TOMOYO Linux Cross Reference
Linux/kernel/printk.c

   /*
    *  linux/kernel/printk.c
    *
    *  Copyright (C) 1991, 1992  Linus Torvalds
    *
    * Modified to make sys_syslog() more flexible: added commands to
    * return the last 4k of kernel messages, regardless of whether
    * they've been read or not.  Added option to suppress kernel printk's
    * to the console.  Added hook for sending the console messages
   * elsewhere, in preparation for a serial line console (someday).
   * Ted Ts'o, 2/11/93.
   * Modified for sysctl support, 1/8/97, Chris Horn.
   * Fixed SMP synchronization, 08/08/99, Manfred Spraul
   *     manfred@colorfullife.com
   * Rewrote bits to get rid of console_lock
   *      01Mar01 Andrew Morton
   */
  
  #include <linux/kernel.h>
  #include <linux/mm.h>
  #include <linux/tty.h>
  #include <linux/tty_driver.h>
  #include <linux/console.h>
  #include <linux/init.h>
  #include <linux/jiffies.h>
  #include <linux/nmi.h>
  #include <linux/module.h>
  #include <linux/moduleparam.h>
  #include <linux/interrupt.h>                    /* For in_interrupt() */
  #include <linux/delay.h>
  #include <linux/smp.h>
  #include <linux/security.h>
  #include <linux/bootmem.h>
  #include <linux/memblock.h>
  #include <linux/aio.h>
  #include <linux/syscalls.h>
  #include <linux/kexec.h>
  #include <linux/kdb.h>
  #include <linux/ratelimit.h>
  #include <linux/kmsg_dump.h>
  #include <linux/syslog.h>
  #include <linux/cpu.h>
  #include <linux/notifier.h>
  #include <linux/rculist.h>
  #include <linux/poll.h>
  #include <linux/irq_work.h>
  #include <linux/utsname.h>
  
  #include <asm/uaccess.h>
  
  #define CREATE_TRACE_POINTS
  #include <trace/events/printk.h>
  
  /* 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 */
  
  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);
  
  #ifdef CONFIG_LOCKDEP
  static struct lockdep_map console_lock_dep_map = {
          .name = "console_lock"
  };
  #endif
  
  /*
   * 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[16];                       /* 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;<message text>\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.
  */
 
 enum log_flags {
         LOG_NOCONS      = 1,    /* already flushed, do not print to console */
         LOG_NEWLINE     = 2,    /* text ended with a newline */
         LOG_PREFIX      = 4,    /* text started with a prefix */
         LOG_CONT        = 8,    /* text is a fragment of a continuation line */
 };
 
 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 */
         u8 facility;            /* syslog facility */
         u8 flags:5;             /* internal record flags */
         u8 level:3;             /* syslog level */
 };
 
 /*
  * 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);
 
 #ifdef CONFIG_PRINTK
 DECLARE_WAIT_QUEUE_HEAD(log_wait);
 /* the next printk record to read by syslog(READ) or /proc/kmsg */
 static u64 syslog_seq;
 static u32 syslog_idx;
 static enum log_flags syslog_prev;
 static size_t syslog_partial;
 
 /* 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;
 static u32 log_next_idx;
 
 /* the next printk record to write to the console */
 static u64 console_seq;
 static u32 console_idx;
 static enum log_flags console_prev;
 
 /* the next printk record to read after the last 'clear' command */
 static u64 clear_seq;
 static u32 clear_idx;
 
 #define PREFIX_MAX              32
 #define LOG_LINE_MAX            1024 - PREFIX_MAX
 
 /* 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,
                       enum log_flags flags, u64 ts_nsec,
                       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->facility = facility;
         msg->level = level & 7;
         msg->flags = flags & 0x1f;
         if (ts_nsec > 0)
                 msg->ts_nsec = ts_nsec;
         else
                 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++;
 }
 
 #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)) {
                         pr_warn_once("%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 security_syslog(type);
 }
 
