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