1 // SPDX-License-Identifier: GPL-2.0-only
85  * console_mutex protects console_list updates and console->flags updates.
92  * console_sem protects updates to console->seq
148 		return -EINVAL;  in __control_devkmsg()
168 	return -EINVAL;  in __control_devkmsg()
210 			return -EINVAL;  in devkmsg_sysctl_set_loglvl()
233 			return -EINVAL;  in devkmsg_sysctl_set_loglvl()
242  * console_list_lock - Lock the console list
244  * For console list or console->flags updates
254 	 * Detecting if this context is really in the read-side critical  in console_list_lock()
266  * console_list_unlock - Unlock the console list
277  * console_srcu_read_lock - Register a new reader for the
278  *	SRCU-protected console list
293  * console_srcu_read_unlock - Unregister an old reader from
294  *	the SRCU-protected console list
322 	 * because spindump/WARN/etc from under console ->lock will  in __down_trylock_console_sem()
323 	 * deadlock in printk()->down_trylock_console_sem() otherwise.  in __down_trylock_console_sem()
394 static int preferred_console = -1;
411  * own meta-data (@info).
413  * Every record meta-data carries the timestamp in microseconds, as well as
415  * messages use LOG_KERN; userspace-injected messages always carry a matching
424  * pairs), to provide userspace with a machine-readable message context.
426  * Examples for well-defined, commonly used property names are:
432  *   SUBSYSTEM=pci              driver-core subsystem name
434  * Valid characters in property names are [a-zA-Z0-9.-_]. Property names
450  * userspace, it is a kernel-private implementation detail that might
461  * non-prinatable characters are escaped in the "\xff" notation.
532  * Define the average message size. This only affects the number of
541 _DEFINE_PRINTKRB(printk_rb_static, CONFIG_LOG_BUF_SHIFT - PRB_AVGBITS,
549  * We cannot access per-CPU data (e.g. per-CPU flush irq_work) before
551  * it's safe to access per-CPU data.
563 	raw_write_seqcount_latch(&ls->latch);  in latched_seq_write()
564 	ls->val[0] = val;  in latched_seq_write()
565 	raw_write_seqcount_latch(&ls->latch);  in latched_seq_write()
566 	ls->val[1] = val;  in latched_seq_write()
577 		seq = raw_read_seqcount_latch(&ls->latch);  in latched_seq_read_nolock()
579 		val = ls->val[idx];  in latched_seq_read_nolock()
580 	} while (raw_read_seqcount_latch_retry(&ls->latch, seq));  in latched_seq_read_nolock()
591 /* Return log buffer size */
619 		*text_len -= *trunc_msg_len;  in truncate_msg()
631 	 * Unless restricted, we allow "read all" and "get buffer size"  in syslog_action_restricted()
650 		return -EPERM;  in check_syslog_permissions()
662 static ssize_t info_print_ext_header(char *buf, size_t size,  in info_print_ext_header()  argument
665 	u64 ts_usec = info->ts_nsec;  in info_print_ext_header()
668 	u32 id = info->caller_id;  in info_print_ext_header()
678 	return scnprintf(buf, size, "%u,%llu,%llu,%c%s;",  in info_print_ext_header()
679 			 (info->facility << 3) | info->level, info->seq,  in info_print_ext_header()
680 			 ts_usec, info->flags & LOG_CONT ? 'c' : '-', caller);  in info_print_ext_header()
683 static ssize_t msg_add_ext_text(char *buf, size_t size,  in msg_add_ext_text()  argument
687 	char *p = buf, *e = buf + size;  in msg_add_ext_text()
690 	/* escape non-printable characters */  in msg_add_ext_text()
695 			p += scnprintf(p, e - p, "\\x%02x", c);  in msg_add_ext_text()
701 	return p - buf;  in msg_add_ext_text()
704 static ssize_t msg_add_dict_text(char *buf, size_t size,  in msg_add_dict_text()  argument
713 	len = msg_add_ext_text(buf, size, "", 0, ' ');	/* dict prefix */  in msg_add_dict_text()
714 	len += msg_add_ext_text(buf + len, size - len, key, strlen(key), '=');  in msg_add_dict_text()
715 	len += msg_add_ext_text(buf + len, size - len, val, val_len, '\n');  in msg_add_dict_text()
720 static ssize_t msg_print_ext_body(char *buf, size_t size,  in msg_print_ext_body()  argument
726 	len = msg_add_ext_text(buf, size, text, text_len, '\n');  in msg_print_ext_body()
731 	len += msg_add_dict_text(buf + len, size - len, "SUBSYSTEM",  in msg_print_ext_body()
732 				 dev_info->subsystem);  in msg_print_ext_body()
733 	len += msg_add_dict_text(buf + len, size - len, "DEVICE",  in msg_print_ext_body()
734 				 dev_info->device);  in msg_print_ext_body()
739 /* /dev/kmsg - userspace message inject/listen interface */
765 	struct file *file = iocb->ki_filp;  in devkmsg_write()
