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/param.h> 37 #include <sys/systm.h> 38 #include <sys/conf.h> 39 #include <sys/proc.h> 40 #include <sys/vnode.h> 41 #include <sys/filio.h> 42 #include <sys/ttycom.h> 43 #include <sys/msgbuf.h> 44 #include <sys/signalvar.h> 45 #include <sys/kernel.h> 46 #include <sys/poll.h> 47 #include <sys/filedesc.h> 48 #include <sys/sysctl.h> 49 50 #define LOG_RDPRI (PZERO + 1) 51 52 #define LOG_ASYNC 0x04 53 54 static d_open_t logopen; 55 static d_close_t logclose; 56 static d_read_t logread; 57 static d_ioctl_t logioctl; 58 static d_poll_t logpoll; 59 static d_kqfilter_t logkqfilter; 60 61 static void logtimeout(void *arg); 62 63 static struct cdevsw log_cdevsw = { 64 .d_version = D_VERSION, 65 .d_open = logopen, 66 .d_close = logclose, 67 .d_read = logread, 68 .d_ioctl = logioctl, 69 .d_poll = logpoll, 70 .d_kqfilter = logkqfilter, 71 .d_name = "log", 72 }; 73 74 static int logkqread(struct knote *note, long hint); 75 static void logkqdetach(struct knote *note); 76 77 static const struct filterops log_read_filterops = { 78 .f_isfd = 1, 79 .f_attach = NULL, 80 .f_detach = logkqdetach, 81 .f_event = logkqread, 82 }; 83 84 static struct logsoftc { 85 int sc_state; /* see above for possibilities */ 86 struct selinfo sc_selp; /* process waiting on select call */ 87 struct sigio *sc_sigio; /* information for async I/O */ 88 struct callout sc_callout; /* callout to wakeup syslog */ 89 } logsoftc; 90 91 int log_open; /* also used in log() */ 92 static struct cv log_wakeup; 93 struct mtx msgbuf_lock; 94 MTX_SYSINIT(msgbuf_lock, &msgbuf_lock, "msgbuf lock", MTX_DEF); 95 96 static int log_wakeups_per_second = 5; 97 SYSCTL_INT(_kern, OID_AUTO, log_wakeups_per_second, CTLFLAG_RW, 98 &log_wakeups_per_second, 0, 99 "How often (times per second) to check for /dev/log waiters."); 100 101 /*ARGSUSED*/ 102 static int 103 logopen(struct cdev *dev, int flags, int mode, struct thread *td) 104 { 105 106 if (log_wakeups_per_second < 1) { 107 printf("syslog wakeup is less than one. Adjusting to 1.\n"); 108 log_wakeups_per_second = 1; 109 } 110 111 mtx_lock(&msgbuf_lock); 112 if (log_open) { 113 mtx_unlock(&msgbuf_lock); 114 return (EBUSY); 115 } 116 log_open = 1; 117 callout_reset_sbt(&logsoftc.sc_callout, 118 SBT_1S / log_wakeups_per_second, 0, logtimeout, NULL, C_PREL(1)); 119 mtx_unlock(&msgbuf_lock); 120 121 fsetown(td->td_proc->p_pid, &logsoftc.sc_sigio); /* signal process only */ 122 return (0); 123 } 124 125 /*ARGSUSED*/ 126 static int 127 logclose(struct cdev *dev, int flag, int mode, struct thread *td) 128 { 129 130 funsetown(&logsoftc.sc_sigio); 131 132 mtx_lock(&msgbuf_lock); 133 callout_stop(&logsoftc.sc_callout); 134 logsoftc.sc_state = 0; 135 log_open = 0; 136 mtx_unlock(&msgbuf_lock); 137 138 return (0); 139 } 140 141 /*ARGSUSED*/ 142 static int 143 logread(struct cdev *dev, struct uio *uio, int flag) 144 { 145 char buf[128]; 146 struct msgbuf *mbp = msgbufp; 147 int error = 0, l; 148 149 mtx_lock(&msgbuf_lock); 150 while (msgbuf_getcount(mbp) == 0) { 151 if (flag & IO_NDELAY) { 152 mtx_unlock(&msgbuf_lock); 153 return (EWOULDBLOCK); 154 } 155 if ((error = cv_wait_sig(&log_wakeup, &msgbuf_lock)) != 0) { 156 mtx_unlock(&msgbuf_lock); 157 return (error); 158 } 159 } 160 161 while (uio->uio_resid > 0) { 162 l = imin(sizeof(buf), uio->uio_resid); 163 l = msgbuf_getbytes(mbp, buf, l); 164 if (l == 0) 165 break; 166 