Re: [PATCH 1/2] x86: Mark __vdso entries as asmlinkage

[H. Peter Anvin]

On 02/27/2014 12:11 PM, Andy Lutomirski wrote:
> 
> Hmm.  This sort of goes against existing x86_32 practice where,
> AFAICT, things that need a particular calling convention specify
> asmlinkage and everything else uses regparm(3) if config/kbuild thinks
> it's appropriate.
> 

That is not really true for things that aren't part of the kernel image
proper (e.g. the real mode code and so on.)  This is a very special case.

> But I'm happy to resubmit the patch if you prefer the CFLAGS approach
> for the 32-bit vdso.  I don't think anything will break, since I don't
> think that the 32-bit vdso has any other exported C code.

I think it is the better way to go.

>> It isn't any faster if the C library has to provide a wrapper just to
>> marshal parameters.
> 
> Probably true, given that the glibc wrapper could, in principle, use
> an optimized tail call.  Also, I see no reason why vdso functions,
> alone of all userspace code, should be special.

Yes, let's stick to the standard ABI.  The syscall entry point was very
special.

	-hpa


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