[Qemu-devel] [PATCH v2 23/23] target-arm: Respect SCR.FW, SCR.AW and SCTLR.NMFI

[Fabian Aggeler <aggelerf@ethz.ch>]

bits when modifying CPSR.

Signed-off-by: Fabian Aggeler <aggelerf@ethz.ch>
---
 target-arm/cpu.h    |  2 ++
 target-arm/helper.c | 41 ++++++++++++++++++++++++++++++++++++++---
 2 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/target-arm/cpu.h b/target-arm/cpu.h
index 212cb64..5de0c77 100644
--- a/target-arm/cpu.h
+++ b/target-arm/cpu.h
@@ -675,6 +675,8 @@ static inline int arm_feature(CPUARMState *env, int feature)
 #define SCR_NS (1U << 0)
 #define SCR_IRQ (1U << 1)
 #define SCR_FIQ (1U << 2)
+#define SCR_FW (1U << 4)
+#define SCR_AW (1U << 5)
 
 /* Return true if the processor is in secure state */
 static inline bool arm_is_secure(CPUARMState *env)
diff --git a/target-arm/helper.c b/target-arm/helper.c
index a5ba480..7151325 100644
--- a/target-arm/helper.c
+++ b/target-arm/helper.c
@@ -3169,9 +3169,6 @@ void cpsr_write(CPUARMState *env, uint32_t val, uint32_t mask)
         env->GE = (val >> 16) & 0xf;
     }
 
-    env->daif &= ~(CPSR_AIF & mask);
-    env->daif |= val & CPSR_AIF & mask;
-
     if ((env->uncached_cpsr ^ val) & mask & CPSR_M) {
         if (bad_mode_switch(env, val & CPSR_M)) {
             /* Attempt to switch to an invalid mode: this is UNPREDICTABLE.
@@ -3183,6 +3180,44 @@ void cpsr_write(CPUARMState *env, uint32_t val, uint32_t mask)
             switch_mode(env, val & CPSR_M);
         }
     }
+
+    /* In an implementation that does not include Virtualization Extensions
+     * the SCR.FW and SCR.AW bit control whether non-secure software is allowed
+     * to change the CPSR_F and CPSR_A bits respectively.
+     */
+    if ((mask & CPSR_A)
+            && (val & CPSR_A) != (env->uncached_cpsr & CPSR_A)
+            && arm_feature(env, ARM_FEATURE_SECURITY_EXTENSIONS)
+            && !(env->cp15.c1_scr & SCR_AW) && !arm_is_secure(env)) {
+        qemu_log_mask(LOG_GUEST_ERROR, "Ignoring attempt to switch CPSR_A "
+                "flag from non-secure world with SCR.AW bit set\n");
+        mask &= ~CPSR_A;
+    }
+
+    if ((mask & CPSR_F)) {
+
+        /* Check whether non-maskable FIQ (NMFI) support is enabled.
+         * If this bit is set software is not allowed to mask FIQs,
+         * but is allowed to set CPSR_F to 0.
+         */
+        if ((arm_current_sctlr(env) & SCTLR_NMFI) && (val & CPSR_F)) {
+            qemu_log_mask(LOG_GUEST_ERROR, "Ignoring attempt to enable CPSR_F "
+                    "flag (non-maskable FIQ [NMFI] support enabled)\n");
+            mask &= ~CPSR_F;
+        }
+
+        if ((val & CPSR_F) != (env->uncached_cpsr & CPSR_F)
+                && arm_feature(env, ARM_FEATURE_SECURITY_EXTENSIONS)
+                && !(env->cp15.c1_scr & SCR_FW) && !arm_is_secure(env)) {
+            qemu_log_mask(LOG_GUEST_ERROR, "Ignoring attempt to switch CPSR_F "
+                    "flag from non-secure world with SCR.FW bit set\n");
+            mask &= ~CPSR_F;
+        }
+    }
+
+    env->daif &= ~(CPSR_AIF & mask);
+    env->daif |= val & CPSR_AIF & mask;
+
     mask &= ~CACHED_CPSR_BITS;
     env->uncached_cpsr = (env->uncached_cpsr & ~mask) | (val & mask);
 }
-- 
1.8.3.2