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/5.3/sys/kern/subr_kdb.c 136588 2004-10-16 08:43:07Z cvs2svn $");
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 int kdb_active = 0;
44 void *kdb_jmpbufp = NULL;
45 struct kdb_dbbe *kdb_dbbe = NULL;
46 struct pcb kdb_pcb;
47 struct pcb *kdb_thrctx = NULL;
48 struct thread *kdb_thread = NULL;
49 struct trapframe *kdb_frame = NULL;
50
51 KDB_BACKEND(null, NULL, NULL, NULL);
52 SET_DECLARE(kdb_dbbe_set, struct kdb_dbbe);
53
54 static int kdb_sysctl_available(SYSCTL_HANDLER_ARGS);
55 static int kdb_sysctl_current(SYSCTL_HANDLER_ARGS);
56 static int kdb_sysctl_enter(SYSCTL_HANDLER_ARGS);
57
58 SYSCTL_NODE(_debug, OID_AUTO, kdb, CTLFLAG_RW, NULL, "KDB nodes");
59
60 SYSCTL_PROC(_debug_kdb, OID_AUTO, available, CTLTYPE_STRING | CTLFLAG_RD, 0, 0,
61 kdb_sysctl_available, "A", "list of available KDB backends");
62
63 SYSCTL_PROC(_debug_kdb, OID_AUTO, current, CTLTYPE_STRING | CTLFLAG_RW, 0, 0,
64 kdb_sysctl_current, "A", "currently selected KDB backend");
65
66 SYSCTL_PROC(_debug_kdb, OID_AUTO, enter, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
67 kdb_sysctl_enter, "I", "set to enter the debugger");
68
69 /*
70 * Flag indicating whether or not to IPI the other CPUs to stop them on
71 * entering the debugger. Sometimes, this will result in a deadlock as
72 * stop_cpus() waits for the other cpus to stop, so we allow it to be
73 * disabled.
74 */
75 #ifdef SMP
76 static int kdb_stop_cpus = 1;
77 SYSCTL_INT(_debug_kdb, OID_AUTO, stop_cpus, CTLTYPE_INT | CTLFLAG_RW,
78 &kdb_stop_cpus, 0, "");
79 TUNABLE_INT("debug.kdb.stop_cpus", &kdb_stop_cpus);
80 #endif
81
82 static int
83 kdb_sysctl_available(SYSCTL_HANDLER_ARGS)
84 {
85 struct kdb_dbbe *be, **iter;
86 char *avail, *p;
87 ssize_t len, sz;
88 int error;
89
90 sz = 0;
91 SET_FOREACH(iter, kdb_dbbe_set) {
92 be = *iter;
93 if (be->dbbe_active == 0)
94 sz += strlen(be->dbbe_name) + 1;
95 }
96 sz++;
97 avail = malloc(sz, M_TEMP, M_WAITOK);
98 p = avail;
99 SET_FOREACH(iter, kdb_dbbe_set) {
100 be = *iter;
101 if (be->dbbe_active == 0) {
102 len = snprintf(p, sz, "%s ", be->dbbe_name);
103 p += len;
104 sz -= len;
105 }
106 }
107 KASSERT(sz >= 0, ("%s", __func__));
108 error = sysctl_handle_string(oidp, avail, 0, req);
109 free(avail, M_TEMP);
110 return (error);
111 }
112
113 static int
114 kdb_sysctl_current(SYSCTL_HANDLER_ARGS)
115 {
116 char buf[16];
117 int error;
118
119 if (kdb_dbbe != NULL) {
120 strncpy(buf, kdb_dbbe->dbbe_name, sizeof(buf));
121 buf[sizeof(buf) - 1] = '\0';
122 } else
123 *buf = '\0';
124 error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
125 if (error != 0 || req->newptr == NULL)
126 return (error);
127 if (kdb_active)
128 return (EBUSY);
129 return (kdb_dbbe_select(buf));
130 }
131
132 static int
133 kdb_sysctl_enter(SYSCTL_HANDLER_ARGS)
134 {
135 int error, i;
136
137 error = sysctl_wire_old_buffer(req, sizeof(int));
138 if (error == 0) {
139 i = 0;
140 error = sysctl_handle_int(oidp, &i, 0, req);
141 }
142 if (error != 0 || req->newptr == NULL)
143 return (error);
144 if (kdb_active)
145 return (EBUSY);
146 kdb_enter("sysctl debug.kdb.enter");
147 return (0);
148 }
149
150 /*
151 * Solaris implements a new BREAK which is initiated by a character sequence
152 * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the
153 * Remote Console.
