diff --git a/Ubiquitous/XiZi_AIoT/hardkernel/arch/arm/armv7-a/cortex-a9/preboot_for_imx6q-sabrelite/config.mk b/Ubiquitous/XiZi_AIoT/hardkernel/arch/arm/armv7-a/cortex-a9/preboot_for_imx6q-sabrelite/config.mk
index 1314d5fb4..af889591a 100644
--- a/Ubiquitous/XiZi_AIoT/hardkernel/arch/arm/armv7-a/cortex-a9/preboot_for_imx6q-sabrelite/config.mk
+++ b/Ubiquitous/XiZi_AIoT/hardkernel/arch/arm/armv7-a/cortex-a9/preboot_for_imx6q-sabrelite/config.mk
@@ -1,8 +1,7 @@
 export CROSS_COMPILE ?= arm-none-eabi-
 export DEVICE = -march=armv7-a -mtune=cortex-a9 -mfpu=vfpv3-d16 -ftree-vectorize -ffast-math -mfloat-abi=softfp
 # export CFLAGS := $(DEVICE) -std=c11 -Wall -O2 -g -gdwarf-2  -Wnull-dereference -Waddress -Warray-bounds -Wchar-subscripts -Wimplicit-int -Wimplicit-function-declaration -Wcomment -Wformat -Wmissing-braces -Wnonnull -Wparentheses -Wpointer-sign -Wreturn-type -Wsequence-point -Wstrict-aliasing -Wstrict-overflow=1 -Wswitch -Wtrigraphs -Wuninitialized -Wunknown-pragmas -Wunused-function -Wunused-label -Wunused-value -Wunused-variable -Wunused-function
-# export CFLAGS := $(DEVICE) -std=c11 -Wall -O2 -g -gdwarf-2 -Waddress -Warray-bounds -Wchar-subscripts -Wimplicit-int -Wimplicit-function-declaration -Wcomment -Wformat -Wmissing-braces -Wnonnull -Wparentheses -Wpointer-sign -Wreturn-type -Wsequence-point -Wstrict-aliasing -Wstrict-overflow=1 -Wswitch -Wtrigraphs -Wuninitialized -Wunknown-pragmas -Wunused-function -Wunused-label -Wunused-value -Wunused-variable -Wunused-function
-export CFLAGS := $(DEVICE) -std=c11 -Wall -O0 -g -gdwarf-2 -Waddress -Warray-bounds -Wchar-subscripts -Wimplicit-int -Wimplicit-function-declaration -Wcomment -Wformat -Wmissing-braces -Wnonnull -Wparentheses -Wpointer-sign -Wreturn-type -Wsequence-point -Wstrict-aliasing -Wstrict-overflow=1 -Wswitch -Wtrigraphs -Wuninitialized -Wunknown-pragmas -Wunused-function -Wunused-label -Wunused-value -Wunused-variable -Wunused-function
+export CFLAGS := $(DEVICE) -std=c11 -Wall -O2 -g -gdwarf-2 -Waddress -Warray-bounds -Wchar-subscripts -Wimplicit-int -Wimplicit-function-declaration -Wcomment -Wformat -Wmissing-braces -Wnonnull -Wparentheses -Wpointer-sign -Wreturn-type -Wsequence-point -Wstrict-aliasing -Wstrict-overflow=1 -Wswitch -Wtrigraphs -Wuninitialized -Wunknown-pragmas -Wunused-function -Wunused-label -Wunused-value -Wunused-variable -Wunused-function
 export AFLAGS := -c $(DEVICE) -x assembler-with-cpp -D__ASSEMBLY__ -gdwarf-2
 # export LFLAGS := $(DEVICE) -Wl,-Map=XiZi-imx6q-sabrelite.map,-cref,-u,_boot_start -T $(KERNEL_ROOT)/hardkernel/arch/arm/armv7-a/cortex-a9/preboot_for_imx6q-sabrelite/nxp_imx6q_sabrelite.lds
 export LFLAGS := $(DEVICE) --specs=nosys.specs -Wl,-Map=XiZi-imx6q-sabrelite.map,-cref,-u,_boot_start -T $(KERNEL_ROOT)/hardkernel/arch/arm/armv7-a/cortex-a9/preboot_for_imx6q-sabrelite/nxp_imx6q_sabrelite.lds
diff --git a/Ubiquitous/XiZi_AIoT/services/Makefile b/Ubiquitous/XiZi_AIoT/services/Makefile
index 2de214d06..7f6bc5fb9 100644
--- a/Ubiquitous/XiZi_AIoT/services/Makefile
+++ b/Ubiquitous/XiZi_AIoT/services/Makefile
@@ -1,5 +1,5 @@
 
