printk.c 31.8 KB
Newer Older
L
Linus Torvalds 已提交
1 2 3 4 5 6 7 8 9 10 11 12
/*
 *  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.
J
Jesper Juhl 已提交
13
 * Fixed SMP synchronization, 08/08/99, Manfred Spraul
14
 *     manfred@colorfullife.com
L
Linus Torvalds 已提交
15
 * Rewrote bits to get rid of console_lock
16
 *	01Mar01 Andrew Morton
L
Linus Torvalds 已提交
17 18 19 20 21 22 23 24
 */

#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/tty.h>
#include <linux/tty_driver.h>
#include <linux/console.h>
#include <linux/init.h>
R
Randy Dunlap 已提交
25 26
#include <linux/jiffies.h>
#include <linux/nmi.h>
L
Linus Torvalds 已提交
27
#include <linux/module.h>
J
Jan Engelhardt 已提交
28
#include <linux/moduleparam.h>
L
Linus Torvalds 已提交
29 30 31 32 33 34 35 36 37
#include <linux/interrupt.h>			/* For in_interrupt() */
#include <linux/delay.h>
#include <linux/smp.h>
#include <linux/security.h>
#include <linux/bootmem.h>
#include <linux/syscalls.h>

#include <asm/uaccess.h>

38 39 40
/*
 * Architectures can override it:
 */
41
void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
42 43 44
{
}

L
Linus Torvalds 已提交
45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63
#define __LOG_BUF_LEN	(1 << CONFIG_LOG_BUF_SHIFT)

/* 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 */
};

/*
P
Patrick Pletscher 已提交
64
 * Low level drivers may need that to know if they can schedule in
L
Linus Torvalds 已提交
65 66 67 68 69 70 71 72 73 74 75 76
 * their unblank() callback or not. So let's export it.
 */
int oops_in_progress;
EXPORT_SYMBOL(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;
I
Ingo Molnar 已提交
77 78
EXPORT_SYMBOL_GPL(console_drivers);

L
Linus Torvalds 已提交
79 80 81 82 83 84 85 86
/*
 * This is used for debugging the mess that is the VT code by
 * keeping track if we have the console semaphore held. It's
 * definitely not the perfect debug tool (we don't know if _WE_
 * hold it are racing, but it helps tracking those weird code
 * path in the console code where we end up in places I want
 * locked without the console sempahore held
 */
87
static int console_locked, console_suspended;
L
Linus Torvalds 已提交
88 89 90 91 92 93 94 95

/*
 * 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 DEFINE_SPINLOCK(logbuf_lock);

96
#define LOG_BUF_MASK (log_buf_len-1)
L
Linus Torvalds 已提交
97 98 99 100 101 102
#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
 */
103 104 105
static unsigned log_start;	/* Index into log_buf: next char to be read by syslog() */
static unsigned con_start;	/* Index into log_buf: next char to be sent to consoles */
static unsigned log_end;	/* Index into log_buf: most-recently-written-char + 1 */
L
Linus Torvalds 已提交
106 107 108 109 110 111 112 113 114

/*
 *	Array of consoles built from command line options (console=)
 */
struct console_cmdline
{
	char	name[8];			/* Name of the driver	    */
	int	index;				/* Minor dev. to use	    */
	char	*options;			/* Options for the driver   */
115 116 117
#ifdef CONFIG_A11Y_BRAILLE_CONSOLE
	char	*brl_options;			/* Options for braille driver */
#endif
L
Linus Torvalds 已提交
118 119 120 121 122 123 124
};

#define MAX_CMDLINECONSOLES 8

static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
static int selected_console = -1;
static int preferred_console = -1;
125 126
int console_set_on_cmdline;
EXPORT_SYMBOL(console_set_on_cmdline);
L
Linus Torvalds 已提交
127 128 129 130

/* Flag: console code may call schedule() */
static int console_may_schedule;

M
Matt Mackall 已提交
131 132 133 134 135
#ifdef CONFIG_PRINTK

static char __log_buf[__LOG_BUF_LEN];
static char *log_buf = __log_buf;
static int log_buf_len = __LOG_BUF_LEN;
136
static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
M
Matt Mackall 已提交
137

