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Date: Wed, 19 Sep 2012 19:03:47 +0200
From: Richard Cochran <richardcochran@gmail.com>
To: John Stultz <john.stultz@linaro.org>
Cc: Andy Lutomirski <luto@amacapital.net>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Tony Luck <tony.luck@intel.com>, Paul Mackerras <paulus@samba.org>,
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        Prarit Bhargava <prarit@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH 0/6][RFC] Rework vsyscall to avoid truncation/rounding
 issue in timekeeping core
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On Wed, Sep 19, 2012 at 09:31:35AM -0700, John Stultz wrote:

> On powerpc, I mean magic addresses where userland can find
> structures that it can use to calculate time.

...
 
> With powerpc, there is no arch specific kernel code involved, its
> just a data structure the kernel exports that is accessible to
> userland. The execution logic lives in userland libraries, or
> sometimes application code itself.

I took a brief look at arch/powerpc/kernel/vdso32/gettimeofday.S and
arch/powerpc/kernel/vdso64/gettimeofday.S, and I see what looks a lot
like functions

$ find arch/powerpc/kernel/vdso* -name gettimeofday.S|xargs grep FUNCTION_BEGIN

arch/powerpc/kernel/vdso32/gettimeofday.S:V_FUNCTION_BEGIN(__kernel_gettimeofday)
arch/powerpc/kernel/vdso32/gettimeofday.S:V_FUNCTION_BEGIN(__kernel_clock_gettime)
arch/powerpc/kernel/vdso32/gettimeofday.S:V_FUNCTION_BEGIN(__kernel_clock_getres)
arch/powerpc/kernel/vdso64/gettimeofday.S:V_FUNCTION_BEGIN(__kernel_gettimeofday)
arch/powerpc/kernel/vdso64/gettimeofday.S:V_FUNCTION_BEGIN(__kernel_clock_gettime)
arch/powerpc/kernel/vdso64/gettimeofday.S:V_FUNCTION_BEGIN(__kernel_clock_getres)
arch/powerpc/kernel/vdso64/gettimeofday.S:V_FUNCTION_BEGIN(__do_get_tspec)

and I wonder whether these could be done in C instead.

Thanks,
Richard