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/11.1/sys/kern/subr_kdb.c 273377 2014-10-21 07:31:21Z hselasky $"); 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, 95 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE, NULL, 0, 96 kdb_sysctl_enter, "I", "set to enter the debugger"); 97 98 SYSCTL_PROC(_debug_kdb, OID_AUTO, panic, 99 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE, NULL, 0, 100 kdb_sysctl_panic, "I", "set to panic the kernel"); 101 102 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap, 103 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE, NULL, 0, 104 kdb_sysctl_trap, "I", "set to cause a page fault via data access"); 105 106 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap_code, 107 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE, NULL, 0, 108 kdb_sysctl_trap_code, "I", "set to cause a page fault via code access"); 109 110 SYSCTL_INT(_debug_kdb, OID_AUTO, break_to_debugger, 111 CTLFLAG_RWTUN | CTLFLAG_SECURE, 112 &kdb_break_to_debugger, 0, "Enable break to debugger"); 113 114 SYSCTL_INT(_debug_kdb, OID_AUTO, alt_break_to_debugger, 115 CTLFLAG_RWTUN | CTLFLAG_SECURE, 116 &kdb_alt_break_to_debugger, 0, "Enable alternative break to debugger"); 117 118 /* 119 * Flag to indicate to debuggers why the debugger was entered. 120 */ 121 const char * volatile kdb_why = KDB_WHY_UNSET; 122 123 static int 124 kdb_sysctl_available(SYSCTL_HANDLER_ARGS) 125 { 126 struct kdb_dbbe **iter; 127 struct sbuf sbuf; 128 int error; 129 130 sbuf_new_for_sysctl(&sbuf, NULL, 64, req); 131 SET_FOREACH(iter, kdb_dbbe_set) { 132 if ((*iter)->dbbe_active == 0) 133 sbuf_printf(&sbuf, "%s ", (*iter)->dbbe_name); 134 } 135 error = sbuf_finish(&sbuf); 136 sbuf_delete(&sbuf); 137 return (error); 138 } 139 140 static int 141 kdb_sysctl_current(SYSCTL_HANDLER_ARGS) 142 { 143 char buf[16]; 144 int error; 145 146 if (kdb_dbbe != NULL) 147 strlcpy(buf, kdb_dbbe->dbbe_name, sizeof(buf)); 148 else 149 *buf = '\0'; 150 error = sysctl_handle_string(oidp, buf, sizeof(buf), req); 151 if (error != 0 || req->newptr == NULL) 152 return (error); 153 if (kdb_active) 154 return (EBUSY); 155 return (kdb_dbbe_select(buf)); 156 } 157 158 static int 159 kdb_sysctl_enter(SYSCTL_HANDLER_ARGS) 160 { 161 int error, i; 162 163 error = sysctl_wire_old_buffer(req, sizeof(int)); 164 if (error == 0) { 165 i = 0; 166 error = sysctl_handle_int(oidp, &i, 0, req); 167 } 168 if (error != 0 || req->newptr == NULL) 169 return (error); 170 if (kdb_active) 171 return (EBUSY); 172 kdb_enter(KDB_WHY_SYSCTL, "sysctl debug.kdb.enter"); 173 return (0); 174 } 175 176 static int 177 kdb_sysctl_panic(SYSCTL_HANDLER_ARGS) 178 { 179 int error, i; 180 181 error = sysctl_wire_old_buffer(req, sizeof(int)); 182 if (error == 0) { 183 i = 0; 184 error = sysctl_handle_int(oidp, &i, 0, req); 185 } 186 if (error != 0 || req->newptr == NULL) 187 return (error); 188 panic("kdb_sysctl_panic"); 189 return (0); 190 } 191 192 static int 193 kdb_sysctl_trap(SYSCTL_HANDLER_ARGS) 194 { 195 int error, i; 196 int *addr = (int *)0x10; 197 198 error = sysctl_wire_old_buffer(req, sizeof(int)); 199 if (error == 0) { 200 i = 0; 201 error = sysctl_handle_int(oidp, &i, 0, req); 202 } 203 if (error != 0 || req->newptr == NULL) 204 return (error); 205 return (*addr); 206 } 207 208 static int 209 kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS) 210 { 211 