printk.c 39.6 KB
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/*
 *  linux/kernel/printk.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 * Modified to make sys_syslog() more flexible: added commands to
 * return the last 4k of kernel messages, regardless of whether
 * they've been read or not.  Added option to suppress kernel printk's
 * to the console.  Added hook for sending the console messages
 * elsewhere, in preparation for a serial line console (someday).
 * Ted Ts'o, 2/11/93.
 * Modified for sysctl support, 1/8/97, Chris Horn.
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 * Fixed SMP synchronization, 08/08/99, Manfred Spraul
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 *     manfred@colorfullife.com
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 * Rewrote bits to get rid of console_lock
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 *	01Mar01 Andrew Morton
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 */

#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/tty.h>
#include <linux/tty_driver.h>
#include <linux/console.h>
#include <linux/init.h>
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#include <linux/jiffies.h>
#include <linux/nmi.h>
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#include <linux/module.h>
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#include <linux/moduleparam.h>
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#include <linux/interrupt.h>			/* For in_interrupt() */
#include <linux/delay.h>
#include <linux/smp.h>
#include <linux/security.h>
#include <linux/bootmem.h>
#include <linux/syscalls.h>
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#include <linux/kexec.h>
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#include <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 <asm/uaccess.h>

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

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

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#define __LOG_BUF_LEN	(1 << CONFIG_LOG_BUF_SHIFT)

/* printk's without a loglevel use this.. */
#define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */

/* We show everything that is MORE important than this.. */
#define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
#define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */

DECLARE_WAIT_QUEUE_HEAD(log_wait);

int console_printk[4] = {
	DEFAULT_CONSOLE_LOGLEVEL,	/* console_loglevel */
	DEFAULT_MESSAGE_LOGLEVEL,	/* default_message_loglevel */
	MINIMUM_CONSOLE_LOGLEVEL,	/* minimum_console_loglevel */
	DEFAULT_CONSOLE_LOGLEVEL,	/* default_console_loglevel */
};

/*
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 * 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
 * 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 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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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;
	int error = 0;

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	/*
	 * If this is from /proc/kmsg we only do the capabilities checks
	 * at open time.
	 */
	if (type == SYSLOG_ACTION_OPEN || !from_file) {
		if (dmesg_restrict && !capable(CAP_SYS_ADMIN))
			return -EPERM;
		if ((type != SYSLOG_ACTION_READ_ALL &&
		     type != SYSLOG_ACTION_SIZE_BUFFER) &&
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		    !capable(CAP_SYSLOG)) {
			/* remove after 2.6.38 */
			if (capable(CAP_SYS_ADMIN))
				WARN_ONCE(1, "Attempt to access syslog with "
				  "CAP_SYS_ADMIN but no CAP_SYSLOG "
				  "(deprecated and denied).\n");
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			return -EPERM;
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		}
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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 ((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 */
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	sema_init(&console_sem, 1);
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}

#if defined(CONFIG_PRINTK_TIME)
static int printk_time = 1;
#else
static int printk_time = 0;
#endif
592
module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
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594 595 596 597 598
/* Check if we have any console registered that can be called early in boot. */
static int have_callable_console(void)
{
	struct console *con;

599
	for_each_console(con)
600 601 602 603 604 605
		if (con->flags & CON_ANYTIME)
			return 1;

	return 0;
}

606 607 608 609
/**
 * printk - print a kernel message
 * @fmt: format string
 *
610
 * This is printk().  It can be called from any context.  We want it to work.
J
Jesper Juhl 已提交
611
 *
L
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612 613 614 615 616 617 618 619 620
 * 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.
621 622 623
 *
 * See also:
 * printf(3)
624 625
 *
 * See the vsnprintf() documentation for format string extensions over C99.
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626
 */
M
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627

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628 629 630 631 632
asmlinkage int printk(const char *fmt, ...)
{
	va_list args;
	int r;

633 634 635 636 637 638 639 640
#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;
}

648 649 650
/* cpu currently holding logbuf_lock */
static volatile unsigned int printk_cpu = UINT_MAX;

651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674
/*
 * 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)
N
Namhyung Kim 已提交
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	__releases(&logbuf_lock)
676 677 678
{
	int retval = 0;

679 680 681 682 683 684 685 686 687 688 689 690 691 692 693
	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;
		}
	}
694 695 696 697
	printk_cpu = UINT_MAX;
	spin_unlock(&logbuf_lock);
	return retval;
}
698 699 700
static const char recursion_bug_msg [] =
		KERN_CRIT "BUG: recent printk recursion!\n";
static int recursion_bug;
701
static int new_text_line = 1;
702
static char printk_buf[1024];
703

