printk.c 41.9 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 <linux/kdb.h>
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#include <linux/ratelimit.h>
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#include <linux/kmsg_dump.h>
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#include <linux/syslog.h>
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#include <linux/cpu.h>
#include <linux/notifier.h>
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#include <linux/rculist.h>
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#include <asm/uaccess.h>

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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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 * 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.
 */
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static DEFINE_SEMAPHORE(console_sem);
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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
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 * console_unlock();.
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 */
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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/*
 * If exclusive_console is non-NULL then only this console is to be printed to.
 */
static struct console *exclusive_console;

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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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static int saved_console_loglevel = -1;
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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

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static int boot_delay; /* msecs delay after each printk during bootup */
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static unsigned long long loops_per_msec;	/* based on boot_delay */
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static int __init boot_delay_setup(char *str)
{
	unsigned long lpj;

	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;

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	pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
		"HZ: %d, loops_per_msec: %llu\n",
		boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
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	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;

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	k = (unsigned long long)loops_per_msec * boot_delay;
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	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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#ifdef CONFIG_SECURITY_DMESG_RESTRICT
int dmesg_restrict = 1;
#else
int dmesg_restrict;
#endif

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static int syslog_action_restricted(int type)
{
	if (dmesg_restrict)
		return 1;
	/* Unless restricted, we allow "read all" and "get buffer size" for everybody */
	return type != SYSLOG_ACTION_READ_ALL && type != SYSLOG_ACTION_SIZE_BUFFER;
}

static int check_syslog_permissions(int type, bool from_file)
{
	/*
	 * If this is from /proc/kmsg and we've already opened it, then we've
	 * already done the capabilities checks at open time.
	 */
	if (from_file && type != SYSLOG_ACTION_OPEN)
		return 0;

	if (syslog_action_restricted(type)) {
		if (capable(CAP_SYSLOG))
			return 0;
		/* For historical reasons, accept CAP_SYS_ADMIN too, with a warning */
		if (capable(CAP_SYS_ADMIN)) {
			WARN_ONCE(1, "Attempt to access syslog with CAP_SYS_ADMIN "
				 "but no CAP_SYSLOG (deprecated).\n");
			return 0;
		}
		return -EPERM;
	}
	return 0;
}

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int do_syslog(int type, char __user *buf, int len, bool from_file)
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{
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	unsigned i, j, limit, count;
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	int do_clear = 0;
	char c;
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	int error;
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	error = check_syslog_permissions(type, from_file);
	if (error)
		goto out;
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	error = security_syslog(type);
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	if (error)
		return error;

	switch (type) {
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	case SYSLOG_ACTION_CLOSE:	/* Close log */
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		break;
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	case SYSLOG_ACTION_OPEN:	/* Open log */
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		break;
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	case SYSLOG_ACTION_READ:	/* Read from log */
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		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;
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	/* Read/clear last kernel messages */
	case SYSLOG_ACTION_READ_CLEAR:
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		do_clear = 1;
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		/* FALL THRU */
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	/* Read last kernel messages */
	case SYSLOG_ACTION_READ_ALL:
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		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;
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	/* Clear ring buffer */
	case SYSLOG_ACTION_CLEAR:
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		logged_chars = 0;
		break;
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	/* Disable logging to console */
	case SYSLOG_ACTION_CONSOLE_OFF:
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		if (saved_console_loglevel == -1)
			saved_console_loglevel = console_loglevel;
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		console_loglevel = minimum_console_loglevel;
		break;
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	/* Enable logging to console */
	case SYSLOG_ACTION_CONSOLE_ON:
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		if (saved_console_loglevel != -1) {
			console_loglevel = saved_console_loglevel;
			saved_console_loglevel = -1;
		}
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		break;
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	/* Set level of messages printed to console */
	case SYSLOG_ACTION_CONSOLE_LEVEL:
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		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;
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	/* Number of chars in the log buffer */
	case SYSLOG_ACTION_SIZE_UNREAD:
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		error = log_end - log_start;
		break;
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	/* Size of the log buffer */
	case SYSLOG_ACTION_SIZE_BUFFER:
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		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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{
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	return do_syslog(type, buf, len, SYSLOG_FROM_CALL);
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}