L
Linus Torvalds 已提交
138 139
static int __init log_buf_len_setup(char *str)
{
140
	unsigned size = memparse(str, &str);
L
Linus Torvalds 已提交
141 142 143 144 145
	unsigned long flags;

	if (size)
		size = roundup_pow_of_two(size);
	if (size > log_buf_len) {
146
		unsigned start, dest_idx, offset;
J
Jesper Juhl 已提交
147
		char *new_log_buf;
L
Linus Torvalds 已提交
148 149 150

		new_log_buf = alloc_bootmem(size);
		if (!new_log_buf) {
J
Jesper Juhl 已提交
151
			printk(KERN_WARNING "log_buf_len: allocation failed\n");
L
Linus Torvalds 已提交
152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170
			goto out;
		}

		spin_lock_irqsave(&logbuf_lock, flags);
		log_buf_len = size;
		log_buf = new_log_buf;

		offset = start = min(con_start, log_start);
		dest_idx = 0;
		while (start != log_end) {
			log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
			start++;
			dest_idx++;
		}
		log_start -= offset;
		con_start -= offset;
		log_end -= offset;
		spin_unlock_irqrestore(&logbuf_lock, flags);

J
Jesper Juhl 已提交
171
		printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
L
Linus Torvalds 已提交
172 173 174 175 176 177 178
	}
out:
	return 1;
}

__setup("log_buf_len=", log_buf_len_setup);

R
Randy Dunlap 已提交
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
#ifdef CONFIG_BOOT_PRINTK_DELAY

static unsigned int boot_delay; /* msecs delay after each printk during bootup */
static unsigned long long printk_delay_msec; /* per msec, based on boot_delay */

static int __init boot_delay_setup(char *str)
{
	unsigned long lpj;
	unsigned long long loops_per_msec;

	lpj = preset_lpj ? preset_lpj : 1000000;	/* some guess */
	loops_per_msec = (unsigned long long)lpj / 1000 * HZ;

	get_option(&str, &boot_delay);
	if (boot_delay > 10 * 1000)
		boot_delay = 0;

	printk_delay_msec = loops_per_msec;
	printk(KERN_DEBUG "boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
		"HZ: %d, printk_delay_msec: %llu\n",
		boot_delay, preset_lpj, lpj, HZ, printk_delay_msec);
	return 1;
}
__setup("boot_delay=", boot_delay_setup);

static void boot_delay_msec(void)
{
	unsigned long long k;
	unsigned long timeout;

	if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
		return;

	k = (unsigned long long)printk_delay_msec * boot_delay;

	timeout = jiffies + msecs_to_jiffies(boot_delay);
	while (k) {
		k--;
		cpu_relax();
		/*
		 * use (volatile) jiffies to prevent
		 * compiler reduction; loop termination via jiffies
		 * is secondary and may or may not happen.
		 */
		if (time_after(jiffies, timeout))
			break;
		touch_nmi_watchdog();
	}
}
#else
static inline void boot_delay_msec(void)
{
}
#endif

L
Linus Torvalds 已提交
234 235 236 237 238 239 240 241 242 243 244 245 246 247 248
/*
 * 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
 *     10 -- Return size of the log buffer
 */
J
Jesper Juhl 已提交
249
int do_syslog(int type, char __user *buf, int len)
L
Linus Torvalds 已提交
250
{
251
	unsigned i, j, limit, count;
L
Linus Torvalds 已提交
252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275
	int do_clear = 0;
	char c;
	int error = 0;

	error = security_syslog(type);
	if (error)
		return error;

	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;
		if (!access_ok(VERIFY_WRITE, buf, len)) {
			error = -EFAULT;
			goto out;
		}
J
Jesper Juhl 已提交
276 277
		error = wait_event_interruptible(log_wait,
							(log_start - log_end));
L
Linus Torvalds 已提交
278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296
		if (error)
			goto out;
		i = 0;
		spin_lock_irq(&logbuf_lock);
		while (!error && (log_start != log_end) && i < len) {
			c = LOG_BUF(log_start);
			log_start++;
			spin_unlock_irq(&logbuf_lock);
			error = __put_user(c,buf);
			buf++;
			i++;
			cond_resched();
			spin_lock_irq(&logbuf_lock);
		}
		spin_unlock_irq(&logbuf_lock);
		if (!error)
			error = i;
		break;
	case 4:		/* Read/clear last kernel messages */
J
Jesper Juhl 已提交
297
		do_clear = 1;
L
Linus Torvalds 已提交
298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320
		/* FALL THRU */
	case 3:		/* Read last kernel messages */
		error = -EINVAL;
		if (!buf || len < 0)
			goto out;
		error = 0;
		if (!len)
			goto out;
		if (!access_ok(VERIFY_WRITE, buf, len)) {
			error = -EFAULT;
			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
J
Jesper Juhl 已提交
321
		 * printk() could overwrite the messages
L
Linus Torvalds 已提交
322 323 324
		 * we try to copy to user space. Therefore
		 * the messages are copied in reverse. <manfreds>
		 */
J
Jesper Juhl 已提交
325
		for (i = 0; i < count && !error; i++) {
L
Linus Torvalds 已提交
326 327 328 329 330 331 332 333 334 335 336 337 338
			j = limit-1-i;
			if (j + log_buf_len < log_end)
				break;
			c = LOG_BUF(j);
			spin_unlock_irq(&logbuf_lock);
			error = __put_user(c,&buf[count-1-i]);
			cond_resched();
			spin_lock_irq(&logbuf_lock);
		}
		spin_unlock_irq(&logbuf_lock);
		if (error)
			break;
		error = i;
J
Jesper Juhl 已提交
339
		if (i != count) {
L
Linus Torvalds 已提交
340 341
			int offset = count-error;
			/* buffer overflow during copy, correct user buffer. */
J
Jesper Juhl 已提交
342
			for (i = 0; i < error; i++) {
L
Linus Torvalds 已提交
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
				if (__get_user(c,&buf[i+offset]) ||
				    __put_user(c,&buf[i])) {
					error = -EFAULT;
					break;
				}
				cond_resched();
			}
		}
		break;
	case 5:		/* Clear ring buffer */
		logged_chars = 0;
		break;
	case 6:		/* Disable logging to console */
		console_loglevel = minimum_console_loglevel;
		break;
	case 7:		/* Enable logging to console */
		console_loglevel = default_console_loglevel;
		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;
		console_loglevel = len;
		error = 0;
		break;
	case 9:		/* Number of chars in the log buffer */
		error = log_end - log_start;
		break;
	case 10:	/* Size of the log buffer */
		error = log_buf_len;
		break;
	default:
		error = -EINVAL;
		break;
	}
out:
	return error;
}

