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/8.1/sys/kern/subr_kdb.c 199583 2009-11-20 15:27:52Z jhb $");
29
30 #include "opt_kdb.h"
31
32 #include <sys/param.h>
33 #include <sys/systm.h>
34 #include <sys/kdb.h>
35 #include <sys/kernel.h>
36 #include <sys/malloc.h>
37 #include <sys/pcpu.h>
38 #include <sys/proc.h>
39 #include <sys/smp.h>
40 #include <sys/sysctl.h>
41
42 #include <machine/kdb.h>
43 #include <machine/pcb.h>
44
45 #ifdef SMP
46 #include <machine/smp.h>
47 #endif
48
49 int kdb_active = 0;
50 static void *kdb_jmpbufp = NULL;
51 struct kdb_dbbe *kdb_dbbe = NULL;
52 static struct pcb kdb_pcb;
53 struct pcb *kdb_thrctx = NULL;
54 struct thread *kdb_thread = NULL;
55 struct trapframe *kdb_frame = NULL;
56
57 KDB_BACKEND(null, NULL, NULL, NULL);
58 SET_DECLARE(kdb_dbbe_set, struct kdb_dbbe);
59
60 static int kdb_sysctl_available(SYSCTL_HANDLER_ARGS);
61 static int kdb_sysctl_current(SYSCTL_HANDLER_ARGS);
62 static int kdb_sysctl_enter(SYSCTL_HANDLER_ARGS);
63 static int kdb_sysctl_panic(SYSCTL_HANDLER_ARGS);
64 static int kdb_sysctl_trap(SYSCTL_HANDLER_ARGS);
65 static int kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS);
66
67 SYSCTL_NODE(_debug, OID_AUTO, kdb, CTLFLAG_RW, NULL, "KDB nodes");
68
69 SYSCTL_PROC(_debug_kdb, OID_AUTO, available, CTLTYPE_STRING | CTLFLAG_RD, NULL,
70 0, kdb_sysctl_available, "A", "list of available KDB backends");
71
72 SYSCTL_PROC(_debug_kdb, OID_AUTO, current, CTLTYPE_STRING | CTLFLAG_RW, NULL,
73 0, kdb_sysctl_current, "A", "currently selected KDB backend");
74
75 SYSCTL_PROC(_debug_kdb, OID_AUTO, enter, CTLTYPE_INT | CTLFLAG_RW, NULL, 0,
76 kdb_sysctl_enter, "I", "set to enter the debugger");
77
78 SYSCTL_PROC(_debug_kdb, OID_AUTO, panic, CTLTYPE_INT | CTLFLAG_RW, NULL, 0,
79 kdb_sysctl_panic, "I", "set to panic the kernel");
80
81 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap, CTLTYPE_INT | CTLFLAG_RW, NULL, 0,
82 kdb_sysctl_trap, "I", "set to cause a page fault via data access");
83
84 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap_code, CTLTYPE_INT | CTLFLAG_RW, NULL, 0,
85 kdb_sysctl_trap_code, "I", "set to cause a page fault via code access");
86
87 /*
88 * Flag indicating whether or not to IPI the other CPUs to stop them on
89 * entering the debugger. Sometimes, this will result in a deadlock as
90 * stop_cpus() waits for the other cpus to stop, so we allow it to be
91 * disabled. In order to maximize the chances of success, use a hard
92 * stop for that.
93 */
94 #ifdef SMP
95 static int kdb_stop_cpus = 1;
96 SYSCTL_INT(_debug_kdb, OID_AUTO, stop_cpus, CTLTYPE_INT | CTLFLAG_RW,
97 &kdb_stop_cpus, 0, "stop other CPUs when entering the debugger");
98 TUNABLE_INT("debug.kdb.stop_cpus", &kdb_stop_cpus);
99 #endif
100
101 /*
102 * Flag to indicate to debuggers why the debugger was entered.
