1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD 3 * 4 * Copyright (c) 2004 The FreeBSD Project 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 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. 16 * 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. 27 */ 28 29 #include <sys/cdefs.h> 30 __FBSDID("$FreeBSD$"); 31 32 #include "opt_kdb.h" 33 #include "opt_stack.h" 34 35 #include <sys/param.h> 36 #include <sys/systm.h> 37 #include <sys/cons.h> 38 #include <sys/kdb.h> 39 #include <sys/kernel.h> 40 #include <sys/malloc.h> 41 #include <sys/lock.h> 42 #include <sys/pcpu.h> 43 #include <sys/proc.h> 44 #include <sys/sbuf.h> 45 #include <sys/smp.h> 46 #include <sys/stack.h> 47 #include <sys/sysctl.h> 48 49 #include <machine/kdb.h> 50 #include <machine/pcb.h> 51 52 #ifdef SMP 53 #include <machine/smp.h> 54 #endif 55 56 u_char __read_frequently kdb_active = 0; 57 static void *kdb_jmpbufp = NULL; 58 struct kdb_dbbe *kdb_dbbe = NULL; 59 static struct pcb kdb_pcb; 60 struct pcb *kdb_thrctx = NULL; 61 struct thread *kdb_thread = NULL; 62 struct trapframe *kdb_frame = NULL; 63 64 #ifdef BREAK_TO_DEBUGGER 65 #define KDB_BREAK_TO_DEBUGGER 1 66 #else 67 #define KDB_BREAK_TO_DEBUGGER 0 68 #endif 69 70 #ifdef ALT_BREAK_TO_DEBUGGER 71 #define KDB_ALT_BREAK_TO_DEBUGGER 1 72 #else 73 #define KDB_ALT_BREAK_TO_DEBUGGER 0 74 #endif 75 76 static int kdb_break_to_debugger = KDB_BREAK_TO_DEBUGGER; 77 static int kdb_alt_break_to_debugger = KDB_ALT_BREAK_TO_DEBUGGER; 78 79 KDB_BACKEND(null, NULL, NULL, NULL, NULL); 80 81 static int kdb_sysctl_available(SYSCTL_HANDLER_ARGS); 82 static int kdb_sysctl_current(SYSCTL_HANDLER_ARGS); 83 static int kdb_sysctl_enter(SYSCTL_HANDLER_ARGS); 84 static int kdb_sysctl_panic(SYSCTL_HANDLER_ARGS); 85 static int kdb_sysctl_trap(SYSCTL_HANDLER_ARGS); 86 static int kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS); 87 static int kdb_sysctl_stack_overflow(SYSCTL_HANDLER_ARGS); 88 89 static SYSCTL_NODE(_debug, OID_AUTO, kdb, CTLFLAG_RW, NULL, "KDB nodes"); 90 91 SYSCTL_PROC(_debug_kdb, OID_AUTO, available, CTLTYPE_STRING | CTLFLAG_RD, NULL, 92 0, kdb_sysctl_available, "A", "list of available KDB backends"); 93 94 SYSCTL_PROC(_debug_kdb, OID_AUTO, current, CTLTYPE_STRING | CTLFLAG_RW, NULL, 95 0, kdb_sysctl_current, "A", "currently selected KDB backend"); 96 97 SYSCTL_PROC(_debug_kdb, OID_AUTO, enter, 98 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE, NULL, 0, 99 kdb_sysctl_enter, "I", "set to enter the debugger"); 100 101 SYSCTL_PROC(_debug_kdb, OID_AUTO, panic, 102 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE, NULL, 0, 103 kdb_sysctl_panic, "I", "set to panic the kernel"); 104 105 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap, 106 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE, NULL, 0, 107 kdb_sysctl_trap, "I", "set to cause a page fault via data access"); 108 109 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap_code, 110 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE, NULL, 0, 111 kdb_sysctl_trap_code, "I", "set to cause a page fault via code access"); 112 113 SYSCTL_PROC(_debug_kdb, OID_AUTO, stack_overflow, 114 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE, NULL, 0, 115 kdb_sysctl_stack_overflow, "I", "set to cause a stack overflow"); 116 117 SYSCTL_INT(_debug_kdb, OID_AUTO, break_to_debugger, 118 CTLFLAG_RWTUN | CTLFLAG_SECURE, 119 &kdb_break_to_debugger, 0, "Enable break to debugger"); 120 121 SYSCTL_INT(_debug_kdb, OID_AUTO, alt_break_to_debugger, 122 CTLFLAG_RWTUN | CTLFLAG_SECURE, 123 &kdb_alt_break_to_debugger, 0, "Enable alternative break to debugger"); 124 125 /* 126 * Flag to indicate to debuggers why the debugger was entered. 