-SRC_DIR := fs shell lib boards drivers tools app 
+SRC_DIR := fs shell lib boards drivers semaphore tools app 
 
 
 include $(KERNEL_ROOT)/compiler.mk
diff --git a/Ubiquitous/XiZi_AIoT/services/app/Makefile b/Ubiquitous/XiZi_AIoT/services/app/Makefile
index 9eac2949b..fdc097b9d 100644
--- a/Ubiquitous/XiZi_AIoT/services/app/Makefile
+++ b/Ubiquitous/XiZi_AIoT/services/app/Makefile
@@ -22,11 +22,12 @@ INC_DIR = 	-I$(KERNEL_ROOT)/services/shell/letter-shell \
 			-I$(KERNEL_ROOT)/services/lib/serial \
 			-I$(KERNEL_ROOT)/services/lib/usyscall \
 			-I$(KERNEL_ROOT)/services/fs/libfs \
+			-I$(KERNEL_ROOT)/services/semaphore \
 			-I$(KERNEL_ROOT)/services/boards/$(BOARD) \
 			-I$(KERNEL_ROOT)/services/app 
 
 ifeq ($(BOARD), imx6q-sabrelite)
-all: init test_fs simple_client simple_server shell fs_server test_thread test_irq_hdlr test_irq_block test_irq_send eth_driver epit_server readme.txt | bin
+all: init test_fs simple_client simple_server shell fs_server semaphore_server test_thread test_irq_hdlr test_irq_block test_irq_send eth_driver epit_server readme.txt | bin
 else 
 all: init test_fs simple_client simple_server shell fs_server test_irq_hdlr readme.txt | bin
 endif
@@ -52,7 +53,11 @@ epit_server: timer.o epit.o ccm_pll.o usyscall.o arch_usyscall.o libserial.o pri
 	@${objdump} -S $@ > $@.asm
 endif
 
-test_thread: test_thread.o libserial.o printf.o usyscall.o arch_usyscall.o
+semaphore_server: semaphore_server.o libserial.o printf.o usyscall.o arch_usyscall.o libipc.o session.o
+	@${ld} ${user_ldflags} -e main -o $@ $^ ${board_specs}
+	@${objdump} -S $@ > $@.asm
+
+test_thread: test_thread.o libserial.o printf.o usyscall.o arch_usyscall.o libfs.o libsemaphore.o libipc.o session.o libmem.o
 	@${ld} ${user_ldflags} -e main -o $@ $^ ${board_specs}
 	@${objdump} -S $@ > $@.asm
 
@@ -64,19 +69,19 @@ test_irq_hdlr: test_irq_handler.o libserial.o printf.o libipc.o session.o usysca
 	@${ld} ${user_ldflags} -e main -o $@ $^ ${board_specs}
 	@${objdump} -S $@ > $@.asm
 
-shell: shell_port.o libserial.o printf.o shell_cmd_list.o shell.o shell_ext.o libfs_to_client.o libipc.o session.o usyscall.o arch_usyscall.o libmem.o
+shell: shell_port.o libserial.o printf.o shell_cmd_list.o shell.o shell_ext.o libfs.o libipc.o session.o usyscall.o arch_usyscall.o libmem.o
 	@${ld} ${user_ldflags} -e main -o $@ $^ ${board_specs}
 	@${objdump} -S $@ > $@.asm
 	
-init: init.o libfs_to_client.o libipc.o session.o libserial.o printf.o usyscall.o arch_usyscall.o libmem.o
+init: init.o libfs.o libipc.o session.o libserial.o printf.o usyscall.o arch_usyscall.o libmem.o
 	@${ld} ${user_ldflags} -e main -o $@ $^ ${board_specs}
 	@${objdump} -S $@ > $@.asm
 
