subr_kdb.c revision 218825
1193323Sed/*- 2193323Sed * Copyright (c) 2004 The FreeBSD Project 3193323Sed * All rights reserved. 4193323Sed * 5193323Sed * Redistribution and use in source and binary forms, with or without 6193323Sed * modification, are permitted provided that the following conditions 7193323Sed * are met: 8193323Sed * 9193323Sed * 1. Redistributions of source code must retain the above copyright 10193323Sed * notice, this list of conditions and the following disclaimer. 11193323Sed * 2. Redistributions in binary form must reproduce the above copyright 12193323Sed * notice, this list of conditions and the following disclaimer in the 13193323Sed * documentation and/or other materials provided with the distribution. 14193323Sed * 15193323Sed * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR 16193323Sed * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17193323Sed * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18193323Sed * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT, 19193323Sed * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20193323Sed * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21193323Sed * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22193323Sed * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23193323Sed * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24193323Sed * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25193323Sed */ 26193323Sed 27193323Sed#include <sys/cdefs.h> 28193323Sed__FBSDID("$FreeBSD: head/sys/kern/subr_kdb.c 218825 2011-02-18 22:25:11Z mdf $"); 29193323Sed 30193323Sed#include "opt_kdb.h" 31193323Sed#include "opt_stack.h" 32195098Sed 33195098Sed#include <sys/param.h> 34195098Sed#include <sys/systm.h> 35193323Sed#include <sys/kdb.h> 36193323Sed#include <sys/kernel.h> 37195098Sed#include <sys/malloc.h> 38193323Sed#include <sys/pcpu.h> 39193323Sed#include <sys/proc.h> 40193323Sed#include <sys/sbuf.h> 41193323Sed#include <sys/smp.h> 42193323Sed#include <sys/stack.h> 43193323Sed#include <sys/sysctl.h> 44193323Sed 45193323Sed#include <machine/kdb.h> 46193323Sed#include <machine/pcb.h> 47193323Sed 48193323Sed#ifdef SMP 49193323Sed#include <machine/smp.h> 50193323Sed#endif 51193323Sed 52193323Sedint kdb_active = 0; 53193323Sedstatic void *kdb_jmpbufp = NULL; 54193323Sedstruct kdb_dbbe *kdb_dbbe = NULL; 55193323Sedstatic struct pcb kdb_pcb; 56193323Sedstruct pcb *kdb_thrctx = NULL; 57193323Sedstruct thread *kdb_thread = NULL; 58193323Sedstruct trapframe *kdb_frame = NULL; 59193323Sed 60193323SedKDB_BACKEND(null, NULL, NULL, NULL); 61193323SedSET_DECLARE(kdb_dbbe_set, struct kdb_dbbe); 62193323Sed 63193323Sedstatic int kdb_sysctl_available(SYSCTL_HANDLER_ARGS); 64193323Sedstatic int kdb_sysctl_current(SYSCTL_HANDLER_ARGS); 65193323Sedstatic int kdb_sysctl_enter(SYSCTL_HANDLER_ARGS); 66193323Sedstatic int kdb_sysctl_panic(SYSCTL_HANDLER_ARGS); 67193323Sedstatic int kdb_sysctl_trap(SYSCTL_HANDLER_ARGS); 68193323Sedstatic int kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS); 69193323Sed 70193323SedSYSCTL_NODE(_debug, OID_AUTO, kdb, CTLFLAG_RW, NULL, "KDB nodes"); 71193323Sed 72193323SedSYSCTL_PROC(_debug_kdb, OID_AUTO, available, CTLTYPE_STRING | CTLFLAG_RD, NULL, 73193323Sed 0, kdb_sysctl_available, "A", "list of available KDB backends"); 74193323Sed 75193323SedSYSCTL_PROC(_debug_kdb, OID_AUTO, current, CTLTYPE_STRING | CTLFLAG_RW, NULL, 76193323Sed 0, kdb_sysctl_current, "A", "currently selected KDB backend"); 77193323Sed 78193323SedSYSCTL_PROC(_debug_kdb, OID_AUTO, enter, CTLTYPE_INT | CTLFLAG_RW, NULL, 0, 79193323Sed kdb_sysctl_enter, "I", "set to enter the debugger"); 80193323Sed 81193323SedSYSCTL_PROC(_debug_kdb, OID_AUTO, panic, CTLTYPE_INT | CTLFLAG_RW, NULL, 0, 82193323Sed kdb_sysctl_panic, "I", "set to panic the kernel"); 83193323Sed 84193323SedSYSCTL_PROC(_debug_kdb, OID_AUTO, trap, CTLTYPE_INT | CTLFLAG_RW, NULL, 0, 85193323Sed kdb_sysctl_trap, "I", "set to cause a page fault via data access"); 86193323Sed 87193323SedSYSCTL_PROC(_debug_kdb, OID_AUTO, trap_code, CTLTYPE_INT | CTLFLAG_RW, NULL, 0, 88193323Sed kdb_sysctl_trap_code, "I", "set to cause a page fault via code access"); 89193323Sed 90193323Sed/* 91193323Sed * Flag indicating whether or not to IPI the other CPUs to stop them on 92193323Sed * entering the debugger. Sometimes, this will result in a deadlock as 93193323Sed * stop_cpus() waits for the other cpus to stop, so we allow it to be 94193323Sed * disabled. In order to maximize the chances of success, use a hard 95193323Sed * stop for that. 96193323Sed */ 97193323Sed#ifdef SMP 98193323Sedstatic int kdb_stop_cpus = 1; 99193323SedSYSCTL_INT(_debug_kdb, OID_AUTO, stop_cpus, CTLFLAG_RW | CTLFLAG_TUN, 100193323Sed &kdb_stop_cpus, 0, "stop other CPUs when entering the debugger"); 101193323SedTUNABLE_INT("debug.kdb.stop_cpus", &kdb_stop_cpus); 102193323Sed#endif 103193323Sed 104193323Sed/* 105193323Sed * Flag to indicate to debuggers why the debugger was entered. 106193323Sed */ 107193323Sedconst char * volatile kdb_why = KDB_WHY_UNSET; 108193323Sed 109193323Sedstatic int 110193323Sedkdb_sysctl_available(SYSCTL_HANDLER_ARGS) 111193323Sed{ 112193323Sed struct kdb_dbbe **iter; 113193323Sed struct sbuf sbuf; 114193323Sed int error; 115193323Sed 116193323Sed sbuf_new_for_sysctl(&sbuf, NULL, 64, req); 117193323Sed SET_FOREACH(iter, kdb_dbbe_set) { 118193323Sed if ((*iter)->dbbe_active == 0) 119193323Sed sbuf_printf(&sbuf, "%s ", (*iter)->dbbe_name); 120193323Sed } 121193323Sed error = sbuf_finish(&sbuf); 122193323Sed sbuf_delete(&sbuf); 123193323Sed return (error); 124193323Sed} 125193323Sed 126193323Sedstatic int 127193323Sedkdb_sysctl_current(SYSCTL_HANDLER_ARGS) 128193323Sed{ 129193323Sed char buf[16]; 130193323Sed int error; 131193323Sed 132193323Sed if (kdb_dbbe != NULL) 133193323Sed strlcpy(buf, kdb_dbbe->dbbe_name, sizeof(buf)); 134193323Sed else 135193323Sed *buf = '\0'; 136193323Sed error = sysctl_handle_string(oidp, buf, sizeof(buf), req); 137193323Sed if (error != 0 || req->newptr == NULL) 138193323Sed return (error); 139193323Sed if (kdb_active) 140193323Sed return (EBUSY); 141193323Sed return (kdb_dbbe_select(buf)); 142193323Sed} 143193323Sed 144193323Sedstatic int 145193323Sedkdb_sysctl_enter(SYSCTL_HANDLER_ARGS) 146193323Sed{ 147193323Sed int error, i; 148193323Sed 149193323Sed error = sysctl_wire_old_buffer(req, sizeof(int)); 150193323Sed if (error == 0) { 151193323Sed i = 0; 152193323Sed error = sysctl_handle_int(oidp, &i, 0, req); 153193323Sed } 154193323Sed if (error != 0 || req->newptr == NULL) 155193323Sed return (error); 156193323Sed if (kdb_active) 157193323Sed return (EBUSY); 158193323Sed kdb_enter(KDB_WHY_SYSCTL, "sysctl debug.kdb.enter"); 159193323Sed