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/delay.h> 30 #include <linux/smp.h> 31 #include <linux/security.h> 32 #include <linux/bootmem.h> 33 #include <linux/memblock.h> 34 #include <linux/syscalls.h> 35 #include <linux/crash_core.h> 36 #include <linux/kdb.h> 37 #include <linux/ratelimit.h> 38 #include <linux/kmsg_dump.h> 39 #include <linux/syslog.h> 40 #include <linux/cpu.h> 41 #include <linux/rculist.h> 42 #include <linux/poll.h> 43 #include <linux/irq_work.h> 44 #include <linux/ctype.h> 45 #include <linux/uio.h> 46 #include <linux/sched/clock.h> 47 #include <linux/sched/debug.h> 48 #include <linux/sched/task_stack.h> 49 50 #include <linux/uaccess.h> 51 #include <asm/sections.h> 52 53 #include <trace/events/initcall.h> 54 #define CREATE_TRACE_POINTS 55 #include <trace/events/printk.h> 56 57 #include "console_cmdline.h" 58 #include "braille.h" 59 #include "internal.h" 60 61 int console_printk[4] = { 62 CONSOLE_LOGLEVEL_DEFAULT, /* console_loglevel */ 63 MESSAGE_LOGLEVEL_DEFAULT, /* default_message_loglevel */ 64 CONSOLE_LOGLEVEL_MIN, /* minimum_console_loglevel */ 65 CONSOLE_LOGLEVEL_DEFAULT, /* default_console_loglevel */ 66 }; 67 68 atomic_t ignore_console_lock_warning __read_mostly = ATOMIC_INIT(0); 69 EXPORT_SYMBOL(ignore_console_lock_warning); 70 71 /* 72 * Low level drivers may need that to know if they can schedule in 73 * their unblank() callback or not. So let's export it. 74 */ 75 int oops_in_progress; 76 EXPORT_SYMBOL(oops_in_progress); 77 78 /* 79 * console_sem protects the console_drivers list, and also 80 * provides serialisation for access to the entire console 81 * driver system. 82 */ 83 static DEFINE_SEMAPHORE(console_sem); 84 struct console *console_drivers; 85 EXPORT_SYMBOL_GPL(console_drivers); 86 87 #ifdef CONFIG_LOCKDEP 88 static struct lockdep_map console_lock_dep_map = { 89 .name = "console_lock" 90 }; 91 #endif 92 93 enum devkmsg_log_bits { 94 __DEVKMSG_LOG_BIT_ON = 0, 95 __DEVKMSG_LOG_BIT_OFF, 96 __DEVKMSG_LOG_BIT_LOCK, 97 }; 98 99 enum devkmsg_log_masks { 100 DEVKMSG_LOG_MASK_ON = BIT(__DEVKMSG_LOG_BIT_ON), 101 DEVKMSG_LOG_MASK_OFF = BIT(__DEVKMSG_LOG_BIT_OFF), 102 DEVKMSG_LOG_MASK_LOCK = BIT(__DEVKMSG_LOG_BIT_LOCK), 103 }; 104 105 /* Keep both the 'on' and 'off' bits clear, i.e. ratelimit by default: */ 106 #define DEVKMSG_LOG_MASK_DEFAULT 0 107 108 static unsigned int __read_mostly devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT; 109 110 static int __control_devkmsg(char *str) 111 { 112 if (!str) 113 return -EINVAL; 114 115 if (!strncmp(str, "on", 2)) { 116 devkmsg_log = DEVKMSG_LOG_MASK_ON; 117 return 2; 118 } else if (!strncmp(str, "off", 3)) { 119 devkmsg_log = DEVKMSG_LOG_MASK_OFF; 120 return 3; 121 } else if (!strncmp(str, "ratelimit", 9)) { 122 devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT; 123 return 9; 124 } 125 return -EINVAL; 126 } 127 128 static int __init control_devkmsg(char *str) 129 { 130 if (__control_devkmsg(str) < 0) 131 return 1; 132 133 /* 134 * Set sysctl string accordingly: 135 */ 136 if (devkmsg_log == DEVKMSG_LOG_MASK_ON) 137 strcpy(devkmsg_log_str, "on"); 138 else if (devkmsg_log == DEVKMSG_LOG_MASK_OFF) 139 strcpy(devkmsg_log_str, "off"); 140 /* else "ratelimit" which is set by default. */ 141 142 /* 143 * Sysctl cannot change it anymore. The kernel command line setting of 144 * this parameter is to force the setting to be permanent throughout the 145 * runtime of the system. This is a precation measure against userspace 146 * trying to be a smarta** and attempting to change it up on us. 147 */ 148 devkmsg_log |= DEVKMSG_LOG_MASK_LOCK; 149 150 return 0; 151 } 152 __setup("printk.devkmsg=", control_devkmsg); 153 154 char devkmsg_log_str[DEVKMSG_STR_MAX_SIZE] = "ratelimit"; 155 156 int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write, 157 void __user *buffer, size_t *lenp, loff_t *ppos) 158 { 159 char old_str[DEVKMSG_STR_MAX_SIZE]; 160 unsigned int old; 161 int err; 162 163 if (write) { 164 if (devkmsg_log & DEVKMSG_LOG_MASK_LOCK) 165 return -EINVAL; 166 167 old = devkmsg_log; 168 strncpy(old_str, devkmsg_log_str, DEVKMSG_STR_MAX_SIZE); 169 } 170 171 err = proc_dostring(table, write, buffer, lenp, ppos); 172 if (err) 173 return err; 174 175 if (write) { 176 err = __control_devkmsg(devkmsg_log_str); 177 178 /* 179 * Do not accept an unknown string OR a known string with 180 * trailing crap... 181 */ 182 if (err < 0 || (err + 1 != *lenp)) { 183 184 /* ... and restore old setting. */ 185 devkmsg_log = old; 186 strncpy(devkmsg_log_str, old_str, DEVKMSG_STR_MAX_SIZE); 187 188 return -EINVAL; 189 } 190 } 191 192 return 0; 193 } 194 195 /* 196 * Number of registered extended console drivers. 197 * 198 * If extended consoles are present, in-kernel cont reassembly is disabled 199 * and each fragment is stored as a separate log entry with proper 200 * continuation flag so that every emitted message has full metadata. This 201 * doesn't change the result for regular consoles or /proc/kmsg. For 202 * /dev/kmsg, as long as the reader concatenates messages according to 203 * consecutive continuation flags, the end result should be the same too. 204 */ 205 static int nr_ext_console_drivers; 206 207 /* 208 * Helper macros to handle lockdep when locking/unlocking console_sem. We use 209 * macros instead of functions so that _RET_IP_ contains useful information. 210 */ 211 #define down_console_sem() do { \ 212 down(&console_sem);\ 213 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\ 214 } while (0) 215 216 static int __down_trylock_console_sem(unsigned long ip) 217 { 218 int lock_failed; 219 unsigned long flags; 220 221 /* 222 * Here and in __up_console_sem() we need to be in safe mode, 223 * because spindump/WARN/etc from under console ->lock will 224 * deadlock in printk()->down_trylock_console_sem() otherwise. 225 */ 226 printk_safe_enter_irqsave(flags); 227 lock_failed = down_trylock(&console_sem); 228 printk_safe_exit_irqrestore(flags); 229 230 if (lock_failed) 231 return 1; 232 mutex_acquire(&console_lock_dep_map, 0, 1, ip); 233 return 0; 234 } 235 #define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_) 236 237 static void __up_console_sem(unsigned long ip) 238 { 239 unsigned long flags; 240 241 mutex_release(&console_lock_dep_map, 1, ip); 242 243 printk_safe_enter_irqsave(flags); 244 up(&console_sem); 245 printk_safe_exit_irqrestore(flags); 246 } 247 #define up_console_sem() __up_console_sem(_RET_IP_) 248 249 /* 250 * This is used for debugging the mess that is the VT code by 251 * keeping track if we have the console semaphore held. It's 252 * definitely not the perfect debug tool (we don't know if _WE_ 253 * hold it and are racing, but it helps tracking those weird code 254 * paths in the console code where we end up in places I want 255 * locked without the console sempahore held). 256 */ 257 static int console_locked, console_suspended; 258 259 /* 260 * If exclusive_console is non-NULL then only this console is to be printed to. 261 */ 262 static struct console *exclusive_console; 263 264 /* 265 * Array of consoles built from command line options (console=) 266 */ 267 268 #define MAX_CMDLINECONSOLES 8 269 270 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES]; 271 272 static int preferred_console = -1; 273 int console_set_on_cmdline; 274 EXPORT_SYMBOL(console_set_on_cmdline); 275 276 /* Flag: console code may call schedule() */ 277 static int console_may_schedule; 278 279 enum con_msg_format_flags { 280 MSG_FORMAT_DEFAULT = 0, 281 MSG_FORMAT_SYSLOG = (1 << 0), 282 }; 283 284 static int console_msg_format = MSG_FORMAT_DEFAULT; 285 286 /* 287 * The printk log buffer consists of a chain of concatenated variable 288 * length records. Every record starts with a record header, containing 289 * the overall length of the record. 290 * 291 * The heads to the first and last entry in the buffer, as well as the 292 * sequence numbers of these entries are maintained when messages are 293 * stored. 294 * 295 * If the heads indicate available messages, the length in the header 296 * tells the start next message. A length == 0 for the next message 297 * indicates a wrap-around to the beginning of the buffer. 298 * 299 * Every record carries the monotonic timestamp in microseconds, as well as 300 * the standard userspace syslog level and syslog facility. The usual 301 * kernel messages use LOG_KERN; userspace-injected messages always carry 302 * a matching syslog facility, by default LOG_USER. The origin of every 303 * message can be reliably determined that way. 304 * 305 * The human readable log message directly follows the message header. The 306 * length of the message text is stored in the header, the stored message 307 * is not terminated. 308 * 309 * Optionally, a message can carry a dictionary of properties (key/value pairs), 310 * to provide userspace with a machine-readable message context. 311 * 312 * Examples for well-defined, commonly used property names are: 313 * DEVICE=b12:8 device identifier 314 * b12:8 block dev_t 315 * c127:3 char dev_t 316 * n8 netdev ifindex 317 * +sound:card0 subsystem:devname 318 * SUBSYSTEM=pci driver-core subsystem name 319 * 320 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value 321 * follows directly after a '=' character. Every property is terminated by 322 * a '\0' character. The last property is not terminated. 323 * 324 * Example of a message structure: 325 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec 326 * 0008 34 00 record is 52 bytes long 327 * 000a 0b 00 text is 11 bytes long 328 * 000c 1f 00 dictionary is 23 bytes long 329 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level) 330 * 0010 69 74 27 73 20 61 20 6c "it's a l" 331 * 69 6e 65 "ine" 332 * 001b 44 45 56 49 43 "DEVIC" 333 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D" 334 * 52 49 56 45 52 3d 62 75 "RIVER=bu" 335 * 67 "g" 336 * 0032 00 00 00 padding to next message header 337 * 338 * The 'struct printk_log' buffer header must never be directly exported to 339 * userspace, it is a kernel-private implementation detail that might 340 * need to be changed in the future, when the requirements change. 341 * 342 * /dev/kmsg exports the structured data in the following line format: 343 * "<level>,<sequnum>,<timestamp>,<contflag>[,additional_values, ... ];<message text>\n" 344 * 345 * Users of the export format should ignore possible additional values 346 * separated by ',', and find the message after the ';' character. 347 * 348 * The optional key/value pairs are attached as continuation lines starting 349 * with a space character and terminated by a newline. All possible 350 * non-prinatable characters are escaped in the "\xff" notation. 351 */ 352 353 enum log_flags { 354 LOG_NEWLINE = 2, /* text ended with a newline */ 355 LOG_PREFIX = 4, /* text started with a prefix */ 356 LOG_CONT = 8, /* text is a fragment of a continuation line */ 357 }; 358 359 struct printk_log { 360 u64 ts_nsec; /* timestamp in nanoseconds */ 361 u16 len; /* length of entire record */ 362 u16 text_len; /* length of text buffer */ 363 u16 dict_len; /* length of dictionary buffer */ 364 u8 facility; /* syslog facility */ 365 u8 flags:5; /* internal record flags */ 366 u8 level:3; /* syslog level */ 367 } 368 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS 369 __packed __aligned(4) 370 #endif 371 ; 372 373 /* 374 * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken 375 * within the scheduler's rq lock. It must be released before calling 376 * console_unlock() or anything else that might wake up a process. 377 */ 378 DEFINE_RAW_SPINLOCK(logbuf_lock); 379 380 /* 381 * Helper macros to lock/unlock logbuf_lock and switch between 382 * printk-safe/unsafe modes. 