diff --git a/app/src/main/cpp/lightswitch.cpp b/app/src/main/cpp/lightswitch.cpp
index 19b394ef..0537ff84 100644
--- a/app/src/main/cpp/lightswitch.cpp
+++ b/app/src/main/cpp/lightswitch.cpp
@@ -2,6 +2,23 @@
 #include <string>
 
 #include <unicorn/unicorn.h>
+#include <syslog.h>
+
+// code to be emulated
+#define ARM_CODE "\xab\x05\x00\xb8\xaf\x05\x40\x38" // str w11, [x13]; ldrb w15, [x13]
+
+// memory address where emulation starts
+#define ADDRESS 0x10000
+
+static void hook_block(uc_engine *uc, uint64_t address, uint32_t size, void *user_data)
+{
+    syslog(LOG_DEBUG, ">>> Tracing basic block at 0x%" PRIx64 ", block size = 0x%x\n", size);
+}
+
+static void hook_code(uc_engine *uc, uint64_t address, uint32_t size, void *user_data)
+{
+    syslog(LOG_DEBUG, ">>> Tracing instruction at 0x%" PRIx64 ", instruction size = 0x%x\n", size);
+}
 
 extern "C" JNIEXPORT jstring JNICALL
 Java_gq_cyuubi_lightswitch_MainActivity_stringFromJNI(
@@ -9,11 +26,54 @@ Java_gq_cyuubi_lightswitch_MainActivity_stringFromJNI(
         jobject /* this */) {
     uc_engine *uc;
     uc_err err;
+    uc_hook trace1, trace2;
+
+    int64_t x11 = 0x12345678;        // X11 register
+    int64_t x13 = 0x10000 + 0x8;     // X13 register
+    int64_t x15 = 0x33;              // X15 register
+
+    syslog(LOG_DEBUG, "Emulate ARM64 code\n");
+
+    // Initialize emulator in ARM mode
     err = uc_open(UC_ARCH_ARM64, UC_MODE_ARM, &uc);
     if (err) {
-        std::string failed = "loading failed!";
-        return env->NewStringUTF(failed.c_str());
+        std::string finished = "failed!";
+        return env->NewStringUTF(finished.c_str());
     }
-    std::string hello = "loaded successfully!";
-    return env->NewStringUTF(hello.c_str());
+
+    // map 2MB memory for this emulation
+    uc_mem_map(uc, ADDRESS, 2 * 1024 * 1024, UC_PROT_ALL);
+
+    // write machine code to be emulated to memory
+    uc_mem_write(uc, ADDRESS, ARM_CODE, sizeof(ARM_CODE) - 1);
+
+    // initialize machine registers
+    uc_reg_write(uc, UC_ARM64_REG_X11, &x11);
+    uc_reg_write(uc, UC_ARM64_REG_X13, &x13);
+    uc_reg_write(uc, UC_ARM64_REG_X15, &x15);
+
+    // tracing all basic blocks with customized callback
+    uc_hook_add(uc, &trace1, UC_HOOK_BLOCK, (void*)hook_block, NULL, 1, 0);
+
+    // tracing one instruction at ADDRESS with customized callback
+    uc_hook_add(uc, &trace2, UC_HOOK_CODE, (void*)hook_code, NULL, ADDRESS, ADDRESS);
+
+    // emulate machine code in infinite time (last param = 0), or when
+    // finishing all the code.
+    err = uc_emu_start(uc, ADDRESS, ADDRESS + sizeof(ARM_CODE) -1, 0, 0);
+    if (err) {
+        syslog(LOG_DEBUG, "Failed on uc_emu_start() with error returned: %u\n", err);
+    }
+
+    // now print out some registers
+    syslog(LOG_DEBUG, ">>> Emulation done. Below is the CPU context\n");
+    syslog(LOG_DEBUG, ">>> As little endian, X15 should be 0x78:\n");
+
+    uc_reg_read(uc, UC_ARM64_REG_X15, &x15);
+    syslog(LOG_DEBUG, ">>> X15 = 0x%" PRIx64 "\n", x15);
+
+    uc_close(uc);
+
+    std::string finished = "finished!";
+    return env->NewStringUTF(finished.c_str());
 }