FROMLIST: arm64: entry: Hook up entry trampoline to exception vectors

FROMLIST: arm64: entry: Hook up entry trampoline to exception vectors

Hook up the entry trampoline to our exception vectors so that all
exceptions from and returns to EL0 go via the trampoline, which swizzles
the vector base register accordingly. Transitioning to and from the
kernel clobbers x30, so we use tpidrro_el0 and far_el1 as scratch
registers for native tasks.

Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Laura Abbott <labbott@redhat.com>
Tested-by: Shanker Donthineni <shankerd@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
(cherry picked from git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git
 commit 4bf3286d29f3a88425d8d8cd53428cbb8f865f04)

Change-Id: Id1e175bdaa0ec2bf8e59f941502183907902a710
[ghackmann@google.com: adjust context, replacing
 alternative_if_not ARM64_WORKAROUND_845719 block with upstream version]
Signed-off-by: Greg Hackmann <ghackmann@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>