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#ifdef	CONFIG_KGDB_KDB
/* kdb dmesg command needs access to the syslog buffer.  do_syslog()
 * uses locks so it cannot be used during debugging.  Just tell kdb
 * where the start and end of the physical and logical logs are.  This
 * is equivalent to do_syslog(3).
 */
void kdb_syslog_data(char *syslog_data[4])
{
	syslog_data[0] = log_buf;
	syslog_data[1] = log_buf + log_buf_len;
	syslog_data[2] = log_buf + log_end -
		(logged_chars < log_buf_len ? logged_chars : log_buf_len);
	syslog_data[3] = log_buf + log_end;
}
#endif	/* CONFIG_KGDB_KDB */

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/*
 * 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 (exclusive_console && con != exclusive_console)
			continue;
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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);
		}
	}
}

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/*
 * Parse the syslog header <[0-9]*>. The decimal value represents 32bit, the
 * lower 3 bit are the log level, the rest are the log facility. In case
 * userspace passes usual userspace syslog messages to /dev/kmsg or
 * /dev/ttyprintk, the log prefix might contain the facility. Printk needs
 * to extract the correct log level for in-kernel processing, and not mangle
 * the original value.
 *
 * If a prefix is found, the length of the prefix is returned. If 'level' is
 * passed, it will be filled in with the log level without a possible facility
 * value. If 'special' is passed, the special printk prefix chars are accepted
 * and returned. If no valid header is found, 0 is returned and the passed
 * variables are not touched.
 */
static size_t log_prefix(const char *p, unsigned int *level, char *special)
{
	unsigned int lev = 0;
	char sp = '\0';
	size_t len;

	if (p[0] != '<' || !p[1])
		return 0;
	if (p[2] == '>') {
		/* usual single digit level number or special char */
		switch (p[1]) {
		case '0' ... '7':
			lev = p[1] - '0';
			break;
		case 'c': /* KERN_CONT */
		case 'd': /* KERN_DEFAULT */
			sp = p[1];
			break;
		default:
			return 0;
		}
		len = 3;
	} else {
		/* multi digit including the level and facility number */
		char *endp = NULL;

		if (p[1] < '0' && p[1] > '9')
			return 0;

		lev = (simple_strtoul(&p[1], &endp, 10) & 7);
		if (endp == NULL || endp[0] != '>')
			return 0;
		len = (endp + 1) - p;
	}

	/* do not accept special char if not asked for */
	if (sp && !special)
		return 0;

	if (special) {
		*special = sp;
		/* return special char, do not touch level */
		if (sp)
			return len;
	}

	if (level)
		*level = lev;
	return len;
}

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/*
 * Call the console drivers, asking them to write out
 * log_buf[start] to log_buf[end - 1].
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 * The console_lock must be held.
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 */
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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;

599
	BUG_ON(((int)(start - end)) > 0);
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	cur_index = start;
	start_print = start;
	while (cur_index != end) {
604 605 606
		if (msg_level < 0 && ((end - cur_index) > 2)) {
			/* strip log prefix */
			cur_index += log_prefix(&LOG_BUF(cur_index), &msg_level, NULL);
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			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) &&
J
Jesper Juhl 已提交
655
			!time_after(jiffies, oops_timestamp + 30 * HZ))
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656 657 658 659 660 661 662
		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 */
663
	sema_init(&console_sem, 1);
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664 665 666 667 668 669 670
}

#if defined(CONFIG_PRINTK_TIME)
static int printk_time = 1;
#else
static int printk_time = 0;
#endif
671
module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
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673 674 675 676 677
/* Check if we have any console registered that can be called early in boot. */
static int have_callable_console(void)
{
	struct console *con;

678
	for_each_console(con)
679 680 681 682 683 684
		if (con->flags & CON_ANYTIME)
			return 1;

	return 0;
}

685 686 687 688
/**
 * printk - print a kernel message
 * @fmt: format string
 *
689
 * This is printk().  It can be called from any context.  We want it to work.
J
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 *
691
 * We try to grab the console_lock.  If we succeed, it's easy - we log the output and
L
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 * 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
694 695
 * notice the new output in console_unlock(); and will send it to the
 * consoles before releasing the lock.
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 *
 * 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.
700 701 702
 *
 * See also:
 * printf(3)
703 704
 *
 * 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;

712 713 714 715 716 717 718 719
#ifdef CONFIG_KGDB_KDB
	if (unlikely(kdb_trap_printk)) {
		va_start(args, fmt);
		r = vkdb_printf(fmt, args);
		va_end(args);
		return r;
	}
#endif
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	va_start(args, fmt);
	r = vprintk(fmt, args);
	va_end(args);

	return r;
}

727 728 729
/* cpu currently holding logbuf_lock */
static volatile unsigned int printk_cpu = UINT_MAX;