return (0); 160193323Sed} 161193323Sed 162193323Sedstatic int 163193323Sedkdb_sysctl_panic(SYSCTL_HANDLER_ARGS) 164193323Sed{ 165193323Sed int error, i; 166193323Sed 167193323Sed error = sysctl_wire_old_buffer(req, sizeof(int)); 168193323Sed if (error == 0) { 169193323Sed i = 0; 170193323Sed error = sysctl_handle_int(oidp, &i, 0, req); 171193323Sed } 172193323Sed if (error != 0 || req->newptr == NULL) 173193323Sed return (error); 174193323Sed panic("kdb_sysctl_panic"); 175193323Sed return (0); 176193323Sed} 177193323Sed 178193323Sedstatic int 179193323Sedkdb_sysctl_trap(SYSCTL_HANDLER_ARGS) 180193323Sed{ 181193323Sed int error, i; 182193323Sed int *addr = (int *)0x10; 183193323Sed 184193323Sed error = sysctl_wire_old_buffer(req, sizeof(int)); 185193323Sed if (error == 0) { 186193323Sed i = 0; 187193323Sed error = sysctl_handle_int(oidp, &i, 0, req); 188193323Sed } 189193323Sed if (error != 0 || req->newptr == NULL) 190193323Sed return (error); 191193323Sed return (*addr); 192193323Sed} 193193323Sed 194193323Sedstatic int 195193323Sedkdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS) 196193323Sed{ 197193323Sed int error, i; 198193323Sed void (*fp)(u_int, u_int, u_int) = (void *)0xdeadc0de; 199193323Sed 200193323Sed error = sysctl_wire_old_buffer(req, sizeof(int)); 201193323Sed if (error == 0) { 202193323Sed i = 0; 203193323Sed error = sysctl_handle_int(oidp, &i, 0, req); 204193323Sed } 205193323Sed if (error != 0 || req->newptr == NULL) 206193323Sed return (error); 207193323Sed (*fp)(0x11111111, 0x22222222, 0x33333333); 208193323Sed return (0); 209193323Sed} 210193323Sed 211193323Sedvoid 212193323Sedkdb_panic(const char *msg) 213193323Sed{ 214193323Sed 215193323Sed#ifdef SMP 216193323Sed stop_cpus_hard(PCPU_GET(other_cpus)); 217193323Sed#endif 218193323Sed printf("KDB: panic\n"); 219193323Sed panic("%s", msg); 220193323Sed} 221193323Sed 222193323Sedvoid 223193323Sedkdb_reboot(void) 224193323Sed{ 225193323Sed 226193323Sed printf("KDB: reboot requested\n"); 227193323Sed shutdown_nice(0); 228193323Sed} 229193323Sed 230193323Sed/* 231193323Sed * Solaris implements a new BREAK which is initiated by a character sequence 232193323Sed * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the 233193323Sed * Remote Console. 234193323Sed * 235193323Sed * Note that this function may be called from almost anywhere, with interrupts 236193323Sed * disabled and with unknown locks held, so it must not access data other than 237193323Sed * its arguments. Its up to the caller to ensure that the state variable is 238193323Sed * consistent. 239193323Sed */ 240193323Sed 241193323Sed#define KEY_CR 13 /* CR '\r' */ 242193323Sed#define KEY_TILDE 126 /* ~ */ 243193323Sed#define KEY_CRTLB 2 /* ^B */ 244193323Sed#define KEY_CRTLP 16 /* ^P */ 245193323Sed#define KEY_CRTLR 18 /* ^R */ 246193323Sed 247194178Sedint 248193323Sedkdb_alt_break(int key, int *state) 249193323Sed{ 250193323Sed int brk; 251193323Sed 252193323Sed brk = 0; 253193323Sed switch (*state) { 254193323Sed case 0: 255193323Sed if (key == KEY_CR) 256193323Sed *state = 1; 257193323Sed break; 258193323Sed case 1: 259193323Sed if (key == KEY_TILDE) 260193323Sed *state = 2; 261193323Sed break; 262193323Sed case 2: 263193323Sed if (key == KEY_CRTLB) 264193323Sed brk = KDB_REQ_DEBUGGER; 265193323Sed else if (key == KEY_CRTLP) 266193323Sed brk = KDB_REQ_PANIC; 267193323Sed else if (key == KEY_CRTLR) 268193323Sed brk = KDB_REQ_REBOOT; 269193323Sed *state = 0; 270193323Sed } 271193323Sed return (brk); 272193323Sed} 273193323Sed 274193323Sed/* 275193323Sed * Print a backtrace of the calling thread. The backtrace is generated by 276193323Sed * the selected debugger, provided it supports backtraces. If no debugger 277193323Sed * is selected or the current debugger does not support backtraces, this 278193323Sed * function silently returns. 