/* * 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 #include #include #include #define CREATE_TRACE_POINTS #include /* * Architectures can override it: */ void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...) { } /* printk's without a loglevel use this.. */ #define DEFAULT_MESSAGE_LOGLEVEL CONFIG_DEFAULT_MESSAGE_LOGLEVEL /* 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; /* * If exclusive_console is non-NULL then only this console is to be printed to. */ static struct console *exclusive_console; /* * 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; /* * The printk log buffer consists of a chain of concatenated variable * length records. Every record starts with a record header, containing * the overall length of the record. * * The heads to the first and last entry in the buffer, as well as the * sequence numbers of these both entries are maintained when messages * are stored.. * * If the heads indicate available messages, the length in the header * tells the start next message. A length == 0 for the next message * indicates a wrap-around to the beginning of the buffer. * * Every record carries the monotonic timestamp in microseconds, as well as * the standard userspace syslog level and syslog facility. The usual * kernel messages use LOG_KERN; userspace-injected messages always carry * a matching syslog facility, by default LOG_USER. The origin of every * message can be reliably determined that way. * * The human readable log message directly follows the message header. The * length of the message text is stored in the header, the stored message * is not terminated. * * Optionally, a message can carry a dictionary of properties (key/value pairs), * to provide userspace with a machine-readable message context. * * Examples for well-defined, commonly used property names are: * DEVICE=b12:8 device identifier * b12:8 block dev_t * c127:3 char dev_t * n8 netdev ifindex * +sound:card0 subsystem:devname * SUBSYSTEM=pci driver-core subsystem name * * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value * follows directly after a '=' character. Every property is terminated by * a '\0' character. The last property is not terminated. * * Example of a message structure: * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec * 0008 34 00 record is 52 bytes long * 000a 0b 00 text is 11 bytes long * 000c 1f 00 dictionary is 23 bytes long * 000e 03 00 LOG_KERN (facility) LOG_ERR (level) * 0010 69 74 27 73 20 61 20 6c "it's a l" * 69 6e 65 "ine" * 001b 44 45 56 49 43 "DEVIC" * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D" * 52 49 56 45 52 3d 62 75 "RIVER=bu" * 67 "g" * 0032 00 00 00 padding to next message header * * The 'struct log' buffer header must never be directly exported to * userspace, it is a kernel-private implementation detail that might * need to be changed in the future, when the requirements change. * * /dev/kmsg exports the structured data in the following line format: * "level,sequnum,timestamp;\n" * * The optional key/value pairs are attached as continuation lines starting * with a space character and terminated by a newline. All possible * non-prinatable characters are escaped in the "\xff" notation. * * Users of the export format should ignore possible additional values * separated by ',', and find the message after the ';' character. */ struct log { u64 ts_nsec; /* timestamp in nanoseconds */ u16 len; /* length of entire record */ u16 text_len; /* length of text buffer */ u16 dict_len; /* length of dictionary buffer */ u16 level; /* syslog level + facility */ }; /* * The logbuf_lock protects kmsg buffer, indices, counters. It is also * used in interesting ways to provide interlocking in console_unlock(); */ static DEFINE_RAW_SPINLOCK(logbuf_lock); /* the next printk record to read by syslog(READ) or /proc/kmsg */ static u64 syslog_seq; static u32 syslog_idx; /* index and sequence number of the first record stored in the buffer */ static u64 log_first_seq; static u32 log_first_idx; /* index and sequence number of the next record to store in the buffer */ static u64 log_next_seq; #ifdef CONFIG_PRINTK static u32 log_next_idx; /* the next printk record to read after the last 'clear' command */ static u64 clear_seq; static u32 clear_idx; #define LOG_LINE_MAX 1024 /* record buffer */ #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) #define LOG_ALIGN 4 #else #define LOG_ALIGN __alignof__(struct log) #endif #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT) static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN); static char *log_buf = __log_buf; static u32 log_buf_len = __LOG_BUF_LEN; /* cpu currently holding logbuf_lock */ static volatile unsigned int logbuf_cpu = UINT_MAX; /* human readable text of the record */ static char *log_text(const struct log *msg) { return (char *)msg + sizeof(struct log); } /* optional key/value pair dictionary attached to the record */ static char *log_dict(const struct log *msg) { return (char *)msg + sizeof(struct log) + msg->text_len; } /* get record by index; idx must point to valid msg */ static struct log *log_from_idx(u32 idx) { struct log *msg = (struct log *)(log_buf + idx); /* * A length == 0 record is the end of buffer marker. Wrap around and * read the message at the start of the buffer. */ if (!msg->len) return (struct log *)log_buf; return msg; } /* get next record; idx must point to valid msg */ static u32 log_next(u32 idx) { struct log *msg = (struct log *)(log_buf + idx); /* length == 0 indicates the end of the buffer; wrap */ /* * A length == 0 record is the end of buffer marker. Wrap around and * read the message at the start of the buffer as *this* one, and * return the one after that. */ if (!msg->len) { msg = (struct log *)log_buf; return msg->len; } return idx + msg->len; } /* insert record into the buffer, discard old ones, update heads */ static void log_store(int facility, int level, const char *dict, u16 dict_len, const char *text, u16 text_len) { struct log *msg; u32 size, pad_len; /* number of '\0' padding bytes to next message */ size = sizeof(struct log) + text_len + dict_len; pad_len = (-size) & (LOG_ALIGN - 1); size += pad_len; while (log_first_seq < log_next_seq) { u32 free; if (log_next_idx > log_first_idx) free = max(log_buf_len - log_next_idx, log_first_idx); else free = log_first_idx - log_next_idx; if (free > size + sizeof(struct log)) break; /* drop old messages until we have enough contiuous space */ log_first_idx = log_next(log_first_idx); log_first_seq++; } if (log_next_idx + size + sizeof(struct log) >= log_buf_len) { /* * This message + an additional empty header does not fit * at the end of the buffer. Add an empty header with len == 0 * to signify a wrap around. */ memset(log_buf + log_next_idx, 0, sizeof(struct log)); log_next_idx = 0; } /* fill message */ msg = (struct log *)(log_buf + log_next_idx); memcpy(log_text(msg), text, text_len); msg->text_len = text_len; memcpy(log_dict(msg), dict, dict_len); msg->dict_len = dict_len; msg->level = (facility << 3) | (level & 7); msg->ts_nsec = local_clock(); memset(log_dict(msg) + dict_len, 0, pad_len); msg->len = sizeof(struct log) + text_len + dict_len + pad_len; /* insert message */ log_next_idx += msg->len; log_next_seq++; } /* /dev/kmsg - userspace message inject/listen interface */ struct devkmsg_user { u64 seq; u32 idx; struct mutex lock; char buf[8192]; }; static ssize_t devkmsg_writev(struct kiocb *iocb, const struct iovec *iv, unsigned long count, loff_t pos) { char *buf, *line; int i; int level = default_message_loglevel; int facility = 1; /* LOG_USER */ size_t len = iov_length(iv, count); ssize_t ret = len; if (len > LOG_LINE_MAX) return -EINVAL; buf = kmalloc(len+1, GFP_KERNEL); if (buf == NULL) return -ENOMEM; line = buf; for (i = 0; i < count; i++) { if (copy_from_user(line, iv[i].iov_base, iv[i].iov_len)) goto out; line += iv[i].iov_len; } /* * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace * the decimal value represents 32bit, the lower 3 bit are the log * level, the rest are the log facility. * * If no prefix or no userspace facility is specified, we * enforce LOG_USER, to be able to reliably distinguish * kernel-generated messages from userspace-injected ones. */ line = buf; if (line[0] == '<') { char *endp = NULL; i = simple_strtoul(line+1, &endp, 10); if (endp && endp[0] == '>') { level = i & 7; if (i >> 3) facility = i >> 3; endp++; len -= endp - line; line = endp; } } line[len] = '\0'; printk_emit(facility, level, NULL, 0, "%s", line); out: kfree(buf); return ret; } static ssize_t devkmsg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos) { struct devkmsg_user *user = file->private_data; struct log *msg; u64 ts_usec; size_t i; size_t len; ssize_t ret; if (!user) return -EBADF; ret = mutex_lock_interruptible(&user->lock); if (ret) return ret; raw_spin_lock(&logbuf_lock); while (user->seq == log_next_seq) { if (file->f_flags & O_NONBLOCK) { ret = -EAGAIN; raw_spin_unlock(&logbuf_lock); goto out; } raw_spin_unlock(&logbuf_lock); ret = wait_event_interruptible(log_wait, user->seq != log_next_seq); if (ret) goto out; raw_spin_lock(&logbuf_lock); } if (user->seq < log_first_seq) { /* our last seen message is gone, return error and reset */ user->idx = log_first_idx; user->seq = log_first_seq; ret = -EPIPE; raw_spin_unlock(&logbuf_lock); goto out; } msg = log_from_idx(user->idx); ts_usec = msg->ts_nsec; do_div(ts_usec, 1000); len = sprintf(user->buf, "%u,%llu,%llu;", msg->level, user->seq, ts_usec); /* escape non-printable characters */ for (i = 0; i < msg->text_len; i++) { unsigned char c = log_text(msg)[i]; if (c < ' ' || c >= 128) len += sprintf(user->buf + len, "\\x%02x", c); else user->buf[len++] = c; } user->buf[len++] = '\n'; if (msg->dict_len) { bool line = true; for (i = 0; i < msg->dict_len; i++) { unsigned char c = log_dict(msg)[i]; if (line) { user->buf[len++] = ' '; line = false; } if (c == '\0') { user->buf[len++] = '\n'; line = true; continue; } if (c < ' ' || c >= 128) { len += sprintf(user->buf + len, "\\x%02x", c); continue; } user->buf[len++] = c; } user->buf[len++] = '\n'; } user->idx = log_next(user->idx); user->seq++; raw_spin_unlock(&logbuf_lock); if (len > count) { ret = -EINVAL; goto out; } if (copy_to_user(buf, user->buf, len)) { ret = -EFAULT; goto out; } ret = len; out: mutex_unlock(&user->lock); return ret; } static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence) { struct devkmsg_user *user = file->private_data; loff_t ret = 0; if (!user) return -EBADF; if (offset) return -ESPIPE; raw_spin_lock(&logbuf_lock); switch (whence) { case SEEK_SET: /* the first record */ user->idx = log_first_idx; user->seq = log_first_seq; break; case SEEK_DATA: /* * The first record after the last SYSLOG_ACTION_CLEAR, * like issued by 'dmesg -c'. Reading /dev/kmsg itself * changes no global state, and does not clear anything. */ user->idx = clear_idx; user->seq = clear_seq; break; case SEEK_END: /* after the last record */ user->idx = log_next_idx; user->seq = log_next_seq; break; default: ret = -EINVAL; } raw_spin_unlock(&logbuf_lock); return ret; } static unsigned int devkmsg_poll(struct file *file, poll_table *wait) { struct devkmsg_user *user = file->private_data; int ret = 0; if (!user) return POLLERR|POLLNVAL; poll_wait(file, &log_wait, wait); raw_spin_lock(&logbuf_lock); if (user->seq < log_next_seq) { /* return error when data has vanished underneath us */ if (user->seq < log_first_seq) ret = POLLIN|POLLRDNORM|POLLERR|POLLPRI; ret = POLLIN|POLLRDNORM; } raw_spin_unlock(&logbuf_lock); return ret; } static int devkmsg_open(struct inode *inode, struct file *file) { struct devkmsg_user *user; int err; /* write-only does not need any file context */ if ((file->f_flags & O_ACCMODE) == O_WRONLY) return 0; err = security_syslog(SYSLOG_ACTION_READ_ALL); if (err) return err; user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL); if (!user) return -ENOMEM; mutex_init(&user->lock); raw_spin_lock(&logbuf_lock); user->idx = log_first_idx; user->seq = log_first_seq; raw_spin_unlock(&logbuf_lock); file->private_data = user; return 0; } static int devkmsg_release(struct inode *inode, struct file *file) { struct devkmsg_user *user = file->private_data; if (!user) return 0; mutex_destroy(&user->lock); kfree(user); return 0; } const struct file_operations kmsg_fops = { .open = devkmsg_open, .read = devkmsg_read, .aio_write = devkmsg_writev, .llseek = devkmsg_llseek, .poll = devkmsg_poll, .release = devkmsg_release, }; #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_buf_len); VMCOREINFO_SYMBOL(log_first_idx); VMCOREINFO_SYMBOL(log_next_idx); } #endif /* requested log_buf_len from kernel cmdline */ static unsigned long __initdata new_log_buf_len; /* save requested log_buf_len since it's too early to process it */ static int __init log_buf_len_setup(char *str) { unsigned size = memparse(str, &str); if (size) size = roundup_pow_of_two(size); if (size > log_buf_len) new_log_buf_len = size; return 0; } early_param("log_buf_len", log_buf_len_setup); void __init setup_log_buf(int early) { unsigned long flags; char *new_log_buf; int free; if (!new_log_buf_len) return; if (early) { unsigned long mem; mem = memblock_alloc(new_log_buf_len, PAGE_SIZE); if (!mem) return; new_log_buf = __va(mem); } else { new_log_buf = alloc_bootmem_nopanic(new_log_buf_len); } if (unlikely(!new_log_buf)) { pr_err("log_buf_len: %ld bytes not available\n", new_log_buf_len); return; } raw_spin_lock_irqsave(&logbuf_lock, flags); log_buf_len = new_log_buf_len; log_buf = new_log_buf; new_log_buf_len = 0; free = __LOG_BUF_LEN - log_next_idx; memcpy(log_buf, __log_buf, __LOG_BUF_LEN); raw_spin_unlock_irqrestore(&logbuf_lock, flags); pr_info("log_buf_len: %d\n", log_buf_len); pr_info("early log buf free: %d(%d%%)\n", free, (free * 100) / __LOG_BUF_LEN); } #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 static int syslog_action_restricted(int type) { if (dmesg_restrict) return 1; /* Unless restricted, we allow "read all" and "get buffer size" for everybody */ return type != SYSLOG_ACTION_READ_ALL && type != SYSLOG_ACTION_SIZE_BUFFER; } static int check_syslog_permissions(int type, bool from_file) { /* * If this is from /proc/kmsg and we've already opened it, then we've * already done the capabilities checks at open time. */ if (from_file && type != SYSLOG_ACTION_OPEN) return 0; if (syslog_action_restricted(type)) { if (capable(CAP_SYSLOG)) return 0; /* For historical reasons, accept CAP_SYS_ADMIN too, with a warning */ if (capable(CAP_SYS_ADMIN)) { printk_once(KERN_WARNING "%s (%d): " "Attempt to access syslog with CAP_SYS_ADMIN " "but no CAP_SYSLOG (deprecated).