| // SPDX-License-Identifier: GPL-2.0-only |
| /* |
| * linux/kernel/printk.c |
| * |
| * Copyright (C) 1991, 1992 Linus Torvalds |
| * |
| * Modified to make sys_syslog() more flexible: added commands to |
| * return the last 4k of kernel messages, regardless of whether |
| * they've been read or not. Added option to suppress kernel printk's |
| * to the console. Added hook for sending the console messages |
| * elsewhere, in preparation for a serial line console (someday). |
| * Ted Ts'o, 2/11/93. |
| * Modified for sysctl support, 1/8/97, Chris Horn. |
| * Fixed SMP synchronization, 08/08/99, Manfred Spraul |
| * manfred@colorfullife.com |
| * Rewrote bits to get rid of console_lock |
| * 01Mar01 Andrew Morton |
| */ |
| |
| #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
| |
| #include <linux/kernel.h> |
| #include <linux/mm.h> |
| #include <linux/tty.h> |
| #include <linux/tty_driver.h> |
| #include <linux/console.h> |
| #include <linux/init.h> |
| #include <linux/jiffies.h> |
| #include <linux/nmi.h> |
| #include <linux/module.h> |
| #include <linux/moduleparam.h> |
| #include <linux/delay.h> |
| #include <linux/smp.h> |
| #include <linux/security.h> |
| #include <linux/memblock.h> |
| #include <linux/syscalls.h> |
| #include <linux/crash_core.h> |
| #include <linux/ratelimit.h> |
| #include <linux/kmsg_dump.h> |
| #include <linux/syslog.h> |
| #include <linux/cpu.h> |
| #include <linux/rculist.h> |
| #include <linux/poll.h> |
| #include <linux/irq_work.h> |
| #include <linux/ctype.h> |
| #include <linux/uio.h> |
| #include <linux/sched/clock.h> |
| #include <linux/sched/debug.h> |
| #include <linux/sched/task_stack.h> |
| |
| #include <linux/uaccess.h> |
| #include <asm/sections.h> |
| |
| #include <trace/events/initcall.h> |
| #define CREATE_TRACE_POINTS |
| #include <trace/events/printk.h> |
| |
| #include "printk_ringbuffer.h" |
| #include "console_cmdline.h" |
| #include "braille.h" |
| #include "internal.h" |
| |
| int console_printk[4] = { |
| CONSOLE_LOGLEVEL_DEFAULT, /* console_loglevel */ |
| MESSAGE_LOGLEVEL_DEFAULT, /* default_message_loglevel */ |
| CONSOLE_LOGLEVEL_MIN, /* minimum_console_loglevel */ |
| CONSOLE_LOGLEVEL_DEFAULT, /* default_console_loglevel */ |
| }; |
| EXPORT_SYMBOL_GPL(console_printk); |
| |
| atomic_t ignore_console_lock_warning __read_mostly = ATOMIC_INIT(0); |
| EXPORT_SYMBOL(ignore_console_lock_warning); |
| |
| /* |
| * Low level drivers may need that to know if they can schedule in |
| * their unblank() callback or not. So let's export it. |
| */ |
| int oops_in_progress; |
| EXPORT_SYMBOL(oops_in_progress); |
| |
| /* |
| * console_sem protects the console_drivers list, and also |
| * provides serialisation for access to the entire console |
| * driver system. |
| */ |
| static DEFINE_SEMAPHORE(console_sem); |
| struct console *console_drivers; |
| EXPORT_SYMBOL_GPL(console_drivers); |
| |
| /* |
| * System may need to suppress printk message under certain |
| * circumstances, like after kernel panic happens. |
| */ |
| int __read_mostly suppress_printk; |
| |
| /* |
| * During panic, heavy printk by other CPUs can delay the |
| * panic and risk deadlock on console resources. |
| */ |
| static int __read_mostly suppress_panic_printk; |
| |
| #ifdef CONFIG_LOCKDEP |
| static struct lockdep_map console_lock_dep_map = { |
| .name = "console_lock" |
| }; |
| #endif |
| |
| enum devkmsg_log_bits { |
| __DEVKMSG_LOG_BIT_ON = 0, |
| __DEVKMSG_LOG_BIT_OFF, |
| __DEVKMSG_LOG_BIT_LOCK, |
| }; |
| |
| enum devkmsg_log_masks { |
| DEVKMSG_LOG_MASK_ON = BIT(__DEVKMSG_LOG_BIT_ON), |
| DEVKMSG_LOG_MASK_OFF = BIT(__DEVKMSG_LOG_BIT_OFF), |
| DEVKMSG_LOG_MASK_LOCK = BIT(__DEVKMSG_LOG_BIT_LOCK), |
| }; |
| |
| /* Keep both the 'on' and 'off' bits clear, i.e. ratelimit by default: */ |
| #define DEVKMSG_LOG_MASK_DEFAULT 0 |
| |
| static unsigned int __read_mostly devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT; |
| |
| static int __control_devkmsg(char *str) |
| { |
| size_t len; |
| |
| if (!str) |
| return -EINVAL; |
| |
| len = str_has_prefix(str, "on"); |
| if (len) { |
| devkmsg_log = DEVKMSG_LOG_MASK_ON; |
| return len; |
| } |
| |
| len = str_has_prefix(str, "off"); |
| if (len) { |
| devkmsg_log = DEVKMSG_LOG_MASK_OFF; |
| return len; |
| } |
| |
| len = str_has_prefix(str, "ratelimit"); |
| if (len) { |
| devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT; |
| return len; |
| } |
| |
| return -EINVAL; |
| } |
| |
| static int __init control_devkmsg(char *str) |
| { |
| if (__control_devkmsg(str) < 0) { |
| pr_warn("printk.devkmsg: bad option string '%s'\n", str); |
| return 1; |
| } |
| |
| /* |
| * Set sysctl string accordingly: |
| */ |
| if (devkmsg_log == DEVKMSG_LOG_MASK_ON) |
| strcpy(devkmsg_log_str, "on"); |
| else if (devkmsg_log == DEVKMSG_LOG_MASK_OFF) |
| strcpy(devkmsg_log_str, "off"); |
| /* else "ratelimit" which is set by default. */ |
| |
| /* |
| * Sysctl cannot change it anymore. The kernel command line setting of |
| * this parameter is to force the setting to be permanent throughout the |
| * runtime of the system. This is a precation measure against userspace |
| * trying to be a smarta** and attempting to change it up on us. |
| */ |
| devkmsg_log |= DEVKMSG_LOG_MASK_LOCK; |
| |
| return 1; |
| } |
| __setup("printk.devkmsg=", control_devkmsg); |
| |
| char devkmsg_log_str[DEVKMSG_STR_MAX_SIZE] = "ratelimit"; |
| #if defined(CONFIG_PRINTK) && defined(CONFIG_SYSCTL) |
| int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write, |
| void *buffer, size_t *lenp, loff_t *ppos) |
| { |
| char old_str[DEVKMSG_STR_MAX_SIZE]; |
| unsigned int old; |
| int err; |
| |
| if (write) { |
| if (devkmsg_log & DEVKMSG_LOG_MASK_LOCK) |
| return -EINVAL; |
| |
| old = devkmsg_log; |
| strncpy(old_str, devkmsg_log_str, DEVKMSG_STR_MAX_SIZE); |
| } |
| |
| err = proc_dostring(table, write, buffer, lenp, ppos); |
| if (err) |
| return err; |
| |
| if (write) { |
| err = __control_devkmsg(devkmsg_log_str); |
| |
| /* |
| * Do not accept an unknown string OR a known string with |
| * trailing crap... |
| */ |
| if (err < 0 || (err + 1 != *lenp)) { |
| |
| /* ... and restore old setting. */ |
| devkmsg_log = old; |
| strncpy(devkmsg_log_str, old_str, DEVKMSG_STR_MAX_SIZE); |
| |
| return -EINVAL; |
| } |
| } |
| |
| return 0; |
| } |
| #endif /* CONFIG_PRINTK && CONFIG_SYSCTL */ |
| |
| /* Number of registered extended console drivers. */ |
| static int nr_ext_console_drivers; |
| |
| /* |
| * Used to synchronize printing kthreads against direct printing via |
| * console_trylock/console_unlock. |
| * |
| * Values: |
| * -1 = console kthreads atomically blocked (via global trylock) |
| * 0 = no kthread printing, console not locked (via trylock) |
| * >0 = kthread(s) actively printing |
| * |
| * Note: For synchronizing against direct printing via |
| * console_lock/console_unlock, see the @lock variable in |
| * struct console. |
| */ |
| static atomic_t console_kthreads_active = ATOMIC_INIT(0); |
| |
| #define console_kthreads_atomic_tryblock() \ |
| (atomic_cmpxchg(&console_kthreads_active, 0, -1) == 0) |
| #define console_kthreads_atomic_unblock() \ |
| atomic_cmpxchg(&console_kthreads_active, -1, 0) |
| #define console_kthreads_atomically_blocked() \ |
| (atomic_read(&console_kthreads_active) == -1) |
| |
| #define console_kthread_printing_tryenter() \ |
| atomic_inc_unless_negative(&console_kthreads_active) |
| #define console_kthread_printing_exit() \ |
| atomic_dec(&console_kthreads_active) |
| |
| /* |
| * Helper macros to handle lockdep when locking/unlocking console_sem. We use |
| * macros instead of functions so that _RET_IP_ contains useful information. |
| */ |
| #define down_console_sem() do { \ |
| down(&console_sem);\ |
| mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\ |
| } while (0) |
| |
| static int __down_trylock_console_sem(unsigned long ip) |
| { |
| int lock_failed; |
| unsigned long flags; |
| |
| /* |
| * Here and in __up_console_sem() we need to be in safe mode, |
| * because spindump/WARN/etc from under console ->lock will |
| * deadlock in printk()->down_trylock_console_sem() otherwise. |
| */ |
| printk_safe_enter_irqsave(flags); |
| lock_failed = down_trylock(&console_sem); |
| printk_safe_exit_irqrestore(flags); |
| |
| if (lock_failed) |
| return 1; |
| mutex_acquire(&console_lock_dep_map, 0, 1, ip); |
| return 0; |
| } |
| #define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_) |
| |
| static void __up_console_sem(unsigned long ip) |
| { |
| unsigned long flags; |
| |
| mutex_release(&console_lock_dep_map, ip); |
| |
| printk_safe_enter_irqsave(flags); |
| up(&console_sem); |
| printk_safe_exit_irqrestore(flags); |
| } |
| #define up_console_sem() __up_console_sem(_RET_IP_) |
| |
| static bool panic_in_progress(void) |
| { |
| return unlikely(atomic_read(&panic_cpu) != PANIC_CPU_INVALID); |
| } |
| |
| /* |
| * Tracks whether kthread printers are all blocked. A value of true implies |
| * that the console is locked via console_lock() or the console is suspended. |
| * Writing to this variable requires holding @console_sem. |
| */ |
| static bool console_kthreads_blocked; |
| |
| /* |
| * Block all kthread printers from a schedulable context. |
| * |
| * Requires holding @console_sem. |
| */ |
| static void console_kthreads_block(void) |
| { |
| struct console *con; |
| |
| for_each_console(con) { |
| mutex_lock(&con->lock); |
| con->blocked = true; |
| mutex_unlock(&con->lock); |
| } |
| |
| console_kthreads_blocked = true; |
| } |
| |
| /* |
| * Unblock all kthread printers from a schedulable context. |
| * |
| * Requires holding @console_sem. |
| */ |
| static void console_kthreads_unblock(void) |
| { |
| struct console *con; |
| |
| for_each_console(con) { |
| mutex_lock(&con->lock); |
| con->blocked = false; |
| mutex_unlock(&con->lock); |
| } |
| |
| console_kthreads_blocked = false; |
| } |
| |
| static int console_suspended; |
| |
| /* |
| * Array of consoles built from command line options (console=) |
| */ |
| |
| #define MAX_CMDLINECONSOLES 8 |
| |
| static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES]; |
| |
| static int preferred_console = -1; |
| int console_set_on_cmdline; |
| EXPORT_SYMBOL(console_set_on_cmdline); |
| |
| /* Flag: console code may call schedule() */ |
| static int console_may_schedule; |
| |
| enum con_msg_format_flags { |
| MSG_FORMAT_DEFAULT = 0, |
| MSG_FORMAT_SYSLOG = (1 << 0), |
| }; |
| |
| static int console_msg_format = MSG_FORMAT_DEFAULT; |
| |
| /* |
| * The printk log buffer consists of a sequenced collection of records, each |
| * containing variable length message text. Every record also contains its |
| * own meta-data (@info). |
| * |
| * Every record meta-data carries the timestamp in microseconds, as well as |
| * the standard userspace syslog level and syslog facility. The usual kernel |
| * messages use LOG_KERN; userspace-injected messages always carry a matching |
| * syslog facility, by default LOG_USER. The origin of every message can be |
| * reliably determined that way. |
| * |
| * The human readable log message of a record is available in @text, the |
| * length of the message text in @text_len. The stored message is not |
| * terminated. |
| * |
| * Optionally, a record can carry a dictionary of properties (key/value |
| * pairs), to provide userspace with a machine-readable message context. |
| * |
| * Examples for well-defined, commonly used property names are: |
| * DEVICE=b12:8 device identifier |
| * b12:8 block dev_t |
| * c127:3 char dev_t |
| * n8 netdev ifindex |
| * +sound:card0 subsystem:devname |
| * SUBSYSTEM=pci driver-core subsystem name |
| * |
| * Valid characters in property names are [a-zA-Z0-9.-_]. Property names |
| * and values are terminated by a '\0' character. |
| * |
| * Example of record values: |
| * record.text_buf = "it's a line" (unterminated) |
| * record.info.seq = 56 |
| * record.info.ts_nsec = 36863 |
| * record.info.text_len = 11 |
| * record.info.facility = 0 (LOG_KERN) |
| * record.info.flags = 0 |
| * record.info.level = 3 (LOG_ERR) |
| * record.info.caller_id = 299 (task 299) |
| * record.info.dev_info.subsystem = "pci" (terminated) |
| * record.info.dev_info.device = "+pci:0000:00:01.0" (terminated) |
| * |
| * The 'struct printk_info' buffer must never be directly exported to |
| * userspace, it is a kernel-private implementation detail that might |
| * need to be changed in the future, when the requirements change. |
| * |
| * /dev/kmsg exports the structured data in the following line format: |
| * "<level>,<sequnum>,<timestamp>,<contflag>[,additional_values, ... ];<message text>\n" |
| * |
| * Users of the export format should ignore possible additional values |
| * separated by ',', and find the message after the ';' character. |
| * |
| * The optional key/value pairs are attached as continuation lines starting |
| * with a space character and terminated by a newline. All possible |
| * non-prinatable characters are escaped in the "\xff" notation. |
| */ |
| |
| /* syslog_lock protects syslog_* variables and write access to clear_seq. */ |
| static DEFINE_MUTEX(syslog_lock); |
| |
| /* |
| * A flag to signify if printk_activate_kthreads() has already started the |
| * kthread printers. If true, any later registered consoles must start their |
| * own kthread directly. The flag is write protected by the console_lock. |
| */ |
| static bool printk_kthreads_available; |
| |
| #ifdef CONFIG_PRINTK |
| static atomic_t printk_prefer_direct = ATOMIC_INIT(0); |
| |
| /** |
| * printk_prefer_direct_enter - cause printk() calls to attempt direct |
| * printing to all enabled consoles |
| * |
| * Since it is not possible to call into the console printing code from any |
| * context, there is no guarantee that direct printing will occur. |
| * |
| * This globally effects all printk() callers. |
| * |
| * Context: Any context. |
| */ |
| void printk_prefer_direct_enter(void) |
| { |
| atomic_inc(&printk_prefer_direct); |
| } |
| |
| /** |
| * printk_prefer_direct_exit - restore printk() behavior |
| * |
| * Context: Any context. |
| */ |
| void printk_prefer_direct_exit(void) |
| { |
| WARN_ON(atomic_dec_if_positive(&printk_prefer_direct) < 0); |
| } |
| |
| /* |
| * Calling printk() always wakes kthread printers so that they can |
| * flush the new message to their respective consoles. Also, if direct |
| * printing is allowed, printk() tries to flush the messages directly. |
| * |
| * Direct printing is allowed in situations when the kthreads |
| * are not available or the system is in a problematic state. |
| * |
| * See the implementation about possible races. |
| */ |
| static inline bool allow_direct_printing(void) |
| { |
| /* |
| * Checking kthread availability is a possible race because the |
| * kthread printers can become permanently disabled during runtime. |
| * However, doing that requires holding the console_lock, so any |
| * pending messages will be direct printed by console_unlock(). |
| */ |
| if (!printk_kthreads_available) |
| return true; |
| |
| /* |
| * Prefer direct printing when the system is in a problematic state. |
| * The context that sets this state will always see the updated value. |
| * The other contexts do not care. Anyway, direct printing is just a |
| * best effort. The direct output is only possible when console_lock |
| * is not already taken and no kthread printers are actively printing. |
| */ |
| return (system_state > SYSTEM_RUNNING || |
| oops_in_progress || |
| atomic_read(&printk_prefer_direct)); |
| } |
| |
| DECLARE_WAIT_QUEUE_HEAD(log_wait); |
| /* All 3 protected by @syslog_lock. */ |
| /* the next printk record to read by syslog(READ) or /proc/kmsg */ |
| static u64 syslog_seq; |
| static size_t syslog_partial; |
| static bool syslog_time; |
| |
| struct latched_seq { |
| seqcount_latch_t latch; |
| u64 val[2]; |
| }; |
| |
| /* |
| * The next printk record to read after the last 'clear' command. There are |