704 705 706 707 708 709 710 711 712 713 714 715 716 717
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)
{
720
	int printed_len = 0;
721
	int current_log_level = default_message_loglevel;
722
	unsigned long flags;
723
	int this_cpu;
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724 725
	char *p;

R
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	boot_delay_msec();
727
	printk_delay();
R
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728

729
	preempt_disable();
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730
	/* This stops the holder of console_sem just where we want him */
731
	raw_local_irq_save(flags);
732 733 734 735 736 737 738 739 740 741 742 743 744 745
	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) {
746
			recursion_bug = 1;
747 748 749 750 751
			goto out_restore_irqs;
		}
		zap_locks();
	}

752 753
	lockdep_off();
	spin_lock(&logbuf_lock);
754
	printk_cpu = this_cpu;
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Linus Torvalds 已提交
755

756 757 758
	if (recursion_bug) {
		recursion_bug = 0;
		strcpy(printk_buf, recursion_bug_msg);
759
		printed_len = strlen(recursion_bug_msg);
760
	}
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761
	/* Emit the output into the temporary buffer */
762
	printed_len += vscnprintf(printk_buf + printed_len,
T
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				  sizeof(printk_buf) - printed_len, fmt, args);
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764

765

766 767 768 769 770 771 772 773 774
	p = printk_buf;

	/* Do we have a loglevel in the string? */
	if (p[0] == '<') {
		unsigned char c = p[1];
		if (c && p[2] == '>') {
			switch (c) {
			case '0' ... '7': /* loglevel */
				current_log_level = c - '0';
775 776
			/* Fallthrough - make sure we're on a new line */
			case 'd': /* KERN_DEFAULT */
777 778 779 780 781 782 783 784 785 786 787 788
				if (!new_text_line) {
					emit_log_char('\n');
					new_text_line = 1;
				}
			/* Fallthrough - skip the loglevel */
			case 'c': /* KERN_CONT */
				p += 3;
				break;
			}
		}
	}

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789 790 791 792
	/*
	 * Copy the output into log_buf.  If the caller didn't provide
	 * appropriate log level tags, we insert them here
	 */
793
	for ( ; *p; p++) {
794 795 796 797 798 799 800 801
		if (new_text_line) {
			/* Always output the token */
			emit_log_char('<');
			emit_log_char(current_log_level + '0');
			emit_log_char('>');
			printed_len += 3;
			new_text_line = 0;

L
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802
			if (printk_time) {
803
				/* Follow the token with the time */
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804 805 806 807 808
				char tbuf[50], *tp;
				unsigned tlen;
				unsigned long long t;
				unsigned long nanosec_rem;

809
				t = cpu_clock(printk_cpu);
L
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810
				nanosec_rem = do_div(t, 1000000000);
811 812 813
				tlen = sprintf(tbuf, "[%5lu.%06lu] ",
						(unsigned long) t,
						nanosec_rem / 1000);
L
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814 815 816

				for (tp = tbuf; tp < tbuf + tlen; tp++)
					emit_log_char(*tp);
817
				printed_len += tlen;
L
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818
			}
819

L
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820 821 822
			if (!*p)
				break;
		}
823

L
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824 825
		emit_log_char(*p);
		if (*p == '\n')
826
			new_text_line = 1;
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827 828
	}

829 830 831 832 833 834 835 836 837 838 839 840
	/*
	 * 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();
841

842
	lockdep_on();
843
out_restore_irqs:
844
	raw_local_irq_restore(flags);
845

846
	preempt_enable();
L
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847 848 849 850 851
	return printed_len;
}
EXPORT_SYMBOL(printk);
EXPORT_SYMBOL(vprintk);

M
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852 853
#else

854
static void call_console_drivers(unsigned start, unsigned end)
J
Jesper Juhl 已提交
855 856
{
}
M
Matt Mackall 已提交
857 858 859

#endif

860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889
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;
}
890 891 892 893 894
/*
 * Set up a list of consoles.  Called from init/main.c
 */
static int __init console_setup(char *str)
{
Y
Yinghai Lu 已提交
895
	char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
896
	char *s, *options, *brl_options = NULL;
897 898
	int idx;

899 900 901 902 903 904 905 906 907 908 909 910 911 912 913
#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