int error, i; 212 void (*fp)(u_int, u_int, u_int) = (void *)0xdeadc0de; 213 214 error = sysctl_wire_old_buffer(req, sizeof(int)); 215 if (error == 0) { 216 i = 0; 217 error = sysctl_handle_int(oidp, &i, 0, req); 218 } 219 if (error != 0 || req->newptr == NULL) 220 return (error); 221 (*fp)(0x11111111, 0x22222222, 0x33333333); 222 return (0); 223 } 224 225 void 226 kdb_panic(const char *msg) 227 { 228 229 printf("KDB: panic\n"); 230 panic("%s", msg); 231 } 232 233 void 234 kdb_reboot(void) 235 { 236 237 printf("KDB: reboot requested\n"); 238 shutdown_nice(0); 239 } 240 241 /* 242 * Solaris implements a new BREAK which is initiated by a character sequence 243 * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the 244 * Remote Console. 245 * 246 * Note that this function may be called from almost anywhere, with interrupts 247 * disabled and with unknown locks held, so it must not access data other than 248 * its arguments. Its up to the caller to ensure that the state variable is 249 * consistent. 250 */ 251 252 #define KEY_CR 13 /* CR '\r' */ 253 #define KEY_TILDE 126 /* ~ */ 254 #define KEY_CRTLB 2 /* ^B */ 255 #define KEY_CRTLP 16 /* ^P */ 256 #define KEY_CRTLR 18 /* ^R */ 257 258 /* States of th KDB "alternate break sequence" detecting state machine. */ 259 enum { 260 KDB_ALT_BREAK_SEEN_NONE, 261 KDB_ALT_BREAK_SEEN_CR, 262 KDB_ALT_BREAK_SEEN_CR_TILDE, 263 }; 264 265 int 266 kdb_break(void) 267 { 268 269 if (!kdb_break_to_debugger) 270 return (0); 271 kdb_enter(KDB_WHY_BREAK, "Break to debugger"); 272 return (KDB_REQ_DEBUGGER); 273 } 274 275 static int 276 kdb_alt_break_state(int key, int *state) 277 { 278 int brk; 279 280 /* All states transition to KDB_ALT_BREAK_SEEN_CR on a CR. */ 281 if (key == KEY_CR) { 282 *state = KDB_ALT_BREAK_SEEN_CR; 283 return (0); 284 } 285 286 brk = 0; 287 switch (*state) { 288 case KDB_ALT_BREAK_SEEN_CR: 289 *state = KDB_ALT_BREAK_SEEN_NONE; 290 if (key == KEY_TILDE) 291 *state = KDB_ALT_BREAK_SEEN_CR_TILDE; 292 break; 293 case KDB_ALT_BREAK_SEEN_CR_TILDE: 294 *state = KDB_ALT_BREAK_SEEN_NONE; 295 if (key == KEY_CRTLB) 296 brk = KDB_REQ_DEBUGGER; 297 else if (key == KEY_CRTLP) 298 brk = KDB_REQ_PANIC; 299 else if (key == KEY_CRTLR) 300 brk = KDB_REQ_REBOOT; 301 break; 302 case KDB_ALT_BREAK_SEEN_NONE: 303 default: 304 *state = KDB_ALT_BREAK_SEEN_NONE; 305 break; 306 } 307 return (brk); 308 } 309 310 static int 311 kdb_alt_break_internal(int key, int *state, int force_gdb) 312 { 313 int brk; 314 315 if (!kdb_alt_break_to_debugger) 316 return (0); 317 brk = kdb_alt_break_state(key, state); 318 switch (brk) { 319 case KDB_REQ_DEBUGGER: 320 if (force_gdb) 321 kdb_dbbe_select("gdb"); 322 kdb_enter(KDB_WHY_BREAK, "Break to debugger"); 323 break; 324 325 case KDB_REQ_PANIC: 326 if (force_gdb) 327 kdb_dbbe_select("gdb"); 328 kdb_panic("Panic sequence on console"); 329 break; 330 331 case KDB_REQ_REBOOT: 332 kdb_reboot(); 333 break; 334 } 335 return (0); 336 } 337 338 int 339 kdb_alt_break(int key, int *state) 340 { 341 342 return (kdb_alt_break_internal(key, state, 0)); 343 } 344 345 /* 346 * This variation on kdb_alt_break() is used only by dcons, which has its own 347 * configuration flag to force GDB use regardless of the global KDB 348 * configuration. 