| 1 | /* |
| 2 | * linux/kernel/printk.c |
| 3 | * |
| 4 | * Copyright (C) 1991, 1992 Linus Torvalds |
| 5 | * |
| 6 | * Modified to make sys_syslog() more flexible: added commands to |
| 7 | * return the last 4k of kernel messages, regardless of whether |
| 8 | * they've been read or not. Added option to suppress kernel printk's |
| 9 | * to the console. Added hook for sending the console messages |
| 10 | * elsewhere, in preparation for a serial line console (someday). |
| 11 | * Ted Ts'o, 2/11/93. |
| 12 | * Modified for sysctl support, 1/8/97, Chris Horn. |
| 13 | * Fixed SMP synchronization, 08/08/99, Manfred Spraul |
| 14 | * manfred@colorfullife.com |
| 15 | * Rewrote bits to get rid of console_lock |
| 16 | * 01Mar01 Andrew Morton <andrewm@uow.edu.au> |
| 17 | */ |
| 18 | |
| 19 | #include <linux/kernel.h> |
| 20 | #include <linux/mm.h> |
| 21 | #include <linux/tty.h> |
| 22 | #include <linux/tty_driver.h> |
| 23 | #include <linux/console.h> |
| 24 | #include <linux/init.h> |
| 25 | #include <linux/jiffies.h> |
| 26 | #include <linux/nmi.h> |
| 27 | #include <linux/module.h> |
| 28 | #include <linux/moduleparam.h> |
| 29 | #include <linux/interrupt.h> /* For in_interrupt() */ |
| 30 | #include <linux/delay.h> |
| 31 | #include <linux/smp.h> |
| 32 | #include <linux/security.h> |
| 33 | #include <linux/bootmem.h> |
| 34 | #include <linux/syscalls.h> |
| 35 | #include <linux/jiffies.h> |
| 36 | |
| 37 | #include <asm/uaccess.h> |
| 38 | |
| 39 | #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT) |
| 40 | |
| 41 | /* printk's without a loglevel use this.. */ |
| 42 | #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */ |
| 43 | |
| 44 | /* We show everything that is MORE important than this.. */ |
| 45 | #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */ |
| 46 | #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */ |
| 47 | |
| 48 | DECLARE_WAIT_QUEUE_HEAD(log_wait); |
| 49 | |
| 50 | int console_printk[4] = { |
| 51 | DEFAULT_CONSOLE_LOGLEVEL, /* console_loglevel */ |
| 52 | DEFAULT_MESSAGE_LOGLEVEL, /* default_message_loglevel */ |
| 53 | MINIMUM_CONSOLE_LOGLEVEL, /* minimum_console_loglevel */ |
| 54 | DEFAULT_CONSOLE_LOGLEVEL, /* default_console_loglevel */ |
| 55 | }; |
| 56 | |
| 57 | /* |
| 58 | * Low level drivers may need that to know if they can schedule in |
| 59 | * their unblank() callback or not. So let's export it. |
| 60 | */ |
| 61 | int oops_in_progress; |
| 62 | EXPORT_SYMBOL(oops_in_progress); |
| 63 | |
| 64 | /* |
| 65 | * console_sem protects the console_drivers list, and also |
| 66 | * provides serialisation for access to the entire console |
| 67 | * driver system. |
| 68 | */ |
| 69 | static DECLARE_MUTEX(console_sem); |
| 70 | static DECLARE_MUTEX(secondary_console_sem); |
| 71 | struct console *console_drivers; |
| 72 | /* |
| 73 | * This is used for debugging the mess that is the VT code by |
| 74 | * keeping track if we have the console semaphore held. It's |
| 75 | * definitely not the perfect debug tool (we don't know if _WE_ |
| 76 | * hold it are racing, but it helps tracking those weird code |
| 77 | * path in the console code where we end up in places I want |
| 78 | * locked without the console sempahore held |
| 79 | */ |
| 80 | static int console_locked, console_suspended; |
| 81 | |
| 82 | /* |
| 83 | * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars |
| 84 | * It is also used in interesting ways to provide interlocking in |
| 85 | * release_console_sem(). |
| 86 | */ |
| 87 | static DEFINE_SPINLOCK(logbuf_lock); |
| 88 | |
| 89 | #define LOG_BUF_MASK (log_buf_len-1) |
| 90 | #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK]) |
| 91 | |
| 92 | /* |
| 93 | * The indices into log_buf are not constrained to log_buf_len - they |
| 94 | * must be masked before subscripting |
| 95 | */ |
| 96 | static unsigned long log_start; /* Index into log_buf: next char to be read by syslog() */ |
| 97 | static unsigned long con_start; /* Index into log_buf: next char to be sent to consoles */ |
| 98 | static unsigned long log_end; /* Index into log_buf: most-recently-written-char + 1 */ |
| 99 | |
| 100 | /* |
| 101 | * Array of consoles built from command line options (console=) |
| 102 | */ |
| 103 | struct console_cmdline |
| 104 | { |
| 105 | char name[8]; /* Name of the driver */ |
| 106 | int index; /* Minor dev. to use */ |
| 107 | char *options; /* Options for the driver */ |
| 108 | }; |
| 109 | |
| 110 | #define MAX_CMDLINECONSOLES 8 |
| 111 | |
| 112 | static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES]; |
| 113 | static int selected_console = -1; |
| 114 | static int preferred_console = -1; |
| 115 | |
| 116 | /* Flag: console code may call schedule() */ |
| 117 | static int console_may_schedule; |
| 118 | |
| 119 | #ifdef CONFIG_PRINTK |
| 120 | |
| 121 | static char __log_buf[__LOG_BUF_LEN]; |
| 122 | static char *log_buf = __log_buf; |
| 123 | static int log_buf_len = __LOG_BUF_LEN; |
| 124 | static unsigned long logged_chars; /* Number of chars produced since last read+clear operation */ |
| 125 | |
| 126 | static int __init log_buf_len_setup(char *str) |
| 127 | { |
| 128 | unsigned long size = memparse(str, &str); |
| 129 | unsigned long flags; |
| 130 | |
| 131 | if (size) |
| 132 | size = roundup_pow_of_two(size); |
| 133 | if (size > log_buf_len) { |
| 134 | unsigned long start, dest_idx, offset; |
| 135 | char *new_log_buf; |
| 136 | |
