target/arm/helper: Check SCR_EL3.{NSE, NS} encoding for AT instructions

The AT instruction is UNDEFINED if the {NSE,NS} configuration is
invalid. Add a function to check this on all AT instructions that apply
to an EL lower than 3.

Suggested-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Message-id: 20230809123706.1842548-6-jean-philippe@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

target/arm/helper.c

@@ -3616,14 +3616,30 @@ static void ats1h_write(CPUARMState *env, const ARMCPRegInfo *ri,
 #endif /* CONFIG_TCG */
 }
 
+static CPAccessResult at_e012_access(CPUARMState *env, const ARMCPRegInfo *ri,
+                                     bool isread)
+{
+    /*
+     * R_NYXTL: instruction is UNDEFINED if it applies to an Exception level
+     * lower than EL3 and the combination SCR_EL3.{NSE,NS} is reserved. This can
+     * only happen when executing at EL3 because that combination also causes an
+     * illegal exception return. We don't need to check FEAT_RME either, because
+     * scr_write() ensures that the NSE bit is not set otherwise.
+     */
+    if ((env->cp15.scr_el3 & (SCR_NSE | SCR_NS)) == SCR_NSE) {
+        return CP_ACCESS_TRAP;
+    }
+    return CP_ACCESS_OK;
+}
+
 static CPAccessResult at_s1e2_access(CPUARMState *env, const ARMCPRegInfo *ri,
                                      bool isread)
 {
     if (arm_current_el(env) == 3 &&
         !(env->cp15.scr_el3 & (SCR_NS | SCR_EEL2))) {
         return CP_ACCESS_TRAP;
     }
-    return CP_ACCESS_OK;
+    return at_e012_access(env, ri, isread);
 }
 
 static void ats_write64(CPUARMState *env, const ARMCPRegInfo *ri,
@@ -5505,38 +5521,38 @@ static const ARMCPRegInfo v8_cp_reginfo[] = {
       .opc0 = 1, .opc1 = 0, .crn = 7, .crm = 8, .opc2 = 0,
       .access = PL1_W, .type = ARM_CP_NO_RAW | ARM_CP_RAISES_EXC,
       .fgt = FGT_ATS1E1R,
-      .writefn = ats_write64 },
+      .accessfn = at_e012_access, .writefn = ats_write64 },
     { .name = "AT_S1E1W", .state = ARM_CP_STATE_AA64,
       .opc0 = 1, .opc1 = 0, .crn = 7, .crm = 8, .opc2 = 1,
       .access = PL1_W, .type = ARM_CP_NO_RAW | ARM_CP_RAISES_EXC,
       .fgt = FGT_ATS1E1W,
-      .writefn = ats_write64 },
+      .accessfn = at_e012_access, .writefn = ats_write64 },
     { .name = "AT_S1E0R", .state = ARM_CP_STATE_AA64,
       .opc0 = 1, .opc1 = 0, .crn = 7, .crm = 8, .opc2 = 2,
       .access = PL1_W, .type = ARM_CP_NO_RAW | ARM_CP_RAISES_EXC,
       .fgt = FGT_ATS1E0R,
-      .writefn = ats_write64 },
+      .accessfn = at_e012_access, .writefn = ats_write64 },
     { .name = "AT_S1E0W", .state = ARM_CP_STATE_AA64,
       .opc0 = 1, .opc1 = 0, .crn = 7, .crm = 8, .opc2 = 3,
       .access = PL1_W, .type = ARM_CP_NO_RAW | ARM_CP_RAISES_EXC,
       .fgt = FGT_ATS1E0W,
-      .writefn = ats_write64 },
+      .accessfn = at_e012_access, .writefn = ats_write64 },
     { .name = "AT_S12E1R", .state = ARM_CP_STATE_AA64,
       .opc0 = 1, .opc1 = 4, .crn = 7, .crm = 8, .opc2 = 4,
       .access = PL2_W, .type = ARM_CP_NO_RAW | ARM_CP_RAISES_EXC,
-      .writefn = ats_write64 },
+      .accessfn = at_e012_access, .writefn = ats_write64 },
     { .name = "AT_S12E1W", .state = ARM_CP_STATE_AA64,
       .opc0 = 1, .opc1 = 4, .crn = 7, .crm = 8, .opc2 = 5,
       .access = PL2_W, .type = ARM_CP_NO_RAW | ARM_CP_RAISES_EXC,
-      .writefn = ats_write64 },
+      .accessfn = at_e012_access, .writefn = ats_write64 },
     { .name = "AT_S12E0R", .state = ARM_CP_STATE_AA64,
       .opc0 = 1, .opc1 = 4, .crn = 7, .crm = 8, .opc2 = 6,
       .access = PL2_W, .type = ARM_CP_NO_RAW | ARM_CP_RAISES_EXC,
-      .writefn = ats_write64 },
+      .accessfn = at_e012_access, .writefn = ats_write64 },
     { .name = "AT_S12E0W", .state = ARM_CP_STATE_AA64,
       .opc0 = 1, .opc1 = 4, .crn = 7, .crm = 8, .opc2 = 7,
       .access = PL2_W, .type = ARM_CP_NO_RAW | ARM_CP_RAISES_EXC,
-      .writefn = ats_write64 },
+      .accessfn = at_e012_access, .writefn = ats_write64 },
     /* AT S1E2* are elsewhere as they UNDEF from EL3 if EL2 is not present */
     { .name = "AT_S1E3R", .state = ARM_CP_STATE_AA64,
       .opc0 = 1, .opc1 = 6, .crn = 7, .crm = 8, .opc2 = 0,
@@ -8079,12 +8095,12 @@ static const ARMCPRegInfo ats1e1_reginfo[] = {
       .opc0 = 1, .opc1 = 0, .crn = 7, .crm = 9, .opc2 = 0,
       .access = PL1_W, .type = ARM_CP_NO_RAW | ARM_CP_RAISES_EXC,
       .fgt = FGT_ATS1E1RP,
-      .writefn = ats_write64 },
+      .accessfn = at_e012_access, .writefn = ats_write64 },
     { .name = "AT_S1E1WP", .state = ARM_CP_STATE_AA64,
       .opc0 = 1, .opc1 = 0, .crn = 7, .crm = 9, .opc2 = 1,
       .access = PL1_W, .type = ARM_CP_NO_RAW | ARM_CP_RAISES_EXC,
       .fgt = FGT_ATS1E1WP,
-      .writefn = ats_write64 },
+      .accessfn = at_e012_access, .writefn = ats_write64 },
 };
 
 static const ARMCPRegInfo ats1cp_reginfo[] = {