 
 /* /dev/kmsg - userspace message inject/listen interface */
 struct devkmsg_user {
         u64 seq;
         u32 idx;
         enum log_flags prev;
         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)) {
                         ret = -EFAULT;
                         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;
         char cont = '-';
         size_t len;
         ssize_t ret;
 
         if (!user)
                 return -EBADF;
 
         ret = mutex_lock_interruptible(&user->lock);
         if (ret)
                 return ret;
         raw_spin_lock_irq(&logbuf_lock);
         while (user->seq == log_next_seq) {
                 if (file->f_flags & O_NONBLOCK) {
                         ret = -EAGAIN;
                         raw_spin_unlock_irq(&logbuf_lock);
                         goto out;
                 }
 
                 raw_spin_unlock_irq(&logbuf_lock);
                 ret = wait_event_interruptible(log_wait,
                                                user->seq != log_next_seq);
                 if (ret)
                         goto out;
                 raw_spin_lock_irq(&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_irq(&logbuf_lock);
                 goto out;
         }
 
         msg = log_from_idx(user->idx);
         ts_usec = msg->ts_nsec;
         do_div(ts_usec, 1000);
 
         /*
          * If we couldn't merge continuation line fragments during the print,
          * export the stored flags to allow an optional external merge of the
          * records. Merging the records isn't always neccessarily correct, like
          * when we hit a race during printing. In most cases though, it produces
          * better readable output. 'c' in the record flags mark the first
          * fragment of a line, '+' the following.
          */
         if (msg->flags & LOG_CONT && !(user->prev & LOG_CONT))
                 cont = 'c';
         else if ((msg->flags & LOG_CONT) ||
                  ((user->prev & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
                 cont = '+';
 
         len = sprintf(user->buf, "%u,%llu,%llu,%c;",
                       (msg->facility << 3) | msg->level,
                       user->seq, ts_usec, cont);
         user->prev = msg->flags;
 
         /* escape non-printable characters */
         for (i = 0; i < msg->text_len; i++) {
                 unsigned char c = log_text(msg)[i];
 
                 if (c < ' ' || c >= 127 || c == '\\')
                         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 >= 127 || c == '\\') {
                                 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_irq(&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_irq(&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_irq(&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_irq(&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;
                 else
                         ret = POLLIN|POLLRDNORM;
         }
         raw_spin_unlock_irq(&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 = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
                                        SYSLOG_FROM_READER);
         if (err)
                 return err;
 
         user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
         if (!user)
                 return -ENOMEM;
 
         mutex_init(&user->lock);
 
         raw_spin_lock_irq(&logbuf_lock);
         user->idx = log_first_idx;
         user->seq = log_first_seq;
         raw_spin_unlock_irq(&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);
         /*
          * Export struct log size and field offsets. User space tools can
          * parse it and detect any changes to structure down the line.
          */
         VMCOREINFO_STRUCT_SIZE(log);
         VMCOREINFO_OFFSET(log, ts_nsec);
         VMCOREINFO_OFFSET(log, len);
         VMCOREINFO_OFFSET(log, text_len);
         VMCOREINFO_OFFSET(log, dict_len);
 }
 #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);
 }
 
 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.");
 
 #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(int level)
 {
         unsigned long long k;
         unsigned long timeout;
 
         if ((boot_delay == 0 || system_state != SYSTEM_BOOTING)
                 || (level >= console_loglevel && !ignore_loglevel)) {
                 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(int level)
 {
 }
 #endif
 
 #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_time(u64 ts, char *buf)
 {
         unsigned long rem_nsec;
 
         if (!printk_time)
                 return 0;
 
         rem_nsec = do_div(ts, 1000000000);
 
         if (!buf)
                 return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);
 
         return sprintf(buf, "[%5lu.%06lu] ",
                        (unsigned long)ts, rem_nsec / 1000);
 }
 
 static size_t print_prefix(const struct log *msg, bool syslog, char *buf)
 {
         size_t len = 0;
         unsigned int prefix = (msg->facility << 3) | msg->level;
 
         if (syslog) {
                 if (buf) {
                         len += sprintf(buf, "<%u>", prefix);
                 } else {
                         len += 3;
                         if (prefix > 999)
                                 len += 3;
                         else if (prefix > 99)
                                 len += 2;
                         else if (prefix > 9)
                                 len++;
                 }
         }
 
         len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
         return len;
 }
 
 static size_t msg_print_text(const struct log *msg, enum log_flags prev,
                              bool syslog, char *buf, size_t size)
 {
         const char *text = log_text(msg);
         size_t text_size = msg->text_len;
         bool prefix = true;
         bool newline = true;
         size_t len = 0;
 
         if ((prev & LOG_CONT) && !(msg->flags & LOG_PREFIX))
                 prefix = false;
 
         if (msg->flags & LOG_CONT) {
                 if ((prev & LOG_CONT) && !(prev & LOG_NEWLINE))
                         prefix = false;
 
                 if (!(msg->flags & LOG_NEWLINE))
                         newline = false;
         }
 
