There is a bug in the new dmesg(1) code, affected are systems without
CONFIG_PRINTK_TIME and maybe some very old systems with kernel <= 2.6.16.
The problem is that dmesg incorrectly works with empty lines (e.g. "<6>\n").
Possible workaround is: dmesg -r
It's possible to reproduce by:
$ dmesg -r | wc -l
$ dmesg | wc -l
on affected systems the commands return different number of lines.
The bugfix is below. ... boys, why nobody uses -rc releases?
Karel
>From 22f69825778f992ff98ed100252bf5e00a15d9d1 Mon Sep 17 00:00:00 2001
From: Karel Zak <kzak@xxxxxxxxxx>
Date: Wed, 31 Aug 2011 12:28:39 +0200
Subject: [PATCH] dmesg: fix for non-CONFIG_PRINTK_TIME kernels
* dmesg(1) incorrectly assumes that lines like "<6>\n"
are broken.
* it's more robust to assume the end of the record is "\n<"
* print \n for empty lines
Reported-by: "Gabor Z. Papp" <gzp@xxxxxxx>
Signed-off-by: Karel Zak <kzak@xxxxxxxxxx>
---
sys-utils/dmesg.c | 16 ++++++++--------
1 files changed, 8 insertions(+), 8 deletions(-)
diff --git a/sys-utils/dmesg.c b/sys-utils/dmesg.c
index 6090f4e..8e7bb4b 100644
--- a/sys-utils/dmesg.c
+++ b/sys-utils/dmesg.c
@@ -442,12 +442,12 @@ static int get_next_record(struct dmesg_control *ctl, struct dmesg_record *rec)
if (!begin)
begin = p;
- if (*p == '\n')
- end = p;
if (i + 1 == rec->next_size) {
end = p + 1;
i++;
- }
+ } else if (*p == '\n' && *(p + 1) == '<')
+ end = p;
+
if (begin && !*begin)
begin = NULL; /* zero(s) at the end of the buffer? */
if (!begin || !end)
@@ -469,9 +469,6 @@ static int get_next_record(struct dmesg_control *ctl, struct dmesg_record *rec)
}
}
- if (end <= begin)
- return -1; /* error */
-
if (*begin == '[' && (*(begin + 1) == ' ' ||
isdigit(*(begin + 1)))) {
if (ctl->delta || ctl->ctime) {
@@ -534,12 +531,15 @@ static void print_buffer(const char *buf, size_t size,
}
while (get_next_record(ctl, &rec) == 0) {
- if (!rec.mesg_size)
- continue;
if (!accept_record(ctl, &rec))
continue;
+ if (!rec.mesg_size) {
+ putchar('\n');
+ continue;
+ }
+
if (ctl->decode && rec.level >= 0 && rec.facility >= 0)
printf("%-6s:%-6s: ", facility_names[rec.facility].name,
level_names[rec.level].name);
--
1.7.6
--
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