Message-ID: <50359FF8.7090609@zytor.com>
Date: Wed, 22 Aug 2012 20:14:00 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Andi Kleen <ak@linux.intel.com>
CC: Andi Kleen <andi@firstfloor.org>, linux-kernel@vger.kernel.org,
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Subject: Re: [PATCH 74/74] lto, workaround: Mark do_futex noinline to prevent
 clobbering ebp
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On 08/22/2012 07:29 PM, Andi Kleen wrote:
> How about just use register arguments for the first three arguments.
> This should work for the syscalls at least (may be too risky for all
> other asm entry points)

Well, it's just an effort to convert each one in turn...

> And for syscalls with more than three generate a stub that saves on the stack
> explicitely.  This could be done using the new fancy SYSCALL definition macros
> (except that arch/x86 would need to start using them too in its own code)

I don't think there is any point.  Just push the six potential arguments 
to the stack and be done with it.

> Or is there some subtle reason with syscall restart and updated args
> that prevents it?
>
> Perhaps newer gcc can do regparm(X), X > 3 too, may be worth trying.

No, there is no such ABI defined.

> Don't have time to look into this currently though.

Always the problem.

	-hpa


-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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