914 915 916 917
	/*
	 * Decode str into name, index, options.
	 */
	if (str[0] >= '0' && str[0] <= '9') {
Y
Yinghai Lu 已提交
918 919
		strcpy(buf, "ttyS");
		strncpy(buf + 4, str, sizeof(buf) - 5);
920
	} else {
Y
Yinghai Lu 已提交
921
		strncpy(buf, str, sizeof(buf) - 1);
922
	}
Y
Yinghai Lu 已提交
923
	buf[sizeof(buf) - 1] = 0;
924 925 926 927
	if ((options = strchr(str, ',')) != NULL)
		*(options++) = 0;
#ifdef __sparc__
	if (!strcmp(str, "ttya"))
Y
Yinghai Lu 已提交
928
		strcpy(buf, "ttyS0");
929
	if (!strcmp(str, "ttyb"))
Y
Yinghai Lu 已提交
930
		strcpy(buf, "ttyS1");
931
#endif
Y
Yinghai Lu 已提交
932
	for (s = buf; *s; s++)
933 934 935 936 937
		if ((*s >= '0' && *s <= '9') || *s == ',')
			break;
	idx = simple_strtoul(s, NULL, 10);
	*s = 0;

938
	__add_preferred_console(buf, idx, options, brl_options);
939
	console_set_on_cmdline = 1;
940 941 942 943
	return 1;
}
__setup("console=", console_setup);

944 945
/**
 * add_preferred_console - add a device to the list of preferred consoles.
946 947 948
 * @name: device name
 * @idx: device index
 * @options: options for this console
949 950 951 952 953 954 955 956
 *
 * 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.
 */
957
int add_preferred_console(char *name, int idx, char *options)
958
{
959
	return __add_preferred_console(name, idx, options, NULL);
960 961
}

962
int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
963 964 965 966 967 968 969 970
{
	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];
971
				strlcpy(c->name, name_new, sizeof(c->name));
972 973 974 975 976 977 978 979 980
				c->name[sizeof(c->name) - 1] = 0;
				c->options = options;
				c->index = idx_new;
				return i;
		}
	/* not found */
	return -1;
}

981 982 983 984 985 986 987 988 989 990
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);

991 992 993 994 995 996 997
/**
 * suspend_console - suspend the console subsystem
 *
 * This disables printk() while we go into suspend states
 */
void suspend_console(void)
{
998 999
	if (!console_suspend_enabled)
		return;
1000
	printk("Suspending console(s) (use no_console_suspend to debug)\n");
1001 1002
	acquire_console_sem();
	console_suspended = 1;
1003
	up(&console_sem);
1004 1005 1006 1007
}

void resume_console(void)
{
1008 1009
	if (!console_suspend_enabled)
		return;
1010
	down(&console_sem);
1011 1012 1013 1014
	console_suspended = 0;
	release_console_sem();
}

1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040
/**
 * 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:
		acquire_console_sem();
		release_console_sem();
	}
	return NOTIFY_OK;
}

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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)
{
1051
	BUG_ON(in_interrupt());
L
Linus Torvalds 已提交
1052
	down(&console_sem);
1053 1054
	if (console_suspended)
		return;
L
Linus Torvalds 已提交
1055 1056 1057 1058 1059 1060 1061 1062 1063
	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;
1064 1065 1066 1067
	if (console_suspended) {
		up(&console_sem);
		return -1;
	}
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	console_locked = 1;
	console_may_schedule = 0;
	return 0;
}
EXPORT_SYMBOL(try_acquire_console_sem);

int is_console_locked(void)
{
	return console_locked;
}

P
Peter Zijlstra 已提交
1079 1080 1081
static DEFINE_PER_CPU(int, printk_pending);

void printk_tick(void)
1082
{
P
Peter Zijlstra 已提交
1083 1084
	if (__get_cpu_var(printk_pending)) {
		__get_cpu_var(printk_pending) = 0;
1085
		wake_up_interruptible(&log_wait);
P
Peter Zijlstra 已提交
1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096
	}
}

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

void wake_up_klogd(void)
{
	if (waitqueue_active(&log_wait))
1097
		__raw_get_cpu_var(printk_pending) = 1;
1098 1099
}

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1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116
/**
 * 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;
1117 1118
	unsigned _con_start, _log_end;
	unsigned wake_klogd = 0;
L
Linus Torvalds 已提交
1119

1120
	if (console_suspended) {
1121
		up(&console_sem);
1122 1123
		return;
	}
1124 1125 1126

	console_may_schedule = 0;

