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>
31 #include "opt_stack.h"
33 #include <sys/param.h>
34 #include <sys/systm.h>
37 #include <sys/kernel.h>
38 #include <sys/malloc.h>
45 #include <sys/stack.h>
46 #include <sys/sysctl.h>
47 #include <sys/tslog.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;
80 static int kdb_enter_securelevel = 0;
82 KDB_BACKEND(null, NULL, NULL, NULL, NULL);
84 static int kdb_sysctl_available(SYSCTL_HANDLER_ARGS);
85 static int kdb_sysctl_current(SYSCTL_HANDLER_ARGS);
86 static int kdb_sysctl_enter(SYSCTL_HANDLER_ARGS);
87 static int kdb_sysctl_panic(SYSCTL_HANDLER_ARGS);
88 static int kdb_sysctl_panic_str(SYSCTL_HANDLER_ARGS);
89 static int kdb_sysctl_trap(SYSCTL_HANDLER_ARGS);
90 static int kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS);
91 static int kdb_sysctl_stack_overflow(SYSCTL_HANDLER_ARGS);
93 static SYSCTL_NODE(_debug, OID_AUTO, kdb, CTLFLAG_RW | CTLFLAG_MPSAFE, NULL,
96 SYSCTL_PROC(_debug_kdb, OID_AUTO, available,
97 CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 0,
98 kdb_sysctl_available, "A",
99 "list of available KDB backends");
101 SYSCTL_PROC(_debug_kdb, OID_AUTO, current,
102 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE, NULL, 0,
103 kdb_sysctl_current, "A",
104 "currently selected KDB backend");
106 SYSCTL_PROC(_debug_kdb, OID_AUTO, enter,
107 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE, NULL, 0,
108 kdb_sysctl_enter, "I",
109 "set to enter the debugger");
111 SYSCTL_PROC(_debug_kdb, OID_AUTO, panic,
112 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
113 kdb_sysctl_panic, "I",
114 "set to panic the kernel");
116 SYSCTL_PROC(_debug_kdb, OID_AUTO, panic_str,
117 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
118 kdb_sysctl_panic_str, "A",
119 "trigger a kernel panic, using the provided string as the panic message");
121 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap,
122 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
123 kdb_sysctl_trap, "I",
124 "set to cause a page fault via data access");
126 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap_code,
127 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
128 kdb_sysctl_trap_code, "I",
129 "set to cause a page fault via code access");
131 SYSCTL_PROC(_debug_kdb, OID_AUTO, stack_overflow,
132 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
133 kdb_sysctl_stack_overflow, "I",
134 "set to cause a stack overflow");
136 SYSCTL_INT(_debug_kdb, OID_AUTO, break_to_debugger,
138 &kdb_break_to_debugger, 0, "Enable break to debugger");
140 SYSCTL_INT(_debug_kdb, OID_AUTO, alt_break_to_debugger,
142 &kdb_alt_break_to_debugger, 0, "Enable alternative break to debugger");
144 SYSCTL_INT(_debug_kdb, OID_AUTO, enter_securelevel,
145 CTLFLAG_RWTUN | CTLFLAG_SECURE,
146 &kdb_enter_securelevel, 0,
147 "Maximum securelevel to enter a KDB backend");
150 * Flag to indicate to debuggers why the debugger was entered.
