diff options
Diffstat (limited to 'kernel/printk/printk.c')
| -rw-r--r-- | kernel/printk/printk.c | 3975 |
1 files changed, 3975 insertions, 0 deletions
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c new file mode 100644 index 000000000..cc53fb77f --- /dev/null +++ b/kernel/printk/printk.c @@ -0,0 +1,3975 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * linux/kernel/printk.c + * + * Copyright (C) 1991, 1992 Linus Torvalds + * + * Modified to make sys_syslog() more flexible: added commands to + * return the last 4k of kernel messages, regardless of whether + * they've been read or not. Added option to suppress kernel printk's + * to the console. Added hook for sending the console messages + * elsewhere, in preparation for a serial line console (someday). + * Ted Ts'o, 2/11/93. + * Modified for sysctl support, 1/8/97, Chris Horn. + * Fixed SMP synchronization, 08/08/99, Manfred Spraul + * manfred@colorfullife.com + * Rewrote bits to get rid of console_lock + * 01Mar01 Andrew Morton + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/kernel.h> +#include <linux/mm.h> +#include <linux/tty.h> +#include <linux/tty_driver.h> +#include <linux/console.h> +#include <linux/init.h> +#include <linux/jiffies.h> +#include <linux/nmi.h> +#include <linux/module.h> +#include <linux/moduleparam.h> +#include <linux/delay.h> +#include <linux/smp.h> +#include <linux/security.h> +#include <linux/memblock.h> +#include <linux/syscalls.h> +#include <linux/crash_core.h> +#include <linux/ratelimit.h> +#include <linux/kmsg_dump.h> +#include <linux/syslog.h> +#include <linux/cpu.h> +#include <linux/rculist.h> +#include <linux/poll.h> +#include <linux/irq_work.h> +#include <linux/ctype.h> +#include <linux/uio.h> +#include <linux/sched/clock.h> +#include <linux/sched/debug.h> +#include <linux/sched/task_stack.h> + +#include <linux/uaccess.h> +#include <asm/sections.h> + +#include <trace/events/initcall.h> +#define CREATE_TRACE_POINTS +#include <trace/events/printk.h> + +#include "printk_ringbuffer.h" +#include "console_cmdline.h" +#include "braille.h" +#include "internal.h" + +int console_printk[4] = { + CONSOLE_LOGLEVEL_DEFAULT, /* console_loglevel */ + MESSAGE_LOGLEVEL_DEFAULT, /* default_message_loglevel */ + CONSOLE_LOGLEVEL_MIN, /* minimum_console_loglevel */ + CONSOLE_LOGLEVEL_DEFAULT, /* default_console_loglevel */ +}; +EXPORT_SYMBOL_GPL(console_printk); + +atomic_t ignore_console_lock_warning __read_mostly = ATOMIC_INIT(0); +EXPORT_SYMBOL(ignore_console_lock_warning); + +/* + * Low level drivers may need that to know if they can schedule in + * their unblank() callback or not. So let's export it. + */ +int oops_in_progress; +EXPORT_SYMBOL(oops_in_progress); + +/* + * console_sem protects the console_drivers list, and also + * provides serialisation for access to the entire console + * driver system. + */ +static DEFINE_SEMAPHORE(console_sem); +struct console *console_drivers; +EXPORT_SYMBOL_GPL(console_drivers); + +/* + * System may need to suppress printk message under certain + * circumstances, like after kernel panic happens. + */ +int __read_mostly suppress_printk; + +/* + * During panic, heavy printk by other CPUs can delay the + * panic and risk deadlock on console resources. + */ +static int __read_mostly suppress_panic_printk; + +#ifdef CONFIG_LOCKDEP +static struct lockdep_map console_lock_dep_map = { + .name = "console_lock" +}; +#endif + +enum devkmsg_log_bits { + __DEVKMSG_LOG_BIT_ON = 0, + __DEVKMSG_LOG_BIT_OFF, + __DEVKMSG_LOG_BIT_LOCK, +}; + +enum devkmsg_log_masks { + DEVKMSG_LOG_MASK_ON = BIT(__DEVKMSG_LOG_BIT_ON), + DEVKMSG_LOG_MASK_OFF = BIT(__DEVKMSG_LOG_BIT_OFF), + DEVKMSG_LOG_MASK_LOCK = BIT(__DEVKMSG_LOG_BIT_LOCK), +}; + +/* Keep both the 'on' and 'off' bits clear, i.e. ratelimit by default: */ +#define DEVKMSG_LOG_MASK_DEFAULT 0 + +static unsigned int __read_mostly devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT; + +static int __control_devkmsg(char *str) +{ + size_t len; + + if (!str) + return -EINVAL; + + len = str_has_prefix(str, "on"); + if (len) { + devkmsg_log = DEVKMSG_LOG_MASK_ON; + return len; + } + + len = str_has_prefix(str, "off"); + if (len) { + devkmsg_log = DEVKMSG_LOG_MASK_OFF; + return len; + } + + len = str_has_prefix(str, "ratelimit"); + if (len) { + devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT; + return len; + } + + return -EINVAL; +} + +static int __init control_devkmsg(char *str) +{ + if (__control_devkmsg(str) < 0) { + pr_warn("printk.devkmsg: bad option string '%s'\n", str); + return 1; + } + + /* + * Set sysctl string accordingly: + */ + if (devkmsg_log == DEVKMSG_LOG_MASK_ON) + strcpy(devkmsg_log_str, "on"); + else if (devkmsg_log == DEVKMSG_LOG_MASK_OFF) + strcpy(devkmsg_log_str, "off"); + /* else "ratelimit" which is set by default. */ + + /* + * Sysctl cannot change it anymore. The kernel command line setting of + * this parameter is to force the setting to be permanent throughout the + * runtime of the system. This is a precation measure against userspace + * trying to be a smarta** and attempting to change it up on us. + */ + devkmsg_log |= DEVKMSG_LOG_MASK_LOCK; + + return 1; +} +__setup("printk.devkmsg=", control_devkmsg); + +char devkmsg_log_str[DEVKMSG_STR_MAX_SIZE] = "ratelimit"; +#if defined(CONFIG_PRINTK) && defined(CONFIG_SYSCTL) +int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write, + void *buffer, size_t *lenp, loff_t *ppos) +{ + char old_str[DEVKMSG_STR_MAX_SIZE]; + unsigned int old; + int err; + + if (write) { + if (devkmsg_log & DEVKMSG_LOG_MASK_LOCK) + return -EINVAL; + + old = devkmsg_log; + strncpy(old_str, devkmsg_log_str, DEVKMSG_STR_MAX_SIZE); + } + + err = proc_dostring(table, write, buffer, lenp, ppos); + if (err) + return err; + + if (write) { + err = __control_devkmsg(devkmsg_log_str); + + /* + * Do not accept an unknown string OR a known string with + * trailing crap... + */ + if (err < 0 || (err + 1 != *lenp)) { + + /* ... and restore old setting. */ + devkmsg_log = old; + strncpy(devkmsg_log_str, old_str, DEVKMSG_STR_MAX_SIZE); + + return -EINVAL; + } + } + + return 0; +} +#endif /* CONFIG_PRINTK && CONFIG_SYSCTL */ + +/* + * Helper macros to handle lockdep when locking/unlocking console_sem. We use + * macros instead of functions so that _RET_IP_ contains useful information. + */ +#define down_console_sem() do { \ + down(&console_sem);\ + mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\ +} while (0) + +static int __down_trylock_console_sem(unsigned long ip) +{ + int lock_failed; + unsigned long flags; + + /* + * Here and in __up_console_sem() we need to be in safe mode, + * because spindump/WARN/etc from under console ->lock will + * deadlock in printk()->down_trylock_console_sem() otherwise. + */ + printk_safe_enter_irqsave(flags); + lock_failed = down_trylock(&console_sem); + printk_safe_exit_irqrestore(flags); + + if (lock_failed) + return 1; + mutex_acquire(&console_lock_dep_map, 0, 1, ip); + return 0; +} +#define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_) + +static void __up_console_sem(unsigned long ip) +{ + unsigned long flags; + + mutex_release(&console_lock_dep_map, ip); + + printk_safe_enter_irqsave(flags); + up(&console_sem); + printk_safe_exit_irqrestore(flags); +} +#define up_console_sem() __up_console_sem(_RET_IP_) + +static bool panic_in_progress(void) +{ + return unlikely(atomic_read(&panic_cpu) != PANIC_CPU_INVALID); +} + +/* + * 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 semaphore held). + */ +static int console_locked, console_suspended; + +/* + * Array of consoles built from command line options (console=) + */ + +#define MAX_CMDLINECONSOLES 8 + +static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES]; + +static int preferred_console = -1; +int console_set_on_cmdline; +EXPORT_SYMBOL(console_set_on_cmdline); + +/* Flag: console code may call schedule() */ +static int console_may_schedule; + +enum con_msg_format_flags { + MSG_FORMAT_DEFAULT = 0, + MSG_FORMAT_SYSLOG = (1 << 0), +}; + +static int console_msg_format = MSG_FORMAT_DEFAULT; + +/* + * The printk log buffer consists of a sequenced collection of records, each + * containing variable length message text. Every record also contains its + * own meta-data (@info). + * + * Every record meta-data carries the timestamp in microseconds, as well as + * the standard userspace syslog level and syslog facility. The usual kernel + * messages use LOG_KERN; userspace-injected messages always carry a matching + * syslog facility, by default LOG_USER. The origin of every message can be + * reliably determined that way. + * + * The human readable log message of a record is available in @text, the + * length of the message text in @text_len. The stored message is not + * terminated. + * + * Optionally, a record can carry a dictionary of properties (key/value + * pairs), to provide userspace with a machine-readable message context. + * + * Examples for well-defined, commonly used property names are: + * DEVICE=b12:8 device identifier + * b12:8 block dev_t + * c127:3 char dev_t + * n8 netdev ifindex + * +sound:card0 subsystem:devname + * SUBSYSTEM=pci driver-core subsystem name + * + * Valid characters in property names are [a-zA-Z0-9.-_]. Property names + * and values are terminated by a '\0' character. + * + * Example of record values: + * record.text_buf = "it's a line" (unterminated) + * record.info.seq = 56 + * record.info.ts_nsec = 36863 + * record.info.text_len = 11 + * record.info.facility = 0 (LOG_KERN) + * record.info.flags = 0 + * record.info.level = 3 (LOG_ERR) + * record.info.caller_id = 299 (task 299) + * record.info.dev_info.subsystem = "pci" (terminated) + * record.info.dev_info.device = "+pci:0000:00:01.0" (terminated) + * + * The 'struct printk_info' buffer must never be directly exported to + * userspace, it is a kernel-private implementation detail that might + * need to be changed in the future, when the requirements change. + * + * /dev/kmsg exports the structured data in the following line format: + * "<level>,<sequnum>,<timestamp>,<contflag>[,additional_values, ... ];<message text>\n" + * + * Users of the export format should ignore possible additional values + * separated by ',', and find the message after the ';' character. + * + * The optional key/value pairs are attached as continuation lines starting + * with a space character and terminated by a newline. All possible + * non-prinatable characters are escaped in the "\xff" notation. + */ + +/* syslog_lock protects syslog_* variables and write access to clear_seq. */ +static DEFINE_MUTEX(syslog_lock); + +#ifdef CONFIG_PRINTK +DECLARE_WAIT_QUEUE_HEAD(log_wait); +/* All 3 protected by @syslog_lock. */ +/* the next printk record to read by syslog(READ) or /proc/kmsg */ +static u64 syslog_seq; +static size_t syslog_partial; +static bool syslog_time; + +struct latched_seq { + seqcount_latch_t latch; + u64 val[2]; +}; + +/* + * The next printk record to read after the last 'clear' command. There are + * two copies (updated with seqcount_latch) so that reads can locklessly + * access a valid value. Writers are synchronized by @syslog_lock. + */ +static struct latched_seq clear_seq = { + .latch = SEQCNT_LATCH_ZERO(clear_seq.latch), + .val[0] = 0, + .val[1] = 0, +}; + +#ifdef CONFIG_PRINTK_CALLER +#define PREFIX_MAX 48 +#else +#define PREFIX_MAX 32 +#endif + +/* the maximum size of a formatted record (i.e. with prefix added per line) */ +#define CONSOLE_LOG_MAX 1024 + +/* the maximum size for a dropped text message */ +#define DROPPED_TEXT_MAX 64 + +/* the maximum size allowed to be reserved for a record */ +#define LOG_LINE_MAX (CONSOLE_LOG_MAX - PREFIX_MAX) + +#define LOG_LEVEL(v) ((v) & 0x07) +#define LOG_FACILITY(v) ((v) >> 3 & 0xff) + +/* record buffer */ +#define LOG_ALIGN __alignof__(unsigned long) +#define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT) +#define LOG_BUF_LEN_MAX (u32)(1 << 31) +static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN); +static char *log_buf = __log_buf; +static u32 log_buf_len = __LOG_BUF_LEN; + +/* + * Define the average message size. This only affects the number of + * descriptors that will be available. Underestimating is better than + * overestimating (too many available descriptors is better than not enough). + */ +#define PRB_AVGBITS 5 /* 32 character average length */ + +#if CONFIG_LOG_BUF_SHIFT <= PRB_AVGBITS +#error CONFIG_LOG_BUF_SHIFT value too small. +#endif +_DEFINE_PRINTKRB(printk_rb_static, CONFIG_LOG_BUF_SHIFT - PRB_AVGBITS, + PRB_AVGBITS, &__log_buf[0]); + +static struct printk_ringbuffer printk_rb_dynamic; + +static struct printk_ringbuffer *prb = &printk_rb_static; + +/* + * We cannot access per-CPU data (e.g. per-CPU flush irq_work) before + * per_cpu_areas are initialised. This variable is set to true when + * it's safe to access per-CPU data. + */ +static bool __printk_percpu_data_ready __ro_after_init; + +bool printk_percpu_data_ready(void) +{ + return __printk_percpu_data_ready; +} + +/* Must be called under syslog_lock. */ +static void