2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
4 * Copyright (c) 2004 The FreeBSD Project
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 #include <sys/cdefs.h>
30 __FBSDID("$FreeBSD$");
33 #include "opt_stack.h"
35 #include <sys/param.h>
36 #include <sys/systm.h>
39 #include <sys/kernel.h>
40 #include <sys/malloc.h>
46 #include <sys/stack.h>
47 #include <sys/sysctl.h>
49 #include <machine/kdb.h>
50 #include <machine/pcb.h>
53 #include <machine/smp.h>
56 u_char __read_frequently kdb_active = 0;
57 static void *kdb_jmpbufp = NULL;
58 struct kdb_dbbe *kdb_dbbe = NULL;
59 static struct pcb kdb_pcb;
60 struct pcb *kdb_thrctx = NULL;
61 struct thread *kdb_thread = NULL;
62 struct trapframe *kdb_frame = NULL;
64 #ifdef BREAK_TO_DEBUGGER
65 #define KDB_BREAK_TO_DEBUGGER 1
67 #define KDB_BREAK_TO_DEBUGGER 0
70 #ifdef ALT_BREAK_TO_DEBUGGER
71 #define KDB_ALT_BREAK_TO_DEBUGGER 1
73 #define KDB_ALT_BREAK_TO_DEBUGGER 0
76 static int kdb_break_to_debugger = KDB_BREAK_TO_DEBUGGER;
77 static int kdb_alt_break_to_debugger = KDB_ALT_BREAK_TO_DEBUGGER;
79 KDB_BACKEND(null, NULL, NULL, NULL, NULL);
81 static int kdb_sysctl_available(SYSCTL_HANDLER_ARGS);
82 static int kdb_sysctl_current(SYSCTL_HANDLER_ARGS);
83 static int kdb_sysctl_enter(SYSCTL_HANDLER_ARGS);
84 static int kdb_sysctl_panic(SYSCTL_HANDLER_ARGS);
85 static int kdb_sysctl_panic_str(SYSCTL_HANDLER_ARGS);
86 static int kdb_sysctl_trap(SYSCTL_HANDLER_ARGS);
87 static int kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS);
88 static int kdb_sysctl_stack_overflow(SYSCTL_HANDLER_ARGS);
90 static SYSCTL_NODE(_debug, OID_AUTO, kdb, CTLFLAG_RW | CTLFLAG_MPSAFE, NULL,
93 SYSCTL_PROC(_debug_kdb, OID_AUTO, available,
94 CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 0,
95 kdb_sysctl_available, "A",
96 "list of available KDB backends");
98 SYSCTL_PROC(_debug_kdb, OID_AUTO, current,
99 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE, NULL, 0,
100 kdb_sysctl_current, "A",
101 "currently selected KDB backend");
103 SYSCTL_PROC(_debug_kdb, OID_AUTO, enter,
104 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
105 kdb_sysctl_enter, "I",
106 "set to enter the debugger");
108 SYSCTL_PROC(_debug_kdb, OID_AUTO, panic,
109 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
110 kdb_sysctl_panic, "I",
111 "set to panic the kernel");
113 SYSCTL_PROC(_debug_kdb, OID_AUTO, panic_str,
114 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
115 kdb_sysctl_panic_str, "A",
116 "trigger a kernel panic, using the provided string as the panic message");
118 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap,
119 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
120 kdb_sysctl_trap, "I",
121 "set to cause a page fault via data access");
123 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap_code,
124 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
125 kdb_sysctl_trap_code, "I",
126 "set to cause a page fault via code access");
128 SYSCTL_PROC(_debug_kdb, OID_AUTO, stack_overflow,
129 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
130 kdb_sysctl_stack_overflow, "I",
131 "set to cause a stack overflow");
133 SYSCTL_INT(_debug_kdb, OID_AUTO, break_to_debugger,
134 CTLFLAG_RWTUN | CTLFLAG_SECURE,
135 &kdb_break_to_debugger, 0, "Enable break to debugger");
137 SYSCTL_INT(_debug_kdb, OID_AUTO, alt_break_to_debugger,
138 CTLFLAG_RWTUN | CTLFLAG_SECURE,
139 &kdb_alt_break_to_debugger, 0, "Enable alternative break to debugger");
142 * Flag to indicate to debuggers why the debugger was entered.
