diff --git a/os/Cargo.toml b/os/Cargo.toml
index 0d1bb342..b53bb700 100644
--- a/os/Cargo.toml
+++ b/os/Cargo.toml
@@ -12,4 +12,4 @@ lazy_static = { version = "1.4.0", features = ["spin_no_std"] }
 
 [features]
 board_qemu = []
-board_k210 = []
\ No newline at end of file
+board_k210 = []
diff --git a/os/build.rs b/os/build.rs
index 5e032311..944b46fe 100644
--- a/os/build.rs
+++ b/os/build.rs
@@ -1,5 +1,5 @@
+use std::fs::{read_dir, File};
 use std::io::{Result, Write};
-use std::fs::{File, read_dir};
 
 fn main() {
     println!("cargo:rerun-if-changed=../user/src/");
@@ -22,12 +22,16 @@ fn insert_app_data() -> Result<()> {
         .collect();
     apps.sort();
 
-    writeln!(f, r#"
+    writeln!(
+        f,
+        r#"
     .align 3
     .section .data
     .global _num_app
 _num_app:
-    .quad {}"#, apps.len())?;
+    .quad {}"#,
+        apps.len()
+    )?;
 
     for i in 0..apps.len() {
         writeln!(f, r#"    .quad app_{}_start"#, i)?;
@@ -36,13 +40,17 @@ _num_app:
 
     for (idx, app) in apps.iter().enumerate() {
         println!("app_{}: {}", idx, app);
-        writeln!(f, r#"
+        writeln!(
+            f,
+            r#"
     .section .data
     .global app_{0}_start
     .global app_{0}_end
 app_{0}_start:
     .incbin "{2}{1}.bin"
-app_{0}_end:"#, idx, app, TARGET_PATH)?;
+app_{0}_end:"#,
+            idx, app, TARGET_PATH
+        )?;
     }
     Ok(())
-}
\ No newline at end of file
+}
diff --git a/os/src/config.rs b/os/src/config.rs
index e50175a0..fe3fb104 100644
--- a/os/src/config.rs
+++ b/os/src/config.rs
@@ -8,4 +8,4 @@ pub const APP_SIZE_LIMIT: usize = 0x20000;
 pub const CLOCK_FREQ: usize = 403000000 / 62;
 
 #[cfg(feature = "board_qemu")]
-pub const CLOCK_FREQ: usize = 12500000;
\ No newline at end of file
+pub const CLOCK_FREQ: usize = 12500000;
diff --git a/os/src/console.rs b/os/src/console.rs
index 2bd55930..dda4911a 100644
--- a/os/src/console.rs
+++ b/os/src/console.rs
@@ -1,5 +1,5 @@
-use core::fmt::{self, Write};
 use crate::sbi::console_putchar;
+use core::fmt::{self, Write};
 
 struct Stdout;
 
@@ -29,5 +29,3 @@ macro_rules! println {
         $crate::console::print(format_args!(concat!($fmt, "\n") $(, $($arg)+)?));
     }
 }
-
-
diff --git a/os/src/lang_items.rs b/os/src/lang_items.rs
index 3f5462ab..af3e5152 100644
--- a/os/src/lang_items.rs
+++ b/os/src/lang_items.rs
@@ -1,10 +1,15 @@
-use core::panic::PanicInfo;
 use crate::sbi::shutdown;
+use core::panic::PanicInfo;
 
 #[panic_handler]
 fn panic(info: &PanicInfo) -> ! {
     if let Some(location) = info.location() {
-        println!("[kernel] Panicked at {}:{} {}", location.file(), location.line(), info.message().unwrap());
+        println!(
+            "[kernel] Panicked at {}:{} {}",
+            location.file(),
+            location.line(),
+            info.message().unwrap()
+        );
     } else {
         println!("[kernel] Panicked: {}", info.message().unwrap());
     }
diff --git a/os/src/loader.rs b/os/src/loader.rs
index 0d0a5774..0f08a174 100644
--- a/os/src/loader.rs
+++ b/os/src/loader.rs
@@ -1,5 +1,5 @@
-use crate::trap::TrapContext;
 use crate::config::*;
+use crate::trap::TrapContext;
 use core::arch::asm;
 
