sys/kern/subr_log.c

   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  * 3. 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  * $FreeBSD: src/sys/kern/subr_log.c,v 1.39.2.2 2001/06/02 08:11:25 phk Exp $
  31  */
  32
  33 /*
  34  * Error log buffer for kernel printf's.
  35  */
  36
  37 #include <sys/param.h>
  38 #include <sys/systm.h>
  39 #include <sys/conf.h>
  40 #include <sys/device.h>
  41 #include <sys/proc.h>
  42 #include <sys/vnode.h>
  43 #include <sys/filio.h>
  44 #include <sys/ttycom.h>
  45 #include <sys/msgbuf.h>
  46 #include <sys/signalvar.h>
  47 #include <sys/kernel.h>
  48 #include <sys/event.h>
  49 #include <sys/filedesc.h>
  50 #include <sys/sysctl.h>
  51 #include <sys/thread2.h>
  52
  53 #define LOG_ASYNC       0x04
  54 #define LOG_RDWAIT      0x08
  55
  56 static  d_open_t        logopen;
  57 static  d_close_t       logclose;
  58 static  d_read_t        logread;
  59 static  d_ioctl_t       logioctl;
  60 static  d_kqfilter_t    logkqfilter;
  61
  62 static  void logtimeout(void *arg);
  63 static  void logfiltdetach(struct knote *kn);
  64 static  int  logfiltread(struct knote *kn, long hint);
  65
  66 #define CDEV_MAJOR 7
  67 static struct dev_ops log_ops = {
  68         { "log", 0, 0 },
  69         .d_open =       logopen,
  70         .d_close =      logclose,
  71         .d_read =       logread,
  72         .d_ioctl =      logioctl,
  73         .d_kqfilter =   logkqfilter
  74 };
  75
  76 static struct logsoftc {
  77         int     sc_state;               /* see above for possibilities */
  78         struct  kqinfo  sc_kqp;         /* processes waiting on I/O */
  79         struct  sigio *sc_sigio;        /* information for async I/O */
  80         struct  callout sc_callout;     /* callout to wakeup syslog  */
  81 } logsoftc;
  82
  83 int     log_open;                       /* also used in log() */
  84
  85 /* Times per second to check for a pending syslog wakeup. */
  86 static int      log_wakeups_per_second = 5;
  87 SYSCTL_INT(_kern, OID_AUTO, log_wakeups_per_second, CTLFLAG_RW,
  88     &log_wakeups_per_second, 0, "");
  89
  90 /*ARGSUSED*/
  91 static  int
  92 logopen(struct dev_open_args *ap)
  93 {
  94         struct proc *p = curproc;
  95
  96         KKASSERT(p != NULL);
  97         if (log_open)
  98                 return (EBUSY);
  99         log_open = 1;
 100         callout_init_mp(&logsoftc.sc_callout);
 101         fsetown(p->p_pid, &logsoftc.sc_sigio);  /* signal process only */
 102         callout_reset(&logsoftc.sc_callout, hz / log_wakeups_per_second,
 103                       logtimeout, NULL);
 104         return (0);
 105 }
 106
 107 /*ARGSUSED*/
 108 static  int
 109 logclose(struct dev_close_args *ap)
 110 {
 111         log_open = 0;
 112         callout_stop_sync(&logsoftc.sc_callout);
 113         logsoftc.sc_state = 0;
 114         funsetown(&logsoftc.sc_sigio);
 115         return (0);
 116 }
 117
 118 /*ARGSUSED*/
 119 static  int
 120 logread(struct dev_read_args *ap)
 121 {
 122         struct uio *uio = ap->a_uio;
 123         struct msgbuf *mbp = msgbufp;
 124         int error = 0;
 125         u_int lindex;
 126         u_int xindex;
 127         u_int lindex_modulo;
 128         u_int n;
 129
 130         /*
 131          * Handle blocking
 132          */
 133         while (mbp->msg_bufl == mbp->msg_bufx) {
 134                 crit_enter();
 135                 if (ap->a_ioflag & IO_NDELAY) {
 136                         crit_exit();
 137                         return (EWOULDBLOCK);
 138                 }
 139                 atomic_set_int(&logsoftc.sc_state, LOG_RDWAIT);
 140                 if ((error = tsleep((caddr_t)mbp, PCATCH, "klog", 0))) {
 141                         crit_exit();
 142                         return (error);
 143                 }
 144                 /* don't bother clearing LOG_RDWAIT */
 145                 crit_exit();
 146         }
 147
 148         /*
 149          * Loop reading data
 150          */
 151         while (uio->uio_resid > 0 && mbp->msg_bufl != mbp->msg_bufx) {
 152                 lindex = mbp->msg_bufl;
 153                 xindex = mbp->msg_bufx;
 154                 cpu_ccfence();
 155
 156                 /*
 157                  * Clean up if too much time has passed causing us to wrap
 158                  * the buffer.  This will lose some data.  If more than ~4GB
 159                  * then this will lose even more data.
 160                  */
 161                 n = xindex - lindex;
 162                 if (n > mbp->msg_size - 1024) {
 163                         lindex = xindex - mbp->msg_size + 2048;
 164                         n = xindex - lindex;
 165                 }
 166
 167                 /*
 168                  * Calculates contiguous bytes we can read in one loop.
