/*
 *  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 
 *     manfreds@colorfullife.com
 * 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/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 <asm/uaccess.h>

#if !defined(CONFIG_LOG_BUF_SHIFT) || (CONFIG_LOG_BUF_SHIFT == 0)
#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
#else /* CONFIG_LOG_BUF_SHIFT */
#define LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
#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 selected_console = -1;
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) {
                                selected_console = i;
                                return 1;
                }
        if (i == MAX_CMDLINECONSOLES)
                return 1;
        selected_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) {
                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) == '>')
                {
                        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);
                        cur_index++;

                        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++;
}

/*
 * This is printk.  It can be called from any context.  We want it to work.
 * 
 * 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.
 */
asmlinkage int printk(const char *fmt, ...)
{
        va_list args;
        unsigned long flags;
        int printed_len;
        char *p;
        static char printk_buf[1024];
        static int log_level_unknown = 1;

        if (oops_in_progress) {
                /* 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);
        }

        /* This stops the holder of console_sem just where we want him */
        spin_lock_irqsave(&logbuf_lock, flags);

        /* Emit the output into the temporary buffer */
        va_start(args, fmt);
        printed_len = vsnprintf(printk_buf, sizeof(printk_buf), fmt, args);
        va_end(args);

        /*
         * Copy the output into log_buf.  If the caller didn't provide
         * appropriate log level tags, we insert them here
         */
        for (p = printk_buf; *p; p++) {
                if (log_level_unknown) {
                        if (p[0] != '<' || p[1] < '0' || p[1] > '7' || p[2] != '>') {
                                emit_log_char('<');
                                emit_log_char(default_message_loglevel + '0');
                                emit_log_char('>');
                        }
                        log_level_unknown = 0;
                }
                emit_log_char(*p);
                if (*p == '\n')
                        log_level_unknown = 1;
        }

        if (!arch_consoles_callable()) {
                /*
                 * On some architectures, the consoles are not usable
                 * on secondary CPUs early in the boot process.
                 */
                spin_unlock_irqrestore(&logbuf_lock, flags);
                goto out;
        }
        if (!down_trylock(&console_sem)) {
                /*
                 * We own the drivers.  We can drop the spinlock and let
                 * release_console_sem() print the text
                 */
                spin_unlock_irqrestore(&logbuf_lock, flags);
                console_may_schedule = 0;
                release_console_sem();
        } else {
                /*
                 * Someone else owns the drivers.  We drop the spinlock, which
                 * allows the semaphore holder to proceed and to call the
                 * console drivers with the output which we just produced.
                 */
                spin_unlock_irqrestore(&logbuf_lock, flags);
        }
out:
        return printed_len;
}
EXPORT_SYMBOL(printk);

/**
 * 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)
{
        if (in_interrupt())
                BUG();
        down(&console_sem);
        console_may_schedule = 1;
}
EXPORT_SYMBOL(acquire_console_sem);

/**
 * 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;
        unsigned long _con_start, _log_end;
        unsigned long must_wake_klogd = 0;

        for ( ; ; ) {
                spin_lock_irqsave(&logbuf_lock, flags);
                must_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_irqrestore(&logbuf_lock, flags);
                call_console_drivers(_con_start, _log_end);
        }
        console_may_schedule = 0;
        up(&console_sem);
        spin_unlock_irqrestore(&logbuf_lock, flags);
        if (must_wake_klogd && !oops_in_progress)
                wake_up_interruptible(&log_wait);
}

/** console_conditional_schedule - yield the CPU if required
 *
 * 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 console_conditional_schedule(void)
{
        if (console_may_schedule && current->need_resched) {
                set_current_state(TASK_RUNNING);
                schedule();
        }
}

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

void console_unblank(void)
{
        struct console *c;

        /*
         * Try to get the console semaphore. If someone else owns it
         * we have to return without unblanking because console_unblank
         * may be called in interrupt context.
         */
        if (down_trylock(&console_sem) != 0)
                return;
        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();
}
EXPORT_SYMBOL(console_unblank);

/*
 * 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.
 */
void register_console(struct console * console)
{
        int     i;
        unsigned long flags;

        if (preferred_console < 0)
                preferred_console = selected_console;

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

        /*
         *      See if this console matches one we selected on
         *      the command line.
         */
        for(i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++) {
                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;
                if (console->setup &&
                    console->setup(console, console_cmdline[i].options) != 0)
                        break;
                console->flags |= CON_ENABLED;
                console->index = console_cmdline[i].index;
                if (i == preferred_console)
                        console->flags |= CON_CONSDEV;
                break;
        }

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

        /*
         *      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;
        } 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);

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

        acquire_console_sem();
        if (console_drivers == console) {
                console_drivers=console->next;
                res = 0;
        } else {
                for (a=console_drivers->next, b=console_drivers ;
                     a; b=a, a=b->next) {
                        if (a == console) {
                                b->next = a->next;
                                res = 0;
                                break;
                        }  
                }
        }
        
        /* If last console is removed, we re-enable picking the first
         * one that gets registered. Without that, pmac early boot console
         * would prevent fbcon from taking over.
         */
        if (console_drivers == NULL)
                preferred_console = selected_console;
                

        release_console_sem();
        return res;
}
EXPORT_SYMBOL(unregister_console);
        
/**
 * tty_write_message - write a message to a certain tty, not just the console.
 *
 * 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)
{
        if (tty && tty->driver.write)
                tty->driver.write(tty, 0, msg, strlen(msg));
        return;
}