144 const char * volatile kdb_why = KDB_WHY_UNSET;
147 kdb_sysctl_available(SYSCTL_HANDLER_ARGS)
149 struct kdb_dbbe **iter;
153 sbuf_new_for_sysctl(&sbuf, NULL, 64, req);
154 SET_FOREACH(iter, kdb_dbbe_set) {
155 if ((*iter)->dbbe_active == 0)
156 sbuf_printf(&sbuf, "%s ", (*iter)->dbbe_name);
158 error = sbuf_finish(&sbuf);
164 kdb_sysctl_current(SYSCTL_HANDLER_ARGS)
169 if (kdb_dbbe != NULL)
170 strlcpy(buf, kdb_dbbe->dbbe_name, sizeof(buf));
173 error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
174 if (error != 0 || req->newptr == NULL)
178 return (kdb_dbbe_select(buf));
182 kdb_sysctl_enter(SYSCTL_HANDLER_ARGS)
186 error = sysctl_wire_old_buffer(req, sizeof(int));
189 error = sysctl_handle_int(oidp, &i, 0, req);
191 if (error != 0 || req->newptr == NULL)
195 kdb_enter(KDB_WHY_SYSCTL, "sysctl debug.kdb.enter");
200 kdb_sysctl_panic(SYSCTL_HANDLER_ARGS)
204 error = sysctl_wire_old_buffer(req, sizeof(int));
207 error = sysctl_handle_int(oidp, &i, 0, req);
209 if (error != 0 || req->newptr == NULL)
211 panic("kdb_sysctl_panic");
216 kdb_sysctl_panic_str(SYSCTL_HANDLER_ARGS)
219 static char buf[256]; /* static buffer to limit mallocs when panicing */
222 error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
223 if (error != 0 || req->newptr == NULL)
225 panic("kdb_sysctl_panic: %s", buf);
230 kdb_sysctl_trap(SYSCTL_HANDLER_ARGS)
233 int *addr = (int *)0x10;
235 error = sysctl_wire_old_buffer(req, sizeof(int));
238 error = sysctl_handle_int(oidp, &i, 0, req);
240 if (error != 0 || req->newptr == NULL)
246 kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS)
249 void (*fp)(u_int, u_int, u_int) = (void *)0xdeadc0de;
251 error = sysctl_wire_old_buffer(req, sizeof(int));
254 error = sysctl_handle_int(oidp, &i, 0, req);
256 if (error != 0 || req->newptr == NULL)
258 (*fp)(0x11111111, 0x22222222, 0x33333333);
262 static void kdb_stack_overflow(volatile int *x) __noinline;
264 kdb_stack_overflow(volatile int *x)
269 kdb_stack_overflow(x);
270 *x += PCPU_GET(cpuid) / 1000000;
274 kdb_sysctl_stack_overflow(SYSCTL_HANDLER_ARGS)
279 error = sysctl_wire_old_buffer(req, sizeof(int));
282 error = sysctl_handle_int(oidp, &i, 0, req);
284 if (error != 0 || req->newptr == NULL)
287 kdb_stack_overflow(&x);
292 kdb_panic(const char *msg)
295 kdb_why = KDB_WHY_PANIC;
296 printf("KDB: panic\n");
304 kdb_why = KDB_WHY_REBOOT;
305 printf("KDB: reboot requested\n");
310 * Solaris implements a new BREAK which is initiated by a character sequence
311 * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the
314 * Note that this function may be called from almost anywhere, with interrupts
315 * disabled and with unknown locks held, so it must not access data other than
316 * its arguments. Its up to the caller to ensure that the state variable is
319 #define KEY_CR 13 /* CR '\r' */
320 #define KEY_TILDE 126 /* ~ */
321 #define KEY_CRTLB 2 /* ^B */
322 #define KEY_CRTLP 16 /* ^P */
323 #define KEY_CRTLR 18 /* ^R */
325 /* States of th KDB "alternate break sequence" detecting state machine. */