384
SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
L
Linus Torvalds 已提交
385 386 387 388 389 390 391
{
	return do_syslog(type, buf, len);
}

/*
 * Call the console drivers on a range of log_buf
 */
392
static void __call_console_drivers(unsigned start, unsigned end)
L
Linus Torvalds 已提交
393 394 395 396
{
	struct console *con;

	for (con = console_drivers; con; con = con->next) {
397 398 399
		if ((con->flags & CON_ENABLED) && con->write &&
				(cpu_online(smp_processor_id()) ||
				(con->flags & CON_ANYTIME)))
L
Linus Torvalds 已提交
400 401 402 403
			con->write(con, &LOG_BUF(start), end - start);
	}
}

404 405
static int __read_mostly ignore_loglevel;

406
static int __init ignore_loglevel_setup(char *str)
407 408 409 410
{
	ignore_loglevel = 1;
	printk(KERN_INFO "debug: ignoring loglevel setting.\n");

411
	return 0;
412 413
}

414
early_param("ignore_loglevel", ignore_loglevel_setup);
415

L
Linus Torvalds 已提交
416 417 418
/*
 * Write out chars from start to end - 1 inclusive
 */
419 420
static void _call_console_drivers(unsigned start,
				unsigned end, int msg_log_level)
L
Linus Torvalds 已提交
421
{
422
	if ((msg_log_level < console_loglevel || ignore_loglevel) &&
L
Linus Torvalds 已提交
423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439
			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.
 */
440
static void call_console_drivers(unsigned start, unsigned end)
L
Linus Torvalds 已提交
441
{
442
	unsigned cur_index, start_print;
L
Linus Torvalds 已提交
443 444
	static int msg_level = -1;

445
	BUG_ON(((int)(start - end)) > 0);
L
Linus Torvalds 已提交
446 447 448 449

	cur_index = start;
	start_print = start;
	while (cur_index != end) {
J
Jesper Juhl 已提交
450 451 452 453 454
		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) == '>') {
L
Linus Torvalds 已提交
455 456 457 458 459 460 461
			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);

J
Jesper Juhl 已提交
462
			cur_index++;
L
Linus Torvalds 已提交
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
			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++;
}

/*
 * Zap console related locks when oopsing. Only zap at most once
 * every 10 seconds, to leave time for slow consoles to print a
 * full oops.
 */
static void zap_locks(void)
{
	static unsigned long oops_timestamp;

	if (time_after_eq(jiffies, oops_timestamp) &&
J
Jesper Juhl 已提交
505
			!time_after(jiffies, oops_timestamp + 30 * HZ))
L
Linus Torvalds 已提交
506 507 508 509 510 511 512 513 514 515 516 517 518 519 520
		return;

	oops_timestamp = jiffies;

	/* 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);
}

#if defined(CONFIG_PRINTK_TIME)
static int printk_time = 1;
#else
static int printk_time = 0;
#endif
521
module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
L
Linus Torvalds 已提交
522