| 137 | new_log_buf = alloc_bootmem(size); |
| 138 | if (!new_log_buf) { |
| 139 | printk(KERN_WARNING "log_buf_len: allocation failed\n"); |
| 140 | goto out; |
| 141 | } |
| 142 | |
| 143 | spin_lock_irqsave(&logbuf_lock, flags); |
| 144 | log_buf_len = size; |
| 145 | log_buf = new_log_buf; |
| 146 | |
| 147 | offset = start = min(con_start, log_start); |
| 148 | dest_idx = 0; |
| 149 | while (start != log_end) { |
| 150 | log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)]; |
| 151 | start++; |
| 152 | dest_idx++; |
| 153 | } |
| 154 | log_start -= offset; |
| 155 | con_start -= offset; |
| 156 | log_end -= offset; |
| 157 | spin_unlock_irqrestore(&logbuf_lock, flags); |
| 158 | |
| 159 | printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len); |
| 160 | } |
| 161 | out: |
| 162 | return 1; |
| 163 | } |
| 164 | |
| 165 | __setup("log_buf_len=", log_buf_len_setup); |
| 166 | |
| 167 | #ifdef CONFIG_BOOT_PRINTK_DELAY |
| 168 | |
| 169 | static unsigned int boot_delay; /* msecs delay after each printk during bootup */ |
| 170 | static unsigned long long printk_delay_msec; /* per msec, based on boot_delay */ |
| 171 | |
| 172 | static int __init boot_delay_setup(char *str) |
| 173 | { |
| 174 | unsigned long lpj; |
| 175 | unsigned long long loops_per_msec; |
| 176 | |
| 177 | lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */ |
| 178 | loops_per_msec = (unsigned long long)lpj / 1000 * HZ; |
| 179 | |
| 180 | get_option(&str, &boot_delay); |
| 181 | if (boot_delay > 10 * 1000) |
| 182 | boot_delay = 0; |
| 183 | |
| 184 | printk_delay_msec = loops_per_msec; |
| 185 | printk(KERN_DEBUG "boot_delay: %u, preset_lpj: %ld, lpj: %lu, " |
| 186 | "HZ: %d, printk_delay_msec: %llu\n", |
| 187 | boot_delay, preset_lpj, lpj, HZ, printk_delay_msec); |
| 188 | return 1; |
| 189 | } |
| 190 | __setup("boot_delay=", boot_delay_setup); |
| 191 | |
| 192 | static void boot_delay_msec(void) |
| 193 | { |
| 194 | unsigned long long k; |
| 195 | unsigned long timeout; |
| 196 | |
| 197 | if (boot_delay == 0 || system_state != SYSTEM_BOOTING) |
| 198 | return; |
| 199 | |
| 200 | k = (unsigned long long)printk_delay_msec * boot_delay; |
| 201 | |
| 202 | timeout = jiffies + msecs_to_jiffies(boot_delay); |
| 203 | while (k) { |
| 204 | k--; |
| 205 | cpu_relax(); |
| 206 | /* |
| 207 | * use (volatile) jiffies to prevent |
| 208 | * compiler reduction; loop termination via jiffies |
| 209 | * is secondary and may or may not happen. |
| 210 | */ |
| 211 | if (time_after(jiffies, timeout)) |
| 212 | break; |
| 213 | touch_nmi_watchdog(); |
| 214 | } |
| 215 | } |
| 216 | #else |
| 217 | static inline void boot_delay_msec(void) |
| 218 | { |
| 219 | } |
| 220 | #endif |
| 221 | |
| 222 | /* |
| 223 | * Return the number of unread characters in the log buffer. |
| 224 | */ |
| 225 | int log_buf_get_len(void) |
| 226 | { |
| 227 | return logged_chars; |
| 228 | } |
| 229 | |
| 230 | /* |
| 231 | * Copy a range of characters from the log buffer. |
| 232 | */ |
| 233 | int log_buf_copy(char *dest, int idx, int len) |
| 234 | { |
| 235 | int ret, max; |
| 236 | bool took_lock = false; |
| 237 | |
| 238 | if (!oops_in_progress) { |
| 239 | spin_lock_irq(&logbuf_lock); |
| 240 | took_lock = true; |
| 241 | } |
| 242 | |
| 243 | max = log_buf_get_len(); |
| 244 | if (idx < 0 || idx >= max) { |
| 245 | ret = -1; |
| 246 | } else { |
| 247 | if (len > max) |
| 248 | len = max; |
| 249 | ret = len; |
| 250 | idx += (log_end - max); |
| 251 | while (len-- > 0) |
| 252 | dest[len] = LOG_BUF(idx + len); |
| 253 | } |
| 254 | |
| 255 | if (took_lock) |
| 256 | spin_unlock_irq(&logbuf_lock); |
| 257 | |
| 258 | return ret; |
| 259 | } |
| 260 | |
| 261 | /* |
| 262 | * Extract a single character from the log buffer. |
| 263 | */ |
| 264 | int log_buf_read(int idx) |
| 265 | { |
| 266 | char ret; |
| 267 | |
| 268 | if (log_buf_copy(&ret, idx, 1) == 1) |
| 269 | return ret; |
| 270 | else |
| 271 | return -1; |
| 272 | } |
| 273 | |
| 274 | /* |
| 275 | * Commands to do_syslog: |
| 276 | * |
| 277 | * 0 -- Close the log. Currently a NOP. |
| 278 | * 1 -- Open the log. Currently a NOP. |
| 279 | * 2 -- Read from the log. |
| 280 | * 3 -- Read all messages remaining in the ring buffer. |
| 281 | * 4 -- Read and clear all messages remaining in the ring buffer |
| 282 | * 5 -- Clear ring buffer. |
| 283 | * 6 -- Disable printk's to console |
| 284 | * 7 -- Enable printk's to console |
| 285 | * 8 -- Set level of messages printed to console |
| 286 | * 9 -- Return number of unread characters in the log buffer |
| 287 | * 10 -- Return size of the log buffer |
| 288 | */ |
| 289 | int do_syslog(int type, char __user *buf, int len) |
| 290 | { |
| 291 | unsigned long i, j, limit, count; |
| 292 | int do_clear = 0; |
| 293 | char c; |
| 294 | int error = 0; |
| 295 | |
| 296 | error = security_syslog(type); |
| 297 | if (error) |
| 298 | return error; |
| 299 | |
| 300 | switch (type) { |
| 301 | case 0: /* Close log */ |
| 302 | break; |
| 303 | case 1: /* Open log */ |
| 304 | break; |
| 305 | case 2: /* Read from log */ |
| 306 | error = -EINVAL; |
| 307 | if (!buf || len < 0) |
| 308 | goto out; |
| 309 | error = 0; |
| 310 | if (!len) |
| 311 | goto out; |
| 312 | if (!access_ok(VERIFY_WRITE, buf, len)) { |
| 313 | error = -EFAULT; |
| 314 | goto out; |
| 315 | } |
| 316 | error = wait_event_interruptible(log_wait, |
| 317 | (log_start - log_end)); |