152 const char * volatile kdb_why = KDB_WHY_UNSET;
155 kdb_sysctl_available(SYSCTL_HANDLER_ARGS)
157 struct kdb_dbbe **iter;
161 sbuf_new_for_sysctl(&sbuf, NULL, 64, req);
162 SET_FOREACH(iter, kdb_dbbe_set) {
163 if ((*iter)->dbbe_active == 0)
164 sbuf_printf(&sbuf, "%s ", (*iter)->dbbe_name);
166 error = sbuf_finish(&sbuf);
172 kdb_sysctl_current(SYSCTL_HANDLER_ARGS)
177 if (kdb_dbbe != NULL)
178 strlcpy(buf, kdb_dbbe->dbbe_name, sizeof(buf));
181 error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
182 if (error != 0 || req->newptr == NULL)
186 return (kdb_dbbe_select(buf));
190 kdb_sysctl_enter(SYSCTL_HANDLER_ARGS)
194 error = sysctl_wire_old_buffer(req, sizeof(int));
197 error = sysctl_handle_int(oidp, &i, 0, req);
199 if (error != 0 || req->newptr == NULL)
203 kdb_enter(KDB_WHY_SYSCTL, "sysctl debug.kdb.enter");
208 kdb_sysctl_panic(SYSCTL_HANDLER_ARGS)
212 error = sysctl_wire_old_buffer(req, sizeof(int));
215 error = sysctl_handle_int(oidp, &i, 0, req);
217 if (error != 0 || req->newptr == NULL)
219 panic("kdb_sysctl_panic");
224 kdb_sysctl_panic_str(SYSCTL_HANDLER_ARGS)
227 static char buf[256]; /* static buffer to limit mallocs when panicing */
230 error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
231 if (error != 0 || req->newptr == NULL)
233 panic("kdb_sysctl_panic: %s", buf);
238 kdb_sysctl_trap(SYSCTL_HANDLER_ARGS)
241 int *addr = (int *)0x10;
243 error = sysctl_wire_old_buffer(req, sizeof(int));
246 error = sysctl_handle_int(oidp, &i, 0, req);
248 if (error != 0 || req->newptr == NULL)
254 kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS)
257 void (*fp)(u_int, u_int, u_int) = (void *)0xdeadc0de;
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)
266 (*fp)(0x11111111, 0x22222222, 0x33333333);
270 static void kdb_stack_overflow(volatile int *x) __noinline;
272 kdb_stack_overflow(volatile int *x)
277 kdb_stack_overflow(x);
278 *x += PCPU_GET(cpuid) / 1000000;
282 kdb_sysctl_stack_overflow(SYSCTL_HANDLER_ARGS)
287 error = sysctl_wire_old_buffer(req, sizeof(int));
290 error = sysctl_handle_int(oidp, &i, 0, req);
292 if (error != 0 || req->newptr == NULL)
295 kdb_stack_overflow(&x);
300 kdb_panic(const char *msg)
303 kdb_why = KDB_WHY_PANIC;
304 printf("KDB: panic\n");
312 kdb_why = KDB_WHY_REBOOT;
313 printf("KDB: reboot requested\n");
318 * Solaris implements a new BREAK which is initiated by a character sequence
319 * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the
322 * Note that this function may be called from almost anywhere, with interrupts
323 * disabled and with unknown locks held, so it must not access data other than
324 * its arguments. Its up to the caller to ensure that the state variable is
327 #define KEY_CR 13 /* CR '\r' */
328 #define KEY_TILDE 126 /* ~ */
329 #define KEY_CRTLB 2 /* ^B */
330 #define KEY_CRTLP 16 /* ^P */
331 #define KEY_CRTLR 18 /* ^R */
333 /* States of th KDB "alternate break sequence" detecting state machine. */
335 KDB_ALT_BREAK_SEEN_NONE,
336 KDB_ALT_BREAK_SEEN_CR,
337 KDB_ALT_BREAK_SEEN_CR_TILDE,
344 if (!kdb_break_to_debugger)
346 kdb_enter(KDB_WHY_BREAK, "Break to debugger");
347 return (KDB_REQ_DEBUGGER);
351 kdb_alt_break_state(int key, int *state)
355 /* All states transition to KDB_ALT_BREAK_SEEN_CR on a CR. */
357 *state = KDB_ALT_BREAK_SEEN_CR;
363 case KDB_ALT_BREAK_SEEN_CR:
364 *state = KDB_ALT_BREAK_SEEN_NONE;
365 if (key == KEY_TILDE)
366 *state = KDB_ALT_BREAK_SEEN_CR_TILDE;