154 *
155 * Note that this function may be called from almost anywhere, with interrupts
156 * disabled and with unknown locks held, so it must not access data other than
157 * its arguments. Its up to the caller to ensure that the state variable is
158 * consistent.
159 */
160
161 #define KEY_CR 13 /* CR '\r' */
162 #define KEY_TILDE 126 /* ~ */
163 #define KEY_CRTLB 2 /* ^B */
164
165 int
166 kdb_alt_break(int key, int *state)
167 {
168 int brk;
169
170 brk = 0;
171 switch (key) {
172 case KEY_CR:
173 *state = KEY_TILDE;
174 break;
175 case KEY_TILDE:
176 *state = (*state == KEY_TILDE) ? KEY_CRTLB : 0;
177 break;
178 case KEY_CRTLB:
179 if (*state == KEY_CRTLB)
180 brk = 1;
181 /* FALLTHROUGH */
182 default:
183 *state = 0;
184 break;
185 }
186 return (brk);
187 }
188
189 /*
190 * Print a backtrace of the calling thread. The backtrace is generated by
191 * the selected debugger, provided it supports backtraces. If no debugger
192 * is selected or the current debugger does not support backtraces, this
193 * function silently returns.
194 */
195
196 void
197 kdb_backtrace()
198 {
199
200 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) {
201 printf("KDB: stack backtrace:\n");
202 kdb_dbbe->dbbe_trace();
203 }
204 }
205
206 /*
207 * Set/change the current backend.
208 */
209
210 int
211 kdb_dbbe_select(const char *name)
212 {
213 struct kdb_dbbe *be, **iter;
214
215 SET_FOREACH(iter, kdb_dbbe_set) {
216 be = *iter;
217 if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) {
218 kdb_dbbe = be;
219 return (0);
220 }
221 }
222 return (EINVAL);
223 }
224
225 /*
226 * Enter the currently selected debugger. If a message has been provided,
227 * it is printed first. If the debugger does not support the enter method,
228 * it is entered by using breakpoint(), which enters the debugger through
229 * kdb_trap().
230 */
231
232 void
233 kdb_enter(const char *msg)
234 {
235
236 if (kdb_dbbe != NULL && kdb_active == 0) {
237 if (msg != NULL)
238 printf("KDB: enter: %s\n", msg);
239 breakpoint();
240 }
241 }
242
243 /*
244 * Initialize the kernel debugger interface.
245 */
246
247 void
248 kdb_init()
249 {
250 struct kdb_dbbe *be, **iter;
251 int cur_pri, pri;
252
253 kdb_active = 0;
254 kdb_dbbe = NULL;
255 cur_pri = -1;
256 SET_FOREACH(iter, kdb_dbbe_set) {
257 be = *iter;
258 pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1;
259 be->dbbe_active = (pri >= 0) ? 0 : -1;
260 if (pri > cur_pri) {
261 cur_pri = pri;
262 kdb_dbbe = be;
263 }
264 }
265 if (kdb_dbbe != NULL) {
266 printf("KDB: debugger backends:");
267 SET_FOREACH(iter, kdb_dbbe_set) {
268 be = *iter;
269 if (be->dbbe_active == 0)
270 printf(" %s", be->dbbe_name);
271 }
272 printf("\n");
273 printf("KDB: current backend: %s\n",
274 kdb_dbbe->dbbe_name);
275 }
276 }
277
278 /*
279 * Handle contexts.
