The Design and Implementation of the FreeBSD Operating System, Second Edition
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/7.3/sys/kern/subr_kdb.c 177734 2008-03-30 09:19:09Z rwatson $");
   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_why(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 /*
  225  * Solaris implements a new BREAK which is initiated by a character sequence
  226  * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the
  227  * Remote Console.
  228  *
  229  * Note that this function may be called from almost anywhere, with interrupts
  230  * disabled and with unknown locks held, so it must not access data other than
  231  * its arguments.  Its up to the caller to ensure that the state variable is
  232  * consistent.
  233  */
  234 
  235 #define KEY_CR          13      /* CR '\r' */
  236 #define KEY_TILDE       126     /* ~ */
  237 #define KEY_CRTLB       2       /* ^B */
  238 
  239 int
  240 kdb_alt_break(int key, int *state)
  241 {
  242         int brk;
  243 
  244         brk = 0;
  245         switch (key) {
  246         case KEY_CR:
  247                 *state = KEY_TILDE;
  248                 break;
  249         case KEY_TILDE:
  250                 *state = (*state == KEY_TILDE) ? KEY_CRTLB : 0;
  251                 break;
  252         case KEY_CRTLB:
  253                 if (*state == KEY_CRTLB)
  254                         brk = 1;
  255                 /* FALLTHROUGH */
  256         default:
  257                 *state = 0;
  258                 break;
  259         }
  260         return (brk);
  261 }
  262 
  263 /*
  264  * Print a backtrace of the calling thread. The backtrace is generated by
  265  * the selected debugger, provided it supports backtraces. If no debugger
  266  * is selected or the current debugger does not support backtraces, this
  267  * function silently returns.
  268  */
  269 
  270 void
  271 kdb_backtrace()
  272 {
  273 
  274         if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) {
  275                 printf("KDB: stack backtrace:\n");
  276                 kdb_dbbe->dbbe_trace();
  277         }
  278 }
  279 
  280 /*
  281  * Set/change the current backend.
  282  */
  283 
  284 int
  285 kdb_dbbe_select(const char *name)
  286 {
  287         struct kdb_dbbe *be, **iter;
  288 
  289         SET_FOREACH(iter, kdb_dbbe_set) {
  290                 be = *iter;
  291                 if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) {
  292                         kdb_dbbe = be;
  293                         return (0);
  294                 }
  295         }
  296         return (EINVAL);
  297 }
  298 
  299 /*
  300  * Enter the currently selected debugger. If a message has been provided,
  301  * it is printed first. If the debugger does not support the enter method,
  302  * it is entered by using breakpoint(), which enters the debugger through
  303  * kdb_trap().  The 'why' argument will contain a more mechanically usable
  304  * string than 'msg', and is relied upon by DDB scripting to identify the
  305  * reason for entering the debugger so that the right script can be run.
  306  */
  307 void
  308 kdb_enter_why(const char *why, const char *msg)
  309 {
  310 
  311         if (kdb_dbbe != NULL && kdb_active == 0) {
  312                 if (msg != NULL)
  313                         printf("KDB: enter: %s\n", msg);
  314                 kdb_why = why;
  315                 breakpoint();
  316                 kdb_why = KDB_WHY_UNSET;
  317         }
  318 }
  319 
  320 /*
  321  * This compatibility function exists so that kernel modules with existing
  322  * dependencies will still link and function.  In FreeBSD 8.0, kdb_enter() is
  323  * kdb_enter_why().  In 7.x, this limits how KDB can use the entry call, and
  324  * means that there won't be specific scripts for event that use the legacy
  325  * interface.
  326  */
  327 void
  328 kdb_enter(const char *msg)
  329 {
  330 
  331         kdb_enter_why(KDB_WHY_UNSET, msg);
  332 }
  333 
  334 /*
  335  * Initialize the kernel debugger interface.
  336  */
  337 
  338 void
  339 kdb_init()
  340 {
  341         struct kdb_dbbe *be, **iter;
  342         int cur_pri, pri;
  343 
  344         kdb_active = 0;
  345         kdb_dbbe = NULL;
  346         cur_pri = -1;
  347         SET_FOREACH(iter, kdb_dbbe_set) {
  348                 be = *iter;
  349                 pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1;
  350                 be->dbbe_active = (pri >= 0) ? 0 : -1;
  351                 if (pri > cur_pri) {
  352                         cur_pri = pri;
  353                         kdb_dbbe = be;
  354                 }
  355         }
  356         if (kdb_dbbe != NULL) {
  357                 printf("KDB: debugger backends:");
  358                 SET_FOREACH(iter, kdb_dbbe_set) {
  359                         be = *iter;
  360                         if (be->dbbe_active == 0)
  361                                 printf(" %s", be->dbbe_name);
  362                 }
  363                 printf("\n");
  364                 printf("KDB: current backend: %s\n",
  365                     kdb_dbbe->dbbe_name);
  366         }
  367 }
  368 
  369 /*
  370  * Handle contexts.
