2 * SPDX-License-Identifier: BSD-2-Clause
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>
47 #include <sys/stack.h>
48 #include <sys/sysctl.h>
49 #include <sys/tslog.h>
51 #include <machine/kdb.h>
52 #include <machine/pcb.h>
55 #include <machine/smp.h>
58 #include <security/mac/mac_framework.h>
60 u_char __read_frequently kdb_active = 0;
61 static void *kdb_jmpbufp = NULL;
62 struct kdb_dbbe *kdb_dbbe = NULL;
63 static struct pcb kdb_pcb;
64 struct pcb *kdb_thrctx = NULL;
65 struct thread *kdb_thread = NULL;
66 struct trapframe *kdb_frame = NULL;
68 #ifdef BREAK_TO_DEBUGGER
69 #define KDB_BREAK_TO_DEBUGGER 1
71 #define KDB_BREAK_TO_DEBUGGER 0
74 #ifdef ALT_BREAK_TO_DEBUGGER
75 #define KDB_ALT_BREAK_TO_DEBUGGER 1
77 #define KDB_ALT_BREAK_TO_DEBUGGER 0
80 static int kdb_break_to_debugger = KDB_BREAK_TO_DEBUGGER;
81 static int kdb_alt_break_to_debugger = KDB_ALT_BREAK_TO_DEBUGGER;
82 static int kdb_enter_securelevel = 0;
84 KDB_BACKEND(null, NULL, NULL, NULL, NULL);
86 static int kdb_sysctl_available(SYSCTL_HANDLER_ARGS);
87 static int kdb_sysctl_current(SYSCTL_HANDLER_ARGS);
88 static int kdb_sysctl_enter(SYSCTL_HANDLER_ARGS);
89 static int kdb_sysctl_panic(SYSCTL_HANDLER_ARGS);
90 static int kdb_sysctl_panic_str(SYSCTL_HANDLER_ARGS);
91 static int kdb_sysctl_trap(SYSCTL_HANDLER_ARGS);
92 static int kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS);
93 static int kdb_sysctl_stack_overflow(SYSCTL_HANDLER_ARGS);
95 static SYSCTL_NODE(_debug, OID_AUTO, kdb, CTLFLAG_RW | CTLFLAG_MPSAFE, NULL,
98 SYSCTL_PROC(_debug_kdb, OID_AUTO, available,
99 CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 0,
100 kdb_sysctl_available, "A",
101 "list of available KDB backends");
103 SYSCTL_PROC(_debug_kdb, OID_AUTO, current,
104 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE, NULL, 0,
105 kdb_sysctl_current, "A",
106 "currently selected KDB backend");
108 SYSCTL_PROC(_debug_kdb, OID_AUTO, enter,
109 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE, NULL, 0,
110 kdb_sysctl_enter, "I",
111 "set to enter the debugger");
113 SYSCTL_PROC(_debug_kdb, OID_AUTO, panic,
114 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
115 kdb_sysctl_panic, "I",
116 "set to panic the kernel");
118 SYSCTL_PROC(_debug_kdb, OID_AUTO, panic_str,
119 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
120 kdb_sysctl_panic_str, "A",
121 "trigger a kernel panic, using the provided string as the panic message");
123 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap,
124 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
125 kdb_sysctl_trap, "I",
126 "set to cause a page fault via data access");
128 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap_code,
129 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
130 kdb_sysctl_trap_code, "I",
131 "set to cause a page fault via code access");
133 SYSCTL_PROC(_debug_kdb, OID_AUTO, stack_overflow,
134 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
135 kdb_sysctl_stack_overflow, "I",
136 "set to cause a stack overflow");
138 SYSCTL_INT(_debug_kdb, OID_AUTO, break_to_debugger,
140 &kdb_break_to_debugger, 0, "Enable break to debugger");
142 SYSCTL_INT(_debug_kdb, OID_AUTO, alt_break_to_debugger,
144 &kdb_alt_break_to_debugger, 0, "Enable alternative break to debugger");
146 SYSCTL_INT(_debug_kdb, OID_AUTO, enter_securelevel,
147 CTLFLAG_RWTUN | CTLFLAG_SECURE,
148 &kdb_enter_securelevel, 0,
149 "Maximum securelevel to enter a KDB backend");
152 * Flag to indicate to debuggers why the debugger was entered.
