printk.c 34.6 KB
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/*
 *  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.
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 * Fixed SMP synchronization, 08/08/99, Manfred Spraul
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 *     manfred@colorfullife.com
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 * Rewrote bits to get rid of console_lock
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 *	01Mar01 Andrew Morton
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 */

#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>
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#include <linux/jiffies.h>
#include <linux/nmi.h>
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#include <linux/module.h>
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#include <linux/moduleparam.h>
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#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>
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#include <linux/kexec.h>
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#include <asm/uaccess.h>

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/*
 * for_each_console() allows you to iterate on each console
 */
#define for_each_console(con) \
	for (con = console_drivers; con != NULL; con = con->next)

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/*
 * Architectures can override it:
 */
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void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
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{
}

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#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 */
};

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static int saved_console_loglevel = -1;

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/*
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 * Low level drivers may need that to know if they can schedule in
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 * 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;
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EXPORT_SYMBOL_GPL(console_drivers);

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/*
 * 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
 */
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static int console_locked, console_suspended;
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/*
 * 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);

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#define LOG_BUF_MASK (log_buf_len-1)
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#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
 */
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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 */
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/*
 *	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   */
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#ifdef CONFIG_A11Y_BRAILLE_CONSOLE
	char	*brl_options;			/* Options for braille driver */
#endif
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};

#define MAX_CMDLINECONSOLES 8

static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
static int selected_console = -1;
static int preferred_console = -1;
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int console_set_on_cmdline;
EXPORT_SYMBOL(console_set_on_cmdline);
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/* Flag: console code may call schedule() */
static int console_may_schedule;

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#ifdef CONFIG_PRINTK

static char __log_buf[__LOG_BUF_LEN];
static char *log_buf = __log_buf;
static int log_buf_len = __LOG_BUF_LEN;
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static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
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#ifdef CONFIG_KEXEC
/*
 * This appends the listed symbols to /proc/vmcoreinfo
 *
 * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
 * obtain access to symbols that are otherwise very difficult to locate.  These
 * symbols are specifically used so that utilities can access and extract the
 * dmesg log from a vmcore file after a crash.
 */
void log_buf_kexec_setup(void)
{
	VMCOREINFO_SYMBOL(log_buf);
	VMCOREINFO_SYMBOL(log_end);
	VMCOREINFO_SYMBOL(log_buf_len);
	VMCOREINFO_SYMBOL(logged_chars);
}
#endif

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static int __init log_buf_len_setup(char *str)
{
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	unsigned size = memparse(str, &str);
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	unsigned long flags;

	if (size)
		size = roundup_pow_of_two(size);
	if (size > log_buf_len) {
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		unsigned start, dest_idx, offset;
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		char *new_log_buf;
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		new_log_buf = alloc_bootmem(size);
		if (!new_log_buf) {
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			printk(KERN_WARNING "log_buf_len: allocation failed\n");
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			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);

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		printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
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	}
out:
	return 1;
}

__setup("log_buf_len=", log_buf_len_setup);

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#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

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/*
 * 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
 */
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int do_syslog(int type, char __user *buf, int len)
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{
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	unsigned i, j, limit, count;
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	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;
		}
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		error = wait_event_interruptible(log_wait,
							(log_start - log_end));
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		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 */
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		do_clear = 1;
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		/* 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
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		 * printk() could overwrite the messages
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		 * we try to copy to user space. Therefore
		 * the messages are copied in reverse. <manfreds>
		 */
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		for (i = 0; i < count && !error; i++) {
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			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;
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		if (i != count) {
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			int offset = count-error;
			/* buffer overflow during copy, correct user buffer. */
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			for (i = 0; i < error; i++) {
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				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 */
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		if (saved_console_loglevel == -1)
			saved_console_loglevel = console_loglevel;
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		console_loglevel = minimum_console_loglevel;
		break;
	case 7:		/* Enable logging to console */
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		if (saved_console_loglevel != -1) {
			console_loglevel = saved_console_loglevel;
			saved_console_loglevel = -1;
		}
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		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;
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		/* Implicitly re-enable logging to console */
		saved_console_loglevel = -1;
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		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;
}

