printk.c 33.4 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
 *	01Mar01 Andrew Morton <andrewm@uow.edu.au>
 */

#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/tty.h>
#include <linux/tty_driver.h>
#include <linux/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>

#include <asm/uaccess.h>

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

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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.
 */
static DECLARE_MUTEX(console_sem);
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static DECLARE_MUTEX(secondary_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
 * 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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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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/*
 * Return the number of unread characters in the log buffer.
 */
int log_buf_get_len(void)
{
	return logged_chars;
}

/*
 * Copy a range of characters from the log buffer.
 */
int log_buf_copy(char *dest, int idx, int len)
{
	int ret, max;
	bool took_lock = false;

	if (!oops_in_progress) {
		spin_lock_irq(&logbuf_lock);
		took_lock = true;
	}

	max = log_buf_get_len();
	if (idx < 0 || idx >= max) {
		ret = -1;
	} else {
		if (len > max)
			len = max;
		ret = len;
		idx += (log_end - max);
		while (len-- > 0)
			dest[len] = LOG_BUF(idx + len);
	}

	if (took_lock)
		spin_unlock_irq(&logbuf_lock);

	return ret;
}

/*
 * Extract a single character from the log buffer.
 */
int log_buf_read(int idx)
{
	char ret;

	if (log_buf_copy(&ret, idx, 1) == 1)
		return ret;
	else
		return -1;
}

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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 */
		console_loglevel = minimum_console_loglevel;
		break;
	case 7:		/* Enable logging to console */
		console_loglevel = default_console_loglevel;
		break;
	case 8:		/* Set level of messages printed to console */
		error = -EINVAL;
		if (len < 1 || len > 8)
			goto out;
		if (len < minimum_console_loglevel)
			len = minimum_console_loglevel;
		console_loglevel = len;
		error = 0;
		break;
	case 9:		/* Number of chars in the log buffer */
		error = log_end - log_start;
		break;
	case 10:	/* Size of the log buffer */
		error = log_buf_len;
		break;
	default:
		error = -EINVAL;
		break;
	}
out:
	return error;
}

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asmlinkage long sys_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;

	for (con = console_drivers; con; con = con->next) {
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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;

	for (con = console_drivers; con; con = con->next)
		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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 * Be aware of the fact that if oops_in_progress is not set, we might try to
 * wake klogd up which could deadlock on runqueue lock if printk() is called
 * from scheduler code.
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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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 */
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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;

653 654 655 656 657 658 659 660 661 662 663 664 665 666 667
	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;
		}
	}
668 669 670 671 672
	printk_cpu = UINT_MAX;
	spin_unlock(&logbuf_lock);
	return retval;
}

673
static const char printk_recursion_bug_msg [] =
674 675 676
			KERN_CRIT "BUG: recent printk recursion!\n";
static int printk_recursion_bug;

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asmlinkage int vprintk(const char *fmt, va_list args)
{
679 680 681
	static int log_level_unknown = 1;
	static char printk_buf[1024];

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682
	unsigned long flags;
683 684
	int printed_len = 0;
	int this_cpu;
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	char *p;

R
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	boot_delay_msec();

689
	preempt_disable();
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	/* This stops the holder of console_sem just where we want him */
691
	raw_local_irq_save(flags);
692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711
	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) {
			printk_recursion_bug = 1;
			goto out_restore_irqs;
		}
		zap_locks();
	}

712 713
	lockdep_off();
	spin_lock(&logbuf_lock);
714
	printk_cpu = this_cpu;
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716 717 718 719 720
	if (printk_recursion_bug) {
		printk_recursion_bug = 0;
		strcpy(printk_buf, printk_recursion_bug_msg);
		printed_len = sizeof(printk_recursion_bug_msg);
	}
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	/* Emit the output into the temporary buffer */
722
	printed_len += vscnprintf(printk_buf + printed_len,
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				  sizeof(printk_buf) - printed_len, fmt, args);
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	/*
	 * Copy the output into log_buf.  If the caller didn't provide
	 * appropriate log level tags, we insert them here
	 */
	for (p = printk_buf; *p; p++) {
		if (log_level_unknown) {
                        /* log_level_unknown signals the start of a new line */
			if (printk_time) {
				int loglev_char;
				char tbuf[50], *tp;
				unsigned tlen;
				unsigned long long t;
				unsigned long nanosec_rem;

