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kdb: Revive dmesg command

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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: Anton Vorontsov <anton.vorontsov@linaro.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Anton Vorontsov 2012-07-20 17:27:37 -07:00 committed by Linus Torvalds
parent 84a1caf145
commit bc792e612e
1 changed files with 33 additions and 58 deletions
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91
kernel/debug/kdb/kdb_main.c
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@ -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))
return 0;
while (start < end && (c = *KDB_WRAP(start)) &&
(p - buf) < sizeof(buf)-1) {
++start;
*p++ = c;
if (c == '\n')
break;
if (skip >= n || skip < 0)
return 0;
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;
}