diff --git a/flake.nix b/flake.nix
index 6656094..4492e28 100644
--- a/flake.nix
+++ b/flake.nix
@@ -65,6 +65,7 @@
         devShells.nemu = pkgs.mkShell {
           packages = with pkgs; [
             clang-tools
+            gdb
           ];
           inputsFrom = [
             self.packages.${system}.nemu
diff --git a/nemu/src/cpu/cpu-exec.c b/nemu/src/cpu/cpu-exec.c
index efb9557..c5696fa 100644
--- a/nemu/src/cpu/cpu-exec.c
+++ b/nemu/src/cpu/cpu-exec.c
@@ -75,6 +75,9 @@ static void exec_once(Decode *s, vaddr_t pc) {
 
 static void execute(uint64_t n) {
   Decode s;
+#ifdef CONFIG_ITRACE
+  memset(s.logbuf, 0, CONFIG_ITRACE_BUFFER * 128 * sizeof(char));
+#endif
   for (;n > 0; n --) {
     exec_once(&s, cpu.pc);
     g_nr_guest_inst ++;