linux/kernel/printk.c
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   1/*
   2 *  linux/kernel/printk.c
   3 *
   4 *  Copyright (C) 1991, 1992  Linus Torvalds
   5 *
   6 * Modified to make sys_syslog() more flexible: added commands to
   7 * return the last 4k of kernel messages, regardless of whether
   8 * they've been read or not.  Added option to suppress kernel printk's
   9 * to the console.  Added hook for sending the console messages
  10 * elsewhere, in preparation for a serial line console (someday).
  11 * Ted Ts'o, 2/11/93.
  12 * Modified for sysctl support, 1/8/97, Chris Horn.
  13 * Fixed SMP synchronization, 08/08/99, Manfred Spraul
  14 *     manfred@colorfullife.com
  15 * Rewrote bits to get rid of console_lock
  16 *      01Mar01 Andrew Morton
  17 */
  18
  19#include <linux/kernel.h>
  20#include <linux/mm.h>
  21#include <linux/tty.h>
  22#include <linux/tty_driver.h>
  23#include <linux/console.h>
  24#include <linux/init.h>
  25#include <linux/jiffies.h>
  26#include <linux/nmi.h>
  27#include <linux/module.h>
  28#include <linux/moduleparam.h>
  29#include <linux/interrupt.h>                    /* For in_interrupt() */
  30#include <linux/delay.h>
  31#include <linux/smp.h>
  32#include <linux/security.h>
  33#include <linux/bootmem.h>
  34#include <linux/memblock.h>
  35#include <linux/aio.h>
  36#include <linux/syscalls.h>
  37#include <linux/kexec.h>
  38#include <linux/kdb.h>
  39#include <linux/ratelimit.h>
  40#include <linux/kmsg_dump.h>
  41#include <linux/syslog.h>
  42#include <linux/cpu.h>
  43#include <linux/notifier.h>
  44#include <linux/rculist.h>
  45#include <linux/poll.h>
  46#include <linux/irq_work.h>
  47#include <linux/utsname.h>
  48
  49#include <asm/uaccess.h>
  50
  51#define CREATE_TRACE_POINTS
  52#include <trace/events/printk.h>
  53
  54/* printk's without a loglevel use this.. */
  55#define DEFAULT_MESSAGE_LOGLEVEL CONFIG_DEFAULT_MESSAGE_LOGLEVEL
  56
  57/* We show everything that is MORE important than this.. */
  58#define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
  59#define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
  60
  61int console_printk[4] = {
  62        DEFAULT_CONSOLE_LOGLEVEL,       /* console_loglevel */
  63        DEFAULT_MESSAGE_LOGLEVEL,       /* default_message_loglevel */
  64        MINIMUM_CONSOLE_LOGLEVEL,       /* minimum_console_loglevel */
  65        DEFAULT_CONSOLE_LOGLEVEL,       /* default_console_loglevel */
  66};
  67
  68/*
  69 * Low level drivers may need that to know if they can schedule in
  70 * their unblank() callback or not. So let's export it.
  71 */
  72int oops_in_progress;
  73EXPORT_SYMBOL(oops_in_progress);
  74
  75/*
  76 * console_sem protects the console_drivers list, and also
  77 * provides serialisation for access to the entire console
  78 * driver system.
  79 */
  80static DEFINE_SEMAPHORE(console_sem);
  81struct console *console_drivers;
  82EXPORT_SYMBOL_GPL(console_drivers);
  83
  84#ifdef CONFIG_LOCKDEP
  85static struct lockdep_map console_lock_dep_map = {
  86        .name = "console_lock"
  87};
  88#endif
  89
  90/*
  91 * This is used for debugging the mess that is the VT code by
  92 * keeping track if we have the console semaphore held. It's
  93 * definitely not the perfect debug tool (we don't know if _WE_
  94 * hold it are racing, but it helps tracking those weird code
  95 * path in the console code where we end up in places I want
  96 * locked without the console sempahore held
  97 */
  98static int console_locked, console_suspended;
  99
 100/*
 101 * If exclusive_console is non-NULL then only this console is to be printed to.
 102 */
 103static struct console *exclusive_console;
 104
 105/*
 106 *      Array of consoles built from command line options (console=)
 107 */
 108struct console_cmdline
 109{
 110        char    name[8];                        /* Name of the driver       */
 111        int     index;                          /* Minor dev. to use        */
 112        char    *options;                       /* Options for the driver   */
 113#ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 114        char    *brl_options;                   /* Options for braille driver */
 115#endif
 116};
 117
 118#define MAX_CMDLINECONSOLES 8
 119
 120static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
 121static int selected_console = -1;
 122static int preferred_console = -1;
 123int console_set_on_cmdline;
 124EXPORT_SYMBOL(console_set_on_cmdline);
 125
 126/* Flag: console code may call schedule() */
 127static int console_may_schedule;
 128
 129/*
 130 * The printk log buffer consists of a chain of concatenated variable
 131 * length records. Every record starts with a record header, containing
 132 * the overall length of the record.
 133 *
 134 * The heads to the first and last entry in the buffer, as well as the
 135 * sequence numbers of these both entries are maintained when messages
 136 * are stored..
 137 *
 138 * If the heads indicate available messages, the length in the header
 139 * tells the start next message. A length == 0 for the next message
 140 * indicates a wrap-around to the beginning of the buffer.
 141 *
 142 * Every record carries the monotonic timestamp in microseconds, as well as
 143 * the standard userspace syslog level and syslog facility. The usual
 144 * kernel messages use LOG_KERN; userspace-injected messages always carry
 145 * a matching syslog facility, by default LOG_USER. The origin of every
 146 * message can be reliably determined that way.
 147 *
 148 * The human readable log message directly follows the message header. The
 149 * length of the message text is stored in the header, the stored message
 150 * is not terminated.
 151 *
 152 * Optionally, a message can carry a dictionary of properties (key/value pairs),
 153 * to provide userspace with a machine-readable message context.
 154 *
 155 * Examples for well-defined, commonly used property names are:
 156 *   DEVICE=b12:8               device identifier
 157 *                                b12:8         block dev_t
 158 *                                c127:3        char dev_t
 159 *                                n8            netdev ifindex
 160 *                                +sound:card0  subsystem:devname
 161 *   SUBSYSTEM=pci              driver-core subsystem name
 162 *
 163 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
 164 * follows directly after a '=' character. Every property is terminated by
 165 * a '\0' character. The last property is not terminated.
 166 *
 167 * Example of a message structure:
 168 *   0000  ff 8f 00 00 00 00 00 00      monotonic time in nsec
 169 *   0008  34 00                        record is 52 bytes long
 170 *   000a        0b 00                  text is 11 bytes long
 171 *   000c              1f 00            dictionary is 23 bytes long
 172 *   000e                    03 00      LOG_KERN (facility) LOG_ERR (level)
 173 *   0010  69 74 27 73 20 61 20 6c      "it's a l"
 174 *         69 6e 65                     "ine"
 175 *   001b           44 45 56 49 43      "DEVIC"
 176 *         45 3d 62 38 3a 32 00 44      "E=b8:2\0D"
 177 *         52 49 56 45 52 3d 62 75      "RIVER=bu"
 178 *         67                           "g"
 179 *   0032     00 00 00                  padding to next message header
 180 *
 181 * The 'struct log' buffer header must never be directly exported to
 182 * userspace, it is a kernel-private implementation detail that might
 183 * need to be changed in the future, when the requirements change.
 184 *
 185 * /dev/kmsg exports the structured data in the following line format:
 186 *   "level,sequnum,timestamp;<message text>\n"
 187 *
 188 * The optional key/value pairs are attached as continuation lines starting
 189 * with a space character and terminated by a newline. All possible
 190 * non-prinatable characters are escaped in the "\xff" notation.
 191 *
 192 * Users of the export format should ignore possible additional values
 193 * separated by ',', and find the message after the ';' character.
 194 */
 195
 196enum log_flags {
 197        LOG_NOCONS      = 1,    /* already flushed, do not print to console */
 198        LOG_NEWLINE     = 2,    /* text ended with a newline */
 199        LOG_PREFIX      = 4,    /* text started with a prefix */
 200        LOG_CONT        = 8,    /* text is a fragment of a continuation line */
 201};
 202
 203struct log {
 204        u64 ts_nsec;            /* timestamp in nanoseconds */
 205        u16 len;                /* length of entire record */
 206        u16 text_len;           /* length of text buffer */
 207        u16 dict_len;           /* length of dictionary buffer */
 208        u8 facility;            /* syslog facility */
 209        u8 flags:5;             /* internal record flags */
 210        u8 level:3;             /* syslog level */
 211};
 212
 213/*
 214 * The logbuf_lock protects kmsg buffer, indices, counters. It is also
 215 * used in interesting ways to provide interlocking in console_unlock();
 216 */
 217static DEFINE_RAW_SPINLOCK(logbuf_lock);
 218
 219#ifdef CONFIG_PRINTK
 220DECLARE_WAIT_QUEUE_HEAD(log_wait);
 221/* the next printk record to read by syslog(READ) or /proc/kmsg */
 222static u64 syslog_seq;
 223static u32 syslog_idx;
 224static enum log_flags syslog_prev;
 225static size_t syslog_partial;
 226
 227/* index and sequence number of the first record stored in the buffer */
 228static u64 log_first_seq;
 229static u32 log_first_idx;
 230
 231/* index and sequence number of the next record to store in the buffer */
 232static u64 log_next_seq;
 233static u32 log_next_idx;
 234
 235/* the next printk record to write to the console */
 236static u64 console_seq;
 237static u32 console_idx;
 238static enum log_flags console_prev;
 239
 240/* the next printk record to read after the last 'clear' command */
 241static u64 clear_seq;
 242static u32 clear_idx;
 243
 244#define PREFIX_MAX              32
 245#define LOG_LINE_MAX            1024 - PREFIX_MAX
 246
 247/* record buffer */
 248#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
 249#define LOG_ALIGN 4
 250#else
 251#define LOG_ALIGN __alignof__(struct log)
 252#endif
 253#define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
 254static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
 255static char *log_buf = __log_buf;
 256static u32 log_buf_len = __LOG_BUF_LEN;
 257
 258/* cpu currently holding logbuf_lock */
 259static volatile unsigned int logbuf_cpu = UINT_MAX;
 260
 261/* human readable text of the record */
 262static char *log_text(const struct log *msg)
 263{
 264        return (char *)msg + sizeof(struct log);
 265}
 266
 267/* optional key/value pair dictionary attached to the record */
 268static char *log_dict(const struct log *msg)
 269{
 270        return (char *)msg + sizeof(struct log) + msg->text_len;
 271}
 272
 273/* get record by index; idx must point to valid msg */
 274static struct log *log_from_idx(u32 idx)
 275{
 276        struct log *msg = (struct log *)(log_buf + idx);
 277
 278        /*
 279         * A length == 0 record is the end of buffer marker. Wrap around and
 280         * read the message at the start of the buffer.
 281         */
 282        if (!msg->len)
 283                return (struct log *)log_buf;
 284        return msg;
 285}
 286
 287/* get next record; idx must point to valid msg */
 288static u32 log_next(u32 idx)
 289{
 290        struct log *msg = (struct log *)(log_buf + idx);
 291
 292        /* length == 0 indicates the end of the buffer; wrap */
 293        /*
 294         * A length == 0 record is the end of buffer marker. Wrap around and
 295         * read the message at the start of the buffer as *this* one, and
 296         * return the one after that.