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SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
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{
	return do_syslog(type, buf, len);
}

/*
 * Call the console drivers on a range of log_buf
 */
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static void __call_console_drivers(unsigned start, unsigned end)
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{
	struct console *con;

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	for_each_console(con) {
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		if ((con->flags & CON_ENABLED) && con->write &&
				(cpu_online(smp_processor_id()) ||
				(con->flags & CON_ANYTIME)))
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			con->write(con, &LOG_BUF(start), end - start);
	}
}

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static int __read_mostly ignore_loglevel;

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

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	return 0;
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}

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early_param("ignore_loglevel", ignore_loglevel_setup);
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/*
 * Write out chars from start to end - 1 inclusive
 */
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static void _call_console_drivers(unsigned start,
				unsigned end, int msg_log_level)
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{
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	if ((msg_log_level < console_loglevel || ignore_loglevel) &&
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			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.
 */
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static void call_console_drivers(unsigned start, unsigned end)
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{
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	unsigned cur_index, start_print;
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	static int msg_level = -1;

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	BUG_ON(((int)(start - end)) > 0);
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	cur_index = start;
	start_print = start;
	while (cur_index != end) {
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		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) == '>') {
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			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);

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			cur_index++;
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			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) &&
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			!time_after(jiffies, oops_timestamp + 30 * HZ))
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		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
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module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
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/* Check if we have any console registered that can be called early in boot. */
static int have_callable_console(void)
{
	struct console *con;

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	for_each_console(con)
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		if (con->flags & CON_ANYTIME)
			return 1;

	return 0;
}

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/**
 * printk - print a kernel message
 * @fmt: format string
 *
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 * This is printk().  It can be called from any context.  We want it to work.
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 *
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 * 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.
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 *
 * See also:
 * printf(3)
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 *
 * See the vsnprintf() documentation for format string extensions over C99.
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 */
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asmlinkage int printk(const char *fmt, ...)
{
	va_list args;
	int r;

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

	return r;
}

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

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/*
 * 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;

633 634 635 636 637 638 639 640 641 642 643 644 645 646 647
	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;
		}
	}
648 649 650 651
	printk_cpu = UINT_MAX;
	spin_unlock(&logbuf_lock);
	return retval;
}
652 653 654
static const char recursion_bug_msg [] =
		KERN_CRIT "BUG: recent printk recursion!\n";
static int recursion_bug;
655
static int new_text_line = 1;
656
static char printk_buf[1024];
657

L
Linus Torvalds 已提交
658 659
asmlinkage int vprintk(const char *fmt, va_list args)
{
660
	int printed_len = 0;
661
	int current_log_level = default_message_loglevel;
662
	unsigned long flags;
663
	int this_cpu;
L
Linus Torvalds 已提交
664 665
	char *p;

R
Randy Dunlap 已提交
666 667
	boot_delay_msec();

668
	preempt_disable();
L
Linus Torvalds 已提交
669
	/* This stops the holder of console_sem just where we want him */
670
	raw_local_irq_save(flags);
671 672 673 674 675 676 677 678 679 680 681 682 683 684
	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) {
685
			recursion_bug = 1;
686 687 688 689 690
			goto out_restore_irqs;
		}
		zap_locks();
	}

691 692
	lockdep_off();
	spin_lock(&logbuf_lock);
693
	printk_cpu = this_cpu;
L
Linus Torvalds 已提交
694

695 696 697
	if (recursion_bug) {
		recursion_bug = 0;
		strcpy(printk_buf, recursion_bug_msg);
698
		printed_len = strlen(recursion_bug_msg);
699
	}
L
Linus Torvalds 已提交
700
	/* Emit the output into the temporary buffer */
701
	printed_len += vscnprintf(printk_buf + printed_len,
T
Tejun Heo 已提交
702
				  sizeof(printk_buf) - printed_len, fmt, args);
L
Linus Torvalds 已提交
703