latched_seq_write(struct latched_seq *ls, u64 val) +{ + raw_write_seqcount_latch(&ls->latch); + ls->val[0] = val; + raw_write_seqcount_latch(&ls->latch); + ls->val[1] = val; +} + +/* Can be called from any context. */ +static u64 latched_seq_read_nolock(struct latched_seq *ls) +{ + unsigned int seq; + unsigned int idx; + u64 val; + + do { + seq = raw_read_seqcount_latch(&ls->latch); + idx = seq & 0x1; + val = ls->val[idx]; + } while (read_seqcount_latch_retry(&ls->latch, seq)); + + return val; +} + +/* Return log buffer address */ +char *log_buf_addr_get(void) +{ + return log_buf; +} + +/* Return log buffer size */ +u32 log_buf_len_get(void) +{ + return log_buf_len; +} + +/* + * Define how much of the log buffer we could take at maximum. The value + * must be greater than two. Note that only half of the buffer is available + * when the index points to the middle. + */ +#define MAX_LOG_TAKE_PART 4 +static const char trunc_msg[] = "<truncated>"; + +static void truncate_msg(u16 *text_len, u16 *trunc_msg_len) +{ + /* + * The message should not take the whole buffer. Otherwise, it might + * get removed too soon. + */ + u32 max_text_len = log_buf_len / MAX_LOG_TAKE_PART; + + if (*text_len > max_text_len) + *text_len = max_text_len; + + /* enable the warning message (if there is room) */ + *trunc_msg_len = strlen(trunc_msg); + if (*text_len >= *trunc_msg_len) + *text_len -= *trunc_msg_len; + else + *trunc_msg_len = 0; +} + +int dmesg_restrict = IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT); + +static int syslog_action_restricted(int type) +{ + if (dmesg_restrict) + return 1; + /* + * Unless restricted, we allow "read all" and "get buffer size" + * for everybody. + */ + return type != SYSLOG_ACTION_READ_ALL && + type != SYSLOG_ACTION_SIZE_BUFFER; +} + +static int check_syslog_permissions(int type, int source) +{ + /* + * If this is from /proc/kmsg and we've already opened it, then we've + * already done the capabilities checks at open time. + */ + if (source == SYSLOG_FROM_PROC && type != SYSLOG_ACTION_OPEN) + goto ok; + + if (syslog_action_restricted(type)) { + if (capable(CAP_SYSLOG)) + goto ok; + /* + * For historical reasons, accept CAP_SYS_ADMIN too, with + * a warning. + */ + if (capable(CAP_SYS_ADMIN)) { + pr_warn_once("%s (%d): Attempt to access syslog with " + "CAP_SYS_ADMIN but no CAP_SYSLOG " + "(deprecated).\n", + current->comm, task_pid_nr(current)); + goto ok; + } + return -EPERM; + } +ok: + return security_syslog(type); +} + +static void append_char(char **pp, char *e, char c) +{ + if (*pp < e) + *(*pp)++ = c; +} + +static ssize_t info_print_ext_header(char *buf, size_t size, + struct printk_info *info) +{ + u64 ts_usec = info->ts_nsec; + char caller[20]; +#ifdef CONFIG_PRINTK_CALLER + u32 id = info->caller_id; + + snprintf(caller, sizeof(caller), ",caller=%c%u", + id & 0x80000000 ? 'C' : 'T', id & ~0x80000000); +#else + caller[0] = '\0'; +#endif + + do_div(ts_usec, 1000); + + return scnprintf(buf, size, "%u,%llu,%llu,%c%s;", + (info->facility << 3) | info->level, info->seq, + ts_usec, info->flags & LOG_CONT ? 'c' : '-', caller); +} + +static ssize_t msg_add_ext_text(char *buf, size_t size, + const char *text, size_t text_len, + unsigned char endc) +{ + char *p = buf, *e = buf + size; + size_t i; + + /* escape non-printable characters */ + for (i = 0; i < text_len; i++) { + unsigned char c = text[i]; + + if (c < ' ' || c >= 127 || c == '\\') + p += scnprintf(p, e - p, "\\x%02x", c); + else + append_char(&p, e, c); + } + append_char(&p, e, endc); + + return p - buf; +} + +static ssize_t msg_add_dict_text(char *buf, size_t size, + const char *key, const char *val) +{ + size_t val_len = strlen(val); + ssize_t len; + + if (!val_len) + return 0; + + len = msg_add_ext_text(buf, size, "", 0, ' '); /* dict prefix */ + len += msg_add_ext_text(buf + len, size - len, key, strlen(key), '='); + len += msg_add_ext_text(buf + len, size - len, val, val_len, '\n'); + + return len; +} + +static ssize_t msg_print_ext_body(char *buf, size_t size, + char *text, size_t text_len, + struct dev_printk_info *dev_info) +{ + ssize_t len; + + len = msg_add_ext_text(buf, size, text, text_len, '\n'); + + if (!dev_info) + goto out; + + len += msg_add_dict_text(buf + len, size - len, "SUBSYSTEM", + dev_info->subsystem); + len += msg_add_dict_text(buf + len, size - len, "DEVICE", + dev_info->device); +out: + return len; +} + +/* /dev/kmsg - userspace message inject/listen interface */ +struct devkmsg_user { + atomic64_t seq; + struct ratelimit_state rs; + struct mutex lock; + char buf[CONSOLE_EXT_LOG_MAX]; + + struct printk_info info; + char text_buf[CONSOLE_EXT_LOG_MAX]; + struct printk_record record; +}; + +static __printf(3, 4) __cold +int devkmsg_emit(int facility, int level, const char *fmt, ...) +{ + va_list args; + int r; + + va_start(args, fmt); + r = vprintk_emit(facility, level, NULL, fmt, args); + va_end(args); + + return r; +} + +static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from) +{ + char *buf, *line; + int level = default_message_loglevel; + int facility = 1; /* LOG_USER */ + struct file *file = iocb->ki_filp; + struct devkmsg_user *user = file->private_data; + size_t len = iov_iter_count(from); + ssize_t ret = len; + + if (!user || len > LOG_LINE_MAX) + return -EINVAL; + + /* Ignore when user logging is disabled. */ + if (devkmsg_log & DEVKMSG_LOG_MASK_OFF) + return len; + + /* Ratelimit when not explicitly enabled. */ + if (!(devkmsg_log & DEVKMSG_LOG_MASK_ON)) { + if (!___ratelimit(&user->rs, current->comm)) + return ret; + } + + buf = kmalloc(len+1, GFP_KERNEL); + if (buf == NULL) + return -ENOMEM; + + buf[len] = '\0'; + if (!copy_from_iter_full(buf, len, from)) { + kfree(buf); + return -EFAULT; + } + + /* + * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace + * the decimal value represents 32bit, the lower 3 bit are the log + * level, the rest are the log facility. + * + * If no prefix or no userspace facility is specified, we + * enforce LOG_USER, to be able to reliably distinguish + * kernel-generated messages from userspace-injected ones. + */ + line = buf; + if (line[0] == '<') { + char *endp = NULL; + unsigned int u; + + u = simple_strtoul(line + 1, &endp, 10); + if (endp && endp[0] == '>') { + level = LOG_LEVEL(u); + if (LOG_FACILITY(u) != 0) + facility = LOG_FACILITY(u); + endp++; + line = endp; + } + } + + devkmsg_emit(facility, level, "%s", line); + kfree(buf); + return ret; +} + +static ssize_t devkmsg_read(struct file *file, char __user *buf, + size_t count, loff_t *ppos) +{ + struct devkmsg_user *user = file->private_data; + struct printk_record *r = &user->record; + size_t len; + ssize_t ret; + + if (!user) + return -EBADF; + + ret = mutex_lock_interruptible(&user->lock); + if (ret) + return ret; + + if (!prb_read_valid(prb, atomic64_read(&user->seq), r)) { + if (file->f_flags & O_NONBLOCK) { + ret = -EAGAIN; + goto out; + } + + /* + * Guarantee this task is visible on the waitqueue before + * checking the wake condition. + * + * The full memory barrier within set_current_state() of + * prepare_to_wait_event() pairs with the full memory barrier + * within wq_has_sleeper(). + * + * This pairs with __wake_up_klogd:A. + */ + ret = wait_event_interruptible(log_wait, + prb_read_valid(prb, + atomic64_read(&user->seq), r)); /* LMM(devkmsg_read:A) */ + if (ret) + goto out; + } + + if (r->info->seq != atomic64_read(&user->seq)) { + /* our last seen message is gone, return error and reset */ + atomic64_set(&user->seq, r->info->seq); + ret = -EPIPE; + goto out; + } + + len = info_print_ext_header(user->buf, sizeof(user->buf), r->info); + len += msg_print_ext_body(user->buf + len, sizeof(user->buf) - len, + &r->text_buf[0], r->info->text_len, + &r->info->dev_info); + + atomic64_set(&user->seq, r->info->seq + 1); + + if (len > count) { + ret = -EINVAL; + goto out; + } + + if (copy_to_user(buf, user->buf, len)) { + ret = -EFAULT; + goto out; + } + ret = len; +out: + mutex_unlock(&user->lock); + return ret; +} + +/* + * Be careful when modifying this function!!! + * + * Only few operations are supported because the device works only with the + * entire variable length messages (records). Non-standard values are + * returned in the other cases and has been this way for quite some time. + * User space applications might depend on this behavior. + */ +static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence) +{ + struct devkmsg_user *user = file->private_data; + loff_t ret = 0; + + if (!user) + return -EBADF; + if (offset) + return -ESPIPE; + + switch (whence) { + case SEEK_SET: + /* the first record */ + atomic64_set(&user->seq, prb_first_valid_seq(prb)); + break; + case SEEK_DATA: + /* + * The first record after the last SYSLOG_ACTION_CLEAR, + * like issued by 'dmesg -c'. Reading /dev/kmsg itself + * changes no global state, and does not clear anything. + */ + atomic64_set(&user->seq, latched_seq_read_nolock(&clear_seq)); + break; + case SEEK_END: + /* after the last record */ + atomic64_set(&user->seq, prb_next_seq(prb)); + break; + default: + ret = -EINVAL; + } + return ret; +} + +static __poll_t devkmsg_poll(struct file *file, poll_table *wait) +{ + struct devkmsg_user *user = file->private_data; + struct printk_info info; + __poll_t ret = 0; + + if (!user) + return EPOLLERR|EPOLLNVAL; + + poll_wait(file, &log_wait, wait); + + if (prb_read_valid_info(prb, atomic64_read(&user->seq), &info, NULL)) { + /* return error when data has vanished underneath us */ + if (info.seq != atomic64_read(&user->seq)) + ret = EPOLLIN|EPOLLRDNORM|EPOLLERR|EPOLLPRI; + else + ret = EPOLLIN|EPOLLRDNORM; + } + + return ret; +} + +static int devkmsg_open(struct inode *inode, struct file *file) +{ + struct devkmsg_user *user; + int err; + + if (devkmsg_log & DEVKMSG_LOG_MASK_OFF) + return -EPERM; + + /* write-only does not need any file context */ + if ((file->f_flags & O_ACCMODE) != O_WRONLY) { + err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL, + SYSLOG_FROM_READER); + if (err) + return err; + } + + user = kvmalloc(sizeof(struct devkmsg_user), GFP_KERNEL); + if (!user) + return -ENOMEM; + + ratelimit_default_init(&user->rs); + ratelimit_set_flags(&user->rs, RATELIMIT_MSG_ON_RELEASE); + + mutex_init(&user->lock); + + prb_rec_init_rd(&user->record, &user->info, + &user->text_buf[0], sizeof(user->text_buf)); + + atomic64_set(&user->seq, prb_first_valid_seq(prb)); + + file->private_data = user; + return 0; +} + +static int devkmsg_release(struct inode *inode, struct file *file) +{ + struct devkmsg_user *user = file->private_data; + + if (!user) + return 0; + + ratelimit_state_exit(&user->rs); + + mutex_destroy(&user->lock); + kvfree(user); + return 0; +} + +const struct file_operations kmsg_fops = { + .open = devkmsg_open, + .read = devkmsg_read, + .write_iter = devkmsg_write, + .llseek = devkmsg_llseek, + .poll = devkmsg_poll, + .release = devkmsg_release, +}; + +#ifdef CONFIG_CRASH_CORE +/* + * This appends the listed symbols to /proc/vmcore + * + * /proc/vmcore is used by various utilities, like crash and makedumpfile to + * obtain access to symbols that are otherwise very difficult to locate. These + * symbols are specifically used so that utilities can access and extract the + * dmesg log from a vmcore file after a crash. + */ +void log_buf_vmcoreinfo_setup(void) +{ + struct dev_printk_info *dev_info = NULL; + + VMCOREINFO_SYMBOL(prb); + VMCOREINFO_SYMBOL(printk_rb_static); + VMCOREINFO_SYMBOL(clear_seq); + + /* + * Export struct size and field offsets. User space tools can + * parse it and detect any changes to structure down the line. + */ + + VMCOREINFO_STRUCT_SIZE(printk_ringbuffer); + VMCOREINFO_OFFSET(printk_ringbuffer, desc_ring); + VMCOREINFO_OFFSET(printk_ringbuffer, text_data_ring); + VMCOREINFO_OFFSET(printk_ringbuffer, fail); + + VMCOREINFO_STRUCT_SIZE(prb_desc_ring); + VMCOREINFO_OFFSET(prb_desc_ring, count_bits); + VMCOREINFO_OFFSET(prb_desc_ring, descs); + VMCOREINFO_OFFSET(prb_desc_ring, infos); + VMCOREINFO_OFFSET(prb_desc_ring, head_id); + VMCOREINFO_OFFSET(prb_desc_ring, tail_id); + + VMCOREINFO_STRUCT_SIZE(prb_desc); + VMCOREINFO_OFFSET(prb_desc, state_var); + VMCOREINFO_OFFSET(prb_desc, text_blk_lpos); + + VMCOREINFO_STRUCT_SIZE(prb_data_blk_lpos); + VMCOREINFO_OFFSET(prb_data_blk_lpos, begin); + VMCOREINFO_OFFSET(prb_data_blk_lpos, next); + + VMCOREINFO_STRUCT_SIZE(printk_info); + VMCOREINFO_OFFSET(printk_info, seq); + VMCOREINFO_OFFSET(printk_info, ts_nsec); + VMCOREINFO_OFFSET(printk_info, text_len); + VMCOREINFO_OFFSET(printk_info, caller_id); + VMCOREINFO_OFFSET(printk_info, dev_info); + + VMCOREINFO_STRUCT_SIZE(dev_printk_info); + VMCOREINFO_OFFSET(dev_printk_info, subsystem); + VMCOREINFO_LENGTH(printk_info_subsystem, sizeof(dev_info->subsystem)); + VMCOREINFO_OFFSET(dev_printk_info, device); + VMCOREINFO_LENGTH(printk_info_device, sizeof(dev_info->device)); + + VMCOREINFO_STRUCT_SIZE(prb_data_ring); + VMCOREINFO_OFFSET(prb_data_ring, size_bits); + VMCOREINFO_OFFSET(prb_data_ring, data); + VMCOREINFO_OFFSET(prb_data_ring, head_lpos); + VMCOREINFO_OFFSET(prb_data_ring, tail_lpos); + + VMCOREINFO_SIZE(atomic_long_t); + VMCOREINFO_TYPE_OFFSET(atomic_long_t, counter); + + VMCOREINFO_STRUCT_SIZE(latched_seq); + VMCOREINFO_OFFSET(latched_seq, val); +} +#endif + +/* requested log_buf_len from kernel cmdline */ +static unsigned long __initdata new_log_buf_len; + +/* we practice scaling the ring buffer by powers of 2 */ +static void __init log_buf_len_update(u64 size) +{ + if (size > (u64)LOG_BUF_LEN_MAX) { + size = (u64)LOG_BUF_LEN_MAX; + pr_err("log_buf over 2G is not supported.