diff options
author | Linus Torvalds <torvalds@linux-foundation.org> | 2023-02-23 13:49:45 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2023-02-23 13:49:45 -0800 |
commit | d8763154455e92a2ffed256e48fa46bb35ef3bdf (patch) | |
tree | c340a9c1c152c7e9121e7d60ab53afe059442fee /kernel | |
parent | cd43b5068647f47d6936ffef4d15d99518fcab94 (diff) | |
parent | 392143c9f2a31a9faaf99a6f8639eae7e71b8e61 (diff) | |
download | lwn-d8763154455e92a2ffed256e48fa46bb35ef3bdf.tar.gz lwn-d8763154455e92a2ffed256e48fa46bb35ef3bdf.zip |
Merge tag 'printk-for-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux
Pull printk updates from Petr Mladek:
- Refactor printk code for formatting messages that are shown on
consoles. This is a preparatory step for introducing atomic consoles
which could not share the global buffers
- Prevent memory leak when removing printk index in debugfs
- Dump also the newest printk message by the sample gdbmacro
- Fix a compiler warning
* tag 'printk-for-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
printf: fix errname.c list
kernel/printk/index.c: fix memory leak with using debugfs_lookup()
printk: Use scnprintf() to print the message about the dropped messages on a console
printk: adjust string limit macros
printk: use printk_buffers for devkmsg
printk: introduce console_prepend_dropped() for dropped messages
printk: introduce printk_get_next_message() and printk_message
printk: introduce struct printk_buffers
console: Document struct console
console: Use BIT() macros for @flags values
printk: move size limit macros into internal.h
docs: gdbmacros: print newest record
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/printk/index.c | 2 | ||||
-rw-r--r-- | kernel/printk/internal.h | 45 | ||||
-rw-r--r-- | kernel/printk/printk.c | 308 |
3 files changed, 225 insertions, 130 deletions
diff --git a/kernel/printk/index.c b/kernel/printk/index.c index c85be186a783..a6b27526baaf 100644 --- a/kernel/printk/index.c +++ b/kernel/printk/index.c @@ -145,7 +145,7 @@ static void pi_create_file(struct module *mod) #ifdef CONFIG_MODULES static void pi_remove_file(struct module *mod) { - debugfs_remove(debugfs_lookup(pi_get_module_name(mod), dfs_index)); + debugfs_lookup_and_remove(pi_get_module_name(mod), dfs_index); } static int pi_module_notify(struct notifier_block *nb, unsigned long op, diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h index d947ca6c84f9..2a17704136f1 100644 --- a/kernel/printk/internal.h +++ b/kernel/printk/internal.h @@ -14,6 +14,21 @@ int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write, #ifdef CONFIG_PRINTK +#ifdef CONFIG_PRINTK_CALLER +#define PRINTK_PREFIX_MAX 48 +#else +#define PRINTK_PREFIX_MAX 32 +#endif + +/* + * the maximum size of a formatted record (i.e. with prefix added + * per line and dropped messages or in extended message format) + */ +#define PRINTK_MESSAGE_MAX 2048 + +/* the maximum size allowed to be reserved for a record */ +#define PRINTKRB_RECORD_MAX 1024 + /* Flags for a single printk record. */ enum printk_info_flags { LOG_NEWLINE = 2, /* text ended with a newline */ @@ -48,6 +63,10 @@ u16 printk_parse_prefix(const char *text, int *level, enum printk_info_flags *flags); #else +#define PRINTK_PREFIX_MAX 0 +#define PRINTK_MESSAGE_MAX 0 +#define PRINTKRB_RECORD_MAX 0 + /* * In !PRINTK builds we still export console_sem * semaphore and some of console functions (console_unlock()/etc.), so @@ -58,3 +77,29 @@ u16 printk_parse_prefix(const char *text, int *level, static inline bool printk_percpu_data_ready(void) { return false; } #endif /* CONFIG_PRINTK */ + +/** + * struct printk_buffers - Buffers to read/format/output printk messages. + * @outbuf: After formatting, contains text to output. + * @scratchbuf: Used as temporary ringbuffer reading and string-print space. + */ +struct printk_buffers { + char outbuf[PRINTK_MESSAGE_MAX]; + char scratchbuf[PRINTKRB_RECORD_MAX]; +}; + +/** + * struct printk_message - Container for a prepared printk message. + * @pbufs: printk buffers used to prepare the message. + * @outbuf_len: The length of prepared text in @pbufs->outbuf to output. This + * does not count the terminator. A value of 0 means there is + * nothing to output and this record should be skipped. + * @seq: The sequence number of the record used for @pbufs->outbuf. + * @dropped: The number of dropped records from reading @seq. + */ +struct printk_message { + struct printk_buffers *pbufs; + unsigned int outbuf_len; + u64 seq; + unsigned long dropped; +}; diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 94f136b25f6a..fd0c9f913940 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -466,21 +466,6 @@ static struct latched_seq clear_seq = { .