704

705 706 707 708 709 710 711 712 713
	p = printk_buf;

	/* Do we have a loglevel in the string? */
	if (p[0] == '<') {
		unsigned char c = p[1];
		if (c && p[2] == '>') {
			switch (c) {
			case '0' ... '7': /* loglevel */
				current_log_level = c - '0';
714 715
			/* Fallthrough - make sure we're on a new line */
			case 'd': /* KERN_DEFAULT */
716 717 718 719 720 721 722 723 724 725 726 727
				if (!new_text_line) {
					emit_log_char('\n');
					new_text_line = 1;
				}
			/* Fallthrough - skip the loglevel */
			case 'c': /* KERN_CONT */
				p += 3;
				break;
			}
		}
	}

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728 729 730 731
	/*
	 * Copy the output into log_buf.  If the caller didn't provide
	 * appropriate log level tags, we insert them here
	 */
732
	for ( ; *p; p++) {
733 734 735 736 737 738 739 740
		if (new_text_line) {
			/* 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
741
			if (printk_time) {
742
				/* Follow the token with the time */
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743 744 745 746 747
				char tbuf[50], *tp;
				unsigned tlen;
				unsigned long long t;
				unsigned long nanosec_rem;

748
				t = cpu_clock(printk_cpu);
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749
				nanosec_rem = do_div(t, 1000000000);
750 751 752
				tlen = sprintf(tbuf, "[%5lu.%06lu] ",
						(unsigned long) t,
						nanosec_rem / 1000);
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				for (tp = tbuf; tp < tbuf + tlen; tp++)
					emit_log_char(*tp);
756
				printed_len += tlen;
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Linus Torvalds 已提交
757
			}
758

L
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759 760 761
			if (!*p)
				break;
		}
762

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763 764
		emit_log_char(*p);
		if (*p == '\n')
765
			new_text_line = 1;
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766 767
	}

768 769 770 771 772 773 774 775 776 777 778 779
	/*
	 * 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();
780

781
	lockdep_on();
782
out_restore_irqs:
783
	raw_local_irq_restore(flags);
784

785
	preempt_enable();
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Linus Torvalds 已提交
786 787 788 789 790
	return printed_len;
}
EXPORT_SYMBOL(printk);
EXPORT_SYMBOL(vprintk);

M
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791 792
#else

793
static void call_console_drivers(unsigned start, unsigned end)
J
Jesper Juhl 已提交
794 795
{
}
M
Matt Mackall 已提交
796 797 798

#endif

799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828
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;
}
829 830 831 832 833
/*
 * Set up a list of consoles.  Called from init/main.c
 */
static int __init console_setup(char *str)
{
Y
Yinghai Lu 已提交
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	char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
835
	char *s, *options, *brl_options = NULL;
836 837
	int idx;

838 839 840 841 842 843 844 845 846 847 848 849 850 851 852
#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

853 854 855 856
	/*
	 * Decode str into name, index, options.
	 */
	if (str[0] >= '0' && str[0] <= '9') {
Y
Yinghai Lu 已提交
857 858
		strcpy(buf, "ttyS");
		strncpy(buf + 4, str, sizeof(buf) - 5);
859
	} else {
Y
Yinghai Lu 已提交
860
		strncpy(buf, str, sizeof(buf) - 1);
861
	}
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Yinghai Lu 已提交
862
	buf[sizeof(buf) - 1] = 0;
863 864 865 866
	if ((options = strchr(str, ',')) != NULL)
		*(options++) = 0;
#ifdef __sparc__
	if (!strcmp(str, "ttya"))
Y
Yinghai Lu 已提交
867
		strcpy(buf, "ttyS0");
868
	if (!strcmp(str, "ttyb"))
Y
Yinghai Lu 已提交
869
		strcpy(buf, "ttyS1");
870
#endif
Y
Yinghai Lu 已提交
871
	for (s = buf; *s; s++)
872 873 874 875 876
		if ((*s >= '0' && *s <= '9') || *s == ',')
			break;
	idx = simple_strtoul(s, NULL, 10);
	*s = 0;