\n"); + } + + if (size) + size = roundup_pow_of_two(size); + if (size > log_buf_len) + new_log_buf_len = (unsigned long)size; +} + +/* save requested log_buf_len since it's too early to process it */ +static int __init log_buf_len_setup(char *str) +{ + u64 size; + + if (!str) + return -EINVAL; + + size = memparse(str, &str); + + log_buf_len_update(size); + + return 0; +} +early_param("log_buf_len", log_buf_len_setup); + +#ifdef CONFIG_SMP +#define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT) + +static void __init log_buf_add_cpu(void) +{ + unsigned int cpu_extra; + + /* + * archs should set up cpu_possible_bits properly with + * set_cpu_possible() after setup_arch() but just in + * case lets ensure this is valid. + */ + if (num_possible_cpus() == 1) + return; + + cpu_extra = (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN; + + /* by default this will only continue through for large > 64 CPUs */ + if (cpu_extra <= __LOG_BUF_LEN / 2) + return; + + pr_info("log_buf_len individual max cpu contribution: %d bytes\n", + __LOG_CPU_MAX_BUF_LEN); + pr_info("log_buf_len total cpu_extra contributions: %d bytes\n", + cpu_extra); + pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN); + + log_buf_len_update(cpu_extra + __LOG_BUF_LEN); +} +#else /* !CONFIG_SMP */ +static inline void log_buf_add_cpu(void) {} +#endif /* CONFIG_SMP */ + +static void __init set_percpu_data_ready(void) +{ + __printk_percpu_data_ready = true; +} + +static unsigned int __init add_to_rb(struct printk_ringbuffer *rb, + struct printk_record *r) +{ + struct prb_reserved_entry e; + struct printk_record dest_r; + + prb_rec_init_wr(&dest_r, r->info->text_len); + + if (!prb_reserve(&e, rb, &dest_r)) + return 0; + + memcpy(&dest_r.text_buf[0], &r->text_buf[0], r->info->text_len); + dest_r.info->text_len = r->info->text_len; + dest_r.info->facility = r->info->facility; + dest_r.info->level = r->info->level; + dest_r.info->flags = r->info->flags; + dest_r.info->ts_nsec = r->info->ts_nsec; + dest_r.info->caller_id = r->info->caller_id; + memcpy(&dest_r.info->dev_info, &r->info->dev_info, sizeof(dest_r.info->dev_info)); + + prb_final_commit(&e); + + return prb_record_text_space(&e); +} + +static char setup_text_buf[LOG_LINE_MAX] __initdata; + +void __init setup_log_buf(int early) +{ + struct printk_info *new_infos; + unsigned int new_descs_count; + struct prb_desc *new_descs; + struct printk_info info; + struct printk_record r; + unsigned int text_size; + size_t new_descs_size; + size_t new_infos_size; + unsigned long flags; + char *new_log_buf; + unsigned int free; + u64 seq; + + /* + * Some archs call setup_log_buf() multiple times - first is very + * early, e.g. from setup_arch(), and second - when percpu_areas + * are initialised. + */ + if (!early) + set_percpu_data_ready(); + + if (log_buf != __log_buf) + return; + + if (!early && !new_log_buf_len) + log_buf_add_cpu(); + + if (!new_log_buf_len) + return; + + new_descs_count = new_log_buf_len >> PRB_AVGBITS; + if (new_descs_count == 0) { + pr_err("new_log_buf_len: %lu too small\n", new_log_buf_len); + return; + } + + new_log_buf = memblock_alloc(new_log_buf_len, LOG_ALIGN); + if (unlikely(!new_log_buf)) { + pr_err("log_buf_len: %lu text bytes not available\n", + new_log_buf_len); + return; + } + + new_descs_size = new_descs_count * sizeof(struct prb_desc); + new_descs = memblock_alloc(new_descs_size, LOG_ALIGN); + if (unlikely(!new_descs)) { + pr_err("log_buf_len: %zu desc bytes not available\n", + new_descs_size); + goto err_free_log_buf; + } + + new_infos_size = new_descs_count * sizeof(struct printk_info); + new_infos = memblock_alloc(new_infos_size, LOG_ALIGN); + if (unlikely(!new_infos)) { + pr_err("log_buf_len: %zu info bytes not available\n", + new_infos_size); + goto err_free_descs; + } + + prb_rec_init_rd(&r, &info, &setup_text_buf[0], sizeof(setup_text_buf)); + + prb_init(&printk_rb_dynamic, + new_log_buf, ilog2(new_log_buf_len), + new_descs, ilog2(new_descs_count), + new_infos); + + local_irq_save(flags); + + log_buf_len = new_log_buf_len; + log_buf = new_log_buf; + new_log_buf_len = 0; + + free = __LOG_BUF_LEN; + prb_for_each_record(0, &printk_rb_static, seq, &r) { + text_size = add_to_rb(&printk_rb_dynamic, &r); + if (text_size > free) + free = 0; + else + free -= text_size; + } + + prb = &printk_rb_dynamic; + + local_irq_restore(flags); + + /* + * Copy any remaining messages that might have appeared from + * NMI context after copying but before switching to the + * dynamic buffer. + */ + prb_for_each_record(seq, &printk_rb_static, seq, &r) { + text_size = add_to_rb(&printk_rb_dynamic, &r); + if (text_size > free) + free = 0; + else + free -= text_size; + } + + if (seq != prb_next_seq(&printk_rb_static)) { + pr_err("dropped %llu messages\n", + prb_next_seq(&printk_rb_static) - seq); + } + + pr_info("log_buf_len: %u bytes\n", log_buf_len); + pr_info("early log buf free: %u(%u%%)\n", + free, (free * 100) / __LOG_BUF_LEN); + return; + +err_free_descs: + memblock_free(new_descs, new_descs_size); +err_free_log_buf: + memblock_free(new_log_buf, new_log_buf_len); +} + +static bool __read_mostly ignore_loglevel; + +static int __init ignore_loglevel_setup(char *str) +{ + ignore_loglevel = true; + pr_info("debug: ignoring loglevel setting.\n"); + + return 0; +} + +early_param("ignore_loglevel", ignore_loglevel_setup); +module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR); +MODULE_PARM_DESC(ignore_loglevel, + "ignore loglevel setting (prints all kernel messages to the console)"); + +static bool suppress_message_printing(int level) +{ + return (level >= console_loglevel && !ignore_loglevel); +} + +#ifdef CONFIG_BOOT_PRINTK_DELAY + +static int boot_delay; /* msecs delay after each printk during bootup */ +static unsigned long long loops_per_msec; /* based on boot_delay */ + +static int __init boot_delay_setup(char *str) +{ + unsigned long lpj; + + lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */ + loops_per_msec = (unsigned long long)lpj / 1000 * HZ; + + get_option(&str, &boot_delay); + if (boot_delay > 10 * 1000) + boot_delay = 0; + + pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, " + "HZ: %d, loops_per_msec: %llu\n", + boot_delay, preset_lpj, lpj, HZ, loops_per_msec); + return 0; +} +early_param("boot_delay", boot_delay_setup); + +static void boot_delay_msec(int level) +{ + unsigned long long k; + unsigned long timeout; + + if ((boot_delay == 0 || system_state >= SYSTEM_RUNNING) + || suppress_message_printing(level)) { + return; + } + + k = (unsigned long long)loops_per_msec * boot_delay; + + timeout = jiffies + msecs_to_jiffies(boot_delay); + while (k) { + k--; + cpu_relax(); + /* + * use (volatile) jiffies to prevent + * compiler reduction; loop termination via jiffies + * is secondary and may or may not happen. + */ + if (time_after(jiffies, timeout)) + break; + touch_nmi_watchdog(); + } +} +#else +static inline void boot_delay_msec(int level) +{ +} +#endif + +static bool printk_time = IS_ENABLED(CONFIG_PRINTK_TIME); +module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR); + +static size_t print_syslog(unsigned int level, char *buf) +{ + return sprintf(buf, "<%u>", level); +} + +static size_t print_time(u64 ts, char *buf) +{ + unsigned long rem_nsec = do_div(ts, 1000000000); + + return sprintf(buf, "[%5lu.%06lu]", + (unsigned long)ts, rem_nsec / 1000); +} + +#ifdef CONFIG_PRINTK_CALLER +static size_t print_caller(u32 id, char *buf) +{ + char caller[12]; + + snprintf(caller, sizeof(caller), "%c%u", + id & 0x80000000 ? 'C' : 'T', id & ~0x80000000); + return sprintf(buf, "[%6s]", caller); +} +#else +#define print_caller(id, buf) 0 +#endif + +static size_t info_print_prefix(const struct printk_info *info, bool syslog, + bool time, char *buf) +{ + size_t len = 0; + + if (syslog) + len = print_syslog((info->facility << 3) | info->level, buf); + + if (time) + len += print_time(info->ts_nsec, buf + len); + + len += print_caller(info->caller_id, buf + len); + + if (IS_ENABLED(CONFIG_PRINTK_CALLER) || time) { + buf[len++] = ' '; + buf[len] = '\0'; + } + + return len; +} + +/* + * Prepare the record for printing. The text is shifted within the given + * buffer to avoid a need for another one. The following operations are + * done: + * + * - Add prefix for each line. + * - Drop truncated lines that no longer fit into the buffer. + * - Add the trailing newline that has been removed in vprintk_store(). + * - Add a string terminator. + * + * Since the produced string is always terminated, the maximum possible + * return value is @r->text_buf_size - 1; + * + * Return: The length of the updated/prepared text, including the added + * prefixes and the newline. The terminator is not counted. The dropped + * line(s) are not counted. + */ +static size_t record_print_text(struct printk_record *r, bool syslog, + bool time) +{ + size_t text_len = r->info->text_len; + size_t buf_size = r->text_buf_size; + char *text = r->text_buf; + char prefix[PREFIX_MAX]; + bool truncated = false; + size_t prefix_len; + size_t line_len; + size_t len = 0; + char *next; + + /* + * If the message was truncated because the buffer was not large + * enough, treat the available text as if it were the full text. + */ + if (text_len > buf_size) + text_len = buf_size; + + prefix_len = info_print_prefix(r->info, syslog, time, prefix); + + /* + * @text_len: bytes of unprocessed text + * @line_len: bytes of current line _without_ newline + * @text: pointer to beginning of current line + * @len: number of bytes prepared in r->text_buf + */ + for (;;) { + next = memchr(text, '\n', text_len); + if (next) { + line_len = next - text; + } else { + /* Drop truncated line(s). */ + if (truncated) + break; + line_len = text_len; + } + + /* + * Truncate the text if there is not enough space to add the + * prefix and a trailing newline and a terminator. + */ + if (len + prefix_len + text_len + 1 + 1 > buf_size) { + /* Drop even the current line if no space. */ + if (len + prefix_len + line_len + 1 + 1 > buf_size) + break; + + text_len = buf_size - len - prefix_len - 1 - 1; + truncated = true; + } + + memmove(text + prefix_len, text, text_len); + memcpy(text, prefix, prefix_len); + + /* + * Increment the prepared length to include the text and + * prefix that were just moved+copied. Also increment for the + * newline at the end of this line. If this is the last line, + * there is no newline, but it will be added immediately below. + */ + len += prefix_len + line_len + 1; + if (text_len == line_len) { + /* + * This is the last line. Add the trailing newline + * removed in vprintk_store(). + */ + text[prefix_len + line_len] = '\n'; + break; + } + + /* + * Advance beyond the added prefix and the related line with + * its newline. + */ + text += prefix_len + line_len + 1; + + /* + * The remaining text has only decreased by the line with its + * newline. + * + * Note that @text_len can become zero. It happens when @text + * ended with a newline (either due to truncation or the + * original string ending with "\n\n"). The loop is correctly + * repeated and (if not truncated) an empty line with a prefix + * will be prepared. + */ + text_len -= line_len + 1; + } + + /* + * If a buffer was provided, it will be terminated. Space for the + * string terminator is guaranteed to be available. The terminator is + * not counted in the return value. + */ + if (buf_size > 0) + r->text_buf[len] = 0; + + return len; +} + +static size_t get_record_print_text_size(struct printk_info *info, + unsigned int line_count, + bool syslog, bool time) +{ + char prefix[PREFIX_MAX]; + size_t prefix_len; + + prefix_len = info_print_prefix(info, syslog, time, prefix); + + /* + * Each line will be preceded with a prefix. The intermediate + * newlines are already within the text, but a final trailing + * newline will be added. + */ + return ((prefix_len * line_count) + info->text_len + 1); +} + +/* + * Beginning with @start_seq, find the first record where it and all following + * records up to (but not including) @max_seq fit into @size. + * + * @max_seq is simply an upper bound and does not need to exist. If the caller + * does not require an upper bound, -1 can be used for @max_seq. + */ +static u64 find_first_fitting_seq(u64 start_seq, u64 max_seq, size_t size, + bool syslog, bool time) +{ + struct printk_info info; + unsigned int line_count; + size_t len = 0; + u64 seq; + + /* Determine the size of the records up to @max_seq. */ + prb_for_each_info(start_seq, prb, seq, &info, &line_count) { + if (info.seq >= max_seq) + break; + len += get_record_print_text_size(&info, line_count, syslog, time); + } + + /* + * Adjust the upper bound for the next loop to avoid subtracting + * lengths that were never added. + */ + if (seq < max_seq) + max_seq = seq; + + /* + * Move first record forward until length fits into the buffer. Ignore + * newest messages that were not counted in the above cycle. Messages + * might appear and get lost in the meantime. This is a best effort + * that prevents an infinite loop that could occur with a retry. + */ + prb_for_each_info(start_seq, prb, seq, &info, &line_count) { + if (len <= size || info.seq >= max_seq) + break; + len -= get_record_print_text_size(&info, line_count, syslog, time); + } + + return seq; +} + +/* The caller is responsible for making sure @size is greater than 0. */ +static int syslog_print(char __user *buf, int size) +{ + struct printk_info info; + struct printk_record r; + char *text; + int len = 0; + u64 seq; + + text = kmalloc(CONSOLE_LOG_MAX, GFP_KERNEL); + if (!text) + return -ENOMEM; + + prb_rec_init_rd(&r, &info, text, CONSOLE_LOG_MAX); + + mutex_lock(&syslog_lock); + + /* + * Wait for the @syslog_seq record to be available. @syslog_seq may + * change while waiting. + */ + do { + seq = syslog_seq; + + mutex_unlock(&syslog_lock); + /* + * Guarantee this task is visible on the waitqueue before + * checking the wake condition. + * + * The full memory barrier within set_current_state() of + * prepare_to_wait_event() pairs with the full memory barrier + * within wq_has_sleeper(). + * + * This pairs with __wake_up_klogd:A. + */ + len = wait_event_interruptible(log_wait, + prb_read_valid(prb, seq, NULL)); /* LMM(syslog_print:A) */ + mutex_lock(&syslog_lock); + + if (len) + goto out; + } while (syslog_seq != seq); + + /* + * Copy records that fit into the buffer. The above cycle makes sure + * that the first record is always available. + */ + do { + size_t n; + size_t skip; + int err; + + if (!prb_read_valid(prb, syslog_seq, &r)) + break; + + if (r.info->seq != syslog_seq) { + /* message is gone, move to next valid one */ + syslog_seq = r.info->seq; + syslog_partial = 0; + } + + /* + * To keep reading/counting partial line consistent, + * use printk_time value as of the beginning of a line. + */ + if (!syslog_partial) + syslog_time = printk_time; + + skip = syslog_partial; + n = record_print_text(&r, true, syslog_time); + if (n - syslog_partial <= size) { + /* message fits into buffer, move forward */ + syslog_seq = r.info->seq + 1; + n -= syslog_partial; + syslog_partial = 0; + } else if (!len){ + /* partial read(), remember position */ + n = size; + syslog_partial += n; + } else + n = 0; + + if (!n) + break; + + mutex_unlock(&syslog_lock); + err = copy_to_user(buf, text + skip, n); + mutex_lock(&syslog_lock); + + if (err) { + if (!len) + len = -EFAULT; + break; + } + + len += n; + size -= n; + buf += n; + } while (size); +out: + mutex_unlock(&syslog_lock); + kfree(text); + return len; +} + +static int syslog_print_all(char __user *buf, int size, bool clear) +{ + struct printk_info info; + struct printk_record r; + char *text; + int len = 0; + u64 seq; + bool time; + + text = kmalloc(CONSOLE_LOG_MAX, GFP_KERNEL); + if (!text) + return -ENOMEM; + + time = printk_time; + /* + * Find first record that fits, including all following records, + * into the user-provided buffer for this dump. + */ + seq = find_first_fitting_seq(latched_seq_read_nolock(&clear_seq), -1, + size, true, time); + + prb_rec_init_rd(&r, &info, text, CONSOLE_LOG_MAX); + + len = 0; + prb_for_each_record(seq, prb, seq, &r) { + int textlen; + + textlen = record_print_text(&r, true, time); + + if (len + textlen > size) { + seq--; + break; + } + + if (copy_to_user(buf + len, text, textlen)) + len = -EFAULT; + else + len += textlen; + + if (len < 0) + break; + } + + if (clear) { + mutex_lock(&syslog_lock); + latched_seq_write(&clear_seq, seq); + mutex_unlock(&syslog_lock); + } + + kfree(text); + return len; +} + +static void syslog_clear(void) +{ + mutex_lock(&syslog_lock); + latched_seq_write(&clear_seq, prb_next_seq(prb)); + mutex_unlock(&syslog_lock); +} + +int do_syslog(int type, char __user *buf, int len, int source) +{ + struct printk_info info; + bool clear = false; + static int saved_console_loglevel = LOGLEVEL_DEFAULT; + int error; + + error = check_syslog_permissions(type, source); + if (error) + return error; + + switch (type) { + case SYSLOG_ACTION_CLOSE: /* Close log */ + break; + case SYSLOG_ACTION_OPEN: /* Open log */ + break; + case SYSLOG_ACTION_READ: /* Read from log */ + if (!buf || len < 0) + return -EINVAL; + if (!len) + return 0; + if (!access_ok(buf, len)) + return -EFAULT; + error = syslog_print(buf, len); + break; + /* Read/clear last kernel messages */ + case SYSLOG_ACTION_READ_CLEAR: + clear = true; + fallthrough; + /* Read last kernel messages */ + case SYSLOG_ACTION_READ_ALL: + if (!buf || len < 0) + return -EINVAL; + if (!len) + return 0; + if (!access_ok(buf, len)) + return -EFAULT; + error = syslog_print_all(buf, len, clear); + break; + /* Clear ring buffer */ + case SYSLOG_ACTION_CLEAR: + syslog_clear(); + break; + /* Disable logging to console */ + case SYSLOG_ACTION_CONSOLE_OFF: + if (saved_console_loglevel == LOGLEVEL_DEFAULT) + saved_console_loglevel = console_loglevel; + console_loglevel = minimum_console_loglevel; + break; + /* Enable logging to console */ + case SYSLOG_ACTION_CONSOLE_ON: + if (saved_console_loglevel != LOGLEVEL_DEFAULT) { + console_loglevel = saved_console_loglevel; + saved_console_loglevel = LOGLEVEL_DEFAULT; + } + break; + /* Set level of messages printed to console */ + case SYSLOG_ACTION_CONSOLE_LEVEL: + if (len < 1 || len > 8) + return -EINVAL; + if (len < minimum_console_loglevel) + len = minimum_console_loglevel; + console_loglevel = len; + /* Implicitly re-enable logging to console */ + saved_console_loglevel = LOGLEVEL_DEFAULT; + break; + /* Number of chars in the log buffer */ + case SYSLOG_ACTION_SIZE_UNREAD: + mutex_lock(&syslog_lock); + if (!prb_read_valid_info(prb, syslog_seq, &info, NULL)) { + /* No unread messages. */ + mutex_unlock(&syslog_lock); + return 0; + } + if (info.seq != syslog_seq) { + /* messages are gone, move to first one */ + syslog_seq = info.seq; + syslog_partial = 0; + } + if (source == SYSLOG_FROM_PROC) { + /* + * Short-cut for poll(/"proc/kmsg") which simply checks + * for pending data, not the size; return the count of + * records, not the length. + */ + error = prb_next_seq(prb) - syslog_seq; + } else { + bool time = syslog_partial ? syslog_time : printk_time; + unsigned int line_count; + u64 seq; + + prb_for_each_info(syslog_seq, prb, seq, &info, + &line_count) { + error += get_record_print_text_size(&info, line_count, + true, time); + time = printk_time; + } + error -= syslog_partial; + } + mutex_unlock(&syslog_lock); + break; + /* Size of the log buffer */ + case SYSLOG_ACTION_SIZE_BUFFER: + error = log_buf_len; + break; + default: + error = -EINVAL; + break; + } + + return error; +} + +SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len) +{ + return do_syslog(type, buf, len, SYSLOG_FROM_READER); +} + +/* + * Special console_lock variants that help to reduce the risk of soft-lockups. + * They allow to pass console_lock to another printk() call using a busy wait. + */ + +#ifdef CONFIG_LOCKDEP +static struct lockdep_map console_owner_dep_map = { + .name = "console_owner" +}; +#endif + +static DEFINE_RAW_SPINLOCK(console_owner_lock); +static struct task_struct *console_owner; +static bool console_waiter; + +/** + * console_lock_spinning_enable - mark beginning of code where another + * thread might safely busy wait + * + * This basically converts console_lock into a spinlock. This marks + * the section where the console_lock owner can not sleep, because + * there may be a waiter spinning (like a spinlock). Also it must be + * ready to hand over the lock at the end of the section. + */ +static void console_lock_spinning_enable(void) +{ + raw_spin_lock(&console_owner_lock); + console_owner = current; + raw_spin_unlock(&console_owner_lock); + + /* The waiter may spin on us after setting console_owner */ + spin_acquire(&console_owner_dep_map, 0, 0, _THIS_IP_); +} + +/** + * console_lock_spinning_disable_and_check - mark end of code where another + * thread was able to busy wait and check if there is a waiter + * + * This is called at the end of the section where spinning is allowed. + * It has two functions. First, it is a signal that it is no longer + * safe to start busy waiting for the lock. Second, it checks if + * there is a busy waiter and passes the lock rights to her. + * + * Important: Callers lose the lock if there was a busy waiter. + * They must not touch items synchronized by console_lock + * in this case. + * + * Return: 1 if the lock rights were passed, 0 otherwise. + */ +static int console_lock_spinning_disable_and_check(void) +{ + int waiter; + + raw_spin_lock(&console_owner_lock); + waiter = READ_ONCE(console_waiter); + console_owner = NULL; + raw_spin_unlock(&console_owner_lock); + + if (!waiter) { + spin_release(&console_owner_dep_map, _THIS_IP_); + return 0; + } + + /* The waiter is now free to continue */ + WRITE_ONCE(console_waiter, false); + + spin_release(&console_owner_dep_map, _THIS_IP_); + + /* + * Hand off console_lock to waiter. The waiter will perform + * the up(). After this, the waiter is the console_lock owner. + */ + mutex_release(&console_lock_dep_map, _THIS_IP_); + return 1; +} + +/** + * console_trylock_spinning - try to get console_lock by busy waiting + * + * This allows to busy wait for the console_lock when the current + * owner is running in specially marked sections. It means that + * the current owner is running and cannot reschedule until it + * is ready to lose the lock. + * + * Return: 1 if we got the lock, 0 othrewise + */ +static int console_trylock_spinning(void) +{ + struct task_struct *owner = NULL; + bool waiter; + bool spin = false; + unsigned long flags; + + if (console_trylock()) + return 1; + + /* + * It's unsafe to spin once a panic has begun. If we are the + * panic CPU, we may have already halted the owner of the + * console_sem. If we are not the panic CPU, then we should + * avoid taking console_sem, so the panic CPU has a better + * chance of cleanly acquiring it later. + */ + if (panic_in_progress()) + return 0; + + printk_safe_enter_irqsave(flags); + + raw_spin_lock(&console_owner_lock); + owner = READ_ONCE(console_owner); + waiter = READ_ONCE(console_waiter); + if (!waiter && owner && owner != current) { + WRITE_ONCE(console_waiter, true); + spin = true; + } + raw_spin_unlock(&console_owner_lock); + + /* + * If there is an active printk() writing to the + * consoles, instead of having it write our data too, + * see if we can offload that load from the active + * printer, and do some printing ourselves. + * Go into a spin only if there isn't already a waiter + * spinning, and there is an active printer, and + * that active printer isn't us (recursive printk?). + */ + if (!spin) { + printk_safe_exit_irqrestore(flags); + return 0; + } + + /* We spin waiting for the owner to release us */ + spin_acquire(&console_owner_dep_map, 0, 0, _THIS_IP_); + /* Owner will clear console_waiter on hand off */ + while (READ_ONCE(console_waiter)) + cpu_relax(); + spin_release(&console_owner_dep_map, _THIS_IP_); + + printk_safe_exit_irqrestore(flags); + /* + * The owner passed the console lock to us. + * Since we did not spin on console lock, annotate + * this as a trylock. Otherwise lockdep will + * complain. + */ + mutex_acquire(&console_lock_dep_map, 0, 1, _THIS_IP_); + + return 1; +} + +/* + * Call the specified console driver, asking it to write out the specified + * text and length. If @dropped_text is non-NULL and any records have been + * dropped, a dropped message will be written out first. + */ +static void call_console_driver(struct console *con, const char *text, size_t len, + char *dropped_text) +{ + size_t dropped_len; + + if (con->dropped && dropped_text) { + dropped_len = snprintf(dropped_text, DROPPED_TEXT_MAX, + "** %lu printk messages dropped **\n", + con->dropped); + con->dropped = 0; + con->write(con, dropped_text, dropped_len); + } + + con->write(con, text, len); +} + +/* + * Recursion is tracked separately on each CPU. If NMIs are supported, an + * additional NMI context per CPU is also separately tracked. Until per-CPU + * is available, a separate "early tracking" is performed. + */ +static DEFINE_PER_CPU(u8, printk_count); +static u8 printk_count_early; +#ifdef CONFIG_HAVE_NMI +static DEFINE_PER_CPU(u8, printk_count_nmi); +static u8 printk_count_nmi_early; +#endif + +/* + * Recursion is limited to keep the output sane. printk() should not require + * more than 1 level of recursion (allowing, for example, printk() to trigger + * a WARN), but a higher value is used in case some printk-internal errors + * exist, such as the ringbuffer validation checks failing. + */ +#define PRINTK_MAX_RECURSION 3 + +/* + * Return a pointer to the dedicated counter for the CPU+context of the + * caller. + */ +static u8 *__printk_recursion_counter(void) +{ +#ifdef CONFIG_HAVE_NMI + if (in_nmi()) { + if (printk_percpu_data_ready()) + return this_cpu_ptr(&printk_count_nmi); + return &printk_count_nmi_early; + } +#endif + if (printk_percpu_data_ready()) + return this_cpu_ptr(&printk_count); + return &printk_count_early; +} + +/* + * Enter recursion tracking. Interrupts are disabled to simplify tracking. + * The caller must check the boolean return value to see if the recursion is + * allowed. On failure, interrupts are not disabled. + * + * @recursion_ptr must be a variable of type (u8 *) and is the same variable + * that is passed to printk_exit_irqrestore(). + */ +#define printk_enter_irqsave(recursion_ptr, flags) \ +({ \ + bool success = true; \ + \ + typecheck(u8 *, recursion_ptr); \ + local_irq_save(flags); \ + (recursion_ptr) = __printk_recursion_counter(); \ + if (*(recursion_ptr) > PRINTK_MAX_RECURSION) { \ + local_irq_restore(flags); \ + success = false; \ + } else { \ + (*(recursion_ptr))++; \ + } \ + success; \ +}) + +/* Exit recursion tracking, restoring interrupts. */ +#define printk_exit_irqrestore(recursion_ptr, flags) \ + do { \ + typecheck(u8 *, recursion_ptr); \ + (*(recursion_ptr))--; \ + local_irq_restore(flags); \ + } while (0) + +int printk_delay_msec __read_mostly; + +static inline void printk_delay(int level) +{ + boot_delay_msec(level); + + if (unlikely(printk_delay_msec)) { + int m = printk_delay_msec; + + while (m--) { + mdelay(1); + touch_nmi_watchdog(); + } + } +} + +static inline u32 printk_caller_id(void) +{ + return in_task() ? task_pid_nr(current) : + 0x80000000 + smp_processor_id(); +} + +/** + * printk_parse_prefix - Parse level and control flags. + * + * @text: The terminated text message. + * @level: A pointer to the current level value, will be updated. + * @flags: A pointer to the current printk_info flags, will be updated. + * + * @level may be NULL if the caller is not interested in the parsed value. + * Otherwise the variable pointed to by @level must be set to + * LOGLEVEL_DEFAULT in order to be updated with the parsed value. + * + * @flags may be NULL if the caller is not interested in the parsed value. + * Otherwise the variable pointed to by @flags will be OR'd with the parsed + * value. + * + * Return: The length of the parsed level and control flags. + */ +u16 printk_parse_prefix(const char *text, int *level, + enum printk_info_flags *flags) +{ + u16 prefix_len = 0; + int kern_level; + + while (*text) { + kern_level = printk_get_level(text); + if (!kern_level) + break; + + switch (kern_level) { + case '0' ... '7': + if (level && *level == LOGLEVEL_DEFAULT) + *level = kern_level - '0'; + break; + case 'c': /* KERN_CONT */ + if (flags) + *flags |= LOG_CONT; + } + + prefix_len += 2; + text += 2; + } + + return prefix_len; +} + +__printf(5, 0) +static u16 printk_sprint(char *text, u16 size, int facility, + enum printk_info_flags *flags, const char *fmt, + va_list args) +{ + u16 text_len; + + text_len = vscnprintf(text, size, fmt, args); + + /* Mark and strip a trailing newline. */ + if (text_len && text[text_len - 1] == '\n') { + text_len--; + *flags |= LOG_NEWLINE; + } + + /* Strip log level and control flags. */ + if (facility == 0) { + u16 prefix_len; + + prefix_len = printk_parse_prefix(text, NULL, NULL); + if (prefix_len) { + text_len -= prefix_len; + memmove(text, text + prefix_len, text_len); + } + } + + trace_console_rcuidle(text, text_len); + + return text_len; +} + +__printf(4, 0) +int vprintk_store(int facility, int level, + const struct dev_printk_info *dev_info, + const char *fmt, va_list args) +{ + struct prb_reserved_entry e; + enum printk_info_flags flags = 0; + struct printk_record r; + unsigned long irqflags; + u16 trunc_msg_len = 0; + char prefix_buf[8]; + u8 *recursion_ptr; + u16 reserve_size; + va_list args2; + u32 caller_id; + u16 text_len; + int ret = 0; + u64 ts_nsec; + + if (!printk_enter_irqsave(recursion_ptr, irqflags)) + return 0; + + /* + * Since the duration of printk() can vary depending on the message + * and state of the ringbuffer, grab the timestamp now so that it is + * close to the call of printk(). This provides a more deterministic + * timestamp with respect to the caller. + */ + ts_nsec = local_clock(); + + caller_id = printk_caller_id(); + + /* + * The sprintf needs to come first since the syslog prefix might be + * passed in as a parameter. An extra byte must be reserved so that + * later the vscnprintf() into the reserved buffer has room for the + * terminating '\0', which is not counted by vsnprintf(). + */ + va_copy(args2, args); + reserve_size = vsnprintf(&prefix_buf[0], sizeof(prefix_buf), fmt, args2) + 1; + va_end(args2); + + if (reserve_size > LOG_LINE_MAX) + reserve_size = LOG_LINE_MAX; + + /* Extract log level or control flags. */ + if (facility == 0) + printk_parse_prefix(&prefix_buf[0], &level, &flags); + + if (level == LOGLEVEL_DEFAULT) + level = default_message_loglevel; + + if (dev_info) + flags |= LOG_NEWLINE; + + if (flags & LOG_CONT) { + prb_rec_init_wr(&r, reserve_size); + if (prb_reserve_in_last(&e, prb, &r, caller_id, LOG_LINE_MAX)) { + text_len = printk_sprint(&r.text_buf[r.info->text_len], reserve_size, + facility, &flags, fmt, args); + r.info->text_len += text_len; + + if (flags & LOG_NEWLINE) { + r.info->flags |= LOG_NEWLINE; + prb_final_commit(&e); + } else { + prb_commit(&e); + } + + ret = text_len; + goto out; + } + } + + /* + * Explicitly initialize the record before every prb_reserve() call. + * prb_reserve_in_last() and prb_reserve() purposely invalidate the + * structure when they fail. + */ + prb_rec_init_wr(&r, reserve_size); + if (!prb_reserve(&e, prb, &r)) { + /* truncate the message if it is too long for empty buffer */ + truncate_msg(&reserve_size, &trunc_msg_len); + + prb_rec_init_wr(&r, reserve_size + trunc_msg_len); + if (!prb_reserve(&e, prb, &r)) + goto out; + } + + /* fill message */ + text_len = printk_sprint(&r.text_buf[0], reserve_size, facility, &flags, fmt, args); + if (trunc_msg_len) + memcpy(&r.text_buf[text_len], trunc_msg, trunc_msg_len); + r.info->text_len = text_len + trunc_msg_len; + r.info->facility = facility; + r.info->level = level & 7; + r.info->flags = flags & 0x1f; + r.info->ts_nsec = ts_nsec; + r.info->caller_id = caller_id; + if (dev_info) + memcpy(&r.info->dev_info, dev_info, sizeof(r.info->dev_info)); + + /* A message without a trailing newline can be continued. */ + if (!(flags & LOG_NEWLINE)) + prb_commit(&e); + else + prb_final_commit(&e); + + ret = text_len + trunc_msg_len; +out: + printk_exit_irqrestore(recursion_ptr, irqflags); + return ret; +} + +asmlinkage int vprintk_emit(int facility, int level, + const struct dev_printk_info *dev_info, + const char *fmt, va_list args) +{ + int printed_len; + bool in_sched = false; + + /* Suppress unimportant messages after panic happens */ + if (unlikely(suppress_printk)) + return 0; + + if (unlikely(suppress_panic_printk) && + atomic_read(&panic_cpu) != raw_smp_processor_id()) + return 0; + + if (level == LOGLEVEL_SCHED) { + level = LOGLEVEL_DEFAULT; + in_sched = true; + } + + printk_delay(level); + + printed_len = vprintk_store(facility, level, dev_info, fmt, args); + + /* If called from the scheduler, we can not call up(). */ + if (!in_sched) { + /* + * The caller may be holding system-critical or + * timing-sensitive locks. Disable preemption during + * printing of all remaining records to all consoles so that + * this context can return as soon as possible. Hopefully + * another printk() caller will take over the printing. + */ + preempt_disable(); + /* + * Try to acquire and then immediately release the console + * semaphore. The release will print out buffers. With the + * spinning variant, this context tries to take over the + * printing from another printing context. + */ + if (console_trylock_spinning()) + console_unlock(); + preempt_enable(); + } + + if (in_sched) + defer_console_output(); + else + wake_up_klogd(); + + return printed_len; +} +EXPORT_SYMBOL(vprintk_emit); + +int vprintk_default(const char *fmt, va_list args) +{ + return vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, fmt, args); +} +EXPORT_SYMBOL_GPL(vprintk_default); + +asmlinkage __visible int _printk(const char *fmt, ...) +{ + va_list args; + int r; + + va_start(args, fmt); + r = vprintk(fmt, args); + va_end(args); + + return r; +} +EXPORT_SYMBOL(_printk); + +static bool pr_flush(int timeout_ms, bool reset_on_progress); +static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress); + +#else /* CONFIG_PRINTK */ + +#define CONSOLE_LOG_MAX 0 +#define DROPPED_TEXT_MAX 0 +#define printk_time false + +#define prb_read_valid(rb, seq, r) false +#define prb_first_valid_seq(rb) 0 +#define prb_next_seq(rb) 0 + +static u64 syslog_seq; + +static size_t record_print_text(const struct printk_record *r, + bool syslog, bool time) +{ + return 0; +} +static ssize_t info_print_ext_header(char *buf, size_t size, + struct printk_info *info) +{ + return 0; +} +static ssize_t msg_print_ext_body(char *buf, size_t size, + char *text, size_t text_len, + struct dev_printk_info *dev_info) { return 0; } +static void console_lock_spinning_enable(void) { } +static int console_lock_spinning_disable_and_check(void) { return 0; } +static void call_console_driver(struct console *con, const char *text, size_t len, + char *dropped_text) +{ +} +static bool suppress_message_printing(int level) { return false; } +static bool pr_flush(int timeout_ms, bool reset_on_progress) { return true; } +static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress) { return true; } + +#endif /* CONFIG_PRINTK */ + +#ifdef CONFIG_EARLY_PRINTK +struct console *early_console; + +asmlinkage __visible void early_printk(const char *fmt, ...) +{ + va_list ap; + char buf[512]; + int n; + + if (!early_console) + return; + + va_start(ap, fmt); + n = vscnprintf(buf, sizeof(buf), fmt, ap); + va_end(ap); + + early_console->write(early_console, buf, n); +} +#endif + +static void set_user_specified(struct console_cmdline *c, bool user_specified) +{ + if (!user_specified) + return; + + /* + * @c console was defined by the user on the command line. + * Do not clear when added twice also by SPCR or the device tree. + */ + c->user_specified = true; + /* At least one console defined by the user on the command line. */ + console_set_on_cmdline = 1; +} + +static int __add_preferred_console(char *name, int idx, char *options, + char *brl_options, bool user_specified) +{ + struct console_cmdline *c; + int i; + + /* + * See if this tty is not yet registered, and + * if we have a slot free. + */ + for (i = 0, c = console_cmdline; + i < MAX_CMDLINECONSOLES && c->name[0]; + i++, c++) { + if (strcmp(c->name, name) == 0 && c->index == idx) { + if (!brl_options) + preferred_console = i; + set_user_specified(c, user_specified); + return 0; + } + } + if (i == MAX_CMDLINECONSOLES) + return -E2BIG; + if (!brl_options) + preferred_console = i; + strlcpy(c->name, name, sizeof(c->name)); + c->options = options; + set_user_specified(c, user_specified); + braille_set_options(c, brl_options); + + c->index = idx; + return 0; +} + +static int __init console_msg_format_setup(char *str) +{ + if (!strcmp(str, "syslog")) + console_msg_format = MSG_FORMAT_SYSLOG; + if (!strcmp(str, "default")) + console_msg_format = MSG_FORMAT_DEFAULT; + return 1; +} +__setup("console_msg_format=", console_msg_format_setup); + +/* + * Set up a console. Called via do_early_param() in init/main.c + * for each "console=" parameter in the boot command line. + */ +static int __init console_setup(char *str) +{ + char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for "ttyS" */ + char *s, *options, *brl_options = NULL; + int idx; + + /* + * console="" or console=null have been suggested as a way to + * disable console output. Use ttynull that has been created + * for exactly this purpose. + */ + if (str[0] == 0 || strcmp(str, "null") == 0) { + __add_preferred_console("ttynull", 0, NULL, NULL, true); + return 1; + } + + if (_braille_console_setup(&str, &brl_options)) + return 1; + + /* + * Decode str into name, index, options. + */ + if (str[0] >= '0' && str[0] <= '9') { + strcpy(buf, "ttyS"); + strncpy(buf + 4, str, sizeof(buf) - 5); + } else { + strncpy(buf, str, sizeof(buf) - 1); + } + buf[sizeof(buf) - 1] = 0; + options = strchr(str, ','); + if (options) + *(options++) = 0; +#ifdef __sparc__ + if (!strcmp(str, "ttya")) + strcpy(buf, "ttyS0"); + if (!strcmp(str, "ttyb")) + strcpy(buf, "ttyS1"); +#endif + for (s = buf; *s; s++) + if (isdigit(*s) || *s == ',') + break; + idx = simple_strtoul(s, NULL, 10); + *s = 0; + + __add_preferred_console(buf, idx, options, brl_options, true); + return 1; +} +__setup("console=", console_setup); + +/** + * add_preferred_console - add a device to the list of preferred consoles. + * @name: device name + * @idx: device index + * @options: options for this console + * + * The last preferred console