subr_log.c revision 1.59.12.1
1 /* $NetBSD: subr_log.c,v 1.59.12.1 2020/12/14 14:38:14 thorpej Exp $ */ 2 3 /*- 4 * Copyright (c) 2007, 2008 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Andrew Doran. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29 * POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32 /* 33 * Copyright (c) 1982, 1986, 1993 34 * The Regents of the University of California. All rights reserved. 35 * 36 * Redistribution and use in source and binary forms, with or without 37 * modification, are permitted provided that the following conditions 38 * are met: 39 * 1. Redistributions of source code must retain the above copyright 40 * notice, this list of conditions and the following disclaimer. 41 * 2. Redistributions in binary form must reproduce the above copyright 42 * notice, this list of conditions and the following disclaimer in the 43 * documentation and/or other materials provided with the distribution. 44 * 3. Neither the name of the University nor the names of its contributors 45 * may be used to endorse or promote products derived from this software 46 * without specific prior written permission. 47 * 48 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 49 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 50 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 51 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 52 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 53 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 54 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 55 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 56 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 57 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 58 * SUCH DAMAGE. 59 * 60 * @(#)subr_log.c 8.3 (Berkeley) 2/14/95 61 */ 62 63 /* 64 * Error log buffer for kernel printf's. 65 */ 66 67 #include <sys/cdefs.h> 68 __KERNEL_RCSID(0, "$NetBSD: subr_log.c,v 1.59.12.1 2020/12/14 14:38:14 thorpej Exp $"); 69 70 #include <sys/param.h> 71 #include <sys/systm.h> 72 #include <sys/kernel.h> 73 #include <sys/proc.h> 74 #include <sys/vnode.h> 75 #include <sys/ioctl.h> 76 #include <sys/msgbuf.h> 77 #include <sys/file.h> 78 #include <sys/syslog.h> 79 #include <sys/conf.h> 80 #include <sys/select.h> 81 #include <sys/poll.h> 82 #include <sys/intr.h> 83 #include <sys/sysctl.h> 84 #include <sys/ktrace.h> 85 86 static int sysctl_msgbuf(SYSCTLFN_PROTO); 87 88 static void logsoftintr(void *); 89 90 static bool log_async; 91 static struct selinfo log_selp; /* process waiting on select call */ 92 static pid_t log_pgid; /* process/group for async I/O */ 93 static kcondvar_t log_cv; 94 static void *log_sih; 95 96 kmutex_t log_lock; 97 int log_open; /* also used in log() */ 98 int msgbufmapped; /* is the message buffer mapped */ 99 int msgbufenabled; /* is logging to the buffer enabled */ 100 struct kern_msgbuf *msgbufp; /* the mapped buffer, itself. */ 101 102 void 103 initmsgbuf(void *bf, size_t bufsize) 104 { 105 struct kern_msgbuf *mbp; 106 long new_bufs; 107 108 /* Sanity-check the given size. */ 109 if (bufsize < sizeof(struct kern_msgbuf)) 110 return; 111 112 mbp = msgbufp = (struct kern_msgbuf *)bf; 113 114 new_bufs = bufsize - offsetof(struct kern_msgbuf, msg_bufc); 115 if ((mbp->msg_magic != MSG_MAGIC) || (mbp->msg_bufs != new_bufs) || 116 (mbp->msg_bufr < 0) || (mbp->msg_bufr >= mbp->msg_bufs) || 117 (mbp->msg_bufx < 0) || (mbp->msg_bufx >= mbp->msg_bufs)) { 118 /* 119 * If the buffer magic number is wrong, has changed 120 * size (which shouldn't happen often), or is 121 * internally inconsistent, initialize it. 122 */ 123 124 memset(bf, 0, bufsize); 125 mbp->msg_magic = MSG_MAGIC; 126 mbp->msg_bufs = new_bufs; 127 } 128 129 /* mark it as ready for use. */ 130 msgbufmapped = msgbufenabled = 1; 131 } 132 133 void 134 loginit(void) 135 { 136 137 mutex_init(&log_lock, MUTEX_DEFAULT, IPL_VM); 138 selinit(&log_selp); 139 cv_init(&log_cv, "klog"); 140 log_sih = softint_establish(SOFTINT_CLOCK | SOFTINT_MPSAFE, 141 logsoftintr, NULL); 142 143 sysctl_createv(NULL, 0, NULL, NULL, 144 CTLFLAG_PERMANENT, 145 CTLTYPE_INT, "msgbufsize", 146 SYSCTL_DESCR("Size of the kernel message buffer"), 147 sysctl_msgbuf, 0, NULL, 0, 148 CTL_KERN, KERN_MSGBUFSIZE, CTL_EOL); 149 sysctl_createv(NULL, 0, NULL, NULL, 150 CTLFLAG_PERMANENT, 151 CTLTYPE_INT, "msgbuf", 152 SYSCTL_DESCR("Kernel message buffer"), 153 sysctl_msgbuf, 0, NULL, 0, 154 CTL_KERN, KERN_MSGBUF, CTL_EOL); 155 } 156 157 /*ARGSUSED*/ 158 static int 159 logopen(dev_t dev, int flags, int mode, struct lwp *l) 160 { 161 struct kern_msgbuf *mbp = msgbufp; 162 int error = 0; 163 164 mutex_spin_enter(&log_lock); 165 if (log_open) { 166 error = EBUSY; 167 } else { 168 log_open = 1; 169 log_pgid = l->l_proc->p_pid; /* signal process only */ 170 /* 171 * The message buffer is initialized during system 172 * configuration. If it's been clobbered, note that 173 * and return an error. (This allows a user to read 174 * the buffer via /dev/kmem, and try to figure out 175 * what clobbered it. 176 */ 177 if (mbp->msg_magic != MSG_MAGIC) { 178 msgbufenabled = 0; 179 error = ENXIO; 180 } 181 } 182 mutex_spin_exit(&log_lock); 183 184 return error; 185 } 186 187 /*ARGSUSED*/ 188 static int 189 logclose(dev_t dev, int flag, int mode, struct lwp *l) 190 { 191 192 mutex_spin_enter(&log_lock); 193 log_pgid = 0; 194 log_open = 0; 195 log_async = 0; 196 mutex_spin_exit(&log_lock); 197 198 return 0; 199 } 200 201 /*ARGSUSED*/ 202 static int 203 logread(dev_t dev, struct uio *uio, int flag) 204 { 205 struct kern_msgbuf *mbp = msgbufp; 206 long l; 207 int error = 0; 208 209 mutex_spin_enter(&log_lock); 210 while (mbp->msg_bufr == mbp->msg_bufx) { 211 if (flag & IO_NDELAY) { 212 mutex_spin_exit(&log_lock); 213 return EWOULDBLOCK; 214 } 215 error = cv_wait_sig(&log_cv, &log_lock); 216 if (error) { 217 mutex_spin_exit(&log_lock); 218 return error; 219 } 220 } 221 while (uio->uio_resid > 0) { 222 l = mbp->msg_bufx - mbp->msg_bufr; 223 if (l < 0) 224 l = mbp->msg_bufs - mbp->msg_bufr; 225 l = uimin(l, uio->uio_resid); 226 if (l == 0) 227 break; 228 mutex_spin_exit(&log_lock); 229 error = uiomove(&mbp->msg_bufc[mbp->msg_bufr], (int)l, uio); 230 mutex_spin_enter(&log_lock); 231 if (error) 232 break; 233 mbp->msg_bufr += l; 234 if (mbp->msg_bufr < 0 || mbp->msg_bufr >= mbp->msg_bufs) 235 mbp->msg_bufr = 0; 236 } 237 mutex_spin_exit(&log_lock); 238 239 return error; 240 } 241 242 /*ARGSUSED*/ 243 static int 244 logpoll(dev_t dev, int events, struct lwp *l) 245 { 246 int revents = 0; 247 248 if (events & (POLLIN | POLLRDNORM)) { 249 mutex_spin_enter(&log_lock); 250 if (msgbufp->msg_bufr != msgbufp->msg_bufx) 251 revents |= events & (POLLIN | POLLRDNORM); 252 else 253 selrecord(l, &log_selp); 254 mutex_spin_exit(&log_lock); 255 } 256 257 return revents; 258 } 259 260 static void 261 filt_logrdetach(struct knote *kn) 262 { 263 264 mutex_spin_enter(&log_lock); 265 selremove_knote(&log_selp, kn); 266 mutex_spin_exit(&log_lock); 267 } 268 269 static int 270 filt_logread(struct knote *kn, long hint) 271 { 272 int rv; 273 274 if ((hint & NOTE_SUBMIT) == 0) 275 mutex_spin_enter(&log_lock); 276 if (msgbufp->msg_bufr == msgbufp->msg_bufx) { 277 rv = 0; 278 } else if (msgbufp->msg_bufr < msgbufp->msg_bufx) { 279 kn->kn_data = msgbufp->msg_bufx - msgbufp->msg_bufr; 280 rv = 1; 281 } else { 282 kn->kn_data = (msgbufp->msg_bufs - msgbufp->msg_bufr) + 283 msgbufp->msg_bufx; 284 rv = 1; 285 } 286 if ((hint & NOTE_SUBMIT) == 0) 287 mutex_spin_exit(&log_lock); 288 289 return rv; 290 } 291 292 static const struct filterops logread_filtops = { 293 .f_isfd = 1, 294 .f_attach = NULL, 295 .f_detach = filt_logrdetach, 296 .f_event = filt_logread, 297 }; 298 299 static int 300 logkqfilter(dev_t dev, struct knote *kn) 301 { 302 303 switch (kn->kn_filter) { 304 case EVFILT_READ: 305 kn->kn_fop = &logread_filtops; 306 break; 307 308 default: 309 return (EINVAL); 310 } 311 312 kn->kn_hook = NULL; 313 314 mutex_spin_enter(&log_lock); 315 selrecord_knote(&log_selp, kn); 316 mutex_spin_exit(&log_lock); 317 318 return (0); 319 } 320 321 void 322 logwakeup(void) 323 { 324 325 if (!cold && log_open) { 326 mutex_spin_enter(&log_lock); 327 selnotify(&log_selp, 0, NOTE_SUBMIT); 328 if (log_async) 329 softint_schedule(log_sih); 330 cv_broadcast(&log_cv); 331 mutex_spin_exit(&log_lock); 332 } 333 } 334 335 static void 336 logsoftintr(void *cookie) 337 { 338 pid_t pid; 339 340 if ((pid = log_pgid) != 0) 341 fownsignal(pid, SIGIO, 0, 0, NULL); 342 } 343 344 /*ARGSUSED*/ 345 static int 346 logioctl(dev_t dev, u_long com, void *data, int flag, struct lwp *lwp) 347 { 348 long l; 349 350 switch (com) { 351 352 /* return number of characters immediately available */ 353 case FIONREAD: 354 mutex_spin_enter(&log_lock); 355 l = msgbufp->msg_bufx - msgbufp->msg_bufr; 356 if (l < 0) 357 l += msgbufp->msg_bufs; 358 mutex_spin_exit(&log_lock); 359 *(int *)data = l; 360 break; 361 362 case FIONBIO: 363 break; 364 365 case FIOASYNC: 366 /* No locking needed, 'thread private'. */ 367 log_async = (*((int *)data) != 0); 368 break; 369 370 case TIOCSPGRP: 371 case FIOSETOWN: 372 return fsetown(&log_pgid, com, data); 373 374 case TIOCGPGRP: 375 case FIOGETOWN: 376 return fgetown(log_pgid, com, data); 377 378 default: 379 return (EPASSTHROUGH); 380 } 381 return (0); 382 } 383 384 static void 385 logskip(struct kern_msgbuf *mbp) 386 { 387 /* 388 * Move forward read pointer to the next line 389 * in the buffer. Note that the buffer is 390 * a ring buffer so we should reset msg_bufr 391 * to 0 when msg_bufr exceeds msg_bufs. 392 * 393 * To prevent to loop forever, give up if we 394 * cannot find a newline in mbp->msg_bufs 395 * characters (the max size of the buffer). 