-test_fs: test_fs.o libfs_to_client.o libipc.o session.o libserial.o printf.o usyscall.o arch_usyscall.o libmem.o
+test_fs: test_fs.o libfs.o libipc.o session.o libserial.o printf.o usyscall.o arch_usyscall.o libmem.o
 	@${ld} ${user_ldflags} -e main -o $@ $^ ${board_specs}
 	@${objdump} -S $@ > $@.asm
 
-simple_client: simple_client.o libserial.o printf.o libipc.o session.o simple_service.o libfs_to_client.o usyscall.o arch_usyscall.o  libmem.o
+simple_client: simple_client.o libserial.o printf.o libipc.o session.o simple_service.o libfs.o usyscall.o arch_usyscall.o  libmem.o
 	@${ld} ${user_ldflags} -e main -o $@ $^ ${board_specs}
 	@${objdump} -S $@ > $@.asm
 
@@ -84,7 +89,7 @@ simple_server: simple_server.o libserial.o printf.o libipc.o session.o simple_se
 	@${ld} ${user_ldflags} -e main -o $@ $^ ${board_specs}
 	@${objdump} -S $@ > $@.asm
 
-fs_server: fs_server.o libfs_to_client.o fs.o libserial.o printf.o libipc.o session.o block_io.o usyscall.o arch_usyscall.o libmem.o
+fs_server: fs_server.o libfs.o fs.o libserial.o printf.o libipc.o session.o block_io.o usyscall.o arch_usyscall.o libmem.o
 	@${ld} ${user_ldflags} -e main -o $@ $^ ${board_specs}
 	@${objdump} -S $@ > $@.asm
 
diff --git a/Ubiquitous/XiZi_AIoT/services/app/init.c b/Ubiquitous/XiZi_AIoT/services/app/init.c
index d204ca4a8..dbedd4795 100755
--- a/Ubiquitous/XiZi_AIoT/services/app/init.c
+++ b/Ubiquitous/XiZi_AIoT/services/app/init.c
@@ -12,7 +12,7 @@
 // init: The initial user-level program
 #include <stdbool.h>
 
-#include "libfs_to_client.h"
+#include "libfs.h"
 #include "libserial.h"
 #include "usyscall.h"
 
diff --git a/Ubiquitous/XiZi_AIoT/services/app/simple_client.c b/Ubiquitous/XiZi_AIoT/services/app/simple_client.c
index 8df8064a1..62689573b 100755
--- a/Ubiquitous/XiZi_AIoT/services/app/simple_client.c
+++ b/Ubiquitous/XiZi_AIoT/services/app/simple_client.c
@@ -14,7 +14,7 @@
 #include <stdint.h>
 #include <stdlib.h>
 
-#include "libfs_to_client.h"
+#include "libfs.h"
 #include "libserial.h"
 #include "simple_service.h"
 #include "usyscall.h"
diff --git a/Ubiquitous/XiZi_AIoT/services/app/test_fs.c b/Ubiquitous/XiZi_AIoT/services/app/test_fs.c
index c6f2e5f95..f1400fac7 100644
--- a/Ubiquitous/XiZi_AIoT/services/app/test_fs.c
+++ b/Ubiquitous/XiZi_AIoT/services/app/test_fs.c
@@ -15,8 +15,8 @@
 #include <stdbool.h>
 #include <string.h>
 
+#include "libfs.h"
 #include "libserial.h"
-#include "libfs_to_client.h"
 #include "usyscall.h"
 
 #define BLOCK_SIZE 256
diff --git a/Ubiquitous/XiZi_AIoT/services/app/test_thread.c b/Ubiquitous/XiZi_AIoT/services/app/test_thread.c
index 63bcac3db..b897414f0 100644
--- a/Ubiquitous/XiZi_AIoT/services/app/test_thread.c
+++ b/Ubiquitous/XiZi_AIoT/services/app/test_thread.c
@@ -10,38 +10,91 @@
  * See the Mulan PSL v2 for more details.
  */
 