877
	__add_preferred_console(buf, idx, options, brl_options);
878
	console_set_on_cmdline = 1;
879 880 881 882
	return 1;
}
__setup("console=", console_setup);

883 884
/**
 * add_preferred_console - add a device to the list of preferred consoles.
885 886 887
 * @name: device name
 * @idx: device index
 * @options: options for this console
888 889 890 891 892 893 894 895
 *
 * 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.
 */
896
int add_preferred_console(char *name, int idx, char *options)
897
{
898
	return __add_preferred_console(name, idx, options, NULL);
899 900
}

901
int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
902 903 904 905 906 907 908 909
{
	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];
910
				strlcpy(c->name, name_new, sizeof(c->name));
911 912 913 914 915 916 917 918 919
				c->name[sizeof(c->name) - 1] = 0;
				c->options = options;
				c->index = idx_new;
				return i;
		}
	/* not found */
	return -1;
}

920 921 922 923 924 925 926 927 928 929
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);

930 931 932 933 934 935 936
/**
 * suspend_console - suspend the console subsystem
 *
 * This disables printk() while we go into suspend states
 */
void suspend_console(void)
{
937 938
	if (!console_suspend_enabled)
		return;
939
	printk("Suspending console(s) (use no_console_suspend to debug)\n");
940 941
	acquire_console_sem();
	console_suspended = 1;
942
	up(&console_sem);
943 944 945 946
}

void resume_console(void)
{
947 948
	if (!console_suspend_enabled)
		return;
949
	down(&console_sem);
950 951 952 953
	console_suspended = 0;
	release_console_sem();
}

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/**
 * 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)
{
964
	BUG_ON(in_interrupt());
L
Linus Torvalds 已提交
965
	down(&console_sem);
966 967
	if (console_suspended)
		return;
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	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;
977 978 979 980
	if (console_suspended) {
		up(&console_sem);
		return -1;
	}
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981 982 983 984 985 986 987 988 989 990 991
	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
992 993 994
static DEFINE_PER_CPU(int, printk_pending);

void printk_tick(void)
995
{
P
Peter Zijlstra 已提交
996 997
	if (__get_cpu_var(printk_pending)) {
		__get_cpu_var(printk_pending) = 0;
998
		wake_up_interruptible(&log_wait);
P
Peter Zijlstra 已提交
999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009
	}
}

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

void wake_up_klogd(void)
{
	if (waitqueue_active(&log_wait))
1010
		__raw_get_cpu_var(printk_pending) = 1;
1011 1012
}

L
Linus Torvalds 已提交
1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029
/**
 * 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;
1030 1031
	unsigned _con_start, _log_end;
	unsigned wake_klogd = 0;
L
Linus Torvalds 已提交
1032

1033
	if (console_suspended) {
1034
		up(&console_sem);
1035 1036
		return;
	}
1037 1038 1039

	console_may_schedule = 0;

L
Linus Torvalds 已提交
1040 1041 1042 1043 1044 1045 1046 1047 1048
	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);
1049
		stop_critical_timings();	/* don't trace print latency */
L
Linus Torvalds 已提交
1050
		call_console_drivers(_con_start, _log_end);
1051
		start_critical_timings();
L
Linus Torvalds 已提交
1052 1053 1054 1055 1056
		local_irq_restore(flags);
	}
	console_locked = 0;
	up(&console_sem);
	spin_unlock_irqrestore(&logbuf_lock, flags);
1057 1058
	if (wake_klogd)
		wake_up_klogd();
L
Linus Torvalds 已提交
1059 1060 1061
}
EXPORT_SYMBOL(release_console_sem);