 297         */
 298        if (!msg->len) {
 299                msg = (struct log *)log_buf;
 300                return msg->len;
 301        }
 302        return idx + msg->len;
 303}
 304
 305/* insert record into the buffer, discard old ones, update heads */
 306static void log_store(int facility, int level,
 307                      enum log_flags flags, u64 ts_nsec,
 308                      const char *dict, u16 dict_len,
 309                      const char *text, u16 text_len)
 310{
 311        struct log *msg;
 312        u32 size, pad_len;
 313
 314        /* number of '\0' padding bytes to next message */
 315        size = sizeof(struct log) + text_len + dict_len;
 316        pad_len = (-size) & (LOG_ALIGN - 1);
 317        size += pad_len;
 318
 319        while (log_first_seq < log_next_seq) {
 320                u32 free;
 321
 322                if (log_next_idx > log_first_idx)
 323                        free = max(log_buf_len - log_next_idx, log_first_idx);
 324                else
 325                        free = log_first_idx - log_next_idx;
 326
 327                if (free > size + sizeof(struct log))
 328                        break;
 329
 330                /* drop old messages until we have enough contiuous space */
 331                log_first_idx = log_next(log_first_idx);
 332                log_first_seq++;
 333        }
 334
 335        if (log_next_idx + size + sizeof(struct log) >= log_buf_len) {
 336                /*
 337                 * This message + an additional empty header does not fit
 338                 * at the end of the buffer. Add an empty header with len == 0
 339                 * to signify a wrap around.
 340                 */
 341                memset(log_buf + log_next_idx, 0, sizeof(struct log));
 342                log_next_idx = 0;
 343        }
 344
 345        /* fill message */
 346        msg = (struct log *)(log_buf + log_next_idx);
 347        memcpy(log_text(msg), text, text_len);
 348        msg->text_len = text_len;
 349        memcpy(log_dict(msg), dict, dict_len);
 350        msg->dict_len = dict_len;
 351        msg->facility = facility;
 352        msg->level = level & 7;
 353        msg->flags = flags & 0x1f;
 354        if (ts_nsec > 0)
 355                msg->ts_nsec = ts_nsec;
 356        else
 357                msg->ts_nsec = local_clock();
 358        memset(log_dict(msg) + dict_len, 0, pad_len);
 359        msg->len = sizeof(struct log) + text_len + dict_len + pad_len;
 360
 361        /* insert message */
 362        log_next_idx += msg->len;
 363        log_next_seq++;
 364}
 365
 366#ifdef CONFIG_SECURITY_DMESG_RESTRICT
 367int dmesg_restrict = 1;
 368#else
 369int dmesg_restrict;
 370#endif
 371
 372static int syslog_action_restricted(int type)
 373{
 374        if (dmesg_restrict)
 375                return 1;
 376        /*
 377         * Unless restricted, we allow "read all" and "get buffer size"
 378         * for everybody.
 379         */
 380        return type != SYSLOG_ACTION_READ_ALL &&
 381               type != SYSLOG_ACTION_SIZE_BUFFER;
 382}
 383
 384static int check_syslog_permissions(int type, bool from_file)
 385{
 386        /*
 387         * If this is from /proc/kmsg and we've already opened it, then we've
 388         * already done the capabilities checks at open time.
 389         */
 390        if (from_file && type != SYSLOG_ACTION_OPEN)
 391                return 0;
 392
 393        if (syslog_action_restricted(type)) {
 394                if (capable(CAP_SYSLOG))
 395                        return 0;
 396                /*
 397                 * For historical reasons, accept CAP_SYS_ADMIN too, with
 398                 * a warning.
 399                 */
 400                if (capable(CAP_SYS_ADMIN)) {
 401                        pr_warn_once("%s (%d): Attempt to access syslog with "
 402                                     "CAP_SYS_ADMIN but no CAP_SYSLOG "
 403                                     "(deprecated).\n",
 404                                 current->comm, task_pid_nr(current));
 405                        return 0;
 406                }
 407                return -EPERM;
 408        }
 409        return security_syslog(type);
 410}
 411
 412
 413/* /dev/kmsg - userspace message inject/listen interface */
 414struct devkmsg_user {
 415        u64 seq;
 416        u32 idx;
 417        enum log_flags prev;
 418        struct mutex lock;
 419        char buf[8192];
 420};
 421
 422static ssize_t devkmsg_writev(struct kiocb *iocb, const struct iovec *iv,
 423                              unsigned long count, loff_t pos)
 424{
 425        char *buf, *line;
 426        int i;
 427        int level = default_message_loglevel;
 428        int facility = 1;       /* LOG_USER */
 429        size_t len = iov_length(iv, count);
 430        ssize_t ret = len;
 431
 432        if (len > LOG_LINE_MAX)
 433                return -EINVAL;
 434        buf = kmalloc(len+1, GFP_KERNEL);
 435        if (buf == NULL)
 436                return -ENOMEM;
 437
 438        line = buf;
 439        for (i = 0; i < count; i++) {
 440                if (copy_from_user(line, iv[i].iov_base, iv[i].iov_len)) {
 441                        ret = -EFAULT;
 442                        goto out;
 443                }
 444                line += iv[i].iov_len;
 445        }
 446
 447        /*
 448         * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
 449         * the decimal value represents 32bit, the lower 3 bit are the log
 450         * level, the rest are the log facility.
 451         *
 452         * If no prefix or no userspace facility is specified, we
 453         * enforce LOG_USER, to be able to reliably distinguish
 454         * kernel-generated messages from userspace-injected ones.
 455         */
 456        line = buf;
 457        if (line[0] == '<') {
 458                char *endp = NULL;
 459
 460                i = simple_strtoul(line+1, &endp, 10);
 461                if (endp && endp[0] == '>') {
 462                        level = i & 7;
 463                        if (i >> 3)
 464                                facility = i >> 3;
 465                        endp++;
 466                        len -= endp - line;
 467                        line = endp;
 468                }
 469        }
 470        line[len] = '\0';
 471
 472        printk_emit(facility, level, NULL, 0, "%s", line);
 473out:
 474        kfree(buf);
 475        return ret;
 476}
 477
 478static ssize_t devkmsg_read(struct file *file, char __user *buf,
 479                            size_t count, loff_t *ppos)
 480{
 481        struct devkmsg_user *user = file->private_data;
 482        struct log *msg;
 483        u64 ts_usec;
 484        size_t i;
 485        char cont = '-';
 486        size_t len;
 487        ssize_t ret;
 488
 489        if (!user)
 490                return -EBADF;
 491
 492        ret = mutex_lock_interruptible(&user->lock);
 493        if (ret)
 494                return ret;
 495        raw_spin_lock_irq(&logbuf_lock);
 496        while (user->seq == log_next_seq) {
 497                if (file->f_flags & O_NONBLOCK) {
 498                        ret = -EAGAIN;
 499                        raw_spin_unlock_irq(&logbuf_lock);
 500                        goto out;
 501                }
 502
 503                raw_spin_unlock_irq(&logbuf_lock);
 504                ret = wait_event_interruptible(log_wait,
 505                                               user->seq != log_next_seq);
 506                if (ret)
 507                        goto out;
 508                raw_spin_lock_irq(&logbuf_lock);
 509        }
 510
 511        if (user->seq < log_first_seq) {
 512                /* our last seen message is gone, return error and reset */
 513                user->idx = log_first_idx;
 514                user->seq = log_first_seq;
 515                ret = -EPIPE;
 516                raw_spin_unlock_irq(&logbuf_lock);
 517                goto out;
 518        }
 519
 520        msg = log_from_idx(user->idx);
 521        ts_usec = msg->ts_nsec;
 522        do_div(ts_usec, 1000);
 523
 524        /*
 525         * If we couldn't merge continuation line fragments during the print,
 526         * export the stored flags to allow an optional external merge of the
 527         * records. Merging the records isn't always neccessarily correct, like
 528         * when we hit a race during printing. In most cases though, it produces
 529         * better readable output. 'c' in the record flags mark the first
 530         * fragment of a line, '+' the following.
 531         */
 532        if (msg->flags & LOG_CONT && !(user->prev & LOG_CONT))
 533                cont = 'c';
 534        else if ((msg->flags & LOG_CONT) ||
 535                 ((user->prev & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
 536                cont = '+';
 537
 538        len = sprintf(user->buf, "%u,%llu,%llu,%c;",
 539                      (msg->facility << 3) | msg->level,
 540                      user->seq, ts_usec, cont);
 541        user->prev = msg->flags;
 542
 543        /* escape non-printable characters */
 544        for (i = 0; i < msg->text_len; i++) {
 545                unsigned char c = log_text(msg)[i];
 546
 547                if (c < ' ' || c >= 127 || c == '\\')
 548                        len += sprintf(user->buf + len, "\\x%02x", c);
 549                else
 550                        user->buf[len++] = c;
 551        }
 552        user->buf[len++] = '\n';
 553
 554        if (msg->dict_len) {
 555                bool line = true;
 556
 557                for (i = 0; i < msg->dict_len; i++) {
 558                        unsigned char c = log_dict(msg)[i];
 559
 560                        if (line) {
 561                                user->buf[len++] = ' ';
 562                                line = false;
 563                        }
 564
 565                        if (c == '\0') {
 566                                user->buf[len++] = '\n';
 567                                line = true;
 568                                continue;
 569                        }
 570
 571                        if (c < ' ' || c >= 127 || c == '\\') {
 572                                len += sprintf(user->buf + len, "\\x%02x", c);
 573                                continue;
 574                        }
 575
 576                        user->buf[len++] = c;
 577                }
 578                user->buf[len++] = '\n';
 579        }
 580
 581        user->idx = log_next(user->idx);
 582        user->seq++;
 583        raw_spin_unlock_irq(&logbuf_lock);
 584
 585        if (len > count) {
 586                ret = -EINVAL;
 587                goto out;
 588        }
 589
 590        if (copy_to_user(buf, user->buf, len)) {
 591                ret = -EFAULT;
 592                goto out;
 593        }
 594        ret = len;
 595out:
 596        mutex_unlock(&user->lock);
 597        return ret;
 598}
 599
 600static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
 601{
 602        struct devkmsg_user *user = file->private_data;
 603        loff_t ret = 0;
 604
 605        if (!user)
 606                return -EBADF;
 607        if (offset)
 608                return -ESPIPE;
 609
 610        raw_spin_lock_irq(&logbuf_lock);
 611        switch (whence) {
 612        case SEEK_SET:
 613                /* the first record */
 614                user->idx = log_first_idx;
 615                user->seq = log_first_seq;
 616                break;
 617        case SEEK_DATA:
 618                /*
 619                 * The first record after the last SYSLOG_ACTION_CLEAR,
 620                 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
 621                 * changes no global state, and does not clear anything.
 622                 */
 623                user->idx = clear_idx;
 624                user->seq = clear_seq;
 625                break;
 626        case SEEK_END:
 627                /* after the last record */
 628                user->idx = log_next_idx;
 629                user->seq = log_next_seq;
 630                break;
 631        default:
 632                ret = -EINVAL;
 633        }
 634        raw_spin_unlock_irq(&logbuf_lock);
 635        return ret;
 636}
 637
 638static unsigned int devkmsg_poll(struct file *file, poll_table *wait)
 639{
 640        struct devkmsg_user *user = file->private_data;
 641        int ret = 0;
 642
 643        if (!user)
 644                return POLLERR|POLLNVAL;
 645
 646        poll_wait(file, &log_wait, wait);
 647
 648        raw_spin_lock_irq(&logbuf_lock);
 649        if (user->seq < log_next_seq) {
 650                /* return error when data has vanished underneath us */
 651                if (user->seq < log_first_seq)
 652                        ret = POLLIN|POLLRDNORM|POLLERR|POLLPRI;
 653                else
 654                        ret = POLLIN|POLLRDNORM;
 655        }
 656        raw_spin_unlock_irq(&logbuf_lock);
 657
 658        return ret;
 659}
 660
 661static int devkmsg_open(struct inode *inode, struct file *file)
 662{
 663        struct devkmsg_user *user;
 664        int err;
 665
 666        /* write-only does not need any file context */
 667        if ((file->f_flags & O_ACCMODE) == O_WRONLY)
 668                return 0;
 669
 670        err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
 671                                       SYSLOG_FROM_READER);
 672        if (err)
 673                return err;
 674
 675        user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
 676        if (!user)
 677                return -ENOMEM;
 678
 679        mutex_init(&user->lock);
 680
 681        raw_spin_lock_irq(&logbuf_lock);
 682        user->idx = log_first_idx;
 683        user->seq = log_first_seq;
 684        raw_spin_unlock_irq(&logbuf_lock);
 685
 686        file->private_data = user;
 687        return 0;
 688}
 689
 690static int devkmsg_release(struct inode *inode, struct file *file)
 691{
 692        struct devkmsg_user *user = file->private_data;
 693
 694        if (!user)
 695                return 0;
 696
 697        mutex_destroy(&user->lock);
 698        kfree(user);
 699        return 0;
 700}
 701
 702const struct file_operations kmsg_fops = {
 703        .open = devkmsg_open,
 704        .read = devkmsg_read,
 705        .aio_write = devkmsg_writev,
 706        .llseek = devkmsg_llseek,
 707        .poll = devkmsg_poll,
 708        .release = devkmsg_release,
 709};
 710
 711#ifdef CONFIG_KEXEC
 712/*
 713 * This appends the listed symbols to /proc/vmcoreinfo
 714 *
 715 * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
 716 * obtain access to symbols that are otherwise very difficult to locate.  These
 717 * symbols are specifically used so that utilities can access and extract the
 718 * dmesg log from a vmcore file after a crash.