766 	struct devkmsg_user *user = file->private_data;  in devkmsg_write()
771 		return -EINVAL;  in devkmsg_write()
779 		if (!___ratelimit(&user->rs, current->comm))  in devkmsg_write()
785 		return -ENOMEM;  in devkmsg_write()
790 		return -EFAULT;  in devkmsg_write()
794 	 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace  in devkmsg_write()
800 	 * kernel-generated messages from userspace-injected ones.  in devkmsg_write()
825 	struct devkmsg_user *user = file->private_data;  in devkmsg_read()
826 	char *outbuf = &user->pbufs.outbuf[0];  in devkmsg_read()
827 	struct printk_message pmsg = {  in devkmsg_read()  local
828 		.pbufs = &user->pbufs,  in devkmsg_read()
832 	ret = mutex_lock_interruptible(&user->lock);  in devkmsg_read()
836 	if (!printk_get_next_message(&pmsg, atomic64_read(&user->seq), true, false)) {  in devkmsg_read()
837 		if (file->f_flags & O_NONBLOCK) {  in devkmsg_read()
838 			ret = -EAGAIN;  in devkmsg_read()
853 				printk_get_next_message(&pmsg, atomic64_read(&user->seq), true,  in devkmsg_read()
859 	if (pmsg.dropped) {  in devkmsg_read()
861 		atomic64_set(&user->seq, pmsg.seq);  in devkmsg_read()
862 		ret = -EPIPE;  in devkmsg_read()
866 	atomic64_set(&user->seq, pmsg.seq + 1);  in devkmsg_read()
868 	if (pmsg.outbuf_len > count) {  in devkmsg_read()
869 		ret = -EINVAL;  in devkmsg_read()
873 	if (copy_to_user(buf, outbuf, pmsg.outbuf_len)) {  in devkmsg_read()
874 		ret = -EFAULT;  in devkmsg_read()
877 	ret = pmsg.outbuf_len;  in devkmsg_read()
879 	mutex_unlock(&user->lock);  in devkmsg_read()
887  * entire variable length messages (records). Non-standard values are
893 	struct devkmsg_user *user = file->private_data;  in devkmsg_llseek()
897 		return -ESPIPE;  in devkmsg_llseek()
902 		atomic64_set(&user->seq, prb_first_valid_seq(prb));  in devkmsg_llseek()
907 		 * like issued by 'dmesg -c'. Reading /dev/kmsg itself  in devkmsg_llseek()
910 		atomic64_set(&user->seq, latched_seq_read_nolock(&clear_seq));  in devkmsg_llseek()
914 		atomic64_set(&user->seq, prb_next_seq(prb));  in devkmsg_llseek()
917 		ret = -EINVAL;  in devkmsg_llseek()
924 	struct devkmsg_user *user = file->private_data;  in devkmsg_poll()
930 	if (prb_read_valid_info(prb, atomic64_read(&user->seq), &info, NULL)) {  in devkmsg_poll()
932 		if (info.seq != atomic64_read(&user->seq))  in devkmsg_poll()
947 		return -EPERM;  in devkmsg_open()
949 	/* write-only does not need any file context */  in devkmsg_open()
950 	if ((file->f_flags & O_ACCMODE) != O_WRONLY) {  in devkmsg_open()
959 		return -ENOMEM;  in devkmsg_open()
961 	ratelimit_default_init(&user->rs);  in devkmsg_open()
962 	ratelimit_set_flags(&user->rs, RATELIMIT_MSG_ON_RELEASE);  in devkmsg_open()
964 	mutex_init(&user->lock);  in devkmsg_open()
966 	atomic64_set(&user->seq, prb_first_valid_seq(prb));  in devkmsg_open()
968 	file->private_data = user;  in devkmsg_open()
974 	struct devkmsg_user *user = file->private_data;  in devkmsg_release()
976 	ratelimit_state_exit(&user->rs);  in devkmsg_release()
978 	mutex_destroy(&user->lock);  in devkmsg_release()
1010 	 * Export struct size and field offsets. User space tools can  in log_buf_vmcoreinfo_setup()
1043 	VMCOREINFO_LENGTH(printk_info_subsystem, sizeof(dev_info->subsystem));  in log_buf_vmcoreinfo_setup()
1045 	VMCOREINFO_LENGTH(printk_info_device, sizeof(dev_info->device));  in log_buf_vmcoreinfo_setup()
1065 static void __init log_buf_len_update(u64 size)  in log_buf_len_update()  argument
1067 	if (size > (u64)LOG_BUF_LEN_MAX) {  in log_buf_len_update()
1068 		size = (u64)LOG_BUF_LEN_MAX;  in log_buf_len_update()
1072 	if (size)  in log_buf_len_update()
1073 		size = roundup_pow_of_two(size);  in log_buf_len_update()
1074 	if (size > log_buf_len)  in log_buf_len_update()
1075 		new_log_buf_len = (unsigned long)size;  in log_buf_len_update()
1081 	u64 size;  in log_buf_len_setup()  local
1084 		return -EINVAL;  in log_buf_len_setup()
1086 	size = memparse(str, &str);  in log_buf_len_setup()
1088 	log_buf_len_update(size);  in log_buf_len_setup()
1109 	cpu_extra = (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN;  in log_buf_add_cpu()
1119 	pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN);  in log_buf_add_cpu()
1138 	prb_rec_init_wr(&dest_r, r->info->text_len);  in add_to_rb()
1143 	memcpy(&dest_r.text_buf[0], &r->text_buf[0], r->info->text_len);  in add_to_rb()
1144 	dest_r.info->text_len = r->info->text_len;  in add_to_rb()