+#include "libfs.h"
+#include "libsemaphore.h"
 #include "libserial.h"
 #include "usyscall.h"
 
 static int global_value;
+static sem_t sem;
+static char sem_server_name[] = "SemTestServer";
 
 int sub_thread_entry(int argc, char** argv)
 {
-    for (int i = 0; i < 1000; i++) {
+    for (int i = 0; i < 100; i++) {
         global_value++;
-        printf("[gval]: %d\n", global_value);
     }
+
+    struct Session sem_session;
+    while (connect_session(&sem_session, sem_server_name, 4096) < 0) {
+        yield(SYS_TASK_YIELD_NO_REASON);
+    }
+
+    printf("Thread signal sem.\n");
+    sem_signal(&sem_session, &sem);
+
     exit(0);
     return 0;
 }
 
+static char sem_file_name[] = "/semaphore_server";
 int main(int argc, char** argv)
 {
     global_value = 0;
 
-    for (int i = 0; i < 10; i++) {
-        global_value++;
-        printf("|gval|: %d\n", global_value);
-    }
+    printf("Test Create Semaphore.\n");
+    struct Session sem_session;
+    bool spawn_sem_server = false;
+    while (connect_session(&sem_session, sem_server_name, 4096) < 0) {
+        if (!spawn_sem_server) {
+            struct Session fs_session;
+            printf("Connect FS.\n");
+            if (connect_session(&fs_session, "MemFS", 8192) < 0) {
+                printf("Connect FS failed.\n");
+                exit(1);
+            }
 
+            printf("Loading semaphore server.\n");
+            int fd = -1;
+            if ((fd = open(&fs_session, sem_file_name)) < 0) {
+                printf("Open %s failed.\n", sem_file_name);
+                free_session(&fs_session);
+                exit(1);
+            }
+
+            printf("Spawn semaphore server.\n");
+            char* sem_server_params[] = { sem_server_name, sem_server_name, NULL };
+            if (spawn(&fs_session, fd, read, fsize, sem_server_name, sem_server_params) < 0) {
+                printf("Spawn %s failed.\n", sem_file_name);
+                free_session(&fs_session);
+                exit(1);
+            }
+
+            spawn_sem_server = true;
+            free_session(&fs_session);
+        }
+    }
+    printf("Create new sem.\n");
+    sem_create(&sem_session, &sem, 0);
+
+    printf("Create new thread.\n");
     char* task_param[2] = { "add_gval", NULL };
-    int tid = thread(sub_thread_entry, "add_gval", task_param);
-
-    for (int i = 0; i < 1000; i++) {
-        global_value++;
-        printf("|gval|: %d\n", global_value);
+    int nr_thread = 0;
+    for (int i = 0; i < 128; i++) {
+        int tid = thread(sub_thread_entry, "add_gval", task_param);
+        if (tid > 0) {
+            nr_thread++;
+        }
     }
 
+    printf("Main thread waiting for sem for %d times.\n", nr_thread);
+    for (int i = 0; i < nr_thread; i++) {
+        int sem_wait_ret = sem_wait(&sem_session, &sem, 0);
+    }
+    printf("Main thread sem %d wait return, global val: %d.\n", sem, global_value);
+
+    sem_delete(&sem_session, &sem);
+    free_session(&sem_session);
     exit(0);
     return 0;
 }
\ No newline at end of file
diff --git a/Ubiquitous/XiZi_AIoT/services/boards/zynq7000-zc702/Makefile b/Ubiquitous/XiZi_AIoT/services/boards/zynq7000-zc702/Makefile
index b5ada4070..64cf9c5e2 100644
--- a/Ubiquitous/XiZi_AIoT/services/boards/zynq7000-zc702/Makefile
+++ b/Ubiquitous/XiZi_AIoT/services/boards/zynq7000-zc702/Makefile
@@ -25,7 +25,7 @@ INC_DIR = 	-I$(KERNEL_ROOT)/services/fs/libfs \
 			-I$(KERNEL_ROOT)/services/app
 
 board: libserial.o stub.o arch_usyscall.o
-	@mv $^ ../../app
+	@mv $^ $(KERNEL_ROOT)/services/app
 