         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;
 
                         if (prefix)
                                 len += print_prefix(msg, syslog, buf + len);
                         memcpy(buf + len, text, text_len);
                         len += text_len;
                         if (next || newline)
                                 buf[len++] = '\n';
                 } else {
                         /* SYSLOG_ACTION_* buffer size only calculation */
                         if (prefix)
                                 len += print_prefix(msg, syslog, NULL);
                         len += text_len;
                         if (next || newline)
                                 len++;
                 }
 
                 prefix = true;
                 text = next;
         } while (text);
 
         return len;
 }
 
 static int syslog_print(char __user *buf, int size)
 {
         char *text;
         struct log *msg;
         int len = 0;
 
         text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
         if (!text)
                 return -ENOMEM;
 
         while (size > 0) {
                 size_t n;
                 size_t skip;
 
                 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;
                         syslog_prev = 0;
                         syslog_partial = 0;
                 }
                 if (syslog_seq == log_next_seq) {
                         raw_spin_unlock_irq(&logbuf_lock);
                         break;
                 }
 
                 skip = syslog_partial;
                 msg = log_from_idx(syslog_idx);
                 n = msg_print_text(msg, syslog_prev, true, text,
                                    LOG_LINE_MAX + PREFIX_MAX);
                 if (n - syslog_partial <= size) {
                         /* message fits into buffer, move forward */
                         syslog_idx = log_next(syslog_idx);
                         syslog_seq++;
                         syslog_prev = msg->flags;
                         n -= syslog_partial;
                         syslog_partial = 0;
                 } else if (!len){
                         /* partial read(), remember position */
                         n = size;
                         syslog_partial += n;
                 } else
                         n = 0;
                 raw_spin_unlock_irq(&logbuf_lock);
 
                 if (!n)
                         break;
 
                 if (copy_to_user(buf, text + skip, n)) {
                         if (!len)
                                 len = -EFAULT;
                         break;
                 }
 
                 len += n;
                 size -= n;
                 buf += n;
         }
 
         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 + PREFIX_MAX, GFP_KERNEL);
         if (!text)
                 return -ENOMEM;
 
         raw_spin_lock_irq(&logbuf_lock);
         if (buf) {
                 u64 next_seq;
                 u64 seq;
                 u32 idx;
                 enum log_flags prev;
 
                 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;
                 prev = 0;
                 while (seq < log_next_seq) {
                         struct log *msg = log_from_idx(idx);
 
                         len += msg_print_text(msg, prev, true, NULL, 0);
                         prev = msg->flags;
                         idx = log_next(idx);
                         seq++;
                 }
 
                 /* move first record forward until length fits into the buffer */
                 seq = clear_seq;
                 idx = clear_idx;
                 prev = 0;
                 while (len > size && seq < log_next_seq) {
                         struct log *msg = log_from_idx(idx);
 
                         len -= msg_print_text(msg, prev, true, NULL, 0);
                         prev = msg->flags;
                         idx = log_next(idx);
                         seq++;
                 }
 
                 /* last message fitting into this dump */
                 next_seq = log_next_seq;
 
                 len = 0;
                 prev = 0;
                 while (len >= 0 && seq < next_seq) {
                         struct log *msg = log_from_idx(idx);
                         int textlen;
 
                         textlen = msg_print_text(msg, prev, true, text,
                                                  LOG_LINE_MAX + PREFIX_MAX);
                         if (textlen < 0) {
                                 len = textlen;
                                 break;
                         }
                         idx = log_next(idx);
                         seq++;
                         prev = msg->flags;
 
                         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;
                                 prev = 0;
                         }
                 }
         }
 
