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 #include <security/mac/mac_framework.h>
58 u_char __read_frequently kdb_active = 0;
59 static void *kdb_jmpbufp = NULL;
60 struct kdb_dbbe *kdb_dbbe = NULL;
61 static struct pcb kdb_pcb;
62 struct pcb *kdb_thrctx = NULL;
63 struct thread *kdb_thread = NULL;
64 struct trapframe *kdb_frame = NULL;
66 #ifdef BREAK_TO_DEBUGGER
67 #define KDB_BREAK_TO_DEBUGGER 1
69 #define KDB_BREAK_TO_DEBUGGER 0
72 #ifdef ALT_BREAK_TO_DEBUGGER
73 #define KDB_ALT_BREAK_TO_DEBUGGER 1
75 #define KDB_ALT_BREAK_TO_DEBUGGER 0
78 static int kdb_break_to_debugger = KDB_BREAK_TO_DEBUGGER;
79 static int kdb_alt_break_to_debugger = KDB_ALT_BREAK_TO_DEBUGGER;
81 KDB_BACKEND(null, NULL, NULL, NULL, NULL);
83 static int kdb_sysctl_available(SYSCTL_HANDLER_ARGS);
84 static int kdb_sysctl_current(SYSCTL_HANDLER_ARGS);
85 static int kdb_sysctl_enter(SYSCTL_HANDLER_ARGS);
86 static int kdb_sysctl_panic(SYSCTL_HANDLER_ARGS);
87 static int kdb_sysctl_panic_str(SYSCTL_HANDLER_ARGS);
88 static int kdb_sysctl_trap(SYSCTL_HANDLER_ARGS);
89 static int kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS);
90 static int kdb_sysctl_stack_overflow(SYSCTL_HANDLER_ARGS);
92 static SYSCTL_NODE(_debug, OID_AUTO, kdb, CTLFLAG_RW | CTLFLAG_MPSAFE, NULL,
95 SYSCTL_PROC(_debug_kdb, OID_AUTO, available,
96 CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 0,
97 kdb_sysctl_available, "A",
98 "list of available KDB backends");
100 SYSCTL_PROC(_debug_kdb, OID_AUTO, current,
101 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE, NULL, 0,
102 kdb_sysctl_current, "A",
103 "currently selected KDB backend");
105 SYSCTL_PROC(_debug_kdb, OID_AUTO, enter,
106 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
107 kdb_sysctl_enter, "I",
108 "set to enter the debugger");
110 SYSCTL_PROC(_debug_kdb, OID_AUTO, panic,
111 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
112 kdb_sysctl_panic, "I",
113 "set to panic the kernel");
115 SYSCTL_PROC(_debug_kdb, OID_AUTO, panic_str,
116 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
117 kdb_sysctl_panic_str, "A",
118 "trigger a kernel panic, using the provided string as the panic message");
120 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap,
121 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
122 kdb_sysctl_trap, "I",
123 "set to cause a page fault via data access");
125 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap_code,
126 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
127 kdb_sysctl_trap_code, "I",
128 "set to cause a page fault via code access");
130 SYSCTL_PROC(_debug_kdb, OID_AUTO, stack_overflow,
131 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
132 kdb_sysctl_stack_overflow, "I",
133 "set to cause a stack overflow");
135 SYSCTL_INT(_debug_kdb, OID_AUTO, break_to_debugger,
136 CTLFLAG_RWTUN | CTLFLAG_SECURE,
137 &kdb_break_to_debugger, 0, "Enable break to debugger");
139 SYSCTL_INT(_debug_kdb, OID_AUTO, alt_break_to_debugger,
140 CTLFLAG_RWTUN | CTLFLAG_SECURE,
141 &kdb_alt_break_to_debugger, 0, "Enable alternative break to debugger");
144 * Flag to indicate to debuggers why the debugger was entered.
