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/8.3/sys/kern/subr_kdb.c 225796 2011-09-27 13:50:30Z 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/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 KDB_BACKEND(null, NULL, NULL, NULL);
60 SET_DECLARE(kdb_dbbe_set, struct kdb_dbbe);
61
62 static int kdb_sysctl_available(SYSCTL_HANDLER_ARGS);
63 static int kdb_sysctl_current(SYSCTL_HANDLER_ARGS);
64 static int kdb_sysctl_enter(SYSCTL_HANDLER_ARGS);
65 static int kdb_sysctl_panic(SYSCTL_HANDLER_ARGS);
66 static int kdb_sysctl_trap(SYSCTL_HANDLER_ARGS);
67 static int kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS);
68
69 SYSCTL_NODE(_debug, OID_AUTO, kdb, CTLFLAG_RW, NULL, "KDB nodes");
70
71 SYSCTL_PROC(_debug_kdb, OID_AUTO, available, CTLTYPE_STRING | CTLFLAG_RD, NULL,
72 0, kdb_sysctl_available, "A", "list of available KDB backends");
73
74 SYSCTL_PROC(_debug_kdb, OID_AUTO, current, CTLTYPE_STRING | CTLFLAG_RW, NULL,
75 0, kdb_sysctl_current, "A", "currently selected KDB backend");
76
77 SYSCTL_PROC(_debug_kdb, OID_AUTO, enter, CTLTYPE_INT | CTLFLAG_RW, NULL, 0,
78 kdb_sysctl_enter, "I", "set to enter the debugger");
79
80 SYSCTL_PROC(_debug_kdb, OID_AUTO, panic, CTLTYPE_INT | CTLFLAG_RW, NULL, 0,
81 kdb_sysctl_panic, "I", "set to panic the kernel");
82
83 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap, CTLTYPE_INT | CTLFLAG_RW, NULL, 0,
84 kdb_sysctl_trap, "I", "set to cause a page fault via data access");
85
86 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap_code, CTLTYPE_INT | CTLFLAG_RW, NULL, 0,
87 kdb_sysctl_trap_code, "I", "set to cause a page fault via code access");
88
89 /*
90 * Flag indicating whether or not to IPI the other CPUs to stop them on
91 * entering the debugger. Sometimes, this will result in a deadlock as
92 * stop_cpus() waits for the other cpus to stop, so we allow it to be
93 * disabled. In order to maximize the chances of success, use a hard
94 * stop for that.
95 */
96 #ifdef SMP
97 static int kdb_stop_cpus = 1;
98 SYSCTL_INT(_debug_kdb, OID_AUTO, stop_cpus, CTLFLAG_RW | CTLFLAG_TUN,
99 &kdb_stop_cpus, 0, "stop other CPUs when entering the debugger");
100 TUNABLE_INT("debug.kdb.stop_cpus", &kdb_stop_cpus);
101 #endif
102
103 /*
104 * Flag to indicate to debuggers why the debugger was entered.