103 */
104 const char * volatile kdb_why = KDB_WHY_UNSET;
105
106 static int
107 kdb_sysctl_available(SYSCTL_HANDLER_ARGS)
108 {
109 struct kdb_dbbe *be, **iter;
110 char *avail, *p;
111 ssize_t len, sz;
112 int error;
113
114 sz = 0;
115 SET_FOREACH(iter, kdb_dbbe_set) {
116 be = *iter;
117 if (be->dbbe_active == 0)
118 sz += strlen(be->dbbe_name) + 1;
119 }
120 sz++;
121 avail = malloc(sz, M_TEMP, M_WAITOK);
122 p = avail;
123 *p = '\0';
124
125 SET_FOREACH(iter, kdb_dbbe_set) {
126 be = *iter;
127 if (be->dbbe_active == 0) {
128 len = snprintf(p, sz, "%s ", be->dbbe_name);
129 p += len;
130 sz -= len;
131 }
132 }
133 KASSERT(sz >= 0, ("%s", __func__));
134 error = sysctl_handle_string(oidp, avail, 0, req);
135 free(avail, M_TEMP);
136 return (error);
137 }
138
139 static int
140 kdb_sysctl_current(SYSCTL_HANDLER_ARGS)
141 {
142 char buf[16];
143 int error;
144
145 if (kdb_dbbe != NULL) {
146 strncpy(buf, kdb_dbbe->dbbe_name, sizeof(buf));
147 buf[sizeof(buf) - 1] = '\0';
148 } else
149 *buf = '\0';
150 error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
151 if (error != 0 || req->newptr == NULL)
152 return (error);
153 if (kdb_active)
154 return (EBUSY);
155 return (kdb_dbbe_select(buf));
156 }
157
158 static int
159 kdb_sysctl_enter(SYSCTL_HANDLER_ARGS)
160 {
161 int error, i;
162
163 error = sysctl_wire_old_buffer(req, sizeof(int));
164 if (error == 0) {
165 i = 0;
166 error = sysctl_handle_int(oidp, &i, 0, req);
167 }
168 if (error != 0 || req->newptr == NULL)
169 return (error);
170 if (kdb_active)
171 return (EBUSY);
172 kdb_enter(KDB_WHY_SYSCTL, "sysctl debug.kdb.enter");
173 return (0);
174 }
175
176 static int
177 kdb_sysctl_panic(SYSCTL_HANDLER_ARGS)
178 {
179 int error, i;
180
181 error = sysctl_wire_old_buffer(req, sizeof(int));
182 if (error == 0) {
183 i = 0;
184 error = sysctl_handle_int(oidp, &i, 0, req);
185 }
186 if (error != 0 || req->newptr == NULL)
187 return (error);
188 panic("kdb_sysctl_panic");
189 return (0);
190 }
191
192 static int
193 kdb_sysctl_trap(SYSCTL_HANDLER_ARGS)
194 {
195 int error, i;
196 int *addr = (int *)0x10;
197
198 error = sysctl_wire_old_buffer(req, sizeof(int));
199 if (error == 0) {
200 i = 0;
201 error = sysctl_handle_int(oidp, &i, 0, req);
202 }
203 if (error != 0 || req->newptr == NULL)
204 return (error);
205 return (*addr);
206 }
207
208 static int
209 kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS)
210 {
211 int error, i;
212 void (*fp)(u_int, u_int, u_int) = (void *)0xdeadc0de;
213
214 error = sysctl_wire_old_buffer(req, sizeof(int));
215 if (error == 0) {
216 i = 0;
217 error = sysctl_handle_int(oidp, &i, 0, req);
218 }
219 if (error != 0 || req->newptr == NULL)
220 return (error);
221 (*fp)(0x11111111, 0x22222222, 0x33333333);
222 return (0);
223 }
224
225 void
226 kdb_panic(const char *msg)
227 {
228
229 #ifdef SMP
230 stop_cpus_hard(PCPU_GET(other_cpus));
231 #endif
232 printf("KDB: panic\n");
233 panic(msg);
234 }
235
236 void
237 kdb_reboot(void)
238 {
239
240 printf("KDB: reboot requested\n");
241 shutdown_nice(0);
242 }
243
244 /*
245 * Solaris implements a new BREAK which is initiated by a character sequence
246 * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the
247 * Remote Console.