383 */ 384 #define logbuf_lock_irq() \ 385 do { \ 386 printk_safe_enter_irq(); \ 387 raw_spin_lock(&logbuf_lock); \ 388 } while (0) 389 390 #define logbuf_unlock_irq() \ 391 do { \ 392 raw_spin_unlock(&logbuf_lock); \ 393 printk_safe_exit_irq(); \ 394 } while (0) 395 396 #define logbuf_lock_irqsave(flags) \ 397 do { \ 398 printk_safe_enter_irqsave(flags); \ 399 raw_spin_lock(&logbuf_lock); \ 400 } while (0) 401 402 #define logbuf_unlock_irqrestore(flags) \ 403 do { \ 404 raw_spin_unlock(&logbuf_lock); \ 405 printk_safe_exit_irqrestore(flags); \ 406 } while (0) 407 408 #ifdef CONFIG_PRINTK 409 DECLARE_WAIT_QUEUE_HEAD(log_wait); 410 /* the next printk record to read by syslog(READ) or /proc/kmsg */ 411 static u64 syslog_seq; 412 static u32 syslog_idx; 413 static size_t syslog_partial; 414 415 /* index and sequence number of the first record stored in the buffer */ 416 static u64 log_first_seq; 417 static u32 log_first_idx; 418 419 /* index and sequence number of the next record to store in the buffer */ 420 static u64 log_next_seq; 421 static u32 log_next_idx; 422 423 /* the next printk record to write to the console */ 424 static u64 console_seq; 425 static u32 console_idx; 426 427 /* the next printk record to read after the last 'clear' command */ 428 static u64 clear_seq; 429 static u32 clear_idx; 430 431 #define PREFIX_MAX 32 432 #define LOG_LINE_MAX (1024 - PREFIX_MAX) 433 434 #define LOG_LEVEL(v) ((v) & 0x07) 435 #define LOG_FACILITY(v) ((v) >> 3 & 0xff) 436 437 /* record buffer */ 438 #define LOG_ALIGN __alignof__(struct printk_log) 439 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT) 440 static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN); 441 static char *log_buf = __log_buf; 442 static u32 log_buf_len = __LOG_BUF_LEN; 443 444 /* Return log buffer address */ 445 char *log_buf_addr_get(void) 446 { 447 return log_buf; 448 } 449 450 /* Return log buffer size */ 451 u32 log_buf_len_get(void) 452 { 453 return log_buf_len; 454 } 455 456 /* human readable text of the record */ 457 static char *log_text(const struct printk_log *msg) 458 { 459 return (char *)msg + sizeof(struct printk_log); 460 } 461 462 /* optional key/value pair dictionary attached to the record */ 463 static char *log_dict(const struct printk_log *msg) 464 { 465 return (char *)msg + sizeof(struct printk_log) + msg->text_len; 466 } 467 468 /* get record by index; idx must point to valid msg */ 469 static struct printk_log *log_from_idx(u32 idx) 470 { 471 struct printk_log *msg = (struct printk_log *)(log_buf + idx); 472 473 /* 474 * A length == 0 record is the end of buffer marker. Wrap around and 475 * read the message at the start of the buffer. 476 */ 477 if (!msg->len) 478 return (struct printk_log *)log_buf; 479 return msg; 480 } 481 482 /* get next record; idx must point to valid msg */ 483 static u32 log_next(u32 idx) 484 { 485 struct printk_log *msg = (struct printk_log *)(log_buf + idx); 486 487 /* length == 0 indicates the end of the buffer; wrap */ 488 /* 489 * A length == 0 record is the end of buffer marker. Wrap around and 490 * read the message at the start of the buffer as *this* one, and 491 * return the one after that. 492 */ 493 if (!msg->len) { 494 msg = (struct printk_log *)log_buf; 495 return msg->len; 496 } 497 return idx + msg->len; 498 } 499 500 /* 501 * Check whether there is enough free space for the given message. 502 * 503 * The same values of first_idx and next_idx mean that the buffer 504 * is either empty or full. 505 * 506 * If the buffer is empty, we must respect the position of the indexes. 507 * They cannot be reset to the beginning of the buffer. 508 */ 509 static int logbuf_has_space(u32 msg_size, bool empty) 510 { 511 u32 free; 512 513 if (log_next_idx > log_first_idx || empty) 514 free = max(log_buf_len - log_next_idx, log_first_idx); 515 else 516 free = log_first_idx - log_next_idx; 517 518 /* 519 * We need space also for an empty header that signalizes wrapping 520 * of the buffer. 521 */ 522 return free >= msg_size + sizeof(struct printk_log); 523 } 524 525 static int log_make_free_space(u32 msg_size) 526 { 527 while (log_first_seq < log_next_seq && 528 !logbuf_has_space(msg_size, false)) { 529 /* drop old messages until we have enough contiguous space */ 530 log_first_idx = log_next(log_first_idx); 531 log_first_seq++; 532 } 533 534 if (clear_seq < log_first_seq) { 535 clear_seq = log_first_seq; 536 clear_idx = log_first_idx; 537 } 538 539 /* sequence numbers are equal, so the log buffer is empty */ 540 if (logbuf_has_space(msg_size, log_first_seq == log_next_seq)) 541 return 0; 542 543 return -ENOMEM; 544 } 545 546 /* compute the message size including the padding bytes */ 547 static u32 msg_used_size(u16 text_len, u16 dict_len, u32 *pad_len) 548 { 549 u32 size; 550 551 size = sizeof(struct printk_log) + text_len + dict_len; 552 *pad_len = (-size) & (LOG_ALIGN - 1); 553 size += *pad_len; 554 555 return size; 556 } 557 558 /* 559 * Define how much of the log buffer we could take at maximum. The value 560 * must be greater than two. Note that only half of the buffer is available 561 * when the index points to the middle. 562 */ 563 #define MAX_LOG_TAKE_PART 4 564 static const char trunc_msg[] = "<truncated>"; 565 566 static u32 truncate_msg(u16 *text_len, u16 *trunc_msg_len, 567 u16 *dict_len, u32 *pad_len) 568 { 569 /* 570 * The message should not take the whole buffer. Otherwise, it might 571 * get removed too soon. 572 */ 573 u32 max_text_len = log_buf_len / MAX_LOG_TAKE_PART; 574 if (*text_len > max_text_len) 575 *text_len = max_text_len; 576 /* enable the warning message */ 577 *trunc_msg_len = strlen(trunc_msg); 578 /* disable the "dict" completely */ 579 *dict_len = 0; 580 /* compute the size again, count also the warning message */ 581 return msg_used_size(*text_len + *trunc_msg_len, 0, pad_len); 582 } 583 584 /* insert record into the buffer, discard old ones, update heads */ 585 static int log_store(int facility, int level, 586 enum log_flags flags, u64 ts_nsec, 587 const char *dict, u16 dict_len, 588 const char *text, u16 text_len) 589 { 590 struct printk_log *msg; 591 u32 size, pad_len; 592 u16 trunc_msg_len = 0; 593 594 /* number of '\0' padding bytes to next message */ 595 size = msg_used_size(text_len, dict_len, &pad_len); 596 597 if (log_make_free_space(size)) { 598 /* truncate the message if it is too long for empty buffer */ 599 size = truncate_msg(&text_len, &trunc_msg_len, 600 &dict_len, &pad_len); 601 /* survive when the log buffer is too small for trunc_msg */ 602 if (log_make_free_space(size)) 603 return 0; 604 } 605 606 if (log_next_idx + size + sizeof(struct printk_log) > log_buf_len) { 607 /* 608 * This message + an additional empty header does not fit 609 * at the end of the buffer. Add an empty header with len == 0 610 * to signify a wrap around. 611 */ 612 memset(log_buf + log_next_idx, 0, sizeof(struct printk_log)); 613 log_next_idx = 0; 614 } 615 616 /* fill message */ 617 msg = (struct printk_log *)(log_buf + log_next_idx); 618 memcpy(log_text(msg), text, text_len); 619 msg->text_len = text_len; 620 if (trunc_msg_len) { 621 memcpy(log_text(msg) + text_len, trunc_msg, trunc_msg_len); 622 msg->text_len += trunc_msg_len; 623 } 624 memcpy(log_dict(msg), dict, dict_len); 625 msg->dict_len = dict_len; 626 msg->facility = facility; 627 msg->level = level & 7; 628 msg->flags = flags & 0x1f; 629 if (ts_nsec > 0) 630 msg->ts_nsec = ts_nsec; 631 else 632 msg->ts_nsec = local_clock(); 633 memset(log_dict(msg) + dict_len, 0, pad_len); 634 msg->len = size; 635 636 /* insert message */ 637 log_next_idx += msg->len; 638 log_next_seq++; 639 640 return msg->text_len; 641 } 642 643 int dmesg_restrict = IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT); 644 645 static int syslog_action_restricted(int type) 646 { 647 if (dmesg_restrict) 648 return 1; 649 /* 650 * Unless restricted, we allow "read all" and "get buffer size" 651 * for everybody. 652 */ 653 return type != SYSLOG_ACTION_READ_ALL && 654 type != SYSLOG_ACTION_SIZE_BUFFER; 655 } 656 657 static int check_syslog_permissions(int type, int source) 658 { 659 /* 660 * If this is from /proc/kmsg and we've already opened it, then we've 661 * already done the capabilities checks at open time. 662 */ 663 if (source == SYSLOG_FROM_PROC && type != SYSLOG_ACTION_OPEN) 664 goto ok; 665 666 if (syslog_action_restricted(type)) { 667 if (capable(CAP_SYSLOG)) 668 goto ok; 669 /* 670 * For historical reasons, accept CAP_SYS_ADMIN too, with 671 * a warning. 672 */ 673 if (capable(CAP_SYS_ADMIN)) { 674 pr_warn_once("%s (%d): Attempt to access syslog with " 675 "CAP_SYS_ADMIN but no CAP_SYSLOG " 676 "(deprecated).\n", 677 current->comm, task_pid_nr(current)); 678 goto ok; 679 } 680 return -EPERM; 681 } 682 ok: 683 return security_syslog(type); 684 } 685 686 static void append_char(char **pp, char *e, char c) 687 { 688 if (*pp < e) 689 *(*pp)++ = c; 690 } 691 692 static ssize_t msg_print_ext_header(char *buf, size_t size, 693 struct printk_log *msg, u64 seq) 694 { 695 u64 ts_usec = msg->ts_nsec; 696 697 do_div(ts_usec, 1000); 698 699 return scnprintf(buf, size, "%u,%llu,%llu,%c;", 700 (msg->facility << 3) | msg->level, seq, ts_usec, 701 msg->flags & LOG_CONT ? 'c' : '-'); 702 } 703 704 static ssize_t msg_print_ext_body(char *buf, size_t size, 705 char *dict, size_t dict_len, 706 char *text, size_t text_len) 707 { 708 char *p = buf, *e = buf + size; 709 size_t i; 710 711 /* escape non-printable characters */ 712 for (i = 0; i < text_len; i++) { 713 unsigned char c = text[i]; 714 715 if (c < ' ' || c >= 127 || c == '\\') 716 p += scnprintf(p, e - p, "\\x%02x", c); 717 else 718 append_char(&p, e, c); 719 } 720 append_char(&p, e, '\n'); 721 722 if (dict_len) { 723 bool line = true; 724 725 for (i = 0; i < dict_len; i++) { 726 unsigned char c = dict[i]; 727 728 if (line) { 729 append_char(&p, e, ' '); 730 line = false; 731 } 732 733 if (c == '\0') { 734 append_char(&p, e, '\n'); 735 line = true; 736 continue; 737 } 738 739 if (c < ' ' || c >= 127 || c == '\\') { 740 p += scnprintf(p, e - p, "\\x%02x", c); 741 continue; 742 } 743 744 append_char(&p, e, c); 745 } 746 append_char(&p, e, '\n'); 747 } 748 749 return p - buf; 750 } 751 752 /* /dev/kmsg - userspace message inject/listen interface */ 753 struct devkmsg_user { 754 u64 seq; 755 u32 idx; 756 struct ratelimit_state rs; 757 struct mutex lock; 758 char buf[CONSOLE_EXT_LOG_MAX]; 759 }; 760 761 static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from) 762 { 763 char *buf, *line; 764 int level = default_message_loglevel; 765 int facility = 1; /* LOG_USER */ 766 struct file *file = iocb->ki_filp; 767 struct devkmsg_user *user = file->private_data; 768 size_t len = iov_iter_count(from); 769 ssize_t ret = len; 770 771 if (!user || len > LOG_LINE_MAX) 772 return -EINVAL; 773 774 /* Ignore when user logging is disabled. */ 775 if (devkmsg_log & DEVKMSG_LOG_MASK_OFF) 776 return len; 777 778 /* Ratelimit when not explicitly enabled. */ 779 if (!(devkmsg_log & DEVKMSG_LOG_MASK_ON)) { 780 if (!___ratelimit(&user->rs, current->comm)) 781 return ret; 782 } 783 784 buf = kmalloc(len+1, GFP_KERNEL); 785 if (buf == NULL) 786 return -ENOMEM; 787 788 buf[len] = '\0'; 789 if (!copy_from_iter_full(buf, len, from)) { 790 kfree(buf); 791 return -EFAULT; 792 } 793 794 /* 795 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace 796 * the decimal value represents 32bit, the lower 3 bit are the log 797 * level, the rest are the log facility. 