				/*
				 * force the log level token to be
				 * before the time output.
				 */
				if (p[0] == '<' && p[1] >='0' &&
				   p[1] <= '7' && p[2] == '>') {
					loglev_char = p[1];
					p += 3;
747
					printed_len -= 3;
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				} else {
					loglev_char = default_message_loglevel
						+ '0';
				}
752
				t = cpu_clock(printk_cpu);
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				nanosec_rem = do_div(t, 1000000000);
				tlen = sprintf(tbuf,
						"<%c>[%5lu.%06lu] ",
						loglev_char,
						(unsigned long)t,
						nanosec_rem/1000);

				for (tp = tbuf; tp < tbuf + tlen; tp++)
					emit_log_char(*tp);
762
				printed_len += tlen;
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			} else {
				if (p[0] != '<' || p[1] < '0' ||
				   p[1] > '7' || p[2] != '>') {
					emit_log_char('<');
					emit_log_char(default_message_loglevel
						+ '0');
					emit_log_char('>');
770
					printed_len += 3;
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				}
			}
			log_level_unknown = 0;
			if (!*p)
				break;
		}
		emit_log_char(*p);
		if (*p == '\n')
			log_level_unknown = 1;
	}

782 783 784 785 786 787 788 789 790 791 792 793
	/*
	 * 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();
794

795
	lockdep_on();
796
out_restore_irqs:
797
	raw_local_irq_restore(flags);
798

799
	preempt_enable();
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	return printed_len;
}
EXPORT_SYMBOL(printk);
EXPORT_SYMBOL(vprintk);

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#else

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asmlinkage long sys_syslog(int type, char __user *buf, int len)
M
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{
809
	return -ENOSYS;
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}

812
static void call_console_drivers(unsigned start, unsigned end)
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{
}
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815 816 817

#endif

818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847
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;
}
848 849 850 851 852
/*
 * 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 */
854
	char *s, *options, *brl_options = NULL;
855 856
	int idx;

857 858 859 860 861 862 863 864 865 866 867 868 869 870 871
#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

872 873 874 875
	/*
	 * Decode str into name, index, options.
	 */
	if (str[0] >= '0' && str[0] <= '9') {
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		strcpy(buf, "ttyS");
		strncpy(buf + 4, str, sizeof(buf) - 5);
878
	} else {
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		strncpy(buf, str, sizeof(buf) - 1);
880
	}
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	buf[sizeof(buf) - 1] = 0;
882 883 884 885
	if ((options = strchr(str, ',')) != NULL)
		*(options++) = 0;
#ifdef __sparc__
	if (!strcmp(str, "ttya"))
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		strcpy(buf, "ttyS0");
887
	if (!strcmp(str, "ttyb"))
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		strcpy(buf, "ttyS1");
889
#endif
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	for (s = buf; *s; s++)
891 892 893 894 895
		if ((*s >= '0' && *s <= '9') || *s == ',')
			break;
	idx = simple_strtoul(s, NULL, 10);
	*s = 0;

896
	__add_preferred_console(buf, idx, options, brl_options);
897
	console_set_on_cmdline = 1;
898 899 900 901
	return 1;
}
__setup("console=", console_setup);

902 903
/**
 * add_preferred_console - add a device to the list of preferred consoles.
904 905 906
 * @name: device name
 * @idx: device index
 * @options: options for this console
907 908 909 910 911 912 913 914
 *
 * 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.
 */
915
int add_preferred_console(char *name, int idx, char *options)
916
{
917
	return __add_preferred_console(name, idx, options, NULL);
918 919
}

