sys/kern/subr_kdb.c

   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("$FreeBSD$");
  29
  30 #include "opt_kdb.h"
  31
  32 #include <sys/param.h>
  33 #include <sys/systm.h>
  34 #include <sys/kdb.h>
  35 #include <sys/kernel.h>
  36 #include <sys/malloc.h>
  37 #include <sys/pcpu.h>
  38 #include <sys/proc.h>
  39 #include <sys/smp.h>
  40 #include <sys/sysctl.h>
  41
  42 #include <machine/kdb.h>
  43 #include <machine/pcb.h>
  44
  45 #ifdef SMP
  46 #include <machine/smp.h>
  47 #endif
  48
  49 int kdb_active = 0;
  50 void *kdb_jmpbufp = NULL;
  51 struct kdb_dbbe *kdb_dbbe = NULL;
  52 struct pcb kdb_pcb;
  53 struct pcb *kdb_thrctx = NULL;
  54 struct thread *kdb_thread = NULL;
  55 struct trapframe *kdb_frame = NULL;
  56
  57 KDB_BACKEND(null, NULL, NULL, NULL);
  58 SET_DECLARE(kdb_dbbe_set, struct kdb_dbbe);
  59
  60 static int kdb_sysctl_available(SYSCTL_HANDLER_ARGS);
  61 static int kdb_sysctl_current(SYSCTL_HANDLER_ARGS);
  62 static int kdb_sysctl_enter(SYSCTL_HANDLER_ARGS);
  63 static int kdb_sysctl_panic(SYSCTL_HANDLER_ARGS);
  64 static int kdb_sysctl_trap(SYSCTL_HANDLER_ARGS);
  65 static int kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS);
  66
  67 SYSCTL_NODE(_debug, OID_AUTO, kdb, CTLFLAG_RW, NULL, "KDB nodes");
  68
  69 SYSCTL_PROC(_debug_kdb, OID_AUTO, available, CTLTYPE_STRING | CTLFLAG_RD, 0, 0,
  70     kdb_sysctl_available, "A", "list of available KDB backends");
  71
  72 SYSCTL_PROC(_debug_kdb, OID_AUTO, current, CTLTYPE_STRING | CTLFLAG_RW, 0, 0,
  73     kdb_sysctl_current, "A", "currently selected KDB backend");
  74
  75 SYSCTL_PROC(_debug_kdb, OID_AUTO, enter, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
  76     kdb_sysctl_enter, "I", "set to enter the debugger");
  77
  78 SYSCTL_PROC(_debug_kdb, OID_AUTO, panic, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
  79     kdb_sysctl_panic, "I", "set to panic the kernel");
  80
  81 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
  82     kdb_sysctl_trap, "I", "set to cause a page fault via data access");
  83
  84 SYSCTL_PROC(_debug_kdb, OID_AUTO, trap_code, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
  85     kdb_sysctl_trap_code, "I", "set to cause a page fault via code access");
  86
  87 /*
  88  * Flag indicating whether or not to IPI the other CPUs to stop them on
  89  * entering the debugger.  Sometimes, this will result in a deadlock as
  90  * stop_cpus() waits for the other cpus to stop, so we allow it to be
  91  * disabled.
  92  */
  93 #ifdef SMP
  94 static int kdb_stop_cpus = 1;
  95 SYSCTL_INT(_debug_kdb, OID_AUTO, stop_cpus, CTLTYPE_INT | CTLFLAG_RW,
  96     &kdb_stop_cpus, 0, "stop other CPUs when entering the debugger");
  97 TUNABLE_INT("debug.kdb.stop_cpus", &kdb_stop_cpus);
  98 #endif
  99
 100 /*
 101  * Flag to indicate to debuggers why the debugger was entered.
