linux-kernel - Duplicate vsyscall/vdso gettimeofday implementations on x86

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Date:	Fri, 17 Jul 2009 15:02:10 -0700
From:	john stultz <johnstul@...ibm.com>
To:	Andi Kleen <andi@...stfloor.org>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...x.de>
Cc:	lkml <linux-kernel@...r.kernel.org>
Subject: Duplicate vsyscall/vdso gettimeofday implementations on x86_64

Hey Andi, Ingo, Thomas,
	I ran across an oddity recently in the x86_64 vsyscall code.
Specifically I was looking at the vsyscall clock_gettime()
implementation in arch/x86/vdso/vclock_gettime.c, and noticed there is a
vsyscall gettimeofday implementation there too! This seems to duplicate
the do_vgettimeofday implementation in arch/x86/kernel/vsyscall_64.c

I think the implementation in vclock_gettime.c is nice, as it mostly
reuses the clock_gettime() code, but I don't think it actually gets
called.

I'm a little worried about just switching it out, and cleaning it up, as
I don't know enough yet about how the vgettimeofday is called from glibc
(I thought it was a static "jump to this page and run" mapping).

Andi: You wrote the vclock_gettime.c, do you have any pointers about
where you were going with this? Is there a reason you didn't clean it up
when you implemented it originally?

thanks
-john

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