248 *
249 * Note that this function may be called from almost anywhere, with interrupts
250 * disabled and with unknown locks held, so it must not access data other than
251 * its arguments. Its up to the caller to ensure that the state variable is
252 * consistent.
253 */
254
255 #define KEY_CR 13 /* CR '\r' */
256 #define KEY_TILDE 126 /* ~ */
257 #define KEY_CRTLB 2 /* ^B */
258 #define KEY_CRTLP 16 /* ^P */
259 #define KEY_CRTLR 18 /* ^R */
260
261 int
262 kdb_alt_break(int key, int *state)
263 {
264 int brk;
265
266 brk = 0;
267 switch (*state) {
268 case 0:
269 if (key == KEY_CR)
270 *state = 1;
271 break;
272 case 1:
273 if (key == KEY_TILDE)
274 *state = 2;
275 break;
276 case 2:
277 if (key == KEY_CRTLB)
278 brk = KDB_REQ_DEBUGGER;
279 else if (key == KEY_CRTLP)
280 brk = KDB_REQ_PANIC;
281 else if (key == KEY_CRTLR)
282 brk = KDB_REQ_REBOOT;
283 *state = 0;
284 }
285 return (brk);
286 }
287
288 /*
289 * Print a backtrace of the calling thread. The backtrace is generated by
290 * the selected debugger, provided it supports backtraces. If no debugger
291 * is selected or the current debugger does not support backtraces, this
292 * function silently returns.
293 */
294
295 void
296 kdb_backtrace(void)
297 {
298
299 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) {
300 printf("KDB: stack backtrace:\n");
301 kdb_dbbe->dbbe_trace();
302 }
303 }
304
305 /*
306 * Set/change the current backend.
307 */
308
309 int
310 kdb_dbbe_select(const char *name)
311 {
312 struct kdb_dbbe *be, **iter;
313
314 SET_FOREACH(iter, kdb_dbbe_set) {
315 be = *iter;
316 if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) {
317 kdb_dbbe = be;
318 return (0);
319 }
320 }
321 return (EINVAL);
322 }
323
324 /*
325 * Enter the currently selected debugger. If a message has been provided,
326 * it is printed first. If the debugger does not support the enter method,
327 * it is entered by using breakpoint(), which enters the debugger through
328 * kdb_trap(). The 'why' argument will contain a more mechanically usable
329 * string than 'msg', and is relied upon by DDB scripting to identify the
330 * reason for entering the debugger so that the right script can be run.
331 */
332 void
333 kdb_enter(const char *why, const char *msg)
334 {
335
336 if (kdb_dbbe != NULL && kdb_active == 0) {
337 if (msg != NULL)
338 printf("KDB: enter: %s\n", msg);
339 kdb_why = why;
340 breakpoint();
341 kdb_why = KDB_WHY_UNSET;
342 }
343 }
344
345 /*
346 * Initialize the kernel debugger interface.
347 */
348
349 void
350 kdb_init(void)
351 {
352 struct kdb_dbbe *be, **iter;
353 int cur_pri, pri;
354
355 kdb_active = 0;
356 kdb_dbbe = NULL;
357 cur_pri = -1;
358 SET_FOREACH(iter, kdb_dbbe_set) {
359 be = *iter;
360 pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1;
361 be->dbbe_active = (pri >= 0) ? 0 : -1;
362 if (pri > cur_pri) {
363 cur_pri = pri;
364 kdb_dbbe = be;
365 }
366 }
367 if (kdb_dbbe != NULL) {
368 printf("KDB: debugger backends:");
369 SET_FOREACH(iter, kdb_dbbe_set) {
370 be = *iter;
371 if (be->dbbe_active == 0)
372 printf(" %s", be->dbbe_name);
373 }
374 printf("\n");
375 printf("KDB: current backend: %s\n",
376 kdb_dbbe->dbbe_name);
377 }
378 }
379
380 /*
381 * Handle contexts.
382 */
383
384 void *
385 kdb_jmpbuf(jmp_buf new)
386 {
387 void *old;
388
389 old = kdb_jmpbufp;
390 kdb_jmpbufp = new;
391 return (old);
392 }
393
394 void
395 kdb_reenter(void)
396 {
397
398 if (!kdb_active || kdb_jmpbufp == NULL)
399 return;
400
401 longjmp(kdb_jmpbufp, 1);
402 /* NOTREACHED */
403 }
404
405 /*
406 * Thread related support functions.