154 const char * volatile kdb_why = KDB_WHY_UNSET;
157 kdb_sysctl_available(SYSCTL_HANDLER_ARGS)
159 struct kdb_dbbe **iter;
163 sbuf_new_for_sysctl(&sbuf, NULL, 64, req);
164 SET_FOREACH(iter, kdb_dbbe_set) {
165 if ((*iter)->dbbe_active == 0)
166 sbuf_printf(&sbuf, "%s ", (*iter)->dbbe_name);
168 error = sbuf_finish(&sbuf);
174 kdb_sysctl_current(SYSCTL_HANDLER_ARGS)
179 if (kdb_dbbe != NULL)
180 strlcpy(buf, kdb_dbbe->dbbe_name, sizeof(buf));
183 error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
184 if (error != 0 || req->newptr == NULL)
188 return (kdb_dbbe_select(buf));
192 kdb_sysctl_enter(SYSCTL_HANDLER_ARGS)
196 error = sysctl_wire_old_buffer(req, sizeof(int));
199 error = sysctl_handle_int(oidp, &i, 0, req);
201 if (error != 0 || req->newptr == NULL)
205 kdb_enter(KDB_WHY_SYSCTL, "sysctl debug.kdb.enter");
210 kdb_sysctl_panic(SYSCTL_HANDLER_ARGS)
214 error = sysctl_wire_old_buffer(req, sizeof(int));
217 error = sysctl_handle_int(oidp, &i, 0, req);
219 if (error != 0 || req->newptr == NULL)
221 panic("kdb_sysctl_panic");
226 kdb_sysctl_panic_str(SYSCTL_HANDLER_ARGS)
229 static char buf[256]; /* static buffer to limit mallocs when panicing */
232 error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
233 if (error != 0 || req->newptr == NULL)
235 panic("kdb_sysctl_panic: %s", buf);
240 kdb_sysctl_trap(SYSCTL_HANDLER_ARGS)
243 int *addr = (int *)0x10;
245 error = sysctl_wire_old_buffer(req, sizeof(int));
248 error = sysctl_handle_int(oidp, &i, 0, req);
250 if (error != 0 || req->newptr == NULL)
256 kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS)
259 void (*fp)(u_int, u_int, u_int) = (void *)0xdeadc0de;
261 error = sysctl_wire_old_buffer(req, sizeof(int));
264 error = sysctl_handle_int(oidp, &i, 0, req);
266 if (error != 0 || req->newptr == NULL)
268 (*fp)(0x11111111, 0x22222222, 0x33333333);
272 static void kdb_stack_overflow(volatile int *x) __noinline;
274 kdb_stack_overflow(volatile int *x)
279 kdb_stack_overflow(x);
280 *x += PCPU_GET(cpuid) / 1000000;
284 kdb_sysctl_stack_overflow(SYSCTL_HANDLER_ARGS)
289 error = sysctl_wire_old_buffer(req, sizeof(int));
292 error = sysctl_handle_int(oidp, &i, 0, req);
294 if (error != 0 || req->newptr == NULL)
297 kdb_stack_overflow(&x);
302 kdb_panic(const char *msg)
305 kdb_why = KDB_WHY_PANIC;
306 printf("KDB: panic\n");
314 kdb_why = KDB_WHY_REBOOT;
315 printf("KDB: reboot requested\n");
320 * Solaris implements a new BREAK which is initiated by a character sequence
321 * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the
324 * Note that this function may be called from almost anywhere, with interrupts
325 * disabled and with unknown locks held, so it must not access data other than
326 * its arguments. Its up to the caller to ensure that the state variable is
329 #define KEY_CR 13 /* CR '\r' */
330 #define KEY_TILDE 126 /* ~ */
331 #define KEY_CRTLB 2 /* ^B */
332 #define KEY_CRTLP 16 /* ^P */
333 #define KEY_CRTLR 18 /* ^R */
335 /* States of th KDB "alternate break sequence" detecting state machine. */
337 KDB_ALT_BREAK_SEEN_NONE,
338 KDB_ALT_BREAK_SEEN_CR,
339 KDB_ALT_BREAK_SEEN_CR_TILDE,
346 if (!kdb_break_to_debugger)
348 kdb_enter(KDB_WHY_BREAK, "Break to debugger");
349 return (KDB_REQ_DEBUGGER);
353 kdb_alt_break_state(int key, int *state)
357 /* All states transition to KDB_ALT_BREAK_SEEN_CR on a CR. */
