printk.c 33.0 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;

/* 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.
 */
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static int log_buf_get_len(void)
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{
	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;
}

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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;

638 639 640 641 642 643 644 645 646 647 648 649 650 651 652
	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;
		}
	}
653 654 655 656
	printk_cpu = UINT_MAX;
	spin_unlock(&logbuf_lock);
	return retval;
}
657 658 659
static const char recursion_bug_msg [] =
		KERN_CRIT "BUG: recent printk recursion!\n";
static int recursion_bug;
660
	static int new_text_line = 1;
661
static char printk_buf[1024];
662

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asmlinkage int vprintk(const char *fmt, va_list args)
{
665
	int printed_len = 0;
666
	int current_log_level = default_message_loglevel;
667
	unsigned long flags;
668
	int this_cpu;
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669 670
	char *p;

R
Randy Dunlap 已提交
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	boot_delay_msec();

673
	preempt_disable();
L
Linus Torvalds 已提交
674
	/* This stops the holder of console_sem just where we want him */
675
	raw_local_irq_save(flags);
676 677 678 679 680 681 682 683 684 685 686 687 688 689
	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) {
690
			recursion_bug = 1;
691 692 693 694 695
			goto out_restore_irqs;
		}
		zap_locks();
	}

696 697
	lockdep_off();
	spin_lock(&logbuf_lock);
698
	printk_cpu = this_cpu;
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700 701 702 703
	if (recursion_bug) {
		recursion_bug = 0;
		strcpy(printk_buf, recursion_bug_msg);
		printed_len = sizeof(recursion_bug_msg);
704
	}
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	/* Emit the output into the temporary buffer */
706
	printed_len += vscnprintf(printk_buf + printed_len,
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Tejun Heo 已提交
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				  sizeof(printk_buf) - printed_len, fmt, args);
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709

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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++) {
715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730
		if (new_text_line) {
			/* If a token, set current_log_level and skip over */
			if (p[0] == '<' && p[1] >= '0' && p[1] <= '7' &&
			    p[2] == '>') {
				current_log_level = p[1] - '0';
				p += 3;
				printed_len -= 3;
			}

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

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			if (printk_time) {
732
				/* Follow the token with the time */
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				char tbuf[50], *tp;
				unsigned tlen;
				unsigned long long t;
				unsigned long nanosec_rem;

738
				t = cpu_clock(printk_cpu);
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				nanosec_rem = do_div(t, 1000000000);
740 741 742
				tlen = sprintf(tbuf, "[%5lu.%06lu] ",
						(unsigned long) t,
						nanosec_rem / 1000);
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				for (tp = tbuf; tp < tbuf + tlen; tp++)
					emit_log_char(*tp);
746
				printed_len += tlen;
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747
			}
748

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749 750 751
			if (!*p)
				break;
		}
752

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		emit_log_char(*p);
		if (*p == '\n')
755
			new_text_line = 1;
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	}

758 759 760 761 762 763 764 765 766 767 768 769
	/*
	 * 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();
770

771
	lockdep_on();
772
out_restore_irqs:
773
	raw_local_irq_restore(flags);
774

775
	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)
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{
785
	return -ENOSYS;
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}

788
static void call_console_drivers(unsigned start, unsigned end)
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{
}
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#endif

794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823
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;
}
824 825 826 827 828
/*
 * Set up a list of consoles.  Called from init/main.c
 */
static int __init console_setup(char *str)
{
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	char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
830
	char *s, *options, *brl_options = NULL;
831 832
	int idx;

833 834 835 836 837 838 839 840 841 842 843 844 845 846 847
#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

848 849 850 851
	/*
	 * Decode str into name, index, options.
	 */
	if (str[0] >= '0' && str[0] <= '9') {
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Yinghai Lu 已提交
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		strcpy(buf, "ttyS");
		strncpy(buf + 4, str, sizeof(buf) - 5);
854
	} else {
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		strncpy(buf, str, sizeof(buf) - 1);
856
	}
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	buf[sizeof(buf) - 1] = 0;
858 859 860 861
	if ((options = strchr(str, ',')) != NULL)
		*(options++) = 0;
#ifdef __sparc__
	if (!strcmp(str, "ttya"))
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Yinghai Lu 已提交
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		strcpy(buf, "ttyS0");
863
	if (!strcmp(str, "ttyb"))
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		strcpy(buf, "ttyS1");
865
#endif
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	for (s = buf; *s; s++)
867 868 869 870 871
		if ((*s >= '0' && *s <= '9') || *s == ',')
			break;
	idx = simple_strtoul(s, NULL, 10);
	*s = 0;

