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/7.4/sys/kern/subr_kdb.c 213557 2010-10-08 07:58:57Z avg $");
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 void *kdb_jmpbufp = NULL;
51 struct kdb_dbbe *kdb_dbbe = NULL;
52 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, 0, 0,
70 kdb_sysctl_available, "A", "list of available KDB backends");
71
72 SYSCTL_PROC(_debug_kdb, OID_AUTO, current, CTLTYPE_STRING | CTLFLAG_RW, 0, 0,
73 kdb_sysctl_current, "A", "currently selected KDB backend");
74
75 SYSCTL_PROC(_debug_kdb, OID_AUTO, enter, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
76 kdb_sysctl_enter, "I", "set to enter the debugger");
77
78 SYSCTL_PROC(_debug_kdb, OID_AUTO, panic, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
79 kdb_sysctl_panic, "I", "set to panic the kernel");
80
81 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap, CTLTYPE_INT | CTLFLAG_RW, 0, 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, 0, 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.
92 */
93 #ifdef SMP
94 static int kdb_stop_cpus = 1;
95 SYSCTL_INT(_debug_kdb, OID_AUTO, stop_cpus, CTLFLAG_RW | CTLFLAG_TUN,
96 &kdb_stop_cpus, 0, "stop other CPUs when entering the debugger");
97 TUNABLE_INT("debug.kdb.stop_cpus", &kdb_stop_cpus);
98 #endif
99
100 /*
101 * Flag to indicate to debuggers why the debugger was entered.
102 */
103 const char * volatile kdb_why = KDB_WHY_UNSET;
104
105 static int
106 kdb_sysctl_available(SYSCTL_HANDLER_ARGS)
107 {
108 struct kdb_dbbe *be, **iter;
109 char *avail, *p;
110 ssize_t len, sz;
111 int error;
112
113 sz = 0;
114 SET_FOREACH(iter, kdb_dbbe_set) {
115 be = *iter;
116 if (be->dbbe_active == 0)
117 sz += strlen(be->dbbe_name) + 1;
118 }
119 sz++;
120 avail = malloc(sz, M_TEMP, M_WAITOK);
121 p = avail;
122 *p = '\0';
123
124 SET_FOREACH(iter, kdb_dbbe_set) {
125 be = *iter;
126 if (be->dbbe_active == 0) {
127 len = snprintf(p, sz, "%s ", be->dbbe_name);
128 p += len;
129 sz -= len;
130 }
131 }
132 KASSERT(sz >= 0, ("%s", __func__));
133 error = sysctl_handle_string(oidp, avail, 0, req);
134 free(avail, M_TEMP);
135 return (error);
136 }
137
138 static int
139 kdb_sysctl_current(SYSCTL_HANDLER_ARGS)
140 {
141 char buf[16];
142 int error;
143
144 if (kdb_dbbe != NULL) {
145 strncpy(buf, kdb_dbbe->dbbe_name, sizeof(buf));
146 buf[sizeof(buf) - 1] = '\0';
147 } else
148 *buf = '\0';
149 error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
150 if (error != 0 || req->newptr == NULL)
151 return (error);
152 if (kdb_active)
153 return (EBUSY);
154 return (kdb_dbbe_select(buf));
155 }
156
157 static int
158 kdb_sysctl_enter(SYSCTL_HANDLER_ARGS)
159 {
160 int error, i;
161
162 error = sysctl_wire_old_buffer(req, sizeof(int));
163 if (error == 0) {
164 i = 0;
165 error = sysctl_handle_int(oidp, &i, 0, req);
166 }
167 if (error != 0 || req->newptr == NULL)
168 return (error);
169 if (kdb_active)
170 return (EBUSY);
171 kdb_enter_why(KDB_WHY_SYSCTL, "sysctl debug.kdb.enter");
172 return (0);
173 }
174
175 static int
176 kdb_sysctl_panic(SYSCTL_HANDLER_ARGS)
177 {
178 int error, i;
179
180 error = sysctl_wire_old_buffer(req, sizeof(int));
181 if (error == 0) {
182 i = 0;
183 error = sysctl_handle_int(oidp, &i, 0, req);
184 }
185 if (error != 0 || req->newptr == NULL)
186 return (error);
187 panic("kdb_sysctl_panic");
188 return (0);
189 }
190
191 static int
192 kdb_sysctl_trap(SYSCTL_HANDLER_ARGS)
193 {
194 int error, i;
195 int *addr = (int *)0x10;
196
197 error = sysctl_wire_old_buffer(req, sizeof(int));
198 if (error == 0) {
199 i = 0;
200 error = sysctl_handle_int(oidp, &i, 0, req);
201 }
202 if (error != 0 || req->newptr == NULL)
203 return (error);
204 return (*addr);
205 }
206
207 static int
208 kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS)
209 {
210 int error, i;
211 void (*fp)(u_int, u_int, u_int) = (void *)0xdeadc0de;
212
213 error = sysctl_wire_old_buffer(req, sizeof(int));
214 if (error == 0) {
215 i = 0;
216 error = sysctl_handle_int(oidp, &i, 0, req);
217 }
218 if (error != 0 || req->newptr == NULL)
219 return (error);
220 (*fp)(0x11111111, 0x22222222, 0x33333333);
221 return (0);
222 }
223
224 /*
225 * Solaris implements a new BREAK which is initiated by a character sequence
226 * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the
227 * Remote Console.