1145 	dest_r.info->facility = r->info->facility;  in add_to_rb()
1146 	dest_r.info->level = r->info->level;  in add_to_rb()
1147 	dest_r.info->flags = r->info->flags;  in add_to_rb()
1148 	dest_r.info->ts_nsec = r->info->ts_nsec;  in add_to_rb()
1149 	dest_r.info->caller_id = r->info->caller_id;  in add_to_rb()
1150 	memcpy(&dest_r.info->dev_info, &r->info->dev_info, sizeof(dest_r.info->dev_info));  in add_to_rb()
1175 	 * Some archs call setup_log_buf() multiple times - first is very  in setup_log_buf()
1176 	 * early, e.g. from setup_arch(), and second - when percpu_areas  in setup_log_buf()
1239 			free -= text_size;  in setup_log_buf()
1256 			free -= text_size;  in setup_log_buf()
1261 		       prb_next_seq(&printk_rb_static) - seq);  in setup_log_buf()
1332 		k--;  in boot_delay_msec()
1385 		len = print_syslog((info->facility << 3) | info->level, buf);  in info_print_prefix()
1388 		len += print_time(info->ts_nsec, buf + len);  in info_print_prefix()
1390 	len += print_caller(info->caller_id, buf + len);  in info_print_prefix()
1405  *   - Add prefix for each line.
1406  *   - Drop truncated lines that no longer fit into the buffer.
1407  *   - Add the trailing newline that has been removed in vprintk_store().
1408  *   - Add a string terminator.
1411  * return value is @r->text_buf_size - 1;
1420 	size_t text_len = r->info->text_len;  in record_print_text()
1421 	size_t buf_size = r->text_buf_size;  in record_print_text()
1422 	char *text = r->text_buf;  in record_print_text()
1437 	prefix_len = info_print_prefix(r->info, syslog, time, prefix);  in record_print_text()
1443 	 * @len:      number of bytes prepared in r->text_buf  in record_print_text()
1448 			line_len = next - text;  in record_print_text()
1465 			text_len = buf_size - len - prefix_len - 1 - 1;  in record_print_text()
1504 		text_len -= line_len + 1;  in record_print_text()
1513 		r->text_buf[len] = 0;  in record_print_text()
1532 	return ((prefix_len * line_count) + info->text_len + 1);  in get_record_print_text_size()
1537  * records up to (but not including) @max_seq fit into @size.
1540  * does not require an upper bound, -1 can be used for @max_seq.
1542 static u64 find_first_fitting_seq(u64 start_seq, u64 max_seq, size_t size,  in find_first_fitting_seq()  argument
1550 	/* Determine the size of the records up to @max_seq. */  in find_first_fitting_seq()
1571 		if (len <= size || info.seq >= max_seq)  in find_first_fitting_seq()
1573 		len -= get_record_print_text_size(&info, line_count, syslog, time);  in find_first_fitting_seq()
1579 /* The caller is responsible for making sure @size is greater than 0. */
1580 static int syslog_print(char __user *buf, int size)  in syslog_print()  argument
1590 		return -ENOMEM;  in syslog_print()
1634 		if (r.info->seq != syslog_seq) {  in syslog_print()
1636 			syslog_seq = r.info->seq;  in syslog_print()
1649 		if (n - syslog_partial <= size) {  in syslog_print()
1651 			syslog_seq = r.info->seq + 1;  in syslog_print()
1652 			n -= syslog_partial;  in syslog_print()
1656 			n = size;  in syslog_print()
1670 				len = -EFAULT;  in syslog_print()
1675 		size -= n;  in syslog_print()
1677 	} while (size);  in syslog_print()
1684 static int syslog_print_all(char __user *buf, int size, bool clear)  in syslog_print_all()  argument
1695 		return -ENOMEM;  in syslog_print_all()
1700 	 * into the user-provided buffer for this dump.  in syslog_print_all()
1702 	seq = find_first_fitting_seq(latched_seq_read_nolock(&clear_seq), -1,  in syslog_print_all()
1703 				     size, true, time);  in syslog_print_all()
1712 		if (len + textlen > size) {  in syslog_print_all()
1713 			seq--;  in syslog_print_all()
1718 			len = -EFAULT;  in syslog_print_all()
1761 			return -EINVAL;  in do_syslog()
1765 			return -EFAULT;  in do_syslog()
1775 			return -EINVAL;  in do_syslog()
1779 			return -EFAULT;  in do_syslog()
1802 			return -EINVAL;  in do_syslog()
1806 		/* Implicitly re-enable logging to console */  in do_syslog()
1824 			 * Short-cut for poll(/"proc/kmsg") which simply checks  in do_syslog()
1825 			 * for pending data, not the size; return the count of  in do_syslog()
1828 			error = prb_next_seq(prb) - syslog_seq;  in do_syslog()
1840 			error -= syslog_partial;  in do_syslog()
1844 	/* Size of the log buffer */  in do_syslog()
1849 		error = -EINVAL;  in do_syslog()
1862  * Special console_lock variants that help to reduce the risk of soft-lockups.