L
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1127 1128 1129 1130 1131 1132 1133 1134 1135
	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);
1136
		stop_critical_timings();	/* don't trace print latency */
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1137
		call_console_drivers(_con_start, _log_end);
1138
		start_critical_timings();
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1139 1140 1141 1142 1143
		local_irq_restore(flags);
	}
	console_locked = 0;
	up(&console_sem);
	spin_unlock_irqrestore(&logbuf_lock, flags);
1144 1145
	if (wake_klogd)
		wake_up_klogd();
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1146 1147 1148
}
EXPORT_SYMBOL(release_console_sem);

1149 1150
/**
 * console_conditional_schedule - yield the CPU if required
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1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180
 *
 * If the console code is currently allowed to sleep, and
 * if this CPU should yield the CPU to another task, do
 * so here.
 *
 * Must be called within acquire_console_sem().
 */
void __sched console_conditional_schedule(void)
{
	if (console_may_schedule)
		cond_resched();
}
EXPORT_SYMBOL(console_conditional_schedule);

void console_unblank(void)
{
	struct console *c;

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

	console_locked = 1;
	console_may_schedule = 0;
1181
	for_each_console(c)
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1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195
		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();
1196
	for_each_console(c) {
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1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232
		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.
1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245
 *
 * 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
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 */
1247
void register_console(struct console *newcon)
L
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{
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	int i;
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	unsigned long flags;
1251
	struct console *bcon = NULL;
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1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265
	/*
	 * 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;
			}
		}
1266 1267
	}

1268 1269 1270 1271
	if (console_drivers && console_drivers->flags & CON_BOOT)
		bcon = console_drivers;

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

1274 1275
	if (newcon->early_setup)
		newcon->early_setup();
1276

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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) {
1283 1284 1285 1286 1287 1288 1289
		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;
1290 1291
				preferred_console = 0;
			}
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		}
	}

	/*
	 *	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++) {
1301
		if (strcmp(console_cmdline[i].name, newcon->name) != 0)
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			continue;
1303 1304
		if (newcon->index >= 0 &&
		    newcon->index != console_cmdline[i].index)
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			continue;
1306 1307
		if (newcon->index < 0)
			newcon->index = console_cmdline[i].index;
1308 1309
#ifdef CONFIG_A11Y_BRAILLE_CONSOLE
		if (console_cmdline[i].brl_options) {
1310 1311
			newcon->flags |= CON_BRL;
			braille_register_console(newcon,
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					console_cmdline[i].index,
					console_cmdline[i].options,
					console_cmdline[i].brl_options);
			return;
		}
#endif
1318 1319
		if (newcon->setup &&
		    newcon->setup(newcon, console_cmdline[i].options) != 0)
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			break;
1321 1322
		newcon->flags |= CON_ENABLED;
		newcon->index = console_cmdline[i].index;
1323
		if (i == selected_console) {
1324
			newcon->flags |= CON_CONSDEV;
1325 1326
			preferred_console = selected_console;
		}
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		break;
	}

1330
	if (!(newcon->flags & CON_ENABLED))
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		return;

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	/*
	 * 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))
1340
		newcon->flags &= ~CON_PRINTBUFFER;
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	/*
	 *	Put this console in the list - keep the
	 *	preferred driver at the head of the list.
	 */
	acquire_console_sem();
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	if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
		newcon->next = console_drivers;
		console_drivers = newcon;
		if (newcon->next)
			newcon->next->flags &= ~CON_CONSDEV;
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	} else {
1353 1354
		newcon->next = console_drivers->next;
		console_drivers->next = newcon;
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	}
1356
	if (newcon->flags & CON_PRINTBUFFER) {
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		/*
		 * release_console_sem() will print out the buffered messages
		 * for us.
		 */
		spin_lock_irqsave(&logbuf_lock, flags);
		con_start = log_start;
		spin_unlock_irqrestore(&logbuf_lock, flags);
	}
	release_console_sem();
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	/*
	 * By unregistering the bootconsoles after we enable the real console
	 * we get the "console xxx enabled" message on all the consoles -
	 * boot consoles, real consoles, etc - this is to ensure that end
	 * users know there might be something in the kernel's log buffer that
	 * went to the bootconsole (that they do not see on the real console)
	 */
	if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) {
		/* we need to iterate through twice, to make sure we print
		 * everything out, before we unregister the console(s)
		 */
		printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
			newcon->name, newcon->index);
		for_each_console(bcon)
			if (bcon->flags & CON_BOOT)
				unregister_console(bcon);
	} else {
		printk(KERN_INFO "%sconsole [%s%d] enabled\n",
			(newcon->flags & CON_BOOT) ? "boot" : "" ,
			newcon->name, newcon->index);
	}
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}
EXPORT_SYMBOL(register_console);

