diff --git a/os/build.rs b/os/build.rs
index e32fa7ab..d7658983 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/");
@@ -22,35 +22,46 @@ 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)?;
     }
     writeln!(f, r#"    .quad app_{}_end"#, apps.len() - 1)?;
 
-    writeln!(f, r#"
+    writeln!(
+        f,
+        r#"
     .global _app_names
-_app_names:"#)?;
+_app_names:"#
+    )?;
     for app in apps.iter() {
         writeln!(f, r#"    .string "{}""#, 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
     .align 3
 app_{0}_start:
     .incbin "{2}{1}"
-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/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 bfdc3970..585c4b34 100644
--- a/os/src/loader.rs
+++ b/os/src/loader.rs
@@ -2,22 +2,24 @@ use alloc::vec::Vec;
 use lazy_static::*;
 
 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 get_app_data(app_id: usize) -> &'static [u8] {
-    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) };
     assert!(app_id < num_app);
     unsafe {
         core::slice::from_raw_parts(
             app_start[app_id] as *const u8,
-            app_start[app_id + 1] - app_start[app_id]
+            app_start[app_id + 1] - app_start[app_id],
         )
     }
 }
@@ -25,7 +27,9 @@ pub fn get_app_data(app_id: usize) -> &'static [u8] {
 lazy_static! {
     static ref APP_NAMES: Vec<&'static str> = {
         let num_app = get_num_app();
-        extern "C" { fn _app_names(); }
+        extern "C" {
+            fn _app_names();
+        }
         let mut start = _app_names as usize as *const u8;
         let mut v = Vec::new();
         unsafe {
@@ -44,7 +48,6 @@ lazy_static! {
     };
 }
 
-
 #[allow(unused)]
 pub fn get_app_data_by_name(name: &str) -> Option<&'static [u8]> {
     let num_app = get_num_app();
@@ -59,4 +62,4 @@ pub fn list_apps() {
         println!("{}", app);
     }
     println!("**************/");
-}
\ No newline at end of file
+}
diff --git a/os/src/main.rs b/os/src/main.rs
index 51f2ec02..b31681b1 100644
--- a/os/src/main.rs
+++ b/os/src/main.rs
@@ -10,16 +10,16 @@ extern crate bitflags;
 
 #[macro_use]
 mod console;
-mod lang_items;
-mod sbi;
-mod syscall;
-mod trap;
-mod loader;
 mod config;
+mod lang_items;
+mod loader;
+mod mm;
+mod sbi;
+mod sync;
+mod syscall;
 mod task;
 mod timer;
-mod sync;
-mod mm;
+mod trap;
 
 use core::arch::global_asm;
 
@@ -32,10 +32,8 @@ 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);
     }
 }
 
@@ -53,4 +51,4 @@ pub fn rust_main() -> ! {
     loader::list_apps();
     task::run_tasks();
     panic!("Unreachable in rust_main!");
-}
\ No newline at end of file
+}
diff --git a/os/src/mm/address.rs b/os/src/mm/address.rs
index 1be9ae74..12864870 100644
--- a/os/src/mm/address.rs
+++ b/os/src/mm/address.rs
@@ -1,5 +1,5 @@
-use crate::config::{PAGE_SIZE, PAGE_SIZE_BITS};
 use super::PageTableEntry;
+use crate::config::{PAGE_SIZE, PAGE_SIZE_BITS};
 use core::fmt::{self, Debug, Formatter};
 
 const PA_WIDTH_SV39: usize = 56;
@@ -48,35 +48,59 @@ impl Debug for PhysPageNum {
 /// usize -> T: usize.into()
 
 impl From<usize> for PhysAddr {
-    fn from(v: usize) -> Self { Self(v & ( (1 << PA_WIDTH_SV39) - 1 )) }
+    fn from(v: usize) -> Self {
+        Self(v & ((1 << PA_WIDTH_SV39) - 1))
+    }
 }
 impl From<usize> for PhysPageNum {
-    fn from(v: usize) -> Self { Self(v & ( (1 << PPN_WIDTH_SV39) - 1 )) }
+    fn from(v: usize) -> Self {
+        Self(v & ((1 << PPN_WIDTH_SV39) - 1))
+    }
 }
 impl From<usize> for VirtAddr {
-    fn from(v: usize) -> Self { Self(v & ( (1 << VA_WIDTH_SV39) - 1 )) }
+    fn from(v: usize) -> Self {
+        Self(v & ((1 << VA_WIDTH_SV39) - 1))
+    }
 }
 impl From<usize> for VirtPageNum {
-    fn from(v: usize) -> Self { Self(v & ( (1 << VPN_WIDTH_SV39) - 1 )) }
+    fn from(v: usize) -> Self {
+        Self(v & ((1 << VPN_WIDTH_SV39) - 1))
+    }
 }
 impl From<PhysAddr> for usize {
-    fn from(v: PhysAddr) -> Self { v.0 }
+    fn from(v: PhysAddr) -> Self {
+        v.0
+    }
 }
 impl From<PhysPageNum> for usize {
-    fn from(v: PhysPageNum) -> Self { v.0 }
+    fn from(v: PhysPageNum) -> Self {
+        v.0
+    }
 }
 impl From<VirtAddr> for usize {
-    fn from(v: VirtAddr) -> Self { v.0 }
+    fn from(v: VirtAddr) -> Self {
+        v.0
+    }
 }
 impl From<VirtPageNum> for usize {
-    fn from(v: VirtPageNum) -> Self { v.0 }
+    fn from(v: VirtPageNum) -> Self {
+        v.0
+    }
 }
 
