subr_log.c

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    1 /*      $NetBSD: subr_log.c,v 1.50 2008/04/28 20:24:04 martin Exp $     */
    2 
    3 /*-
    4  * Copyright (c) 2007, 2008 The NetBSD Foundation, Inc.
    5  * All rights reserved.
    6  *
    7  * This code is derived from software contributed to The NetBSD Foundation
    8  * by Andrew Doran.
    9  *
   10  * Redistribution and use in source and binary forms, with or without
   11  * modification, are permitted provided that the following conditions
   12  * are met:
   13  * 1. Redistributions of source code must retain the above copyright
   14  *    notice, this list of conditions and the following disclaimer.
   15  * 2. Redistributions in binary form must reproduce the above copyright
   16  *    notice, this list of conditions and the following disclaimer in the
   17  *    documentation and/or other materials provided with the distribution.
   18  *
   19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
   20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
   21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
   22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
   23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   29  * POSSIBILITY OF SUCH DAMAGE.
   30  */
   31 
   32 /*
   33  * Copyright (c) 1982, 1986, 1993
   34  *      The Regents of the University of California.  All rights reserved.
   35  *
   36  * Redistribution and use in source and binary forms, with or without
   37  * modification, are permitted provided that the following conditions
   38  * are met:
   39  * 1. Redistributions of source code must retain the above copyright
   40  *    notice, this list of conditions and the following disclaimer.
   41  * 2. Redistributions in binary form must reproduce the above copyright
   42  *    notice, this list of conditions and the following disclaimer in the
   43  *    documentation and/or other materials provided with the distribution.
   44  * 3. Neither the name of the University nor the names of its contributors
   45  *    may be used to endorse or promote products derived from this software
   46  *    without specific prior written permission.
   47  *
   48  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   49  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   50  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   51  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   52  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   53  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   54  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   55  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   56  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   57  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   58  * SUCH DAMAGE.
   59  *
   60  *      @(#)subr_log.c  8.3 (Berkeley) 2/14/95
   61  */
   62 
   63 /*
   64  * Error log buffer for kernel printf's.
   65  */
   66 
   67 #include <sys/cdefs.h>
   68 __KERNEL_RCSID(0, "$NetBSD: subr_log.c,v 1.50 2008/04/28 20:24:04 martin Exp $");
   69 
   70 #include <sys/param.h>
   71 #include <sys/systm.h>
   72 #include <sys/kernel.h>
   73 #include <sys/proc.h>
   74 #include <sys/vnode.h>
   75 #include <sys/ioctl.h>
   76 #include <sys/msgbuf.h>
   77 #include <sys/file.h>
   78 #include <sys/syslog.h>
   79 #include <sys/conf.h>
   80 #include <sys/select.h>
   81 #include <sys/poll.h> 
   82 #include <sys/intr.h>
   83 
   84 static void     logsoftintr(void *);
   85 
   86 static bool     log_async;
   87 static struct selinfo log_selp;         /* process waiting on select call */
   88 static pid_t    log_pgid;               /* process/group for async I/O */
   89 static kcondvar_t log_cv;
   90 static void     *log_sih;
   91 
   92 kmutex_t log_lock;
   93 int     log_open;                       /* also used in log() */
   94 int     msgbufmapped;                   /* is the message buffer mapped */
   95 int     msgbufenabled;                  /* is logging to the buffer enabled */
   96 struct  kern_msgbuf *msgbufp;           /* the mapped buffer, itself. */
   97 
   98 void
   99 initmsgbuf(void *bf, size_t bufsize)
  100 {
  101         struct kern_msgbuf *mbp;
  102         long new_bufs;
  103 
  104         /* Sanity-check the given size. */
  105         if (bufsize < sizeof(struct kern_msgbuf))
  106                 return;
  107 
  108         mbp = msgbufp = (struct kern_msgbuf *)bf;
  109 
  110         new_bufs = bufsize - offsetof(struct kern_msgbuf, msg_bufc);
  111         if ((mbp->msg_magic != MSG_MAGIC) || (mbp->msg_bufs != new_bufs) ||
  112             (mbp->msg_bufr < 0) || (mbp->msg_bufr >= mbp->msg_bufs) ||
  113             (mbp->msg_bufx < 0) || (mbp->msg_bufx >= mbp->msg_bufs)) {
  114                 /*
  115                  * If the buffer magic number is wrong, has changed
  116                  * size (which shouldn't happen often), or is
  117                  * internally inconsistent, initialize it.
