Re: Extboot Option Rom rewritten in C

[Anthony Liguori <aliguori@us.ibm.com>]

Hi Nguyen,

Nguyen Anh Quynh wrote:
> Hi Anthony,
>
> I spot a bug and few dead code in the extboot option rom. Perhaps the
> reason they are there is because less people want to look at assembly
> code, and it looks indeed scary.
>
> So I decided to rewrite it in C, using .code16gcc directive. Some advantages:
> - C code is easier to understand, find bugs, maintain and hack (so we
> can add more features in the future)
> - The binary image is same: 1.5K. The actual code size is also about
> the same size: around 1.2K. (gcc can optimize really well)
>   

I think converting to code16gcc is a good direction to go in.  I 
actually rewrote it myself using code16gcc but I ran into problems with 
segment assumptions and Windows guests.  I tried out your version with a 
Linux guest with good success but it fails with a win2k guest.

Have you tested with a Windows guest?  If we can work through the 
Windows issues, this is definitely the right way to go.

Regards,

Anthony Liguori

> See the code in attachment. The new code consists of a very small
> assembly file boot.S, which merely interfaces with the C code.
> "signrom" is modified to work with the new binary image.
>
> - To compile code, just run "make"
> - To save the original /usr/share/qemu/extboot.bin (to
> /usr/share/qemu/extboot.bin.org), just run "make save"
> - Then "make install" to install the new extboot.bin into /usr/share/qemu/
>
> I succesfully compile and run this option rom with virtio from
> 2.6.25-rc8 on Ubuntu 7.10.
>
> Any comment?
>
> Many thanks,
> Quynh
>   


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