1877  * console_lock_spinning_enable - mark beginning of code where another
1889 	 * Non-panic CPUs abandon the flush anyway.  in console_lock_spinning_enable()
1891 	 * Just keep the lockdep annotation. The panic-CPU should avoid  in console_lock_spinning_enable()
1909  * console_lock_spinning_disable_and_check - mark end of code where another
1974  * console_trylock_spinning - try to get console_lock by busy waiting
2055  * additional NMI context per CPU is also separately tracked. Until per-CPU
2068  * a WARN), but a higher value is used in case some printk-internal errors
2119 		(*(recursion_ptr))--;			\
2132 		while (m--) {  in printk_delay()
2146  * printk_parse_prefix - Parse level and control flags.
2176 				*level = kern_level - '0';  in printk_parse_prefix()
2191 static u16 printk_sprint(char *text, u16 size, int facility,  in printk_sprint()  argument
2197 	text_len = vscnprintf(text, size, fmt, args);  in printk_sprint()
2200 	if (text_len && text[text_len - 1] == '\n') {  in printk_sprint()
2201 		text_len--;  in printk_sprint()
2211 			text_len -= prefix_len;  in printk_sprint()
2279 			text_len = printk_sprint(&r.text_buf[r.info->text_len], reserve_size,  in vprintk_store()
2281 			r.info->text_len += text_len;  in vprintk_store()
2284 				r.info->flags |= LOG_NEWLINE;  in vprintk_store()
2314 	r.info->text_len = text_len + trunc_msg_len;  in vprintk_store()
2315 	r.info->facility = facility;  in vprintk_store()
2316 	r.info->level = level & 7;  in vprintk_store()
2317 	r.info->flags = flags & 0x1f;  in vprintk_store()
2318 	r.info->ts_nsec = ts_nsec;  in vprintk_store()
2319 	r.info->caller_id = caller_id;  in vprintk_store()
2321 		memcpy(&r.info->dev_info, dev_info, sizeof(r.info->dev_info));  in vprintk_store()
2336  * This acts as a one-way switch to allow legacy consoles to print from
2366 	 * non-panic CPUs are generating any messages, they will be  in vprintk_emit()
2393 		 * The caller may be holding system-critical or  in vprintk_emit()
2394 		 * timing-sensitive locks. Disable preemption during  in vprintk_emit()
2473 	early_console->write(early_console, buf, n);  in early_printk()
2486 	c->user_specified = true;  in set_user_specified()
2499 		return -EINVAL;  in __add_preferred_console()
2508 		return -EINVAL;  in __add_preferred_console()
2515 	     i < MAX_CMDLINECONSOLES && (c->name[0] || c->devname[0]);  in __add_preferred_console()
2517 		if ((name && strcmp(c->name, name) == 0 && c->index == idx) ||  in __add_preferred_console()
2518 		    (devname && strcmp(c->devname, devname) == 0)) {  in __add_preferred_console()
2526 		return -E2BIG;  in __add_preferred_console()
2530 		strscpy(c->name, name);  in __add_preferred_console()
2532 		strscpy(c->devname, devname);  in __add_preferred_console()
2533 	c->options = options;  in __add_preferred_console()
2537 	c->index = idx;  in __add_preferred_console()
2610 		idx = -1;  in console_setup()
2622  * add_preferred_console - add a device to the list of preferred consoles.
2629  * above to handle user-supplied console arguments; however it can also
2630  * be used by arch-specific code either to override the user or more
2640  * match_devname_and_update_preferred_console - Update a preferred console
2667 		return -EINVAL;  in match_devname_and_update_preferred_console()
2669 	for (i = 0; i < MAX_CMDLINECONSOLES && (c->name[0] || c->devname[0]);  in match_devname_and_update_preferred_console()
2671 		if (!strcmp(devname, c->devname)) {  in match_devname_and_update_preferred_console()
2674 			strscpy(c->name, name);  in match_devname_and_update_preferred_console()
2675 			c->index = idx;  in match_devname_and_update_preferred_console()
2680 	return -ENOENT;  in match_devname_and_update_preferred_console()
2711  * suspend_console - suspend the console subsystem
2726 		console_srcu_write_flags(con, con->flags | CON_SUSPENDED);  in suspend_console()
2748 		console_srcu_write_flags(con, con->flags & ~CON_SUSPENDED);  in resume_console()
2768  * console_cpu_notify - print deferred console messages after CPU hotplug
2793  * console_lock - block the console subsystem from printing
2815  * console_trylock - try to block the console subsystem from printing
2850  * Prepend the message in @pmsg->pbufs->outbuf. This is achieved by shifting
2853  * @pmsg is the original printk message.
