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("$FreeBSD$");
   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, CTLFLAG_RW | CTLFLAG_TUN,
   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                 strlcpy(buf, kdb_dbbe->dbbe_name, sizeof(buf));
  146         else
  147                 *buf = '\0';
  148         error = sysctl_handle_string(oidp, buf, sizeof(buf), req);
  149         if (error != 0 || req->newptr == NULL)
  150                 return (error);
  151         if (kdb_active)
  152                 return (EBUSY);
  153         return (kdb_dbbe_select(buf));
  154 }
  155 
  156 static int
  157 kdb_sysctl_enter(SYSCTL_HANDLER_ARGS)
  158 {
  159         int error, i;
  160 
  161         error = sysctl_wire_old_buffer(req, sizeof(int));
  162         if (error == 0) {
  163                 i = 0;
  164                 error = sysctl_handle_int(oidp, &i, 0, req);
  165         }
  166         if (error != 0 || req->newptr == NULL)
  167                 return (error);
  168         if (kdb_active)
  169                 return (EBUSY);
  170         kdb_enter_why(KDB_WHY_SYSCTL, "sysctl debug.kdb.enter");
  171         return (0);
  172 }
  173 
  174 static int
  175 kdb_sysctl_panic(SYSCTL_HANDLER_ARGS)
  176 {
  177         int error, i;
  178 
  179         error = sysctl_wire_old_buffer(req, sizeof(int));
  180         if (error == 0) {
  181                 i = 0;
  182                 error = sysctl_handle_int(oidp, &i, 0, req);
  183         }
  184         if (error != 0 || req->newptr == NULL)
  185                 return (error);
  186         panic("kdb_sysctl_panic");
  187         return (0);
  188 }
  189 
  190 static int
  191 kdb_sysctl_trap(SYSCTL_HANDLER_ARGS)
  192 {
  193         int error, i;
  194         int *addr = (int *)0x10;
  195 
  196         error = sysctl_wire_old_buffer(req, sizeof(int));
  197         if (error == 0) {
  198                 i = 0;
  199                 error = sysctl_handle_int(oidp, &i, 0, req);
  200         }
  201         if (error != 0 || req->newptr == NULL)
  202                 return (error);
  203         return (*addr);
  204 }
  205 
  206 static int
  207 kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS)
  208 {
  209         int error, i;
  210         void (*fp)(u_int, u_int, u_int) = (void *)0xdeadc0de;
  211 
  212         error = sysctl_wire_old_buffer(req, sizeof(int));
  213         if (error == 0) {
  214                 i = 0;
  215                 error = sysctl_handle_int(oidp, &i, 0, req);
  216         }
  217         if (error != 0 || req->newptr == NULL)
  218                 return (error);
  219         (*fp)(0x11111111, 0x22222222, 0x33333333);
  220         return (0);
  221 }
  222 
  223 /*
  224  * Solaris implements a new BREAK which is initiated by a character sequence
  225  * CR ~ ^b which is similar to a familiar pattern used on Sun servers by the
  226  * Remote Console.
  227  *
  228  * Note that this function may be called from almost anywhere, with interrupts
  229  * disabled and with unknown locks held, so it must not access data other than
  230  * its arguments.  Its up to the caller to ensure that the state variable is
  231  * consistent.
  232  */
  233 
  234 #define KEY_CR          13      /* CR '\r' */
  235 #define KEY_TILDE       126     /* ~ */
  236 #define KEY_CRTLB       2       /* ^B */
  237 
  238 int
  239 kdb_alt_break(int key, int *state)
  240 {
  241         int brk;
  242 
  243         brk = 0;
  244         switch (key) {
  245         case KEY_CR:
  246                 *state = KEY_TILDE;
  247                 break;
  248         case KEY_TILDE:
  249                 *state = (*state == KEY_TILDE) ? KEY_CRTLB : 0;
  250                 break;
  251         case KEY_CRTLB:
  252                 if (*state == KEY_CRTLB)
  253                         brk = 1;
  254                 /* FALLTHROUGH */
  255         default:
  256                 *state = 0;
  257                 break;
  258         }
  259         return (brk);
  260 }
  261 
  262 /*
  263  * Print a backtrace of the calling thread. The backtrace is generated by
  264  * the selected debugger, provided it supports backtraces. If no debugger
  265  * is selected or the current debugger does not support backtraces, this
  266  * function silently returns.
