linux-kernel - Re: [PATCH -v2] x86/hweight: Get rid of the special calling convention

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Message-ID: <ca79a89a-7240-8572-1688-ec5506c12665@zytor.com>
Date:	Tue, 10 May 2016 15:30:48 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Borislav Petkov <bp@...e.de>
Cc:	Peter Zijlstra <peterz@...radead.org>, x86-ml <x86@...nel.org>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Brian Gerst <brgerst@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Andi Kleen <andi@...stfloor.org>, zengzhaoxiu@....com,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kees Cook <keescook@...omium.org>,
	Zhaoxiu Zeng <zhaoxiu.zeng@...il.com>,
	Andy Lutomirski <luto@...capital.net>
Subject: Re: [PATCH -v2] x86/hweight: Get rid of the special calling
 convention

On 05/10/16 12:10, Borislav Petkov wrote:
> On Tue, May 10, 2016 at 12:03:48PM -0700, H. Peter Anvin wrote:
>> Also, to be fair... if the problem is with these being in C then we
>> could just do it in assembly easily enough.
> 
> I thought about converting the __sw_hweight* variants to asm but
> __sw_hweight32, for example, is 55 bytes here and that's a lot.
> 
> Or do you have a better idea?
> 
> peterz's sounds ok to me: we call a thunk which then calls __sw_hweight*
> after having saved regs properly - problem solved.
> 

I didn't mean inline assembly.

	-hpa