added will be used for kernel messages + * and stdin/out/err for init. Normally this is used by console_setup + * above to handle user-supplied console arguments; however it can also + * be used by arch-specific code either to override the user or more + * commonly to provide a default console (ie from PROM variables) when + * the user has not supplied one. + */ +int add_preferred_console(char *name, int idx, char *options) +{ + return __add_preferred_console(name, idx, options, NULL, false); +} + +bool console_suspend_enabled = true; +EXPORT_SYMBOL(console_suspend_enabled); + +static int __init console_suspend_disable(char *str) +{ + console_suspend_enabled = false; + return 1; +} +__setup("no_console_suspend", console_suspend_disable); +module_param_named(console_suspend, console_suspend_enabled, + bool, S_IRUGO | S_IWUSR); +MODULE_PARM_DESC(console_suspend, "suspend console during suspend" + " and hibernate operations"); + +static bool printk_console_no_auto_verbose; + +void console_verbose(void) +{ + if (console_loglevel && !printk_console_no_auto_verbose) + console_loglevel = CONSOLE_LOGLEVEL_MOTORMOUTH; +} +EXPORT_SYMBOL_GPL(console_verbose); + +module_param_named(console_no_auto_verbose, printk_console_no_auto_verbose, bool, 0644); +MODULE_PARM_DESC(console_no_auto_verbose, "Disable console loglevel raise to highest on oops/panic/etc"); + +/** + * suspend_console - suspend the console subsystem + * + * This disables printk() while we go into suspend states + */ +void suspend_console(void) +{ + if (!console_suspend_enabled) + return; + pr_info("Suspending console(s) (use no_console_suspend to debug)\n"); + pr_flush(1000, true); + console_lock(); + console_suspended = 1; + up_console_sem(); +} + +void resume_console(void) +{ + if (!console_suspend_enabled) + return; + down_console_sem(); + console_suspended = 0; + console_unlock(); + pr_flush(1000, true); +} + +/** + * console_cpu_notify - print deferred console messages after CPU hotplug + * @cpu: unused + * + * If printk() is called from a CPU that is not online yet, the messages + * will be printed on the console only if there are CON_ANYTIME consoles. + * This function is called when a new CPU comes online (or fails to come + * up) or goes offline. + */ +static int console_cpu_notify(unsigned int cpu) +{ + if (!cpuhp_tasks_frozen) { + /* If trylock fails, someone else is doing the printing */ + if (console_trylock()) + console_unlock(); + } + return 0; +} + +/* + * Return true when this CPU should unlock console_sem without pushing all + * messages to the console. This reduces the chance that the console is + * locked when the panic CPU tries to use it. + */ +static bool abandon_console_lock_in_panic(void) +{ + if (!panic_in_progress()) + return false; + + /* + * We can use raw_smp_processor_id() here because it is impossible for + * the task to be migrated to the panic_cpu, or away from it. If + * panic_cpu has already been set, and we're not currently executing on + * that CPU, then we never will be. + */ + return atomic_read(&panic_cpu) != raw_smp_processor_id(); +} + +/** + * 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(); + + /* On panic, the console_lock must be left to the panic cpu. */ + while (abandon_console_lock_in_panic()) + msleep(1000); + + 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) +{ + /* On panic, the console_lock must be left to the panic cpu. */ + if (abandon_console_lock_in_panic()) + return 0; + 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 the given console is currently capable and allowed to print + * records. + * + * Requires the console_lock. + */ +static inline bool console_is_usable(struct console *con) +{ + if (!(con->flags & CON_ENABLED)) + return false; + + if (!con->write) + return false; + + /* + * Console drivers may assume that per-cpu resources have been + * allocated. So unless they're explicitly marked as being able to + * cope (CON_ANYTIME) don't call them until this CPU is officially up. + */ + if (!cpu_online(raw_smp_processor_id()) && + !(con->flags & CON_ANYTIME)) + return false; + + return true; +} + +static void __console_unlock(void) +{ + console_locked = 0; + up_console_sem(); +} + +/* + * Print one record for the given console. The record printed is whatever + * record is the next available record for the given console. + * + * @text is a buffer of size CONSOLE_LOG_MAX. + * + * If extended messages should be printed, @ext_text is a buffer of size + * CONSOLE_EXT_LOG_MAX. Otherwise @ext_text must be NULL. + * + * If dropped messages should be printed, @dropped_text is a buffer of size + * DROPPED_TEXT_MAX. Otherwise @dropped_text must be NULL. + * + * @handover will be set to true if a printk waiter has taken over the + * console_lock, in which case the caller is no longer holding the + * console_lock. Otherwise it is set to false. + * + * Returns false if the given console has no next record to print, otherwise + * true. + * + * Requires the console_lock. + */ +static bool console_emit_next_record(struct console *con, char *text, char *ext_text, + char *dropped_text, bool *handover) +{ + static int panic_console_dropped; + struct printk_info info; + struct printk_record r; + unsigned long flags; + char *write_text; + size_t len; + + prb_rec_init_rd(&r, &info, text, CONSOLE_LOG_MAX); + + *handover = false; + + if (!prb_read_valid(prb, con->seq, &r)) + return false; + + if (con->seq != r.info->seq) { + con->dropped += r.info->seq - con->seq; + con->seq = r.info->seq; + if (panic_in_progress() && panic_console_dropped++ > 10) { + suppress_panic_printk = 1; + pr_warn_once("Too many dropped messages. Suppress messages on non-panic CPUs to prevent livelock.\n"); + } + } + + /* Skip record that has level above the console loglevel. */ + if (suppress_message_printing(r.info->level)) { + con->seq++; + goto skip; + } + + if (ext_text) { + write_text = ext_text; + len = info_print_ext_header(ext_text, CONSOLE_EXT_LOG_MAX, r.info); + len += msg_print_ext_body(ext_text + len, CONSOLE_EXT_LOG_MAX - len, + &r.text_buf[0], r.info->text_len, &r.info->dev_info); + } else { + write_text = text; + len = record_print_text(&r, console_msg_format & MSG_FORMAT_SYSLOG, printk_time); + } + + /* + * While actively printing out messages, if another printk() + * were to occur on another CPU, it may wait for this one to + * finish. This task can not be preempted if there is a + * waiter waiting to take over. + * + * Interrupts are disabled because the hand over to a waiter + * must not be interrupted until the hand over is completed + * (@console_waiter is cleared). + */ + printk_safe_enter_irqsave(flags); + console_lock_spinning_enable(); + + stop_critical_timings(); /* don't trace print latency */ + call_console_driver(con, write_text, len, dropped_text); + start_critical_timings(); + + con->seq++; + + *handover = console_lock_spinning_disable_and_check(); + printk_safe_exit_irqrestore(flags); +skip: + return true; +} + +/* + * Print out all remaining records to all consoles. + * + * @do_cond_resched is set by the caller. It can be true only in schedulable + * context. + * + * @next_seq is set to the sequence number after the last available record. + * The value is valid only when this function returns true. It means that all + * usable consoles are completely flushed. + * + * @handover will be set to true if a printk waiter has taken over the + * console_lock, in which case the caller is no longer holding the + * console_lock. Otherwise it is set to false. + * + * Returns true when there was at least one usable console and all messages + * were flushed to all usable consoles. A returned false informs the caller + * that everything was not flushed (either there were no usable consoles or + * another context has taken over printing or it is a panic situation and this + * is not the panic CPU). Regardless the reason, the caller should assume it + * is not useful to immediately try again. + * + * Requires the console_lock. + */ +static bool console_flush_all(bool do_cond_resched, u64 *next_seq, bool *handover) +{ + static char dropped_text[DROPPED_TEXT_MAX]; + static char ext_text[CONSOLE_EXT_LOG_MAX]; + static char text[CONSOLE_LOG_MAX]; + bool any_usable = false; + struct console *con; + bool any_progress; + + *next_seq = 0; + *handover = false; + + do { + any_progress = false; + + for_each_console(con) { + bool progress; + + if (!console_is_usable(con)) + continue; + any_usable = true; + + if (con->flags & CON_EXTENDED) { + /* Extended consoles do not print "dropped messages". */ + progress = console_emit_next_record(con, &text[0], + &ext_text[0], NULL, + handover); + } else { + progress = console_emit_next_record(con, &text[0], + NULL, &dropped_text[0], + handover); + } + if (*handover) + return false; + + /* Track the next of the highest seq flushed. */ + if (con->seq > *next_seq) + *next_seq = con->seq; + + if (!progress) + continue; + any_progress = true; + + /* Allow panic_cpu to take over the consoles safely. */ + if (abandon_console_lock_in_panic()) + return false; + + if (do_cond_resched) + cond_resched(); + } + } while (any_progress); + + return any_usable; +} + +/** + * console_unlock - unlock the console system + * + * Releases the console_lock which the caller holds on the console system + * and the console driver list. + * + * While the console_lock was held, console output may have been buffered + * by printk(). If this is the case, console_unlock(); emits + * the output prior to releasing the lock. + * + * console_unlock(); may be called from any context. + */ +void console_unlock(void) +{ + bool do_cond_resched; + bool handover; + bool flushed; + u64 next_seq; + + if (console_suspended) { + up_console_sem(); + return; + } + + /* + * Console drivers are called with interrupts disabled, so + * @console_may_schedule should be cleared before; however, we may + * end up dumping a lot of lines, for example, if called from + * console registration path, and should invoke cond_resched() + * between lines if allowable. Not doing so can cause a very long + * scheduling stall on a slow console leading to RCU stall and + * softlockup warnings which exacerbate the issue with more + * messages practically incapacitating the system. Therefore, create + * a local to use for the printing loop. + */ + do_cond_resched = console_may_schedule; + + do { + console_may_schedule = 0; + + flushed = console_flush_all(do_cond_resched, &next_seq, &handover); + if (!handover) + __console_unlock(); + + /* + * Abort if there was a failure to flush all messages to all + * usable consoles. Either it is not possible to flush (in + * which case it would be an infinite loop of retrying) or + * another context has taken over printing. + */ + if (!flushed) + break; + + /* + * Some context may have added new records after + * console_flush_all() but before unlocking the console. + * Re-check if there is a new record to flush. If the trylock + * fails, another context is already handling the printing. + */ + } while (prb_read_valid(prb, next_seq, NULL) && console_trylock()); +} +EXPORT_SYMBOL(console_unlock); + +/** + * console_conditional_schedule - yield the CPU if required + * + * If the console code is currently allowed to sleep, and + * if this CPU should yield the CPU to another task, do + * so here. + * + * Must be called within console_lock();. + */ +void __sched console_conditional_schedule(void) +{ + if (console_may_schedule) + cond_resched(); +} +EXPORT_SYMBOL(console_conditional_schedule); + +void console_unblank(void) +{ + struct console *c; + + /* + * console_unblank can no longer be called in interrupt context unless + * oops_in_progress is set to 1.. + */ + if (oops_in_progress) { + if (down_trylock_console_sem() != 0) + return; + } 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(); + + if (!oops_in_progress) + pr_flush(1000, true); +} + +/** + * console_flush_on_panic - flush console content on panic + * @mode: flush all messages in buffer or just the pending ones + * + * Immediately output all pending messages no matter what. + */ +void console_flush_on_panic(enum con_flush_mode mode) +{ + /* + * If someone else is holding the console lock, trylock will fail + * and may_schedule may be set. Ignore and proceed to unlock so + * that messages are flushed out. As this can be called from any + * context and we don't want to get preempted while flushing, + * ensure may_schedule is cleared. + */ + console_trylock(); + console_may_schedule = 0; + + if (mode == CONSOLE_REPLAY_ALL) { + struct console *c; + u64 seq; + + seq = prb_first_valid_seq(prb); + for_each_console(c) + c->seq = seq; + } + console_unlock(); +} + +/* + * Return the console tty driver structure and its associated index + */ +struct tty_driver *console_device(int *index) +{ + struct console *c; + struct tty_driver *driver = NULL; + + console_lock(); + for_each_console(c) { + if (!c->device) + continue; + driver = c->device(c, index); + if (driver) + break; + } + console_unlock(); + return driver; +} + +/* + * Prevent further output on the passed console device so that (for example) + * serial drivers can disable console output before suspending a port, and can + * re-enable output afterwards. + */ +void console_stop(struct console *console) +{ + __pr_flush(console, 1000, true); + console_lock(); + console->flags &= ~CON_ENABLED; + console_unlock(); +} +EXPORT_SYMBOL(console_stop); + +void console_start(struct console *console) +{ + console_lock(); + console->flags |= CON_ENABLED; + console_unlock(); + __pr_flush(console, 1000, true); +} +EXPORT_SYMBOL(console_start); + +static int __read_mostly keep_bootcon; + +static int __init keep_bootcon_setup(char *str) +{ + keep_bootcon = 1; + pr_info("debug: skip boot console de-registration.