349 */ 350 int 351 kdb_alt_break_gdb(int key, int *state) 352 { 353 354 return (kdb_alt_break_internal(key, state, 1)); 355 } 356 357 /* 358 * Print a backtrace of the calling thread. The backtrace is generated by 359 * the selected debugger, provided it supports backtraces. If no debugger 360 * is selected or the current debugger does not support backtraces, this 361 * function silently returns. 362 */ 363 364 void 365 kdb_backtrace(void) 366 { 367 368 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) { 369 printf("KDB: stack backtrace:\n"); 370 kdb_dbbe->dbbe_trace(); 371 } 372 #ifdef STACK 373 else { 374 struct stack st; 375 376 printf("KDB: stack backtrace:\n"); 377 stack_zero(&st); 378 stack_save(&st); 379 stack_print_ddb(&st); 380 } 381 #endif 382 } 383 384 /* 385 * Similar to kdb_backtrace() except that it prints a backtrace of an 386 * arbitrary thread rather than the calling thread. 387 */ 388 void 389 kdb_backtrace_thread(struct thread *td) 390 { 391 392 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace_thread != NULL) { 393 printf("KDB: stack backtrace of thread %d:\n", td->td_tid); 394 kdb_dbbe->dbbe_trace_thread(td); 395 } 396 #ifdef STACK 397 else { 398 struct stack st; 399 400 printf("KDB: stack backtrace of thread %d:\n", td->td_tid); 401 stack_zero(&st); 402 stack_save_td(&st, td); 403 stack_print_ddb(&st); 404 } 405 #endif 406 } 407 408 /* 409 * Set/change the current backend. 410 */ 411 412 int 413 kdb_dbbe_select(const char *name) 414 { 415 struct kdb_dbbe *be, **iter; 416 417 SET_FOREACH(iter, kdb_dbbe_set) { 418 be = *iter; 419 if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) { 420 kdb_dbbe = be; 421 return (0); 422 } 423 } 424 return (EINVAL); 425 } 426 427 /* 428 * Enter the currently selected debugger. If a message has been provided, 429 * it is printed first. If the debugger does not support the enter method, 430 * it is entered by using breakpoint(), which enters the debugger through 431 * kdb_trap(). The 'why' argument will contain a more mechanically usable 432 * string than 'msg', and is relied upon by DDB scripting to identify the 433 * reason for entering the debugger so that the right script can be run. 434 */ 435 void 436 kdb_enter(const char *why, const char *msg) 437 { 438 439 if (kdb_dbbe != NULL && kdb_active == 0) { 440 if (msg != NULL) 441 printf("KDB: enter: %s\n", msg); 442 kdb_why = why; 443 breakpoint(); 444 kdb_why = KDB_WHY_UNSET; 445 } 446 } 447 448 /* 449 * Initialize the kernel debugger interface. 450 */ 451 452 void 453 kdb_init(void) 454 { 455 struct kdb_dbbe *be, **iter; 456 int cur_pri, pri; 457 458 kdb_active = 0; 459 kdb_dbbe = NULL; 460 cur_pri = -1; 461 SET_FOREACH(iter, kdb_dbbe_set) { 462 be = *iter; 463 pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1; 464 be->dbbe_active = (pri >= 0) ? 0 : -1; 465 if (pri > cur_pri) { 466 cur_pri = pri; 467 kdb_dbbe = be; 468 } 469 } 470 if (kdb_dbbe != NULL) { 471 printf("KDB: debugger backends:"); 472 SET_FOREACH(iter, kdb_dbbe_set) { 473 be = *iter; 474 if (be->dbbe_active == 0) 475 printf(" %s", be->dbbe_name); 476 } 477 printf("\n"); 478 printf("KDB: current backend: %s\n", 479 kdb_dbbe->dbbe_name); 480 } 481 } 482 483 /* 484 * Handle contexts. 485 */ 486 487 void * 488 kdb_jmpbuf(jmp_buf new) 489 { 490 void *old; 491 492 old = kdb_jmpbufp; 493 kdb_jmpbufp = new; 494 return (old); 495 } 496 497 void 498 kdb_reenter(void) 499 { 500 501 if (!kdb_active || kdb_jmpbufp == NULL) 502 return; 503 504 printf("KDB: reentering\n"); 505 kdb_backtrace(); 506 longjmp(kdb_jmpbufp, 1); 507 /* NOTREACHED */ 508 } 509 510 /* 511 * Thread related support functions. 