105 */
106 const char * volatile kdb_why = KDB_WHY_UNSET;
107
108 static int
109 kdb_sysctl_available(SYSCTL_HANDLER_ARGS)
110 {
111 struct kdb_dbbe *be, **iter;
112 char *avail, *p;
113 ssize_t len, sz;
114 int error;
115
116 sz = 0;
117 SET_FOREACH(iter, kdb_dbbe_set) {
118 be = *iter;
119 if (be->dbbe_active == 0)
120 sz += strlen(be->dbbe_name) + 1;
121 }
122 sz++;
123 avail = malloc(sz, M_TEMP, M_WAITOK);
124 p = avail;
125 *p = '\0';
126
127 SET_FOREACH(iter, kdb_dbbe_set) {
128 be = *iter;
129 if (be->dbbe_active == 0) {
130 len = snprintf(p, sz, "%s ", be->dbbe_name);
131 p += len;
132 sz -= len;
133 }
134 }
135 KASSERT(sz >= 0, ("%s", __func__));
136 error = sysctl_handle_string(oidp, avail, 0, req);
137 free(avail, M_TEMP);
138 return (error);
139 }
140
141 static int
142 kdb_sysctl_current(SYSCTL_HANDLER_ARGS)
143 {
144 char buf[16];
145 int error;
146
147 if (kdb_dbbe != NULL)
148 strlcpy(buf, kdb_dbbe->dbbe_name, sizeof(buf));
149 else
150 *buf = '\0';
151 error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
152 if (error != 0 || req->newptr == NULL)
153 return (error);
154 if (kdb_active)
155 return (EBUSY);
156 return (kdb_dbbe_select(buf));
157 }
158
159 static int
160 kdb_sysctl_enter(SYSCTL_HANDLER_ARGS)
161 {
162 int error, i;
163
164 error = sysctl_wire_old_buffer(req, sizeof(int));
165 if (error == 0) {
166 i = 0;
167 error = sysctl_handle_int(oidp, &i, 0, req);
168 }
169 if (error != 0 || req->newptr == NULL)
170 return (error);
171 if (kdb_active)
172 return (EBUSY);
173 kdb_enter(KDB_WHY_SYSCTL, "sysctl debug.kdb.enter");
174 return (0);
175 }
176
177 static int
178 kdb_sysctl_panic(SYSCTL_HANDLER_ARGS)
179 {
180 int error, i;
181
182 error = sysctl_wire_old_buffer(req, sizeof(int));
183 if (error == 0) {
184 i = 0;
185 error = sysctl_handle_int(oidp, &i, 0, req);
186 }
187 if (error != 0 || req->newptr == NULL)
188 return (error);
189 panic("kdb_sysctl_panic");
190 return (0);
191 }
192
193 static int
194 kdb_sysctl_trap(SYSCTL_HANDLER_ARGS)
195 {
196 int error, i;
197 int *addr = (int *)0x10;
198
199 error = sysctl_wire_old_buffer(req, sizeof(int));
200 if (error == 0) {
201 i = 0;
202 error = sysctl_handle_int(oidp, &i, 0, req);
203 }
204 if (error != 0 || req->newptr == NULL)
205 return (error);
206 return (*addr);
207 }
208
209 static int
210 kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS)
211 {
212 int error, i;
213 void (*fp)(u_int, u_int, u_int) = (void *)0xdeadc0de;
214
215 error = sysctl_wire_old_buffer(req, sizeof(int));
216 if (error == 0) {
217 i = 0;
218 error = sysctl_handle_int(oidp, &i, 0, req);
219 }
220 if (error != 0 || req->newptr == NULL)
221 return (error);
222 (*fp)(0x11111111, 0x22222222, 0x33333333);
223 return (0);
224 }
225
226 void
227 kdb_panic(const char *msg)
228 {
229
230 #ifdef SMP
231 stop_cpus_hard(PCPU_GET(other_cpus));
232 #endif
233 printf("KDB: panic\n");
234 panic("%s", msg);
235 }
236
237 void
238 kdb_reboot(void)
239 {
240
241 printf("KDB: reboot requested\n");
242 shutdown_nice(0);
243 }
244
245 /*
246 * Solaris implements a new BREAK which is initiated by a character sequence
247 * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the
248 * Remote Console.
249 *
250 * Note that this function may be called from almost anywhere, with interrupts
251 * disabled and with unknown locks held, so it must not access data other than
252 * its arguments. Its up to the caller to ensure that the state variable is
253 * consistent.