| 318 | if (error) |
| 319 | goto out; |
| 320 | i = 0; |
| 321 | spin_lock_irq(&logbuf_lock); |
| 322 | while (!error && (log_start != log_end) && i < len) { |
| 323 | c = LOG_BUF(log_start); |
| 324 | log_start++; |
| 325 | spin_unlock_irq(&logbuf_lock); |
| 326 | error = __put_user(c,buf); |
| 327 | buf++; |
| 328 | i++; |
| 329 | cond_resched(); |
| 330 | spin_lock_irq(&logbuf_lock); |
| 331 | } |
| 332 | spin_unlock_irq(&logbuf_lock); |
| 333 | if (!error) |
| 334 | error = i; |
| 335 | break; |
| 336 | case 4: /* Read/clear last kernel messages */ |
| 337 | do_clear = 1; |
| 338 | /* FALL THRU */ |
| 339 | case 3: /* Read last kernel messages */ |
| 340 | error = -EINVAL; |
| 341 | if (!buf || len < 0) |
| 342 | goto out; |
| 343 | error = 0; |
| 344 | if (!len) |
| 345 | goto out; |
| 346 | if (!access_ok(VERIFY_WRITE, buf, len)) { |
| 347 | error = -EFAULT; |
| 348 | goto out; |
| 349 | } |
| 350 | count = len; |
| 351 | if (count > log_buf_len) |
| 352 | count = log_buf_len; |
| 353 | spin_lock_irq(&logbuf_lock); |
| 354 | if (count > logged_chars) |
| 355 | count = logged_chars; |
| 356 | if (do_clear) |
| 357 | logged_chars = 0; |
| 358 | limit = log_end; |
| 359 | /* |
| 360 | * __put_user() could sleep, and while we sleep |
| 361 | * printk() could overwrite the messages |
| 362 | * we try to copy to user space. Therefore |
| 363 | * the messages are copied in reverse. <manfreds> |
| 364 | */ |
| 365 | for (i = 0; i < count && !error; i++) { |
| 366 | j = limit-1-i; |
| 367 | if (j + log_buf_len < log_end) |
| 368 | break; |
| 369 | c = LOG_BUF(j); |
| 370 | spin_unlock_irq(&logbuf_lock); |
| 371 | error = __put_user(c,&buf[count-1-i]); |
| 372 | cond_resched(); |
| 373 | spin_lock_irq(&logbuf_lock); |
| 374 | } |
| 375 | spin_unlock_irq(&logbuf_lock); |
| 376 | if (error) |
| 377 | break; |
| 378 | error = i; |
| 379 | if (i != count) { |
| 380 | int offset = count-error; |
| 381 | /* buffer overflow during copy, correct user buffer. */ |
| 382 | for (i = 0; i < error; i++) { |
| 383 | if (__get_user(c,&buf[i+offset]) || |
| 384 | __put_user(c,&buf[i])) { |
| 385 | error = -EFAULT; |
| 386 | break; |
| 387 | } |
| 388 | cond_resched(); |
| 389 | } |
| 390 | } |
| 391 | break; |
| 392 | case 5: /* Clear ring buffer */ |
| 393 | logged_chars = 0; |
| 394 | break; |
| 395 | case 6: /* Disable logging to console */ |
| 396 | console_loglevel = minimum_console_loglevel; |
| 397 | break; |
| 398 | case 7: /* Enable logging to console */ |
| 399 | console_loglevel = default_console_loglevel; |
| 400 | break; |
| 401 | case 8: /* Set level of messages printed to console */ |
| 402 | error = -EINVAL; |
| 403 | if (len < 1 || len > 8) |
| 404 | goto out; |
| 405 | if (len < minimum_console_loglevel) |
| 406 | len = minimum_console_loglevel; |
| 407 | console_loglevel = len; |
| 408 | error = 0; |
| 409 | break; |
| 410 | case 9: /* Number of chars in the log buffer */ |
| 411 | error = log_end - log_start; |
| 412 | break; |
| 413 | case 10: /* Size of the log buffer */ |
| 414 | error = log_buf_len; |
| 415 | break; |
| 416 | default: |
| 417 | error = -EINVAL; |
| 418 | break; |
| 419 | } |
| 420 | out: |
| 421 | return error; |
| 422 | } |
| 423 | |
| 424 | asmlinkage long sys_syslog(int type, char __user *buf, int len) |
| 425 | { |
| 426 | return do_syslog(type, buf, len); |
| 427 | } |
| 428 | |
| 429 | /* |
| 430 | * Call the console drivers on a range of log_buf |
| 431 | */ |
| 432 | static void __call_console_drivers(unsigned long start, unsigned long end) |
| 433 | { |
| 434 | struct console *con; |
| 435 | |
| 436 | for (con = console_drivers; con; con = con->next) { |
| 437 | if ((con->flags & CON_ENABLED) && con->write && |
| 438 | (cpu_online(smp_processor_id()) || |
| 439 | (con->flags & CON_ANYTIME))) |
| 440 | con->write(con, &LOG_BUF(start), end - start); |
| 441 | } |
| 442 | } |
| 443 | |
| 444 | static int __read_mostly ignore_loglevel; |
| 445 | |
| 446 | static int __init ignore_loglevel_setup(char *str) |
| 447 | { |
| 448 | ignore_loglevel = 1; |
| 449 | printk(KERN_INFO "debug: ignoring loglevel setting.\n"); |
| 450 | |
| 451 | return 1; |
| 452 | } |
| 453 | |
| 454 | __setup("ignore_loglevel", ignore_loglevel_setup); |
| 455 | |
| 456 | /* |
| 457 | * Write out chars from start to end - 1 inclusive |
| 458 | */ |
| 459 | static void _call_console_drivers(unsigned long start, |
| 460 | unsigned long end, int msg_log_level) |
| 461 | { |
| 462 | if ((msg_log_level < console_loglevel || ignore_loglevel) && |
| 463 | console_drivers && start != end) { |
| 464 | if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) { |
| 465 | /* wrapped write */ |
| 466 | __call_console_drivers(start & LOG_BUF_MASK, |
| 467 | log_buf_len); |
| 468 | __call_console_drivers(0, end & LOG_BUF_MASK); |
| 469 | } else { |
| 470 | __call_console_drivers(start, end); |
| 471 | } |
| 472 | } |
| 473 | } |
| 474 | |
| 475 | /* |
| 476 | * Call the console drivers, asking them to write out |
| 477 | * log_buf[start] to log_buf[end - 1]. |
| 478 | * The console_sem must be held. |
| 479 | */ |
| 480 | static void call_console_drivers(unsigned long start, unsigned long end) |
| 481 | { |
| 482 | unsigned long cur_index, start_print; |
| 483 | static int msg_level = -1; |
| 484 | |
| 485 | BUG_ON(((long)(start - end)) > 0); |
| 486 | |
| 487 | cur_index = start; |
| 488 | start_print = start; |
| 489 | while (cur_index != end) { |
