diff options
Diffstat (limited to 'kernel/printk.c')
| -rw-r--r-- | kernel/printk.c | 996 |
1 files changed, 996 insertions, 0 deletions
diff --git a/kernel/printk.c b/kernel/printk.c new file mode 100644 index 00000000000..1498689548d --- /dev/null +++ b/kernel/printk.c @@ -0,0 +1,996 @@ +/* + * 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); + +static char __log_buf[__LOG_BUF_LEN]; +static char *log_buf = __log_buf; +static int log_buf_len = __LOG_BUF_LEN; + +#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 */ +static unsigned long logged_chars; /* Number of chars produced since last read+clear operation */ + +/* + * 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; + +/* + * 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); + +/** + * 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); |