diff options
Diffstat (limited to 'kernel/printk.c')
| -rw-r--r-- | kernel/printk.c | 1299 |
1 files changed, 1299 insertions, 0 deletions
diff --git a/kernel/printk.c b/kernel/printk.c new file mode 100644 index 0000000..b84eec7 --- /dev/null +++ b/kernel/printk.c @@ -0,0 +1,1299 @@ +/* + * 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 + * manfred@colorfullife.com + * Rewrote bits to get rid of console_lock + * 01Mar01 Andrew Morton + */ + +#include <linux/kernel.h> +#include <linux/mm.h> +#include <linux/tty.h> +#include <linux/tty_driver.h> +#include <linux/console.h> +#include <linux/init.h> +#include <linux/jiffies.h> +#include <linux/nmi.h> +#include <linux/module.h> +#include <linux/moduleparam.h> +#include <linux/interrupt.h> /* For in_interrupt() */ +#include <linux/delay.h> +#include <linux/smp.h> +#include <linux/security.h> +#include <linux/bootmem.h> +#include <linux/syscalls.h> + +#include <asm/uaccess.h> + +/* + * Architectures can override it: + */ +void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...) +{ +} + +#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 */ +}; + +/* + * Low level 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); +static DECLARE_MUTEX(secondary_console_sem); +struct console *console_drivers; +EXPORT_SYMBOL_GPL(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, console_suspended; + +/* + * 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 log_start; /* Index into log_buf: next char to be read by syslog() */ +static unsigned con_start; /* Index into log_buf: next char to be sent to consoles */ +static unsigned 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 */ +#ifdef CONFIG_A11Y_BRAILLE_CONSOLE + char *brl_options; /* Options for braille driver */ +#endif +}; + +#define MAX_CMDLINECONSOLES 8 + +static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES]; +static int selected_console = -1; +static int preferred_console = -1; +int console_set_on_cmdline; +EXPORT_SYMBOL(console_set_on_cmdline); + +/* 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 logged_chars; /* Number of chars produced since last read+clear operation */ + +static int __init log_buf_len_setup(char *str) +{ + unsigned size = memparse(str, &str); + unsigned long flags; + + if (size) + size = roundup_pow_of_two(size); + if (size > log_buf_len) { + unsigned 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); + +#ifdef CONFIG_BOOT_PRINTK_DELAY + +static unsigned int boot_delay; /* msecs delay after each printk during bootup */ +static unsigned long long printk_delay_msec; /* per msec, based on boot_delay */ + +static int __init boot_delay_setup(char *str) +{ + unsigned long lpj; + unsigned long long loops_per_msec; + + lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */ + loops_per_msec = (unsigned long long)lpj / 1000 * HZ; + + get_option(&str, &boot_delay); + if (boot_delay > 10 * 1000) + boot_delay = 0; + + printk_delay_msec = loops_per_msec; + printk(KERN_DEBUG "boot_delay: %u, preset_lpj: %ld, lpj: %lu, " + "HZ: %d, printk_delay_msec: %llu\n", + boot_delay, preset_lpj, lpj, HZ, printk_delay_msec); + return 1; +} +__setup("boot_delay=", boot_delay_setup); + +static void boot_delay_msec(void) +{ + unsigned long long k; + unsigned long timeout; + + if (boot_delay == 0 || system_state != SYSTEM_BOOTING) + return; + + k = (unsigned long long)printk_delay_msec * boot_delay; + + timeout = jiffies + msecs_to_jiffies(boot_delay); + while (k) { + k--; + cpu_relax(); + /* + * use (volatile) jiffies to prevent + * compiler reduction; loop termination via jiffies + * is secondary and may or may not happen. + */ + if (time_after(jiffies, timeout)) + break; + touch_nmi_watchdog(); + } +} +#else +static inline void boot_delay_msec(void) +{ +} +#endif + +/* + * 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 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; +} + +SYSCALL_DEFINE3(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 start, unsigned end) +{ + struct console *con; + + for (con = console_drivers; con; con = con->next) { + if ((con->flags & CON_ENABLED) && con->write && + (cpu_online(smp_processor_id()) || + (con->flags & CON_ANYTIME))) + con->write(con, &LOG_BUF(start), end - start); + } +} + +static int __read_mostly ignore_loglevel; + +static int __init ignore_loglevel_setup(char *str) +{ + ignore_loglevel = 1; + printk(KERN_INFO "debug: ignoring loglevel setting.