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: src/sys/kern/subr_kdb.c,v 1.5.2.5 2005/10/02 10:20:04 rwatson Exp $");
29
30 #include <sys/param.h>
31 #include <sys/systm.h>
32 #include <sys/kdb.h>
33 #include <sys/kernel.h>
34 #include <sys/malloc.h>
35 #include <sys/pcpu.h>
36 #include <sys/proc.h>
37 #include <sys/smp.h>
38 #include <sys/sysctl.h>
39
40 #include <machine/kdb.h>
41 #include <machine/pcb.h>
42
43 #ifdef KDB_STOP_NMI
44 #include <machine/smp.h>
45 #endif
46
47 /*
48 * KDB_STOP_NMI requires SMP to pick up the right dependencies
49 * (And isn't useful on UP anyway)
50 */
51 #if defined(KDB_STOP_NMI) && !defined(SMP)
52 #error "options KDB_STOP_NMI" requires "options SMP"
53 #endif
54
55 int kdb_active = 0;
56 void *kdb_jmpbufp = NULL;
57 struct kdb_dbbe *kdb_dbbe = NULL;
58 struct pcb kdb_pcb;
59 struct pcb *kdb_thrctx = NULL;
60 struct thread *kdb_thread = NULL;
61 struct trapframe *kdb_frame = NULL;
62
63 KDB_BACKEND(null, NULL, NULL, NULL);
64 SET_DECLARE(kdb_dbbe_set, struct kdb_dbbe);
65
66 static int kdb_sysctl_available(SYSCTL_HANDLER_ARGS);
67 static int kdb_sysctl_current(SYSCTL_HANDLER_ARGS);
68 static int kdb_sysctl_enter(SYSCTL_HANDLER_ARGS);
69
70 SYSCTL_NODE(_debug, OID_AUTO, kdb, CTLFLAG_RW, NULL, "KDB nodes");
71
72 SYSCTL_PROC(_debug_kdb, OID_AUTO, available, CTLTYPE_STRING | CTLFLAG_RD, 0, 0,
73 kdb_sysctl_available, "A", "list of available KDB backends");
74
75 SYSCTL_PROC(_debug_kdb, OID_AUTO, current, CTLTYPE_STRING | CTLFLAG_RW, 0, 0,
76 kdb_sysctl_current, "A", "currently selected KDB backend");
77
78 SYSCTL_PROC(_debug_kdb, OID_AUTO, enter, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
79 kdb_sysctl_enter, "I", "set to enter the debugger");
80
81 /*
82 * Flag indicating whether or not to IPI the other CPUs to stop them on
83 * entering the debugger. Sometimes, this will result in a deadlock as
84 * stop_cpus() waits for the other cpus to stop, so we allow it to be
85 * disabled.
86 */
87 #ifdef SMP
88 static int kdb_stop_cpus = 1;
89 SYSCTL_INT(_debug_kdb, OID_AUTO, stop_cpus, CTLTYPE_INT | CTLFLAG_RW,
90 &kdb_stop_cpus, 0, "");
91 TUNABLE_INT("debug.kdb.stop_cpus", &kdb_stop_cpus);
92
93 #ifdef KDB_STOP_NMI
94 /*
95 * Provide an alternate method of stopping other CPUs. If another CPU has
96 * disabled interrupts the conventional STOP IPI will be blocked. This
97 * NMI-based stop should get through in that case.
98 */
99 static int kdb_stop_cpus_with_nmi = 1;
100 SYSCTL_INT(_debug_kdb, OID_AUTO, stop_cpus_with_nmi, CTLTYPE_INT | CTLFLAG_RW,
101 &kdb_stop_cpus_with_nmi, 0, "");
102 TUNABLE_INT("debug.kdb.stop_cpus_with_nmi", &kdb_stop_cpus_with_nmi);
103 #endif /* KDB_STOP_NMI */
104
105 #endif
106
107 static int
108 kdb_sysctl_available(SYSCTL_HANDLER_ARGS)
109 {
110 struct kdb_dbbe *be, **iter;
111 char *avail, *p;
112 ssize_t len, sz;
113 int error;
114
115 sz = 0;
116 SET_FOREACH(iter, kdb_dbbe_set) {
117 be = *iter;
118 if (be->dbbe_active == 0)
119 sz += strlen(be->dbbe_name) + 1;
120 }
121 sz++;
122 avail = malloc(sz, M_TEMP, M_WAITOK);
123 p = avail;
124 *p = '\0';
125
126 SET_FOREACH(iter, kdb_dbbe_set) {
127 be = *iter;
128 if (be->dbbe_active == 0) {
129 len = snprintf(p, sz, "%s ", be->dbbe_name);
130 p += len;
131 sz -= len;
132 }
133 }
134 KASSERT(sz >= 0, ("%s", __func__));
135 error = sysctl_handle_string(oidp, avail, 0, req);
136 free(avail, M_TEMP);
137 return (error);
138 }
139
140 static int
141 kdb_sysctl_current(SYSCTL_HANDLER_ARGS)
142 {
143 char buf[16];
144 int error;
145
146 if (kdb_dbbe != NULL) {
147 strncpy(buf, kdb_dbbe->dbbe_name, sizeof(buf));
148 buf[sizeof(buf) - 1] = '\0';
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("sysctl debug.kdb.enter");
174 return (0);
175 }
176
177 /*
178 * Solaris implements a new BREAK which is initiated by a character sequence
179 * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the
180 * Remote Console.
