diff --git a/src/bin/ch3_taskinfo.rs b/src/bin/ch3_taskinfo.rs
index 7f55f15..b536599 100644
--- a/src/bin/ch3_taskinfo.rs
+++ b/src/bin/ch3_taskinfo.rs
@@ -11,12 +11,12 @@ use user_lib::{
 #[no_mangle]
 pub fn main() -> usize {
     let t1 = get_time() as usize;
-    let info = TaskInfo::new();
+    let mut info = TaskInfo::new();
     get_time();
     sleep(500);
     let t2 = get_time() as usize;
     // 注意本次 task info 调用也计入
-    assert_eq!(0, task_info(&info));
+    assert_eq!(0, task_info(&mut info));
     let t3 = get_time() as usize;
     assert!(3 <= info.syscall_times[SYSCALL_GETTIMEOFDAY]);
     assert_eq!(1, info.syscall_times[SYSCALL_TASK_INFO]);
@@ -30,7 +30,7 @@ pub fn main() -> usize {
     // 想想为什么 write 调用是两次
     println!("string from task info test\n");
     let t4 = get_time() as usize;
-    assert_eq!(0, task_info(&info));
+    assert_eq!(0, task_info(&mut info));
     let t5 = get_time() as usize;
     assert!(5 <= info.syscall_times[SYSCALL_GETTIMEOFDAY]);
     assert_eq!(2, info.syscall_times[SYSCALL_TASK_INFO]);
diff --git a/src/bin/ch6_file1.rs b/src/bin/ch6_file1.rs
index 6565121..26c3ed8 100644
--- a/src/bin/ch6_file1.rs
+++ b/src/bin/ch6_file1.rs
@@ -13,8 +13,8 @@ pub fn main() -> i32 {
     let fd = open(fname, OpenFlags::CREATE | OpenFlags::WRONLY);
     assert!(fd > 0);
     let fd = fd as usize;
-    let stat: Stat = Stat::new();
-    let ret = fstat(fd, &stat);
+    let mut stat: Stat = Stat::new();
+    let ret = fstat(fd, &mut stat);
     assert_eq!(ret, 0);
     assert_eq!(stat.mode, StatMode::FILE);
     assert_eq!(stat.nlink, 1);
diff --git a/src/bin/ch6_file2.rs b/src/bin/ch6_file2.rs
index c646314..a49c4d1 100644
--- a/src/bin/ch6_file2.rs
+++ b/src/bin/ch6_file2.rs
@@ -14,29 +14,29 @@ pub fn main() -> i32 {
     let (lname0, lname1, lname2) = ("linkname0\0", "linkname1\0", "linkname2\0");
     let fd = open(fname, OpenFlags::CREATE | OpenFlags::WRONLY) as usize;
     link(fname, lname0);
-    let stat = Stat::new();
-    fstat(fd, &stat);
+    let mut stat = Stat::new();
+    fstat(fd, &mut stat);
     assert_eq!(stat.nlink, 2);
     link(fname, lname1);
     link(fname, lname2);
-    fstat(fd, &stat);
+    fstat(fd, &mut stat);
     assert_eq!(stat.nlink, 4);
     write(fd, test_str.as_bytes());
     close(fd);
 
     unlink(fname);
     let fd = open(lname0, OpenFlags::RDONLY) as usize;
-    let stat2 = Stat::new();
+    let mut stat2 = Stat::new();
     let mut buf = [0u8; 100];
     let read_len = read(fd, &mut buf) as usize;
     assert_eq!(test_str, core::str::from_utf8(&buf[..read_len]).unwrap(),);
-    fstat(fd, &stat2);
+    fstat(fd, &mut stat2);
     assert_eq!(stat2.dev, stat.dev);
     assert_eq!(stat2.ino, stat.ino);
     assert_eq!(stat2.nlink, 3);
     unlink(lname1);
     unlink(lname2);
-    fstat(fd, &stat2);
+    fstat(fd, &mut stat2);
     assert_eq!(stat2.nlink, 1);
     close(fd);
     unlink(lname0);
diff --git a/src/lib.rs b/src/lib.rs
index 233349e..4068f6d 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -203,7 +203,7 @@ pub fn unlink(path: &str) -> isize {
     sys_unlinkat(AT_FDCWD as usize, path, 0)
 }
 
-pub fn fstat(fd: usize, st: &Stat) -> isize {
+pub fn fstat(fd: usize, st: &mut Stat) -> isize {
     sys_fstat(fd, st)
 }
 
@@ -307,7 +307,7 @@ pub fn pipe(pipe_fd: &mut [usize]) -> isize {
     sys_pipe(pipe_fd)
 }
 
-pub fn task_info(info: &TaskInfo) -> isize {
+pub fn task_info(info: &mut TaskInfo) -> isize {
     sys_task_info(info)
 }
 
diff --git a/src/syscall.rs b/src/syscall.rs
index c186281..776f7b7 100644
--- a/src/syscall.rs
+++ b/src/syscall.rs
@@ -128,7 +128,7 @@ pub fn sys_unlinkat(dirfd: usize, path: &str, flags: usize) -> isize {
     syscall(SYSCALL_UNLINKAT, [dirfd, path.as_ptr() as usize, flags])
 }
 
-pub fn sys_fstat(fd: usize, st: &Stat) -> isize {
+pub fn sys_fstat(fd: usize, st: &mut Stat) -> isize {
     syscall(SYSCALL_FSTAT, [fd, st as *const _ as usize, 0])
 }
 
@@ -210,7 +210,7 @@ pub fn sys_pipe(pipe: &mut [usize]) -> isize {
     syscall(SYSCALL_PIPE, [pipe.as_mut_ptr() as usize, 0, 0])
 }
 
-pub fn sys_task_info(info: &TaskInfo) -> isize {
+pub fn sys_task_info(info: &mut TaskInfo) -> isize {
     syscall(SYSCALL_TASK_INFO, [info as *const _ as usize, 0, 0])
 }