 719 */
 720void log_buf_kexec_setup(void)
 721{
 722        VMCOREINFO_SYMBOL(log_buf);
 723        VMCOREINFO_SYMBOL(log_buf_len);
 724        VMCOREINFO_SYMBOL(log_first_idx);
 725        VMCOREINFO_SYMBOL(log_next_idx);
 726        /*
 727         * Export struct log size and field offsets. User space tools can
 728         * parse it and detect any changes to structure down the line.
 729         */
 730        VMCOREINFO_STRUCT_SIZE(log);
 731        VMCOREINFO_OFFSET(log, ts_nsec);
 732        VMCOREINFO_OFFSET(log, len);
 733        VMCOREINFO_OFFSET(log, text_len);
 734        VMCOREINFO_OFFSET(log, dict_len);
 735}
 736#endif
 737
 738/* requested log_buf_len from kernel cmdline */
 739static unsigned long __initdata new_log_buf_len;
 740
 741/* save requested log_buf_len since it's too early to process it */
 742static int __init log_buf_len_setup(char *str)
 743{
 744        unsigned size = memparse(str, &str);
 745
 746        if (size)
 747                size = roundup_pow_of_two(size);
 748        if (size > log_buf_len)
 749                new_log_buf_len = size;
 750
 751        return 0;
 752}
 753early_param("log_buf_len", log_buf_len_setup);
 754
 755void __init setup_log_buf(int early)
 756{
 757        unsigned long flags;
 758        char *new_log_buf;
 759        int free;
 760
 761        if (!new_log_buf_len)
 762                return;
 763
 764        if (early) {
 765                unsigned long mem;
 766
 767                mem = memblock_alloc(new_log_buf_len, PAGE_SIZE);
 768                if (!mem)
 769                        return;
 770                new_log_buf = __va(mem);
 771        } else {
 772                new_log_buf = alloc_bootmem_nopanic(new_log_buf_len);
 773        }
 774
 775        if (unlikely(!new_log_buf)) {
 776                pr_err("log_buf_len: %ld bytes not available\n",
 777                        new_log_buf_len);
 778                return;
 779        }
 780
 781        raw_spin_lock_irqsave(&logbuf_lock, flags);
 782        log_buf_len = new_log_buf_len;
 783        log_buf = new_log_buf;
 784        new_log_buf_len = 0;
 785        free = __LOG_BUF_LEN - log_next_idx;
 786        memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
 787        raw_spin_unlock_irqrestore(&logbuf_lock, flags);
 788
 789        pr_info("log_buf_len: %d\n", log_buf_len);
 790        pr_info("early log buf free: %d(%d%%)\n",
 791                free, (free * 100) / __LOG_BUF_LEN);
 792}
 793
 794static bool __read_mostly ignore_loglevel;
 795
 796static int __init ignore_loglevel_setup(char *str)
 797{
 798        ignore_loglevel = 1;
 799        printk(KERN_INFO "debug: ignoring loglevel setting.\n");
 800
 801        return 0;
 802}
 803
 804early_param("ignore_loglevel", ignore_loglevel_setup);
 805module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
 806MODULE_PARM_DESC(ignore_loglevel, "ignore loglevel setting, to"
 807        "print all kernel messages to the console.");
 808
 809#ifdef CONFIG_BOOT_PRINTK_DELAY
 810
 811static int boot_delay; /* msecs delay after each printk during bootup */
 812static unsigned long long loops_per_msec;       /* based on boot_delay */
 813
 814static int __init boot_delay_setup(char *str)
 815{
 816        unsigned long lpj;
 817
 818        lpj = preset_lpj ? preset_lpj : 1000000;        /* some guess */
 819        loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
 820
 821        get_option(&str, &boot_delay);
 822        if (boot_delay > 10 * 1000)
 823                boot_delay = 0;
 824
 825        pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
 826                "HZ: %d, loops_per_msec: %llu\n",
 827                boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
 828        return 1;
 829}
 830__setup("boot_delay=", boot_delay_setup);
 831
 832static void boot_delay_msec(int level)
 833{
 834        unsigned long long k;
 835        unsigned long timeout;
 836
 837        if ((boot_delay == 0 || system_state != SYSTEM_BOOTING)
 838                || (level >= console_loglevel && !ignore_loglevel)) {
 839                return;
 840        }
 841
 842        k = (unsigned long long)loops_per_msec * boot_delay;
 843
 844        timeout = jiffies + msecs_to_jiffies(boot_delay);
 845        while (k) {
 846                k--;
 847                cpu_relax();
 848                /*
 849                 * use (volatile) jiffies to prevent
 850                 * compiler reduction; loop termination via jiffies
 851                 * is secondary and may or may not happen.
 852                 */
 853                if (time_after(jiffies, timeout))
 854                        break;
 855                touch_nmi_watchdog();
 856        }
 857}
 858#else
 859static inline void boot_delay_msec(int level)
 860{
 861}
 862#endif
 863
 864#if defined(CONFIG_PRINTK_TIME)
 865static bool printk_time = 1;
 866#else
 867static bool printk_time;
 868#endif
 869module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
 870
 871static size_t print_time(u64 ts, char *buf)
 872{
 873        unsigned long rem_nsec;
 874
 875        if (!printk_time)
 876                return 0;
 877
 878        rem_nsec = do_div(ts, 1000000000);
 879
 880        if (!buf)
 881                return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);
 882
 883        return sprintf(buf, "[%5lu.%06lu] ",
 884                       (unsigned long)ts, rem_nsec / 1000);
 885}
 886
 887static size_t print_prefix(const struct log *msg, bool syslog, char *buf)
 888{
 889        size_t len = 0;
 890        unsigned int prefix = (msg->facility << 3) | msg->level;
 891
 892        if (syslog) {
 893                if (buf) {
 894                        len += sprintf(buf, "<%u>", prefix);
 895                } else {
 896                        len += 3;
 897                        if (prefix > 999)
 898                                len += 3;
 899                        else if (prefix > 99)
 900                                len += 2;
 901                        else if (prefix > 9)
 902                                len++;
 903                }
 904        }
 905
 906        len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
 907        return len;
 908}
 909
 910static size_t msg_print_text(const struct log *msg, enum log_flags prev,
 911                             bool syslog, char *buf, size_t size)
 912{
 913        const char *text = log_text(msg);
 914        size_t text_size = msg->text_len;
 915        bool prefix = true;
 916        bool newline = true;
 917        size_t len = 0;
 918
 919        if ((prev & LOG_CONT) && !(msg->flags & LOG_PREFIX))
 920                prefix = false;
 921
 922        if (msg->flags & LOG_CONT) {
 923                if ((prev & LOG_CONT) && !(prev & LOG_NEWLINE))
 924                        prefix = false;
 925
 926                if (!(msg->flags & LOG_NEWLINE))
 927                        newline = false;
 928        }
 929
 930        do {
 931                const char *next = memchr(text, '\n', text_size);
 932                size_t text_len;
 933
 934                if (next) {
 935                        text_len = next - text;
 936                        next++;
 937                        text_size -= next - text;
 938                } else {
 939                        text_len = text_size;
 940                }
 941
 942                if (buf) {
 943                        if (print_prefix(msg, syslog, NULL) +
 944                            text_len + 1 >= size - len)
 945                                break;
 946
 947                        if (prefix)
 948                                len += print_prefix(msg, syslog, buf + len);
 949                        memcpy(buf + len, text, text_len);
 950                        len += text_len;
 951                        if (next || newline)
 952                                buf[len++] = '\n';
 953                } else {
 954                        /* SYSLOG_ACTION_* buffer size only calculation */
 955                        if (prefix)
 956                                len += print_prefix(msg, syslog, NULL);
 957                        len += text_len;
 958                        if (next || newline)
 959                                len++;
 960                }
 961
 962                prefix = true;
 963                text = next;
 964        } while (text);
 965
 966        return len;
 967}
 968
 969static int syslog_print(char __user *buf, int size)
 970{
 971        char *text;
 972        struct log *msg;
 973        int len = 0;
 974
 975        text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
 976        if (!text)
 977                return -ENOMEM;
 978
 979        while (size > 0) {
 980                size_t n;
 981                size_t skip;
 982
 983                raw_spin_lock_irq(&logbuf_lock);
 984                if (syslog_seq < log_first_seq) {
 985                        /* messages are gone, move to first one */
 986                        syslog_seq = log_first_seq;
 987                        syslog_idx = log_first_idx;
 988                        syslog_prev = 0;
 989                        syslog_partial = 0;
 990                }
 991                if (syslog_seq == log_next_seq) {
 992                        raw_spin_unlock_irq(&logbuf_lock);
 993                        break;
 994                }
 995
 996                skip = syslog_partial;
 997                msg = log_from_idx(syslog_idx);
 998                n = msg_print_text(msg, syslog_prev, true, text,
 999                                   LOG_LINE_MAX + PREFIX_MAX);
1000                if (n - syslog_partial <= size) {
1001                        /* message fits into buffer, move forward */
1002                        syslog_idx = log_next(syslog_idx);
1003                        syslog_seq++;
1004                        syslog_prev = msg->flags;
1005                        n -= syslog_partial;
1006                        syslog_partial = 0;
1007                } else if (!len){
1008                        /* partial read(), remember position */
1009                        n = size;
1010                        syslog_partial += n;
1011                } else
1012                        n = 0;
1013                raw_spin_unlock_irq(&logbuf_lock);
1014
1015                if (!n)
1016                        break;
1017
1018                if (copy_to_user(buf, text + skip, n)) {
1019                        if (!len)
1020                                len = -EFAULT;
1021                        break;
1022                }
1023
1024                len += n;
1025                size -= n;
1026                buf += n;
1027        }
1028
1029        kfree(text);
1030        return len;
1031}
1032
1033static int syslog_print_all(char __user *buf, int size, bool clear)
1034{
1035        char *text;
1036        int len = 0;
1037
1038        text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1039        if (!text)
1040                return -ENOMEM;
1041
1042        raw_spin_lock_irq(&logbuf_lock);
1043        if (buf) {
1044                u64 next_seq;
1045                u64 seq;
1046                u32 idx;
1047                enum log_flags prev;
1048
1049                if (clear_seq < log_first_seq) {
1050                        /* messages are gone, move to first available one */
1051                        clear_seq = log_first_seq;
1052                        clear_idx = log_first_idx;
1053                }
1054
1055                /*
1056                 * Find first record that fits, including all following records,
1057                 * into the user-provided buffer for this dump.