         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;
         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 = wait_event_interruptible(log_wait,
                                                  syslog_seq != log_next_seq);
                 if (error)
                         goto out;
                 error = syslog_print(buf, len);
                 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);
                 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:
                 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;
                         syslog_prev = 0;
                         syslog_partial = 0;
                 }
                 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 = syslog_seq;
                         u32 idx = syslog_idx;
                         enum log_flags prev = syslog_prev;
 
                         error = 0;
                         while (seq < log_next_seq) {
                                 struct log *msg = log_from_idx(idx);
 
                                 error += msg_print_text(msg, prev, true, NULL, 0);
                                 idx = log_next(idx);
                                 seq++;
                                 prev = msg->flags;
                         }
                         error -= syslog_partial;
                 }
                 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_READER);
 }
 
 /*
  * 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_rcuidle(text, 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;
         raw_spin_unlock(&logbuf_lock);
         if (wake)
                 up(&console_sem);
         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();
                 }
         }
 }
 
 /*
  * Continuation lines are buffered, and not committed to the record buffer
  * until the line is complete, or a race forces it. The line fragments
  * though, are printed immediately to the consoles to ensure everything has
  * reached the console in case of a kernel crash.
  */
 static struct cont {
         char buf[LOG_LINE_MAX];
         size_t len;                     /* length == 0 means unused buffer */
         size_t cons;                    /* bytes written to console */
         struct task_struct *owner;      /* task of first print*/
         u64 ts_nsec;                    /* time of first print */
         u8 level;                       /* log level of first message */
         u8 facility;                    /* log level of first message */
         enum log_flags flags;           /* prefix, newline flags */
         bool flushed:1;                 /* buffer sealed and committed */
 } cont;
 
 static void cont_flush(enum log_flags flags)
 {
         if (cont.flushed)
                 return;
         if (cont.len == 0)
                 return;
 
         if (cont.cons) {
                 /*
                  * If a fragment of this line was directly flushed to the
                  * console; wait for the console to pick up the rest of the
                  * line. LOG_NOCONS suppresses a duplicated output.
                  */
                 log_store(cont.facility, cont.level, flags | LOG_NOCONS,
                           cont.ts_nsec, NULL, 0, cont.buf, cont.len);
                 cont.flags = flags;
                 cont.flushed = true;
         } else {
                 /*
                  * If no fragment of this line ever reached the console,
                  * just submit it to the store and free the buffer.
                  */
                 log_store(cont.facility, cont.level, flags, 0,
                           NULL, 0, cont.buf, cont.len);
                 cont.len = 0;
         }
 }
 
 static bool cont_add(int facility, int level, const char *text, size_t len)
 {
         if (cont.len && cont.flushed)
                 return false;
 
         if (cont.len + len > sizeof(cont.buf)) {
                 /* the line gets too long, split it up in separate records */
                 cont_flush(LOG_CONT);
                 return false;
         }
 
         if (!cont.len) {
                 cont.facility = facility;
                 cont.level = level;
                 cont.owner = current;
                 cont.ts_nsec = local_clock();
                 cont.flags = 0;
                 cont.cons = 0;
                 cont.flushed = false;
         }
 
         memcpy(cont.buf + cont.len, text, len);
         cont.len += len;
 
         if (cont.len > (sizeof(cont.buf) * 80) / 100)
                 cont_flush(LOG_CONT);
 
         return true;
 }
 
 static size_t cont_print_text(char *text, size_t size)
 {
         size_t textlen = 0;
         size_t len;
 
         if (cont.cons == 0 && (console_prev & LOG_NEWLINE)) {
                 textlen += print_time(cont.ts_nsec, text);
                 size -= textlen;
         }
 
         len = cont.len - cont.cons;
         if (len > 0) {
                 if (len+1 > size)
                         len = size-1;
                 memcpy(text + textlen, cont.buf + cont.cons, len);
                 textlen += len;
                 cont.cons = cont.len;
         }
 
         if (cont.flushed) {
                 if (cont.flags & LOG_NEWLINE)
                         text[textlen++] = '\n';
                 /* got everything, release buffer */
                 cont.len = 0;
         }
         return textlen;
 }
 