730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745
/*
 * 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
746
 * console_lock held, and 'console_locked' set) if it
747 748 749 750 751 752
 * 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.
 */
753
static int console_trylock_for_printk(unsigned int cpu)
N
Namhyung Kim 已提交
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	__releases(&logbuf_lock)
755 756 757
{
	int retval = 0;

758
	if (console_trylock()) {
759 760 761 762 763 764 765 766 767 768 769 770 771 772
		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;
		}
	}
773 774 775 776
	printk_cpu = UINT_MAX;
	spin_unlock(&logbuf_lock);
	return retval;
}
777 778 779
static const char recursion_bug_msg [] =
		KERN_CRIT "BUG: recent printk recursion!\n";
static int recursion_bug;
780
static int new_text_line = 1;
781
static char printk_buf[1024];
782

783 784 785 786 787 788 789 790 791 792 793 794 795 796
int printk_delay_msec __read_mostly;

static inline void printk_delay(void)
{
	if (unlikely(printk_delay_msec)) {
		int m = printk_delay_msec;

		while (m--) {
			mdelay(1);
			touch_nmi_watchdog();
		}
	}
}

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asmlinkage int vprintk(const char *fmt, va_list args)
{
799
	int printed_len = 0;
800
	int current_log_level = default_message_loglevel;
801
	unsigned long flags;
802
	int this_cpu;
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	char *p;
804 805
	size_t plen;
	char special;
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806

R
Randy Dunlap 已提交
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	boot_delay_msec();
808
	printk_delay();
R
Randy Dunlap 已提交
809

810
	preempt_disable();
L
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811
	/* This stops the holder of console_sem just where we want him */
812
	raw_local_irq_save(flags);
813 814 815 816 817 818 819 820 821 822 823 824 825 826
	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) {
827
			recursion_bug = 1;
828 829 830 831 832
			goto out_restore_irqs;
		}
		zap_locks();
	}

833 834
	lockdep_off();
	spin_lock(&logbuf_lock);
835
	printk_cpu = this_cpu;
L
Linus Torvalds 已提交
836

837 838 839
	if (recursion_bug) {
		recursion_bug = 0;
		strcpy(printk_buf, recursion_bug_msg);
840
		printed_len = strlen(recursion_bug_msg);
841
	}
L
Linus Torvalds 已提交
842
	/* Emit the output into the temporary buffer */
843
	printed_len += vscnprintf(printk_buf + printed_len,
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Tejun Heo 已提交
844
				  sizeof(printk_buf) - printed_len, fmt, args);
L
Linus Torvalds 已提交
845

846 847
	p = printk_buf;

848 849 850 851 852 853 854 855 856 857 858 859 860 861 862
	/* Read log level and handle special printk prefix */
	plen = log_prefix(p, &current_log_level, &special);
	if (plen) {
		p += plen;

		switch (special) {
		case 'c': /* Strip <c> KERN_CONT, continue line */
			plen = 0;
			break;
		case 'd': /* Strip <d> KERN_DEFAULT, start new line */
			plen = 0;
		default:
			if (!new_text_line) {
				emit_log_char('\n');
				new_text_line = 1;
863 864 865 866
			}
		}
	}

L
Linus Torvalds 已提交
867
	/*
868 869
	 * Copy the output into log_buf. If the caller didn't provide
	 * the appropriate log prefix, we insert them here
L
Linus Torvalds 已提交
870
	 */
871
	for (; *p; p++) {
872 873 874
		if (new_text_line) {
			new_text_line = 0;

875 876 877 878 879 880 881 882 883 884 885 886 887 888 889
			if (plen) {
				/* Copy original log prefix */
				int i;

				for (i = 0; i < plen; i++)
					emit_log_char(printk_buf[i]);
				printed_len += plen;
			} else {
				/* Add log prefix */
				emit_log_char('<');
				emit_log_char(current_log_level + '0');
				emit_log_char('>');
				printed_len += 3;
			}

L
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890
			if (printk_time) {
891
				/* Add the current time stamp */
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892 893 894 895 896
				char tbuf[50], *tp;
				unsigned tlen;
				unsigned long long t;
				unsigned long nanosec_rem;

897
				t = cpu_clock(printk_cpu);
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				nanosec_rem = do_div(t, 1000000000);
899 900 901
				tlen = sprintf(tbuf, "[%5lu.%06lu] ",
						(unsigned long) t,
						nanosec_rem / 1000);
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902 903 904

				for (tp = tbuf; tp < tbuf + tlen; tp++)
					emit_log_char(*tp);
905
				printed_len += tlen;
L
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906
			}
907