1058                 */
1059                seq = clear_seq;
1060                idx = clear_idx;
1061                prev = 0;
1062                while (seq < log_next_seq) {
1063                        struct log *msg = log_from_idx(idx);
1064
1065                        len += msg_print_text(msg, prev, true, NULL, 0);
1066                        prev = msg->flags;
1067                        idx = log_next(idx);
1068                        seq++;
1069                }
1070
1071                /* move first record forward until length fits into the buffer */
1072                seq = clear_seq;
1073                idx = clear_idx;
1074                prev = 0;
1075                while (len > size && seq < log_next_seq) {
1076                        struct log *msg = log_from_idx(idx);
1077
1078                        len -= msg_print_text(msg, prev, true, NULL, 0);
1079                        prev = msg->flags;
1080                        idx = log_next(idx);
1081                        seq++;
1082                }
1083
1084                /* last message fitting into this dump */
1085                next_seq = log_next_seq;
1086
1087                len = 0;
1088                prev = 0;
1089                while (len >= 0 && seq < next_seq) {
1090                        struct log *msg = log_from_idx(idx);
1091                        int textlen;
1092
1093                        textlen = msg_print_text(msg, prev, true, text,
1094                                                 LOG_LINE_MAX + PREFIX_MAX);
1095                        if (textlen < 0) {
1096                                len = textlen;
1097                                break;
1098                        }
1099                        idx = log_next(idx);
1100                        seq++;
1101                        prev = msg->flags;
1102
1103                        raw_spin_unlock_irq(&logbuf_lock);
1104                        if (copy_to_user(buf + len, text, textlen))
1105                                len = -EFAULT;
1106                        else
1107                                len += textlen;
1108                        raw_spin_lock_irq(&logbuf_lock);
1109
1110                        if (seq < log_first_seq) {
1111                                /* messages are gone, move to next one */
1112                                seq = log_first_seq;
1113                                idx = log_first_idx;
1114                                prev = 0;
1115                        }
1116                }
1117        }
1118
1119        if (clear) {
1120                clear_seq = log_next_seq;
1121                clear_idx = log_next_idx;
1122        }
1123        raw_spin_unlock_irq(&logbuf_lock);
1124
1125        kfree(text);
1126        return len;
1127}
1128
1129int do_syslog(int type, char __user *buf, int len, bool from_file)
1130{
1131        bool clear = false;
1132        static int saved_console_loglevel = -1;
1133        int error;
1134
1135        error = check_syslog_permissions(type, from_file);
1136        if (error)
1137                goto out;
1138
1139        error = security_syslog(type);
1140        if (error)
1141                return error;
1142
1143        switch (type) {
1144        case SYSLOG_ACTION_CLOSE:       /* Close log */
1145                break;
1146        case SYSLOG_ACTION_OPEN:        /* Open log */
1147                break;
1148        case SYSLOG_ACTION_READ:        /* Read from log */
1149                error = -EINVAL;
1150                if (!buf || len < 0)
1151                        goto out;
1152                error = 0;
1153                if (!len)
1154                        goto out;
1155                if (!access_ok(VERIFY_WRITE, buf, len)) {
1156                        error = -EFAULT;
1157                        goto out;
1158                }
1159                error = wait_event_interruptible(log_wait,
1160                                                 syslog_seq != log_next_seq);
1161                if (error)
1162                        goto out;
1163                error = syslog_print(buf, len);
1164                break;
1165        /* Read/clear last kernel messages */
1166        case SYSLOG_ACTION_READ_CLEAR:
1167                clear = true;
1168                /* FALL THRU */
1169        /* Read last kernel messages */
1170        case SYSLOG_ACTION_READ_ALL:
1171                error = -EINVAL;
1172                if (!buf || len < 0)
1173                        goto out;
1174                error = 0;
1175                if (!len)
1176                        goto out;
1177                if (!access_ok(VERIFY_WRITE, buf, len)) {
1178                        error = -EFAULT;
1179                        goto out;
1180                }
1181                error = syslog_print_all(buf, len, clear);
1182                break;
1183        /* Clear ring buffer */
1184        case SYSLOG_ACTION_CLEAR:
1185                syslog_print_all(NULL, 0, true);
1186                break;
1187        /* Disable logging to console */
1188        case SYSLOG_ACTION_CONSOLE_OFF:
1189                if (saved_console_loglevel == -1)
1190                        saved_console_loglevel = console_loglevel;
1191                console_loglevel = minimum_console_loglevel;
1192                break;
1193        /* Enable logging to console */
1194        case SYSLOG_ACTION_CONSOLE_ON:
1195                if (saved_console_loglevel != -1) {
1196                        console_loglevel = saved_console_loglevel;
1197                        saved_console_loglevel = -1;
1198                }
1199                break;
1200        /* Set level of messages printed to console */
1201        case SYSLOG_ACTION_CONSOLE_LEVEL:
1202                error = -EINVAL;
1203                if (len < 1 || len > 8)
1204                        goto out;
1205                if (len < minimum_console_loglevel)
1206                        len = minimum_console_loglevel;
1207                console_loglevel = len;
1208                /* Implicitly re-enable logging to console */
1209                saved_console_loglevel = -1;
1210                error = 0;
1211                break;
1212        /* Number of chars in the log buffer */
1213        case SYSLOG_ACTION_SIZE_UNREAD:
1214                raw_spin_lock_irq(&logbuf_lock);
1215                if (syslog_seq < log_first_seq) {
1216                        /* messages are gone, move to first one */
1217                        syslog_seq = log_first_seq;
1218                        syslog_idx = log_first_idx;
1219                        syslog_prev = 0;
1220                        syslog_partial = 0;
1221                }
1222                if (from_file) {
1223                        /*
1224                         * Short-cut for poll(/"proc/kmsg") which simply checks
1225                         * for pending data, not the size; return the count of
1226                         * records, not the length.
1227                         */
1228                        error = log_next_idx - syslog_idx;
1229                } else {
1230                        u64 seq = syslog_seq;
1231                        u32 idx = syslog_idx;
1232                        enum log_flags prev = syslog_prev;
1233
1234                        error = 0;
1235                        while (seq < log_next_seq) {
1236                                struct log *msg = log_from_idx(idx);
1237
1238                                error += msg_print_text(msg, prev, true, NULL, 0);
1239                                idx = log_next(idx);
1240                                seq++;
1241                                prev = msg->flags;
1242                        }
1243                        error -= syslog_partial;
1244                }
1245                raw_spin_unlock_irq(&logbuf_lock);
1246                break;
1247        /* Size of the log buffer */
1248        case SYSLOG_ACTION_SIZE_BUFFER:
1249                error = log_buf_len;
1250                break;
1251        default:
1252                error = -EINVAL;
1253                break;
1254        }
1255out:
1256        return error;
1257}
1258
1259SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1260{
1261        return do_syslog(type, buf, len, SYSLOG_FROM_READER);
1262}
1263
1264/*
1265 * Call the console drivers, asking them to write out
1266 * log_buf[start] to log_buf[end - 1].
1267 * The console_lock must be held.
1268 */
1269static void call_console_drivers(int level, const char *text, size_t len)
1270{
1271        struct console *con;
1272
1273        trace_console(text, len);
1274
1275        if (level >= console_loglevel && !ignore_loglevel)
1276                return;
1277        if (!console_drivers)
1278                return;
1279
1280        for_each_console(con) {
1281                if (exclusive_console && con != exclusive_console)
1282                        continue;
1283                if (!(con->flags & CON_ENABLED))
1284                        continue;
1285                if (!con->write)
1286                        continue;
1287                if (!cpu_online(smp_processor_id()) &&
1288                    !(con->flags & CON_ANYTIME))
1289                        continue;
1290                con->write(con, text, len);
1291        }
1292}
1293
1294/*
1295 * Zap console related locks when oopsing. Only zap at most once
1296 * every 10 seconds, to leave time for slow consoles to print a
1297 * full oops.
1298 */
1299static void zap_locks(void)
1300{
1301        static unsigned long oops_timestamp;
1302
1303        if (time_after_eq(jiffies, oops_timestamp) &&
1304                        !time_after(jiffies, oops_timestamp + 30 * HZ))
1305                return;
1306
1307        oops_timestamp = jiffies;
1308
1309        debug_locks_off();
1310        /* If a crash is occurring, make sure we can't deadlock */
1311        raw_spin_lock_init(&logbuf_lock);
1312        /* And make sure that we print immediately */
1313        sema_init(&console_sem, 1);
1314}
1315
1316/* Check if we have any console registered that can be called early in boot. */
1317static int have_callable_console(void)
1318{
1319        struct console *con;
1320
1321        for_each_console(con)
1322                if (con->flags & CON_ANYTIME)
1323                        return 1;
1324
1325        return 0;
1326}
1327
1328/*
1329 * Can we actually use the console at this time on this cpu?
1330 *
1331 * Console drivers may assume that per-cpu resources have
1332 * been allocated. So unless they're explicitly marked as
1333 * being able to cope (CON_ANYTIME) don't call them until
1334 * this CPU is officially up.
1335 */
1336static inline int can_use_console(unsigned int cpu)
1337{
1338        return cpu_online(cpu) || have_callable_console();
1339}
1340
1341/*
1342 * Try to get console ownership to actually show the kernel
1343 * messages from a 'printk'. Return true (and with the
1344 * console_lock held, and 'console_locked' set) if it
1345 * is successful, false otherwise.
1346 *
1347 * This gets called with the 'logbuf_lock' spinlock held and
1348 * interrupts disabled. It should return with 'lockbuf_lock'
1349 * released but interrupts still disabled.
1350 */
1351static int console_trylock_for_printk(unsigned int cpu)
1352        __releases(&logbuf_lock)
1353{
1354        int retval = 0, wake = 0;
1355
1356        if (console_trylock()) {
1357                retval = 1;
1358
1359                /*
1360                 * If we can't use the console, we need to release
1361                 * the console semaphore by hand to avoid flushing
1362                 * the buffer. We need to hold the console semaphore
1363                 * in order to do this test safely.
1364                 */
1365                if (!can_use_console(cpu)) {
1366                        console_locked = 0;
1367                        wake = 1;
1368                        retval = 0;
1369                }
1370        }
1371        logbuf_cpu = UINT_MAX;
1372        if (wake)
1373                up(&console_sem);
1374        raw_spin_unlock(&logbuf_lock);
1375        return retval;
1376}
1377
1378int printk_delay_msec __read_mostly;
1379
1380static inline void printk_delay(void)
1381{
1382        if (unlikely(printk_delay_msec)) {
1383                int m = printk_delay_msec;
1384
1385                while (m--) {
1386                        mdelay(1);
1387                        touch_nmi_watchdog();
1388                }
1389        }
1390}
1391
1392/*
1393 * Continuation lines are buffered, and not committed to the record buffer
1394 * until the line is complete, or a race forces it. The line fragments
1395 * though, are printed immediately to the consoles to ensure everything has
1396 * reached the console in case of a kernel crash.
1397 */
1398static struct cont {
1399        char buf[LOG_LINE_MAX];
1400        size_t len;                     /* length == 0 means unused buffer */
1401        size_t cons;                    /* bytes written to console */
1402        struct task_struct *owner;      /* task of first print*/
1403        u64 ts_nsec;                    /* time of first print */
1404        u8 level;                       /* log level of first message */
1405        u8 facility;                    /* log level of first message */
1406        enum log_flags flags;           /* prefix, newline flags */
1407        bool flushed:1;                 /* buffer sealed and committed */
1408} cont;
1409
1410static void cont_flush(enum log_flags flags)
1411{
1412        if (cont.flushed)
1413                return;
1414        if (cont.len == 0)
1415                return;
1416
1417        if (cont.cons) {
1418                /*
1419                 * If a fragment of this line was directly flushed to the
1420                 * console; wait for the console to pick up the rest of the
1421                 * line. LOG_NOCONS suppresses a duplicated output.
1422                 */
1423                log_store(cont.facility, cont.level, flags | LOG_NOCONS,
1424                          cont.ts_nsec, NULL, 0, cont.buf, cont.len);
1425                cont.flags = flags;
1426                cont.flushed = true;
1427        } else {
1428                /*
1429                 * If no fragment of this line ever reached the console,
1430                 * just submit it to the store and free the buffer.
