v4.19.13 snapshot.
diff --git a/kernel/printk/Makefile b/kernel/printk/Makefile
new file mode 100644
index 0000000..4a2ffc3
--- /dev/null
+++ b/kernel/printk/Makefile
@@ -0,0 +1,3 @@
+obj-y = printk.o
+obj-$(CONFIG_PRINTK) += printk_safe.o
+obj-$(CONFIG_A11Y_BRAILLE_CONSOLE) += braille.o
diff --git a/kernel/printk/braille.c b/kernel/printk/braille.c
new file mode 100644
index 0000000..1d21eba
--- /dev/null
+++ b/kernel/printk/braille.c
@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: GPL-2.0
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/console.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+
+#include "console_cmdline.h"
+#include "braille.h"
+
+int _braille_console_setup(char **str, char **brl_options)
+{
+ if (!strncmp(*str, "brl,", 4)) {
+ *brl_options = "";
+ *str += 4;
+ } else if (!strncmp(*str, "brl=", 4)) {
+ *brl_options = *str + 4;
+ *str = strchr(*brl_options, ',');
+ if (!*str) {
+ pr_err("need port name after brl=\n");
+ return -EINVAL;
+ }
+ *((*str)++) = 0;
+ }
+
+ return 0;
+}
+
+int
+_braille_register_console(struct console *console, struct console_cmdline *c)
+{
+ int rtn = 0;
+
+ if (c->brl_options) {
+ console->flags |= CON_BRL;
+ rtn = braille_register_console(console, c->index, c->options,
+ c->brl_options);
+ }
+
+ return rtn;
+}
+
+int
+_braille_unregister_console(struct console *console)
+{
+ if (console->flags & CON_BRL)
+ return braille_unregister_console(console);
+
+ return 0;
+}
diff --git a/kernel/printk/braille.h b/kernel/printk/braille.h
new file mode 100644
index 0000000..123154f
--- /dev/null
+++ b/kernel/printk/braille.h
@@ -0,0 +1,56 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _PRINTK_BRAILLE_H
+#define _PRINTK_BRAILLE_H
+
+#ifdef CONFIG_A11Y_BRAILLE_CONSOLE
+
+static inline void
+braille_set_options(struct console_cmdline *c, char *brl_options)
+{
+ c->brl_options = brl_options;
+}
+
+/*
+ * Setup console according to braille options.
+ * Return -EINVAL on syntax error, 0 on success (or no braille option was
+ * actually given).
+ * Modifies str to point to the serial options
+ * Sets brl_options to the parsed braille options.
+ */
+int
+_braille_console_setup(char **str, char **brl_options);
+
+int
+_braille_register_console(struct console *console, struct console_cmdline *c);
+
+int
+_braille_unregister_console(struct console *console);
+
+#else
+
+static inline void
+braille_set_options(struct console_cmdline *c, char *brl_options)
+{
+}
+
+static inline int
+_braille_console_setup(char **str, char **brl_options)
+{
+ return 0;
+}
+
+static inline int
+_braille_register_console(struct console *console, struct console_cmdline *c)
+{
+ return 0;
+}
+
+static inline int
+_braille_unregister_console(struct console *console)
+{
+ return 0;
+}
+
+#endif
+
+#endif
diff --git a/kernel/printk/console_cmdline.h b/kernel/printk/console_cmdline.h
new file mode 100644
index 0000000..11f19c4
--- /dev/null
+++ b/kernel/printk/console_cmdline.h
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _CONSOLE_CMDLINE_H
+#define _CONSOLE_CMDLINE_H
+
+struct console_cmdline
+{
+ char name[16]; /* Name of the driver */
+ int index; /* Minor dev. to use */
+ char *options; /* Options for the driver */
+#ifdef CONFIG_A11Y_BRAILLE_CONSOLE
+ char *brl_options; /* Options for braille driver */
+#endif
+};
+
+#endif
diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h
new file mode 100644
index 0000000..0f18988
--- /dev/null
+++ b/kernel/printk/internal.h
@@ -0,0 +1,79 @@
+/*
+ * internal.h - printk internal definitions
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+#include <linux/percpu.h>
+
+#ifdef CONFIG_PRINTK
+
+#define PRINTK_SAFE_CONTEXT_MASK 0x3fffffff
+#define PRINTK_NMI_DIRECT_CONTEXT_MASK 0x40000000
+#define PRINTK_NMI_CONTEXT_MASK 0x80000000
+
+extern raw_spinlock_t logbuf_lock;
+
+__printf(5, 0)
+int vprintk_store(int facility, int level,
+ const char *dict, size_t dictlen,
+ const char *fmt, va_list args);
+
+__printf(1, 0) int vprintk_default(const char *fmt, va_list args);
+__printf(1, 0) int vprintk_deferred(const char *fmt, va_list args);
+__printf(1, 0) int vprintk_func(const char *fmt, va_list args);
+void __printk_safe_enter(void);
+void __printk_safe_exit(void);
+
+#define printk_safe_enter_irqsave(flags) \
+ do { \
+ local_irq_save(flags); \
+ __printk_safe_enter(); \
+ } while (0)
+
+#define printk_safe_exit_irqrestore(flags) \
+ do { \
+ __printk_safe_exit(); \
+ local_irq_restore(flags); \
+ } while (0)
+
+#define printk_safe_enter_irq() \
+ do { \
+ local_irq_disable(); \
+ __printk_safe_enter(); \
+ } while (0)
+
+#define printk_safe_exit_irq() \
+ do { \
+ __printk_safe_exit(); \
+ local_irq_enable(); \
+ } while (0)
+
+void defer_console_output(void);
+
+#else
+
+__printf(1, 0) int vprintk_func(const char *fmt, va_list args) { return 0; }
+
+/*
+ * In !PRINTK builds we still export logbuf_lock spin_lock, console_sem
+ * semaphore and some of console functions (console_unlock()/etc.), so
+ * printk-safe must preserve the existing local IRQ guarantees.
+ */
+#define printk_safe_enter_irqsave(flags) local_irq_save(flags)
+#define printk_safe_exit_irqrestore(flags) local_irq_restore(flags)
+
+#define printk_safe_enter_irq() local_irq_disable()
+#define printk_safe_exit_irq() local_irq_enable()
+
+#endif /* CONFIG_PRINTK */
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
new file mode 100644
index 0000000..06045ab
--- /dev/null
+++ b/kernel/printk/printk.c
@@ -0,0 +1,3281 @@
+/*
+ * linux/kernel/printk.c
+ *
+ * Copyright (C) 1991, 1992 Linus Torvalds
+ *
+ * Modified to make sys_syslog() more flexible: added commands to
+ * return the last 4k of kernel messages, regardless of whether
+ * they've been read or not. Added option to suppress kernel printk's
+ * to the console. Added hook for sending the console messages
+ * elsewhere, in preparation for a serial line console (someday).
+ * Ted Ts'o, 2/11/93.
+ * Modified for sysctl support, 1/8/97, Chris Horn.
+ * Fixed SMP synchronization, 08/08/99, Manfred Spraul
+ * manfred@colorfullife.com
+ * Rewrote bits to get rid of console_lock
+ * 01Mar01 Andrew Morton
+ */
+
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/tty.h>
+#include <linux/tty_driver.h>
+#include <linux/console.h>
+#include <linux/init.h>
+#include <linux/jiffies.h>
+#include <linux/nmi.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/delay.h>
+#include <linux/smp.h>
+#include <linux/security.h>
+#include <linux/bootmem.h>
+#include <linux/memblock.h>
+#include <linux/syscalls.h>
+#include <linux/crash_core.h>
+#include <linux/kdb.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 "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 */
+};
+
+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);
+
+#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)
+{
+ if (!str)
+ return -EINVAL;
+
+ if (!strncmp(str, "on", 2)) {
+ devkmsg_log = DEVKMSG_LOG_MASK_ON;
+ return 2;
+ } else if (!strncmp(str, "off", 3)) {
+ devkmsg_log = DEVKMSG_LOG_MASK_OFF;
+ return 3;
+ } else if (!strncmp(str, "ratelimit", 9)) {
+ devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT;
+ return 9;
+ }
+ return -EINVAL;
+}
+
+static int __init control_devkmsg(char *str)
+{
+ if (__control_devkmsg(str) < 0)
+ 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 0;
+}
+__setup("printk.devkmsg=", control_devkmsg);
+
+char devkmsg_log_str[DEVKMSG_STR_MAX_SIZE] = "ratelimit";
+
+int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write,
+ void __user *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;
+}
+
+/*
+ * Number of registered extended console drivers.
+ *
+ * If extended consoles are present, in-kernel cont reassembly is disabled
+ * and each fragment is stored as a separate log entry with proper
+ * continuation flag so that every emitted message has full metadata. This
+ * doesn't change the result for regular consoles or /proc/kmsg. For
+ * /dev/kmsg, as long as the reader concatenates messages according to
+ * consecutive continuation flags, the end result should be the same too.
+ */
+static int nr_ext_console_drivers;
+
+/*
+ * 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, 1, ip);
+
+ printk_safe_enter_irqsave(flags);
+ up(&console_sem);
+ printk_safe_exit_irqrestore(flags);
+}
+#define up_console_sem() __up_console_sem(_RET_IP_)
+
+/*
+ * This is used for debugging the mess that is the VT code by
+ * keeping track if we have the console semaphore held. It's
+ * definitely not the perfect debug tool (we don't know if _WE_
+ * hold it and are racing, but it helps tracking those weird code
+ * paths in the console code where we end up in places I want
+ * locked without the console sempahore held).
+ */
+static int console_locked, console_suspended;
+
+/*
+ * If exclusive_console is non-NULL then only this console is to be printed to.
+ */
+static struct console *exclusive_console;
+
+/*
+ * Array of consoles built from command line options (console=)
+ */
+
+#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 chain of concatenated variable
+ * length records. Every record starts with a record header, containing
+ * the overall length of the record.
+ *
+ * The heads to the first and last entry in the buffer, as well as the
+ * sequence numbers of these entries are maintained when messages are
+ * stored.
+ *
+ * If the heads indicate available messages, the length in the header
+ * tells the start next message. A length == 0 for the next message
+ * indicates a wrap-around to the beginning of the buffer.
+ *
+ * Every record carries the monotonic timestamp in microseconds, as well as
+ * the standard userspace syslog level and syslog facility. The usual
+ * kernel messages use LOG_KERN; userspace-injected messages always carry
+ * a matching syslog facility, by default LOG_USER. The origin of every
+ * message can be reliably determined that way.