2856  * If there is not enough space in @pmsg->pbufs->outbuf, the existing
2859  * If @pmsg->pbufs->outbuf is modified, @pmsg->outbuf_len is updated.
2862 static void console_prepend_message(struct printk_message *pmsg, const char *fmt, ...)  in console_prepend_message()  argument
2864 	struct printk_buffers *pbufs = pmsg->pbufs;  in console_prepend_message()
2865 	const size_t scratchbuf_sz = sizeof(pbufs->scratchbuf);  in console_prepend_message()
2866 	const size_t outbuf_sz = sizeof(pbufs->outbuf);  in console_prepend_message()
2867 	char *scratchbuf = &pbufs->scratchbuf[0];  in console_prepend_message()
2868 	char *outbuf = &pbufs->outbuf[0];  in console_prepend_message()
2885 	if (pmsg->outbuf_len + len >= outbuf_sz) {  in console_prepend_message()
2887 		pmsg->outbuf_len = outbuf_sz - (len + 1);  in console_prepend_message()
2888 		outbuf[pmsg->outbuf_len] = 0;  in console_prepend_message()
2891 	memmove(outbuf + len, outbuf, pmsg->outbuf_len + 1);  in console_prepend_message()
2893 	pmsg->outbuf_len += len;  in console_prepend_message()
2897  * Prepend the message in @pmsg->pbufs->outbuf with a "dropped message".
2898  * @pmsg->outbuf_len is updated appropriately.
2900  * @pmsg is the printk message to prepend.
2904 void console_prepend_dropped(struct printk_message *pmsg, unsigned long dropped)  in console_prepend_dropped()  argument
2906 	console_prepend_message(pmsg, "** %lu printk messages dropped **\n", dropped);  in console_prepend_dropped()
2910  * Prepend the message in @pmsg->pbufs->outbuf with a "replay message".
2911  * @pmsg->outbuf_len is updated appropriately.
2913  * @pmsg is the printk message to prepend.
2915 void console_prepend_replay(struct printk_message *pmsg)  in console_prepend_replay()  argument
2917 	console_prepend_message(pmsg, "** replaying previous printk message **\n");  in console_prepend_replay()
2924  * @pmsg will contain the formatted result. @pmsg->pbufs must point to a
2936  * of @pmsg are valid. (See the documentation of struct printk_message
2937  * for information about the @pmsg fields.)
2939 bool printk_get_next_message(struct printk_message *pmsg, u64 seq,  in printk_get_next_message()  argument
2942 	struct printk_buffers *pbufs = pmsg->pbufs;  in printk_get_next_message()
2943 	const size_t scratchbuf_sz = sizeof(pbufs->scratchbuf);  in printk_get_next_message()
2944 	const size_t outbuf_sz = sizeof(pbufs->outbuf);  in printk_get_next_message()
2945 	char *scratchbuf = &pbufs->scratchbuf[0];  in printk_get_next_message()
2946 	char *outbuf = &pbufs->outbuf[0];  in printk_get_next_message()
2955 	 * Formatting normal messages is done in-place, so read the ringbuffer  in printk_get_next_message()
2966 	pmsg->seq = r.info->seq;  in printk_get_next_message()
2967 	pmsg->dropped = r.info->seq - seq;  in printk_get_next_message()
2970 	if (may_suppress && suppress_message_printing(r.info->level))  in printk_get_next_message()
2975 		len += msg_print_ext_body(outbuf + len, outbuf_sz - len,  in printk_get_next_message()
2976 					  &r.text_buf[0], r.info->text_len, &r.info->dev_info);  in printk_get_next_message()
2981 	pmsg->outbuf_len = len;  in printk_get_next_message()
3014  * Used as the printk buffers for non-panic, serialized console printing.
3039 	struct printk_message pmsg = {  in console_emit_next_record()  local
3046 	if (!printk_get_next_message(&pmsg, con->seq, is_extended, true))  in console_emit_next_record()
3049 	con->dropped += pmsg.dropped;  in console_emit_next_record()
3052 	if (pmsg.outbuf_len == 0) {  in console_emit_next_record()
3053 		con->seq = pmsg.seq + 1;  in console_emit_next_record()
3057 	if (con->dropped && !is_extended) {  in console_emit_next_record()
3058 		console_prepend_dropped(&pmsg, con->dropped);  in console_emit_next_record()
3059 		con->dropped = 0;  in console_emit_next_record()
3072 		con->write(con, outbuf, pmsg.outbuf_len);  in console_emit_next_record()
3073 		con->seq = pmsg.seq + 1;  in console_emit_next_record()
3092 		con->write(con, outbuf, pmsg.outbuf_len);  in console_emit_next_record()
3097 		con->seq = pmsg.seq + 1;  in console_emit_next_record()
3181 				printk_seq = con->seq;  in console_flush_all()
3255 		 * Re-check if there is a new record to flush. If the trylock  in __console_flush_and_unlock()
3262  * console_unlock - unblock the legacy console subsystem from printing
3286  * console_conditional_schedule - yield the CPU if required
3315 		if ((console_srcu_read_flags(c) & CON_ENABLED) && c->unblank) {  in console_unblank()
3329 	 * In that case, attempt a trylock as best-effort.  in console_unblank()
3332 		/* Semaphores are not NMI-safe. */  in console_unblank()
3352 		if ((console_srcu_read_flags(c) & CON_ENABLED) && c->unblank)  in console_unblank()
3353 			c->unblank();  in console_unblank()
3391 			c->seq = seq;  in __console_rewind_all()
3398  * console_flush_on_panic - flush console content on panic
3413 	 *   - if it is contended, it must be ignored anyway  in console_flush_on_panic()
3414 	 *   - console_lock() and console_trylock() block and fail  in console_flush_on_panic()
3415 	 *     respectively in panic for non-panic CPUs  in console_flush_on_panic()
3416 	 *   - semaphores are not NMI-safe  in console_flush_on_panic()
3456 		if (!c->device)  in console_device()
3458 		driver = c->device(c, index);  in console_device()
3471  * re-enable output afterwards.