 impl VirtAddr {
-    pub fn floor(&self) -> VirtPageNum { VirtPageNum(self.0 / PAGE_SIZE) }
-    pub fn ceil(&self) -> VirtPageNum  { VirtPageNum((self.0 - 1 + PAGE_SIZE) / PAGE_SIZE) }
-    pub fn page_offset(&self) -> usize { self.0 & (PAGE_SIZE - 1) }
-    pub fn aligned(&self) -> bool { self.page_offset() == 0 }
+    pub fn floor(&self) -> VirtPageNum {
+        VirtPageNum(self.0 / PAGE_SIZE)
+    }
+    pub fn ceil(&self) -> VirtPageNum {
+        VirtPageNum((self.0 - 1 + PAGE_SIZE) / PAGE_SIZE)
+    }
+    pub fn page_offset(&self) -> usize {
+        self.0 & (PAGE_SIZE - 1)
+    }
+    pub fn aligned(&self) -> bool {
+        self.page_offset() == 0
+    }
 }
 impl From<VirtAddr> for VirtPageNum {
     fn from(v: VirtAddr) -> Self {
@@ -85,13 +109,23 @@ impl From<VirtAddr> for VirtPageNum {
     }
 }
 impl From<VirtPageNum> for VirtAddr {
-    fn from(v: VirtPageNum) -> Self { Self(v.0 << PAGE_SIZE_BITS) }
+    fn from(v: VirtPageNum) -> Self {
+        Self(v.0 << PAGE_SIZE_BITS)
+    }
 }
 impl PhysAddr {
-    pub fn floor(&self) -> PhysPageNum { PhysPageNum(self.0 / PAGE_SIZE) }
-    pub fn ceil(&self) -> PhysPageNum { PhysPageNum((self.0 - 1 + PAGE_SIZE) / PAGE_SIZE) }
-    pub fn page_offset(&self) -> usize { self.0 & (PAGE_SIZE - 1) }
-    pub fn aligned(&self) -> bool { self.page_offset() == 0 }
+    pub fn floor(&self) -> PhysPageNum {
+        PhysPageNum(self.0 / PAGE_SIZE)
+    }
+    pub fn ceil(&self) -> PhysPageNum {
+        PhysPageNum((self.0 - 1 + PAGE_SIZE) / PAGE_SIZE)
+    }
+    pub fn page_offset(&self) -> usize {
+        self.0 & (PAGE_SIZE - 1)
+    }
+    pub fn aligned(&self) -> bool {
+        self.page_offset() == 0
+    }
 }
 impl From<PhysAddr> for PhysPageNum {
     fn from(v: PhysAddr) -> Self {
@@ -100,7 +134,9 @@ impl From<PhysAddr> for PhysPageNum {
     }
 }
 impl From<PhysPageNum> for PhysAddr {
-    fn from(v: PhysPageNum) -> Self { Self(v.0 << PAGE_SIZE_BITS) }
+    fn from(v: PhysPageNum) -> Self {
+        Self(v.0 << PAGE_SIZE_BITS)
+    }
 }
 
 impl VirtPageNum {
@@ -117,23 +153,17 @@ impl VirtPageNum {
 
 impl PhysAddr {
     pub fn get_mut<T>(&self) -> &'static mut T {
-        unsafe {
-            (self.0 as *mut T).as_mut().unwrap()
-        }
+        unsafe { (self.0 as *mut T).as_mut().unwrap() }
     }
 }
 impl PhysPageNum {
     pub fn get_pte_array(&self) -> &'static mut [PageTableEntry] {
         let pa: PhysAddr = self.clone().into();
-        unsafe {
-            core::slice::from_raw_parts_mut(pa.0 as *mut PageTableEntry, 512)
-        }
+        unsafe { core::slice::from_raw_parts_mut(pa.0 as *mut PageTableEntry, 512) }
     }
     pub fn get_bytes_array(&self) -> &'static mut [u8] {
         let pa: PhysAddr = self.clone().into();
-        unsafe {
-            core::slice::from_raw_parts_mut(pa.0 as *mut u8, 4096)
-        }
+        unsafe { core::slice::from_raw_parts_mut(pa.0 as *mut u8, 4096) }
     }
     pub fn get_mut<T>(&self) -> &'static mut T {
         let pa: PhysAddr = self.clone().into();
@@ -151,41 +181,57 @@ impl StepByOne for VirtPageNum {
 }
 
