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_trap(SYSCTL_HANDLER_ARGS);
86 static int kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS);
87 static int kdb_sysctl_stack_overflow(SYSCTL_HANDLER_ARGS);
89 static SYSCTL_NODE(_debug, OID_AUTO, kdb, CTLFLAG_RW | CTLFLAG_MPSAFE, NULL,
92 SYSCTL_PROC(_debug_kdb, OID_AUTO, available,
93 CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 0,
94 kdb_sysctl_available, "A",
95 "list of available KDB backends");
97 SYSCTL_PROC(_debug_kdb, OID_AUTO, current,
98 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE, NULL, 0,
99 kdb_sysctl_current, "A",
100 "currently selected KDB backend");
102 SYSCTL_PROC(_debug_kdb, OID_AUTO, enter,
103 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
104 kdb_sysctl_enter, "I",
105 "set to enter the debugger");
107 SYSCTL_PROC(_debug_kdb, OID_AUTO, panic,
108 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
109 kdb_sysctl_panic, "I",
110 "set to panic the kernel");
112 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap,
113 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
114 kdb_sysctl_trap, "I",
115 "set to cause a page fault via data access");
117 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap_code,
118 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
119 kdb_sysctl_trap_code, "I",
120 "set to cause a page fault via code access");
122 SYSCTL_PROC(_debug_kdb, OID_AUTO, stack_overflow,
123 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
124 kdb_sysctl_stack_overflow, "I",
125 "set to cause a stack overflow");
127 SYSCTL_INT(_debug_kdb, OID_AUTO, break_to_debugger,
128 CTLFLAG_RWTUN | CTLFLAG_SECURE,
129 &kdb_break_to_debugger, 0, "Enable break to debugger");
131 SYSCTL_INT(_debug_kdb, OID_AUTO, alt_break_to_debugger,
132 CTLFLAG_RWTUN | CTLFLAG_SECURE,
133 &kdb_alt_break_to_debugger, 0, "Enable alternative break to debugger");
136 * Flag to indicate to debuggers why the debugger was entered.
138 const char * volatile kdb_why = KDB_WHY_UNSET;
141 kdb_sysctl_available(SYSCTL_HANDLER_ARGS)
143 struct kdb_dbbe **iter;
147 sbuf_new_for_sysctl(&sbuf, NULL, 64, req);
148 SET_FOREACH(iter, kdb_dbbe_set) {
149 if ((*iter)->dbbe_active == 0)
150 sbuf_printf(&sbuf, "%s ", (*iter)->dbbe_name);
152 error = sbuf_finish(&sbuf);
158 kdb_sysctl_current(SYSCTL_HANDLER_ARGS)
163 if (kdb_dbbe != NULL)
164 strlcpy(buf, kdb_dbbe->dbbe_name, sizeof(buf));
167 error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
168 if (error != 0 || req->newptr == NULL)
172 return (kdb_dbbe_select(buf));
176 kdb_sysctl_enter(SYSCTL_HANDLER_ARGS)
180 error = sysctl_wire_old_buffer(req, sizeof(int));
183 error = sysctl_handle_int(oidp, &i, 0, req);
185 if (error != 0 || req->newptr == NULL)
189 kdb_enter(KDB_WHY_SYSCTL, "sysctl debug.kdb.enter");
194 kdb_sysctl_panic(SYSCTL_HANDLER_ARGS)
198 error = sysctl_wire_old_buffer(req, sizeof(int));
201 error = sysctl_handle_int(oidp, &i, 0, req);
203 if (error != 0 || req->newptr == NULL)
205 panic("kdb_sysctl_panic");
210 kdb_sysctl_trap(SYSCTL_HANDLER_ARGS)
213 int *addr = (int *)0x10;
215 error = sysctl_wire_old_buffer(req, sizeof(int));
218 error = sysctl_handle_int(oidp, &i, 0, req);
220 if (error != 0 || req->newptr == NULL)
226 kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS)
229 void (*fp)(u_int, u_int, u_int) = (void *)0xdeadc0de;
231 error = sysctl_wire_old_buffer(req, sizeof(int));
234 error = sysctl_handle_int(oidp, &i, 0, req);
236 if (error != 0 || req->newptr == NULL)
238 (*fp)(0x11111111, 0x22222222, 0x33333333);
