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_log.c

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    1 /*-
    2  * Copyright (c) 1982, 1986, 1993
    3  *      The Regents of the University of California.  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  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  * 4. Neither the name of the University nor the names of its contributors
   14  *    may be used to endorse or promote products derived from this software
   15  *    without specific prior written permission.
   16  *
   17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   27  * SUCH DAMAGE.
   28  *
   29  *      @(#)subr_log.c  8.1 (Berkeley) 6/10/93
   30  */
   31 
   32 /*
   33  * Error log buffer for kernel printf's.
   34  */
   35 
   36 #include <sys/cdefs.h>
   37 __FBSDID("$FreeBSD: stable/10/sys/kern/subr_log.c 247798 2013-03-04 16:07:55Z davide $");
   38 
   39 #include <sys/param.h>
   40 #include <sys/systm.h>
   41 #include <sys/conf.h>
   42 #include <sys/proc.h>
   43 #include <sys/vnode.h>
   44 #include <sys/filio.h>
   45 #include <sys/ttycom.h>
   46 #include <sys/msgbuf.h>
   47 #include <sys/signalvar.h>
   48 #include <sys/kernel.h>
   49 #include <sys/poll.h>
   50 #include <sys/filedesc.h>
   51 #include <sys/sysctl.h>
   52 
   53 #define LOG_RDPRI       (PZERO + 1)
   54 
   55 #define LOG_ASYNC       0x04
   56 
   57 static  d_open_t        logopen;
   58 static  d_close_t       logclose;
   59 static  d_read_t        logread;
   60 static  d_ioctl_t       logioctl;
   61 static  d_poll_t        logpoll;
   62 static  d_kqfilter_t    logkqfilter;
   63 
   64 static  void logtimeout(void *arg);
   65 
   66 static struct cdevsw log_cdevsw = {
   67         .d_version =    D_VERSION,
   68         .d_open =       logopen,
   69         .d_close =      logclose,
   70         .d_read =       logread,
   71         .d_ioctl =      logioctl,
   72         .d_poll =       logpoll,
   73         .d_kqfilter =   logkqfilter,
   74         .d_name =       "log",
   75 };
   76 
   77 static int      logkqread(struct knote *note, long hint);
   78 static void     logkqdetach(struct knote *note);
   79 
   80 static struct filterops log_read_filterops = {
   81         .f_isfd =       1,
   82         .f_attach =     NULL,
   83         .f_detach =     logkqdetach,
   84         .f_event =      logkqread,
   85 };
   86 
   87 static struct logsoftc {
   88         int     sc_state;               /* see above for possibilities */
   89         struct  selinfo sc_selp;        /* process waiting on select call */
   90         struct  sigio *sc_sigio;        /* information for async I/O */
   91         struct  callout sc_callout;     /* callout to wakeup syslog  */
   92 } logsoftc;
   93 
   94 int                     log_open;       /* also used in log() */
   95 static struct cv        log_wakeup;
   96 struct mtx              msgbuf_lock;
   97 MTX_SYSINIT(msgbuf_lock, &msgbuf_lock, "msgbuf lock", MTX_DEF);
   98 
   99 /* Times per second to check for a pending syslog wakeup. */
  100 static int      log_wakeups_per_second = 5;
  101 SYSCTL_INT(_kern, OID_AUTO, log_wakeups_per_second, CTLFLAG_RW,
  102     &log_wakeups_per_second, 0, "");
  103 
  104 /*ARGSUSED*/
  105 static  int
  106 logopen(struct cdev *dev, int flags, int mode, struct thread *td)
  107 {
  108 
  109         if (log_wakeups_per_second < 1) {
  110                 printf("syslog wakeup is less than one.  Adjusting to 1.\n");
  111                 log_wakeups_per_second = 1;
  112         }
  113 
  114         mtx_lock(&msgbuf_lock);
  115         if (log_open) {
  116                 mtx_unlock(&msgbuf_lock);
  117                 return (EBUSY);
  118         }
  119         log_open = 1;
  120         callout_reset_sbt(&logsoftc.sc_callout,
  121             SBT_1S / log_wakeups_per_second, 0, logtimeout, NULL, C_PREL(1));
  122         mtx_unlock(&msgbuf_lock);
  123 
  124         fsetown(td->td_proc->p_pid, &logsoftc.sc_sigio);        /* signal process only */
  125         return (0);
  126 }
  127 
  128 /*ARGSUSED*/
  129 static  int
  130 logclose(struct cdev *dev, int flag, int mode, struct thread *td)
  131 {
  132 
  133         funsetown(&logsoftc.sc_sigio);
  134 
  135         mtx_lock(&msgbuf_lock);
  136         callout_stop(&logsoftc.sc_callout);
  137         logsoftc.sc_state = 0;
  138         log_open = 0;
  139         mtx_unlock(&msgbuf_lock);
  140 
  141         return (0);
  142 }
  143 
  144 /*ARGSUSED*/
  145 static  int
  146 logread(struct cdev *dev, struct uio *uio, int flag)
  147 {
  148         char buf[128];
  149         struct msgbuf *mbp = msgbufp;
  150         int error = 0, l;
  151 
  152         mtx_lock(&msgbuf_lock);
  153         while (msgbuf_getcount(mbp) == 0) {
  154                 if (flag & IO_NDELAY) {
  155                         mtx_unlock(&msgbuf_lock);
  156                         return (EWOULDBLOCK);
  157                 }
  158                 if ((error = cv_wait_sig(&log_wakeup, &msgbuf_lock)) != 0) {
  159                         mtx_unlock(&msgbuf_lock);