L
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908 909 910
			if (!*p)
				break;
		}
911

L
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912 913
		emit_log_char(*p);
		if (*p == '\n')
914
			new_text_line = 1;
L
Linus Torvalds 已提交
915 916
	}

917 918 919 920 921 922
	/*
	 * 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). 
	 *
923
	 * The console_trylock_for_printk() function
924 925 926
	 * will release 'logbuf_lock' regardless of whether it
	 * actually gets the semaphore or not.
	 */
927 928
	if (console_trylock_for_printk(this_cpu))
		console_unlock();
929

930
	lockdep_on();
931
out_restore_irqs:
932
	raw_local_irq_restore(flags);
933

934
	preempt_enable();
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935 936 937 938 939
	return printed_len;
}
EXPORT_SYMBOL(printk);
EXPORT_SYMBOL(vprintk);

M
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940 941
#else

942
static void call_console_drivers(unsigned start, unsigned end)
J
Jesper Juhl 已提交
943 944
{
}
M
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945 946 947

#endif

948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977
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;
}
978 979 980 981 982
/*
 * Set up a list of consoles.  Called from init/main.c
 */
static int __init console_setup(char *str)
{
Y
Yinghai Lu 已提交
983
	char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
984
	char *s, *options, *brl_options = NULL;
985 986
	int idx;

987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001
#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

1002 1003 1004 1005
	/*
	 * Decode str into name, index, options.
	 */
	if (str[0] >= '0' && str[0] <= '9') {
Y
Yinghai Lu 已提交
1006 1007
		strcpy(buf, "ttyS");
		strncpy(buf + 4, str, sizeof(buf) - 5);
1008
	} else {
Y
Yinghai Lu 已提交
1009
		strncpy(buf, str, sizeof(buf) - 1);
1010
	}
Y
Yinghai Lu 已提交
1011
	buf[sizeof(buf) - 1] = 0;
1012 1013 1014 1015
	if ((options = strchr(str, ',')) != NULL)
		*(options++) = 0;
#ifdef __sparc__
	if (!strcmp(str, "ttya"))
Y
Yinghai Lu 已提交
1016
		strcpy(buf, "ttyS0");
1017
	if (!strcmp(str, "ttyb"))
Y
Yinghai Lu 已提交
1018
		strcpy(buf, "ttyS1");
1019
#endif
Y
Yinghai Lu 已提交
1020
	for (s = buf; *s; s++)
1021 1022 1023 1024 1025
		if ((*s >= '0' && *s <= '9') || *s == ',')
			break;
	idx = simple_strtoul(s, NULL, 10);
	*s = 0;

1026
	__add_preferred_console(buf, idx, options, brl_options);
1027
	console_set_on_cmdline = 1;
1028 1029 1030 1031
	return 1;
}
__setup("console=", console_setup);

1032 1033
/**
 * add_preferred_console - add a device to the list of preferred consoles.
1034 1035 1036
 * @name: device name
 * @idx: device index
 * @options: options for this console
1037 1038 1039 1040 1041 1042 1043 1044
 *
 * 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.
 */
1045
int add_preferred_console(char *name, int idx, char *options)
1046
{
1047
	return __add_preferred_console(name, idx, options, NULL);
1048 1049
}

1050
int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
1051 1052 1053 1054 1055 1056 1057 1058
{
	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];
1059
				strlcpy(c->name, name_new, sizeof(c->name));
1060 1061 1062 1063 1064 1065 1066 1067 1068
				c->name[sizeof(c->name) - 1] = 0;
				c->options = options;
				c->index = idx_new;
				return i;
		}
	/* not found */
	return -1;
}

1069 1070 1071 1072 1073 1074 1075 1076 1077 1078
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);

1079 1080 1081 1082 1083 1084 1085
/**
 * suspend_console - suspend the console subsystem
 *
 * This disables printk() while we go into suspend states
 */
void suspend_console(void)
{
1086 1087
	if (!console_suspend_enabled)
		return;
1088
	printk("Suspending console(s) (use no_console_suspend to debug)\n");
1089
	console_lock();
1090
	console_suspended = 1;
1091
	up(&console_sem);
1092 1093 1094 1095
}

void resume_console(void)
{
1096 1097
	if (!console_suspend_enabled)
		return;
1098
	down(&console_sem);
1099
	console_suspended = 0;
1100
	console_unlock();
1101 1102
}

