Re: [question] x86/x86_64 boot process

[Brandon Falk]

All I really see related to the post-setup stage is:

'The 32-bit (non-real-mode) kernel starts at offset (setup_sects+1)*512
in the kernel file (again, if setup_sects == 0 the real value is 4.)
It should be loaded at address 0x10000 for Image/zImage kernels and
0x100000 for bzImage kernels.'

I've read this document a few times, and it doesn't seem to mention if
the kernel assists in loading. Do I have to load up the whole
protected-mode kernel? Just the first few sectors? I guess that's what
I'm trying to figure out, and I feel the boot.txt has not answered
that for me.

On Tue, Jun 12, 2012 at 5:05 PM, H. Peter Anvin <hpa@xxxxxxxxx> wrote:
> 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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