 #[repr(align(4096))]
@@ -14,15 +14,13 @@ struct UserStack {
     data: [u8; USER_STACK_SIZE],
 }
 
-static KERNEL_STACK: [KernelStack; MAX_APP_NUM] = [
-    KernelStack { data: [0; KERNEL_STACK_SIZE], };
-    MAX_APP_NUM
-];
+static KERNEL_STACK: [KernelStack; MAX_APP_NUM] = [KernelStack {
+    data: [0; KERNEL_STACK_SIZE],
+}; MAX_APP_NUM];
 
-static USER_STACK: [UserStack; MAX_APP_NUM] = [
-    UserStack { data: [0; USER_STACK_SIZE], };
-    MAX_APP_NUM
-];
+static USER_STACK: [UserStack; MAX_APP_NUM] = [UserStack {
+    data: [0; USER_STACK_SIZE],
+}; MAX_APP_NUM];
 
 impl KernelStack {
     fn get_sp(&self) -> usize {
@@ -30,7 +28,9 @@ impl KernelStack {
     }
     pub fn push_context(&self, trap_cx: TrapContext) -> usize {
         let trap_cx_ptr = (self.get_sp() - core::mem::size_of::<TrapContext>()) as *mut TrapContext;
-        unsafe { *trap_cx_ptr = trap_cx; }
+        unsafe {
+            *trap_cx_ptr = trap_cx;
+        }
         trap_cx_ptr as usize
     }
 }
@@ -46,39 +46,41 @@ fn get_base_i(app_id: usize) -> usize {
 }
 
 pub fn get_num_app() -> usize {
-    extern "C" { fn _num_app(); }
+    extern "C" {
+        fn _num_app();
+    }
     unsafe { (_num_app as usize as *const usize).read_volatile() }
 }
 
 pub fn load_apps() {
-    extern "C" { fn _num_app(); }
+    extern "C" {
+        fn _num_app();
+    }
     let num_app_ptr = _num_app as usize as *const usize;
     let num_app = get_num_app();
-    let app_start = unsafe {
-        core::slice::from_raw_parts(num_app_ptr.add(1), num_app + 1)
-    };
+    let app_start = unsafe { core::slice::from_raw_parts(num_app_ptr.add(1), num_app + 1) };
     // clear i-cache first
-    unsafe { asm!("fence.i"); }
+    unsafe {
+        asm!("fence.i");
+    }
     // load apps
     for i in 0..num_app {
         let base_i = get_base_i(i);
         // clear region
-        (base_i..base_i + APP_SIZE_LIMIT).for_each(|addr| unsafe {
-            (addr as *mut u8).write_volatile(0)
-        });
+        (base_i..base_i + APP_SIZE_LIMIT)
+            .for_each(|addr| unsafe { (addr as *mut u8).write_volatile(0) });
         // load app from data section to memory
         let src = unsafe {
             core::slice::from_raw_parts(app_start[i] as *const u8, app_start[i + 1] - app_start[i])
         };
-        let dst = unsafe {
-            core::slice::from_raw_parts_mut(base_i as *mut u8, src.len())
-        };
+        let dst = unsafe { core::slice::from_raw_parts_mut(base_i as *mut u8, src.len()) };
         dst.copy_from_slice(src);
     }
 }
 
 pub fn init_app_cx(app_id: usize) -> usize {
-    KERNEL_STACK[app_id].push_context(
-        TrapContext::app_init_context(get_base_i(app_id), USER_STACK[app_id].get_sp()),
-    )
+    KERNEL_STACK[app_id].push_context(TrapContext::app_init_context(
+        get_base_i(app_id),
+        USER_STACK[app_id].get_sp(),
+    ))
 }
diff --git a/os/src/main.rs b/os/src/main.rs
index 61e7213a..cd2cecaa 100644
--- a/os/src/main.rs
+++ b/os/src/main.rs
@@ -6,15 +6,15 @@ use core::arch::global_asm;
 
