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Commit bc792e61 authored by Anton Vorontsov's avatar Anton Vorontsov Committed by Linus Torvalds
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kdb: Revive dmesg command 



The kgdb dmesg command is broken after the printk rework.  The old logic
in kdb code makes no sense in terms of current printk/logging storage
format, and KDB simply hangs forever.

This patch revives the command by switching to kmsg_dumper iterator.

The code is now much more simpler and shorter.

Signed-off-by: default avatarAnton Vorontsov <anton.vorontsov@linaro.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 84a1caf1

kernel/debug/kdb/kdb_main.c

+33 −58
Original line number Diff line number Diff line
@@ -14,6 +14,7 @@ 
#include <linux/ctype.h>

#include <linux/string.h>

#include <linux/kernel.h>

#include <linux/kmsg_dump.h>

#include <linux/reboot.h>

#include <linux/sched.h>

#include <linux/sysrq.h>
@@ -2040,8 +2041,15 @@ static int kdb_env(int argc, const char **argv) 
 */

static int kdb_dmesg(int argc, const char **argv)

{

	char *syslog_data[4], *start, *end, c = '\0', *p;

	int diag, logging, logsize, lines = 0, adjust = 0, n;

	int diag;

	int logging;

	int lines = 0;

	int adjust = 0;

	int n = 0;

	int skip = 0;

	struct kmsg_dumper dumper = { .active = 1 };

	size_t len;

	char buf[201];



	if (argc > 2)

		return KDB_ARGCOUNT;
@@ -2064,22 +2072,10 @@ static int kdb_dmesg(int argc, const char **argv) 
		kdb_set(2, setargs);

	}



	/* syslog_data[0,1] physical start, end+1.  syslog_data[2,3]

	 * logical start, end+1. */

	kdb_syslog_data(syslog_data);

	if (syslog_data[2] == syslog_data[3])

		return 0;

	logsize = syslog_data[1] - syslog_data[0];

	start = syslog_data[2];

	end = syslog_data[3];

#define KDB_WRAP(p) (((p - syslog_data[0]) % logsize) + syslog_data[0])

	for (n = 0, p = start; p < end; ++p) {

		c = *KDB_WRAP(p);

		if (c == '\n')

			++n;

	}

	if (c != '\n')

		++n;

	kmsg_dump_rewind(&dumper);

	while (kmsg_dump_get_line(&dumper, 1, NULL, 0, NULL))

		n++;



	if (lines < 0) {

		if (adjust >= n)

			kdb_printf("buffer only contains %d lines, nothing "
@@ -2087,21 +2083,11 @@ static int kdb_dmesg(int argc, const char **argv) 
		else if (adjust - lines >= n)

			kdb_printf("buffer only contains %d lines, last %d "

				   "lines printed\n", n, n - adjust);

		if (adjust) {

			for (; start < end && adjust; ++start) {

				if (*KDB_WRAP(start) == '\n')

					--adjust;

			}

			if (start < end)

				++start;

		}

		for (p = start; p < end && lines; ++p) {

			if (*KDB_WRAP(p) == '\n')

				++lines;

		}

		end = p;

		skip = adjust;

		lines = abs(lines);

	} else if (lines > 0) {

		int skip = n - (adjust + lines);

		skip = n - lines - adjust;

		lines = abs(lines);

		if (adjust >= n) {

			kdb_printf("buffer only contains %d lines, "

				   "nothing printed\n", n);
@@ -2112,35 +2098,24 @@ static int kdb_dmesg(int argc, const char **argv) 
			kdb_printf("buffer only contains %d lines, first "

				   "%d lines printed\n", n, lines);

		}

		for (; start < end && skip; ++start) {

			if (*KDB_WRAP(start) == '\n')

				--skip;

		}

		for (p = start; p < end && lines; ++p) {

			if (*KDB_WRAP(p) == '\n')

				--lines;

		}

		end = p;

	} else {

		lines = n;

	}

	/* Do a line at a time (max 200 chars) to reduce protocol overhead */

	c = '\n';

	while (start != end) {

		char buf[201];

		p = buf;

		if (KDB_FLAG(CMD_INTERRUPT))



	if (skip >= n || skip < 0)

		return 0;

		while (start < end && (c = *KDB_WRAP(start)) &&

		       (p - buf) < sizeof(buf)-1) {

			++start;

			*p++ = c;

			if (c == '\n')

				break;



	kmsg_dump_rewind(&dumper);

	while (kmsg_dump_get_line(&dumper, 1, buf, sizeof(buf), &len)) {

		if (skip) {

			skip--;

			continue;

		}

		*p = '\0';

		kdb_printf("%s", buf);

		if (!lines--)

			break;



		kdb_printf("%.*s\n", (int)len - 1, buf);

	}

	if (c != '\n')

		kdb_printf("\n");



	return 0;

}