Re: [Qemu-arm] [PATCH 8/8] target-arm: ignore ELR_ELx[1] for exception return to 32-bit ARM mode

[Edgar E. Iglesias]

On Thu, Jan 14, 2016 at 06:34:11PM +0000, Peter Maydell wrote:
> The architecture requires that for an exception return to AArch32 the
> low bits of ELR_ELx are ignored when the PC is set from them:
>  * if returning to Thumb mode, ignore ELR_ELx[0]
>  * if returning to ARM mode, ignore ELR_ELx[1:0]
> 
> We were only squashing bit 0; also squash bit 1 if the SPSR T bit
> indicates this is a return to ARM code.
> 
> Signed-off-by: Peter Maydell <address@hidden>


Reviewed-by: Edgar E. Iglesias <address@hidden>



> ---
>  target-arm/op_helper.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/target-arm/op_helper.c b/target-arm/op_helper.c
> index 5789ccb..171d6b8 100644
> --- a/target-arm/op_helper.c
> +++ b/target-arm/op_helper.c
> @@ -738,7 +738,11 @@ void HELPER(exception_return)(CPUARMState *env)
>          }
>          aarch64_sync_64_to_32(env);
>  
> -        env->regs[15] = env->elr_el[cur_el] & ~0x1;
> +        if (spsr & CPSR_T) {
> +            env->regs[15] = env->elr_el[cur_el] & ~0x1;
> +        } else {
> +            env->regs[15] = env->elr_el[cur_el] & ~0x3;
> +        }
>      } else {
>          env->aarch64 = 1;
>          pstate_write(env, spsr);
> -- 
> 1.9.1
>