523 524 525 526 527 528 529 530 531 532 533 534
/* Check if we have any console registered that can be called early in boot. */
static int have_callable_console(void)
{
	struct console *con;

	for (con = console_drivers; con; con = con->next)
		if (con->flags & CON_ANYTIME)
			return 1;

	return 0;
}

535 536 537 538
/**
 * printk - print a kernel message
 * @fmt: format string
 *
539
 * This is printk().  It can be called from any context.  We want it to work.
J
Jesper Juhl 已提交
540
 *
L
Linus Torvalds 已提交
541 542 543 544 545 546 547 548 549
 * 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.
550 551 552
 *
 * See also:
 * printf(3)
553 554
 *
 * See the vsnprintf() documentation for format string extensions over C99.
L
Linus Torvalds 已提交
555
 */
M
Matt Mackall 已提交
556

L
Linus Torvalds 已提交
557 558 559 560 561 562 563 564 565 566 567 568
asmlinkage int printk(const char *fmt, ...)
{
	va_list args;
	int r;

	va_start(args, fmt);
	r = vprintk(fmt, args);
	va_end(args);

	return r;
}

569 570 571
/* cpu currently holding logbuf_lock */
static volatile unsigned int printk_cpu = UINT_MAX;

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
/*
 * Can we actually use the console at this time on this cpu?
 *
 * Console drivers may assume that per-cpu resources have
 * been allocated. So unless they're explicitly marked as
 * being able to cope (CON_ANYTIME) don't call them until
 * this CPU is officially up.
 */
static inline int can_use_console(unsigned int cpu)
{
	return cpu_online(cpu) || have_callable_console();
}

/*
 * Try to get console ownership to actually show the kernel
 * messages from a 'printk'. Return true (and with the
 * console_semaphore held, and 'console_locked' set) if it
 * is successful, false otherwise.
 *
 * This gets called with the 'logbuf_lock' spinlock held and
 * interrupts disabled. It should return with 'lockbuf_lock'
 * released but interrupts still disabled.
 */
static int acquire_console_semaphore_for_printk(unsigned int cpu)
{
	int retval = 0;

599 600 601 602 603 604 605 606 607 608 609 610 611 612 613
	if (!try_acquire_console_sem()) {
		retval = 1;

		/*
		 * If we can't use the console, we need to release
		 * the console semaphore by hand to avoid flushing
		 * the buffer. We need to hold the console semaphore
		 * in order to do this test safely.
		 */
		if (!can_use_console(cpu)) {
			console_locked = 0;
			up(&console_sem);
			retval = 0;
		}
	}
614 615 616 617
	printk_cpu = UINT_MAX;
	spin_unlock(&logbuf_lock);
	return retval;
}
618 619 620
static const char recursion_bug_msg [] =
		KERN_CRIT "BUG: recent printk recursion!\n";
static int recursion_bug;
621
static int new_text_line = 1;
622
static char printk_buf[1024];
623

L
Linus Torvalds 已提交
624 625
asmlinkage int vprintk(const char *fmt, va_list args)
{
626
	int printed_len = 0;
627
	int current_log_level = default_message_loglevel;
628
	unsigned long flags;
629
	int this_cpu;
L
Linus Torvalds 已提交
630 631
	char *p;

R
Randy Dunlap 已提交
632 633
	boot_delay_msec();

634
	preempt_disable();
L
Linus Torvalds 已提交
635
	/* This stops the holder of console_sem just where we want him */
636
	raw_local_irq_save(flags);
637 638 639 640 641 642 643 644 645 646 647 648 649 650
	this_cpu = smp_processor_id();

	/*
	 * Ouch, printk recursed into itself!
	 */
	if (unlikely(printk_cpu == this_cpu)) {
		/*
		 * If a crash is occurring during printk() on this CPU,
		 * then try to get the crash message out but make sure
		 * we can't deadlock. Otherwise just return to avoid the
		 * recursion and return - but flag the recursion so that
		 * it can be printed at the next appropriate moment:
		 */
		if (!oops_in_progress) {
651
			recursion_bug = 1;
652 653 654 655 656
			goto out_restore_irqs;
		}
		zap_locks();
	}

657 658
	lockdep_off();
	spin_lock(&logbuf_lock);
659
	printk_cpu = this_cpu;
L
Linus Torvalds 已提交
660

661 662 663
	if (recursion_bug) {
		recursion_bug = 0;
		strcpy(printk_buf, recursion_bug_msg);
664
		printed_len = strlen(recursion_bug_msg);
665
	}
L
Linus Torvalds 已提交
666
	/* Emit the output into the temporary buffer */
667
	printed_len += vscnprintf(printk_buf + printed_len,
T
Tejun Heo 已提交
668
				  sizeof(printk_buf) - printed_len, fmt, args);
L
Linus Torvalds 已提交
669

