linux-kernel - Re: [question] x86/x86

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Message-ID: <4FD7AF24.8080607@zytor.com>
Date:	Tue, 12 Jun 2012 14:05:40 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Brandon Falk <bfalk@...ozolabs.com>
CC:	linux-kernel@...r.kernel.org
Subject: Re: [question] x86/x86_64 boot process

On 06/12/2012 01:49 PM, Brandon Falk wrote:
> Greetings. Please CC me on any responses as I do not subscribe to the list.
> 
> I'm currently working on a very very small boot loader. Currently it
> uses BIOS int 0x13 to load up the 'setup' segments to 0x9000:0x0000. I
> jump to this location, set up the kernel options, and then jump to
> 0x9020:0x0000. Everything goes great. However, I get the message 'No
> setup signature found...'. I'm assuming this is due to not loading up
> the protected-mode code. I'm slightly confused as to how the protected
> mode code is to be loaded. As my 'bzImage' is 2.6MB, I would need to
> raise the A20 line to possibly load this up. Does the kernel assist in
> this process at all? Should I set up a code32_start routine for my
> code to load up the kernel? Once I'm in protected mode, how will I
> even access the medium that the kernel is loaded from without creating
> a driver?
> 
> Currently the medium is a floppy image loaded in VMWare. It's a 64-bit
> system. I'm just looking to be pointed in the right direction for the
> next step (and if my current steps are valid for Protocol 2.10).
> 
> Here's the current code (the code is manually overwritten onto the
> bzImage, however only the code... the headers are left intact on the
> bzImage):
> 

Please read Documentation/x86/boot.txt.

	-hpa

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