1431                 */
1432                log_store(cont.facility, cont.level, flags, 0,
1433                          NULL, 0, cont.buf, cont.len);
1434                cont.len = 0;
1435        }
1436}
1437
1438static bool cont_add(int facility, int level, const char *text, size_t len)
1439{
1440        if (cont.len && cont.flushed)
1441                return false;
1442
1443        if (cont.len + len > sizeof(cont.buf)) {
1444                /* the line gets too long, split it up in separate records */
1445                cont_flush(LOG_CONT);
1446                return false;
1447        }
1448
1449        if (!cont.len) {
1450                cont.facility = facility;
1451                cont.level = level;
1452                cont.owner = current;
1453                cont.ts_nsec = local_clock();
1454                cont.flags = 0;
1455                cont.cons = 0;
1456                cont.flushed = false;
1457        }
1458
1459        memcpy(cont.buf + cont.len, text, len);
1460        cont.len += len;
1461
1462        if (cont.len > (sizeof(cont.buf) * 80) / 100)
1463                cont_flush(LOG_CONT);
1464
1465        return true;
1466}
1467
1468static size_t cont_print_text(char *text, size_t size)
1469{
1470        size_t textlen = 0;
1471        size_t len;
1472
1473        if (cont.cons == 0 && (console_prev & LOG_NEWLINE)) {
1474                textlen += print_time(cont.ts_nsec, text);
1475                size -= textlen;
1476        }
1477
1478        len = cont.len - cont.cons;
1479        if (len > 0) {
1480                if (len+1 > size)
1481                        len = size-1;
1482                memcpy(text + textlen, cont.buf + cont.cons, len);
1483                textlen += len;
1484                cont.cons = cont.len;
1485        }
1486
1487        if (cont.flushed) {
1488                if (cont.flags & LOG_NEWLINE)
1489                        text[textlen++] = '\n';
1490                /* got everything, release buffer */
1491                cont.len = 0;
1492        }
1493        return textlen;
1494}
1495
1496asmlinkage int vprintk_emit(int facility, int level,
1497                            const char *dict, size_t dictlen,
1498                            const char *fmt, va_list args)
1499{
1500        static int recursion_bug;
1501        static char textbuf[LOG_LINE_MAX];
1502        char *text = textbuf;
1503        size_t text_len;
1504        enum log_flags lflags = 0;
1505        unsigned long flags;
1506        int this_cpu;
1507        int printed_len = 0;
1508
1509        boot_delay_msec(level);
1510        printk_delay();
1511
1512        /* This stops the holder of console_sem just where we want him */
1513        local_irq_save(flags);
1514        this_cpu = smp_processor_id();
1515
1516        /*
1517         * Ouch, printk recursed into itself!
1518         */
1519        if (unlikely(logbuf_cpu == this_cpu)) {
1520                /*
1521                 * If a crash is occurring during printk() on this CPU,
1522                 * then try to get the crash message out but make sure
1523                 * we can't deadlock. Otherwise just return to avoid the
1524                 * recursion and return - but flag the recursion so that
1525                 * it can be printed at the next appropriate moment:
1526                 */
1527                if (!oops_in_progress && !lockdep_recursing(current)) {
1528                        recursion_bug = 1;
1529                        goto out_restore_irqs;
1530                }
1531                zap_locks();
1532        }
1533
1534        lockdep_off();
1535        raw_spin_lock(&logbuf_lock);
1536        logbuf_cpu = this_cpu;
1537
1538        if (recursion_bug) {
1539                static const char recursion_msg[] =
1540                        "BUG: recent printk recursion!";
1541
1542                recursion_bug = 0;
1543                printed_len += strlen(recursion_msg);
1544                /* emit KERN_CRIT message */
1545                log_store(0, 2, LOG_PREFIX|LOG_NEWLINE, 0,
1546                          NULL, 0, recursion_msg, printed_len);
1547        }
1548
1549        /*
1550         * The printf needs to come first; we need the syslog
1551         * prefix which might be passed-in as a parameter.
1552         */
1553        text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
1554
1555        /* mark and strip a trailing newline */
1556        if (text_len && text[text_len-1] == '\n') {
1557                text_len--;
1558                lflags |= LOG_NEWLINE;
1559        }
1560
1561        /* strip kernel syslog prefix and extract log level or control flags */
1562        if (facility == 0) {
1563                int kern_level = printk_get_level(text);
1564
1565                if (kern_level) {
1566                        const char *end_of_header = printk_skip_level(text);
1567                        switch (kern_level) {
1568                        case '0' ... '7':
1569                                if (level == -1)
1570                                        level = kern_level - '0';
1571                        case 'd':       /* KERN_DEFAULT */
1572                                lflags |= LOG_PREFIX;
1573                        case 'c':       /* KERN_CONT */
1574                                break;
1575                        }
1576                        text_len -= end_of_header - text;
1577                        text = (char *)end_of_header;
1578                }
1579        }
1580
1581        if (level == -1)
1582                level = default_message_loglevel;
1583
1584        if (dict)
1585                lflags |= LOG_PREFIX|LOG_NEWLINE;
1586
1587        if (!(lflags & LOG_NEWLINE)) {
1588                /*
1589                 * Flush the conflicting buffer. An earlier newline was missing,
1590                 * or another task also prints continuation lines.
1591                 */
1592                if (cont.len && (lflags & LOG_PREFIX || cont.owner != current))
1593                        cont_flush(LOG_NEWLINE);
1594
1595                /* buffer line if possible, otherwise store it right away */
1596                if (!cont_add(facility, level, text, text_len))
1597                        log_store(facility, level, lflags | LOG_CONT, 0,
1598                                  dict, dictlen, text, text_len);
1599        } else {
1600                bool stored = false;
1601
1602                /*
1603                 * If an earlier newline was missing and it was the same task,
1604                 * either merge it with the current buffer and flush, or if
1605                 * there was a race with interrupts (prefix == true) then just
1606                 * flush it out and store this line separately.
1607                 */
1608                if (cont.len && cont.owner == current) {
1609                        if (!(lflags & LOG_PREFIX))
1610                                stored = cont_add(facility, level, text, text_len);
1611                        cont_flush(LOG_NEWLINE);
1612                }
1613
1614                if (!stored)
1615                        log_store(facility, level, lflags, 0,
1616                                  dict, dictlen, text, text_len);
1617        }
1618        printed_len += text_len;
1619
1620        /*
1621         * Try to acquire and then immediately release the console semaphore.
1622         * The release will print out buffers and wake up /dev/kmsg and syslog()
1623         * users.
1624         *
1625         * The console_trylock_for_printk() function will release 'logbuf_lock'
1626         * regardless of whether it actually gets the console semaphore or not.
1627         */
1628        if (console_trylock_for_printk(this_cpu))
1629                console_unlock();
1630
1631        lockdep_on();
1632out_restore_irqs:
1633        local_irq_restore(flags);
1634
1635        return printed_len;
1636}
1637EXPORT_SYMBOL(vprintk_emit);
1638
1639asmlinkage int vprintk(const char *fmt, va_list args)
1640{
1641        return vprintk_emit(0, -1, NULL, 0, fmt, args);
1642}
1643EXPORT_SYMBOL(vprintk);
1644
1645asmlinkage int printk_emit(int facility, int level,
1646                           const char *dict, size_t dictlen,
1647                           const char *fmt, ...)
1648{
1649        va_list args;
1650        int r;
1651
1652        va_start(args, fmt);
1653        r = vprintk_emit(facility, level, dict, dictlen, fmt, args);
1654        va_end(args);
1655
1656        return r;
1657}
1658EXPORT_SYMBOL(printk_emit);
1659
1660/**
1661 * printk - print a kernel message
1662 * @fmt: format string
1663 *
1664 * This is printk(). It can be called from any context. We want it to work.
1665 *
1666 * We try to grab the console_lock. If we succeed, it's easy - we log the
1667 * output and call the console drivers.  If we fail to get the semaphore, we
1668 * place the output into the log buffer and return. The current holder of
1669 * the console_sem will notice the new output in console_unlock(); and will
1670 * send it to the consoles before releasing the lock.
1671 *
1672 * One effect of this deferred printing is that code which calls printk() and
1673 * then changes console_loglevel may break. This is because console_loglevel
1674 * is inspected when the actual printing occurs.
1675 *
1676 * See also:
1677 * printf(3)
1678 *
1679 * See the vsnprintf() documentation for format string extensions over C99.
1680 */
1681asmlinkage int printk(const char *fmt, ...)
1682{
1683        va_list args;
1684        int r;
1685
1686#ifdef CONFIG_KGDB_KDB
1687        if (unlikely(kdb_trap_printk)) {
1688                va_start(args, fmt);
1689                r = vkdb_printf(fmt, args);
1690                va_end(args);
1691                return r;
1692        }
1693#endif
1694        va_start(args, fmt);
1695        r = vprintk_emit(0, -1, NULL, 0, fmt, args);
1696        va_end(args);
1697
1698        return r;
1699}
1700EXPORT_SYMBOL(printk);
1701
1702#else /* CONFIG_PRINTK */
1703
1704#define LOG_LINE_MAX            0
1705#define PREFIX_MAX              0
1706#define LOG_LINE_MAX 0
1707static u64 syslog_seq;
1708static u32 syslog_idx;
1709static u64 console_seq;
1710static u32 console_idx;
1711static enum log_flags syslog_prev;
1712static u64 log_first_seq;
1713static u32 log_first_idx;
1714static u64 log_next_seq;
1715static enum log_flags console_prev;
1716static struct cont {
1717        size_t len;
1718        size_t cons;
1719        u8 level;
1720        bool flushed:1;
1721} cont;
1722static struct log *log_from_idx(u32 idx) { return NULL; }
1723static u32 log_next(u32 idx) { return 0; }
1724static void call_console_drivers(int level, const char *text, size_t len) {}
1725static size_t msg_print_text(const struct log *msg, enum log_flags prev,
1726                             bool syslog, char *buf, size_t size) { return 0; }
1727static size_t cont_print_text(char *text, size_t size) { return 0; }
1728
1729#endif /* CONFIG_PRINTK */
1730
1731#ifdef CONFIG_EARLY_PRINTK
1732struct console *early_console;
1733
1734void early_vprintk(const char *fmt, va_list ap)
1735{
1736        if (early_console) {
1737                char buf[512];
1738                int n = vscnprintf(buf, sizeof(buf), fmt, ap);
1739
1740                early_console->write(early_console, buf, n);
1741        }
1742}
1743
1744asmlinkage void early_printk(const char *fmt, ...)
1745{
1746        va_list ap;
1747
1748        va_start(ap, fmt);
1749        early_vprintk(fmt, ap);
1750        va_end(ap);
1751}
1752#endif
1753
1754static int __add_preferred_console(char *name, int idx, char *options,
1755                                   char *brl_options)
1756{
1757        struct console_cmdline *c;
1758        int i;
1759
1760        /*
1761         *      See if this tty is not yet registered, and
1762         *      if we have a slot free.
1763         */
1764        for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
1765                if (strcmp(console_cmdline[i].name, name) == 0 &&
1766                          console_cmdline[i].index == idx) {
1767                                if (!brl_options)
1768                                        selected_console = i;
1769                                return 0;
1770                }
1771        if (i == MAX_CMDLINECONSOLES)
1772                return -E2BIG;
1773        if (!brl_options)
1774                selected_console = i;
1775        c = &console_cmdline[i];
1776        strlcpy(c->name, name, sizeof(c->name));
1777        c->options = options;
1778#ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1779        c->brl_options = brl_options;
1780#endif
1781        c->index = idx;
1782        return 0;
1783}
1784/*
1785 * Set up a list of consoles.  Called from init/main.c
1786 */
1787static int __init console_setup(char *str)
1788{
1789        char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
1790        char *s, *options, *brl_options = NULL;
1791        int idx;
1792
1793#ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1794        if (!memcmp(str, "brl,", 4)) {
1795                brl_options = "";
1796                str += 4;
1797        } else if (!memcmp(str, "brl=", 4)) {
1798                brl_options = str + 4;
1799                str = strchr(brl_options, ',');
1800                if (!str) {
1801                        printk(KERN_ERR "need port name after brl=\n");
1802                        return 1;
1803                }
1804                *(str++) = 0;
1805        }
1806#endif
1807
1808        /*
1809         * Decode str into name, index, options.
