/* * 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 #include #include #include #include #include #include #include #include #include #include /* For in_interrupt() */ #include #include #include #include #include #include #include #include #include #include #include #include #include /* * for_each_console() allows you to iterate on each console */ #define for_each_console(con) \ for (con = console_drivers; con != NULL; con = con->next) /* * 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 DEFINE_SEMAPHORE(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 saved_console_loglevel = -1; #ifdef CONFIG_KEXEC /* * This appends the listed symbols to /proc/vmcoreinfo * * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to * obtain access to symbols that are otherwise very difficult to locate. These * symbols are specifically used so that utilities can access and extract the * dmesg log from a vmcore file after a crash. */ void log_buf_kexec_setup(void) { VMCOREINFO_SYMBOL(log_buf); VMCOREINFO_SYMBOL(log_end); VMCOREINFO_SYMBOL(log_buf_len); VMCOREINFO_SYMBOL(logged_chars); } #endif 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 int boot_delay; /* msecs delay after each printk during bootup */ static unsigned long long loops_per_msec; /* based on boot_delay */ static int __init boot_delay_setup(char *str) { unsigned long lpj; 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; pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, " "HZ: %d, loops_per_msec: %llu\n", boot_delay, preset_lpj, lpj, HZ, loops_per_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)loops_per_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 #ifdef CONFIG_SECURITY_DMESG_RESTRICT int dmesg_restrict = 1; #else int dmesg_restrict; #endif int do_syslog(int type, char __user *buf, int len, bool from_file) { unsigned i, j, limit, count; int do_clear = 0; char c; int error = 0; /* * If this is from /proc/kmsg we only do the capabilities checks * at open time. */ if (type == SYSLOG_ACTION_OPEN || !from_file) { if (dmesg_restrict && !capable(CAP_SYS_ADMIN)) return -EPERM; if ((type != SYSLOG_ACTION_READ_ALL && type != SYSLOG_ACTION_SIZE_BUFFER) && !capable(CAP_SYS_ADMIN)) return -EPERM; } error = security_syslog(type); if (error) return error; switch (type) { case SYSLOG_ACTION_CLOSE: /* Close log */ break; case SYSLOG_ACTION_OPEN: /* Open log */ break; case SYSLOG_ACTION_READ: /* 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; /* Read/clear last kernel messages */ case SYSLOG_ACTION_READ_CLEAR: do_clear = 1; /* FALL THRU */ /* Read last kernel messages */ case SYSLOG_ACTION_READ_ALL: 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. */ 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; /* Clear ring buffer */ case SYSLOG_ACTION_CLEAR: logged_chars = 0; break; /* Disable logging to console */ case SYSLOG_ACTION_CONSOLE_OFF: if (saved_console_loglevel == -1) saved_console_loglevel = console_loglevel; console_loglevel = minimum_console_loglevel; break; /* Enable logging to console */ case SYSLOG_ACTION_CONSOLE_ON: if (saved_console_loglevel != -1) { console_loglevel = saved_console_loglevel; saved_console_loglevel = -1; } break; /* Set level of messages printed to console */ case SYSLOG_ACTION_CONSOLE_LEVEL: error = -EINVAL; if (len < 1 || len > 8) goto out; if (len < minimum_console_loglevel) len = minimum_console_loglevel; console_loglevel = len; /* Implicitly re-enable logging to console */ saved_console_loglevel = -1; error = 0; break; /* Number of chars in the log buffer */ case SYSLOG_ACTION_SIZE_UNREAD: error = log_end - log_start; break; /* Size of the log buffer */ case SYSLOG_ACTION_SIZE_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, SYSLOG_FROM_CALL); } #ifdef CONFIG_KGDB_KDB /* kdb dmesg command needs access to the syslog buffer. do_syslog() * uses locks so it cannot be used during debugging. Just tell kdb * where the start and end of the physical and logical logs are. This * is equivalent to do_syslog(3). */ void kdb_syslog_data(char *syslog_data[4]) { syslog_data[0] = log_buf; syslog_data[1] = log_buf + log_buf_len; syslog_data[2] = log_buf + log_end - (logged_chars < log_buf_len ? logged_chars : log_buf_len); syslog_data[3] = log_buf + log_end; } #endif /* CONFIG_KGDB_KDB */ /* * Call the console drivers on a range of log_buf */ static void __call_console_drivers(unsigned start, unsigned end) { struct console *con; for_each_console(con) { 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 */ sema_init(&console_sem, 1); } #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_each_console(con) 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; #ifdef CONFIG_KGDB_KDB if (unlikely(kdb_trap_printk)) { va_start(args, fmt); r = vkdb_printf(fmt, args); va_end(args); return r; } #endif 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) __releases(&logbuf_lock) { 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]; int printk_delay_msec __read_mostly; static