670

L
Linus Torvalds 已提交
671 672 673 674 675
	/*
	 * 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++) {
676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691
		if (new_text_line) {
			/* If a token, set current_log_level and skip over */
			if (p[0] == '<' && p[1] >= '0' && p[1] <= '7' &&
			    p[2] == '>') {
				current_log_level = p[1] - '0';
				p += 3;
				printed_len -= 3;
			}

			/* Always output the token */
			emit_log_char('<');
			emit_log_char(current_log_level + '0');
			emit_log_char('>');
			printed_len += 3;
			new_text_line = 0;

L
Linus Torvalds 已提交
692
			if (printk_time) {
693
				/* Follow the token with the time */
L
Linus Torvalds 已提交
694 695 696 697 698
				char tbuf[50], *tp;
				unsigned tlen;
				unsigned long long t;
				unsigned long nanosec_rem;

699
				t = cpu_clock(printk_cpu);
L
Linus Torvalds 已提交
700
				nanosec_rem = do_div(t, 1000000000);
701 702 703
				tlen = sprintf(tbuf, "[%5lu.%06lu] ",
						(unsigned long) t,
						nanosec_rem / 1000);
L
Linus Torvalds 已提交
704 705 706

				for (tp = tbuf; tp < tbuf + tlen; tp++)
					emit_log_char(*tp);
707
				printed_len += tlen;
L
Linus Torvalds 已提交
708
			}
709

L
Linus Torvalds 已提交
710 711 712
			if (!*p)
				break;
		}
713

L
Linus Torvalds 已提交
714 715
		emit_log_char(*p);
		if (*p == '\n')
716
			new_text_line = 1;
L
Linus Torvalds 已提交
717 718
	}

719 720 721 722 723 724 725 726 727 728 729 730
	/*
	 * Try to acquire and then immediately release the
	 * console semaphore. The release will do all the
	 * actual magic (print out buffers, wake up klogd,
	 * etc). 
	 *
	 * The acquire_console_semaphore_for_printk() function
	 * will release 'logbuf_lock' regardless of whether it
	 * actually gets the semaphore or not.
	 */
	if (acquire_console_semaphore_for_printk(this_cpu))
		release_console_sem();
731

732
	lockdep_on();
733
out_restore_irqs:
734
	raw_local_irq_restore(flags);
735

736
	preempt_enable();
L
Linus Torvalds 已提交
737 738 739 740 741
	return printed_len;
}
EXPORT_SYMBOL(printk);
EXPORT_SYMBOL(vprintk);

M
Matt Mackall 已提交
742 743
#else

744
static void call_console_drivers(unsigned start, unsigned end)
J
Jesper Juhl 已提交
745 746
{
}
M
Matt Mackall 已提交
747 748 749

#endif

750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779
static int __add_preferred_console(char *name, int idx, char *options,
				   char *brl_options)
{
	struct console_cmdline *c;
	int i;

	/*
	 *	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) {
				if (!brl_options)
					selected_console = i;
				return 0;
		}
	if (i == MAX_CMDLINECONSOLES)
		return -E2BIG;
	if (!brl_options)
		selected_console = i;
	c = &console_cmdline[i];
	strlcpy(c->name, name, sizeof(c->name));
	c->options = options;
#ifdef CONFIG_A11Y_BRAILLE_CONSOLE
	c->brl_options = brl_options;
#endif
	c->index = idx;
	return 0;
}
780 781 782 783 784
/*
 * Set up a list of consoles.  Called from init/main.c
 */
static int __init console_setup(char *str)
{
Y
Yinghai Lu 已提交
785
	char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
786
	char *s, *options, *brl_options = NULL;
787 788
	int idx;

789 790 791 792 793 794 795 796 797 798 799 800 801 802 803
#ifdef CONFIG_A11Y_BRAILLE_CONSOLE
	if (!memcmp(str, "brl,", 4)) {
		brl_options = "";
		str += 4;
	} else if (!memcmp(str, "brl=", 4)) {
		brl_options = str + 4;
		str = strchr(brl_options, ',');
		if (!str) {
			printk(KERN_ERR "need port name after brl=\n");
			return 1;
		}
		*(str++) = 0;
	}
#endif

804 805 806 807
	/*
	 * Decode str into name, index, options.
	 */
	if (str[0] >= '0' && str[0] <= '9') {
Y
Yinghai Lu 已提交
808 809
		strcpy(buf, "ttyS");
		strncpy(buf + 4, str, sizeof(buf) - 5);
810
	} else {
Y
Yinghai Lu 已提交
811
		strncpy(buf, str, sizeof(buf) - 1);
812
	}
Y
Yinghai Lu 已提交
813
	buf[sizeof(buf) - 1] = 0;
814 815 816 817
	if ((options = strchr(str, ',')) != NULL)
		*(options++) = 0;
#ifdef __sparc__
	if (!strcmp(str, "ttya"))
Y
Yinghai Lu 已提交
818
		strcpy(buf, "ttyS0");
819
	if (!strcmp(str, "ttyb"))
Y
Yinghai Lu 已提交
820
		strcpy(buf, "ttyS1");
821
#endif
Y
Yinghai Lu 已提交
822
	for (s = buf; *s; s++)
823 824 825 826 827
		if ((*s >= '0' && *s <= '9') || *s == ',')
			break;
	idx = simple_strtoul(s, NULL, 10);
	*s = 0;