146 const char * volatile kdb_why = KDB_WHY_UNSET;
149 kdb_sysctl_available(SYSCTL_HANDLER_ARGS)
151 struct kdb_dbbe **iter;
155 sbuf_new_for_sysctl(&sbuf, NULL, 64, req);
156 SET_FOREACH(iter, kdb_dbbe_set) {
157 if ((*iter)->dbbe_active == 0)
158 sbuf_printf(&sbuf, "%s ", (*iter)->dbbe_name);
160 error = sbuf_finish(&sbuf);
166 kdb_sysctl_current(SYSCTL_HANDLER_ARGS)
171 if (kdb_dbbe != NULL)
172 strlcpy(buf, kdb_dbbe->dbbe_name, sizeof(buf));
175 error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
176 if (error != 0 || req->newptr == NULL)
180 return (kdb_dbbe_select(buf));
184 kdb_sysctl_enter(SYSCTL_HANDLER_ARGS)
188 error = sysctl_wire_old_buffer(req, sizeof(int));
191 error = sysctl_handle_int(oidp, &i, 0, req);
193 if (error != 0 || req->newptr == NULL)
197 kdb_enter(KDB_WHY_SYSCTL, "sysctl debug.kdb.enter");
202 kdb_sysctl_panic(SYSCTL_HANDLER_ARGS)
206 error = sysctl_wire_old_buffer(req, sizeof(int));
209 error = sysctl_handle_int(oidp, &i, 0, req);
211 if (error != 0 || req->newptr == NULL)
213 panic("kdb_sysctl_panic");
218 kdb_sysctl_panic_str(SYSCTL_HANDLER_ARGS)
221 static char buf[256]; /* static buffer to limit mallocs when panicing */
224 error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
225 if (error != 0 || req->newptr == NULL)
227 panic("kdb_sysctl_panic: %s", buf);
232 kdb_sysctl_trap(SYSCTL_HANDLER_ARGS)
235 int *addr = (int *)0x10;
237 error = sysctl_wire_old_buffer(req, sizeof(int));
240 error = sysctl_handle_int(oidp, &i, 0, req);
242 if (error != 0 || req->newptr == NULL)
248 kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS)
251 void (*fp)(u_int, u_int, u_int) = (void *)0xdeadc0de;
253 error = sysctl_wire_old_buffer(req, sizeof(int));
256 error = sysctl_handle_int(oidp, &i, 0, req);
258 if (error != 0 || req->newptr == NULL)
260 (*fp)(0x11111111, 0x22222222, 0x33333333);
264 static void kdb_stack_overflow(volatile int *x) __noinline;
266 kdb_stack_overflow(volatile int *x)
271 kdb_stack_overflow(x);
272 *x += PCPU_GET(cpuid) / 1000000;
276 kdb_sysctl_stack_overflow(SYSCTL_HANDLER_ARGS)
281 error = sysctl_wire_old_buffer(req, sizeof(int));
284 error = sysctl_handle_int(oidp, &i, 0, req);
286 if (error != 0 || req->newptr == NULL)
289 kdb_stack_overflow(&x);
294 kdb_panic(const char *msg)
297 kdb_why = KDB_WHY_PANIC;
298 printf("KDB: panic\n");
306 kdb_why = KDB_WHY_REBOOT;
307 printf("KDB: reboot requested\n");
312 * Solaris implements a new BREAK which is initiated by a character sequence
313 * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the
316 * Note that this function may be called from almost anywhere, with interrupts
317 * disabled and with unknown locks held, so it must not access data other than
318 * its arguments. Its up to the caller to ensure that the state variable is
321 #define KEY_CR 13 /* CR '\r' */
322 #define KEY_TILDE 126 /* ~ */
323 #define KEY_CRTLB 2 /* ^B */
324 #define KEY_CRTLP 16 /* ^P */
325 #define KEY_CRTLR 18 /* ^R */
327 /* States of th KDB "alternate break sequence" detecting state machine. */
329 KDB_ALT_BREAK_SEEN_NONE,
330 KDB_ALT_BREAK_SEEN_CR,
331 KDB_ALT_BREAK_SEEN_CR_TILDE,
338 if (!kdb_break_to_debugger)