mtx_unlock(&msgbuf_lock); 167 error = uiomove(buf, l, uio); 168 if (error || uio->uio_resid == 0) 169 return (error); 170 mtx_lock(&msgbuf_lock); 171 } 172 mtx_unlock(&msgbuf_lock); 173 return (error); 174 } 175 176 /*ARGSUSED*/ 177 static int 178 logpoll(struct cdev *dev, int events, struct thread *td) 179 { 180 int revents = 0; 181 182 if (events & (POLLIN | POLLRDNORM)) { 183 mtx_lock(&msgbuf_lock); 184 if (msgbuf_getcount(msgbufp) > 0) 185 revents |= events & (POLLIN | POLLRDNORM); 186 else 187 selrecord(td, &logsoftc.sc_selp); 188 mtx_unlock(&msgbuf_lock); 189 } 190 return (revents); 191 } 192 193 static int 194 logkqfilter(struct cdev *dev, struct knote *kn) 195 { 196 197 if (kn->kn_filter != EVFILT_READ) 198 return (EINVAL); 199 200 kn->kn_fop = &log_read_filterops; 201 kn->kn_hook = NULL; 202 203 mtx_lock(&msgbuf_lock); 204 knlist_add(&logsoftc.sc_selp.si_note, kn, 1); 205 mtx_unlock(&msgbuf_lock); 206 return (0); 207 } 208 209 static int 210 logkqread(struct knote *kn, long hint) 211 { 212 213 mtx_assert(&msgbuf_lock, MA_OWNED); 214 kn->kn_data = msgbuf_getcount(msgbufp); 215 return (kn->kn_data != 0); 216 } 217 218 static void 219 logkqdetach(struct knote *kn) 220 { 221 222 mtx_lock(&msgbuf_lock); 223 knlist_remove(&logsoftc.sc_selp.si_note, kn, 1); 224 mtx_unlock(&msgbuf_lock); 225 } 226 227 static void 228 logtimeout(void *arg) 229 { 230 231 if (!log_open) 232 return; 233 if (msgbuftrigger == 0) 234 goto done; 235 msgbuftrigger = 0; 236 selwakeuppri(&logsoftc.sc_selp, LOG_RDPRI); 237 KNOTE_LOCKED(&logsoftc.sc_selp.si_note, 0); 238 if ((logsoftc.sc_state & LOG_ASYNC) && logsoftc.sc_sigio != NULL) 239 pgsigio(&logsoftc.sc_sigio, SIGIO, 0); 240 cv_broadcastpri(&log_wakeup, LOG_RDPRI); 241 done: 242 if (log_wakeups_per_second < 1) { 243 printf("syslog wakeup is less than one. Adjusting to 1.\n"); 244 log_wakeups_per_second = 1; 245 } 246 callout_reset_sbt(&logsoftc.sc_callout, 247 SBT_1S / log_wakeups_per_second, 0, logtimeout, NULL, C_PREL(1)); 248 } 249 250 /*ARGSUSED*/ 251 static int 252 logioctl(struct cdev *dev, u_long com, caddr_t data, int flag, struct thread *td) 253 { 254 255 switch (com) { 256 /* return number of characters immediately available */ 257 case FIONREAD: 258 *(int *)data = msgbuf_getcount(msgbufp); 259 break; 260 261 case FIONBIO: 262 break; 263 264 case FIOASYNC: 265 mtx_lock(&msgbuf_lock); 266 if (*(int *)data) 267 logsoftc.sc_state |= LOG_ASYNC; 268 else 269 logsoftc.sc_state &= ~LOG_ASYNC; 270 mtx_unlock(&msgbuf_lock); 271 break; 272 273 case FIOSETOWN: 274 return (fsetown(*(int *)data, &logsoftc.sc_sigio)); 275 276 case FIOGETOWN: 277 *(int *)data = fgetown(&logsoftc.sc_sigio); 278 break; 279 280 /* This is deprecated, FIOSETOWN should be used instead. */ 281 case TIOCSPGRP: 282 return (fsetown(-(*(int *)data), &logsoftc.sc_sigio)); 283 284 /* This is deprecated, FIOGETOWN should be used instead */ 285 case TIOCGPGRP: 286 *(int *)data = -fgetown(&logsoftc.sc_sigio); 287 break; 288 289 default: 290 return (ENOTTY); 291 } 292 return (0); 293 } 294 295 static void 296 log_drvinit(void *unused) 297 { 298 299 cv_init(&log_wakeup, "klog"); 300 callout_init_mtx(&logsoftc.sc_callout, &msgbuf_lock, 0); 301 knlist_init_mtx(&logsoftc.sc_selp.si_note, &msgbuf_lock); 302 make_dev_credf(MAKEDEV_ETERNAL, &log_cdevsw, 0, NULL, UID_ROOT, 303 GID_WHEEL, 0600, "klog"); 304 } 305 306 SYSINIT(logdev,SI_SUB_DRIVERS,SI_ORDER_MIDDLE,log_drvinit,NULL); 307