+ *
+ * The human readable log message directly follows the message header. The
+ * length of the message text is stored in the header, the stored message
+ * is not terminated.
+ *
+ * Optionally, a message can carry a dictionary of properties (key/value pairs),
+ * to provide userspace with a machine-readable message context.
+ *
+ * Examples for well-defined, commonly used property names are:
+ * DEVICE=b12:8 device identifier
+ * b12:8 block dev_t
+ * c127:3 char dev_t
+ * n8 netdev ifindex
+ * +sound:card0 subsystem:devname
+ * SUBSYSTEM=pci driver-core subsystem name
+ *
+ * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
+ * follows directly after a '=' character. Every property is terminated by
+ * a '\0' character. The last property is not terminated.
+ *
+ * Example of a message structure:
+ * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
+ * 0008 34 00 record is 52 bytes long
+ * 000a 0b 00 text is 11 bytes long
+ * 000c 1f 00 dictionary is 23 bytes long
+ * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
+ * 0010 69 74 27 73 20 61 20 6c "it's a l"
+ * 69 6e 65 "ine"
+ * 001b 44 45 56 49 43 "DEVIC"
+ * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
+ * 52 49 56 45 52 3d 62 75 "RIVER=bu"
+ * 67 "g"
+ * 0032 00 00 00 padding to next message header
+ *
+ * The 'struct printk_log' buffer header must never be directly exported to
+ * userspace, it is a kernel-private implementation detail that might
+ * need to be changed in the future, when the requirements change.
+ *
+ * /dev/kmsg exports the structured data in the following line format:
+ * "<level>,<sequnum>,<timestamp>,<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.
+ */
+
+enum log_flags {
+ LOG_NEWLINE = 2, /* text ended with a newline */
+ LOG_PREFIX = 4, /* text started with a prefix */
+ LOG_CONT = 8, /* text is a fragment of a continuation line */
+};
+
+struct printk_log {
+ u64 ts_nsec; /* timestamp in nanoseconds */
+ u16 len; /* length of entire record */
+ u16 text_len; /* length of text buffer */
+ u16 dict_len; /* length of dictionary buffer */
+ u8 facility; /* syslog facility */
+ u8 flags:5; /* internal record flags */
+ u8 level:3; /* syslog level */
+}
+#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
+__packed __aligned(4)
+#endif
+;
+
+/*
+ * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
+ * within the scheduler's rq lock. It must be released before calling
+ * console_unlock() or anything else that might wake up a process.
+ */
+DEFINE_RAW_SPINLOCK(logbuf_lock);
+
+/*
+ * Helper macros to lock/unlock logbuf_lock and switch between
+ * printk-safe/unsafe modes.
+ */
+#define logbuf_lock_irq() \
+ do { \
+ printk_safe_enter_irq(); \
+ raw_spin_lock(&logbuf_lock); \
+ } while (0)
+
+#define logbuf_unlock_irq() \
+ do { \
+ raw_spin_unlock(&logbuf_lock); \
+ printk_safe_exit_irq(); \
+ } while (0)
+
+#define logbuf_lock_irqsave(flags) \
+ do { \
+ printk_safe_enter_irqsave(flags); \
+ raw_spin_lock(&logbuf_lock); \
+ } while (0)
+
+#define logbuf_unlock_irqrestore(flags) \
+ do { \
+ raw_spin_unlock(&logbuf_lock); \
+ printk_safe_exit_irqrestore(flags); \
+ } while (0)
+
+#ifdef CONFIG_PRINTK
+DECLARE_WAIT_QUEUE_HEAD(log_wait);
+/* the next printk record to read by syslog(READ) or /proc/kmsg */
+static u64 syslog_seq;
+static u32 syslog_idx;
+static size_t syslog_partial;
+
+/* index and sequence number of the first record stored in the buffer */
+static u64 log_first_seq;
+static u32 log_first_idx;
+
+/* index and sequence number of the next record to store in the buffer */
+static u64 log_next_seq;
+static u32 log_next_idx;
+
+/* the next printk record to write to the console */
+static u64 console_seq;
+static u32 console_idx;
+
+/* the next printk record to read after the last 'clear' command */
+static u64 clear_seq;
+static u32 clear_idx;
+
+#define PREFIX_MAX 32
+#define LOG_LINE_MAX (1024 - PREFIX_MAX)
+
+#define LOG_LEVEL(v) ((v) & 0x07)
+#define LOG_FACILITY(v) ((v) >> 3 & 0xff)
+
+/* record buffer */
+#define LOG_ALIGN __alignof__(struct printk_log)
+#define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
+static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
+static char *log_buf = __log_buf;
+static u32 log_buf_len = __LOG_BUF_LEN;
+
+/* 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;
+}
+
+/* human readable text of the record */
+static char *log_text(const struct printk_log *msg)
+{
+ return (char *)msg + sizeof(struct printk_log);
+}
+
+/* optional key/value pair dictionary attached to the record */
+static char *log_dict(const struct printk_log *msg)
+{
+ return (char *)msg + sizeof(struct printk_log) + msg->text_len;
+}
+
+/* get record by index; idx must point to valid msg */
+static struct printk_log *log_from_idx(u32 idx)
+{
+ struct printk_log *msg = (struct printk_log *)(log_buf + idx);
+
+ /*
+ * A length == 0 record is the end of buffer marker. Wrap around and
+ * read the message at the start of the buffer.
+ */
+ if (!msg->len)
+ return (struct printk_log *)log_buf;
+ return msg;
+}
+
+/* get next record; idx must point to valid msg */
+static u32 log_next(u32 idx)
+{
+ struct printk_log *msg = (struct printk_log *)(log_buf + idx);
+
+ /* length == 0 indicates the end of the buffer; wrap */
+ /*
+ * A length == 0 record is the end of buffer marker. Wrap around and
+ * read the message at the start of the buffer as *this* one, and
+ * return the one after that.
+ */
+ if (!msg->len) {
+ msg = (struct printk_log *)log_buf;
+ return msg->len;
+ }
+ return idx + msg->len;
+}
+
+/*
+ * Check whether there is enough free space for the given message.
+ *
+ * The same values of first_idx and next_idx mean that the buffer
+ * is either empty or full.
+ *
+ * If the buffer is empty, we must respect the position of the indexes.
+ * They cannot be reset to the beginning of the buffer.
+ */
+static int logbuf_has_space(u32 msg_size, bool empty)
+{
+ u32 free;
+
+ if (log_next_idx > log_first_idx || empty)
+ free = max(log_buf_len - log_next_idx, log_first_idx);
+ else
+ free = log_first_idx - log_next_idx;
+
+ /*
+ * We need space also for an empty header that signalizes wrapping
+ * of the buffer.
+ */
+ return free >= msg_size + sizeof(struct printk_log);
+}
+
+static int log_make_free_space(u32 msg_size)
+{
+ while (log_first_seq < log_next_seq &&
+ !logbuf_has_space(msg_size, false)) {
+ /* drop old messages until we have enough contiguous space */
+ log_first_idx = log_next(log_first_idx);
+ log_first_seq++;
+ }
+
+ if (clear_seq < log_first_seq) {
+ clear_seq = log_first_seq;
+ clear_idx = log_first_idx;
+ }
+
+ /* sequence numbers are equal, so the log buffer is empty */
+ if (logbuf_has_space(msg_size, log_first_seq == log_next_seq))
+ return 0;
+
+ return -ENOMEM;
+}
+
+/* compute the message size including the padding bytes */
+static u32 msg_used_size(u16 text_len, u16 dict_len, u32 *pad_len)
+{
+ u32 size;
+
+ size = sizeof(struct printk_log) + text_len + dict_len;
+ *pad_len = (-size) & (LOG_ALIGN - 1);
+ size += *pad_len;
+
+ return size;
+}
+
+/*
+ * 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 u32 truncate_msg(u16 *text_len, u16 *trunc_msg_len,
+ u16 *dict_len, u32 *pad_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 */
+ *trunc_msg_len = strlen(trunc_msg);
+ /* disable the "dict" completely */
+ *dict_len = 0;
+ /* compute the size again, count also the warning message */
+ return msg_used_size(*text_len + *trunc_msg_len, 0, pad_len);
+}
+
+/* insert record into the buffer, discard old ones, update heads */
+static int log_store(int facility, int level,
+ enum log_flags flags, u64 ts_nsec,
+ const char *dict, u16 dict_len,
+ const char *text, u16 text_len)
+{
+ struct printk_log *msg;
+ u32 size, pad_len;
+ u16 trunc_msg_len = 0;
+
+ /* number of '\0' padding bytes to next message */
+ size = msg_used_size(text_len, dict_len, &pad_len);
+
+ if (log_make_free_space(size)) {
+ /* truncate the message if it is too long for empty buffer */
+ size = truncate_msg(&text_len, &trunc_msg_len,
+ &dict_len, &pad_len);
+ /* survive when the log buffer is too small for trunc_msg */
+ if (log_make_free_space(size))
+ return 0;
+ }
+
+ if (log_next_idx + size + sizeof(struct printk_log) > log_buf_len) {
+ /*
+ * This message + an additional empty header does not fit
+ * at the end of the buffer. Add an empty header with len == 0
+ * to signify a wrap around.