798 * 799 * If no prefix or no userspace facility is specified, we 800 * enforce LOG_USER, to be able to reliably distinguish 801 * kernel-generated messages from userspace-injected ones. 802 */ 803 line = buf; 804 if (line[0] == '<') { 805 char *endp = NULL; 806 unsigned int u; 807 808 u = simple_strtoul(line + 1, &endp, 10); 809 if (endp && endp[0] == '>') { 810 level = LOG_LEVEL(u); 811 if (LOG_FACILITY(u) != 0) 812 facility = LOG_FACILITY(u); 813 endp++; 814 len -= endp - line; 815 line = endp; 816 } 817 } 818 819 printk_emit(facility, level, NULL, 0, "%s", line); 820 kfree(buf); 821 return ret; 822 } 823 824 static ssize_t devkmsg_read(struct file *file, char __user *buf, 825 size_t count, loff_t *ppos) 826 { 827 struct devkmsg_user *user = file->private_data; 828 struct printk_log *msg; 829 size_t len; 830 ssize_t ret; 831 832 if (!user) 833 return -EBADF; 834 835 ret = mutex_lock_interruptible(&user->lock); 836 if (ret) 837 return ret; 838 839 logbuf_lock_irq(); 840 while (user->seq == log_next_seq) { 841 if (file->f_flags & O_NONBLOCK) { 842 ret = -EAGAIN; 843 logbuf_unlock_irq(); 844 goto out; 845 } 846 847 logbuf_unlock_irq(); 848 ret = wait_event_interruptible(log_wait, 849 user->seq != log_next_seq); 850 if (ret) 851 goto out; 852 logbuf_lock_irq(); 853 } 854 855 if (user->seq < log_first_seq) { 856 /* our last seen message is gone, return error and reset */ 857 user->idx = log_first_idx; 858 user->seq = log_first_seq; 859 ret = -EPIPE; 860 logbuf_unlock_irq(); 861 goto out; 862 } 863 864 msg = log_from_idx(user->idx); 865 len = msg_print_ext_header(user->buf, sizeof(user->buf), 866 msg, user->seq); 867 len += msg_print_ext_body(user->buf + len, sizeof(user->buf) - len, 868 log_dict(msg), msg->dict_len, 869 log_text(msg), msg->text_len); 870 871 user->idx = log_next(user->idx); 872 user->seq++; 873 logbuf_unlock_irq(); 874 875 if (len > count) { 876 ret = -EINVAL; 877 goto out; 878 } 879 880 if (copy_to_user(buf, user->buf, len)) { 881 ret = -EFAULT; 882 goto out; 883 } 884 ret = len; 885 out: 886 mutex_unlock(&user->lock); 887 return ret; 888 } 889 890 static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence) 891 { 892 struct devkmsg_user *user = file->private_data; 893 loff_t ret = 0; 894 895 if (!user) 896 return -EBADF; 897 if (offset) 898 return -ESPIPE; 899 900 logbuf_lock_irq(); 901 switch (whence) { 902 case SEEK_SET: 903 /* the first record */ 904 user->idx = log_first_idx; 905 user->seq = log_first_seq; 906 break; 907 case SEEK_DATA: 908 /* 909 * The first record after the last SYSLOG_ACTION_CLEAR, 910 * like issued by 'dmesg -c'. Reading /dev/kmsg itself 911 * changes no global state, and does not clear anything. 912 */ 913 user->idx = clear_idx; 914 user->seq = clear_seq; 915 break; 916 case SEEK_END: 917 /* after the last record */ 918 user->idx = log_next_idx; 919 user->seq = log_next_seq; 920 break; 921 default: 922 ret = -EINVAL; 923 } 924 logbuf_unlock_irq(); 925 return ret; 926 } 927 928 static __poll_t devkmsg_poll(struct file *file, poll_table *wait) 929 { 930 struct devkmsg_user *user = file->private_data; 931 __poll_t ret = 0; 932 933 if (!user) 934 return EPOLLERR|EPOLLNVAL; 935 936 poll_wait(file, &log_wait, wait); 937 938 logbuf_lock_irq(); 939 if (user->seq < log_next_seq) { 940 /* return error when data has vanished underneath us */ 941 if (user->seq < log_first_seq) 942 ret = EPOLLIN|EPOLLRDNORM|EPOLLERR|EPOLLPRI; 943 else 944 ret = EPOLLIN|EPOLLRDNORM; 945 } 946 logbuf_unlock_irq(); 947 948 return ret; 949 } 950 951 static int devkmsg_open(struct inode *inode, struct file *file) 952 { 953 struct devkmsg_user *user; 954 int err; 955 956 if (devkmsg_log & DEVKMSG_LOG_MASK_OFF) 957 return -EPERM; 958 959 /* write-only does not need any file context */ 960 if ((file->f_flags & O_ACCMODE) != O_WRONLY) { 961 err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL, 962 SYSLOG_FROM_READER); 963 if (err) 964 return err; 965 } 966 967 user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL); 968 if (!user) 969 return -ENOMEM; 970 971 ratelimit_default_init(&user->rs); 972 ratelimit_set_flags(&user->rs, RATELIMIT_MSG_ON_RELEASE); 973 974 mutex_init(&user->lock); 975 976 logbuf_lock_irq(); 977 user->idx = log_first_idx; 978 user->seq = log_first_seq; 979 logbuf_unlock_irq(); 980 981 file->private_data = user; 982 return 0; 983 } 984 985 static int devkmsg_release(struct inode *inode, struct file *file) 986 { 987 struct devkmsg_user *user = file->private_data; 988 989 if (!user) 990 return 0; 991 992 ratelimit_state_exit(&user->rs); 993 994 mutex_destroy(&user->lock); 995 kfree(user); 996 return 0; 997 } 998 999 const struct file_operations kmsg_fops = { 1000 .open = devkmsg_open, 1001 .read = devkmsg_read, 1002 .write_iter = devkmsg_write, 1003 .llseek = devkmsg_llseek, 1004 .poll = devkmsg_poll, 1005 .release = devkmsg_release, 1006 }; 1007 1008 #ifdef CONFIG_CRASH_CORE 1009 /* 1010 * This appends the listed symbols to /proc/vmcore 1011 * 1012 * /proc/vmcore is used by various utilities, like crash and makedumpfile to 1013 * obtain access to symbols that are otherwise very difficult to locate. These 1014 * symbols are specifically used so that utilities can access and extract the 1015 * dmesg log from a vmcore file after a crash. 1016 */ 1017 void log_buf_vmcoreinfo_setup(void) 1018 { 1019 VMCOREINFO_SYMBOL(log_buf); 1020 VMCOREINFO_SYMBOL(log_buf_len); 1021 VMCOREINFO_SYMBOL(log_first_idx); 1022 VMCOREINFO_SYMBOL(clear_idx); 1023 VMCOREINFO_SYMBOL(log_next_idx); 1024 /* 1025 * Export struct printk_log size and field offsets. User space tools can 1026 * parse it and detect any changes to structure down the line. 1027 */ 1028 VMCOREINFO_STRUCT_SIZE(printk_log); 1029 VMCOREINFO_OFFSET(printk_log, ts_nsec); 1030 VMCOREINFO_OFFSET(printk_log, len); 1031 VMCOREINFO_OFFSET(printk_log, text_len); 1032 VMCOREINFO_OFFSET(printk_log, dict_len); 1033 } 1034 #endif 1035 1036 /* requested log_buf_len from kernel cmdline */ 1037 static unsigned long __initdata new_log_buf_len; 1038 1039 /* we practice scaling the ring buffer by powers of 2 */ 1040 static void __init log_buf_len_update(unsigned size) 1041 { 1042 if (size) 1043 size = roundup_pow_of_two(size); 1044 if (size > log_buf_len) 1045 new_log_buf_len = size; 1046 } 1047 1048 /* save requested log_buf_len since it's too early to process it */ 1049 static int __init log_buf_len_setup(char *str) 1050 { 1051 unsigned size = memparse(str, &str); 1052 1053 log_buf_len_update(size); 1054 1055 return 0; 1056 } 1057 early_param("log_buf_len", log_buf_len_setup); 1058 1059 #ifdef CONFIG_SMP 1060 #define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT) 1061 1062 static void __init log_buf_add_cpu(void) 1063 { 1064 unsigned int cpu_extra; 1065 1066 /* 1067 * archs should set up cpu_possible_bits properly with 1068 * set_cpu_possible() after setup_arch() but just in 1069 * case lets ensure this is valid. 1070 */ 1071 if (num_possible_cpus() == 1) 1072 return; 1073 1074 cpu_extra = (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN; 1075 1076 /* by default this will only continue through for large > 64 CPUs */ 1077 if (cpu_extra <= __LOG_BUF_LEN / 2) 1078 return; 1079 1080 pr_info("log_buf_len individual max cpu contribution: %d bytes\n", 1081 __LOG_CPU_MAX_BUF_LEN); 1082 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n", 1083 cpu_extra); 1084 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN); 1085 1086 log_buf_len_update(cpu_extra + __LOG_BUF_LEN); 1087 } 1088 #else /* !CONFIG_SMP */ 1089 static inline void log_buf_add_cpu(void) {} 1090 #endif /* CONFIG_SMP */ 1091 1092 void __init setup_log_buf(int early) 1093 { 1094 unsigned long flags; 1095 char *new_log_buf; 1096 int free; 1097 1098 if (log_buf != __log_buf) 1099 return; 1100 1101 if (!early && !new_log_buf_len) 1102 log_buf_add_cpu(); 1103 1104 if (!new_log_buf_len) 1105 return; 1106 1107 if (early) { 1108 new_log_buf = 1109 memblock_virt_alloc(new_log_buf_len, LOG_ALIGN); 1110 } else { 1111 new_log_buf = memblock_virt_alloc_nopanic(new_log_buf_len, 1112 LOG_ALIGN); 1113 } 1114 1115 if (unlikely(!new_log_buf)) { 1116 pr_err("log_buf_len: %ld bytes not available\n", 1117 new_log_buf_len); 1118 return; 1119 } 1120 1121 logbuf_lock_irqsave(flags); 1122 log_buf_len = new_log_buf_len; 1123 log_buf = new_log_buf; 1124 new_log_buf_len = 0; 1125 free = __LOG_BUF_LEN - log_next_idx; 1126 memcpy(log_buf, __log_buf, __LOG_BUF_LEN); 1127 logbuf_unlock_irqrestore(flags); 1128 1129 pr_info("log_buf_len: %d bytes\n", log_buf_len); 1130 pr_info("early log buf free: %d(%d%%)\n", 1131 free, (free * 100) / __LOG_BUF_LEN); 1132 } 1133 1134 static bool __read_mostly ignore_loglevel; 1135 1136 static int __init ignore_loglevel_setup(char *str) 1137 { 1138 ignore_loglevel = true; 1139 pr_info("debug: ignoring loglevel setting.\n"); 1140 1141 return 0; 1142 } 1143 1144 early_param("ignore_loglevel", ignore_loglevel_setup); 1145 module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR); 1146 MODULE_PARM_DESC(ignore_loglevel, 1147 "ignore loglevel setting (prints all kernel messages to the console)"); 1148 1149 static bool suppress_message_printing(int level) 1150 { 1151 return (level >= console_loglevel && !ignore_loglevel); 1152 } 1153 1154 #ifdef CONFIG_BOOT_PRINTK_DELAY 1155 1156 static int boot_delay; /* msecs delay after each printk during bootup */ 1157 static unsigned long long loops_per_msec; /* based on boot_delay */ 1158 1159 static int __init boot_delay_setup(char *str) 1160 { 1161 unsigned long lpj; 1162 1163 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */ 1164 loops_per_msec = (unsigned long long)lpj / 1000 * HZ; 1165 1166 get_option(&str, &boot_delay); 1167 if (boot_delay > 10 * 1000) 1168 boot_delay = 0; 1169 1170 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, " 1171 "HZ: %d, loops_per_msec: %llu\n", 1172 boot_delay, preset_lpj, lpj, HZ, loops_per_msec); 1173 return 0; 1174 } 1175 early_param("boot_delay", boot_delay_setup); 1176 1177 static void boot_delay_msec(int level) 1178 { 1179 unsigned long long k; 1180 unsigned long timeout; 1181 1182 if ((boot_delay == 0 || system_state >= SYSTEM_RUNNING) 1183 || suppress_message_printing(level)) { 1184 return; 1185 } 1186 1187 k = (unsigned long long)loops_per_msec * boot_delay; 1188 1189 timeout = jiffies + msecs_to_jiffies(boot_delay); 1190 while (k) { 1191 k--; 1192 cpu_relax(); 1193 /* 1194 * use (volatile) jiffies to prevent 1195 * compiler reduction; loop termination via jiffies 1196 * is secondary and may or may not happen. 1197 */ 1198 if (time_after(jiffies, timeout)) 1199 break; 1200 touch_nmi_watchdog(); 1201 } 1202 } 1203 #else 1204 static inline void boot_delay_msec(int level) 1205 { 1206 } 1207 #endif 1208 1209 static bool printk_time = IS_ENABLED(CONFIG_PRINTK_TIME); 1210 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR); 1211 1212 static size_t print_time(u64 ts, char *buf) 1213 { 1214 unsigned long rem_nsec; 1215 1216 if (!printk_time) 1217 return 0; 1218 1219 rem_nsec = do_div(ts, 1000000000); 1220 1221 if (!buf) 1222 return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts); 1223 1224 return sprintf(buf, "[%5lu.