 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 textbuf[LOG_LINE_MAX];
         char *text = textbuf;
         size_t text_len;
         enum log_flags lflags = 0;
         unsigned long flags;
         int this_cpu;
         int printed_len = 0;
 
         boot_delay_msec(level);
         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, LOG_PREFIX|LOG_NEWLINE, 0,
                           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--;
                 lflags |= LOG_NEWLINE;
         }
 
         /* strip kernel syslog prefix and extract log level or control flags */
         if (facility == 0) {
                 int kern_level = printk_get_level(text);
 
                 if (kern_level) {
                         const char *end_of_header = printk_skip_level(text);
                         switch (kern_level) {
                         case '' ... '7':
                                 if (level == -1)
                                         level = kern_level - '';
                         case 'd':       /* KERN_DEFAULT */
                                 lflags |= LOG_PREFIX;
                         case 'c':       /* KERN_CONT */
                                 break;
                         }
                         text_len -= end_of_header - text;
                         text = (char *)end_of_header;
                 }
         }
 
         if (level == -1)
                 level = default_message_loglevel;
 
         if (dict)
                 lflags |= LOG_PREFIX|LOG_NEWLINE;
 
         if (!(lflags & LOG_NEWLINE)) {
                 /*
                  * Flush the conflicting buffer. An earlier newline was missing,
                  * or another task also prints continuation lines.
                  */
                 if (cont.len && (lflags & LOG_PREFIX || cont.owner != current))
                         cont_flush(LOG_NEWLINE);
 
                 /* buffer line if possible, otherwise store it right away */
                 if (!cont_add(facility, level, text, text_len))
                         log_store(facility, level, lflags | LOG_CONT, 0,
                                   dict, dictlen, text, text_len);
         } else {
                 bool stored = false;
 
                 /*
                  * If an earlier newline was missing and it was the same task,
                  * either merge it with the current buffer and flush, or if
                  * there was a race with interrupts (prefix == true) then just
                  * flush it out and store this line separately.
                  */
                 if (cont.len && cont.owner == current) {
                         if (!(lflags & LOG_PREFIX))
                                 stored = cont_add(facility, level, text, text_len);
                         cont_flush(LOG_NEWLINE);
                 }
 
                 if (!stored)
                         log_store(facility, level, lflags, 0,
                                   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 /* CONFIG_PRINTK */
 
 #define LOG_LINE_MAX            0
 #define PREFIX_MAX              0
 #define LOG_LINE_MAX 0
 static u64 syslog_seq;
 static u32 syslog_idx;
 static u64 console_seq;
 static u32 console_idx;
 static enum log_flags syslog_prev;
 static u64 log_first_seq;
 static u32 log_first_idx;
 static u64 log_next_seq;
 static enum log_flags console_prev;
 static struct cont {
         size_t len;
         size_t cons;
         u8 level;
         bool flushed:1;
 } cont;
 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, enum log_flags prev,
                              bool syslog, char *buf, size_t size) { return 0; }
 static size_t cont_print_text(char *text, size_t size) { return 0; }
 
 #endif /* CONFIG_PRINTK */
 
 #ifdef CONFIG_EARLY_PRINTK
 struct console *early_console;
 
 void early_vprintk(const char *fmt, va_list ap)
 {
         if (early_console) {
                 char buf[512];
                 int n = vscnprintf(buf, sizeof(buf), fmt, ap);
 
                 early_console->write(early_console, buf, n);
         }
 }
 
 asmlinkage void early_printk(const char *fmt, ...)
 {
         va_list ap;
 
         va_start(ap, fmt);
         early_vprintk(fmt, ap);
         va_end(ap);
 }
 #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] >= '' && 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 >= '' && *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_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)
 {
         might_sleep();
 
         down(&console_sem);
         if (console_suspended)
                 return;
         console_locked = 1;
         console_may_schedule = 1;
         mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);
 }
 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;
         mutex_acquire(&console_lock_dep_map, 0, 1, _RET_IP_);
         return 1;
 }
 EXPORT_SYMBOL(console_trylock);
 
 int is_console_locked(void)
 {
         return console_locked;
 }
 
 static void console_cont_flush(char *text, size_t size)
 {
         unsigned long flags;
         size_t len;
 
         raw_spin_lock_irqsave(&logbuf_lock, flags);
 
         if (!cont.len)
                 goto out;
 
