of an
388 * arbitrary thread rather than the calling thread.
389 */
390 void
391 kdb_backtrace_thread(struct thread *td)
392 {
393
394 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace_thread != NULL) {
395 printf("KDB: stack backtrace of thread %d:\n", td->td_tid);
396 kdb_dbbe->dbbe_trace_thread(td);
397 }
398 #ifdef STACK
399 else {
400 struct stack st;
401
402 printf("KDB: stack backtrace of thread %d:\n", td->td_tid);
403 stack_zero(&st);
404 stack_save_td(&st, td);
405 stack_print_ddb(&st);
406 }
407 #endif
408 }
409
410 /*
411 * Set/change the current backend.
412 */
413
414 int
415 kdb_dbbe_select(const char *name)
416 {
417 struct kdb_dbbe *be, **iter;
418
419 SET_FOREACH(iter, kdb_dbbe_set) {
420 be = *iter;
421 if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) {
422 kdb_dbbe = be;
423 return (0);
424 }
425 }
426 return (EINVAL);
427 }
428
429 /*
430 * Enter the currently selected debugger. If a message has been provided,
431 * it is printed first. If the debugger does not support the enter method,
432 * it is entered by using breakpoint(), which enters the debugger through
433 * kdb_trap(). The 'why' argument will contain a more mechanically usable
434 * string than 'msg', and is relied upon by DDB scripting to identify the
435 * reason for entering the debugger so that the right script can be run.
436 */
437 void
438 kdb_enter(const char *why, const char *msg)
439 {
440
441 if (kdb_dbbe != NULL && kdb_active == 0) {
442 if (msg != NULL)
443 printf("KDB: enter: %s\n", msg);
444 kdb_why = why;
445 breakpoint();
446 kdb_why = KDB_WHY_UNSET;
447 }
448 }
449
450 /*
451 * Initialize the kernel debugger interface.
452 */
453
454 void
455 kdb_init(void)
456 {
457 struct kdb_dbbe *be, **iter;
458 int cur_pri, pri;
459
460 kdb_active = 0;
461 kdb_dbbe = NULL;
462 cur_pri = -1;
463 SET_FOREACH(iter, kdb_dbbe_set) {
464 be = *iter;
465 pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1;
466 be->dbbe_active = (pri >= 0) ? 0 : -1;
467 if (pri > cur_pri) {
468 cur_pri = pri;
469 kdb_dbbe = be;
470 }
471 }
472 if (kdb_dbbe != NULL) {
473 printf("KDB: debugger backends:");
474 SET_FOREACH(iter, kdb_dbbe_set) {
475 be = *iter;
476 if (be->dbbe_active == 0)
477 printf(" %s", be->dbbe_name);
478 }
479 printf("\n");
480 printf("KDB: current backend: %s\n",
481 kdb_dbbe->dbbe_name);
482 }
483 }
484
485 /*
486 * Handle contexts.
487 */
488
489 void *
490 kdb_jmpbuf(jmp_buf new)
491 {
492 void *old;
493
494 old = kdb_jmpbufp;
495 kdb_jmpbufp = new;
496 return (old);
497 }
498
499 void
500 kdb_reenter(void)
501 {
502
503 if (!kdb_active || kdb_jmpbufp == NULL)
504 return;
505
506 printf("KDB: reentering\n");
507 kdb_backtrace();
508 longjmp(kdb_jmpbufp, 1);
509 /* NOTREACHED */
510 }
511
512 /*
513 * Thread related support functions.
514 */
515
516 struct pcb *
517 kdb_thr_ctx(struct thread *thr)
518 {
519 #if defined(SMP) && defined(KDB_STOPPEDPCB)
520 struct pcpu *pc;
521 #endif
522
523 if (thr == curthread)
524 return (&kdb_pcb);
525
526 #if defined(SMP) && defined(KDB_STOPPEDPCB)
527 STAILQ_FOREACH(pc, &cpuhead, pc_allcpu) {
528 if (pc->pc_curthread == thr &&
529 CPU_ISSET(pc->pc_cpuid, &stopped_cpus))
530 return (KDB_STOPPEDPCB(pc));
531 }
532 #endif
533 return (thr->td_pcb);
534 }
535
536 struct thread *
537 kdb_thr_first(void)
538 {
539 struct proc *p;
540 struct thread *thr;
541
542 p = LIST_FIRST(&allproc);
543 while (p != NULL) {
544 if (p->p_flag & P_INMEM) {
545 thr = FIRST_THREAD_IN_PROC(p);
546 if (thr != NULL)
547 return (thr);
548 }
549 p = LIST_NEXT(p, p_list);
550 }
551 return (NULL);
552 }
553
554 struct thread *
555 kdb_thr_from_pid(pid_t pid)
556 {
557 struct proc *p;
558
559 p = LIST_FIRST(&allproc);
560 while (p != NULL) {
561 if (p->p_flag & P_INMEM && p->p_pid == pid)
562 return (FIRST_THREAD_IN_PROC(p));
563 p = LIST_NEXT(p, p_list);
564 }
565 return (NULL);
566 }
567
568 struct thread *
569 kdb_thr_lookup(lwpid_t tid)
570 {
571 struct thread *thr;
572
573 thr = kdb_thr_first();
574 while (thr != NULL && thr->td_tid != tid)
575 thr = kdb_thr_next(thr);
576 return (thr);
577 }
578
579 struct thread *
580 kdb_thr_next(struct thread *thr)
581 {
582 struct proc *p;
583
584 p = thr->td_proc;
585 thr = TAILQ_NEXT(thr, td_plist);
586 do {
587 if (thr != NULL)
588 return (thr);
589 p = LIST_NEXT(p, p_list);
590 if (p != NULL && (p->p_flag & P_INMEM))
591 thr = FIRST_THREAD_IN_PROC(p);
592 } while (p != NULL);
593 return (NULL);
594 }
595
596 int
597 kdb_thr_select(struct thread *thr)
598 {
599 if (thr == NULL)
600 return (EINVAL);
601 kdb_thread = thr;
602 kdb_thrctx = kdb_thr_ctx(thr);
603 return (0);
604 }
605
606 /*
607 * Enter the debugger due to a trap.
608 */
609
610 int
611 kdb_trap(int type, int code, struct trapframe *tf)
612 {
613 #ifdef SMP
614 cpuset_t other_cpus;
615 #endif
616 struct kdb_dbbe *be;
617 register_t intr;
618 int handled;
619 #ifdef SMP
620 int did_stop_cpus;
621 #endif
622
623 be = kdb_dbbe;
624 if (be == NULL || be->dbbe_trap == NULL)
625 return (0);
626
627 /* We reenter the debugger through kdb_reenter(). */
628 if (kdb_active)
629 return (0);
630
631 intr = intr_disable();
632
633 #ifdef SMP
634 if (!SCHEDULER_STOPPED()) {
635 other_cpus = all_cpus;
636 CPU_CLR(PCPU_GET(cpuid), &other_cpus);
637 stop_cpus_hard(other_cpus);
638 did_stop_cpus = 1;
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 cngrab();
654
655 for (;;) {
656 handled = be->dbbe_trap(type, code);
657 if (be == kdb_dbbe)
658 break;
659 be = kdb_dbbe;
660 if (be == NULL || be->dbbe_trap == NULL)
661 break;
662 printf("Switching to %s back-end\n", be->dbbe_name);
663 }
664
665 cnungrab();
666
667 kdb_active--;
668
669 #ifdef SMP
670 if (did_stop_cpus)
671 restart_cpus(stopped_cpus);
672 #endif
673
674 intr_restore(intr);
675
676 return (handled);
677 }
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