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/6.2/sys/kern/subr_kdb.c 164286 2006-11-14 20:42:41Z cvs2svn $");
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 KDB_STOP_NMI
46 #include <machine/smp.h>
47 #endif
48
49 /*
50 * KDB_STOP_NMI requires SMP to pick up the right dependencies
51 * (And isn't useful on UP anyway)
52 */
53 #if defined(KDB_STOP_NMI) && !defined(SMP)
54 #error "options KDB_STOP_NMI" requires "options SMP"
55 #endif
56
57 int kdb_active = 0;
58 void *kdb_jmpbufp = NULL;
59 struct kdb_dbbe *kdb_dbbe = NULL;
60 struct pcb kdb_pcb;
61 struct pcb *kdb_thrctx = NULL;
62 struct thread *kdb_thread = NULL;
63 struct trapframe *kdb_frame = NULL;
64
65 KDB_BACKEND(null, NULL, NULL, NULL);
66 SET_DECLARE(kdb_dbbe_set, struct kdb_dbbe);
67
68 static int kdb_sysctl_available(SYSCTL_HANDLER_ARGS);
69 static int kdb_sysctl_current(SYSCTL_HANDLER_ARGS);
70 static int kdb_sysctl_enter(SYSCTL_HANDLER_ARGS);
71
72 SYSCTL_NODE(_debug, OID_AUTO, kdb, CTLFLAG_RW, NULL, "KDB nodes");
73
74 SYSCTL_PROC(_debug_kdb, OID_AUTO, available, CTLTYPE_STRING | CTLFLAG_RD, 0, 0,
75 kdb_sysctl_available, "A", "list of available KDB backends");
76
77 SYSCTL_PROC(_debug_kdb, OID_AUTO, current, CTLTYPE_STRING | CTLFLAG_RW, 0, 0,
78 kdb_sysctl_current, "A", "currently selected KDB backend");
79
80 SYSCTL_PROC(_debug_kdb, OID_AUTO, enter, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
81 kdb_sysctl_enter, "I", "set to enter the debugger");
82
83 /*
84 * Flag indicating whether or not to IPI the other CPUs to stop them on
85 * entering the debugger. Sometimes, this will result in a deadlock as
86 * stop_cpus() waits for the other cpus to stop, so we allow it to be
87 * disabled.
88 */
89 #ifdef SMP
90 static int kdb_stop_cpus = 1;
91 SYSCTL_INT(_debug_kdb, OID_AUTO, stop_cpus, CTLTYPE_INT | CTLFLAG_RW,
92 &kdb_stop_cpus, 0, "");
93 TUNABLE_INT("debug.kdb.stop_cpus", &kdb_stop_cpus);
94
95 #ifdef KDB_STOP_NMI
96 /*
97 * Provide an alternate method of stopping other CPUs. If another CPU has
98 * disabled interrupts the conventional STOP IPI will be blocked. This
99 * NMI-based stop should get through in that case.
100 */
101 static int kdb_stop_cpus_with_nmi = 1;
102 SYSCTL_INT(_debug_kdb, OID_AUTO, stop_cpus_with_nmi, CTLTYPE_INT | CTLFLAG_RW,
103 &kdb_stop_cpus_with_nmi, 0, "");
104 TUNABLE_INT("debug.kdb.stop_cpus_with_nmi", &kdb_stop_cpus_with_nmi);
105 #endif /* KDB_STOP_NMI */
106
107 #endif
108
109 static int
110 kdb_sysctl_available(SYSCTL_HANDLER_ARGS)
111 {
112 struct kdb_dbbe *be, **iter;
113 char *avail, *p;
114 ssize_t len, sz;
115 int error;
116
117 sz = 0;
118 SET_FOREACH(iter, kdb_dbbe_set) {
119 be = *iter;
120 if (be->dbbe_active == 0)
121 sz += strlen(be->dbbe_name) + 1;
122 }
123 sz++;
124 avail = malloc(sz, M_TEMP, M_WAITOK);
125 p = avail;
126 *p = '\0';
127
128 SET_FOREACH(iter, kdb_dbbe_set) {
129 be = *iter;
130 if (be->dbbe_active == 0) {
131 len = snprintf(p, sz, "%s ", be->dbbe_name);
132 p += len;
133 sz -= len;
134 }
135 }
136 KASSERT(sz >= 0, ("%s", __func__));
137 error = sysctl_handle_string(oidp, avail, 0, req);
138 free(avail, M_TEMP);
139 return (error);
140 }
141
142 static int
143 kdb_sysctl_current(SYSCTL_HANDLER_ARGS)
144 {
145 char buf[16];
146 int error;
147
148 if (kdb_dbbe != NULL) {
149 strncpy(buf, kdb_dbbe->dbbe_name, sizeof(buf));
150 buf[sizeof(buf) - 1] = '\0';
151 } else
152 *buf = '\0';
153 error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
154 if (error != 0 || req->newptr == NULL)
155 return (error);
156 if (kdb_active)
157 return (EBUSY);
158 return (kdb_dbbe_select(buf));
159 }
160
161 static int
162 kdb_sysctl_enter(SYSCTL_HANDLER_ARGS)
163 {
164 int error, i;
165
166 error = sysctl_wire_old_buffer(req, sizeof(int));
167 if (error == 0) {
168 i = 0;
169 error = sysctl_handle_int(oidp, &i, 0, req);
170 }
171 if (error != 0 || req->newptr == NULL)
172 return (error);
173 if (kdb_active)
174 return (EBUSY);
175 kdb_enter("sysctl debug.kdb.enter");
176 return (0);
177 }
178
179 /*
180 * Solaris implements a new BREAK which is initiated by a character sequence
181 * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the
182 * Remote Console.