| * two copies (updated with seqcount_latch) so that reads can locklessly |
| * access a valid value. Writers are synchronized by @syslog_lock. |
| */ |
| static struct latched_seq clear_seq = { |
| .latch = SEQCNT_LATCH_ZERO(clear_seq.latch), |
| .val[0] = 0, |
| .val[1] = 0, |
| }; |
| |
| #ifdef CONFIG_PRINTK_CALLER |
| #define PREFIX_MAX 48 |
| #else |
| #define PREFIX_MAX 32 |
| #endif |
| |
| /* the maximum size of a formatted record (i.e. with prefix added per line) */ |
| #define CONSOLE_LOG_MAX 1024 |
| |
| /* the maximum size for a dropped text message */ |
| #define DROPPED_TEXT_MAX 64 |
| |
| /* the maximum size allowed to be reserved for a record */ |
| #define LOG_LINE_MAX (CONSOLE_LOG_MAX - PREFIX_MAX) |
| |
| #define LOG_LEVEL(v) ((v) & 0x07) |
| #define LOG_FACILITY(v) ((v) >> 3 & 0xff) |
| |
| /* record buffer */ |
| #define LOG_ALIGN __alignof__(unsigned long) |
| #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT) |
| #define LOG_BUF_LEN_MAX (u32)(1 << 31) |
| static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN); |
| static char *log_buf = __log_buf; |
| static u32 log_buf_len = __LOG_BUF_LEN; |
| |
| /* |
| * Define the average message size. This only affects the number of |
| * descriptors that will be available. Underestimating is better than |
| * overestimating (too many available descriptors is better than not enough). |
| */ |
| #define PRB_AVGBITS 5 /* 32 character average length */ |
| |
| #if CONFIG_LOG_BUF_SHIFT <= PRB_AVGBITS |
| #error CONFIG_LOG_BUF_SHIFT value too small. |
| #endif |
| _DEFINE_PRINTKRB(printk_rb_static, CONFIG_LOG_BUF_SHIFT - PRB_AVGBITS, |
| PRB_AVGBITS, &__log_buf[0]); |
| |
| static struct printk_ringbuffer printk_rb_dynamic; |
| |
| static struct printk_ringbuffer *prb = &printk_rb_static; |
| |
| /* |
| * We cannot access per-CPU data (e.g. per-CPU flush irq_work) before |
| * per_cpu_areas are initialised. This variable is set to true when |
| * it's safe to access per-CPU data. |
| */ |
| static bool __printk_percpu_data_ready __read_mostly; |
| |
| bool printk_percpu_data_ready(void) |
| { |
| return __printk_percpu_data_ready; |
| } |
| |
| /* Must be called under syslog_lock. */ |
| static void latched_seq_write(struct latched_seq *ls, u64 val) |
| { |
| raw_write_seqcount_latch(&ls->latch); |
| ls->val[0] = val; |
| raw_write_seqcount_latch(&ls->latch); |
| ls->val[1] = val; |
| } |
| |
| /* Can be called from any context. */ |
| static u64 latched_seq_read_nolock(struct latched_seq *ls) |
| { |
| unsigned int seq; |
| unsigned int idx; |
| u64 val; |
| |
| do { |
| seq = raw_read_seqcount_latch(&ls->latch); |
| idx = seq & 0x1; |
| val = ls->val[idx]; |
| } while (read_seqcount_latch_retry(&ls->latch, seq)); |
| |
| return val; |
| } |
| |
| /* Return log buffer address */ |
| char *log_buf_addr_get(void) |
| { |
| return log_buf; |
| } |
| |
| /* Return log buffer size */ |
| u32 log_buf_len_get(void) |
| { |
| return log_buf_len; |
| } |
| |
| /* |
| * Define how much of the log buffer we could take at maximum. The value |
| * must be greater than two. Note that only half of the buffer is available |
| * when the index points to the middle. |
| */ |
| #define MAX_LOG_TAKE_PART 4 |
| static const char trunc_msg[] = "<truncated>"; |
| |
| static void truncate_msg(u16 *text_len, u16 *trunc_msg_len) |
| { |
| /* |
| * The message should not take the whole buffer. Otherwise, it might |
| * get removed too soon. |
| */ |
| u32 max_text_len = log_buf_len / MAX_LOG_TAKE_PART; |
| |
| if (*text_len > max_text_len) |
| *text_len = max_text_len; |
| |
| /* enable the warning message (if there is room) */ |
| *trunc_msg_len = strlen(trunc_msg); |
| if (*text_len >= *trunc_msg_len) |
| *text_len -= *trunc_msg_len; |
| else |
| *trunc_msg_len = 0; |
| } |
| |
| int dmesg_restrict = IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT); |
| |
| static int syslog_action_restricted(int type) |
| { |
| if (dmesg_restrict) |
| return 1; |
| /* |
| * Unless restricted, we allow "read all" and "get buffer size" |
| * for everybody. |
| */ |
| return type != SYSLOG_ACTION_READ_ALL && |
| type != SYSLOG_ACTION_SIZE_BUFFER; |
| } |
| |
| static int check_syslog_permissions(int type, int source) |
| { |
| /* |
| * If this is from /proc/kmsg and we've already opened it, then we've |
| * already done the capabilities checks at open time. |
| */ |
| if (source == SYSLOG_FROM_PROC && type != SYSLOG_ACTION_OPEN) |
| goto ok; |
| |
| if (syslog_action_restricted(type)) { |
| if (capable(CAP_SYSLOG)) |
| goto ok; |
| /* |
| * For historical reasons, accept CAP_SYS_ADMIN too, with |
| * a warning. |
| */ |
| if (capable(CAP_SYS_ADMIN)) { |
| pr_warn_once("%s (%d): Attempt to access syslog with " |
| "CAP_SYS_ADMIN but no CAP_SYSLOG " |
| "(deprecated).\n", |
| current->comm, task_pid_nr(current)); |
| goto ok; |
| } |
| return -EPERM; |
| } |
| ok: |
| return security_syslog(type); |
| } |
| |
| static void append_char(char **pp, char *e, char c) |
| { |
| if (*pp < e) |
| *(*pp)++ = c; |
| } |
| |
| static ssize_t info_print_ext_header(char *buf, size_t size, |
| struct printk_info *info) |
| { |
| u64 ts_usec = info->ts_nsec; |
| char caller[20]; |
| #ifdef CONFIG_PRINTK_CALLER |
| u32 id = info->caller_id; |
| |
| snprintf(caller, sizeof(caller), ",caller=%c%u", |
| id & 0x80000000 ? 'C' : 'T', id & ~0x80000000); |
| #else |
| caller[0] = '\0'; |
| #endif |
| |
| do_div(ts_usec, 1000); |
| |
| return scnprintf(buf, size, "%u,%llu,%llu,%c%s;", |
| (info->facility << 3) | info->level, info->seq, |
| ts_usec, info->flags & LOG_CONT ? 'c' : '-', caller); |
| } |
| |
| static ssize_t msg_add_ext_text(char *buf, size_t size, |
| const char *text, size_t text_len, |
| unsigned char endc) |
| { |
| char *p = buf, *e = buf + size; |
| size_t i; |
| |
| /* escape non-printable characters */ |
| for (i = 0; i < text_len; i++) { |
| unsigned char c = text[i]; |
| |
| if (c < ' ' || c >= 127 || c == '\\') |
| p += scnprintf(p, e - p, "\\x%02x", c); |
| else |
| append_char(&p, e, c); |
| } |
| append_char(&p, e, endc); |
| |
| return p - buf; |
| } |
| |
| static ssize_t msg_add_dict_text(char *buf, size_t size, |
| const char *key, const char *val) |
| { |
| size_t val_len = strlen(val); |
| ssize_t len; |
| |
| if (!val_len) |
| return 0; |
| |
| len = msg_add_ext_text(buf, size, "", 0, ' '); /* dict prefix */ |
| len += msg_add_ext_text(buf + len, size - len, key, strlen(key), '='); |
| len += msg_add_ext_text(buf + len, size - len, val, val_len, '\n'); |
| |
| return len; |
| } |
| |
| static ssize_t msg_print_ext_body(char *buf, size_t size, |
| char *text, size_t text_len, |
| struct dev_printk_info *dev_info) |
| { |
| ssize_t len; |
| |
| len = msg_add_ext_text(buf, size, text, text_len, '\n'); |
| |
| if (!dev_info) |
| goto out; |
| |
| len += msg_add_dict_text(buf + len, size - len, "SUBSYSTEM", |
| dev_info->subsystem); |
| len += msg_add_dict_text(buf + len, size - len, "DEVICE", |
| dev_info->device); |
| out: |
| return len; |
| } |
| |
| /* /dev/kmsg - userspace message inject/listen interface */ |
| struct devkmsg_user { |
| atomic64_t seq; |
| struct ratelimit_state rs; |
| struct mutex lock; |
| char buf[CONSOLE_EXT_LOG_MAX]; |
| |
| struct printk_info info; |
| char text_buf[CONSOLE_EXT_LOG_MAX]; |
| struct printk_record record; |
| }; |
| |
| static __printf(3, 4) __cold |
| int devkmsg_emit(int facility, int level, const char *fmt, ...) |
| { |
| va_list args; |
| int r; |
| |
| va_start(args, fmt); |
| r = vprintk_emit(facility, level, NULL, fmt, args); |
| va_end(args); |
| |
| return r; |
| } |
| |
| static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from) |
| { |
| char *buf, *line; |
| int level = default_message_loglevel; |
| int facility = 1; /* LOG_USER */ |
| struct file *file = iocb->ki_filp; |
| struct devkmsg_user *user = file->private_data; |
| size_t len = iov_iter_count(from); |
| ssize_t ret = len; |
| |
| if (!user || len > LOG_LINE_MAX) |
| return -EINVAL; |
| |
| /* Ignore when user logging is disabled. */ |
| if (devkmsg_log & DEVKMSG_LOG_MASK_OFF) |
| return len; |
| |
| /* Ratelimit when not explicitly enabled. */ |
| if (!(devkmsg_log & DEVKMSG_LOG_MASK_ON)) { |
| if (!___ratelimit(&user->rs, current->comm)) |
| return ret; |
| } |
| |
| buf = kmalloc(len+1, GFP_KERNEL); |
| if (buf == NULL) |
| return -ENOMEM; |
| |
| buf[len] = '\0'; |
| if (!copy_from_iter_full(buf, len, from)) { |
| kfree(buf); |
| return -EFAULT; |
| } |
| |
| /* |
| * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace |
| * the decimal value represents 32bit, the lower 3 bit are the log |
| * level, the rest are the log facility. |
| * |
| * If no prefix or no userspace facility is specified, we |
| * enforce LOG_USER, to be able to reliably distinguish |
| * kernel-generated messages from userspace-injected ones. |
| */ |
| line = buf; |
| if (line[0] == '<') { |
| char *endp = NULL; |
| unsigned int u; |
| |
| u = simple_strtoul(line + 1, &endp, 10); |
| if (endp && endp[0] == '>') { |
| level = LOG_LEVEL(u); |
| if (LOG_FACILITY(u) != 0) |
| facility = LOG_FACILITY(u); |
| endp++; |
| line = endp; |
| } |
| } |
| |
| devkmsg_emit(facility, level, "%s", line); |
| kfree(buf); |
| return ret; |
| } |
| |
| static ssize_t devkmsg_read(struct file *file, char __user *buf, |
| size_t count, loff_t *ppos) |
| { |
| struct devkmsg_user *user = file->private_data; |
| struct printk_record *r = &user->record; |
| size_t len; |
| ssize_t ret; |
| |
| if (!user) |
| return -EBADF; |
| |
| ret = mutex_lock_interruptible(&user->lock); |
| if (ret) |
| return ret; |
| |
| if (!prb_read_valid(prb, atomic64_read(&user->seq), r)) { |
| if (file->f_flags & O_NONBLOCK) { |
| ret = -EAGAIN; |
| goto out; |
| } |
| |
| /* |
| * Guarantee this task is visible on the waitqueue before |
| * checking the wake condition. |
| * |
| * The full memory barrier within set_current_state() of |
| * prepare_to_wait_event() pairs with the full memory barrier |
| * within wq_has_sleeper(). |
| * |
| * This pairs with __wake_up_klogd:A. |
| */ |
| ret = wait_event_interruptible(log_wait, |
| prb_read_valid(prb, |
| atomic64_read(&user->seq), r)); /* LMM(devkmsg_read:A) */ |
| if (ret) |
| goto out; |
| } |
| |
| if (r->info->seq != atomic64_read(&user->seq)) { |
| /* our last seen message is gone, return error and reset */ |
| atomic64_set(&user->seq, r->info->seq); |
| ret = -EPIPE; |
| goto out; |
| } |
| |
| len = info_print_ext_header(user->buf, sizeof(user->buf), r->info); |
| len += msg_print_ext_body(user->buf + len, sizeof(user->buf) - len, |
| &r->text_buf[0], r->info->text_len, |
| &r->info->dev_info); |
| |
| atomic64_set(&user->seq, r->info->seq + 1); |
| |
| if (len > count) { |
| ret = -EINVAL; |
| goto out; |
| } |
| |
| if (copy_to_user(buf, user->buf, len)) { |
| ret = -EFAULT; |
| goto out; |
| } |
| ret = len; |
| out: |
| mutex_unlock(&user->lock); |
| return ret; |
| } |
| |
| /* |
| * Be careful when modifying this function!!! |
| * |
| * Only few operations are supported because the device works only with the |
| * entire variable length messages (records). Non-standard values are |
| * returned in the other cases and has been this way for quite some time. |
| * User space applications might depend on this behavior. |
| */ |
| static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence) |
| { |
| struct devkmsg_user *user = file->private_data; |
| loff_t ret = 0; |
| |
| if (!user) |
| return -EBADF; |
| if (offset) |
| return -ESPIPE; |
| |
| switch (whence) { |
| case SEEK_SET: |
| /* the first record */ |
| atomic64_set(&user->seq, prb_first_valid_seq(prb)); |
| break; |
| case SEEK_DATA: |
| /* |
| * The first record after the last SYSLOG_ACTION_CLEAR, |
| * like issued by 'dmesg -c'. Reading /dev/kmsg itself |
| * changes no global state, and does not clear anything. |
| */ |
| atomic64_set(&user->seq, latched_seq_read_nolock(&clear_seq)); |
| break; |
| case SEEK_END: |
| /* after the last record */ |
| atomic64_set(&user->seq, prb_next_seq(prb)); |
| break; |
| default: |
| ret = -EINVAL; |
| } |
| return ret; |
| } |
| |
| static __poll_t devkmsg_poll(struct file *file, poll_table *wait) |
| { |
| struct devkmsg_user *user = file->private_data; |
| struct printk_info info; |
| __poll_t ret = 0; |
| |
| if (!user) |
| return EPOLLERR|EPOLLNVAL; |
| |
| poll_wait(file, &log_wait, wait); |
| |
| if (prb_read_valid_info(prb, atomic64_read(&user->seq), &info, NULL)) { |
| /* return error when data has vanished underneath us */ |
| if (info.seq != atomic64_read(&user->seq)) |
| ret = EPOLLIN|EPOLLRDNORM|EPOLLERR|EPOLLPRI; |
| else |
| ret = EPOLLIN|EPOLLRDNORM; |
| } |
| |
| return ret; |
| } |
| |
| static int devkmsg_open(struct inode *inode, struct file *file) |
| { |
| struct devkmsg_user *user; |
| int err; |
| |
| if (devkmsg_log & DEVKMSG_LOG_MASK_OFF) |
| return -EPERM; |
| |
| /* write-only does not need any file context */ |
| if ((file->f_flags & O_ACCMODE) != O_WRONLY) { |
| err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL, |
| SYSLOG_FROM_READER); |
| if (err) |
| return err; |
| } |
| |
| user = kvmalloc(sizeof(struct devkmsg_user), GFP_KERNEL); |
| if (!user) |
| return -ENOMEM; |
| |
| ratelimit_default_init(&user->rs); |
| ratelimit_set_flags(&user->rs, RATELIMIT_MSG_ON_RELEASE); |
| |
| mutex_init(&user->lock); |
| |
| prb_rec_init_rd(&user->record, &user->info, |
| &user->text_buf[0], sizeof(user->text_buf)); |
| |
| atomic64_set(&user->seq, prb_first_valid_seq(prb)); |
| |
| file->private_data = user; |
| return 0; |
| } |
| |
| static int devkmsg_release(struct inode *inode, struct file *file) |
| { |
| struct devkmsg_user *user = file->private_data; |
| |
| if (!user) |
| return 0; |
| |
| ratelimit_state_exit(&user->rs); |
| |
| mutex_destroy(&user->lock); |
| kvfree(user); |
| return 0; |
| } |
| |
| const struct file_operations kmsg_fops = { |
| .open = devkmsg_open, |
| .read = devkmsg_read, |
| .write_iter = devkmsg_write, |
| .llseek = devkmsg_llseek, |
| .poll = devkmsg_poll, |
| .release = devkmsg_release, |
| }; |
| |
| #ifdef CONFIG_CRASH_CORE |
| /* |
| * This appends the listed symbols to /proc/vmcore |
| * |
| * /proc/vmcore is used by various utilities, like crash and makedumpfile to |
| * obtain access to symbols that are otherwise very difficult to locate. These |
| * symbols are specifically used so that utilities can access and extract the |
| * dmesg log from a vmcore file after a crash. |
| */ |
| void log_buf_vmcoreinfo_setup(void) |
| { |
| struct dev_printk_info *dev_info = NULL; |
| |
| VMCOREINFO_SYMBOL(prb); |
| VMCOREINFO_SYMBOL(printk_rb_static); |
| VMCOREINFO_SYMBOL(clear_seq); |
| |
| /* |
| * Export struct size and field offsets. User space tools can |
| * parse it and detect any changes to structure down the line. |
| */ |
| |
| VMCOREINFO_STRUCT_SIZE(printk_ringbuffer); |
| VMCOREINFO_OFFSET(printk_ringbuffer, desc_ring); |
| VMCOREINFO_OFFSET(printk_ringbuffer, text_data_ring); |
| VMCOREINFO_OFFSET(printk_ringbuffer, fail); |
| |
| VMCOREINFO_STRUCT_SIZE(prb_desc_ring); |
| VMCOREINFO_OFFSET(prb_desc_ring, count_bits); |
| VMCOREINFO_OFFSET(prb_desc_ring, descs); |
| VMCOREINFO_OFFSET(prb_desc_ring, infos); |
| VMCOREINFO_OFFSET(prb_desc_ring, head_id); |
| VMCOREINFO_OFFSET(prb_desc_ring, tail_id); |
| |
| VMCOREINFO_STRUCT_SIZE(prb_desc); |
| VMCOREINFO_OFFSET(prb_desc, state_var); |
| VMCOREINFO_OFFSET(prb_desc, text_blk_lpos); |
| |
| VMCOREINFO_STRUCT_SIZE(prb_data_blk_lpos); |
| VMCOREINFO_OFFSET(prb_data_blk_lpos, begin); |
| VMCOREINFO_OFFSET(prb_data_blk_lpos, next); |
| |
| VMCOREINFO_STRUCT_SIZE(printk_info); |
| VMCOREINFO_OFFSET(printk_info, seq); |
| VMCOREINFO_OFFSET(printk_info, ts_nsec); |
| VMCOREINFO_OFFSET(printk_info, text_len); |
| VMCOREINFO_OFFSET(printk_info, caller_id); |
| VMCOREINFO_OFFSET(printk_info, dev_info); |
| |
| VMCOREINFO_STRUCT_SIZE(dev_printk_info); |