\n", current->comm, task_pid_nr(current)); return 0; } return -EPERM; } return 0; } #if defined(CONFIG_PRINTK_TIME) static bool printk_time = 1; #else static bool printk_time; #endif module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR); static size_t print_prefix(const struct log *msg, bool syslog, char *buf) { size_t len = 0; if (syslog) { if (buf) { len += sprintf(buf, "<%u>", msg->level); } else { len += 3; if (msg->level > 9) len++; if (msg->level > 99) len++; } } if (printk_time) { if (buf) { unsigned long long ts = msg->ts_nsec; unsigned long rem_nsec = do_div(ts, 1000000000); len += sprintf(buf + len, "[%5lu.%06lu] ", (unsigned long) ts, rem_nsec / 1000); } else { len += 15; } } return len; } static size_t msg_print_text(const struct log *msg, bool syslog, char *buf, size_t size) { const char *text = log_text(msg); size_t text_size = msg->text_len; size_t len = 0; do { const char *next = memchr(text, '\n', text_size); size_t text_len; if (next) { text_len = next - text; next++; text_size -= next - text; } else { text_len = text_size; } if (buf) { if (print_prefix(msg, syslog, NULL) + text_len + 1>= size - len) break; len += print_prefix(msg, syslog, buf + len); memcpy(buf + len, text, text_len); len += text_len; buf[len++] = '\n'; } else { /* SYSLOG_ACTION_* buffer size only calculation */ len += print_prefix(msg, syslog, NULL); len += text_len + 1; } text = next; } while (text); return len; } static int syslog_print(char __user *buf, int size) { char *text; struct log *msg; int len; text = kmalloc(LOG_LINE_MAX, GFP_KERNEL); if (!text) return -ENOMEM; raw_spin_lock_irq(&logbuf_lock); if (syslog_seq < log_first_seq) { /* messages are gone, move to first one */ syslog_seq = log_first_seq; syslog_idx = log_first_idx; } msg = log_from_idx(syslog_idx); len = msg_print_text(msg, true, text, LOG_LINE_MAX); syslog_idx = log_next(syslog_idx); syslog_seq++; raw_spin_unlock_irq(&logbuf_lock); if (len > 0 && copy_to_user(buf, text, len)) len = -EFAULT; kfree(text); return len; } static int syslog_print_all(char __user *buf, int size, bool clear) { char *text; int len = 0; text = kmalloc(LOG_LINE_MAX, GFP_KERNEL); if (!text) return -ENOMEM; raw_spin_lock_irq(&logbuf_lock); if (buf) { u64 next_seq; u64 seq; u32 idx; if (clear_seq < log_first_seq) { /* messages are gone, move to first available one */ clear_seq = log_first_seq; clear_idx = log_first_idx; } /* * Find first record that fits, including all following records, * into the user-provided buffer for this dump. */ seq = clear_seq; idx = clear_idx; while (seq < log_next_seq) { struct log *msg = log_from_idx(idx); len += msg_print_text(msg, true, NULL, 0); idx = log_next(idx); seq++; } /* move first record forward until length fits into the buffer */ seq = clear_seq; idx = clear_idx; while (len > size && seq < log_next_seq) { struct log *msg = log_from_idx(idx); len -= msg_print_text(msg, true, NULL, 0); idx = log_next(idx); seq++; } /* last message fitting into this dump */ next_seq = log_next_seq; len = 0; while (len >= 0 && seq < next_seq) { struct log *msg = log_from_idx(idx); int textlen; textlen = msg_print_text(msg, true, text, LOG_LINE_MAX); if (textlen < 0) { len = textlen; break; } idx = log_next(idx); seq++; raw_spin_unlock_irq(&logbuf_lock); if (copy_to_user(buf + len, text, textlen)) len = -EFAULT; else len += textlen; raw_spin_lock_irq(&logbuf_lock); if (seq < log_first_seq) { /* messages are gone, move to next one */ seq = log_first_seq; idx = log_first_idx; } } } if (clear) { clear_seq = log_next_seq; clear_idx = log_next_idx; } raw_spin_unlock_irq(&logbuf_lock); kfree(text); return len; } int do_syslog(int type, char __user *buf, int len, bool from_file) { bool clear = false; static int saved_console_loglevel = -1; static DEFINE_MUTEX(syslog_mutex); int error; error = check_syslog_permissions(type, from_file); if (error) goto out; 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 = mutex_lock_interruptible(&syslog_mutex); if (error) goto out; error = wait_event_interruptible(log_wait, syslog_seq != log_next_seq); if (error) { mutex_unlock(&syslog_mutex); goto out; } error = syslog_print(buf, len); mutex_unlock(&syslog_mutex); break; /* Read/clear last kernel messages */ case SYSLOG_ACTION_READ_CLEAR: clear = true; /* 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; } error = syslog_print_all(buf, len, clear); break; /* Clear ring buffer */ case SYSLOG_ACTION_CLEAR: syslog_print_all(NULL, 0, true); /* 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: raw_spin_lock_irq(&logbuf_lock); if (syslog_seq < log_first_seq) { /* messages are gone, move to first one */ syslog_seq = log_first_seq; syslog_idx = log_first_idx; } if (from_file) { /* * Short-cut for poll(/"proc/kmsg") which simply checks * for pending data, not the size; return the count of * records, not the length. */ error = log_next_idx - syslog_idx; } else { u64 seq; u32 idx; error = 0; seq = syslog_seq; idx = syslog_idx; while (seq < log_next_seq) { struct log *msg = log_from_idx(idx); error += msg_print_text(msg, true, NULL, 0); idx = log_next(idx); seq++; } } raw_spin_unlock_irq(&logbuf_lock); 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_first_idx; syslog_data[3] = log_buf + log_next_idx; } #endif /* CONFIG_KGDB_KDB */ static bool __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); module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR); MODULE_PARM_DESC(ignore_loglevel, "ignore loglevel setting, to" "print all kernel messages to the console."); /* * Call the console drivers, asking them to write out * log_buf[start] to log_buf[end - 1]. * The console_lock must be held. */ static void call_console_drivers(int level, const char *text, size_t len) { struct console *con; trace_console(text, 0, len, len); if (level >= console_loglevel && !ignore_loglevel) return; if (!console_drivers) return; for_each_console(con) { if (exclusive_console && con != exclusive_console) continue; if (!(con->flags & CON_ENABLED)) continue; if (!con->write) continue; if (!cpu_online(smp_processor_id()) && !(con->flags & CON_ANYTIME)) continue; con->write(con, text, len); } } /* * 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; debug_locks_off(); /* If a crash is occurring, make sure we can't deadlock */ raw_spin_lock_init(&logbuf_lock); /* And make sure that we print immediately */ sema_init(&console_sem, 1); } /* 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; } /* * 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_lock 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 console_trylock_for_printk(unsigned int cpu) __releases(&logbuf_lock) { int retval = 0, wake = 0; if (console_trylock()) { 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; wake = 1; retval = 0; } } logbuf_cpu = UINT_MAX; if (wake) up(&console_sem); raw_spin_unlock(&logbuf_lock); return retval; } 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_emit(int facility, int level, const char *dict, size_t dictlen, const char *fmt, va_list args) { static int recursion_bug; static char cont_buf[LOG_LINE_MAX]; static size_t cont_len; static int cont_level; static struct task_struct *cont_task; static char textbuf[LOG_LINE_MAX]; char *text = textbuf; size_t text_len; unsigned long flags; int this_cpu; bool newline = false; bool prefix = false; int printed_len = 0; boot_delay_msec(); printk_delay(); /* This stops the holder of console_sem just where we want him */ local_irq_save(flags); this_cpu = smp_processor_id(); /* * Ouch, printk recursed into itself! */ if (unlikely(logbuf_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 && !lockdep_recursing(current)) { recursion_bug = 1; goto out_restore_irqs; } zap_locks(); } lockdep_off(); raw_spin_lock(&logbuf_lock); logbuf_cpu = this_cpu; if (recursion_bug) { static const char recursion_msg[] = "BUG: recent printk recursion!"; recursion_bug = 0; printed_len += strlen(recursion_msg); /* emit KERN_CRIT message */ log_store(0, 2, NULL, 0, recursion_msg, printed_len); } /* * The printf needs to come first; we need the syslog * prefix which might be passed-in as a parameter. */ text_len = vscnprintf(text, sizeof(textbuf), fmt, args); /* mark and strip a trailing newline */ if (text_len && text[text_len-1] == '\n') { text_len--; newline = true; } /* strip syslog prefix and extract log level or control flags */ if (text[0] == '<' && text[1] && text[2] == '>') { switch (text[1]) { case '0' ... '7': if (level == -1) level = text[1] - '0'; case 'd': /* KERN_DEFAULT */ prefix = true; case 'c': /* KERN_CONT */ text += 3; text_len -= 3; } } if (level == -1) level = default_message_loglevel; if (dict) { prefix = true; newline = true; } if (!newline) { if (cont_len && (prefix || cont_task != current)) { /* * Flush earlier buffer, which is either from a * different thread, or when we got a new prefix. */ log_store(facility, cont_level, NULL, 0, cont_buf, cont_len); cont_len = 0; } if (!cont_len) { cont_level = level; cont_task = current; } /* buffer or append to earlier buffer from the same thread */ if (cont_len + text_len > sizeof(cont_buf)) text_len = sizeof(cont_buf) - cont_len; memcpy(cont_buf + cont_len, text, text_len); cont_len += text_len; } else { if (cont_len && cont_task == current) { if (prefix) { /* * New prefix from the same thread; flush. We * either got no earlier newline, or we race * with an interrupt. */ log_store(facility, cont_level, NULL, 0, cont_buf, cont_len); cont_len = 0; } /* append to the earlier buffer