1810         */
1811        if (str[0] >= '0' && str[0] <= '9') {
1812                strcpy(buf, "ttyS");
1813                strncpy(buf + 4, str, sizeof(buf) - 5);
1814        } else {
1815                strncpy(buf, str, sizeof(buf) - 1);
1816        }
1817        buf[sizeof(buf) - 1] = 0;
1818        if ((options = strchr(str, ',')) != NULL)
1819                *(options++) = 0;
1820#ifdef __sparc__
1821        if (!strcmp(str, "ttya"))
1822                strcpy(buf, "ttyS0");
1823        if (!strcmp(str, "ttyb"))
1824                strcpy(buf, "ttyS1");
1825#endif
1826        for (s = buf; *s; s++)
1827                if ((*s >= '0' && *s <= '9') || *s == ',')
1828                        break;
1829        idx = simple_strtoul(s, NULL, 10);
1830        *s = 0;
1831
1832        __add_preferred_console(buf, idx, options, brl_options);
1833        console_set_on_cmdline = 1;
1834        return 1;
1835}
1836__setup("console=", console_setup);
1837
1838/**
1839 * add_preferred_console - add a device to the list of preferred consoles.
1840 * @name: device name
1841 * @idx: device index
1842 * @options: options for this console
1843 *
1844 * The last preferred console added will be used for kernel messages
1845 * and stdin/out/err for init.  Normally this is used by console_setup
1846 * above to handle user-supplied console arguments; however it can also
1847 * be used by arch-specific code either to override the user or more
1848 * commonly to provide a default console (ie from PROM variables) when
1849 * the user has not supplied one.
1850 */
1851int add_preferred_console(char *name, int idx, char *options)
1852{
1853        return __add_preferred_console(name, idx, options, NULL);
1854}
1855
1856int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
1857{
1858        struct console_cmdline *c;
1859        int i;
1860
1861        for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
1862                if (strcmp(console_cmdline[i].name, name) == 0 &&
1863                          console_cmdline[i].index == idx) {
1864                                c = &console_cmdline[i];
1865                                strlcpy(c->name, name_new, sizeof(c->name));
1866                                c->name[sizeof(c->name) - 1] = 0;
1867                                c->options = options;
1868                                c->index = idx_new;
1869                                return i;
1870                }
1871        /* not found */
1872        return -1;
1873}
1874
1875bool console_suspend_enabled = 1;
1876EXPORT_SYMBOL(console_suspend_enabled);
1877
1878static int __init console_suspend_disable(char *str)
1879{
1880        console_suspend_enabled = 0;
1881        return 1;
1882}
1883__setup("no_console_suspend", console_suspend_disable);
1884module_param_named(console_suspend, console_suspend_enabled,
1885                bool, S_IRUGO | S_IWUSR);
1886MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
1887        " and hibernate operations");
1888
1889/**
1890 * suspend_console - suspend the console subsystem
1891 *
1892 * This disables printk() while we go into suspend states
1893 */
1894void suspend_console(void)
1895{
1896        if (!console_suspend_enabled)
1897                return;
1898        printk("Suspending console(s) (use no_console_suspend to debug)\n");
1899        console_lock();
1900        console_suspended = 1;
1901        up(&console_sem);
1902}
1903
1904void resume_console(void)
1905{
1906        if (!console_suspend_enabled)
1907                return;
1908        down(&console_sem);
1909        console_suspended = 0;
1910        console_unlock();
1911}
1912
1913/**
1914 * console_cpu_notify - print deferred console messages after CPU hotplug
1915 * @self: notifier struct
1916 * @action: CPU hotplug event
1917 * @hcpu: unused
1918 *
1919 * If printk() is called from a CPU that is not online yet, the messages
1920 * will be spooled but will not show up on the console.  This function is
1921 * called when a new CPU comes online (or fails to come up), and ensures
1922 * that any such output gets printed.
1923 */
1924static int __cpuinit console_cpu_notify(struct notifier_block *self,
1925        unsigned long action, void *hcpu)
1926{
1927        switch (action) {
1928        case CPU_ONLINE:
1929        case CPU_DEAD:
1930        case CPU_DOWN_FAILED:
1931        case CPU_UP_CANCELED:
1932                console_lock();
1933                console_unlock();
1934        }
1935        return NOTIFY_OK;
1936}
1937
1938/**
1939 * console_lock - lock the console system for exclusive use.
1940 *
1941 * Acquires a lock which guarantees that the caller has
1942 * exclusive access to the console system and the console_drivers list.
1943 *
1944 * Can sleep, returns nothing.
1945 */
1946void console_lock(void)
1947{
1948        might_sleep();
1949
1950        down(&console_sem);
1951        if (console_suspended)
1952                return;
1953        console_locked = 1;
1954        console_may_schedule = 1;
1955        mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);
1956}
1957EXPORT_SYMBOL(console_lock);
1958
1959/**
1960 * console_trylock - try to lock the console system for exclusive use.
1961 *
1962 * Tried to acquire a lock which guarantees that the caller has
1963 * exclusive access to the console system and the console_drivers list.
1964 *
1965 * returns 1 on success, and 0 on failure to acquire the lock.
1966 */
1967int console_trylock(void)
1968{
1969        if (down_trylock(&console_sem))
1970                return 0;
1971        if (console_suspended) {
1972                up(&console_sem);
1973                return 0;
1974        }
1975        console_locked = 1;
1976        console_may_schedule = 0;
1977        mutex_acquire(&console_lock_dep_map, 0, 1, _RET_IP_);
1978        return 1;
1979}
1980EXPORT_SYMBOL(console_trylock);
1981
1982int is_console_locked(void)
1983{
1984        return console_locked;
1985}
1986
1987static void console_cont_flush(char *text, size_t size)
1988{
1989        unsigned long flags;
1990        size_t len;
1991
1992        raw_spin_lock_irqsave(&logbuf_lock, flags);
1993
1994        if (!cont.len)
1995                goto out;
1996
1997        /*
1998         * We still queue earlier records, likely because the console was
1999         * busy. The earlier ones need to be printed before this one, we
2000         * did not flush any fragment so far, so just let it queue up.
2001         */
2002        if (console_seq < log_next_seq && !cont.cons)
2003                goto out;
2004
2005        len = cont_print_text(text, size);
2006        raw_spin_unlock(&logbuf_lock);
2007        stop_critical_timings();
2008        call_console_drivers(cont.level, text, len);
2009        start_critical_timings();
2010        local_irq_restore(flags);
2011        return;
2012out:
2013        raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2014}
2015
2016/**
2017 * console_unlock - unlock the console system
2018 *
2019 * Releases the console_lock which the caller holds on the console system
2020 * and the console driver list.
2021 *
2022 * While the console_lock was held, console output may have been buffered
2023 * by printk().  If this is the case, console_unlock(); emits
2024 * the output prior to releasing the lock.
2025 *
2026 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2027 *
2028 * console_unlock(); may be called from any context.
2029 */
2030void console_unlock(void)
2031{
2032        static char text[LOG_LINE_MAX + PREFIX_MAX];
2033        static u64 seen_seq;
2034        unsigned long flags;
2035        bool wake_klogd = false;
2036        bool retry;
2037
2038        if (console_suspended) {
2039                up(&console_sem);
2040                return;
2041        }
2042
2043        console_may_schedule = 0;
2044
2045        /* flush buffered message fragment immediately to console */
2046        console_cont_flush(text, sizeof(text));
2047again:
2048        for (;;) {
2049                struct log *msg;
2050                size_t len;
2051                int level;
2052
2053                raw_spin_lock_irqsave(&logbuf_lock, flags);
2054                if (seen_seq != log_next_seq) {
2055                        wake_klogd = true;
2056                        seen_seq = log_next_seq;
2057                }
2058
2059                if (console_seq < log_first_seq) {
2060                        /* messages are gone, move to first one */
2061                        console_seq = log_first_seq;
2062                        console_idx = log_first_idx;
2063                        console_prev = 0;
2064                }
2065skip:
2066                if (console_seq == log_next_seq)
2067                        break;
2068
2069                msg = log_from_idx(console_idx);
2070                if (msg->flags & LOG_NOCONS) {
2071                        /*
2072                         * Skip record we have buffered and already printed
2073                         * directly to the console when we received it.
2074                         */
2075                        console_idx = log_next(console_idx);
2076                        console_seq++;
2077                        /*
2078                         * We will get here again when we register a new
2079                         * CON_PRINTBUFFER console. Clear the flag so we
2080                         * will properly dump everything later.
2081                         */
2082                        msg->flags &= ~LOG_NOCONS;
2083                        console_prev = msg->flags;
2084                        goto skip;
2085                }
2086
2087                level = msg->level;
2088                len = msg_print_text(msg, console_prev, false,
2089                                     text, sizeof(text));
2090                console_idx = log_next(console_idx);
2091                console_seq++;
2092                console_prev = msg->flags;
2093                raw_spin_unlock(&logbuf_lock);
2094
2095                stop_critical_timings();        /* don't trace print latency */
2096                call_console_drivers(level, text, len);
2097                start_critical_timings();
2098                local_irq_restore(flags);
2099        }
2100        console_locked = 0;
2101        mutex_release(&console_lock_dep_map, 1, _RET_IP_);
2102
2103        /* Release the exclusive_console once it is used */
2104        if (unlikely(exclusive_console))
2105                exclusive_console = NULL;
2106
2107        raw_spin_unlock(&logbuf_lock);
2108
2109        up(&console_sem);
2110
2111        /*
2112         * Someone could have filled up the buffer again, so re-check if there's
2113         * something to flush. In case we cannot trylock the console_sem again,
2114         * there's a new owner and the console_unlock() from them will do the
2115         * flush, no worries.
2116         */
2117        raw_spin_lock(&logbuf_lock);
2118        retry = console_seq != log_next_seq;
2119        raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2120
2121        if (retry && console_trylock())
2122                goto again;
2123
2124        if (wake_klogd)
2125                wake_up_klogd();
2126}
2127EXPORT_SYMBOL(console_unlock);
2128
2129/**
2130 * console_conditional_schedule - yield the CPU if required
2131 *
2132 * If the console code is currently allowed to sleep, and
2133 * if this CPU should yield the CPU to another task, do
2134 * so here.
2135 *
2136 * Must be called within console_lock();.
2137 */
2138void __sched console_conditional_schedule(void)
2139{
2140        if (console_may_schedule)
2141                cond_resched();
2142}
2143EXPORT_SYMBOL(console_conditional_schedule);
2144
2145void console_unblank(void)
2146{
2147        struct console *c;
2148
2149        /*
2150         * console_unblank can no longer be called in interrupt context unless
2151         * oops_in_progress is set to 1..
2152         */
2153        if (oops_in_progress) {
2154                if (down_trylock(&console_sem) != 0)
2155                        return;
2156        } else
2157                console_lock();
2158
2159        console_locked = 1;
2160        console_may_schedule = 0;
2161        for_each_console(c)
2162                if ((c->flags & CON_ENABLED) && c->unblank)
2163                        c->unblank();
2164        console_unlock();
2165}
2166
2167/*
2168 * Return the console tty driver structure and its associated index
2169 */
2170struct tty_driver *console_device(int *index)
2171{
2172        struct console *c;
2173        struct tty_driver *driver = NULL;
2174
2175        console_lock();
2176        for_each_console(c) {
2177                if (!c->device)
2178                        continue;
2179                driver = c->device(c, index);
2180                if (driver)
2181                        break;
2182        }
2183        console_unlock();
2184        return driver;
2185}
2186
2187/*
2188 * Prevent further output on the passed console device so that (for example)
2189 * serial drivers can disable console output before suspending a port, and can
2190 * re-enable output afterwards.