| 490 | if (msg_level < 0 && ((end - cur_index) > 2) && |
| 491 | LOG_BUF(cur_index + 0) == '<' && |
| 492 | LOG_BUF(cur_index + 1) >= '0' && |
| 493 | LOG_BUF(cur_index + 1) <= '7' && |
| 494 | LOG_BUF(cur_index + 2) == '>') { |
| 495 | msg_level = LOG_BUF(cur_index + 1) - '0'; |
| 496 | cur_index += 3; |
| 497 | start_print = cur_index; |
| 498 | } |
| 499 | while (cur_index != end) { |
| 500 | char c = LOG_BUF(cur_index); |
| 501 | |
| 502 | cur_index++; |
| 503 | if (c == '\n') { |
| 504 | if (msg_level < 0) { |
| 505 | /* |
| 506 | * printk() has already given us loglevel tags in |
| 507 | * the buffer. This code is here in case the |
| 508 | * log buffer has wrapped right round and scribbled |
| 509 | * on those tags |
| 510 | */ |
| 511 | msg_level = default_message_loglevel; |
| 512 | } |
| 513 | _call_console_drivers(start_print, cur_index, msg_level); |
| 514 | msg_level = -1; |
| 515 | start_print = cur_index; |
| 516 | break; |
| 517 | } |
| 518 | } |
| 519 | } |
| 520 | _call_console_drivers(start_print, end, msg_level); |
| 521 | } |
| 522 | |
| 523 | static void emit_log_char(char c) |
| 524 | { |
| 525 | LOG_BUF(log_end) = c; |
| 526 | log_end++; |
| 527 | if (log_end - log_start > log_buf_len) |
| 528 | log_start = log_end - log_buf_len; |
| 529 | if (log_end - con_start > log_buf_len) |
| 530 | con_start = log_end - log_buf_len; |
| 531 | if (logged_chars < log_buf_len) |
| 532 | logged_chars++; |
| 533 | } |
| 534 | |
| 535 | /* |
| 536 | * Zap console related locks when oopsing. Only zap at most once |
| 537 | * every 10 seconds, to leave time for slow consoles to print a |
| 538 | * full oops. |
| 539 | */ |
| 540 | static void zap_locks(void) |
| 541 | { |
| 542 | static unsigned long oops_timestamp; |
| 543 | |
| 544 | if (time_after_eq(jiffies, oops_timestamp) && |
| 545 | !time_after(jiffies, oops_timestamp + 30 * HZ)) |
| 546 | return; |
| 547 | |
| 548 | oops_timestamp = jiffies; |
| 549 | |
| 550 | /* If a crash is occurring, make sure we can't deadlock */ |
| 551 | spin_lock_init(&logbuf_lock); |
| 552 | /* And make sure that we print immediately */ |
| 553 | init_MUTEX(&console_sem); |
| 554 | } |
| 555 | |
| 556 | #if defined(CONFIG_PRINTK_TIME) |
| 557 | static int printk_time = 1; |
| 558 | #else |
| 559 | static int printk_time = 0; |
| 560 | #endif |
| 561 | module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR); |
| 562 | |
| 563 | static int __init printk_time_setup(char *str) |
| 564 | { |
| 565 | if (*str) |
| 566 | return 0; |
| 567 | printk_time = 1; |
| 568 | printk(KERN_NOTICE "The 'time' option is deprecated and " |
| 569 | "is scheduled for removal in early 2008\n"); |
| 570 | printk(KERN_NOTICE "Use 'printk.time=<value>' instead\n"); |
| 571 | return 1; |
| 572 | } |
| 573 | |
| 574 | __setup("time", printk_time_setup); |
| 575 | |
| 576 | __attribute__((weak)) unsigned long long printk_clock(void) |
| 577 | { |
| 578 | return sched_clock(); |
| 579 | } |
| 580 | |
| 581 | /* Check if we have any console registered that can be called early in boot. */ |
| 582 | static int have_callable_console(void) |
| 583 | { |
| 584 | struct console *con; |
| 585 | |
| 586 | for (con = console_drivers; con; con = con->next) |
| 587 | if (con->flags & CON_ANYTIME) |
| 588 | return 1; |
| 589 | |
| 590 | return 0; |
| 591 | } |
| 592 | |
| 593 | /** |
| 594 | * printk - print a kernel message |
| 595 | * @fmt: format string |
| 596 | * |
| 597 | * This is printk(). It can be called from any context. We want it to work. |
| 598 | * Be aware of the fact that if oops_in_progress is not set, we might try to |
| 599 | * wake klogd up which could deadlock on runqueue lock if printk() is called |
| 600 | * from scheduler code. |
| 601 | * |
| 602 | * We try to grab the console_sem. If we succeed, it's easy - we log the output and |
| 603 | * call the console drivers. If we fail to get the semaphore we place the output |
| 604 | * into the log buffer and return. The current holder of the console_sem will |
| 605 | * notice the new output in release_console_sem() and will send it to the |
| 606 | * consoles before releasing the semaphore. |
| 607 | * |
| 608 | * One effect of this deferred printing is that code which calls printk() and |
| 609 | * then changes console_loglevel may break. This is because console_loglevel |
| 610 | * is inspected when the actual printing occurs. |
| 611 | * |
| 612 | * See also: |
| 613 | * printf(3) |
| 614 | */ |
| 615 | |
| 616 | asmlinkage int printk(const char *fmt, ...) |
| 617 | { |
| 618 | va_list args; |
| 619 | int r; |
| 620 | |
| 621 | va_start(args, fmt); |
| 622 | r = vprintk(fmt, args); |
| 623 | va_end(args); |
| 624 | |
| 625 | return r; |
| 626 | } |
| 627 | |
| 628 | /* cpu currently holding logbuf_lock */ |
| 629 | static volatile unsigned int printk_cpu = UINT_MAX; |
| 630 | |
| 631 | asmlinkage int vprintk(const char *fmt, va_list args) |
| 632 | { |
| 633 | unsigned long flags; |
| 634 | int printed_len; |
| 635 | char *p; |
| 636 | static char printk_buf[1024]; |
| 637 | static int log_level_unknown = 1; |
| 638 | |
| 639 | boot_delay_msec(); |
| 640 | |
| 641 | preempt_disable(); |
| 642 | if (unlikely(oops_in_progress) && printk_cpu == smp_processor_id()) |
| 643 | /* If a crash is occurring during printk() on this CPU, |
| 644 | * make sure we can't deadlock */ |
| 645 | zap_locks(); |
| 646 | |
| 647 | /* This stops the holder of console_sem just where we want him */ |