183 *
184 * Note that this function may be called from almost anywhere, with interrupts
185 * disabled and with unknown locks held, so it must not access data other than
186 * its arguments. Its up to the caller to ensure that the state variable is
187 * consistent.
188 */
189
190 #define KEY_CR 13 /* CR '\r' */
191 #define KEY_TILDE 126 /* ~ */
192 #define KEY_CRTLB 2 /* ^B */
193
194 int
195 kdb_alt_break(int key, int *state)
196 {
197 int brk;
198
199 brk = 0;
200 switch (key) {
201 case KEY_CR:
202 *state = KEY_TILDE;
203 break;
204 case KEY_TILDE:
205 *state = (*state == KEY_TILDE) ? KEY_CRTLB : 0;
206 break;
207 case KEY_CRTLB:
208 if (*state == KEY_CRTLB)
209 brk = 1;
210 /* FALLTHROUGH */
211 default:
212 *state = 0;
213 break;
214 }
215 return (brk);
216 }
217
218 /*
219 * Print a backtrace of the calling thread. The backtrace is generated by
220 * the selected debugger, provided it supports backtraces. If no debugger
221 * is selected or the current debugger does not support backtraces, this
222 * function silently returns.
223 */
224
225 void
226 kdb_backtrace()
227 {
228
229 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) {
230 printf("KDB: stack backtrace:\n");
231 kdb_dbbe->dbbe_trace();
232 }
233 }
234
235 /*
236 * Set/change the current backend.
237 */
238
239 int
240 kdb_dbbe_select(const char *name)
241 {
242 struct kdb_dbbe *be, **iter;
243
244 SET_FOREACH(iter, kdb_dbbe_set) {
245 be = *iter;
246 if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) {
247 kdb_dbbe = be;
248 return (0);
249 }
250 }
251 return (EINVAL);
252 }
253
254 /*
255 * Enter the currently selected debugger. If a message has been provided,
256 * it is printed first. If the debugger does not support the enter method,
257 * it is entered by using breakpoint(), which enters the debugger through
258 * kdb_trap().
259 */
260
261 void
262 kdb_enter(const char *msg)
263 {
264
265 if (kdb_dbbe != NULL && kdb_active == 0) {
266 if (msg != NULL)
267 printf("KDB: enter: %s\n", msg);
268 breakpoint();
269 }
270 }
271
272 /*
273 * Initialize the kernel debugger interface.
274 */
275
276 void
277 kdb_init()
278 {
279 struct kdb_dbbe *be, **iter;
280 int cur_pri, pri;
281
282 kdb_active = 0;
283 kdb_dbbe = NULL;
284 cur_pri = -1;
285 SET_FOREACH(iter, kdb_dbbe_set) {
286 be = *iter;
287 pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1;
288 be->dbbe_active = (pri >= 0) ? 0 : -1;
289 if (pri > cur_pri) {
290 cur_pri = pri;
291 kdb_dbbe = be;
292 }
293 }
294 if (kdb_dbbe != NULL) {
295 printf("KDB: debugger backends:");
296 SET_FOREACH(iter, kdb_dbbe_set) {
297 be = *iter;
298 if (be->dbbe_active == 0)
299 printf(" %s", be->dbbe_name);
300 }
301 printf("\n");
302 printf("KDB: current backend: %s\n",
303 kdb_dbbe->dbbe_name);
304 }
305 }
306
307 /*
308 * Handle contexts.
