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 printf("KDB: panic\n");
303 printf("KDB: reboot requested\n");
308 * Solaris implements a new BREAK which is initiated by a character sequence
309 * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the
312 * Note that this function may be called from almost anywhere, with interrupts
313 * disabled and with unknown locks held, so it must not access data other than
314 * its arguments. Its up to the caller to ensure that the state variable is
317 #define KEY_CR 13 /* CR '\r' */
318 #define KEY_TILDE 126 /* ~ */
319 #define KEY_CRTLB 2 /* ^B */
320 #define KEY_CRTLP 16 /* ^P */
321 #define KEY_CRTLR 18 /* ^R */
323 /* States of th KDB "alternate break sequence" detecting state machine. */
325 KDB_ALT_BREAK_SEEN_NONE,
326 KDB_ALT_BREAK_SEEN_CR,
327 KDB_ALT_BREAK_SEEN_CR_TILDE,
334 if (!kdb_break_to_debugger)
336 kdb_enter(KDB_WHY_BREAK, "Break to debugger");
337 return (KDB_REQ_DEBUGGER);
341 kdb_alt_break_state(int key, int *state)
345 /* All states transition to KDB_ALT_BREAK_SEEN_CR on a CR. */
347 *state = KDB_ALT_BREAK_SEEN_CR;
353 case KDB_ALT_BREAK_SEEN_CR:
354 *state = KDB_ALT_BREAK_SEEN_NONE;
355 if (key == KEY_TILDE)
356 *state = KDB_ALT_BREAK_SEEN_CR_TILDE;
358 case KDB_ALT_BREAK_SEEN_CR_TILDE:
359 *state = KDB_ALT_BREAK_SEEN_NONE;
360 if (key == KEY_CRTLB)
361 brk = KDB_REQ_DEBUGGER;
362 else if (key == KEY_CRTLP)
364 else if (key == KEY_CRTLR)
365 brk = KDB_REQ_REBOOT;
367 case KDB_ALT_BREAK_SEEN_NONE:
369 *state = KDB_ALT_BREAK_SEEN_NONE;
376 kdb_alt_break_internal(int key, int *state, int force_gdb)
380 if (!kdb_alt_break_to_debugger)
382 brk = kdb_alt_break_state(key, state);
384 case KDB_REQ_DEBUGGER:
386 kdb_dbbe_select("gdb");
387 kdb_enter(KDB_WHY_BREAK, "Break to debugger");
392 kdb_dbbe_select("gdb");
393 kdb_panic("Panic sequence on console");
404 kdb_alt_break(int key, int *state)
407 return (kdb_alt_break_internal(key, state, 0));
411 * This variation on kdb_alt_break() is used only by dcons, which has its own
412 * configuration flag to force GDB use regardless of the global KDB
416 kdb_alt_break_gdb(int key, int *state)
419 return (kdb_alt_break_internal(key, state, 1));
423 * Print a backtrace of the calling thread. The backtrace is generated by
424 * the selected debugger, provided it supports backtraces. If no debugger
425 * is selected or the current debugger does not support backtraces, this
426 * function silently returns.
432 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) {
433 printf("KDB: stack backtrace:\n");
434 kdb_dbbe->dbbe_trace();
440 printf("KDB: stack backtrace:\n");
443 stack_print_ddb(&st);
449 * Similar to kdb_backtrace() except that it prints a backtrace of an
450 * arbitrary thread rather than the calling thread.
453 kdb_backtrace_thread(struct thread *td)
456 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace_thread != NULL) {
457 printf("KDB: stack backtrace of thread %d:\n", td->td_tid);
458 kdb_dbbe->dbbe_trace_thread(td);
464 printf("KDB: stack backtrace of thread %d:\n", td->td_tid);
465 if (stack_save_td(&st, td) == 0)
466 stack_print_ddb(&st);
472 * Set/change the current backend.
475 kdb_dbbe_select(const char *name)
477 struct kdb_dbbe *be, **iter;
479 SET_FOREACH(iter, kdb_dbbe_set) {
481 if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) {
490 * Enter the currently selected debugger. If a message has been provided,
491 * it is printed first. If the debugger does not support the enter method,
492 * it is entered by using breakpoint(), which enters the debugger through
493 * kdb_trap(). The 'why' argument will contain a more mechanically usable
494 * string than 'msg', and is relied upon by DDB scripting to identify the
495 * reason for entering the debugger so that the right script can be run.