| 648 | raw_local_irq_save(flags); |
| 649 | lockdep_off(); |
| 650 | spin_lock(&logbuf_lock); |
| 651 | printk_cpu = smp_processor_id(); |
| 652 | |
| 653 | /* Emit the output into the temporary buffer */ |
| 654 | printed_len = vscnprintf(printk_buf, sizeof(printk_buf), fmt, args); |
| 655 | |
| 656 | /* |
| 657 | * Copy the output into log_buf. If the caller didn't provide |
| 658 | * appropriate log level tags, we insert them here |
| 659 | */ |
| 660 | for (p = printk_buf; *p; p++) { |
| 661 | if (log_level_unknown) { |
| 662 | /* log_level_unknown signals the start of a new line */ |
| 663 | if (printk_time) { |
| 664 | int loglev_char; |
| 665 | char tbuf[50], *tp; |
| 666 | unsigned tlen; |
| 667 | unsigned long long t; |
| 668 | unsigned long nanosec_rem; |
| 669 | |
| 670 | /* |
| 671 | * force the log level token to be |
| 672 | * before the time output. |
| 673 | */ |
| 674 | if (p[0] == '<' && p[1] >='0' && |
| 675 | p[1] <= '7' && p[2] == '>') { |
| 676 | loglev_char = p[1]; |
| 677 | p += 3; |
| 678 | printed_len -= 3; |
| 679 | } else { |
| 680 | loglev_char = default_message_loglevel |
| 681 | + '0'; |
| 682 | } |
| 683 | t = printk_clock(); |
| 684 | nanosec_rem = do_div(t, 1000000000); |
| 685 | tlen = sprintf(tbuf, |
| 686 | "<%c>[%5lu.%06lu] ", |
| 687 | loglev_char, |
| 688 | (unsigned long)t, |
| 689 | nanosec_rem/1000); |
| 690 | |
| 691 | for (tp = tbuf; tp < tbuf + tlen; tp++) |
| 692 | emit_log_char(*tp); |
| 693 | printed_len += tlen; |
| 694 | } else { |
| 695 | if (p[0] != '<' || p[1] < '0' || |
| 696 | p[1] > '7' || p[2] != '>') { |
| 697 | emit_log_char('<'); |
| 698 | emit_log_char(default_message_loglevel |
| 699 | + '0'); |
| 700 | emit_log_char('>'); |
| 701 | printed_len += 3; |
| 702 | } |
| 703 | } |
| 704 | log_level_unknown = 0; |
| 705 | if (!*p) |
| 706 | break; |
| 707 | } |
| 708 | emit_log_char(*p); |
| 709 | if (*p == '\n') |
| 710 | log_level_unknown = 1; |
| 711 | } |
| 712 | |
| 713 | if (!down_trylock(&console_sem)) { |
| 714 | /* |
| 715 | * We own the drivers. We can drop the spinlock and |
| 716 | * let release_console_sem() print the text, maybe ... |
| 717 | */ |
| 718 | console_locked = 1; |
| 719 | printk_cpu = UINT_MAX; |
| 720 | spin_unlock(&logbuf_lock); |
| 721 | |
| 722 | /* |
| 723 | * Console drivers may assume that per-cpu resources have |
| 724 | * been allocated. So unless they're explicitly marked as |
| 725 | * being able to cope (CON_ANYTIME) don't call them until |
| 726 | * this CPU is officially up. |
| 727 | */ |
| 728 | if (cpu_online(smp_processor_id()) || have_callable_console()) { |
| 729 | console_may_schedule = 0; |
| 730 | release_console_sem(); |
| 731 | } else { |
| 732 | /* Release by hand to avoid flushing the buffer. */ |
| 733 | console_locked = 0; |
| 734 | up(&console_sem); |
| 735 | } |
| 736 | lockdep_on(); |
| 737 | raw_local_irq_restore(flags); |
| 738 | } else { |
| 739 | /* |
| 740 | * Someone else owns the drivers. We drop the spinlock, which |
| 741 | * allows the semaphore holder to proceed and to call the |
| 742 | * console drivers with the output which we just produced. |
| 743 | */ |
| 744 | printk_cpu = UINT_MAX; |
| 745 | spin_unlock(&logbuf_lock); |
| 746 | lockdep_on(); |
| 747 | raw_local_irq_restore(flags); |
| 748 | } |
| 749 | |
| 750 | preempt_enable(); |
| 751 | return printed_len; |
| 752 | } |
| 753 | EXPORT_SYMBOL(printk); |
| 754 | EXPORT_SYMBOL(vprintk); |
| 755 | |
| 756 | #else |
| 757 | |
| 758 | asmlinkage long sys_syslog(int type, char __user *buf, int len) |
| 759 | { |
| 760 | return -ENOSYS; |
| 761 | } |
| 762 | |
| 763 | static void call_console_drivers(unsigned long start, unsigned long end) |
| 764 | { |
| 765 | } |
| 766 | |
| 767 | #endif |
| 768 | |
| 769 | /* |
| 770 | * Set up a list of consoles. Called from init/main.c |
| 771 | */ |
| 772 | static int __init console_setup(char *str) |
| 773 | { |
| 774 | char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */ |
| 775 | char *s, *options; |
| 776 | int idx; |
| 777 | |
| 778 | /* |
| 779 | * Decode str into name, index, options. |
| 780 | */ |
| 781 | if (str[0] >= '0' && str[0] <= '9') { |
| 782 | strcpy(buf, "ttyS"); |
| 783 | strncpy(buf + 4, str, sizeof(buf) - 5); |
| 784 | } else { |
| 785 | strncpy(buf, str, sizeof(buf) - 1); |
| 786 | } |
| 787 | buf[sizeof(buf) - 1] = 0; |
| 788 | if ((options = strchr(str, ',')) != NULL) |
| 789 | *(options++) = 0; |
| 790 | #ifdef __sparc__ |
| 791 | if (!strcmp(str, "ttya")) |
| 792 | strcpy(buf, "ttyS0"); |
| 793 | if (!strcmp(str, "ttyb")) |
| 794 | strcpy(buf, "ttyS1"); |
| 795 | #endif |
| 796 | for (s = buf; *s; s++) |
| 797 | if ((*s >= '0' && *s <= '9') || *s == ',') |
| 798 | break; |
| 799 | idx = simple_strtoul(s, NULL, 10); |
| 800 | *s = 0; |
| 801 | |
| 802 | add_preferred_console(buf, idx, options); |
| 803 | return 1; |
| 804 | } |
| 805 | __setup("console=", console_setup); |
| 806 | |
| 807 | /** |
| 808 | * add_preferred_console - add a device to the list of preferred consoles. |
| 809 | * @name: device name |
| 810 | * @idx: device index |
| 811 | * @options: options for this console |
| 812 | * |
| 813 | * The last preferred console added will be used for kernel messages |
| 814 | * and stdin/out/err for init. Normally this is used by console_setup |
| 815 | * above to handle user-supplied console arguments; however it can also |
| 816 | * be used by arch-specific code either to override the user or more |
