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printk.c 25.20 KiB
/*
* 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 <linux/security.h>
#include <linux/bootmem.h>
#include <linux/syscalls.h>
#include <asm/uaccess.h>
#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 */
};
EXPORT_SYMBOL(console_printk);
/*
* Low lever drivers may need that to know if they can schedule in
* their unblank() callback or not. So let's export it.
*/
int oops_in_progress;
EXPORT_SYMBOL(oops_in_progress);
/*
* console_sem protects the console_drivers list, and also
* provides serialisation for access to the entire console
* driver system.
*/
static DECLARE_MUTEX(console_sem);
struct console *console_drivers;/*
* 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
*/
static int console_locked;
/*
* 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);
#define LOG_BUF_MASK (log_buf_len-1)
#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 */
/*
* 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 */
};
#define MAX_CMDLINECONSOLES 8
static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
static int selected_console = -1;
static int preferred_console = -1;
/* Flag: console code may call schedule() */
static int console_may_schedule;
#ifdef CONFIG_PRINTK
static char __log_buf[__LOG_BUF_LEN];
static char *log_buf = __log_buf;
static int log_buf_len = __LOG_BUF_LEN;
static unsigned long logged_chars; /* Number of chars produced since last read+clear operation */
/*
* Setup a list of consoles. Called from init/main.c
*/
static int __init console_setup(char *str)
{
char name[sizeof(console_cmdline[0].name)];
char *s, *options;
int 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') || *s == ',')
break;
idx = simple_strtoul(s, NULL, 10);
*s = 0;
add_preferred_console(name, idx, options);
return 1;
}
__setup("console=", console_setup);
/**
* add_preferred_console - add a device to the list of preferred consoles.
*
* 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.
*/
int __init add_preferred_console(char *name, int idx, char *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) {
selected_console = i;
return 0;
}
if (i == MAX_CMDLINECONSOLES)
return -E2BIG;
selected_console = i;
c = &console_cmdline[i];
memcpy(c->name, name, sizeof(c->name));
c->name[sizeof(c->name) - 1] = 0;
c->options = options;
c->index = idx;
return 0;
}
static int __init log_buf_len_setup(char *str)
{
unsigned long size = memparse(str, &str);
unsigned long flags;
if (size)
size = roundup_pow_of_two(size);
if (size > log_buf_len) {
unsigned long start, dest_idx, offset;
char * new_log_buf;
new_log_buf = alloc_bootmem(size); if (!new_log_buf) {
printk("log_buf_len: allocation failed\n");
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);
printk("log_buf_len: %d\n", log_buf_len);
}
out:
return 1;
}
__setup("log_buf_len=", log_buf_len_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
* 10 -- Return size of the log buffer
*/
int do_syslog(int type, char __user * buf, int len)
{
unsigned long i, j, limit, count;
int do_clear = 0;
char c;
int error = 0;
error = security_syslog(type);
if (error)
return error;
switch (type) {
case 0: /* Close log */
break;
case 1: /* Open log */
break;
case 2: /* Read from log */
error = -EINVAL;
if (!buf || len < 0)
goto out;
error = 0;
if (!len)
goto out;
if (!access_ok(VERIFY_WRITE, buf, len)) {
error = -EFAULT; goto out;
}
error = wait_event_interruptible(log_wait, (log_start - log_end));
if (error)
goto out;
i = 0;
spin_lock_irq(&logbuf_lock);
while (!error && (log_start != log_end) && i < len) {
c = LOG_BUF(log_start);
log_start++;
spin_unlock_irq(&logbuf_lock);
error = __put_user(c,buf);
buf++;
i++;
cond_resched();
spin_lock_irq(&logbuf_lock);
}
spin_unlock_irq(&logbuf_lock);
if (!error)
error = i;
break;
case 4: /* Read/clear last kernel messages */
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;
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
* 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 && !error; i++) {
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;
if(i != count) {
int offset = count-error;
/* buffer overflow during copy, correct user buffer. */
for(i=0;i<error;i++) {
if (__get_user(c,&buf[i+offset]) ||
__put_user(c,&buf[i])) { error = -EFAULT;
break;
}