  371  */
  372 
  373 void *
  374 kdb_jmpbuf(jmp_buf new)
  375 {
  376         void *old;
  377 
  378         old = kdb_jmpbufp;
  379         kdb_jmpbufp = new;
  380         return (old);
  381 }
  382 
  383 void
  384 kdb_reenter(void)
  385 {
  386 
  387         if (!kdb_active || kdb_jmpbufp == NULL)
  388                 return;
  389 
  390         longjmp(kdb_jmpbufp, 1);
  391         /* NOTREACHED */
  392 }
  393 
  394 /*
  395  * Thread related support functions.
  396  */
  397 
  398 struct pcb *
  399 kdb_thr_ctx(struct thread *thr)
  400 {  
  401 #if defined(SMP) && defined(KDB_STOPPEDPCB)
  402         struct pcpu *pc;
  403 #endif
  404  
  405         if (thr == curthread) 
  406                 return (&kdb_pcb);
  407 
  408 #if defined(SMP) && defined(KDB_STOPPEDPCB)
  409         SLIST_FOREACH(pc, &cpuhead, pc_allcpu)  {
  410                 if (pc->pc_curthread == thr && (stopped_cpus & pc->pc_cpumask))
  411                         return (KDB_STOPPEDPCB(pc));
  412         }
  413 #endif
  414         return (thr->td_pcb);
  415 }
  416 
  417 struct thread *
  418 kdb_thr_first(void)
  419 {
  420         struct proc *p;
  421         struct thread *thr;
  422 
  423         p = LIST_FIRST(&allproc);
  424         while (p != NULL) {
  425                 if (p->p_flag & P_INMEM) {
  426                         thr = FIRST_THREAD_IN_PROC(p);
  427                         if (thr != NULL)
  428                                 return (thr);
  429                 }
  430                 p = LIST_NEXT(p, p_list);
  431         }
  432         return (NULL);
  433 }
  434 
  435 struct thread *
  436 kdb_thr_from_pid(pid_t pid)
  437 {
  438         struct proc *p;
  439 
  440         p = LIST_FIRST(&allproc);
  441         while (p != NULL) {
  442                 if (p->p_flag & P_INMEM && p->p_pid == pid)
  443                         return (FIRST_THREAD_IN_PROC(p));
  444                 p = LIST_NEXT(p, p_list);
  445         }
  446         return (NULL);
  447 }
  448 
  449 struct thread *
  450 kdb_thr_lookup(lwpid_t tid)
  451 {
  452         struct thread *thr;
  453 
  454         thr = kdb_thr_first();
  455         while (thr != NULL && thr->td_tid != tid)
  456                 thr = kdb_thr_next(thr);
  457         return (thr);
  458 }
  459 
  460 struct thread *
  461 kdb_thr_next(struct thread *thr)
  462 {
  463         struct proc *p;
  464 
  465         p = thr->td_proc;
  466         thr = TAILQ_NEXT(thr, td_plist);
  467         do {
  468                 if (thr != NULL)
  469                         return (thr);
  470                 p = LIST_NEXT(p, p_list);
  471                 if (p != NULL && (p->p_flag & P_INMEM))
  472                         thr = FIRST_THREAD_IN_PROC(p);
  473         } while (p != NULL);
  474         return (NULL);
  475 }
  476 
  477 int
  478 kdb_thr_select(struct thread *thr)
  479 {
  480         if (thr == NULL)
  481                 return (EINVAL);
  482         kdb_thread = thr;
  483         kdb_thrctx = kdb_thr_ctx(thr);
  484         return (0);
  485 }
  486 
  487 /*
  488  * Enter the debugger due to a trap.
  489  */
  490 
  491 int
  492 kdb_trap(int type, int code, struct trapframe *tf)
  493 {
  494         register_t intr;
  495 #ifdef SMP
  496         int did_stop_cpus;
  497 #endif
  498         int handled;
  499 
  500         if (kdb_dbbe == NULL || kdb_dbbe->dbbe_trap == NULL)
  501                 return (0);
  502 
  503         /* We reenter the debugger through kdb_reenter(). */
  504         if (kdb_active)
  505                 return (0);
  506 
  507         intr = intr_disable();
  508 
  509 #ifdef SMP
  510         if ((did_stop_cpus = kdb_stop_cpus) != 0)
  511                 stop_cpus(PCPU_GET(other_cpus));
  512 #endif
  513 
  514         kdb_active++;
  515 
  516         kdb_frame = tf;
  517 
  518         /* Let MD code do its thing first... */
  519         kdb_cpu_trap(type, code);
  520 
  521         makectx(tf, &kdb_pcb);
  522         kdb_thr_select(curthread);
  523 
  524         handled = kdb_dbbe->dbbe_trap(type, code);
  525 
  526         kdb_active--;
  527 
  528 #ifdef SMP
  529         if (did_stop_cpus)
  530                 restart_cpus(stopped_cpus);
  531 #endif
  532 
  533         intr_restore(intr);
  534 
  535         return (handled);
  536 }

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