Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_kdb.c
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1 /*- 2 * Copyright (c) 2004 The FreeBSD Project 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 */ 26 27 #include <sys/cdefs.h> 28 __FBSDID("$FreeBSD: releng/9.2/sys/kern/subr_kdb.c 248085 2013-03-09 02:36:32Z marius $"); 29 30 #include "opt_kdb.h" 31 #include "opt_stack.h" 32 33 #include <sys/param.h> 34 #include <sys/systm.h> 35 #include <sys/cons.h> 36 #include <sys/kdb.h> 37 #include <sys/kernel.h> 38 #include <sys/malloc.h> 39 #include <sys/pcpu.h> 40 #include <sys/proc.h> 41 #include <sys/sbuf.h> 42 #include <sys/smp.h> 43 #include <sys/stack.h> 44 #include <sys/sysctl.h> 45 46 #include <machine/kdb.h> 47 #include <machine/pcb.h> 48 49 #ifdef SMP 50 #include <machine/smp.h> 51 #endif 52 53 int kdb_active = 0; 54 static void *kdb_jmpbufp = NULL; 55 struct kdb_dbbe *kdb_dbbe = NULL; 56 static struct pcb kdb_pcb; 57 struct pcb *kdb_thrctx = NULL; 58 struct thread *kdb_thread = NULL; 59 struct trapframe *kdb_frame = NULL; 60 61 #ifdef BREAK_TO_DEBUGGER 62 #define KDB_BREAK_TO_DEBUGGER 1 63 #else 64 #define KDB_BREAK_TO_DEBUGGER 0 65 #endif 66 67 #ifdef ALT_BREAK_TO_DEBUGGER 68 #define KDB_ALT_BREAK_TO_DEBUGGER 1 69 #else 70 #define KDB_ALT_BREAK_TO_DEBUGGER 0 71 #endif 72 73 static int kdb_break_to_debugger = KDB_BREAK_TO_DEBUGGER; 74 static int kdb_alt_break_to_debugger = KDB_ALT_BREAK_TO_DEBUGGER; 75 76 KDB_BACKEND(null, NULL, NULL, NULL, NULL); 77 SET_DECLARE(kdb_dbbe_set, struct kdb_dbbe); 78 79 static int kdb_sysctl_available(SYSCTL_HANDLER_ARGS); 80 static int kdb_sysctl_current(SYSCTL_HANDLER_ARGS); 81 static int kdb_sysctl_enter(SYSCTL_HANDLER_ARGS); 82 static int kdb_sysctl_panic(SYSCTL_HANDLER_ARGS); 83 static int kdb_sysctl_trap(SYSCTL_HANDLER_ARGS); 84 static int kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS); 85 86 static SYSCTL_NODE(_debug, OID_AUTO, kdb, CTLFLAG_RW, NULL, "KDB nodes"); 87 88 SYSCTL_PROC(_debug_kdb, OID_AUTO, available, CTLTYPE_STRING | CTLFLAG_RD, NULL, 89 0, kdb_sysctl_available, "A", "list of available KDB backends"); 90 91 SYSCTL_PROC(_debug_kdb, OID_AUTO, current, CTLTYPE_STRING | CTLFLAG_RW, NULL, 92 0, kdb_sysctl_current, "A", "currently selected KDB backend"); 93 94 SYSCTL_PROC(_debug_kdb, OID_AUTO, enter, CTLTYPE_INT | CTLFLAG_RW, NULL, 0, 95 kdb_sysctl_enter, "I", "set to enter the debugger"); 96 97 SYSCTL_PROC(_debug_kdb, OID_AUTO, panic, CTLTYPE_INT | CTLFLAG_RW, NULL, 0, 98 kdb_sysctl_panic, "I", "set to panic the kernel"); 99 100 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap, CTLTYPE_INT | CTLFLAG_RW, NULL, 0, 101 kdb_sysctl_trap, "I", "set to cause a page fault via data access"); 102 103 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap_code, CTLTYPE_INT | CTLFLAG_RW, NULL, 0, 104 kdb_sysctl_trap_code, "I", "set to cause a page fault via code access"); 105 106 SYSCTL_INT(_debug_kdb, OID_AUTO, break_to_debugger, CTLTYPE_INT | CTLFLAG_RW | 107 CTLFLAG_TUN, &kdb_break_to_debugger, 0, "Enable break to debugger"); 108 TUNABLE_INT("debug.kdb.break_to_debugger", &kdb_break_to_debugger); 109 110 SYSCTL_INT(_debug_kdb, OID_AUTO, alt_break_to_debugger, CTLTYPE_INT | 111 CTLFLAG_RW | CTLFLAG_TUN, &kdb_alt_break_to_debugger, 0, 112 "Enable alternative break to debugger"); 113 TUNABLE_INT("debug.kdb.alt_break_to_debugger", &kdb_alt_break_to_debugger); 114 115 /* 116 * Flag to indicate to debuggers why the debugger was entered. 