 %.o: %.c
 	@echo "cc $^"
diff --git a/Ubiquitous/XiZi_AIoT/services/fs/fs_server/fs_server.c b/Ubiquitous/XiZi_AIoT/services/fs/fs_server/fs_server.c
index bf2f31646..f84e109df 100644
--- a/Ubiquitous/XiZi_AIoT/services/fs/fs_server/fs_server.c
+++ b/Ubiquitous/XiZi_AIoT/services/fs/fs_server/fs_server.c
@@ -14,7 +14,7 @@
 
 #include "block_io.h"
 #include "fs.h"
-#include "libfs_to_client.h"
+#include "libfs.h"
 #include "libserial.h"
 #include "usyscall.h"
 
diff --git a/Ubiquitous/XiZi_AIoT/services/fs/libfs/Makefile b/Ubiquitous/XiZi_AIoT/services/fs/libfs/Makefile
index 3ad9655b9..69365fd69 100644
--- a/Ubiquitous/XiZi_AIoT/services/fs/libfs/Makefile
+++ b/Ubiquitous/XiZi_AIoT/services/fs/libfs/Makefile
@@ -23,8 +23,8 @@ INC_DIR = 	-I$(KERNEL_ROOT)/services/fs/libfs \
 			-I$(KERNEL_ROOT)/services/boards/$(BOARD) \
 			-I$(KERNEL_ROOT)/services/app
 
-fs_server: libfs_to_client.o
-	@mv $^ ../../app
+fs_server: libfs.o
+	@mv $^ $(KERNEL_ROOT)/services/app
 
 %.o: %.c
 	@echo "cc $^"
diff --git a/Ubiquitous/XiZi_AIoT/services/fs/libfs/libfs_to_client.c b/Ubiquitous/XiZi_AIoT/services/fs/libfs/libfs.c
similarity index 98%
rename from Ubiquitous/XiZi_AIoT/services/fs/libfs/libfs_to_client.c
rename to Ubiquitous/XiZi_AIoT/services/fs/libfs/libfs.c
index b2109b944..855f95dfe 100644
--- a/Ubiquitous/XiZi_AIoT/services/fs/libfs/libfs_to_client.c
+++ b/Ubiquitous/XiZi_AIoT/services/fs/libfs/libfs.c
@@ -9,7 +9,7 @@
  * MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
  * See the Mulan PSL v2 for more details.
  */
-#include "libfs_to_client.h"
+#include "libfs.h"
 
 IPC_INTERFACE(Ipc_ls, 1, path, strlen(path) + 1);
 int ls(struct Session* session, char* path)
diff --git a/Ubiquitous/XiZi_AIoT/services/fs/libfs/libfs_to_client.h b/Ubiquitous/XiZi_AIoT/services/fs/libfs/libfs.h
similarity index 100%
rename from Ubiquitous/XiZi_AIoT/services/fs/libfs/libfs_to_client.h
rename to Ubiquitous/XiZi_AIoT/services/fs/libfs/libfs.h
diff --git a/Ubiquitous/XiZi_AIoT/services/lib/ipc/Makefile b/Ubiquitous/XiZi_AIoT/services/lib/ipc/Makefile
index 01eb7ec78..fbcfc9073 100644
--- a/Ubiquitous/XiZi_AIoT/services/lib/ipc/Makefile
+++ b/Ubiquitous/XiZi_AIoT/services/lib/ipc/Makefile
@@ -23,7 +23,7 @@ INC_DIR = 	-I$(KERNEL_ROOT)/services/lib/ipc \
 			-I$(KERNEL_ROOT)/services/app
 
 all: libipc.o session.o
-	@mv $^ ../../app
+	@mv $^ $(KERNEL_ROOT)/services/app
 
 %.o: %.c
 	@echo "cc $^"
diff --git a/Ubiquitous/XiZi_AIoT/services/lib/memory/Makefile b/Ubiquitous/XiZi_AIoT/services/lib/memory/Makefile
index a0f0330ba..bc5bcdd18 100644
--- a/Ubiquitous/XiZi_AIoT/services/lib/memory/Makefile
+++ b/Ubiquitous/XiZi_AIoT/services/lib/memory/Makefile
@@ -21,7 +21,7 @@ INC_DIR = 	-I$(KERNEL_ROOT)/services/app \
 		  	-I$(KERNEL_ROOT)/services/lib/ipc 
 