 #[derive(Copy, Clone)]
-pub struct SimpleRange<T> where
-    T: StepByOne + Copy + PartialEq + PartialOrd + Debug, {
+pub struct SimpleRange<T>
+where
+    T: StepByOne + Copy + PartialEq + PartialOrd + Debug,
+{
     l: T,
     r: T,
 }
-impl<T> SimpleRange<T> where
-    T: StepByOne + Copy + PartialEq + PartialOrd + Debug, {
+impl<T> SimpleRange<T>
+where
+    T: StepByOne + Copy + PartialEq + PartialOrd + Debug,
+{
     pub fn new(start: T, end: T) -> Self {
         assert!(start <= end, "start {:?} > end {:?}!", start, end);
         Self { l: start, r: end }
     }
-    pub fn get_start(&self) -> T { self.l }
-    pub fn get_end(&self) -> T { self.r }
+    pub fn get_start(&self) -> T {
+        self.l
+    }
+    pub fn get_end(&self) -> T {
+        self.r
+    }
 }
-impl<T> IntoIterator for SimpleRange<T> where
-    T: StepByOne + Copy + PartialEq + PartialOrd + Debug, {
+impl<T> IntoIterator for SimpleRange<T>
+where
+    T: StepByOne + Copy + PartialEq + PartialOrd + Debug,
+{
     type Item = T;
     type IntoIter = SimpleRangeIterator<T>;
     fn into_iter(self) -> Self::IntoIter {
         SimpleRangeIterator::new(self.l, self.r)
     }
 }
-pub struct SimpleRangeIterator<T> where
-    T: StepByOne + Copy + PartialEq + PartialOrd + Debug, {
+pub struct SimpleRangeIterator<T>
+where
+    T: StepByOne + Copy + PartialEq + PartialOrd + Debug,
+{
     current: T,
     end: T,
 }
-impl<T> SimpleRangeIterator<T> where
-    T: StepByOne + Copy + PartialEq + PartialOrd + Debug, {
+impl<T> SimpleRangeIterator<T>
+where
+    T: StepByOne + Copy + PartialEq + PartialOrd + Debug,
+{
     pub fn new(l: T, r: T) -> Self {
-        Self { current: l, end: r, }
+        Self { current: l, end: r }
     }
 }
-impl<T> Iterator for SimpleRangeIterator<T> where
-    T: StepByOne + Copy + PartialEq + PartialOrd + Debug, {
+impl<T> Iterator for SimpleRangeIterator<T>
+where
+    T: StepByOne + Copy + PartialEq + PartialOrd + Debug,
+{
     type Item = T;
     fn next(&mut self) -> Option<Self::Item> {
         if self.current == self.end {
diff --git a/os/src/mm/frame_allocator.rs b/os/src/mm/frame_allocator.rs
index 85d06cce..66b3c121 100644
--- a/os/src/mm/frame_allocator.rs
+++ b/os/src/mm/frame_allocator.rs
@@ -1,9 +1,9 @@
 use super::{PhysAddr, PhysPageNum};
-use alloc::vec::Vec;
-use crate::sync::UPSafeCell;
 use crate::config::MEMORY_END;
-use lazy_static::*;
+use crate::sync::UPSafeCell;
+use alloc::vec::Vec;
 use core::fmt::{self, Debug, Formatter};
+use lazy_static::*;
 
 pub struct FrameTracker {
     pub ppn: PhysPageNum,
@@ -62,22 +62,17 @@ impl FrameAllocator for StackFrameAllocator {
     fn alloc(&mut self) -> Option<PhysPageNum> {
         if let Some(ppn) = self.recycled.pop() {
             Some(ppn.into())
+        } else if self.current == self.end {
+            None
         } else {
-            if self.current == self.end {
-                None
-            } else {
-                self.current += 1;
-                Some((self.current - 1).into())
-            }
+            self.current += 1;
+            Some((self.current - 1).into())
         }
     }
     fn dealloc(&mut self, ppn: PhysPageNum) {
         let ppn = ppn.0;
         // validity check
-        if ppn >= self.current || self.recycled
-            .iter()
-            .find(|&v| {*v == ppn})
-            .is_some() {
+        if ppn >= self.current || self.recycled.iter().find(|&v| *v == ppn).is_some() {
             panic!("Frame ppn={:#x} has not been allocated!", ppn);
         }
         // recycle
@@ -88,18 +83,18 @@ impl FrameAllocator for StackFrameAllocator {
 type FrameAllocatorImpl = StackFrameAllocator;
 
 lazy_static! {
-    pub static ref FRAME_ALLOCATOR: UPSafeCell<FrameAllocatorImpl> = unsafe {
-        UPSafeCell::new(FrameAllocatorImpl::new())
-    };
+    pub static ref FRAME_ALLOCATOR: UPSafeCell<FrameAllocatorImpl> =
+        unsafe { UPSafeCell::new(FrameAllocatorImpl::new()) };
 }
 
 pub fn init_frame_allocator() {
     extern "C" {
         fn ekernel();
     }
-    FRAME_ALLOCATOR
-        .exclusive_access()
-        .init(PhysAddr::from(ekernel as usize).ceil(), PhysAddr::from(MEMORY_END).floor());
+    FRAME_ALLOCATOR.exclusive_access().init(
+        PhysAddr::from(ekernel as usize).ceil(),
+        PhysAddr::from(MEMORY_END).floor(),
+    );
 }
 
 pub fn frame_alloc() -> Option<FrameTracker> {
@@ -110,9 +105,7 @@ pub fn frame_alloc() -> Option<FrameTracker> {
 }
 
 fn frame_dealloc(ppn: PhysPageNum) {
-    FRAME_ALLOCATOR
-        .exclusive_access()
-        .dealloc(ppn);
+    FRAME_ALLOCATOR.exclusive_access().dealloc(ppn);
 }
 
 #[allow(unused)]
@@ -131,4 +124,4 @@ pub fn frame_allocator_test() {
     }
     drop(v);
     println!("frame_allocator_test passed!");
-}
\ No newline at end of file
+}
diff --git a/os/src/mm/heap_allocator.rs b/os/src/mm/heap_allocator.rs
index 2c7468f2..b802bbd3 100644
--- a/os/src/mm/heap_allocator.rs
+++ b/os/src/mm/heap_allocator.rs
@@ -1,5 +1,5 @@
-use buddy_system_allocator::LockedHeap;
 use crate::config::KERNEL_HEAP_SIZE;
+use buddy_system_allocator::LockedHeap;
 