228 *
229 * Note that this function may be called from almost anywhere, with interrupts
230 * disabled and with unknown locks held, so it must not access data other than
231 * its arguments. Its up to the caller to ensure that the state variable is
232 * consistent.
233 */
234
235 #define KEY_CR 13 /* CR '\r' */
236 #define KEY_TILDE 126 /* ~ */
237 #define KEY_CRTLB 2 /* ^B */
238
239 int
240 kdb_alt_break(int key, int *state)
241 {
242 int brk;
243
244 brk = 0;
245 switch (key) {
246 case KEY_CR:
247 *state = KEY_TILDE;
248 break;
249 case KEY_TILDE:
250 *state = (*state == KEY_TILDE) ? KEY_CRTLB : 0;
251 break;
252 case KEY_CRTLB:
253 if (*state == KEY_CRTLB)
254 brk = 1;
255 /* FALLTHROUGH */
256 default:
257 *state = 0;
258 break;
259 }
260 return (brk);
261 }
262
263 /*
264 * Print a backtrace of the calling thread. The backtrace is generated by
265 * the selected debugger, provided it supports backtraces. If no debugger
266 * is selected or the current debugger does not support backtraces, this
267 * function silently returns.
268 */
269
270 void
271 kdb_backtrace()
272 {
273
274 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) {
275 printf("KDB: stack backtrace:\n");
276 kdb_dbbe->dbbe_trace();
277 }
278 }
279
280 /*
281 * Set/change the current backend.
282 */
283
284 int
285 kdb_dbbe_select(const char *name)
286 {
287 struct kdb_dbbe *be, **iter;
288
289 SET_FOREACH(iter, kdb_dbbe_set) {
290 be = *iter;
291 if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) {
292 kdb_dbbe = be;
293 return (0);
294 }
295 }
296 return (EINVAL);
297 }
298
299 /*
300 * Enter the currently selected debugger. If a message has been provided,
301 * it is printed first. If the debugger does not support the enter method,
302 * it is entered by using breakpoint(), which enters the debugger through
303 * kdb_trap(). The 'why' argument will contain a more mechanically usable
304 * string than 'msg', and is relied upon by DDB scripting to identify the
305 * reason for entering the debugger so that the right script can be run.
306 */
307 void
308 kdb_enter_why(const char *why, const char *msg)
309 {
310
311 if (kdb_dbbe != NULL && kdb_active == 0) {
312 if (msg != NULL)
313 printf("KDB: enter: %s\n", msg);
314 kdb_why = why;
315 breakpoint();
316 kdb_why = KDB_WHY_UNSET;
317 }
318 }
319
320 /*
321 * This compatibility function exists so that kernel modules with existing
322 * dependencies will still link and function. In FreeBSD 8.0, kdb_enter() is
323 * kdb_enter_why(). In 7.x, this limits how KDB can use the entry call, and
324 * means that there won't be specific scripts for event that use the legacy
325 * interface.
326 */
327 void
328 kdb_enter(const char *msg)
329 {
330
331 kdb_enter_why(KDB_WHY_UNSET, msg);
332 }
333
334 /*
335 * Initialize the kernel debugger interface.
336 */
337
338 void
339 kdb_init()
340 {
341 struct kdb_dbbe *be, **iter;
342 int cur_pri, pri;
343
344 kdb_active = 0;
345 kdb_dbbe = NULL;
346 cur_pri = -1;
347 SET_FOREACH(iter, kdb_dbbe_set) {
348 be = *iter;
349 pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1;
350 be->dbbe_active = (pri >= 0) ? 0 : -1;
351 if (pri > cur_pri) {
352 cur_pri = pri;
353 kdb_dbbe = be;
354 }
355 }
356 if (kdb_dbbe != NULL) {
357 printf("KDB: debugger backends:");
358 SET_FOREACH(iter, kdb_dbbe_set) {
359 be = *iter;
360 if (be->dbbe_active == 0)
361 printf(" %s", be->dbbe_name);
362 }
363 printf("\n");
364 printf("KDB: current backend: %s\n",
365 kdb_dbbe->dbbe_name);
366 }
367 }
368
369 /*
370 * Handle contexts.