+ */
+ memset(log_buf + log_next_idx, 0, sizeof(struct printk_log));
+ log_next_idx = 0;
+ }
+
+ /* fill message */
+ msg = (struct printk_log *)(log_buf + log_next_idx);
+ memcpy(log_text(msg), text, text_len);
+ msg->text_len = text_len;
+ if (trunc_msg_len) {
+ memcpy(log_text(msg) + text_len, trunc_msg, trunc_msg_len);
+ msg->text_len += trunc_msg_len;
+ }
+ memcpy(log_dict(msg), dict, dict_len);
+ msg->dict_len = dict_len;
+ msg->facility = facility;
+ msg->level = level & 7;
+ msg->flags = flags & 0x1f;
+ if (ts_nsec > 0)
+ msg->ts_nsec = ts_nsec;
+ else
+ msg->ts_nsec = local_clock();
+ memset(log_dict(msg) + dict_len, 0, pad_len);
+ msg->len = size;
+
+ /* insert message */
+ log_next_idx += msg->len;
+ log_next_seq++;
+
+ return msg->text_len;
+}
+
+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 msg_print_ext_header(char *buf, size_t size,
+ struct printk_log *msg, u64 seq)
+{
+ u64 ts_usec = msg->ts_nsec;
+
+ do_div(ts_usec, 1000);
+
+ return scnprintf(buf, size, "%u,%llu,%llu,%c;",
+ (msg->facility << 3) | msg->level, seq, ts_usec,
+ msg->flags & LOG_CONT ? 'c' : '-');
+}
+
+static ssize_t msg_print_ext_body(char *buf, size_t size,
+ char *dict, size_t dict_len,
+ char *text, size_t text_len)
+{
+ 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, '\n');
+
+ if (dict_len) {
+ bool line = true;
+
+ for (i = 0; i < dict_len; i++) {
+ unsigned char c = dict[i];
+
+ if (line) {
+ append_char(&p, e, ' ');
+ line = false;
+ }
+
+ if (c == '\0') {
+ append_char(&p, e, '\n');
+ line = true;
+ continue;
+ }
+
+ if (c < ' ' || c >= 127 || c == '\\') {
+ p += scnprintf(p, e - p, "\\x%02x", c);
+ continue;
+ }
+
+ append_char(&p, e, c);
+ }
+ append_char(&p, e, '\n');
+ }
+
+ return p - buf;
+}
+
+/* /dev/kmsg - userspace message inject/listen interface */
+struct devkmsg_user {
+ u64 seq;
+ u32 idx;
+ struct ratelimit_state rs;
+ struct mutex lock;
+ char buf[CONSOLE_EXT_LOG_MAX];
+};
+
+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++;
+ len -= endp - line;
+ line = endp;
+ }
+ }
+
+ printk_emit(facility, level, NULL, 0, "%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_log *msg;
+ size_t len;
+ ssize_t ret;
+
+ if (!user)
+ return -EBADF;
+
+ ret = mutex_lock_interruptible(&user->lock);
+ if (ret)
+ return ret;
+
+ logbuf_lock_irq();
+ while (user->seq == log_next_seq) {
+ if (file->f_flags & O_NONBLOCK) {
+ ret = -EAGAIN;
+ logbuf_unlock_irq();
+ goto out;
+ }
+
+ logbuf_unlock_irq();
+ ret = wait_event_interruptible(log_wait,
+ user->seq != log_next_seq);
+ if (ret)
+ goto out;
+ logbuf_lock_irq();
+ }
+
+ if (user->seq < log_first_seq) {
+ /* our last seen message is gone, return error and reset */
+ user->idx = log_first_idx;
+ user->seq = log_first_seq;
+ ret = -EPIPE;
+ logbuf_unlock_irq();
+ goto out;
+ }
+
+ msg = log_from_idx(user->idx);
+ len = msg_print_ext_header(user->buf, sizeof(user->buf),
+ msg, user->seq);
+ len += msg_print_ext_body(user->buf + len, sizeof(user->buf) - len,
+ log_dict(msg), msg->dict_len,
+ log_text(msg), msg->text_len);
+
+ user->idx = log_next(user->idx);
+ user->seq++;
+ logbuf_unlock_irq();
+
+ if (len > count) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ if (copy_to_user(buf, user->buf, len)) {
+ ret = -EFAULT;
+ goto out;
+ }
+ ret = len;
+out:
+ mutex_unlock(&user->lock);
+ return ret;
+}
+
+static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
+{
+ struct devkmsg_user *user = file->private_data;
+ loff_t ret = 0;
+
+ if (!user)
+ return -EBADF;
+ if (offset)
+ return -ESPIPE;
+
+ logbuf_lock_irq();
+ switch (whence) {
+ case SEEK_SET:
+ /* the first record */
+ user->idx = log_first_idx;
+ user->seq = log_first_seq;
+ break;
+ case SEEK_DATA:
+ /*
+ * The first record after the last SYSLOG_ACTION_CLEAR,
+ * like issued by 'dmesg -c'. Reading /dev/kmsg itself
+ * changes no global state, and does not clear anything.
+ */
+ user->idx = clear_idx;
+ user->seq = clear_seq;
+ break;
+ case SEEK_END:
+ /* after the last record */
+ user->idx = log_next_idx;
+ user->seq = log_next_seq;
+ break;
+ default:
+ ret = -EINVAL;
+ }
+ logbuf_unlock_irq();
+ return ret;
+}
+
+static __poll_t devkmsg_poll(struct file *file, poll_table *wait)
+{
+ struct devkmsg_user *user = file->private_data;
+ __poll_t ret = 0;
+
+ if (!user)
+ return EPOLLERR|EPOLLNVAL;
+
+ poll_wait(file, &log_wait, wait);
+
+ logbuf_lock_irq();
+ if (user->seq < log_next_seq) {
+ /* return error when data has vanished underneath us */
+ if (user->seq < log_first_seq)
+ ret = EPOLLIN|EPOLLRDNORM|EPOLLERR|EPOLLPRI;
+ else
+ ret = EPOLLIN|EPOLLRDNORM;
+ }
+ logbuf_unlock_irq();
+
+ 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 = kmalloc(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);
+
+ logbuf_lock_irq();
+ user->idx = log_first_idx;
+ user->seq = log_first_seq;
+ logbuf_unlock_irq();
+
+ 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);
+ kfree(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)
+{
+ VMCOREINFO_SYMBOL(log_buf);
+ VMCOREINFO_SYMBOL(log_buf_len);
+ VMCOREINFO_SYMBOL(log_first_idx);
+ VMCOREINFO_SYMBOL(clear_idx);
+ VMCOREINFO_SYMBOL(log_next_idx);
+ /*
+ * Export struct printk_log size and field offsets. User space tools can
+ * parse it and detect any changes to structure down the line.
+ */
+ VMCOREINFO_STRUCT_SIZE(printk_log);
+ VMCOREINFO_OFFSET(printk_log, ts_nsec);
+ VMCOREINFO_OFFSET(printk_log, len);
+ VMCOREINFO_OFFSET(printk_log, text_len);
+ VMCOREINFO_OFFSET(printk_log, dict_len);
+}
+#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(unsigned size)
+{
+ if (size)
+ size = roundup_pow_of_two(size);
+ if (size > log_buf_len)
+ new_log_buf_len = size;
+}
+
+/* save requested log_buf_len since it's too early to process it */
+static int __init log_buf_len_setup(char *str)
+{
+ unsigned int 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 */
+
+void __init setup_log_buf(int early)
+{
+ unsigned long flags;
+ char *new_log_buf;
+ int free;
+
+ if (log_buf != __log_buf)
+ return;
+
+ if (!early && !new_log_buf_len)
+ log_buf_add_cpu();
+
+ if (!new_log_buf_len)
+ return;
+
+ if (early) {
+ new_log_buf =
+ memblock_virt_alloc(new_log_buf_len, LOG_ALIGN);
+ } else {
+ new_log_buf = memblock_virt_alloc_nopanic(new_log_buf_len,
+ LOG_ALIGN);
+ }
+
+ if (unlikely(!new_log_buf)) {
+ pr_err("log_buf_len: %ld bytes not available\n",
+ new_log_buf_len);
+ return;
+ }
+
+ logbuf_lock_irqsave(flags);
+ log_buf_len = new_log_buf_len;
+ log_buf = new_log_buf;
+ new_log_buf_len = 0;
+ free = __LOG_BUF_LEN - log_next_idx;
+ memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
+ logbuf_unlock_irqrestore(flags);
+
+ pr_info("log_buf_len: %d bytes\n", log_buf_len);
+ pr_info("early log buf free: %d(%d%%)\n",
+ free, (free * 100) / __LOG_BUF_LEN);
+}
+
+static bool __read_mostly ignore_loglevel;
+
+static int __init ignore_loglevel_setup(char *str)
+{
+ ignore_loglevel = 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_time(u64 ts, char *buf)
+{
+ unsigned long rem_nsec;
+
+ if (!printk_time)
+ return 0;
+
+ rem_nsec = do_div(ts, 1000000000);
+
+ if (!buf)
+ return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);
+
+ return sprintf(buf, "[%5lu.%06lu] ",
+ (unsigned long)ts, rem_nsec / 1000);
+}
+
+static size_t print_prefix(const struct printk_log *msg, bool syslog, char *buf)
+{
+ size_t len = 0;
+ unsigned int prefix = (msg->facility << 3) | msg->level;
+
+ if (syslog) {
+ if (buf) {
+ len += sprintf(buf, "<%u>", prefix);
+ } else {
+ len += 3;
+ if (prefix > 999)
+ len += 3;
+ else if (prefix > 99)
+ len += 2;
+ else if (prefix > 9)
+ len++;
+ }
+ }
+
+ len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
+ return len;
+}
+
+static size_t msg_print_text(const struct printk_log *msg, bool syslog, char *buf, size_t size)
+{
+ const char *text = log_text(msg);
+ size_t text_size = msg->text_len;
+ size_t len = 0;
+
+ do {
+ const char *next = memchr(text, '\n', text_size);
+ size_t text_len;
+
+ if (next) {
+ text_len = next - text;
+ next++;
+ text_size -= next - text;
+ } else {
+ text_len = text_size;
+ }
+
+ if (buf) {
+ if (print_prefix(msg, syslog, NULL) +
+ text_len + 1 >= size - len)
+ break;
+
+ len += print_prefix(msg, syslog, buf + len);
+ memcpy(buf + len, text, text_len);
+ len += text_len;
+ buf[len++] = '\n';
+ } else {
+ /* SYSLOG_ACTION_* buffer size only calculation */
+ len += print_prefix(msg, syslog, NULL);
+ len += text_len;
+ len++;
+ }
+
+ text = next;
+ } while (text);
+
+ return len;
+}
+
+static int syslog_print(char __user *buf, int size)
+{
+ char *text;
+ struct printk_log *msg;
+ int len = 0;
+
+ text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
+ if (!text)
+ return -ENOMEM;
+
+ while (size > 0) {
+ size_t n;
+ size_t skip;
+
+ logbuf_lock_irq();
+ if (syslog_seq < log_first_seq) {
+ /* messages are gone, move to first one */
+ syslog_seq = log_first_seq;
+ syslog_idx = log_first_idx;
+ syslog_partial = 0;
+ }
+ if (syslog_seq == log_next_seq) {
+ logbuf_unlock_irq();
+ break;
+ }
+
+ skip = syslog_partial;
+ msg = log_from_idx(syslog_idx);
+ n = msg_print_text(msg, true, text, LOG_LINE_MAX + PREFIX_MAX);
+ if (n - syslog_partial <= size) {
+ /* message fits into buffer, move forward */
+ syslog_idx = log_next(syslog_idx);
+ syslog_seq++;
+ n -= syslog_partial;
+ syslog_partial = 0;
+ } else if (!len){
+ /* partial read(), remember position */
+ n = size;
+ syslog_partial += n;
+ } else
+ n = 0;
+ logbuf_unlock_irq();
+
+ if (!n)
+ break;
+
+ if (copy_to_user(buf, text + skip, n)) {
+ if (!len)
+ len = -EFAULT;
+ break;
+ }
+
+ len += n;
+ size -= n;
+ buf += n;
+ }
+
+ kfree(text);
+ return len;
+}
+
+static int syslog_print_all(char __user *buf, int size, bool clear)
+{
+ char *text;
+ int len = 0;
+ u64 next_seq;
+ u64 seq;
+ u32 idx;
+
+ text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
+ if (!text)
+ return -ENOMEM;
+
+ logbuf_lock_irq();
+ /*
+ * Find first record that fits, including all following records,
+ * into the user-provided buffer for this dump.
