ARM: poison memory between kuser helpers

Poison the memory between each kuser helper.  This ensures that any
branch between the kuser helpers will be appropriately trapped.

Change-Id: Ifa4abe51d3dd89a96670a8609cd472fa03988e7e
Cc: <stable@vger.kernel.org>
Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Git-commit: 5b43e7a383d69381ffe53423e46dd0fafae07da3
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
CRs-fixed: 561044
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>
Signed-off-by: Willi Ye <williye97@gmail.com>

Conflicts:
	arch/arm/kernel/entry-armv.S
Revert "ARM: poison memory between kuser helpers"

This reverts commit f28684a36654dcc99508e2fdd97f4609d8dfb73e.

Conflicts:
	arch/arm/kernel/entry-armv.S
Revert "kernel: gtod: vsyscall"

This reverts commit ae62ada36d6f79c6dd4e3d20a01c45e14e2bc766.
Revert "ARM: poison memory between kuser helpers"

This reverts commit b77063625841a7ce042909f10e587d8e00b26ffe.

Conflicts:
	arch/arm/kernel/entry-armv.S