  118                  */
  119 
  120                 memset(bf, 0, bufsize);
  121                 mbp->msg_magic = MSG_MAGIC;
  122                 mbp->msg_bufs = new_bufs;
  123         }
  124 
  125         /* mark it as ready for use. */
  126         msgbufmapped = msgbufenabled = 1;
  127 }
  128 
  129 void
  130 loginit(void)
  131 {
  132 
  133         mutex_init(&log_lock, MUTEX_DEFAULT, IPL_VM);
  134         selinit(&log_selp);
  135         cv_init(&log_cv, "klog");
  136         log_sih = softint_establish(SOFTINT_CLOCK | SOFTINT_MPSAFE,
  137             logsoftintr, NULL);
  138 }
  139 
  140 /*ARGSUSED*/
  141 static int
  142 logopen(dev_t dev, int flags, int mode, struct lwp *l)
  143 {
  144         struct kern_msgbuf *mbp = msgbufp;
  145         int error = 0;
  146 
  147         mutex_spin_enter(&log_lock);
  148         if (log_open) {
  149                 error = EBUSY;
  150         } else {
  151                 log_open = 1;
  152                 log_pgid = l->l_proc->p_pid;    /* signal process only */
  153                 /*
  154                  * The message buffer is initialized during system
  155                  * configuration.  If it's been clobbered, note that
  156                  * and return an error.  (This allows a user to read
  157                  * the buffer via /dev/kmem, and try to figure out
  158                  * what clobbered it.
  159                  */
  160                 if (mbp->msg_magic != MSG_MAGIC) {
  161                         msgbufenabled = 0;
  162                         error = ENXIO;
  163                 }
  164         }
  165         mutex_spin_exit(&log_lock);
  166 
  167         return error;
  168 }
  169 
  170 /*ARGSUSED*/
  171 static int
  172 logclose(dev_t dev, int flag, int mode, struct lwp *l)
  173 {
  174 
  175         mutex_spin_enter(&log_lock);
  176         log_pgid = 0;
  177         log_open = 0;
  178         log_async = 0;
  179         mutex_spin_exit(&log_lock);
  180 
  181         return 0;
  182 }
  183 
  184 /*ARGSUSED*/
  185 static int
  186 logread(dev_t dev, struct uio *uio, int flag)
  187 {
  188         struct kern_msgbuf *mbp = msgbufp;
  189         long l;
  190         int error = 0;
  191 
  192         mutex_spin_enter(&log_lock);
  193         while (mbp->msg_bufr == mbp->msg_bufx) {
  194                 if (flag & IO_NDELAY) {
  195                         mutex_spin_exit(&log_lock);
  196                         return EWOULDBLOCK;
  197                 }
  198                 error = cv_wait_sig(&log_cv, &log_lock);
  199                 if (error) {
  200                         mutex_spin_exit(&log_lock);
  201                         return error;
  202                 }
  203         }
  204         while (uio->uio_resid > 0) {
  205                 l = mbp->msg_bufx - mbp->msg_bufr;
  206                 if (l < 0)
  207                         l = mbp->msg_bufs - mbp->msg_bufr;
  208                 l = min(l, uio->uio_resid);
  209                 if (l == 0)
  210                         break;
  211                 mutex_spin_exit(&log_lock);
  212                 error = uiomove(&mbp->msg_bufc[mbp->msg_bufr], (int)l, uio);
  213                 mutex_spin_enter(&log_lock);
  214                 if (error)
  215                         break;
  216                 mbp->msg_bufr += l;
  217                 if (mbp->msg_bufr < 0 || mbp->msg_bufr >= mbp->msg_bufs)
  218                         mbp->msg_bufr = 0;
  219         }
  220         mutex_spin_exit(&log_lock);
  221 
  222         return error;
  223 }
  224 
  225 /*ARGSUSED*/
  226 static int
  227 logpoll(dev_t dev, int events, struct lwp *l)
  228 {
  229         int revents = 0;
  230 
  231         if (events & (POLLIN | POLLRDNORM)) {
  232                 mutex_spin_enter(&log_lock);
  233                 if (msgbufp->msg_bufr != msgbufp->msg_bufx)
  234                         revents |= events & (POLLIN | POLLRDNORM);
  235                 else
  236                         selrecord(l, &log_selp);
  237                 mutex_spin_exit(&log_lock);
  238         }
  239 
  240         return revents;
  241 }
  242 
  243 static void
  244 filt_logrdetach(struct knote *kn)
  245 {
  246 
  247         mutex_spin_enter(&log_lock);
  248         SLIST_REMOVE(&log_selp.sel_klist, kn, knote, kn_selnext);
  249         mutex_spin_exit(&log_lock);
  250 }
  251 
  252 static int
  253 filt_logread(struct knote *kn, long hint)
  254 {
  255         int rv;
  256 
  257         if ((hint & NOTE_SUBMIT) == 0)
  258                 mutex_spin_enter(&log_lock);
  259         if (msgbufp->msg_bufr == msgbufp->msg_bufx) {
  260                 rv = 0;
  261         } else if (msgbufp->msg_bufr < msgbufp->msg_bufx) {
  262                 kn->kn_data = msgbufp->msg_bufx - msgbufp->msg_bufr;
  263                 rv = 1;
  264         } else {