+ */
+ seq = clear_seq;
+ idx = clear_idx;
+ while (seq < log_next_seq) {
+ struct printk_log *msg = log_from_idx(idx);
+
+ len += msg_print_text(msg, true, NULL, 0);
+ idx = log_next(idx);
+ seq++;
+ }
+
+ /* move first record forward until length fits into the buffer */
+ seq = clear_seq;
+ idx = clear_idx;
+ while (len > size && seq < log_next_seq) {
+ struct printk_log *msg = log_from_idx(idx);
+
+ len -= msg_print_text(msg, true, NULL, 0);
+ idx = log_next(idx);
+ seq++;
+ }
+
+ /* last message fitting into this dump */
+ next_seq = log_next_seq;
+
+ len = 0;
+ while (len >= 0 && seq < next_seq) {
+ struct printk_log *msg = log_from_idx(idx);
+ int textlen;
+
+ textlen = msg_print_text(msg, true, text,
+ LOG_LINE_MAX + PREFIX_MAX);
+ if (textlen < 0) {
+ len = textlen;
+ break;
+ }
+ idx = log_next(idx);
+ seq++;
+
+ logbuf_unlock_irq();
+ if (copy_to_user(buf + len, text, textlen))
+ len = -EFAULT;
+ else
+ len += textlen;
+ logbuf_lock_irq();
+
+ if (seq < log_first_seq) {
+ /* messages are gone, move to next one */
+ seq = log_first_seq;
+ idx = log_first_idx;
+ }
+ }
+
+ if (clear) {
+ clear_seq = log_next_seq;
+ clear_idx = log_next_idx;
+ }
+ logbuf_unlock_irq();
+
+ kfree(text);
+ return len;
+}
+
+static void syslog_clear(void)
+{
+ logbuf_lock_irq();
+ clear_seq = log_next_seq;
+ clear_idx = log_next_idx;
+ logbuf_unlock_irq();
+}
+
+int do_syslog(int type, char __user *buf, int len, int source)
+{
+ 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(VERIFY_WRITE, buf, len))
+ return -EFAULT;
+ error = wait_event_interruptible(log_wait,
+ syslog_seq != log_next_seq);
+ if (error)
+ return error;
+ error = syslog_print(buf, len);
+ break;
+ /* Read/clear last kernel messages */
+ case SYSLOG_ACTION_READ_CLEAR:
+ clear = true;
+ /* FALL THRU */
+ /* Read last kernel messages */
+ case SYSLOG_ACTION_READ_ALL:
+ if (!buf || len < 0)
+ return -EINVAL;
+ if (!len)
+ return 0;
+ if (!access_ok(VERIFY_WRITE, 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:
+ logbuf_lock_irq();
+ if (syslog_seq < log_first_seq) {
+ /* messages are gone, move to first one */
+ syslog_seq = log_first_seq;
+ syslog_idx = log_first_idx;
+ 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 = log_next_seq - syslog_seq;
+ } else {
+ u64 seq = syslog_seq;
+ u32 idx = syslog_idx;
+
+ while (seq < log_next_seq) {
+ struct printk_log *msg = log_from_idx(idx);
+
+ error += msg_print_text(msg, true, NULL, 0);
+ idx = log_next(idx);
+ seq++;
+ }
+ error -= syslog_partial;
+ }
+ logbuf_unlock_irq();
+ 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, 1, _THIS_IP_);
+ return 0;
+ }
+
+ /* The waiter is now free to continue */
+ WRITE_ONCE(console_waiter, false);
+
+ spin_release(&console_owner_dep_map, 1, _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, 1, _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;
+
+ 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, 1, _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 console drivers, asking them to write out
+ * log_buf[start] to log_buf[end - 1].
+ * The console_lock must be held.
+ */
+static void call_console_drivers(const char *ext_text, size_t ext_len,
+ const char *text, size_t len)
+{
+ struct console *con;
+
+ trace_console_rcuidle(text, len);
+
+ if (!console_drivers)
+ return;
+
+ for_each_console(con) {
+ if (exclusive_console && con != exclusive_console)
+ continue;
+ if (!(con->flags & CON_ENABLED))
+ continue;
+ if (!con->write)
+ continue;
+ if (!cpu_online(smp_processor_id()) &&
+ !(con->flags & CON_ANYTIME))
+ continue;
+ if (con->flags & CON_EXTENDED)
+ con->write(con, ext_text, ext_len);
+ else
+ con->write(con, text, len);
+ }
+}
+
+int printk_delay_msec __read_mostly;
+
+static inline void printk_delay(void)
+{
+ if (unlikely(printk_delay_msec)) {
+ int m = printk_delay_msec;
+
+ while (m--) {
+ mdelay(1);
+ touch_nmi_watchdog();
+ }
+ }
+}
+
+/*
+ * Continuation lines are buffered, and not committed to the record buffer
+ * until the line is complete, or a race forces it. The line fragments
+ * though, are printed immediately to the consoles to ensure everything has
+ * reached the console in case of a kernel crash.
+ */
+static struct cont {
+ char buf[LOG_LINE_MAX];
+ size_t len; /* length == 0 means unused buffer */
+ struct task_struct *owner; /* task of first print*/
+ u64 ts_nsec; /* time of first print */
+ u8 level; /* log level of first message */
+ u8 facility; /* log facility of first message */
+ enum log_flags flags; /* prefix, newline flags */
+} cont;
+
+static void cont_flush(void)
+{
+ if (cont.len == 0)
+ return;
+
+ log_store(cont.facility, cont.level, cont.flags, cont.ts_nsec,
+ NULL, 0, cont.buf, cont.len);
+ cont.len = 0;
+}
+
+static bool cont_add(int facility, int level, enum log_flags flags, const char *text, size_t len)
+{
+ /*
+ * If ext consoles are present, flush and skip in-kernel
+ * continuation. See nr_ext_console_drivers definition. Also, if
+ * the line gets too long, split it up in separate records.
+ */
+ if (nr_ext_console_drivers || cont.len + len > sizeof(cont.buf)) {
+ cont_flush();
+ return false;
+ }
+
+ if (!cont.len) {
+ cont.facility = facility;
+ cont.level = level;
+ cont.owner = current;
+ cont.ts_nsec = local_clock();
+ cont.flags = flags;
+ }
+
+ memcpy(cont.buf + cont.len, text, len);
+ cont.len += len;
+
+ // The original flags come from the first line,
+ // but later continuations can add a newline.
+ if (flags & LOG_NEWLINE) {
+ cont.flags |= LOG_NEWLINE;
+ cont_flush();
+ }
+
+ if (cont.len > (sizeof(cont.buf) * 80) / 100)
+ cont_flush();
+
+ return true;
+}
+
+static size_t log_output(int facility, int level, enum log_flags lflags, const char *dict, size_t dictlen, char *text, size_t text_len)
+{
+ /*
+ * If an earlier line was buffered, and we're a continuation
+ * write from the same process, try to add it to the buffer.
+ */
+ if (cont.len) {
+ if (cont.owner == current && (lflags & LOG_CONT)) {
+ if (cont_add(facility, level, lflags, text, text_len))
+ return text_len;
+ }
+ /* Otherwise, make sure it's flushed */
+ cont_flush();
+ }
+
+ /* Skip empty continuation lines that couldn't be added - they just flush */
+ if (!text_len && (lflags & LOG_CONT))
+ return 0;
+
+ /* If it doesn't end in a newline, try to buffer the current line */
+ if (!(lflags & LOG_NEWLINE)) {
+ if (cont_add(facility, level, lflags, text, text_len))
+ return text_len;
+ }
+
+ /* Store it in the record log */
+ return log_store(facility, level, lflags, 0, dict, dictlen, text, text_len);
+}
+
+/* Must be called under logbuf_lock. */
+int vprintk_store(int facility, int level,
+ const char *dict, size_t dictlen,
+ const char *fmt, va_list args)
+{
+ static char textbuf[LOG_LINE_MAX];
+ char *text = textbuf;
+ size_t text_len;
+ enum log_flags lflags = 0;
+
+ /*
+ * The printf needs to come first; we need the syslog
+ * prefix which might be passed-in as a parameter.
+ */
+ text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
+
+ /* mark and strip a trailing newline */
+ if (text_len && text[text_len-1] == '\n') {
+ text_len--;
+ lflags |= LOG_NEWLINE;
+ }
+
+ /* strip kernel syslog prefix and extract log level or control flags */
+ if (facility == 0) {
+ int kern_level;
+
+ while ((kern_level = printk_get_level(text)) != 0) {
+ switch (kern_level) {
+ case '0' ... '7':
+ if (level == LOGLEVEL_DEFAULT)
+ level = kern_level - '0';
+ /* fallthrough */
+ case 'd': /* KERN_DEFAULT */
+ lflags |= LOG_PREFIX;
+ break;
+ case 'c': /* KERN_CONT */
+ lflags |= LOG_CONT;
+ }
+
+ text_len -= 2;
+ text += 2;
+ }
+ }
+
+ if (level == LOGLEVEL_DEFAULT)
+ level = default_message_loglevel;
+
+ if (dict)
+ lflags |= LOG_PREFIX|LOG_NEWLINE;
+
+ return log_output(facility, level, lflags,
+ dict, dictlen, text, text_len);
+}
+
+asmlinkage int vprintk_emit(int facility, int level,
+ const char *dict, size_t dictlen,
+ const char *fmt, va_list args)
+{
+ int printed_len;
+ bool in_sched = false;
+ unsigned long flags;
+
+ if (level == LOGLEVEL_SCHED) {
+ level = LOGLEVEL_DEFAULT;
+ in_sched = true;
+ }
+
+ boot_delay_msec(level);
+ printk_delay();
+
+ /* This stops the holder of console_sem just where we want him */
+ logbuf_lock_irqsave(flags);
+ printed_len = vprintk_store(facility, level, dict, dictlen, fmt, args);
+ logbuf_unlock_irqrestore(flags);
+
+ /* If called from the scheduler, we can not call up(). */
+ if (!in_sched) {
+ /*
+ * Disable preemption to avoid being preempted while holding
+ * console_sem which would prevent anyone from printing to
+ * console
+ */
+ preempt_disable();
+ /*
+ * Try to acquire and then immediately release the console
+ * semaphore. The release will print out buffers and wake up
+ * /dev/kmsg and syslog() users.