%06lu] ", 1225 (unsigned long)ts, rem_nsec / 1000); 1226 } 1227 1228 static size_t print_prefix(const struct printk_log *msg, bool syslog, char *buf) 1229 { 1230 size_t len = 0; 1231 unsigned int prefix = (msg->facility << 3) | msg->level; 1232 1233 if (syslog) { 1234 if (buf) { 1235 len += sprintf(buf, "<%u>", prefix); 1236 } else { 1237 len += 3; 1238 if (prefix > 999) 1239 len += 3; 1240 else if (prefix > 99) 1241 len += 2; 1242 else if (prefix > 9) 1243 len++; 1244 } 1245 } 1246 1247 len += print_time(msg->ts_nsec, buf ? buf + len : NULL); 1248 return len; 1249 } 1250 1251 static size_t msg_print_text(const struct printk_log *msg, bool syslog, char *buf, size_t size) 1252 { 1253 const char *text = log_text(msg); 1254 size_t text_size = msg->text_len; 1255 size_t len = 0; 1256 1257 do { 1258 const char *next = memchr(text, '\n', text_size); 1259 size_t text_len; 1260 1261 if (next) { 1262 text_len = next - text; 1263 next++; 1264 text_size -= next - text; 1265 } else { 1266 text_len = text_size; 1267 } 1268 1269 if (buf) { 1270 if (print_prefix(msg, syslog, NULL) + 1271 text_len + 1 >= size - len) 1272 break; 1273 1274 len += print_prefix(msg, syslog, buf + len); 1275 memcpy(buf + len, text, text_len); 1276 len += text_len; 1277 buf[len++] = '\n'; 1278 } else { 1279 /* SYSLOG_ACTION_* buffer size only calculation */ 1280 len += print_prefix(msg, syslog, NULL); 1281 len += text_len; 1282 len++; 1283 } 1284 1285 text = next; 1286 } while (text); 1287 1288 return len; 1289 } 1290 1291 static int syslog_print(char __user *buf, int size) 1292 { 1293 char *text; 1294 struct printk_log *msg; 1295 int len = 0; 1296 1297 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL); 1298 if (!text) 1299 return -ENOMEM; 1300 1301 while (size > 0) { 1302 size_t n; 1303 size_t skip; 1304 1305 logbuf_lock_irq(); 1306 if (syslog_seq < log_first_seq) { 1307 /* messages are gone, move to first one */ 1308 syslog_seq = log_first_seq; 1309 syslog_idx = log_first_idx; 1310 syslog_partial = 0; 1311 } 1312 if (syslog_seq == log_next_seq) { 1313 logbuf_unlock_irq(); 1314 break; 1315 } 1316 1317 skip = syslog_partial; 1318 msg = log_from_idx(syslog_idx); 1319 n = msg_print_text(msg, true, text, LOG_LINE_MAX + PREFIX_MAX); 1320 if (n - syslog_partial <= size) { 1321 /* message fits into buffer, move forward */ 1322 syslog_idx = log_next(syslog_idx); 1323 syslog_seq++; 1324 n -= syslog_partial; 1325 syslog_partial = 0; 1326 } else if (!len){ 1327 /* partial read(), remember position */ 1328 n = size; 1329 syslog_partial += n; 1330 } else 1331 n = 0; 1332 logbuf_unlock_irq(); 1333 1334 if (!n) 1335 break; 1336 1337 if (copy_to_user(buf, text + skip, n)) { 1338 if (!len) 1339 len = -EFAULT; 1340 break; 1341 } 1342 1343 len += n; 1344 size -= n; 1345 buf += n; 1346 } 1347 1348 kfree(text); 1349 return len; 1350 } 1351 1352 static int syslog_print_all(char __user *buf, int size, bool clear) 1353 { 1354 char *text; 1355 int len = 0; 1356 u64 next_seq; 1357 u64 seq; 1358 u32 idx; 1359 1360 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL); 1361 if (!text) 1362 return -ENOMEM; 1363 1364 logbuf_lock_irq(); 1365 /* 1366 * Find first record that fits, including all following records, 1367 * into the user-provided buffer for this dump. 1368 */ 1369 seq = clear_seq; 1370 idx = clear_idx; 1371 while (seq < log_next_seq) { 1372 struct printk_log *msg = log_from_idx(idx); 1373 1374 len += msg_print_text(msg, true, NULL, 0); 1375 idx = log_next(idx); 1376 seq++; 1377 } 1378 1379 /* move first record forward until length fits into the buffer */ 1380 seq = clear_seq; 1381 idx = clear_idx; 1382 while (len > size && seq < log_next_seq) { 1383 struct printk_log *msg = log_from_idx(idx); 1384 1385 len -= msg_print_text(msg, true, NULL, 0); 1386 idx = log_next(idx); 1387 seq++; 1388 } 1389 1390 /* last message fitting into this dump */ 1391 next_seq = log_next_seq; 1392 1393 len = 0; 1394 while (len >= 0 && seq < next_seq) { 1395 struct printk_log *msg = log_from_idx(idx); 1396 int textlen; 1397 1398 textlen = msg_print_text(msg, true, text, 1399 LOG_LINE_MAX + PREFIX_MAX); 1400 if (textlen < 0) { 1401 len = textlen; 1402 break; 1403 } 1404 idx = log_next(idx); 1405 seq++; 1406 1407 logbuf_unlock_irq(); 1408 if (copy_to_user(buf + len, text, textlen)) 1409 len = -EFAULT; 1410 else 1411 len += textlen; 1412 logbuf_lock_irq(); 1413 1414 if (seq < log_first_seq) { 1415 /* messages are gone, move to next one */ 1416 seq = log_first_seq; 1417 idx = log_first_idx; 1418 } 1419 } 1420 1421 if (clear) { 1422 clear_seq = log_next_seq; 1423 clear_idx = log_next_idx; 1424 } 1425 logbuf_unlock_irq(); 1426 1427 kfree(text); 1428 return len; 1429 } 1430 1431 static void syslog_clear(void) 1432 { 1433 logbuf_lock_irq(); 1434 clear_seq = log_next_seq; 1435 clear_idx = log_next_idx; 1436 logbuf_unlock_irq(); 1437 } 1438 1439 int do_syslog(int type, char __user *buf, int len, int source) 1440 { 1441 bool clear = false; 1442 static int saved_console_loglevel = LOGLEVEL_DEFAULT; 1443 int error; 1444 1445 error = check_syslog_permissions(type, source); 1446 if (error) 1447 return error; 1448 1449 switch (type) { 1450 case SYSLOG_ACTION_CLOSE: /* Close log */ 1451 break; 1452 case SYSLOG_ACTION_OPEN: /* Open log */ 1453 break; 1454 case SYSLOG_ACTION_READ: /* Read from log */ 1455 if (!buf || len < 0) 1456 return -EINVAL; 1457 if (!len) 1458 return 0; 1459 if (!access_ok(VERIFY_WRITE, buf, len)) 1460 return -EFAULT; 1461 error = wait_event_interruptible(log_wait, 1462 syslog_seq != log_next_seq); 1463 if (error) 1464 return error; 1465 error = syslog_print(buf, len); 1466 break; 1467 /* Read/clear last kernel messages */ 1468 case SYSLOG_ACTION_READ_CLEAR: 1469 clear = true; 1470 /* FALL THRU */ 1471 /* Read last kernel messages */ 1472 case SYSLOG_ACTION_READ_ALL: 1473 if (!buf || len < 0) 1474 return -EINVAL; 1475 if (!len) 1476 return 0; 1477 if (!access_ok(VERIFY_WRITE, buf, len)) 1478 return -EFAULT; 1479 error = syslog_print_all(buf, len, clear); 1480 break; 1481 /* Clear ring buffer */ 1482 case SYSLOG_ACTION_CLEAR: 1483 syslog_clear(); 1484 break; 1485 /* Disable logging to console */ 1486 case SYSLOG_ACTION_CONSOLE_OFF: 1487 if (saved_console_loglevel == LOGLEVEL_DEFAULT) 1488 saved_console_loglevel = console_loglevel; 1489 console_loglevel = minimum_console_loglevel; 1490 break; 1491 /* Enable logging to console */ 1492 case SYSLOG_ACTION_CONSOLE_ON: 1493 if (saved_console_loglevel != LOGLEVEL_DEFAULT) { 1494 console_loglevel = saved_console_loglevel; 1495 saved_console_loglevel = LOGLEVEL_DEFAULT; 1496 } 1497 break; 1498 /* Set level of messages printed to console */ 1499 case SYSLOG_ACTION_CONSOLE_LEVEL: 1500 if (len < 1 || len > 8) 1501 return -EINVAL; 1502 if (len < minimum_console_loglevel) 1503 len = minimum_console_loglevel; 1504 console_loglevel = len; 1505 /* Implicitly re-enable logging to console */ 1506 saved_console_loglevel = LOGLEVEL_DEFAULT; 1507 break; 1508 /* Number of chars in the log buffer */ 1509 case SYSLOG_ACTION_SIZE_UNREAD: 1510 logbuf_lock_irq(); 1511 if (syslog_seq < log_first_seq) { 1512 /* messages are gone, move to first one */ 1513 syslog_seq = log_first_seq; 1514 syslog_idx = log_first_idx; 1515 syslog_partial = 0; 1516 } 1517 if (source == SYSLOG_FROM_PROC) { 1518 /* 1519 * Short-cut for poll(/"proc/kmsg") which simply checks 1520 * for pending data, not the size; return the count of 1521 * records, not the length. 1522 */ 1523 error = log_next_seq - syslog_seq; 1524 } else { 1525 u64 seq = syslog_seq; 1526 u32 idx = syslog_idx; 1527 1528 while (seq < log_next_seq) { 1529 struct printk_log *msg = log_from_idx(idx); 1530 1531 error += msg_print_text(msg, true, NULL, 0); 1532 idx = log_next(idx); 1533 seq++; 1534 } 1535 error -= syslog_partial; 1536 } 1537 logbuf_unlock_irq(); 1538 break; 1539 /* Size of the log buffer */ 1540 case SYSLOG_ACTION_SIZE_BUFFER: 1541 error = log_buf_len; 1542 break; 1543 default: 1544 error = -EINVAL; 1545 break; 1546 } 1547 1548 return error; 1549 } 1550 1551 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len) 1552 { 1553 return do_syslog(type, buf, len, SYSLOG_FROM_READER); 1554 } 1555 1556 /* 1557 * Special console_lock variants that help to reduce the risk of soft-lockups. 1558 * They allow to pass console_lock to another printk() call using a busy wait. 1559 */ 1560 1561 #ifdef CONFIG_LOCKDEP 1562 static struct lockdep_map console_owner_dep_map = { 1563 .name = "console_owner" 1564 }; 1565 #endif 1566 1567 static DEFINE_RAW_SPINLOCK(console_owner_lock); 1568 static struct task_struct *console_owner; 1569 static bool console_waiter; 1570 1571 /** 1572 * console_lock_spinning_enable - mark beginning of code where another 1573 * thread might safely busy wait 1574 * 1575 * This basically converts console_lock into a spinlock. This marks 1576 * the section where the console_lock owner can not sleep, because 1577 * there may be a waiter spinning (like a spinlock). Also it must be 1578 * ready to hand over the lock at the end of the section. 1579 */ 1580 static void console_lock_spinning_enable(void) 1581 { 1582 raw_spin_lock(&console_owner_lock); 1583 console_owner = current; 1584 raw_spin_unlock(&console_owner_lock); 1585 1586 /* The waiter may spin on us after setting console_owner */ 1587 spin_acquire(&console_owner_dep_map, 0, 0, _THIS_IP_); 1588 } 1589 1590 /** 1591 * console_lock_spinning_disable_and_check - mark end of code where another 1592 * thread was able to busy wait and check if there is a waiter 1593 * 1594 * This is called at the end of the section where spinning is allowed. 1595 * It has two functions. First, it is a signal that it is no longer 1596 * safe to start busy waiting for the lock. Second, it checks if 1597 * there is a busy waiter and passes the lock rights to her. 1598 * 1599 * Important: Callers lose the lock if there was a busy waiter. 1600 * They must not touch items synchronized by console_lock 1601 * in this case. 1602 * 1603 * Return: 1 if the lock rights were passed, 0 otherwise. 1604 */ 1605 static int console_lock_spinning_disable_and_check(void) 1606 { 1607 int waiter; 1608 1609 raw_spin_lock(&console_owner_lock); 1610 waiter = READ_ONCE(console_waiter); 1611 console_owner = NULL; 1612 raw_spin_unlock(&console_owner_lock); 1613 1614 if (!waiter) { 1615 spin_release(&console_owner_dep_map, 1, _THIS_IP_); 1616 return 0; 1617 } 1618 1619 /* The waiter is now free to continue */ 1620 WRITE_ONCE(console_waiter, false); 1621 1622 spin_release(&console_owner_dep_map, 1, _THIS_IP_); 1623 1624 /* 1625 * Hand off console_lock to waiter. The waiter will perform 1626 * the up(). After this, the waiter is the console_lock owner. 1627 */ 1628 mutex_release(&console_lock_dep_map, 1, _THIS_IP_); 1629 return 1; 1630 } 1631 1632 /** 1633 * console_trylock_spinning - try to get console_lock by busy waiting 1634 * 1635 * This allows to busy wait for the console_lock when the current 1636 * owner is running in specially marked sections. It means that 1637 * the current owner is running and cannot reschedule until it 1638 * is ready to lose the lock. 1639 * 1640 * Return: 1 if we got the lock, 0 othrewise 1641 */ 1642 static int console_trylock_spinning(void) 1643 { 1644 struct task_struct *owner = NULL; 1645 bool waiter; 1646 bool spin = false; 1647 unsigned long flags; 1648 1649 if (console_trylock()) 1650 return 1; 1651 1652 printk_safe_enter_irqsave(flags); 1653 1654 raw_spin_lock(&console_owner_lock); 1655 owner = READ_ONCE(console_owner); 1656 waiter = READ_ONCE(console_waiter); 1657 if (!waiter && owner && owner != current) { 1658 WRITE_ONCE(console_waiter, true); 1659 spin = true; 1660 } 1661 raw_spin_unlock(&console_owner_lock); 1662 1663 /* 1664 * If there is an active printk() writing to the 1665 * consoles, instead of having it write our data too, 1666 * see if we can offload that load from the active 1667 * printer, and do some printing ourselves. 1668 * Go into a spin only if there isn't already a waiter 1669 * spinning, and there is an active printer, and 1670 * that active printer isn't us (recursive printk?). 1671 */ 1672 if (!spin) { 1673 printk_safe_exit_irqrestore(flags); 1674 return 0; 1675 } 1676 1677 /* We spin waiting for the owner to release us */ 1678 spin_acquire(&console_owner_dep_map, 0, 0, _THIS_IP_); 1679 /* Owner will clear console_waiter on hand off */ 1680 while (READ_ONCE(console_waiter)) 1681 cpu_relax(); 1682 spin_release(&console_owner_dep_map, 1, _THIS_IP_); 1683 1684 printk_safe_exit_irqrestore(flags); 1685 /* 1686 * The owner passed the console lock to us. 1687 * Since we did not spin on console lock, annotate 1688 * this as a trylock. Otherwise lockdep will 1689 * complain. 