Re: [Qemu-devel] [PATCH v6] Add optionrom compatible with fw_cfg DMA version

[Richard W.M. Jones]

On Tue, May 10, 2016 at 07:24:28PM +0200, Paolo Bonzini wrote:
> 
> 
> On 09/05/2016 18:48, Richard W.M. Jones wrote:
> > 
> > Of course we're well outside any standards here.  Can we tell clang
> > users to use the GCC/pre-compiled option ROMs :-?  Any other ideas?  I
> > don't think I've missed a flag (GCC has -fno-toplevel-reorder, but
> > clang 3.8 doesn't ...)
> 
> I guess the checksumming script (scripts/signrom.py) could take care of
> padding the file to a multiple of 512 bytes, and fill in the size in the
> third byte.  Then "_end" would not be necessary anymore and -m16 could
> replace the .code16 directive.

In my rather limited testing on gcc, gcc -m16 broke booting.  However
I've not investigated this further.  I'll do so shortly.

However I have a question: is there a formal standard or documentation
for the option ROM format?  Are we sticking to the (ancient) "BIOS Boot
Specification" or is there something newer?  (My copy is from 1996).

Rich.

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