kernel: gtod: vsyscall

Introduce kernel user helper vsyscall to allow a higher performance
gettimeofday implementation in user-space.

Change-Id: I9b9971d217382129170ecd6a35461539dac9eebb
Signed-off-by: Brent DeGraaf <bdegraaf@codeaurora.org>
kernel: Add hooks for user-accessible timers in the kernel.

Hooks for user-accessible timers allow implementation of a
more efficient gettimeofday in user-space.

Change-Id: If2f63d010c1cf142eb84f3745617e756913e46f7
Signed-off-by: Brent DeGraaf <bdegraaf@codeaurora.org>
kernel: ARM-specific implementation of user-accessible timers

Expose a read-only timer page to user-space to allow for a more
efficient implementation of gettimeofday in user-space.

Change-Id: Ibd6ce41f5f4ff9435e4bf4582ef5de721283d56b
Signed-off-by: Brent DeGraaf <bdegraaf@codeaurora.org>
kernel: gtod: Add MSM-specific user-accessible timers

Enable MSM-specific timers to be readable from user-space.
This allows implementation of a higher-performance
gettimeofday in user-space.

Change-Id: I1f322b5396ee335b10aeb81c681593621d151176
Signed-off-by: Brent DeGraaf <bdegraaf@codeaurora.org>