| VMCOREINFO_OFFSET(dev_printk_info, subsystem); |
| VMCOREINFO_LENGTH(printk_info_subsystem, sizeof(dev_info->subsystem)); |
| VMCOREINFO_OFFSET(dev_printk_info, device); |
| VMCOREINFO_LENGTH(printk_info_device, sizeof(dev_info->device)); |
| |
| VMCOREINFO_STRUCT_SIZE(prb_data_ring); |
| VMCOREINFO_OFFSET(prb_data_ring, size_bits); |
| VMCOREINFO_OFFSET(prb_data_ring, data); |
| VMCOREINFO_OFFSET(prb_data_ring, head_lpos); |
| VMCOREINFO_OFFSET(prb_data_ring, tail_lpos); |
| |
| VMCOREINFO_SIZE(atomic_long_t); |
| VMCOREINFO_TYPE_OFFSET(atomic_long_t, counter); |
| |
| VMCOREINFO_STRUCT_SIZE(latched_seq); |
| VMCOREINFO_OFFSET(latched_seq, val); |
| } |
| #endif |
| |
| /* requested log_buf_len from kernel cmdline */ |
| static unsigned long __initdata new_log_buf_len; |
| |
| /* we practice scaling the ring buffer by powers of 2 */ |
| static void __init log_buf_len_update(u64 size) |
| { |
| if (size > (u64)LOG_BUF_LEN_MAX) { |
| size = (u64)LOG_BUF_LEN_MAX; |
| pr_err("log_buf over 2G is not supported.\n"); |
| } |
| |
| if (size) |
| size = roundup_pow_of_two(size); |
| if (size > log_buf_len) |
| new_log_buf_len = (unsigned long)size; |
| } |
| |
| /* save requested log_buf_len since it's too early to process it */ |
| static int __init log_buf_len_setup(char *str) |
| { |
| u64 size; |
| |
| if (!str) |
| return -EINVAL; |
| |
| size = memparse(str, &str); |
| |
| log_buf_len_update(size); |
| |
| return 0; |
| } |
| early_param("log_buf_len", log_buf_len_setup); |
| |
| #ifdef CONFIG_SMP |
| #define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT) |
| |
| static void __init log_buf_add_cpu(void) |
| { |
| unsigned int cpu_extra; |
| |
| /* |
| * archs should set up cpu_possible_bits properly with |
| * set_cpu_possible() after setup_arch() but just in |
| * case lets ensure this is valid. |
| */ |
| if (num_possible_cpus() == 1) |
| return; |
| |
| cpu_extra = (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN; |
| |
| /* by default this will only continue through for large > 64 CPUs */ |
| if (cpu_extra <= __LOG_BUF_LEN / 2) |
| return; |
| |
| pr_info("log_buf_len individual max cpu contribution: %d bytes\n", |
| __LOG_CPU_MAX_BUF_LEN); |
| pr_info("log_buf_len total cpu_extra contributions: %d bytes\n", |
| cpu_extra); |
| pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN); |
| |
| log_buf_len_update(cpu_extra + __LOG_BUF_LEN); |
| } |
| #else /* !CONFIG_SMP */ |
| static inline void log_buf_add_cpu(void) {} |
| #endif /* CONFIG_SMP */ |
| |
| static void __init set_percpu_data_ready(void) |
| { |
| __printk_percpu_data_ready = true; |
| } |
| |
| static unsigned int __init add_to_rb(struct printk_ringbuffer *rb, |
| struct printk_record *r) |
| { |
| struct prb_reserved_entry e; |
| struct printk_record dest_r; |
| |
| prb_rec_init_wr(&dest_r, r->info->text_len); |
| |
| if (!prb_reserve(&e, rb, &dest_r)) |
| return 0; |
| |
| memcpy(&dest_r.text_buf[0], &r->text_buf[0], r->info->text_len); |
| dest_r.info->text_len = r->info->text_len; |
| dest_r.info->facility = r->info->facility; |
| dest_r.info->level = r->info->level; |
| dest_r.info->flags = r->info->flags; |
| dest_r.info->ts_nsec = r->info->ts_nsec; |
| dest_r.info->caller_id = r->info->caller_id; |
| memcpy(&dest_r.info->dev_info, &r->info->dev_info, sizeof(dest_r.info->dev_info)); |
| |
| prb_final_commit(&e); |
| |
| return prb_record_text_space(&e); |
| } |
| |
| static char setup_text_buf[LOG_LINE_MAX] __initdata; |
| |
| void __init setup_log_buf(int early) |
| { |
| struct printk_info *new_infos; |
| unsigned int new_descs_count; |
| struct prb_desc *new_descs; |
| struct printk_info info; |
| struct printk_record r; |
| unsigned int text_size; |
| size_t new_descs_size; |
| size_t new_infos_size; |
| unsigned long flags; |
| char *new_log_buf; |
| unsigned int free; |
| u64 seq; |
| |
| /* |
| * Some archs call setup_log_buf() multiple times - first is very |
| * early, e.g. from setup_arch(), and second - when percpu_areas |
| * are initialised. |
| */ |
| if (!early) |
| set_percpu_data_ready(); |
| |
| if (log_buf != __log_buf) |
| return; |
| |
| if (!early && !new_log_buf_len) |
| log_buf_add_cpu(); |
| |
| if (!new_log_buf_len) |
| return; |
| |
| new_descs_count = new_log_buf_len >> PRB_AVGBITS; |
| if (new_descs_count == 0) { |
| pr_err("new_log_buf_len: %lu too small\n", new_log_buf_len); |
| return; |
| } |
| |
| new_log_buf = memblock_alloc(new_log_buf_len, LOG_ALIGN); |
| if (unlikely(!new_log_buf)) { |
| pr_err("log_buf_len: %lu text bytes not available\n", |
| new_log_buf_len); |
| return; |
| } |
| |
| new_descs_size = new_descs_count * sizeof(struct prb_desc); |
| new_descs = memblock_alloc(new_descs_size, LOG_ALIGN); |
| if (unlikely(!new_descs)) { |
| pr_err("log_buf_len: %zu desc bytes not available\n", |
| new_descs_size); |
| goto err_free_log_buf; |
| } |
| |
| new_infos_size = new_descs_count * sizeof(struct printk_info); |
| new_infos = memblock_alloc(new_infos_size, LOG_ALIGN); |
| if (unlikely(!new_infos)) { |
| pr_err("log_buf_len: %zu info bytes not available\n", |
| new_infos_size); |
| goto err_free_descs; |
| } |
| |
| prb_rec_init_rd(&r, &info, &setup_text_buf[0], sizeof(setup_text_buf)); |
| |
| prb_init(&printk_rb_dynamic, |
| new_log_buf, ilog2(new_log_buf_len), |
| new_descs, ilog2(new_descs_count), |
| new_infos); |
| |
| local_irq_save(flags); |
| |
| log_buf_len = new_log_buf_len; |
| log_buf = new_log_buf; |
| new_log_buf_len = 0; |
| |
| free = __LOG_BUF_LEN; |
| prb_for_each_record(0, &printk_rb_static, seq, &r) { |
| text_size = add_to_rb(&printk_rb_dynamic, &r); |
| if (text_size > free) |
| free = 0; |
| else |
| free -= text_size; |
| } |
| |
| prb = &printk_rb_dynamic; |
| |
| local_irq_restore(flags); |
| |
| /* |
| * Copy any remaining messages that might have appeared from |
| * NMI context after copying but before switching to the |
| * dynamic buffer. |
| */ |
| prb_for_each_record(seq, &printk_rb_static, seq, &r) { |
| text_size = add_to_rb(&printk_rb_dynamic, &r); |
| if (text_size > free) |
| free = 0; |
| else |
| free -= text_size; |
| } |
| |
| if (seq != prb_next_seq(&printk_rb_static)) { |
| pr_err("dropped %llu messages\n", |
| prb_next_seq(&printk_rb_static) - seq); |
| } |
| |
| pr_info("log_buf_len: %u bytes\n", log_buf_len); |
| pr_info("early log buf free: %u(%u%%)\n", |
| free, (free * 100) / __LOG_BUF_LEN); |
| return; |
| |
| err_free_descs: |
| memblock_free(new_descs, new_descs_size); |
| err_free_log_buf: |
| memblock_free(new_log_buf, new_log_buf_len); |
| } |
| |
| static bool __read_mostly ignore_loglevel; |
| |
| static int __init ignore_loglevel_setup(char *str) |
| { |
| ignore_loglevel = true; |
| pr_info("debug: ignoring loglevel setting.\n"); |
| |
| return 0; |
| } |
| |
| early_param("ignore_loglevel", ignore_loglevel_setup); |
| module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR); |
| MODULE_PARM_DESC(ignore_loglevel, |
| "ignore loglevel setting (prints all kernel messages to the console)"); |
| |
| static bool suppress_message_printing(int level) |
| { |
| return (level >= console_loglevel && !ignore_loglevel); |
| } |
| |
| #ifdef CONFIG_BOOT_PRINTK_DELAY |
| |
| static int boot_delay; /* msecs delay after each printk during bootup */ |
| static unsigned long long loops_per_msec; /* based on boot_delay */ |
| |
| static int __init boot_delay_setup(char *str) |
| { |
| unsigned long lpj; |
| |
| lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */ |
| loops_per_msec = (unsigned long long)lpj / 1000 * HZ; |
| |
| get_option(&str, &boot_delay); |
| if (boot_delay > 10 * 1000) |
| boot_delay = 0; |
| |
| pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, " |
| "HZ: %d, loops_per_msec: %llu\n", |
| boot_delay, preset_lpj, lpj, HZ, loops_per_msec); |
| return 0; |
| } |
| early_param("boot_delay", boot_delay_setup); |
| |
| static void boot_delay_msec(int level) |
| { |
| unsigned long long k; |
| unsigned long timeout; |
| |
| if ((boot_delay == 0 || system_state >= SYSTEM_RUNNING) |
| || suppress_message_printing(level)) { |
| return; |
| } |
| |
| k = (unsigned long long)loops_per_msec * boot_delay; |
| |
| timeout = jiffies + msecs_to_jiffies(boot_delay); |
| while (k) { |
| k--; |
| cpu_relax(); |
| /* |
| * use (volatile) jiffies to prevent |
| * compiler reduction; loop termination via jiffies |
| * is secondary and may or may not happen. |
| */ |
| if (time_after(jiffies, timeout)) |
| break; |
| touch_nmi_watchdog(); |
| } |
| } |
| #else |
| static inline void boot_delay_msec(int level) |
| { |
| } |
| #endif |
| |
| static bool printk_time = IS_ENABLED(CONFIG_PRINTK_TIME); |
| module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR); |
| |
| static size_t print_syslog(unsigned int level, char *buf) |
| { |
| return sprintf(buf, "<%u>", level); |
| } |
| |
| static size_t print_time(u64 ts, char *buf) |
| { |
| unsigned long rem_nsec = do_div(ts, 1000000000); |
| |
| return sprintf(buf, "[%5lu.%06lu]", |
| (unsigned long)ts, rem_nsec / 1000); |
| } |
| |
| #ifdef CONFIG_PRINTK_CALLER |
| static size_t print_caller(u32 id, char *buf) |
| { |
| char caller[12]; |
| |
| snprintf(caller, sizeof(caller), "%c%u", |
| id & 0x80000000 ? 'C' : 'T', id & ~0x80000000); |
| return sprintf(buf, "[%6s]", caller); |
| } |
| #else |
| #define print_caller(id, buf) 0 |
| #endif |
| |
| static size_t info_print_prefix(const struct printk_info *info, bool syslog, |
| bool time, char *buf) |
| { |
| size_t len = 0; |
| |
| if (syslog) |
| len = print_syslog((info->facility << 3) | info->level, buf); |
| |
| if (time) |
| len += print_time(info->ts_nsec, buf + len); |
| |
| len += print_caller(info->caller_id, buf + len); |
| |
| if (IS_ENABLED(CONFIG_PRINTK_CALLER) || time) { |
| buf[len++] = ' '; |
| buf[len] = '\0'; |
| } |
| |
| return len; |
| } |
| |
| /* |
| * Prepare the record for printing. The text is shifted within the given |
| * buffer to avoid a need for another one. The following operations are |
| * done: |
| * |
| * - Add prefix for each line. |
| * - Drop truncated lines that no longer fit into the buffer. |
| * - Add the trailing newline that has been removed in vprintk_store(). |
| * - Add a string terminator. |
| * |
| * Since the produced string is always terminated, the maximum possible |
| * return value is @r->text_buf_size - 1; |
| * |
| * Return: The length of the updated/prepared text, including the added |
| * prefixes and the newline. The terminator is not counted. The dropped |
| * line(s) are not counted. |
| */ |
| static size_t record_print_text(struct printk_record *r, bool syslog, |
| bool time) |
| { |
| size_t text_len = r->info->text_len; |
| size_t buf_size = r->text_buf_size; |
| char *text = r->text_buf; |
| char prefix[PREFIX_MAX]; |
| bool truncated = false; |
| size_t prefix_len; |
| size_t line_len; |
| size_t len = 0; |
| char *next; |
| |
| /* |
| * If the message was truncated because the buffer was not large |
| * enough, treat the available text as if it were the full text. |
| */ |
| if (text_len > buf_size) |
| text_len = buf_size; |
| |
| prefix_len = info_print_prefix(r->info, syslog, time, prefix); |
| |
| /* |
| * @text_len: bytes of unprocessed text |
| * @line_len: bytes of current line _without_ newline |
| * @text: pointer to beginning of current line |
| * @len: number of bytes prepared in r->text_buf |
| */ |
| for (;;) { |
| next = memchr(text, '\n', text_len); |
| if (next) { |
| line_len = next - text; |
| } else { |
| /* Drop truncated line(s). */ |
| if (truncated) |
| break; |
| line_len = text_len; |
| } |
| |
| /* |
| * Truncate the text if there is not enough space to add the |
| * prefix and a trailing newline and a terminator. |
| */ |
| if (len + prefix_len + text_len + 1 + 1 > buf_size) { |
| /* Drop even the current line if no space. */ |
| if (len + prefix_len + line_len + 1 + 1 > buf_size) |
| break; |
| |
| text_len = buf_size - len - prefix_len - 1 - 1; |
| truncated = true; |
| } |
| |
| memmove(text + prefix_len, text, text_len); |
| memcpy(text, prefix, prefix_len); |
| |
| /* |
| * Increment the prepared length to include the text and |
| * prefix that were just moved+copied. Also increment for the |
| * newline at the end of this line. If this is the last line, |
| * there is no newline, but it will be added immediately below. |
| */ |
| len += prefix_len + line_len + 1; |
| if (text_len == line_len) { |
| /* |
| * This is the last line. Add the trailing newline |
| * removed in vprintk_store(). |
| */ |
| text[prefix_len + line_len] = '\n'; |
| break; |
| } |
| |
| /* |
| * Advance beyond the added prefix and the related line with |
| * its newline. |
| */ |
| text += prefix_len + line_len + 1; |
| |
| /* |
| * The remaining text has only decreased by the line with its |
| * newline. |
| * |
| * Note that @text_len can become zero. It happens when @text |
| * ended with a newline (either due to truncation or the |
| * original string ending with "\n\n"). The loop is correctly |
| * repeated and (if not truncated) an empty line with a prefix |
| * will be prepared. |
| */ |
| text_len -= line_len + 1; |
| } |
| |
| /* |
| * If a buffer was provided, it will be terminated. Space for the |
| * string terminator is guaranteed to be available. The terminator is |
| * not counted in the return value. |
| */ |
| if (buf_size > 0) |
| r->text_buf[len] = 0; |
| |
| return len; |
| } |
| |
| static size_t get_record_print_text_size(struct printk_info *info, |
| unsigned int line_count, |
| bool syslog, bool time) |
| { |
| char prefix[PREFIX_MAX]; |
| size_t prefix_len; |
| |
| prefix_len = info_print_prefix(info, syslog, time, prefix); |
| |
| /* |
| * Each line will be preceded with a prefix. The intermediate |
| * newlines are already within the text, but a final trailing |
| * newline will be added. |
| */ |
| return ((prefix_len * line_count) + info->text_len + 1); |
| } |
| |
| /* |
| * Beginning with @start_seq, find the first record where it and all following |
| * records up to (but not including) @max_seq fit into @size. |
| * |
| * @max_seq is simply an upper bound and does not need to exist. If the caller |
| * does not require an upper bound, -1 can be used for @max_seq. |
| */ |
| static u64 find_first_fitting_seq(u64 start_seq, u64 max_seq, size_t size, |
| bool syslog, bool time) |
| { |
| struct printk_info info; |
| unsigned int line_count; |
| size_t len = 0; |
| u64 seq; |
| |
| /* Determine the size of the records up to @max_seq. */ |
| prb_for_each_info(start_seq, prb, seq, &info, &line_count) { |
| if (info.seq >= max_seq) |
| break; |
| len += get_record_print_text_size(&info, line_count, syslog, time); |
| } |
| |
| /* |
| * Adjust the upper bound for the next loop to avoid subtracting |
| * lengths that were never added. |
| */ |
| if (seq < max_seq) |
| max_seq = seq; |
| |
| /* |
| * Move first record forward until length fits into the buffer. Ignore |
| * newest messages that were not counted in the above cycle. Messages |
| * might appear and get lost in the meantime. This is a best effort |
| * that prevents an infinite loop that could occur with a retry. |
| */ |
| prb_for_each_info(start_seq, prb, seq, &info, &line_count) { |
| if (len <= size || info.seq >= max_seq) |
| break; |
| len -= get_record_print_text_size(&info, line_count, syslog, time); |
| } |
| |
| return seq; |
| } |
| |
| /* The caller is responsible for making sure @size is greater than 0. */ |
| static int syslog_print(char __user *buf, int size) |
| { |
| struct printk_info info; |
| struct printk_record r; |
| char *text; |
| int len = 0; |
| u64 seq; |
| |
| text = kmalloc(CONSOLE_LOG_MAX, GFP_KERNEL); |
| if (!text) |
| return -ENOMEM; |
| |
| prb_rec_init_rd(&r, &info, text, CONSOLE_LOG_MAX); |
| |
| mutex_lock(&syslog_lock); |
| |
| /* |
| * Wait for the @syslog_seq record to be available. @syslog_seq may |
| * change while waiting. |
| */ |
| do { |
