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>
50 #include <machine/kdb.h>
51 #include <machine/pcb.h>
54 #include <machine/smp.h>
57 #include <security/mac/mac_framework.h>
59 u_char __read_frequently kdb_active = 0;
60 static void *kdb_jmpbufp = NULL;
61 struct kdb_dbbe *kdb_dbbe = NULL;
62 static struct pcb kdb_pcb;
63 struct pcb *kdb_thrctx = NULL;
64 struct thread *kdb_thread = NULL;
65 struct trapframe *kdb_frame = NULL;
67 #ifdef BREAK_TO_DEBUGGER
68 #define KDB_BREAK_TO_DEBUGGER 1
70 #define KDB_BREAK_TO_DEBUGGER 0
73 #ifdef ALT_BREAK_TO_DEBUGGER
74 #define KDB_ALT_BREAK_TO_DEBUGGER 1
76 #define KDB_ALT_BREAK_TO_DEBUGGER 0
79 static int kdb_break_to_debugger = KDB_BREAK_TO_DEBUGGER;
80 static int kdb_alt_break_to_debugger = KDB_ALT_BREAK_TO_DEBUGGER;
81 static int kdb_enter_securelevel = 0;
83 KDB_BACKEND(null, NULL, NULL, NULL, NULL);
85 static int kdb_sysctl_available(SYSCTL_HANDLER_ARGS);
86 static int kdb_sysctl_current(SYSCTL_HANDLER_ARGS);
87 static int kdb_sysctl_enter(SYSCTL_HANDLER_ARGS);
88 static int kdb_sysctl_panic(SYSCTL_HANDLER_ARGS);
89 static int kdb_sysctl_panic_str(SYSCTL_HANDLER_ARGS);
90 static int kdb_sysctl_trap(SYSCTL_HANDLER_ARGS);
91 static int kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS);
92 static int kdb_sysctl_stack_overflow(SYSCTL_HANDLER_ARGS);
94 static SYSCTL_NODE(_debug, OID_AUTO, kdb, CTLFLAG_RW | CTLFLAG_MPSAFE, NULL,
97 SYSCTL_PROC(_debug_kdb, OID_AUTO, available,
98 CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 0,
99 kdb_sysctl_available, "A",
100 "list of available KDB backends");
102 SYSCTL_PROC(_debug_kdb, OID_AUTO, current,
103 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_MPSAFE, NULL, 0,
104 kdb_sysctl_current, "A",
105 "currently selected KDB backend");
107 SYSCTL_PROC(_debug_kdb, OID_AUTO, enter,
108 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE, NULL, 0,
109 kdb_sysctl_enter, "I",
110 "set to enter the debugger");
112 SYSCTL_PROC(_debug_kdb, OID_AUTO, panic,
113 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
114 kdb_sysctl_panic, "I",
115 "set to panic the kernel");
117 SYSCTL_PROC(_debug_kdb, OID_AUTO, panic_str,
118 CTLTYPE_STRING | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
119 kdb_sysctl_panic_str, "A",
120 "trigger a kernel panic, using the provided string as the panic message");
122 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap,
123 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
124 kdb_sysctl_trap, "I",
125 "set to cause a page fault via data access");
127 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap_code,
128 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
129 kdb_sysctl_trap_code, "I",
130 "set to cause a page fault via code access");
132 SYSCTL_PROC(_debug_kdb, OID_AUTO, stack_overflow,
133 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE | CTLFLAG_MPSAFE, NULL, 0,
134 kdb_sysctl_stack_overflow, "I",
135 "set to cause a stack overflow");
137 SYSCTL_INT(_debug_kdb, OID_AUTO, break_to_debugger,
139 &kdb_break_to_debugger, 0, "Enable break to debugger");
141 SYSCTL_INT(_debug_kdb, OID_AUTO, alt_break_to_debugger,
143 &kdb_alt_break_to_debugger, 0, "Enable alternative break to debugger");
145 SYSCTL_INT(_debug_kdb, OID_AUTO, enter_securelevel,
146 CTLFLAG_RWTUN | CTLFLAG_SECURE,
147 &kdb_enter_securelevel, 0,
148 "Maximum securelevel to enter a KDB backend");
151 * Flag to indicate to debuggers why the debugger was entered.