1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122
/**
 * console_cpu_notify - print deferred console messages after CPU hotplug
 * @self: notifier struct
 * @action: CPU hotplug event
 * @hcpu: unused
 *
 * If printk() is called from a CPU that is not online yet, the messages
 * will be spooled but will not show up on the console.  This function is
 * called when a new CPU comes online (or fails to come up), and ensures
 * that any such output gets printed.
 */
static int __cpuinit console_cpu_notify(struct notifier_block *self,
	unsigned long action, void *hcpu)
{
	switch (action) {
	case CPU_ONLINE:
	case CPU_DEAD:
	case CPU_DYING:
	case CPU_DOWN_FAILED:
	case CPU_UP_CANCELED:
1123 1124
		console_lock();
		console_unlock();
1125 1126 1127 1128
	}
	return NOTIFY_OK;
}

L
Linus Torvalds 已提交
1129
/**
1130
 * console_lock - lock the console system for exclusive use.
L
Linus Torvalds 已提交
1131
 *
1132
 * Acquires a lock which guarantees that the caller has
L
Linus Torvalds 已提交
1133 1134 1135 1136
 * exclusive access to the console system and the console_drivers list.
 *
 * Can sleep, returns nothing.
 */
1137
void console_lock(void)
L
Linus Torvalds 已提交
1138
{
1139
	BUG_ON(in_interrupt());
L
Linus Torvalds 已提交
1140
	down(&console_sem);
1141 1142
	if (console_suspended)
		return;
L
Linus Torvalds 已提交
1143 1144 1145
	console_locked = 1;
	console_may_schedule = 1;
}
1146
EXPORT_SYMBOL(console_lock);
L
Linus Torvalds 已提交
1147

1148 1149 1150 1151 1152 1153 1154 1155 1156
/**
 * console_trylock - try to lock the console system for exclusive use.
 *
 * Tried to acquire a lock which guarantees that the caller has
 * exclusive access to the console system and the console_drivers list.
 *
 * returns 1 on success, and 0 on failure to acquire the lock.
 */
int console_trylock(void)
L
Linus Torvalds 已提交
1157 1158
{
	if (down_trylock(&console_sem))
1159
		return 0;
1160 1161
	if (console_suspended) {
		up(&console_sem);
1162
		return 0;
1163
	}
L
Linus Torvalds 已提交
1164 1165
	console_locked = 1;
	console_may_schedule = 0;
1166
	return 1;
L
Linus Torvalds 已提交
1167
}
1168
EXPORT_SYMBOL(console_trylock);
L
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1169 1170 1171 1172 1173 1174

int is_console_locked(void)
{
	return console_locked;
}

P
Peter Zijlstra 已提交
1175 1176 1177
static DEFINE_PER_CPU(int, printk_pending);

void printk_tick(void)
1178
{
1179 1180
	if (__this_cpu_read(printk_pending)) {
		__this_cpu_write(printk_pending, 0);
1181
		wake_up_interruptible(&log_wait);
P
Peter Zijlstra 已提交
1182 1183 1184 1185 1186
	}
}

int printk_needs_cpu(int cpu)
{
1187
	if (cpu_is_offline(cpu))
1188
		printk_tick();
1189
	return __this_cpu_read(printk_pending);
P
Peter Zijlstra 已提交
1190 1191 1192 1193 1194
}

void wake_up_klogd(void)
{
	if (waitqueue_active(&log_wait))
1195
		this_cpu_write(printk_pending, 1);
1196 1197
}

L
Linus Torvalds 已提交
1198
/**
1199
 * console_unlock - unlock the console system
L
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1200
 *
1201
 * Releases the console_lock which the caller holds on the console system
L
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1202 1203
 * and the console driver list.
 *
1204 1205 1206
 * While the console_lock was held, console output may have been buffered
 * by printk().  If this is the case, console_unlock(); emits
 * the output prior to releasing the lock.
L
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1207 1208 1209
 *
 * If there is output waiting for klogd, we wake it up.
 *
1210
 * console_unlock(); may be called from any context.
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1211
 */
1212
void console_unlock(void)
L
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1213 1214
{
	unsigned long flags;
1215 1216
	unsigned _con_start, _log_end;
	unsigned wake_klogd = 0;
L
Linus Torvalds 已提交
1217