cond_resched();
}
}
break;
case 5: /* Clear ring buffer */
logged_chars = 0;
break;
case 6: /* Disable logging to console */
console_loglevel = minimum_console_loglevel;
break;
case 7: /* Enable logging to console */
console_loglevel = default_console_loglevel;
break;
case 8: /* Set level of messages printed to console */
error = -EINVAL;
if (len < 1 || len > 8)
goto out;
if (len < minimum_console_loglevel)
len = minimum_console_loglevel;
console_loglevel = len;
error = 0;
break;
case 9: /* Number of chars in the log buffer */
error = log_end - log_start;
break;
case 10: /* Size of the log buffer */
error = log_buf_len;
break;
default:
error = -EINVAL;
break;
}
out:
return error;
}
asmlinkage long sys_syslog(int type, char __user * buf, int len)
{
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++;
}
/* * 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) &&
!time_after(jiffies, oops_timestamp + 30*HZ))
return;
oops_timestamp = jiffies;
/* If a crash is occurring, make sure we can't deadlock */
spin_lock_init(&logbuf_lock);
/* And make sure that we print immediately */
init_MUTEX(&console_sem);
}
#if defined(CONFIG_PRINTK_TIME)
static int printk_time = 1;
#else
static int printk_time = 0;
#endif
static int __init printk_time_setup(char *str)
{
if (*str)
return 0;
printk_time = 1;
return 1;
}
__setup("time", printk_time_setup);
/*
* 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;
int r;
va_start(args, fmt);
r = vprintk(fmt, args);
va_end(args);
return r;
}
asmlinkage int vprintk(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 (unlikely(oops_in_progress))
zap_locks();
/* 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 */
printed_len = vscnprintf(printk_buf, sizeof(printk_buf), fmt, 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) {
/* log_level_unknown signals the start of a new line */
if (printk_time) {
int loglev_char;
char tbuf[50], *tp;
unsigned tlen;
unsigned long long t;
unsigned long nanosec_rem;
/*
* force the log level token to be
* before the time output.
*/
if (p[0] == '<' && p[1] >='0' &&
p[1] <= '7' && p[2] == '>') {
loglev_char = p[1];
p += 3;
printed_len += 3;
} else {
loglev_char = default_message_loglevel
+ '0';
}
t = sched_clock();
nanosec_rem = do_div(t, 1000000000);
tlen = sprintf(tbuf,
"<%c>[%5lu.%06lu] ",
loglev_char,
(unsigned long)t,
nanosec_rem/1000);
for (tp = tbuf; tp < tbuf + tlen; tp++)
emit_log_char(*tp);
printed_len += tlen - 3;
} else {
if (p[0] != '<' || p[1] < '0' ||
p[1] > '7' || p[2] != '>') {
emit_log_char('<');
emit_log_char(default_message_loglevel
+ '0');
emit_log_char('>');
}
printed_len += 3;
}
log_level_unknown = 0;
if (!*p)
break;
}
emit_log_char(*p);
if (*p == '\n')
log_level_unknown = 1;
}
if (!cpu_online(smp_processor_id()) &&
system_state != SYSTEM_RUNNING) {
/*
* 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)) {
console_locked = 1;
/*
* 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);
EXPORT_SYMBOL(vprintk);
#else
asmlinkage long sys_syslog(int type, char __user * buf, int len)
{
return 0;
}
int do_syslog(int type, char __user * buf, int len) { return 0; }
static void call_console_drivers(unsigned long start, unsigned long end) {}
#endif
/**
* 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_locked = 1;
console_may_schedule = 1;
}
EXPORT_SYMBOL(acquire_console_sem);
int try_acquire_console_sem(void)
{
if (down_trylock(&console_sem))
return -1;
console_locked = 1;
console_may_schedule = 0;
return 0;
}
EXPORT_SYMBOL(try_acquire_console_sem);
int is_console_locked(void)
{
return console_locked;
}
EXPORT_SYMBOL(is_console_locked);
/**
* 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(&logbuf_lock);
call_console_drivers(_con_start, _log_end);
local_irq_restore(flags);
}
console_locked = 0;
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);
}
EXPORT_SYMBOL(release_console_sem);
/** 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 __sched console_conditional_schedule(void)
{
if (console_may_schedule)
cond_resched();
}
EXPORT_SYMBOL(console_conditional_schedule);
void console_print(const char *s)
{
printk(KERN_EMERG "%s", s);
}
EXPORT_SYMBOL(console_print);
void console_unblank(void)
{ struct console *c;
/*
* console_unblank can no longer be called in interrupt context unless
* oops_in_progress is set to 1..