2191 */
2192void console_stop(struct console *console)
2193{
2194        console_lock();
2195        console->flags &= ~CON_ENABLED;
2196        console_unlock();
2197}
2198EXPORT_SYMBOL(console_stop);
2199
2200void console_start(struct console *console)
2201{
2202        console_lock();
2203        console->flags |= CON_ENABLED;
2204        console_unlock();
2205}
2206EXPORT_SYMBOL(console_start);
2207
2208static int __read_mostly keep_bootcon;
2209
2210static int __init keep_bootcon_setup(char *str)
2211{
2212        keep_bootcon = 1;
2213        printk(KERN_INFO "debug: skip boot console de-registration.\n");
2214
2215        return 0;
2216}
2217
2218early_param("keep_bootcon", keep_bootcon_setup);
2219
2220/*
2221 * The console driver calls this routine during kernel initialization
2222 * to register the console printing procedure with printk() and to
2223 * print any messages that were printed by the kernel before the
2224 * console driver was initialized.
2225 *
2226 * This can happen pretty early during the boot process (because of
2227 * early_printk) - sometimes before setup_arch() completes - be careful
2228 * of what kernel features are used - they may not be initialised yet.
2229 *
2230 * There are two types of consoles - bootconsoles (early_printk) and
2231 * "real" consoles (everything which is not a bootconsole) which are
2232 * handled differently.
2233 *  - Any number of bootconsoles can be registered at any time.
2234 *  - As soon as a "real" console is registered, all bootconsoles
2235 *    will be unregistered automatically.
2236 *  - Once a "real" console is registered, any attempt to register a
2237 *    bootconsoles will be rejected
2238 */
2239void register_console(struct console *newcon)
2240{
2241        int i;
2242        unsigned long flags;
2243        struct console *bcon = NULL;
2244
2245        /*
2246         * before we register a new CON_BOOT console, make sure we don't
2247         * already have a valid console
2248         */
2249        if (console_drivers && newcon->flags & CON_BOOT) {
2250                /* find the last or real console */
2251                for_each_console(bcon) {
2252                        if (!(bcon->flags & CON_BOOT)) {
2253                                printk(KERN_INFO "Too late to register bootconsole %s%d\n",
2254                                        newcon->name, newcon->index);
2255                                return;
2256                        }
2257                }
2258        }
2259
2260        if (console_drivers && console_drivers->flags & CON_BOOT)
2261                bcon = console_drivers;
2262
2263        if (preferred_console < 0 || bcon || !console_drivers)
2264                preferred_console = selected_console;
2265
2266        if (newcon->early_setup)
2267                newcon->early_setup();
2268
2269        /*
2270         *      See if we want to use this console driver. If we
2271         *      didn't select a console we take the first one
2272         *      that registers here.
2273         */
2274        if (preferred_console < 0) {
2275                if (newcon->index < 0)
2276                        newcon->index = 0;
2277                if (newcon->setup == NULL ||
2278                    newcon->setup(newcon, NULL) == 0) {
2279                        newcon->flags |= CON_ENABLED;
2280                        if (newcon->device) {
2281                                newcon->flags |= CON_CONSDEV;
2282                                preferred_console = 0;
2283                        }
2284                }
2285        }
2286
2287        /*
2288         *      See if this console matches one we selected on
2289         *      the command line.
2290         */
2291        for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
2292                        i++) {
2293                if (strcmp(console_cmdline[i].name, newcon->name) != 0)
2294                        continue;
2295                if (newcon->index >= 0 &&
2296                    newcon->index != console_cmdline[i].index)
2297                        continue;
2298                if (newcon->index < 0)
2299                        newcon->index = console_cmdline[i].index;
2300#ifdef CONFIG_A11Y_BRAILLE_CONSOLE
2301                if (console_cmdline[i].brl_options) {
2302                        newcon->flags |= CON_BRL;
2303                        braille_register_console(newcon,
2304                                        console_cmdline[i].index,
2305                                        console_cmdline[i].options,
2306                                        console_cmdline[i].brl_options);
2307                        return;
2308                }
2309#endif
2310                if (newcon->setup &&
2311                    newcon->setup(newcon, console_cmdline[i].options) != 0)
2312                        break;
2313                newcon->flags |= CON_ENABLED;
2314                newcon->index = console_cmdline[i].index;
2315                if (i == selected_console) {
2316                        newcon->flags |= CON_CONSDEV;
2317                        preferred_console = selected_console;
2318                }
2319                break;
2320        }
2321
2322        if (!(newcon->flags & CON_ENABLED))
2323                return;
2324
2325        /*
2326         * If we have a bootconsole, and are switching to a real console,
2327         * don't print everything out again, since when the boot console, and
2328         * the real console are the same physical device, it's annoying to
2329         * see the beginning boot messages twice
2330         */
2331        if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
2332                newcon->flags &= ~CON_PRINTBUFFER;
2333
2334        /*
2335         *      Put this console in the list - keep the
2336         *      preferred driver at the head of the list.
2337         */
2338        console_lock();
2339        if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
2340                newcon->next = console_drivers;
2341                console_drivers = newcon;
2342                if (newcon->next)
2343                        newcon->next->flags &= ~CON_CONSDEV;
2344        } else {
2345                newcon->next = console_drivers->next;
2346                console_drivers->next = newcon;
2347        }
2348        if (newcon->flags & CON_PRINTBUFFER) {
2349                /*
2350                 * console_unlock(); will print out the buffered messages
2351                 * for us.
2352                 */
2353                raw_spin_lock_irqsave(&logbuf_lock, flags);
2354                console_seq = syslog_seq;
2355                console_idx = syslog_idx;
2356                console_prev = syslog_prev;
2357                raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2358                /*
2359                 * We're about to replay the log buffer.  Only do this to the
2360                 * just-registered console to avoid excessive message spam to
2361                 * the already-registered consoles.
2362                 */
2363                exclusive_console = newcon;
2364        }
2365        console_unlock();
2366        console_sysfs_notify();
2367
2368        /*
2369         * By unregistering the bootconsoles after we enable the real console
2370         * we get the "console xxx enabled" message on all the consoles -
2371         * boot consoles, real consoles, etc - this is to ensure that end
2372         * users know there might be something in the kernel's log buffer that
2373         * went to the bootconsole (that they do not see on the real console)
2374         */
2375        if (bcon &&
2376            ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
2377            !keep_bootcon) {
2378                /* we need to iterate through twice, to make sure we print
2379                 * everything out, before we unregister the console(s)
2380                 */
2381                printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
2382                        newcon->name, newcon->index);
2383                for_each_console(bcon)
2384                        if (bcon->flags & CON_BOOT)
2385                                unregister_console(bcon);
2386        } else {
2387                printk(KERN_INFO "%sconsole [%s%d] enabled\n",
2388                        (newcon->flags & CON_BOOT) ? "boot" : "" ,
2389                        newcon->name, newcon->index);
2390        }
2391}
2392EXPORT_SYMBOL(register_console);
2393
2394int unregister_console(struct console *console)
2395{
2396        struct console *a, *b;
2397        int res = 1;
2398
2399#ifdef CONFIG_A11Y_BRAILLE_CONSOLE
2400        if (console->flags & CON_BRL)
2401                return braille_unregister_console(console);
2402#endif
2403
2404        console_lock();
2405        if (console_drivers == console) {
2406                console_drivers=console->next;
2407                res = 0;
2408        } else if (console_drivers) {
2409                for (a=console_drivers->next, b=console_drivers ;
2410                     a; b=a, a=b->next) {
2411                        if (a == console) {
2412                                b->next = a->next;
2413                                res = 0;
2414                                break;
2415                        }
2416                }
2417        }
2418
2419        /*
2420         * If this isn't the last console and it has CON_CONSDEV set, we
2421         * need to set it on the next preferred console.
2422         */
2423        if (console_drivers != NULL && console->flags & CON_CONSDEV)
2424                console_drivers->flags |= CON_CONSDEV;
2425
2426        console_unlock();
2427        console_sysfs_notify();
2428        return res;
2429}
2430EXPORT_SYMBOL(unregister_console);
2431
2432static int __init printk_late_init(void)
2433{
2434        struct console *con;
2435
2436        for_each_console(con) {
2437                if (!keep_bootcon && con->flags & CON_BOOT) {
2438                        printk(KERN_INFO "turn off boot console %s%d\n",
2439                                con->name, con->index);
2440                        unregister_console(con);
2441                }
2442        }
2443        hotcpu_notifier(console_cpu_notify, 0);
2444        return 0;
2445}
2446late_initcall(printk_late_init);
2447
2448#if defined CONFIG_PRINTK
2449/*
2450 * Delayed printk version, for scheduler-internal messages:
2451 */
2452#define PRINTK_BUF_SIZE         512
2453
2454#define PRINTK_PENDING_WAKEUP   0x01
2455#define PRINTK_PENDING_SCHED    0x02
2456
2457static DEFINE_PER_CPU(int, printk_pending);
2458static DEFINE_PER_CPU(char [PRINTK_BUF_SIZE], printk_sched_buf);
2459
2460static void wake_up_klogd_work_func(struct irq_work *irq_work)
2461{
2462        int pending = __this_cpu_xchg(printk_pending, 0);
2463
2464        if (pending & PRINTK_PENDING_SCHED) {
2465                char *buf = __get_cpu_var(printk_sched_buf);
2466                printk(KERN_WARNING "[sched_delayed] %s", buf);
2467        }
2468
2469        if (pending & PRINTK_PENDING_WAKEUP)
2470                wake_up_interruptible(&log_wait);
2471}
2472
2473static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
2474        .func = wake_up_klogd_work_func,
2475        .flags = IRQ_WORK_LAZY,
2476};
2477
2478void wake_up_klogd(void)
2479{
2480        preempt_disable();
2481        if (waitqueue_active(&log_wait)) {
2482                this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
2483                irq_work_queue(&__get_cpu_var(wake_up_klogd_work));
2484        }
2485        preempt_enable();
2486}
2487
2488int printk_sched(const char *fmt, ...)
2489{
2490        unsigned long flags;
2491        va_list args;
2492        char *buf;
2493        int r;
2494
2495        local_irq_save(flags);
2496        buf = __get_cpu_var(printk_sched_buf);
2497
2498        va_start(args, fmt);
2499        r = vsnprintf(buf, PRINTK_BUF_SIZE, fmt, args);
2500        va_end(args);
2501
2502        __this_cpu_or(printk_pending, PRINTK_PENDING_SCHED);
2503        irq_work_queue(&__get_cpu_var(wake_up_klogd_work));
2504        local_irq_restore(flags);
2505
2506        return r;
2507}
2508
2509/*
2510 * printk rate limiting, lifted from the networking subsystem.
2511 *
2512 * This enforces a rate limit: not more than 10 kernel messages
2513 * every 5s to make a denial-of-service attack impossible.
2514 */
2515DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
2516
2517int __printk_ratelimit(const char *func)
2518{
2519        return ___ratelimit(&printk_ratelimit_state, func);
2520}
2521EXPORT_SYMBOL(__printk_ratelimit);
2522
2523/**
2524 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2525 * @caller_jiffies: pointer to caller's state
2526 * @interval_msecs: minimum interval between prints
2527 *
2528 * printk_timed_ratelimit() returns true if more than @interval_msecs
2529 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2530 * returned true.
2531 */
2532bool printk_timed_ratelimit(unsigned long *caller_jiffies,
2533                        unsigned int interval_msecs)
2534{
2535        if (*caller_jiffies == 0
2536                        || !time_in_range(jiffies, *caller_jiffies,
2537                                        *caller_jiffies
2538                                        + msecs_to_jiffies(interval_msecs))) {
2539                *caller_jiffies = jiffies;
2540                return true;
2541        }
2542        return false;
2543}
2544EXPORT_SYMBOL(printk_timed_ratelimit);
2545
2546static DEFINE_SPINLOCK(dump_list_lock);
2547static LIST_HEAD(dump_list);
2548
2549/**
2550 * kmsg_dump_register - register a kernel log dumper.