1218
	if (console_suspended) {
1219
		up(&console_sem);
1220 1221
		return;
	}
1222 1223 1224

	console_may_schedule = 0;

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1225 1226 1227 1228 1229 1230 1231 1232 1233
	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);
1234
		stop_critical_timings();	/* don't trace print latency */
L
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1235
		call_console_drivers(_con_start, _log_end);
1236
		start_critical_timings();
L
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1237 1238 1239
		local_irq_restore(flags);
	}
	console_locked = 0;
1240 1241 1242 1243 1244

	/* Release the exclusive_console once it is used */
	if (unlikely(exclusive_console))
		exclusive_console = NULL;

L
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1245 1246
	up(&console_sem);
	spin_unlock_irqrestore(&logbuf_lock, flags);
1247 1248
	if (wake_klogd)
		wake_up_klogd();
L
Linus Torvalds 已提交
1249
}
1250
EXPORT_SYMBOL(console_unlock);
L
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1251

1252 1253
/**
 * console_conditional_schedule - yield the CPU if required
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1254 1255 1256 1257 1258
 *
 * If the console code is currently allowed to sleep, and
 * if this CPU should yield the CPU to another task, do
 * so here.
 *
1259
 * Must be called within console_lock();.
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 */
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
1280
		console_lock();
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1281 1282 1283

	console_locked = 1;
	console_may_schedule = 0;
1284
	for_each_console(c)
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1285 1286
		if ((c->flags & CON_ENABLED) && c->unblank)
			c->unblank();
1287
	console_unlock();
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1288 1289 1290 1291 1292 1293 1294 1295 1296 1297
}

/*
 * 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;

1298
	console_lock();
1299
	for_each_console(c) {
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1300 1301 1302 1303 1304 1305
		if (!c->device)
			continue;
		driver = c->device(c, index);
		if (driver)
			break;
	}
1306
	console_unlock();
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1307 1308 1309 1310 1311 1312 1313 1314 1315 1316
	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)
{
1317
	console_lock();
L
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1318
	console->flags &= ~CON_ENABLED;
1319
	console_unlock();
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1320 1321 1322 1323 1324
}
EXPORT_SYMBOL(console_stop);

void console_start(struct console *console)
{
1325
	console_lock();
L
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1326
	console->flags |= CON_ENABLED;
1327
	console_unlock();
L
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1328 1329 1330
}
EXPORT_SYMBOL(console_start);

1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342
static int __read_mostly keep_bootcon;

static int __init keep_bootcon_setup(char *str)
{
	keep_bootcon = 1;
	printk(KERN_INFO "debug: skip boot console de-registration.\n");

	return 0;
}

early_param("keep_bootcon", keep_bootcon_setup);

L
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1343 1344 1345 1346 1347
/*
 * 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.
1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360
 *
 * 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
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1361
 */
1362
void register_console(struct console *newcon)
L
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1363
{
J
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1364
	int i;
L
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1365
	unsigned long flags;
1366
	struct console *bcon = NULL;
L
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1367

1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380
	/*
	 * 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;
			}
		}
1381 1382
	}

1383 1384 1385 1386
	if (console_drivers && console_drivers->flags & CON_BOOT)
		bcon = console_drivers;

	if (preferred_console < 0 || bcon || !console_drivers)
L
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1387 1388
		preferred_console = selected_console;

1389 1390
	if (newcon->early_setup)
		newcon->early_setup();
1391

L
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1392 1393 1394 1395 1396 1397
	/*
	 *	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) {
1398 1399 1400 1401 1402 1403 1404
		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;
1405 1406
				preferred_console = 0;
			}
L
Linus Torvalds 已提交
1407 1408 1409 1410 1411 1412 1413
		}
	}

	/*
	 *	See if this console matches one we selected on
	 *	the command line.
	 */
J
Jesper Juhl 已提交
1414 1415
	for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
			i++) {
1416
		if (strcmp(console_cmdline[i].name, newcon->name) != 0)
L
Linus Torvalds 已提交
1417
			continue;
1418 1419
		if (newcon->index >= 0 &&
		    newcon->index != console_cmdline[i].index)
L
Linus Torvalds 已提交
1420
			continue;
1421 1422
		if (newcon->index < 0)
			newcon->index = console_cmdline[i].index;
1423 1424
#ifdef CONFIG_A11Y_BRAILLE_CONSOLE
		if (console_cmdline[i].brl_options) {
1425 1426
			newcon->flags |= CON_BRL;
			braille_register_console(newcon,
1427 1428 1429 1430 1431 1432
					console_cmdline[i].index,
					console_cmdline[i].options,
					console_cmdline[i].brl_options);
			return;
		}
#endif
1433 1434
		if (newcon->setup &&
		    newcon->setup(newcon, console_cmdline[i].options) != 0)
L
Linus Torvalds 已提交
1435
			break;
1436 1437
		newcon->flags |= CON_ENABLED;
		newcon->index = console_cmdline[i].index;
1438
		if (i == selected_console) {
1439
			newcon->flags |= CON_CONSDEV;
1440 1441
			preferred_console = selected_console;
		}
L
Linus Torvalds 已提交
1442 1443 1444
		break;
	}