 all: libmem.o
-	@mv $^ ../../app
+	@mv $^ $(KERNEL_ROOT)/services/app
 
 %.o: %.c
 	@echo "cc $^"
diff --git a/Ubiquitous/XiZi_AIoT/services/lib/usyscall/Makefile b/Ubiquitous/XiZi_AIoT/services/lib/usyscall/Makefile
index 32c99e269..71972c252 100644
--- a/Ubiquitous/XiZi_AIoT/services/lib/usyscall/Makefile
+++ b/Ubiquitous/XiZi_AIoT/services/lib/usyscall/Makefile
@@ -21,7 +21,7 @@ INC_DIR = 	-I$(KERNEL_ROOT)/services/app \
 		  	-I$(KERNEL_ROOT)/services/lib/ipc 
 
 all: usyscall.o
-	@mv $^ ../../app
+	@mv $^ $(KERNEL_ROOT)/services/app
 
 %.o: %.c
 	@echo "cc $^"
diff --git a/Ubiquitous/XiZi_AIoT/services/semaphore/Makefile b/Ubiquitous/XiZi_AIoT/services/semaphore/Makefile
new file mode 100644
index 000000000..9a1651097
--- /dev/null
+++ b/Ubiquitous/XiZi_AIoT/services/semaphore/Makefile
@@ -0,0 +1,29 @@
+ifeq ($(BOARD), imx6q-sabrelite)
+toolchain ?= arm-none-eabi-
+user_ldflags = -N -Ttext 0
+cflags = -std=c11 -march=armv7-a -mtune=cortex-a9 -nostdlib -nodefaultlibs -mfloat-abi=soft -fno-pic -static -fno-builtin -fno-strict-aliasing -Wall -ggdb -Wno-unused -Werror -fno-omit-frame-pointer -fno-stack-protector -fno-pie
+endif
+ifeq ($(BOARD), zynq7000-zc702)
+toolchain ?= arm-xilinx-eabi-
+user_ldflags = --start-group,-lgcc,-lc,--end-group
+cflags = -std=c11 -march=armv7-a -mtune=cortex-a9 -nostdlib -nodefaultlibs -mfloat-abi=soft -fno-pic -static -fno-builtin -fno-strict-aliasing -Wall -ggdb -Wno-unused -Werror -fno-omit-frame-pointer -fno-stack-protector -fno-pie
+#cflags = -Wall -g -std=c11 
+endif
+cc = ${toolchain}gcc
+ld = ${toolchain}g++
+objdump = ${toolchain}objdump
+
+c_useropts = -O2
+
+INC_DIR = 	-I$(KERNEL_ROOT)/services/lib/ipc \
+			-I$(KERNEL_ROOT)/services/lib/serial \
+			-I$(KERNEL_ROOT)/services/lib/usyscall \
+			-I$(KERNEL_ROOT)/services/semaphore \
+			-I$(KERNEL_ROOT)/services/app
+
+fs_server: libsemaphore.o semaphore_server.o
+	@mv $^ $(KERNEL_ROOT)/services/app
+
+%.o: %.c
+	@echo "cc $^"
+	@${cc} ${cflags} ${c_useropts} ${INC_DIR} -o $@ -c $^
\ No newline at end of file
diff --git a/Ubiquitous/XiZi_AIoT/services/semaphore/libsemaphore.c b/Ubiquitous/XiZi_AIoT/services/semaphore/libsemaphore.c
new file mode 100644
index 000000000..62e1f3d53
--- /dev/null
+++ b/Ubiquitous/XiZi_AIoT/services/semaphore/libsemaphore.c
@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2020 AIIT XUOS Lab
+ * XiUOS is licensed under Mulan PSL v2.
+ * You can use this software according to the terms and conditions of the Mulan PSL v2.
+ * You may obtain a copy of Mulan PSL v2 at:
+ *        http://license.coscl.org.cn/MulanPSL2
+ * THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
+ * EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
+ * MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
+ * See the Mulan PSL v2 for more details.
+ */
+
+#include "libsemaphore.h"
+
+IPC_INTERFACE(Ipc_sem_create, 2, sem, count, sizeof(sem_t), sizeof(int));
+sem_err_t sem_create(struct Session* session, sem_t* sem, int count)
+{