279193323Sed */ 280195098Sed 281195098Sedvoid 282195098Sedkdb_backtrace(void) 283195098Sed{ 284195098Sed 285195098Sed if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) { 286195098Sed printf("KDB: stack backtrace:\n"); 287195098Sed kdb_dbbe->dbbe_trace(); 288193323Sed } 289193323Sed#ifdef STACK 290193323Sed else { 291193323Sed struct stack st; 292193323Sed 293193323Sed printf("KDB: stack backtrace:\n"); 294193323Sed stack_save(&st); 295193323Sed stack_print_ddb(&st); 296193323Sed } 297193323Sed#endif 298193323Sed} 299193323Sed 300193323Sed/* 301193323Sed * Set/change the current backend. 302193323Sed */ 303193323Sed 304193323Sedint 305193323Sedkdb_dbbe_select(const char *name) 306193323Sed{ 307193323Sed struct kdb_dbbe *be, **iter; 308193323Sed 309193323Sed SET_FOREACH(iter, kdb_dbbe_set) { 310193323Sed be = *iter; 311193323Sed if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) { 312193323Sed kdb_dbbe = be; 313193323Sed return (0); 314193323Sed } 315193323Sed } 316193323Sed return (EINVAL); 317193323Sed} 318193323Sed 319193323Sed/* 320193323Sed * Enter the currently selected debugger. If a message has been provided, 321193323Sed * it is printed first. If the debugger does not support the enter method, 322193323Sed * it is entered by using breakpoint(), which enters the debugger through 323193323Sed * kdb_trap(). The 'why' argument will contain a more mechanically usable 324193323Sed * string than 'msg', and is relied upon by DDB scripting to identify the 325193323Sed * reason for entering the debugger so that the right script can be run. 326193323Sed */ 327193323Sedvoid 328193323Sedkdb_enter(const char *why, const char *msg) 329193323Sed{ 330193323Sed 331193323Sed if (kdb_dbbe != NULL && kdb_active == 0) { 332193323Sed if (msg != NULL) 333193323Sed printf("KDB: enter: %s\n", msg); 334193323Sed kdb_why = why; 335193323Sed breakpoint(); 336193323Sed kdb_why = KDB_WHY_UNSET; 337193323Sed } 338193323Sed} 339193323Sed 340193323Sed/* 341193323Sed * Initialize the kernel debugger interface. 342193323Sed */ 343193323Sed 344193323Sedvoid 345193323Sedkdb_init(void) 346193323Sed{ 347193323Sed struct kdb_dbbe *be, **iter; 348193323Sed int cur_pri, pri; 349193323Sed 350193323Sed kdb_active = 0; 351193323Sed kdb_dbbe = NULL; 352193323Sed cur_pri = -1; 353193323Sed SET_FOREACH(iter, kdb_dbbe_set) { 354193323Sed be = *iter; 355193323Sed pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1; 356193323Sed be->dbbe_active = (pri >= 0) ? 0 : -1; 357193323Sed if (pri > cur_pri) { 358193323Sed cur_pri = pri; 359193323Sed kdb_dbbe = be; 360193323Sed } 361193323Sed } 362193323Sed if (kdb_dbbe != NULL) { 363 printf("KDB: debugger backends:"); 364 SET_FOREACH(iter, kdb_dbbe_set) { 365 be = *iter; 366 if (be->dbbe_active == 0) 367 printf(" %s", be->dbbe_name); 368 } 369 printf("\n"); 370 printf("KDB: current backend: %s\n", 371 kdb_dbbe->dbbe_name); 372 } 373} 374 375/* 376 * Handle contexts. 