 #[global_allocator]
 static HEAP_ALLOCATOR: LockedHeap = LockedHeap::empty();
diff --git a/os/src/mm/memory_set.rs b/os/src/mm/memory_set.rs
index 84262537..b5bad756 100644
--- a/os/src/mm/memory_set.rs
+++ b/os/src/mm/memory_set.rs
@@ -1,21 +1,15 @@
-use super::{PageTable, PageTableEntry, PTEFlags};
-use super::{VirtPageNum, VirtAddr, PhysPageNum, PhysAddr};
-use super::{FrameTracker, frame_alloc};
-use super::{VPNRange, StepByOne};
-use alloc::collections::BTreeMap;
-use alloc::vec::Vec;
-use riscv::register::satp;
-use alloc::sync::Arc;
-use lazy_static::*;
+use super::{frame_alloc, FrameTracker};
+use super::{PTEFlags, PageTable, PageTableEntry};
+use super::{PhysAddr, PhysPageNum, VirtAddr, VirtPageNum};
+use super::{StepByOne, VPNRange};
+use crate::config::{MEMORY_END, PAGE_SIZE, TRAMPOLINE, TRAP_CONTEXT, USER_STACK_SIZE};
 use crate::sync::UPSafeCell;
-use crate::config::{
-    MEMORY_END,
-    PAGE_SIZE,
-    TRAMPOLINE,
-    TRAP_CONTEXT,
-    USER_STACK_SIZE
-};
+use alloc::collections::BTreeMap;
+use alloc::sync::Arc;
+use alloc::vec::Vec;
 use core::arch::asm;
+use lazy_static::*;
+use riscv::register::satp;
 
 extern "C" {
     fn stext();
@@ -31,9 +25,8 @@ extern "C" {
 }
 
 lazy_static! {
-    pub static ref KERNEL_SPACE: Arc<UPSafeCell<MemorySet>> = Arc::new(unsafe {
-        UPSafeCell::new(MemorySet::new_kernel())
-    });
+    pub static ref KERNEL_SPACE: Arc<UPSafeCell<MemorySet>> =
+        Arc::new(unsafe { UPSafeCell::new(MemorySet::new_kernel()) });
 }
 