1062 1063
/**
 * console_conditional_schedule - yield the CPU if required
L
Linus Torvalds 已提交
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
 *
 * 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_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;
1094
	for_each_console(c)
L
Linus Torvalds 已提交
1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108
		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();
1109
	for_each_console(c) {
L
Linus Torvalds 已提交
1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145
		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.
1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158
 *
 * This can happen pretty early during the boot process (because of
 * early_printk) - sometimes before setup_arch() completes - be careful
 * of what kernel features are used - they may not be initialised yet.
 *
 * There are two types of consoles - bootconsoles (early_printk) and
 * "real" consoles (everything which is not a bootconsole) which are
 * handled differently.
 *  - Any number of bootconsoles can be registered at any time.
 *  - As soon as a "real" console is registered, all bootconsoles
 *    will be unregistered automatically.
 *  - Once a "real" console is registered, any attempt to register a
 *    bootconsoles will be rejected
L
Linus Torvalds 已提交
1159
 */
1160
void register_console(struct console *newcon)
L
Linus Torvalds 已提交
1161
{
J
Jesper Juhl 已提交
1162
	int i;
L
Linus Torvalds 已提交
1163
	unsigned long flags;
1164
	struct console *bcon = NULL;
L
Linus Torvalds 已提交
1165

1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178
	/*
	 * before we register a new CON_BOOT console, make sure we don't
	 * already have a valid console
	 */
	if (console_drivers && newcon->flags & CON_BOOT) {
		/* find the last or real console */
		for_each_console(bcon) {
			if (!(bcon->flags & CON_BOOT)) {
				printk(KERN_INFO "Too late to register bootconsole %s%d\n",
					newcon->name, newcon->index);
				return;
			}
		}
1179 1180
	}

1181 1182 1183 1184
	if (console_drivers && console_drivers->flags & CON_BOOT)
		bcon = console_drivers;

	if (preferred_console < 0 || bcon || !console_drivers)
L
Linus Torvalds 已提交
1185 1186
		preferred_console = selected_console;

1187 1188
	if (newcon->early_setup)
		newcon->early_setup();
1189

L
Linus Torvalds 已提交
1190 1191 1192 1193 1194 1195
	/*
	 *	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) {
1196 1197 1198 1199 1200 1201 1202
		if (newcon->index < 0)
			newcon->index = 0;
		if (newcon->setup == NULL ||
		    newcon->setup(newcon, NULL) == 0) {
			newcon->flags |= CON_ENABLED;
			if (newcon->device) {
				newcon->flags |= CON_CONSDEV;
1203 1204
				preferred_console = 0;
			}
L
Linus Torvalds 已提交
1205 1206 1207 1208 1209 1210 1211
		}
	}

	/*
	 *	See if this console matches one we selected on
	 *	the command line.
	 */
J
Jesper Juhl 已提交
1212 1213
	for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
			i++) {
1214
		if (strcmp(console_cmdline[i].name, newcon->name) != 0)
L
Linus Torvalds 已提交
1215
			continue;
1216 1217
		if (newcon->index >= 0 &&
		    newcon->index != console_cmdline[i].index)
L
Linus Torvalds 已提交
1218
			continue;
1219 1220
		if (newcon->index < 0)
			newcon->index = console_cmdline[i].index;
1221 1222
#ifdef CONFIG_A11Y_BRAILLE_CONSOLE
		if (console_cmdline[i].brl_options) {
1223 1224
			newcon->flags |= CON_BRL;
			braille_register_console(newcon,
1225 1226 1227 1228 1229 1230
					console_cmdline[i].index,
					console_cmdline[i].options,
					console_cmdline[i].brl_options);
			return;
		}
#endif
1231 1232
		if (newcon->setup &&
		    newcon->setup(newcon, console_cmdline[i].options) != 0)
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			break;
1234 1235
		newcon->flags |= CON_ENABLED;
		newcon->index = console_cmdline[i].index;
1236
		if (i == selected_console) {
1237
			newcon->flags |= CON_CONSDEV;
1238 1239
			preferred_console = selected_console;
		}
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		break;
	}

1243
	if (!(newcon->flags & CON_ENABLED))
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		return;