127 */ 128 const char * volatile kdb_why = KDB_WHY_UNSET; 129 130 static int 131 kdb_sysctl_available(SYSCTL_HANDLER_ARGS) 132 { 133 struct kdb_dbbe **iter; 134 struct sbuf sbuf; 135 int error; 136 137 sbuf_new_for_sysctl(&sbuf, NULL, 64, req); 138 SET_FOREACH(iter, kdb_dbbe_set) { 139 if ((*iter)->dbbe_active == 0) 140 sbuf_printf(&sbuf, "%s ", (*iter)->dbbe_name); 141 } 142 error = sbuf_finish(&sbuf); 143 sbuf_delete(&sbuf); 144 return (error); 145 } 146 147 static int 148 kdb_sysctl_current(SYSCTL_HANDLER_ARGS) 149 { 150 char buf[16]; 151 int error; 152 153 if (kdb_dbbe != NULL) 154 strlcpy(buf, kdb_dbbe->dbbe_name, sizeof(buf)); 155 else 156 *buf = '\0'; 157 error = sysctl_handle_string(oidp, buf, sizeof(buf), req); 158 if (error != 0 || req->newptr == NULL) 159 return (error); 160 if (kdb_active) 161 return (EBUSY); 162 return (kdb_dbbe_select(buf)); 163 } 164 165 static int 166 kdb_sysctl_enter(SYSCTL_HANDLER_ARGS) 167 { 168 int error, i; 169 170 error = sysctl_wire_old_buffer(req, sizeof(int)); 171 if (error == 0) { 172 i = 0; 173 error = sysctl_handle_int(oidp, &i, 0, req); 174 } 175 if (error != 0 || req->newptr == NULL) 176 return (error); 177 if (kdb_active) 178 return (EBUSY); 179 kdb_enter(KDB_WHY_SYSCTL, "sysctl debug.kdb.enter"); 180 return (0); 181 } 182 183 static int 184 kdb_sysctl_panic(SYSCTL_HANDLER_ARGS) 185 { 186 int error, i; 187 188 error = sysctl_wire_old_buffer(req, sizeof(int)); 189 if (error == 0) { 190 i = 0; 191 error = sysctl_handle_int(oidp, &i, 0, req); 192 } 193 if (error != 0 || req->newptr == NULL) 194 return (error); 195 panic("kdb_sysctl_panic"); 196 return (0); 197 } 198 199 static int 200 kdb_sysctl_trap(SYSCTL_HANDLER_ARGS) 201 { 202 int error, i; 203 int *addr = (int *)0x10; 204 205 error = sysctl_wire_old_buffer(req, sizeof(int)); 206 if (error == 0) { 207 i = 0; 208 error = sysctl_handle_int(oidp, &i, 0, req); 209 } 210 if (error != 0 || req->newptr == NULL) 211 return (error); 212 return (*addr); 213 } 214 215 static int 216 kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS) 217 { 218 int error, i; 219 void (*fp)(u_int, u_int, u_int) = (void *)0xdeadc0de; 220 221 error = sysctl_wire_old_buffer(req, sizeof(int)); 222 if (error == 0) { 223 i = 0; 224 error = sysctl_handle_int(oidp, &i, 0, req); 225 } 226 if (error != 0 || req->newptr == NULL) 227 return (error); 228 (*fp)(0x11111111, 0x22222222, 0x33333333); 229 return (0); 230 } 231 232 static void kdb_stack_overflow(volatile int *x) __noinline; 233 static void 234 kdb_stack_overflow(volatile int *x) 235 { 236 237 if (*x > 10000000) 238 return; 239 kdb_stack_overflow(x); 240 *x += PCPU_GET(cpuid) / 1000000; 241 } 242 243 static int 244 kdb_sysctl_stack_overflow(SYSCTL_HANDLER_ARGS) 245 { 246 int error, i; 247 volatile int x; 248 249 error = sysctl_wire_old_buffer(req, sizeof(int)); 250 if (error == 0) { 251 i = 0; 252 error = sysctl_handle_int(oidp, &i, 0, req); 253 } 254 if (error != 0 || req->newptr == NULL) 255 return (error); 256 x = 0; 257 kdb_stack_overflow(&x); 258 return (0); 259 } 260 261 void 262 kdb_panic(const char *msg) 263 { 264 265 printf("KDB: panic\n"); 266 panic("%s", msg); 267 } 268 269 void 270 kdb_reboot(void) 271 { 272 273 printf("KDB: reboot requested\n"); 274 shutdown_nice(0); 275 } 276 277 /* 278 * Solaris implements a new BREAK which is initiated by a character sequence 279 * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the 280 * Remote Console. 