+ */
+ if (console_trylock_spinning())
+ console_unlock();
+ preempt_enable();
+ }
+
+ wake_up_klogd();
+ return printed_len;
+}
+EXPORT_SYMBOL(vprintk_emit);
+
+asmlinkage int vprintk(const char *fmt, va_list args)
+{
+ return vprintk_func(fmt, args);
+}
+EXPORT_SYMBOL(vprintk);
+
+asmlinkage int printk_emit(int facility, int level,
+ const char *dict, size_t dictlen,
+ const char *fmt, ...)
+{
+ va_list args;
+ int r;
+
+ va_start(args, fmt);
+ r = vprintk_emit(facility, level, dict, dictlen, fmt, args);
+ va_end(args);
+
+ return r;
+}
+EXPORT_SYMBOL(printk_emit);
+
+int vprintk_default(const char *fmt, va_list args)
+{
+ int r;
+
+#ifdef CONFIG_KGDB_KDB
+ /* Allow to pass printk() to kdb but avoid a recursion. */
+ if (unlikely(kdb_trap_printk && kdb_printf_cpu < 0)) {
+ r = vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
+ return r;
+ }
+#endif
+ r = vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
+
+ return r;
+}
+EXPORT_SYMBOL_GPL(vprintk_default);
+
+/**
+ * printk - print a kernel message
+ * @fmt: format string
+ *
+ * This is printk(). It can be called from any context. We want it to work.
+ *
+ * We try to grab the console_lock. If we succeed, it's easy - we log the
+ * output and call the console drivers. If we fail to get the semaphore, we
+ * place the output into the log buffer and return. The current holder of
+ * the console_sem will notice the new output in console_unlock(); and will
+ * send it to the consoles before releasing the lock.
+ *
+ * One effect of this deferred printing is that code which calls printk() and
+ * then changes console_loglevel may break. This is because console_loglevel
+ * is inspected when the actual printing occurs.
+ *
+ * See also:
+ * printf(3)
+ *
+ * See the vsnprintf() documentation for format string extensions over C99.
+ */
+asmlinkage __visible int printk(const char *fmt, ...)
+{
+ va_list args;
+ int r;
+
+ va_start(args, fmt);
+ r = vprintk_func(fmt, args);
+ va_end(args);
+
+ return r;
+}
+EXPORT_SYMBOL(printk);
+
+#else /* CONFIG_PRINTK */
+
+#define LOG_LINE_MAX 0
+#define PREFIX_MAX 0
+
+static u64 syslog_seq;
+static u32 syslog_idx;
+static u64 console_seq;
+static u32 console_idx;
+static u64 log_first_seq;
+static u32 log_first_idx;
+static u64 log_next_seq;
+static char *log_text(const struct printk_log *msg) { return NULL; }
+static char *log_dict(const struct printk_log *msg) { return NULL; }
+static struct printk_log *log_from_idx(u32 idx) { return NULL; }
+static u32 log_next(u32 idx) { return 0; }
+static ssize_t msg_print_ext_header(char *buf, size_t size,
+ struct printk_log *msg,
+ u64 seq) { return 0; }
+static ssize_t msg_print_ext_body(char *buf, size_t size,
+ char *dict, size_t dict_len,
+ char *text, size_t text_len) { return 0; }
+static void console_lock_spinning_enable(void) { }
+static int console_lock_spinning_disable_and_check(void) { return 0; }
+static void call_console_drivers(const char *ext_text, size_t ext_len,
+ const char *text, size_t len) {}
+static size_t msg_print_text(const struct printk_log *msg,
+ bool syslog, char *buf, size_t size) { return 0; }
+static bool suppress_message_printing(int level) { return false; }
+
+#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 int __add_preferred_console(char *name, int idx, char *options,
+ char *brl_options)
+{
+ struct console_cmdline *c;
+ int i;
+
+ /*
+ * See if this tty is not yet registered, and
+ * if we have a slot free.
+ */
+ for (i = 0, 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;
+ return 0;
+ }
+ }
+ if (i == MAX_CMDLINECONSOLES)
+ return -E2BIG;
+ if (!brl_options)
+ preferred_console = i;
+ strlcpy(c->name, name, sizeof(c->name));
+ c->options = options;
+ 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;
+
+ 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);
+ console_set_on_cmdline = 1;
+ return 1;
+}
+__setup("console=", console_setup);
+
+/**
+ * add_preferred_console - add a device to the list of preferred consoles.
+ * @name: device name
+ * @idx: device index
+ * @options: options for this console
+ *
+ * The last preferred console added will be used for kernel messages
+ * and stdin/out/err for init. Normally this is used by console_setup
+ * above to handle user-supplied console arguments; however it can also
+ * be used by arch-specific code either to override the user or more
+ * commonly to provide a default console (ie from PROM variables) when
+ * the user has not supplied one.
+ */
+int add_preferred_console(char *name, int idx, char *options)
+{
+ return __add_preferred_console(name, idx, options, NULL);
+}
+
+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");
+
+/**
+ * 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");
+ console_lock();
+ console_suspended = 1;
+ up_console_sem();
+}
+
+void resume_console(void)
+{
+ if (!console_suspend_enabled)
+ return;
+ down_console_sem();
+ console_suspended = 0;
+ console_unlock();
+}
+
+/**
+ * console_cpu_notify - print deferred console messages after CPU hotplug
+ * @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();
+ }
+ 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_locked = 1;
+ 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;
+ }
+ console_locked = 1;
+ console_may_schedule = 0;
+ return 1;
+}
+EXPORT_SYMBOL(console_trylock);
+
+int is_console_locked(void)
+{
+ return console_locked;
+}
+EXPORT_SYMBOL(is_console_locked);
+
+/*
+ * Check if we have any console that is capable of printing while cpu is
+ * booting or shutting down. Requires console_sem.
+ */
+static int have_callable_console(void)
+{
+ struct console *con;
+
+ for_each_console(con)
+ if ((con->flags & CON_ENABLED) &&
+ (con->flags & CON_ANYTIME))
+ return 1;
+
+ return 0;
+}
+
+/*
+ * Can we actually use the console at this time on this cpu?
+ *
+ * Console drivers may assume that per-cpu resources have been allocated. So
+ * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
+ * call them until this CPU is officially up.
+ */
+static inline int can_use_console(void)
+{
+ return cpu_online(raw_smp_processor_id()) || have_callable_console();
+}
+
+/**
+ * console_unlock - unlock the console system
+ *
+ * Releases the console_lock which the caller holds on the console system
+ * and the console driver list.
+ *
+ * While the console_lock was held, console output may have been buffered
+ * by printk(). If this is the case, console_unlock(); emits
+ * the output prior to releasing the lock.
+ *
+ * If there is output waiting, we wake /dev/kmsg and syslog() users.
+ *
+ * console_unlock(); may be called from any context.
+ */
+void console_unlock(void)
+{
+ static char ext_text[CONSOLE_EXT_LOG_MAX];
+ static char text[LOG_LINE_MAX + PREFIX_MAX];
+ unsigned long flags;
+ bool do_cond_resched, retry;
+
+ 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.
+ *
+ * console_trylock() is not able to detect the preemptive
+ * context reliably. Therefore the value must be stored before
+ * and cleared after the the "again" goto label.
+ */
+ do_cond_resched = console_may_schedule;
+again:
+ console_may_schedule = 0;
+
+ /*
+ * We released the console_sem lock, so we need to recheck if
+ * cpu is online and (if not) is there at least one CON_ANYTIME
+ * console.
+ */
+ if (!can_use_console()) {
+ console_locked = 0;
+ up_console_sem();
+ return;
+ }
+
+ for (;;) {
+ struct printk_log *msg;
+ size_t ext_len = 0;
+ size_t len;
+
+ printk_safe_enter_irqsave(flags);
+ raw_spin_lock(&logbuf_lock);
+ if (console_seq < log_first_seq) {
+ len = sprintf(text, "** %u printk messages dropped **\n",
+ (unsigned)(log_first_seq - console_seq));
+
+ /* messages are gone, move to first one */
+ console_seq = log_first_seq;
+ console_idx = log_first_idx;
+ } else {
+ len = 0;
+ }
+skip:
+ if (console_seq == log_next_seq)
+ break;
+
+ msg = log_from_idx(console_idx);
+ if (suppress_message_printing(msg->level)) {
+ /*
+ * Skip record we have buffered and already printed
+ * directly to the console when we received it, and
+ * record that has level above the console loglevel.
+ */
+ console_idx = log_next(console_idx);
+ console_seq++;
+ goto skip;
+ }
+
+ len += msg_print_text(msg,
+ console_msg_format & MSG_FORMAT_SYSLOG,
+ text + len,
+ sizeof(text) - len);
+ if (nr_ext_console_drivers) {
+ ext_len = msg_print_ext_header(ext_text,
+ sizeof(ext_text),
+ msg, console_seq);
+ ext_len += msg_print_ext_body(ext_text + ext_len,
+ sizeof(ext_text) - ext_len,
+ log_dict(msg), msg->dict_len,
+ log_text(msg), msg->text_len);
+ }
+ console_idx = log_next(console_idx);
+ console_seq++;
+ raw_spin_unlock(&logbuf_lock);
+
+ /*
+ * 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.
+ */
+ console_lock_spinning_enable();
+
+ stop_critical_timings(); /* don't trace print latency */
+ call_console_drivers(ext_text, ext_len, text, len);
+ start_critical_timings();
+
+ if (console_lock_spinning_disable_and_check()) {
+ printk_safe_exit_irqrestore(flags);
+ return;
+ }
+
+ printk_safe_exit_irqrestore(flags);
+
+ if (do_cond_resched)
+ cond_resched();
+ }
+
+ console_locked = 0;
+
+ /* Release the exclusive_console once it is used */
+ if (unlikely(exclusive_console))
+ exclusive_console = NULL;
+
+ raw_spin_unlock(&logbuf_lock);
+
+ up_console_sem();
+
+ /*
+ * Someone could have filled up the buffer again, so re-check if there's
+ * something to flush. In case we cannot trylock the console_sem again,
+ * there's a new owner and the console_unlock() from them will do the
+ * flush, no worries.