 pub struct MemorySet {
@@ -52,17 +45,24 @@ impl MemorySet {
         self.page_table.token()
     }
     /// Assume that no conflicts.
-    pub fn insert_framed_area(&mut self, start_va: VirtAddr, end_va: VirtAddr, permission: MapPermission) {
-        self.push(MapArea::new(
-            start_va,
-            end_va,
-            MapType::Framed,
-            permission,
-        ), None);
+    pub fn insert_framed_area(
+        &mut self,
+        start_va: VirtAddr,
+        end_va: VirtAddr,
+        permission: MapPermission,
+    ) {
+        self.push(
+            MapArea::new(start_va, end_va, MapType::Framed, permission),
+            None,
+        );
     }
     pub fn remove_area_with_start_vpn(&mut self, start_vpn: VirtPageNum) {
-        if let Some((idx, area)) = self.areas.iter_mut().enumerate()
-            .find(|(_, area)| area.vpn_range.get_start() == start_vpn) {
+        if let Some((idx, area)) = self
+            .areas
+            .iter_mut()
+            .enumerate()
+            .find(|(_, area)| area.vpn_range.get_start() == start_vpn)
+        {
             area.unmap(&mut self.page_table);
             self.areas.remove(idx);
         }
@@ -91,42 +91,60 @@ impl MemorySet {
         println!(".text [{:#x}, {:#x})", stext as usize, etext as usize);
         println!(".rodata [{:#x}, {:#x})", srodata as usize, erodata as usize);
         println!(".data [{:#x}, {:#x})", sdata as usize, edata as usize);
-        println!(".bss [{:#x}, {:#x})", sbss_with_stack as usize, ebss as usize);
+        println!(
+            ".bss [{:#x}, {:#x})",
+            sbss_with_stack as usize, ebss as usize
+        );
         println!("mapping .text section");
-        memory_set.push(MapArea::new(
-            (stext as usize).into(),
-            (etext as usize).into(),
-            MapType::Identical,
-            MapPermission::R | MapPermission::X,
-        ), None);
+        memory_set.push(
+            MapArea::new(
+                (stext as usize).into(),
+                (etext as usize).into(),
+                MapType::Identical,
+                MapPermission::R | MapPermission::X,
+            ),
+            None,
+        );
         println!("mapping .rodata section");
-        memory_set.push(MapArea::new(
-            (srodata as usize).into(),
-            (erodata as usize).into(),
-            MapType::Identical,
-            MapPermission::R,
-        ), None);
+        memory_set.push(
+            MapArea::new(
+                (srodata as usize).into(),
+                (erodata as usize).into(),
+                MapType::Identical,
+                MapPermission::R,
+            ),
+            None,
+        );
         println!("mapping .data section");
-        memory_set.push(MapArea::new(
-            (sdata as usize).into(),
-            (edata as usize).into(),
-            MapType::Identical,
-            MapPermission::R | MapPermission::W,
-        ), None);
+        memory_set.push(
+            MapArea::new(
+                (sdata as usize).into(),
+                (edata as usize).into(),
+                MapType::Identical,
+                MapPermission::R | MapPermission::W,
+            ),
+            None,
+        );
         println!("mapping .bss section");
-        memory_set.push(MapArea::new(
-            (sbss_with_stack as usize).into(),
-            (ebss as usize).into(),
-            MapType::Identical,
-            MapPermission::R | MapPermission::W,
-        ), None);
+        memory_set.push(
+            MapArea::new(
+                (sbss_with_stack as usize).into(),
+                (ebss as usize).into(),
+                MapType::Identical,
+                MapPermission::R | MapPermission::W,
+            ),
+            None,
+        );
         println!("mapping physical memory");
-        memory_set.push(MapArea::new(
-            (ekernel as usize).into(),
-            MEMORY_END.into(),
-            MapType::Identical,
-            MapPermission::R | MapPermission::W,
-        ), None);
+        memory_set.push(
+            MapArea::new(
+                (ekernel as usize).into(),
+                MEMORY_END.into(),
+                MapType::Identical,
+                MapPermission::R | MapPermission::W,
+            ),
+            None,
+        );
         memory_set
     }
     /// Include sections in elf and trampoline and TrapContext and user stack,
@@ -149,19 +167,20 @@ impl MemorySet {
                 let end_va: VirtAddr = ((ph.virtual_addr() + ph.mem_size()) as usize).into();
                 let mut map_perm = MapPermission::U;
                 let ph_flags = ph.flags();
-                if ph_flags.is_read() { map_perm |= MapPermission::R; }
-                if ph_flags.is_write() { map_perm |= MapPermission::W; }
-                if ph_flags.is_execute() { map_perm |= MapPermission::X; }
-                let map_area = MapArea::new(
-                    start_va,
-                    end_va,
-                    MapType::Framed,
-                    map_perm,
-                );
+                if ph_flags.is_read() {
+                    map_perm |= MapPermission::R;
+                }
+                if ph_flags.is_write() {
+                    map_perm |= MapPermission::W;
+                }
+                if ph_flags.is_execute() {
+                    map_perm |= MapPermission::X;
+                }
+                let map_area = MapArea::new(start_va, end_va, MapType::Framed, map_perm);
                 max_end_vpn = map_area.vpn_range.get_end();
                 memory_set.push(
                     map_area,
-                    Some(&elf.input[ph.offset() as usize..(ph.offset() + ph.file_size()) as usize])
+                    Some(&elf.input[ph.offset() as usize..(ph.offset() + ph.file_size()) as usize]),
                 );
             }
         }
@@ -171,20 +190,30 @@ impl MemorySet {
         // guard page
         user_stack_bottom += PAGE_SIZE;
         let user_stack_top = user_stack_bottom + USER_STACK_SIZE;
-        memory_set.push(MapArea::new(
-            user_stack_bottom.into(),
-            user_stack_top.into(),
-            MapType::Framed,
-            MapPermission::R | MapPermission::W | MapPermission::U,
-        ), None);
+        memory_set.push(
+            MapArea::new(
+                user_stack_bottom.into(),
+                user_stack_top.into(),
+                MapType::Framed,
+                MapPermission::R | MapPermission::W | MapPermission::U,
+            ),
+            None,
+        );
         // map TrapContext
-        memory_set.push(MapArea::new(
-            TRAP_CONTEXT.into(),
-            TRAMPOLINE.into(),
-            MapType::Framed,
-            MapPermission::R | MapPermission::W,
-        ), None);
-        (memory_set, user_stack_top, elf.header.pt2.entry_point() as usize)
+        memory_set.push(
+            MapArea::new(
+                TRAP_CONTEXT.into(),
+                TRAMPOLINE.into(),
+                MapType::Framed,
+                MapPermission::R | MapPermission::W,
+            ),
+            None,
+        );
+        (
+            memory_set,
+            user_stack_top,
+            elf.header.pt2.entry_point() as usize,
+        )
     }
     pub fn from_existed_user(user_space: &MemorySet) -> MemorySet {
         let mut memory_set = Self::new_bare();
@@ -198,7 +227,9 @@ impl MemorySet {
             for vpn in area.vpn_range {
                 let src_ppn = user_space.translate(vpn).unwrap().ppn();
                 let dst_ppn = memory_set.translate(vpn).unwrap().ppn();
-                dst_ppn.get_bytes_array().copy_from_slice(src_ppn.get_bytes_array());
+                dst_ppn
+                    .get_bytes_array()
+                    .copy_from_slice(src_ppn.get_bytes_array());
             }
         }
         memory_set
@@ -231,7 +262,7 @@ impl MapArea {
         start_va: VirtAddr,
         end_va: VirtAddr,
         map_type: MapType,
-        map_perm: MapPermission
+        map_perm: MapPermission,
     ) -> Self {
         let start_vpn: VirtPageNum = start_va.floor();
         let end_vpn: VirtPageNum = end_va.ceil();
@@ -330,15 +361,27 @@ pub fn remap_test() {
     let mid_rodata: VirtAddr = ((srodata as usize + erodata as usize) / 2).into();
     let mid_data: VirtAddr = ((sdata as usize + edata as usize) / 2).into();
     assert_eq!(
-        kernel_space.page_table.translate(mid_text.floor()).unwrap().writable(),
+        kernel_space
+            .page_table
+            .translate(mid_text.floor())
+            .unwrap()
+            .writable(),
         false
     );
     assert_eq!(
-        kernel_space.page_table.translate(mid_rodata.floor()).unwrap().writable(),
+        kernel_space
+            .page_table
+            .translate(mid_rodata.floor())
+            .unwrap()
+            .writable(),
         false,
     );
     assert_eq!(
-        kernel_space.page_table.translate(mid_data.floor()).unwrap().executable(),
+        kernel_space
+            .page_table
+            .translate(mid_data.floor())
+            .unwrap()
+            .executable(),
         false,
     );
     println!("remap_test passed!");
diff --git a/os/src/mm/mod.rs b/os/src/mm/mod.rs
index 30e05577..52c5223a 100644
--- a/os/src/mm/mod.rs
+++ b/os/src/mm/mod.rs
@@ -1,21 +1,16 @@
-mod heap_allocator;
 mod address;
 mod frame_allocator;
-mod page_table;
+mod heap_allocator;
 mod memory_set;
+mod page_table;
 