\n"); + + return 0; +} + +early_param("ignore_loglevel", ignore_loglevel_setup); + +/* + * Write out chars from start to end - 1 inclusive + */ +static void _call_console_drivers(unsigned start, + unsigned end, int msg_log_level) +{ + if ((msg_log_level < console_loglevel || ignore_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 start, unsigned end) +{ + unsigned cur_index, start_print; + static int msg_level = -1; + + BUG_ON(((int)(start - end)) > 0); + + 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 +module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR); + +/* Check if we have any console registered that can be called early in boot. */ +static int have_callable_console(void) +{ + struct console *con; + + for (con = console_drivers; con; con = con->next) + if (con->flags & CON_ANYTIME) + return 1; + + return 0; +} + +/** + * 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) + * + * See the vsnprintf() documentation for format string extensions over C99. + */ + +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; + +/* + * Can we actually use the console at this time on this cpu? + * + * Console drivers may assume that per-cpu resources have + * been allocated. So unless they're explicitly marked as + * being able to cope (CON_ANYTIME) don't call them until + * this CPU is officially up. + */ +static inline int can_use_console(unsigned int cpu) +{ + return cpu_online(cpu) || have_callable_console(); +} + +/* + * Try to get console ownership to actually show the kernel + * messages from a 'printk'. Return true (and with the + * console_semaphore held, and 'console_locked' set) if it + * is successful, false otherwise. + * + * This gets called with the 'logbuf_lock' spinlock held and + * interrupts disabled. It should return with 'lockbuf_lock' + * released but interrupts still disabled. + */ +static int acquire_console_semaphore_for_printk(unsigned int cpu) +{ + int retval = 0; + + if (!try_acquire_console_sem()) { + retval = 1; + + /* + * If we can't use the console, we need to release + * the console semaphore by hand to avoid flushing + * the buffer. We need to hold the console semaphore + * in order to do this test safely. + */ + if (!can_use_console(cpu)) { + console_locked = 0; + up(&console_sem); + retval = 0; + } + } + printk_cpu = UINT_MAX; + spin_unlock(&logbuf_lock); + return retval; +} +static const char recursion_bug_msg [] = + KERN_CRIT "BUG: recent printk recursion!\n"; +static int recursion_bug; + static int new_text_line = 1; +static char printk_buf[1024]; + +asmlinkage int vprintk(const char *fmt, va_list args) +{ + int printed_len = 0; + int current_log_level = default_message_loglevel; + unsigned long flags; + int this_cpu; + char *p; + + boot_delay_msec(); + + preempt_disable(); + /* This stops the holder of console_sem just where we want him */ + raw_local_irq_save(flags); + this_cpu = smp_processor_id(); + + /* + * Ouch, printk recursed into itself! + */ + if (unlikely(printk_cpu == this_cpu)) { + /* + * If a crash is occurring during printk() on this CPU, + * then try to get the crash message out but make sure + * we can't deadlock. Otherwise just return to avoid the + * recursion and return - but flag the recursion so that + * it can be printed at the next appropriate moment: + */ + if (!oops_in_progress) { + recursion_bug = 1; + goto out_restore_irqs; + } + zap_locks(); + } + + lockdep_off(); + spin_lock(&logbuf_lock); + printk_cpu = this_cpu; + + if (recursion_bug) { + recursion_bug = 0; + strcpy(printk_buf, recursion_bug_msg); + printed_len = sizeof(recursion_bug_msg); + } + /* Emit the output into the temporary buffer */ + printed_len += vscnprintf(printk_buf + printed_len, + sizeof(printk_buf) - printed_len, 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 (new_text_line) { + /* If a token, set current_log_level and skip over */ + if (p[0] == '<' && p[1] >= '0' && p[1] <= '7' && + p[2] == '>') { + current_log_level = p[1] - '0'; + p += 3; + printed_len -= 3; + } + + /* Always output the token */ + emit_log_char('<'); + emit_log_char(current_log_level + '0'); + emit_log_char('>'); + printed_len += 3; + new_text_line = 0; + + if (printk_time) { + /* Follow the token with the time */ + char tbuf[50], *tp; + unsigned tlen; + unsigned long long t; + unsigned long nanosec_rem; + + t = cpu_clock(printk_cpu); + nanosec_rem = do_div(t, 1000000000); + tlen = sprintf(tbuf, "[%5lu.