Re: [Qemu-devel] [PATCH 7/8] target-arm: Implement remaining illegal return event checks

["Edgar E. Iglesias" <edgar.iglesias@gmail.com>]

On Thu, Jan 14, 2016 at 06:34:10PM +0000, Peter Maydell wrote:
> We already implement almost all the checks for the illegal
> return events from AArch64 state described in the ARM ARM section
> D1.11.2. Add the two missing ones:
>  * return to EL2 when EL3 is implemented and SCR_EL3.NS is 0
>  * return to Non-secure EL1 when EL2 is implemented and HCR_EL2.TGE is 1
> 
> (We don't implement external debug, so the case of "debug state exit
> from EL0 using AArch64 state to EL0 using AArch32 state" doesn't apply
> for QEMU.)
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  target-arm/op_helper.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/target-arm/op_helper.c b/target-arm/op_helper.c
> index 38d46d8..5789ccb 100644
> --- a/target-arm/op_helper.c
> +++ b/target-arm/op_helper.c
> @@ -718,6 +718,17 @@ void HELPER(exception_return)(CPUARMState *env)
>          goto illegal_return;
>      }
>  
> +    if (new_el == 2 && arm_is_secure_below_el3(env)) {
> +        /* Return to the non-existent secure-EL2 */
> +        goto illegal_return;
> +    }
> +
> +    if (new_el == 1 &&
> +        arm_feature(env, ARM_FEATURE_EL2) && (env->cp15.hcr_el2 & HCR_TGE)

I'm not sure you need to check for EL2 as hcr_el2.tge cannot be reached/set otherwise.

Anyway:
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>



> +        && !arm_is_secure_below_el3(env)) {
> +        goto illegal_return;
> +    }
> +
>      if (!return_to_aa64) {
>          env->aarch64 = 0;
>          env->uncached_cpsr = spsr & CPSR_M;
> -- 
> 1.9.1
>