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

1396 1397 1398 1399 1400
#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;
1405
	} 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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1416
	/*
1417 1418
	 * 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
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	 */
1420
	if (console_drivers != NULL && console->flags & CON_CONSDEV)
1421
		console_drivers->flags |= CON_CONSDEV;
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	release_console_sem();
	return res;
}
EXPORT_SYMBOL(unregister_console);
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1428
static int __init printk_late_init(void)
1429
{
1430 1431 1432 1433
	struct console *con;

	for_each_console(con) {
		if (con->flags & CON_BOOT) {
1434
			printk(KERN_INFO "turn off boot console %s%d\n",
1435
				con->name, con->index);
1436
			unregister_console(con);
1437
		}
1438
	}
1439
	hotcpu_notifier(console_cpu_notify, 0);
1440 1441
	return 0;
}
1442
late_initcall(printk_late_init);
1443

1444
#if defined CONFIG_PRINTK
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Dave Young 已提交
1445

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/*
 * printk rate limiting, lifted from the networking subsystem.
 *
1449 1450
 * This enforces a rate limit: not more than 10 kernel messages
 * every 5s to make a denial-of-service attack impossible.
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Linus Torvalds 已提交
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 */
1452 1453
DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);

1454
int __printk_ratelimit(const char *func)
L
Linus Torvalds 已提交
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{
1456
	return ___ratelimit(&printk_ratelimit_state, func);
L
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}
1458
EXPORT_SYMBOL(__printk_ratelimit);
1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471

/**
 * 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)
{
1472 1473 1474 1475 1476
	if (*caller_jiffies == 0
			|| !time_in_range(jiffies, *caller_jiffies,
					*caller_jiffies
					+ msecs_to_jiffies(interval_msecs))) {
		*caller_jiffies = jiffies;
1477 1478 1479 1480 1481
		return true;
	}
	return false;
}
EXPORT_SYMBOL(printk_timed_ratelimit);
1482 1483 1484 1485 1486 1487

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

/**
 * kmsg_dump_register - register a kernel log dumper.
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Randy Dunlap 已提交
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 * @dumper: pointer to the kmsg_dumper structure
1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517
 *
 * 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;
		list_add_tail(&dumper->list, &dump_list);
		err = 0;
	}
	spin_unlock_irqrestore(&dump_list_lock, flags);

	return err;
}
EXPORT_SYMBOL_GPL(kmsg_dump_register);

/**
 * kmsg_dump_unregister - unregister a kmsg dumper.
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Randy Dunlap 已提交
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 * @dumper: pointer to the kmsg_dumper structure
1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539
 *
 * 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;
		list_del(&dumper->list);
		err = 0;
	}
	spin_unlock_irqrestore(&dump_list_lock, flags);

	return err;
}
EXPORT_SYMBOL_GPL(kmsg_dump_unregister);

1540
static const char * const kmsg_reasons[] = {
1541 1542
	[KMSG_DUMP_OOPS]	= "oops",
	[KMSG_DUMP_PANIC]	= "panic",
1543
	[KMSG_DUMP_KEXEC]	= "kexec",
1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577
};

static const char *kmsg_to_str(enum kmsg_dump_reason reason)
{
	if (reason >= ARRAY_SIZE(kmsg_reasons) || reason < 0)
		return "unknown";

	return kmsg_reasons[reason];
}

/**
 * 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);

1578 1579 1580
	if (chars > end) {
		s1 = log_buf + log_buf_len - chars + end;
		l1 = chars - end;
1581 1582 1583 1584 1585 1586 1587

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

1588 1589
		s2 = log_buf + end - chars;
		l2 = chars;
1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600
	}

	if (!spin_trylock_irqsave(&dump_list_lock, flags)) {
		printk(KERN_ERR "dump_kmsg: dump list lock is held during %s, skipping dump\n",
				kmsg_to_str(reason));
		return;
	}
	list_for_each_entry(dumper, &dump_list, list)
		dumper->dump(dumper, reason, s1, l1, s2, l2);
	spin_unlock_irqrestore(&dump_list_lock, flags);
}
1601
#endif