920
int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
921 922 923 924 925 926 927 928
{
	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];
929
				strlcpy(c->name, name_new, sizeof(c->name));
930 931 932 933 934 935 936 937 938
				c->name[sizeof(c->name) - 1] = 0;
				c->options = options;
				c->index = idx_new;
				return i;
		}
	/* not found */
	return -1;
}

939 940 941 942 943 944 945 946 947 948
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);

949 950 951 952 953 954 955
/**
 * suspend_console - suspend the console subsystem
 *
 * This disables printk() while we go into suspend states
 */
void suspend_console(void)
{
956 957
	if (!console_suspend_enabled)
		return;
958
	printk("Suspending console(s)\n");
959 960 961 962 963 964
	acquire_console_sem();
	console_suspended = 1;
}

void resume_console(void)
{
965 966
	if (!console_suspend_enabled)
		return;
967 968 969 970
	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)
{
981
	BUG_ON(in_interrupt());
982 983 984 985
	if (console_suspended) {
		down(&secondary_console_sem);
		return;
	}
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	down(&console_sem);
	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;
	console_locked = 1;
	console_may_schedule = 0;
	return 0;
}
EXPORT_SYMBOL(try_acquire_console_sem);

int is_console_locked(void)
{
	return console_locked;
}

1007 1008 1009 1010 1011 1012
void wake_up_klogd(void)
{
	if (!oops_in_progress && waitqueue_active(&log_wait))
		wake_up_interruptible(&log_wait);
}

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

	console_may_schedule = 0;

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	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);
		call_console_drivers(_con_start, _log_end);
		local_irq_restore(flags);
	}
	console_locked = 0;
	up(&console_sem);
	spin_unlock_irqrestore(&logbuf_lock, flags);
1055 1056
	if (wake_klogd)
		wake_up_klogd();
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}
EXPORT_SYMBOL(release_console_sem);

1060 1061
/**
 * console_conditional_schedule - yield the CPU if required
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 *
 * If the console code is currently allowed to sleep, and
 * if this CPU should yield the CPU to another task, do
 * so here.
 *
 * Must be called within acquire_console_sem().
 */
void __sched console_conditional_schedule(void)
{
	if (console_may_schedule)
		cond_resched();
}
EXPORT_SYMBOL(console_conditional_schedule);

void console_print(const char *s)
{
	printk(KERN_EMERG "%s", s);
}
EXPORT_SYMBOL(console_print);

void console_unblank(void)
{
	struct console *c;

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

	console_locked = 1;
	console_may_schedule = 0;
	for (c = console_drivers; c != NULL; c = c->next)
		if ((c->flags & CON_ENABLED) && c->unblank)
			c->unblank();
	release_console_sem();
}

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

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

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

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

/*
 * The console driver calls this routine during kernel initialization
 * to register the console printing procedure with printk() and to
 * print any messages that were printed by the kernel before the
 * console driver was initialized.
 */
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void register_console(struct console *console)
L
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1152
{
J
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	int i;
L
Linus Torvalds 已提交
1154
	unsigned long flags;
1155
	struct console *bootconsole = NULL;
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1157 1158 1159 1160 1161 1162 1163 1164
	if (console_drivers) {
		if (console->flags & CON_BOOT)
			return;
		if (console_drivers->flags & CON_BOOT)
			bootconsole = console_drivers;
	}

	if (preferred_console < 0 || bootconsole || !console_drivers)
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		preferred_console = selected_console;

1167 1168 1169
	if (console->early_setup)
		console->early_setup();

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	/*
	 *	See if we want to use this console driver. If we
	 *	didn't select a console we take the first one
	 *	that registers here.
	 */
	if (preferred_console < 0) {
		if (console->index < 0)
			console->index = 0;
		if (console->setup == NULL ||
		    console->setup(console, NULL) == 0) {
			console->flags |= CON_ENABLED | CON_CONSDEV;
			preferred_console = 0;
		}
	}