inline void printk_delay(void) { if (unlikely(printk_delay_msec)) { int m = printk_delay_msec; while (m--) { mdelay(1); touch_nmi_watchdog(); } } } 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(); printk_delay(); 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 = strlen(recursion_bug_msg); } /* Emit the output into the temporary buffer */ printed_len += vscnprintf(printk_buf + printed_len, sizeof(printk_buf) - printed_len, fmt, args); p = printk_buf; /* Do we have a loglevel in the string? */ if (p[0] == '<') { unsigned char c = p[1]; if (c && p[2] == '>') { switch (c) { case '0' ... '7': /* loglevel */ current_log_level = c - '0'; /* Fallthrough - make sure we're on a new line */ case 'd': /* KERN_DEFAULT */ if (!new_text_line) { emit_log_char('\n'); new_text_line = 1; } /* Fallthrough - skip the loglevel */ case 'c': /* KERN_CONT */ p += 3; break; } } } /* * Copy the output into log_buf. If the caller didn't provide * appropriate log level tags, we insert them here */ for ( ; *p; p++) { if (new_text_line) { /* 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; up(&console_sem); } void resume_console(void) { if (!console_suspend_enabled) return; down(&console_sem); console_suspended = 0; release_console_sem(); } /** * console_cpu_notify - print deferred console messages after CPU hotplug * @self: notifier struct * @action: CPU hotplug event * @hcpu: unused * * If printk() is called from a CPU that is not online yet, the messages * will be spooled but will not show up on the console. This function is * called when a new CPU comes online (or fails to come up), and ensures * that any such output gets printed. */ static int __cpuinit console_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu) { switch (action) { case CPU_ONLINE: case CPU_DEAD: case CPU_DYING: case CPU_DOWN_FAILED: case CPU_UP_CANCELED: acquire_console_sem(); release_console_sem(); } return NOTIFY_OK; } /** * 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()); down(&console_sem); if (console_suspended) return; 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; if (console_suspended) { up(&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 (__this_cpu_read(printk_pending)) { __this_cpu_write(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(&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_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_each_console(c) 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_each_console(c) { 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. * * This can happen pretty early during the boot process (because of * early_printk) - sometimes before setup_arch() completes - be careful * of what kernel features are used - they may not be initialised yet. * * There are two types of consoles - bootconsoles (early_printk) and * "real" consoles (everything which is not a bootconsole) which are * handled differently. * - Any number of bootconsoles can be registered at any time. * - As soon as a "real" console is registered, all bootconsoles * will be unregistered automatically. * - Once a "real" console is registered, any attempt to register a * bootconsoles will be rejected */ void register_console(struct console *newcon) { int i; unsigned long flags; struct console *bcon = NULL; /* * before we register a new CON_BOOT console, make sure we don't * already have a valid console */ if (console_drivers && newcon->flags & CON_BOOT) { /* find the last or real console */ for_each_console(bcon) { if (!(bcon->flags & CON_BOOT)) { printk(KERN_INFO "Too late to register bootconsole %s%d\n", newcon->name, newcon->index); return; } } } if (console_drivers && console_drivers->flags & CON_BOOT) bcon = console_drivers; if (preferred_console < 0 || bcon || !console_drivers) preferred_console = selected_console; if (newcon->early_setup) newcon->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 (newcon->index < 0) newcon->index = 0; if (newcon->setup == NULL || newcon->setup(newcon, NULL) == 0) { newcon->flags |= CON_ENABLED; if (newcon->device) { newcon->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, newcon->name) != 0) continue; if (newcon->index >= 0 && newcon->index != console_cmdline[i].index) continue; if (newcon->index < 0) newcon->index = console_cmdline[i].index; #ifdef CONFIG_A11Y_BRAILLE_CONSOLE if (console_cmdline[i].brl_options) { newcon->flags |= CON_BRL; braille_register_console(newcon, console_cmdline[i].index, console_cmdline[i].options, console_cmdline[i].brl_options); return; } #endif if (newcon->setup && newcon->setup(newcon, console_cmdline[i].options) != 0) break; newcon->flags |= CON_ENABLED; newcon->index = console_cmdline[i].index; if (i == selected_console) { newcon->flags |= CON_CONSDEV; preferred_console = selected_console; } break; } if (!