327 KDB_ALT_BREAK_SEEN_NONE,
328 KDB_ALT_BREAK_SEEN_CR,
329 KDB_ALT_BREAK_SEEN_CR_TILDE,
336 if (!kdb_break_to_debugger)
338 kdb_enter(KDB_WHY_BREAK, "Break to debugger");
339 return (KDB_REQ_DEBUGGER);
343 kdb_alt_break_state(int key, int *state)
347 /* All states transition to KDB_ALT_BREAK_SEEN_CR on a CR. */
349 *state = KDB_ALT_BREAK_SEEN_CR;
355 case KDB_ALT_BREAK_SEEN_CR:
356 *state = KDB_ALT_BREAK_SEEN_NONE;
357 if (key == KEY_TILDE)
358 *state = KDB_ALT_BREAK_SEEN_CR_TILDE;
360 case KDB_ALT_BREAK_SEEN_CR_TILDE:
361 *state = KDB_ALT_BREAK_SEEN_NONE;
362 if (key == KEY_CRTLB)
363 brk = KDB_REQ_DEBUGGER;
364 else if (key == KEY_CRTLP)
366 else if (key == KEY_CRTLR)
367 brk = KDB_REQ_REBOOT;
369 case KDB_ALT_BREAK_SEEN_NONE:
371 *state = KDB_ALT_BREAK_SEEN_NONE;
378 kdb_alt_break_internal(int key, int *state, int force_gdb)
382 if (!kdb_alt_break_to_debugger)
384 brk = kdb_alt_break_state(key, state);
386 case KDB_REQ_DEBUGGER:
388 kdb_dbbe_select("gdb");
389 kdb_enter(KDB_WHY_BREAK, "Break to debugger");
394 kdb_dbbe_select("gdb");
395 kdb_panic("Panic sequence on console");
406 kdb_alt_break(int key, int *state)
409 return (kdb_alt_break_internal(key, state, 0));
413 * This variation on kdb_alt_break() is used only by dcons, which has its own
414 * configuration flag to force GDB use regardless of the global KDB
418 kdb_alt_break_gdb(int key, int *state)
421 return (kdb_alt_break_internal(key, state, 1));
425 * Print a backtrace of the calling thread. The backtrace is generated by
426 * the selected debugger, provided it supports backtraces. If no debugger
427 * is selected or the current debugger does not support backtraces, this
428 * function silently returns.
434 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) {
435 printf("KDB: stack backtrace:\n");
436 kdb_dbbe->dbbe_trace();
442 printf("KDB: stack backtrace:\n");
444 stack_print_ddb(&st);
450 * Similar to kdb_backtrace() except that it prints a backtrace of an
451 * arbitrary thread rather than the calling thread.
454 kdb_backtrace_thread(struct thread *td)
457 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace_thread != NULL) {
458 printf("KDB: stack backtrace of thread %d:\n", td->td_tid);
459 kdb_dbbe->dbbe_trace_thread(td);
465 printf("KDB: stack backtrace of thread %d:\n", td->td_tid);
466 if (stack_save_td(&st, td) == 0)
467 stack_print_ddb(&st);
473 * Set/change the current backend.
476 kdb_dbbe_select(const char *name)
478 struct kdb_dbbe *be, **iter;
480 SET_FOREACH(iter, kdb_dbbe_set) {
482 if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) {
491 * Enter the currently selected debugger. If a message has been provided,
492 * it is printed first. If the debugger does not support the enter method,
493 * it is entered by using breakpoint(), which enters the debugger through
494 * kdb_trap(). The 'why' argument will contain a more mechanically usable
495 * string than 'msg', and is relied upon by DDB scripting to identify the
496 * reason for entering the debugger so that the right script can be run.
