linux-kernel - Re: [GIT PULL] x86/paravirt for v2.6.33

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Date:	Wed, 09 Dec 2009 10:54:54 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Jeremy Fitzhardinge <jeremy@...p.org>, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [GIT PULL] x86/paravirt for v2.6.33

On 12/09/2009 10:47 AM, Linus Torvalds wrote:
> 
> NOTE NOTE NOTE! Totally untested. Is the second argument even in %edx? I 
> don't remember, I didn't check, I'm just throwing this out as a "hey, 
> maybe something _like_ this can work" patch, and will be immediately 
> removing it from my machine after sending this email.
> 

The second argument is in %edx, but unlike 64 bits, it is not loaded
into that register a priory ("asmlinkage" means arguments are on the stack.)

As such, we need something looking like:

#define PTREGSCALL0(name)	\
ptregs_##name:			\
	leal	4(%esp),%eax;	\
	jmp sys_##name

#define PTREGSCALL1(name)	\
ptregs_##name:			\
	movl	4(%esp),%eax;	\
	leal	4(%esp),%edx;	\
	jmp sys_##name

#define PTREGSCALL2(name)	\
ptregs_##name:			\
	movl	4(%esp),%eax;	\
	movl	8(%esp),%edx;	\
	leal	4(%esp),%ecx;	\
	jmp sys_##name

If we need more than two arguments + pt_regs, then we have to set up a
temporary stack frame.

[Sorry, I'm sitting in a meeting so I can't actually write up a real patch]

	-hpa
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