377 */ 378 379void * 380kdb_jmpbuf(jmp_buf new) 381{ 382 void *old; 383 384 old = kdb_jmpbufp; 385 kdb_jmpbufp = new; 386 return (old); 387} 388 389void 390kdb_reenter(void) 391{ 392 393 if (!kdb_active || kdb_jmpbufp == NULL) 394 return; 395 396 longjmp(kdb_jmpbufp, 1); 397 /* NOTREACHED */ 398} 399 400/* 401 * Thread related support functions. 402 */ 403 404struct pcb * 405kdb_thr_ctx(struct thread *thr) 406{ 407#if defined(SMP) && defined(KDB_STOPPEDPCB) 408 struct pcpu *pc; 409#endif 410 411 if (thr == curthread) 412 return (&kdb_pcb); 413 414#if defined(SMP) && defined(KDB_STOPPEDPCB) 415 SLIST_FOREACH(pc, &cpuhead, pc_allcpu) { 416 if (pc->pc_curthread == thr && (stopped_cpus & pc->pc_cpumask)) 417 return (KDB_STOPPEDPCB(pc)); 418 } 419#endif 420 return (thr->td_pcb); 421} 422 423struct thread * 424kdb_thr_first(void) 425{ 426 struct proc *p; 427 struct thread *thr; 428 429 p = LIST_FIRST(&allproc); 430 while (p != NULL) { 431 if (p->p_flag & P_INMEM) { 432 thr = FIRST_THREAD_IN_PROC(p); 433 if (thr != NULL) 434 return (thr); 435 } 436 p = LIST_NEXT(p, p_list); 437 } 438 return (NULL); 439} 440 441struct thread * 442kdb_thr_from_pid(pid_t pid) 443{ 444 struct proc *p; 445 446 p = LIST_FIRST(&allproc); 447 while (p != NULL) { 448 if (p->p_flag & P_INMEM && p->p_pid == pid) 449 return (FIRST_THREAD_IN_PROC(p)); 450 p = LIST_NEXT(p, p_list); 451 } 452 return (NULL); 453} 454 455struct thread * 456kdb_thr_lookup(lwpid_t tid) 457{ 458 struct thread *thr; 459 460 thr = kdb_thr_first(); 461 while (thr != NULL && thr->td_tid != tid) 462 thr = kdb_thr_next(thr); 463 return (thr); 464} 465 466struct thread * 467kdb_thr_next(struct thread *thr) 468{ 469 struct proc *p; 470 471 p = thr->td_proc; 472 thr = TAILQ_NEXT(thr, td_plist); 473 do { 474 if (thr != NULL) 475 return (thr); 476 p = LIST_NEXT(p, p_list); 477 if (p != NULL && (p->p_flag & P_INMEM)) 478 thr = FIRST_THREAD_IN_PROC(p); 479 } while (p != NULL); 480 return (NULL); 481} 482 483int 484kdb_thr_select(struct thread *thr) 485{ 486 if (thr == NULL) 487 return (EINVAL); 488 kdb_thread = thr; 489 kdb_thrctx = kdb_thr_ctx(thr); 490 return (0); 491} 492 493/* 494 * Enter the debugger due to a trap. 495 */ 496 497int 498kdb_trap(int type, int code, struct trapframe *tf) 499{ 500 struct kdb_dbbe *be; 501 register_t intr; 502#ifdef SMP 503 int did_stop_cpus; 504#endif 505 int handled; 506 507 be = kdb_dbbe; 508 if (be == NULL || be->dbbe_trap == NULL) 509 return (0); 510 511 /* We reenter the debugger through kdb_reenter(). */ 512 if (kdb_active) 513 return (0); 514 515 intr = intr_disable(); 516 517#ifdef SMP 518 if ((did_stop_cpus = kdb_stop_cpus) != 0) 519 stop_cpus_hard(PCPU_GET(other_cpus)); 520#endif 521 522 kdb_active++; 523 524 kdb_frame = tf; 525 526 /* Let MD code do its thing first... */ 527 kdb_cpu_trap(type, code); 528 529 makectx(tf, &kdb_pcb); 530 kdb_thr_select(curthread); 531 532 for (;;) { 533 handled = be->dbbe_trap(type, code); 534 if (be == kdb_dbbe) 535 break; 536 be = kdb_dbbe; 537 if (be == NULL || be->dbbe_trap == NULL) 538 break; 539 printf("Switching to %s back-end\n", be->dbbe_name); 540 } 541 542 kdb_active--; 543 544#ifdef SMP 545 if (did_stop_cpus) 546 restart_cpus(stopped_cpus); 547#endif 548 549 intr_restore(intr); 550 551 return (handled); 552} 553