  267  */
  268 
  269 void
  270 kdb_backtrace()
  271 {
  272 
  273         if (kdb_dbbe != NULL && kdb_dbbe->dbbe_trace != NULL) {
  274                 printf("KDB: stack backtrace:\n");
  275                 kdb_dbbe->dbbe_trace();
  276         }
  277 }
  278 
  279 /*
  280  * Set/change the current backend.
  281  */
  282 
  283 int
  284 kdb_dbbe_select(const char *name)
  285 {
  286         struct kdb_dbbe *be, **iter;
  287 
  288         SET_FOREACH(iter, kdb_dbbe_set) {
  289                 be = *iter;
  290                 if (be->dbbe_active == 0 && strcmp(be->dbbe_name, name) == 0) {
  291                         kdb_dbbe = be;
  292                         return (0);
  293                 }
  294         }
  295         return (EINVAL);
  296 }
  297 
  298 /*
  299  * Enter the currently selected debugger. If a message has been provided,
  300  * it is printed first. If the debugger does not support the enter method,
  301  * it is entered by using breakpoint(), which enters the debugger through
  302  * kdb_trap().  The 'why' argument will contain a more mechanically usable
  303  * string than 'msg', and is relied upon by DDB scripting to identify the
  304  * reason for entering the debugger so that the right script can be run.
  305  */
  306 void
  307 kdb_enter_why(const char *why, const char *msg)
  308 {
  309 
  310         if (kdb_dbbe != NULL && kdb_active == 0) {
  311                 if (msg != NULL)
  312                         printf("KDB: enter: %s\n", msg);
  313                 kdb_why = why;
  314                 breakpoint();
  315                 kdb_why = KDB_WHY_UNSET;
  316         }
  317 }
  318 
  319 /*
  320  * This compatibility function exists so that kernel modules with existing
  321  * dependencies will still link and function.  In FreeBSD 8.0, kdb_enter() is
  322  * kdb_enter_why().  In 7.x, this limits how KDB can use the entry call, and
  323  * means that there won't be specific scripts for event that use the legacy
  324  * interface.
  325  */
  326 void
  327 kdb_enter(const char *msg)
  328 {
  329 
  330         kdb_enter_why(KDB_WHY_UNSET, msg);
  331 }
  332 
  333 /*
  334  * Initialize the kernel debugger interface.
  335  */
  336 
  337 void
  338 kdb_init()
  339 {
  340         struct kdb_dbbe *be, **iter;
  341         int cur_pri, pri;
  342 
  343         kdb_active = 0;
  344         kdb_dbbe = NULL;
  345         cur_pri = -1;
  346         SET_FOREACH(iter, kdb_dbbe_set) {
  347                 be = *iter;
  348                 pri = (be->dbbe_init != NULL) ? be->dbbe_init() : -1;
  349                 be->dbbe_active = (pri >= 0) ? 0 : -1;
  350                 if (pri > cur_pri) {
  351                         cur_pri = pri;
  352                         kdb_dbbe = be;
  353                 }
  354         }
  355         if (kdb_dbbe != NULL) {
  356                 printf("KDB: debugger backends:");
  357                 SET_FOREACH(iter, kdb_dbbe_set) {
  358                         be = *iter;
  359                         if (be->dbbe_active == 0)
  360                                 printf(" %s", be->dbbe_name);
  361                 }
  362                 printf("\n");
  363                 printf("KDB: current backend: %s\n",
  364                     kdb_dbbe->dbbe_name);
  365         }
  366 }
  367 
  368 /*
  369  * Handle contexts.
  370  */
  371 
  372 void *
  373 kdb_jmpbuf(jmp_buf new)
  374 {
  375         void *old;
  376 
  377         old = kdb_jmpbufp;
  378         kdb_jmpbufp = new;
  379         return (old);
  380 }
  381 
  382 void
  383 kdb_reenter(void)
  384 {
  385 
  386         if (!kdb_active || kdb_jmpbufp == NULL)
  387                 return;
  388 
  389         longjmp(kdb_jmpbufp, 1);
  390         /* NOTREACHED */
  391 }
  392 
  393 /*
  394  * Thread related support functions.