254 */
255
256 #define KEY_CR 13 /* CR '\r' */
257 #define KEY_TILDE 126 /* ~ */
258 #define KEY_CRTLB 2 /* ^B */
259 #define KEY_CRTLP 16 /* ^P */
260 #define KEY_CRTLR 18 /* ^R */
261
262 int
263 kdb_alt_break(int key, int *state)
264 {
265 int brk;
266
267 brk = 0;
268 switch (*state) {
269 case 0:
270 if (key == KEY_CR)
271 *state = 1;
272 break;
273 case 1:
274 if (key == KEY_TILDE)
275 *state = 2;
276 break;
277 case 2:
278 if (key == KEY_CRTLB)
279 brk = KDB_REQ_DEBUGGER;
280 else if (key == KEY_CRTLP)
281 brk = KDB_REQ_PANIC;
282 else if (key == KEY_CRTLR)
283 brk = KDB_REQ_REBOOT;
284 *state = 0;
285 }
286 return (brk);
287 }
288
289 /*
290 * Print a backtrace of the calling thread. The backtrace is generated by
291 * the selected debugger, provided it supports backtraces. If no debugger
292 * is selected or the current debugger does not support backtraces, this
293 * function silently returns.
294 */
295
296 void
297 kdb_backtrace(void)
298 {
299
300 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) {
301 printf("KDB: stack backtrace:\n");
302 kdb_dbbe->dbbe_trace();
303 }
304 #ifdef STACK
305 else {
306 struct stack st;
307
308 printf("KDB: stack backtrace:\n");
309 stack_save(&st);
310 stack_print_ddb(&st);
311 }
312 #endif
313 }
314
315 /*
316 * Set/change the current backend.
317 */
318
319 int
320 kdb_dbbe_select(const char *name)
321 {
322 struct kdb_dbbe *be, **iter;
323
324 SET_FOREACH(iter, kdb_dbbe_set) {
325 be = *iter;
326 if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) {
327 kdb_dbbe = be;
328 return (0);
329 }
330 }
331 return (EINVAL);
332 }
333
334 /*
335 * Enter the currently selected debugger. If a message has been provided,
336 * it is printed first. If the debugger does not support the enter method,
337 * it is entered by using breakpoint(), which enters the debugger through
338 * kdb_trap(). The 'why' argument will contain a more mechanically usable
339 * string than 'msg', and is relied upon by DDB scripting to identify the
340 * reason for entering the debugger so that the right script can be run.
341 */
342 void
343 kdb_enter(const char *why, const char *msg)
344 {
345
346 if (kdb_dbbe != NULL && kdb_active == 0) {
347 if (msg != NULL)
348 printf("KDB: enter: %s\n", msg);
349 kdb_why = why;
350 breakpoint();
351 kdb_why = KDB_WHY_UNSET;
352 }
353 }
354
355 /*
356 * Initialize the kernel debugger interface.
357 */
358
359 void
360 kdb_init(void)
361 {
362 struct kdb_dbbe *be, **iter;
363 int cur_pri, pri;
364
365 kdb_active = 0;
366 kdb_dbbe = NULL;
367 cur_pri = -1;
368 SET_FOREACH(iter, kdb_dbbe_set) {
369 be = *iter;
370 pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1;
371 be->dbbe_active = (pri >= 0) ? 0 : -1;
372 if (pri > cur_pri) {
373 cur_pri = pri;
374 kdb_dbbe = be;
375 }
376 }
377 if (kdb_dbbe != NULL) {
378 printf("KDB: debugger backends:");
379 SET_FOREACH(iter, kdb_dbbe_set) {
380 be = *iter;
381 if (be->dbbe_active == 0)
382 printf(" %s", be->dbbe_name);
383 }
384 printf("\n");
385 printf("KDB: current backend: %s\n",
386 kdb_dbbe->dbbe_name);
387 }
388 }
389
390 /*
391 * Handle contexts.
392 */
393
394 void *
395 kdb_jmpbuf(jmp_buf new)
396 {
397 void *old;
398
399 old = kdb_jmpbufp;
400 kdb_jmpbufp = new;
401 return (old);
402 }
403
404 void
405 kdb_reenter(void)
406 {
407
408 if (!kdb_active || kdb_jmpbufp == NULL)
409 return;
410
411 longjmp(kdb_jmpbufp, 1);
412 /* NOTREACHED */
413 }
414
415 /*
416 * Thread related support functions.
