Enable ARM and THUMB AOT support, enable Android platform support (#182)

* Sync with internal/feature: enable arm aot and android platform

core/shared/platform/zephyr/bh_platform.c

@@ -8,6 +8,9 @@
 #include "bh_common.h"
 #include <stdlib.h>
 #include <string.h>
+#ifdef CONFIG_ARM_MPU
+#include <arch/arm/aarch32/cortex_m/cmsis.h>
+#endif
 
 char *bh_strdup(const char *s)
 {
@@ -22,6 +25,28 @@ char *bh_strdup(const char *s)
     return s1;
 }
 
+#ifdef CONFIG_ARM_MPU
+/**
+ * This function will allow execute from sram region.
+ * This is needed for AOT code because by default all soc will
+ * disable the execute from SRAM.
+ */
+static void
+disable_mpu_rasr_xn(void)
+{
+    u32_t index;
+    /* Kept the max index as 8 (irrespective of soc) because the sram
+       would most likely be set at index 2. */
+    for (index = 0U; index < 8; index++) {
+        MPU->RNR = index;
+        if (MPU->RASR & MPU_RASR_XN_Msk) {
+            MPU->RASR |= ~MPU_RASR_XN_Msk;
+        }
+    }
+
+}
+#endif  /* end of CONFIG_ARM_MPU */
+
 static int
 _stdout_hook_iwasm(int c)
 {
@@ -34,6 +59,14 @@ int bh_platform_init()
     extern void __stdout_hook_install(int (*hook)(int));
     /* Enable printf() in Zephyr */
     __stdout_hook_install(_stdout_hook_iwasm);
+
+#if WASM_ENABLE_AOT != 0
+#ifdef CONFIG_ARM_MPU
+    /* Enable executable memory support */
+    disable_mpu_rasr_xn();
+#endif
+#endif
+
     return 0;
 }
 
@@ -54,3 +87,14 @@ bh_mprotect(void *addr, uint32 size, int prot)
 {
     return 0;
 }
+
+void
+bh_dcache_flush()
+{
+#if defined(CONFIG_CPU_CORTEX_M7)
+    uint32 key;
+    key = irq_lock();
+    SCB_CleanDCache();
+    irq_unlock(key);
+#endif
+}

core/shared/platform/zephyr/bh_platform.h

@@ -153,5 +153,6 @@ enum {
 void *bh_mmap(void *hint, unsigned int size, int prot, int flags);
 void bh_munmap(void *addr, uint32 size);
 int bh_mprotect(void *addr, uint32 size, int prot);
+void bh_dcache_flush();
 
 #endif

core/shared/platform/zephyr/bh_thread.c

@@ -404,8 +404,8 @@ void vm_mutex_unlock(korp_mutex *mutex)
 
 int _vm_sem_init(korp_sem* sem, unsigned int c)
 {
-    k_sem_init(sem, 0, c);
-    return BHT_OK;
+    int ret = k_sem_init(sem, 0, c);
+    return ret == 0 ? BHT_OK : BHT_ERROR;
 }
 
 int _vm_sem_destroy(korp_sem *sem)