242 static void kdb_stack_overflow(volatile int *x) __noinline;
244 kdb_stack_overflow(volatile int *x)
249 kdb_stack_overflow(x);
250 *x += PCPU_GET(cpuid) / 1000000;
254 kdb_sysctl_stack_overflow(SYSCTL_HANDLER_ARGS)
259 error = sysctl_wire_old_buffer(req, sizeof(int));
262 error = sysctl_handle_int(oidp, &i, 0, req);
264 if (error != 0 || req->newptr == NULL)
267 kdb_stack_overflow(&x);
272 kdb_panic(const char *msg)
275 printf("KDB: panic\n");
283 printf("KDB: reboot requested\n");
288 * Solaris implements a new BREAK which is initiated by a character sequence
289 * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the
292 * Note that this function may be called from almost anywhere, with interrupts
293 * disabled and with unknown locks held, so it must not access data other than
294 * its arguments. Its up to the caller to ensure that the state variable is
297 #define KEY_CR 13 /* CR '\r' */
298 #define KEY_TILDE 126 /* ~ */
299 #define KEY_CRTLB 2 /* ^B */
300 #define KEY_CRTLP 16 /* ^P */
301 #define KEY_CRTLR 18 /* ^R */
303 /* States of th KDB "alternate break sequence" detecting state machine. */
305 KDB_ALT_BREAK_SEEN_NONE,
306 KDB_ALT_BREAK_SEEN_CR,
307 KDB_ALT_BREAK_SEEN_CR_TILDE,
314 if (!kdb_break_to_debugger)
316 kdb_enter(KDB_WHY_BREAK, "Break to debugger");
317 return (KDB_REQ_DEBUGGER);
321 kdb_alt_break_state(int key, int *state)
325 /* All states transition to KDB_ALT_BREAK_SEEN_CR on a CR. */
327 *state = KDB_ALT_BREAK_SEEN_CR;
333 case KDB_ALT_BREAK_SEEN_CR:
334 *state = KDB_ALT_BREAK_SEEN_NONE;
335 if (key == KEY_TILDE)
336 *state = KDB_ALT_BREAK_SEEN_CR_TILDE;
338 case KDB_ALT_BREAK_SEEN_CR_TILDE:
339 *state = KDB_ALT_BREAK_SEEN_NONE;
340 if (key == KEY_CRTLB)
341 brk = KDB_REQ_DEBUGGER;
342 else if (key == KEY_CRTLP)
344 else if (key == KEY_CRTLR)
345 brk = KDB_REQ_REBOOT;
347 case KDB_ALT_BREAK_SEEN_NONE:
349 *state = KDB_ALT_BREAK_SEEN_NONE;
356 kdb_alt_break_internal(int key, int *state, int force_gdb)
360 if (!kdb_alt_break_to_debugger)
362 brk = kdb_alt_break_state(key, state);
364 case KDB_REQ_DEBUGGER:
366 kdb_dbbe_select("gdb");
367 kdb_enter(KDB_WHY_BREAK, "Break to debugger");
372 kdb_dbbe_select("gdb");
373 kdb_panic("Panic sequence on console");
384 kdb_alt_break(int key, int *state)
387 return (kdb_alt_break_internal(key, state, 0));
391 * This variation on kdb_alt_break() is used only by dcons, which has its own
392 * configuration flag to force GDB use regardless of the global KDB
396 kdb_alt_break_gdb(int key, int *state)
399 return (kdb_alt_break_internal(key, state, 1));
403 * Print a backtrace of the calling thread. The backtrace is generated by
404 * the selected debugger, provided it supports backtraces. If no debugger
405 * is selected or the current debugger does not support backtraces, this
406 * function silently returns.
412 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) {
413 printf("KDB: stack backtrace:\n");
414 kdb_dbbe->dbbe_trace();
420 printf("KDB: stack backtrace:\n");
423 stack_print_ddb(&st);
429 * Similar to kdb_backtrace() except that it prints a backtrace of an
430 * arbitrary thread rather than the calling thread.
433 kdb_backtrace_thread(struct thread *td)
436 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace_thread != NULL) {
437 printf("KDB: stack backtrace of thread %d:\n", td->td_tid);
438 kdb_dbbe->dbbe_trace_thread(td);
444 printf("KDB: stack backtrace of thread %d:\n", td->td_tid);
445 if (stack_save_td(&st, td) == 0)
446 stack_print_ddb(&st);
452 * Set/change the current backend.
