subr_log.c revision 1.65
1 /* $NetBSD: subr_log.c,v 1.65 2025/04/08 04:19:28 rin 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 1.65 2025/04/08 04:19:28 rin 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 static 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 = ulmin(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], 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_flags = FILTEROP_ISFD | FILTEROP_MPSAFE, 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 mutex_spin_enter(&log_lock); 307 selrecord_knote(&log_selp, kn); 308 mutex_spin_exit(&log_lock); 309 break; 310 311 default: 312 return (EINVAL); 313 } 314 315 return (0); 316 } 317 318 void 319 logwakeup(void) 320 { 321 322 if (!cold && log_open) { 323 mutex_spin_enter(&log_lock); 324 selnotify(&log_selp, 0, NOTE_SUBMIT); 325 if (log_async) 326 softint_schedule(log_sih); 327 cv_broadcast(&log_cv); 328 mutex_spin_exit(&log_lock); 329 } 330 } 331 332 static void 333 logsoftintr(void *cookie) 334 { 335 pid_t pid; 336 337 if ((pid = log_pgid) != 0) 338 fownsignal(pid, SIGIO, 0, 0, NULL); 339 } 340 341 /*ARGSUSED*/ 342 static int 343 logioctl(dev_t dev, u_long com, void *data, int flag, struct lwp *lwp) 344 { 345 long l; 346 347 switch (com) { 348 349 /* return number of characters immediately available */ 350 case FIONREAD: 351 mutex_spin_enter(&log_lock); 352 l = msgbufp->msg_bufx - msgbufp->msg_bufr; 353 if (l < 0) 354 l += msgbufp->msg_bufs; 355 mutex_spin_exit(&log_lock); 356 *(int *)data = l; 357 break; 358 359 case FIONBIO: 360 break; 361 362 case FIOASYNC: 363 /* No locking needed, 'thread private'. */ 364 log_async = (*((int *)data) != 0); 365 break; 366 367 case TIOCSPGRP: 368 case FIOSETOWN: 369 return fsetown(&log_pgid, com, data); 370 371 case TIOCGPGRP: 372 case FIOGETOWN: 373 return fgetown(log_pgid, com, data); 374 375 default: 376 return (EPASSTHROUGH); 377 } 378 return (0); 379 } 380 381 static void 382 logskip(struct kern_msgbuf *mbp) 383 { 384 /* 385 * Move forward read pointer to the next line 386 * in the buffer. Note that the buffer is 387 * a ring buffer so we should reset msg_bufr 388 * to 0 when msg_bufr exceeds msg_bufs. 389 * 390 * To prevent to loop forever, give up if we 391 * cannot find a newline in mbp->msg_bufs 392 * characters (the max size of the buffer). 393 */ 394 for (int i = 0; i < mbp->msg_bufs; i++) { 395 char c0 = mbp->msg_bufc[mbp->msg_bufr]; 396 if (++mbp->msg_bufr >= mbp->msg_bufs) 397 mbp->msg_bufr = 0; 398 if (c0 == '\n') 399 break; 400 } 401 } 402 403 static void 404 logaddchar(struct kern_msgbuf *mbp, int c) 405 { 406 mbp->msg_bufc[mbp->msg_bufx++] = c; 407 if (mbp->msg_bufx < 0 || mbp->msg_bufx >= mbp->msg_bufs) 408 mbp->msg_bufx = 0; 409 410 /* If the buffer is full, keep the most recent data. */ 411 if (mbp->msg_bufr == mbp->msg_bufx) 412 logskip(mbp); 413 } 414 415 void 416 logputchar(int c) 417 { 418 struct kern_msgbuf *mbp; 419 420 if (!cold) 421 mutex_spin_enter(&log_lock); 422 423 if (!msgbufenabled) 424 goto out; 425 426 mbp = msgbufp; 427 if (mbp->msg_magic != MSG_MAGIC) { 428 /* 429 * Arguably should panic or somehow notify the 430 * user... but how? Panic may be too drastic, 431 * and would obliterate the message being kicked 432 * out (maybe a panic itself), and printf 433 * would invoke us recursively. Silently punt 434 * for now. If syslog is running, it should 435 * notice. 436 */ 437 msgbufenabled = 0; 438 goto out; 439 440 } 441 442 logaddchar(mbp, c); 443 444 out: 445 if (!cold) 446 mutex_spin_exit(&log_lock); 447 } 448 449 /* 450 * sysctl helper routine for kern.msgbufsize and kern.msgbuf. For the 451 * former it merely checks the message buffer is set up. For the latter, 452 * it also copies out the data if necessary. 453 */ 454 static int 455 sysctl_msgbuf(SYSCTLFN_ARGS) 456 { 457 char *where = oldp; 458 size_t len, maxlen; 459 long beg, end; 460 int error; 461 462 if (!logenabled(msgbufp)) { 463 msgbufenabled = 0; 464 return (ENXIO); 465 } 466 467 switch (rnode->sysctl_num) { 468 case KERN_MSGBUFSIZE: { 469 struct sysctlnode node = *rnode; 470 int msg_bufs = (int)msgbufp->msg_bufs; 471 node.sysctl_data = &msg_bufs; 472 return (sysctl_lookup(SYSCTLFN_CALL(&node))); 473 } 474 case KERN_MSGBUF: 475 break; 476 default: 477 return (EOPNOTSUPP); 478 } 479 480 if (newp != NULL) 481 return (EPERM); 482 483 if (oldp == NULL) { 484 /* always return full buffer size */ 485 *oldlenp = msgbufp->msg_bufs; 486 return (0); 487 } 488 489 sysctl_unlock(); 490 491 /* 492 * First, copy from the write pointer to the end of 493 * message buffer. 494 */ 495 error = 0; 496 mutex_spin_enter(&log_lock); 497 maxlen = MIN(msgbufp->msg_bufs, *oldlenp); 498 beg = msgbufp->msg_bufx; 499 end = msgbufp->msg_bufs; 500 mutex_spin_exit(&log_lock); 501 502 while (maxlen > 0) { 503 len = MIN(end - beg, maxlen); 504 if (len == 0) 505 break; 506 /* XXX unlocked, but hardly matters. */ 507 error = copyout(&msgbufp->msg_bufc[beg], where, len); 508 ktrmibio(-1, UIO_READ, where, len, error); 509 if (error) 510 break; 511 where += len; 512 maxlen -= len; 513 514 /* 515 * ... then, copy from the beginning of message buffer to 516 * the write pointer. 517 */ 518 beg = 0; 519 end = msgbufp->msg_bufx; 520 } 521 522 sysctl_relock(); 523 return (error); 524 } 525 526 const struct cdevsw log_cdevsw = { 527 .d_open = logopen, 528 .d_close = logclose, 529 .d_read = logread, 530 .d_write = nowrite, 531 .d_ioctl = logioctl, 532 .d_stop = nostop, 533 .d_tty = notty, 534 .d_poll = logpoll, 535 .d_mmap = nommap, 536 .d_kqfilter = logkqfilter, 537 .d_discard = nodiscard, 538 .d_flag = D_OTHER | D_MPSAFE 539 }; 540
Indexes created Sun Sep 21 15:09:59 GMT 2025