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author | Linus Torvalds <torvalds@linux-foundation.org> | 2020-12-16 10:45:11 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-12-16 10:45:11 -0800 |
commit | d3eb52113d162cc88975fbd03c9e6f9cf2f8a771 (patch) | |
tree | 7ef2b73e6174d355d625c2a05377b14c0939cca7 | |
parent | 5e60366d56c630e32befce7ef05c569e04391ca3 (diff) | |
parent | 5ed37174e6c7e1ed4abfd0d8e932a3044441fb5f (diff) | |
download | linux-riscv-d3eb52113d162cc88975fbd03c9e6f9cf2f8a771.tar.gz linux-riscv-d3eb52113d162cc88975fbd03c9e6f9cf2f8a771.tar.bz2 linux-riscv-d3eb52113d162cc88975fbd03c9e6f9cf2f8a771.zip |
Merge tag 'printk-for-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux
Pull printk updates from Petr Mladek:
- Finally allow parallel writes and reads into/from the lockless
ringbuffer. But it is not a complete solution. Readers are still
serialized against each other. And nested writes are still prevented
by printk_safe per-CPU buffers.
- Use ttynull as the ultimate fallback for /dev/console.
- Officially allow disabling console output by using console="" or
console=null
- A few code cleanups
* tag 'printk-for-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
printk: remove logbuf_lock writer-protection of ringbuffer
printk: inline log_output(),log_store() in vprintk_store()
printk: remove obsolete dead assignment
printk/console: Allow to disable console output by using console="" or console=null
init/console: Use ttynull as a fallback when there is no console
printk: ringbuffer: Reference text_data_ring directly in callees.
-rw-r--r-- | drivers/tty/Kconfig | 14 | ||||
-rw-r--r-- | drivers/tty/Makefile | 3 | ||||
-rw-r--r-- | drivers/tty/ttynull.c | 18 | ||||
-rw-r--r-- | include/linux/console.h | 3 | ||||
-rw-r--r-- | init/main.c | 10 | ||||
-rw-r--r-- | kernel/printk/printk.c | 257 | ||||
-rw-r--r-- | kernel/printk/printk_ringbuffer.c | 32 |
7 files changed, 200 insertions, 137 deletions
diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig index e15cd6b5bb99..47a6e42f0d04 100644 --- a/drivers/tty/Kconfig +++ b/drivers/tty/Kconfig @@ -401,20 +401,6 @@ config MIPS_EJTAG_FDC_KGDB_CHAN help FDC channel number to use for KGDB. -config NULL_TTY - tristate "NULL TTY driver" - help - Say Y here if you want a NULL TTY which simply discards messages. - - This is useful to allow userspace applications which expect a console - device to work without modifications even when no console is - available or desired. - - In order to use this driver, you should redirect the console to this - TTY, or boot the kernel with console=ttynull. - - If unsure, say N. - config TRACE_ROUTER tristate "Trace data router for MIPI P1149.7 cJTAG standard" depends on TRACE_SINK diff --git a/drivers/tty/Makefile b/drivers/tty/Makefile index b3ccae932660..3c1c5a9240a7 100644 --- a/drivers/tty/Makefile +++ b/drivers/tty/Makefile @@ -2,7 +2,7 @@ obj-$(CONFIG_TTY) += tty_io.o n_tty.o tty_ioctl.o tty_ldisc.o \ tty_buffer.o tty_port.o tty_mutex.o \ tty_ldsem.o tty_baudrate.o tty_jobctrl.o \ - n_null.o + n_null.o ttynull.o obj-$(CONFIG_LEGACY_PTYS) += pty.o obj-$(CONFIG_UNIX98_PTYS) += pty.o obj-$(CONFIG_AUDIT) += tty_audit.o @@ -25,7 +25,6 @@ obj-$(CONFIG_ISI) += isicom.o obj-$(CONFIG_MOXA_INTELLIO) += moxa.o obj-$(CONFIG_MOXA_SMARTIO) += mxser.o obj-$(CONFIG_NOZOMI) += nozomi.o -obj-$(CONFIG_NULL_TTY) += ttynull.o obj-$(CONFIG_ROCKETPORT) += rocket.o obj-$(CONFIG_SYNCLINK_GT) += synclink_gt.o obj-$(CONFIG_PPC_EPAPR_HV_BYTECHAN) += ehv_bytechan.o diff --git a/drivers/tty/ttynull.c b/drivers/tty/ttynull.c index 17f05b7eb6d3..eced70ec54e1 100644 --- a/drivers/tty/ttynull.c +++ b/drivers/tty/ttynull.c @@ -2,6 +2,13 @@ /* * Copyright (C) 2019 Axis Communications AB * + * The console is useful for userspace applications which expect a console + * device to work without modifications even when no console is available + * or desired. + * + * In order to use this driver, you should redirect the console to this + * TTY, or boot the kernel with console=ttynull. + * * Based on ttyprintk.c: * Copyright (C) 2010 Samo Pogacnik */ @@ -59,6 +66,17 @@ static struct console ttynull_console = { .device = ttynull_device, }; +void __init register_ttynull_console(void) +{ + if (!ttynull_driver) + return; + + if (add_preferred_console(ttynull_console.name, 0, NULL)) + return; + + register_console(&ttynull_console); +} + static int __init ttynull_init(void) { struct tty_driver *driver; diff --git a/include/linux/console.h b/include/linux/console.h index 20874db50bc8..dbe78e8e2602 100644 --- a/include/linux/console.h +++ b/include/linux/console.h @@ -186,9 +186,12 @@ extern int braille_register_console(struct console *, int index, extern int braille_unregister_console(struct console *); #ifdef CONFIG_TTY extern void console_sysfs_notify(void); +extern void register_ttynull_console(void); #else static inline void console_sysfs_notify(void) { } +static inline void register_ttynull_console(void) +{ } #endif extern bool console_suspend_enabled; diff --git a/init/main.c b/init/main.c index 3024c4db17a9..6feee7f11eaf 100644 --- a/init/main.c +++ b/init/main.c @@ -1480,8 +1480,14 @@ void __init console_on_rootfs(void) struct file *file = filp_open("/dev/console", O_RDWR, 0); if (IS_ERR(file)) { - pr_err("Warning: unable to open an initial console.\n"); - return; + pr_err("Warning: unable to open an initial console. Fallback to ttynull.\n"); + register_ttynull_console(); + + file = filp_open("/dev/console", O_RDWR, 0); + if (IS_ERR(file)) { + pr_err("Warning: Failed to add ttynull console. No stdin, stdout, and stderr for the init process!\n"); + return; + } } init_dup(file); init_dup(file); diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 28713dda3f6b..ffdd0dc7ec6d 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -491,52 +491,6 @@ static void truncate_msg(u16 *text_len, u16 *trunc_msg_len) *trunc_msg_len = 0; } -/* insert record into the buffer, discard old ones, update heads */ -static int log_store(u32 caller_id, int facility, int level, - enum log_flags flags, u64 ts_nsec, - const struct dev_printk_info *dev_info, - const char *text, u16 text_len) -{ - struct prb_reserved_entry e; - struct printk_record r; - u16 trunc_msg_len = 0; - - prb_rec_init_wr(&r, text_len); - - if (!prb_reserve(&e, prb, &r)) { - /* truncate the message if it is too long for empty buffer */ - truncate_msg(&text_len, &trunc_msg_len); - prb_rec_init_wr(&r, text_len + trunc_msg_len); - /* survive when the log buffer is too small for trunc_msg */ - if (!prb_reserve(&e, prb, &r)) - return 0; - } - - /* fill message */ - memcpy(&r.text_buf[0], text, text_len); - 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; - if (ts_nsec > 0) - r.info->ts_nsec = ts_nsec; - else - r.info->ts_nsec = local_clock(); - 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); - - return (text_len + trunc_msg_len); -} - int dmesg_restrict = IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT); static int syslog_action_restricted(int type) @@ -741,7 +695,6 @@ static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from) if (LOG_FACILITY(u) != 0) facility = LOG_FACILITY(u); endp++; - len -= endp - line; line = endp; } } @@ -1172,7 +1125,7 @@ void __init setup_log_buf(int early) new_descs, ilog2(new_descs_count), new_infos); - logbuf_lock_irqsave(flags); + printk_safe_enter_irqsave(flags); log_buf_len = new_log_buf_len; log_buf = new_log_buf; @@ -1189,7 +1142,7 @@ void __init setup_log_buf(int early) */ prb = &printk_rb_dynamic; - logbuf_unlock_irqrestore(flags); + printk_safe_exit_irqrestore(flags); if (seq != prb_next_seq(&printk_rb_static)) { pr_err("dropped %llu messages\n", @@ -1907,83 +1860,177 @@ static inline u32 printk_caller_id(void) 0x80000000 + raw_smp_processor_id(); } -static size_t log_output(int facility, int level, enum log_flags lflags, - const struct dev_printk_info *dev_info, - char *text, size_t text_len) +/** + * parse_prefix - Parse level and control flags. + * + * @text: The terminated text message. + * @level: A pointer to the current level value, will be updated. + * @lflags: A pointer to the current log 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. + * + * @lflags may be NULL if the caller is not interested in the parsed value. + * Otherwise the variable pointed to by @lflags will be OR'd with the parsed + * value. + * + * Return: The length of the parsed level and control flags. + */ +static u16 parse_prefix(char *text, int *level, enum log_flags *lflags) { - const u32 caller_id = printk_caller_id(); + u16 prefix_len = 0; + int kern_level; - if (lflags & LOG_CONT) { - struct prb_reserved_entry e; - struct printk_record r; + while (*text) { + kern_level = printk_get_level(text); + if (!kern_level) + break; - prb_rec_init_wr(&r, text_len); - if (prb_reserve_in_last(&e, prb, &r, caller_id, LOG_LINE_MAX)) { - memcpy(&r.text_buf[r.info->text_len], text, text_len); - r.info->text_len += text_len; - if (lflags & LOG_NEWLINE) { - r.info->flags |= LOG_NEWLINE; - prb_final_commit(&e); - } else { - prb_commit(&e); - } - return text_len; + switch (kern_level) { + case '0' ... '7': + if (level && *level == LOGLEVEL_DEFAULT) + *level = kern_level - '0'; + break; + case 'c': /* KERN_CONT */ + if (lflags) + *lflags |= LOG_CONT; + } + + prefix_len += 2; + text += 2; + } + + return prefix_len; +} + +static u16 printk_sprint(char *text, u16 size, int facility, enum log_flags *lflags, + 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--; + *lflags |= LOG_NEWLINE; + } + + /* Strip log level and control flags. */ + if (facility == 0) { + u16 prefix_len; + + prefix_len = parse_prefix(text, NULL, NULL); + if (prefix_len) { + text_len -= prefix_len; + memmove(text, text + prefix_len, text_len); } } - /* Store it in the record log */ - return log_store(caller_id, facility, level, lflags, 0, - dev_info, text, text_len); + return text_len; } -/* Must be called under logbuf_lock. */ +__printf(4, 0) int vprintk_store(int facility, int level, const struct dev_printk_info *dev_info, const char *fmt, va_list args) { - static char textbuf[LOG_LINE_MAX]; - char *text = textbuf; - size_t text_len; + const u32 caller_id = printk_caller_id(); + struct prb_reserved_entry e; enum log_flags lflags = 0; + struct printk_record r; + u16 trunc_msg_len = 0; + char prefix_buf[8]; + u16 reserve_size; + va_list args2; + u16 text_len; + u64 ts_nsec; /* - * The printf needs to come first; we need the syslog - * prefix which might be passed-in as a parameter. + * 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. */ - text_len = vscnprintf(text, sizeof(textbuf), fmt, args); + ts_nsec = local_clock(); - /* mark and strip a trailing newline */ - if (text_len && text[text_len-1] == '\n') { - text_len--; + /* + * 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) + parse_prefix(&prefix_buf[0], &level, &lflags); + + if (level == LOGLEVEL_DEFAULT) + level = default_message_loglevel; + + if (dev_info) lflags |= LOG_NEWLINE; - } - /* strip kernel syslog prefix and extract log level or control flags */ - if (facility == 0) { - int kern_level; + if (lflags & 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, &lflags, fmt, args); + r.info->text_len += text_len; - while ((kern_level = printk_get_level(text)) != 0) { - switch (kern_level) { - case '0' ... '7': - if (level == LOGLEVEL_DEFAULT) - level = kern_level - '0'; - break; - case 'c': /* KERN_CONT */ - lflags |= LOG_CONT; + if (lflags & LOG_NEWLINE) { + r.info->flags |= LOG_NEWLINE; + prb_final_commit(&e); + } else { + prb_commit(&e); } - text_len -= 2; - text += 2; + return text_len; } } - if (level == LOGLEVEL_DEFAULT) - level = default_message_loglevel; + /* + * 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)) + return 0; + } + /* fill message */ + text_len = printk_sprint(&r.text_buf[0], reserve_size, facility, &lflags, 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 = lflags & 0x1f; + r.info->ts_nsec = ts_nsec; + r.info->caller_id = caller_id; if (dev_info) - lflags |= LOG_NEWLINE; + memcpy(&r.info->dev_info, dev_info, sizeof(r.info->dev_info)); + + /* A message without a trailing newline can be continued. */ + if (!(lflags & LOG_NEWLINE)) + prb_commit(&e); + else + prb_final_commit(&e); - return log_output(facility, level, lflags, dev_info, text, text_len); + return (text_len + trunc_msg_len); } asmlinkage int vprintk_emit(int facility, int level, @@ -2006,10 +2053,9 @@ asmlinkage int vprintk_emit(int facility, int level, boot_delay_msec(level); printk_delay(); - /* This stops the holder of console_sem just where we want him */ - logbuf_lock_irqsave(flags); + printk_safe_enter_irqsave(flags); printed_len = vprintk_store(facility, level, dev_info, fmt, args); - logbuf_unlock_irqrestore(flags); + printk_safe_exit_irqrestore(flags); /* If called from the scheduler, we can not call up(). */ if (!in_sched) { @@ -2189,8 +2235,15 @@ static int __init console_setup(char *str) char *s, *options, *brl_options = NULL; int idx; - if (str[0] == 0) + /* + * console="" or console=null have been suggested as a way to + * disable console output. Use ttynull that has been created + * for exacly 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; diff --git a/kernel/printk/printk_ringbuffer.c b/kernel/printk/printk_ringbuffer.c index 74e25a1704f2..6704f06e0417 100644 --- a/kernel/printk/printk_ringbuffer.c +++ b/kernel/printk/printk_ringbuffer.c @@ -559,11 +559,12 @@ static void desc_make_reusable(struct prb_desc_ring *desc_ring, * on error the caller can re-load the tail lpos to determine the situation. */ static bool data_make_reusable(struct printk_ringbuffer *rb, - struct prb_data_ring *data_ring, unsigned long lpos_begin, unsigned long lpos_end, unsigned long *lpos_out) { + + struct prb_data_ring *data_ring = &rb->text_data_ring; struct prb_desc_ring *desc_ring = &rb->desc_ring; struct prb_data_block *blk; enum desc_state d_state; @@ -625,10 +626,9 @@ static bool data_make_reusable(struct printk_ringbuffer *rb, * descriptors into the reusable state if the tail is pushed beyond * their associated data block. */ -static bool data_push_tail(struct printk_ringbuffer *rb, - struct prb_data_ring *data_ring, - unsigned long lpos) +static bool data_push_tail(struct printk_ringbuffer *rb, unsigned long lpos) { + struct prb_data_ring *data_ring = &rb->text_data_ring; unsigned long tail_lpos_new; unsigned long tail_lpos; unsigned long next_lpos; @@ -669,8 +669,7 @@ static bool data_push_tail(struct printk_ringbuffer *rb, * Make all descriptors reusable that are associated with * data blocks before @lpos. */ - if (!data_make_reusable(rb, data_ring, tail_lpos, lpos, - &next_lpos)) { + if (!data_make_reusable(rb, tail_lpos, lpos, &next_lpos)) { /* * 1. Guarantee the block ID loaded in * data_make_reusable() is performed before @@ -807,7 +806,7 @@ static bool desc_push_tail(struct printk_ringbuffer *rb, * data blocks once their associated descriptor is gone. */ - if (!data_push_tail(rb, &rb->text_data_ring, desc.text_blk_lpos.next)) + if (!data_push_tail(rb, desc.text_blk_lpos.next)) return false; /* @@ -1019,10 +1018,10 @@ static unsigned long get_next_lpos(struct prb_data_ring *data_ring, * if necessary. This function also associates the data block with * a specified descriptor. */ -static char *data_alloc(struct printk_ringbuffer *rb, - struct prb_data_ring *data_ring, unsigned int size, +static char *data_alloc(struct printk_ringbuffer *rb, unsigned int size, struct prb_data_blk_lpos *blk_lpos, unsigned long id) { + struct prb_data_ring *data_ring = &rb->text_data_ring; struct prb_data_block *blk; unsigned long begin_lpos; unsigned long next_lpos; @@ -1041,7 +1040,7 @@ static char *data_alloc(struct printk_ringbuffer *rb, do { next_lpos = get_next_lpos(data_ring, begin_lpos, size); - if (!data_push_tail(rb, data_ring, next_lpos - DATA_SIZE(data_ring))) { + if (!data_push_tail(rb, next_lpos - DATA_SIZE(data_ring))) { /* Failed to allocate, specify a data-less block. */ blk_lpos->begin = FAILED_LPOS; blk_lpos->next = FAILED_LPOS; @@ -1100,10 +1099,10 @@ static char *data_alloc(struct printk_ringbuffer *rb, * Return a pointer to the beginning of the entire data buffer or NULL on * failure. */ -static char *data_realloc(struct printk_ringbuffer *rb, - struct prb_data_ring *data_ring, unsigned int size, +static char *data_realloc(struct printk_ringbuffer *rb, unsigned int size, struct prb_data_blk_lpos *blk_lpos, unsigned long id) { + struct prb_data_ring *data_ring = &rb->text_data_ring; struct prb_data_block *blk; unsigned long head_lpos; unsigned long next_lpos; @@ -1130,7 +1129,7 @@ static char *data_realloc(struct printk_ringbuffer *rb, return &blk->data[0]; } - if (!data_push_tail(rb, data_ring, next_lpos - DATA_SIZE(data_ring))) + if (!data_push_tail(rb, next_lpos - DATA_SIZE(data_ring))) return NULL; /* The memory barrier involvement is the same as data_alloc:A. */ @@ -1395,7 +1394,7 @@ bool prb_reserve_in_last(struct prb_reserved_entry *e, struct printk_ringbuffer if (r->text_buf_size > max_size) goto fail; - r->text_buf = data_alloc(rb, &rb->text_data_ring, r->text_buf_size, + r->text_buf = data_alloc(rb, r->text_buf_size, &d->text_blk_lpos, id); } else { if (!get_data(&rb->text_data_ring, &d->text_blk_lpos, &data_size)) @@ -1419,7 +1418,7 @@ bool prb_reserve_in_last(struct prb_reserved_entry *e, struct printk_ringbuffer if (r->text_buf_size > max_size) goto fail; - r->text_buf = data_realloc(rb, &rb->text_data_ring, r->text_buf_size, + r->text_buf = data_realloc(rb, r->text_buf_size, &d->text_blk_lpos, id); } if (r->text_buf_size && !r->text_buf) @@ -1547,8 +1546,7 @@ bool prb_reserve(struct prb_reserved_entry *e, struct printk_ringbuffer *rb, if (info->seq > 0) desc_make_final(desc_ring, DESC_ID(id - 1)); - r->text_buf = data_alloc(rb, &rb->text_data_ring, r->text_buf_size, - &d->text_blk_lpos, id); + r->text_buf = data_alloc(rb, r->text_buf_size, &d->text_blk_lpos, id); /* If text data allocation fails, a data-less record is committed. */ if (r->text_buf_size && !r->text_buf) { prb_commit(e); |