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/batch.rs b/os/src/batch.rs
index 7f29b21b..06764a0c 100644
--- a/os/src/batch.rs
+++ b/os/src/batch.rs
@@ -1,7 +1,7 @@
-use lazy_static::*;
-use crate::trap::TrapContext;
 use crate::sync::UPSafeCell;
+use crate::trap::TrapContext;
 use core::arch::asm;
+use lazy_static::*;
 
 const USER_STACK_SIZE: usize = 4096 * 2;
 const KERNEL_STACK_SIZE: usize = 4096 * 2;
@@ -19,8 +19,12 @@ struct UserStack {
     data: [u8; USER_STACK_SIZE],
 }
 
-static KERNEL_STACK: KernelStack = KernelStack { data: [0; KERNEL_STACK_SIZE] };
-static USER_STACK: UserStack = UserStack { data: [0; USER_STACK_SIZE] };
+static KERNEL_STACK: KernelStack = KernelStack {
+    data: [0; KERNEL_STACK_SIZE],
+};
+static USER_STACK: UserStack = UserStack {
+    data: [0; USER_STACK_SIZE],
+};
 
 impl KernelStack {
     fn get_sp(&self) -> usize {
@@ -28,7 +32,9 @@ impl KernelStack {
     }
     pub fn push_context(&self, cx: TrapContext) -> &'static mut TrapContext {
         let cx_ptr = (self.get_sp() - core::mem::size_of::<TrapContext>()) as *mut TrapContext;
-        unsafe { *cx_ptr = cx; }
+        unsafe {
+            *cx_ptr = cx;
+        }
         unsafe { cx_ptr.as_mut().unwrap() }
     }
 }
@@ -49,7 +55,12 @@ impl AppManager {
     pub fn print_app_info(&self) {
         println!("[kernel] num_app = {}", self.num_app);
         for i in 0..self.num_app {
-            println!("[kernel] app_{} [{:#x}, {:#x})", i, self.app_start[i], self.app_start[i + 1]);
+            println!(
+                "[kernel] app_{} [{:#x}, {:#x})",
+                i,
+                self.app_start[i],
+                self.app_start[i + 1]
+            );
         }
     }
 
@@ -61,22 +72,18 @@ impl AppManager {
         // clear icache
         asm!("fence.i");
         // clear app area
-        core::slice::from_raw_parts_mut(
-            APP_BASE_ADDRESS as *mut u8,
-            APP_SIZE_LIMIT
-        ).fill(0);
+        core::slice::from_raw_parts_mut(APP_BASE_ADDRESS as *mut u8, APP_SIZE_LIMIT).fill(0);
         let app_src = core::slice::from_raw_parts(
             self.app_start[app_id] as *const u8,
-            self.app_start[app_id + 1] - self.app_start[app_id]
-        );
-        let app_dst = core::slice::from_raw_parts_mut(
-            APP_BASE_ADDRESS as *mut u8,
-            app_src.len()
+            self.app_start[app_id + 1] - self.app_start[app_id],
         );
+        let app_dst = core::slice::from_raw_parts_mut(APP_BASE_ADDRESS as *mut u8, app_src.len());
         app_dst.copy_from_slice(app_src);
     }
 
-    pub fn get_current_app(&self) -> usize { self.current_app }
+    pub fn get_current_app(&self) -> usize {
+        self.current_app
+    }
 
     pub fn move_to_next_app(&mut self) {
         self.current_app += 1;
@@ -84,21 +91,24 @@ impl AppManager {
 }
 
 lazy_static! {
-    static ref APP_MANAGER: UPSafeCell<AppManager> = unsafe { UPSafeCell::new({
-        extern "C" { fn _num_app(); }
-        let num_app_ptr = _num_app as usize as *const usize;
-        let num_app = num_app_ptr.read_volatile();
-        let mut app_start: [usize; MAX_APP_NUM + 1] = [0; MAX_APP_NUM + 1];
-        let app_start_raw: &[usize] =  core::slice::from_raw_parts(
-            num_app_ptr.add(1), num_app + 1
-        );
-        app_start[..=num_app].copy_from_slice(app_start_raw);
-        AppManager {
-            num_app,
-            current_app: 0,
-            app_start,
-        }
-    })};
+    static ref APP_MANAGER: UPSafeCell<AppManager> = unsafe {
+        UPSafeCell::new({
+            extern "C" {
+                fn _num_app();
+            }
+            let num_app_ptr = _num_app as usize as *const usize;
+            let num_app = num_app_ptr.read_volatile();
+            let mut app_start: [usize; MAX_APP_NUM + 1] = [0; MAX_APP_NUM + 1];
+            let app_start_raw: &[usize] =
+                core::slice::from_raw_parts(num_app_ptr.add(1), num_app + 1);
+            app_start[..=num_app].copy_from_slice(app_start_raw);
+            AppManager {
+                num_app,
+                current_app: 0,
+                app_start,
+            }
+        })
+    };
 }
 