| seq = syslog_seq; |
| |
| mutex_unlock(&syslog_lock); |
| /* |
| * Guarantee this task is visible on the waitqueue before |
| * checking the wake condition. |
| * |
| * The full memory barrier within set_current_state() of |
| * prepare_to_wait_event() pairs with the full memory barrier |
| * within wq_has_sleeper(). |
| * |
| * This pairs with __wake_up_klogd:A. |
| */ |
| len = wait_event_interruptible(log_wait, |
| prb_read_valid(prb, seq, NULL)); /* LMM(syslog_print:A) */ |
| mutex_lock(&syslog_lock); |
| |
| if (len) |
| goto out; |
| } while (syslog_seq != seq); |
| |
| /* |
| * Copy records that fit into the buffer. The above cycle makes sure |
| * that the first record is always available. |
| */ |
| do { |
| size_t n; |
| size_t skip; |
| int err; |
| |
| if (!prb_read_valid(prb, syslog_seq, &r)) |
| break; |
| |
| if (r.info->seq != syslog_seq) { |
| /* message is gone, move to next valid one */ |
| syslog_seq = r.info->seq; |
| syslog_partial = 0; |
| } |
| |
| /* |
| * To keep reading/counting partial line consistent, |
| * use printk_time value as of the beginning of a line. |
| */ |
| if (!syslog_partial) |
| syslog_time = printk_time; |
| |
| skip = syslog_partial; |
| n = record_print_text(&r, true, syslog_time); |
| if (n - syslog_partial <= size) { |
| /* message fits into buffer, move forward */ |
| syslog_seq = r.info->seq + 1; |
| n -= syslog_partial; |
| syslog_partial = 0; |
| } else if (!len){ |
| /* partial read(), remember position */ |
| n = size; |
| syslog_partial += n; |
| } else |
| n = 0; |
| |
| if (!n) |
| break; |
| |
| mutex_unlock(&syslog_lock); |
| err = copy_to_user(buf, text + skip, n); |
| mutex_lock(&syslog_lock); |
| |
| if (err) { |
| if (!len) |
| len = -EFAULT; |
| break; |
| } |
| |
| len += n; |
| size -= n; |
| buf += n; |
| } while (size); |
| out: |
| mutex_unlock(&syslog_lock); |
| kfree(text); |
| return len; |
| } |
| |
| static int syslog_print_all(char __user *buf, int size, bool clear) |
| { |
| struct printk_info info; |
| struct printk_record r; |
| char *text; |
| int len = 0; |
| u64 seq; |
| bool time; |
| |
| text = kmalloc(CONSOLE_LOG_MAX, GFP_KERNEL); |
| if (!text) |
| return -ENOMEM; |
| |
| time = printk_time; |
| /* |
| * Find first record that fits, including all following records, |
| * into the user-provided buffer for this dump. |
| */ |
| seq = find_first_fitting_seq(latched_seq_read_nolock(&clear_seq), -1, |
| size, true, time); |
| |
| prb_rec_init_rd(&r, &info, text, CONSOLE_LOG_MAX); |
| |
| len = 0; |
| prb_for_each_record(seq, prb, seq, &r) { |
| int textlen; |
| |
| textlen = record_print_text(&r, true, time); |
| |
| if (len + textlen > size) { |
| seq--; |
| break; |
| } |
| |
| if (copy_to_user(buf + len, text, textlen)) |
| len = -EFAULT; |
| else |
| len += textlen; |
| |
| if (len < 0) |
| break; |
| } |
| |
| if (clear) { |
| mutex_lock(&syslog_lock); |
| latched_seq_write(&clear_seq, seq); |
| mutex_unlock(&syslog_lock); |
| } |
| |
| kfree(text); |
| return len; |
| } |
| |
| static void syslog_clear(void) |
| { |
| mutex_lock(&syslog_lock); |
| latched_seq_write(&clear_seq, prb_next_seq(prb)); |
| mutex_unlock(&syslog_lock); |
| } |
| |
| int do_syslog(int type, char __user *buf, int len, int source) |
| { |
| struct printk_info info; |
| bool clear = false; |
| static int saved_console_loglevel = LOGLEVEL_DEFAULT; |
| int error; |
| |
| error = check_syslog_permissions(type, source); |
| if (error) |
| return error; |
| |
| switch (type) { |
| case SYSLOG_ACTION_CLOSE: /* Close log */ |
| break; |
| case SYSLOG_ACTION_OPEN: /* Open log */ |
| break; |
| case SYSLOG_ACTION_READ: /* Read from log */ |
| if (!buf || len < 0) |
| return -EINVAL; |
| if (!len) |
| return 0; |
| if (!access_ok(buf, len)) |
| return -EFAULT; |
| error = syslog_print(buf, len); |
| break; |
| /* Read/clear last kernel messages */ |
| case SYSLOG_ACTION_READ_CLEAR: |
| clear = true; |
| fallthrough; |
| /* Read last kernel messages */ |
| case SYSLOG_ACTION_READ_ALL: |
| if (!buf || len < 0) |
| return -EINVAL; |
| if (!len) |
| return 0; |
| if (!access_ok(buf, len)) |
| return -EFAULT; |
| error = syslog_print_all(buf, len, clear); |
| break; |
| /* Clear ring buffer */ |
| case SYSLOG_ACTION_CLEAR: |
| syslog_clear(); |
| break; |
| /* Disable logging to console */ |
| case SYSLOG_ACTION_CONSOLE_OFF: |
| if (saved_console_loglevel == LOGLEVEL_DEFAULT) |
| saved_console_loglevel = console_loglevel; |
| console_loglevel = minimum_console_loglevel; |
| break; |
| /* Enable logging to console */ |
| case SYSLOG_ACTION_CONSOLE_ON: |
| if (saved_console_loglevel != LOGLEVEL_DEFAULT) { |
| console_loglevel = saved_console_loglevel; |
| saved_console_loglevel = LOGLEVEL_DEFAULT; |
| } |
| break; |
| /* Set level of messages printed to console */ |
| case SYSLOG_ACTION_CONSOLE_LEVEL: |
| if (len < 1 || len > 8) |
| return -EINVAL; |
| if (len < minimum_console_loglevel) |
| len = minimum_console_loglevel; |
| console_loglevel = len; |
| /* Implicitly re-enable logging to console */ |
| saved_console_loglevel = LOGLEVEL_DEFAULT; |
| break; |
| /* Number of chars in the log buffer */ |
| case SYSLOG_ACTION_SIZE_UNREAD: |
| mutex_lock(&syslog_lock); |
| if (!prb_read_valid_info(prb, syslog_seq, &info, NULL)) { |
| /* No unread messages. */ |
| mutex_unlock(&syslog_lock); |
| return 0; |
| } |
| if (info.seq != syslog_seq) { |
| /* messages are gone, move to first one */ |
| syslog_seq = info.seq; |
| syslog_partial = 0; |
| } |
| if (source == SYSLOG_FROM_PROC) { |
| /* |
| * Short-cut for poll(/"proc/kmsg") which simply checks |
| * for pending data, not the size; return the count of |
| * records, not the length. |
| */ |
| error = prb_next_seq(prb) - syslog_seq; |
| } else { |
| bool time = syslog_partial ? syslog_time : printk_time; |
| unsigned int line_count; |
| u64 seq; |
| |
| prb_for_each_info(syslog_seq, prb, seq, &info, |
| &line_count) { |
| error += get_record_print_text_size(&info, line_count, |
| true, time); |
| time = printk_time; |
| } |
| error -= syslog_partial; |
| } |
| mutex_unlock(&syslog_lock); |
| break; |
| /* Size of the log buffer */ |
| case SYSLOG_ACTION_SIZE_BUFFER: |
| error = log_buf_len; |
| break; |
| default: |
| error = -EINVAL; |
| break; |
| } |
| |
| return error; |
| } |
| |
| SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len) |
| { |
| return do_syslog(type, buf, len, SYSLOG_FROM_READER); |
| } |
| |
| /* |
| * Special console_lock variants that help to reduce the risk of soft-lockups. |
| * They allow to pass console_lock to another printk() call using a busy wait. |
| */ |
| |
| #ifdef CONFIG_LOCKDEP |
| static struct lockdep_map console_owner_dep_map = { |
| .name = "console_owner" |
| }; |
| #endif |
| |
| static DEFINE_RAW_SPINLOCK(console_owner_lock); |
| static struct task_struct *console_owner; |
| static bool console_waiter; |
| |
| /** |
| * console_lock_spinning_enable - mark beginning of code where another |
| * thread might safely busy wait |
| * |
| * This basically converts console_lock into a spinlock. This marks |
| * the section where the console_lock owner can not sleep, because |
| * there may be a waiter spinning (like a spinlock). Also it must be |
| * ready to hand over the lock at the end of the section. |
| */ |
| static void console_lock_spinning_enable(void) |
| { |
| raw_spin_lock(&console_owner_lock); |
| console_owner = current; |
| raw_spin_unlock(&console_owner_lock); |
| |
| /* The waiter may spin on us after setting console_owner */ |
| spin_acquire(&console_owner_dep_map, 0, 0, _THIS_IP_); |
| } |
| |
| /** |
| * console_lock_spinning_disable_and_check - mark end of code where another |
| * thread was able to busy wait and check if there is a waiter |
| * |
| * This is called at the end of the section where spinning is allowed. |
| * It has two functions. First, it is a signal that it is no longer |
| * safe to start busy waiting for the lock. Second, it checks if |
| * there is a busy waiter and passes the lock rights to her. |
| * |
| * Important: Callers lose the lock if there was a busy waiter. |
| * They must not touch items synchronized by console_lock |
| * in this case. |
| * |
| * Return: 1 if the lock rights were passed, 0 otherwise. |
| */ |
| static int console_lock_spinning_disable_and_check(void) |
| { |
| int waiter; |
| |
| raw_spin_lock(&console_owner_lock); |
| waiter = READ_ONCE(console_waiter); |
| console_owner = NULL; |
| raw_spin_unlock(&console_owner_lock); |
| |
| if (!waiter) { |
| spin_release(&console_owner_dep_map, _THIS_IP_); |
| return 0; |
| } |
| |
| /* The waiter is now free to continue */ |
| WRITE_ONCE(console_waiter, false); |
| |
| spin_release(&console_owner_dep_map, _THIS_IP_); |
| |
| /* |
| * Hand off console_lock to waiter. The waiter will perform |
| * the up(). After this, the waiter is the console_lock owner. |
| */ |
| mutex_release(&console_lock_dep_map, _THIS_IP_); |
| return 1; |
| } |
| |
| /** |
| * console_trylock_spinning - try to get console_lock by busy waiting |
| * |
| * This allows to busy wait for the console_lock when the current |
| * owner is running in specially marked sections. It means that |
| * the current owner is running and cannot reschedule until it |
| * is ready to lose the lock. |
| * |
| * Return: 1 if we got the lock, 0 othrewise |
| */ |
| static int console_trylock_spinning(void) |
| { |
| struct task_struct *owner = NULL; |
| bool waiter; |
| bool spin = false; |
| unsigned long flags; |
| |
| if (console_trylock()) |
| return 1; |
| |
| /* |
| * It's unsafe to spin once a panic has begun. If we are the |
| * panic CPU, we may have already halted the owner of the |
| * console_sem. If we are not the panic CPU, then we should |
| * avoid taking console_sem, so the panic CPU has a better |
| * chance of cleanly acquiring it later. |
| */ |
| if (panic_in_progress()) |
| return 0; |
| |
| printk_safe_enter_irqsave(flags); |
| |
| raw_spin_lock(&console_owner_lock); |
| owner = READ_ONCE(console_owner); |
| waiter = READ_ONCE(console_waiter); |
| if (!waiter && owner && owner != current) { |
| WRITE_ONCE(console_waiter, true); |
| spin = true; |
| } |
| raw_spin_unlock(&console_owner_lock); |
| |
| /* |
| * If there is an active printk() writing to the |
| * consoles, instead of having it write our data too, |
| * see if we can offload that load from the active |
| * printer, and do some printing ourselves. |
| * Go into a spin only if there isn't already a waiter |
| * spinning, and there is an active printer, and |
| * that active printer isn't us (recursive printk?). |
| */ |
| if (!spin) { |
| printk_safe_exit_irqrestore(flags); |
| return 0; |
| } |
| |
| /* We spin waiting for the owner to release us */ |
| spin_acquire(&console_owner_dep_map, 0, 0, _THIS_IP_); |
| /* Owner will clear console_waiter on hand off */ |
| while (READ_ONCE(console_waiter)) |
| cpu_relax(); |
| spin_release(&console_owner_dep_map, _THIS_IP_); |
| |
| printk_safe_exit_irqrestore(flags); |
| /* |
| * The owner passed the console lock to us. |
| * Since we did not spin on console lock, annotate |
| * this as a trylock. Otherwise lockdep will |
| * complain. |
| */ |
| mutex_acquire(&console_lock_dep_map, 0, 1, _THIS_IP_); |
| |
| return 1; |
| } |
| |
| /* |
| * Call the specified console driver, asking it to write out the specified |
| * text and length. If @dropped_text is non-NULL and any records have been |
| * dropped, a dropped message will be written out first. |
| */ |
| static void call_console_driver(struct console *con, const char *text, size_t len, |
| char *dropped_text) |
| { |
| size_t dropped_len; |
| |
| if (con->dropped && dropped_text) { |
| dropped_len = snprintf(dropped_text, DROPPED_TEXT_MAX, |
| "** %lu printk messages dropped **\n", |
| con->dropped); |
| con->dropped = 0; |
| con->write(con, dropped_text, dropped_len); |
| } |
| |
| con->write(con, text, len); |
| } |
| |
| /* |
| * Recursion is tracked separately on each CPU. If NMIs are supported, an |
| * additional NMI context per CPU is also separately tracked. Until per-CPU |
| * is available, a separate "early tracking" is performed. |
| */ |
| static DEFINE_PER_CPU(u8, printk_count); |
| static u8 printk_count_early; |
| #ifdef CONFIG_HAVE_NMI |
| static DEFINE_PER_CPU(u8, printk_count_nmi); |
| static u8 printk_count_nmi_early; |
| #endif |
| |
| /* |
| * Recursion is limited to keep the output sane. printk() should not require |
| * more than 1 level of recursion (allowing, for example, printk() to trigger |
| * a WARN), but a higher value is used in case some printk-internal errors |
| * exist, such as the ringbuffer validation checks failing. |
| */ |
| #define PRINTK_MAX_RECURSION 3 |
| |
| /* |
| * Return a pointer to the dedicated counter for the CPU+context of the |
| * caller. |
| */ |
| static u8 *__printk_recursion_counter(void) |
| { |
| #ifdef CONFIG_HAVE_NMI |
| if (in_nmi()) { |
| if (printk_percpu_data_ready()) |
| return this_cpu_ptr(&printk_count_nmi); |
| return &printk_count_nmi_early; |
| } |
| #endif |
| if (printk_percpu_data_ready()) |
| return this_cpu_ptr(&printk_count); |
| return &printk_count_early; |
| } |
| |
| /* |
| * Enter recursion tracking. Interrupts are disabled to simplify tracking. |
| * The caller must check the boolean return value to see if the recursion is |
| * allowed. On failure, interrupts are not disabled. |
| * |
| * @recursion_ptr must be a variable of type (u8 *) and is the same variable |
| * that is passed to printk_exit_irqrestore(). |
| */ |
| #define printk_enter_irqsave(recursion_ptr, flags) \ |
| ({ \ |
| bool success = true; \ |
| \ |
| typecheck(u8 *, recursion_ptr); \ |
| local_irq_save(flags); \ |
| (recursion_ptr) = __printk_recursion_counter(); \ |
| if (*(recursion_ptr) > PRINTK_MAX_RECURSION) { \ |
| local_irq_restore(flags); \ |
| success = false; \ |
| } else { \ |
| (*(recursion_ptr))++; \ |
| } \ |
| success; \ |
| }) |
| |
| /* Exit recursion tracking, restoring interrupts. */ |
| #define printk_exit_irqrestore(recursion_ptr, flags) \ |
| do { \ |
| typecheck(u8 *, recursion_ptr); \ |
| (*(recursion_ptr))--; \ |
| local_irq_restore(flags); \ |
| } while (0) |
| |
| int printk_delay_msec __read_mostly; |
| |
| static inline void printk_delay(int level) |
| { |
| boot_delay_msec(level); |
| |
| if (unlikely(printk_delay_msec)) { |
| int m = printk_delay_msec; |
| |
| while (m--) { |
| mdelay(1); |
| touch_nmi_watchdog(); |
| } |
| } |
| } |
| |
| static inline u32 printk_caller_id(void) |
| { |
| return in_task() ? task_pid_nr(current) : |
| 0x80000000 + smp_processor_id(); |
| } |
| |
| /** |
| * printk_parse_prefix - Parse level and control flags. |
| * |
| * @text: The terminated text message. |
| * @level: A pointer to the current level value, will be updated. |
| * @flags: A pointer to the current printk_info flags, will be updated. |
| * |
| * @level may be NULL if the caller is not interested in the parsed value. |
| * Otherwise the variable pointed to by @level must be set to |
| * LOGLEVEL_DEFAULT in order to be updated with the parsed value. |
| * |
| * @flags may be NULL if the caller is not interested in the parsed value. |
| * Otherwise the variable pointed to by @flags will be OR'd with the parsed |
| * value. |
| * |
| * Return: The length of the parsed level and control flags. |
| */ |
| u16 printk_parse_prefix(const char *text, int *level, |
| enum printk_info_flags *flags) |
| { |
| u16 prefix_len = 0; |
| int kern_level; |
| |
| while (*text) { |
| kern_level = printk_get_level(text); |
| if (!kern_level) |
| break; |
| |
| switch (kern_level) { |
| case '0' ... '7': |
| if (level && *level == LOGLEVEL_DEFAULT) |
| *level = kern_level - '0'; |
| break; |
| case 'c': /* KERN_CONT */ |
| if (flags) |
| *flags |= LOG_CONT; |
| } |
| |
| prefix_len += 2; |
| text += 2; |
| } |
| |
| return prefix_len; |
| } |
| |
| __printf(5, 0) |
| static u16 printk_sprint(char *text, u16 size, int facility, |
