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: releng/9.0/sys/kern/subr_log.c 216952 2011-01-04 10:59:38Z kib $");
   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 
   63 static  void logtimeout(void *arg);
   64 
   65 static struct cdevsw log_cdevsw = {
   66         .d_version =    D_VERSION,
   67         .d_open =       logopen,
   68         .d_close =      logclose,
   69         .d_read =       logread,
   70         .d_ioctl =      logioctl,
   71         .d_poll =       logpoll,
   72         .d_name =       "log",
   73 };
   74 
   75 static struct logsoftc {
   76         int     sc_state;               /* see above for possibilities */
   77         struct  selinfo sc_selp;        /* process waiting on select call */
   78         struct  sigio *sc_sigio;        /* information for async I/O */
   79         struct  callout sc_callout;     /* callout to wakeup syslog  */
   80 } logsoftc;
   81 
   82 int                     log_open;       /* also used in log() */
   83 static struct cv        log_wakeup;
   84 struct mtx              msgbuf_lock;
   85 MTX_SYSINIT(msgbuf_lock, &msgbuf_lock, "msgbuf lock", MTX_DEF);
   86 
   87 /* Times per second to check for a pending syslog wakeup. */
   88 static int      log_wakeups_per_second = 5;
   89 SYSCTL_INT(_kern, OID_AUTO, log_wakeups_per_second, CTLFLAG_RW,
   90     &log_wakeups_per_second, 0, "");
   91 
   92 /*ARGSUSED*/
   93 static  int
   94 logopen(struct cdev *dev, int flags, int mode, struct thread *td)
   95 {
   96 
   97         if (log_wakeups_per_second < 1) {
   98                 printf("syslog wakeup is less than one.  Adjusting to 1.\n");
   99                 log_wakeups_per_second = 1;
  100         }
  101 
  102         mtx_lock(&msgbuf_lock);
  103         if (log_open) {
  104                 mtx_unlock(&msgbuf_lock);
  105                 return (EBUSY);
  106         }
  107         log_open = 1;
  108         callout_reset(&logsoftc.sc_callout, hz / log_wakeups_per_second,
  109             logtimeout, NULL);
  110         mtx_unlock(&msgbuf_lock);
  111 
  112         fsetown(td->td_proc->p_pid, &logsoftc.sc_sigio);        /* signal process only */
  113         return (0);
  114 }
  115 
  116 /*ARGSUSED*/
  117 static  int
  118 logclose(struct cdev *dev, int flag, int mode, struct thread *td)
  119 {
  120 
  121         funsetown(&logsoftc.sc_sigio);
  122 
  123         mtx_lock(&msgbuf_lock);
  124         callout_stop(&logsoftc.sc_callout);
  125         logsoftc.sc_state = 0;
  126         log_open = 0;
  127         mtx_unlock(&msgbuf_lock);
  128 
  129         return (0);
  130 }
  131 
  132 /*ARGSUSED*/
  133 static  int
  134 logread(struct cdev *dev, struct uio *uio, int flag)
  135 {
  136         char buf[128];
  137         struct msgbuf *mbp = msgbufp;
  138         int error = 0, l;
  139 
  140         mtx_lock(&msgbuf_lock);
  141         while (msgbuf_getcount(mbp) == 0) {
  142                 if (flag & IO_NDELAY) {
  143                         mtx_unlock(&msgbuf_lock);
  144                         return (EWOULDBLOCK);
  145                 }
  146                 if ((error = cv_wait_sig(&log_wakeup, &msgbuf_lock)) != 0) {
  147                         mtx_unlock(&msgbuf_lock);
  148                         return (error);
  149                 }
  150         }
  151 
  152         while (uio->uio_resid > 0) {
  153                 l = imin(sizeof(buf), uio->uio_resid);
  154                 l = msgbuf_getbytes(mbp, buf, l);
  155                 if (l == 0)
  156                         break;
  157                 mtx_unlock(&msgbuf_lock);
  158                 error = uiomove(buf, l, uio);
  159                 if (error || uio->uio_resid == 0)
