target/arm: Reorg CPAccessResult and access_check_cp_reg

Rearrange the values of the enumerators of CPAccessResult
so that we may directly extract the target el. For the two
special cases in access_check_cp_reg, use CPAccessResult.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20220501055028.646596-3-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

target/arm/cpregs.h

@@ -167,26 +167,32 @@ static inline bool cptype_valid(int cptype)
 typedef enum CPAccessResult {
     /* Access is permitted */
     CP_ACCESS_OK = 0,
+
+    /*
+     * Combined with one of the following, the low 2 bits indicate the
+     * target exception level.  If 0, the exception is taken to the usual
+     * target EL (EL1 or PL1 if in EL0, otherwise to the current EL).
+     */
+    CP_ACCESS_EL_MASK = 3,
+
     /*
      * Access fails due to a configurable trap or enable which would
      * result in a categorized exception syndrome giving information about
      * the failing instruction (ie syndrome category 0x3, 0x4, 0x5, 0x6,
-     * 0xc or 0x18). The exception is taken to the usual target EL (EL1 or
+     * 0xc or 0x18).
-     * PL1 if in EL0, otherwise to the current EL).
      */
-    CP_ACCESS_TRAP = 1,
+    CP_ACCESS_TRAP = (1 << 2),
+    CP_ACCESS_TRAP_EL2 = CP_ACCESS_TRAP | 2,
+    CP_ACCESS_TRAP_EL3 = CP_ACCESS_TRAP | 3,
+
     /*
      * Access fails and results in an exception syndrome 0x0 ("uncategorized").
      * Note that this is not a catch-all case -- the set of cases which may
      * result in this failure is specifically defined by the architecture.
      */
-    CP_ACCESS_TRAP_UNCATEGORIZED = 2,
+    CP_ACCESS_TRAP_UNCATEGORIZED = (2 << 2),
-    /* As CP_ACCESS_TRAP, but for traps directly to EL2 or EL3 */
+    CP_ACCESS_TRAP_UNCATEGORIZED_EL2 = CP_ACCESS_TRAP_UNCATEGORIZED | 2,
-    CP_ACCESS_TRAP_EL2 = 3,
+    CP_ACCESS_TRAP_UNCATEGORIZED_EL3 = CP_ACCESS_TRAP_UNCATEGORIZED | 3,
-    CP_ACCESS_TRAP_EL3 = 4,
-    /* As CP_ACCESS_UNCATEGORIZED, but for traps directly to EL2 or EL3 */
-    CP_ACCESS_TRAP_UNCATEGORIZED_EL2 = 5,
-    CP_ACCESS_TRAP_UNCATEGORIZED_EL3 = 6,
 } CPAccessResult;
 
 typedef struct ARMCPRegInfo ARMCPRegInfo;

target/arm/op_helper.c

@@ -632,11 +632,13 @@ void HELPER(access_check_cp_reg)(CPUARMState *env, void *rip, uint32_t syndrome,
                                  uint32_t isread)
 {
     const ARMCPRegInfo *ri = rip;
+    CPAccessResult res = CP_ACCESS_OK;
     int target_el;
 
     if (arm_feature(env, ARM_FEATURE_XSCALE) && ri->cp < 14
         && extract32(env->cp15.c15_cpar, ri->cp, 1) == 0) {
-        raise_exception(env, EXCP_UDEF, syndrome, exception_target_el(env));
+        res = CP_ACCESS_TRAP;
+        goto fail;
     }
 
     /*
@@ -655,48 +657,46 @@ void HELPER(access_check_cp_reg)(CPUARMState *env, void *rip, uint32_t syndrome,
         mask &= ~((1 << 4) | (1 << 14));
 
         if (env->cp15.hstr_el2 & mask) {
-            target_el = 2;
+            res = CP_ACCESS_TRAP_EL2;
-            goto exept;
+            goto fail;
         }
     }
 
-    if (!ri->accessfn) {
+    if (ri->accessfn) {
+        res = ri->accessfn(env, ri, isread);
+    }
+    if (likely(res == CP_ACCESS_OK)) {
         return;
     }
 
-    switch (ri->accessfn(env, ri, isread)) {
+ fail:
-    case CP_ACCESS_OK:
+    switch (res & ~CP_ACCESS_EL_MASK) {
-        return;
     case CP_ACCESS_TRAP:
-        target_el = exception_target_el(env);
-        break;
-    case CP_ACCESS_TRAP_EL2:
-        /* Requesting a trap to EL2 when we're in EL3 is
-         * a bug in the access function.
-         */
-        assert(arm_current_el(env) != 3);
-        target_el = 2;
-        break;
-    case CP_ACCESS_TRAP_EL3:
-        target_el = 3;
         break;
     case CP_ACCESS_TRAP_UNCATEGORIZED:
-        target_el = exception_target_el(env);
-        syndrome = syn_uncategorized();
-        break;
-    case CP_ACCESS_TRAP_UNCATEGORIZED_EL2:
-        target_el = 2;
-        syndrome = syn_uncategorized();
-        break;
-    case CP_ACCESS_TRAP_UNCATEGORIZED_EL3:
-        target_el = 3;
         syndrome = syn_uncategorized();
         break;
     default:
         g_assert_not_reached();
     }
 
-exept:
+    target_el = res & CP_ACCESS_EL_MASK;
+    switch (target_el) {
+    case 0:
+        target_el = exception_target_el(env);
+        break;
+    case 2:
+        assert(arm_current_el(env) != 3);
+        assert(arm_is_el2_enabled(env));
+        break;
+    case 3:
+        assert(arm_feature(env, ARM_FEATURE_EL3));
+        break;
+    default:
+        /* No "direct" traps to EL1 */
+        g_assert_not_reached();
+    }
+
     raise_exception(env, EXCP_UDEF, syndrome, target_el);
 }