+ */
+ raw_spin_lock(&logbuf_lock);
+ retry = console_seq != log_next_seq;
+ raw_spin_unlock(&logbuf_lock);
+ printk_safe_exit_irqrestore(flags);
+
+ if (retry && console_trylock())
+ goto again;
+}
+EXPORT_SYMBOL(console_unlock);
+
+/**
+ * console_conditional_schedule - yield the CPU if required
+ *
+ * If the console code is currently allowed to sleep, and
+ * if this CPU should yield the CPU to another task, do
+ * so here.
+ *
+ * Must be called within console_lock();.
+ */
+void __sched console_conditional_schedule(void)
+{
+ if (console_may_schedule)
+ cond_resched();
+}
+EXPORT_SYMBOL(console_conditional_schedule);
+
+void console_unblank(void)
+{
+ struct console *c;
+
+ /*
+ * console_unblank can no longer be called in interrupt context unless
+ * oops_in_progress is set to 1..
+ */
+ if (oops_in_progress) {
+ if (down_trylock_console_sem() != 0)
+ return;
+ } else
+ console_lock();
+
+ console_locked = 1;
+ console_may_schedule = 0;
+ for_each_console(c)
+ if ((c->flags & CON_ENABLED) && c->unblank)
+ c->unblank();
+ console_unlock();
+}
+
+/**
+ * console_flush_on_panic - flush console content on panic
+ *
+ * Immediately output all pending messages no matter what.
+ */
+void console_flush_on_panic(void)
+{
+ /*
+ * If someone else is holding the console lock, trylock will fail
+ * and may_schedule may be set. Ignore and proceed to unlock so
+ * that messages are flushed out. As this can be called from any
+ * context and we don't want to get preempted while flushing,
+ * ensure may_schedule is cleared.
+ */
+ console_trylock();
+ console_may_schedule = 0;
+ console_unlock();
+}
+
+/*
+ * Return the console tty driver structure and its associated index
+ */
+struct tty_driver *console_device(int *index)
+{
+ struct console *c;
+ struct tty_driver *driver = NULL;
+
+ console_lock();
+ for_each_console(c) {
+ if (!c->device)
+ continue;
+ driver = c->device(c, index);
+ if (driver)
+ break;
+ }
+ console_unlock();
+ return driver;
+}
+
+/*
+ * Prevent further output on the passed console device so that (for example)
+ * serial drivers can disable console output before suspending a port, and can
+ * re-enable output afterwards.
+ */
+void console_stop(struct console *console)
+{
+ console_lock();
+ console->flags &= ~CON_ENABLED;
+ console_unlock();
+}
+EXPORT_SYMBOL(console_stop);
+
+void console_start(struct console *console)
+{
+ console_lock();
+ console->flags |= CON_ENABLED;
+ console_unlock();
+}
+EXPORT_SYMBOL(console_start);
+
+static int __read_mostly keep_bootcon;
+
+static int __init keep_bootcon_setup(char *str)
+{
+ keep_bootcon = 1;
+ pr_info("debug: skip boot console de-registration.\n");
+
+ return 0;
+}
+
+early_param("keep_bootcon", keep_bootcon_setup);
+
+/*
+ * The console driver calls this routine during kernel initialization
+ * to register the console printing procedure with printk() and to
+ * print any messages that were printed by the kernel before the
+ * console driver was initialized.
+ *
+ * This can happen pretty early during the boot process (because of
+ * early_printk) - sometimes before setup_arch() completes - be careful
+ * of what kernel features are used - they may not be initialised yet.
+ *
+ * There are two types of consoles - bootconsoles (early_printk) and
+ * "real" consoles (everything which is not a bootconsole) which are
+ * handled differently.
+ * - Any number of bootconsoles can be registered at any time.
+ * - As soon as a "real" console is registered, all bootconsoles
+ * will be unregistered automatically.
+ * - Once a "real" console is registered, any attempt to register a
+ * bootconsoles will be rejected
+ */
+void register_console(struct console *newcon)
+{
+ int i;
+ unsigned long flags;
+ struct console *bcon = NULL;
+ struct console_cmdline *c;
+ static bool has_preferred;
+
+ if (console_drivers)
+ for_each_console(bcon)
+ if (WARN(bcon == newcon,
+ "console '%s%d' already registered\n",
+ bcon->name, bcon->index))
+ return;
+
+ /*
+ * before we register a new CON_BOOT console, make sure we don't
+ * already have a valid console
+ */
+ if (console_drivers && newcon->flags & CON_BOOT) {
+ /* find the last or real console */
+ for_each_console(bcon) {
+ if (!(bcon->flags & CON_BOOT)) {
+ pr_info("Too late to register bootconsole %s%d\n",
+ newcon->name, newcon->index);
+ return;
+ }
+ }
+ }
+
+ if (console_drivers && console_drivers->flags & CON_BOOT)
+ bcon = console_drivers;
+
+ if (!has_preferred || bcon || !console_drivers)
+ has_preferred = preferred_console >= 0;
+
+ /*
+ * See if we want to use this console driver. If we
+ * didn't select a console we take the first one
+ * that registers here.
+ */
+ if (!has_preferred) {
+ if (newcon->index < 0)
+ newcon->index = 0;
+ if (newcon->setup == NULL ||
+ newcon->setup(newcon, NULL) == 0) {
+ newcon->flags |= CON_ENABLED;
+ if (newcon->device) {
+ newcon->flags |= CON_CONSDEV;
+ has_preferred = true;
+ }
+ }
+ }
+
+ /*
+ * See if this console matches one we selected on
+ * the command line.
+ */
+ for (i = 0, c = console_cmdline;
+ i < MAX_CMDLINECONSOLES && c->name[0];
+ i++, c++) {
+ 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;
+
+ if (newcon->setup &&
+ newcon->setup(newcon, c->options) != 0)
+ break;
+ }
+
+ newcon->flags |= CON_ENABLED;
+ if (i == preferred_console) {
+ newcon->flags |= CON_CONSDEV;
+ has_preferred = true;
+ }
+ break;
+ }
+
+ if (!(newcon->flags & CON_ENABLED))
+ return;
+
+ /*
+ * If we have a bootconsole, and are switching to a real console,
+ * don't print everything out again, since when the boot console, and
+ * the real console are the same physical device, it's annoying to
+ * see the beginning boot messages twice
+ */
+ if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
+ newcon->flags &= ~CON_PRINTBUFFER;
+
+ /*
+ * Put this console in the list - keep the
+ * preferred driver at the head of the list.
+ */
+ console_lock();
+ if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
+ newcon->next = console_drivers;
+ console_drivers = newcon;
+ if (newcon->next)
+ newcon->next->flags &= ~CON_CONSDEV;
+ } else {
+ newcon->next = console_drivers->next;
+ console_drivers->next = newcon;
+ }
+
+ if (newcon->flags & CON_EXTENDED)
+ if (!nr_ext_console_drivers++)
+ pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
+
+ if (newcon->flags & CON_PRINTBUFFER) {
+ /*
+ * console_unlock(); will print out the buffered messages
+ * for us.
+ */
+ logbuf_lock_irqsave(flags);
+ console_seq = syslog_seq;
+ console_idx = syslog_idx;
+ logbuf_unlock_irqrestore(flags);
+ /*
+ * We're about to replay the log buffer. Only do this to the
+ * just-registered console to avoid excessive message spam to
+ * the already-registered consoles.
+ */
+ exclusive_console = newcon;
+ }
+ console_unlock();
+ console_sysfs_notify();
+
+ /*
+ * By unregistering the bootconsoles after we enable the real console
+ * we get the "console xxx enabled" message on all the consoles -
+ * boot consoles, real consoles, etc - this is to ensure that end
+ * users know there might be something in the kernel's log buffer that
+ * went to the bootconsole (that they do not see on the real console)
+ */
+ pr_info("%sconsole [%s%d] enabled\n",
+ (newcon->flags & CON_BOOT) ? "boot" : "" ,
+ newcon->name, newcon->index);
+ if (bcon &&
+ ((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(bcon)
+ if (bcon->flags & CON_BOOT)
+ unregister_console(bcon);
+ }
+}
+EXPORT_SYMBOL(register_console);
+
+int unregister_console(struct console *console)
+{
+ struct console *a, *b;
+ int res;
+
+ pr_info("%sconsole [%s%d] disabled\n",
+ (console->flags & CON_BOOT) ? "boot" : "" ,
+ console->name, console->index);
+
+ res = _braille_unregister_console(console);
+ if (res)
+ return res;
+
+ res = 1;
+ console_lock();
+ if (console_drivers == console) {
+ console_drivers=console->next;
+ res = 0;
+ } else if (console_drivers) {
+ for (a=console_drivers->next, b=console_drivers ;
+ a; b=a, a=b->next) {
+ if (a == console) {
+ b->next = a->next;
+ res = 0;
+ break;
+ }
+ }
+ }
+
+ if (!res && (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_unlock();
+ console_sysfs_notify();
+ 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 unregistred 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);
+ return 0;
+}
+late_initcall(printk_late_init);
+
+#if defined CONFIG_PRINTK
+/*
+ * Delayed printk version, for scheduler-internal messages:
+ */
+#define PRINTK_PENDING_WAKEUP 0x01
+#define PRINTK_PENDING_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_OUTPUT) {
+ /* If trylock fails, someone else is doing the printing */
+ if (console_trylock())
+ console_unlock();
+ }
+
+ if (pending & PRINTK_PENDING_WAKEUP)
+ wake_up_interruptible(&log_wait);
+}
+
+static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
+ .func = wake_up_klogd_work_func,
+ .flags = IRQ_WORK_LAZY,
+};
+
+void wake_up_klogd(void)
+{
+ preempt_disable();
+ if (waitqueue_active(&log_wait)) {
+ this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
+ irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
+ }
+ preempt_enable();
+}
+
+void defer_console_output(void)
+{
+ preempt_disable();
+ __this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
+ irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
+ preempt_enable();
+}
+
+int vprintk_deferred(const char *fmt, va_list args)
+{
+ int r;
+
+ r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, 0, 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);
+
+/**
+ * kmsg_dump - dump kernel log to kernel message dumpers.
