Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
diff --git a/kernel/printk.c b/kernel/printk.c
new file mode 100644
index 0000000..1498689
--- /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);