828
	__add_preferred_console(buf, idx, options, brl_options);
829
	console_set_on_cmdline = 1;
830 831 832 833
	return 1;
}
__setup("console=", console_setup);

834 835
/**
 * add_preferred_console - add a device to the list of preferred consoles.
836 837 838
 * @name: device name
 * @idx: device index
 * @options: options for this console
839 840 841 842 843 844 845 846
 *
 * The last preferred console added will be used for kernel messages
 * and stdin/out/err for init.  Normally this is used by console_setup
 * above to handle user-supplied console arguments; however it can also
 * be used by arch-specific code either to override the user or more
 * commonly to provide a default console (ie from PROM variables) when
 * the user has not supplied one.
 */
847
int add_preferred_console(char *name, int idx, char *options)
848
{
849
	return __add_preferred_console(name, idx, options, NULL);
850 851
}

852
int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
853 854 855 856 857 858 859 860
{
	struct console_cmdline *c;
	int i;

	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) {
				c = &console_cmdline[i];
861
				strlcpy(c->name, name_new, sizeof(c->name));
862 863 864 865 866 867 868 869 870
				c->name[sizeof(c->name) - 1] = 0;
				c->options = options;
				c->index = idx_new;
				return i;
		}
	/* not found */
	return -1;
}

871 872 873 874 875 876 877 878 879 880
int console_suspend_enabled = 1;
EXPORT_SYMBOL(console_suspend_enabled);

static int __init console_suspend_disable(char *str)
{
	console_suspend_enabled = 0;
	return 1;
}
__setup("no_console_suspend", console_suspend_disable);

881 882 883 884 885 886 887
/**
 * suspend_console - suspend the console subsystem
 *
 * This disables printk() while we go into suspend states
 */
void suspend_console(void)
{
888 889
	if (!console_suspend_enabled)
		return;
890
	printk("Suspending console(s) (use no_console_suspend to debug)\n");
891 892
	acquire_console_sem();
	console_suspended = 1;
893
	up(&console_sem);
894 895 896 897
}

void resume_console(void)
{
898 899
	if (!console_suspend_enabled)
		return;
900
	down(&console_sem);
901 902 903 904
	console_suspended = 0;
	release_console_sem();
}

L
Linus Torvalds 已提交
905 906 907 908 909 910 911 912 913 914
/**
 * 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)
{
915
	BUG_ON(in_interrupt());
L
Linus Torvalds 已提交
916
	down(&console_sem);
917 918
	if (console_suspended)
		return;
L
Linus Torvalds 已提交
919 920 921 922 923 924 925 926 927
	console_locked = 1;
	console_may_schedule = 1;
}
EXPORT_SYMBOL(acquire_console_sem);

int try_acquire_console_sem(void)
{
	if (down_trylock(&console_sem))
		return -1;
928 929 930 931
	if (console_suspended) {
		up(&console_sem);
		return -1;
	}
L
Linus Torvalds 已提交
932 933 934 935 936 937 938 939 940 941 942
	console_locked = 1;
	console_may_schedule = 0;
	return 0;
}
EXPORT_SYMBOL(try_acquire_console_sem);

int is_console_locked(void)
{
	return console_locked;
}

P
Peter Zijlstra 已提交
943 944 945
static DEFINE_PER_CPU(int, printk_pending);

void printk_tick(void)
946
{
P
Peter Zijlstra 已提交
947 948
	if (__get_cpu_var(printk_pending)) {
		__get_cpu_var(printk_pending) = 0;
949
		wake_up_interruptible(&log_wait);
P
Peter Zijlstra 已提交
950 951 952 953 954 955 956 957 958 959 960
	}
}

int printk_needs_cpu(int cpu)
{
	return per_cpu(printk_pending, cpu);
}

void wake_up_klogd(void)
{
	if (waitqueue_active(&log_wait))
961
		__raw_get_cpu_var(printk_pending) = 1;
962 963
}

L
Linus Torvalds 已提交
964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980
/**
 * 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;
981 982
	unsigned _con_start, _log_end;
	unsigned wake_klogd = 0;
L
Linus Torvalds 已提交
983