117 */ 118 const char * volatile kdb_why = KDB_WHY_UNSET; 119 120 static int 121 kdb_sysctl_available(SYSCTL_HANDLER_ARGS) 122 { 123 struct kdb_dbbe **iter; 124 struct sbuf sbuf; 125 int error; 126 127 sbuf_new_for_sysctl(&sbuf, NULL, 64, req); 128 SET_FOREACH(iter, kdb_dbbe_set) { 129 if ((*iter)->dbbe_active == 0) 130 sbuf_printf(&sbuf, "%s ", (*iter)->dbbe_name); 131 } 132 error = sbuf_finish(&sbuf); 133 sbuf_delete(&sbuf); 134 return (error); 135 } 136 137 static int 138 kdb_sysctl_current(SYSCTL_HANDLER_ARGS) 139 { 140 char buf[16]; 141 int error; 142 143 if (kdb_dbbe != NULL) 144 strlcpy(buf, kdb_dbbe->dbbe_name, sizeof(buf)); 145 else 146 *buf = '\0'; 147 error = sysctl_handle_string(oidp, buf, sizeof(buf), req); 148 if (error != 0 || req->newptr == NULL) 149 return (error); 150 if (kdb_active) 151 return (EBUSY); 152 return (kdb_dbbe_select(buf)); 153 } 154 155 static int 156 kdb_sysctl_enter(SYSCTL_HANDLER_ARGS) 157 { 158 int error, i; 159 160 error = sysctl_wire_old_buffer(req, sizeof(int)); 161 if (error == 0) { 162 i = 0; 163 error = sysctl_handle_int(oidp, &i, 0, req); 164 } 165 if (error != 0 || req->newptr == NULL) 166 return (error); 167 if (kdb_active) 168 return (EBUSY); 169 kdb_enter(KDB_WHY_SYSCTL, "sysctl debug.kdb.enter"); 170 return (0); 171 } 172 173 static int 174 kdb_sysctl_panic(SYSCTL_HANDLER_ARGS) 175 { 176 int error, i; 177 178 error = sysctl_wire_old_buffer(req, sizeof(int)); 179 if (error == 0) { 180 i = 0; 181 error = sysctl_handle_int(oidp, &i, 0, req); 182 } 183 if (error != 0 || req->newptr == NULL) 184 return (error); 185 panic("kdb_sysctl_panic"); 186 return (0); 187 } 188 189 static int 190 kdb_sysctl_trap(SYSCTL_HANDLER_ARGS) 191 { 192 int error, i; 193 int *addr = (int *)0x10; 194 195 error = sysctl_wire_old_buffer(req, sizeof(int)); 196 if (error == 0) { 197 i = 0; 198 error = sysctl_handle_int(oidp, &i, 0, req); 199 } 200 if (error != 0 || req->newptr == NULL) 201 return (error); 202 return (*addr); 203 } 204 205 static int 206 kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS) 207 { 208 int error, i; 209 void (*fp)(u_int, u_int, u_int) = (void *)0xdeadc0de; 210 211 error = sysctl_wire_old_buffer(req, sizeof(int)); 212 if (error == 0) { 213 i = 0; 214 error = sysctl_handle_int(oidp, &i, 0, req); 215 } 216 if (error != 0 || req->newptr == NULL) 217 return (error); 218 (*fp)(0x11111111, 0x22222222, 0x33333333); 219 return (0); 220 } 221 222 void 223 kdb_panic(const char *msg) 224 { 225 226 printf("KDB: panic\n"); 227 panic("%s", msg); 228 } 229 230 void 231 kdb_reboot(void) 232 { 233 234 printf("KDB: reboot requested\n"); 235 shutdown_nice(0); 236 } 237 238 /* 239 * Solaris implements a new BREAK which is initiated by a character sequence 240 * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the 241 * Remote Console. 