181 *
182 * Note that this function may be called from almost anywhere, with interrupts
183 * disabled and with unknown locks held, so it must not access data other than
184 * its arguments. Its up to the caller to ensure that the state variable is
185 * consistent.
186 */
187
188 #define KEY_CR 13 /* CR '\r' */
189 #define KEY_TILDE 126 /* ~ */
190 #define KEY_CRTLB 2 /* ^B */
191
192 int
193 kdb_alt_break(int key, int *state)
194 {
195 int brk;
196
197 brk = 0;
198 switch (key) {
199 case KEY_CR:
200 *state = KEY_TILDE;
201 break;
202 case KEY_TILDE:
203 *state = (*state == KEY_TILDE) ? KEY_CRTLB : 0;
204 break;
205 case KEY_CRTLB:
206 if (*state == KEY_CRTLB)
207 brk = 1;
208 /* FALLTHROUGH */
209 default:
210 *state = 0;
211 break;
212 }
213 return (brk);
214 }
215
216 /*
217 * Print a backtrace of the calling thread. The backtrace is generated by
218 * the selected debugger, provided it supports backtraces. If no debugger
219 * is selected or the current debugger does not support backtraces, this
220 * function silently returns.
221 */
222
223 void
224 kdb_backtrace()
225 {
226
227 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) {
228 printf("KDB: stack backtrace:\n");
229 kdb_dbbe->dbbe_trace();
230 }
231 }
232
233 /*
234 * Set/change the current backend.
235 */
236
237 int
238 kdb_dbbe_select(const char *name)
239 {
240 struct kdb_dbbe *be, **iter;
241
242 SET_FOREACH(iter, kdb_dbbe_set) {
243 be = *iter;
244 if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) {
245 kdb_dbbe = be;
246 return (0);
247 }
248 }
249 return (EINVAL);
250 }
251
252 /*
253 * Enter the currently selected debugger. If a message has been provided,
254 * it is printed first. If the debugger does not support the enter method,
255 * it is entered by using breakpoint(), which enters the debugger through
256 * kdb_trap().
257 */
258
259 void
260 kdb_enter(const char *msg)
261 {
262
263 if (kdb_dbbe != NULL && kdb_active == 0) {
264 if (msg != NULL)
265 printf("KDB: enter: %s\n", msg);
266 breakpoint();
267 }
268 }
269
270 /*
271 * Initialize the kernel debugger interface.
272 */
273
274 void
275 kdb_init()
276 {
277 struct kdb_dbbe *be, **iter;
278 int cur_pri, pri;
279
280 kdb_active = 0;
281 kdb_dbbe = NULL;
282 cur_pri = -1;
283 SET_FOREACH(iter, kdb_dbbe_set) {
284 be = *iter;
285 pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1;
286 be->dbbe_active = (pri >= 0) ? 0 : -1;
287 if (pri > cur_pri) {
288 cur_pri = pri;
289 kdb_dbbe = be;
290 }
291 }
292 if (kdb_dbbe != NULL) {
293 printf("KDB: debugger backends:");
294 SET_FOREACH(iter, kdb_dbbe_set) {
295 be = *iter;
296 if (be->dbbe_active == 0)
297 printf(" %s", be->dbbe_name);
298 }
299 printf("\n");
300 printf("KDB: current backend: %s\n",
301 kdb_dbbe->dbbe_name);
302 }
303 }
304
305 /*
306 * Handle contexts.