1690 */ 1691 mutex_acquire(&console_lock_dep_map, 0, 1, _THIS_IP_); 1692 1693 return 1; 1694 } 1695 1696 /* 1697 * Call the console drivers, asking them to write out 1698 * log_buf[start] to log_buf[end - 1]. 1699 * The console_lock must be held. 1700 */ 1701 static void call_console_drivers(const char *ext_text, size_t ext_len, 1702 const char *text, size_t len) 1703 { 1704 struct console *con; 1705 1706 trace_console_rcuidle(text, len); 1707 1708 if (!console_drivers) 1709 return; 1710 1711 for_each_console(con) { 1712 if (exclusive_console && con != exclusive_console) 1713 continue; 1714 if (!(con->flags & CON_ENABLED)) 1715 continue; 1716 if (!con->write) 1717 continue; 1718 if (!cpu_online(smp_processor_id()) && 1719 !(con->flags & CON_ANYTIME)) 1720 continue; 1721 if (con->flags & CON_EXTENDED) 1722 con->write(con, ext_text, ext_len); 1723 else 1724 con->write(con, text, len); 1725 } 1726 } 1727 1728 int printk_delay_msec __read_mostly; 1729 1730 static inline void printk_delay(void) 1731 { 1732 if (unlikely(printk_delay_msec)) { 1733 int m = printk_delay_msec; 1734 1735 while (m--) { 1736 mdelay(1); 1737 touch_nmi_watchdog(); 1738 } 1739 } 1740 } 1741 1742 /* 1743 * Continuation lines are buffered, and not committed to the record buffer 1744 * until the line is complete, or a race forces it. The line fragments 1745 * though, are printed immediately to the consoles to ensure everything has 1746 * reached the console in case of a kernel crash. 1747 */ 1748 static struct cont { 1749 char buf[LOG_LINE_MAX]; 1750 size_t len; /* length == 0 means unused buffer */ 1751 struct task_struct *owner; /* task of first print*/ 1752 u64 ts_nsec; /* time of first print */ 1753 u8 level; /* log level of first message */ 1754 u8 facility; /* log facility of first message */ 1755 enum log_flags flags; /* prefix, newline flags */ 1756 } cont; 1757 1758 static void cont_flush(void) 1759 { 1760 if (cont.len == 0) 1761 return; 1762 1763 log_store(cont.facility, cont.level, cont.flags, cont.ts_nsec, 1764 NULL, 0, cont.buf, cont.len); 1765 cont.len = 0; 1766 } 1767 1768 static bool cont_add(int facility, int level, enum log_flags flags, const char *text, size_t len) 1769 { 1770 /* 1771 * If ext consoles are present, flush and skip in-kernel 1772 * continuation. See nr_ext_console_drivers definition. Also, if 1773 * the line gets too long, split it up in separate records. 1774 */ 1775 if (nr_ext_console_drivers || cont.len + len > sizeof(cont.buf)) { 1776 cont_flush(); 1777 return false; 1778 } 1779 1780 if (!cont.len) { 1781 cont.facility = facility; 1782 cont.level = level; 1783 cont.owner = current; 1784 cont.ts_nsec = local_clock(); 1785 cont.flags = flags; 1786 } 1787 1788 memcpy(cont.buf + cont.len, text, len); 1789 cont.len += len; 1790 1791 // The original flags come from the first line, 1792 // but later continuations can add a newline. 1793 if (flags & LOG_NEWLINE) { 1794 cont.flags |= LOG_NEWLINE; 1795 cont_flush(); 1796 } 1797 1798 if (cont.len > (sizeof(cont.buf) * 80) / 100) 1799 cont_flush(); 1800 1801 return true; 1802 } 1803 1804 static size_t log_output(int facility, int level, enum log_flags lflags, const char *dict, size_t dictlen, char *text, size_t text_len) 1805 { 1806 /* 1807 * If an earlier line was buffered, and we're a continuation 1808 * write from the same process, try to add it to the buffer. 1809 */ 1810 if (cont.len) { 1811 if (cont.owner == current && (lflags & LOG_CONT)) { 1812 if (cont_add(facility, level, lflags, text, text_len)) 1813 return text_len; 1814 } 1815 /* Otherwise, make sure it's flushed */ 1816 cont_flush(); 1817 } 1818 1819 /* Skip empty continuation lines that couldn't be added - they just flush */ 1820 if (!text_len && (lflags & LOG_CONT)) 1821 return 0; 1822 1823 /* If it doesn't end in a newline, try to buffer the current line */ 1824 if (!(lflags & LOG_NEWLINE)) { 1825 if (cont_add(facility, level, lflags, text, text_len)) 1826 return text_len; 1827 } 1828 1829 /* Store it in the record log */ 1830 return log_store(facility, level, lflags, 0, dict, dictlen, text, text_len); 1831 } 1832 1833 /* Must be called under logbuf_lock. */ 1834 int vprintk_store(int facility, int level, 1835 const char *dict, size_t dictlen, 1836 const char *fmt, va_list args) 1837 { 1838 static char textbuf[LOG_LINE_MAX]; 1839 char *text = textbuf; 1840 size_t text_len; 1841 enum log_flags lflags = 0; 1842 1843 /* 1844 * The printf needs to come first; we need the syslog 1845 * prefix which might be passed-in as a parameter. 1846 */ 1847 text_len = vscnprintf(text, sizeof(textbuf), fmt, args); 1848 1849 /* mark and strip a trailing newline */ 1850 if (text_len && text[text_len-1] == '\n') { 1851 text_len--; 1852 lflags |= LOG_NEWLINE; 1853 } 1854 1855 /* strip kernel syslog prefix and extract log level or control flags */ 1856 if (facility == 0) { 1857 int kern_level; 1858 1859 while ((kern_level = printk_get_level(text)) != 0) { 1860 switch (kern_level) { 1861 case '0' ... '7': 1862 if (level == LOGLEVEL_DEFAULT) 1863 level = kern_level - '0'; 1864 /* fallthrough */ 1865 case 'd': /* KERN_DEFAULT */ 1866 lflags |= LOG_PREFIX; 1867 break; 1868 case 'c': /* KERN_CONT */ 1869 lflags |= LOG_CONT; 1870 } 1871 1872 text_len -= 2; 1873 text += 2; 1874 } 1875 } 1876 1877 if (level == LOGLEVEL_DEFAULT) 1878 level = default_message_loglevel; 1879 1880 if (dict) 1881 lflags |= LOG_PREFIX|LOG_NEWLINE; 1882 1883 return log_output(facility, level, lflags, 1884 dict, dictlen, text, text_len); 1885 } 1886 1887 asmlinkage int vprintk_emit(int facility, int level, 1888 const char *dict, size_t dictlen, 1889 const char *fmt, va_list args) 1890 { 1891 int printed_len; 1892 bool in_sched = false; 1893 unsigned long flags; 1894 1895 if (level == LOGLEVEL_SCHED) { 1896 level = LOGLEVEL_DEFAULT; 1897 in_sched = true; 1898 } 1899 1900 boot_delay_msec(level); 1901 printk_delay(); 1902 1903 /* This stops the holder of console_sem just where we want him */ 1904 logbuf_lock_irqsave(flags); 1905 printed_len = vprintk_store(facility, level, dict, dictlen, fmt, args); 1906 logbuf_unlock_irqrestore(flags); 1907 1908 /* If called from the scheduler, we can not call up(). */ 1909 if (!in_sched) { 1910 /* 1911 * Disable preemption to avoid being preempted while holding 1912 * console_sem which would prevent anyone from printing to 1913 * console 1914 */ 1915 preempt_disable(); 1916 /* 1917 * Try to acquire and then immediately release the console 1918 * semaphore. The release will print out buffers and wake up 1919 * /dev/kmsg and syslog() users. 1920 */ 1921 if (console_trylock_spinning()) 1922 console_unlock(); 1923 preempt_enable(); 1924 } 1925 1926 wake_up_klogd(); 1927 return printed_len; 1928 } 1929 EXPORT_SYMBOL(vprintk_emit); 1930 1931 asmlinkage int vprintk(const char *fmt, va_list args) 1932 { 1933 return vprintk_func(fmt, args); 1934 } 1935 EXPORT_SYMBOL(vprintk); 1936 1937 asmlinkage int printk_emit(int facility, int level, 1938 const char *dict, size_t dictlen, 1939 const char *fmt, ...) 1940 { 1941 va_list args; 1942 int r; 1943 1944 va_start(args, fmt); 1945 r = vprintk_emit(facility, level, dict, dictlen, fmt, args); 1946 va_end(args); 1947 1948 return r; 1949 } 1950 EXPORT_SYMBOL(printk_emit); 1951 1952 int vprintk_default(const char *fmt, va_list args) 1953 { 1954 int r; 1955 1956 #ifdef CONFIG_KGDB_KDB 1957 /* Allow to pass printk() to kdb but avoid a recursion. */ 1958 if (unlikely(kdb_trap_printk && kdb_printf_cpu < 0)) { 1959 r = vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args); 1960 return r; 1961 } 1962 #endif 1963 r = vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args); 1964 1965 return r; 1966 } 1967 EXPORT_SYMBOL_GPL(vprintk_default); 1968 1969 /** 1970 * printk - print a kernel message 1971 * @fmt: format string 1972 * 1973 * This is printk(). It can be called from any context. We want it to work. 1974 * 1975 * We try to grab the console_lock. If we succeed, it's easy - we log the 1976 * output and call the console drivers. If we fail to get the semaphore, we 1977 * place the output into the log buffer and return. The current holder of 1978 * the console_sem will notice the new output in console_unlock(); and will 1979 * send it to the consoles before releasing the lock. 1980 * 1981 * One effect of this deferred printing is that code which calls printk() and 1982 * then changes console_loglevel may break. This is because console_loglevel 1983 * is inspected when the actual printing occurs. 1984 * 1985 * See also: 1986 * printf(3) 1987 * 1988 * See the vsnprintf() documentation for format string extensions over C99. 1989 */ 1990 asmlinkage __visible int printk(const char *fmt, ...) 1991 { 1992 va_list args; 1993 int r; 1994 1995 va_start(args, fmt); 1996 r = vprintk_func(fmt, args); 1997 va_end(args); 1998 1999 return r; 2000 } 2001 EXPORT_SYMBOL(printk); 2002 2003 #else /* CONFIG_PRINTK */ 2004 2005 #define LOG_LINE_MAX 0 2006 #define PREFIX_MAX 0 2007 2008 static u64 syslog_seq; 2009 static u32 syslog_idx; 2010 static u64 console_seq; 2011 static u32 console_idx; 2012 static u64 log_first_seq; 2013 static u32 log_first_idx; 2014 static u64 log_next_seq; 2015 static char *log_text(const struct printk_log *msg) { return NULL; } 2016 static char *log_dict(const struct printk_log *msg) { return NULL; } 2017 static struct printk_log *log_from_idx(u32 idx) { return NULL; } 2018 static u32 log_next(u32 idx) { return 0; } 2019 static ssize_t msg_print_ext_header(char *buf, size_t size, 2020 struct printk_log *msg, 2021 u64 seq) { return 0; } 2022 static ssize_t msg_print_ext_body(char *buf, size_t size, 2023 char *dict, size_t dict_len, 2024 char *text, size_t text_len) { return 0; } 2025 static void console_lock_spinning_enable(void) { } 2026 static int console_lock_spinning_disable_and_check(void) { return 0; } 2027 static void call_console_drivers(const char *ext_text, size_t ext_len, 2028 const char *text, size_t len) {} 2029 static size_t msg_print_text(const struct printk_log *msg, 2030 bool syslog, char *buf, size_t size) { return 0; } 2031 static bool suppress_message_printing(int level) { return false; } 2032 2033 #endif /* CONFIG_PRINTK */ 2034 2035 #ifdef CONFIG_EARLY_PRINTK 2036 struct console *early_console; 2037 2038 asmlinkage __visible void early_printk(const char *fmt, ...) 2039 { 2040 va_list ap; 2041 char buf[512]; 2042 int n; 2043 2044 if (!early_console) 2045 return; 2046 2047 va_start(ap, fmt); 2048 n = vscnprintf(buf, sizeof(buf), fmt, ap); 2049 va_end(ap); 2050 2051 early_console->write(early_console, buf, n); 2052 } 2053 #endif 2054 2055 static int __add_preferred_console(char *name, int idx, char *options, 2056 char *brl_options) 2057 { 2058 struct console_cmdline *c; 2059 int i; 2060 2061 /* 2062 * See if this tty is not yet registered, and 2063 * if we have a slot free. 2064 */ 2065 for (i = 0, c = console_cmdline; 2066 i < MAX_CMDLINECONSOLES && c->name[0]; 2067 i++, c++) { 2068 if (strcmp(c->name, name) == 0 && c->index == idx) { 2069 if (!brl_options) 2070 preferred_console = i; 2071 return 0; 2072 } 2073 } 2074 if (i == MAX_CMDLINECONSOLES) 2075 return -E2BIG; 2076 if (!brl_options) 2077 preferred_console = i; 2078 strlcpy(c->name, name, sizeof(c->name)); 2079 c->options = options; 2080 braille_set_options(c, brl_options); 2081 2082 c->index = idx; 2083 return 0; 2084 } 2085 2086 static int __init console_msg_format_setup(char *str) 2087 { 2088 if (!strcmp(str, "syslog")) 2089 console_msg_format = MSG_FORMAT_SYSLOG; 2090 if (!strcmp(str, "default")) 2091 console_msg_format = MSG_FORMAT_DEFAULT; 2092 return 1; 2093 } 2094 __setup("console_msg_format=", console_msg_format_setup); 2095 2096 /* 2097 * Set up a console. Called via do_early_param() in init/main.c 2098 * for each "console=" parameter in the boot command line. 2099 */ 2100 static int __init console_setup(char *str) 2101 { 2102 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for "ttyS" */ 2103 char *s, *options, *brl_options = NULL; 2104 int idx; 2105 2106 if (_braille_console_setup(&str, &brl_options)) 2107 return 1; 2108 2109 /* 2110 * Decode str into name, index, options. 