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/5.4/sys/kern/subr_kdb.c 145750 2005-05-01 05:38:14Z dwhite $");
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 = 0;
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 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("sysctl debug.kdb.enter");
172 return (0);
173 }
174
175 /*
176 * Solaris implements a new BREAK which is initiated by a character sequence
177 * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the
178 * Remote Console.
179 *
180 * Note that this function may be called from almost anywhere, with interrupts
181 * disabled and with unknown locks held, so it must not access data other than
182 * its arguments. Its up to the caller to ensure that the state variable is
183 * consistent.
184 */
185
186 #define KEY_CR 13 /* CR '\r' */
187 #define KEY_TILDE 126 /* ~ */
188 #define KEY_CRTLB 2 /* ^B */
189
190 int
191 kdb_alt_break(int key, int *state)
192 {
193 int brk;
194
195 brk = 0;
196 switch (key) {
197 case KEY_CR:
198 *state = KEY_TILDE;
199 break;
200 case KEY_TILDE:
201 *state = (*state == KEY_TILDE) ? KEY_CRTLB : 0;
202 break;
203 case KEY_CRTLB:
204 if (*state == KEY_CRTLB)
205 brk = 1;
206 /* FALLTHROUGH */
207 default:
208 *state = 0;
209 break;
210 }
211 return (brk);
212 }
213
214 /*
215 * Print a backtrace of the calling thread. The backtrace is generated by
216 * the selected debugger, provided it supports backtraces. If no debugger
217 * is selected or the current debugger does not support backtraces, this
218 * function silently returns.
219 */
220
221 void
222 kdb_backtrace()
223 {
224
225 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) {
226 printf("KDB: stack backtrace:\n");
227 kdb_dbbe->dbbe_trace();
228 }
229 }
230
231 /*
232 * Set/change the current backend.
233 */
234
235 int
236 kdb_dbbe_select(const char *name)
237 {
238 struct kdb_dbbe *be, **iter;
239
240 SET_FOREACH(iter, kdb_dbbe_set) {
241 be = *iter;
242 if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) {
243 kdb_dbbe = be;
244 return (0);
245 }
246 }
247 return (EINVAL);
248 }
249
250 /*
251 * Enter the currently selected debugger. If a message has been provided,
252 * it is printed first. If the debugger does not support the enter method,
253 * it is entered by using breakpoint(), which enters the debugger through
254 * kdb_trap().
255 */
256
257 void
258 kdb_enter(const char *msg)
259 {
260
261 if (kdb_dbbe != NULL && kdb_active == 0) {
262 if (msg != NULL)
263 printf("KDB: enter: %s\n", msg);
264 breakpoint();
265 }
266 }
267
268 /*
269 * Initialize the kernel debugger interface.
270 */
271
272 void
273 kdb_init()
274 {
275 struct kdb_dbbe *be, **iter;
276 int cur_pri, pri;
277
278 kdb_active = 0;
279 kdb_dbbe = NULL;
280 cur_pri = -1;
281 SET_FOREACH(iter, kdb_dbbe_set) {
282 be = *iter;
283 pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1;
284 be->dbbe_active = (pri >= 0) ? 0 : -1;
285 if (pri > cur_pri) {
286 cur_pri = pri;
287 kdb_dbbe = be;
288 }
289 }
290 if (kdb_dbbe != NULL) {
291 printf("KDB: debugger backends:");
292 SET_FOREACH(iter, kdb_dbbe_set) {
293 be = *iter;
294 if (be->dbbe_active == 0)
295 printf(" %s", be->dbbe_name);
296 }
297 printf("\n");
298 printf("KDB: current backend: %s\n",
299 kdb_dbbe->dbbe_name);
300 }
301 }
302
303 /*
304 * Handle contexts.
305 */
306
307 void *
308 kdb_jmpbuf(jmp_buf new)
309 {
310 void *old;
311
312 old = kdb_jmpbufp;
313 kdb_jmpbufp = new;
314 return (old);
315 }
316
317 void
318 kdb_reenter(void)
319 {
320
321 if (!kdb_active || kdb_jmpbufp == NULL)
322 return;
323
324 longjmp(kdb_jmpbufp, 1);
325 /* NOTREACHED */
326 }
327
328 /*
329 * Thread related support functions.