3477 	console_srcu_write_flags(console, console->flags & ~CON_ENABLED);  in console_stop()
3496 	console_srcu_write_flags(console, console->flags | CON_ENABLED);  in console_start()
3497 	is_nbcon = console->flags & CON_NBCON;  in console_start()
3560 			printk_seq = con->seq;  in legacy_kthread_should_wakeup()
3606 	sched_set_normal(printk_legacy_kthread, -20);  in legacy_kthread_create()
3612  * printk_kthreads_shutdown - shutdown all threaded printers
3627 			if (con->flags & CON_NBCON)  in printk_kthreads_shutdown()
3670 				if (con->flags & CON_NBCON)  in printk_kthreads_check_locked()
3698 		if (!(con->flags & CON_NBCON))  in printk_kthreads_check_locked()
3727 	pr_info("debug: skip boot console de-registration.\n");  in keep_bootcon_setup()
3738 	if (!newcon->setup)  in console_call_setup()
3743 	err = newcon->setup(newcon, options);  in console_call_setup()
3765 	     i < MAX_CMDLINECONSOLES && (c->name[0] || c->devname[0]);  in try_enable_preferred_console()
3768 		if (!c->name[0])  in try_enable_preferred_console()
3770 		if (c->user_specified != user_specified)  in try_enable_preferred_console()
3772 		if (!newcon->match ||  in try_enable_preferred_console()
3773 		    newcon->match(newcon, c->name, c->index, c->options) != 0) {  in try_enable_preferred_console()
3775 			BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name));  in try_enable_preferred_console()
3776 			if (strcmp(c->name, newcon->name) != 0)  in try_enable_preferred_console()
3778 			if (newcon->index >= 0 &&  in try_enable_preferred_console()
3779 			    newcon->index != c->index)  in try_enable_preferred_console()
3781 			if (newcon->index < 0)  in try_enable_preferred_console()
3782 				newcon->index = c->index;  in try_enable_preferred_console()
3787 			err = console_call_setup(newcon, c->options);  in try_enable_preferred_console()
3791 		newcon->flags |= CON_ENABLED;  in try_enable_preferred_console()
3793 			newcon->flags |= CON_CONSDEV;  in try_enable_preferred_console()
3799 	 * without matching. Accept the pre-enabled consoles only when match()  in try_enable_preferred_console()
3802 	if (newcon->flags & CON_ENABLED && c->user_specified ==	user_specified)  in try_enable_preferred_console()
3805 	return -ENOENT;  in try_enable_preferred_console()
3811 	if (newcon->index < 0)  in try_enable_default_console()
3812 		newcon->index = 0;  in try_enable_default_console()
3817 	newcon->flags |= CON_ENABLED;  in try_enable_default_console()
3819 	if (newcon->device)  in try_enable_default_console()
3820 		newcon->flags |= CON_CONSDEV;  in try_enable_default_console()
3830 	if (newcon->flags & (CON_PRINTBUFFER | CON_BOOT)) {  in get_init_console_seq()
3850 			 * guarantee safe access to console->seq.  in get_init_console_seq()
3875 					if (!(con->flags & CON_BOOT) ||  in get_init_console_seq()
3876 					    !(con->flags & CON_ENABLED)) {  in get_init_console_seq()
3880 					if (con->flags & CON_NBCON)  in get_init_console_seq()
3883 						seq = con->seq;  in get_init_console_seq()
3909  * early_printk) - sometimes before setup_arch() completes - be careful
3910  * of what kernel features are used - they may not be initialised yet.
3912  * There are two types of consoles - bootconsoles (early_printk) and
3915  *  - Any number of bootconsoles can be registered at any time.