1445
	if (!(newcon->flags & CON_ENABLED))
L
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1446 1447
		return;

1448 1449 1450 1451 1452 1453 1454
	/*
	 * 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))
1455
		newcon->flags &= ~CON_PRINTBUFFER;
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1456 1457 1458 1459 1460

	/*
	 *	Put this console in the list - keep the
	 *	preferred driver at the head of the list.
	 */
1461
	console_lock();
1462 1463 1464 1465 1466
	if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
		newcon->next = console_drivers;
		console_drivers = newcon;
		if (newcon->next)
			newcon->next->flags &= ~CON_CONSDEV;
L
Linus Torvalds 已提交
1467
	} else {
1468 1469
		newcon->next = console_drivers->next;
		console_drivers->next = newcon;
L
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1470
	}
1471
	if (newcon->flags & CON_PRINTBUFFER) {
L
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1472
		/*
1473
		 * console_unlock(); will print out the buffered messages
L
Linus Torvalds 已提交
1474 1475 1476 1477 1478
		 * for us.
		 */
		spin_lock_irqsave(&logbuf_lock, flags);
		con_start = log_start;
		spin_unlock_irqrestore(&logbuf_lock, flags);
1479 1480 1481 1482 1483 1484
		/*
		 * We're about to replay the log buffer.  Only do this to the
		 * just-registered console to avoid excessive message spam to
		 * the already-registered consoles.
		 */
		exclusive_console = newcon;
L
Linus Torvalds 已提交
1485
	}
1486
	console_unlock();
1487
	console_sysfs_notify();
1488 1489 1490 1491 1492 1493 1494 1495

	/*
	 * 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)
	 */
1496 1497 1498
	if (bcon &&
	    ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
	    !keep_bootcon) {
1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511
		/* 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);
	}
L
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1512 1513 1514
}
EXPORT_SYMBOL(register_console);

J
Jesper Juhl 已提交
1515
int unregister_console(struct console *console)
L
Linus Torvalds 已提交
1516
{
J
Jesper Juhl 已提交
1517
        struct console *a, *b;
L
Linus Torvalds 已提交
1518 1519
	int res = 1;

1520 1521 1522 1523 1524
#ifdef CONFIG_A11Y_BRAILLE_CONSOLE
	if (console->flags & CON_BRL)
		return braille_unregister_console(console);
#endif

1525
	console_lock();
L
Linus Torvalds 已提交
1526 1527 1528
	if (console_drivers == console) {
		console_drivers=console->next;
		res = 0;
1529
	} else if (console_drivers) {
L
Linus Torvalds 已提交
1530 1531 1532 1533 1534 1535
		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
1536
			}
L
Linus Torvalds 已提交
1537 1538
		}
	}
J
Jesper Juhl 已提交
1539

1540
	/*
1541 1542
	 * 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
1543
	 */
1544
	if (console_drivers != NULL && console->flags & CON_CONSDEV)
1545
		console_drivers->flags |= CON_CONSDEV;
L
Linus Torvalds 已提交
1546

1547
	console_unlock();
1548
	console_sysfs_notify();
L
Linus Torvalds 已提交
1549 1550 1551
	return res;
}
EXPORT_SYMBOL(unregister_console);
M
Matt Mackall 已提交
1552

1553
static int __init printk_late_init(void)
1554
{
1555 1556 1557 1558
	struct console *con;

	for_each_console(con) {
		if (con->flags & CON_BOOT) {
1559
			printk(KERN_INFO "turn off boot console %s%d\n",
1560
				con->name, con->index);
1561
			unregister_console(con);
1562
		}
1563
	}
1564
	hotcpu_notifier(console_cpu_notify, 0);
1565 1566
	return 0;
}
1567
late_initcall(printk_late_init);
1568

