Xen hypercall calling convention

Xen hypercall calling convention

[Carl Patenaude Poulin]

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Hi folks,

On page 12 of "The Definitive Guide to the Xen Hypervisor", it is mentioned
that "Xen, like Linux, uses the MS-DOS calling convention, rather than the
UNIX convention used by FreeBSD."

I keep digging online and I can't find any information about an "MS-DOS
calling convention". We've already reverse engineered which registers are
used in what order from the Mini-OS source code, but I'm wondering if
there's a specification of this calling convention floating anywhere.

Also, is the x86_64 calling convention much different? Are the differences
following any particular standard?

Best

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Re: Xen hypercall calling convention

[Andrew Cooper]

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On 04/12/15 03:21, Carl Patenaude Poulin wrote:
> Hi folks,
>
> On page 12 of "The Definitive Guide to the Xen Hypervisor", it is
> mentioned that "Xen, like Linux, uses the MS-DOS calling convention,
> rather than the UNIX convention used by FreeBSD."
>
> I keep digging online and I can't find any information about an
> "MS-DOS calling convention".

Second google link,

www.agner.org/optimize/calling_conventions.pdf

except that you want to be looking for Windows 16bit as its alternative
name.


> We've already reverse engineered which registers are used in what
> order from the Mini-OS source code, but I'm wondering if there's a
> specification of this calling convention floating anywhere.

The in-tree public header files are the authoritative source of
information, so

http://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=xen/include/public/arch-x86/xen-x86_32.h;hb=HEAD

and

http://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=xen/include/public/arch-x86/xen-x86_64.h;hb=HEAD

respectively.

~Andrew


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