498 kdb_enter(const char *why, const char *msg)
501 if (kdb_dbbe != NULL && kdb_active == 0) {
503 printf("KDB: enter: %s\n", msg);
506 kdb_why = KDB_WHY_UNSET;
511 * Initialize the kernel debugger interface.
516 struct kdb_dbbe *be, **iter;
522 SET_FOREACH(iter, kdb_dbbe_set) {
524 pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1;
525 be->dbbe_active = (pri >= 0) ? 0 : -1;
531 if (kdb_dbbe != NULL) {
532 printf("KDB: debugger backends:");
533 SET_FOREACH(iter, kdb_dbbe_set) {
535 if (be->dbbe_active == 0)
536 printf(" %s", be->dbbe_name);
539 printf("KDB: current backend: %s\n",
540 kdb_dbbe->dbbe_name);
548 kdb_jmpbuf(jmp_buf new)
561 if (!kdb_active || kdb_jmpbufp == NULL)
564 printf("KDB: reentering\n");
566 longjmp(kdb_jmpbufp, 1);
571 kdb_reenter_silent(void)
574 if (!kdb_active || kdb_jmpbufp == NULL)
577 longjmp(kdb_jmpbufp, 1);
582 * Thread-related support functions.
585 kdb_thr_ctx(struct thread *thr)
587 #if defined(SMP) && defined(KDB_STOPPEDPCB)
591 if (thr == curthread)
594 #if defined(SMP) && defined(KDB_STOPPEDPCB)
595 STAILQ_FOREACH(pc, &cpuhead, pc_allcpu) {
596 if (pc->pc_curthread == thr &&
597 CPU_ISSET(pc->pc_cpuid, &stopped_cpus))
598 return (KDB_STOPPEDPCB(pc));
601 return (thr->td_pcb);
611 for (i = 0; i <= pidhash; i++) {
612 LIST_FOREACH(p, &pidhashtbl[i], p_hash) {
613 thr = FIRST_THREAD_IN_PROC(p);
622 kdb_thr_from_pid(pid_t pid)
626 LIST_FOREACH(p, PIDHASH(pid), p_hash) {
628 return (FIRST_THREAD_IN_PROC(p));
634 kdb_thr_lookup(lwpid_t tid)
638 thr = kdb_thr_first();
639 while (thr != NULL && thr->td_tid != tid)
640 thr = kdb_thr_next(thr);
645 kdb_thr_next(struct thread *thr)
651 thr = TAILQ_NEXT(thr, td_plist);
654 hash = p->p_pid & pidhash;
656 p = LIST_NEXT(p, p_hash);
658 if (++hash > pidhash)
660 p = LIST_FIRST(&pidhashtbl[hash]);
662 thr = FIRST_THREAD_IN_PROC(p);
669 kdb_thr_select(struct thread *thr)
674 kdb_thrctx = kdb_thr_ctx(thr);
679 * Enter the debugger due to a trap.
682 kdb_trap(int type, int code, struct trapframe *tf)
693 if (be == NULL || be->dbbe_trap == NULL)
696 /* We reenter the debugger through kdb_reenter(). */
700 intr = intr_disable();
702 if (!SCHEDULER_STOPPED()) {
704 other_cpus = all_cpus;
705 CPU_ANDNOT(&other_cpus, &stopped_cpus);
706 CPU_CLR(PCPU_GET(cpuid), &other_cpus);
707 stop_cpus_hard(other_cpus);
709 curthread->td_stopsched = 1;
718 /* Let MD code do its thing first... */
719 kdb_cpu_trap(type, code);
721 makectx(tf, &kdb_pcb);
722 kdb_thr_select(curthread);
727 handled = be->dbbe_trap(type, code);
731 if (be == NULL || be->dbbe_trap == NULL)
733 printf("Switching to %s back-end\n", be->dbbe_name);
741 curthread->td_stopsched = 0;
743 CPU_AND(&other_cpus, &stopped_cpus);
744 restart_cpus(other_cpus);