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