153 const char * volatile kdb_why = KDB_WHY_UNSET;
156 kdb_sysctl_available(SYSCTL_HANDLER_ARGS)
158 struct kdb_dbbe **iter;
162 sbuf_new_for_sysctl(&sbuf, NULL, 64, req);
163 SET_FOREACH(iter, kdb_dbbe_set) {
164 if ((*iter)->dbbe_active == 0)
165 sbuf_printf(&sbuf, "%s ", (*iter)->dbbe_name);
167 error = sbuf_finish(&sbuf);
173 kdb_sysctl_current(SYSCTL_HANDLER_ARGS)
178 if (kdb_dbbe != NULL)
179 strlcpy(buf, kdb_dbbe->dbbe_name, sizeof(buf));
182 error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
183 if (error != 0 || req->newptr == NULL)
187 return (kdb_dbbe_select(buf));
191 kdb_sysctl_enter(SYSCTL_HANDLER_ARGS)
195 error = sysctl_wire_old_buffer(req, sizeof(int));
198 error = sysctl_handle_int(oidp, &i, 0, req);
200 if (error != 0 || req->newptr == NULL)
204 kdb_enter(KDB_WHY_SYSCTL, "sysctl debug.kdb.enter");
209 kdb_sysctl_panic(SYSCTL_HANDLER_ARGS)
213 error = sysctl_wire_old_buffer(req, sizeof(int));
216 error = sysctl_handle_int(oidp, &i, 0, req);
218 if (error != 0 || req->newptr == NULL)
220 panic("kdb_sysctl_panic");
225 kdb_sysctl_panic_str(SYSCTL_HANDLER_ARGS)
228 static char buf[256]; /* static buffer to limit mallocs when panicing */
231 error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
232 if (error != 0 || req->newptr == NULL)
234 panic("kdb_sysctl_panic: %s", buf);
239 kdb_sysctl_trap(SYSCTL_HANDLER_ARGS)
242 int *addr = (int *)0x10;
244 error = sysctl_wire_old_buffer(req, sizeof(int));
247 error = sysctl_handle_int(oidp, &i, 0, req);
249 if (error != 0 || req->newptr == NULL)
255 kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS)
258 void (*fp)(u_int, u_int, u_int) = (void *)0xdeadc0de;
260 error = sysctl_wire_old_buffer(req, sizeof(int));
263 error = sysctl_handle_int(oidp, &i, 0, req);
265 if (error != 0 || req->newptr == NULL)
267 (*fp)(0x11111111, 0x22222222, 0x33333333);
271 static void kdb_stack_overflow(volatile int *x) __noinline;
273 kdb_stack_overflow(volatile int *x)
278 kdb_stack_overflow(x);
279 *x += PCPU_GET(cpuid) / 1000000;
283 kdb_sysctl_stack_overflow(SYSCTL_HANDLER_ARGS)
288 error = sysctl_wire_old_buffer(req, sizeof(int));
291 error = sysctl_handle_int(oidp, &i, 0, req);
293 if (error != 0 || req->newptr == NULL)
296 kdb_stack_overflow(&x);
301 kdb_panic(const char *msg)
304 kdb_why = KDB_WHY_PANIC;
305 printf("KDB: panic\n");
313 kdb_why = KDB_WHY_REBOOT;
314 printf("KDB: reboot requested\n");
319 * Solaris implements a new BREAK which is initiated by a character sequence
320 * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the
323 * Note that this function may be called from almost anywhere, with interrupts
324 * disabled and with unknown locks held, so it must not access data other than
325 * its arguments. Its up to the caller to ensure that the state variable is
328 #define KEY_CR 13 /* CR '\r' */
329 #define KEY_TILDE 126 /* ~ */
330 #define KEY_CRTLB 2 /* ^B */
331 #define KEY_CRTLP 16 /* ^P */
332 #define KEY_CRTLR 18 /* ^R */
334 /* States of th KDB "alternate break sequence" detecting state machine. */
336 KDB_ALT_BREAK_SEEN_NONE,
337 KDB_ALT_BREAK_SEEN_CR,
338 KDB_ALT_BREAK_SEEN_CR_TILDE,
345 if (!kdb_break_to_debugger)
347 kdb_enter(KDB_WHY_BREAK, "Break to debugger");
348 return (KDB_REQ_DEBUGGER);
352 kdb_alt_break_state(int key, int *state)
356 /* All states transition to KDB_ALT_BREAK_SEEN_CR on a CR. */