1569
#if defined CONFIG_PRINTK
D
Dave Young 已提交
1570

L
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1571 1572 1573
/*
 * printk rate limiting, lifted from the networking subsystem.
 *
1574 1575
 * 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
1576
 */
1577 1578
DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);

1579
int __printk_ratelimit(const char *func)
L
Linus Torvalds 已提交
1580
{
1581
	return ___ratelimit(&printk_ratelimit_state, func);
L
Linus Torvalds 已提交
1582
}
1583
EXPORT_SYMBOL(__printk_ratelimit);
1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596

/**
 * 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)
{
1597 1598 1599 1600 1601
	if (*caller_jiffies == 0
			|| !time_in_range(jiffies, *caller_jiffies,
					*caller_jiffies
					+ msecs_to_jiffies(interval_msecs))) {
		*caller_jiffies = jiffies;
1602 1603 1604 1605 1606
		return true;
	}
	return false;
}
EXPORT_SYMBOL(printk_timed_ratelimit);
1607 1608 1609 1610 1611 1612

static DEFINE_SPINLOCK(dump_list_lock);
static LIST_HEAD(dump_list);

/**
 * kmsg_dump_register - register a kernel log dumper.
R
Randy Dunlap 已提交
1613
 * @dumper: pointer to the kmsg_dumper structure
1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631
 *
 * Adds a kernel log dumper to the system. The dump callback in the
 * structure will be called when the kernel oopses or panics and must be
 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
 */
int kmsg_dump_register(struct kmsg_dumper *dumper)
{
	unsigned long flags;
	int err = -EBUSY;

	/* The dump callback needs to be set */
	if (!dumper->dump)
		return -EINVAL;

	spin_lock_irqsave(&dump_list_lock, flags);
	/* Don't allow registering multiple times */
	if (!dumper->registered) {
		dumper->registered = 1;
1632
		list_add_tail_rcu(&dumper->list, &dump_list);
1633 1634 1635 1636 1637 1638 1639 1640 1641 1642
		err = 0;
	}
	spin_unlock_irqrestore(&dump_list_lock, flags);

	return err;
}
EXPORT_SYMBOL_GPL(kmsg_dump_register);

/**
 * kmsg_dump_unregister - unregister a kmsg dumper.
R
Randy Dunlap 已提交
1643
 * @dumper: pointer to the kmsg_dumper structure
1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655
 *
 * Removes a dump device from the system. Returns zero on success and
 * %-EINVAL otherwise.
 */
int kmsg_dump_unregister(struct kmsg_dumper *dumper)
{
	unsigned long flags;
	int err = -EINVAL;

	spin_lock_irqsave(&dump_list_lock, flags);
	if (dumper->registered) {
		dumper->registered = 0;
1656
		list_del_rcu(&dumper->list);
1657 1658 1659
		err = 0;
	}
	spin_unlock_irqrestore(&dump_list_lock, flags);
1660
	synchronize_rcu();
1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689

	return err;
}
EXPORT_SYMBOL_GPL(kmsg_dump_unregister);

/**
 * kmsg_dump - dump kernel log to kernel message dumpers.
 * @reason: the reason (oops, panic etc) for dumping
 *
 * Iterate through each of the dump devices and call the oops/panic
 * callbacks with the log buffer.
 */
void kmsg_dump(enum kmsg_dump_reason reason)
{
	unsigned long end;
	unsigned chars;
	struct kmsg_dumper *dumper;
	const char *s1, *s2;
	unsigned long l1, l2;
	unsigned long flags;

	/* Theoretically, the log could move on after we do this, but
	   there's not a lot we can do about that. The new messages
	   will overwrite the start of what we dump. */
	spin_lock_irqsave(&logbuf_lock, flags);
	end = log_end & LOG_BUF_MASK;
	chars = logged_chars;
	spin_unlock_irqrestore(&logbuf_lock, flags);

1690 1691 1692
	if (chars > end) {
		s1 = log_buf + log_buf_len - chars + end;
		l1 = chars - end;
1693 1694 1695 1696 1697 1698 1699

		s2 = log_buf;
		l2 = end;
	} else {
		s1 = "";
		l1 = 0;

1700 1701
		s2 = log_buf + end - chars;
		l2 = chars;
1702 1703
	}

1704 1705
	rcu_read_lock();
	list_for_each_entry_rcu(dumper, &dump_list, list)
1706
		dumper->dump(dumper, reason, s1, l1, s2, l2);
1707
	rcu_read_unlock();
1708
}
1709
#endif