2111 */ 2112 if (str[0] >= '0' && str[0] <= '9') { 2113 strcpy(buf, "ttyS"); 2114 strncpy(buf + 4, str, sizeof(buf) - 5); 2115 } else { 2116 strncpy(buf, str, sizeof(buf) - 1); 2117 } 2118 buf[sizeof(buf) - 1] = 0; 2119 options = strchr(str, ','); 2120 if (options) 2121 *(options++) = 0; 2122 #ifdef __sparc__ 2123 if (!strcmp(str, "ttya")) 2124 strcpy(buf, "ttyS0"); 2125 if (!strcmp(str, "ttyb")) 2126 strcpy(buf, "ttyS1"); 2127 #endif 2128 for (s = buf; *s; s++) 2129 if (isdigit(*s) || *s == ',') 2130 break; 2131 idx = simple_strtoul(s, NULL, 10); 2132 *s = 0; 2133 2134 __add_preferred_console(buf, idx, options, brl_options); 2135 console_set_on_cmdline = 1; 2136 return 1; 2137 } 2138 __setup("console=", console_setup); 2139 2140 /** 2141 * add_preferred_console - add a device to the list of preferred consoles. 2142 * @name: device name 2143 * @idx: device index 2144 * @options: options for this console 2145 * 2146 * The last preferred console added will be used for kernel messages 2147 * and stdin/out/err for init. Normally this is used by console_setup 2148 * above to handle user-supplied console arguments; however it can also 2149 * be used by arch-specific code either to override the user or more 2150 * commonly to provide a default console (ie from PROM variables) when 2151 * the user has not supplied one. 2152 */ 2153 int add_preferred_console(char *name, int idx, char *options) 2154 { 2155 return __add_preferred_console(name, idx, options, NULL); 2156 } 2157 2158 bool console_suspend_enabled = true; 2159 EXPORT_SYMBOL(console_suspend_enabled); 2160 2161 static int __init console_suspend_disable(char *str) 2162 { 2163 console_suspend_enabled = false; 2164 return 1; 2165 } 2166 __setup("no_console_suspend", console_suspend_disable); 2167 module_param_named(console_suspend, console_suspend_enabled, 2168 bool, S_IRUGO | S_IWUSR); 2169 MODULE_PARM_DESC(console_suspend, "suspend console during suspend" 2170 " and hibernate operations"); 2171 2172 /** 2173 * suspend_console - suspend the console subsystem 2174 * 2175 * This disables printk() while we go into suspend states 2176 */ 2177 void suspend_console(void) 2178 { 2179 if (!console_suspend_enabled) 2180 return; 2181 pr_info("Suspending console(s) (use no_console_suspend to debug)\n"); 2182 console_lock(); 2183 console_suspended = 1; 2184 up_console_sem(); 2185 } 2186 2187 void resume_console(void) 2188 { 2189 if (!console_suspend_enabled) 2190 return; 2191 down_console_sem(); 2192 console_suspended = 0; 2193 console_unlock(); 2194 } 2195 2196 /** 2197 * console_cpu_notify - print deferred console messages after CPU hotplug 2198 * @cpu: unused 2199 * 2200 * If printk() is called from a CPU that is not online yet, the messages 2201 * will be printed on the console only if there are CON_ANYTIME consoles. 2202 * This function is called when a new CPU comes online (or fails to come 2203 * up) or goes offline. 2204 */ 2205 static int console_cpu_notify(unsigned int cpu) 2206 { 2207 if (!cpuhp_tasks_frozen) { 2208 /* If trylock fails, someone else is doing the printing */ 2209 if (console_trylock()) 2210 console_unlock(); 2211 } 2212 return 0; 2213 } 2214 2215 /** 2216 * console_lock - lock the console system for exclusive use. 2217 * 2218 * Acquires a lock which guarantees that the caller has 2219 * exclusive access to the console system and the console_drivers list. 2220 * 2221 * Can sleep, returns nothing. 2222 */ 2223 void console_lock(void) 2224 { 2225 might_sleep(); 2226 2227 down_console_sem(); 2228 if (console_suspended) 2229 return; 2230 console_locked = 1; 2231 console_may_schedule = 1; 2232 } 2233 EXPORT_SYMBOL(console_lock); 2234 2235 /** 2236 * console_trylock - try to lock the console system for exclusive use. 2237 * 2238 * Try to acquire a lock which guarantees that the caller has exclusive 2239 * access to the console system and the console_drivers list. 2240 * 2241 * returns 1 on success, and 0 on failure to acquire the lock. 2242 */ 2243 int console_trylock(void) 2244 { 2245 if (down_trylock_console_sem()) 2246 return 0; 2247 if (console_suspended) { 2248 up_console_sem(); 2249 return 0; 2250 } 2251 console_locked = 1; 2252 console_may_schedule = 0; 2253 return 1; 2254 } 2255 EXPORT_SYMBOL(console_trylock); 2256 2257 int is_console_locked(void) 2258 { 2259 return console_locked; 2260 } 2261 EXPORT_SYMBOL(is_console_locked); 2262 2263 /* 2264 * Check if we have any console that is capable of printing while cpu is 2265 * booting or shutting down. Requires console_sem. 2266 */ 2267 static int have_callable_console(void) 2268 { 2269 struct console *con; 2270 2271 for_each_console(con) 2272 if ((con->flags & CON_ENABLED) && 2273 (con->flags & CON_ANYTIME)) 2274 return 1; 2275 2276 return 0; 2277 } 2278 2279 /* 2280 * Can we actually use the console at this time on this cpu? 2281 * 2282 * Console drivers may assume that per-cpu resources have been allocated. So 2283 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't 2284 * call them until this CPU is officially up. 2285 */ 2286 static inline int can_use_console(void) 2287 { 2288 return cpu_online(raw_smp_processor_id()) || have_callable_console(); 2289 } 2290 2291 /** 2292 * console_unlock - unlock the console system 2293 * 2294 * Releases the console_lock which the caller holds on the console system 2295 * and the console driver list. 2296 * 2297 * While the console_lock was held, console output may have been buffered 2298 * by printk(). If this is the case, console_unlock(); emits 2299 * the output prior to releasing the lock. 2300 * 2301 * If there is output waiting, we wake /dev/kmsg and syslog() users. 2302 * 2303 * console_unlock(); may be called from any context. 2304 */ 2305 void console_unlock(void) 2306 { 2307 static char ext_text[CONSOLE_EXT_LOG_MAX]; 2308 static char text[LOG_LINE_MAX + PREFIX_MAX]; 2309 unsigned long flags; 2310 bool do_cond_resched, retry; 2311 2312 if (console_suspended) { 2313 up_console_sem(); 2314 return; 2315 } 2316 2317 /* 2318 * Console drivers are called with interrupts disabled, so 2319 * @console_may_schedule should be cleared before; however, we may 2320 * end up dumping a lot of lines, for example, if called from 2321 * console registration path, and should invoke cond_resched() 2322 * between lines if allowable. Not doing so can cause a very long 2323 * scheduling stall on a slow console leading to RCU stall and 2324 * softlockup warnings which exacerbate the issue with more 2325 * messages practically incapacitating the system. 2326 * 2327 * console_trylock() is not able to detect the preemptive 2328 * context reliably. Therefore the value must be stored before 2329 * and cleared after the the "again" goto label. 2330 */ 2331 do_cond_resched = console_may_schedule; 2332 again: 2333 console_may_schedule = 0; 2334 2335 /* 2336 * We released the console_sem lock, so we need to recheck if 2337 * cpu is online and (if not) is there at least one CON_ANYTIME 2338 * console. 2339 */ 2340 if (!can_use_console()) { 2341 console_locked = 0; 2342 up_console_sem(); 2343 return; 2344 } 2345 2346 for (;;) { 2347 struct printk_log *msg; 2348 size_t ext_len = 0; 2349 size_t len; 2350 2351 printk_safe_enter_irqsave(flags); 2352 raw_spin_lock(&logbuf_lock); 2353 if (console_seq < log_first_seq) { 2354 len = sprintf(text, "** %u printk messages dropped **\n", 2355 (unsigned)(log_first_seq - console_seq)); 2356 2357 /* messages are gone, move to first one */ 2358 console_seq = log_first_seq; 2359 console_idx = log_first_idx; 2360 } else { 2361 len = 0; 2362 } 2363 skip: 2364 if (console_seq == log_next_seq) 2365 break; 2366 2367 msg = log_from_idx(console_idx); 2368 if (suppress_message_printing(msg->level)) { 2369 /* 2370 * Skip record we have buffered and already printed 2371 * directly to the console when we received it, and 2372 * record that has level above the console loglevel. 2373 */ 2374 console_idx = log_next(console_idx); 2375 console_seq++; 2376 goto skip; 2377 } 2378 2379 len += msg_print_text(msg, 2380 console_msg_format & MSG_FORMAT_SYSLOG, 2381 text + len, 2382 sizeof(text) - len); 2383 if (nr_ext_console_drivers) { 2384 ext_len = msg_print_ext_header(ext_text, 2385 sizeof(ext_text), 2386 msg, console_seq); 2387 ext_len += msg_print_ext_body(ext_text + ext_len, 2388 sizeof(ext_text) - ext_len, 2389 log_dict(msg), msg->dict_len, 2390 log_text(msg), msg->text_len); 2391 } 2392 console_idx = log_next(console_idx); 2393 console_seq++; 2394 raw_spin_unlock(&logbuf_lock); 2395 2396 /* 2397 * While actively printing out messages, if another printk() 2398 * were to occur on another CPU, it may wait for this one to 2399 * finish. This task can not be preempted if there is a 2400 * waiter waiting to take over. 2401 */ 2402 console_lock_spinning_enable(); 2403 2404 stop_critical_timings(); /* don't trace print latency */ 2405 call_console_drivers(ext_text, ext_len, text, len); 2406 start_critical_timings(); 2407 2408 if (console_lock_spinning_disable_and_check()) { 2409 printk_safe_exit_irqrestore(flags); 2410 return; 2411 } 2412 2413 printk_safe_exit_irqrestore(flags); 2414 2415 if (do_cond_resched) 2416 cond_resched(); 2417 } 2418 2419 console_locked = 0; 2420 2421 /* Release the exclusive_console once it is used */ 2422 if (unlikely(exclusive_console)) 2423 exclusive_console = NULL; 2424 2425 raw_spin_unlock(&logbuf_lock); 2426 2427 up_console_sem(); 2428 2429 /* 2430 * Someone could have filled up the buffer again, so re-check if there's 2431 * something to flush. In case we cannot trylock the console_sem again, 2432 * there's a new owner and the console_unlock() from them will do the 2433 * flush, no worries. 2434 */ 2435 raw_spin_lock(&logbuf_lock); 2436 retry = console_seq != log_next_seq; 2437 raw_spin_unlock(&logbuf_lock); 2438 printk_safe_exit_irqrestore(flags); 2439 2440 if (retry && console_trylock()) 2441 goto again; 2442 } 2443 EXPORT_SYMBOL(console_unlock); 2444 2445 /** 2446 * console_conditional_schedule - yield the CPU if required 2447 * 2448 * If the console code is currently allowed to sleep, and 2449 * if this CPU should yield the CPU to another task, do 2450 * so here. 2451 * 2452 * Must be called within console_lock();. 2453 */ 2454 void __sched console_conditional_schedule(void) 2455 { 2456 if (console_may_schedule) 2457 cond_resched(); 2458 } 2459 EXPORT_SYMBOL(console_conditional_schedule); 2460 2461 void console_unblank(void) 2462 { 2463 struct console *c; 2464 2465 /* 2466 * console_unblank can no longer be called in interrupt context unless 2467 * oops_in_progress is set to 1.. 2468 */ 2469 if (oops_in_progress) { 2470 if (down_trylock_console_sem() != 0) 2471 return; 2472 } else 2473 console_lock(); 2474 2475 console_locked = 1; 2476 console_may_schedule = 0; 2477 for_each_console(c) 2478 if ((c->flags & CON_ENABLED) && c->unblank) 2479 c->unblank(); 2480 console_unlock(); 2481 } 2482 2483 /** 2484 * console_flush_on_panic - flush console content on panic 2485 * 2486 * Immediately output all pending messages no matter what. 2487 */ 2488 void console_flush_on_panic(void) 2489 { 2490 /* 2491 * If someone else is holding the console lock, trylock will fail 2492 * and may_schedule may be set. Ignore and proceed to unlock so 2493 * that messages are flushed out. As this can be called from any 2494 * context and we don't want to get preempted while flushing, 2495 * ensure may_schedule is cleared. 