printk.c

Linux2.4.20针对三星公司的s3c2410开发板的内核改造。

/*
 *  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.
 * Fixed SMP synchronization, 08/08/99, Manfred Spraul 
 *     [e-mail]
 * Rewrote bits to get rid of console_lock
 *	01Mar01 Andrew Morton <[e-mail]>
 */

#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/tty.h>
#include <linux/tty_driver.h>
#include <linux/smp_lock.h>
#include <linux/console.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/interrupt.h>			/* For in_interrupt() */
#include <linux/config.h>
#include <linux/delay.h>

#include <asm/uaccess.h>

#if defined(CONFIG_MULTIQUAD) || defined(CONFIG_IA64)
#define LOG_BUF_LEN	(65536)
#elif defined(CONFIG_ARCH_S390)
#define LOG_BUF_LEN	(131072)
#elif defined(CONFIG_SMP)
#define LOG_BUF_LEN	(32768)
#else	
#define LOG_BUF_LEN	(16384)			/* This must be a power of two */
#endif

#define LOG_BUF_MASK	(LOG_BUF_LEN-1)

#ifndef arch_consoles_callable
#define arch_consoles_callable() (1)
#endif

/* 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 */
};

int oops_in_progress;

/*
 * console_sem protects the console_drivers list, and also
 * provides serialisation for access to the entire console
 * driver system.
 */
static DECLARE_MUTEX(console_sem);
struct console *console_drivers;


/*
 * 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 spinlock_t logbuf_lock = SPIN_LOCK_UNLOCKED;

static char log_buf[LOG_BUF_LEN];
#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
 */
static unsigned long log_start;			/* Index into log_buf: next char to be read by syslog() */
static unsigned long con_start;			/* Index into log_buf: next char to be sent to consoles */
static unsigned long log_end;			/* Index into log_buf: most-recently-written-char + 1 */
static unsigned long logged_chars;		/* Number of chars produced since last read+clear operation */

struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
static int preferred_console = -1;

/* Flag: console code may call schedule() */
static int console_may_schedule;

/*
 *	Setup a list of consoles. Called from init/main.c
 */
static int __init console_setup(char *str)
{
	struct console_cmdline *c;
	char name[sizeof(c->name)];
	char *s, *options;
	int i, idx;

	/*
	 *	Decode str into name, index, options.
	 */
	if (str[0] >= '0' && str[0] <= '9') {
		strcpy(name, "ttyS");
		strncpy(name + 4, str, sizeof(name) - 5);
	} else
		strncpy(name, str, sizeof(name) - 1);
	name[sizeof(name) - 1] = 0;
	if ((options = strchr(str, ',')) != NULL)
		*(options++) = 0;
#ifdef __sparc__
	if (!strcmp(str, "ttya"))
		strcpy(name, "ttyS0");
	if (!strcmp(str, "ttyb"))
		strcpy(name, "ttyS1");
#endif
	for(s = name; *s; s++)
		if (*s >= '0' && *s <= '9')
			break;
	idx = simple_strtoul(s, NULL, 10);
	*s = 0;

	/*
	 *	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) {
				preferred_console = i;
				return 1;
		}
	if (i == MAX_CMDLINECONSOLES)
		return 1;
	preferred_console = i;
	c = &console_cmdline[i];
	memcpy(c->name, name, sizeof(c->name));
	c->options = options;
	c->index = idx;
	return 1;
}

__setup("console=", console_setup);

/*
 * 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
 */
int do_syslog(int type, char * buf, int len)
{
	unsigned long i, j, limit, count;
	int do_clear = 0;
	char c;
	int error = 0;

	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;
		error = verify_area(VERIFY_WRITE,buf,len);
		if (error)
			goto out;
		error = wait_event_interruptible(log_wait, (log_start - log_end));
		if (error)
			goto out;
		i = 0;
		spin_lock_irq(&logbuf_lock);
		while ((log_start != log_end) && i < len) {
			c = LOG_BUF(log_start);
			log_start++;
			spin_unlock_irq(&logbuf_lock);
			__put_user(c,buf);
			buf++;
			i++;
			spin_lock_irq(&logbuf_lock);
		}
		spin_unlock_irq(&logbuf_lock);
		error = i;
		break;
	case 4:		/* Read/clear last kernel messages */
		do_clear = 1; 
		/* FALL THRU */
	case 3:		/* Read last kernel messages */
		error = -EINVAL;
		if (!buf || len < 0)
			goto out;
		error = 0;
		if (!len)
			goto out;
		error = verify_area(VERIFY_WRITE,buf,len);
		if (error)
			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
		 * printk() could overwrite the messages 
		 * we try to copy to user space. Therefore
		 * the messages are copied in reverse. <manfreds>
		 */
		for(i=0;i < count;i++) {
			j = limit-1-i;
			if (j+LOG_BUF_LEN < log_end)
				break;
			c = LOG_BUF(j);
			spin_unlock_irq(&logbuf_lock);
			__put_user(c,&buf[count-1-i]);
			spin_lock_irq(&logbuf_lock);
		}
		spin_unlock_irq(&logbuf_lock);
		error = i;
		if(i != count) {
			int offset = count-error;
			/* buffer overflow during copy, correct user buffer. */
			for(i=0;i<error;i++) {
				__get_user(c,&buf[i+offset]);
				__put_user(c,&buf[i]);
			}
		}

		break;
	case 5:		/* Clear ring buffer */
		spin_lock_irq(&logbuf_lock);
		logged_chars = 0;
		spin_unlock_irq(&logbuf_lock);
		break;
	case 6:		/* Disable logging to console */
		spin_lock_irq(&logbuf_lock);
		console_loglevel = minimum_console_loglevel;
		spin_unlock_irq(&logbuf_lock);
		break;
	case 7:		/* Enable logging to console */
		spin_lock_irq(&logbuf_lock);
		console_loglevel = default_console_loglevel;
		spin_unlock_irq(&logbuf_lock);
		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;
		spin_lock_irq(&logbuf_lock);
		console_loglevel = len;
		spin_unlock_irq(&logbuf_lock);
		error = 0;
		break;
	case 9:		/* Number of chars in the log buffer */
		spin_lock_irq(&logbuf_lock);
		error = log_end - log_start;
		spin_unlock_irq(&logbuf_lock);
		break;
	default:
		error = -EINVAL;
		break;
	}
out:
	return error;
}

asmlinkage long sys_syslog(int type, char * buf, int len)
{
	if ((type != 3) && !capable(CAP_SYS_ADMIN))
		return -EPERM;
	return do_syslog(type, buf, len);
}

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

	for (con = console_drivers; con; con = con->next) {
		if ((con->flags & CON_ENABLED) && con->write)
			con->write(con, &LOG_BUF(start), end - start);
	}
}

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

	if (((long)(start - end)) > 0)
		BUG();

	cur_index = start;
	start_print = start;
	while (cur_index != end) {