242 * 243 * Note that this function may be called from almost anywhere, with interrupts 244 * disabled and with unknown locks held, so it must not access data other than 245 * its arguments. Its up to the caller to ensure that the state variable is 246 * consistent. 247 */ 248 249 #define KEY_CR 13 /* CR '\r' */ 250 #define KEY_TILDE 126 /* ~ */ 251 #define KEY_CRTLB 2 /* ^B */ 252 #define KEY_CRTLP 16 /* ^P */ 253 #define KEY_CRTLR 18 /* ^R */ 254 255 /* States of th KDB "alternate break sequence" detecting state machine. */ 256 enum { 257 KDB_ALT_BREAK_SEEN_NONE, 258 KDB_ALT_BREAK_SEEN_CR, 259 KDB_ALT_BREAK_SEEN_CR_TILDE, 260 }; 261 262 int 263 kdb_break(void) 264 { 265 266 if (!kdb_break_to_debugger) 267 return (0); 268 kdb_enter(KDB_WHY_BREAK, "Break to debugger"); 269 return (KDB_REQ_DEBUGGER); 270 } 271 272 static int 273 kdb_alt_break_state(int key, int *state) 274 { 275 int brk; 276 277 /* All states transition to KDB_ALT_BREAK_SEEN_CR on a CR. */ 278 if (key == KEY_CR) { 279 *state = KDB_ALT_BREAK_SEEN_CR; 280 return (0); 281 } 282 283 brk = 0; 284 switch (*state) { 285 case KDB_ALT_BREAK_SEEN_CR: 286 *state = KDB_ALT_BREAK_SEEN_NONE; 287 if (key == KEY_TILDE) 288 *state = KDB_ALT_BREAK_SEEN_CR_TILDE; 289 break; 290 case KDB_ALT_BREAK_SEEN_CR_TILDE: 291 *state = KDB_ALT_BREAK_SEEN_NONE; 292 if (key == KEY_CRTLB) 293 brk = KDB_REQ_DEBUGGER; 294 else if (key == KEY_CRTLP) 295 brk = KDB_REQ_PANIC; 296 else if (key == KEY_CRTLR) 297 brk = KDB_REQ_REBOOT; 298 break; 299 case KDB_ALT_BREAK_SEEN_NONE: 300 default: 301 *state = KDB_ALT_BREAK_SEEN_NONE; 302 break; 303 } 304 return (brk); 305 } 306 307 static int 308 kdb_alt_break_internal(int key, int *state, int force_gdb) 309 { 310 int brk; 311 312 if (!kdb_alt_break_to_debugger) 313 return (0); 314 brk = kdb_alt_break_state(key, state); 315 switch (brk) { 316 case KDB_REQ_DEBUGGER: 317 if (force_gdb) 318 kdb_dbbe_select("gdb"); 319 kdb_enter(KDB_WHY_BREAK, "Break to debugger"); 320 break; 321 322 case KDB_REQ_PANIC: 323 if (force_gdb) 324 kdb_dbbe_select("gdb"); 325 kdb_panic("Panic sequence on console"); 326 break; 327 328 case KDB_REQ_REBOOT: 329 kdb_reboot(); 330 break; 331 } 332 return (0); 333 } 334 335 int 336 kdb_alt_break(int key, int *state) 337 { 338 339 return (kdb_alt_break_internal(key, state, 0)); 340 } 341 342 /* 343 * This variation on kdb_alt_break() is used only by dcons, which has its own 344 * configuration flag to force GDB use regardless of the global KDB 345 * configuration. 346 */ 347 int 348 kdb_alt_break_gdb(int key, int *state) 349 { 350 351 return (kdb_alt_break_internal(key, state, 1)); 352 } 353 354 /* 355 * Print a backtrace of the calling thread. The backtrace is generated by 356 * the selected debugger, provided it supports backtraces. If no debugger 357 * is selected or the current debugger does not support backtraces, this 358 * function silently returns. 