984
	if (console_suspended) {
985
		up(&console_sem);
986 987
		return;
	}
988 989 990

	console_may_schedule = 0;

L
Linus Torvalds 已提交
991 992 993 994 995 996 997 998 999
	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(&logbuf_lock);
1000
		stop_critical_timings();	/* don't trace print latency */
L
Linus Torvalds 已提交
1001
		call_console_drivers(_con_start, _log_end);
1002
		start_critical_timings();
L
Linus Torvalds 已提交
1003 1004 1005 1006 1007
		local_irq_restore(flags);
	}
	console_locked = 0;
	up(&console_sem);
	spin_unlock_irqrestore(&logbuf_lock, flags);
1008 1009
	if (wake_klogd)
		wake_up_klogd();
L
Linus Torvalds 已提交
1010 1011 1012
}
EXPORT_SYMBOL(release_console_sem);

1013 1014
/**
 * console_conditional_schedule - yield the CPU if required
L
Linus Torvalds 已提交
1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103
 *
 * 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 __sched console_conditional_schedule(void)
{
	if (console_may_schedule)
		cond_resched();
}
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;

	/*
	 * console_unblank can no longer be called in interrupt context unless
	 * oops_in_progress is set to 1..
	 */
	if (oops_in_progress) {
		if (down_trylock(&console_sem) != 0)
			return;
	} else
		acquire_console_sem();

	console_locked = 1;
	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();
}

/*
 * Return the console tty driver structure and its associated index
 */
struct tty_driver *console_device(int *index)
{
	struct console *c;
	struct tty_driver *driver = NULL;

	acquire_console_sem();
	for (c = console_drivers; c != NULL; c = c->next) {
		if (!c->device)
			continue;
		driver = c->device(c, index);
		if (driver)
			break;
	}
	release_console_sem();
	return driver;
}

/*
 * Prevent further output on the passed console device so that (for example)
 * serial drivers can disable console output before suspending a port, and can
 * re-enable output afterwards.
 */
void console_stop(struct console *console)
{
	acquire_console_sem();
	console->flags &= ~CON_ENABLED;
	release_console_sem();
}
EXPORT_SYMBOL(console_stop);

void console_start(struct console *console)
{
	acquire_console_sem();
	console->flags |= CON_ENABLED;
	release_console_sem();
}
EXPORT_SYMBOL(console_start);

/*
 * 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.
 */
J
Jesper Juhl 已提交
1104
void register_console(struct console *console)
L
Linus Torvalds 已提交
1105
{
J
Jesper Juhl 已提交
1106
	int i;
L
Linus Torvalds 已提交
1107
	unsigned long flags;
1108
	struct console *bootconsole = NULL;
L
Linus Torvalds 已提交
1109

1110 1111 1112 1113 1114 1115 1116 1117
	if (console_drivers) {
		if (console->flags & CON_BOOT)
			return;
		if (console_drivers->flags & CON_BOOT)
			bootconsole = console_drivers;
	}

	if (preferred_console < 0 || bootconsole || !console_drivers)
L
Linus Torvalds 已提交
1118 1119
		preferred_console = selected_console;

1120 1121 1122
	if (console->early_setup)
		console->early_setup();

L
Linus Torvalds 已提交
1123 1124 1125 1126 1127 1128 1129 1130 1131 1132
	/*
	 *	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) {
1133 1134 1135 1136 1137
			console->flags |= CON_ENABLED;
			if (console->device) {
				console->flags |= CON_CONSDEV;
				preferred_console = 0;
			}
L
Linus Torvalds 已提交
1138 1139 1140 1141 1142 1143 1144
		}
	}

	/*
	 *	See if this console matches one we selected on
	 *	the command line.
	 */
J
Jesper Juhl 已提交
1145 1146
	for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
			i++) {
L
Linus Torvalds 已提交
1147 1148 1149 1150 1151 1152 1153
		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;
1154 1155 1156 1157 1158 1159 1160 1161 1162 1163
#ifdef CONFIG_A11Y_BRAILLE_CONSOLE
		if (console_cmdline[i].brl_options) {
			console->flags |= CON_BRL;
			braille_register_console(console,
					console_cmdline[i].index,
					console_cmdline[i].options,
					console_cmdline[i].brl_options);
			return;
		}
#endif
L
Linus Torvalds 已提交
1164 1165 1166 1167 1168
		if (console->setup &&
		    console->setup(console, console_cmdline[i].options) != 0)
			break;
		console->flags |= CON_ENABLED;
		console->index = console_cmdline[i].index;
1169
		if (i == selected_console) {
L
Linus Torvalds 已提交
1170
			console->flags |= CON_CONSDEV;
1171 1172
			preferred_console = selected_console;
		}
L
Linus Torvalds 已提交
1173 1174 1175 1176 1177 1178
		break;
	}

	if (!(console->flags & CON_ENABLED))
		return;