  265                 kn->kn_data = (msgbufp->msg_bufs - msgbufp->msg_bufr) +
  266                     msgbufp->msg_bufx;
  267                 rv = 1;
  268         }
  269         if ((hint & NOTE_SUBMIT) == 0)
  270                 mutex_spin_exit(&log_lock);
  271 
  272         return rv;
  273 }
  274 
  275 static const struct filterops logread_filtops =
  276         { 1, NULL, filt_logrdetach, filt_logread };
  277 
  278 static int
  279 logkqfilter(dev_t dev, struct knote *kn)
  280 {
  281         struct klist *klist;
  282 
  283         switch (kn->kn_filter) {
  284         case EVFILT_READ:
  285                 klist = &log_selp.sel_klist;
  286                 kn->kn_fop = &logread_filtops;
  287                 break;
  288 
  289         default:
  290                 return (EINVAL);
  291         }
  292 
  293         mutex_spin_enter(&log_lock);
  294         kn->kn_hook = NULL;
  295         SLIST_INSERT_HEAD(klist, kn, kn_selnext);
  296         mutex_spin_exit(&log_lock);
  297 
  298         return (0);
  299 }
  300 
  301 void
  302 logwakeup(void)
  303 {
  304 
  305         if (!cold && log_open) {
  306                 mutex_spin_enter(&log_lock);
  307                 selnotify(&log_selp, 0, NOTE_SUBMIT);
  308                 if (log_async)
  309                         softint_schedule(log_sih);
  310                 cv_broadcast(&log_cv);
  311                 mutex_spin_exit(&log_lock);
  312         }
  313 }
  314 
  315 static void
  316 logsoftintr(void *cookie)
  317 {
  318         pid_t pid;
  319 
  320         if ((pid = log_pgid) != 0)
  321                 fownsignal(pid, SIGIO, 0, 0, NULL);
  322 }
  323 
  324 /*ARGSUSED*/
  325 static int
  326 logioctl(dev_t dev, u_long com, void *data, int flag, struct lwp *lwp)
  327 {
  328         long l;
  329 
  330         switch (com) {
  331 
  332         /* return number of characters immediately available */
  333         case FIONREAD:
  334                 mutex_spin_enter(&log_lock);
  335                 l = msgbufp->msg_bufx - msgbufp->msg_bufr;
  336                 if (l < 0)
  337                         l += msgbufp->msg_bufs;
  338                 mutex_spin_exit(&log_lock);
  339                 *(int *)data = l;
  340                 break;
  341 
  342         case FIONBIO:
  343                 break;
  344 
  345         case FIOASYNC:
  346                 /* No locking needed, 'thread private'. */
  347                 log_async = (*((int *)data) != 0);
  348                 break;
  349 
  350         case TIOCSPGRP:
  351         case FIOSETOWN:
  352                 return fsetown(&log_pgid, com, data);
  353 
  354         case TIOCGPGRP:
  355         case FIOGETOWN:
  356                 return fgetown(log_pgid, com, data);
  357 
  358         default:
  359                 return (EPASSTHROUGH);
  360         }
  361         return (0);
  362 }
  363 
  364 void
  365 logputchar(int c)
  366 {
  367         struct kern_msgbuf *mbp;
  368 
  369         if (!cold)
  370                 mutex_spin_enter(&log_lock);
  371         if (msgbufenabled) {
  372                 mbp = msgbufp;
  373                 if (mbp->msg_magic != MSG_MAGIC) {
  374                         /*
  375                          * Arguably should panic or somehow notify the
  376                          * user...  but how?  Panic may be too drastic,
  377                          * and would obliterate the message being kicked
  378                          * out (maybe a panic itself), and printf
  379                          * would invoke us recursively.  Silently punt
  380                          * for now.  If syslog is running, it should
  381                          * notice.
  382                          */
  383                         msgbufenabled = 0;
  384                 } else {
  385                         mbp->msg_bufc[mbp->msg_bufx++] = c;
  386                         if (mbp->msg_bufx < 0 || mbp->msg_bufx >= mbp->msg_bufs)
  387                                 mbp->msg_bufx = 0;
  388                         /* If the buffer is full, keep the most recent data. */
  389                         if (mbp->msg_bufr == mbp->msg_bufx) {
  390                                  if (++mbp->msg_bufr >= mbp->msg_bufs)
  391                                         mbp->msg_bufr = 0;
  392                         }
  393                 }
  394         }
  395         if (!cold)
  396                 mutex_spin_exit(&log_lock);
  397 }
  398 
  399 const struct cdevsw log_cdevsw = {
  400         logopen, logclose, logread, nowrite, logioctl,
  401         nostop, notty, logpoll, nommap, logkqfilter,
  402         D_OTHER | D_MPSAFE
  403 };
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FreeBSD/Linux Kernel Cross Reference sys/kern/subr_log.c

FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_log.c