| 817 | * commonly to provide a default console (ie from PROM variables) when |
| 818 | * the user has not supplied one. |
| 819 | */ |
| 820 | int __init add_preferred_console(char *name, int idx, char *options) |
| 821 | { |
| 822 | struct console_cmdline *c; |
| 823 | int i; |
| 824 | |
| 825 | /* |
| 826 | * See if this tty is not yet registered, and |
| 827 | * if we have a slot free. |
| 828 | */ |
| 829 | for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++) |
| 830 | if (strcmp(console_cmdline[i].name, name) == 0 && |
| 831 | console_cmdline[i].index == idx) { |
| 832 | selected_console = i; |
| 833 | return 0; |
| 834 | } |
| 835 | if (i == MAX_CMDLINECONSOLES) |
| 836 | return -E2BIG; |
| 837 | selected_console = i; |
| 838 | c = &console_cmdline[i]; |
| 839 | memcpy(c->name, name, sizeof(c->name)); |
| 840 | c->name[sizeof(c->name) - 1] = 0; |
| 841 | c->options = options; |
| 842 | c->index = idx; |
| 843 | return 0; |
| 844 | } |
| 845 | |
| 846 | int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options) |
| 847 | { |
| 848 | struct console_cmdline *c; |
| 849 | int i; |
| 850 | |
| 851 | for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++) |
| 852 | if (strcmp(console_cmdline[i].name, name) == 0 && |
| 853 | console_cmdline[i].index == idx) { |
| 854 | c = &console_cmdline[i]; |
| 855 | memcpy(c->name, name_new, sizeof(c->name)); |
| 856 | c->name[sizeof(c->name) - 1] = 0; |
| 857 | c->options = options; |
| 858 | c->index = idx_new; |
| 859 | return i; |
| 860 | } |
| 861 | /* not found */ |
| 862 | return -1; |
| 863 | } |
| 864 | |
| 865 | #ifndef CONFIG_DISABLE_CONSOLE_SUSPEND |
| 866 | /** |
| 867 | * suspend_console - suspend the console subsystem |
| 868 | * |
| 869 | * This disables printk() while we go into suspend states |
| 870 | */ |
| 871 | void suspend_console(void) |
| 872 | { |
| 873 | printk("Suspending console(s)\n"); |
| 874 | acquire_console_sem(); |
| 875 | console_suspended = 1; |
| 876 | } |
| 877 | |
| 878 | void resume_console(void) |
| 879 | { |
| 880 | console_suspended = 0; |
| 881 | release_console_sem(); |
| 882 | } |
| 883 | #endif /* CONFIG_DISABLE_CONSOLE_SUSPEND */ |
| 884 | |
| 885 | /** |
| 886 | * acquire_console_sem - lock the console system for exclusive use. |
| 887 | * |
| 888 | * Acquires a semaphore which guarantees that the caller has |
| 889 | * exclusive access to the console system and the console_drivers list. |
| 890 | * |
| 891 | * Can sleep, returns nothing. |
| 892 | */ |
| 893 | void acquire_console_sem(void) |
| 894 | { |
| 895 | BUG_ON(in_interrupt()); |
| 896 | if (console_suspended) { |
| 897 | down(&secondary_console_sem); |
| 898 | return; |
| 899 | } |
| 900 | down(&console_sem); |
| 901 | console_locked = 1; |
| 902 | console_may_schedule = 1; |
| 903 | } |
| 904 | EXPORT_SYMBOL(acquire_console_sem); |
| 905 | |
| 906 | int try_acquire_console_sem(void) |
| 907 | { |
| 908 | if (down_trylock(&console_sem)) |
| 909 | return -1; |
| 910 | console_locked = 1; |
| 911 | console_may_schedule = 0; |
| 912 | return 0; |
| 913 | } |
| 914 | EXPORT_SYMBOL(try_acquire_console_sem); |
| 915 | |
| 916 | int is_console_locked(void) |
| 917 | { |
| 918 | return console_locked; |
| 919 | } |
| 920 | |
| 921 | void wake_up_klogd(void) |
| 922 | { |
| 923 | if (!oops_in_progress && waitqueue_active(&log_wait)) |
| 924 | wake_up_interruptible(&log_wait); |
| 925 | } |
| 926 | |
| 927 | /** |
| 928 | * release_console_sem - unlock the console system |
| 929 | * |
| 930 | * Releases the semaphore which the caller holds on the console system |
| 931 | * and the console driver list. |
| 932 | * |
| 933 | * While the semaphore was held, console output may have been buffered |
| 934 | * by printk(). If this is the case, release_console_sem() emits |
| 935 | * the output prior to releasing the semaphore. |
| 936 | * |
| 937 | * If there is output waiting for klogd, we wake it up. |
| 938 | * |
| 939 | * release_console_sem() may be called from any context. |
| 940 | */ |
| 941 | void release_console_sem(void) |
| 942 | { |
| 943 | unsigned long flags; |
| 944 | unsigned long _con_start, _log_end; |
| 945 | unsigned long wake_klogd = 0; |
| 946 | |
| 947 | if (console_suspended) { |
| 948 | up(&secondary_console_sem); |
| 949 | return; |
| 950 | } |
| 951 | |
| 952 | console_may_schedule = 0; |
| 953 | |
| 954 | for ( ; ; ) { |
| 955 | spin_lock_irqsave(&logbuf_lock, flags); |
| 956 | wake_klogd |= log_start - log_end; |
| 957 | if (con_start == log_end) |
| 958 | break; /* Nothing to print */ |
| 959 | _con_start = con_start; |
| 960 | _log_end = log_end; |
| 961 | con_start = log_end; /* Flush */ |
| 962 | spin_unlock(&logbuf_lock); |
| 963 | call_console_drivers(_con_start, _log_end); |
| 964 | local_irq_restore(flags); |
| 965 | } |
| 966 | console_locked = 0; |
| 967 | up(&console_sem); |
| 968 | spin_unlock_irqrestore(&logbuf_lock, flags); |
| 969 | if (wake_klogd) |
| 970 | wake_up_klogd(); |
| 971 | } |
| 972 | EXPORT_SYMBOL(release_console_sem); |
| 973 | |
| 974 | /** |
| 975 | * console_conditional_schedule - yield the CPU if required |
| 976 | * |
| 977 | * If the console code is currently allowed to sleep, and |
| 978 | * if this CPU should yield the CPU to another task, do |
| 979 | * so here. |
| 980 | * |
| 981 | * Must be called within acquire_console_sem(). |
| 982 | */ |
| 983 | void __sched console_conditional_schedule(void) |