| enum printk_info_flags *flags, const char *fmt, |
| va_list args) |
| { |
| u16 text_len; |
| |
| text_len = vscnprintf(text, size, fmt, args); |
| |
| /* Mark and strip a trailing newline. */ |
| if (text_len && text[text_len - 1] == '\n') { |
| text_len--; |
| *flags |= LOG_NEWLINE; |
| } |
| |
| /* Strip log level and control flags. */ |
| if (facility == 0) { |
| u16 prefix_len; |
| |
| prefix_len = printk_parse_prefix(text, NULL, NULL); |
| if (prefix_len) { |
| text_len -= prefix_len; |
| memmove(text, text + prefix_len, text_len); |
| } |
| } |
| |
| trace_console_rcuidle(text, text_len); |
| |
| return text_len; |
| } |
| |
| __printf(4, 0) |
| int vprintk_store(int facility, int level, |
| const struct dev_printk_info *dev_info, |
| const char *fmt, va_list args) |
| { |
| struct prb_reserved_entry e; |
| enum printk_info_flags flags = 0; |
| struct printk_record r; |
| unsigned long irqflags; |
| u16 trunc_msg_len = 0; |
| char prefix_buf[8]; |
| u8 *recursion_ptr; |
| u16 reserve_size; |
| va_list args2; |
| u32 caller_id; |
| u16 text_len; |
| int ret = 0; |
| u64 ts_nsec; |
| |
| if (!printk_enter_irqsave(recursion_ptr, irqflags)) |
| return 0; |
| |
| /* |
| * Since the duration of printk() can vary depending on the message |
| * and state of the ringbuffer, grab the timestamp now so that it is |
| * close to the call of printk(). This provides a more deterministic |
| * timestamp with respect to the caller. |
| */ |
| ts_nsec = local_clock(); |
| |
| caller_id = printk_caller_id(); |
| |
| /* |
| * The sprintf needs to come first since the syslog prefix might be |
| * passed in as a parameter. An extra byte must be reserved so that |
| * later the vscnprintf() into the reserved buffer has room for the |
| * terminating '\0', which is not counted by vsnprintf(). |
| */ |
| va_copy(args2, args); |
| reserve_size = vsnprintf(&prefix_buf[0], sizeof(prefix_buf), fmt, args2) + 1; |
| va_end(args2); |
| |
| if (reserve_size > LOG_LINE_MAX) |
| reserve_size = LOG_LINE_MAX; |
| |
| /* Extract log level or control flags. */ |
| if (facility == 0) |
| printk_parse_prefix(&prefix_buf[0], &level, &flags); |
| |
| if (level == LOGLEVEL_DEFAULT) |
| level = default_message_loglevel; |
| |
| if (dev_info) |
| flags |= LOG_NEWLINE; |
| |
| if (flags & LOG_CONT) { |
| prb_rec_init_wr(&r, reserve_size); |
| if (prb_reserve_in_last(&e, prb, &r, caller_id, LOG_LINE_MAX)) { |
| text_len = printk_sprint(&r.text_buf[r.info->text_len], reserve_size, |
| facility, &flags, fmt, args); |
| r.info->text_len += text_len; |
| |
| if (flags & LOG_NEWLINE) { |
| r.info->flags |= LOG_NEWLINE; |
| prb_final_commit(&e); |
| } else { |
| prb_commit(&e); |
| } |
| |
| ret = text_len; |
| goto out; |
| } |
| } |
| |
| /* |
| * Explicitly initialize the record before every prb_reserve() call. |
| * prb_reserve_in_last() and prb_reserve() purposely invalidate the |
| * structure when they fail. |
| */ |
| prb_rec_init_wr(&r, reserve_size); |
| if (!prb_reserve(&e, prb, &r)) { |
| /* truncate the message if it is too long for empty buffer */ |
| truncate_msg(&reserve_size, &trunc_msg_len); |
| |
| prb_rec_init_wr(&r, reserve_size + trunc_msg_len); |
| if (!prb_reserve(&e, prb, &r)) |
| goto out; |
| } |
| |
| /* fill message */ |
| text_len = printk_sprint(&r.text_buf[0], reserve_size, facility, &flags, fmt, args); |
| if (trunc_msg_len) |
| memcpy(&r.text_buf[text_len], trunc_msg, trunc_msg_len); |
| r.info->text_len = text_len + trunc_msg_len; |
| r.info->facility = facility; |
| r.info->level = level & 7; |
| r.info->flags = flags & 0x1f; |
| r.info->ts_nsec = ts_nsec; |
| r.info->caller_id = caller_id; |
| if (dev_info) |
| memcpy(&r.info->dev_info, dev_info, sizeof(r.info->dev_info)); |
| |
| /* A message without a trailing newline can be continued. */ |
| if (!(flags & LOG_NEWLINE)) |
| prb_commit(&e); |
| else |
| prb_final_commit(&e); |
| |
| ret = text_len + trunc_msg_len; |
| out: |
| printk_exit_irqrestore(recursion_ptr, irqflags); |
| return ret; |
| } |
| |
| asmlinkage int vprintk_emit(int facility, int level, |
| const struct dev_printk_info *dev_info, |
| const char *fmt, va_list args) |
| { |
| int printed_len; |
| bool in_sched = false; |
| |
| /* Suppress unimportant messages after panic happens */ |
| if (unlikely(suppress_printk)) |
| return 0; |
| |
| if (unlikely(suppress_panic_printk) && |
| atomic_read(&panic_cpu) != raw_smp_processor_id()) |
| return 0; |
| |
| if (level == LOGLEVEL_SCHED) { |
| level = LOGLEVEL_DEFAULT; |
| in_sched = true; |
| } |
| |
| printk_delay(level); |
| |
| printed_len = vprintk_store(facility, level, dev_info, fmt, args); |
| |
| /* If called from the scheduler, we can not call up(). */ |
| if (!in_sched && allow_direct_printing()) { |
| /* |
| * The caller may be holding system-critical or |
| * timing-sensitive locks. Disable preemption during direct |
| * printing of all remaining records to all consoles so that |
| * this context can return as soon as possible. Hopefully |
| * another printk() caller will take over the printing. |
| */ |
| preempt_disable(); |
| /* |
| * Try to acquire and then immediately release the console |
| * semaphore. The release will print out buffers. With the |
| * spinning variant, this context tries to take over the |
| * printing from another printing context. |
| */ |
| if (console_trylock_spinning()) |
| console_unlock(); |
| preempt_enable(); |
| } |
| |
| wake_up_klogd(); |
| return printed_len; |
| } |
| EXPORT_SYMBOL(vprintk_emit); |
| |
| int vprintk_default(const char *fmt, va_list args) |
| { |
| return vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, fmt, args); |
| } |
| EXPORT_SYMBOL_GPL(vprintk_default); |
| |
| asmlinkage __visible int _printk(const char *fmt, ...) |
| { |
| va_list args; |
| int r; |
| |
| va_start(args, fmt); |
| r = vprintk(fmt, args); |
| va_end(args); |
| |
| return r; |
| } |
| EXPORT_SYMBOL(_printk); |
| |
| static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress); |
| |
| static void printk_start_kthread(struct console *con); |
| |
| #else /* CONFIG_PRINTK */ |
| |
| #define CONSOLE_LOG_MAX 0 |
| #define DROPPED_TEXT_MAX 0 |
| #define printk_time false |
| |
| #define prb_read_valid(rb, seq, r) false |
| #define prb_first_valid_seq(rb) 0 |
| #define prb_next_seq(rb) 0 |
| |
| static u64 syslog_seq; |
| |
| static size_t record_print_text(const struct printk_record *r, |
| bool syslog, bool time) |
| { |
| return 0; |
| } |
| static ssize_t info_print_ext_header(char *buf, size_t size, |
| struct printk_info *info) |
| { |
| return 0; |
| } |
| static ssize_t msg_print_ext_body(char *buf, size_t size, |
| char *text, size_t text_len, |
| struct dev_printk_info *dev_info) { return 0; } |
| static void console_lock_spinning_enable(void) { } |
| static int console_lock_spinning_disable_and_check(void) { return 0; } |
| static void call_console_driver(struct console *con, const char *text, size_t len, |
| char *dropped_text) |
| { |
| } |
| static bool suppress_message_printing(int level) { return false; } |
| static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress) { return true; } |
| static void printk_start_kthread(struct console *con) { } |
| static bool allow_direct_printing(void) { return true; } |
| |
| #endif /* CONFIG_PRINTK */ |
| |
| #ifdef CONFIG_EARLY_PRINTK |
| struct console *early_console; |
| |
| asmlinkage __visible void early_printk(const char *fmt, ...) |
| { |
| va_list ap; |
| char buf[512]; |
| int n; |
| |
| if (!early_console) |
| return; |
| |
| va_start(ap, fmt); |
| n = vscnprintf(buf, sizeof(buf), fmt, ap); |
| va_end(ap); |
| |
| early_console->write(early_console, buf, n); |
| } |
| #endif |
| |
| static void set_user_specified(struct console_cmdline *c, bool user_specified) |
| { |
| if (!user_specified) |
| return; |
| |
| /* |
| * @c console was defined by the user on the command line. |
| * Do not clear when added twice also by SPCR or the device tree. |
| */ |
| c->user_specified = true; |
| /* At least one console defined by the user on the command line. */ |
| console_set_on_cmdline = 1; |
| } |
| |
| static int __add_preferred_console(char *name, int idx, char *options, |
| char *brl_options, bool user_specified) |
| { |
| struct console_cmdline *c; |
| int i; |
| |
| /* |
| * See if this tty is not yet registered, and |
| * if we have a slot free. |
| */ |
| for (i = 0, c = console_cmdline; |
| i < MAX_CMDLINECONSOLES && c->name[0]; |
| i++, c++) { |
| if (strcmp(c->name, name) == 0 && c->index == idx) { |
| if (!brl_options) |
| preferred_console = i; |
| set_user_specified(c, user_specified); |
| return 0; |
| } |
| } |
| if (i == MAX_CMDLINECONSOLES) |
| return -E2BIG; |
| if (!brl_options) |
| preferred_console = i; |
| strlcpy(c->name, name, sizeof(c->name)); |
| c->options = options; |
| set_user_specified(c, user_specified); |
| braille_set_options(c, brl_options); |
| |
| c->index = idx; |
| return 0; |
| } |
| |
| static int __init console_msg_format_setup(char *str) |
| { |
| if (!strcmp(str, "syslog")) |
| console_msg_format = MSG_FORMAT_SYSLOG; |
| if (!strcmp(str, "default")) |
| console_msg_format = MSG_FORMAT_DEFAULT; |
| return 1; |
| } |
| __setup("console_msg_format=", console_msg_format_setup); |
| |
| /* |
| * Set up a console. Called via do_early_param() in init/main.c |
| * for each "console=" parameter in the boot command line. |
| */ |
| static int __init console_setup(char *str) |
| { |
| char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for "ttyS" */ |
| char *s, *options, *brl_options = NULL; |
| int idx; |
| |
| /* |
| * console="" or console=null have been suggested as a way to |
| * disable console output. Use ttynull that has been created |
| * for exactly this purpose. |
| */ |
| if (str[0] == 0 || strcmp(str, "null") == 0) { |
| __add_preferred_console("ttynull", 0, NULL, NULL, true); |
| return 1; |
| } |
| |
| if (_braille_console_setup(&str, &brl_options)) |
| return 1; |
| |
| /* |
| * Decode str into name, index, options. |
| */ |
| if (str[0] >= '0' && str[0] <= '9') { |
| strcpy(buf, "ttyS"); |
| strncpy(buf + 4, str, sizeof(buf) - 5); |
| } else { |
| strncpy(buf, str, sizeof(buf) - 1); |
| } |
| buf[sizeof(buf) - 1] = 0; |
| options = strchr(str, ','); |
| if (options) |
| *(options++) = 0; |
| #ifdef __sparc__ |
| if (!strcmp(str, "ttya")) |
| strcpy(buf, "ttyS0"); |
| if (!strcmp(str, "ttyb")) |
| strcpy(buf, "ttyS1"); |
| #endif |
| for (s = buf; *s; s++) |
| if (isdigit(*s) || *s == ',') |
| break; |
| idx = simple_strtoul(s, NULL, 10); |
| *s = 0; |
| |
| __add_preferred_console(buf, idx, options, brl_options, true); |
| return 1; |
| } |
| __setup("console=", console_setup); |
| |
| /** |
| * add_preferred_console - add a device to the list of preferred consoles. |
| * @name: device name |
| * @idx: device index |
| * @options: options for this console |
| * |
| * The last preferred console added will be used for kernel messages |
| * and stdin/out/err for init. Normally this is used by console_setup |
| * above to handle user-supplied console arguments; however it can also |
| * be used by arch-specific code either to override the user or more |
| * commonly to provide a default console (ie from PROM variables) when |
| * the user has not supplied one. |
| */ |
| int add_preferred_console(char *name, int idx, char *options) |
| { |
| return __add_preferred_console(name, idx, options, NULL, false); |
| } |
| |
| bool console_suspend_enabled = true; |
| EXPORT_SYMBOL(console_suspend_enabled); |
| |
| static int __init console_suspend_disable(char *str) |
| { |
| console_suspend_enabled = false; |
| return 1; |
| } |
| __setup("no_console_suspend", console_suspend_disable); |
| module_param_named(console_suspend, console_suspend_enabled, |
| bool, S_IRUGO | S_IWUSR); |
| MODULE_PARM_DESC(console_suspend, "suspend console during suspend" |
| " and hibernate operations"); |
| |
| static bool printk_console_no_auto_verbose; |
| |
| void console_verbose(void) |
| { |
| if (console_loglevel && !printk_console_no_auto_verbose) |
| console_loglevel = CONSOLE_LOGLEVEL_MOTORMOUTH; |
| } |
| EXPORT_SYMBOL_GPL(console_verbose); |
| |
| module_param_named(console_no_auto_verbose, printk_console_no_auto_verbose, bool, 0644); |
| MODULE_PARM_DESC(console_no_auto_verbose, "Disable console loglevel raise to highest on oops/panic/etc"); |
| |
| /** |
| * suspend_console - suspend the console subsystem |
| * |
| * This disables printk() while we go into suspend states |
| */ |
| void suspend_console(void) |
| { |
| if (!console_suspend_enabled) |
| return; |
| pr_info("Suspending console(s) (use no_console_suspend to debug)\n"); |
| pr_flush(1000, true); |
| console_lock(); |
| console_suspended = 1; |
| up_console_sem(); |
| } |
| |
| void resume_console(void) |
| { |
| if (!console_suspend_enabled) |
| return; |
| down_console_sem(); |
| console_suspended = 0; |
| console_unlock(); |
| pr_flush(1000, true); |
| } |
| |
| /** |
| * console_cpu_notify - print deferred console messages after CPU hotplug |
| * @cpu: unused |
| * |
| * If printk() is called from a CPU that is not online yet, the messages |
| * will be printed on the console only if there are CON_ANYTIME consoles. |
| * This function is called when a new CPU comes online (or fails to come |
| * up) or goes offline. |
| */ |
| static int console_cpu_notify(unsigned int cpu) |
| { |
| if (!cpuhp_tasks_frozen) { |
| /* If trylock fails, someone else is doing the printing */ |
| if (console_trylock()) |
| console_unlock(); |
| else { |
| /* |
| * If a new CPU comes online, the conditions for |
| * printer_should_wake() may have changed for some |
| * kthread printer with !CON_ANYTIME. |
| */ |
| wake_up_klogd(); |
| } |
| } |
| return 0; |
| } |
| |
| /** |
| * console_lock - lock the console system for exclusive use. |
| * |
| * Acquires a lock which guarantees that the caller has |
| * exclusive access to the console system and the console_drivers list. |
| * |
| * Can sleep, returns nothing. |
| */ |
| void console_lock(void) |
| { |
| might_sleep(); |
| |
| down_console_sem(); |
| if (console_suspended) |
| return; |
| console_kthreads_block(); |
| console_may_schedule = 1; |
| } |
| EXPORT_SYMBOL(console_lock); |
| |
| /** |
| * console_trylock - try to lock the console system for exclusive use. |
| * |
| * Try to acquire a lock which guarantees that the caller has exclusive |
| * access to the console system and the console_drivers list. |
| * |
| * returns 1 on success, and 0 on failure to acquire the lock. |
| */ |
| int console_trylock(void) |
| { |
| if (down_trylock_console_sem()) |
| return 0; |
| if (console_suspended) { |
| up_console_sem(); |
| return 0; |
| } |
| if (!console_kthreads_atomic_tryblock()) { |
| up_console_sem(); |
| return 0; |
| } |
| console_may_schedule = 0; |
| return 1; |
| } |
| EXPORT_SYMBOL(console_trylock); |
| |
| /* |
| * This is used to help to make sure that certain paths within the VT code are |
| * running with the console lock held. It is definitely not the perfect debug |
| * tool (it is not known if the VT code is the task holding the console lock), |
| * but it helps tracking those weird code paths in the console code such as |
| * when the console is suspended: where the console is not locked but no |
| * console printing may occur. |
| * |
| * Note: This returns true when the console is suspended but is not locked. |
| * This is intentional because the VT code must consider that situation |
| * the same as if the console was locked. |
| */ |
| int is_console_locked(void) |
| { |
| return (console_kthreads_blocked || atomic_read(&console_kthreads_active)); |
| } |
| EXPORT_SYMBOL(is_console_locked); |
| |
| /* |
| * Return true when this CPU should unlock console_sem without pushing all |
| * messages to the console. This reduces the chance that the console is |
| * locked when the panic CPU tries to use it. |
| */ |