 pub fn init() {
@@ -119,11 +129,14 @@ pub fn run_next_app() -> ! {
     drop(app_manager);
     // before this we have to drop local variables related to resources manually
     // and release the resources
-    extern "C" { fn __restore(cx_addr: usize); }
+    extern "C" {
+        fn __restore(cx_addr: usize);
+    }
     unsafe {
-        __restore(KERNEL_STACK.push_context(
-            TrapContext::app_init_context(APP_BASE_ADDRESS, USER_STACK.get_sp())
-        ) as *const _ as usize);
+        __restore(KERNEL_STACK.push_context(TrapContext::app_init_context(
+            APP_BASE_ADDRESS,
+            USER_STACK.get_sp(),
+        )) as *const _ as usize);
     }
     panic!("Unreachable in batch::run_current_app!");
 }
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/main.rs b/os/src/main.rs
index 3cea360f..7c661b43 100644
--- a/os/src/main.rs
+++ b/os/src/main.rs
@@ -6,12 +6,12 @@ use core::arch::global_asm;
 
 #[macro_use]
 mod console;
+mod batch;
 mod lang_items;
 mod sbi;
+mod sync;
 mod syscall;
 mod trap;
-mod batch;
-mod sync;
 
 global_asm!(include_str!("entry.asm"));
 global_asm!(include_str!("link_app.S"));
@@ -22,10 +22,8 @@ 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);
     }
 }
 
@@ -36,4 +34,4 @@ pub fn rust_main() -> ! {
     trap::init();
     batch::init();
     batch::run_next_app();
-}
\ No newline at end of file
+}
diff --git a/os/src/sbi.rs b/os/src/sbi.rs
index aa12b7f3..90ba2c2a 100644
--- a/os/src/sbi.rs
+++ b/os/src/sbi.rs
@@ -39,4 +39,3 @@ 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 51dea1e7..430af564 100644
--- a/os/src/syscall/mod.rs
+++ b/os/src/syscall/mod.rs
@@ -14,4 +14,3 @@ 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 66808bcf..8f4170d1 100644
--- a/os/src/syscall/process.rs
+++ b/os/src/syscall/process.rs
@@ -3,4 +3,4 @@ use crate::batch::run_next_app;
 pub fn sys_exit(exit_code: i32) -> ! {
     println!("[kernel] Application exited with code {}", exit_code);
     run_next_app()
-}
\ No newline at end of file
+}
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 83396231..0210809e 100644
--- a/os/src/trap/mod.rs
+++ b/os/src/trap/mod.rs
@@ -1,23 +1,20 @@
 mod context;
 
+use crate::batch::run_next_app;
+use crate::syscall::syscall;
+use core::arch::global_asm;
 use riscv::register::{
     mtvec::TrapMode,
-    stvec,
-    scause::{
-        self,
-        Trap,
-        Exception,
-    },
-    stval,
+    scause::{self, Exception, Trap},
+    stval, stvec,
 };
-use crate::syscall::syscall;
-use crate::batch::run_next_app;
-use core::arch::global_asm;
 
 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);
     }
@@ -32,8 +29,7 @@ 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, kernel killed it.");
             run_next_app();
         }
@@ -42,7 +38,11 @@ pub fn trap_handler(cx: &mut TrapContext) -> &mut TrapContext {
             run_next_app();
         }
         _ => {
-            panic!("Unsupported trap {:?}, stval = {:#x}!", scause.cause(), stval);
+            panic!(
+                "Unsupported trap {:?}, stval = {:#x}!",
+                scause.cause(),
+                stval
+            );
         }
     }
     cx
diff --git a/user/src/bin/01store_fault.rs b/user/src/bin/01store_fault.rs
index 994d8bfd..f8023eb7 100644
--- a/user/src/bin/01store_fault.rs
+++ b/user/src/bin/01store_fault.rs
@@ -8,6 +8,8 @@ extern crate user_lib;
 fn main() -> i32 {
     println!("Into Test store_fault, we will insert an invalid store operation...");
     println!("Kernel should kill this application!");
-    unsafe { (0x0 as *mut u8).write_volatile(0); }
+    unsafe {
+        core::ptr::null_mut::<u8>().write_volatile(0);
+    }
     0
-}
\ No newline at end of file
+}
diff --git a/user/src/bin/02power.rs b/user/src/bin/02power.rs
index 54fde244..f628f348 100644
--- a/user/src/bin/02power.rs
+++ b/user/src/bin/02power.rs
@@ -24,4 +24,4 @@ fn main() -> i32 {
     }
     println!("Test power 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 baa59e81..73a4037f 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"]
@@ -26,12 +26,16 @@ 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 write(fd: usize, buf: &[u8]) -> isize {
+    sys_write(fd, buf)
+}
+pub fn exit(exit_code: i32) -> isize {
+    sys_exit(exit_code)
+}