407 */
408
409 struct pcb *
410 kdb_thr_ctx(struct thread *thr)
411 {
412 #if defined(SMP) && defined(KDB_STOPPEDPCB)
413 struct pcpu *pc;
414 #endif
415
416 if (thr == curthread)
417 return (&kdb_pcb);
418
419 #if defined(SMP) && defined(KDB_STOPPEDPCB)
420 SLIST_FOREACH(pc, &cpuhead, pc_allcpu) {
421 if (pc->pc_curthread == thr && (stopped_cpus & pc->pc_cpumask))
422 return (KDB_STOPPEDPCB(pc));
423 }
424 #endif
425 return (thr->td_pcb);
426 }
427
428 struct thread *
429 kdb_thr_first(void)
430 {
431 struct proc *p;
432 struct thread *thr;
433
434 p = LIST_FIRST(&allproc);
435 while (p != NULL) {
436 if (p->p_flag & P_INMEM) {
437 thr = FIRST_THREAD_IN_PROC(p);
438 if (thr != NULL)
439 return (thr);
440 }
441 p = LIST_NEXT(p, p_list);
442 }
443 return (NULL);
444 }
445
446 struct thread *
447 kdb_thr_from_pid(pid_t pid)
448 {
449 struct proc *p;
450
451 p = LIST_FIRST(&allproc);
452 while (p != NULL) {
453 if (p->p_flag & P_INMEM && p->p_pid == pid)
454 return (FIRST_THREAD_IN_PROC(p));
455 p = LIST_NEXT(p, p_list);
456 }
457 return (NULL);
458 }
459
460 struct thread *
461 kdb_thr_lookup(lwpid_t tid)
462 {
463 struct thread *thr;
464
465 thr = kdb_thr_first();
466 while (thr != NULL && thr->td_tid != tid)
467 thr = kdb_thr_next(thr);
468 return (thr);
469 }
470
471 struct thread *
472 kdb_thr_next(struct thread *thr)
473 {
474 struct proc *p;
475
476 p = thr->td_proc;
477 thr = TAILQ_NEXT(thr, td_plist);
478 do {
479 if (thr != NULL)
480 return (thr);
481 p = LIST_NEXT(p, p_list);
482 if (p != NULL && (p->p_flag & P_INMEM))
483 thr = FIRST_THREAD_IN_PROC(p);
484 } while (p != NULL);
485 return (NULL);
486 }
487
488 int
489 kdb_thr_select(struct thread *thr)
490 {
491 if (thr == NULL)
492 return (EINVAL);
493 kdb_thread = thr;
494 kdb_thrctx = kdb_thr_ctx(thr);
495 return (0);
496 }
497
498 /*
499 * Enter the debugger due to a trap.
500 */
501
502 int
503 kdb_trap(int type, int code, struct trapframe *tf)
504 {
505 register_t intr;
506 #ifdef SMP
507 int did_stop_cpus;
508 #endif
509 int handled;
510
511 if (kdb_dbbe == NULL || kdb_dbbe->dbbe_trap == NULL)
512 return (0);
513
514 /* We reenter the debugger through kdb_reenter(). */
515 if (kdb_active)
516 return (0);
517
518 intr = intr_disable();
519
520 #ifdef SMP
521 if ((did_stop_cpus = kdb_stop_cpus) != 0)
522 stop_cpus_hard(PCPU_GET(other_cpus));
523 #endif
524
525 kdb_active++;
526
527 kdb_frame = tf;
528
529 /* Let MD code do its thing first... */
530 kdb_cpu_trap(type, code);
531
532 makectx(tf, &kdb_pcb);
533 kdb_thr_select(curthread);
534
535 handled = kdb_dbbe->dbbe_trap(type, code);
536
537 kdb_active--;
538
539 #ifdef SMP
540 if (did_stop_cpus)
541 restart_cpus(stopped_cpus);
542 #endif
543
544 intr_restore(intr);
545
546 return (handled);
547 }
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