309 */
310
311 void *
312 kdb_jmpbuf(jmp_buf new)
313 {
314 void *old;
315
316 old = kdb_jmpbufp;
317 kdb_jmpbufp = new;
318 return (old);
319 }
320
321 void
322 kdb_reenter(void)
323 {
324
325 if (!kdb_active || kdb_jmpbufp == NULL)
326 return;
327
328 longjmp(kdb_jmpbufp, 1);
329 /* NOTREACHED */
330 }
331
332 /*
333 * Thread related support functions.
334 */
335
336 struct pcb *
337 kdb_thr_ctx(struct thread *thr)
338 #ifdef KDB_STOP_NMI
339 {
340 u_int cpuid;
341 struct pcpu *pc;
342
343 if (thr == curthread)
344 return &kdb_pcb;
345
346 SLIST_FOREACH(pc, &cpuhead, pc_allcpu) {
347 cpuid = pc->pc_cpuid;
348 if (pc->pc_curthread == thr && (atomic_load_acq_int(&stopped_cpus) & (1 << cpuid)))
349 return &stoppcbs[cpuid];
350 }
351
352 return thr->td_pcb;
353 }
354 #else
355 {
356 return ((thr == curthread) ? &kdb_pcb : thr->td_pcb);
357 }
358 #endif /* KDB_STOP_NMI */
359
360 struct thread *
361 kdb_thr_first(void)
362 {
363 struct proc *p;
364 struct thread *thr;
365
366 p = LIST_FIRST(&allproc);
367 while (p != NULL) {
368 if (p->p_sflag & PS_INMEM) {
369 thr = FIRST_THREAD_IN_PROC(p);
370 if (thr != NULL)
371 return (thr);
372 }
373 p = LIST_NEXT(p, p_list);
374 }
375 return (NULL);
376 }
377
378 struct thread *
379 kdb_thr_from_pid(pid_t pid)
380 {
381 struct proc *p;
382
383 p = LIST_FIRST(&allproc);
384 while (p != NULL) {
385 if (p->p_sflag & PS_INMEM && p->p_pid == pid)
386 return (FIRST_THREAD_IN_PROC(p));
387 p = LIST_NEXT(p, p_list);
388 }
389 return (NULL);
390 }
391
392 struct thread *
393 kdb_thr_lookup(lwpid_t tid)
394 {
395 struct thread *thr;
396
397 thr = kdb_thr_first();
398 while (thr != NULL && thr->td_tid != tid)
399 thr = kdb_thr_next(thr);
400 return (thr);
401 }
402
403 struct thread *
404 kdb_thr_next(struct thread *thr)
405 {
406 struct proc *p;
407
408 p = thr->td_proc;
409 thr = TAILQ_NEXT(thr, td_plist);
410 do {
411 if (thr != NULL)
412 return (thr);
413 p = LIST_NEXT(p, p_list);
414 if (p != NULL && (p->p_sflag & PS_INMEM))
415 thr = FIRST_THREAD_IN_PROC(p);
416 } while (p != NULL);
417 return (NULL);
418 }
419
420 int
421 kdb_thr_select(struct thread *thr)
422 {
423 if (thr == NULL)
424 return (EINVAL);
425 kdb_thread = thr;
426 kdb_thrctx = kdb_thr_ctx(thr);
427 return (0);
428 }
429
430 /*
431 * Enter the debugger due to a trap.
432 */
433
434 int
435 kdb_trap(int type, int code, struct trapframe *tf)
436 {
437 #ifdef SMP
438 int did_stop_cpus;
439 #endif
440 int handled;
441
442 if (kdb_dbbe == NULL || kdb_dbbe->dbbe_trap == NULL)
443 return (0);
444
445 /* We reenter the debugger through kdb_reenter(). */
446 if (kdb_active)
447 return (0);
448
449 critical_enter();
450
451 kdb_active++;
452
453 #ifdef SMP
454 if ((did_stop_cpus = kdb_stop_cpus) != 0)
455 {
456 #ifdef KDB_STOP_NMI
457 if(kdb_stop_cpus_with_nmi)
458 stop_cpus_nmi(PCPU_GET(other_cpus));
459 else
460 #endif /* KDB_STOP_NMI */
461 stop_cpus(PCPU_GET(other_cpus));
462 }
463 #endif
464
465 kdb_frame = tf;
466
467 /* Let MD code do its thing first... */
468 kdb_cpu_trap(type, code);
469
470 makectx(tf, &kdb_pcb);
471 kdb_thr_select(curthread);
472
473 handled = kdb_dbbe->dbbe_trap(type, code);
474
475 #ifdef SMP
476 if (did_stop_cpus)
477 restart_cpus(stopped_cpus);
478 #endif
479
480 kdb_active--;
481
482 critical_exit();
483
484 return (handled);
485 }
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