2496 */ 2497 console_trylock(); 2498 console_may_schedule = 0; 2499 console_unlock(); 2500 } 2501 2502 /* 2503 * Return the console tty driver structure and its associated index 2504 */ 2505 struct tty_driver *console_device(int *index) 2506 { 2507 struct console *c; 2508 struct tty_driver *driver = NULL; 2509 2510 console_lock(); 2511 for_each_console(c) { 2512 if (!c->device) 2513 continue; 2514 driver = c->device(c, index); 2515 if (driver) 2516 break; 2517 } 2518 console_unlock(); 2519 return driver; 2520 } 2521 2522 /* 2523 * Prevent further output on the passed console device so that (for example) 2524 * serial drivers can disable console output before suspending a port, and can 2525 * re-enable output afterwards. 2526 */ 2527 void console_stop(struct console *console) 2528 { 2529 console_lock(); 2530 console->flags &= ~CON_ENABLED; 2531 console_unlock(); 2532 } 2533 EXPORT_SYMBOL(console_stop); 2534 2535 void console_start(struct console *console) 2536 { 2537 console_lock(); 2538 console->flags |= CON_ENABLED; 2539 console_unlock(); 2540 } 2541 EXPORT_SYMBOL(console_start); 2542 2543 static int __read_mostly keep_bootcon; 2544 2545 static int __init keep_bootcon_setup(char *str) 2546 { 2547 keep_bootcon = 1; 2548 pr_info("debug: skip boot console de-registration.\n"); 2549 2550 return 0; 2551 } 2552 2553 early_param("keep_bootcon", keep_bootcon_setup); 2554 2555 /* 2556 * The console driver calls this routine during kernel initialization 2557 * to register the console printing procedure with printk() and to 2558 * print any messages that were printed by the kernel before the 2559 * console driver was initialized. 2560 * 2561 * This can happen pretty early during the boot process (because of 2562 * early_printk) - sometimes before setup_arch() completes - be careful 2563 * of what kernel features are used - they may not be initialised yet. 2564 * 2565 * There are two types of consoles - bootconsoles (early_printk) and 2566 * "real" consoles (everything which is not a bootconsole) which are 2567 * handled differently. 2568 * - Any number of bootconsoles can be registered at any time. 2569 * - As soon as a "real" console is registered, all bootconsoles 2570 * will be unregistered automatically. 2571 * - Once a "real" console is registered, any attempt to register a 2572 * bootconsoles will be rejected 2573 */ 2574 void register_console(struct console *newcon) 2575 { 2576 int i; 2577 unsigned long flags; 2578 struct console *bcon = NULL; 2579 struct console_cmdline *c; 2580 static bool has_preferred; 2581 2582 if (console_drivers) 2583 for_each_console(bcon) 2584 if (WARN(bcon == newcon, 2585 "console '%s%d' already registered\n", 2586 bcon->name, bcon->index)) 2587 return; 2588 2589 /* 2590 * before we register a new CON_BOOT console, make sure we don't 2591 * already have a valid console 2592 */ 2593 if (console_drivers && newcon->flags & CON_BOOT) { 2594 /* find the last or real console */ 2595 for_each_console(bcon) { 2596 if (!(bcon->flags & CON_BOOT)) { 2597 pr_info("Too late to register bootconsole %s%d\n", 2598 newcon->name, newcon->index); 2599 return; 2600 } 2601 } 2602 } 2603 2604 if (console_drivers && console_drivers->flags & CON_BOOT) 2605 bcon = console_drivers; 2606 2607 if (!has_preferred || bcon || !console_drivers) 2608 has_preferred = preferred_console >= 0; 2609 2610 /* 2611 * See if we want to use this console driver. If we 2612 * didn't select a console we take the first one 2613 * that registers here. 2614 */ 2615 if (!has_preferred) { 2616 if (newcon->index < 0) 2617 newcon->index = 0; 2618 if (newcon->setup == NULL || 2619 newcon->setup(newcon, NULL) == 0) { 2620 newcon->flags |= CON_ENABLED; 2621 if (newcon->device) { 2622 newcon->flags |= CON_CONSDEV; 2623 has_preferred = true; 2624 } 2625 } 2626 } 2627 2628 /* 2629 * See if this console matches one we selected on 2630 * the command line. 2631 */ 2632 for (i = 0, c = console_cmdline; 2633 i < MAX_CMDLINECONSOLES && c->name[0]; 2634 i++, c++) { 2635 if (!newcon->match || 2636 newcon->match(newcon, c->name, c->index, c->options) != 0) { 2637 /* default matching */ 2638 BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name)); 2639 if (strcmp(c->name, newcon->name) != 0) 2640 continue; 2641 if (newcon->index >= 0 && 2642 newcon->index != c->index) 2643 continue; 2644 if (newcon->index < 0) 2645 newcon->index = c->index; 2646 2647 if (_braille_register_console(newcon, c)) 2648 return; 2649 2650 if (newcon->setup && 2651 newcon->setup(newcon, c->options) != 0) 2652 break; 2653 } 2654 2655 newcon->flags |= CON_ENABLED; 2656 if (i == preferred_console) { 2657 newcon->flags |= CON_CONSDEV; 2658 has_preferred = true; 2659 } 2660 break; 2661 } 2662 2663 if (!(newcon->flags & CON_ENABLED)) 2664 return; 2665 2666 /* 2667 * If we have a bootconsole, and are switching to a real console, 2668 * don't print everything out again, since when the boot console, and 2669 * the real console are the same physical device, it's annoying to 2670 * see the beginning boot messages twice 2671 */ 2672 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) 2673 newcon->flags &= ~CON_PRINTBUFFER; 2674 2675 /* 2676 * Put this console in the list - keep the 2677 * preferred driver at the head of the list. 2678 */ 2679 console_lock(); 2680 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) { 2681 newcon->next = console_drivers; 2682 console_drivers = newcon; 2683 if (newcon->next) 2684 newcon->next->flags &= ~CON_CONSDEV; 2685 } else { 2686 newcon->next = console_drivers->next; 2687 console_drivers->next = newcon; 2688 } 2689 2690 if (newcon->flags & CON_EXTENDED) 2691 if (!nr_ext_console_drivers++) 2692 pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n"); 2693 2694 if (newcon->flags & CON_PRINTBUFFER) { 2695 /* 2696 * console_unlock(); will print out the buffered messages 2697 * for us. 2698 */ 2699 logbuf_lock_irqsave(flags); 2700 console_seq = syslog_seq; 2701 console_idx = syslog_idx; 2702 logbuf_unlock_irqrestore(flags); 2703 /* 2704 * We're about to replay the log buffer. Only do this to the 2705 * just-registered console to avoid excessive message spam to 2706 * the already-registered consoles. 2707 */ 2708 exclusive_console = newcon; 2709 } 2710 console_unlock(); 2711 console_sysfs_notify(); 2712 2713 /* 2714 * By unregistering the bootconsoles after we enable the real console 2715 * we get the "console xxx enabled" message on all the consoles - 2716 * boot consoles, real consoles, etc - this is to ensure that end 2717 * users know there might be something in the kernel's log buffer that 2718 * went to the bootconsole (that they do not see on the real console) 2719 */ 2720 pr_info("%sconsole [%s%d] enabled\n", 2721 (newcon->flags & CON_BOOT) ? "boot" : "" , 2722 newcon->name, newcon->index); 2723 if (bcon && 2724 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) && 2725 !keep_bootcon) { 2726 /* We need to iterate through all boot consoles, to make 2727 * sure we print everything out, before we unregister them. 2728 */ 2729 for_each_console(bcon) 2730 if (bcon->flags & CON_BOOT) 2731 unregister_console(bcon); 2732 } 2733 } 2734 EXPORT_SYMBOL(register_console); 2735 2736 int unregister_console(struct console *console) 2737 { 2738 struct console *a, *b; 2739 int res; 2740 2741 pr_info("%sconsole [%s%d] disabled\n", 2742 (console->flags & CON_BOOT) ? "boot" : "" , 2743 console->name, console->index); 2744 2745 res = _braille_unregister_console(console); 2746 if (res) 2747 return res; 2748 2749 res = 1; 2750 console_lock(); 2751 if (console_drivers == console) { 2752 console_drivers=console->next; 2753 res = 0; 2754 } else if (console_drivers) { 2755 for (a=console_drivers->next, b=console_drivers ; 2756 a; b=a, a=b->next) { 2757 if (a == console) { 2758 b->next = a->next; 2759 res = 0; 2760 break; 2761 } 2762 } 2763 } 2764 2765 if (!res && (console->flags & CON_EXTENDED)) 2766 nr_ext_console_drivers--; 2767 2768 /* 2769 * If this isn't the last console and it has CON_CONSDEV set, we 2770 * need to set it on the next preferred console. 2771 */ 2772 if (console_drivers != NULL && console->flags & CON_CONSDEV) 2773 console_drivers->flags |= CON_CONSDEV; 2774 2775 console->flags &= ~CON_ENABLED; 2776 console_unlock(); 2777 console_sysfs_notify(); 2778 return res; 2779 } 2780 EXPORT_SYMBOL(unregister_console); 2781 2782 /* 2783 * Initialize the console device. This is called *early*, so 2784 * we can't necessarily depend on lots of kernel help here. 2785 * Just do some early initializations, and do the complex setup 2786 * later. 2787 */ 2788 void __init console_init(void) 2789 { 2790 int ret; 2791 initcall_t call; 2792 initcall_entry_t *ce; 2793 2794 /* Setup the default TTY line discipline. */ 2795 n_tty_init(); 2796 2797 /* 2798 * set up the console device so that later boot sequences can 2799 * inform about problems etc.. 2800 */ 2801 ce = __con_initcall_start; 2802 trace_initcall_level("console"); 2803 while (ce < __con_initcall_end) { 2804 call = initcall_from_entry(ce); 2805 trace_initcall_start(call); 2806 ret = call(); 2807 trace_initcall_finish(call, ret); 2808 ce++; 2809 } 2810 } 2811 2812 /* 2813 * Some boot consoles access data that is in the init section and which will 2814 * be discarded after the initcalls have been run. To make sure that no code 2815 * will access this data, unregister the boot consoles in a late initcall. 2816 * 2817 * If for some reason, such as deferred probe or the driver being a loadable 2818 * module, the real console hasn't registered yet at this point, there will 2819 * be a brief interval in which no messages are logged to the console, which 2820 * makes it difficult to diagnose problems that occur during this time. 2821 * 2822 * To mitigate this problem somewhat, only unregister consoles whose memory 2823 * intersects with the init section. Note that all other boot consoles will 2824 * get unregistred when the real preferred console is registered. 2825 */ 2826 static int __init printk_late_init(void) 2827 { 2828 struct console *con; 2829 int ret; 2830 2831 for_each_console(con) { 2832 if (!(con->flags & CON_BOOT)) 2833 continue; 2834 2835 /* Check addresses that might be used for enabled consoles. */ 2836 if (init_section_intersects(con, sizeof(*con)) || 2837 init_section_contains(con->write, 0) || 2838 init_section_contains(con->read, 0) || 2839 init_section_contains(con->device, 0) || 2840 init_section_contains(con->unblank, 0) || 2841 init_section_contains(con->data, 0)) { 2842 /* 2843 * Please, consider moving the reported consoles out 2844 * of the init section. 