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
Version:
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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/9.1/sys/kern/subr_log.c 231203 2012-02-08 14:21:20Z 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 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(&logsoftc.sc_callout, hz / log_wakeups_per_second, 121 logtimeout, NULL); 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 (log_wakeups_per_second < 1) { 237 printf("syslog wakeup is less than one. Adjusting to 1.\n"); 238 log_wakeups_per_second = 1; 239 } 240 if (msgbuftrigger == 0) { 241 callout_schedule(&logsoftc.sc_callout, 242 hz / log_wakeups_per_second); 243 return; 244 } 245 msgbuftrigger = 0; 246 selwakeuppri(&logsoftc.sc_selp, LOG_RDPRI); 247 KNOTE_LOCKED(&logsoftc.sc_selp.si_note, 0); 248 if ((logsoftc.sc_state & LOG_ASYNC) && logsoftc.sc_sigio != NULL) 249 pgsigio(&logsoftc.sc_sigio, SIGIO, 0); 250 cv_broadcastpri(&log_wakeup, LOG_RDPRI); 251 callout_schedule(&logsoftc.sc_callout, hz / log_wakeups_per_second); 252 } 253 254 /*ARGSUSED*/ 255 static int 256 logioctl(struct cdev *dev, u_long com, caddr_t data, int flag, struct thread *td) 257 { 258 259 switch (com) { 260 261 /* return number of characters immediately available */ 262 case FIONREAD: 263 *(int *)data = msgbuf_getcount(msgbufp); 264 break; 265 266 case FIONBIO: 267 break; 268 269 case FIOASYNC: 270 mtx_lock(&msgbuf_lock); 271 if (*(int *)data) 272 logsoftc.sc_state |= LOG_ASYNC; 273 else 274 logsoftc.sc_state &= ~LOG_ASYNC; 275 mtx_unlock(&msgbuf_lock); 276 break; 277 278 case FIOSETOWN: 279 return (fsetown(*(int *)data, &logsoftc.sc_sigio)); 280 281 case FIOGETOWN: 282 *(int *)data = fgetown(&logsoftc.sc_sigio); 283 break; 284 285 /* This is deprecated, FIOSETOWN should be used instead. */ 286 case TIOCSPGRP: 287 return (fsetown(-(*(int *)data), &logsoftc.sc_sigio)); 288 289 /* This is deprecated, FIOGETOWN should be used instead */ 290 case TIOCGPGRP: 291 *(int *)data = -fgetown(&logsoftc.sc_sigio); 292 break; 293 294 default: 295 return (ENOTTY); 296 } 297 return (0); 298 } 299 300 static void 301 log_drvinit(void *unused) 302 { 303 304 cv_init(&log_wakeup, "klog"); 305 callout_init_mtx(&logsoftc.sc_callout, &msgbuf_lock, 0); 306 knlist_init_mtx(&logsoftc.sc_selp.si_note, &msgbuf_lock); 307 make_dev_credf(MAKEDEV_ETERNAL, &log_cdevsw, 0, NULL, UID_ROOT, 308 GID_WHEEL, 0600, "klog"); 309 } 310 311 SYSINIT(logdev,SI_SUB_DRIVERS,SI_ORDER_MIDDLE,log_drvinit,NULL);
Cache object: 5de521cd74278e16f5e902f70e9a0dff
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