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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 | /* * linux/kernel/printk.c * * Copyright (C) 1991, 1992 Linus Torvalds * * Modified to make sys_syslog() more flexible: added commands to * return the last 4k of kernel messages, regardless of whether * they've been read or not. Added option to suppress kernel printk's * to the console. Added hook for sending the console messages * elsewhere, in preparation for a serial line console (someday). * Ted Ts'o, 2/11/93. * Modified for sysctl support, 1/8/97, Chris Horn. * Fixed SMP synchronization, 08/08/99, Manfred Spraul * manfreds@colorfullife.com * Rewrote bits to get rid of console_lock * 01Mar01 Andrew Morton <andrewm@uow.edu.au> */ #include <linux/kernel.h> #include <linux/mm.h> #include <linux/tty.h> #include <linux/tty_driver.h> #include <linux/smp_lock.h> #include <linux/console.h> #include <linux/init.h> #include <linux/module.h> #include <linux/interrupt.h> /* For in_interrupt() */ #include <linux/config.h> #include <linux/delay.h> #include <asm/uaccess.h> #if defined(CONFIG_X86_NUMAQ) || defined(CONFIG_IA64) #define LOG_BUF_LEN (65536) #elif defined(CONFIG_ARCH_S390) #define LOG_BUF_LEN (131072) #elif defined(CONFIG_SMP) #define LOG_BUF_LEN (32768) #else #define LOG_BUF_LEN (16384) /* This must be a power of two */ #endif #define LOG_BUF_MASK (LOG_BUF_LEN-1) #ifndef arch_consoles_callable #define arch_consoles_callable() (1) #endif /* printk's without a loglevel use this.. */ #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */ /* We show everything that is MORE important than this.. */ #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */ #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */ DECLARE_WAIT_QUEUE_HEAD(log_wait); int console_printk[4] = { DEFAULT_CONSOLE_LOGLEVEL, /* console_loglevel */ DEFAULT_MESSAGE_LOGLEVEL, /* default_message_loglevel */ MINIMUM_CONSOLE_LOGLEVEL, /* minimum_console_loglevel */ DEFAULT_CONSOLE_LOGLEVEL, /* default_console_loglevel */ }; int oops_in_progress; /* * console_sem protects the console_drivers list, and also * provides serialisation for access to the entire console * driver system. */ static DECLARE_MUTEX(console_sem); struct console *console_drivers; /* * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars * It is also used in interesting ways to provide interlocking in * release_console_sem(). */ static spinlock_t logbuf_lock = SPIN_LOCK_UNLOCKED; static char log_buf[LOG_BUF_LEN]; #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK]) /* * The indices into log_buf are not constrained to LOG_BUF_LEN - they * must be masked before subscripting */ static unsigned long log_start; /* Index into log_buf: next char to be read by syslog() */ static unsigned long con_start; /* Index into log_buf: next char to be sent to consoles */ static unsigned long log_end; /* Index into log_buf: most-recently-written-char + 1 */ static unsigned long logged_chars; /* Number of chars produced since last read+clear operation */ struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES]; static int preferred_console = -1; /* Flag: console code may call schedule() */ static int console_may_schedule; /* * Setup a list of consoles. Called from init/main.c */ static int __init console_setup(char *str) { struct console_cmdline *c; char name[sizeof(c->name)]; char *s, *options; int i, idx; /* * Decode str into name, index, options. */ if (str[0] >= '0' && str[0] <= '9') { strcpy(name, "ttyS"); strncpy(name + 4, str, sizeof(name) - 5); } else strncpy(name, str, sizeof(name) - 1); name[sizeof(name) - 1] = 0; if ((options = strchr(str, ',')) != NULL) *(options++) = 0; #ifdef __sparc__ if (!strcmp(str, "ttya")) strcpy(name, "ttyS0"); if (!strcmp(str, "ttyb")) strcpy(name, "ttyS1"); #endif for(s = name; *s; s++) if (*s >= '0' && *s <= '9') break; idx = simple_strtoul(s, NULL, 10); *s = 0; /* * See if this tty is not yet registered, and * if we have a slot free. */ for(i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++) if (strcmp(console_cmdline[i].name, name) == 0 && console_cmdline[i].index == idx) { preferred_console = i; return 1; } if (i == MAX_CMDLINECONSOLES) return 1; preferred_console = i; c = &console_cmdline[i]; memcpy(c->name, name, sizeof(c->name)); c->options = options; c->index = idx; return 1; } __setup("console=", console_setup); /* * Commands