  395  */
  396 
  397 struct pcb *
  398 kdb_thr_ctx(struct thread *thr)
  399 {  
  400 #if defined(SMP) && defined(KDB_STOPPEDPCB)
  401         struct pcpu *pc;
  402 #endif
  403  
  404         if (thr == curthread) 
  405                 return (&kdb_pcb);
  406 
  407 #if defined(SMP) && defined(KDB_STOPPEDPCB)
  408         SLIST_FOREACH(pc, &cpuhead, pc_allcpu)  {
  409                 if (pc->pc_curthread == thr && (stopped_cpus & pc->pc_cpumask))
  410                         return (KDB_STOPPEDPCB(pc));
  411         }
  412 #endif
  413         return (thr->td_pcb);
  414 }
  415 
  416 struct thread *
  417 kdb_thr_first(void)
  418 {
  419         struct proc *p;
  420         struct thread *thr;
  421 
  422         p = LIST_FIRST(&allproc);
  423         while (p != NULL) {
  424                 if (p->p_flag & P_INMEM) {
  425                         thr = FIRST_THREAD_IN_PROC(p);
  426                         if (thr != NULL)
  427                                 return (thr);
  428                 }
  429                 p = LIST_NEXT(p, p_list);
  430         }
  431         return (NULL);
  432 }
  433 
  434 struct thread *
  435 kdb_thr_from_pid(pid_t pid)
  436 {
  437         struct proc *p;
  438 
  439         p = LIST_FIRST(&allproc);
  440         while (p != NULL) {
  441                 if (p->p_flag & P_INMEM && p->p_pid == pid)
  442                         return (FIRST_THREAD_IN_PROC(p));
  443                 p = LIST_NEXT(p, p_list);
  444         }
  445         return (NULL);
  446 }
  447 
  448 struct thread *
  449 kdb_thr_lookup(lwpid_t tid)
  450 {
  451         struct thread *thr;
  452 
  453         thr = kdb_thr_first();
  454         while (thr != NULL && thr->td_tid != tid)
  455                 thr = kdb_thr_next(thr);
  456         return (thr);
  457 }
  458 
  459 struct thread *
  460 kdb_thr_next(struct thread *thr)
  461 {
  462         struct proc *p;
  463 
  464         p = thr->td_proc;
  465         thr = TAILQ_NEXT(thr, td_plist);
  466         do {
  467                 if (thr != NULL)
  468                         return (thr);
  469                 p = LIST_NEXT(p, p_list);
  470                 if (p != NULL && (p->p_flag & P_INMEM))
  471                         thr = FIRST_THREAD_IN_PROC(p);
  472         } while (p != NULL);
  473         return (NULL);
  474 }
  475 
  476 int
  477 kdb_thr_select(struct thread *thr)
  478 {
  479         if (thr == NULL)
  480                 return (EINVAL);
  481         kdb_thread = thr;
  482         kdb_thrctx = kdb_thr_ctx(thr);
  483         return (0);
  484 }
  485 
  486 /*
  487  * Enter the debugger due to a trap.
  488  */
  489 
  490 int
  491 kdb_trap(int type, int code, struct trapframe *tf)
  492 {
  493         struct kdb_dbbe *be;
  494         register_t intr;
  495 #ifdef SMP
  496         int did_stop_cpus;
  497 #endif
  498         int handled;
  499 
  500         be = kdb_dbbe;
  501         if (be == NULL || be->dbbe_trap == NULL)
  502                 return (0);
  503 
  504         /* We reenter the debugger through kdb_reenter(). */
  505         if (kdb_active)
  506                 return (0);
  507 
  508         intr = intr_disable();
  509 
  510 #ifdef SMP
  511         if ((did_stop_cpus = kdb_stop_cpus) != 0)
  512                 stop_cpus(PCPU_GET(other_cpus));
  513 #endif
  514 
  515         kdb_active++;
  516 
  517         kdb_frame = tf;
  518 
  519         /* Let MD code do its thing first... */
  520         kdb_cpu_trap(type, code);
  521 
  522         makectx(tf, &kdb_pcb);
  523         kdb_thr_select(curthread);
  524 
  525         for (;;) {
  526                 handled = be->dbbe_trap(type, code);
  527                 if (be == kdb_dbbe)
  528                         break;
  529                 be = kdb_dbbe;
  530                 if (be == NULL || be->dbbe_trap == NULL)
  531                         break;
  532                 printf("Switching to %s back-end\n", be->dbbe_name);
  533         }
  534 
  535         kdb_active--;
  536 
  537 #ifdef SMP
  538         if (did_stop_cpus)
  539                 restart_cpus(stopped_cpus);
  540 #endif
  541 
  542         intr_restore(intr);
  543 
  544         return (handled);
  545 }

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