 #[macro_use]
 mod console;
-mod lang_items;
-mod sbi;
-mod syscall;
-mod trap;
-mod loader;
 mod config;
+mod lang_items;
+mod loader;
+mod sbi;
+mod sync;
+mod syscall;
 mod task;
 mod timer;
-mod sync;
+mod trap;
 
 global_asm!(include_str!("entry.asm"));
 global_asm!(include_str!("link_app.S"));
@@ -25,10 +25,8 @@ fn clear_bss() {
         fn ebss();
     }
     unsafe {
-        core::slice::from_raw_parts_mut(
-            sbss as usize as *mut u8,
-            ebss as usize - sbss as usize,
-        ).fill(0);
+        core::slice::from_raw_parts_mut(sbss as usize as *mut u8, ebss as usize - sbss as usize)
+            .fill(0);
     }
 }
 
@@ -42,4 +40,4 @@ pub fn rust_main() -> ! {
     timer::set_next_trigger();
     task::run_first_task();
     panic!("Unreachable in rust_main!");
-}
\ No newline at end of file
+}
diff --git a/os/src/sbi.rs b/os/src/sbi.rs
index c8ecbf1d..2e2804b2 100644
--- a/os/src/sbi.rs
+++ b/os/src/sbi.rs
@@ -43,4 +43,3 @@ pub fn shutdown() -> ! {
     sbi_call(SBI_SHUTDOWN, 0, 0, 0);
     panic!("It should shutdown!");
 }
-
diff --git a/os/src/sync/mod.rs b/os/src/sync/mod.rs
index 77295248..d1ce5bcf 100644
--- a/os/src/sync/mod.rs
+++ b/os/src/sync/mod.rs
@@ -1,3 +1,3 @@
 mod up;
 
-pub use up::UPSafeCell;
\ No newline at end of file
+pub use up::UPSafeCell;
diff --git a/os/src/sync/up.rs b/os/src/sync/up.rs
index 642668c1..c7b2c9ee 100644
--- a/os/src/sync/up.rs
+++ b/os/src/sync/up.rs
@@ -18,10 +18,12 @@ impl<T> UPSafeCell<T> {
     /// User is responsible to guarantee that inner struct is only used in
     /// uniprocessor.
     pub unsafe fn new(value: T) -> Self {
-        Self { inner: RefCell::new(value) }
+        Self {
+            inner: RefCell::new(value),
+        }
     }
     /// Panic if the data has been borrowed.
     pub fn exclusive_access(&self) -> RefMut<'_, T> {
         self.inner.borrow_mut()
     }
-}
\ No newline at end of file
+}
diff --git a/os/src/syscall/fs.rs b/os/src/syscall/fs.rs
index b8c46591..3e38eae7 100644
--- a/os/src/syscall/fs.rs
+++ b/os/src/syscall/fs.rs
@@ -7,9 +7,9 @@ pub fn sys_write(fd: usize, buf: *const u8, len: usize) -> isize {
             let str = core::str::from_utf8(slice).unwrap();
             print!("{}", str);
             len as isize
-        },
+        }
         _ => {
             panic!("Unsupported fd in sys_write!");
         }
     }
-}
\ No newline at end of file
+}
diff --git a/os/src/syscall/mod.rs b/os/src/syscall/mod.rs
index da411680..572b081a 100644
--- a/os/src/syscall/mod.rs
+++ b/os/src/syscall/mod.rs
@@ -18,4 +18,3 @@ pub fn syscall(syscall_id: usize, args: [usize; 3]) -> isize {
         _ => panic!("Unsupported syscall_id: {}", syscall_id),
     }
 }
-
diff --git a/os/src/syscall/process.rs b/os/src/syscall/process.rs
index 23eab1ff..55856e70 100644
--- a/os/src/syscall/process.rs
+++ b/os/src/syscall/process.rs
@@ -1,7 +1,4 @@
-use crate::task::{
-    suspend_current_and_run_next,
-    exit_current_and_run_next,
-};
+use crate::task::{exit_current_and_run_next, suspend_current_and_run_next};
 use crate::timer::get_time_ms;
 
 pub fn sys_exit(exit_code: i32) -> ! {
@@ -17,4 +14,4 @@ pub fn sys_yield() -> isize {
 
