Commit 726b5097 authored by John Ogness's avatar John Ogness Committed by Petr Mladek
Browse files

printk: refactor kmsg_dump_get_buffer() 



kmsg_dump_get_buffer() requires nearly the same logic as
syslog_print_all(), but uses different variable names and
does not make use of the ringbuffer loop macros. Modify
kmsg_dump_get_buffer() so that the implementation is as similar
to syslog_print_all() as possible.

A follow-up commit will move this common logic into a
separate helper function.

Signed-off-by: default avatarJohn Ogness <john.ogness@linutronix.de>
Reviewed-by: default avatarPetr Mladek <pmladek@suse.com>
Signed-off-by: default avatarPetr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210303101528.29901-6-john.ogness@linutronix.de
parent e831e400

include/linux/kmsg_dump.h

+1 −1
Original line number Diff line number Diff line
@@ -62,7 +62,7 @@ bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog, 
			char *line, size_t size, size_t *len);



bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,

			  char *buf, size_t size, size_t *len);

			  char *buf, size_t size, size_t *len_out);



void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper);

kernel/printk/printk.c

+33 −29
Original line number Diff line number Diff line
@@ -3410,7 +3410,7 @@ EXPORT_SYMBOL_GPL(kmsg_dump_get_line); 
 * @syslog: include the "<4>" prefixes

 * @buf: buffer to copy the line to

 * @size: maximum size of the buffer

 * @len: length of line placed into buffer

 * @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.
@@ -3424,7 +3424,7 @@ EXPORT_SYMBOL_GPL(kmsg_dump_get_line); 
 * read.

 */

bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,

			  char *buf, size_t size, size_t *len)

			  char *buf, size_t size, size_t *len_out)

{

	struct printk_info info;

	unsigned int line_count;
@@ -3432,12 +3432,10 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog, 
	unsigned long flags;

	u64 seq;

	u64 next_seq;

	size_t l = 0;

	size_t len = 0;

	bool ret = false;

	bool time = printk_time;



	prb_rec_init_rd(&r, &info, buf, size);



	if (!dumper->active || !buf || !size)

		goto out;
@@ -3455,48 +3453,54 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog, 
		goto out;

	}



	/* calculate length of entire buffer */

	seq = dumper->cur_seq;

	while (prb_read_valid_info(prb, seq, &info, &line_count)) {

		if (r.info->seq >= dumper->next_seq)

	/*

	 * Find first record that fits, including all following records,

	 * into the user-provided buffer for this dump.

	 */



	prb_for_each_info(dumper->cur_seq, prb, seq, &info, &line_count) {

		if (info.seq >= dumper->next_seq)

			break;

		l += get_record_print_text_size(&info, line_count, syslog, time);

		seq = r.info->seq + 1;

		len += get_record_print_text_size(&info, line_count, syslog, time);

	}



	/* move first record forward until length fits into the buffer */

	seq = dumper->cur_seq;

	while (l >= size && prb_read_valid_info(prb, seq,

						&info, &line_count)) {

		if (r.info->seq >= dumper->next_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 the best effort

	 * that prevents an infinite loop.

	 */

	prb_for_each_info(dumper->cur_seq, prb, seq, &info, &line_count) {

		if (len < size || info.seq >= dumper->next_seq)

			break;

		l -= get_record_print_text_size(&info, line_count, syslog, time);

		seq = r.info->seq + 1;

		len -= get_record_print_text_size(&info, line_count, syslog, time);

	}



	/* last message in next interation */

	/*

	 * Next kmsg_dump_get_buffer() invocation will dump block of

	 * older records stored right before this one.

	 */

	next_seq = seq;



	/* actually read text into the buffer now */

	l = 0;

	while (prb_read_valid(prb, seq, &r)) {

	prb_rec_init_rd(&r, &info, buf, size);



	len = 0;

	prb_for_each_record(seq, prb, seq, &r) {

		if (r.info->seq >= dumper->next_seq)

			break;



		l += record_print_text(&r, syslog, time);

		len += record_print_text(&r, syslog, time);



		/* adjust record to store to remaining buffer space */

		prb_rec_init_rd(&r, &info, buf + l, size - l);



		seq = r.info->seq + 1;

		/* Adjust record to store to remaining buffer space. */

		prb_rec_init_rd(&r, &info, buf + len, size - len);

	}



	dumper->next_seq = next_seq;

	ret = true;

	logbuf_unlock_irqrestore(flags);

out:

	if (len)

		*len = l;

	if (len_out)

		*len_out = len;

	return ret;

}

EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);