| 984 | { |
| 985 | if (console_may_schedule) |
| 986 | cond_resched(); |
| 987 | } |
| 988 | EXPORT_SYMBOL(console_conditional_schedule); |
| 989 | |
| 990 | void console_print(const char *s) |
| 991 | { |
| 992 | printk(KERN_EMERG "%s", s); |
| 993 | } |
| 994 | EXPORT_SYMBOL(console_print); |
| 995 | |
| 996 | void console_unblank(void) |
| 997 | { |
| 998 | struct console *c; |
| 999 | |
| 1000 | /* |
| 1001 | * console_unblank can no longer be called in interrupt context unless |
| 1002 | * oops_in_progress is set to 1.. |
| 1003 | */ |
| 1004 | if (oops_in_progress) { |
| 1005 | if (down_trylock(&console_sem) != 0) |
| 1006 | return; |
| 1007 | } else |
| 1008 | acquire_console_sem(); |
| 1009 | |
| 1010 | console_locked = 1; |
| 1011 | console_may_schedule = 0; |
| 1012 | for (c = console_drivers; c != NULL; c = c->next) |
| 1013 | if ((c->flags & CON_ENABLED) && c->unblank) |
| 1014 | c->unblank(); |
| 1015 | release_console_sem(); |
| 1016 | } |
| 1017 | |
| 1018 | /* |
| 1019 | * Return the console tty driver structure and its associated index |
| 1020 | */ |
| 1021 | struct tty_driver *console_device(int *index) |
| 1022 | { |
| 1023 | struct console *c; |
| 1024 | struct tty_driver *driver = NULL; |
| 1025 | |
| 1026 | acquire_console_sem(); |
| 1027 | for (c = console_drivers; c != NULL; c = c->next) { |
| 1028 | if (!c->device) |
| 1029 | continue; |
| 1030 | driver = c->device(c, index); |
| 1031 | if (driver) |
| 1032 | break; |
| 1033 | } |
| 1034 | release_console_sem(); |
| 1035 | return driver; |
| 1036 | } |
| 1037 | |
| 1038 | /* |
| 1039 | * Prevent further output on the passed console device so that (for example) |
| 1040 | * serial drivers can disable console output before suspending a port, and can |
| 1041 | * re-enable output afterwards. |
| 1042 | */ |
| 1043 | void console_stop(struct console *console) |
| 1044 | { |
| 1045 | acquire_console_sem(); |
| 1046 | console->flags &= ~CON_ENABLED; |
| 1047 | release_console_sem(); |
| 1048 | } |
| 1049 | EXPORT_SYMBOL(console_stop); |
| 1050 | |
| 1051 | void console_start(struct console *console) |
| 1052 | { |
| 1053 | acquire_console_sem(); |
| 1054 | console->flags |= CON_ENABLED; |
| 1055 | release_console_sem(); |
| 1056 | } |
| 1057 | EXPORT_SYMBOL(console_start); |
| 1058 | |
| 1059 | /* |
| 1060 | * The console driver calls this routine during kernel initialization |
| 1061 | * to register the console printing procedure with printk() and to |
| 1062 | * print any messages that were printed by the kernel before the |
| 1063 | * console driver was initialized. |
| 1064 | */ |
| 1065 | void register_console(struct console *console) |
| 1066 | { |
| 1067 | int i; |
| 1068 | unsigned long flags; |
| 1069 | struct console *bootconsole = NULL; |
| 1070 | |
| 1071 | if (console_drivers) { |
| 1072 | if (console->flags & CON_BOOT) |
| 1073 | return; |
| 1074 | if (console_drivers->flags & CON_BOOT) |
| 1075 | bootconsole = console_drivers; |
| 1076 | } |
| 1077 | |
| 1078 | if (preferred_console < 0 || bootconsole || !console_drivers) |
| 1079 | preferred_console = selected_console; |
| 1080 | |
| 1081 | if (console->early_setup) |
| 1082 | console->early_setup(); |
| 1083 | |
| 1084 | /* |
| 1085 | * See if we want to use this console driver. If we |
| 1086 | * didn't select a console we take the first one |
| 1087 | * that registers here. |
| 1088 | */ |
| 1089 | if (preferred_console < 0) { |
| 1090 | if (console->index < 0) |
| 1091 | console->index = 0; |
| 1092 | if (console->setup == NULL || |
| 1093 | console->setup(console, NULL) == 0) { |
| 1094 | console->flags |= CON_ENABLED | CON_CONSDEV; |
| 1095 | preferred_console = 0; |
| 1096 | } |
| 1097 | } |
| 1098 | |
| 1099 | /* |
| 1100 | * See if this console matches one we selected on |
| 1101 | * the command line. |
| 1102 | */ |
| 1103 | for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; |
| 1104 | i++) { |
| 1105 | if (strcmp(console_cmdline[i].name, console->name) != 0) |
| 1106 | continue; |
| 1107 | if (console->index >= 0 && |
| 1108 | console->index != console_cmdline[i].index) |
| 1109 | continue; |
| 1110 | if (console->index < 0) |
| 1111 | console->index = console_cmdline[i].index; |
| 1112 | if (console->setup && |
| 1113 | console->setup(console, console_cmdline[i].options) != 0) |
| 1114 | break; |
| 1115 | console->flags |= CON_ENABLED; |
| 1116 | console->index = console_cmdline[i].index; |
| 1117 | if (i == selected_console) { |
| 1118 | console->flags |= CON_CONSDEV; |
| 1119 | preferred_console = selected_console; |
| 1120 | } |
| 1121 | break; |
| 1122 | } |
| 1123 | |
| 1124 | if (!(console->flags & CON_ENABLED)) |
| 1125 | return; |
| 1126 | |
| 1127 | if (bootconsole && (console->flags & CON_CONSDEV)) { |
| 1128 | printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n", |
| 1129 | bootconsole->name, bootconsole->index, |
| 1130 | console->name, console->index); |
| 1131 | unregister_console(bootconsole); |
| 1132 | console->flags &= ~CON_PRINTBUFFER; |
| 1133 | } else { |
| 1134 | printk(KERN_INFO "console [%s%d] enabled\n", |
| 1135 | console->name, console->index); |
| 1136 | } |
| 1137 | |
| 1138 | /* |
| 1139 | * Put this console in the list - keep the |
| 1140 | * preferred driver at the head of the list. |
| 1141 | */ |
| 1142 | acquire_console_sem(); |
| 1143 | if ((console->flags & CON_CONSDEV) || console_drivers == NULL) { |