281 * 282 * Note that this function may be called from almost anywhere, with interrupts 283 * disabled and with unknown locks held, so it must not access data other than 284 * its arguments. Its up to the caller to ensure that the state variable is 285 * consistent. 286 */ 287 #define KEY_CR 13 /* CR '\r' */ 288 #define KEY_TILDE 126 /* ~ */ 289 #define KEY_CRTLB 2 /* ^B */ 290 #define KEY_CRTLP 16 /* ^P */ 291 #define KEY_CRTLR 18 /* ^R */ 292 293 /* States of th KDB "alternate break sequence" detecting state machine. */ 294 enum { 295 KDB_ALT_BREAK_SEEN_NONE, 296 KDB_ALT_BREAK_SEEN_CR, 297 KDB_ALT_BREAK_SEEN_CR_TILDE, 298 }; 299 300 int 301 kdb_break(void) 302 { 303 304 if (!kdb_break_to_debugger) 305 return (0); 306 kdb_enter(KDB_WHY_BREAK, "Break to debugger"); 307 return (KDB_REQ_DEBUGGER); 308 } 309 310 static int 311 kdb_alt_break_state(int key, int *state) 312 { 313 int brk; 314 315 /* All states transition to KDB_ALT_BREAK_SEEN_CR on a CR. */ 316 if (key == KEY_CR) { 317 *state = KDB_ALT_BREAK_SEEN_CR; 318 return (0); 319 } 320 321 brk = 0; 322 switch (*state) { 323 case KDB_ALT_BREAK_SEEN_CR: 324 *state = KDB_ALT_BREAK_SEEN_NONE; 325 if (key == KEY_TILDE) 326 *state = KDB_ALT_BREAK_SEEN_CR_TILDE; 327 break; 328 case KDB_ALT_BREAK_SEEN_CR_TILDE: 329 *state = KDB_ALT_BREAK_SEEN_NONE; 330 if (key == KEY_CRTLB) 331 brk = KDB_REQ_DEBUGGER; 332 else if (key == KEY_CRTLP) 333 brk = KDB_REQ_PANIC; 334 else if (key == KEY_CRTLR) 335 brk = KDB_REQ_REBOOT; 336 break; 337 case KDB_ALT_BREAK_SEEN_NONE: 338 default: 339 *state = KDB_ALT_BREAK_SEEN_NONE; 340 break; 341 } 342 return (brk); 343 } 344 345 static int 346 kdb_alt_break_internal(int key, int *state, int force_gdb) 347 { 348 int brk; 349 350 if (!kdb_alt_break_to_debugger) 351 return (0); 352 brk = kdb_alt_break_state(key, state); 353 switch (brk) { 354 case KDB_REQ_DEBUGGER: 355 if (force_gdb) 356 kdb_dbbe_select("gdb"); 357 kdb_enter(KDB_WHY_BREAK, "Break to debugger"); 358 break; 359 360 case KDB_REQ_PANIC: 361 if (force_gdb) 362 kdb_dbbe_select("gdb"); 363 kdb_panic("Panic sequence on console"); 364 break; 365 366 case KDB_REQ_REBOOT: 367 kdb_reboot(); 368 break; 369 } 370 return (0); 371 } 372 373 int 374 kdb_alt_break(int key, int *state) 375 { 376 377 return (kdb_alt_break_internal(key, state, 0)); 378 } 379 380 /* 381 * This variation on kdb_alt_break() is used only by dcons, which has its own 382 * configuration flag to force GDB use regardless of the global KDB 383 * configuration. 384 */ 385 int 386 kdb_alt_break_gdb(int key, int *state) 387 { 388 389 return (kdb_alt_break_internal(key, state, 1)); 390 } 391 392 /* 393 * Print a backtrace of the calling thread. The backtrace is generated by 394 * the selected debugger, provided it supports backtraces. If no debugger 395 * is selected or the current debugger does not support backtraces, this 396 * function silently returns. 