and flush */ if (cont_len + text_len > sizeof(cont_buf)) text_len = sizeof(cont_buf) - cont_len; memcpy(cont_buf + cont_len, text, text_len); cont_len += text_len; log_store(facility, cont_level, NULL, 0, cont_buf, cont_len); cont_len = 0; cont_task = NULL; printed_len = cont_len; } else { /* ordinary single and terminated line */ log_store(facility, level, dict, dictlen, text, text_len); printed_len = text_len; } } /* * Try to acquire and then immediately release the console semaphore. * The release will print out buffers and wake up /dev/kmsg and syslog() * users. * * The console_trylock_for_printk() function will release 'logbuf_lock' * regardless of whether it actually gets the console semaphore or not. */ if (console_trylock_for_printk(this_cpu)) console_unlock(); lockdep_on(); out_restore_irqs: local_irq_restore(flags); return printed_len; } EXPORT_SYMBOL(vprintk_emit); asmlinkage int vprintk(const char *fmt, va_list args) { return vprintk_emit(0, -1, NULL, 0, fmt, args); } EXPORT_SYMBOL(vprintk); asmlinkage int printk_emit(int facility, int level, const char *dict, size_t dictlen, const char *fmt, ...) { va_list args; int r; va_start(args, fmt); r = vprintk_emit(facility, level, dict, dictlen, fmt, args); va_end(args); return r; } EXPORT_SYMBOL(printk_emit); /** * 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_lock. 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 console_unlock(); and will * send it to the consoles before releasing the lock. * * 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_emit(0, -1, NULL, 0, fmt, args); va_end(args); return r; } EXPORT_SYMBOL(printk); #else #define LOG_LINE_MAX 0 static struct log *log_from_idx(u32 idx) { return NULL; } static u32 log_next(u32 idx) { return 0; } static void call_console_drivers(int level, const char *text, size_t len) {} static size_t msg_print_text(const struct log *msg, bool syslog, char *buf, size_t size) { return 0; } #endif /* CONFIG_PRINTK */ 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; } bool 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); module_param_named(console_suspend, console_suspend_enabled, bool, S_IRUGO | S_IWUSR); MODULE_PARM_DESC(console_suspend, "suspend console during suspend" " and hibernate operations"); /** * 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"); console_lock(); console_suspended = 1; up(&console_sem); } void resume_console(void) { if (!console_suspend_enabled) return; down(&console_sem); console_suspended = 0; console_unlock(); } /** * 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: console_lock(); console_unlock(); } return NOTIFY_OK; } /** * console_lock - lock the console system for exclusive use. * * Acquires a lock which guarantees that the caller has * exclusive access to the console system and the console_drivers list. * * Can sleep, returns nothing. */ void console_lock(void) { BUG_ON(in_interrupt()); down(&console_sem); if (console_suspended) return; console_locked = 1; console_may_schedule = 1; } EXPORT_SYMBOL(console_lock); /** * console_trylock - try to lock the console system for exclusive use. * * Tried to acquire a lock which guarantees that the caller has * exclusive access to the console system and the console_drivers list. * * returns 1 on success, and 0 on failure to acquire the lock. */ int console_trylock(void) { if (down_trylock(&console_sem)) return 0; if (console_suspended) { up(&console_sem); return 0; } console_locked = 1; console_may_schedule = 0; return 1; } EXPORT_SYMBOL(console_trylock); int is_console_locked(void) { return console_locked; } /* * Delayed printk version, for scheduler-internal messages: */ #define PRINTK_BUF_SIZE 512 #define PRINTK_PENDING_WAKEUP 0x01 #define PRINTK_PENDING_SCHED 0x02 static DEFINE_PER_CPU(int, printk_pending); static DEFINE_PER_CPU(char [PRINTK_BUF_SIZE], printk_sched_buf); void printk_tick(void) { if (__this_cpu_read(printk_pending)) { int pending = __this_cpu_xchg(printk_pending, 0); if (pending & PRINTK_PENDING_SCHED) { char *buf = __get_cpu_var(printk_sched_buf); printk(KERN_WARNING "[sched_delayed] %s", buf); } if (pending & PRINTK_PENDING_WAKEUP) wake_up_interruptible(&log_wait); } } int printk_needs_cpu(int cpu) { if (cpu_is_offline(cpu)) printk_tick(); return __this_cpu_read(printk_pending); } void wake_up_klogd(void) { if (waitqueue_active(&log_wait)) this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP); } /* the next printk record to write to the console */ static u64 console_seq; static u32 console_idx; /** * console_unlock - unlock the console system * * Releases the console_lock which the caller holds on the console system * and the console driver list. * * While the console_lock was held, console output may have been buffered * by printk(). If this is the case, console_unlock(); emits * the output