| static bool abandon_console_lock_in_panic(void) |
| { |
| if (!panic_in_progress()) |
| return false; |
| |
| /* |
| * We can use raw_smp_processor_id() here because it is impossible for |
| * the task to be migrated to the panic_cpu, or away from it. If |
| * panic_cpu has already been set, and we're not currently executing on |
| * that CPU, then we never will be. |
| */ |
| return atomic_read(&panic_cpu) != raw_smp_processor_id(); |
| } |
| |
| static inline bool __console_is_usable(short flags) |
| { |
| if (!(flags & CON_ENABLED)) |
| return false; |
| |
| /* |
| * Console drivers may assume that per-cpu resources have been |
| * allocated. So unless they're explicitly marked as being able to |
| * cope (CON_ANYTIME) don't call them until this CPU is officially up. |
| */ |
| if (!cpu_online(raw_smp_processor_id()) && |
| !(flags & CON_ANYTIME)) |
| return false; |
| |
| return true; |
| } |
| |
| /* |
| * Check if the given console is currently capable and allowed to print |
| * records. |
| * |
| * Requires holding the console_lock. |
| */ |
| static inline bool console_is_usable(struct console *con) |
| { |
| if (!con->write) |
| return false; |
| |
| return __console_is_usable(con->flags); |
| } |
| |
| static void __console_unlock(void) |
| { |
| /* |
| * Depending on whether console_lock() or console_trylock() was used, |
| * appropriately allow the kthread printers to continue. |
| */ |
| if (console_kthreads_blocked) |
| console_kthreads_unblock(); |
| else |
| console_kthreads_atomic_unblock(); |
| |
| /* |
| * New records may have arrived while the console was locked. |
| * Wake the kthread printers to print them. |
| */ |
| wake_up_klogd(); |
| |
| up_console_sem(); |
| } |
| |
| /* |
| * Print one record for the given console. The record printed is whatever |
| * record is the next available record for the given console. |
| * |
| * @text is a buffer of size CONSOLE_LOG_MAX. |
| * |
| * If extended messages should be printed, @ext_text is a buffer of size |
| * CONSOLE_EXT_LOG_MAX. Otherwise @ext_text must be NULL. |
| * |
| * If dropped messages should be printed, @dropped_text is a buffer of size |
| * DROPPED_TEXT_MAX. Otherwise @dropped_text must be NULL. |
| * |
| * @handover will be set to true if a printk waiter has taken over the |
| * console_lock, in which case the caller is no longer holding the |
| * console_lock. Otherwise it is set to false. A NULL pointer may be provided |
| * to disable allowing the console_lock to be taken over by a printk waiter. |
| * |
| * Returns false if the given console has no next record to print, otherwise |
| * true. |
| * |
| * Requires the console_lock if @handover is non-NULL. |
| * Requires con->lock otherwise. |
| */ |
| static bool __console_emit_next_record(struct console *con, char *text, char *ext_text, |
| char *dropped_text, bool *handover) |
| { |
| static atomic_t panic_console_dropped = ATOMIC_INIT(0); |
| struct printk_info info; |
| struct printk_record r; |
| unsigned long flags; |
| char *write_text; |
| size_t len; |
| |
| prb_rec_init_rd(&r, &info, text, CONSOLE_LOG_MAX); |
| |
| if (handover) |
| *handover = false; |
| |
| if (!prb_read_valid(prb, con->seq, &r)) |
| return false; |
| |
| if (con->seq != r.info->seq) { |
| con->dropped += r.info->seq - con->seq; |
| con->seq = r.info->seq; |
| if (panic_in_progress() && |
| atomic_fetch_inc_relaxed(&panic_console_dropped) > 10) { |
| suppress_panic_printk = 1; |
| pr_warn_once("Too many dropped messages. Suppress messages on non-panic CPUs to prevent livelock.\n"); |
| } |
| } |
| |
| /* Skip record that has level above the console loglevel. */ |
| if (suppress_message_printing(r.info->level)) { |
| con->seq++; |
| goto skip; |
| } |
| |
| if (ext_text) { |
| write_text = ext_text; |
| len = info_print_ext_header(ext_text, CONSOLE_EXT_LOG_MAX, r.info); |
| len += msg_print_ext_body(ext_text + len, CONSOLE_EXT_LOG_MAX - len, |
| &r.text_buf[0], r.info->text_len, &r.info->dev_info); |
| } else { |
| write_text = text; |
| len = record_print_text(&r, console_msg_format & MSG_FORMAT_SYSLOG, printk_time); |
| } |
| |
| if (handover) { |
| /* |
| * While actively printing out messages, if another printk() |
| * were to occur on another CPU, it may wait for this one to |
| * finish. This task can not be preempted if there is a |
| * waiter waiting to take over. |
| * |
| * Interrupts are disabled because the hand over to a waiter |
| * must not be interrupted until the hand over is completed |
| * (@console_waiter is cleared). |
| */ |
| printk_safe_enter_irqsave(flags); |
| console_lock_spinning_enable(); |
| |
| /* don't trace irqsoff print latency */ |
| stop_critical_timings(); |
| } |
| |
| call_console_driver(con, write_text, len, dropped_text); |
| |
| con->seq++; |
| |
| if (handover) { |
| start_critical_timings(); |
| *handover = console_lock_spinning_disable_and_check(); |
| printk_safe_exit_irqrestore(flags); |
| } |
| skip: |
| return true; |
| } |
| |
| /* |
| * Print a record for a given console, but allow another printk() caller to |
| * take over the console_lock and continue printing. |
| * |
| * Requires the console_lock, but depending on @handover after the call, the |
| * caller may no longer have the console_lock. |
| * |
| * See __console_emit_next_record() for argument and return details. |
| */ |
| static bool console_emit_next_record_transferable(struct console *con, char *text, char *ext_text, |
| char *dropped_text, bool *handover) |
| { |
| /* |
| * Handovers are only supported if threaded printers are atomically |
| * blocked. The context taking over the console_lock may be atomic. |
| */ |
| if (!console_kthreads_atomically_blocked()) { |
| *handover = false; |
| handover = NULL; |
| } |
| |
| return __console_emit_next_record(con, text, ext_text, dropped_text, handover); |
| } |
| |
| /* |
| * Print out all remaining records to all consoles. |
| * |
| * @do_cond_resched is set by the caller. It can be true only in schedulable |
| * context. |
| * |
| * @next_seq is set to the sequence number after the last available record. |
| * The value is valid only when this function returns true. It means that all |
| * usable consoles are completely flushed. |
| * |
| * @handover will be set to true if a printk waiter has taken over the |
| * console_lock, in which case the caller is no longer holding the |
| * console_lock. Otherwise it is set to false. |
| * |
| * Returns true when there was at least one usable console and all messages |
| * were flushed to all usable consoles. A returned false informs the caller |
| * that everything was not flushed (either there were no usable consoles or |
| * another context has taken over printing or it is a panic situation and this |
| * is not the panic CPU or direct printing is not preferred). Regardless the |
| * reason, the caller should assume it is not useful to immediately try again. |
| * |
| * Requires the console_lock. |
| */ |
| static bool console_flush_all(bool do_cond_resched, u64 *next_seq, bool *handover) |
| { |
| static char dropped_text[DROPPED_TEXT_MAX]; |
| static char ext_text[CONSOLE_EXT_LOG_MAX]; |
| static char text[CONSOLE_LOG_MAX]; |
| bool any_usable = false; |
| struct console *con; |
| bool any_progress; |
| |
| *next_seq = 0; |
| *handover = false; |
| |
| do { |
| /* Let the kthread printers do the work if they can. */ |
| if (!allow_direct_printing()) |
| return false; |
| |
| any_progress = false; |
| |
| for_each_console(con) { |
| bool progress; |
| |
| if (!console_is_usable(con)) |
| continue; |
| any_usable = true; |
| |
| if (con->flags & CON_EXTENDED) { |
| /* Extended consoles do not print "dropped messages". */ |
| progress = console_emit_next_record_transferable(con, &text[0], |
| &ext_text[0], NULL, handover); |
| } else { |
| progress = console_emit_next_record_transferable(con, &text[0], |
| NULL, &dropped_text[0], handover); |
| } |
| if (*handover) |
| return false; |
| |
| /* Track the next of the highest seq flushed. */ |
| if (con->seq > *next_seq) |
| *next_seq = con->seq; |
| |
| if (!progress) |
| continue; |
| any_progress = true; |
| |
| /* Allow panic_cpu to take over the consoles safely. */ |
| if (abandon_console_lock_in_panic()) |
| return false; |
| |
| if (do_cond_resched) |
| cond_resched(); |
| } |
| } while (any_progress); |
| |
| return any_usable; |
| } |
| |
| /** |
| * console_unlock - unlock the console system |
| * |
| * Releases the console_lock which the caller holds on the console system |
| * and the console driver list. |
| * |
| * While the console_lock was held, console output may have been buffered |
| * by printk(). If this is the case, console_unlock(); emits |
| * the output prior to releasing the lock. |
| * |
| * console_unlock(); may be called from any context. |
| */ |
| void console_unlock(void) |
| { |
| bool do_cond_resched; |
| bool handover; |
| bool flushed; |
| u64 next_seq; |
| |
| if (console_suspended) { |
| up_console_sem(); |
| return; |
| } |
| |
| /* |
| * Console drivers are called with interrupts disabled, so |
| * @console_may_schedule should be cleared before; however, we may |
| * end up dumping a lot of lines, for example, if called from |
| * console registration path, and should invoke cond_resched() |
| * between lines if allowable. Not doing so can cause a very long |
| * scheduling stall on a slow console leading to RCU stall and |
| * softlockup warnings which exacerbate the issue with more |
| * messages practically incapacitating the system. Therefore, create |
| * a local to use for the printing loop. |
| */ |
| do_cond_resched = console_may_schedule; |
| |
| do { |
| console_may_schedule = 0; |
| |
| flushed = console_flush_all(do_cond_resched, &next_seq, &handover); |
| if (!handover) |
| __console_unlock(); |
| |
| /* |
| * Abort if there was a failure to flush all messages to all |
| * usable consoles. Either it is not possible to flush (in |
| * which case it would be an infinite loop of retrying) or |
| * another context has taken over printing. |
| */ |
| if (!flushed) |
| break; |
| |
| /* |
| * Some context may have added new records after |
| * console_flush_all() but before unlocking the console. |
| * Re-check if there is a new record to flush. If the trylock |
| * fails, another context is already handling the printing. |
| */ |
| } while (prb_read_valid(prb, next_seq, NULL) && console_trylock()); |
| } |
| EXPORT_SYMBOL(console_unlock); |
| |
| /** |
| * console_conditional_schedule - yield the CPU if required |
| * |
| * If the console code is currently allowed to sleep, and |
| * if this CPU should yield the CPU to another task, do |
| * so here. |
| * |
| * Must be called within console_lock();. |
| */ |
| void __sched console_conditional_schedule(void) |
| { |
| if (console_may_schedule) |
| cond_resched(); |
| } |
| EXPORT_SYMBOL(console_conditional_schedule); |
| |
| void console_unblank(void) |
| { |
| struct console *c; |
| |
| /* |
| * console_unblank can no longer be called in interrupt context unless |
| * oops_in_progress is set to 1.. |
| */ |
| if (oops_in_progress) { |
| if (down_trylock_console_sem() != 0) |
| return; |
| if (!console_kthreads_atomic_tryblock()) { |
| up_console_sem(); |
| return; |
| } |
| } else |
| console_lock(); |
| |
| console_may_schedule = 0; |
| for_each_console(c) |
| if ((c->flags & CON_ENABLED) && c->unblank) |
| c->unblank(); |
| console_unlock(); |
| |
| if (!oops_in_progress) |
| pr_flush(1000, true); |
| } |
| |
| /** |
| * console_flush_on_panic - flush console content on panic |
| * @mode: flush all messages in buffer or just the pending ones |
| * |
| * Immediately output all pending messages no matter what. |
| */ |
| void console_flush_on_panic(enum con_flush_mode mode) |
| { |
| /* |
| * If someone else is holding the console lock, trylock will fail |
| * and may_schedule may be set. Ignore and proceed to unlock so |
| * that messages are flushed out. As this can be called from any |
| * context and we don't want to get preempted while flushing, |
| * ensure may_schedule is cleared. |
| */ |
| console_trylock(); |
| console_may_schedule = 0; |
| |
| if (mode == CONSOLE_REPLAY_ALL) { |
| struct console *c; |
| u64 seq; |
| |
| seq = prb_first_valid_seq(prb); |
| for_each_console(c) |
| c->seq = seq; |
| } |
| console_unlock(); |
| } |
| |
| /* |
| * Return the console tty driver structure and its associated index |
| */ |
| struct tty_driver *console_device(int *index) |
| { |
| struct console *c; |
| struct tty_driver *driver = NULL; |
| |
| console_lock(); |
| for_each_console(c) { |
| if (!c->device) |
| continue; |
| driver = c->device(c, index); |
| if (driver) |
| break; |
| } |
| console_unlock(); |
| return driver; |
| } |
| |
| /* |
| * Prevent further output on the passed console device so that (for example) |
| * serial drivers can disable console output before suspending a port, and can |
| * re-enable output afterwards. |
| */ |
| void console_stop(struct console *console) |
| { |
| __pr_flush(console, 1000, true); |
| console_lock(); |
| console->flags &= ~CON_ENABLED; |
| console_unlock(); |
| } |
| EXPORT_SYMBOL(console_stop); |
| |
| void console_start(struct console *console) |
| { |
| console_lock(); |
| console->flags |= CON_ENABLED; |
| console_unlock(); |
| __pr_flush(console, 1000, true); |
| } |
| EXPORT_SYMBOL(console_start); |
| |
| static int __read_mostly keep_bootcon; |
| |
| static int __init keep_bootcon_setup(char *str) |
| { |
| keep_bootcon = 1; |
| pr_info("debug: skip boot console de-registration.\n"); |
| |
| return 0; |
| } |
| |
| early_param("keep_bootcon", keep_bootcon_setup); |
| |
| /* |
| * This is called by register_console() to try to match |
| * the newly registered console with any of the ones selected |
| * by either the command line or add_preferred_console() and |
| * setup/enable it. |
| * |
| * Care need to be taken with consoles that are statically |
| * enabled such as netconsole |
| */ |
| static int try_enable_preferred_console(struct console *newcon, |
| bool user_specified) |
| { |
| struct console_cmdline *c; |
| int i, err; |
| |
| for (i = 0, c = console_cmdline; |
| i < MAX_CMDLINECONSOLES && c->name[0]; |
| i++, c++) { |
| if (c->user_specified != user_specified) |
| continue; |
| if (!newcon->match || |
| newcon->match(newcon, c->name, c->index, c->options) != 0) { |
| /* default matching */ |
| BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name)); |
| if (strcmp(c->name, newcon->name) != 0) |
| continue; |
| if (newcon->index >= 0 && |
| newcon->index != c->index) |
| continue; |
| if (newcon->index < 0) |
| newcon->index = c->index; |
| |
| if (_braille_register_console(newcon, c)) |
| return 0; |
| |
| if (newcon->setup && |
| (err = newcon->setup(newcon, c->options)) != 0) |
| return err; |
| } |
| newcon->flags |= CON_ENABLED; |
| if (i == preferred_console) |
| newcon->flags |= CON_CONSDEV; |
| return 0; |
| } |
| |
| /* |
| * Some consoles, such as pstore and netconsole, can be enabled even |
| * without matching. Accept the pre-enabled consoles only when match() |
| * and setup() had a chance to be called. |
| */ |
| if (newcon->flags & CON_ENABLED && c->user_specified == user_specified) |
| return 0; |
| |
| return -ENOENT; |
| } |
| |
| /* Try to enable the console unconditionally */ |
| static void try_enable_default_console(struct console *newcon) |
| { |
| if (newcon->index < 0) |
| newcon->index = 0; |
| |
| if (newcon->setup && newcon->setup(newcon, NULL) != 0) |
| return; |
| |
| newcon->flags |= CON_ENABLED; |
| |
| if (newcon->device) |
| newcon->flags |= CON_CONSDEV; |
| } |
| |
| #define con_printk(lvl, con, fmt, ...) \ |
| printk(lvl pr_fmt("%sconsole [%s%d] " fmt), \ |
| (con->flags & CON_BOOT) ? "boot" : "", \ |
| con->name, con->index, ##__VA_ARGS__) |
| |
| /* |
| * The console driver calls this routine during kernel initialization |
| * to register the console printing procedure with printk() and to |