	/*
	 *	See if this console matches one we selected on
	 *	the command line.
	 */
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	for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
			i++) {
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		if (strcmp(console_cmdline[i].name, console->name) != 0)
			continue;
		if (console->index >= 0 &&
		    console->index != console_cmdline[i].index)
			continue;
		if (console->index < 0)
			console->index = console_cmdline[i].index;
1198 1199 1200 1201 1202 1203 1204 1205 1206 1207
#ifdef CONFIG_A11Y_BRAILLE_CONSOLE
		if (console_cmdline[i].brl_options) {
			console->flags |= CON_BRL;
			braille_register_console(console,
					console_cmdline[i].index,
					console_cmdline[i].options,
					console_cmdline[i].brl_options);
			return;
		}
#endif
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		if (console->setup &&
		    console->setup(console, console_cmdline[i].options) != 0)
			break;
		console->flags |= CON_ENABLED;
		console->index = console_cmdline[i].index;
1213
		if (i == selected_console) {
L
Linus Torvalds 已提交
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			console->flags |= CON_CONSDEV;
1215 1216
			preferred_console = selected_console;
		}
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		break;
	}

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

1223
	if (bootconsole && (console->flags & CON_CONSDEV)) {
1224 1225 1226 1227
		printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
		       bootconsole->name, bootconsole->index,
		       console->name, console->index);
		unregister_console(bootconsole);
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		console->flags &= ~CON_PRINTBUFFER;
1229 1230 1231
	} else {
		printk(KERN_INFO "console [%s%d] enabled\n",
		       console->name, console->index);
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	}

	/*
	 *	Put this console in the list - keep the
	 *	preferred driver at the head of the list.
	 */
	acquire_console_sem();
	if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
		console->next = console_drivers;
		console_drivers = console;
1242 1243
		if (console->next)
			console->next->flags &= ~CON_CONSDEV;
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	} else {
		console->next = console_drivers->next;
		console_drivers->next = console;
	}
	if (console->flags & CON_PRINTBUFFER) {
		/*
		 * release_console_sem() will print out the buffered messages
		 * for us.
		 */
		spin_lock_irqsave(&logbuf_lock, flags);
		con_start = log_start;
		spin_unlock_irqrestore(&logbuf_lock, flags);
	}
	release_console_sem();
}
EXPORT_SYMBOL(register_console);

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

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#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;
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	} 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;
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			}
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		}
	}
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	/*
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	 * 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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	 */
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	if (console_drivers != NULL && console->flags & CON_CONSDEV)
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		console_drivers->flags |= CON_CONSDEV;
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	release_console_sem();
	return res;
}
EXPORT_SYMBOL(unregister_console);
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static int __init disable_boot_consoles(void)
{
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	if (console_drivers != NULL) {
		if (console_drivers->flags & CON_BOOT) {
			printk(KERN_INFO "turn off boot console %s%d\n",
				console_drivers->name, console_drivers->index);
			return unregister_console(console_drivers);
		}
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	}
	return 0;
}
late_initcall(disable_boot_consoles);

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/**
 * tty_write_message - write a message to a certain tty, not just the console.
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 * @tty: the destination tty_struct
 * @msg: the message to write
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 *
 * This is used for messages that need to be redirected to a specific tty.
 * We don't put it into the syslog queue right now maybe in the future if
 * really needed.
 */
void tty_write_message(struct tty_struct *tty, char *msg)
{
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	if (tty && tty->ops->write)
		tty->ops->write(tty, msg, strlen(msg));
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	return;
}

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#if defined CONFIG_PRINTK
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/*
 * printk rate limiting, lifted from the networking subsystem.
 *
 * This enforces a rate limit: not more than one kernel message
 * every printk_ratelimit_jiffies to make a denial-of-service
 * attack impossible.
 */
int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst)
{
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	return __ratelimit(ratelimit_jiffies, ratelimit_burst);
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}
EXPORT_SYMBOL(__printk_ratelimit);

/* minimum time in jiffies between messages */
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int printk_ratelimit_jiffies = 5 * HZ;
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/* number of messages we send before ratelimiting */
int printk_ratelimit_burst = 10;

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