368 case KDB_ALT_BREAK_SEEN_CR_TILDE:
369 *state = KDB_ALT_BREAK_SEEN_NONE;
370 if (key == KEY_CRTLB)
371 brk = KDB_REQ_DEBUGGER;
372 else if (key == KEY_CRTLP)
374 else if (key == KEY_CRTLR)
375 brk = KDB_REQ_REBOOT;
377 case KDB_ALT_BREAK_SEEN_NONE:
379 *state = KDB_ALT_BREAK_SEEN_NONE;
386 kdb_alt_break_internal(int key, int *state, int force_gdb)
390 if (!kdb_alt_break_to_debugger)
392 brk = kdb_alt_break_state(key, state);
394 case KDB_REQ_DEBUGGER:
396 kdb_dbbe_select("gdb");
397 kdb_enter(KDB_WHY_BREAK, "Break to debugger");
402 kdb_dbbe_select("gdb");
403 kdb_panic("Panic sequence on console");
414 kdb_alt_break(int key, int *state)
417 return (kdb_alt_break_internal(key, state, 0));
421 * This variation on kdb_alt_break() is used only by dcons, which has its own
422 * configuration flag to force GDB use regardless of the global KDB
426 kdb_alt_break_gdb(int key, int *state)
429 return (kdb_alt_break_internal(key, state, 1));
433 * Print a backtrace of the calling thread. The backtrace is generated by
434 * the selected debugger, provided it supports backtraces. If no debugger
435 * is selected or the current debugger does not support backtraces, this
436 * function silently returns.
442 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) {
443 printf("KDB: stack backtrace:\n");
444 kdb_dbbe->dbbe_trace();
450 printf("KDB: stack backtrace:\n");
452 stack_print_ddb(&st);
458 * Similar to kdb_backtrace() except that it prints a backtrace of an
459 * arbitrary thread rather than the calling thread.
462 kdb_backtrace_thread(struct thread *td)
465 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace_thread != NULL) {
466 printf("KDB: stack backtrace of thread %d:\n", td->td_tid);
467 kdb_dbbe->dbbe_trace_thread(td);
473 printf("KDB: stack backtrace of thread %d:\n", td->td_tid);
474 if (stack_save_td(&st, td) == 0)
475 stack_print_ddb(&st);
481 * Set/change the current backend.
484 kdb_dbbe_select(const char *name)
486 struct kdb_dbbe *be, **iter;
489 error = priv_check(curthread, PRIV_KDB_SET_BACKEND);
493 SET_FOREACH(iter, kdb_dbbe_set) {
495 if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) {
504 kdb_backend_permitted(struct kdb_dbbe *be, struct thread *td)
511 KASSERT(td == &thread0 && cold,
512 ("%s: missing cred for %p", __func__, td));
515 error = securelevel_gt(cred, kdb_enter_securelevel);
519 * Give MAC a chance to weigh in on the policy: if the securelevel is
520 * not raised, then MAC may veto the backend, otherwise MAC may
521 * explicitly grant access.
524 error = mac_kdb_check_backend(be);
526 printf("MAC prevented execution of KDB backend: %s\n",
530 } else if (mac_kdb_grant_backend(be) == 0) {
535 printf("refusing to enter KDB with elevated securelevel\n");
540 * Enter the currently selected debugger. If a message has been provided,
541 * it is printed first. If the debugger does not support the enter method,
542 * it is entered by using breakpoint(), which enters the debugger through
543 * kdb_trap(). The 'why' argument will contain a more mechanically usable
544 * string than 'msg', and is relied upon by DDB scripting to identify the
545 * reason for entering the debugger so that the right script can be run.
548 kdb_enter(const char *why, const char *msg)
551 if (kdb_dbbe != NULL && kdb_active == 0) {
554 printf("KDB: enter: %s\n", msg);
556 kdb_why = KDB_WHY_UNSET;
561 * Initialize the kernel debugger interface.