-use page_table::{PageTable, PTEFlags};
-use address::{VPNRange, StepByOne};
-pub use address::{PhysAddr, VirtAddr, PhysPageNum, VirtPageNum};
-pub use frame_allocator::{FrameTracker, frame_alloc};
-pub use page_table::{
-    PageTableEntry,
-    translated_byte_buffer,
-    translated_str,
-    translated_refmut,
-};
-pub use memory_set::{MemorySet, KERNEL_SPACE, MapPermission};
+pub use address::{PhysAddr, PhysPageNum, VirtAddr, VirtPageNum};
+use address::{StepByOne, VPNRange};
+pub use frame_allocator::{frame_alloc, FrameTracker};
 pub use memory_set::remap_test;
+pub use memory_set::{MapPermission, MemorySet, KERNEL_SPACE};
+pub use page_table::{translated_byte_buffer, translated_refmut, translated_str, PageTableEntry};
+use page_table::{PTEFlags, PageTable};
 
 pub fn init() {
     heap_allocator::init_heap();
diff --git a/os/src/mm/page_table.rs b/os/src/mm/page_table.rs
index a13bae23..419f088e 100644
--- a/os/src/mm/page_table.rs
+++ b/os/src/mm/page_table.rs
@@ -1,15 +1,7 @@
-use super::{
-    frame_alloc,
-    PhysPageNum,
-    FrameTracker,
-    VirtPageNum,
-    VirtAddr,
-    PhysAddr,
-    StepByOne
-};
-use alloc::vec::Vec;
-use alloc::vec;
+use super::{frame_alloc, FrameTracker, PhysAddr, PhysPageNum, StepByOne, VirtAddr, VirtPageNum};
 use alloc::string::String;
+use alloc::vec;
+use alloc::vec::Vec;
 use bitflags::*;
 
 bitflags! {
@@ -38,9 +30,7 @@ impl PageTableEntry {
         }
     }
     pub fn empty() -> Self {
-        PageTableEntry {
-            bits: 0,
-        }
+        PageTableEntry { bits: 0 }
     }
     pub fn ppn(&self) -> PhysPageNum {
         (self.bits >> 10 & ((1usize << 44) - 1)).into()
@@ -132,19 +122,17 @@ impl PageTable {
         *pte = PageTableEntry::empty();
     }
     pub fn translate(&self, vpn: VirtPageNum) -> Option<PageTableEntry> {
-        self.find_pte(vpn)
-            .map(|pte| {pte.clone()})
+        self.find_pte(vpn).map(|pte| pte.clone())
     }
     pub fn translate_va(&self, va: VirtAddr) -> Option<PhysAddr> {
-        self.find_pte(va.clone().floor())
-            .map(|pte| {
-                //println!("translate_va:va = {:?}", va);
-                let aligned_pa: PhysAddr = pte.ppn().into();
-                //println!("translate_va:pa_align = {:?}", aligned_pa);
-                let offset = va.page_offset();
-                let aligned_pa_usize: usize = aligned_pa.into();
-                (aligned_pa_usize + offset).into()
-            })
+        self.find_pte(va.clone().floor()).map(|pte| {
+            //println!("translate_va:va = {:?}", va);
+            let aligned_pa: PhysAddr = pte.ppn().into();
+            //println!("translate_va:pa_align = {:?}", aligned_pa);
+            let offset = va.page_offset();
+            let aligned_pa_usize: usize = aligned_pa.into();
+            (aligned_pa_usize + offset).into()
+        })
     }
     pub fn token(&self) -> usize {
         8usize << 60 | self.root_ppn.0
@@ -159,10 +147,7 @@ pub fn translated_byte_buffer(token: usize, ptr: *const u8, len: usize) -> Vec<&
     while start < end {
         let start_va = VirtAddr::from(start);
         let mut vpn = start_va.floor();
-        let ppn = page_table
-            .translate(vpn)
-            .unwrap()
-            .ppn();
+        let ppn = page_table.translate(vpn).unwrap().ppn();
         vpn.step();
         let mut end_va: VirtAddr = vpn.into();
         end_va = end_va.min(VirtAddr::from(end));
@@ -181,7 +166,10 @@ pub fn translated_str(token: usize, ptr: *const u8) -> String {
     let mut string = String::new();
     let mut va = ptr as usize;
     loop {
-        let ch: u8 = *(page_table.translate_va(VirtAddr::from(va)).unwrap().get_mut());
+        let ch: u8 = *(page_table
+            .translate_va(VirtAddr::from(va))
+            .unwrap()
+            .get_mut());
         if ch == 0 {
             break;
         } else {
@@ -197,6 +185,8 @@ pub fn translated_refmut<T>(token: usize, ptr: *mut T) -> &'static mut T {
     let page_table = PageTable::from_token(token);
     let va = ptr as usize;
     //println!("translated_refmut: before translate_va");
-    page_table.translate_va(VirtAddr::from(va)).unwrap().get_mut()
+    page_table
+        .translate_va(VirtAddr::from(va))
+        .unwrap()
+        .get_mut()
 }
-
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 a10b53e9..557f282c 100644
--- a/os/src/syscall/fs.rs
+++ b/os/src/syscall/fs.rs
@@ -1,6 +1,6 @@
 use crate::mm::translated_byte_buffer;
-use crate::task::{current_user_token, suspend_current_and_run_next};
 use crate::sbi::console_getchar;
+use crate::task::{current_user_token, suspend_current_and_run_next};
 