397 */ 398 void 399 kdb_backtrace(void) 400 { 401 402 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) { 403 printf("KDB: stack backtrace:\n"); 404 kdb_dbbe->dbbe_trace(); 405 } 406 #ifdef STACK 407 else { 408 struct stack st; 409 410 printf("KDB: stack backtrace:\n"); 411 stack_zero(&st); 412 stack_save(&st); 413 stack_print_ddb(&st); 414 } 415 #endif 416 } 417 418 /* 419 * Similar to kdb_backtrace() except that it prints a backtrace of an 420 * arbitrary thread rather than the calling thread. 421 */ 422 void 423 kdb_backtrace_thread(struct thread *td) 424 { 425 426 if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace_thread != NULL) { 427 printf("KDB: stack backtrace of thread %d:\n", td->td_tid); 428 kdb_dbbe->dbbe_trace_thread(td); 429 } 430 #ifdef STACK 431 else { 432 struct stack st; 433 434 printf("KDB: stack backtrace of thread %d:\n", td->td_tid); 435 if (stack_save_td(&st, td) == 0) 436 stack_print_ddb(&st); 437 } 438 #endif 439 } 440 441 /* 442 * Set/change the current backend. 443 */ 444 int 445 kdb_dbbe_select(const char *name) 446 { 447 struct kdb_dbbe *be, **iter; 448 449 SET_FOREACH(iter, kdb_dbbe_set) { 450 be = *iter; 451 if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) { 452 kdb_dbbe = be; 453 return (0); 454 } 455 } 456 return (EINVAL); 457 } 458 459 /* 460 * Enter the currently selected debugger. If a message has been provided, 461 * it is printed first. If the debugger does not support the enter method, 462 * it is entered by using breakpoint(), which enters the debugger through 463 * kdb_trap(). The 'why' argument will contain a more mechanically usable 464 * string than 'msg', and is relied upon by DDB scripting to identify the 465 * reason for entering the debugger so that the right script can be run. 466 */ 467 void 468 kdb_enter(const char *why, const char *msg) 469 { 470 471 if (kdb_dbbe != NULL && kdb_active == 0) { 472 if (msg != NULL) 473 printf("KDB: enter: %s\n", msg); 474 kdb_why = why; 475 breakpoint(); 476 kdb_why = KDB_WHY_UNSET; 477 } 478 } 479 480 /* 481 * Initialize the kernel debugger interface. 482 */ 483 void 484 kdb_init(void) 485 { 486 struct kdb_dbbe *be, **iter; 487 int cur_pri, pri; 488 489 kdb_active = 0; 490 kdb_dbbe = NULL; 491 cur_pri = -1; 492 SET_FOREACH(iter, kdb_dbbe_set) { 493 be = *iter; 494 pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1; 495 be->dbbe_active = (pri >= 0) ? 0 : -1; 496 if (pri > cur_pri) { 497 cur_pri = pri; 498 kdb_dbbe = be; 499 } 500 } 501 if (kdb_dbbe != NULL) { 502 printf("KDB: debugger backends:"); 503 SET_FOREACH(iter, kdb_dbbe_set) { 504 be = *iter; 505 if (be->dbbe_active == 0) 506 printf(" %s", be->dbbe_name); 507 } 508 printf("\n"); 509 printf("KDB: current backend: %s\n", 510 kdb_dbbe->dbbe_name); 511 } 512 } 513 514 /* 515 * Handle contexts. 516 */ 517 void * 518 kdb_jmpbuf(jmp_buf new) 519 { 520 void *old; 521 522 old = kdb_jmpbufp; 523 kdb_jmpbufp = new; 524 return (old); 525 } 526 527 void 528 kdb_reenter(void) 529 { 530 531 if (!kdb_active || kdb_jmpbufp == NULL) 532 return; 533 534 printf("KDB: reentering\n"); 535 kdb_backtrace(); 536 longjmp(kdb_jmpbufp, 1); 537 /* NOTREACHED */ 538 } 539 540 void 541 kdb_reenter_silent(void) 542 { 543 544 if (!kdb_active || kdb_jmpbufp == NULL) 545 return; 546 547 longjmp(kdb_jmpbufp, 1); 548 /* NOTREACHED */ 549 } 550 551 /* 552 * Thread-related support functions. 