*/
if (oops_in_progress) {
if (down_trylock(&console_sem) != 0)
return;
} else
acquire_console_sem();
console_locked = 1;
console_may_schedule = 0;
for (c = console_drivers; c != NULL; c = c->next)
if ((c->flags & CON_ENABLED) && c->unblank)
c->unblank();
release_console_sem();
}
EXPORT_SYMBOL(console_unblank);
/*
* Return the console tty driver structure and its associated index
*/
struct tty_driver *console_device(int *index)
{
struct console *c;
struct tty_driver *driver = NULL;
acquire_console_sem();
for (c = console_drivers; c != NULL; c = c->next) {
if (!c->device)
continue;
driver = c->device(c, index);
if (driver)
break;
}
release_console_sem();
return driver;
}
/*
* Prevent further output on the passed console device so that (for example)
* serial drivers can disable console output before suspending a port, and can
* re-enable output afterwards.
*/
void console_stop(struct console *console)
{
acquire_console_sem();
console->flags &= ~CON_ENABLED;
release_console_sem();
}
EXPORT_SYMBOL(console_stop);
void console_start(struct console *console)
{
acquire_console_sem();
console->flags |= CON_ENABLED;
release_console_sem();
}
EXPORT_SYMBOL(console_start);
/*
* The console driver calls this routine during kernel initialization
* to register the console printing procedure with printk() and to
* print any messages that were printed by the kernel before the
* console driver was initialized.
*/
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;
if (console_drivers && (console_drivers->flags & CON_BOOT)) {
unregister_console(console_drivers);
console->flags &= ~CON_PRINTBUFFER;
}
/*
* 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, msg, strlen(msg));
return;
}
/*
* printk rate limiting, lifted from the networking subsystem.
*
* This enforces a rate limit: not more than one kernel message
* every printk_ratelimit_jiffies to make a denial-of-service
* attack impossible.
*/
int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst)
{
static DEFINE_SPINLOCK(ratelimit_lock);
static unsigned long toks = 10*5*HZ;
static unsigned long last_msg;
static int missed;
unsigned long flags;
unsigned long now = jiffies;
spin_lock_irqsave(&ratelimit_lock, flags); toks += now - last_msg;
last_msg = now;
if (toks > (ratelimit_burst * ratelimit_jiffies))
toks = ratelimit_burst * ratelimit_jiffies;
if (toks >= ratelimit_jiffies) {
int lost = missed;
missed = 0;
toks -= ratelimit_jiffies;
spin_unlock_irqrestore(&ratelimit_lock, flags);
if (lost)
printk(KERN_WARNING "printk: %d messages suppressed.\n", lost);
return 1;
}
missed++;
spin_unlock_irqrestore(&ratelimit_lock, flags);
return 0;
}
EXPORT_SYMBOL(__printk_ratelimit);
/* minimum time in jiffies between messages */
int printk_ratelimit_jiffies = 5*HZ;
/* number of messages we send before ratelimiting */
int printk_ratelimit_burst = 10;
int printk_ratelimit(void)
{
return __printk_ratelimit(printk_ratelimit_jiffies,
printk_ratelimit_burst);
}
EXPORT_SYMBOL(printk_ratelimit);