+ * @reason: the reason (oops, panic etc) for dumping
+ *
+ * Call each of the registered dumper's dump() callback, which can
+ * retrieve the kmsg records with kmsg_dump_get_line() or
+ * kmsg_dump_get_buffer().
+ */
+void kmsg_dump(enum kmsg_dump_reason reason)
+{
+ struct kmsg_dumper *dumper;
+ unsigned long flags;
+
+ if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
+ return;
+
+ rcu_read_lock();
+ list_for_each_entry_rcu(dumper, &dump_list, list) {
+ if (dumper->max_reason && reason > dumper->max_reason)
+ continue;
+
+ /* initialize iterator with data about the stored records */
+ dumper->active = true;
+
+ logbuf_lock_irqsave(flags);
+ dumper->cur_seq = clear_seq;
+ dumper->cur_idx = clear_idx;
+ dumper->next_seq = log_next_seq;
+ dumper->next_idx = log_next_idx;
+ logbuf_unlock_irqrestore(flags);
+
+ /* invoke dumper which will iterate over records */
+ dumper->dump(dumper, reason);
+
+ /* reset iterator */
+ dumper->active = false;
+ }
+ rcu_read_unlock();
+}
+
+/**
+ * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
+ * @dumper: registered kmsg dumper
+ * @syslog: include the "<4>" prefixes
+ * @line: buffer to copy the line to
+ * @size: maximum size of the buffer
+ * @len: length of line placed into buffer
+ *
+ * Start at the beginning of the kmsg buffer, with the oldest kmsg
+ * record, and copy one record into the provided buffer.
+ *
+ * Consecutive calls will return the next available record moving
+ * towards the end of the buffer with the youngest messages.
+ *
+ * A return value of FALSE indicates that there are no more records to
+ * read.
+ *
+ * The function is similar to kmsg_dump_get_line(), but grabs no locks.
+ */
+bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
+ char *line, size_t size, size_t *len)
+{
+ struct printk_log *msg;
+ size_t l = 0;
+ bool ret = false;
+
+ if (!dumper->active)
+ goto out;
+
+ if (dumper->cur_seq < log_first_seq) {
+ /* messages are gone, move to first available one */
+ dumper->cur_seq = log_first_seq;
+ dumper->cur_idx = log_first_idx;
+ }
+
+ /* last entry */
+ if (dumper->cur_seq >= log_next_seq)
+ goto out;
+
+ msg = log_from_idx(dumper->cur_idx);
+ l = msg_print_text(msg, syslog, line, size);
+
+ dumper->cur_idx = log_next(dumper->cur_idx);
+ dumper->cur_seq++;
+ ret = true;
+out:
+ if (len)
+ *len = l;
+ return ret;
+}
+
+/**
+ * kmsg_dump_get_line - retrieve one kmsg log line
+ * @dumper: registered kmsg dumper
+ * @syslog: include the "<4>" prefixes
+ * @line: buffer to copy the line to
+ * @size: maximum size of the buffer
+ * @len: length of line placed into buffer
+ *
+ * Start at the beginning of the kmsg buffer, with the oldest kmsg
+ * record, and copy one record into the provided buffer.
+ *
+ * Consecutive calls will return the next available record moving
+ * towards the end of the buffer with the youngest messages.
+ *
+ * A return value of FALSE indicates that there are no more records to
+ * read.
+ */
+bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
+ char *line, size_t size, size_t *len)
+{
+ unsigned long flags;
+ bool ret;
+
+ logbuf_lock_irqsave(flags);
+ ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
+ logbuf_unlock_irqrestore(flags);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
+
+/**
+ * kmsg_dump_get_buffer - copy kmsg log lines
+ * @dumper: registered kmsg dumper
+ * @syslog: include the "<4>" prefixes
+ * @buf: buffer to copy the line to
+ * @size: maximum size of the buffer
+ * @len: length of line placed into buffer
+ *
+ * Start at the end of the kmsg buffer and fill the provided buffer
+ * with as many of the the *youngest* kmsg records that fit into it.
+ * If the buffer is large enough, all available kmsg records will be
+ * copied with a single call.
+ *
+ * Consecutive calls will fill the buffer with the next block of
+ * available older records, not including the earlier retrieved ones.
+ *
+ * A return value of FALSE indicates that there are no more records to
+ * read.
+ */
+bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
+ char *buf, size_t size, size_t *len)
+{
+ unsigned long flags;
+ u64 seq;
+ u32 idx;
+ u64 next_seq;
+ u32 next_idx;
+ size_t l = 0;
+ bool ret = false;
+
+ if (!dumper->active)
+ goto out;
+
+ logbuf_lock_irqsave(flags);
+ if (dumper->cur_seq < log_first_seq) {
+ /* messages are gone, move to first available one */
+ dumper->cur_seq = log_first_seq;
+ dumper->cur_idx = log_first_idx;
+ }
+
+ /* last entry */
+ if (dumper->cur_seq >= dumper->next_seq) {
+ logbuf_unlock_irqrestore(flags);
+ goto out;
+ }
+
+ /* calculate length of entire buffer */
+ seq = dumper->cur_seq;
+ idx = dumper->cur_idx;
+ while (seq < dumper->next_seq) {
+ struct printk_log *msg = log_from_idx(idx);
+
+ l += msg_print_text(msg, true, NULL, 0);
+ idx = log_next(idx);
+ seq++;
+ }
+
+ /* move first record forward until length fits into the buffer */
+ seq = dumper->cur_seq;
+ idx = dumper->cur_idx;
+ while (l > size && seq < dumper->next_seq) {
+ struct printk_log *msg = log_from_idx(idx);
+
+ l -= msg_print_text(msg, true, NULL, 0);
+ idx = log_next(idx);
+ seq++;
+ }
+
+ /* last message in next interation */
+ next_seq = seq;
+ next_idx = idx;
+
+ l = 0;
+ while (seq < dumper->next_seq) {
+ struct printk_log *msg = log_from_idx(idx);
+
+ l += msg_print_text(msg, syslog, buf + l, size - l);
+ idx = log_next(idx);
+ seq++;
+ }
+
+ dumper->next_seq = next_seq;
+ dumper->next_idx = next_idx;
+ ret = true;
+ logbuf_unlock_irqrestore(flags);
+out:
+ if (len)
+ *len = l;
+ return ret;
+}
+EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
+
+/**
+ * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
+ * @dumper: registered kmsg dumper
+ *
+ * Reset the dumper's iterator so that kmsg_dump_get_line() and
+ * kmsg_dump_get_buffer() can be called again and used multiple
+ * times within the same dumper.dump() callback.
+ *
+ * The function is similar to kmsg_dump_rewind(), but grabs no locks.
+ */
+void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
+{
+ dumper->cur_seq = clear_seq;
+ dumper->cur_idx = clear_idx;
+ dumper->next_seq = log_next_seq;
+ dumper->next_idx = log_next_idx;
+}
+
+/**
+ * kmsg_dump_rewind - reset the interator
+ * @dumper: registered kmsg dumper
+ *
+ * Reset the dumper's iterator so that kmsg_dump_get_line() and
+ * kmsg_dump_get_buffer() can be called again and used multiple
+ * times within the same dumper.dump() callback.
+ */
+void kmsg_dump_rewind(struct kmsg_dumper *dumper)
+{
+ unsigned long flags;
+
+ logbuf_lock_irqsave(flags);
+ kmsg_dump_rewind_nolock(dumper);
+ logbuf_unlock_irqrestore(flags);
+}
+EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
+
+#endif
diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c
new file mode 100644
index 0000000..0913b4d
--- /dev/null
+++ b/kernel/printk/printk_safe.c
@@ -0,0 +1,427 @@
+/*
+ * printk_safe.c - Safe printk for printk-deadlock-prone contexts
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/preempt.h>
+#include <linux/spinlock.h>
+#include <linux/debug_locks.h>
+#include <linux/smp.h>
+#include <linux/cpumask.h>
+#include <linux/irq_work.h>
+#include <linux/printk.h>
+
+#include "internal.h"
+
+/*
+ * printk() could not take logbuf_lock in NMI context. Instead,
+ * it uses an alternative implementation that temporary stores
+ * the strings into a per-CPU buffer. The content of the buffer
+ * is later flushed into the main ring buffer via IRQ work.
+ *
+ * The alternative implementation is chosen transparently
+ * by examinig current printk() context mask stored in @printk_context
+ * per-CPU variable.
+ *
+ * The implementation allows to flush the strings also from another CPU.
+ * There are situations when we want to make sure that all buffers
+ * were handled or when IRQs are blocked.
+ */
+static int printk_safe_irq_ready __read_mostly;
+
+#define SAFE_LOG_BUF_LEN ((1 << CONFIG_PRINTK_SAFE_LOG_BUF_SHIFT) - \
+ sizeof(atomic_t) - \
+ sizeof(atomic_t) - \
+ sizeof(struct irq_work))
+
+struct printk_safe_seq_buf {
+ atomic_t len; /* length of written data */
+ atomic_t message_lost;
+ struct irq_work work; /* IRQ work that flushes the buffer */
+ unsigned char buffer[SAFE_LOG_BUF_LEN];
+};
+
+static DEFINE_PER_CPU(struct printk_safe_seq_buf, safe_print_seq);
+static DEFINE_PER_CPU(int, printk_context);
+
+#ifdef CONFIG_PRINTK_NMI
+static DEFINE_PER_CPU(struct printk_safe_seq_buf, nmi_print_seq);
+#endif
+
+/* Get flushed in a more safe context. */
+static void queue_flush_work(struct printk_safe_seq_buf *s)
+{
+ if (printk_safe_irq_ready)
+ irq_work_queue(&s->work);
+}
+
+/*
+ * Add a message to per-CPU context-dependent buffer. NMI and printk-safe
+ * have dedicated buffers, because otherwise printk-safe preempted by
+ * NMI-printk would have overwritten the NMI messages.
+ *
+ * The messages are flushed from irq work (or from panic()), possibly,
+ * from other CPU, concurrently with printk_safe_log_store(). Should this
+ * happen, printk_safe_log_store() will notice the buffer->len mismatch
+ * and repeat the write.
+ */
+static __printf(2, 0) int printk_safe_log_store(struct printk_safe_seq_buf *s,
+ const char *fmt, va_list args)
+{
+ int add;
+ size_t len;
+ va_list ap;
+
+again:
+ len = atomic_read(&s->len);
+
+ /* The trailing '\0' is not counted into len. */
+ if (len >= sizeof(s->buffer) - 1) {
+ atomic_inc(&s->message_lost);
+ queue_flush_work(s);
+ return 0;
+ }
+
+ /*
+ * Make sure that all old data have been read before the buffer
+ * was reset. This is not needed when we just append data.