+    return IPC_CALL(Ipc_sem_create)(session, sem, &count);
+}
+
+IPC_INTERFACE(Ipc_sem_delete, 1, sem, sizeof(sem_t));
+sem_err_t sem_delete(struct Session* session, sem_t* sem)
+{
+    return IPC_CALL(Ipc_sem_delete)(session, sem);
+}
+
+IPC_INTERFACE(Ipc_sem_signal, 1, sem, sizeof(sem_t));
+int sem_signal(struct Session* session, sem_t* sem)
+{
+    return IPC_CALL(Ipc_sem_signal)(session, sem);
+}
+
+IPC_INTERFACE(Ipc_sem_wait, 2, sem, timeout, sizeof(sem_t), sizeof(int));
+int sem_wait(struct Session* session, sem_t* sem, int timeout)
+{
+    return IPC_CALL(Ipc_sem_wait)(session, sem, &timeout);
+}
\ No newline at end of file
diff --git a/Ubiquitous/XiZi_AIoT/services/semaphore/libsemaphore.h b/Ubiquitous/XiZi_AIoT/services/semaphore/libsemaphore.h
new file mode 100644
index 000000000..36e374c31
--- /dev/null
+++ b/Ubiquitous/XiZi_AIoT/services/semaphore/libsemaphore.h
@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2020 AIIT XUOS Lab
+ * XiUOS is licensed under Mulan PSL v2.
+ * You can use this software according to the terms and conditions of the Mulan PSL v2.
+ * You may obtain a copy of Mulan PSL v2 at:
+ *        http://license.coscl.org.cn/MulanPSL2
+ * THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
+ * EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
+ * MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
+ * See the Mulan PSL v2 for more details.
+ */
+#pragma once
+
+#include <stddef.h>
+#include <stdint.h>
+#include <string.h>
+
+#include "libipc.h"
+
+#define MAX_SUPPORT_SEMAPHORES NR_MAX_SESSION
+
+typedef uint32_t sem_t;
+typedef int sem_err_t;
+
+enum {
+    SEMAPHORE_ERR = -1,
+    SEMAPHORE_SUC = 1,
+};
+
+IPC_SERVICES(IpcSemaphoreServer, Ipc_sem_create, Ipc_sem_delete, Ipc_sem_signal, Ipc_sem_wait);
+
+sem_err_t sem_create(struct Session* session, sem_t* sem, int count);
+sem_err_t sem_delete(struct Session* session, sem_t* sem);
+int sem_signal(struct Session* session, sem_t* sem);
+int sem_wait(struct Session* session, sem_t* sem, int timeout);
\ 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
new file mode 100644
index 000000000..47d6d858c
--- /dev/null
+++ b/Ubiquitous/XiZi_AIoT/services/semaphore/semaphore_server.c
@@ -0,0 +1,121 @@
+/*
+ * Copyright (c) 2020 AIIT XUOS Lab
+ * XiUOS is licensed under Mulan PSL v2.
+ * You can use this software according to the terms and conditions of the Mulan PSL v2.
+ * You may obtain a copy of Mulan PSL v2 at:
+ *        http://license.coscl.org.cn/MulanPSL2
+ * THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
+ * EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
+ * MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
+ * See the Mulan PSL v2 for more details.
+ */
+
+#include "libsemaphore.h"
+#include "libserial.h"
+#include "usyscall.h"
+
+struct Semaphore {
+    bool valid;
+    int count;
+};
+
+struct Semaphore sem_pool[MAX_SUPPORT_SEMAPHORES];
+
+int IPC_DO_SERVE_FUNC(Ipc_sem_create)(sem_t* sem, int* count)
+{
+    int idx = 0;