3916  *  - As soon as a "real" console is registered, all bootconsoles
3918  *  - Once a "real" console is registered, any attempt to register a
3923 	bool use_device_lock = (newcon->flags & CON_NBCON) && newcon->write_atomic;  in register_console()
3935 					 con->name, con->index)) {  in register_console()
3939 		if (con->flags & CON_BOOT)  in register_console()
3946 	if ((newcon->flags & CON_BOOT) && realcon_registered) {  in register_console()
3948 			newcon->name, newcon->index);  in register_console()
3952 	if (newcon->flags & CON_NBCON) {  in register_console()
3974 		if (hlist_empty(&console_list) || !console_first()->device ||  in register_console()
3975 		    console_first()->flags & CON_BOOT) {  in register_console()
3984 	if (err == -ENOENT)  in register_console()
3988 	if (err || newcon->flags & CON_BRL) {  in register_console()
3989 		if (newcon->flags & CON_NBCON)  in register_console()
4001 	    ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) {  in register_console()
4002 		newcon->flags &= ~CON_PRINTBUFFER;  in register_console()
4005 	newcon->dropped = 0;  in register_console()
4008 	if (newcon->flags & CON_NBCON) {  in register_console()
4013 		newcon->seq = init_seq;  in register_console()
4016 	if (newcon->flags & CON_BOOT)  in register_console()
4030 		newcon->device_lock(newcon, &flags);  in register_console()
4033 	 * Put this console in the list - keep the  in register_console()
4038 		newcon->flags |= CON_CONSDEV;  in register_console()
4039 		hlist_add_head_rcu(&newcon->node, &console_list);  in register_console()
4041 	} else if (newcon->flags & CON_CONSDEV) {  in register_console()
4043 		console_srcu_write_flags(console_first(), console_first()->flags & ~CON_CONSDEV);  in register_console()
4044 		hlist_add_head_rcu(&newcon->node, &console_list);  in register_console()
4047 		hlist_add_behind_rcu(&newcon->node, console_list.first);  in register_console()
4058 		newcon->device_unlock(newcon, flags);  in register_console()
4064 	 * we get the "console xxx enabled" message on all the consoles -  in register_console()
4065 	 * boot consoles, real consoles, etc - this is to ensure that end  in register_console()
4071 	    ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&  in register_console()
4076 			if (con->flags & CON_BOOT)  in register_console()
4091 	bool use_device_lock = (console->flags & CON_NBCON) && console->write_atomic;  in unregister_console_locked()
4110 		res = -ENODEV;  in unregister_console_locked()
4111 	else if (console_is_usable(console, console->flags, true))  in unregister_console_locked()
4115 	console_srcu_write_flags(console, console->flags & ~CON_ENABLED);  in unregister_console_locked()
4125 		console->device_lock(console, &flags);  in unregister_console_locked()
4127 	hlist_del_init_rcu(&console->node);  in unregister_console_locked()
4130 		console->device_unlock(console, flags);  in unregister_console_locked()
4141 	if (!hlist_empty(&console_list) && console->flags & CON_CONSDEV)  in unregister_console_locked()
4142 		console_srcu_write_flags(console_first(), console_first()->flags | CON_CONSDEV);  in unregister_console_locked()
4151 	if (console->flags & CON_NBCON)  in unregister_console_locked()
4156 	if (console->exit)  in unregister_console_locked()
4157 		res = console->exit(console);  in unregister_console_locked()
4164 		if (c->flags & CON_BOOT)  in unregister_console_locked()
4167 		if (c->flags & CON_NBCON)  in unregister_console_locked()
4197  * console_force_preferred_locked - force a registered console preferred
4216 	 * Delete, but do not re-initialize the entry. This allows the console  in console_force_preferred_locked()
4220 	hlist_del_rcu(&con->node);  in console_force_preferred_locked()
4225 	 * list pointer can be re-initialized.  in console_force_preferred_locked()
4229 	con->flags |= CON_CONSDEV;  in console_force_preferred_locked()
4230 	WARN_ON(!con->device);  in console_force_preferred_locked()
4233 	console_srcu_write_flags(cur_pref_con, cur_pref_con->flags & ~CON_CONSDEV);  in console_force_preferred_locked()
4234 	hlist_add_head_rcu(&con->node, &console_list);  in console_force_preferred_locked()
4290 		if (!(con->flags & CON_BOOT))  in printk_late_init()
4295 		    init_section_contains(con->write, 0) ||  in printk_late_init()
4296 		    init_section_contains(con->read, 0) ||  in printk_late_init()
4297 		    init_section_contains(con->device, 0) ||  in printk_late_init()
4298 		    init_section_contains(con->unblank, 0) ||  in printk_late_init()
4299 		    init_section_contains(con->data, 0)) {  in printk_late_init()
4305 				con->name, con->index);  in printk_late_init()
4362 		 * console->seq. Releasing console_lock flushes more  in __pr_flush()
4394 				printk_seq = c->seq;  in __pr_flush()
4398 				diff += seq - printk_seq;  in __pr_flush()
4414 		slept_jiffies = jiffies - begin_jiffies;  in __pr_flush()
4416 		remaining_jiffies -= min(slept_jiffies, remaining_jiffies);  in __pr_flush()
4425  * pr_flush() - Wait for printing threads to catch up.
4430  * A value of 0 for @timeout_ms means no waiting will occur. A value of -1
4445  * Delayed printk version, for scheduler-internal messages:
4499  * wake_up_klogd - Wake kernel logging daemon
4514  * defer_console_output - Wake kernel logging daemon and trigger
4560  * every 5s to make a denial-of-service attack impossible.