417 */
418
419 struct pcb *
420 kdb_thr_ctx(struct thread *thr)
421 {
422 #if defined(SMP) && defined(KDB_STOPPEDPCB)
423 struct pcpu *pc;
424 #endif
425
426 if (thr == curthread)
427 return (&kdb_pcb);
428
429 #if defined(SMP) && defined(KDB_STOPPEDPCB)
430 SLIST_FOREACH(pc, &cpuhead, pc_allcpu) {
431 if (pc->pc_curthread == thr && (stopped_cpus & pc->pc_cpumask))
432 return (KDB_STOPPEDPCB(pc));
433 }
434 #endif
435 return (thr->td_pcb);
436 }
437
438 struct thread *
439 kdb_thr_first(void)
440 {
441 struct proc *p;
442 struct thread *thr;
443
444 p = LIST_FIRST(&allproc);
445 while (p != NULL) {
446 if (p->p_flag & P_INMEM) {
447 thr = FIRST_THREAD_IN_PROC(p);
448 if (thr != NULL)
449 return (thr);
450 }
451 p = LIST_NEXT(p, p_list);
452 }
453 return (NULL);
454 }
455
456 struct thread *
457 kdb_thr_from_pid(pid_t pid)
458 {
459 struct proc *p;
460
461 p = LIST_FIRST(&allproc);
462 while (p != NULL) {
463 if (p->p_flag & P_INMEM && p->p_pid == pid)
464 return (FIRST_THREAD_IN_PROC(p));
465 p = LIST_NEXT(p, p_list);
466 }
467 return (NULL);
468 }
469
470 struct thread *
471 kdb_thr_lookup(lwpid_t tid)
472 {
473 struct thread *thr;
474
475 thr = kdb_thr_first();
476 while (thr != NULL && thr->td_tid != tid)
477 thr = kdb_thr_next(thr);
478 return (thr);
479 }
480
481 struct thread *
482 kdb_thr_next(struct thread *thr)
483 {
484 struct proc *p;
485
486 p = thr->td_proc;
487 thr = TAILQ_NEXT(thr, td_plist);
488 do {
489 if (thr != NULL)
490 return (thr);
491 p = LIST_NEXT(p, p_list);
492 if (p != NULL && (p->p_flag & P_INMEM))
493 thr = FIRST_THREAD_IN_PROC(p);
494 } while (p != NULL);
495 return (NULL);
496 }
497
498 int
499 kdb_thr_select(struct thread *thr)
500 {
501 if (thr == NULL)
502 return (EINVAL);
503 kdb_thread = thr;
504 kdb_thrctx = kdb_thr_ctx(thr);
505 return (0);
506 }
507
508 /*
509 * Enter the debugger due to a trap.
510 */
511
512 int
513 kdb_trap(int type, int code, struct trapframe *tf)
514 {
515 struct kdb_dbbe *be;
516 register_t intr;
517 #ifdef SMP
518 int did_stop_cpus;
519 #endif
520 int handled;
521
522 be = kdb_dbbe;
523 if (be == NULL || be->dbbe_trap == NULL)
524 return (0);
525
526 /* We reenter the debugger through kdb_reenter(). */
527 if (kdb_active)
528 return (0);
529
530 intr = intr_disable();
531
532 #ifdef SMP
533 if ((did_stop_cpus = kdb_stop_cpus) != 0)
534 stop_cpus_hard(PCPU_GET(other_cpus));
535 #endif
536
537 kdb_active++;
538
539 kdb_frame = tf;
540
541 /* Let MD code do its thing first... */
542 kdb_cpu_trap(type, code);
543
544 makectx(tf, &kdb_pcb);
545 kdb_thr_select(curthread);
546
547 for (;;) {
548 handled = be->dbbe_trap(type, code);
549 if (be == kdb_dbbe)
550 break;
551 be = kdb_dbbe;
552 if (be == NULL || be->dbbe_trap == NULL)
553 break;
554 printf("Switching to %s back-end\n", be->dbbe_name);
555 }
556
557 kdb_active--;
558
559 #ifdef SMP
560 if (did_stop_cpus)
561 restart_cpus(stopped_cpus);
562 #endif
563
564 intr_restore(intr);
565
566 return (handled);
567 }
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