499 kdb_enter(const char *why, const char *msg)
502 if (kdb_dbbe != NULL && kdb_active == 0) {
505 printf("KDB: enter: %s\n", msg);
507 kdb_why = KDB_WHY_UNSET;
512 * Initialize the kernel debugger interface.
517 struct kdb_dbbe *be, **iter;
523 SET_FOREACH(iter, kdb_dbbe_set) {
525 pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1;
526 be->dbbe_active = (pri >= 0) ? 0 : -1;
532 if (kdb_dbbe != NULL) {
533 printf("KDB: debugger backends:");
534 SET_FOREACH(iter, kdb_dbbe_set) {
536 if (be->dbbe_active == 0)
537 printf(" %s", be->dbbe_name);
540 printf("KDB: current backend: %s\n",
541 kdb_dbbe->dbbe_name);
549 kdb_jmpbuf(jmp_buf new)
562 if (!kdb_active || kdb_jmpbufp == NULL)
565 printf("KDB: reentering\n");
567 longjmp(kdb_jmpbufp, 1);
572 kdb_reenter_silent(void)
575 if (!kdb_active || kdb_jmpbufp == NULL)
578 longjmp(kdb_jmpbufp, 1);
583 * Thread-related support functions.
586 kdb_thr_ctx(struct thread *thr)
588 #if defined(SMP) && defined(KDB_STOPPEDPCB)
592 if (thr == curthread)
595 #if defined(SMP) && defined(KDB_STOPPEDPCB)
596 STAILQ_FOREACH(pc, &cpuhead, pc_allcpu) {
597 if (pc->pc_curthread == thr &&
598 CPU_ISSET(pc->pc_cpuid, &stopped_cpus))
599 return (KDB_STOPPEDPCB(pc));
602 return (thr->td_pcb);
612 /* This function may be called early. */
613 if (pidhashtbl == NULL)
616 for (i = 0; i <= pidhash; i++) {
617 LIST_FOREACH(p, &pidhashtbl[i], p_hash) {
618 thr = FIRST_THREAD_IN_PROC(p);
627 kdb_thr_from_pid(pid_t pid)
631 LIST_FOREACH(p, PIDHASH(pid), p_hash) {
633 return (FIRST_THREAD_IN_PROC(p));
639 kdb_thr_lookup(lwpid_t tid)
643 thr = kdb_thr_first();
644 while (thr != NULL && thr->td_tid != tid)
645 thr = kdb_thr_next(thr);
650 kdb_thr_next(struct thread *thr)
656 thr = TAILQ_NEXT(thr, td_plist);
659 if (pidhashtbl == NULL)
661 hash = p->p_pid & pidhash;
663 p = LIST_NEXT(p, p_hash);
665 if (++hash > pidhash)
667 p = LIST_FIRST(&pidhashtbl[hash]);
669 thr = FIRST_THREAD_IN_PROC(p);
676 kdb_thr_select(struct thread *thr)
681 kdb_thrctx = kdb_thr_ctx(thr);
686 * Enter the debugger due to a trap.
689 kdb_trap(int type, int code, struct trapframe *tf)
700 if (be == NULL || be->dbbe_trap == NULL)
703 /* We reenter the debugger through kdb_reenter(). */
707 intr = intr_disable();
709 if (!SCHEDULER_STOPPED()) {
711 other_cpus = all_cpus;
712 CPU_ANDNOT(&other_cpus, &other_cpus, &stopped_cpus);
713 CPU_CLR(PCPU_GET(cpuid), &other_cpus);
714 stop_cpus_hard(other_cpus);
716 curthread->td_stopsched = 1;
725 /* Let MD code do its thing first... */
726 kdb_cpu_trap(type, code);
728 makectx(tf, &kdb_pcb);
729 kdb_thr_select(curthread);
734 handled = be->dbbe_trap(type, code);
738 if (be == NULL || be->dbbe_trap == NULL)
740 printf("Switching to %s back-end\n", be->dbbe_name);
748 curthread->td_stopsched = 0;
750 CPU_AND(&other_cpus, &other_cpus, &stopped_cpus);
751 restart_cpus(other_cpus);