1179
	if (bootconsole && (console->flags & CON_CONSDEV)) {
1180 1181 1182 1183
		printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
		       bootconsole->name, bootconsole->index,
		       console->name, console->index);
		unregister_console(bootconsole);
L
Linus Torvalds 已提交
1184
		console->flags &= ~CON_PRINTBUFFER;
1185 1186 1187
	} else {
		printk(KERN_INFO "console [%s%d] enabled\n",
		       console->name, console->index);
L
Linus Torvalds 已提交
1188 1189 1190 1191 1192 1193 1194 1195 1196 1197
	}

	/*
	 *	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;
1198 1199
		if (console->next)
			console->next->flags &= ~CON_CONSDEV;
L
Linus Torvalds 已提交
1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216
	} else {
		console->next = console_drivers->next;
		console_drivers->next = console;
	}
	if (console->flags & CON_PRINTBUFFER) {
		/*
		 * release_console_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);

J
Jesper Juhl 已提交
1217
int unregister_console(struct console *console)
L
Linus Torvalds 已提交
1218
{
J
Jesper Juhl 已提交
1219
        struct console *a, *b;
L
Linus Torvalds 已提交
1220 1221
	int res = 1;

1222 1223 1224 1225 1226
#ifdef CONFIG_A11Y_BRAILLE_CONSOLE
	if (console->flags & CON_BRL)
		return braille_unregister_console(console);
#endif

L
Linus Torvalds 已提交
1227 1228 1229 1230
	acquire_console_sem();
	if (console_drivers == console) {
		console_drivers=console->next;
		res = 0;
1231
	} else if (console_drivers) {
L
Linus Torvalds 已提交
1232 1233 1234 1235 1236 1237
		for (a=console_drivers->next, b=console_drivers ;
		     a; b=a, a=b->next) {
			if (a == console) {
				b->next = a->next;
				res = 0;
				break;
J
Jesper Juhl 已提交
1238
			}
L
Linus Torvalds 已提交
1239 1240
		}
	}
J
Jesper Juhl 已提交
1241

1242
	/*
1243 1244
	 * If this isn't the last console and it has CON_CONSDEV set, we
	 * need to set it on the next preferred console.
L
Linus Torvalds 已提交
1245
	 */
1246
	if (console_drivers != NULL && console->flags & CON_CONSDEV)
1247
		console_drivers->flags |= CON_CONSDEV;
L
Linus Torvalds 已提交
1248 1249 1250 1251 1252

	release_console_sem();
	return res;
}
EXPORT_SYMBOL(unregister_console);
M
Matt Mackall 已提交
1253

1254 1255
static int __init disable_boot_consoles(void)
{
1256 1257 1258 1259 1260 1261
	if (console_drivers != NULL) {
		if (console_drivers->flags & CON_BOOT) {
			printk(KERN_INFO "turn off boot console %s%d\n",
				console_drivers->name, console_drivers->index);
			return unregister_console(console_drivers);
		}
1262 1263 1264 1265 1266
	}
	return 0;
}
late_initcall(disable_boot_consoles);

1267
#if defined CONFIG_PRINTK
D
Dave Young 已提交
1268

L
Linus Torvalds 已提交
1269 1270 1271
/*
 * printk rate limiting, lifted from the networking subsystem.
 *
1272 1273
 * This enforces a rate limit: not more than 10 kernel messages
 * every 5s to make a denial-of-service attack impossible.
L
Linus Torvalds 已提交
1274
 */
1275 1276
DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);

L
Linus Torvalds 已提交
1277 1278
int printk_ratelimit(void)
{
D
Dave Young 已提交
1279
	return __ratelimit(&printk_ratelimit_state);
L
Linus Torvalds 已提交
1280 1281
}
EXPORT_SYMBOL(printk_ratelimit);
1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301

/**
 * printk_timed_ratelimit - caller-controlled printk ratelimiting
 * @caller_jiffies: pointer to caller's state
 * @interval_msecs: minimum interval between prints
 *
 * printk_timed_ratelimit() returns true if more than @interval_msecs
 * milliseconds have elapsed since the last time printk_timed_ratelimit()
 * returned true.
 */
bool printk_timed_ratelimit(unsigned long *caller_jiffies,
			unsigned int interval_msecs)
{
	if (*caller_jiffies == 0 || time_after(jiffies, *caller_jiffies)) {
		*caller_jiffies = jiffies + msecs_to_jiffies(interval_msecs);
		return true;
	}
	return false;
}
EXPORT_SYMBOL(printk_timed_ratelimit);
1302
#endif