4571  * printk_timed_ratelimit - caller-controlled printk ratelimiting
4582 	unsigned long elapsed = jiffies - *caller_jiffies;  in printk_timed_ratelimit()
4596  * kmsg_dump_register - register a kernel log dumper.
4601  * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
4606 	int err = -EBUSY;  in kmsg_dump_register()
4609 	if (!dumper->dump)  in kmsg_dump_register()
4610 		return -EINVAL;  in kmsg_dump_register()
4614 	if (!dumper->registered) {  in kmsg_dump_register()
4615 		dumper->registered = 1;  in kmsg_dump_register()
4616 		list_add_tail_rcu(&dumper->list, &dump_list);  in kmsg_dump_register()
4626  * kmsg_dump_unregister - unregister a kmsg dumper.
4630  * %-EINVAL otherwise.
4635 	int err = -EINVAL;  in kmsg_dump_unregister()
4638 	if (dumper->registered) {  in kmsg_dump_unregister()
4639 		dumper->registered = 0;  in kmsg_dump_unregister()
4640 		list_del_rcu(&dumper->list);  in kmsg_dump_unregister()
4671  * kmsg_dump_desc - dump kernel log to kernel message dumpers.
4689 		enum kmsg_dump_reason max_reason = dumper->max_reason;  in kmsg_dump_desc()
4703 		dumper->dump(dumper, &detail);  in kmsg_dump_desc()
4709  * kmsg_dump_get_line - retrieve one kmsg log line
4713  * @size: maximum size of the buffer
4726 			char *line, size_t size, size_t *len)  in kmsg_dump_get_line()  argument
4735 	if (iter->cur_seq < min_seq)  in kmsg_dump_get_line()
4736 		iter->cur_seq = min_seq;  in kmsg_dump_get_line()
4738 	prb_rec_init_rd(&r, &info, line, size);  in kmsg_dump_get_line()
4742 		if (!prb_read_valid(prb, iter->cur_seq, &r))  in kmsg_dump_get_line()
4746 		if (!prb_read_valid_info(prb, iter->cur_seq,  in kmsg_dump_get_line()
4755 	iter->cur_seq = r.info->seq + 1;  in kmsg_dump_get_line()
4765  * kmsg_dump_get_buffer - copy kmsg log lines
4769  * @size: maximum size of the buffer
4784 			  char *buf, size_t size, size_t *len_out)  in kmsg_dump_get_buffer()  argument
4795 	if (!buf || !size)  in kmsg_dump_get_buffer()
4798 	if (iter->cur_seq < min_seq)  in kmsg_dump_get_buffer()
4799 		iter->cur_seq = min_seq;  in kmsg_dump_get_buffer()
4801 	if (prb_read_valid_info(prb, iter->cur_seq, &info, NULL)) {  in kmsg_dump_get_buffer()
4802 		if (info.seq != iter->cur_seq) {  in kmsg_dump_get_buffer()
4804 			iter->cur_seq = info.seq;  in kmsg_dump_get_buffer()
4809 	if (iter->cur_seq >= iter->next_seq)  in kmsg_dump_get_buffer()
4814 	 * into the user-provided buffer for this dump. Pass in size-1  in kmsg_dump_get_buffer()
4816 	 * not write more than size-1 bytes of text into @buf.  in kmsg_dump_get_buffer()
4818 	seq = find_first_fitting_seq(iter->cur_seq, iter->next_seq,  in kmsg_dump_get_buffer()
4819 				     size - 1, syslog, time);  in kmsg_dump_get_buffer()
4827 	prb_rec_init_rd(&r, &info, buf, size);  in kmsg_dump_get_buffer()
4830 		if (r.info->seq >= iter->next_seq)  in kmsg_dump_get_buffer()
4836 		prb_rec_init_rd(&r, &info, buf + len, size - len);  in kmsg_dump_get_buffer()
4839 	iter->next_seq = next_seq;  in kmsg_dump_get_buffer()
4849  * kmsg_dump_rewind - reset the iterator
4858 	iter->cur_seq = latched_seq_read_nolock(&clear_seq);  in kmsg_dump_rewind()
4859 	iter->next_seq = prb_next_seq(prb);  in kmsg_dump_rewind()
4864  * console_try_replay_all - try to replay kernel log on consoles
4892 static atomic_t printk_cpu_sync_owner = ATOMIC_INIT(-1);
4896  * __printk_cpu_sync_wait() - Busy wait until the printk cpu-reentrant
4905 	} while (atomic_read(&printk_cpu_sync_owner) != -1);  in __printk_cpu_sync_wait()
4910  * __printk_cpu_sync_try_get() - Try to acquire the printk cpu-reentrant
4946 	old = atomic_cmpxchg_acquire(&printk_cpu_sync_owner, -1,  in __printk_cpu_sync_try_get()
4948 	if (old == -1) {  in __printk_cpu_sync_try_get()
4966  * __printk_cpu_sync_put() - Release the printk cpu-reentrant spinning lock.
5003 			   -1); /* LMM(__printk_cpu_sync_put:B) */  in __printk_cpu_sync_put()