359 */ 360 361 void 362 kdb_backtrace(void) 363 { 364 365 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) { 366 printf("KDB: stack backtrace:\n"); 367 kdb_dbbe->dbbe_trace(); 368 } 369 #ifdef STACK 370 else { 371 struct stack st; 372 373 printf("KDB: stack backtrace:\n"); 374 stack_zero(&st); 375 stack_save(&st); 376 stack_print_ddb(&st); 377 } 378 #endif 379 } 380 381 /* 382 * Similar to kdb_backtrace() except that it prints a backtrace of an 383 * arbitrary thread rather than the calling thread. 384 */ 385 void 386 kdb_backtrace_thread(struct thread *td) 387 { 388 389 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace_thread != NULL) { 390 printf("KDB: stack backtrace of thread %d:\n", td->td_tid); 391 kdb_dbbe->dbbe_trace_thread(td); 392 } 393 #ifdef STACK 394 else { 395 struct stack st; 396 397 printf("KDB: stack backtrace of thread %d:\n", td->td_tid); 398 stack_zero(&st); 399 stack_save_td(&st, td); 400 stack_print_ddb(&st); 401 } 402 #endif 403 } 404 405 /* 406 * Set/change the current backend. 407 */ 408 409 int 410 kdb_dbbe_select(const char *name) 411 { 412 struct kdb_dbbe *be, **iter; 413 414 SET_FOREACH(iter, kdb_dbbe_set) { 415 be = *iter; 416 if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) { 417 kdb_dbbe = be; 418 return (0); 419 } 420 } 421 return (EINVAL); 422 } 423 424 /* 425 * Enter the currently selected debugger. If a message has been provided, 426 * it is printed first. If the debugger does not support the enter method, 427 * it is entered by using breakpoint(), which enters the debugger through 428 * kdb_trap(). The 'why' argument will contain a more mechanically usable 429 * string than 'msg', and is relied upon by DDB scripting to identify the 430 * reason for entering the debugger so that the right script can be run. 431 */ 432 void 433 kdb_enter(const char *why, const char *msg) 434 { 435 436 if (kdb_dbbe != NULL && kdb_active == 0) { 437 if (msg != NULL) 438 printf("KDB: enter: %s\n", msg); 439 kdb_why = why; 440 breakpoint(); 441 kdb_why = KDB_WHY_UNSET; 442 } 443 } 444 445 /* 446 * Initialize the kernel debugger interface. 447 */ 448 449 void 450 kdb_init(void) 451 { 452 struct kdb_dbbe *be, **iter; 453 int cur_pri, pri; 454 455 kdb_active = 0; 456 kdb_dbbe = NULL; 457 cur_pri = -1; 458 SET_FOREACH(iter, kdb_dbbe_set) { 459 be = *iter; 460 pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1; 461 be->dbbe_active = (pri >= 0) ? 0 : -1; 462 if (pri > cur_pri) { 463 cur_pri = pri; 464 kdb_dbbe = be; 465 } 466 } 467 if (kdb_dbbe != NULL) { 468 printf("KDB: debugger backends:"); 469 SET_FOREACH(iter, kdb_dbbe_set) { 470 be = *iter; 471 if (be->dbbe_active == 0) 472 printf(" %s", be->dbbe_name); 473 } 474 printf("\n"); 475 printf("KDB: current backend: %s\n", 476 kdb_dbbe->dbbe_name); 477 } 478 } 479 480 /* 481 * Handle contexts. 482 */ 483 484 void * 485 kdb_jmpbuf(jmp_buf new) 486 { 487 void *old; 488 489 old = kdb_jmpbufp; 490 kdb_jmpbufp = new; 491 return (old); 492 } 493 494 void 495 kdb_reenter(void) 496 { 497 498 if (!kdb_active || kdb_jmpbufp == NULL) 499 return; 500 501 longjmp(kdb_jmpbufp, 1); 502 /* NOTREACHED */ 503 } 504 505 /* 506 * Thread related support functions. 