litmus-rt.git - The LITMUS^RT kernel.

	Commit message (Expand)	Author	Age
*	ARM: 6112/1: Use the Inner Shareable I-cache and BTB ops on ARMv7 SMP	Catalin Marinas	2010-05-08
*	ARM: 5858/1: Remove unused vma_vm_flags macro from v7wbi_flush_user_tlb_range	Bahadir Balban	2010-01-05
*	Check whether the TLB operations need broadcasting on SMP systems	Catalin Marinas	2009-05-30
*	arm: Use __INIT macro instead of .text.init.	Tim Abbott	2009-04-27
*	[ARM] 5227/1: Add the ENDPROC declarations to the .S files	Catalin Marinas	2008-09-01
*	[ARM] 4394/1: ARMv7: Add the TLB range operations	Catalin Marinas	2007-05-30

/* * 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); 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(KERN_WARNING "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(KERN_NOTICE "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); __attribute__((weak)) unsigned long long printk_clock(void) { return sched_clock(); } /** * printk - print a kernel message * @fmt: format string * * 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. * * See also: * printf(3) */ asmlinkage int printk(const char *fmt, ...) { va_list args; int r; va_start(args, fmt); r = vprintk(fmt, args); va_end(args); return r; } /* cpu currently holding logbuf_lock */ static volatile unsigned int printk_cpu = UINT_MAX; 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; preempt_disable(); if (unlikely(oops_in_progress) && printk_cpu == smp_processor_id()) /* If a crash is occurring during printk() on this CPU, * make sure we can't deadlock */ zap_locks(); /* This stops the holder of console_sem just where we want him */ spin_lock_irqsave(&logbuf_lock, flags); printk_cpu = smp_processor_id(); /* 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 = printk_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())) { /* * 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.. */ printk_cpu = UINT_MAX; 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 */ printk_cpu = UINT_MAX; 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. */ printk_cpu = UINT_MAX; spin_unlock_irqrestore(&logbuf_lock, flags); } out: preempt_enable(); 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 /** * add_preferred_console - add a device to the list of preferred consoles. * @name: device name * @idx: device index * @options: options for this console * * 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; } /** * 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(); } /* * 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 == selected_console) { console->flags |= CON_CONSDEV; preferred_console = selected_console; } 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; if (console->next) console->next->flags &= ~CON_CONSDEV; } 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 if (console_drivers) { 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 this isn't the last console and it has CON_CONSDEV set, we * need to set it on the next preferred console. */ if (console_drivers == NULL) preferred_console = selected_console; else if (console->flags & CON_CONSDEV) console_drivers->flags |= CON_CONSDEV; release_console_sem(); return res; } EXPORT_SYMBOL(unregister_console); /** * tty_write_message - write a message to a certain tty, not just the console. * @tty: the destination tty_struct * @msg: the message to write * * 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);