 102  */
 103 const char * volatile kdb_why = KDB_WHY_UNSET;
 104
 105 static int
 106 kdb_sysctl_available(SYSCTL_HANDLER_ARGS)
 107 {
 108         struct kdb_dbbe *be, **iter;
 109         char *avail, *p;
 110         ssize_t len, sz;
 111         int error;
 112
 113         sz = 0;
 114         SET_FOREACH(iter, kdb_dbbe_set) {
 115                 be = *iter;
 116                 if (be->dbbe_active == 0)
 117                         sz += strlen(be->dbbe_name) + 1;
 118         }
 119         sz++;
 120         avail = malloc(sz, M_TEMP, M_WAITOK);
 121         p = avail;
 122         *p = '\0';
 123
 124         SET_FOREACH(iter, kdb_dbbe_set) {
 125                 be = *iter;
 126                 if (be->dbbe_active == 0) {
 127                         len = snprintf(p, sz, "%s ", be->dbbe_name);
 128                         p += len;
 129                         sz -= len;
 130                 }
 131         }
 132         KASSERT(sz >= 0, ("%s", __func__));
 133         error = sysctl_handle_string(oidp, avail, 0, req);
 134         free(avail, M_TEMP);
 135         return (error);
 136 }
 137
 138 static int
 139 kdb_sysctl_current(SYSCTL_HANDLER_ARGS)
 140 {
 141         char buf[16];
 142         int error;
 143
 144         if (kdb_dbbe != NULL) {
 145                 strncpy(buf, kdb_dbbe->dbbe_name, sizeof(buf));
 146                 buf[sizeof(buf) - 1] = '\0';
 147         } else
 148                 *buf = '\0';
 149         error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
 150         if (error != 0 || req->newptr == NULL)
 151                 return (error);
 152         if (kdb_active)
 153                 return (EBUSY);
 154         return (kdb_dbbe_select(buf));
 155 }
 156
 157 static int
 158 kdb_sysctl_enter(SYSCTL_HANDLER_ARGS)
 159 {
 160         int error, i;
 161
 162         error = sysctl_wire_old_buffer(req, sizeof(int));
 163         if (error == 0) {
 164                 i = 0;
 165                 error = sysctl_handle_int(oidp, &i, 0, req);
 166         }
 167         if (error != 0 || req->newptr == NULL)
 168                 return (error);
 169         if (kdb_active)
 170                 return (EBUSY);
 171         kdb_enter(KDB_WHY_SYSCTL, "sysctl debug.kdb.enter");
 172         return (0);
 173 }
 174
 175 static int
 176 kdb_sysctl_panic(SYSCTL_HANDLER_ARGS)
 177 {
 178         int error, i;
 179
 180         error = sysctl_wire_old_buffer(req, sizeof(int));
 181         if (error == 0) {
 182                 i = 0;
 183                 error = sysctl_handle_int(oidp, &i, 0, req);
 184         }
 185         if (error != 0 || req->newptr == NULL)
 186                 return (error);
 187         panic("kdb_sysctl_panic");
 188         return (0);
 189 }
 190
 191 static int
 192 kdb_sysctl_trap(SYSCTL_HANDLER_ARGS)
 193 {
 194         int error, i;
 195         int *addr = (int *)0x10;
 196
 197         error = sysctl_wire_old_buffer(req, sizeof(int));
 198         if (error == 0) {
 199                 i = 0;
 200                 error = sysctl_handle_int(oidp, &i, 0, req);
 201         }
 202         if (error != 0 || req->newptr == NULL)
 203                 return (error);
 204         return (*addr);
 205 }
 206
 207 static int
 208 kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS)
 209 {
 210         int error, i;
 211         void (*fp)(u_int, u_int, u_int) = (void *)0xdeadc0de;
 212
 213         error = sysctl_wire_old_buffer(req, sizeof(int));
 214         if (error == 0) {
 215                 i = 0;
 216                 error = sysctl_handle_int(oidp, &i, 0, req);
 217         }
 218         if (error != 0 || req->newptr == NULL)
 219                 return (error);
 220         (*fp)(0x11111111, 0x22222222, 0x33333333);
 221         return (0);
 222 }
 223
 224 void
 225 kdb_panic(const char *msg)
 226 {
 227
 228 #ifdef SMP
 229         stop_cpus(PCPU_GET(other_cpus));
 230 #endif
 231         printf("KDB: panic\n");
 232         panic(msg);
 233 }
 234
 235 void
 236 kdb_reboot(void)
 237 {
 238
 239         printf("KDB: reboot requested\n");
 240         shutdown_nice(0);
 241 }
 242
 243 /*
 244  * Solaris implements a new BREAK which is initiated by a character sequence
 245  * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the
 246  * Remote Console.
 247  *
 248  * Note that this function may be called from almost anywhere, with interrupts
 249  * disabled and with unknown locks held, so it must not access data other than
 250  * its arguments.  Its up to the caller to ensure that the state variable is
 251  * consistent.