+ */
+ if (!len)
+ smp_rmb();
+
+ va_copy(ap, args);
+ add = vscnprintf(s->buffer + len, sizeof(s->buffer) - len, fmt, ap);
+ va_end(ap);
+ if (!add)
+ return 0;
+
+ /*
+ * Do it once again if the buffer has been flushed in the meantime.
+ * Note that atomic_cmpxchg() is an implicit memory barrier that
+ * makes sure that the data were written before updating s->len.
+ */
+ if (atomic_cmpxchg(&s->len, len, len + add) != len)
+ goto again;
+
+ queue_flush_work(s);
+ return add;
+}
+
+static inline void printk_safe_flush_line(const char *text, int len)
+{
+ /*
+ * Avoid any console drivers calls from here, because we may be
+ * in NMI or printk_safe context (when in panic). The messages
+ * must go only into the ring buffer at this stage. Consoles will
+ * get explicitly called later when a crashdump is not generated.
+ */
+ printk_deferred("%.*s", len, text);
+}
+
+/* printk part of the temporary buffer line by line */
+static int printk_safe_flush_buffer(const char *start, size_t len)
+{
+ const char *c, *end;
+ bool header;
+
+ c = start;
+ end = start + len;
+ header = true;
+
+ /* Print line by line. */
+ while (c < end) {
+ if (*c == '\n') {
+ printk_safe_flush_line(start, c - start + 1);
+ start = ++c;
+ header = true;
+ continue;
+ }
+
+ /* Handle continuous lines or missing new line. */
+ if ((c + 1 < end) && printk_get_level(c)) {
+ if (header) {
+ c = printk_skip_level(c);
+ continue;
+ }
+
+ printk_safe_flush_line(start, c - start);
+ start = c++;
+ header = true;
+ continue;
+ }
+
+ header = false;
+ c++;
+ }
+
+ /* Check if there was a partial line. Ignore pure header. */
+ if (start < end && !header) {
+ static const char newline[] = KERN_CONT "\n";
+
+ printk_safe_flush_line(start, end - start);
+ printk_safe_flush_line(newline, strlen(newline));
+ }
+
+ return len;
+}
+
+static void report_message_lost(struct printk_safe_seq_buf *s)
+{
+ int lost = atomic_xchg(&s->message_lost, 0);
+
+ if (lost)
+ printk_deferred("Lost %d message(s)!\n", lost);
+}
+
+/*
+ * Flush data from the associated per-CPU buffer. The function
+ * can be called either via IRQ work or independently.
+ */
+static void __printk_safe_flush(struct irq_work *work)
+{
+ static raw_spinlock_t read_lock =
+ __RAW_SPIN_LOCK_INITIALIZER(read_lock);
+ struct printk_safe_seq_buf *s =
+ container_of(work, struct printk_safe_seq_buf, work);
+ unsigned long flags;
+ size_t len;
+ int i;
+
+ /*
+ * The lock has two functions. First, one reader has to flush all
+ * available message to make the lockless synchronization with
+ * writers easier. Second, we do not want to mix messages from
+ * different CPUs. This is especially important when printing
+ * a backtrace.
+ */
+ raw_spin_lock_irqsave(&read_lock, flags);
+
+ i = 0;
+more:
+ len = atomic_read(&s->len);
+
+ /*
+ * This is just a paranoid check that nobody has manipulated
+ * the buffer an unexpected way. If we printed something then
+ * @len must only increase. Also it should never overflow the
+ * buffer size.
+ */
+ if ((i && i >= len) || len > sizeof(s->buffer)) {
+ const char *msg = "printk_safe_flush: internal error\n";
+
+ printk_safe_flush_line(msg, strlen(msg));
+ len = 0;
+ }
+
+ if (!len)
+ goto out; /* Someone else has already flushed the buffer. */
+
+ /* Make sure that data has been written up to the @len */
+ smp_rmb();
+ i += printk_safe_flush_buffer(s->buffer + i, len - i);
+
+ /*
+ * Check that nothing has got added in the meantime and truncate
+ * the buffer. Note that atomic_cmpxchg() is an implicit memory
+ * barrier that makes sure that the data were copied before
+ * updating s->len.
+ */
+ if (atomic_cmpxchg(&s->len, len, 0) != len)
+ goto more;
+
+out:
+ report_message_lost(s);
+ raw_spin_unlock_irqrestore(&read_lock, flags);
+}
+
+/**
+ * printk_safe_flush - flush all per-cpu nmi buffers.
+ *
+ * The buffers are flushed automatically via IRQ work. This function
+ * is useful only when someone wants to be sure that all buffers have
+ * been flushed at some point.
+ */
+void printk_safe_flush(void)
+{
+ int cpu;
+
+ for_each_possible_cpu(cpu) {
+#ifdef CONFIG_PRINTK_NMI
+ __printk_safe_flush(&per_cpu(nmi_print_seq, cpu).work);
+#endif
+ __printk_safe_flush(&per_cpu(safe_print_seq, cpu).work);
+ }
+}
+
+/**
+ * printk_safe_flush_on_panic - flush all per-cpu nmi buffers when the system
+ * goes down.
+ *
+ * Similar to printk_safe_flush() but it can be called even in NMI context when
+ * the system goes down. It does the best effort to get NMI messages into
+ * the main ring buffer.
+ *
+ * Note that it could try harder when there is only one CPU online.
+ */
+void printk_safe_flush_on_panic(void)
+{
+ /*
+ * Make sure that we could access the main ring buffer.
+ * Do not risk a double release when more CPUs are up.
+ */
+ if (raw_spin_is_locked(&logbuf_lock)) {
+ if (num_online_cpus() > 1)
+ return;
+
+ debug_locks_off();
+ raw_spin_lock_init(&logbuf_lock);
+ }
+
+ printk_safe_flush();
+}
+
+#ifdef CONFIG_PRINTK_NMI
+/*
+ * Safe printk() for NMI context. It uses a per-CPU buffer to
+ * store the message. NMIs are not nested, so there is always only
+ * one writer running. But the buffer might get flushed from another
+ * CPU, so we need to be careful.
+ */
+static __printf(1, 0) int vprintk_nmi(const char *fmt, va_list args)
+{
+ struct printk_safe_seq_buf *s = this_cpu_ptr(&nmi_print_seq);
+
+ return printk_safe_log_store(s, fmt, args);
+}
+
+void notrace printk_nmi_enter(void)
+{
+ this_cpu_or(printk_context, PRINTK_NMI_CONTEXT_MASK);
+}
+
+void notrace printk_nmi_exit(void)
+{
+ this_cpu_and(printk_context, ~PRINTK_NMI_CONTEXT_MASK);
+}
+
+/*
+ * Marks a code that might produce many messages in NMI context
+ * and the risk of losing them is more critical than eventual
+ * reordering.
+ *
+ * It has effect only when called in NMI context. Then printk()
+ * will try to store the messages into the main logbuf directly
+ * and use the per-CPU buffers only as a fallback when the lock
+ * is not available.
+ */
+void printk_nmi_direct_enter(void)
+{
+ if (this_cpu_read(printk_context) & PRINTK_NMI_CONTEXT_MASK)
+ this_cpu_or(printk_context, PRINTK_NMI_DIRECT_CONTEXT_MASK);
+}
+
+void printk_nmi_direct_exit(void)
+{
+ this_cpu_and(printk_context, ~PRINTK_NMI_DIRECT_CONTEXT_MASK);
+}
+
+#else
+
+static __printf(1, 0) int vprintk_nmi(const char *fmt, va_list args)
+{
+ return 0;
+}
+
+#endif /* CONFIG_PRINTK_NMI */
+
+/*
+ * Lock-less printk(), to avoid deadlocks should the printk() recurse
+ * into itself. It uses a per-CPU buffer to store the message, just like
+ * NMI.
+ */
+static __printf(1, 0) int vprintk_safe(const char *fmt, va_list args)
+{
+ struct printk_safe_seq_buf *s = this_cpu_ptr(&safe_print_seq);
+
+ return printk_safe_log_store(s, fmt, args);
+}
+
+/* Can be preempted by NMI. */
+void __printk_safe_enter(void)
+{
+ this_cpu_inc(printk_context);
+}
+
+/* Can be preempted by NMI. */
+void __printk_safe_exit(void)
+{
+ this_cpu_dec(printk_context);
+}
+
+__printf(1, 0) int vprintk_func(const char *fmt, va_list args)
+{
+ /*
+ * Try to use the main logbuf even in NMI. But avoid calling console
+ * drivers that might have their own locks.
+ */
+ if ((this_cpu_read(printk_context) & PRINTK_NMI_DIRECT_CONTEXT_MASK) &&
+ raw_spin_trylock(&logbuf_lock)) {
+ int len;
+
+ len = vprintk_store(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
+ raw_spin_unlock(&logbuf_lock);
+ defer_console_output();
+ return len;
+ }
+
+ /* Use extra buffer in NMI when logbuf_lock is taken or in safe mode. */
+ if (this_cpu_read(printk_context) & PRINTK_NMI_CONTEXT_MASK)
+ return vprintk_nmi(fmt, args);
+
+ /* Use extra buffer to prevent a recursion deadlock in safe mode. */
+ if (this_cpu_read(printk_context) & PRINTK_SAFE_CONTEXT_MASK)
+ return vprintk_safe(fmt, args);
+
+ /* No obstacles. */
+ return vprintk_default(fmt, args);
+}
+
+void __init printk_safe_init(void)
+{
+ int cpu;
+
+ for_each_possible_cpu(cpu) {
+ struct printk_safe_seq_buf *s;
+
+ s = &per_cpu(safe_print_seq, cpu);
+ init_irq_work(&s->work, __printk_safe_flush);
+
+#ifdef CONFIG_PRINTK_NMI
+ s = &per_cpu(nmi_print_seq, cpu);
+ init_irq_work(&s->work, __printk_safe_flush);
+#endif
+ }
+
+ /*
+ * In the highly unlikely event that a NMI were to trigger at
+ * this moment. Make sure IRQ work is set up before this
+ * variable is set.
+ */
+ barrier();
+ printk_safe_irq_ready = 1;
+
+ /* Flush pending messages that did not have scheduled IRQ works. */
+ printk_safe_flush();
+}