872
	__add_preferred_console(buf, idx, options, brl_options);
873 874 875 876
	return 1;
}
__setup("console=", console_setup);

877 878
/**
 * add_preferred_console - add a device to the list of preferred consoles.
879 880 881
 * @name: device name
 * @idx: device index
 * @options: options for this console
882 883 884 885 886 887 888 889
 *
 * 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.
 */
890
int add_preferred_console(char *name, int idx, char *options)
891
{
892
	return __add_preferred_console(name, idx, options, NULL);
893 894
}

895
int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
896 897 898 899 900 901 902 903
{
	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];
904
				strlcpy(c->name, name_new, sizeof(c->name));
905 906 907 908 909 910 911 912 913
				c->name[sizeof(c->name) - 1] = 0;
				c->options = options;
				c->index = idx_new;
				return i;
		}
	/* not found */
	return -1;
}

914 915 916 917 918 919 920 921 922 923
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);

924 925 926 927 928 929 930
/**
 * suspend_console - suspend the console subsystem
 *
 * This disables printk() while we go into suspend states
 */
void suspend_console(void)
{
931 932
	if (!console_suspend_enabled)
		return;
933
	printk("Suspending console(s)\n");
934 935 936 937 938 939
	acquire_console_sem();
	console_suspended = 1;
}

void resume_console(void)
{
940 941
	if (!console_suspend_enabled)
		return;
942 943 944 945
	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)
{
956
	BUG_ON(in_interrupt());
957 958 959 960
	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;
}

982 983 984 985 986 987
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;
1005 1006
	unsigned _con_start, _log_end;
	unsigned wake_klogd = 0;
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1008 1009 1010 1011
	if (console_suspended) {
		up(&secondary_console_sem);
		return;
	}
1012 1013 1014

	console_may_schedule = 0;

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1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029
	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);
1030 1031
	if (wake_klogd)
		wake_up_klogd();
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1032 1033 1034
}
EXPORT_SYMBOL(release_console_sem);

1035 1036
/**
 * console_conditional_schedule - yield the CPU if required
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1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125
 *
 * 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)
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1127
{
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1128
	int i;
L
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1129
	unsigned long flags;
1130
	struct console *bootconsole = NULL;
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1131

1132 1133 1134 1135 1136 1137 1138 1139
	if (console_drivers) {
		if (console->flags & CON_BOOT)
			return;
		if (console_drivers->flags & CON_BOOT)
			bootconsole = console_drivers;
	}

	if (preferred_console < 0 || bootconsole || !console_drivers)
L
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1140 1141
		preferred_console = selected_console;

1142 1143 1144
	if (console->early_setup)
		console->early_setup();

L
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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) {
1155 1156 1157 1158 1159
			console->flags |= CON_ENABLED;
			if (console->device) {
				console->flags |= CON_CONSDEV;
				preferred_console = 0;
			}
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1160 1161 1162 1163 1164 1165 1166
		}
	}

	/*
	 *	See if this console matches one we selected on
	 *	the command line.
	 */
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1167 1168
	for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
			i++) {
L
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1169 1170 1171 1172 1173 1174 1175
		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;
1176 1177 1178 1179 1180 1181 1182 1183 1184 1185
#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;
1191
		if (i == selected_console) {
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			console->flags |= CON_CONSDEV;
1193 1194
			preferred_console = selected_console;
		}
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		break;
	}

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

1201
	if (bootconsole && (console->flags & CON_CONSDEV)) {
1202 1203 1204 1205
		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;
1207 1208 1209
	} 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;
1220 1221
		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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1239
int unregister_console(struct console *console)
L
Linus Torvalds 已提交
1240
{
J
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1241
        struct console *a, *b;
L
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1242 1243
	int res = 1;

1244 1245 1246 1247 1248
#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