 169                  */
 170                 lindex_modulo = lindex % mbp->msg_size;
 171                 n = mbp->msg_size - lindex_modulo;
 172                 if (n > xindex - lindex)
 173                         n = xindex - lindex;
 174                 if ((size_t)n > uio->uio_resid)
 175                         n = (u_int)uio->uio_resid;
 176
 177                 /*
 178                  * Copy (n) bytes of data.
 179                  */
 180                 error = uiomove((caddr_t)msgbufp->msg_ptr + lindex_modulo,
 181                                 (size_t)n, uio);
 182                 if (error)
 183                         break;
 184                 mbp->msg_bufl = lindex + n;
 185         }
 186         return (error);
 187 }
 188
 189 static struct filterops logread_filtops =
 190         { FILTEROP_ISFD, NULL, logfiltdetach, logfiltread };
 191
 192 static int
 193 logkqfilter(struct dev_kqfilter_args *ap)
 194 {
 195         struct knote *kn = ap->a_kn;
 196         struct klist *klist = &logsoftc.sc_kqp.ki_note;
 197
 198         ap->a_result = 0;
 199         switch (kn->kn_filter) {
 200         case EVFILT_READ:
 201                 kn->kn_fop = &logread_filtops;
 202                 break;
 203         default:
 204                 ap->a_result = EOPNOTSUPP;
 205                 return (0);
 206         }
 207
 208         knote_insert(klist, kn);
 209
 210         return (0);
 211 }
 212
 213 static void
 214 logfiltdetach(struct knote *kn)
 215 {
 216         struct klist *klist = &logsoftc.sc_kqp.ki_note;
 217
 218         knote_remove(klist, kn);
 219 }
 220
 221 static int
 222 logfiltread(struct knote *kn, long hint)
 223 {
 224         int ret = 0;
 225
 226         crit_enter();
 227         if (msgbufp->msg_bufl != msgbufp->msg_bufx)
 228                 ret = 1;
 229         crit_exit();
 230
 231         return (ret);
 232 }
 233
 234 static void
 235 logtimeout(void *arg)
 236 {
 237         if (!log_open)
 238                 return;
 239         if (msgbuftrigger == 0) {
 240                 callout_reset(&logsoftc.sc_callout,
 241                               hz / log_wakeups_per_second, logtimeout, NULL);
 242                 return;
 243         }
 244         msgbuftrigger = 0;
 245         KNOTE(&logsoftc.sc_kqp.ki_note, 0);
 246         if ((logsoftc.sc_state & LOG_ASYNC) && logsoftc.sc_sigio != NULL)
 247                 pgsigio(logsoftc.sc_sigio, SIGIO, 0);
 248         if (logsoftc.sc_state & LOG_RDWAIT) {
 249                 atomic_clear_int(&logsoftc.sc_state, LOG_RDWAIT);
 250                 wakeup((caddr_t)msgbufp);
 251         }
 252         callout_reset(&logsoftc.sc_callout, hz / log_wakeups_per_second,
 253                       logtimeout, NULL);
 254 }
 255
 256 /*ARGSUSED*/
 257 static  int
 258 logioctl(struct dev_ioctl_args *ap)
 259 {
 260         struct msgbuf *mbp = msgbufp;
 261         u_int lindex;
 262         u_int xindex;
 263         u_int n;
 264
 265         switch (ap->a_cmd) {
 266         case FIONREAD:
 267                 lindex = mbp->msg_bufl;
 268                 xindex = mbp->msg_bufx;
 269                 cpu_ccfence();
 270
 271                 /*
 272                  * Clean up if too much time has passed causing us to wrap
 273                  * the buffer.  This will lose some data.  If more than ~4GB
 274                  * then this will lose even more data.
 275                  */
 276                 n = xindex - lindex;
 277                 if (n > mbp->msg_size - 1024) {
 278                         lindex = xindex - mbp->msg_size + 2048;
 279                         n = xindex - lindex;
 280                 }
 281                 *(int *)ap->a_data = n;
 282                 break;
 283
 284         case FIOASYNC:
 285                 if (*(int *)ap->a_data)
 286                         atomic_set_int(&logsoftc.sc_state, LOG_ASYNC);
 287                 else
 288                         atomic_clear_int(&logsoftc.sc_state, LOG_ASYNC);
 289                 break;
 290
 291         case FIOSETOWN:
 292                 return (fsetown(*(int *)ap->a_data, &logsoftc.sc_sigio));
 293
 294         case FIOGETOWN:
 295                 *(int *)ap->a_data = fgetown(&logsoftc.sc_sigio);
 296                 break;
 297
 298         /* This is deprecated, FIOSETOWN should be used instead. */
 299         case TIOCSPGRP:
 300                 return (fsetown(-(*(int *)ap->a_data), &logsoftc.sc_sigio));
 301
 302         /* This is deprecated, FIOGETOWN should be used instead */
 303         case TIOCGPGRP:
 304                 *(int *)ap->a_data = -fgetown(&logsoftc.sc_sigio);
 305                 break;
 306
 307         default:
 308                 return (ENOTTY);
 309         }
 310         return (0);
 311 }
 312
 313 static void
 314 log_drvinit(void *unused)
 315 {
 316         make_dev(&log_ops, 0, UID_ROOT, GID_WHEEL, 0600, "klog");
 317 }
 318
 319 SYSINIT(logdev, SI_SUB_DRIVERS, SI_ORDER_MIDDLE + CDEV_MAJOR, log_drvinit,
 320     NULL);