target/arm: Add v8M stack checks for MSR to SP_NS

Updating the NS stack pointer via MSR to SP_NS should include
a check whether the new SP value is below the stack limit.
No other kinds of update to the various stack pointer and
limit registers via MSR should perform a check.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20181002163556.10279-14-peter.maydell@linaro.org

1 files changed, 13 insertions, 1 deletions

diff --git a/target/arm/helper.c b/target/arm/helper.c
index 33c7e2f48e..c83f7c1109 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -10994,11 +10994,23 @@ void HELPER(v7m_msr)(CPUARMState *env, uint32_t maskreg, uint32_t val)
              * currently in handler mode or not, using the NS CONTROL.SPSEL.
              */
             bool spsel = env->v7m.control[M_REG_NS] & R_V7M_CONTROL_SPSEL_MASK;
+            bool is_psp = !arm_v7m_is_handler_mode(env) && spsel;
+            uint32_t limit;
 
             if (!env->v7m.secure) {
                 return;
             }
-            if (!arm_v7m_is_handler_mode(env) && spsel) {
+
+            limit = is_psp ? env->v7m.psplim[false] : env->v7m.msplim[false];
+
+            if (val < limit) {
+                CPUState *cs = CPU(arm_env_get_cpu(env));
+
+                cpu_restore_state(cs, GETPC(), true);
+                raise_exception(env, EXCP_STKOF, 0, 1);
+            }
+
+            if (is_psp) {
                 env->v7m.other_ss_psp = val;
             } else {
                 env->v7m.other_ss_msp = val;