2845 */ 2846 pr_warn("bootconsole [%s%d] uses init memory and must be disabled even before the real one is ready\n", 2847 con->name, con->index); 2848 unregister_console(con); 2849 } 2850 } 2851 ret = cpuhp_setup_state_nocalls(CPUHP_PRINTK_DEAD, "printk:dead", NULL, 2852 console_cpu_notify); 2853 WARN_ON(ret < 0); 2854 ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "printk:online", 2855 console_cpu_notify, NULL); 2856 WARN_ON(ret < 0); 2857 return 0; 2858 } 2859 late_initcall(printk_late_init); 2860 2861 #if defined CONFIG_PRINTK 2862 /* 2863 * Delayed printk version, for scheduler-internal messages: 2864 */ 2865 #define PRINTK_PENDING_WAKEUP 0x01 2866 #define PRINTK_PENDING_OUTPUT 0x02 2867 2868 static DEFINE_PER_CPU(int, printk_pending); 2869 2870 static void wake_up_klogd_work_func(struct irq_work *irq_work) 2871 { 2872 int pending = __this_cpu_xchg(printk_pending, 0); 2873 2874 if (pending & PRINTK_PENDING_OUTPUT) { 2875 /* If trylock fails, someone else is doing the printing */ 2876 if (console_trylock()) 2877 console_unlock(); 2878 } 2879 2880 if (pending & PRINTK_PENDING_WAKEUP) 2881 wake_up_interruptible(&log_wait); 2882 } 2883 2884 static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = { 2885 .func = wake_up_klogd_work_func, 2886 .flags = IRQ_WORK_LAZY, 2887 }; 2888 2889 void wake_up_klogd(void) 2890 { 2891 preempt_disable(); 2892 if (waitqueue_active(&log_wait)) { 2893 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP); 2894 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work)); 2895 } 2896 preempt_enable(); 2897 } 2898 2899 void defer_console_output(void) 2900 { 2901 preempt_disable(); 2902 __this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT); 2903 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work)); 2904 preempt_enable(); 2905 } 2906 2907 int vprintk_deferred(const char *fmt, va_list args) 2908 { 2909 int r; 2910 2911 r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, 0, fmt, args); 2912 defer_console_output(); 2913 2914 return r; 2915 } 2916 2917 int printk_deferred(const char *fmt, ...) 2918 { 2919 va_list args; 2920 int r; 2921 2922 va_start(args, fmt); 2923 r = vprintk_deferred(fmt, args); 2924 va_end(args); 2925 2926 return r; 2927 } 2928 2929 /* 2930 * printk rate limiting, lifted from the networking subsystem. 2931 * 2932 * This enforces a rate limit: not more than 10 kernel messages 2933 * every 5s to make a denial-of-service attack impossible. 2934 */ 2935 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10); 2936 2937 int __printk_ratelimit(const char *func) 2938 { 2939 return ___ratelimit(&printk_ratelimit_state, func); 2940 } 2941 EXPORT_SYMBOL(__printk_ratelimit); 2942 2943 /** 2944 * printk_timed_ratelimit - caller-controlled printk ratelimiting 2945 * @caller_jiffies: pointer to caller's state 2946 * @interval_msecs: minimum interval between prints 2947 * 2948 * printk_timed_ratelimit() returns true if more than @interval_msecs 2949 * milliseconds have elapsed since the last time printk_timed_ratelimit() 2950 * returned true. 2951 */ 2952 bool printk_timed_ratelimit(unsigned long *caller_jiffies, 2953 unsigned int interval_msecs) 2954 { 2955 unsigned long elapsed = jiffies - *caller_jiffies; 2956 2957 if (*caller_jiffies && elapsed <= msecs_to_jiffies(interval_msecs)) 2958 return false; 2959 2960 *caller_jiffies = jiffies; 2961 return true; 2962 } 2963 EXPORT_SYMBOL(printk_timed_ratelimit); 2964 2965 static DEFINE_SPINLOCK(dump_list_lock); 2966 static LIST_HEAD(dump_list); 2967 2968 /** 2969 * kmsg_dump_register - register a kernel log dumper. 2970 * @dumper: pointer to the kmsg_dumper structure 2971 * 2972 * Adds a kernel log dumper to the system. The dump callback in the 2973 * structure will be called when the kernel oopses or panics and must be 2974 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise. 2975 */ 2976 int kmsg_dump_register(struct kmsg_dumper *dumper) 2977 { 2978 unsigned long flags; 2979 int err = -EBUSY; 2980 2981 /* The dump callback needs to be set */ 2982 if (!dumper->dump) 2983 return -EINVAL; 2984 2985 spin_lock_irqsave(&dump_list_lock, flags); 2986 /* Don't allow registering multiple times */ 2987 if (!dumper->registered) { 2988 dumper->registered = 1; 2989 list_add_tail_rcu(&dumper->list, &dump_list); 2990 err = 0; 2991 } 2992 spin_unlock_irqrestore(&dump_list_lock, flags); 2993 2994 return err; 2995 } 2996 EXPORT_SYMBOL_GPL(kmsg_dump_register); 2997 2998 /** 2999 * kmsg_dump_unregister - unregister a kmsg dumper. 3000 * @dumper: pointer to the kmsg_dumper structure 3001 * 3002 * Removes a dump device from the system. Returns zero on success and 3003 * %-EINVAL otherwise. 3004 */ 3005 int kmsg_dump_unregister(struct kmsg_dumper *dumper) 3006 { 3007 unsigned long flags; 3008 int err = -EINVAL; 3009 3010 spin_lock_irqsave(&dump_list_lock, flags); 3011 if (dumper->registered) { 3012 dumper->registered = 0; 3013 list_del_rcu(&dumper->list); 3014 err = 0; 3015 } 3016 spin_unlock_irqrestore(&dump_list_lock, flags); 3017 synchronize_rcu(); 3018 3019 return err; 3020 } 3021 EXPORT_SYMBOL_GPL(kmsg_dump_unregister); 3022 3023 static bool always_kmsg_dump; 3024 module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR); 3025 3026 /** 3027 * kmsg_dump - dump kernel log to kernel message dumpers. 3028 * @reason: the reason (oops, panic etc) for dumping 3029 * 3030 * Call each of the registered dumper's dump() callback, which can 3031 * retrieve the kmsg records with kmsg_dump_get_line() or 3032 * kmsg_dump_get_buffer(). 3033 */ 3034 void kmsg_dump(enum kmsg_dump_reason reason) 3035 { 3036 struct kmsg_dumper *dumper; 3037 unsigned long flags; 3038 3039 if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump) 3040 return; 3041 3042 rcu_read_lock(); 3043 list_for_each_entry_rcu(dumper, &dump_list, list) { 3044 if (dumper->max_reason && reason > dumper->max_reason) 3045 continue; 3046 3047 /* initialize iterator with data about the stored records */ 3048 dumper->active = true; 3049 3050 logbuf_lock_irqsave(flags); 3051 dumper->cur_seq = clear_seq; 3052 dumper->cur_idx = clear_idx; 3053 dumper->next_seq = log_next_seq; 3054 dumper->next_idx = log_next_idx; 3055 logbuf_unlock_irqrestore(flags); 3056 3057 /* invoke dumper which will iterate over records */ 3058 dumper->dump(dumper, reason); 3059 3060 /* reset iterator */ 3061 dumper->active = false; 3062 } 3063 rcu_read_unlock(); 3064 } 3065 3066 /** 3067 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version) 3068 * @dumper: registered kmsg dumper 3069 * @syslog: include the "<4>" prefixes 3070 * @line: buffer to copy the line to 3071 * @size: maximum size of the buffer 3072 * @len: length of line placed into buffer 3073 * 3074 * Start at the beginning of the kmsg buffer, with the oldest kmsg 3075 * record, and copy one record into the provided buffer. 3076 * 3077 * Consecutive calls will return the next available record moving 3078 * towards the end of the buffer with the youngest messages. 3079 * 3080 * A return value of FALSE indicates that there are no more records to 3081 * read. 3082 * 3083 * The function is similar to kmsg_dump_get_line(), but grabs no locks. 3084 */ 3085 bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog, 3086 char *line, size_t size, size_t *len) 3087 { 3088 struct printk_log *msg; 3089 size_t l = 0; 3090 bool ret = false; 3091 3092 if (!dumper->active) 3093 goto out; 3094 3095 if (dumper->cur_seq < log_first_seq) { 3096 /* messages are gone, move to first available one */ 3097 dumper->cur_seq = log_first_seq; 3098 dumper->cur_idx = log_first_idx; 3099 } 3100 3101 /* last entry */ 3102 if (dumper->cur_seq >= log_next_seq) 3103 goto out; 3104 3105 msg = log_from_idx(dumper->cur_idx); 3106 l = msg_print_text(msg, syslog, line, size); 3107 3108 dumper->cur_idx = log_next(dumper->cur_idx); 3109 dumper->cur_seq++; 3110 ret = true; 3111 out: 3112 if (len) 3113 *len = l; 3114 return ret; 3115 } 3116 3117 /** 3118 * kmsg_dump_get_line - retrieve one kmsg log line 3119 * @dumper: registered kmsg dumper 3120 * @syslog: include the "<4>" prefixes 3121 * @line: buffer to copy the line to 3122 * @size: maximum size of the buffer 3123 * @len: length of line placed into buffer 3124 * 3125 * Start at the beginning of the kmsg buffer, with the oldest kmsg 3126 * record, and copy one record into the provided buffer. 3127 * 3128 * Consecutive calls will return the next available record moving 3129 * towards the end of the buffer with the youngest messages. 3130 * 3131 * A return value of FALSE indicates that there are no more records to 3132 * read. 3133 */ 3134 bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog, 3135 char *line, size_t size, size_t *len) 3136 { 3137 unsigned long flags; 3138 bool ret; 3139 3140 logbuf_lock_irqsave(flags); 3141 ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len); 3142 logbuf_unlock_irqrestore(flags); 3143 3144 return ret; 3145 } 3146 EXPORT_SYMBOL_GPL(kmsg_dump_get_line); 3147 3148 /** 3149 * kmsg_dump_get_buffer - copy kmsg log lines 3150 * @dumper: registered kmsg dumper 3151 * @syslog: include the "<4>" prefixes 3152 * @buf: buffer to copy the line to 3153 * @size: maximum size of the buffer 3154 * @len: length of line placed into buffer 3155 * 3156 * Start at the end of the kmsg buffer and fill the provided buffer 3157 * with as many of the the *youngest* kmsg records that fit into it. 3158 * If the buffer is large enough, all available kmsg records will be 3159 * copied with a single call. 3160 * 3161 * Consecutive calls will fill the buffer with the next block of 3162 * available older records, not including the earlier retrieved ones. 3163 * 3164 * A return value of FALSE indicates that there are no more records to 3165 * read. 3166 */ 3167 bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog, 3168 char *buf, size_t size, size_t *len) 3169 { 3170 unsigned long flags; 3171 u64 seq; 3172 u32 idx; 3173 u64 next_seq; 3174 u32 next_idx; 3175 size_t l = 0; 3176 bool ret = false; 3177 3178 if (!dumper->active) 3179 goto out; 3180 3181 logbuf_lock_irqsave(flags); 3182 if (dumper->cur_seq < log_first_seq) { 3183 /* messages are gone, move to first available one */ 3184 dumper->cur_seq = log_first_seq; 3185 dumper->cur_idx = log_first_idx; 3186 } 3187 3188 /* last entry */ 3189 if (dumper->cur_seq >= dumper->next_seq) { 3190 logbuf_unlock_irqrestore(flags); 3191 goto out; 3192 } 3193 3194 /* calculate length of entire buffer */ 3195 seq = dumper->cur_seq; 3196 idx = dumper->cur_idx; 3197 while (seq < dumper->next_seq) { 3198 struct printk_log *msg = log_from_idx(idx); 3199 3200 l += msg_print_text(msg, true, NULL, 0); 3201 idx = log_next(idx); 3202 seq++; 3203 } 3204 3205 /* move first record forward until length fits into the buffer */ 3206 seq = dumper->cur_seq; 3207 idx = dumper->cur_idx; 3208 while (l > size && seq < dumper->next_seq) { 3209 struct printk_log *msg = log_from_idx(idx); 3210 3211 l -= msg_print_text(msg, true, NULL, 0); 3212 idx = log_next(idx); 3213 seq++; 3214 } 3215 3216 /* last message in next interation */ 3217 next_seq = seq; 3218 next_idx = idx; 3219 3220 l = 0; 3221 while (seq < dumper->next_seq) { 3222 struct printk_log *msg = log_from_idx(idx); 3223 3224 l += msg_print_text(msg, syslog, buf + l, size - l); 3225 idx = log_next(idx); 3226 seq++; 3227 } 3228 3229 dumper->next_seq = next_seq; 3230 dumper->next_idx = next_idx; 3231 ret = true; 3232 logbuf_unlock_irqrestore(flags); 3233 out: 3234 if (len) 3235 *len = l; 3236 return ret; 3237 } 3238 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer); 3239 3240 /** 3241 * kmsg_dump_rewind_nolock - reset the interator (unlocked version) 3242 * @dumper: registered kmsg dumper 3243 * 3244 * Reset the dumper's iterator so that kmsg_dump_get_line() and 3245 * kmsg_dump_get_buffer() can be called again and used multiple 3246 * times within the same dumper.dump() callback. 3247 * 3248 * The function is similar to kmsg_dump_rewind(), but grabs no locks. 3249 */ 3250 void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper) 3251 { 3252 dumper->cur_seq = clear_seq; 3253 dumper->cur_idx = clear_idx; 3254 dumper->next_seq = log_next_seq; 3255 dumper->next_idx = log_next_idx; 3256 } 3257 3258 /** 3259 * kmsg_dump_rewind - reset the interator 3260 * @dumper: registered kmsg dumper 3261 * 3262 * Reset the dumper's iterator so that kmsg_dump_get_line() and 3263 * kmsg_dump_get_buffer() can be called again and used multiple 3264 * times within the same dumper.dump() callback. 3265 */ 3266 void kmsg_dump_rewind(struct kmsg_dumper *dumper) 3267 { 3268 unsigned long flags; 3269 3270 logbuf_lock_irqsave(flags); 3271 kmsg_dump_rewind_nolock(dumper); 3272 logbuf_unlock_irqrestore(flags); 3273 } 3274 EXPORT_SYMBOL_GPL(kmsg_dump_rewind); 3275 3276 #endif 3277