330 */
331
332 struct pcb *
333 kdb_thr_ctx(struct thread *thr)
334 #ifdef KDB_STOP_NMI
335 {
336 u_int cpuid;
337 struct pcpu *pc;
338
339 if (thr == curthread)
340 return &kdb_pcb;
341
342 SLIST_FOREACH(pc, &cpuhead, pc_allcpu) {
343 cpuid = pc->pc_cpuid;
344 if (pc->pc_curthread == thr && (atomic_load_acq_int(&stopped_cpus) & (1 << cpuid)))
345 return &stoppcbs[cpuid];
346 }
347
348 return thr->td_pcb;
349 }
350 #else
351 {
352 return ((thr == curthread) ? &kdb_pcb : thr->td_pcb);
353 }
354 #endif /* KDB_STOP_NMI */
355
356 struct thread *
357 kdb_thr_first(void)
358 {
359 struct proc *p;
360 struct thread *thr;
361
362 p = LIST_FIRST(&allproc);
363 while (p != NULL) {
364 if (p->p_sflag & PS_INMEM) {
365 thr = FIRST_THREAD_IN_PROC(p);
366 if (thr != NULL)
367 return (thr);
368 }
369 p = LIST_NEXT(p, p_list);
370 }
371 return (NULL);
372 }
373
374 struct thread *
375 kdb_thr_from_pid(pid_t pid)
376 {
377 struct proc *p;
378
379 p = LIST_FIRST(&allproc);
380 while (p != NULL) {
381 if (p->p_sflag & PS_INMEM && p->p_pid == pid)
382 return (FIRST_THREAD_IN_PROC(p));
383 p = LIST_NEXT(p, p_list);
384 }
385 return (NULL);
386 }
387
388 struct thread *
389 kdb_thr_lookup(lwpid_t tid)
390 {
391 struct thread *thr;
392
393 thr = kdb_thr_first();
394 while (thr != NULL && thr->td_tid != tid)
395 thr = kdb_thr_next(thr);
396 return (thr);
397 }
398
399 struct thread *
400 kdb_thr_next(struct thread *thr)
401 {
402 struct proc *p;
403
404 p = thr->td_proc;
405 thr = TAILQ_NEXT(thr, td_plist);
406 do {
407 if (thr != NULL)
408 return (thr);
409 p = LIST_NEXT(p, p_list);
410 if (p != NULL && (p->p_sflag & PS_INMEM))
411 thr = FIRST_THREAD_IN_PROC(p);
412 } while (p != NULL);
413 return (NULL);
414 }
415
416 int
417 kdb_thr_select(struct thread *thr)
418 {
419 if (thr == NULL)
420 return (EINVAL);
421 kdb_thread = thr;
422 kdb_thrctx = kdb_thr_ctx(thr);
423 return (0);
424 }
425
426 /*
427 * Enter the debugger due to a trap.
428 */
429
430 int
431 kdb_trap(int type, int code, struct trapframe *tf)
432 {
433 #ifdef SMP
434 int did_stop_cpus;
435 #endif
436 int handled;
437
438 if (kdb_dbbe == NULL || kdb_dbbe->dbbe_trap == NULL)
439 return (0);
440
441 /* We reenter the debugger through kdb_reenter(). */
442 if (kdb_active)
443 return (0);
444
445 makectx(tf, &kdb_pcb);
446
447 critical_enter();
448
449 kdb_active++;
450 kdb_frame = tf;
451 kdb_thr_select(curthread);
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 /* Let MD code do its thing first... */
466 kdb_cpu_trap(type, code);
467
468 handled = kdb_dbbe->dbbe_trap(type, code);
469
470 #ifdef SMP
471 if (did_stop_cpus)
472 restart_cpus(stopped_cpus);
473 #endif
474
475 kdb_active--;
476
477 critical_exit();
478
479 return (handled);
480 }
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