359 *state = KDB_ALT_BREAK_SEEN_CR;
365 case KDB_ALT_BREAK_SEEN_CR:
366 *state = KDB_ALT_BREAK_SEEN_NONE;
367 if (key == KEY_TILDE)
368 *state = KDB_ALT_BREAK_SEEN_CR_TILDE;
370 case KDB_ALT_BREAK_SEEN_CR_TILDE:
371 *state = KDB_ALT_BREAK_SEEN_NONE;
372 if (key == KEY_CRTLB)
373 brk = KDB_REQ_DEBUGGER;
374 else if (key == KEY_CRTLP)
376 else if (key == KEY_CRTLR)
377 brk = KDB_REQ_REBOOT;
379 case KDB_ALT_BREAK_SEEN_NONE:
381 *state = KDB_ALT_BREAK_SEEN_NONE;
388 kdb_alt_break_internal(int key, int *state, int force_gdb)
392 if (!kdb_alt_break_to_debugger)
394 brk = kdb_alt_break_state(key, state);
396 case KDB_REQ_DEBUGGER:
398 kdb_dbbe_select("gdb");
399 kdb_enter(KDB_WHY_BREAK, "Break to debugger");
404 kdb_dbbe_select("gdb");
405 kdb_panic("Panic sequence on console");
416 kdb_alt_break(int key, int *state)
419 return (kdb_alt_break_internal(key, state, 0));
423 * This variation on kdb_alt_break() is used only by dcons, which has its own
424 * configuration flag to force GDB use regardless of the global KDB
428 kdb_alt_break_gdb(int key, int *state)
431 return (kdb_alt_break_internal(key, state, 1));
435 * Print a backtrace of the calling thread. The backtrace is generated by
436 * the selected debugger, provided it supports backtraces. If no debugger
437 * is selected or the current debugger does not support backtraces, this
438 * function silently returns.
444 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) {
445 printf("KDB: stack backtrace:\n");
446 kdb_dbbe->dbbe_trace();
452 printf("KDB: stack backtrace:\n");
454 stack_print_ddb(&st);
460 * Similar to kdb_backtrace() except that it prints a backtrace of an
461 * arbitrary thread rather than the calling thread.
464 kdb_backtrace_thread(struct thread *td)
467 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace_thread != NULL) {
468 printf("KDB: stack backtrace of thread %d:\n", td->td_tid);
469 kdb_dbbe->dbbe_trace_thread(td);
475 printf("KDB: stack backtrace of thread %d:\n", td->td_tid);
476 if (stack_save_td(&st, td) == 0)
477 stack_print_ddb(&st);
483 * Set/change the current backend.
486 kdb_dbbe_select(const char *name)
488 struct kdb_dbbe *be, **iter;
491 error = priv_check(curthread, PRIV_KDB_SET_BACKEND);
495 SET_FOREACH(iter, kdb_dbbe_set) {
497 if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) {
506 kdb_backend_permitted(struct kdb_dbbe *be, struct ucred *cred)
510 error = securelevel_gt(cred, kdb_enter_securelevel);
513 * Give MAC a chance to weigh in on the policy: if the securelevel is
514 * not raised, then MAC may veto the backend, otherwise MAC may
515 * explicitly grant access.
518 error = mac_kdb_check_backend(be);
520 printf("MAC prevented execution of KDB backend: %s\n",
524 } else if (mac_kdb_grant_backend(be) == 0) {
529 printf("refusing to enter KDB with elevated securelevel\n");
534 * Enter the currently selected debugger. If a message has been provided,
535 * it is printed first. If the debugger does not support the enter method,
536 * it is entered by using breakpoint(), which enters the debugger through
537 * kdb_trap(). The 'why' argument will contain a more mechanically usable
538 * string than 'msg', and is relied upon by DDB scripting to identify the
539 * reason for entering the debugger so that the right script can be run.