 const FD_STDIN: usize = 0;
 const FD_STDOUT: usize = 1;
@@ -13,7 +13,7 @@ pub fn sys_write(fd: usize, buf: *const u8, len: usize) -> isize {
                 print!("{}", core::str::from_utf8(buffer).unwrap());
             }
             len as isize
-        },
+        }
         _ => {
             panic!("Unsupported fd in sys_write!");
         }
@@ -36,11 +36,13 @@ pub fn sys_read(fd: usize, buf: *const u8, len: usize) -> isize {
             }
             let ch = c as u8;
             let mut buffers = translated_byte_buffer(current_user_token(), buf, len);
-            unsafe { buffers[0].as_mut_ptr().write_volatile(ch); }
+            unsafe {
+                buffers[0].as_mut_ptr().write_volatile(ch);
+            }
             1
         }
         _ => {
             panic!("Unsupported fd in sys_read!");
         }
     }
-}
\ No newline at end of file
+}
diff --git a/os/src/syscall/mod.rs b/os/src/syscall/mod.rs
index 81ade837..583f1e12 100644
--- a/os/src/syscall/mod.rs
+++ b/os/src/syscall/mod.rs
@@ -28,4 +28,3 @@ 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 b425d87d..871cec22 100644
--- a/os/src/syscall/process.rs
+++ b/os/src/syscall/process.rs
@@ -1,16 +1,10 @@
+use crate::loader::get_app_data_by_name;
+use crate::mm::{translated_refmut, translated_str};
 use crate::task::{
+    add_task, current_task, current_user_token, exit_current_and_run_next,
     suspend_current_and_run_next,
-    exit_current_and_run_next,
-    current_task,
-    current_user_token,
-    add_task,
 };
 use crate::timer::get_time_ms;
-use crate::mm::{
-    translated_str,
-    translated_refmut,
-};
-use crate::loader::get_app_data_by_name;
 use alloc::sync::Arc;
 
 pub fn sys_exit(exit_code: i32) -> ! {
@@ -65,21 +59,20 @@ pub fn sys_waitpid(pid: isize, exit_code_ptr: *mut i32) -> isize {
 
     // ---- access current TCB exclusively
     let mut inner = task.inner_exclusive_access();
-    if inner.children
+    if inner
+        .children
         .iter()
-        .find(|p| {pid == -1 || pid as usize == p.getpid()})
-        .is_none() {
+        .find(|p| pid == -1 || pid as usize == p.getpid())
+        .is_none()
+    {
         return -1;
         // ---- release current PCB
     }
-    let pair = inner.children
-        .iter()
-        .enumerate()
-        .find(|(_, p)| {
-            // ++++ temporarily access child PCB lock exclusively
-            p.inner_exclusive_access().is_zombie() && (pid == -1 || pid as usize == p.getpid())
-            // ++++ release child PCB
-        });
+    let pair = inner.children.iter().enumerate().find(|(_, p)| {
+        // ++++ temporarily access child PCB lock exclusively
+        p.inner_exclusive_access().is_zombie() && (pid == -1 || pid as usize == p.getpid())
+        // ++++ release child PCB
+    });
     if let Some((idx, _)) = pair {
         let child = inner.children.remove(idx);
         // confirm that child will be deallocated after removing from children list
@@ -94,4 +87,4 @@ pub fn sys_waitpid(pid: isize, exit_code_ptr: *mut i32) -> isize {
         -2
     }
     // ---- release current PCB lock automatically
-}
\ No newline at end of file
+}
diff --git a/os/src/task/context.rs b/os/src/task/context.rs
index d25cc2c8..e4f59d8a 100644
--- a/os/src/task/context.rs
+++ b/os/src/task/context.rs
@@ -23,4 +23,3 @@ impl TaskContext {
         }
     }
 }
-
diff --git a/os/src/task/manager.rs b/os/src/task/manager.rs
index 2e3708d7..542a0b87 100644
--- a/os/src/task/manager.rs
+++ b/os/src/task/manager.rs
@@ -1,5 +1,5 @@
-use crate::sync::UPSafeCell;
 use super::TaskControlBlock;
+use crate::sync::UPSafeCell;
 use alloc::collections::VecDeque;
 use alloc::sync::Arc;
 use lazy_static::*;
@@ -11,7 +11,9 @@ pub struct TaskManager {
 /// A simple FIFO scheduler.
 impl TaskManager {
     pub fn new() -> Self {
-        Self { ready_queue: VecDeque::new(), }
+        Self {
+            ready_queue: VecDeque::new(),
+        }
     }
     pub fn add(&mut self, task: Arc<TaskControlBlock>) {
         self.ready_queue.push_back(task);
@@ -22,9 +24,8 @@ impl TaskManager {
 }
 
 lazy_static! {
-    pub static ref TASK_MANAGER: UPSafeCell<TaskManager> = unsafe {
-        UPSafeCell::new(TaskManager::new())
-    };
+    pub static ref TASK_MANAGER: UPSafeCell<TaskManager> =
+        unsafe { UPSafeCell::new(TaskManager::new()) };
 }
 
 pub fn add_task(task: Arc<TaskControlBlock>) {
@@ -33,4 +34,4 @@ pub fn add_task(task: Arc<TaskControlBlock>) {
 
 pub fn fetch_task() -> Option<Arc<TaskControlBlock>> {
     TASK_MANAGER.exclusive_access().fetch()
-}
\ No newline at end of file
+}
diff --git a/os/src/task/mod.rs b/os/src/task/mod.rs
index d5301040..bc67daf6 100644
--- a/os/src/task/mod.rs
+++ b/os/src/task/mod.rs
@@ -1,28 +1,23 @@
 mod context;
+mod manager;
+mod pid;
+mod processor;
 mod switch;
 mod task;
-mod manager;
-mod processor;
-mod pid;
 
