[RFC/PATCH] ARM: VDSO support

[Adhemerval Zanella]

Hi,

On 03-04-2015 14:25, Nathan Lynch wrote:
> Future versions of Linux on 32-bit ARM are expected to provide fast
> user-space implementations of the following system calls:
>
> - gettimeofday
> - clock_gettime
>
> The kernel implementation depends on the ARMv7 Generic Timers
> Extension to accelerate these system calls.  So CPUs such as
> Cortex-A15 and -A7 benefit, while Cortex-A9, -A8, and pre-v7 CPUs do
> not.
>
> The kernel support is currently in linux-next and is slated for
> inclusion in Linux 4.1.  I plan to ping or resubmit this patch once
> Linux 4.1 is released, but would appreciate any preliminary review in
> the meantime.  For reference, the current kernel patch submission may
> be found here:
>
> http://lists.infradead.org/pipermail/linux-arm-kernel/2015-March/332573.html
>
> This patch adds support for the ARM VDSO to glibc.  I have run make
> check on OMAP5 using kernels with and without the VDSO, with no new
> failures.

LGTM. Also, you can tune latency a bit more by using IFUNC on gettimeofday.