[syslinux] PXE in wonderland

H. Peter Anvin hpa at zytor.com
Wed Nov 14 14:13:49 PST 2007

Firas Swidan, PhD wrote:
> After downloading and struggling a bit with pxelinux assembler code, I
> found out the problem: on the top of the file cpuinit.inc that is
> included from pxelinux.asm, the instruction "int 16h" causes havoc on my
> pc. Literally, a single instruction causes the whole pc to hang.
> Amazing! Would have never believed that. Anyhow, I disabled this
> instruction, compiled, and ran pxelinux and things went fine till it
> tried to download the kernel. For some reason, tftp refused to give the
> kernel, with permission denied. Digging more, I found that this is
> related to something called "checksum offload" and accompanied with a
> checksum error. I have also noticed that my pc's keyboard does not
> function at all once pxelinux starts executing.
> Now I am not sure how to proceed. I am also wondering if the instruction
> "int 16h" has such a far reaching effects. Could it be the reason for
> the failing checksum and the not responding keyboard (after all it
> managed to stuck my whole pc)?

Yes, INT 16h is calling the keyboard BIOS, and apparently your keyboard 
BIOS is screwed.


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