 252  */
 253
 254 #define KEY_CR          13      /* CR '\r' */
 255 #define KEY_TILDE       126     /* ~ */
 256 #define KEY_CRTLB       2       /* ^B */
 257 #define KEY_CRTLP       16      /* ^P */
 258 #define KEY_CRTLR       18      /* ^R */
 259
 260 int
 261 kdb_alt_break(int key, int *state)
 262 {
 263         int brk;
 264
 265         brk = 0;
 266         switch (*state) {
 267         case 0:
 268                 if (key == KEY_CR)
 269                         *state = 1;
 270                 break;
 271         case 1:
 272                 if (key == KEY_TILDE)
 273                         *state = 2;
 274                 break;
 275         case 2:
 276                 if (key == KEY_CRTLB)
 277                         brk = KDB_REQ_DEBUGGER;
 278                 else if (key == KEY_CRTLP)
 279                         brk = KDB_REQ_PANIC;
 280                 else if (key == KEY_CRTLR)
 281                         brk = KDB_REQ_REBOOT;
 282                 *state = 0;
 283         }
 284         return (brk);
 285 }
 286
 287 /*
 288  * Print a backtrace of the calling thread. The backtrace is generated by
 289  * the selected debugger, provided it supports backtraces. If no debugger
 290  * is selected or the current debugger does not support backtraces, this
 291  * function silently returns.
 292  */
 293
 294 void
 295 kdb_backtrace()
 296 {
 297
 298         if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) {
 299                 printf("KDB: stack backtrace:\n");
 300                 kdb_dbbe->dbbe_trace();
 301         }
 302 }
 303
 304 /*
 305  * Set/change the current backend.
 306  */
 307
 308 int
 309 kdb_dbbe_select(const char *name)
 310 {
 311         struct kdb_dbbe *be, **iter;
 312
 313         SET_FOREACH(iter, kdb_dbbe_set) {
 314                 be = *iter;
 315                 if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) {
 316                         kdb_dbbe = be;
 317                         return (0);
 318                 }
 319         }
 320         return (EINVAL);
 321 }
 322
 323 /*
 324  * Enter the currently selected debugger. If a message has been provided,
 325  * it is printed first. If the debugger does not support the enter method,
 326  * it is entered by using breakpoint(), which enters the debugger through
 327  * kdb_trap().  The 'why' argument will contain a more mechanically usable
 328  * string than 'msg', and is relied upon by DDB scripting to identify the
 329  * reason for entering the debugger so that the right script can be run.
 330  */
 331 void
 332 kdb_enter(const char *why, const char *msg)
 333 {
 334
 335         if (kdb_dbbe != NULL && kdb_active == 0) {
 336                 if (msg != NULL)
 337                         printf("KDB: enter: %s\n", msg);
 338                 kdb_why = why;
 339                 breakpoint();
 340                 kdb_why = KDB_WHY_UNSET;
 341         }
 342 }
 343
 344 /*
 345  * Initialize the kernel debugger interface.
 346  */
 347
 348 void
 349 kdb_init()
 350 {
 351         struct kdb_dbbe *be, **iter;
 352         int cur_pri, pri;
 353
 354         kdb_active = 0;
 355         kdb_dbbe = NULL;
 356         cur_pri = -1;
 357         SET_FOREACH(iter, kdb_dbbe_set) {
 358                 be = *iter;
 359                 pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1;
 360                 be->dbbe_active = (pri >= 0) ? 0 : -1;
 361                 if (pri > cur_pri) {
 362                         cur_pri = pri;
 363                         kdb_dbbe = be;
 364                 }
 365         }
 366         if (kdb_dbbe != NULL) {
 367                 printf("KDB: debugger backends:");
 368                 SET_FOREACH(iter, kdb_dbbe_set) {
 369                         be = *iter;
 370                         if (be->dbbe_active == 0)
 371                                 printf(" %s", be->dbbe_name);
 372                 }
 373                 printf("\n");
 374                 printf("KDB: current backend: %s\n",
 375                     kdb_dbbe->dbbe_name);
 376         }
 377 }
 378
 379 /*
 380  * Handle contexts.
 381  */
 382
 383 void *
 384 kdb_jmpbuf(jmp_buf new)
 385 {
 386         void *old;
 387
 388         old = kdb_jmpbufp;
 389         kdb_jmpbufp = new;
 390         return (old);
 391 }
 392
 393 void
 394 kdb_reenter(void)
 395 {
 396
 397         if (!kdb_active || kdb_jmpbufp == NULL)
 398                 return;
 399
 400         longjmp(kdb_jmpbufp, 1);
 401         /* NOTREACHED */
 402 }
 403
 404 /*
 405  * Thread related support functions.