307 */
308
309 void *
310 kdb_jmpbuf(jmp_buf new)
311 {
312 void *old;
313
314 old = kdb_jmpbufp;
315 kdb_jmpbufp = new;
316 return (old);
317 }
318
319 void
320 kdb_reenter(void)
321 {
322
323 if (!kdb_active || kdb_jmpbufp == NULL)
324 return;
325
326 longjmp(kdb_jmpbufp, 1);
327 /* NOTREACHED */
328 }
329
330 /*
331 * Thread related support functions.
332 */
333
334 struct pcb *
335 kdb_thr_ctx(struct thread *thr)
336 #ifdef KDB_STOP_NMI
337 {
338 u_int cpuid;
339 struct pcpu *pc;
340
341 if (thr == curthread)
342 return &kdb_pcb;
343
344 SLIST_FOREACH(pc, &cpuhead, pc_allcpu) {
345 cpuid = pc->pc_cpuid;
346 if (pc->pc_curthread == thr && (atomic_load_acq_int(&stopped_cpus) & (1 << cpuid)))
347 return &stoppcbs[cpuid];
348 }
349
350 return thr->td_pcb;
351 }
352 #else
353 {
354 return ((thr == curthread) ? &kdb_pcb : thr->td_pcb);
355 }
356 #endif /* KDB_STOP_NMI */
357
358 struct thread *
359 kdb_thr_first(void)
360 {
361 struct proc *p;
362 struct thread *thr;
363
364 p = LIST_FIRST(&allproc);
365 while (p != NULL) {
366 if (p->p_sflag & PS_INMEM) {
367 thr = FIRST_THREAD_IN_PROC(p);
368 if (thr != NULL)
369 return (thr);
370 }
371 p = LIST_NEXT(p, p_list);
372 }
373 return (NULL);
374 }
375
376 struct thread *
377 kdb_thr_from_pid(pid_t pid)
378 {
379 struct proc *p;
380
381 p = LIST_FIRST(&allproc);
382 while (p != NULL) {
383 if (p->p_sflag & PS_INMEM && p->p_pid == pid)
384 return (FIRST_THREAD_IN_PROC(p));
385 p = LIST_NEXT(p, p_list);
386 }
387 return (NULL);
388 }
389
390 struct thread *
391 kdb_thr_lookup(lwpid_t tid)
392 {
393 struct thread *thr;
394
395 thr = kdb_thr_first();
396 while (thr != NULL && thr->td_tid != tid)
397 thr = kdb_thr_next(thr);
398 return (thr);
399 }
400
401 struct thread *
402 kdb_thr_next(struct thread *thr)
403 {
404 struct proc *p;
405
406 p = thr->td_proc;
407 thr = TAILQ_NEXT(thr, td_plist);
408 do {
409 if (thr != NULL)
410 return (thr);
411 p = LIST_NEXT(p, p_list);
412 if (p != NULL && (p->p_sflag & PS_INMEM))
413 thr = FIRST_THREAD_IN_PROC(p);
414 } while (p != NULL);
415 return (NULL);
416 }
417
418 int
419 kdb_thr_select(struct thread *thr)
420 {
421 if (thr == NULL)
422 return (EINVAL);
423 kdb_thread = thr;
424 kdb_thrctx = kdb_thr_ctx(thr);
425 return (0);
426 }
427
428 /*
429 * Enter the debugger due to a trap.
430 */
431
432 int
433 kdb_trap(int type, int code, struct trapframe *tf)
434 {
435 #ifdef SMP
436 int did_stop_cpus;
437 #endif
438 int handled;
439
440 if (kdb_dbbe == NULL || kdb_dbbe->dbbe_trap == NULL)
441 return (0);
442
443 /* We reenter the debugger through kdb_reenter(). */
444 if (kdb_active)
445 return (0);
446
447 makectx(tf, &kdb_pcb);
448
449 critical_enter();
450
451 kdb_active++;
452 kdb_frame = tf;
453 kdb_thr_select(curthread);
454
455 #ifdef SMP
456 if ((did_stop_cpus = kdb_stop_cpus) != 0)
457 {
458 #ifdef KDB_STOP_NMI
459 if(kdb_stop_cpus_with_nmi)
460 stop_cpus_nmi(PCPU_GET(other_cpus));
461 else
462 #endif /* KDB_STOP_NMI */
463 stop_cpus(PCPU_GET(other_cpus));
464 }
465 #endif
466
467 /* Let MD code do its thing first... */
468 kdb_cpu_trap(type, code);
469
470 handled = kdb_dbbe->dbbe_trap(type, code);
471
472 #ifdef SMP
473 if (did_stop_cpus)
474 restart_cpus(stopped_cpus);
475 #endif
476
477 kdb_active--;
478
479 critical_exit();
480
481 return (handled);
482 }
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