arm64: allow building with kcov coverage on ARM64

Add ARCH_HAS_KCOV to ARM64 config. To avoid potential crashes, disable
instrumentation of the files in arch/arm64/kvm/hyp/*.
Signed-off-by: Alexander Potapenko <glider@google.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Tested-by: James Morse <james.morse@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/Kconfig

@@ -7,6 +7,7 @@ config ARM64
 	select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
 	select ARCH_HAS_ELF_RANDOMIZE
 	select ARCH_HAS_GCOV_PROFILE_ALL
+	select ARCH_HAS_KCOV
 	select ARCH_HAS_SG_CHAIN
 	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
 	select ARCH_USE_CMPXCHG_LOCKREF

arch/arm64/kvm/hyp/Makefile

@@ -17,6 +17,10 @@ obj-$(CONFIG_KVM_ARM_HOST) += tlb.o
 obj-$(CONFIG_KVM_ARM_HOST) += hyp-entry.o
 obj-$(CONFIG_KVM_ARM_HOST) += s2-setup.o
 
+# KVM code is run at a different exception code with a different map, so
+# compiler instrumentation that inserts callbacks or checks into the code may
+# cause crashes. Just disable it.
 GCOV_PROFILE	:= n
 KASAN_SANITIZE	:= n
 UBSAN_SANITIZE	:= n
+KCOV_INSTRUMENT	:= n