455 kdb_dbbe_select(const char *name)
457 struct kdb_dbbe *be, **iter;
459 SET_FOREACH(iter, kdb_dbbe_set) {
461 if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) {
470 * Enter the currently selected debugger. If a message has been provided,
471 * it is printed first. If the debugger does not support the enter method,
472 * it is entered by using breakpoint(), which enters the debugger through
473 * kdb_trap(). The 'why' argument will contain a more mechanically usable
474 * string than 'msg', and is relied upon by DDB scripting to identify the
475 * reason for entering the debugger so that the right script can be run.
478 kdb_enter(const char *why, const char *msg)
481 if (kdb_dbbe != NULL && kdb_active == 0) {
483 printf("KDB: enter: %s\n", msg);
486 kdb_why = KDB_WHY_UNSET;
491 * Initialize the kernel debugger interface.
496 struct kdb_dbbe *be, **iter;
502 SET_FOREACH(iter, kdb_dbbe_set) {
504 pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1;
505 be->dbbe_active = (pri >= 0) ? 0 : -1;
511 if (kdb_dbbe != NULL) {
512 printf("KDB: debugger backends:");
513 SET_FOREACH(iter, kdb_dbbe_set) {
515 if (be->dbbe_active == 0)
516 printf(" %s", be->dbbe_name);
519 printf("KDB: current backend: %s\n",
520 kdb_dbbe->dbbe_name);
528 kdb_jmpbuf(jmp_buf new)
541 if (!kdb_active || kdb_jmpbufp == NULL)
544 printf("KDB: reentering\n");
546 longjmp(kdb_jmpbufp, 1);
551 kdb_reenter_silent(void)
554 if (!kdb_active || kdb_jmpbufp == NULL)
557 longjmp(kdb_jmpbufp, 1);
562 * Thread-related support functions.
565 kdb_thr_ctx(struct thread *thr)
567 #if defined(SMP) && defined(KDB_STOPPEDPCB)
571 if (thr == curthread)
574 #if defined(SMP) && defined(KDB_STOPPEDPCB)
575 STAILQ_FOREACH(pc, &cpuhead, pc_allcpu) {
576 if (pc->pc_curthread == thr &&
577 CPU_ISSET(pc->pc_cpuid, &stopped_cpus))
578 return (KDB_STOPPEDPCB(pc));
581 return (thr->td_pcb);
590 FOREACH_PROC_IN_SYSTEM(p) {
591 if (p->p_flag & P_INMEM) {
592 thr = FIRST_THREAD_IN_PROC(p);
601 kdb_thr_from_pid(pid_t pid)
605 FOREACH_PROC_IN_SYSTEM(p) {
606 if (p->p_flag & P_INMEM && p->p_pid == pid)
607 return (FIRST_THREAD_IN_PROC(p));
613 kdb_thr_lookup(lwpid_t tid)
617 thr = kdb_thr_first();
618 while (thr != NULL && thr->td_tid != tid)
619 thr = kdb_thr_next(thr);
624 kdb_thr_next(struct thread *thr)
629 thr = TAILQ_NEXT(thr, td_plist);
633 p = LIST_NEXT(p, p_list);
634 if (p != NULL && (p->p_flag & P_INMEM))
635 thr = FIRST_THREAD_IN_PROC(p);
641 kdb_thr_select(struct thread *thr)
646 kdb_thrctx = kdb_thr_ctx(thr);
651 * Enter the debugger due to a trap.
654 kdb_trap(int type, int code, struct trapframe *tf)
665 if (be == NULL || be->dbbe_trap == NULL)
668 /* We reenter the debugger through kdb_reenter(). */
672 intr = intr_disable();
674 if (!SCHEDULER_STOPPED()) {
676 other_cpus = all_cpus;
677 CPU_ANDNOT(&other_cpus, &stopped_cpus);
678 CPU_CLR(PCPU_GET(cpuid), &other_cpus);
679 stop_cpus_hard(other_cpus);
681 curthread->td_stopsched = 1;
690 /* Let MD code do its thing first... */
691 kdb_cpu_trap(type, code);
693 makectx(tf, &kdb_pcb);
694 kdb_thr_select(curthread);
699 handled = be->dbbe_trap(type, code);
703 if (be == NULL || be->dbbe_trap == NULL)
705 printf("Switching to %s back-end\n", be->dbbe_name);
713 curthread->td_stopsched = 0;
715 CPU_AND(&other_cpus, &stopped_cpus);
716 restart_cpus(other_cpus);