arm/arm64: KVM: Enforce HYP read-only mapping of the kernel's rodata section

In order to be able to use C code in HYP, we're now mapping the kernel's
rodata in HYP. It works absolutely fine, except that we're mapping it RWX,
which is not what it should be.

Add a new HYP_PAGE_RO protection, and pass it as the protection flags
when mapping the rodata section.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

arch/arm/kvm/arm.c

@@ -1300,7 +1300,7 @@ static int init_hyp_mode(void)
 	}
 
 	err = create_hyp_mappings(kvm_ksym_ref(__start_rodata),
-				  kvm_ksym_ref(__end_rodata), PAGE_HYP);
+				  kvm_ksym_ref(__end_rodata), PAGE_HYP_RO);
 	if (err) {
 		kvm_err("Cannot map rodata section\n");
 		goto out_err;