| * print any messages that were printed by the kernel before the |
| * console driver was initialized. |
| * |
| * This can happen pretty early during the boot process (because of |
| * early_printk) - sometimes before setup_arch() completes - be careful |
| * of what kernel features are used - they may not be initialised yet. |
| * |
| * There are two types of consoles - bootconsoles (early_printk) and |
| * "real" consoles (everything which is not a bootconsole) which are |
| * handled differently. |
| * - Any number of bootconsoles can be registered at any time. |
| * - As soon as a "real" console is registered, all bootconsoles |
| * will be unregistered automatically. |
| * - Once a "real" console is registered, any attempt to register a |
| * bootconsoles will be rejected |
| */ |
| void register_console(struct console *newcon) |
| { |
| struct console *con; |
| bool bootcon_enabled = false; |
| bool realcon_enabled = false; |
| int err; |
| |
| for_each_console(con) { |
| if (WARN(con == newcon, "console '%s%d' already registered\n", |
| con->name, con->index)) |
| return; |
| } |
| |
| for_each_console(con) { |
| if (con->flags & CON_BOOT) |
| bootcon_enabled = true; |
| else |
| realcon_enabled = true; |
| } |
| |
| /* Do not register boot consoles when there already is a real one. */ |
| if (newcon->flags & CON_BOOT && realcon_enabled) { |
| pr_info("Too late to register bootconsole %s%d\n", |
| newcon->name, newcon->index); |
| return; |
| } |
| |
| /* |
| * See if we want to enable this console driver by default. |
| * |
| * Nope when a console is preferred by the command line, device |
| * tree, or SPCR. |
| * |
| * The first real console with tty binding (driver) wins. More |
| * consoles might get enabled before the right one is found. |
| * |
| * Note that a console with tty binding will have CON_CONSDEV |
| * flag set and will be first in the list. |
| */ |
| if (preferred_console < 0) { |
| if (!console_drivers || !console_drivers->device || |
| console_drivers->flags & CON_BOOT) { |
| try_enable_default_console(newcon); |
| } |
| } |
| |
| /* See if this console matches one we selected on the command line */ |
| err = try_enable_preferred_console(newcon, true); |
| |
| /* If not, try to match against the platform default(s) */ |
| if (err == -ENOENT) |
| err = try_enable_preferred_console(newcon, false); |
| |
| /* printk() messages are not printed to the Braille console. */ |
| if (err || newcon->flags & CON_BRL) |
| return; |
| |
| /* |
| * If we have a bootconsole, and are switching to a real console, |
| * don't print everything out again, since when the boot console, and |
| * the real console are the same physical device, it's annoying to |
| * see the beginning boot messages twice |
| */ |
| if (bootcon_enabled && |
| ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) { |
| newcon->flags &= ~CON_PRINTBUFFER; |
| } |
| |
| /* |
| * Put this console in the list - keep the |
| * preferred driver at the head of the list. |
| */ |
| console_lock(); |
| if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) { |
| newcon->next = console_drivers; |
| console_drivers = newcon; |
| if (newcon->next) |
| newcon->next->flags &= ~CON_CONSDEV; |
| /* Ensure this flag is always set for the head of the list */ |
| newcon->flags |= CON_CONSDEV; |
| } else { |
| newcon->next = console_drivers->next; |
| console_drivers->next = newcon; |
| } |
| |
| if (newcon->flags & CON_EXTENDED) |
| nr_ext_console_drivers++; |
| |
| newcon->dropped = 0; |
| newcon->thread = NULL; |
| newcon->blocked = true; |
| mutex_init(&newcon->lock); |
| |
| if (newcon->flags & CON_PRINTBUFFER) { |
| /* Get a consistent copy of @syslog_seq. */ |
| mutex_lock(&syslog_lock); |
| newcon->seq = syslog_seq; |
| mutex_unlock(&syslog_lock); |
| } else { |
| /* Begin with next message. */ |
| newcon->seq = prb_next_seq(prb); |
| } |
| |
| if (printk_kthreads_available) |
| printk_start_kthread(newcon); |
| |
| console_unlock(); |
| console_sysfs_notify(); |
| |
| /* |
| * By unregistering the bootconsoles after we enable the real console |
| * we get the "console xxx enabled" message on all the consoles - |
| * boot consoles, real consoles, etc - this is to ensure that end |
| * users know there might be something in the kernel's log buffer that |
| * went to the bootconsole (that they do not see on the real console) |
| */ |
| con_printk(KERN_INFO, newcon, "enabled\n"); |
| if (bootcon_enabled && |
| ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) && |
| !keep_bootcon) { |
| /* We need to iterate through all boot consoles, to make |
| * sure we print everything out, before we unregister them. |
| */ |
| for_each_console(con) |
| if (con->flags & CON_BOOT) |
| unregister_console(con); |
| } |
| } |
| EXPORT_SYMBOL(register_console); |
| |
| int unregister_console(struct console *console) |
| { |
| struct task_struct *thd; |
| struct console *con; |
| int res; |
| |
| con_printk(KERN_INFO, console, "disabled\n"); |
| |
| res = _braille_unregister_console(console); |
| if (res < 0) |
| return res; |
| if (res > 0) |
| return 0; |
| |
| res = -ENODEV; |
| console_lock(); |
| if (console_drivers == console) { |
| console_drivers=console->next; |
| res = 0; |
| } else { |
| for_each_console(con) { |
| if (con->next == console) { |
| con->next = console->next; |
| res = 0; |
| break; |
| } |
| } |
| } |
| |
| if (res) |
| goto out_disable_unlock; |
| |
| if (console->flags & CON_EXTENDED) |
| nr_ext_console_drivers--; |
| |
| /* |
| * If this isn't the last console and it has CON_CONSDEV set, we |
| * need to set it on the next preferred console. |
| */ |
| if (console_drivers != NULL && console->flags & CON_CONSDEV) |
| console_drivers->flags |= CON_CONSDEV; |
| |
| console->flags &= ~CON_ENABLED; |
| |
| /* |
| * console->thread can only be cleared under the console lock. But |
| * stopping the thread must be done without the console lock. The |
| * task that clears @thread is the task that stops the kthread. |
| */ |
| thd = console->thread; |
| console->thread = NULL; |
| |
| console_unlock(); |
| |
| if (thd) |
| kthread_stop(thd); |
| |
| console_sysfs_notify(); |
| |
| if (console->exit) |
| res = console->exit(console); |
| |
| return res; |
| |
| out_disable_unlock: |
| console->flags &= ~CON_ENABLED; |
| console_unlock(); |
| |
| return res; |
| } |
| EXPORT_SYMBOL(unregister_console); |
| |
| /* |
| * Initialize the console device. This is called *early*, so |
| * we can't necessarily depend on lots of kernel help here. |
| * Just do some early initializations, and do the complex setup |
| * later. |
| */ |
| void __init console_init(void) |
| { |
| int ret; |
| initcall_t call; |
| initcall_entry_t *ce; |
| |
| /* Setup the default TTY line discipline. */ |
| n_tty_init(); |
| |
| /* |
| * set up the console device so that later boot sequences can |
| * inform about problems etc.. |
| */ |
| ce = __con_initcall_start; |
| trace_initcall_level("console"); |
| while (ce < __con_initcall_end) { |
| call = initcall_from_entry(ce); |
| trace_initcall_start(call); |
| ret = call(); |
| trace_initcall_finish(call, ret); |
| ce++; |
| } |
| } |
| |
| /* |
| * Some boot consoles access data that is in the init section and which will |
| * be discarded after the initcalls have been run. To make sure that no code |
| * will access this data, unregister the boot consoles in a late initcall. |
| * |
| * If for some reason, such as deferred probe or the driver being a loadable |
| * module, the real console hasn't registered yet at this point, there will |
| * be a brief interval in which no messages are logged to the console, which |
| * makes it difficult to diagnose problems that occur during this time. |
| * |
| * To mitigate this problem somewhat, only unregister consoles whose memory |
| * intersects with the init section. Note that all other boot consoles will |
| * get unregistered when the real preferred console is registered. |
| */ |
| static int __init printk_late_init(void) |
| { |
| struct console *con; |
| int ret; |
| |
| for_each_console(con) { |
| if (!(con->flags & CON_BOOT)) |
| continue; |
| |
| /* Check addresses that might be used for enabled consoles. */ |
| if (init_section_intersects(con, sizeof(*con)) || |
| init_section_contains(con->write, 0) || |
| init_section_contains(con->read, 0) || |
| init_section_contains(con->device, 0) || |
| init_section_contains(con->unblank, 0) || |
| init_section_contains(con->data, 0)) { |
| /* |
| * Please, consider moving the reported consoles out |
| * of the init section. |
| */ |
| pr_warn("bootconsole [%s%d] uses init memory and must be disabled even before the real one is ready\n", |
| con->name, con->index); |
| unregister_console(con); |
| } |
| } |
| ret = cpuhp_setup_state_nocalls(CPUHP_PRINTK_DEAD, "printk:dead", NULL, |
| console_cpu_notify); |
| WARN_ON(ret < 0); |
| ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "printk:online", |
| console_cpu_notify, NULL); |
| WARN_ON(ret < 0); |
| printk_sysctl_init(); |
| return 0; |
| } |
| late_initcall(printk_late_init); |
| |
| static int __init printk_activate_kthreads(void) |
| { |
| struct console *con; |
| |
| console_lock(); |
| printk_kthreads_available = true; |
| for_each_console(con) |
| printk_start_kthread(con); |
| console_unlock(); |
| |
| return 0; |
| } |
| early_initcall(printk_activate_kthreads); |
| |
| #if defined CONFIG_PRINTK |
| /* If @con is specified, only wait for that console. Otherwise wait for all. */ |
| static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress) |
| { |
| int remaining = timeout_ms; |
| struct console *c; |
| u64 last_diff = 0; |
| u64 printk_seq; |
| u64 diff; |
| u64 seq; |
| |
| might_sleep(); |
| |
| seq = prb_next_seq(prb); |
| |
| for (;;) { |
| diff = 0; |
| |
| console_lock(); |
| for_each_console(c) { |
| if (con && con != c) |
| continue; |
| if (!console_is_usable(c)) |
| continue; |
| printk_seq = c->seq; |
| if (printk_seq < seq) |
| diff += seq - printk_seq; |
| } |
| console_unlock(); |
| |
| if (diff != last_diff && reset_on_progress) |
| remaining = timeout_ms; |
| |
| if (diff == 0 || remaining == 0) |
| break; |
| |
| if (remaining < 0) { |
| /* no timeout limit */ |
| msleep(100); |
| } else if (remaining < 100) { |
| msleep(remaining); |
| remaining = 0; |
| } else { |
| msleep(100); |
| remaining -= 100; |
| } |
| |
| last_diff = diff; |
| } |
| |
| return (diff == 0); |
| } |
| |
| /** |
| * pr_flush() - Wait for printing threads to catch up. |
| * |
| * @timeout_ms: The maximum time (in ms) to wait. |
| * @reset_on_progress: Reset the timeout if forward progress is seen. |
| * |
| * A value of 0 for @timeout_ms means no waiting will occur. A value of -1 |
| * represents infinite waiting. |
| * |
| * If @reset_on_progress is true, the timeout will be reset whenever any |
| * printer has been seen to make some forward progress. |
| * |
| * Context: Process context. May sleep while acquiring console lock. |
| * Return: true if all enabled printers are caught up. |
| */ |
| bool pr_flush(int timeout_ms, bool reset_on_progress) |
| { |
| return __pr_flush(NULL, timeout_ms, reset_on_progress); |
| } |
| EXPORT_SYMBOL(pr_flush); |
| |
| static void __printk_fallback_preferred_direct(void) |
| { |
| printk_prefer_direct_enter(); |
| pr_err("falling back to preferred direct printing\n"); |
| printk_kthreads_available = false; |
| } |
| |
| /* |
| * Enter preferred direct printing, but never exit. Mark console threads as |
| * unavailable. The system is then forever in preferred direct printing and |
| * any printing threads will exit. |
| * |
| * Must *not* be called under console_lock. Use |
| * __printk_fallback_preferred_direct() if already holding console_lock. |
| */ |
| static void printk_fallback_preferred_direct(void) |
| { |
| console_lock(); |
| __printk_fallback_preferred_direct(); |
| console_unlock(); |
| } |
| |
| /* |
| * Print a record for a given console, not allowing another printk() caller |
| * to take over. This is appropriate for contexts that do not have the |
| * console_lock. |
| * |
| * See __console_emit_next_record() for argument and return details. |
| */ |
| static bool console_emit_next_record(struct console *con, char *text, char *ext_text, |
| char *dropped_text) |
| { |
| return __console_emit_next_record(con, text, ext_text, dropped_text, NULL); |
| } |
| |
| static bool printer_should_wake(struct console *con, u64 seq) |
| { |
| short flags; |
| |
| if (kthread_should_stop() || !printk_kthreads_available) |
| return true; |
| |
| if (con->blocked || |
| console_kthreads_atomically_blocked()) { |
| return false; |
| } |
| |
| /* |
| * This is an unsafe read from con->flags, but a false positive is |
| * not a problem. Worst case it would allow the printer to wake up |
| * although it is disabled. But the printer will notice that when |
| * attempting to print and instead go back to sleep. |
| */ |
| flags = data_race(READ_ONCE(con->flags)); |
| |
| if (!__console_is_usable(flags)) |
| return false; |
| |
| return prb_read_valid(prb, seq, NULL); |
| } |
| |
| static int printk_kthread_func(void *data) |
| { |
| struct console *con = data; |
| char *dropped_text = NULL; |
| char *ext_text = NULL; |
| u64 seq = 0; |
| char *text; |
| int error; |
| |
| text = kmalloc(CONSOLE_LOG_MAX, GFP_KERNEL); |
| if (!text) { |
| con_printk(KERN_ERR, con, "failed to allocate text buffer\n"); |
| printk_fallback_preferred_direct(); |
| goto out; |
| } |
| |
| if (con->flags & CON_EXTENDED) { |
| ext_text = kmalloc(CONSOLE_EXT_LOG_MAX, GFP_KERNEL); |
| if (!ext_text) { |
| con_printk(KERN_ERR, con, "failed to allocate ext_text buffer\n"); |
| printk_fallback_preferred_direct(); |
| goto out; |
| } |
| } else { |
| dropped_text = kmalloc(DROPPED_TEXT_MAX, GFP_KERNEL); |
| if (!dropped_text) { |
| con_printk(KERN_ERR, con, "failed to allocate dropped_text buffer\n"); |
| printk_fallback_preferred_direct(); |
| goto out; |
| } |
| } |
| |
| con_printk(KERN_INFO, con, "printing thread started\n"); |
| |
| for (;;) { |
| /* |
| * Guarantee this task is visible on the waitqueue before |
| * checking the wake condition. |
| * |
| * The full memory barrier within set_current_state() of |
| * prepare_to_wait_event() pairs with the full memory barrier |
| * within wq_has_sleeper(). |
| * |
| * This pairs with __wake_up_klogd:A. |
| */ |
| error = wait_event_interruptible(log_wait, |
| printer_should_wake(con, seq)); /* LMM(printk_kthread_func:A) */ |
| |
| if (kthread_should_stop() || !printk_kthreads_available) |
| break; |
| |
| if (error) |
| continue; |
| |
| error = mutex_lock_interruptible(&con->lock); |
| if (error) |
| continue; |
| |
| if (con->blocked || |
| !console_kthread_printing_tryenter()) { |
| /* Another context has locked the console_lock. */ |
| mutex_unlock(&con->lock); |
| continue; |
| } |
| |
| /* |
| * Although this context has not locked the console_lock, it |
| * is known that the console_lock is not locked and it is not |
| * possible for any other context to lock the console_lock. |
| * Therefore it is safe to read con->flags. |
| */ |
| |
| if (!__console_is_usable(con->flags)) { |
| console_kthread_printing_exit(); |
| mutex_unlock(&con->lock); |
| continue; |
| } |
| |
| /* |
| * Even though the printk kthread is always preemptible, it is |
| * still not allowed to call cond_resched() from within |
| * console drivers. The task may become non-preemptible in the |
| * console driver call chain. For example, vt_console_print() |
| * takes a spinlock and then can call into fbcon_redraw(), |
| * which can conditionally invoke cond_resched(). |
| */ |
| console_may_schedule = 0; |
| console_emit_next_record(con, text, ext_text, dropped_text); |
| |
| seq = con->seq; |
| |
| console_kthread_printing_exit(); |
| |
| mutex_unlock(&con->lock); |
| } |
| |
| con_printk(KERN_INFO, con, "printing thread stopped\n"); |
| out: |