         /*
          * We still queue earlier records, likely because the console was
          * busy. The earlier ones need to be printed before this one, we
          * did not flush any fragment so far, so just let it queue up.
          */
         if (console_seq < log_next_seq && !cont.cons)
                 goto out;
 
         len = cont_print_text(text, size);
         raw_spin_unlock(&logbuf_lock);
         stop_critical_timings();
         call_console_drivers(cont.level, text, len);
         start_critical_timings();
         local_irq_restore(flags);
         return;
 out:
         raw_spin_unlock_irqrestore(&logbuf_lock, flags);
 }
 
 /**
  * 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 char text[LOG_LINE_MAX + PREFIX_MAX];
         static u64 seen_seq;
         unsigned long flags;
         bool wake_klogd = false;
         bool do_cond_resched, retry;
 
         if (console_suspended) {
                 up(&console_sem);
                 return;
         }
 
         /*
          * Console drivers are called under logbuf_lock, so
          * @console_may_schedule should be cleared before; however, we may
          * end up dumping a lot of lines, for example, if called from
          * console registration path, and should invoke cond_resched()
          * between lines if allowable.  Not doing so can cause a very long
          * scheduling stall on a slow console leading to RCU stall and
          * softlockup warnings which exacerbate the issue with more
          * messages practically incapacitating the system.
          */
         do_cond_resched = console_may_schedule;
         console_may_schedule = 0;
 
         /* flush buffered message fragment immediately to console */
         console_cont_flush(text, sizeof(text));
 again:
         for (;;) {
                 struct log *msg;
                 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;
                         console_prev = 0;
                 }
 skip:
                 if (console_seq == log_next_seq)
                         break;
 
                 msg = log_from_idx(console_idx);
                 if (msg->flags & LOG_NOCONS) {
                         /*
                          * Skip record we have buffered and already printed
                          * directly to the console when we received it.
                          */
                         console_idx = log_next(console_idx);
                         console_seq++;
                         /*
                          * We will get here again when we register a new
                          * CON_PRINTBUFFER console. Clear the flag so we
                          * will properly dump everything later.
                          */
                         msg->flags &= ~LOG_NOCONS;
                         console_prev = msg->flags;
                         goto skip;
                 }
 
                 level = msg->level;
                 len = msg_print_text(msg, console_prev, false,
                                      text, sizeof(text));
                 console_idx = log_next(console_idx);
                 console_seq++;
                 console_prev = msg->flags;
                 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);
 
                 if (do_cond_resched)
                         cond_resched();
         }
         console_locked = 0;
         mutex_release(&console_lock_dep_map, 1, _RET_IP_);
 
         /* 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();
 }
 
 /**
  * console_flush_on_panic - flush console content on panic
  *
  * Immediately output all pending messages no matter what.
  */
 void console_flush_on_panic(void)
 {
         /*
          * If someone else is holding the console lock, trylock will fail
          * and may_schedule may be set.  Ignore and proceed to unlock so
          * that messages are flushed out.  As this can be called from any
          * context and we don't want to get preempted while flushing,
          * ensure may_schedule is cleared.
          */
         console_trylock();
         console_may_schedule = 0;
         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++) {
                 BUILD_BUG_ON(sizeof(console_cmdline[i].name) !=
                              sizeof(newcon->name));
                 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;
                 console_prev = syslog_prev;
                 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
 /*
  * 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);
 
 static void wake_up_klogd_work_func(struct irq_work *irq_work)
 {
         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);
 }
 
 static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
         .func = wake_up_klogd_work_func,
         .flags = IRQ_WORK_LAZY,
 };
 
 void wake_up_klogd(void)
 {
         preempt_disable();
         if (waitqueue_active(&log_wait)) {
                 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
                 irq_work_queue(&__get_cpu_var(wake_up_klogd_work));
         }
         preempt_enable();
 }
 
 int printk_deferred(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);
         irq_work_queue(&__get_cpu_var(wake_up_klogd_work));
         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_nolock - retrieve one kmsg log line (unlocked version)
  * @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.
  *
  * The function is similar to kmsg_dump_get_line(), but grabs no locks.
  */
 bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
                                char *line, size_t size, size_t *len)
 {
         struct log *msg;
         size_t l = 0;
         bool ret = false;
 
         if (!dumper->active)
                 goto out;
 
