[PATCH] kvm: arm64: Disable compiler instrumentation for hypervisor code

[PATCH] kvm: arm64: Disable compiler instrumentation for hypervisor code

[Catalin Marinas]

With the recent rewrite of the arm64 KVM hypervisor code in C, enabling
certain options like KASAN would allow the compiler to generate memory
accesses or function calls to addresses not mapped at EL2. This patch
disables the compiler instrumentation on the arm64 hypervisor code for
gcov-based profiling (GCOV_KERNEL), undefined behaviour sanity checker
(UBSAN) and kernel address sanitizer (KASAN).

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christoffer Dall <christoffer.dall@linaro.org>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: <stable@vger.kernel.org> # 4.5+
---

A better fix, at least for KASAN, would be nice but that's a lot more
intrusive as we need to map the KASAN shadow into the EL2 space. In the
meantime, especially since it needs backporting to 4.5, this patch would
solve KASAN getting stuck with KVM (similar to what we do for EFI_STUB).

 arch/arm64/kvm/hyp/Makefile | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm64/kvm/hyp/Makefile b/arch/arm64/kvm/hyp/Makefile
index 826032bc3945..acde4782621a 100644
--- a/arch/arm64/kvm/hyp/Makefile
+++ b/arch/arm64/kvm/hyp/Makefile
@@ -12,3 +12,7 @@ obj-$(CONFIG_KVM_ARM_HOST) += switch.o
 obj-$(CONFIG_KVM_ARM_HOST) += fpsimd.o
 obj-$(CONFIG_KVM_ARM_HOST) += tlb.o
 obj-$(CONFIG_KVM_ARM_HOST) += hyp-entry.o
+
+GCOV_PROFILE	:= n
+KASAN_SANITIZE	:= n
+UBSAN_SANITIZE	:= n

[PATCH] kvm: arm64: Disable compiler instrumentation for hypervisor code

[Christoffer Dall]

On Mon, Mar 21, 2016 at 11:00:17AM +0000, Catalin Marinas wrote:
> With the recent rewrite of the arm64 KVM hypervisor code in C, enabling
> certain options like KASAN would allow the compiler to generate memory
> accesses or function calls to addresses not mapped at EL2. This patch
> disables the compiler instrumentation on the arm64 hypervisor code for
> gcov-based profiling (GCOV_KERNEL), undefined behaviour sanity checker
> (UBSAN) and kernel address sanitizer (KASAN).
> 
> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Christoffer Dall <christoffer.dall@linaro.org>
> Cc: Marc Zyngier <marc.zyngier@arm.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: <stable@vger.kernel.org> # 4.5+

Acked-by: Christoffer Dall <christoffer.dall@linaro.org>

Applied, thanks.
-Christoffer

> ---
> 
> A better fix, at least for KASAN, would be nice but that's a lot more
> intrusive as we need to map the KASAN shadow into the EL2 space. In the
> meantime, especially since it needs backporting to 4.5, this patch would
> solve KASAN getting stuck with KVM (similar to what we do for EFI_STUB).
> 
>  arch/arm64/kvm/hyp/Makefile | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/arch/arm64/kvm/hyp/Makefile b/arch/arm64/kvm/hyp/Makefile
> index 826032bc3945..acde4782621a 100644
> --- a/arch/arm64/kvm/hyp/Makefile
> +++ b/arch/arm64/kvm/hyp/Makefile
> @@ -12,3 +12,7 @@ obj-$(CONFIG_KVM_ARM_HOST) += switch.o
>  obj-$(CONFIG_KVM_ARM_HOST) += fpsimd.o
>  obj-$(CONFIG_KVM_ARM_HOST) += tlb.o
>  obj-$(CONFIG_KVM_ARM_HOST) += hyp-entry.o
> +
> +GCOV_PROFILE	:= n
> +KASAN_SANITIZE	:= n
> +UBSAN_SANITIZE	:= n