blob: 9f2eb4b45669833b5655c5f630eabc58259cd031 [file] [log] [blame]
/*
* 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 <linux/delay.h>
#include <linux/smp.h>
#include <asm/uaccess.h>
#define LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
#define LOG_BUF_MASK (LOG_BUF_LEN-1)
/* 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 */
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;
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 (!cpu_online(smp_processor_id())) {
/*
* Some console drivers may assume that per-cpu resources have
* been allocated. So don't allow them to be called by this
* CPU until it is officially up. We shouldn't be calling into
* random console drivers on a CPU which doesn't exist yet..
*/
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 wake_klogd = 0;
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_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 (wake_klogd && !oops_in_progress && waitqueue_active(&log_wait))
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 && need_resched()) {
set_current_state(TASK_RUNNING);
schedule();
}
}
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;
/*
* 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;
/*
* 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 = -1;
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;
}