553 */ 554 struct pcb * 555 kdb_thr_ctx(struct thread *thr) 556 { 557 #if defined(SMP) && defined(KDB_STOPPEDPCB) 558 struct pcpu *pc; 559 #endif 560 561 if (thr == curthread) 562 return (&kdb_pcb); 563 564 #if defined(SMP) && defined(KDB_STOPPEDPCB) 565 STAILQ_FOREACH(pc, &cpuhead, pc_allcpu) { 566 if (pc->pc_curthread == thr && 567 CPU_ISSET(pc->pc_cpuid, &stopped_cpus)) 568 return (KDB_STOPPEDPCB(pc)); 569 } 570 #endif 571 return (thr->td_pcb); 572 } 573 574 struct thread * 575 kdb_thr_first(void) 576 { 577 struct proc *p; 578 struct thread *thr; 579 580 FOREACH_PROC_IN_SYSTEM(p) { 581 if (p->p_flag & P_INMEM) { 582 thr = FIRST_THREAD_IN_PROC(p); 583 if (thr != NULL) 584 return (thr); 585 } 586 } 587 return (NULL); 588 } 589 590 struct thread * 591 kdb_thr_from_pid(pid_t pid) 592 { 593 struct proc *p; 594 595 FOREACH_PROC_IN_SYSTEM(p) { 596 if (p->p_flag & P_INMEM && p->p_pid == pid) 597 return (FIRST_THREAD_IN_PROC(p)); 598 } 599 return (NULL); 600 } 601 602 struct thread * 603 kdb_thr_lookup(lwpid_t tid) 604 { 605 struct thread *thr; 606 607 thr = kdb_thr_first(); 608 while (thr != NULL && thr->td_tid != tid) 609 thr = kdb_thr_next(thr); 610 return (thr); 611 } 612 613 struct thread * 614 kdb_thr_next(struct thread *thr) 615 { 616 struct proc *p; 617 618 p = thr->td_proc; 619 thr = TAILQ_NEXT(thr, td_plist); 620 do { 621 if (thr != NULL) 622 return (thr); 623 p = LIST_NEXT(p, p_list); 624 if (p != NULL && (p->p_flag & P_INMEM)) 625 thr = FIRST_THREAD_IN_PROC(p); 626 } while (p != NULL); 627 return (NULL); 628 } 629 630 int 631 kdb_thr_select(struct thread *thr) 632 { 633 if (thr == NULL) 634 return (EINVAL); 635 kdb_thread = thr; 636 kdb_thrctx = kdb_thr_ctx(thr); 637 return (0); 638 } 639 640 /* 641 * Enter the debugger due to a trap. 642 */ 643 int 644 kdb_trap(int type, int code, struct trapframe *tf) 645 { 646 #ifdef SMP 647 cpuset_t other_cpus; 648 #endif 649 struct kdb_dbbe *be; 650 register_t intr; 651 int handled; 652 int did_stop_cpus; 653 654 be = kdb_dbbe; 655 if (be == NULL || be->dbbe_trap == NULL) 656 return (0); 657 658 /* We reenter the debugger through kdb_reenter(). */ 659 if (kdb_active) 660 return (0); 661 662 intr = intr_disable(); 663 664 if (!SCHEDULER_STOPPED()) { 665 #ifdef SMP 666 other_cpus = all_cpus; 667 CPU_ANDNOT(&other_cpus, &stopped_cpus); 668 CPU_CLR(PCPU_GET(cpuid), &other_cpus); 669 stop_cpus_hard(other_cpus); 670 #endif 671 curthread->td_stopsched = 1; 672 did_stop_cpus = 1; 673 } else 674 did_stop_cpus = 0; 675 676 kdb_active++; 677 678 kdb_frame = tf; 679 680 /* Let MD code do its thing first... */ 681 kdb_cpu_trap(type, code); 682 683 makectx(tf, &kdb_pcb); 684 kdb_thr_select(curthread); 685 686 cngrab(); 687 688 for (;;) { 689 handled = be->dbbe_trap(type, code); 690 if (be == kdb_dbbe) 691 break; 692 be = kdb_dbbe; 693 if (be == NULL || be->dbbe_trap == NULL) 694 break; 695 printf("Switching to %s back-end\n", be->dbbe_name); 696 } 697 698 cnungrab(); 699 700 kdb_active--; 701 702 if (did_stop_cpus) { 703 curthread->td_stopsched = 0; 704 #ifdef SMP 705 CPU_AND(&other_cpus, &stopped_cpus); 706 restart_cpus(other_cpus); 707 #endif 708 } 709 710 intr_restore(intr); 711 712 return (handled); 713 } 714