512 */ 513 514 struct pcb * 515 kdb_thr_ctx(struct thread *thr) 516 { 517 #if defined(SMP) && defined(KDB_STOPPEDPCB) 518 struct pcpu *pc; 519 #endif 520 521 if (thr == curthread) 522 return (&kdb_pcb); 523 524 #if defined(SMP) && defined(KDB_STOPPEDPCB) 525 STAILQ_FOREACH(pc, &cpuhead, pc_allcpu) { 526 if (pc->pc_curthread == thr && 527 CPU_ISSET(pc->pc_cpuid, &stopped_cpus)) 528 return (KDB_STOPPEDPCB(pc)); 529 } 530 #endif 531 return (thr->td_pcb); 532 } 533 534 struct thread * 535 kdb_thr_first(void) 536 { 537 struct proc *p; 538 struct thread *thr; 539 540 p = LIST_FIRST(&allproc); 541 while (p != NULL) { 542 if (p->p_flag & P_INMEM) { 543 thr = FIRST_THREAD_IN_PROC(p); 544 if (thr != NULL) 545 return (thr); 546 } 547 p = LIST_NEXT(p, p_list); 548 } 549 return (NULL); 550 } 551 552 struct thread * 553 kdb_thr_from_pid(pid_t pid) 554 { 555 struct proc *p; 556 557 p = LIST_FIRST(&allproc); 558 while (p != NULL) { 559 if (p->p_flag & P_INMEM && p->p_pid == pid) 560 return (FIRST_THREAD_IN_PROC(p)); 561 p = LIST_NEXT(p, p_list); 562 } 563 return (NULL); 564 } 565 566 struct thread * 567 kdb_thr_lookup(lwpid_t tid) 568 { 569 struct thread *thr; 570 571 thr = kdb_thr_first(); 572 while (thr != NULL && thr->td_tid != tid) 573 thr = kdb_thr_next(thr); 574 return (thr); 575 } 576 577 struct thread * 578 kdb_thr_next(struct thread *thr) 579 { 580 struct proc *p; 581 582 p = thr->td_proc; 583 thr = TAILQ_NEXT(thr, td_plist); 584 do { 585 if (thr != NULL) 586 return (thr); 587 p = LIST_NEXT(p, p_list); 588 if (p != NULL && (p->p_flag & P_INMEM)) 589 thr = FIRST_THREAD_IN_PROC(p); 590 } while (p != NULL); 591 return (NULL); 592 } 593 594 int 595 kdb_thr_select(struct thread *thr) 596 { 597 if (thr == NULL) 598 return (EINVAL); 599 kdb_thread = thr; 600 kdb_thrctx = kdb_thr_ctx(thr); 601 return (0); 602 } 603 604 /* 605 * Enter the debugger due to a trap. 606 */ 607 608 int 609 kdb_trap(int type, int code, struct trapframe *tf) 610 { 611 #ifdef SMP 612 cpuset_t other_cpus; 613 #endif 614 struct kdb_dbbe *be; 615 register_t intr; 616 int handled; 617 #ifdef SMP 618 int did_stop_cpus; 619 #endif 620 621 be = kdb_dbbe; 622 if (be == NULL || be->dbbe_trap == NULL) 623 return (0); 624 625 /* We reenter the debugger through kdb_reenter(). */ 626 if (kdb_active) 627 return (0); 628 629 intr = intr_disable(); 630 631 #ifdef SMP 632 if (!SCHEDULER_STOPPED()) { 633 other_cpus = all_cpus; 634 CPU_CLR(PCPU_GET(cpuid), &other_cpus); 635 stop_cpus_hard(other_cpus); 636 did_stop_cpus = 1; 637 } else 638 did_stop_cpus = 0; 639 #endif 640 641 kdb_active++; 642 643 kdb_frame = tf; 644 645 /* Let MD code do its thing first... */ 646 kdb_cpu_trap(type, code); 647 648 makectx(tf, &kdb_pcb); 649 kdb_thr_select(curthread); 650 651 cngrab(); 652 653 for (;;) { 654 handled = be->dbbe_trap(type, code); 655 if (be == kdb_dbbe) 656 break; 657 be = kdb_dbbe; 658 if (be == NULL || be->dbbe_trap == NULL) 659 break; 660 printf("Switching to %s back-end\n", be->dbbe_name); 661 } 662 663 cnungrab(); 664 665 kdb_active--; 666 667 #ifdef SMP 668 if (did_stop_cpus) 669 restart_cpus(stopped_cpus); 670 #endif 671 672 intr_restore(intr); 673 674 return (handled); 675 }
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