Syslinux - Jul 2003 - Weird PXE calling convention question

Hi,

I am mucking around with the pxelinux code for S&G's and I have a
generic question about the pxe calling convention:

Does the parameter structure and opcode HAVE to be passed onto the stack
the PXE BIOS passed in when the pxelinux binary is executed at 0:7C00?

The PXE spec says:

"SS:SP is to contain the address of the beginning of the unused portion
of the PXE services stack."

(not sure exactly what that means yet)

I ask this because I'm getting a General Failure Error (ax = 0x1) and I
think its because I am using a different stack.  I also notice that when I do
get this error status nothing is copied into the buffer I supply (like a PXENV
error code) which kinda sucks.  This leads me to believe an issue with
me setting up a different stack before the far call.
>From the code:
; That is all pushed onto the PXE stack.  Save the pointer to it 
; and switch to an internal stack.
mov [InitStack],sp
mov [InitStack+2],ss

Comment by me: I believe USE_PXE_PROVIDED_STACK is always set???

%if USE_PXE_PROVIDED_STACK
; Apparently some platforms go bonkers if we
; set up our own stack...
mov [BaseStack],sp
mov [BaseStack+4],ss
%endif

Basically, what do you mean by bonkers?! :-)!  Do calls start to fail
like I described or the box just hangs (general fault or something)?

Thanks!

-aps

-- 
"We've duplicated this [horror] in the Sega Labs before - it's
where the Sega CD came from."
-MegaTokyo

Alexander Sack wrote:
> Hi,
> 
> I am mucking around with the pxelinux code for S&G's and I have a
> generic question about the pxe calling convention:
> 
> Does the parameter structure and opcode HAVE to be passed onto the stack
> the PXE BIOS passed in when the pxelinux binary is executed at 0:7C00?
> 
I have found stacks that fail if they don't.
> 
> Basically, what do you mean by bonkers?! :-)!  Do calls start to fail
> like I described or the box just hangs (general fault or something)?
> 
It varies :(

	-hpa