566 struct kdb_dbbe *be, **iter;
573 SET_FOREACH(iter, kdb_dbbe_set) {
575 pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1;
576 be->dbbe_active = (pri >= 0) ? 0 : -1;
582 if (kdb_dbbe != NULL) {
583 printf("KDB: debugger backends:");
584 SET_FOREACH(iter, kdb_dbbe_set) {
586 if (be->dbbe_active == 0)
587 printf(" %s", be->dbbe_name);
590 printf("KDB: current backend: %s\n",
591 kdb_dbbe->dbbe_name);
600 kdb_jmpbuf(jmp_buf new)
613 if (!kdb_active || kdb_jmpbufp == NULL)
616 printf("KDB: reentering\n");
618 longjmp(kdb_jmpbufp, 1);
623 kdb_reenter_silent(void)
626 if (!kdb_active || kdb_jmpbufp == NULL)
629 longjmp(kdb_jmpbufp, 1);
634 * Thread-related support functions.
637 kdb_thr_ctx(struct thread *thr)
643 if (thr == curthread)
647 STAILQ_FOREACH(pc, &cpuhead, pc_allcpu) {
648 if (pc->pc_curthread == thr &&
649 CPU_ISSET(pc->pc_cpuid, &stopped_cpus))
650 return (&stoppcbs[pc->pc_cpuid]);
653 return (thr->td_pcb);
663 /* This function may be called early. */
664 if (pidhashtbl == NULL)
667 for (i = 0; i <= pidhash; i++) {
668 LIST_FOREACH(p, &pidhashtbl[i], p_hash) {
669 thr = FIRST_THREAD_IN_PROC(p);
678 kdb_thr_from_pid(pid_t pid)
682 LIST_FOREACH(p, PIDHASH(pid), p_hash) {
684 return (FIRST_THREAD_IN_PROC(p));
690 kdb_thr_lookup(lwpid_t tid)
694 thr = kdb_thr_first();
695 while (thr != NULL && thr->td_tid != tid)
696 thr = kdb_thr_next(thr);
701 kdb_thr_next(struct thread *thr)
707 thr = TAILQ_NEXT(thr, td_plist);
710 if (pidhashtbl == NULL)
712 hash = p->p_pid & pidhash;
714 p = LIST_NEXT(p, p_hash);
716 if (++hash > pidhash)
718 p = LIST_FIRST(&pidhashtbl[hash]);
720 thr = FIRST_THREAD_IN_PROC(p);
727 kdb_thr_select(struct thread *thr)
732 kdb_thrctx = kdb_thr_ctx(thr);
737 * Enter the debugger due to a trap.
740 kdb_trap(int type, int code, struct trapframe *tf)
751 if (be == NULL || be->dbbe_trap == NULL)
754 /* We reenter the debugger through kdb_reenter(). */
758 intr = intr_disable();
760 if (!SCHEDULER_STOPPED()) {
762 other_cpus = all_cpus;
763 CPU_ANDNOT(&other_cpus, &other_cpus, &stopped_cpus);
764 CPU_CLR(PCPU_GET(cpuid), &other_cpus);
765 stop_cpus_hard(other_cpus);
767 curthread->td_stopsched = 1;
776 /* Let MD code do its thing first... */
777 kdb_cpu_trap(type, code);
779 makectx(tf, &kdb_pcb);
780 kdb_thr_select(curthread);
785 if (!kdb_backend_permitted(be, curthread)) {
786 /* Unhandled breakpoint traps are fatal. */
790 handled = be->dbbe_trap(type, code);
794 if (be == NULL || be->dbbe_trap == NULL)
796 printf("Switching to %s back-end\n", be->dbbe_name);
804 curthread->td_stopsched = 0;
806 CPU_AND(&other_cpus, &other_cpus, &stopped_cpus);
807 restart_cpus(other_cpus);