[PATCH qemu 1/3] target/arm: Unify checking for M Main Extension in MRS/MSR

[~dreiss-meta]

From: David Reiss <dreiss@meta.com>

BASEPRI, FAULTMASK, and their _NS equivalents only exist on devices with
the Main Extension.  However, the MRS instruction did not check this,
and the MSR instruction handled it inconsistently (warning BASEPRI, but
silently ignoring writes to BASEPRI_NS).  Unify this behavior and always
warn when reading or writing any of these registers if the extension is
not present.

Signed-off-by: David Reiss <dreiss@meta.com>
---
 target/arm/m_helper.c | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/target/arm/m_helper.c b/target/arm/m_helper.c
index 355cd4d60a..e5ccfa9615 100644
--- a/target/arm/m_helper.c
+++ b/target/arm/m_helper.c
@@ -2481,11 +2481,17 @@ uint32_t HELPER(v7m_mrs)(CPUARMState *env, uint32_t reg)
             }
             return env->v7m.primask[M_REG_NS];
         case 0x91: /* BASEPRI_NS */
+            if (!arm_feature(env, ARM_FEATURE_M_MAIN)) {
+                goto bad_reg;
+            }
             if (!env->v7m.secure) {
                 return 0;
             }
             return env->v7m.basepri[M_REG_NS];
         case 0x93: /* FAULTMASK_NS */
+            if (!arm_feature(env, ARM_FEATURE_M_MAIN)) {
+                goto bad_reg;
+            }
             if (!env->v7m.secure) {
                 return 0;
             }
@@ -2531,8 +2537,14 @@ uint32_t HELPER(v7m_mrs)(CPUARMState *env, uint32_t reg)
         return env->v7m.primask[env->v7m.secure];
     case 17: /* BASEPRI */
     case 18: /* BASEPRI_MAX */
+        if (!arm_feature(env, ARM_FEATURE_M_MAIN)) {
+            goto bad_reg;
+        }
         return env->v7m.basepri[env->v7m.secure];
     case 19: /* FAULTMASK */
+        if (!arm_feature(env, ARM_FEATURE_M_MAIN)) {
+            goto bad_reg;
+        }
         return env->v7m.faultmask[env->v7m.secure];
     default:
     bad_reg:
@@ -2597,13 +2609,19 @@ void HELPER(v7m_msr)(CPUARMState *env, uint32_t 
maskreg, uint32_t val)
             env->v7m.primask[M_REG_NS] = val & 1;
             return;
         case 0x91: /* BASEPRI_NS */
-            if (!env->v7m.secure || !arm_feature(env, ARM_FEATURE_M_MAIN)) {
+            if (!arm_feature(env, ARM_FEATURE_M_MAIN)) {
+                goto bad_reg;
+            }
+            if (!env->v7m.secure) {
                 return;
             }
             env->v7m.basepri[M_REG_NS] = val & 0xff;
             return;
         case 0x93: /* FAULTMASK_NS */
-            if (!env->v7m.secure || !arm_feature(env, ARM_FEATURE_M_MAIN)) {
+            if (!arm_feature(env, ARM_FEATURE_M_MAIN)) {
+                goto bad_reg;
+            }
+            if (!env->v7m.secure) {
                 return;
             }
             env->v7m.faultmask[M_REG_NS] = val & 1;
-- 
2.34.5