| 1144 | console->next = console_drivers; |
| 1145 | console_drivers = console; |
| 1146 | if (console->next) |
| 1147 | console->next->flags &= ~CON_CONSDEV; |
| 1148 | } else { |
| 1149 | console->next = console_drivers->next; |
| 1150 | console_drivers->next = console; |
| 1151 | } |
| 1152 | if (console->flags & CON_PRINTBUFFER) { |
| 1153 | /* |
| 1154 | * release_console_sem() will print out the buffered messages |
| 1155 | * for us. |
| 1156 | */ |
| 1157 | spin_lock_irqsave(&logbuf_lock, flags); |
| 1158 | con_start = log_start; |
| 1159 | spin_unlock_irqrestore(&logbuf_lock, flags); |
| 1160 | } |
| 1161 | release_console_sem(); |
| 1162 | } |
| 1163 | EXPORT_SYMBOL(register_console); |
| 1164 | |
| 1165 | int unregister_console(struct console *console) |
| 1166 | { |
| 1167 | struct console *a, *b; |
| 1168 | int res = 1; |
| 1169 | |
| 1170 | acquire_console_sem(); |
| 1171 | if (console_drivers == console) { |
| 1172 | console_drivers=console->next; |
| 1173 | res = 0; |
| 1174 | } else if (console_drivers) { |
| 1175 | for (a=console_drivers->next, b=console_drivers ; |
| 1176 | a; b=a, a=b->next) { |
| 1177 | if (a == console) { |
| 1178 | b->next = a->next; |
| 1179 | res = 0; |
| 1180 | break; |
| 1181 | } |
| 1182 | } |
| 1183 | } |
| 1184 | |
| 1185 | /* |
| 1186 | * If this isn't the last console and it has CON_CONSDEV set, we |
| 1187 | * need to set it on the next preferred console. |
| 1188 | */ |
| 1189 | if (console_drivers != NULL && console->flags & CON_CONSDEV) |
| 1190 | console_drivers->flags |= CON_CONSDEV; |
| 1191 | |
| 1192 | release_console_sem(); |
| 1193 | return res; |
| 1194 | } |
| 1195 | EXPORT_SYMBOL(unregister_console); |
| 1196 | |
| 1197 | static int __init disable_boot_consoles(void) |
| 1198 | { |
| 1199 | if (console_drivers != NULL) { |
| 1200 | if (console_drivers->flags & CON_BOOT) { |
| 1201 | printk(KERN_INFO "turn off boot console %s%d\n", |
| 1202 | console_drivers->name, console_drivers->index); |
| 1203 | return unregister_console(console_drivers); |
| 1204 | } |
| 1205 | } |
| 1206 | return 0; |
| 1207 | } |
| 1208 | late_initcall(disable_boot_consoles); |
| 1209 | |
| 1210 | /** |
| 1211 | * tty_write_message - write a message to a certain tty, not just the console. |
| 1212 | * @tty: the destination tty_struct |
| 1213 | * @msg: the message to write |
| 1214 | * |
| 1215 | * This is used for messages that need to be redirected to a specific tty. |
| 1216 | * We don't put it into the syslog queue right now maybe in the future if |
| 1217 | * really needed. |
| 1218 | */ |
| 1219 | void tty_write_message(struct tty_struct *tty, char *msg) |
| 1220 | { |
| 1221 | if (tty && tty->driver->write) |
| 1222 | tty->driver->write(tty, msg, strlen(msg)); |
| 1223 | return; |
| 1224 | } |
| 1225 | |
| 1226 | /* |
| 1227 | * printk rate limiting, lifted from the networking subsystem. |
| 1228 | * |
| 1229 | * This enforces a rate limit: not more than one kernel message |
| 1230 | * every printk_ratelimit_jiffies to make a denial-of-service |
| 1231 | * attack impossible. |
| 1232 | */ |
| 1233 | int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst) |
| 1234 | { |
| 1235 | static DEFINE_SPINLOCK(ratelimit_lock); |
| 1236 | static unsigned long toks = 10 * 5 * HZ; |
| 1237 | static unsigned long last_msg; |
| 1238 | static int missed; |
| 1239 | unsigned long flags; |
| 1240 | unsigned long now = jiffies; |
| 1241 | |
| 1242 | spin_lock_irqsave(&ratelimit_lock, flags); |
| 1243 | toks += now - last_msg; |
| 1244 | last_msg = now; |
| 1245 | if (toks > (ratelimit_burst * ratelimit_jiffies)) |
| 1246 | toks = ratelimit_burst * ratelimit_jiffies; |
| 1247 | if (toks >= ratelimit_jiffies) { |
| 1248 | int lost = missed; |
| 1249 | |
| 1250 | missed = 0; |
| 1251 | toks -= ratelimit_jiffies; |
| 1252 | spin_unlock_irqrestore(&ratelimit_lock, flags); |
| 1253 | if (lost) |
| 1254 | printk(KERN_WARNING "printk: %d messages suppressed.\n", lost); |
| 1255 | return 1; |
| 1256 | } |
| 1257 | missed++; |
| 1258 | spin_unlock_irqrestore(&ratelimit_lock, flags); |
| 1259 | return 0; |
| 1260 | } |
| 1261 | EXPORT_SYMBOL(__printk_ratelimit); |
| 1262 | |
| 1263 | /* minimum time in jiffies between messages */ |
| 1264 | int printk_ratelimit_jiffies = 5 * HZ; |
| 1265 | |
| 1266 | /* number of messages we send before ratelimiting */ |
| 1267 | int printk_ratelimit_burst = 10; |
| 1268 | |
| 1269 | int printk_ratelimit(void) |
| 1270 | { |
| 1271 | return __printk_ratelimit(printk_ratelimit_jiffies, |
| 1272 | printk_ratelimit_burst); |
| 1273 | } |
| 1274 | EXPORT_SYMBOL(printk_ratelimit); |
| 1275 | |
| 1276 | /** |
| 1277 | * printk_timed_ratelimit - caller-controlled printk ratelimiting |
| 1278 | * @caller_jiffies: pointer to caller's state |
| 1279 | * @interval_msecs: minimum interval between prints |
| 1280 | * |
| 1281 | * printk_timed_ratelimit() returns true if more than @interval_msecs |
| 1282 | * milliseconds have elapsed since the last time printk_timed_ratelimit() |
| 1283 | * returned true. |
| 1284 | */ |
| 1285 | bool printk_timed_ratelimit(unsigned long *caller_jiffies, |
| 1286 | unsigned int interval_msecs) |
| 1287 | { |
| 1288 | if (*caller_jiffies == 0 || time_after(jiffies, *caller_jiffies)) { |
| 1289 | *caller_jiffies = jiffies + msecs_to_jiffies(interval_msecs); |
| 1290 | return true; |
| 1291 | } |
| 1292 | return false; |
| 1293 | } |
| 1294 | EXPORT_SYMBOL(printk_timed_ratelimit); |