\n"); + + return 0; +} + +early_param("keep_bootcon", keep_bootcon_setup); + +/* + * This is called by register_console() to try to match + * the newly registered console with any of the ones selected + * by either the command line or add_preferred_console() and + * setup/enable it. + * + * Care need to be taken with consoles that are statically + * enabled such as netconsole + */ +static int try_enable_preferred_console(struct console *newcon, + bool user_specified) +{ + struct console_cmdline *c; + int i, err; + + for (i = 0, c = console_cmdline; + i < MAX_CMDLINECONSOLES && c->name[0]; + i++, c++) { + if (c->user_specified != user_specified) + continue; + if (!newcon->match || + newcon->match(newcon, c->name, c->index, c->options) != 0) { + /* default matching */ + BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name)); + if (strcmp(c->name, newcon->name) != 0) + continue; + if (newcon->index >= 0 && + newcon->index != c->index) + continue; + if (newcon->index < 0) + newcon->index = c->index; + + if (_braille_register_console(newcon, c)) + return 0; + + if (newcon->setup && + (err = newcon->setup(newcon, c->options)) != 0) + return err; + } + newcon->flags |= CON_ENABLED; + if (i == preferred_console) + newcon->flags |= CON_CONSDEV; + return 0; + } + + /* + * Some consoles, such as pstore and netconsole, can be enabled even + * without matching. Accept the pre-enabled consoles only when match() + * and setup() had a chance to be called. + */ + if (newcon->flags & CON_ENABLED && c->user_specified == user_specified) + return 0; + + return -ENOENT; +} + +/* Try to enable the console unconditionally */ +static void try_enable_default_console(struct console *newcon) +{ + if (newcon->index < 0) + newcon->index = 0; + + if (newcon->setup && newcon->setup(newcon, NULL) != 0) + return; + + newcon->flags |= CON_ENABLED; + + if (newcon->device) + newcon->flags |= CON_CONSDEV; +} + +#define con_printk(lvl, con, fmt, ...) \ + printk(lvl pr_fmt("%sconsole [%s%d] " fmt), \ + (con->flags & CON_BOOT) ? "boot" : "", \ + con->name, con->index, ##__VA_ARGS__) + +/* + * The console driver calls this routine during kernel initialization + * to register the console printing procedure with printk() and to + * print any messages that were printed by the kernel before the + * console driver was initialized. + * + * This can happen pretty early during the boot process (because of + * early_printk) - sometimes before setup_arch() completes - be careful + * of what kernel features are used - they may not be initialised yet. + * + * There are two types of consoles - bootconsoles (early_printk) and + * "real" consoles (everything which is not a bootconsole) which are + * handled differently. + * - Any number of bootconsoles can be registered at any time. + * - As soon as a "real" console is registered, all bootconsoles + * will be unregistered automatically. + * - Once a "real" console is registered, any attempt to register a + * bootconsoles will be rejected + */ +void register_console(struct console *newcon) +{ + struct console *con; + bool bootcon_enabled = false; + bool realcon_enabled = false; + int err; + + for_each_console(con) { + if (WARN(con == newcon, "console '%s%d' already registered\n", + con->name, con->index)) + return; + } + + for_each_console(con) { + if (con->flags & CON_BOOT) + bootcon_enabled = true; + else + realcon_enabled = true; + } + + /* Do not register boot consoles when there already is a real one. */ + if (newcon->flags & CON_BOOT && realcon_enabled) { + pr_info("Too late to register bootconsole %s%d\n", + newcon->name, newcon->index); + return; + } + + /* + * See if we want to enable this console driver by default. + * + * Nope when a console is preferred by the command line, device + * tree, or SPCR. + * + * The first real console with tty binding (driver) wins. More + * consoles might get enabled before the right one is found. + * + * Note that a console with tty binding will have CON_CONSDEV + * flag set and will be first in the list. + */ + if (preferred_console < 0) { + if (!console_drivers || !console_drivers->device || + console_drivers->flags & CON_BOOT) { + try_enable_default_console(newcon); + } + } + + /* See if this console matches one we selected on the command line */ + err = try_enable_preferred_console(newcon, true); + + /* If not, try to match against the platform default(s) */ + if (err == -ENOENT) + err = try_enable_preferred_console(newcon, false); + + /* printk() messages are not printed to the Braille console. */ + if (err || newcon->flags & CON_BRL) + return; + + /* + * If we have a bootconsole, and are switching to a real console, + * don't print everything out again, since when the boot console, and + * the real console are the same physical device, it's annoying to + * see the beginning boot messages twice + */ + if (bootcon_enabled && + ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) { + newcon->flags &= ~CON_PRINTBUFFER; + } + + /* + * Put this console in the list - keep the + * preferred driver at the head of the list. + */ + console_lock(); + if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) { + newcon->next = console_drivers; + console_drivers = newcon; + if (newcon->next) + newcon->next->flags &= ~CON_CONSDEV; + /* Ensure this flag is always set for the head of the list */ + newcon->flags |= CON_CONSDEV; + } else { + newcon->next = console_drivers->next; + console_drivers->next = newcon; + } + + newcon->dropped = 0; + if (newcon->flags & CON_PRINTBUFFER) { + /* Get a consistent copy of @syslog_seq. */ + mutex_lock(&syslog_lock); + newcon->seq = syslog_seq; + mutex_unlock(&syslog_lock); + } else { + /* Begin with next message. */ + newcon->seq = prb_next_seq(prb); + } + console_unlock(); + console_sysfs_notify(); + + /* + * By unregistering the bootconsoles after we enable the real console + * we get the "console xxx enabled" message on all the consoles - + * boot consoles, real consoles, etc - this is to ensure that end + * users know there might be something in the kernel's log buffer that + * went to the bootconsole (that they do not see on the real console) + */ + con_printk(KERN_INFO, newcon, "enabled\n"); + if (bootcon_enabled && + ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) && + !keep_bootcon) { + for_each_console(con) + if (con->flags & CON_BOOT) + unregister_console(con); + } +} +EXPORT_SYMBOL(register_console); + +int unregister_console(struct console *console) +{ + struct console *con; + int res; + + con_printk(KERN_INFO, console, "disabled\n"); + + res = _braille_unregister_console(console); + if (res < 0) + return res; + if (res > 0) + return 0; + + res = -ENODEV; + console_lock(); + if (console_drivers == console) { + console_drivers=console->next; + res = 0; + } else { + for_each_console(con) { + if (con->next == console) { + con->next = console->next; + res = 0; + break; + } + } + } + + if (res) + goto out_disable_unlock; + + /* + * If 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(); + + if (console->exit) + res = console->exit(console); + + return res; + +out_disable_unlock: + console->flags &= ~CON_ENABLED; + console_unlock(); + + return res; +} +EXPORT_SYMBOL(unregister_console); + +/* + * Initialize the console device. This is called *early*, so + * we can't necessarily depend on lots of kernel help here. + * Just do some early initializations, and do the complex setup + * later. + */ +void __init console_init(void) +{ + int ret; + initcall_t call; + initcall_entry_t *ce; + + /* Setup the default TTY line discipline. */ + n_tty_init(); + + /* + * set up the console device so that later boot sequences can + * inform about problems etc.. + */ + ce = __con_initcall_start; + trace_initcall_level("console"); + while (ce < __con_initcall_end) { + call = initcall_from_entry(ce); + trace_initcall_start(call); + ret = call(); + trace_initcall_finish(call, ret); + ce++; + } +} + +/* + * Some boot consoles access data that is in the init section and which will + * be discarded after the initcalls have been run. To make sure that no code + * will access this data, unregister the boot consoles in a late initcall. + * + * If for some reason, such as deferred probe or the driver being a loadable + * module, the real console hasn't registered yet at this point, there will + * be a brief interval in which no messages are logged to the console, which + * makes it difficult to diagnose problems that occur during this time. + * + * To mitigate this problem somewhat, only unregister consoles whose memory + * intersects with the init section. Note that all other boot consoles will + * get unregistered when the real preferred console is registered. + */ +static int __init printk_late_init(void) +{ + struct console *con; + int ret; + + for_each_console(con) { + if (!(con->flags & CON_BOOT)) + continue; + + /* Check addresses that might be used for enabled consoles. */ + if (init_section_intersects(con, sizeof(*con)) || + init_section_contains(con->write, 0) || + init_section_contains(con->read, 0) || + init_section_contains(con->device, 0) || + init_section_contains(con->unblank, 0) || + init_section_contains(con->data, 0)) { + /* + * Please, consider moving the reported consoles out + * of the init section. + */ + pr_warn("bootconsole [%s%d] uses init memory and must be disabled even before the real one is ready\n", + con->name, con->index); + unregister_console(con); + } + } + ret = cpuhp_setup_state_nocalls(CPUHP_PRINTK_DEAD, "printk:dead", NULL, + console_cpu_notify); + WARN_ON(ret < 0); + ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "printk:online", + console_cpu_notify, NULL); + WARN_ON(ret < 0); + printk_sysctl_init(); + return 0; +} +late_initcall(printk_late_init); + +#if defined CONFIG_PRINTK +/* If @con is specified, only wait for that console. Otherwise wait for all. */ +static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress) +{ + int remaining = timeout_ms; + struct console *c; + u64 last_diff = 0; + u64 printk_seq; + u64 diff; + u64 seq; + + might_sleep(); + + seq = prb_next_seq(prb); + + for (;;) { + diff = 0; + + console_lock(); + + for_each_console(c) { + if (con && con != c) + continue; + if (!console_is_usable(c)) + continue; + printk_seq = c->seq; + if (printk_seq < seq) + diff += seq - printk_seq; + } + + /* + * If consoles are suspended, it cannot be expected that they + * make forward progress, so timeout immediately. @diff is + * still used to return a valid flush status. + */ + if (console_suspended) + remaining = 0; + else if (diff != last_diff && reset_on_progress) + remaining = timeout_ms; + + console_unlock(); + + if (diff == 0 || remaining == 0) + break; + + if (remaining < 0) { + /* no timeout limit */ + msleep(100); + } else if (remaining < 100) { + msleep(remaining); + remaining = 0; + } else { + msleep(100); + remaining -= 100; + } + + last_diff = diff; + } + + return (diff == 0); +} + +/** + * pr_flush() - Wait for printing threads to catch up. + * + * @timeout_ms: The maximum time (in ms) to wait. + * @reset_on_progress: Reset the timeout if forward progress is seen. + * + * A value of 0 for @timeout_ms means no waiting will occur. A value of -1 + * represents infinite waiting. + * + * If @reset_on_progress is true, the timeout will be reset whenever any + * printer has been seen to make some forward progress. + * + * Context: Process context. May sleep while acquiring console lock. + * Return: true if all enabled printers are caught up. + */ +static bool pr_flush(int timeout_ms, bool reset_on_progress) +{ + return __pr_flush(NULL, timeout_ms, reset_on_progress); +} + +/* + * 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) = + IRQ_WORK_INIT_LAZY(wake_up_klogd_work_func); + +static void __wake_up_klogd(int val) +{ + if (!printk_percpu_data_ready()) + return; + + preempt_disable(); + /* + * Guarantee any new records can be seen by tasks preparing to wait + * before this context checks if the wait queue is empty. + * + * The full memory barrier within wq_has_sleeper() pairs with the full + * memory barrier within set_current_state() of + * prepare_to_wait_event(), which is called after ___wait_event() adds + * the waiter but before it has checked the wait condition. + * + * This pairs with devkmsg_read:A and syslog_print:A. + */ + if (wq_has_sleeper(&log_wait) || /* LMM(__wake_up_klogd:A) */ + (val & PRINTK_PENDING_OUTPUT)) { + this_cpu_or(printk_pending, val); + irq_work_queue(this_cpu_ptr(&wake_up_klogd_work)); + } + preempt_enable(); +} + +/** + * wake_up_klogd - Wake kernel logging daemon + * + * Use this function when new records have been added to the ringbuffer + * and the console printing of those records has already occurred or is + * known to be handled by some other context. This function will only + * wake the logging daemon. + * + * Context: Any context. + */ +void wake_up_klogd(void) +{ + __wake_up_klogd(PRINTK_PENDING_WAKEUP); +} + +/** + * defer_console_output - Wake kernel logging daemon and trigger + * console printing in a deferred context + * + * Use this function when new records have been added to the ringbuffer, + * this context is responsible for console printing those records, but + * the current context is not allowed to perform the console printing. + * Trigger an irq_work context to perform the console printing. This + * function also wakes the logging daemon. + * + * Context: Any context. + */ +void defer_console_output(void) +{ + /* + * New messages may have been added directly to the ringbuffer + * using vprintk_store(), so wake any waiters as well. + */ + __wake_up_klogd(PRINTK_PENDING_WAKEUP | PRINTK_PENDING_OUTPUT); +} + +void printk_trigger_flush(void) +{ + defer_console_output(); +} + +int vprintk_deferred(const char *fmt, va_list args) +{ + return vprintk_emit(0, LOGLEVEL_SCHED, NULL, fmt, args); +} + +int _printk_deferred(const char *fmt, ...) +{ + va_list args; + int r; + + va_start(args, fmt); + r = vprintk_deferred(fmt, args); + va_end(args); + + return r; +} + +/* + * printk rate limiting, lifted from the networking subsystem. + * + * This enforces a rate limit: not more than 10 kernel messages + * every 5s to make a denial-of-service attack impossible. + */ +DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10); + +int __printk_ratelimit(const char *func) +{ + return ___ratelimit(&printk_ratelimit_state, func); +} +EXPORT_SYMBOL(__printk_ratelimit); + +/** + * printk_timed_ratelimit - caller-controlled printk ratelimiting + * @caller_jiffies: pointer to caller's state + * @interval_msecs: minimum interval between prints + * + * printk_timed_ratelimit() returns true if more than @interval_msecs + * milliseconds have elapsed since the last time printk_timed_ratelimit() + * returned true. + */ +bool printk_timed_ratelimit(unsigned long *caller_jiffies, + unsigned int interval_msecs) +{ + unsigned long elapsed = jiffies - *caller_jiffies; + + if (*caller_jiffies && elapsed <= msecs_to_jiffies(interval_msecs)) + return false; + + *caller_jiffies = jiffies; + return true; +} +EXPORT_SYMBOL(printk_timed_ratelimit); + +static DEFINE_SPINLOCK(dump_list_lock); +static LIST_HEAD(dump_list); + +/** + * kmsg_dump_register - register a kernel log dumper. + * @dumper: pointer to the kmsg_dumper structure + * + * Adds a kernel log dumper to the system. The dump callback in the + * structure will be called when the kernel oopses or panics and must be + * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise. + */ +int kmsg_dump_register(struct kmsg_dumper *dumper) +{ + unsigned long flags; + int err = -EBUSY; + + /* The dump callback needs to be set */ + if (!dumper->dump) + return -EINVAL; + + spin_lock_irqsave(&dump_list_lock, flags); + /* Don't allow registering multiple times */ + if (!dumper->registered) { + dumper->registered = 1; + list_add_tail_rcu(&dumper->list, &dump_list); + err = 0; + } + spin_unlock_irqrestore(&dump_list_lock, flags); + + return err; +} +EXPORT_SYMBOL_GPL(kmsg_dump_register); + +/** + * kmsg_dump_unregister - unregister a kmsg dumper. + * @dumper: pointer to the kmsg_dumper structure + * + * Removes a dump device from the system. Returns zero on success and + * %-EINVAL otherwise. + */ +int kmsg_dump_unregister(struct kmsg_dumper *dumper) +{ + unsigned long flags; + int err = -EINVAL; + + spin_lock_irqsave(&dump_list_lock, flags); + if (dumper->registered) { + dumper->registered = 0; + list_del_rcu(&dumper->list); + err = 0; + } + spin_unlock_irqrestore(&dump_list_lock, flags); + synchronize_rcu(); + + return err; +} +EXPORT_SYMBOL_GPL(kmsg_dump_unregister); + +static bool always_kmsg_dump; +module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR); + +const char *kmsg_dump_reason_str(enum kmsg_dump_reason reason) +{ + switch (reason) { + case KMSG_DUMP_PANIC: + return "Panic"; + case KMSG_DUMP_OOPS: + return "Oops"; + case KMSG_DUMP_EMERG: + return "Emergency"; + case KMSG_DUMP_SHUTDOWN: + return "Shutdown"; + default: + return "Unknown"; + } +} +EXPORT_SYMBOL_GPL(kmsg_dump_reason_str); + +/** + * kmsg_dump - dump kernel log to kernel message dumpers. + * @reason: the reason (oops, panic etc) for dumping + * + * Call each of the registered dumper's dump() callback, which can + * retrieve the kmsg records with kmsg_dump_get_line() or + * kmsg_dump_get_buffer(). + */ +void kmsg_dump(enum kmsg_dump_reason reason) +{ + struct kmsg_dumper *dumper; + + rcu_read_lock(); + list_for_each_entry_rcu(dumper, &dump_list, list) { + enum kmsg_dump_reason max_reason = dumper->max_reason; + + /* + * If client has not provided a specific max_reason, default + * to KMSG_DUMP_OOPS, unless always_kmsg_dump was set. + */ + if (max_reason == KMSG_DUMP_UNDEF) { + max_reason = always_kmsg_dump ? KMSG_DUMP_MAX : + KMSG_DUMP_OOPS; + } + if (reason > max_reason) + continue; + + /* invoke dumper which will iterate over records */ + dumper->dump(dumper, reason); + } + rcu_read_unlock(); +} + +/** + * kmsg_dump_get_line - retrieve one kmsg log line + * @iter: kmsg dump iterator + * @syslog: include the "<4>" prefixes + * @line: buffer to copy the line to + * @size: maximum size of the buffer + * @len: length of line placed into buffer + * + * Start at the beginning of the kmsg buffer, with the oldest kmsg + * record, and copy one record into the provided buffer. + * + * Consecutive calls will return the next available record moving + * towards the end of the buffer with the youngest messages. + * + * A return value of FALSE indicates that there are no more records to + * read. + */ +bool kmsg_dump_get_line(struct kmsg_dump_iter *iter, bool syslog, + char *line, size_t size, size_t *len) +{ + u64 min_seq = latched_seq_read_nolock(&clear_seq); + struct printk_info info; + unsigned int line_count; + struct printk_record r; + size_t l = 0; + bool ret = false; + + if (iter->cur_seq < min_seq) + iter->cur_seq = min_seq; + + prb_rec_init_rd(&r, &info, line, size); + + /* Read text or count text lines? */ + if (line) { + if (!prb_read_valid(prb, iter->cur_seq, &r)) + goto out; + l = record_print_text(&r, syslog, printk_time); + } else { + if (!prb_read_valid_info(prb, iter->cur_seq, + &info, &line_count)) { + goto out; + } + l = get_record_print_text_size(&info, line_count, syslog, + printk_time); + + } + + iter->cur_seq = r.info->seq + 1; + ret = true; +out: + if (len) + *len = l; + return ret; +} +EXPORT_SYMBOL_GPL(kmsg_dump_get_line); + +/** + * kmsg_dump_get_buffer - copy kmsg log lines + * @iter: kmsg dump iterator + * @syslog: include the "<4>" prefixes + * @buf: buffer to copy the line to + * @size: maximum size of the buffer + * @len_out: length of line placed into buffer + * + * Start at the end of the kmsg buffer and fill the provided buffer + * with as many of the *youngest* kmsg records that fit into it. + * If the buffer is large enough, all available kmsg records will be + * copied with a single call. + * + * Consecutive calls will fill the buffer with the next block of + * available older records, not including the earlier retrieved ones. + * + * A return value of FALSE indicates that there are no more records to + * read. + */ +bool kmsg_dump_get_buffer(struct kmsg_dump_iter *iter, bool syslog, + char *buf, size_t size, size_t *len_out) +{ + u64 min_seq = latched_seq_read_nolock(&clear_seq); + struct printk_info info; + struct printk_record r; + u64 seq; + u64 next_seq; + size_t len = 0; + bool ret = false; + bool time = printk_time; + + if (!buf || !size) + goto out; + + if (iter->cur_seq < min_seq) + iter->cur_seq = min_seq; + + if (prb_read_valid_info(prb, iter->cur_seq, &info, NULL)) { + if (info.seq != iter->cur_seq) { + /* messages are gone, move to first available one */ + iter->cur_seq = info.seq; + } + } + + /* last entry */ + if (iter->cur_seq >= iter->next_seq) + goto out; + + /* + * Find first record that fits, including all following records, + * into the user-provided buffer for this dump. Pass in size-1 + * because this function (by way of record_print_text()) will + * not write more than size-1 bytes of text into @buf. + */ + seq = find_first_fitting_seq(iter->cur_seq, iter->next_seq, + size - 1, syslog, time); + + /* + * Next kmsg_dump_get_buffer() invocation will dump block of + * older records stored right before this one. + */ + next_seq = seq; + + prb_rec_init_rd(&r, &info, buf, size); + + len = 0; + prb_for_each_record(seq, prb, seq, &r) { + if (r.info->seq >= iter->next_seq) + break; + + len += record_print_text(&r, syslog, time); + + /* Adjust record to store to remaining buffer space. */ + prb_rec_init_rd(&r, &info, buf + len, size - len); + } + + iter->next_seq = next_seq; + ret = true; +out: + if (len_out) + *len_out = len; + return ret; +} +EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer); + +/** + * kmsg_dump_rewind - reset the iterator + * @iter: kmsg dump iterator + * + * Reset the dumper's iterator so that kmsg_dump_get_line() and + * kmsg_dump_get_buffer() can be called again and used multiple + * times within the same dumper.dump() callback. + */ +void kmsg_dump_rewind(struct kmsg_dump_iter *iter) +{ + iter->cur_seq = latched_seq_read_nolock(&clear_seq); + iter->next_seq = prb_next_seq(prb); +} +EXPORT_SYMBOL_GPL(kmsg_dump_rewind); + +#endif + +#ifdef CONFIG_SMP +static atomic_t printk_cpu_sync_owner = ATOMIC_INIT(-1); +static atomic_t printk_cpu_sync_nested = ATOMIC_INIT(0); + +/** + * __printk_cpu_sync_wait() - Busy wait until the printk cpu-reentrant + * spinning lock is not owned by any CPU. + * + * Context: Any context. + */ +void __printk_cpu_sync_wait(void) +{ + do { + cpu_relax(); + } while (atomic_read(&printk_cpu_sync_owner) != -1); +} +EXPORT_SYMBOL(__printk_cpu_sync_wait); + +/** + * __printk_cpu_sync_try_get() - Try to acquire the printk cpu-reentrant + * spinning lock. + * + * If no processor has the lock, the calling processor takes the lock and + * becomes the owner. If the calling processor is already the owner of the + * lock, this function succeeds immediately. + * + * Context: Any context. Expects interrupts to be disabled. + * Return: 1 on success, otherwise 0. + */ +int __printk_cpu_sync_try_get(void) +{ + int cpu; + int old; + + cpu = smp_processor_id(); + + /* + * Guarantee loads and stores from this CPU when it is the lock owner + * are _not_ visible to the previous lock owner. This pairs with + * __printk_cpu_sync_put:B. + * + * Memory barrier involvement: + * + * If __printk_cpu_sync_try_get:A reads from __printk_cpu_sync_put:B, + * then __printk_cpu_sync_put:A can never read from + * __printk_cpu_sync_try_get:B. + * + * Relies on: + * + * RELEASE from __printk_cpu_sync_put:A to __printk_cpu_sync_put:B + * of the previous CPU + * matching + * ACQUIRE from __printk_cpu_sync_try_get:A to + * __printk_cpu_sync_try_get:B of this CPU + */ + old = atomic_cmpxchg_acquire(&printk_cpu_sync_owner, -1, + cpu); /* LMM(__printk_cpu_sync_try_get:A) */ + if (old == -1) { + /* + * This CPU is now the owner and begins loading/storing + * data: LMM(__printk_cpu_sync_try_get:B) + */ + return 1; + + } else if (old == cpu) { + /* This CPU is already the owner. */ + atomic_inc(&printk_cpu_sync_nested); + return 1; + } + + return 0; +} +EXPORT_SYMBOL(__printk_cpu_sync_try_get); + +/** + * __printk_cpu_sync_put() - Release the printk cpu-reentrant spinning lock. + * + * The calling processor must be the owner of the lock. + * + * Context: Any context. Expects interrupts to be disabled. + */ +void __printk_cpu_sync_put(void) +{ + if (atomic_read(&printk_cpu_sync_nested)) { + atomic_dec(&printk_cpu_sync_nested); + return; + } + + /* + * This CPU is finished loading/storing data: + * LMM(__printk_cpu_sync_put:A) + */ + + /* + * Guarantee loads and stores from this CPU when it was the + * lock owner are visible to the next lock owner. This pairs + * with __printk_cpu_sync_try_get:A. + * + * Memory barrier involvement: + * + * If __printk_cpu_sync_try_get:A reads from __printk_cpu_sync_put:B, + * then __printk_cpu_sync_try_get:B reads from __printk_cpu_sync_put:A. + * + * Relies on: + * + * RELEASE from __printk_cpu_sync_put:A to __printk_cpu_sync_put:B + * of this CPU + * matching + * ACQUIRE from __printk_cpu_sync_try_get:A to + * __printk_cpu_sync_try_get:B of the next CPU + */ + atomic_set_release(&printk_cpu_sync_owner, + -1); /* LMM(__printk_cpu_sync_put:B) */ +} +EXPORT_SYMBOL(__printk_cpu_sync_put); +#endif /* CONFIG_SMP */ |