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Date:      Wed, 23 Jan 2002 09:39:46 -0800
From:      Michael Smith <msmith@freebsd.org>
To:        Brian Reichert <reichert@numachi.com>
Cc:        Greg Black <gjb@gbch.net>, "Roger 'Rocky' Vetterberg" <listsub@rambo.simx.org>, Brooks Davis <brooks@one-eyed-alien.net>, hackers@freebsd.org
Subject:   Re: cpu info in userland 
Message-ID:  <200201231739.g0NHdkb00871@mass.dis.org>
In-Reply-To: Your message of "Wed, 23 Jan 2002 11:39:09 EST." <20020123113909.P2872@numachi.com> 

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> On Tue, Jan 22, 2002 at 05:47:00PM -0800, Michael Smith wrote:
> > The message buffer is not perturbed by the boot process unless the BIOS 
> > overwrites it.  If the BIOS doesn't overwrite it, it's preserved from one 
> > boot to the next.
> 
> I'm confused then.  Is this 'message buffer' not a construct of
> the kernel?  Where does it exist?

It's just a region of memory; given an unchanged system configuration, 
it'll be in the same place every time you boot.

The reason it's not cleared is simple; if the system crashes for some 
reason, and the crash message can't be written to disk (eg. it's a kernel 
trap, etc.), when the system reboots it will be picked up out of the 
message buffer and saved.



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