 406  */
 407
 408 struct pcb *
 409 kdb_thr_ctx(struct thread *thr)
 410 {
 411 #if defined(SMP) && defined(KDB_STOPPEDPCB)
 412         struct pcpu *pc;
 413 #endif
 414
 415         if (thr == curthread)
 416                 return (&kdb_pcb);
 417
 418 #if defined(SMP) && defined(KDB_STOPPEDPCB)
 419         SLIST_FOREACH(pc, &cpuhead, pc_allcpu)  {
 420                 if (pc->pc_curthread == thr && (stopped_cpus & pc->pc_cpumask))
 421                         return (KDB_STOPPEDPCB(pc));
 422         }
 423 #endif
 424         return (thr->td_pcb);
 425 }
 426
 427 struct thread *
 428 kdb_thr_first(void)
 429 {
 430         struct proc *p;
 431         struct thread *thr;
 432
 433         p = LIST_FIRST(&allproc);
 434         while (p != NULL) {
 435                 if (p->p_flag & P_INMEM) {
 436                         thr = FIRST_THREAD_IN_PROC(p);
 437                         if (thr != NULL)
 438                                 return (thr);
 439                 }
 440                 p = LIST_NEXT(p, p_list);
 441         }
 442         return (NULL);
 443 }
 444
 445 struct thread *
 446 kdb_thr_from_pid(pid_t pid)
 447 {
 448         struct proc *p;
 449
 450         p = LIST_FIRST(&allproc);
 451         while (p != NULL) {
 452                 if (p->p_flag & P_INMEM && p->p_pid == pid)
 453                         return (FIRST_THREAD_IN_PROC(p));
 454                 p = LIST_NEXT(p, p_list);
 455         }
 456         return (NULL);
 457 }
 458
 459 struct thread *
 460 kdb_thr_lookup(lwpid_t tid)
 461 {
 462         struct thread *thr;
 463
 464         thr = kdb_thr_first();
 465         while (thr != NULL && thr->td_tid != tid)
 466                 thr = kdb_thr_next(thr);
 467         return (thr);
 468 }
 469
 470 struct thread *
 471 kdb_thr_next(struct thread *thr)
 472 {
 473         struct proc *p;
 474
 475         p = thr->td_proc;
 476         thr = TAILQ_NEXT(thr, td_plist);
 477         do {
 478                 if (thr != NULL)
 479                         return (thr);
 480                 p = LIST_NEXT(p, p_list);
 481                 if (p != NULL && (p->p_flag & P_INMEM))
 482                         thr = FIRST_THREAD_IN_PROC(p);
 483         } while (p != NULL);
 484         return (NULL);
 485 }
 486
 487 int
 488 kdb_thr_select(struct thread *thr)
 489 {
 490         if (thr == NULL)
 491                 return (EINVAL);
 492         kdb_thread = thr;
 493         kdb_thrctx = kdb_thr_ctx(thr);
 494         return (0);
 495 }
 496
 497 /*
 498  * Enter the debugger due to a trap.
 499  */
 500
 501 int
 502 kdb_trap(int type, int code, struct trapframe *tf)
 503 {
 504         register_t intr;
 505 #ifdef SMP
 506         int did_stop_cpus;
 507 #endif
 508         int handled;
 509
 510         if (kdb_dbbe == NULL || kdb_dbbe->dbbe_trap == NULL)
 511                 return (0);
 512
 513         /* We reenter the debugger through kdb_reenter(). */
 514         if (kdb_active)
 515                 return (0);
 516
 517         intr = intr_disable();
 518
 519 #ifdef SMP
 520         if ((did_stop_cpus = kdb_stop_cpus) != 0)
 521                 stop_cpus(PCPU_GET(other_cpus));
 522 #endif
 523
 524         kdb_active++;
 525
 526         kdb_frame = tf;
 527
 528         /* Let MD code do its thing first... */
 529         kdb_cpu_trap(type, code);
 530
 531         makectx(tf, &kdb_pcb);
 532         kdb_thr_select(curthread);
 533
 534         handled = kdb_dbbe->dbbe_trap(type, code);
 535
 536         kdb_active--;
 537
 538 #ifdef SMP
 539         if (did_stop_cpus)
 540                 restart_cpus(stopped_cpus);
 541 #endif
 542
 543         intr_restore(intr);
 544
 545         return (handled);
 546 }