prior to releasing the lock. * * If there is output waiting, we wake /dev/kmsg and syslog() users. * * console_unlock(); may be called from any context. */ void console_unlock(void) { static u64 seen_seq; unsigned long flags; bool wake_klogd = false; bool retry; if (console_suspended) { up(&console_sem); return; } console_may_schedule = 0; again: for (;;) { struct log *msg; static char text[LOG_LINE_MAX]; size_t len; int level; raw_spin_lock_irqsave(&logbuf_lock, flags); if (seen_seq != log_next_seq) { wake_klogd = true; seen_seq = log_next_seq; } if (console_seq < log_first_seq) { /* messages are gone, move to first one */ console_seq = log_first_seq; console_idx = log_first_idx; } if (console_seq == log_next_seq) break; msg = log_from_idx(console_idx); level = msg->level & 7; len = msg_print_text(msg, false, text, sizeof(text)); console_idx = log_next(console_idx); console_seq++; raw_spin_unlock(&logbuf_lock); stop_critical_timings(); /* don't trace print latency */ call_console_drivers(level, text, len); start_critical_timings(); local_irq_restore(flags); } console_locked = 0; /* Release the exclusive_console once it is used */ if (unlikely(exclusive_console)) exclusive_console = NULL; raw_spin_unlock(&logbuf_lock); up(&console_sem); /* * Someone could have filled up the buffer again, so re-check if there's * something to flush. In case we cannot trylock the console_sem again, * there's a new owner and the console_unlock() from them will do the * flush, no worries. */ raw_spin_lock(&logbuf_lock); retry = console_seq != log_next_seq; raw_spin_unlock_irqrestore(&logbuf_lock, flags); if (retry && console_trylock()) goto again; if (wake_klogd) wake_up_klogd(); } EXPORT_SYMBOL(console_unlock); /** * 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 console_lock();. */ 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 console_lock(); console_locked = 1; console_may_schedule = 0; for_each_console(c) if ((c->flags & CON_ENABLED) && c->unblank) c->unblank(); console_unlock(); } /* * 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; console_lock(); for_each_console(c) { if (!c->device) continue; driver = c->device(c, index); if (driver) break; } console_unlock(); 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) { console_lock(); console->flags &= ~CON_ENABLED; console_unlock(); } EXPORT_SYMBOL(console_stop); void console_start(struct console *console) { console_lock(); console->flags |= CON_ENABLED; console_unlock(); } EXPORT_SYMBOL(console_start); static int __read_mostly keep_bootcon; static int __init keep_bootcon_setup(char *str) { keep_bootcon = 1; printk(KERN_INFO "debug: skip boot console de-registration.\n"); return 0; } early_param("keep_bootcon", keep_bootcon_setup); /* * 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. */ console_lock(); 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) { /* * console_unlock(); will print out the buffered messages * for us. */ raw_spin_lock_irqsave(&logbuf_lock, flags); console_seq = syslog_seq; console_idx = syslog_idx; raw_spin_unlock_irqrestore(&logbuf_lock, flags); /* * We're about to replay the log buffer. Only do this to the * just-registered console to avoid excessive message spam to * the already-registered consoles. */ exclusive_console = newcon; } console_unlock(); console_sysfs_notify(); /* * 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) && !keep_bootcon) { /* 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 console_lock(); 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; console_unlock(); console_sysfs_notify(); return res; } EXPORT_SYMBOL(unregister_console); static int __init printk_late_init(void) { struct console *con; for_each_console(con) { if (!keep_bootcon && 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 int printk_sched(const char *fmt, ...) { unsigned long flags; va_list args; char *buf; int r; local_irq_save(flags); buf = __get_cpu_var(printk_sched_buf); va_start(args, fmt); r = vsnprintf(buf, PRINTK_BUF_SIZE, fmt, args); va_end(args); __this_cpu_or(printk_pending, PRINTK_PENDING_SCHED); local_irq_restore(flags); return r; } /* * 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_rcu(&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_rcu(&dumper->list); err = 0; } spin_unlock_irqrestore(&dump_list_lock, flags); synchronize_rcu(); return err; } EXPORT_SYMBOL_GPL(kmsg_dump_unregister); static bool always_kmsg_dump; module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR); /** * kmsg_dump - dump kernel log to kernel message dumpers. * @reason: the reason (oops, panic etc) for dumping * * Call each of the registered dumper's dump() callback, which can * retrieve the kmsg records with kmsg_dump_get_line() or * kmsg_dump_get_buffer(). */ void kmsg_dump(enum kmsg_dump_reason reason) { struct kmsg_dumper *dumper; unsigned long flags; if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump) return; rcu_read_lock(); list_for_each_entry_rcu(dumper, &dump_list, list) { if (dumper->max_reason && reason > dumper->max_reason) continue; /* initialize iterator with data about the stored records */ dumper->active = true; raw_spin_lock_irqsave(&logbuf_lock, flags); dumper->cur_seq = clear_seq; dumper->cur_idx = clear_idx; dumper->next_seq = log_next_seq; dumper->next_idx = log_next_idx; raw_spin_unlock_irqrestore(&logbuf_lock, flags); /* invoke dumper which will iterate over records */ dumper->dump(dumper, reason); /* reset iterator */ dumper->active = false; } rcu_read_unlock(); } /** * kmsg_dump_get_line - retrieve one kmsg log line * @dumper: registered kmsg dumper * @syslog: include the "<4>" prefixes * @line: buffer to copy the line to * @size: maximum size of the buffer * @len: length of line placed into buffer * * Start at the beginning of the kmsg buffer, with the oldest kmsg * record, and copy one record into the provided buffer. * * Consecutive calls will return the next available record moving * towards the end of the buffer with the youngest messages. * * A return value of FALSE indicates that there are no more records to * read. */ bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog, char *line, size_t size, size_t *len) { unsigned long flags; struct log *msg; size_t l = 0; bool ret = false; if (!dumper->active) goto out; raw_spin_lock_irqsave(&logbuf_lock, flags); if (dumper->cur_seq < log_first_seq) { /* messages are gone, move to first available one */ dumper->cur_seq = log_first_seq; dumper->cur_idx = log_first_idx; } /* last entry */ if (dumper->cur_seq >= log_next_seq) { raw_spin_unlock_irqrestore(&logbuf_lock, flags); goto out; } msg = log_from_idx(dumper->cur_idx); l = msg_print_text(msg, syslog, line, size); dumper->cur_idx = log_next(dumper->cur_idx); dumper->cur_seq++; ret = true; raw_spin_unlock_irqrestore(&logbuf_lock, flags); out: if (len) *len = l; return ret; } EXPORT_SYMBOL_GPL(kmsg_dump_get_line); /** * kmsg_dump_get_buffer - copy kmsg log lines * @dumper: registered kmsg dumper * @syslog: include the "<4>" prefixes * @line: buffer to copy the line to * @size: maximum size of the buffer * @len: length of line placed into buffer * * Start at the end of the kmsg buffer and fill the provided buffer * with as many of the the *youngest* kmsg records that fit into it. * If the buffer is large enough, all available kmsg records will be * copied with a single call. * * Consecutive calls will fill the buffer with the next block of * available older records, not including the earlier retrieved ones. * * A return value of FALSE indicates that there are no more records to * read. */ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog, char *buf, size_t size, size_t *len) { unsigned long flags; u64 seq; u32 idx; u64 next_seq; u32 next_idx; size_t l = 0; bool ret = false; if (!dumper->active) goto out; raw_spin_lock_irqsave(&logbuf_lock, flags); if (dumper->cur_seq < log_first_seq) { /* messages are gone, move to first available one */ dumper->cur_seq = log_first_seq; dumper->cur_idx = log_first_idx; } /* last entry */ if (dumper->cur_seq >= dumper->next_seq) { raw_spin_unlock_irqrestore(&logbuf_lock, flags); goto out; } /* calculate length of entire buffer */ seq = dumper->cur_seq; idx = dumper->cur_idx; while (seq < dumper->next_seq) { struct log *msg = log_from_idx(idx); l += msg_print_text(msg, true, NULL, 0); idx = log_next(idx); seq++; } /* move first record forward until length fits into the buffer */ seq = dumper->cur_seq; idx = dumper->cur_idx; while (l > size && seq < dumper->next_seq) { struct log *msg = log_from_idx(idx); l -= msg_print_text(msg, true, NULL, 0); idx = log_next(idx); seq++; } /* last message in next interation */ next_seq = seq; next_idx = idx; l = 0; while (seq < dumper->next_seq) { struct log *msg = log_from_idx(idx); l += msg_print_text(msg, syslog, buf + l, size - l); idx = log_next(idx); seq++; } dumper->next_seq = next_seq; dumper->next_idx = next_idx; ret = true; raw_spin_unlock_irqrestore(&logbuf_lock, flags); out: if (len) *len = l; return ret; } EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer); /** * kmsg_dump_rewind - reset the interator * @dumper: registered kmsg dumper * * Reset the dumper's iterator so that kmsg_dump_get_line() and * kmsg_dump_get_buffer() can be called again and used multiple * times within the same dumper.dump() callback. */ void kmsg_dump_rewind(struct kmsg_dumper *dumper) { unsigned long flags; raw_spin_lock_irqsave(&logbuf_lock, flags); dumper->cur_seq = clear_seq; dumper->cur_idx = clear_idx; dumper->next_seq = log_next_seq; dumper->next_idx = log_next_idx; raw_spin_unlock_irqrestore(&logbuf_lock, flags); } EXPORT_SYMBOL_GPL(kmsg_dump_rewind); #endif