371 */
372
373 void *
374 kdb_jmpbuf(jmp_buf new)
375 {
376 void *old;
377
378 old = kdb_jmpbufp;
379 kdb_jmpbufp = new;
380 return (old);
381 }
382
383 void
384 kdb_reenter(void)
385 {
386
387 if (!kdb_active || kdb_jmpbufp == NULL)
388 return;
389
390 longjmp(kdb_jmpbufp, 1);
391 /* NOTREACHED */
392 }
393
394 /*
395 * Thread related support functions.
396 */
397
398 struct pcb *
399 kdb_thr_ctx(struct thread *thr)
400 {
401 #if defined(SMP) && defined(KDB_STOPPEDPCB)
402 struct pcpu *pc;
403 #endif
404
405 if (thr == curthread)
406 return (&kdb_pcb);
407
408 #if defined(SMP) && defined(KDB_STOPPEDPCB)
409 SLIST_FOREACH(pc, &cpuhead, pc_allcpu) {
410 if (pc->pc_curthread == thr && (stopped_cpus & pc->pc_cpumask))
411 return (KDB_STOPPEDPCB(pc));
412 }
413 #endif
414 return (thr->td_pcb);
415 }
416
417 struct thread *
418 kdb_thr_first(void)
419 {
420 struct proc *p;
421 struct thread *thr;
422
423 p = LIST_FIRST(&allproc);
424 while (p != NULL) {
425 if (p->p_flag & P_INMEM) {
426 thr = FIRST_THREAD_IN_PROC(p);
427 if (thr != NULL)
428 return (thr);
429 }
430 p = LIST_NEXT(p, p_list);
431 }
432 return (NULL);
433 }
434
435 struct thread *
436 kdb_thr_from_pid(pid_t pid)
437 {
438 struct proc *p;
439
440 p = LIST_FIRST(&allproc);
441 while (p != NULL) {
442 if (p->p_flag & P_INMEM && p->p_pid == pid)
443 return (FIRST_THREAD_IN_PROC(p));
444 p = LIST_NEXT(p, p_list);
445 }
446 return (NULL);
447 }
448
449 struct thread *
450 kdb_thr_lookup(lwpid_t tid)
451 {
452 struct thread *thr;
453
454 thr = kdb_thr_first();
455 while (thr != NULL && thr->td_tid != tid)
456 thr = kdb_thr_next(thr);
457 return (thr);
458 }
459
460 struct thread *
461 kdb_thr_next(struct thread *thr)
462 {
463 struct proc *p;
464
465 p = thr->td_proc;
466 thr = TAILQ_NEXT(thr, td_plist);
467 do {
468 if (thr != NULL)
469 return (thr);
470 p = LIST_NEXT(p, p_list);
471 if (p != NULL && (p->p_flag & P_INMEM))
472 thr = FIRST_THREAD_IN_PROC(p);
473 } while (p != NULL);
474 return (NULL);
475 }
476
477 int
478 kdb_thr_select(struct thread *thr)
479 {
480 if (thr == NULL)
481 return (EINVAL);
482 kdb_thread = thr;
483 kdb_thrctx = kdb_thr_ctx(thr);
484 return (0);
485 }
486
487 /*
488 * Enter the debugger due to a trap.
489 */
490
491 int
492 kdb_trap(int type, int code, struct trapframe *tf)
493 {
494 register_t intr;
495 #ifdef SMP
496 int did_stop_cpus;
497 #endif
498 int handled;
499
500 if (kdb_dbbe == NULL || kdb_dbbe->dbbe_trap == NULL)
501 return (0);
502
503 /* We reenter the debugger through kdb_reenter(). */
504 if (kdb_active)
505 return (0);
506
507 intr = intr_disable();
508
509 #ifdef SMP
510 if ((did_stop_cpus = kdb_stop_cpus) != 0)
511 stop_cpus(PCPU_GET(other_cpus));
512 #endif
513
514 kdb_active++;
515
516 kdb_frame = tf;
517
518 /* Let MD code do its thing first... */
519 kdb_cpu_trap(type, code);
520
521 makectx(tf, &kdb_pcb);
522 kdb_thr_select(curthread);
523
524 handled = kdb_dbbe->dbbe_trap(type, code);
525
526 kdb_active--;
527
528 #ifdef SMP
529 if (did_stop_cpus)
530 restart_cpus(stopped_cpus);
531 #endif
532
533 intr_restore(intr);
534
535 return (handled);
536 }
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