2551 * @dumper: pointer to the kmsg_dumper structure
2552 *
2553 * Adds a kernel log dumper to the system. The dump callback in the
2554 * structure will be called when the kernel oopses or panics and must be
2555 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2556 */
2557int kmsg_dump_register(struct kmsg_dumper *dumper)
2558{
2559        unsigned long flags;
2560        int err = -EBUSY;
2561
2562        /* The dump callback needs to be set */
2563        if (!dumper->dump)
2564                return -EINVAL;
2565
2566        spin_lock_irqsave(&dump_list_lock, flags);
2567        /* Don't allow registering multiple times */
2568        if (!dumper->registered) {
2569                dumper->registered = 1;
2570                list_add_tail_rcu(&dumper->list, &dump_list);
2571                err = 0;
2572        }
2573        spin_unlock_irqrestore(&dump_list_lock, flags);
2574
2575        return err;
2576}
2577EXPORT_SYMBOL_GPL(kmsg_dump_register);
2578
2579/**
2580 * kmsg_dump_unregister - unregister a kmsg dumper.
2581 * @dumper: pointer to the kmsg_dumper structure
2582 *
2583 * Removes a dump device from the system. Returns zero on success and
2584 * %-EINVAL otherwise.
2585 */
2586int kmsg_dump_unregister(struct kmsg_dumper *dumper)
2587{
2588        unsigned long flags;
2589        int err = -EINVAL;
2590
2591        spin_lock_irqsave(&dump_list_lock, flags);
2592        if (dumper->registered) {
2593                dumper->registered = 0;
2594                list_del_rcu(&dumper->list);
2595                err = 0;
2596        }
2597        spin_unlock_irqrestore(&dump_list_lock, flags);
2598        synchronize_rcu();
2599
2600        return err;
2601}
2602EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
2603
2604static bool always_kmsg_dump;
2605module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
2606
2607/**
2608 * kmsg_dump - dump kernel log to kernel message dumpers.
2609 * @reason: the reason (oops, panic etc) for dumping
2610 *
2611 * Call each of the registered dumper's dump() callback, which can
2612 * retrieve the kmsg records with kmsg_dump_get_line() or
2613 * kmsg_dump_get_buffer().
2614 */
2615void kmsg_dump(enum kmsg_dump_reason reason)
2616{
2617        struct kmsg_dumper *dumper;
2618        unsigned long flags;
2619
2620        if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
2621                return;
2622
2623        rcu_read_lock();
2624        list_for_each_entry_rcu(dumper, &dump_list, list) {
2625                if (dumper->max_reason && reason > dumper->max_reason)
2626                        continue;
2627
2628                /* initialize iterator with data about the stored records */
2629                dumper->active = true;
2630
2631                raw_spin_lock_irqsave(&logbuf_lock, flags);
2632                dumper->cur_seq = clear_seq;
2633                dumper->cur_idx = clear_idx;
2634                dumper->next_seq = log_next_seq;
2635                dumper->next_idx = log_next_idx;
2636                raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2637
2638                /* invoke dumper which will iterate over records */
2639                dumper->dump(dumper, reason);
2640
2641                /* reset iterator */
2642                dumper->active = false;
2643        }
2644        rcu_read_unlock();
2645}
2646
2647/**
2648 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
2649 * @dumper: registered kmsg dumper
2650 * @syslog: include the "<4>" prefixes
2651 * @line: buffer to copy the line to
2652 * @size: maximum size of the buffer
2653 * @len: length of line placed into buffer
2654 *
2655 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2656 * record, and copy one record into the provided buffer.
2657 *
2658 * Consecutive calls will return the next available record moving
2659 * towards the end of the buffer with the youngest messages.
2660 *
2661 * A return value of FALSE indicates that there are no more records to
2662 * read.
2663 *
2664 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
2665 */
2666bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
2667                               char *line, size_t size, size_t *len)
2668{
2669        struct log *msg;
2670        size_t l = 0;
2671        bool ret = false;
2672
2673        if (!dumper->active)
2674                goto out;
2675
2676        if (dumper->cur_seq < log_first_seq) {
2677                /* messages are gone, move to first available one */
2678                dumper->cur_seq = log_first_seq;
2679                dumper->cur_idx = log_first_idx;
2680        }
2681
2682        /* last entry */
2683        if (dumper->cur_seq >= log_next_seq)
2684                goto out;
2685
2686        msg = log_from_idx(dumper->cur_idx);
2687        l = msg_print_text(msg, 0, syslog, line, size);
2688
2689        dumper->cur_idx = log_next(dumper->cur_idx);
2690        dumper->cur_seq++;
2691        ret = true;
2692out:
2693        if (len)
2694                *len = l;
2695        return ret;
2696}
2697
2698/**
2699 * kmsg_dump_get_line - retrieve one kmsg log line
2700 * @dumper: registered kmsg dumper
2701 * @syslog: include the "<4>" prefixes
2702 * @line: buffer to copy the line to
2703 * @size: maximum size of the buffer
2704 * @len: length of line placed into buffer
2705 *
2706 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2707 * record, and copy one record into the provided buffer.
2708 *
2709 * Consecutive calls will return the next available record moving
2710 * towards the end of the buffer with the youngest messages.
2711 *
2712 * A return value of FALSE indicates that there are no more records to
2713 * read.
2714 */
2715bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
2716                        char *line, size_t size, size_t *len)
2717{
2718        unsigned long flags;
2719        bool ret;
2720
2721        raw_spin_lock_irqsave(&logbuf_lock, flags);
2722        ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
2723        raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2724
2725        return ret;
2726}
2727EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
2728
2729/**
2730 * kmsg_dump_get_buffer - copy kmsg log lines
2731 * @dumper: registered kmsg dumper
2732 * @syslog: include the "<4>" prefixes
2733 * @buf: buffer to copy the line to
2734 * @size: maximum size of the buffer
2735 * @len: length of line placed into buffer
2736 *
2737 * Start at the end of the kmsg buffer and fill the provided buffer
2738 * with as many of the the *youngest* kmsg records that fit into it.
2739 * If the buffer is large enough, all available kmsg records will be
2740 * copied with a single call.
2741 *
2742 * Consecutive calls will fill the buffer with the next block of
2743 * available older records, not including the earlier retrieved ones.
2744 *
2745 * A return value of FALSE indicates that there are no more records to
2746 * read.
2747 */
2748bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
2749                          char *buf, size_t size, size_t *len)
2750{
2751        unsigned long flags;
2752        u64 seq;
2753        u32 idx;
2754        u64 next_seq;
2755        u32 next_idx;
2756        enum log_flags prev;
2757        size_t l = 0;
2758        bool ret = false;
2759
2760        if (!dumper->active)
2761                goto out;
2762
2763        raw_spin_lock_irqsave(&logbuf_lock, flags);
2764        if (dumper->cur_seq < log_first_seq) {
2765                /* messages are gone, move to first available one */
2766                dumper->cur_seq = log_first_seq;
2767                dumper->cur_idx = log_first_idx;
2768        }
2769
2770        /* last entry */
2771        if (dumper->cur_seq >= dumper->next_seq) {
2772                raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2773                goto out;
2774        }
2775
2776        /* calculate length of entire buffer */
2777        seq = dumper->cur_seq;
2778        idx = dumper->cur_idx;
2779        prev = 0;
2780        while (seq < dumper->next_seq) {
2781                struct log *msg = log_from_idx(idx);
2782
2783                l += msg_print_text(msg, prev, true, NULL, 0);
2784                idx = log_next(idx);
2785                seq++;
2786                prev = msg->flags;
2787        }
2788
2789        /* move first record forward until length fits into the buffer */
2790        seq = dumper->cur_seq;
2791        idx = dumper->cur_idx;
2792        prev = 0;
2793        while (l > size && seq < dumper->next_seq) {
2794                struct log *msg = log_from_idx(idx);
2795
2796                l -= msg_print_text(msg, prev, true, NULL, 0);
2797                idx = log_next(idx);
2798                seq++;
2799                prev = msg->flags;
2800        }
2801
2802        /* last message in next interation */
2803        next_seq = seq;
2804        next_idx = idx;
2805
2806        l = 0;
2807        prev = 0;
2808        while (seq < dumper->next_seq) {
2809                struct log *msg = log_from_idx(idx);
2810
2811                l += msg_print_text(msg, prev, syslog, buf + l, size - l);
2812                idx = log_next(idx);
2813                seq++;
2814                prev = msg->flags;
2815        }
2816
2817        dumper->next_seq = next_seq;
2818        dumper->next_idx = next_idx;
2819        ret = true;
2820        raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2821out:
2822        if (len)
2823                *len = l;
2824        return ret;
2825}
2826EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
2827
2828/**
2829 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
2830 * @dumper: registered kmsg dumper
2831 *
2832 * Reset the dumper's iterator so that kmsg_dump_get_line() and
2833 * kmsg_dump_get_buffer() can be called again and used multiple
2834 * times within the same dumper.dump() callback.
2835 *
2836 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
2837 */
2838void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
2839{
2840        dumper->cur_seq = clear_seq;
2841        dumper->cur_idx = clear_idx;
2842        dumper->next_seq = log_next_seq;
2843        dumper->next_idx = log_next_idx;
2844}
2845
2846/**
2847 * kmsg_dump_rewind - reset the interator
2848 * @dumper: registered kmsg dumper
2849 *
2850 * Reset the dumper's iterator so that kmsg_dump_get_line() and
2851 * kmsg_dump_get_buffer() can be called again and used multiple
2852 * times within the same dumper.dump() callback.
2853 */
2854void kmsg_dump_rewind(struct kmsg_dumper *dumper)
2855{
2856        unsigned long flags;
2857
2858        raw_spin_lock_irqsave(&logbuf_lock, flags);
2859        kmsg_dump_rewind_nolock(dumper);
2860        raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2861}
2862EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
2863
2864static char dump_stack_arch_desc_str[128];
2865
2866/**
2867 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
2868 * @fmt: printf-style format string
2869 * @...: arguments for the format string
2870 *
2871 * The configured string will be printed right after utsname during task
2872 * dumps.  Usually used to add arch-specific system identifiers.  If an
2873 * arch wants to make use of such an ID string, it should initialize this
2874 * as soon as possible during boot.
2875 */
2876void __init dump_stack_set_arch_desc(const char *fmt, ...)
2877{
2878        va_list args;
2879
2880        va_start(args, fmt);
2881        vsnprintf(dump_stack_arch_desc_str, sizeof(dump_stack_arch_desc_str),
2882                  fmt, args);
2883        va_end(args);
2884}
2885
2886/**
2887 * dump_stack_print_info - print generic debug info for dump_stack()
2888 * @log_lvl: log level
2889 *
2890 * Arch-specific dump_stack() implementations can use this function to
2891 * print out the same debug information as the generic dump_stack().
2892 */
2893void dump_stack_print_info(const char *log_lvl)
2894{
2895        printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
2896               log_lvl, raw_smp_processor_id(), current->pid, current->comm,
2897               print_tainted(), init_utsname()->release,
2898               (int)strcspn(init_utsname()->version, " "),
2899               init_utsname()->version);
2900
2901        if (dump_stack_arch_desc_str[0] != '\0')
2902                printk("%sHardware name: %s\n",
2903                       log_lvl, dump_stack_arch_desc_str);
2904
2905        print_worker_info(log_lvl, current);
2906}
2907
2908/**
2909 * show_regs_print_info - print generic debug info for show_regs()
2910 * @log_lvl: log level
2911 *
2912 * show_regs() implementations can use this function to print out generic
2913 * debug information.
2914 */
2915void show_regs_print_info(const char *log_lvl)
2916{
2917        dump_stack_print_info(log_lvl);
2918
2919        printk("%stask: %p ti: %p task.ti: %p\n",
2920               log_lvl, current, current_thread_info(),
2921               task_thread_info(current));
2922}
2923
2924#endif
2925
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