%06lu] ", + (unsigned long) t, + nanosec_rem / 1000); + + for (tp = tbuf; tp < tbuf + tlen; tp++) + emit_log_char(*tp); + printed_len += tlen; + } + + if (!*p) + break; + } + + emit_log_char(*p); + if (*p == '\n') + new_text_line = 1; + } + + /* + * Try to acquire and then immediately release the + * console semaphore. The release will do all the + * actual magic (print out buffers, wake up klogd, + * etc). + * + * The acquire_console_semaphore_for_printk() function + * will release 'logbuf_lock' regardless of whether it + * actually gets the semaphore or not. + */ + if (acquire_console_semaphore_for_printk(this_cpu)) + release_console_sem(); + + lockdep_on(); +out_restore_irqs: + raw_local_irq_restore(flags); + + preempt_enable(); + return printed_len; +} +EXPORT_SYMBOL(printk); +EXPORT_SYMBOL(vprintk); + +#else + +static void call_console_drivers(unsigned start, unsigned end) +{ +} + +#endif + +static int __add_preferred_console(char *name, int idx, char *options, + char *brl_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) { + if (!brl_options) + selected_console = i; + return 0; + } + if (i == MAX_CMDLINECONSOLES) + return -E2BIG; + if (!brl_options) + selected_console = i; + c = &console_cmdline[i]; + strlcpy(c->name, name, sizeof(c->name)); + c->options = options; +#ifdef CONFIG_A11Y_BRAILLE_CONSOLE + c->brl_options = brl_options; +#endif + c->index = idx; + return 0; +} +/* + * Set up a list of consoles. Called from init/main.c + */ +static int __init console_setup(char *str) +{ + char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */ + char *s, *options, *brl_options = NULL; + int idx; + +#ifdef CONFIG_A11Y_BRAILLE_CONSOLE + if (!memcmp(str, "brl,", 4)) { + brl_options = ""; + str += 4; + } else if (!memcmp(str, "brl=", 4)) { + brl_options = str + 4; + str = strchr(brl_options, ','); + if (!str) { + printk(KERN_ERR "need port name after brl=\n"); + return 1; + } + *(str++) = 0; + } +#endif + + /* + * Decode str into name, index, options. + */ + if (str[0] >= '0' && str[0] <= '9') { + strcpy(buf, "ttyS"); + strncpy(buf + 4, str, sizeof(buf) - 5); + } else { + strncpy(buf, str, sizeof(buf) - 1); + } + buf[sizeof(buf) - 1] = 0; + if ((options = strchr(str, ',')) != NULL) + *(options++) = 0; +#ifdef __sparc__ + if (!strcmp(str, "ttya")) + strcpy(buf, "ttyS0"); + if (!strcmp(str, "ttyb")) + strcpy(buf, "ttyS1"); +#endif + for (s = buf; *s; s++) + if ((*s >= '0' && *s <= '9') || *s == ',') + break; + idx = simple_strtoul(s, NULL, 10); + *s = 0; + + __add_preferred_console(buf, idx, options, brl_options); + console_set_on_cmdline = 1; + return 1; +} +__setup("console=", console_setup); + +/** + * 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 add_preferred_console(char *name, int idx, char *options) +{ + return __add_preferred_console(name, idx, options, NULL); +} + +int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options) +{ + struct console_cmdline *c; + int i; + + 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) { + c = &console_cmdline[i]; + strlcpy(c->name, name_new, sizeof(c->name)); + c->name[sizeof(c->name) - 1] = 0; + c->options = options; + c->index = idx_new; + return i; + } + /* not found */ + return -1; +} + +int console_suspend_enabled = 1; +EXPORT_SYMBOL(console_suspend_enabled); + +static int __init console_suspend_disable(char *str) +{ + console_suspend_enabled = 0; + return 1; +} +__setup("no_console_suspend", console_suspend_disable); + +/** + * suspend_console - suspend the console subsystem + * + * This disables printk() while we go into suspend states + */ +void suspend_console(void) +{ + if (!console_suspend_enabled) + return; + printk("Suspending console(s) (use no_console_suspend to debug)\n"); + acquire_console_sem(); + console_suspended = 1; +} + +void resume_console(void) +{ + if (!console_suspend_enabled) + return; + console_suspended = 0; + release_console_sem(); +} + +/** + * 