Assembler coding help needed. [solved, patch enclosed]

[John Baldwin]

On Sunday 11 January 2004 04:39 pm, Martin Nilsson wrote:
> Marcin Dalecki wrote:
>  > Martin Nilsson wrote:
>  >> I'm trying to find out why I can't boot 5.2 from USB CDROM on
>  >> Supermicro  motherboards. (I have an old Gateway P3 that can!).
>  >>
>  >> I've found out that that only 0x20 of 0x4c sectors of the loader are
>  >> read in and it therfor traps when executed. (read is only called once).
>  >>
>  >> load_notrunc:    sub %dh,%cl            # Update count
>  >>         push %eax            # Save
>  >>         call read            # Read it in
>  >
>  > The fun will be ^^^^ here. The rest is self contained and
>  > doesn't depend on CPU variant or periphery.
>
> I found the problem!
> The bios trashes %cx when reading from USB CD but not when reading from
> ATAPI CD.
>
> The attached patch fixes this and two other small nits in
> sys/boot/i386/cdboot/cdboot.s

Thanks for the nit fixes.

> Can somebody (jhb) commit this?
>
> This probably affects all Phoenix-Award bios equipped boxes. My old
> Gateway with AMI BIOS works as it should.

I will commit something similar.  I will save %cx around the BIOS call itself 
in the read function.

-- 
John Baldwin <jhb at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org