 pub fn sys_get_time() -> isize {
     get_time_ms() as isize
-}
\ No newline at end of file
+}
diff --git a/os/src/task/context.rs b/os/src/task/context.rs
index 35055d0c..375042d8 100644
--- a/os/src/task/context.rs
+++ b/os/src/task/context.rs
@@ -15,7 +15,9 @@ impl TaskContext {
         }
     }
     pub fn goto_restore(kstack_ptr: usize) -> Self {
-        extern "C" { fn __restore(); }
+        extern "C" {
+            fn __restore();
+        }
         Self {
             ra: __restore as usize,
             sp: kstack_ptr,
@@ -23,4 +25,3 @@ impl TaskContext {
         }
     }
 }
-
diff --git a/os/src/task/mod.rs b/os/src/task/mod.rs
index 66c8a796..7d0ccb5d 100644
--- a/os/src/task/mod.rs
+++ b/os/src/task/mod.rs
@@ -4,10 +4,10 @@ mod task;
 
 use crate::config::MAX_APP_NUM;
 use crate::loader::{get_num_app, init_app_cx};
+use crate::sync::UPSafeCell;
 use lazy_static::*;
 use switch::__switch;
 use task::{TaskControlBlock, TaskStatus};
-use crate::sync::UPSafeCell;
 
 pub use context::TaskContext;
 
@@ -24,23 +24,22 @@ struct TaskManagerInner {
 lazy_static! {
     pub static ref TASK_MANAGER: TaskManager = {
         let num_app = get_num_app();
-        let mut tasks = [
-            TaskControlBlock {
-                task_cx: TaskContext::zero_init(),
-                task_status: TaskStatus::UnInit
-            };
-            MAX_APP_NUM
-        ];
+        let mut tasks = [TaskControlBlock {
+            task_cx: TaskContext::zero_init(),
+            task_status: TaskStatus::UnInit,
+        }; MAX_APP_NUM];
         for i in 0..num_app {
             tasks[i].task_cx = TaskContext::goto_restore(init_app_cx(i));
             tasks[i].task_status = TaskStatus::Ready;
         }
         TaskManager {
             num_app,
-            inner: unsafe { UPSafeCell::new(TaskManagerInner {
-                tasks,
-                current_task: 0,
-            })},
+            inner: unsafe {
+                UPSafeCell::new(TaskManagerInner {
+                    tasks,
+                    current_task: 0,
+                })
+            },
         }
     };
 }
@@ -55,10 +54,7 @@ impl TaskManager {
         let mut _unused = TaskContext::zero_init();
         // before this, we should drop local variables that must be dropped manually
         unsafe {
-            __switch(
-                &mut _unused as *mut TaskContext,
-                next_task_cx_ptr,
-            );
+            __switch(&mut _unused as *mut TaskContext, next_task_cx_ptr);
         }
         panic!("unreachable in run_first_task!");
     }
@@ -80,9 +76,7 @@ impl TaskManager {
         let current = inner.current_task;
         (current + 1..current + self.num_app + 1)
             .map(|id| id % self.num_app)
-            .find(|id| {
-                inner.tasks[*id].task_status == TaskStatus::Ready
-            })
+            .find(|id| inner.tasks[*id].task_status == TaskStatus::Ready)
     }
 
     fn run_next_task(&self) {
@@ -96,10 +90,7 @@ impl TaskManager {
             drop(inner);
             // before this, we should drop local variables that must be dropped manually
             unsafe {
-                __switch(
-                    current_task_cx_ptr,
-                    next_task_cx_ptr,
-                );
+                __switch(current_task_cx_ptr, next_task_cx_ptr);
             }
             // go back to user mode
         } else {
@@ -132,4 +123,4 @@ pub fn suspend_current_and_run_next() {
 pub fn exit_current_and_run_next() {
     mark_current_exited();
     run_next_task();
-}
\ No newline at end of file
+}
diff --git a/os/src/task/switch.rs b/os/src/task/switch.rs
index dd3a2d3e..59f8b1a0 100644
--- a/os/src/task/switch.rs
+++ b/os/src/task/switch.rs
@@ -4,8 +4,5 @@ use core::arch::global_asm;
 global_asm!(include_str!("switch.S"));
 