280 */
281
282 void *
283 kdb_jmpbuf(jmp_buf new)
284 {
285 void *old;
286
287 old = kdb_jmpbufp;
288 kdb_jmpbufp = new;
289 return (old);
290 }
291
292 void
293 kdb_reenter(void)
294 {
295
296 if (!kdb_active || kdb_jmpbufp == NULL)
297 return;
298
299 longjmp(kdb_jmpbufp, 1);
300 /* NOTREACHED */
301 }
302
303 /*
304 * Thread related support functions.
305 */
306
307 struct pcb *
308 kdb_thr_ctx(struct thread *thr)
309 {
310 return ((thr == curthread) ? &kdb_pcb : thr->td_pcb);
311 }
312
313 struct thread *
314 kdb_thr_first(void)
315 {
316 struct proc *p;
317 struct thread *thr;
318
319 p = LIST_FIRST(&allproc);
320 while (p != NULL) {
321 if (p->p_sflag & PS_INMEM) {
322 thr = FIRST_THREAD_IN_PROC(p);
323 if (thr != NULL)
324 return (thr);
325 }
326 p = LIST_NEXT(p, p_list);
327 }
328 return (NULL);
329 }
330
331 struct thread *
332 kdb_thr_from_pid(pid_t pid)
333 {
334 struct proc *p;
335
336 p = LIST_FIRST(&allproc);
337 while (p != NULL) {
338 if (p->p_sflag & PS_INMEM && p->p_pid == pid)
339 return (FIRST_THREAD_IN_PROC(p));
340 p = LIST_NEXT(p, p_list);
341 }
342 return (NULL);
343 }
344
345 struct thread *
346 kdb_thr_lookup(lwpid_t tid)
347 {
348 struct thread *thr;
349
350 thr = kdb_thr_first();
351 while (thr != NULL && thr->td_tid != tid)
352 thr = kdb_thr_next(thr);
353 return (thr);
354 }
355
356 struct thread *
357 kdb_thr_next(struct thread *thr)
358 {
359 struct proc *p;
360
361 p = thr->td_proc;
362 thr = TAILQ_NEXT(thr, td_plist);
363 do {
364 if (thr != NULL)
365 return (thr);
366 p = LIST_NEXT(p, p_list);
367 if (p != NULL && (p->p_sflag & PS_INMEM))
368 thr = FIRST_THREAD_IN_PROC(p);
369 } while (p != NULL);
370 return (NULL);
371 }
372
373 int
374 kdb_thr_select(struct thread *thr)
375 {
376 if (thr == NULL)
377 return (EINVAL);
378 kdb_thread = thr;
379 kdb_thrctx = kdb_thr_ctx(thr);
380 return (0);
381 }
382
383 /*
384 * Enter the debugger due to a trap.
385 */
386
387 int
388 kdb_trap(int type, int code, struct trapframe *tf)
389 {
390 #ifdef SMP
391 int did_stop_cpus;
392 #endif
393 int handled;
394
395 if (kdb_dbbe == NULL || kdb_dbbe->dbbe_trap == NULL)
396 return (0);
397
398 /* We reenter the debugger through kdb_reenter(). */
399 if (kdb_active)
400 return (0);
401
402 makectx(tf, &kdb_pcb);
403
404 critical_enter();
405
406 kdb_active++;
407 kdb_frame = tf;
408 kdb_thr_select(curthread);
409
410 #ifdef SMP
411 if ((did_stop_cpus = kdb_stop_cpus) != 0)
412 stop_cpus(PCPU_GET(other_cpus));
413 #endif
414
415 /* Let MD code do its thing first... */
416 kdb_cpu_trap(type, code);
417
418 handled = kdb_dbbe->dbbe_trap(type, code);
419
420 #ifdef SMP
421 if (did_stop_cpus)
422 restart_cpus(stopped_cpus);
423 #endif
424
425 kdb_active--;
426
427 critical_exit();
428
429 return (handled);
430 }
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