Check the v8M stack limits when pushing the frame for a
non-secure function call via BLXNS.

In order to be able to generate the exception we need to
promote raise_exception() from being local to op_helper.c
so we can call it from helper.c.

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: 20181002163556.10279-8-peter.maydell@linaro.org
---
 target/arm/internals.h | 9 +++++++++
 target/arm/helper.c    | 4 ++++
 target/arm/op_helper.c | 4 ++--
 3 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/target/arm/internals.h b/target/arm/internals.h
index bb5a63d6fe2..a4fc709bcc7 100644
--- a/target/arm/internals.h
+++ b/target/arm/internals.h
@@ -94,6 +94,15 @@ FIELD(V7M_EXCRET, RES1, 7, 25) /* including the must-be-1 prefix */
 #define M_FAKE_FSR_NSC_EXEC 0xf /* NS executing in S&NSC memory */
 #define M_FAKE_FSR_SFAULT 0xe /* SecureFault INVTRAN, INVEP or AUVIOL */
 
+/**
+ * raise_exception: Raise the specified exception.
+ * Raise a guest exception with the specified value, syndrome register
+ * and target exception level. This should be called from helper functions,
+ * and never returns because we will longjump back up to the CPU main loop.
+ */
+void QEMU_NORETURN raise_exception(CPUARMState *env, uint32_t excp,
+                                   uint32_t syndrome, uint32_t target_el);
+
 /*
  * For AArch64, map a given EL to an index in the banked_spsr array.
  * Note that this mapping and the AArch32 mapping defined in bank_number()
diff --git a/target/arm/helper.c b/target/arm/helper.c
index 4cc43692550..33c7e2f48e3 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -6738,6 +6738,10 @@ void HELPER(v7m_blxns)(CPUARMState *env, uint32_t dest)
                       "BLXNS with misaligned SP is UNPREDICTABLE\n");
     }
 
+    if (sp < v7m_sp_limit(env)) {
+        raise_exception(env, EXCP_STKOF, 0, 1);
+    }
+
     saved_psr = env->v7m.exception;
     if (env->v7m.control[M_REG_S] & R_V7M_CONTROL_SFPA_MASK) {
         saved_psr |= XPSR_SFPA;
diff --git a/target/arm/op_helper.c b/target/arm/op_helper.c
index ef3fd87e79e..fb15a13e6c9 100644
--- a/target/arm/op_helper.c
+++ b/target/arm/op_helper.c
@@ -28,8 +28,8 @@
 #define SIGNBIT (uint32_t)0x80000000
 #define SIGNBIT64 ((uint64_t)1 << 63)
 
-static void raise_exception(CPUARMState *env, uint32_t excp,
-                            uint32_t syndrome, uint32_t target_el)
+void raise_exception(CPUARMState *env, uint32_t excp,
+                     uint32_t syndrome, uint32_t target_el)
 {
     CPUState *cs = CPU(arm_env_get_cpu(env));
 
-- 
2.19.0