1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1982, 1986, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. Neither the name of the University nor the names of its contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 */ 31 32 /* 33 * Error log buffer for kernel printf's. 34 */ 35 36 #include <sys/cdefs.h> 37 #include <sys/param.h> 38 #include <sys/systm.h> 39 #include <sys/conf.h> 40 #include <sys/proc.h> 41 #include <sys/vnode.h> 42 #include <sys/filio.h> 43 #include <sys/ttycom.h> 44 #include <sys/msgbuf.h> 45 #include <sys/signalvar.h> 46 #include <sys/kernel.h> 47 #include <sys/poll.h> 48 #include <sys/filedesc.h> 49 #include <sys/sysctl.h> 50 51 #define LOG_RDPRI (PZERO + 1) 52 53 #define LOG_ASYNC 0x04 54 55 static d_open_t logopen; 56 static d_close_t logclose; 57 static d_read_t logread; 58 static d_ioctl_t logioctl; 59 static d_poll_t logpoll; 60 static d_kqfilter_t logkqfilter; 61 62 static void logtimeout(void *arg); 63 64 static struct cdevsw log_cdevsw = { 65 .d_version = D_VERSION, 66 .d_open = logopen, 67 .d_close = logclose, 68 .d_read = logread, 69 .d_ioctl = logioctl, 70 .d_poll = logpoll, 71 .d_kqfilter = logkqfilter, 72 .d_name = "log", 73 }; 74 75 static int logkqread(struct knote *note, long hint); 76 static void logkqdetach(struct knote *note); 77 78 static struct filterops log_read_filterops = { 79 .f_isfd = 1, 80 .f_attach = NULL, 81 .f_detach = logkqdetach, 82 .f_event = logkqread, 83 }; 84 85 static struct logsoftc { 86 int sc_state; /* see above for possibilities */ 87 struct selinfo sc_selp; /* process waiting on select call */ 88 struct sigio *sc_sigio; /* information for async I/O */ 89 struct callout sc_callout; /* callout to wakeup syslog */ 90 } logsoftc; 91 92 int log_open; /* also used in log() */ 93 static struct cv log_wakeup; 94 struct mtx msgbuf_lock; 95 MTX_SYSINIT(msgbuf_lock, &msgbuf_lock, "msgbuf lock", MTX_DEF); 96 97 static int log_wakeups_per_second = 5; 98 SYSCTL_INT(_kern, OID_AUTO, log_wakeups_per_second, CTLFLAG_RW, 99 &log_wakeups_per_second, 0, 100 "How often (times per second) to check for /dev/log waiters."); 101 102 /*ARGSUSED*/ 103 static int 104 logopen(struct cdev *dev, int flags, int mode, struct thread *td) 105 { 106 107 if (log_wakeups_per_second < 1) { 108 printf("syslog wakeup is less than one. Adjusting to 1.\n"); 109 log_wakeups_per_second = 1; 110 } 111 112 mtx_lock(&msgbuf_lock); 113 if (log_open) { 114 mtx_unlock(&msgbuf_lock); 115 return (EBUSY); 116 } 117 log_open = 1; 118 callout_reset_sbt(&logsoftc.sc_callout, 119 SBT_1S / log_wakeups_per_second, 0, logtimeout, NULL, C_PREL(1)); 120 mtx_unlock(&msgbuf_lock); 121 122 fsetown(td->td_proc->p_pid, &logsoftc.sc_sigio); /* signal process only */ 123 return (0); 124 } 125 126 /*ARGSUSED*/ 127 static int 128 logclose(struct cdev *dev, int flag, int mode, struct thread *td) 129 { 130 131 funsetown(&logsoftc.sc_sigio); 132 133 mtx_lock(&msgbuf_lock); 134 callout_stop(&logsoftc.sc_callout); 135 logsoftc.sc_state = 0; 136 log_open = 0; 137 mtx_unlock(&msgbuf_lock); 138 139 return (0); 140 } 141 142 /*ARGSUSED*/ 143 static int 144 logread(struct cdev *dev, struct uio *uio, int flag) 145 { 146 char buf[128]; 147 struct msgbuf *mbp = msgbufp; 148 int error = 0, l; 149 150 mtx_lock(&msgbuf_lock); 151 while (msgbuf_getcount(mbp) == 0) { 152 if (flag & IO_NDELAY) { 153 mtx_unlock(&msgbuf_lock); 154 return (EWOULDBLOCK); 155 } 156 if ((error = cv_wait_sig(&log_wakeup, &msgbuf_lock)) != 0) { 157 mtx_unlock(&msgbuf_lock); 158 return (error); 159 } 160 } 161 162 while (uio->uio_resid > 0) { 163 l = imin(sizeof(buf), uio->uio_resid); 164 l = msgbuf_getbytes(mbp, buf, l); 165 if (l == 0) 166 break; 167 mtx_unlock(&msgbuf_lock); 168 error = uiomove(buf, l, uio); 169 if (error || uio->uio_resid == 0) 170 return (error); 171 mtx_lock(&msgbuf_lock); 172 } 173 mtx_unlock(&msgbuf_lock); 174 return (error); 175 } 176 177 /*ARGSUSED*/ 178 static int 179 logpoll(struct cdev *dev, int events, struct thread *td) 180 { 181 int revents = 0; 182 183 if (events & (POLLIN | POLLRDNORM)) { 184 mtx_lock(&msgbuf_lock); 185 if (msgbuf_getcount(msgbufp) > 0) 186 revents |= events & (POLLIN | POLLRDNORM); 187 else 188 selrecord(td, &logsoftc.sc_selp); 189 mtx_unlock(&msgbuf_lock); 190 } 191 return (revents); 192 } 193 194 static int 195 logkqfilter(struct cdev *dev, struct knote *kn) 196 { 197 198 if (kn->kn_filter != EVFILT_READ) 199 return (EINVAL); 200 201 kn->kn_fop = &log_read_filterops; 202 kn->kn_hook = NULL; 203 204 mtx_lock(&msgbuf_lock); 205 knlist_add(&logsoftc.sc_selp.si_note, kn, 1); 206 mtx_unlock(&msgbuf_lock); 207 return (0); 208 } 209 210 static int 211 logkqread(struct knote *kn, long hint) 212 { 213 214 mtx_assert(&msgbuf_lock, MA_OWNED); 215 kn->kn_data = msgbuf_getcount(msgbufp); 216 return (kn->kn_data != 0); 217 } 218 219 static void 220 logkqdetach(struct knote *kn) 221 { 222 223 mtx_lock(&msgbuf_lock); 224 knlist_remove(&logsoftc.sc_selp.si_note, kn, 1); 225 mtx_unlock(&msgbuf_lock); 226 } 227 228 static void 229 logtimeout(void *arg) 230 { 231 232 if (!log_open) 233 return; 234 if (msgbuftrigger == 0) 235 goto done; 236 msgbuftrigger = 0; 237 selwakeuppri(&logsoftc.sc_selp, LOG_RDPRI); 238 KNOTE_LOCKED(&logsoftc.sc_selp.si_note, 0); 239 if ((logsoftc.sc_state & LOG_ASYNC) && logsoftc.sc_sigio != NULL) 240 pgsigio(&logsoftc.sc_sigio, SIGIO, 0); 241 cv_broadcastpri(&log_wakeup, LOG_RDPRI); 242 done: 243 if (log_wakeups_per_second < 1) { 244 printf("syslog wakeup is less than one. Adjusting to 1.\n"); 245 log_wakeups_per_second = 1; 246 } 247 callout_reset_sbt(&logsoftc.sc_callout, 248 SBT_1S / log_wakeups_per_second, 0, logtimeout, NULL, C_PREL(1)); 249 } 250 251 /*ARGSUSED*/ 252 static int 253 logioctl(struct cdev *dev, u_long com, caddr_t data, int flag, struct thread *td) 254 { 255 256 switch (com) { 257 /* return number of characters immediately available */ 258 case FIONREAD: 259 *(int *)data = msgbuf_getcount(msgbufp); 260 break; 261 262 case FIONBIO: 263 break; 264 265 case FIOASYNC: 266 mtx_lock(&msgbuf_lock); 267 if (*(int *)data) 268 logsoftc.sc_state |= LOG_ASYNC; 269 else 270 logsoftc.sc_state &= ~LOG_ASYNC; 271 mtx_unlock(&msgbuf_lock); 272 break; 273 274 case FIOSETOWN: 275 return (fsetown(*(int *)data, &logsoftc.sc_sigio)); 276 277 case FIOGETOWN: 278 *(int *)data = fgetown(&logsoftc.sc_sigio); 279 break; 280 281 /* This is deprecated, FIOSETOWN should be used instead. */ 282 case TIOCSPGRP: 283 return (fsetown(-(*(int *)data), &logsoftc.sc_sigio)); 284 285 /* This is deprecated, FIOGETOWN should be used instead */ 286 case TIOCGPGRP: 287 *(int *)data = -fgetown(&logsoftc.sc_sigio); 288 break; 289 290 default: 291 return (ENOTTY); 292 } 293 return (0); 294 } 295 296 static void 297 log_drvinit(void *unused) 298 { 299 300 cv_init(&log_wakeup, "klog"); 301 callout_init_mtx(&logsoftc.sc_callout, &msgbuf_lock, 0); 302 knlist_init_mtx(&logsoftc.sc_selp.si_note, &msgbuf_lock); 303 make_dev_credf(MAKEDEV_ETERNAL, &log_cdevsw, 0, NULL, UID_ROOT, 304 GID_WHEEL, 0600, "klog"); 305 } 306 307 SYSINIT(logdev,SI_SUB_DRIVERS,SI_ORDER_MIDDLE,log_drvinit,NULL); 308