396 */ 397 for (int i = 0; i < mbp->msg_bufs; i++) { 398 char c0 = mbp->msg_bufc[mbp->msg_bufr]; 399 if (++mbp->msg_bufr >= mbp->msg_bufs) 400 mbp->msg_bufr = 0; 401 if (c0 == '\n') 402 break; 403 } 404 } 405 406 static void 407 logaddchar(struct kern_msgbuf *mbp, int c) 408 { 409 mbp->msg_bufc[mbp->msg_bufx++] = c; 410 if (mbp->msg_bufx < 0 || mbp->msg_bufx >= mbp->msg_bufs) 411 mbp->msg_bufx = 0; 412 413 /* If the buffer is full, keep the most recent data. */ 414 if (mbp->msg_bufr == mbp->msg_bufx) 415 logskip(mbp); 416 } 417 418 void 419 logputchar(int c) 420 { 421 struct kern_msgbuf *mbp; 422 423 if (!cold) 424 mutex_spin_enter(&log_lock); 425 426 if (!msgbufenabled) 427 goto out; 428 429 mbp = msgbufp; 430 if (mbp->msg_magic != MSG_MAGIC) { 431 /* 432 * Arguably should panic or somehow notify the 433 * user... but how? Panic may be too drastic, 434 * and would obliterate the message being kicked 435 * out (maybe a panic itself), and printf 436 * would invoke us recursively. Silently punt 437 * for now. If syslog is running, it should 438 * notice. 439 */ 440 msgbufenabled = 0; 441 goto out; 442 443 } 444 445 logaddchar(mbp, c); 446 447 out: 448 if (!cold) 449 mutex_spin_exit(&log_lock); 450 } 451 452 /* 453 * sysctl helper routine for kern.msgbufsize and kern.msgbuf. For the 454 * former it merely checks the message buffer is set up. For the latter, 455 * it also copies out the data if necessary. 456 */ 457 static int 458 sysctl_msgbuf(SYSCTLFN_ARGS) 459 { 460 char *where = oldp; 461 size_t len, maxlen; 462 long beg, end; 463 extern kmutex_t log_lock; 464 int error; 465 466 if (!logenabled(msgbufp)) { 467 msgbufenabled = 0; 468 return (ENXIO); 469 } 470 471 switch (rnode->sysctl_num) { 472 case KERN_MSGBUFSIZE: { 473 struct sysctlnode node = *rnode; 474 int msg_bufs = (int)msgbufp->msg_bufs; 475 node.sysctl_data = &msg_bufs; 476 return (sysctl_lookup(SYSCTLFN_CALL(&node))); 477 } 478 case KERN_MSGBUF: 479 break; 480 default: 481 return (EOPNOTSUPP); 482 } 483 484 if (newp != NULL) 485 return (EPERM); 486 487 if (oldp == NULL) { 488 /* always return full buffer size */ 489 *oldlenp = msgbufp->msg_bufs; 490 return (0); 491 } 492 493 sysctl_unlock(); 494 495 /* 496 * First, copy from the write pointer to the end of 497 * message buffer. 498 */ 499 error = 0; 500 mutex_spin_enter(&log_lock); 501 maxlen = MIN(msgbufp->msg_bufs, *oldlenp); 502 beg = msgbufp->msg_bufx; 503 end = msgbufp->msg_bufs; 504 mutex_spin_exit(&log_lock); 505 506 while (maxlen > 0) { 507 len = MIN(end - beg, maxlen); 508 if (len == 0) 509 break; 510 /* XXX unlocked, but hardly matters. */ 511 error = copyout(&msgbufp->msg_bufc[beg], where, len); 512 ktrmibio(-1, UIO_READ, where, len, error); 513 if (error) 514 break; 515 where += len; 516 maxlen -= len; 517 518 /* 519 * ... then, copy from the beginning of message buffer to 520 * the write pointer. 521 */ 522 beg = 0; 523 end = msgbufp->msg_bufx; 524 } 525 526 sysctl_relock(); 527 return (error); 528 } 529 530 const struct cdevsw log_cdevsw = { 531 .d_open = logopen, 532 .d_close = logclose, 533 .d_read = logread, 534 .d_write = nowrite, 535 .d_ioctl = logioctl, 536 .d_stop = nostop, 537 .d_tty = notty, 538 .d_poll = logpoll, 539 .d_mmap = nommap, 540 .d_kqfilter = logkqfilter, 541 .d_discard = nodiscard, 542 .d_flag = D_OTHER | D_MPSAFE 543 }; 544
Indexes created Sun Sep 28 16:09:52 GMT 2025