Fix a QEMU NULL derefence that occurs when the guest attempts to
enable PMU counters with a non-v8 cpu model or a v8 cpu model
which has not configured a PMU.

Fixes: 4e7beb0cc0f3 ("target/arm: Add a timer to predict PMU counter overflow")
Signed-off-by: Andrew Jones <drjones@redhat.com>
---
 target/arm/helper.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/target/arm/helper.c b/target/arm/helper.c
index c8d3c213b6b7..fc73488f6cc0 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -1259,6 +1259,10 @@ static bool pmu_counter_enabled(CPUARMState *env, uint8_t counter)
     int el = arm_current_el(env);
     uint8_t hpmn = env->cp15.mdcr_el2 & MDCR_HPMN;
 
+    if (!arm_feature(env, ARM_FEATURE_PMU)) {
+        return false;
+    }
+
     if (!arm_feature(env, ARM_FEATURE_EL2) ||
             (counter < hpmn || counter == 31)) {
         e = env->cp15.c9_pmcr & PMCRE;
-- 
2.17.2

On Mar 22 17:23, Andrew Jones wrote:
> Fix a QEMU NULL derefence that occurs when the guest attempts to
> enable PMU counters with a non-v8 cpu model or a v8 cpu model
> which has not configured a PMU.
> 
> Fixes: 4e7beb0cc0f3 ("target/arm: Add a timer to predict PMU counter overflow")
> Signed-off-by: Andrew Jones <drjones@redhat.com>

Reviewed-by: Aaron Lindsay <aaron@os.amperecomputing.com>

> ---
>  target/arm/helper.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/target/arm/helper.c b/target/arm/helper.c
> index c8d3c213b6b7..fc73488f6cc0 100644
> --- a/target/arm/helper.c
> +++ b/target/arm/helper.c
> @@ -1259,6 +1259,10 @@ static bool pmu_counter_enabled(CPUARMState *env, uint8_t counter)
>      int el = arm_current_el(env);
>      uint8_t hpmn = env->cp15.mdcr_el2 & MDCR_HPMN;
>  
> +    if (!arm_feature(env, ARM_FEATURE_PMU)) {
> +        return false;
> +    }
> +
>      if (!arm_feature(env, ARM_FEATURE_EL2) ||
>              (counter < hpmn || counter == 31)) {
>          e = env->cp15.c9_pmcr & PMCRE;
> -- 
> 2.17.2
>