From mboxrd@z Thu Jan  1 00:00:00 1970
From: joe@perches.com (Joe Perches)
Date: Tue, 05 Jun 2012 17:19:31 -0700
Subject: [PATCH 0/8] Rework KERN_<LEVEL>
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To: linux-arm-kernel@lists.infradead.org
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On Wed, 2012-06-06 at 02:13 +0200, Kay Sievers wrote:
> The question is what happens if you inject your new binary two-byte
> prefix, like:
>   echo -e "\x01\x02Hello" > /dev/kmsg

It's not a 2 byte binary.
It's a leading ascii SOH and a standard ascii char
'0' ... '7' or 'd'.

#define KERN_EMERG	KERN_SOH "0"	/* system is unusable */
#define KERN_ALERT	KERN_SOH "1"	/* action must be taken immediately */
etc...

> And if that changes the log-level to "2" instead of the default "4"?

No it doesn't.

It's not triggering that because devkmsg_writev does
prefix parsing only on the old "<n>" form.