542 kdb_enter(const char *why, const char *msg)
545 if (kdb_dbbe != NULL && kdb_active == 0) {
548 printf("KDB: enter: %s\n", msg);
550 kdb_why = KDB_WHY_UNSET;
555 * Initialize the kernel debugger interface.
560 struct kdb_dbbe *be, **iter;
567 SET_FOREACH(iter, kdb_dbbe_set) {
569 pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1;
570 be->dbbe_active = (pri >= 0) ? 0 : -1;
576 if (kdb_dbbe != NULL) {
577 printf("KDB: debugger backends:");
578 SET_FOREACH(iter, kdb_dbbe_set) {
580 if (be->dbbe_active == 0)
581 printf(" %s", be->dbbe_name);
584 printf("KDB: current backend: %s\n",
585 kdb_dbbe->dbbe_name);
594 kdb_jmpbuf(jmp_buf new)
607 if (!kdb_active || kdb_jmpbufp == NULL)
610 printf("KDB: reentering\n");
612 longjmp(kdb_jmpbufp, 1);
617 kdb_reenter_silent(void)
620 if (!kdb_active || kdb_jmpbufp == NULL)
623 longjmp(kdb_jmpbufp, 1);
628 * Thread-related support functions.
631 kdb_thr_ctx(struct thread *thr)
637 if (thr == curthread)
641 STAILQ_FOREACH(pc, &cpuhead, pc_allcpu) {
642 if (pc->pc_curthread == thr &&
643 CPU_ISSET(pc->pc_cpuid, &stopped_cpus))
644 return (&stoppcbs[pc->pc_cpuid]);
647 return (thr->td_pcb);
657 /* This function may be called early. */
658 if (pidhashtbl == NULL)
661 for (i = 0; i <= pidhash; i++) {
662 LIST_FOREACH(p, &pidhashtbl[i], p_hash) {
663 thr = FIRST_THREAD_IN_PROC(p);
672 kdb_thr_from_pid(pid_t pid)
676 LIST_FOREACH(p, PIDHASH(pid), p_hash) {
678 return (FIRST_THREAD_IN_PROC(p));
684 kdb_thr_lookup(lwpid_t tid)
688 thr = kdb_thr_first();
689 while (thr != NULL && thr->td_tid != tid)
690 thr = kdb_thr_next(thr);
695 kdb_thr_next(struct thread *thr)
701 thr = TAILQ_NEXT(thr, td_plist);
704 if (pidhashtbl == NULL)
706 hash = p->p_pid & pidhash;
708 p = LIST_NEXT(p, p_hash);
710 if (++hash > pidhash)
712 p = LIST_FIRST(&pidhashtbl[hash]);
714 thr = FIRST_THREAD_IN_PROC(p);
721 kdb_thr_select(struct thread *thr)
726 kdb_thrctx = kdb_thr_ctx(thr);
731 * Enter the debugger due to a trap.
734 kdb_trap(int type, int code, struct trapframe *tf)
745 if (be == NULL || be->dbbe_trap == NULL)
748 /* We reenter the debugger through kdb_reenter(). */
752 intr = intr_disable();
754 if (!SCHEDULER_STOPPED()) {
756 other_cpus = all_cpus;
757 CPU_ANDNOT(&other_cpus, &other_cpus, &stopped_cpus);
758 CPU_CLR(PCPU_GET(cpuid), &other_cpus);
759 stop_cpus_hard(other_cpus);
761 curthread->td_stopsched = 1;
770 /* Let MD code do its thing first... */
771 kdb_cpu_trap(type, code);
773 makectx(tf, &kdb_pcb);
774 kdb_thr_select(curthread);
779 if (!kdb_backend_permitted(be, curthread->td_ucred)) {
780 /* Unhandled breakpoint traps are fatal. */
784 handled = be->dbbe_trap(type, code);
788 if (be == NULL || be->dbbe_trap == NULL)
790 printf("Switching to %s back-end\n", be->dbbe_name);
798 curthread->td_stopsched = 0;
800 CPU_AND(&other_cpus, &other_cpus, &stopped_cpus);
801 restart_cpus(other_cpus);