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) +{ + BUG_ON(in_interrupt()); + if (console_suspended) { + down(&secondary_console_sem); + return; + } + 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; +} + +static DEFINE_PER_CPU(int, printk_pending); + +void printk_tick(void) +{ + if (__get_cpu_var(printk_pending)) { + __get_cpu_var(printk_pending) = 0; + wake_up_interruptible(&log_wait); + } +} + +int printk_needs_cpu(int cpu) +{ + return per_cpu(printk_pending, cpu); +} + +void wake_up_klogd(void) +{ + if (waitqueue_active(&log_wait)) + __raw_get_cpu_var(printk_pending) = 1; +} + +/** + * 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 _con_start, _log_end; + unsigned wake_klogd = 0; + + if (console_suspended) { + up(&secondary_console_sem); + return; + } + + console_may_schedule = 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); + stop_critical_timings(); /* don't trace print latency */ + call_console_drivers(_con_start, _log_end); + start_critical_timings(); + local_irq_restore(flags); + } + console_locked = 0; + up(&console_sem); + spin_unlock_irqrestore(&logbuf_lock, flags); + if (wake_klogd) + wake_up_klogd(); +} +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; + struct console *bootconsole = NULL; + + if (console_drivers) { + if (console->flags & CON_BOOT) + return; + if (console_drivers->flags & CON_BOOT) + bootconsole = console_drivers; + } + + if (preferred_console < 0 || bootconsole || !console_drivers) + preferred_console = selected_console; + + if (console->early_setup) + console->early_setup(); + + /* + * 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; + if (console->device) { + console->flags |= 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; +#ifdef CONFIG_A11Y_BRAILLE_CONSOLE + if (console_cmdline[i].brl_options) { + console->flags |= CON_BRL; + braille_register_console(console, + console_cmdline[i].index, + console_cmdline[i].options, + console_cmdline[i].brl_options); + return; + } +#endif + 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 (bootconsole && (console->flags & CON_CONSDEV)) { + printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n", + bootconsole->name, bootconsole->index, + console->name, console->index); + unregister_console(bootconsole); + console->flags &= ~CON_PRINTBUFFER; + } else { + printk(KERN_INFO "console [%s%d] enabled\n", + console->name, console->index); + } + + /* + * 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; + +#ifdef CONFIG_A11Y_BRAILLE_CONSOLE + if (console->flags & CON_BRL) + return braille_unregister_console(console); +#endif + + 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 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 && console->flags & CON_CONSDEV) + console_drivers->flags |= CON_CONSDEV; + + release_console_sem(); + return res; +} +EXPORT_SYMBOL(unregister_console); + +static int __init disable_boot_consoles(void) +{ + if (console_drivers != NULL) { + if (console_drivers->flags & CON_BOOT) { + printk(KERN_INFO "turn off boot console %s%d\n", + console_drivers->name, console_drivers->index); + return unregister_console(console_drivers); + } + } + return 0; +} +late_initcall(disable_boot_consoles); + +#if defined CONFIG_PRINTK + +/* + * printk rate limiting, lifted from the networking subsystem. + * + * This enforces a rate limit: not more than 10 kernel messages + * every 5s to make a denial-of-service attack impossible. + */ +DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10); + +int printk_ratelimit(void) +{ + return __ratelimit(&printk_ratelimit_state); +} +EXPORT_SYMBOL(printk_ratelimit); + +/** + * printk_timed_ratelimit - caller-controlled printk ratelimiting + * @caller_jiffies: pointer to caller's state + * @interval_msecs: minimum interval between prints + * + * printk_timed_ratelimit() returns true if more than @interval_msecs + * milliseconds have elapsed since the last time printk_timed_ratelimit() + * returned true. + */ +bool printk_timed_ratelimit(unsigned long *caller_jiffies, + unsigned int interval_msecs) +{ + if (*caller_jiffies == 0 || time_after(jiffies, *caller_jiffies)) { + *caller_jiffies = jiffies + msecs_to_jiffies(interval_msecs); + return true; + } + return false; +} +EXPORT_SYMBOL(printk_timed_ratelimit); +#endif |