1246 1247 1248 1249 1250 1251 1252
	/*
	 * If we have a bootconsole, and are switching to a real console,
	 * don't print everything out again, since when the boot console, and
	 * the real console are the same physical device, it's annoying to
	 * see the beginning boot messages twice
	 */
	if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
1253
		newcon->flags &= ~CON_PRINTBUFFER;
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	/*
	 *	Put this console in the list - keep the
	 *	preferred driver at the head of the list.
	 */
	acquire_console_sem();
1260 1261 1262 1263 1264
	if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
		newcon->next = console_drivers;
		console_drivers = newcon;
		if (newcon->next)
			newcon->next->flags &= ~CON_CONSDEV;
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	} else {
1266 1267
		newcon->next = console_drivers->next;
		console_drivers->next = newcon;
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1268
	}
1269
	if (newcon->flags & CON_PRINTBUFFER) {
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		/*
		 * 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();
1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300

	/*
	 * By unregistering the bootconsoles after we enable the real console
	 * we get the "console xxx enabled" message on all the consoles -
	 * boot consoles, real consoles, etc - this is to ensure that end
	 * users know there might be something in the kernel's log buffer that
	 * went to the bootconsole (that they do not see on the real console)
	 */
	if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) {
		/* we need to iterate through twice, to make sure we print
		 * everything out, before we unregister the console(s)
		 */
		printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
			newcon->name, newcon->index);
		for_each_console(bcon)
			if (bcon->flags & CON_BOOT)
				unregister_console(bcon);
	} else {
		printk(KERN_INFO "%sconsole [%s%d] enabled\n",
			(newcon->flags & CON_BOOT) ? "boot" : "" ,
			newcon->name, newcon->index);
	}
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}
EXPORT_SYMBOL(register_console);

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int unregister_console(struct console *console)
L
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{
J
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1306
        struct console *a, *b;
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	int res = 1;

1309 1310 1311 1312 1313
#ifdef CONFIG_A11Y_BRAILLE_CONSOLE
	if (console->flags & CON_BRL)
		return braille_unregister_console(console);
#endif

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	acquire_console_sem();
	if (console_drivers == console) {
		console_drivers=console->next;
		res = 0;
1318
	} else if (console_drivers) {
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		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
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1325
			}
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1326 1327
		}
	}
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1328

1329
	/*
1330 1331
	 * If this isn't the last console and it has CON_CONSDEV set, we
	 * need to set it on the next preferred console.
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1332
	 */
1333
	if (console_drivers != NULL && console->flags & CON_CONSDEV)
1334
		console_drivers->flags |= CON_CONSDEV;
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	release_console_sem();
	return res;
}
EXPORT_SYMBOL(unregister_console);
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1341 1342
static int __init disable_boot_consoles(void)
{
1343 1344 1345 1346
	struct console *con;

	for_each_console(con) {
		if (con->flags & CON_BOOT) {
1347
			printk(KERN_INFO "turn off boot console %s%d\n",
1348
				con->name, con->index);
1349
			unregister_console(con);
1350
		}
1351 1352 1353 1354 1355
	}
	return 0;
}
late_initcall(disable_boot_consoles);

1356
#if defined CONFIG_PRINTK
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1357

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/*
 * printk rate limiting, lifted from the networking subsystem.
 *
1361 1362
 * This enforces a rate limit: not more than 10 kernel messages
 * every 5s to make a denial-of-service attack impossible.
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1363
 */
1364 1365
DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);

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int printk_ratelimit(void)
{
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	return __ratelimit(&printk_ratelimit_state);
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}
EXPORT_SYMBOL(printk_ratelimit);
1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383

/**
 * 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)
{
1384 1385 1386 1387 1388
	if (*caller_jiffies == 0
			|| !time_in_range(jiffies, *caller_jiffies,
					*caller_jiffies
					+ msecs_to_jiffies(interval_msecs))) {
		*caller_jiffies = jiffies;
1389 1390 1391 1392 1393
		return true;
	}
	return false;
}
EXPORT_SYMBOL(printk_timed_ratelimit);
1394
#endif