  160                         return (error);
  161                 mtx_lock(&msgbuf_lock);
  162         }
  163         mtx_unlock(&msgbuf_lock);
  164         return (error);
  165 }
  166 
  167 /*ARGSUSED*/
  168 static  int
  169 logpoll(struct cdev *dev, int events, struct thread *td)
  170 {
  171         int revents = 0;
  172 
  173         if (events & (POLLIN | POLLRDNORM)) {
  174                 mtx_lock(&msgbuf_lock);
  175                 if (msgbuf_getcount(msgbufp) > 0)
  176                         revents |= events & (POLLIN | POLLRDNORM);
  177                 else
  178                         selrecord(td, &logsoftc.sc_selp);
  179                 mtx_unlock(&msgbuf_lock);
  180         }
  181         return (revents);
  182 }
  183 
  184 static void
  185 logtimeout(void *arg)
  186 {
  187 
  188         if (!log_open)
  189                 return;
  190         if (log_wakeups_per_second < 1) {
  191                 printf("syslog wakeup is less than one.  Adjusting to 1.\n");
  192                 log_wakeups_per_second = 1;
  193         }
  194         if (msgbuftrigger == 0) {
  195                 callout_schedule(&logsoftc.sc_callout,
  196                     hz / log_wakeups_per_second);
  197                 return;
  198         }
  199         msgbuftrigger = 0;
  200         selwakeuppri(&logsoftc.sc_selp, LOG_RDPRI);
  201         if ((logsoftc.sc_state & LOG_ASYNC) && logsoftc.sc_sigio != NULL)
  202                 pgsigio(&logsoftc.sc_sigio, SIGIO, 0);
  203         cv_broadcastpri(&log_wakeup, LOG_RDPRI);
  204         callout_schedule(&logsoftc.sc_callout, hz / log_wakeups_per_second);
  205 }
  206 
  207 /*ARGSUSED*/
  208 static  int
  209 logioctl(struct cdev *dev, u_long com, caddr_t data, int flag, struct thread *td)
  210 {
  211 
  212         switch (com) {
  213 
  214         /* return number of characters immediately available */
  215         case FIONREAD:
  216                 *(int *)data = msgbuf_getcount(msgbufp);
  217                 break;
  218 
  219         case FIONBIO:
  220                 break;
  221 
  222         case FIOASYNC:
  223                 mtx_lock(&msgbuf_lock);
  224                 if (*(int *)data)
  225                         logsoftc.sc_state |= LOG_ASYNC;
  226                 else
  227                         logsoftc.sc_state &= ~LOG_ASYNC;
  228                 mtx_unlock(&msgbuf_lock);
  229                 break;
  230 
  231         case FIOSETOWN:
  232                 return (fsetown(*(int *)data, &logsoftc.sc_sigio));
  233 
  234         case FIOGETOWN:
  235                 *(int *)data = fgetown(&logsoftc.sc_sigio);
  236                 break;
  237 
  238         /* This is deprecated, FIOSETOWN should be used instead. */
  239         case TIOCSPGRP:
  240                 return (fsetown(-(*(int *)data), &logsoftc.sc_sigio));
  241 
  242         /* This is deprecated, FIOGETOWN should be used instead */
  243         case TIOCGPGRP:
  244                 *(int *)data = -fgetown(&logsoftc.sc_sigio);
  245                 break;
  246 
  247         default:
  248                 return (ENOTTY);
  249         }
  250         return (0);
  251 }
  252 
  253 static void
  254 log_drvinit(void *unused)
  255 {
  256 
  257         cv_init(&log_wakeup, "klog");
  258         callout_init_mtx(&logsoftc.sc_callout, &msgbuf_lock, 0);
  259         make_dev_credf(MAKEDEV_ETERNAL, &log_cdevsw, 0, NULL, UID_ROOT,
  260             GID_WHEEL, 0600, "klog");
  261 }
  262 
  263 SYSINIT(logdev,SI_SUB_DRIVERS,SI_ORDER_MIDDLE,log_drvinit,NULL);

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

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