| kfree(dropped_text); |
| kfree(ext_text); |
| kfree(text); |
| |
| console_lock(); |
| /* |
| * If this kthread is being stopped by another task, con->thread will |
| * already be NULL. That is fine. The important thing is that it is |
| * NULL after the kthread exits. |
| */ |
| con->thread = NULL; |
| console_unlock(); |
| |
| return 0; |
| } |
| |
| /* Must be called under console_lock. */ |
| static void printk_start_kthread(struct console *con) |
| { |
| /* |
| * Do not start a kthread if there is no write() callback. The |
| * kthreads assume the write() callback exists. |
| */ |
| if (!con->write) |
| return; |
| |
| con->thread = kthread_run(printk_kthread_func, con, |
| "pr/%s%d", con->name, con->index); |
| if (IS_ERR(con->thread)) { |
| con->thread = NULL; |
| con_printk(KERN_ERR, con, "unable to start printing thread\n"); |
| __printk_fallback_preferred_direct(); |
| return; |
| } |
| } |
| |
| /* |
| * Delayed printk version, for scheduler-internal messages: |
| */ |
| #define PRINTK_PENDING_WAKEUP 0x01 |
| #define PRINTK_PENDING_DIRECT_OUTPUT 0x02 |
| |
| static DEFINE_PER_CPU(int, printk_pending); |
| |
| static void wake_up_klogd_work_func(struct irq_work *irq_work) |
| { |
| int pending = this_cpu_xchg(printk_pending, 0); |
| |
| if (pending & PRINTK_PENDING_DIRECT_OUTPUT) { |
| printk_prefer_direct_enter(); |
| |
| /* If trylock fails, someone else is doing the printing */ |
| if (console_trylock()) |
| console_unlock(); |
| |
| printk_prefer_direct_exit(); |
| } |
| |
| if (pending & PRINTK_PENDING_WAKEUP) |
| wake_up_interruptible_all(&log_wait); |
| } |
| |
| static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = |
| IRQ_WORK_INIT_LAZY(wake_up_klogd_work_func); |
| |
| static void __wake_up_klogd(int val) |
| { |
| if (!printk_percpu_data_ready()) |
| return; |
| |
| preempt_disable(); |
| /* |
| * Guarantee any new records can be seen by tasks preparing to wait |
| * before this context checks if the wait queue is empty. |
| * |
| * The full memory barrier within wq_has_sleeper() pairs with the full |
| * memory barrier within set_current_state() of |
| * prepare_to_wait_event(), which is called after ___wait_event() adds |
| * the waiter but before it has checked the wait condition. |
| * |
| * This pairs with devkmsg_read:A, syslog_print:A, and |
| * printk_kthread_func:A. |
| */ |
| if (wq_has_sleeper(&log_wait) || /* LMM(__wake_up_klogd:A) */ |
| (val & PRINTK_PENDING_DIRECT_OUTPUT)) { |
| this_cpu_or(printk_pending, val); |
| irq_work_queue(this_cpu_ptr(&wake_up_klogd_work)); |
| } |
| preempt_enable(); |
| } |
| |
| void wake_up_klogd(void) |
| { |
| __wake_up_klogd(PRINTK_PENDING_WAKEUP); |
| } |
| |
| void defer_console_output(void) |
| { |
| /* |
| * New messages may have been added directly to the ringbuffer |
| * using vprintk_store(), so wake any waiters as well. |
| */ |
| int val = PRINTK_PENDING_WAKEUP; |
| |
| /* |
| * Make sure that some context will print the messages when direct |
| * printing is allowed. This happens in situations when the kthreads |
| * may not be as reliable or perhaps unusable. |
| */ |
| if (allow_direct_printing()) |
| val |= PRINTK_PENDING_DIRECT_OUTPUT; |
| |
| __wake_up_klogd(val); |
| } |
| |
| void printk_trigger_flush(void) |
| { |
| defer_console_output(); |
| } |
| |
| int vprintk_deferred(const char *fmt, va_list args) |
| { |
| int r; |
| |
| r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, fmt, args); |
| defer_console_output(); |
| |
| return r; |
| } |
| |
| int _printk_deferred(const char *fmt, ...) |
| { |
| va_list args; |
| int r; |
| |
| va_start(args, fmt); |
| r = vprintk_deferred(fmt, args); |
| va_end(args); |
| |
| return r; |
| } |
| |
| /* |
| * printk rate limiting, lifted from the networking subsystem. |
| * |
| * This enforces a rate limit: not more than 10 kernel messages |
| * every 5s to make a denial-of-service attack impossible. |
| */ |
| DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10); |
| |
| int __printk_ratelimit(const char *func) |
| { |
| return ___ratelimit(&printk_ratelimit_state, func); |
| } |
| EXPORT_SYMBOL(__printk_ratelimit); |
| |
| /** |
| * printk_timed_ratelimit - caller-controlled printk ratelimiting |
| * @caller_jiffies: pointer to caller's state |
| * @interval_msecs: minimum interval between prints |
| * |
| * printk_timed_ratelimit() returns true if more than @interval_msecs |
| * milliseconds have elapsed since the last time printk_timed_ratelimit() |
| * returned true. |
| */ |
| bool printk_timed_ratelimit(unsigned long *caller_jiffies, |
| unsigned int interval_msecs) |
| { |
| unsigned long elapsed = jiffies - *caller_jiffies; |
| |
| if (*caller_jiffies && elapsed <= msecs_to_jiffies(interval_msecs)) |
| return false; |
| |
| *caller_jiffies = jiffies; |
| return true; |
| } |
| EXPORT_SYMBOL(printk_timed_ratelimit); |
| |
| static DEFINE_SPINLOCK(dump_list_lock); |
| static LIST_HEAD(dump_list); |
| |
| /** |
| * kmsg_dump_register - register a kernel log dumper. |
| * @dumper: pointer to the kmsg_dumper structure |
| * |
| * Adds a kernel log dumper to the system. The dump callback in the |
| * structure will be called when the kernel oopses or panics and must be |
| * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise. |
| */ |
| int kmsg_dump_register(struct kmsg_dumper *dumper) |
| { |
| unsigned long flags; |
| int err = -EBUSY; |
| |
| /* The dump callback needs to be set */ |
| if (!dumper->dump) |
| return -EINVAL; |
| |
| spin_lock_irqsave(&dump_list_lock, flags); |
| /* Don't allow registering multiple times */ |
| if (!dumper->registered) { |
| dumper->registered = 1; |
| list_add_tail_rcu(&dumper->list, &dump_list); |
| err = 0; |
| } |
| spin_unlock_irqrestore(&dump_list_lock, flags); |
| |
| return err; |
| } |
| EXPORT_SYMBOL_GPL(kmsg_dump_register); |
| |
| /** |
| * kmsg_dump_unregister - unregister a kmsg dumper. |
| * @dumper: pointer to the kmsg_dumper structure |
| * |
| * Removes a dump device from the system. Returns zero on success and |
| * %-EINVAL otherwise. |
| */ |
| int kmsg_dump_unregister(struct kmsg_dumper *dumper) |
| { |
| unsigned long flags; |
| int err = -EINVAL; |
| |
| spin_lock_irqsave(&dump_list_lock, flags); |
| if (dumper->registered) { |
| dumper->registered = 0; |
| list_del_rcu(&dumper->list); |
| err = 0; |
| } |
| spin_unlock_irqrestore(&dump_list_lock, flags); |
| synchronize_rcu(); |
| |
| return err; |
| } |
| EXPORT_SYMBOL_GPL(kmsg_dump_unregister); |
| |
| static bool always_kmsg_dump; |
| module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR); |
| |
| const char *kmsg_dump_reason_str(enum kmsg_dump_reason reason) |
| { |
| switch (reason) { |
| case KMSG_DUMP_PANIC: |
| return "Panic"; |
| case KMSG_DUMP_OOPS: |
| return "Oops"; |
| case KMSG_DUMP_EMERG: |
| return "Emergency"; |
| case KMSG_DUMP_SHUTDOWN: |
| return "Shutdown"; |
| default: |
| return "Unknown"; |
| } |
| } |
| EXPORT_SYMBOL_GPL(kmsg_dump_reason_str); |
| |
| /** |
| * kmsg_dump - dump kernel log to kernel message dumpers. |
| * @reason: the reason (oops, panic etc) for dumping |
| * |
| * Call each of the registered dumper's dump() callback, which can |
| * retrieve the kmsg records with kmsg_dump_get_line() or |
| * kmsg_dump_get_buffer(). |
| */ |
| void kmsg_dump(enum kmsg_dump_reason reason) |
| { |
| struct kmsg_dumper *dumper; |
| |
| rcu_read_lock(); |
| list_for_each_entry_rcu(dumper, &dump_list, list) { |
| enum kmsg_dump_reason max_reason = dumper->max_reason; |
| |
| /* |
| * If client has not provided a specific max_reason, default |
| * to KMSG_DUMP_OOPS, unless always_kmsg_dump was set. |
| */ |
| if (max_reason == KMSG_DUMP_UNDEF) { |
| max_reason = always_kmsg_dump ? KMSG_DUMP_MAX : |
| KMSG_DUMP_OOPS; |
| } |
| if (reason > max_reason) |
| continue; |
| |
| /* invoke dumper which will iterate over records */ |
| dumper->dump(dumper, reason); |
| } |
| rcu_read_unlock(); |
| } |
| |
| /** |
| * kmsg_dump_get_line - retrieve one kmsg log line |
| * @iter: kmsg dump iterator |
| * @syslog: include the "<4>" prefixes |
| * @line: buffer to copy the line to |
| * @size: maximum size of the buffer |
| * @len: length of line placed into buffer |
| * |
| * Start at the beginning of the kmsg buffer, with the oldest kmsg |
| * record, and copy one record into the provided buffer. |
| * |
| * Consecutive calls will return the next available record moving |
| * towards the end of the buffer with the youngest messages. |
| * |
| * A return value of FALSE indicates that there are no more records to |
| * read. |
| */ |
| bool kmsg_dump_get_line(struct kmsg_dump_iter *iter, bool syslog, |
| char *line, size_t size, size_t *len) |
| { |
| u64 min_seq = latched_seq_read_nolock(&clear_seq); |
| struct printk_info info; |
| unsigned int line_count; |
| struct printk_record r; |
| size_t l = 0; |
| bool ret = false; |
| |
| if (iter->cur_seq < min_seq) |
| iter->cur_seq = min_seq; |
| |
| prb_rec_init_rd(&r, &info, line, size); |
| |
| /* Read text or count text lines? */ |
| if (line) { |
| if (!prb_read_valid(prb, iter->cur_seq, &r)) |
| goto out; |
| l = record_print_text(&r, syslog, printk_time); |
| } else { |
| if (!prb_read_valid_info(prb, iter->cur_seq, |
| &info, &line_count)) { |
| goto out; |
| } |
| l = get_record_print_text_size(&info, line_count, syslog, |
| printk_time); |
| |
| } |
| |
| iter->cur_seq = r.info->seq + 1; |
| ret = true; |
| out: |
| if (len) |
| *len = l; |
| return ret; |
| } |
| EXPORT_SYMBOL_GPL(kmsg_dump_get_line); |
| |
| /** |
| * kmsg_dump_get_buffer - copy kmsg log lines |
| * @iter: kmsg dump iterator |
| * @syslog: include the "<4>" prefixes |
| * @buf: buffer to copy the line to |
| * @size: maximum size of the buffer |
| * @len_out: length of line placed into buffer |
| * |
| * Start at the end of the kmsg buffer and fill the provided buffer |
| * with as many of the *youngest* kmsg records that fit into it. |
| * If the buffer is large enough, all available kmsg records will be |
| * copied with a single call. |
| * |
| * Consecutive calls will fill the buffer with the next block of |
| * available older records, not including the earlier retrieved ones. |
| * |
| * A return value of FALSE indicates that there are no more records to |
| * read. |
| */ |
| bool kmsg_dump_get_buffer(struct kmsg_dump_iter *iter, bool syslog, |
| char *buf, size_t size, size_t *len_out) |
| { |
| u64 min_seq = latched_seq_read_nolock(&clear_seq); |
| struct printk_info info; |
| struct printk_record r; |
| u64 seq; |
| u64 next_seq; |
| size_t len = 0; |
| bool ret = false; |
| bool time = printk_time; |
| |
| if (!buf || !size) |
| goto out; |
| |
| if (iter->cur_seq < min_seq) |
| iter->cur_seq = min_seq; |
| |
| if (prb_read_valid_info(prb, iter->cur_seq, &info, NULL)) { |
| if (info.seq != iter->cur_seq) { |
| /* messages are gone, move to first available one */ |
| iter->cur_seq = info.seq; |
| } |
| } |
| |
| /* last entry */ |
| if (iter->cur_seq >= iter->next_seq) |
| goto out; |
| |
| /* |
| * Find first record that fits, including all following records, |
| * into the user-provided buffer for this dump. Pass in size-1 |
| * because this function (by way of record_print_text()) will |
| * not write more than size-1 bytes of text into @buf. |
| */ |
| seq = find_first_fitting_seq(iter->cur_seq, iter->next_seq, |
| size - 1, syslog, time); |
| |
| /* |
| * Next kmsg_dump_get_buffer() invocation will dump block of |
| * older records stored right before this one. |
| */ |
| next_seq = seq; |
| |
| prb_rec_init_rd(&r, &info, buf, size); |
| |
| len = 0; |
| prb_for_each_record(seq, prb, seq, &r) { |
| if (r.info->seq >= iter->next_seq) |
| break; |
| |
| len += record_print_text(&r, syslog, time); |
| |
| /* Adjust record to store to remaining buffer space. */ |
| prb_rec_init_rd(&r, &info, buf + len, size - len); |
| } |
| |
| iter->next_seq = next_seq; |
| ret = true; |
| out: |
| if (len_out) |
| *len_out = len; |
| return ret; |
| } |
| EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer); |
| |
| /** |
| * kmsg_dump_rewind - reset the iterator |
| * @iter: kmsg dump iterator |
| * |
| * Reset the dumper's iterator so that kmsg_dump_get_line() and |
| * kmsg_dump_get_buffer() can be called again and used multiple |
| * times within the same dumper.dump() callback. |
| */ |
| void kmsg_dump_rewind(struct kmsg_dump_iter *iter) |
| { |
| iter->cur_seq = latched_seq_read_nolock(&clear_seq); |
| iter->next_seq = prb_next_seq(prb); |
| } |
| EXPORT_SYMBOL_GPL(kmsg_dump_rewind); |
| |
| #endif |
| |
| #ifdef CONFIG_SMP |
| static atomic_t printk_cpu_sync_owner = ATOMIC_INIT(-1); |
| static atomic_t printk_cpu_sync_nested = ATOMIC_INIT(0); |
| |
| /** |
| * __printk_cpu_sync_wait() - Busy wait until the printk cpu-reentrant |
| * spinning lock is not owned by any CPU. |
| * |
| * Context: Any context. |
| */ |
| void __printk_cpu_sync_wait(void) |
| { |
| do { |
| cpu_relax(); |
| } while (atomic_read(&printk_cpu_sync_owner) != -1); |
| } |
| EXPORT_SYMBOL(__printk_cpu_sync_wait); |
| |
| /** |
| * __printk_cpu_sync_try_get() - Try to acquire the printk cpu-reentrant |
| * spinning lock. |
| * |
| * If no processor has the lock, the calling processor takes the lock and |
| * becomes the owner. If the calling processor is already the owner of the |
| * lock, this function succeeds immediately. |
| * |
| * Context: Any context. Expects interrupts to be disabled. |
| * Return: 1 on success, otherwise 0. |
| */ |
| int __printk_cpu_sync_try_get(void) |
| { |
| int cpu; |
| int old; |
| |
| cpu = smp_processor_id(); |
| |
| /* |
| * Guarantee loads and stores from this CPU when it is the lock owner |
| * are _not_ visible to the previous lock owner. This pairs with |
| * __printk_cpu_sync_put:B. |
| * |
| * Memory barrier involvement: |
| * |
| * If __printk_cpu_sync_try_get:A reads from __printk_cpu_sync_put:B, |
| * then __printk_cpu_sync_put:A can never read from |
| * __printk_cpu_sync_try_get:B. |
| * |
| * Relies on: |
| * |
| * RELEASE from __printk_cpu_sync_put:A to __printk_cpu_sync_put:B |
| * of the previous CPU |
| * matching |
| * ACQUIRE from __printk_cpu_sync_try_get:A to |
| * __printk_cpu_sync_try_get:B of this CPU |
| */ |
| old = atomic_cmpxchg_acquire(&printk_cpu_sync_owner, -1, |
| cpu); /* LMM(__printk_cpu_sync_try_get:A) */ |
| if (old == -1) { |
| /* |
| * This CPU is now the owner and begins loading/storing |
| * data: LMM(__printk_cpu_sync_try_get:B) |
| */ |
| return 1; |
| |
| } else if (old == cpu) { |
| /* This CPU is already the owner. */ |
| atomic_inc(&printk_cpu_sync_nested); |
| return 1; |
| } |
| |
| return 0; |
| } |
| EXPORT_SYMBOL(__printk_cpu_sync_try_get); |
| |
| /** |
| * __printk_cpu_sync_put() - Release the printk cpu-reentrant spinning lock. |
| * |
| * The calling processor must be the owner of the lock. |
| * |
| * Context: Any context. Expects interrupts to be disabled. |
| */ |
| void __printk_cpu_sync_put(void) |
| { |
| if (atomic_read(&printk_cpu_sync_nested)) { |
| atomic_dec(&printk_cpu_sync_nested); |
| return; |
| } |
| |
| /* |
| * This CPU is finished loading/storing data: |
| * LMM(__printk_cpu_sync_put:A) |
| */ |
| |
| /* |
| * Guarantee loads and stores from this CPU when it was the |
| * lock owner are visible to the next lock owner. This pairs |
| * with __printk_cpu_sync_try_get:A. |
| * |
| * Memory barrier involvement: |
| * |
| * If __printk_cpu_sync_try_get:A reads from __printk_cpu_sync_put:B, |
| * then __printk_cpu_sync_try_get:B reads from __printk_cpu_sync_put:A. |
| * |
| * Relies on: |
| * |
| * RELEASE from __printk_cpu_sync_put:A to __printk_cpu_sync_put:B |
| * of this CPU |
| * matching |
| * ACQUIRE from __printk_cpu_sync_try_get:A to |
| * __printk_cpu_sync_try_get:B of the next CPU |
| */ |
| atomic_set_release(&printk_cpu_sync_owner, |
| -1); /* LMM(__printk_cpu_sync_put:B) */ |
| } |
| EXPORT_SYMBOL(__printk_cpu_sync_put); |
| #endif /* CONFIG_SMP */ |