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