340 kdb_enter(KDB_WHY_BREAK, "Break to debugger");
341 return (KDB_REQ_DEBUGGER);
345 kdb_alt_break_state(int key, int *state)
349 /* All states transition to KDB_ALT_BREAK_SEEN_CR on a CR. */
351 *state = KDB_ALT_BREAK_SEEN_CR;
357 case KDB_ALT_BREAK_SEEN_CR:
358 *state = KDB_ALT_BREAK_SEEN_NONE;
359 if (key == KEY_TILDE)
360 *state = KDB_ALT_BREAK_SEEN_CR_TILDE;
362 case KDB_ALT_BREAK_SEEN_CR_TILDE:
363 *state = KDB_ALT_BREAK_SEEN_NONE;
364 if (key == KEY_CRTLB)
365 brk = KDB_REQ_DEBUGGER;
366 else if (key == KEY_CRTLP)
368 else if (key == KEY_CRTLR)
369 brk = KDB_REQ_REBOOT;
371 case KDB_ALT_BREAK_SEEN_NONE:
373 *state = KDB_ALT_BREAK_SEEN_NONE;
380 kdb_alt_break_internal(int key, int *state, int force_gdb)
384 if (!kdb_alt_break_to_debugger)
386 brk = kdb_alt_break_state(key, state);
388 case KDB_REQ_DEBUGGER:
390 kdb_dbbe_select("gdb");
391 kdb_enter(KDB_WHY_BREAK, "Break to debugger");
396 kdb_dbbe_select("gdb");
397 kdb_panic("Panic sequence on console");
408 kdb_alt_break(int key, int *state)
411 return (kdb_alt_break_internal(key, state, 0));
415 * This variation on kdb_alt_break() is used only by dcons, which has its own
416 * configuration flag to force GDB use regardless of the global KDB
420 kdb_alt_break_gdb(int key, int *state)
423 return (kdb_alt_break_internal(key, state, 1));
427 * Print a backtrace of the calling thread. The backtrace is generated by
428 * the selected debugger, provided it supports backtraces. If no debugger
429 * is selected or the current debugger does not support backtraces, this
430 * function silently returns.
436 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) {
437 printf("KDB: stack backtrace:\n");
438 kdb_dbbe->dbbe_trace();
444 printf("KDB: stack backtrace:\n");
446 stack_print_ddb(&st);
452 * Similar to kdb_backtrace() except that it prints a backtrace of an
453 * arbitrary thread rather than the calling thread.
456 kdb_backtrace_thread(struct thread *td)
459 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace_thread != NULL) {
460 printf("KDB: stack backtrace of thread %d:\n", td->td_tid);
461 kdb_dbbe->dbbe_trace_thread(td);
467 printf("KDB: stack backtrace of thread %d:\n", td->td_tid);
468 if (stack_save_td(&st, td) == 0)
469 stack_print_ddb(&st);
475 * Set/change the current backend.
478 kdb_dbbe_select(const char *name)
480 struct kdb_dbbe *be, **iter;
482 SET_FOREACH(iter, kdb_dbbe_set) {
484 if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) {
493 * Enter the currently selected debugger. If a message has been provided,
494 * it is printed first. If the debugger does not support the enter method,
495 * it is entered by using breakpoint(), which enters the debugger through
496 * kdb_trap(). The 'why' argument will contain a more mechanically usable
497 * string than 'msg', and is relied upon by DDB scripting to identify the
498 * reason for entering the debugger so that the right script can be run.
501 kdb_enter(const char *why, const char *msg)
504 if (kdb_dbbe != NULL && kdb_active == 0) {
507 printf("KDB: enter: %s\n", msg);
509 kdb_why = KDB_WHY_UNSET;
514 * Initialize the kernel debugger interface.
