arm64: kernel: avoid literal load of virtual address with MMU off

arm64: kernel: avoid literal load of virtual address with MMU off

Literal loads of virtual addresses are subject to runtime relocation when
CONFIG_RELOCATABLE=y, and given that the relocation routines run with the
MMU and caches enabled, literal loads of relocated values performed with
the MMU off are not guaranteed to return the latest value unless the
memory covering the literal is cleaned to the PoC explicitly.

So defer the literal load until after the MMU has been enabled, just like
we do for primary_switch() and secondary_switch() in head.S.

Change-Id: I11b1884662f37bc2664f286f6278e4a6af2d5c76
Fixes: 1e48ef7fcc37 ("arm64: add support for building vmlinux as a relocatable PIE binary")
Cc: <stable@vger.kernel.org> # 4.6+
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Git-Commit: bc9f3d7788a88d080a30599bde68f383daf8f8a5
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Signed-off-by: Arun KS <arunks@codeaurora.org>