to do_syslog: * * 0 -- Close the log. Currently a NOP. * 1 -- Open the log. Currently a NOP. * 2 -- Read from the log. * 3 -- Read all messages remaining in the ring buffer. * 4 -- Read and clear all messages remaining in the ring buffer * 5 -- Clear ring buffer. * 6 -- Disable printk's to console * 7 -- Enable printk's to console * 8 -- Set level of messages printed to console * 9 -- Return number of unread characters in the log buffer */ int do_syslog(int type, char * buf, int len) { unsigned long i, j, limit, count; int do_clear = 0; char c; int error = 0; switch (type) { case 0: /* Close log */ break; case 1: /* Open log */ break; case 2: /* Read from log */ error = -EINVAL; if (!buf || len < 0) goto out; error = 0; if (!len) goto out; error = verify_area(VERIFY_WRITE,buf,len); if (error) goto out; error = wait_event_interruptible(log_wait, (log_start - log_end)); if (error) goto out; i = 0; spin_lock_irq(&logbuf_lock); while ((log_start != log_end) && i < len) { c = LOG_BUF(log_start); log_start++; spin_unlock_irq(&logbuf_lock); __put_user(c,buf); buf++; i++; spin_lock_irq(&logbuf_lock); } spin_unlock_irq(&logbuf_lock); error = i; break; case 4: /* Read/clear last kernel messages */ do_clear = 1; /* FALL THRU */ case 3: /* Read last kernel messages */ error = -EINVAL; if (!buf || len < 0) goto out; error = 0; if (!len) goto out; error = verify_area(VERIFY_WRITE,buf,len); if (error) goto out; count = len; if (count > LOG_BUF_LEN) count = LOG_BUF_LEN; spin_lock_irq(&logbuf_lock); if (count > logged_chars) count = logged_chars; if (do_clear) logged_chars = 0; limit = log_end; /* * __put_user() could sleep, and while we sleep * printk() could overwrite the messages * we try to copy to user space. Therefore * the messages are copied in reverse. <manfreds> */ for(i=0;i < count;i++) { j = limit-1-i; if (j+LOG_BUF_LEN < log_end) break; c = LOG_BUF(j); spin_unlock_irq(&logbuf_lock); __put_user(c,&buf[count-1-i]); spin_lock_irq(&logbuf_lock); } spin_unlock_irq(&logbuf_lock); error = i; if(i != count) { int offset = count-error; /* buffer overflow during copy, correct user buffer. */ for(i=0;i<error;i++) { __get_user(c,&buf[i+offset]); __put_user(c,&buf[i]); } } break; case 5: /* Clear ring buffer */ spin_lock_irq(&logbuf_lock); logged_chars = 0; spin_unlock_irq(&logbuf_lock); break; case 6: /* Disable logging to console */ spin_lock_irq(&logbuf_lock); console_loglevel = minimum_console_loglevel; spin_unlock_irq(&logbuf_lock); break; case 7: /* Enable logging to console */ spin_lock_irq(&logbuf_lock); console_loglevel = default_console_loglevel; spin_unlock_irq(&logbuf_lock); break; case 8: /* Set level of messages printed to console */ error = -EINVAL; if (len < 1 || len > 8) goto out; if (len < minimum_console_loglevel) len = minimum_console_loglevel; spin_lock_irq(&logbuf_lock); console_loglevel = len; spin_unlock_irq(&logbuf_lock); error = 0; break; case 9: /* Number of chars in the log buffer */ spin_lock_irq(&logbuf_lock); error = log_end - log_start; spin_unlock_irq(&logbuf_lock); break; default: error = -EINVAL; break; } out: return error; } asmlinkage long sys_syslog(int type, char * buf, int len) { if ((type != 3) && !capable(CAP_SYS_ADMIN)) return -EPERM; return do_syslog(type, buf, len); } /* * Call the console drivers on a range of log_buf */ static void __call_console_drivers(unsigned long start, unsigned long end) { struct console *con; for (con = console_drivers; con; con = con->next) { if ((con->flags & CON_ENABLED) && con->write) con->write(con, &LOG_BUF(start), end - start); } } /* * Write out chars from start to end - 1 inclusive */ static void _call_console_drivers(unsigned long start, unsigned long end, int msg_log_level) { if (msg_log_level < console_loglevel && console_drivers && start != end) { if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) { /* wrapped write */ __call_console_drivers(start & LOG_BUF_MASK, LOG_BUF_LEN); __call_console_drivers(0, end & LOG_BUF_MASK); } else { __call_console_drivers(start, end); } } } /* * Call the console drivers, asking them to write out * log_buf[start] to log_buf[end - 1]. * The console_sem must be held. */ static void call_console_drivers(unsigned long start, unsigned long end) { unsigned long cur_index, start_print; static int msg_level = -1; if (((long)(start - end)) > 0) BUG(); cur_index = start; start_print = start; while (cur_index != end) { if ( msg_level < 0 && ((end - cur_index) > 2) && LOG_BUF(cur_index + 0) == '<' && LOG_BUF(cur_index + 1) >= '0' && LOG_BUF(cur_index + 1) <= '7' && LOG_BUF(cur_index + 2) == '>') { msg_level = LOG_BUF(cur_index + 1) - '0'; cur_index += 3; start_print = cur_index; } while (cur_index != end) { char c = LOG_BUF(cur_index); cur_index++; if (c == '\n') { if (msg_level < 0) { /* * printk() has already given us loglevel tags in * the buffer. This code is here in case the * log buffer has wrapped right round and scribbled * on those tags */ msg_level = default_message_loglevel; } _call_console_drivers(start_print, cur_index, msg_level); msg_level = -1; start_print = cur_index; break; } } } _call_console_drivers(start_print, end, msg_level); } static void emit_log_char(char c) { LOG_BUF(log_end) = c; log_end++; if (log_end - log_start > LOG_BUF_LEN) log_start = log_end - LOG_BUF_LEN; if (log_end - con_start > LOG_BUF_LEN) con_start = log_end - LOG_BUF_LEN; if (logged_chars < LOG_BUF_LEN) logged_chars++; } /* * This is printk. It can be called from any context. We want it to work. * * We try to grab the console_sem. If we succeed, it's easy - we log the output and * call the console drivers. If we fail to get the semaphore we place the output * into the log buffer and return. The current holder of the console_sem will * notice the new output in release_console_sem() and will send it to the * consoles before releasing the semaphore. * * One effect of this deferred printing is that code which calls printk() and * then changes console_loglevel may break. This is because console_loglevel * is inspected when the actual printing occurs. */ asmlinkage int printk(const char *fmt, ...) { va_list args; unsigned long flags; int printed_len; char *p; static char printk_buf[1024]; static int log_level_unknown = 1; if (oops_in_progress) { /* If a crash is occurring, make sure we can't deadlock */ spin_lock_init(&logbuf_lock); /* And make sure that we print immediately */ init_MUTEX(&console_sem); } /* This stops the holder of console_sem just where we want him */ spin_lock_irqsave(&logbuf_lock, flags); /* Emit the output into the temporary buffer */ va_start(args, fmt); printed_len = vsnprintf(printk_buf, sizeof(printk_buf), fmt, args); va_end(args); /* * Copy the output into log_buf. If the caller didn't provide * appropriate log level tags, we insert them here */ for (p = printk_buf; *p; p++) { if (log_level_unknown) { if (p[0] != '<' || p[1] < '0' || p[1] > '7' || p[2] != '>') { emit_log_char('<'); emit_log_char(default_message_loglevel + '0'); emit_log_char('>'); } log_level_unknown = 0; } emit_log_char(*p); if (*p == '\n') log_level_unknown = 1; } if (!arch_consoles_callable()) { /* * On some architectures, the consoles are not usable * on secondary CPUs early in the boot process. */ spin_unlock_irqrestore(&logbuf_lock, flags); goto out; } if (!down_trylock(&console_sem)) { /* * We own the drivers. We can drop the spinlock and let * release_console_sem() print the text */ spin_unlock_irqrestore(&logbuf_lock, flags); console_may_schedule = 0; release_console_sem(); } else { /* * Someone else owns the drivers. We drop the spinlock, which * allows the semaphore holder to proceed and to call the * console drivers with the output which we just produced. */ spin_unlock_irqrestore(&logbuf_lock, flags); } out: return printed_len; } EXPORT_SYMBOL(printk); /** * acquire_console_sem - lock the console system for exclusive use. * * Acquires a semaphore which guarantees that the caller has * exclusive access to the console system and the console_drivers list. * * Can sleep, returns nothing. */ void acquire_console_sem(void) { if (in_interrupt()) BUG(); down(&console_sem); console_may_schedule = 1; } EXPORT_SYMBOL(acquire_console_sem); /** * release_console_sem - unlock the console system * * Releases the semaphore which the caller holds on the console system * and the console driver list. * * While the semaphore was held, console output may have been buffered * by printk(). If this is the case, release_console_sem() emits * the output prior to releasing the semaphore. * * If there is output waiting for klogd, we wake it up. * * release_console_sem() may be called from any context. */ void release_console_sem(void) { unsigned long flags; unsigned long _con_start, _log_end; unsigned long wake_klogd = 0; for ( ; ; ) { spin_lock_irqsave(&logbuf_lock, flags); wake_klogd |= log_start - log_end; if (con_start == log_end) break; /* Nothing to print */ _con_start = con_start; _log_end = log_end; con_start = log_end; /* Flush */ spin_unlock_irqrestore(&logbuf_lock, flags); call_console_drivers(_con_start, _log_end); } console_may_schedule = 0; up(&console_sem); spin_unlock_irqrestore(&logbuf_lock, flags); if (wake_klogd && !oops_in_progress && waitqueue_active(&log_wait)) wake_up_interruptible(&log_wait); } /** console_conditional_schedule - yield the CPU if required * * If the console code is currently allowed to sleep, and * if this CPU should yield the CPU to another task, do * so here. * * Must be called within acquire_console_sem(). */ void console_conditional_schedule(void) { if (console_may_schedule && need_resched()) { set_current_state(TASK_RUNNING); schedule(); } } EXPORT_SYMBOL(console_conditional_schedule); void console_print(const char *s) { printk(KERN_EMERG "%s", s); } EXPORT_SYMBOL(console_print); void console_unblank(void) { struct console *c; /* * Try to get the console semaphore. If someone else owns it * we have to return without unblanking because console_unblank * may be called in interrupt context. */ if (down_trylock(&console_sem) != 0) return; console_may_schedule = 0; for (c = console_drivers; c != NULL; c = c->next) if ((c->flags & CON_ENABLED) && c->unblank) c->unblank(); release_console_sem(); } EXPORT_SYMBOL(console_unblank); /* * The console driver calls this routine during kernel initialization * to register the console printing procedure with printk() and to * print any messages that were printed by the kernel before the * console driver was initialized. */ void register_console(struct console * console) { int i; unsigned long flags; /* * See if we want to use this console driver. If we * didn't select a console we take the first one * that registers here. */ if (preferred_console < 0) { if (console->index < 0) console->index = 0; if (console->setup == NULL || console->setup(console, NULL) == 0) { console->flags |= CON_ENABLED | CON_CONSDEV; preferred_console = 0; } } /* * See if this console matches one we selected on * the command line. */ for(i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++) { if (strcmp(console_cmdline[i].name, console->name) != 0) continue; if (console->index >= 0 && console->index != console_cmdline[i].index) continue; if (console->index < 0) console->index = console_cmdline[i].index; if (console->setup && console->setup(console, console_cmdline[i].options) != 0) break; console->flags |= CON_ENABLED; console->index = console_cmdline[i].index; if (i == preferred_console) console->flags |= CON_CONSDEV; break; } if (!(console->flags & CON_ENABLED)) return; /* * Put this console in the list - keep the * preferred driver at the head of the list. */ acquire_console_sem(); if ((console->flags & CON_CONSDEV) || console_drivers == NULL) { console->next = console_drivers; console_drivers = console; } else { console->next = console_drivers->next; console_drivers->next = console; } if (console->flags & CON_PRINTBUFFER) { /* * release_cosole_sem() will print out the buffered messages for us. */ spin_lock_irqsave(&logbuf_lock, flags); con_start = log_start; spin_unlock_irqrestore(&logbuf_lock, flags); } release_console_sem(); } EXPORT_SYMBOL(register_console); int unregister_console(struct console * console) { struct console *a,*b; int res = 1; acquire_console_sem(); if (console_drivers == console) { console_drivers=console->next; res = 0; } else { for (a=console_drivers->next, b=console_drivers ; a; b=a, a=b->next) { if (a == console) { b->next = a->next; res = 0; break; } } } /* If last console is removed, we re-enable picking the first * one that gets registered. Without that, pmac early boot console * would prevent fbcon from taking over. */ if (console_drivers == NULL) preferred_console = -1; release_console_sem(); return res; } EXPORT_SYMBOL(unregister_console); /** * tty_write_message - write a message to a certain tty, not just the console. * * This is used for messages that need to be redirected to a specific tty. * We don't put it into the syslog queue right now maybe in the future if * really needed. */ void tty_write_message(struct tty_struct *tty, char *msg) { if (tty && tty->driver.write) tty->driver.write(tty, 0, msg, strlen(msg)); return; } |