Re: [Xen-devel] [PATCH] 32on64 call gate support

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 26/1/07 10:07 am, "Petersson, Mats" <Mats.Petersson@xxxxxxx> wrote:

>> Do we know that anyone uses 64-bit call gates? I would have thought it
>> unlikely.
> 
> I agree, it's VERY unlikely that anyone uses call-gates in 64-bit mode.
> There are other, better, ways to do system calls, including the
> dedicated SYSCALL instruction. Since 64-bit code is "new", it's unlikely
> to use old ways of doing things "just because there was nothing else
> around at the time".

Of course, it begs the question why call gates weren't stripped from long
mode along with other ancient architectural baggage.

Perhaps the idea was to allow compat-mode applications relying on call gates
to be supported? So the OS would be responsible for allocating 64-bit call
gates instead of 32-bit call gates?

Anyhow, this is a bridge we should probably only cross if we come to it.

 -- Keir



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