From: Richard Henderson <richard.henderson@linaro.org>

Use this along the exception return path, where we previously
accepted any values.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20200208125816.14954-11-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/internals.h  | 12 ++++++++++++
 target/arm/helper-a64.c |  1 +
 2 files changed, 13 insertions(+)

diff --git a/target/arm/internals.h b/target/arm/internals.h
index 0569c96fd94..034d98ad538 100644
--- a/target/arm/internals.h
+++ b/target/arm/internals.h
@@ -1085,6 +1085,18 @@ static inline uint32_t aarch32_cpsr_valid_mask(uint64_t features,
     return valid;
 }
 
+static inline uint32_t aarch64_pstate_valid_mask(const ARMISARegisters *id)
+{
+    uint32_t valid;
+
+    valid = PSTATE_M | PSTATE_DAIF | PSTATE_IL | PSTATE_SS | PSTATE_NZCV;
+    if (isar_feature_aa64_bti(id)) {
+        valid |= PSTATE_BTYPE;
+    }
+
+    return valid;
+}
+
 /*
  * Parameters of a given virtual address, as extracted from the
  * translation control register (TCR) for a given regime.
diff --git a/target/arm/helper-a64.c b/target/arm/helper-a64.c
index 0c9feba3929..509ae930698 100644
--- a/target/arm/helper-a64.c
+++ b/target/arm/helper-a64.c
@@ -1032,6 +1032,7 @@ void HELPER(exception_return)(CPUARMState *env, uint64_t new_pc)
                       cur_el, new_el, env->regs[15]);
     } else {
         env->aarch64 = 1;
+        spsr &= aarch64_pstate_valid_mask(&env_archcpu(env)->isar);
         pstate_write(env, spsr);
         if (!arm_singlestep_active(env)) {
             env->pstate &= ~PSTATE_SS;
-- 
2.20.1