507 */ 508 509 struct pcb * 510 kdb_thr_ctx(struct thread *thr) 511 { 512 #if defined(SMP) && defined(KDB_STOPPEDPCB) 513 struct pcpu *pc; 514 #endif 515 516 if (thr == curthread) 517 return (&kdb_pcb); 518 519 #if defined(SMP) && defined(KDB_STOPPEDPCB) 520 STAILQ_FOREACH(pc, &cpuhead, pc_allcpu) { 521 if (pc->pc_curthread == thr && 522 CPU_ISSET(pc->pc_cpuid, &stopped_cpus)) 523 return (KDB_STOPPEDPCB(pc)); 524 } 525 #endif 526 return (thr->td_pcb); 527 } 528 529 struct thread * 530 kdb_thr_first(void) 531 { 532 struct proc *p; 533 struct thread *thr; 534 535 p = LIST_FIRST(&allproc); 536 while (p != NULL) { 537 if (p->p_flag & P_INMEM) { 538 thr = FIRST_THREAD_IN_PROC(p); 539 if (thr != NULL) 540 return (thr); 541 } 542 p = LIST_NEXT(p, p_list); 543 } 544 return (NULL); 545 } 546 547 struct thread * 548 kdb_thr_from_pid(pid_t pid) 549 { 550 struct proc *p; 551 552 p = LIST_FIRST(&allproc); 553 while (p != NULL) { 554 if (p->p_flag & P_INMEM && p->p_pid == pid) 555 return (FIRST_THREAD_IN_PROC(p)); 556 p = LIST_NEXT(p, p_list); 557 } 558 return (NULL); 559 } 560 561 struct thread * 562 kdb_thr_lookup(lwpid_t tid) 563 { 564 struct thread *thr; 565 566 thr = kdb_thr_first(); 567 while (thr != NULL && thr->td_tid != tid) 568 thr = kdb_thr_next(thr); 569 return (thr); 570 } 571 572 struct thread * 573 kdb_thr_next(struct thread *thr) 574 { 575 struct proc *p; 576 577 p = thr->td_proc; 578 thr = TAILQ_NEXT(thr, td_plist); 579 do { 580 if (thr != NULL) 581 return (thr); 582 p = LIST_NEXT(p, p_list); 583 if (p != NULL && (p->p_flag & P_INMEM)) 584 thr = FIRST_THREAD_IN_PROC(p); 585 } while (p != NULL); 586 return (NULL); 587 } 588 589 int 590 kdb_thr_select(struct thread *thr) 591 { 592 if (thr == NULL) 593 return (EINVAL); 594 kdb_thread = thr; 595 kdb_thrctx = kdb_thr_ctx(thr); 596 return (0); 597 } 598 599 /* 600 * Enter the debugger due to a trap. 601 */ 602 603 int 604 kdb_trap(int type, int code, struct trapframe *tf) 605 { 606 #ifdef SMP 607 cpuset_t other_cpus; 608 #endif 609 struct kdb_dbbe *be; 610 register_t intr; 611 int handled; 612 #ifdef SMP 613 int did_stop_cpus; 614 #endif 615 616 be = kdb_dbbe; 617 if (be == NULL || be->dbbe_trap == NULL) 618 return (0); 619 620 /* We reenter the debugger through kdb_reenter(). */ 621 if (kdb_active) 622 return (0); 623 624 intr = intr_disable(); 625 626 #ifdef SMP 627 if (!SCHEDULER_STOPPED()) { 628 other_cpus = all_cpus; 629 CPU_CLR(PCPU_GET(cpuid), &other_cpus); 630 stop_cpus_hard(other_cpus); 631 did_stop_cpus = 1; 632 } else 633 did_stop_cpus = 0; 634 #endif 635 636 kdb_active++; 637 638 kdb_frame = tf; 639 640 /* Let MD code do its thing first... */ 641 kdb_cpu_trap(type, code); 642 643 makectx(tf, &kdb_pcb); 644 kdb_thr_select(curthread); 645 646 cngrab(); 647 648 for (;;) { 649 handled = be->dbbe_trap(type, code); 650 if (be == kdb_dbbe) 651 break; 652 be = kdb_dbbe; 653 if (be == NULL || be->dbbe_trap == NULL) 654 break; 655 printf("Switching to %s back-end\n", be->dbbe_name); 656 } 657 658 cnungrab(); 659 660 kdb_active--; 661 662 #ifdef SMP 663 if (did_stop_cpus) 664 restart_cpus(stopped_cpus); 665 #endif 666 667 intr_restore(intr); 668 669 return (handled); 670 }
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