linux-kernel - Re: 64-syscall args on 32-bit vs syscall()

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Message-ID: <4BA11FD2.2090104@zytor.com>
Date:	Wed, 17 Mar 2010 11:30:42 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
CC:	Ulrich Drepper <drepper@...hat.com>, munroesj@...ibm.com,
	David Miller <davem@...emloft.net>, ralf@...ux-mips.org,
	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel@...savvy.com, torvalds@...ux-foundation.org
Subject: Re: 64-syscall args on 32-bit vs syscall()

On 03/17/2010 01:56 AM, Benjamin Herrenschmidt wrote:
>
> Ok, so I -may- be missing something, but I believe this won't break
> anything:
>
>   - You keep the existing syscall() exported by glibc for binary
> compatibility
>
>   - You add a new __syscall() (or whatever you want to name it) that adds
> a dummy argument at the beginning, and whose implementation shifts
> everything by 2 instead of 1 argument before calling into the kernel
>
>   - You define in unistd.h or whatever is relevant, a macro that does:
>
> #define syscall(__sysno, __args..) __syscall(0, _sysno, __args)
>

Again, this is *exactly* symbol versioning done by hand... we have 
proper symbol versioning, let's use it.

	-hpa
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