arm64: use generic strnlen_user and strncpy_from_user functions

This patch implements the word-at-a-time interface for arm64 using the
same algorithm as ARM. We use the fls64 macro, which expands to a clz
instruction via a compiler builtin. Big-endian configurations make use
of the implementation from asm-generic.

With this implemented, we can replace our byte-at-a-time strnlen_user
and strncpy_from_user functions with the optimised generic versions.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 6d4dd22ee4b7..295bf2de7128 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -17,6 +17,8 @@ config ARM64
         select GENERIC_IRQ_SHOW
         select GENERIC_SCHED_CLOCK
         select GENERIC_SMP_IDLE_THREAD
+        select GENERIC_STRNCPY_FROM_USER
+        select GENERIC_STRNLEN_USER
         select GENERIC_TIME_VSYSCALL
         select HARDIRQS_SW_RESEND
         select HAVE_ARCH_TRACEHOOK