519 struct kdb_dbbe *be, **iter;
525 SET_FOREACH(iter, kdb_dbbe_set) {
527 pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1;
528 be->dbbe_active = (pri >= 0) ? 0 : -1;
534 if (kdb_dbbe != NULL) {
535 printf("KDB: debugger backends:");
536 SET_FOREACH(iter, kdb_dbbe_set) {
538 if (be->dbbe_active == 0)
539 printf(" %s", be->dbbe_name);
542 printf("KDB: current backend: %s\n",
543 kdb_dbbe->dbbe_name);
551 kdb_jmpbuf(jmp_buf new)
564 if (!kdb_active || kdb_jmpbufp == NULL)
567 printf("KDB: reentering\n");
569 longjmp(kdb_jmpbufp, 1);
574 kdb_reenter_silent(void)
577 if (!kdb_active || kdb_jmpbufp == NULL)
580 longjmp(kdb_jmpbufp, 1);
585 * Thread-related support functions.
588 kdb_thr_ctx(struct thread *thr)
590 #if defined(SMP) && defined(KDB_STOPPEDPCB)
594 if (thr == curthread)
597 #if defined(SMP) && defined(KDB_STOPPEDPCB)
598 STAILQ_FOREACH(pc, &cpuhead, pc_allcpu) {
599 if (pc->pc_curthread == thr &&
600 CPU_ISSET(pc->pc_cpuid, &stopped_cpus))
601 return (KDB_STOPPEDPCB(pc));
604 return (thr->td_pcb);
614 /* This function may be called early. */
615 if (pidhashtbl == NULL)
618 for (i = 0; i <= pidhash; i++) {
619 LIST_FOREACH(p, &pidhashtbl[i], p_hash) {
620 thr = FIRST_THREAD_IN_PROC(p);
629 kdb_thr_from_pid(pid_t pid)
633 LIST_FOREACH(p, PIDHASH(pid), p_hash) {
635 return (FIRST_THREAD_IN_PROC(p));
641 kdb_thr_lookup(lwpid_t tid)
645 thr = kdb_thr_first();
646 while (thr != NULL && thr->td_tid != tid)
647 thr = kdb_thr_next(thr);
652 kdb_thr_next(struct thread *thr)
658 thr = TAILQ_NEXT(thr, td_plist);
661 if (pidhashtbl == NULL)
663 hash = p->p_pid & pidhash;
665 p = LIST_NEXT(p, p_hash);
667 if (++hash > pidhash)
669 p = LIST_FIRST(&pidhashtbl[hash]);
671 thr = FIRST_THREAD_IN_PROC(p);
678 kdb_thr_select(struct thread *thr)
683 kdb_thrctx = kdb_thr_ctx(thr);
688 * Enter the debugger due to a trap.
691 kdb_trap(int type, int code, struct trapframe *tf)
702 if (be == NULL || be->dbbe_trap == NULL)
705 /* We reenter the debugger through kdb_reenter(). */
709 intr = intr_disable();
711 if (!SCHEDULER_STOPPED()) {
713 other_cpus = all_cpus;
714 CPU_ANDNOT(&other_cpus, &other_cpus, &stopped_cpus);
715 CPU_CLR(PCPU_GET(cpuid), &other_cpus);
716 stop_cpus_hard(other_cpus);
718 curthread->td_stopsched = 1;
727 /* Let MD code do its thing first... */
728 kdb_cpu_trap(type, code);
730 makectx(tf, &kdb_pcb);
731 kdb_thr_select(curthread);
737 if (mac_kdb_check_backend(be) != 0) {
738 printf("MAC prevented execution of KDB backend: %s\n",
740 /* Unhandled breakpoint traps are fatal. */
745 handled = be->dbbe_trap(type, code);
749 if (be == NULL || be->dbbe_trap == NULL)
751 printf("Switching to %s back-end\n", be->dbbe_name);
759 curthread->td_stopsched = 0;
761 CPU_AND(&other_cpus, &other_cpus, &stopped_cpus);
762 restart_cpus(other_cpus);