+    for (idx = 0; idx < MAX_SUPPORT_SEMAPHORES; idx++) {
+        if (!sem_pool[idx].valid) {
+            break;
+        }
+    }
+
+    if (idx == MAX_SUPPORT_SEMAPHORES) {
+        return SEMAPHORE_ERR;
+    }
+
+    sem_pool[idx].valid = true;
+    sem_pool[idx].count = *count;
+
+    *sem = idx;
+    return SEMAPHORE_SUC;
+}
+
+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;
+    }
+
+    sem_pool[*sem].valid = false;
+    return SEMAPHORE_SUC;
+}
+
+int IPC_DO_SERVE_FUNC(Ipc_sem_wait)(sem_t* sem, int* timeout)
+{
+    if (*sem < 0 || *sem > MAX_SUPPORT_SEMAPHORES) {
+        return SEMAPHORE_ERR;
+    }
+
+    /// @todo support timeout
+    // return if sem is freed(no valid) or sem count is sufficient
+    if (!sem_pool[*sem].valid || sem_pool[*sem].count > 0) {
+        sem_pool[*sem].count--;
+        return SEMAPHORE_SUC;
+    }
+
+    // block current session
+    delay_session();
+    return SEMAPHORE_ERR;
+}
+
+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;
+    }
+
+    sem_pool[*sem].count++;
+    return SEMAPHORE_SUC;
+}
+
+IPC_SERVER_INTERFACE(Ipc_sem_create, 2);
+IPC_SERVER_INTERFACE(Ipc_sem_delete, 1);
+IPC_SERVER_INTERFACE(Ipc_sem_signal, 1);
+IPC_SERVER_INTERFACE(Ipc_sem_wait, 2);
+IPC_SERVER_REGISTER_INTERFACES(IpcSemaphoreServer, 4, //
+    Ipc_sem_create, Ipc_sem_delete, Ipc_sem_signal, Ipc_sem_wait);
+
+int main(int argc, char** argv)
+{
+    /// @todo support custom server name
+    static char default_server_name[] = "DefaultSemaphoreServer";
+
+    char* server_name = default_server_name;
+    if (argc == 2) {
+        server_name = argv[1];
+    }
+
+    if (register_server(server_name) < 0) {
+        printf("[%s] Register server failed.\n", server_name);
+        exit(1);
+    }
+
+    for (int idx = 0; idx < MAX_SUPPORT_SEMAPHORES; idx++) {
+        sem_pool[idx].valid = false;
+    }
+
+    ipc_server_loop(&IpcSemaphoreServer);
+
+    // never reaching here
+    exit(0);
+    return 0;
+}
\ No newline at end of file
diff --git a/Ubiquitous/XiZi_AIoT/services/shell/letter-shell/Makefile b/Ubiquitous/XiZi_AIoT/services/shell/letter-shell/Makefile
index 1d979f0f2..7a195298f 100644
--- a/Ubiquitous/XiZi_AIoT/services/shell/letter-shell/Makefile
+++ b/Ubiquitous/XiZi_AIoT/services/shell/letter-shell/Makefile
@@ -24,7 +24,7 @@ INC_DIR = 	-I$(KERNEL_ROOT)/services/app \
 			-I$(KERNEL_ROOT)/services/boards/$(BOARD) 
 
 all: shell_cmd_list.o shell_ext.o shell.o
-	@mv $^ ../../app
+	@mv $^ $(KERNEL_ROOT)/services/app
 
 shell_cmd_list.o: shell_cmd_list.c
 	@echo "cc shell_cmd_list"
diff --git a/Ubiquitous/XiZi_AIoT/services/shell/letter-shell/shell.c b/Ubiquitous/XiZi_AIoT/services/shell/letter-shell/shell.c
index d7588636c..5813d3b37 100644
--- a/Ubiquitous/XiZi_AIoT/services/shell/letter-shell/shell.c
+++ b/Ubiquitous/XiZi_AIoT/services/shell/letter-shell/shell.c
@@ -17,7 +17,7 @@
 #include "shell_cfg.h"
 #include "shell_ext.h"
 
-#include "libfs_to_client.h"
+#include "libfs.h"
 #include "libipc.h"
 
 #if SHELL_USING_CMD_EXPORT == 1