  160                         return (error);
  161                 }
  162         }
  163 
  164         while (uio->uio_resid > 0) {
  165                 l = imin(sizeof(buf), uio->uio_resid);
  166                 l = msgbuf_getbytes(mbp, buf, l);
  167                 if (l == 0)
  168                         break;
  169                 mtx_unlock(&msgbuf_lock);
  170                 error = uiomove(buf, l, uio);
  171                 if (error || uio->uio_resid == 0)
  172                         return (error);
  173                 mtx_lock(&msgbuf_lock);
  174         }
  175         mtx_unlock(&msgbuf_lock);
  176         return (error);
  177 }
  178 
  179 /*ARGSUSED*/
  180 static  int
  181 logpoll(struct cdev *dev, int events, struct thread *td)
  182 {
  183         int revents = 0;
  184 
  185         if (events & (POLLIN | POLLRDNORM)) {
  186                 mtx_lock(&msgbuf_lock);
  187                 if (msgbuf_getcount(msgbufp) > 0)
  188                         revents |= events & (POLLIN | POLLRDNORM);
  189                 else
  190                         selrecord(td, &logsoftc.sc_selp);
  191                 mtx_unlock(&msgbuf_lock);
  192         }
  193         return (revents);
  194 }
  195 
  196 static int
  197 logkqfilter(struct cdev *dev, struct knote *kn)
  198 {
  199 
  200         if (kn->kn_filter != EVFILT_READ)
  201                 return (EINVAL);
  202 
  203         kn->kn_fop = &log_read_filterops;
  204         kn->kn_hook = NULL;
  205 
  206         mtx_lock(&msgbuf_lock);
  207         knlist_add(&logsoftc.sc_selp.si_note, kn, 1);
  208         mtx_unlock(&msgbuf_lock);
  209         return (0);
  210 }
  211 
  212 static int
  213 logkqread(struct knote *kn, long hint)
  214 {
  215 
  216         mtx_assert(&msgbuf_lock, MA_OWNED);
  217         kn->kn_data = msgbuf_getcount(msgbufp);
  218         return (kn->kn_data != 0);
  219 }
  220 
  221 static void
  222 logkqdetach(struct knote *kn)
  223 {
  224 
  225         mtx_lock(&msgbuf_lock);
  226         knlist_remove(&logsoftc.sc_selp.si_note, kn, 1);
  227         mtx_unlock(&msgbuf_lock);
  228 }
  229 
  230 static void
  231 logtimeout(void *arg)
  232 {
  233 
  234         if (!log_open)
  235                 return;
  236         if (msgbuftrigger == 0)
  237                 goto done;
  238         msgbuftrigger = 0;
  239         selwakeuppri(&logsoftc.sc_selp, LOG_RDPRI);
  240         KNOTE_LOCKED(&logsoftc.sc_selp.si_note, 0);
  241         if ((logsoftc.sc_state & LOG_ASYNC) && logsoftc.sc_sigio != NULL)
  242                 pgsigio(&logsoftc.sc_sigio, SIGIO, 0);
  243         cv_broadcastpri(&log_wakeup, LOG_RDPRI);
  244 done:
  245         if (log_wakeups_per_second < 1) {
  246                 printf("syslog wakeup is less than one.  Adjusting to 1.\n");
  247                 log_wakeups_per_second = 1;
  248         }
  249         callout_reset_sbt(&logsoftc.sc_callout,
  250             SBT_1S / log_wakeups_per_second, 0, logtimeout, NULL, C_PREL(1));
  251 }
  252 
  253 /*ARGSUSED*/
  254 static  int
  255 logioctl(struct cdev *dev, u_long com, caddr_t data, int flag, struct thread *td)
  256 {
  257 
  258         switch (com) {
  259 
  260         /* return number of characters immediately available */
  261         case FIONREAD:
  262                 *(int *)data = msgbuf_getcount(msgbufp);
  263                 break;
  264 
  265         case FIONBIO:
  266                 break;
  267 
  268         case FIOASYNC:
  269                 mtx_lock(&msgbuf_lock);
  270                 if (*(int *)data)
  271                         logsoftc.sc_state |= LOG_ASYNC;
  272                 else
  273                         logsoftc.sc_state &= ~LOG_ASYNC;
  274                 mtx_unlock(&msgbuf_lock);
  275                 break;
  276 
  277         case FIOSETOWN:
  278                 return (fsetown(*(int *)data, &logsoftc.sc_sigio));
  279 
  280         case FIOGETOWN:
  281                 *(int *)data = fgetown(&logsoftc.sc_sigio);
  282                 break;
  283 
  284         /* This is deprecated, FIOSETOWN should be used instead. */
  285         case TIOCSPGRP:
  286                 return (fsetown(-(*(int *)data), &logsoftc.sc_sigio));
  287 
  288         /* This is deprecated, FIOGETOWN should be used instead */
  289         case TIOCGPGRP:
  290                 *(int *)data = -fgetown(&logsoftc.sc_sigio);
  291                 break;
  292 
  293         default:
  294                 return (ENOTTY);
  295         }
  296         return (0);
  297 }
  298 
  299 static void
  300 log_drvinit(void *unused)
  301 {
  302 
  303         cv_init(&log_wakeup, "klog");
  304         callout_init_mtx(&logsoftc.sc_callout, &msgbuf_lock, 0);
  305         knlist_init_mtx(&logsoftc.sc_selp.si_note, &msgbuf_lock);
  306         make_dev_credf(MAKEDEV_ETERNAL, &log_cdevsw, 0, NULL, UID_ROOT,
  307             GID_WHEEL, 0600, "klog");
  308 }
  309 
  310 SYSINIT(logdev,SI_SUB_DRIVERS,SI_ORDER_MIDDLE,log_drvinit,NULL);

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