 extern "C" {
-    pub fn __switch(
-        current_task_cx_ptr: *mut TaskContext,
-        next_task_cx_ptr: *const TaskContext
-    );
+    pub fn __switch(current_task_cx_ptr: *mut TaskContext, next_task_cx_ptr: *const TaskContext);
 }
diff --git a/os/src/task/task.rs b/os/src/task/task.rs
index fd5f5f9c..43c4f9c2 100644
--- a/os/src/task/task.rs
+++ b/os/src/task/task.rs
@@ -12,4 +12,4 @@ pub enum TaskStatus {
     Ready,
     Running,
     Exited,
-}
\ No newline at end of file
+}
diff --git a/os/src/timer.rs b/os/src/timer.rs
index ad226e64..048aa3b7 100644
--- a/os/src/timer.rs
+++ b/os/src/timer.rs
@@ -1,6 +1,6 @@
-use riscv::register::time;
-use crate::sbi::set_timer;
 use crate::config::CLOCK_FREQ;
+use crate::sbi::set_timer;
+use riscv::register::time;
 
 const TICKS_PER_SEC: usize = 100;
 const MSEC_PER_SEC: usize = 1000;
diff --git a/os/src/trap/context.rs b/os/src/trap/context.rs
index e2575de9..af5a53a8 100644
--- a/os/src/trap/context.rs
+++ b/os/src/trap/context.rs
@@ -1,4 +1,4 @@
-use riscv::register::sstatus::{Sstatus, self, SPP};
+use riscv::register::sstatus::{self, Sstatus, SPP};
 
 #[repr(C)]
 pub struct TrapContext {
@@ -8,7 +8,9 @@ pub struct TrapContext {
 }
 
 impl TrapContext {
-    pub fn set_sp(&mut self, sp: usize) { self.x[2] = sp; }
+    pub fn set_sp(&mut self, sp: usize) {
+        self.x[2] = sp;
+    }
     pub fn app_init_context(entry: usize, sp: usize) -> Self {
         let mut sstatus = sstatus::read();
         sstatus.set_spp(SPP::User);
diff --git a/os/src/trap/mod.rs b/os/src/trap/mod.rs
index bae775d6..527d6b4b 100644
--- a/os/src/trap/mod.rs
+++ b/os/src/trap/mod.rs
@@ -1,36 +1,30 @@
 mod context;
 
-use riscv::register::{
-    mtvec::TrapMode,
-    stvec,
-    scause::{
-        self,
-        Trap,
-        Exception,
-        Interrupt,
-    },
-    stval,
-    sie,
-};
 use crate::syscall::syscall;
-use crate::task::{
-    exit_current_and_run_next,
-    suspend_current_and_run_next,
-};
+use crate::task::{exit_current_and_run_next, suspend_current_and_run_next};
 use crate::timer::set_next_trigger;
 use core::arch::global_asm;
+use riscv::register::{
+    mtvec::TrapMode,
+    scause::{self, Exception, Interrupt, Trap},
+    sie, stval, stvec,
+};
 
 global_asm!(include_str!("trap.S"));
 
 pub fn init() {
-    extern "C" { fn __alltraps(); }
+    extern "C" {
+        fn __alltraps();
+    }
     unsafe {
         stvec::write(__alltraps as usize, TrapMode::Direct);
     }
 }
 
 pub fn enable_timer_interrupt() {
-    unsafe { sie::set_stimer(); }
+    unsafe {
+        sie::set_stimer();
+    }
 }
 