358 *state = KDB_ALT_BREAK_SEEN_CR;
364 case KDB_ALT_BREAK_SEEN_CR:
365 *state = KDB_ALT_BREAK_SEEN_NONE;
366 if (key == KEY_TILDE)
367 *state = KDB_ALT_BREAK_SEEN_CR_TILDE;
369 case KDB_ALT_BREAK_SEEN_CR_TILDE:
370 *state = KDB_ALT_BREAK_SEEN_NONE;
371 if (key == KEY_CRTLB)
372 brk = KDB_REQ_DEBUGGER;
373 else if (key == KEY_CRTLP)
375 else if (key == KEY_CRTLR)
376 brk = KDB_REQ_REBOOT;
378 case KDB_ALT_BREAK_SEEN_NONE:
380 *state = KDB_ALT_BREAK_SEEN_NONE;
387 kdb_alt_break_internal(int key, int *state, int force_gdb)
391 if (!kdb_alt_break_to_debugger)
393 brk = kdb_alt_break_state(key, state);
395 case KDB_REQ_DEBUGGER:
397 kdb_dbbe_select("gdb");
398 kdb_enter(KDB_WHY_BREAK, "Break to debugger");
403 kdb_dbbe_select("gdb");
404 kdb_panic("Panic sequence on console");
415 kdb_alt_break(int key, int *state)
418 return (kdb_alt_break_internal(key, state, 0));
422 * This variation on kdb_alt_break() is used only by dcons, which has its own
423 * configuration flag to force GDB use regardless of the global KDB
427 kdb_alt_break_gdb(int key, int *state)
430 return (kdb_alt_break_internal(key, state, 1));
434 * Print a backtrace of the calling thread. The backtrace is generated by
435 * the selected debugger, provided it supports backtraces. If no debugger
436 * is selected or the current debugger does not support backtraces, this
437 * function silently returns.
443 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) {
444 printf("KDB: stack backtrace:\n");
445 kdb_dbbe->dbbe_trace();
451 printf("KDB: stack backtrace:\n");
453 stack_print_ddb(&st);
459 * Similar to kdb_backtrace() except that it prints a backtrace of an
460 * arbitrary thread rather than the calling thread.
463 kdb_backtrace_thread(struct thread *td)
466 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace_thread != NULL) {
467 printf("KDB: stack backtrace of thread %d:\n", td->td_tid);
468 kdb_dbbe->dbbe_trace_thread(td);
474 printf("KDB: stack backtrace of thread %d:\n", td->td_tid);
475 if (stack_save_td(&st, td) == 0)
476 stack_print_ddb(&st);
482 * Set/change the current backend.
485 kdb_dbbe_select(const char *name)
487 struct kdb_dbbe *be, **iter;
490 error = priv_check(curthread, PRIV_KDB_SET_BACKEND);
494 SET_FOREACH(iter, kdb_dbbe_set) {
496 if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) {
505 kdb_backend_permitted(struct kdb_dbbe *be, struct ucred *cred)
509 error = securelevel_gt(cred, kdb_enter_securelevel);
512 * Give MAC a chance to weigh in on the policy: if the securelevel is
513 * not raised, then MAC may veto the backend, otherwise MAC may
514 * explicitly grant access.
517 error = mac_kdb_check_backend(be);
519 printf("MAC prevented execution of KDB backend: %s\n",
523 } else if (mac_kdb_grant_backend(be) == 0) {
528 printf("refusing to enter KDB with elevated securelevel\n");
533 * Enter the currently selected debugger. If a message has been provided,
534 * it is printed first. If the debugger does not support the enter method,
535 * it is entered by using breakpoint(), which enters the debugger through
536 * kdb_trap(). The 'why' argument will contain a more mechanically usable
537 * string than 'msg', and is relied upon by DDB scripting to identify the
538 * reason for entering the debugger so that the right script can be run.