(newcon->flags & CON_ENABLED)) return; /* * If we have a bootconsole, and are switching to a real console, * don't print everything out again, since when the boot console, and * the real console are the same physical device, it's annoying to * see the beginning boot messages twice */ if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) newcon->flags &= ~CON_PRINTBUFFER; /* * Put this console in the list - keep the * preferred driver at the head of the list. */ acquire_console_sem(); if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) { newcon->next = console_drivers; console_drivers = newcon; if (newcon->next) newcon->next->flags &= ~CON_CONSDEV; } else { newcon->next = console_drivers->next; console_drivers->next = newcon; } if (newcon->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(); /* * By unregistering the bootconsoles after we enable the real console * we get the "console xxx enabled" message on all the consoles - * boot consoles, real consoles, etc - this is to ensure that end * users know there might be something in the kernel's log buffer that * went to the bootconsole (that they do not see on the real console) */ if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) { /* we need to iterate through twice, to make sure we print * everything out, before we unregister the console(s) */ printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n", newcon->name, newcon->index); for_each_console(bcon) if (bcon->flags & CON_BOOT) unregister_console(bcon); } else { printk(KERN_INFO "%sconsole [%s%d] enabled\n", (newcon->flags & CON_BOOT) ? "boot" : "" , newcon->name, newcon->index); } } 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 printk_late_init(void) { struct console *con; for_each_console(con) { if (con->flags & CON_BOOT) { printk(KERN_INFO "turn off boot console %s%d\n", con->name, con->index); unregister_console(con); } } hotcpu_notifier(console_cpu_notify, 0); return 0; } late_initcall(printk_late_init); #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(const char *func) { return ___ratelimit(&printk_ratelimit_state, func); } 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_in_range(jiffies, *caller_jiffies, *caller_jiffies + msecs_to_jiffies(interval_msecs))) { *caller_jiffies = jiffies; return true; } return false; } EXPORT_SYMBOL(printk_timed_ratelimit); static DEFINE_SPINLOCK(dump_list_lock); static LIST_HEAD(dump_list); /** * kmsg_dump_register - register a kernel log dumper. * @dumper: pointer to the kmsg_dumper structure * * Adds a kernel log dumper to the system. The dump callback in the * structure will be called when the kernel oopses or panics and must be * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise. */ int kmsg_dump_register(struct kmsg_dumper *dumper) { unsigned long flags; int err = -EBUSY; /* The dump callback needs to be set */ if (!dumper->dump) return -EINVAL; spin_lock_irqsave(&dump_list_lock, flags); /* Don't allow registering multiple times */ if (!dumper->registered) { dumper->registered = 1; list_add_tail(&dumper->list, &dump_list); err = 0; } spin_unlock_irqrestore(&dump_list_lock, flags); return err; } EXPORT_SYMBOL_GPL(kmsg_dump_register); /** * kmsg_dump_unregister - unregister a kmsg dumper. * @dumper: pointer to the kmsg_dumper structure * * Removes a dump device from the system. Returns zero on success and * %-EINVAL otherwise. */ int kmsg_dump_unregister(struct kmsg_dumper *dumper) { unsigned long flags; int err = -EINVAL; spin_lock_irqsave(&dump_list_lock, flags); if (dumper->registered) { dumper->registered = 0; list_del(&dumper->list); err = 0; } spin_unlock_irqrestore(&dump_list_lock, flags); return err; } EXPORT_SYMBOL_GPL(kmsg_dump_unregister); static const char * const kmsg_reasons[] = { [KMSG_DUMP_OOPS] = "oops", [KMSG_DUMP_PANIC] = "panic", [KMSG_DUMP_KEXEC] = "kexec", }; static const char *kmsg_to_str(enum kmsg_dump_reason reason) { if (reason >= ARRAY_SIZE(kmsg_reasons) || reason < 0) return "unknown"; return kmsg_reasons[reason]; } /** * kmsg_dump - dump kernel log to kernel message dumpers. * @reason: the reason (oops, panic etc) for dumping * * Iterate through each of the dump devices and call the oops/panic * callbacks with the log buffer. */ void kmsg_dump(enum kmsg_dump_reason reason) { unsigned long end; unsigned chars; struct kmsg_dumper *dumper; const char *s1, *s2; unsigned long l1, l2; unsigned long flags; /* Theoretically, the log could move on after we do this, but there's not a lot we can do about that. The new messages will overwrite the start of what we dump. */ spin_lock_irqsave(&logbuf_lock, flags); end = log_end & LOG_BUF_MASK; chars = logged_chars; spin_unlock_irqrestore(&logbuf_lock, flags); if (chars > end) { s1 = log_buf + log_buf_len - chars + end; l1 = chars - end; s2 = log_buf; l2 = end; } else { s1 = ""; l1 = 0; s2 = log_buf + end - chars; l2 = chars; } if (!spin_trylock_irqsave(&dump_list_lock, flags)) { printk(KERN_ERR "dump_kmsg: dump list lock is held during %s, skipping dump\n", kmsg_to_str(reason)); return; } list_for_each_entry(dumper, &dump_list, list) dumper->dump(dumper, reason, s1, l1, s2, l2); spin_unlock_irqrestore(&dump_list_lock, flags); } #endif