diff --git a/Ubiquitous/XiZi_AIoT/.gitignore b/Ubiquitous/XiZi_AIoT/.gitignore
new file mode 100644
index 000000000..c795b054e
--- /dev/null
+++ b/Ubiquitous/XiZi_AIoT/.gitignore
@@ -0,0 +1 @@
+build
\ No newline at end of file
diff --git a/Ubiquitous/XiZi_AIoT/Makefile b/Ubiquitous/XiZi_AIoT/Makefile
index ddd3dab82..3697be3ed 100755
--- a/Ubiquitous/XiZi_AIoT/Makefile
+++ b/Ubiquitous/XiZi_AIoT/Makefile
@@ -140,3 +140,12 @@ distclean:
 	@rm -f .config*
 	@rm -f $(KERNEL_ROOT)/lib/musllib/libmusl.a
 	@rm -f $(KERNEL_ROOT)/board/*/.config
+
+
+# Run qemu with config discribed in README.md.
+.PHONY: qemu-default
+qemu-default:
+	qemu-system-arm -M sabrelite -m 1G -smp 4 -cpu cortex-a9 \
+    -display none -serial null -serial stdio \
+    -kernel ./build/XiZi-imx6q-sabrelite.elf
+
diff --git a/Ubiquitous/XiZi_AIoT/services/app/.gitignore b/Ubiquitous/XiZi_AIoT/services/app/.gitignore
new file mode 100644
index 000000000..46078f320
--- /dev/null
+++ b/Ubiquitous/XiZi_AIoT/services/app/.gitignore
@@ -0,0 +1,3 @@
+bin
+fs.img
+user.map
\ No newline at end of file
diff --git a/Ubiquitous/XiZi_AIoT/services/semaphore/semaphore_server.c b/Ubiquitous/XiZi_AIoT/services/semaphore/semaphore_server.c
index a835ff8e9..ad4d9978b 100644
--- a/Ubiquitous/XiZi_AIoT/services/semaphore/semaphore_server.c
+++ b/Ubiquitous/XiZi_AIoT/services/semaphore/semaphore_server.c
@@ -41,15 +41,28 @@ int IPC_DO_SERVE_FUNC(Ipc_sem_create)(sem_t* sem, int* count)
     return SEMAPHORE_SUC;
 }
 
+
+#define CHECK_SEM_RANGE(sem) \
+    do { \
+        if (*sem < 0 || *sem >= MAX_SUPPORT_SEMAPHORES) { \
+            return SEMAPHORE_ERR; \
+        } \
+    } while (0)
+
+
+#define CHECK_SEM_RANGE_AND_VALID(sem) \
+    do { \
+        CHECK_SEM_RANGE(sem); \
+        \
+        if (!sem_pool[*sem].valid) { \
+            return SEMAPHORE_ERR; \
+        } \
+    } while (0)
+
+
 int IPC_DO_SERVE_FUNC(Ipc_sem_delete)(sem_t* sem)
 {
-    if (*sem < 0 || *sem > MAX_SUPPORT_SEMAPHORES) {
-        return SEMAPHORE_ERR;
-    }
-
-    if (!sem_pool[*sem].valid) {
-        return SEMAPHORE_ERR;
-    }
+    CHECK_SEM_RANGE_AND_VALID(sem);
 
     sem_pool[*sem].valid = false;
     return SEMAPHORE_SUC;
@@ -57,9 +70,7 @@ int IPC_DO_SERVE_FUNC(Ipc_sem_delete)(sem_t* sem)
 
 int IPC_DO_SERVE_FUNC(Ipc_sem_wait)(sem_t* sem, int* timeout)
 {
-    if (*sem < 0 || *sem > MAX_SUPPORT_SEMAPHORES) {
-        return SEMAPHORE_ERR;
-    }
+    CHECK_SEM_RANGE(sem);
 
     /// @todo support timeout
     // return if sem is freed(no valid) or sem count is sufficient
@@ -72,13 +83,7 @@ int IPC_DO_SERVE_FUNC(Ipc_sem_wait)(sem_t* sem, int* timeout)
 
 int IPC_DO_SERVE_FUNC(Ipc_sem_signal)(sem_t* sem)
 {
-    if (*sem < 0 || *sem >= MAX_SUPPORT_SEMAPHORES) {
-        return SEMAPHORE_ERR;
-    }
-
-    if (!sem_pool[*sem].valid) {
-        return SEMAPHORE_ERR;
-    }
+    CHECK_SEM_RANGE_AND_VALID(sem);
 
     sem_pool[*sem].count++;
     return SEMAPHORE_SUC;
diff --git a/Ubiquitous/XiZi_AIoT/services/tools/mkfs/.gitignore b/Ubiquitous/XiZi_AIoT/services/tools/mkfs/.gitignore
new file mode 100644
index 000000000..3337b041d
--- /dev/null
+++ b/Ubiquitous/XiZi_AIoT/services/tools/mkfs/.gitignore
@@ -0,0 +1 @@
+mkfs
\ No newline at end of file
diff --git a/Ubiquitous/XiZi_AIoT/softkernel/memory/buddy.c b/Ubiquitous/XiZi_AIoT/softkernel/memory/buddy.c
index 97817851a..ffebd5ea5 100644
--- a/Ubiquitous/XiZi_AIoT/softkernel/memory/buddy.c
+++ b/Ubiquitous/XiZi_AIoT/softkernel/memory/buddy.c
@@ -77,8 +77,13 @@ static struct KPage* KBuddyPagesAlloc(struct KBuddy* pbuddy, int nPages)
     int i = 0, order = 0;
 
     // find order
+#if defined(__GNUC__)
+    // see: https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html
+    order = nPages ? (sizeof(int) * 8 - __builtin_clz(nPages) - 1) + !!(__builtin_popcount(nPages) != 1) : 0;
+#else
     for (order = 0; (FREE_LIST_INDEX(order)) < nPages; order++)
         ;
+#endif
 
     // find the free page list
     for (i = order; i < MAX_BUDDY_ORDER; i++) {