[PATCH] target/arm: Don't set EXC_RETURN.ES if Security Extension not present

[PATCH] target/arm: Don't set EXC_RETURN.ES if Security Extension not present

[Peter Maydell]

In v7m_exception_taken(), for v8M we set the EXC_RETURN.ES bit if
either the exception targets Secure or if the CPU doesn't implement
the Security Extension.  This is incorrect: the v8M Arm ARM specifies
that the ES bit should be RES0 if the Security Extension is not
implemented, and the pseudocode agrees.

Remove the incorrect condition, so that we leave the ES bit 0
if the Security Extension isn't implemented.

This doesn't have any guest-visible effects for our current set of
emulated CPUs, because all our v8M CPUs implement the Security
Extension; but it's worth fixing in case we add a v8M CPU without
the extension in future.

Reported-by: Igor Kotrasinski <i.kotrasinsk@samsung.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/m_helper.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/target/arm/m_helper.c b/target/arm/m_helper.c
index 355cd4d60a7..2b55e90ea9d 100644
--- a/target/arm/m_helper.c
+++ b/target/arm/m_helper.c
@@ -895,7 +895,7 @@ static void v7m_exception_taken(ARMCPU *cpu, uint32_t lr, bool dotailchain,
         }
 
         lr &= ~R_V7M_EXCRET_ES_MASK;
-        if (targets_secure || !arm_feature(env, ARM_FEATURE_M_SECURITY)) {
+        if (targets_secure) {
             lr |= R_V7M_EXCRET_ES_MASK;
         }
         lr &= ~R_V7M_EXCRET_SPSEL_MASK;
-- 
2.25.1

Re: [PATCH] target/arm: Don't set EXC_RETURN.ES if Security Extension not present

[Richard Henderson]

On 12/16/22 07:24, Peter Maydell wrote:
> In v7m_exception_taken(), for v8M we set the EXC_RETURN.ES bit if
> either the exception targets Secure or if the CPU doesn't implement
> the Security Extension.  This is incorrect: the v8M Arm ARM specifies
> that the ES bit should be RES0 if the Security Extension is not
> implemented, and the pseudocode agrees.
> 
> Remove the incorrect condition, so that we leave the ES bit 0
> if the Security Extension isn't implemented.
> 
> This doesn't have any guest-visible effects for our current set of
> emulated CPUs, because all our v8M CPUs implement the Security
> Extension; but it's worth fixing in case we add a v8M CPU without
> the extension in future.
> 
> Reported-by: Igor Kotrasinski <i.kotrasinsk@samsung.com>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~

> ---
>   target/arm/m_helper.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/target/arm/m_helper.c b/target/arm/m_helper.c
> index 355cd4d60a7..2b55e90ea9d 100644
> --- a/target/arm/m_helper.c
> +++ b/target/arm/m_helper.c
> @@ -895,7 +895,7 @@ static void v7m_exception_taken(ARMCPU *cpu, uint32_t lr, bool dotailchain,
>           }
>   
>           lr &= ~R_V7M_EXCRET_ES_MASK;
> -        if (targets_secure || !arm_feature(env, ARM_FEATURE_M_SECURITY)) {
> +        if (targets_secure) {
>               lr |= R_V7M_EXCRET_ES_MASK;
>           }
>           lr &= ~R_V7M_EXCRET_SPSEL_MASK;