541 kdb_enter(const char *why, const char *msg)
544 if (kdb_dbbe != NULL && kdb_active == 0) {
547 printf("KDB: enter: %s\n", msg);
549 kdb_why = KDB_WHY_UNSET;
554 * Initialize the kernel debugger interface.
559 struct kdb_dbbe *be, **iter;
565 SET_FOREACH(iter, kdb_dbbe_set) {
567 pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1;
568 be->dbbe_active = (pri >= 0) ? 0 : -1;
574 if (kdb_dbbe != NULL) {
575 printf("KDB: debugger backends:");
576 SET_FOREACH(iter, kdb_dbbe_set) {
578 if (be->dbbe_active == 0)
579 printf(" %s", be->dbbe_name);
582 printf("KDB: current backend: %s\n",
583 kdb_dbbe->dbbe_name);
591 kdb_jmpbuf(jmp_buf new)
604 if (!kdb_active || kdb_jmpbufp == NULL)
607 printf("KDB: reentering\n");
609 longjmp(kdb_jmpbufp, 1);
614 kdb_reenter_silent(void)
617 if (!kdb_active || kdb_jmpbufp == NULL)
620 longjmp(kdb_jmpbufp, 1);
625 * Thread-related support functions.
628 kdb_thr_ctx(struct thread *thr)
634 if (thr == curthread)
638 STAILQ_FOREACH(pc, &cpuhead, pc_allcpu) {
639 if (pc->pc_curthread == thr &&
640 CPU_ISSET(pc->pc_cpuid, &stopped_cpus))
641 return (&stoppcbs[pc->pc_cpuid]);
644 return (thr->td_pcb);
654 /* This function may be called early. */
655 if (pidhashtbl == NULL)
658 for (i = 0; i <= pidhash; i++) {
659 LIST_FOREACH(p, &pidhashtbl[i], p_hash) {
660 thr = FIRST_THREAD_IN_PROC(p);
669 kdb_thr_from_pid(pid_t pid)
673 LIST_FOREACH(p, PIDHASH(pid), p_hash) {
675 return (FIRST_THREAD_IN_PROC(p));
681 kdb_thr_lookup(lwpid_t tid)
685 thr = kdb_thr_first();
686 while (thr != NULL && thr->td_tid != tid)
687 thr = kdb_thr_next(thr);
692 kdb_thr_next(struct thread *thr)
698 thr = TAILQ_NEXT(thr, td_plist);
701 if (pidhashtbl == NULL)
703 hash = p->p_pid & pidhash;
705 p = LIST_NEXT(p, p_hash);
707 if (++hash > pidhash)
709 p = LIST_FIRST(&pidhashtbl[hash]);
711 thr = FIRST_THREAD_IN_PROC(p);
718 kdb_thr_select(struct thread *thr)
723 kdb_thrctx = kdb_thr_ctx(thr);
728 * Enter the debugger due to a trap.
731 kdb_trap(int type, int code, struct trapframe *tf)
742 if (be == NULL || be->dbbe_trap == NULL)
745 /* We reenter the debugger through kdb_reenter(). */
749 intr = intr_disable();
751 if (!SCHEDULER_STOPPED()) {
753 other_cpus = all_cpus;
754 CPU_ANDNOT(&other_cpus, &other_cpus, &stopped_cpus);
755 CPU_CLR(PCPU_GET(cpuid), &other_cpus);
756 stop_cpus_hard(other_cpus);
758 curthread->td_stopsched = 1;
767 /* Let MD code do its thing first... */
768 kdb_cpu_trap(type, code);
770 makectx(tf, &kdb_pcb);
771 kdb_thr_select(curthread);
776 if (!kdb_backend_permitted(be, curthread->td_ucred)) {
777 /* Unhandled breakpoint traps are fatal. */
781 handled = be->dbbe_trap(type, code);
785 if (be == NULL || be->dbbe_trap == NULL)
787 printf("Switching to %s back-end\n", be->dbbe_name);
795 curthread->td_stopsched = 0;
797 CPU_AND(&other_cpus, &other_cpus, &stopped_cpus);
798 restart_cpus(other_cpus);