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) @@ -711,16 +696,15 @@ out: return len; } +static bool printk_get_next_message(struct printk_message *pmsg, u64 seq, + bool is_extended, bool may_supress); + /* /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; + struct printk_buffers pbufs; }; static __printf(3, 4) __cold @@ -746,7 +730,7 @@ static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from) size_t len = iov_iter_count(from); ssize_t ret = len; - if (!user || len > LOG_LINE_MAX) + if (!user || len > PRINTKRB_RECORD_MAX) return -EINVAL; /* Ignore when user logging is disabled. */ @@ -802,8 +786,10 @@ 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; + char *outbuf = &user->pbufs.outbuf[0]; + struct printk_message pmsg = { + .pbufs = &user->pbufs, + }; ssize_t ret; if (!user) @@ -813,7 +799,7 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf, if (ret) return ret; - if (!prb_read_valid(prb, atomic64_read(&user->seq), r)) { + if (!printk_get_next_message(&pmsg, atomic64_read(&user->seq), true, false)) { if (file->f_flags & O_NONBLOCK) { ret = -EAGAIN; goto out; @@ -830,36 +816,31 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf, * 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) */ + printk_get_next_message(&pmsg, atomic64_read(&user->seq), true, + false)); /* LMM(devkmsg_read:A) */ if (ret) goto out; } - if (r->info->seq != atomic64_read(&user->seq)) { + if (pmsg.dropped) { /* our last seen message is gone, return error and reset */ - atomic64_set(&user->seq, r->info->seq); + atomic64_set(&user->seq, pmsg.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); + atomic64_set(&user->seq, pmsg.seq + 1); - if (len > count) { + if (pmsg.outbuf_len > count) { ret = -EINVAL; goto out; } - if (copy_to_user(buf, user->buf, len)) { + if (copy_to_user(buf, outbuf, pmsg.outbuf_len)) { ret = -EFAULT; goto out; } - ret = len; + ret = pmsg.outbuf_len; out: mutex_unlock(&user->lock); return ret; @@ -953,9 +934,6 @@ static int devkmsg_open(struct inode *inode, struct file *file) 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; @@ -1150,7 +1128,7 @@ static unsigned int __init add_to_rb(struct printk_ringbuffer *rb, return prb_record_text_space(&e); } -static char setup_text_buf[LOG_LINE_MAX] __initdata; +static char setup_text_buf[PRINTKRB_RECORD_MAX] __initdata; void __init setup_log_buf(int early) { @@ -1416,7 +1394,7 @@ static size_t record_print_text(struct printk_record *r, bool syslog, 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]; + char prefix[PRINTK_PREFIX_MAX]; bool truncated = false; size_t prefix_len; size_t line_len; @@ -1515,7 +1493,7 @@ static size_t get_record_print_text_size(struct printk_info *info, unsigned int line_count, bool syslog, bool time) { - char prefix[PREFIX_MAX]; + char prefix[PRINTK_PREFIX_MAX]; size_t prefix_len; prefix_len = info_print_prefix(info, syslog, time, prefix); @@ -1581,11 +1559,11 @@ static int syslog_print(char __user *buf, int size) int len = 0; u64 seq; - text = kmalloc(CONSOLE_LOG_MAX, GFP_KERNEL); + text = kmalloc(PRINTK_MESSAGE_MAX, GFP_KERNEL); if (!text) return -ENOMEM; - prb_rec_init_rd(&r, &info, text, CONSOLE_LOG_MAX); + prb_rec_init_rd(&r, &info, text, PRINTK_MESSAGE_MAX); mutex_lock(&syslog_lock); @@ -1686,7 +1664,7 @@ static int syslog_print_all(char __user *buf, int size, bool clear) u64 seq; bool time; - text = kmalloc(CONSOLE_LOG_MAX, GFP_KERNEL); + text = kmalloc(PRINTK_MESSAGE_MAX, GFP_KERNEL); if (!text) return -ENOMEM; @@ -1698,7 +1676,7 @@ static int syslog_print_all(char __user *buf, int size, bool clear) 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); + prb_rec_init_rd(&r, &info, text, PRINTK_MESSAGE_MAX); len = 0; prb_for_each_record(seq, prb, seq, &r) { @@ -2013,27 +1991,6 @@ static int console_trylock_spinning(void) } /* - * 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. @@ -2243,8 +2200,8 @@ int vprintk_store(int facility, int level, 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; + if (reserve_size > PRINTKRB_RECORD_MAX) + reserve_size = PRINTKRB_RECORD_MAX; /* Extract log level or control flags. */ if (facility == 0) @@ -2258,7 +2215,7 @@ int vprintk_store(int facility, int level, if (flags & LOG_CONT) { prb_rec_init_wr(&r, reserve_size); - if (prb_reserve_in_last(&e, prb, &r, caller_id, LOG_LINE_MAX)) { + if (prb_reserve_in_last(&e, prb, &r, caller_id, PRINTKRB_RECORD_MAX)) { text_len = printk_sprint(&r.text_buf[r.info->text_len], reserve_size, facility, &flags, fmt, args); r.info->text_len += text_len; @@ -2389,8 +2346,6 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre #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 @@ -2414,10 +2369,6 @@ static ssize_t msg_print_ext_body(char *buf, size_t size, struct dev_printk_info *dev_info) { return 0; } static void console_lock_spinning_enable(void) { } static int console_lock_spinning_disable_and_check(int cookie) { 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; } @@ -2744,16 +2695,136 @@ static void __console_unlock(void) } /* - * Print one record for the given console. The record printed is whatever - * record is the next available record for the given console. + * Prepend the message in @pmsg->pbufs->outbuf with a "dropped message". This + * is achieved by shifting the existing message over and inserting the dropped + * message. + * + * @pmsg is the printk message to prepend. * - * @text is a buffer of size CONSOLE_LOG_MAX. + * @dropped is the dropped count to report in the dropped message. * - * If extended messages should be printed, @ext_text is a buffer of size - * CONSOLE_EXT_LOG_MAX. Otherwise @ext_text must be NULL. + * If the message text in @pmsg->pbufs->outbuf does not have enough space for + * the dropped message, the message text will be sufficiently truncated. * - * If dropped messages should be printed, @dropped_text is a buffer of size - * DROPPED_TEXT_MAX. Otherwise @dropped_text must be NULL. + * If @pmsg->pbufs->outbuf is modified, @pmsg->outbuf_len is updated. + */ +#ifdef CONFIG_PRINTK +static void console_prepend_dropped(struct printk_message *pmsg, unsigned long dropped) +{ + struct printk_buffers *pbufs = pmsg->pbufs; + const size_t scratchbuf_sz = sizeof(pbufs->scratchbuf); + const size_t outbuf_sz = sizeof(pbufs->outbuf); + char *scratchbuf = &pbufs->scratchbuf[0]; + char *outbuf = &pbufs->outbuf[0]; + size_t len; + + len = scnprintf(scratchbuf, scratchbuf_sz, + "** %lu printk messages dropped **\n", dropped); + + /* + * Make sure outbuf is sufficiently large before prepending. + * Keep at least the prefix when the message must be truncated. + * It is a rather theoretical problem when someone tries to + * use a minimalist buffer. + */ + if (WARN_ON_ONCE(len + PRINTK_PREFIX_MAX >= outbuf_sz)) + return; + + if (pmsg->outbuf_len + len >= outbuf_sz) { + /* Truncate the message, but keep it terminated. */ + pmsg->outbuf_len = outbuf_sz - (len + 1); + outbuf[pmsg->outbuf_len] = 0; + } + + memmove(outbuf + len, outbuf, pmsg->outbuf_len + 1); + memcpy(outbuf, scratchbuf, len); + pmsg->outbuf_len += len; +} +#else +#define console_prepend_dropped(pmsg, dropped) +#endif /* CONFIG_PRINTK */ + +/* + * Read and format the specified record (or a later record if the specified + * record is not available). + * + * @pmsg will contain the formatted result. @pmsg->pbufs must point to a + * struct printk_buffers. + * + * @seq is the record to read and format. If it is not available, the next + * valid record is read. + * + * @is_extended specifies if the message should be formatted for extended + * console output. + * + * @may_supress specifies if records may be skipped based on loglevel. + * + * Returns false if no record is available. Otherwise true and all fields + * of @pmsg are valid. (See the documentation of struct printk_message + * for information about the @pmsg fields.) + */ +static bool printk_get_next_message(struct printk_message *pmsg, u64 seq, + bool is_extended, bool may_suppress) +{ + static int panic_console_dropped; + + struct printk_buffers *pbufs = pmsg->pbufs; + const size_t scratchbuf_sz = sizeof(pbufs->scratchbuf); + const size_t outbuf_sz = sizeof(pbufs->outbuf); + char *scratchbuf = &pbufs->scratchbuf[0]; + char *outbuf = &pbufs->outbuf[0]; + struct printk_info info; + struct printk_record r; + size_t len = 0; + + /* + * Formatting extended messages requires a separate buffer, so use the + * scratch buffer to read in the ringbuffer text. + * + * Formatting normal messages is done in-place, so read the ringbuffer + * text directly into the output buffer. + */ + if (is_extended) + prb_rec_init_rd(&r, &info, scratchbuf, scratchbuf_sz); + else + prb_rec_init_rd(&r, &info, outbuf, outbuf_sz); + + if (!prb_read_valid(prb, seq, &r)) + return false; + + pmsg->seq = r.info->seq; + pmsg->dropped = r.info->seq - seq; + + /* + * Check for dropped messages in panic here so that printk + * suppression can occur as early as possible if necessary. + */ + if (pmsg->dropped && + 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 (may_suppress && suppress_message_printing(r.info->level)) + goto out; + + if (is_extended) { + len = info_print_ext_header(outbuf, outbuf_sz, r.info); + len += msg_print_ext_body(outbuf + len, outbuf_sz - len, + &r.text_buf[0], r.info->text_len, &r.info->dev_info); + } else { + len = record_print_text(&r, console_msg_format & MSG_FORMAT_SYSLOG, printk_time); + } +out: + pmsg->outbuf_len = len; + return true; +} + +/* + * Print one record for the given console. The record printed is whatever + * record is the next available record for the given console. * * @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 both the @@ -2766,46 +2837,33 @@ static void __console_unlock(void) * * Requires the console_lock and the SRCU read lock. */ -static bool console_emit_next_record(struct console *con, char *text, char *ext_text, - char *dropped_text, bool *handover, int cookie) +static bool console_emit_next_record(struct console *con, bool *handover, int cookie) { - static int panic_console_dropped; - struct printk_info info; - struct printk_record r; - unsigned long flags; - char *write_text; - size_t len; + static struct printk_buffers pbufs; - prb_rec_init_rd(&r, &info, text, CONSOLE_LOG_MAX); + bool is_extended = console_srcu_read_flags(con) & CON_EXTENDED; + char *outbuf = &pbufs.outbuf[0]; + struct printk_message pmsg = { + .pbufs = &pbufs, + }; + unsigned long flags; *handover = false; - if (!prb_read_valid(prb, con->seq, &r)) + if (!printk_get_next_message(&pmsg, con->seq, is_extended, true)) 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"); - } - } + con->dropped += pmsg.dropped; - /* Skip record that has level above the console loglevel. */ - if (suppress_message_printing(r.info->level)) { - con->seq++; + /* Skip messages of formatted length 0. */ + if (pmsg.outbuf_len == 0) { + con->seq = pmsg.seq + 1; goto skip; } - if (ext_text) { - write_text = ext_text; - len = info_print_ext_header(ext_text, CONSOLE_EXT_LOG_MAX, r.info); - len += msg_print_ext_body(ext_text + len, CONSOLE_EXT_LOG_MAX - len, - &r.text_buf[0], r.info->text_len, &r.info->dev_info); - } else { - write_text = text; - len = record_print_text(&r, console_msg_format & MSG_FORMAT_SYSLOG, printk_time); + if (con->dropped && !is_extended) { + console_prepend_dropped(&pmsg, con->dropped); + con->dropped = 0; } /* @@ -2821,11 +2879,15 @@ static bool console_emit_next_record(struct console *con, char *text, char *ext_ 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); + /* Do not trace print latency. */ + stop_critical_timings(); + + /* Write everything out to the hardware. */ + con->write(con, outbuf, pmsg.outbuf_len); + start_critical_timings(); - con->seq++; + con->seq = pmsg.seq + 1; *handover = console_lock_spinning_disable_and_check(cookie); printk_safe_exit_irqrestore(flags); @@ -2858,9 +2920,6 @@ skip: */ 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; @@ -2880,16 +2939,7 @@ static bool console_flush_all(bool do_cond_resched, u64 *next_seq, bool *handove continue; any_usable = true; - if (console_srcu_read_flags(con) & CON_EXTENDED) { - /* Extended consoles do not print "dropped messages". */ - progress = console_emit_next_record(con, &text[0], - &ext_text[0], NULL, - handover, cookie); - } else { - progress = console_emit_next_record(con, &text[0], - NULL, &dropped_text[0], - handover, cookie); - } + progress = console_emit_next_record(con, handover, cookie); /* * If a handover has occurred, the SRCU read lock |