         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)
                 goto out;
 
         msg = log_from_idx(dumper->cur_idx);
         l = msg_print_text(msg, 0, syslog, line, size);
 
         dumper->cur_idx = log_next(dumper->cur_idx);
         dumper->cur_seq++;
         ret = true;
 out:
         if (len)
                 *len = l;
         return ret;
 }
 
 /**
  * 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;
         bool ret;
 
         raw_spin_lock_irqsave(&logbuf_lock, flags);
         ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
         raw_spin_unlock_irqrestore(&logbuf_lock, flags);
 
         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
  * @buf: 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;
         enum log_flags prev;
         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;
         prev = 0;
         while (seq < dumper->next_seq) {
                 struct log *msg = log_from_idx(idx);
 
                 l += msg_print_text(msg, prev, true, NULL, 0);
                 idx = log_next(idx);
                 seq++;
                 prev = msg->flags;
         }
 
         /* move first record forward until length fits into the buffer */
         seq = dumper->cur_seq;
         idx = dumper->cur_idx;
         prev = 0;
         while (l > size && seq < dumper->next_seq) {
                 struct log *msg = log_from_idx(idx);
 
                 l -= msg_print_text(msg, prev, true, NULL, 0);
                 idx = log_next(idx);
                 seq++;
                 prev = msg->flags;
         }
 
         /* last message in next interation */
         next_seq = seq;
         next_idx = idx;
 
         l = 0;
         prev = 0;
         while (seq < dumper->next_seq) {
                 struct log *msg = log_from_idx(idx);
 
                 l += msg_print_text(msg, prev, syslog, buf + l, size - l);
                 idx = log_next(idx);
                 seq++;
                 prev = msg->flags;
         }
 
         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_nolock - reset the interator (unlocked version)
  * @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.
  *
  * The function is similar to kmsg_dump_rewind(), but grabs no locks.
  */
 void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
 {
         dumper->cur_seq = clear_seq;
         dumper->cur_idx = clear_idx;
         dumper->next_seq = log_next_seq;
         dumper->next_idx = log_next_idx;
 }
 
 /**
  * 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);
         kmsg_dump_rewind_nolock(dumper);
         raw_spin_unlock_irqrestore(&logbuf_lock, flags);
 }
 EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
 
 static char dump_stack_arch_desc_str[128];
 
 /**
  * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
  * @fmt: printf-style format string
  * @...: arguments for the format string
  *
  * The configured string will be printed right after utsname during task
  * dumps.  Usually used to add arch-specific system identifiers.  If an
  * arch wants to make use of such an ID string, it should initialize this
  * as soon as possible during boot.
  */
 void __init dump_stack_set_arch_desc(const char *fmt, ...)
 {
         va_list args;
 
         va_start(args, fmt);
         vsnprintf(dump_stack_arch_desc_str, sizeof(dump_stack_arch_desc_str),
                   fmt, args);
         va_end(args);
 }
 
 /**
  * dump_stack_print_info - print generic debug info for dump_stack()
  * @log_lvl: log level
  *
  * Arch-specific dump_stack() implementations can use this function to
  * print out the same debug information as the generic dump_stack().
  */
 void dump_stack_print_info(const char *log_lvl)
 {
         printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
                log_lvl, raw_smp_processor_id(), current->pid, current->comm,
                print_tainted(), init_utsname()->release,
                (int)strcspn(init_utsname()->version, " "),
                init_utsname()->version);
 
         if (dump_stack_arch_desc_str[0] != '\0')
                 printk("%sHardware name: %s\n",
                        log_lvl, dump_stack_arch_desc_str);
 
         print_worker_info(log_lvl, current);
 }
 
 /**
  * show_regs_print_info - print generic debug info for show_regs()
  * @log_lvl: log level
  *
  * show_regs() implementations can use this function to print out generic
  * debug information.
  */
 void show_regs_print_info(const char *log_lvl)
 {
         dump_stack_print_info(log_lvl);
 
         printk("%stask: %p ti: %p task.ti: %p\n",
                log_lvl, current, current_thread_info(),
                task_thread_info(current));
 }
 
 #endif
 

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