 #[no_mangle]
@@ -42,8 +36,7 @@ pub fn trap_handler(cx: &mut TrapContext) -> &mut TrapContext {
             cx.sepc += 4;
             cx.x[10] = syscall(cx.x[17], [cx.x[10], cx.x[11], cx.x[12]]) as usize;
         }
-        Trap::Exception(Exception::StoreFault) |
-        Trap::Exception(Exception::StorePageFault) => {
+        Trap::Exception(Exception::StoreFault) | Trap::Exception(Exception::StorePageFault) => {
             println!("[kernel] PageFault in application, bad addr = {:#x}, bad instruction = {:#x}, kernel killed it.", stval, cx.sepc);
             exit_current_and_run_next();
         }
@@ -56,7 +49,11 @@ pub fn trap_handler(cx: &mut TrapContext) -> &mut TrapContext {
             suspend_current_and_run_next();
         }
         _ => {
-            panic!("Unsupported trap {:?}, stval = {:#x}!", scause.cause(), stval);
+            panic!(
+                "Unsupported trap {:?}, stval = {:#x}!",
+                scause.cause(),
+                stval
+            );
         }
     }
     cx
diff --git a/user/src/bin/00power_3.rs b/user/src/bin/00power_3.rs
index e0ec5f3d..1a04dc7a 100644
--- a/user/src/bin/00power_3.rs
+++ b/user/src/bin/00power_3.rs
@@ -25,4 +25,4 @@ fn main() -> i32 {
     println!("{}^{} = {}(MOD {})", p, iter, s[cur], m);
     println!("Test power_3 OK!");
     0
-}
\ No newline at end of file
+}
diff --git a/user/src/bin/03sleep.rs b/user/src/bin/03sleep.rs
index 83411233..7e43d9c2 100644
--- a/user/src/bin/03sleep.rs
+++ b/user/src/bin/03sleep.rs
@@ -15,4 +15,4 @@ fn main() -> i32 {
     }
     println!("Test sleep OK!");
     0
-}
\ No newline at end of file
+}
diff --git a/user/src/console.rs b/user/src/console.rs
index ac801174..d37e867c 100644
--- a/user/src/console.rs
+++ b/user/src/console.rs
@@ -1,5 +1,5 @@
-use core::fmt::{self, Write};
 use super::write;
+use core::fmt::{self, Write};
 
 struct Stdout;
 
@@ -28,4 +28,4 @@ macro_rules! println {
     ($fmt: literal $(, $($arg: tt)+)?) => {
         $crate::console::print(format_args!(concat!($fmt, "\n") $(, $($arg)+)?));
     }
-}
\ No newline at end of file
+}
diff --git a/user/src/lang_items.rs b/user/src/lang_items.rs
index c90d297f..3aee17ba 100644
--- a/user/src/lang_items.rs
+++ b/user/src/lang_items.rs
@@ -2,9 +2,14 @@
 fn panic_handler(panic_info: &core::panic::PanicInfo) -> ! {
     let err = panic_info.message().unwrap();
     if let Some(location) = panic_info.location() {
-        println!("Panicked at {}:{}, {}", location.file(), location.line(), err);
+        println!(
+            "Panicked at {}:{}, {}",
+            location.file(),
+            location.line(),
+            err
+        );
     } else {
         println!("Panicked: {}", err);
     }
     loop {}
-}
\ No newline at end of file
+}
diff --git a/user/src/lib.rs b/user/src/lib.rs
index 4e0da5e3..1491afc2 100644
--- a/user/src/lib.rs
+++ b/user/src/lib.rs
@@ -4,8 +4,8 @@
 
 #[macro_use]
 pub mod console;
-mod syscall;
 mod lang_items;
+mod syscall;
 
 #[no_mangle]
 #[link_section = ".text.entry"]
@@ -26,14 +26,22 @@ fn clear_bss() {
         fn start_bss();
         fn end_bss();
     }
-    (start_bss as usize..end_bss as usize).for_each(|addr| {
-        unsafe { (addr as *mut u8).write_volatile(0); }
+    (start_bss as usize..end_bss as usize).for_each(|addr| unsafe {
+        (addr as *mut u8).write_volatile(0);
     });
 }
 
 use syscall::*;
 
-pub fn write(fd: usize, buf: &[u8]) -> isize { sys_write(fd, buf) }
-pub fn exit(exit_code: i32) -> isize { sys_exit(exit_code) }
-pub fn yield_() -> isize { sys_yield() }
-pub fn get_time() -> isize { sys_get_time() }
\ No newline at end of file
+pub fn write(fd: usize, buf: &[u8]) -> isize {
+    sys_write(fd, buf)
+}
+pub fn exit(exit_code: i32) -> isize {
+    sys_exit(exit_code)
+}
+pub fn yield_() -> isize {
+    sys_yield()
+}
+pub fn get_time() -> isize {
+    sys_get_time()
+}