 use crate::loader::get_app_data_by_name;
+use alloc::sync::Arc;
+use lazy_static::*;
+use manager::fetch_task;
 use switch::__switch;
 use task::{TaskControlBlock, TaskStatus};
-use alloc::sync::Arc;
-use manager::fetch_task;
-use lazy_static::*;
 
 pub use context::TaskContext;
-pub use processor::{
-    run_tasks,
-    current_task,
-    current_user_token,
-    current_trap_cx,
-    take_current_task,
-    schedule,
-};
 pub use manager::add_task;
-pub use pid::{PidHandle, pid_alloc, KernelStack};
+pub use pid::{pid_alloc, KernelStack, PidHandle};
+pub use processor::{
+    current_task, current_trap_cx, current_user_token, run_tasks, schedule, take_current_task,
+};
 
 pub fn suspend_current_and_run_next() {
     // There must be an application running.
@@ -76,9 +71,9 @@ pub fn exit_current_and_run_next(exit_code: i32) {
 }
 
 lazy_static! {
-    pub static ref INITPROC: Arc<TaskControlBlock> = Arc::new(
-        TaskControlBlock::new(get_app_data_by_name("initproc").unwrap())
-    );
+    pub static ref INITPROC: Arc<TaskControlBlock> = Arc::new(TaskControlBlock::new(
+        get_app_data_by_name("initproc").unwrap()
+    ));
 }
 
 pub fn add_initproc() {
diff --git a/os/src/task/pid.rs b/os/src/task/pid.rs
index 517cd1d4..f460f063 100644
--- a/os/src/task/pid.rs
+++ b/os/src/task/pid.rs
@@ -1,12 +1,8 @@
+use crate::config::{KERNEL_STACK_SIZE, PAGE_SIZE, TRAMPOLINE};
+use crate::mm::{MapPermission, VirtAddr, KERNEL_SPACE};
+use crate::sync::UPSafeCell;
 use alloc::vec::Vec;
 use lazy_static::*;
-use crate::sync::UPSafeCell;
-use crate::mm::{KERNEL_SPACE, MapPermission, VirtAddr};
-use crate::config::{
-    PAGE_SIZE,
-    TRAMPOLINE,
-    KERNEL_STACK_SIZE,
-};
 
 struct PidAllocator {
     current: usize,
@@ -32,16 +28,16 @@ impl PidAllocator {
         assert!(pid < self.current);
         assert!(
             self.recycled.iter().find(|ppid| **ppid == pid).is_none(),
-            "pid {} has been deallocated!", pid
+            "pid {} has been deallocated!",
+            pid
         );
         self.recycled.push(pid);
     }
 }
 
 lazy_static! {
-    static ref PID_ALLOCATOR : UPSafeCell<PidAllocator> = unsafe {
-        UPSafeCell::new(PidAllocator::new())
-    };
+    static ref PID_ALLOCATOR: UPSafeCell<PidAllocator> =
+        unsafe { UPSafeCell::new(PidAllocator::new()) };
 }
 
 pub struct PidHandle(pub usize);
@@ -72,23 +68,23 @@ impl KernelStack {
     pub fn new(pid_handle: &PidHandle) -> Self {
         let pid = pid_handle.0;
         let (kernel_stack_bottom, kernel_stack_top) = kernel_stack_position(pid);
-        KERNEL_SPACE
-            .exclusive_access()
-            .insert_framed_area(
-                kernel_stack_bottom.into(),
-                kernel_stack_top.into(),
-                MapPermission::R | MapPermission::W,
-            );
-        KernelStack {
-            pid: pid_handle.0,
-        }
+        KERNEL_SPACE.exclusive_access().insert_framed_area(
+            kernel_stack_bottom.into(),
+            kernel_stack_top.into(),
+            MapPermission::R | MapPermission::W,
+        );
+        KernelStack { pid: pid_handle.0 }
     }
     #[allow(unused)]
-    pub fn push_on_top<T>(&self, value: T) -> *mut T where
-        T: Sized, {
+    pub fn push_on_top<T>(&self, value: T) -> *mut T
+    where
+        T: Sized,
+    {
         let kernel_stack_top = self.get_top();
         let ptr_mut = (kernel_stack_top - core::mem::size_of::<T>()) as *mut T;
-        unsafe { *ptr_mut = value; }
+        unsafe {
+            *ptr_mut = value;
+        }
         ptr_mut
     }
     pub fn get_top(&self) -> usize {
@@ -105,4 +101,4 @@ impl Drop for KernelStack {
             .exclusive_access()
             .remove_area_with_start_vpn(kernel_stack_bottom_va.into());
     }
-}
\ No newline at end of file
+}
diff --git a/os/src/task/processor.rs b/os/src/task/processor.rs
index a9f9db8c..6ad4534c 100644
--- a/os/src/task/processor.rs
+++ b/os/src/task/processor.rs
@@ -1,10 +1,10 @@
+use super::__switch;
+use super::{fetch_task, TaskStatus};
 use super::{TaskContext, TaskControlBlock};
+use crate::sync::UPSafeCell;
+use crate::trap::TrapContext;
 use alloc::sync::Arc;
 use lazy_static::*;
-use super::{fetch_task, TaskStatus};
-use super::__switch;
-use crate::trap::TrapContext;
-use crate::sync::UPSafeCell;
 
 pub struct Processor {
     current: Option<Arc<TaskControlBlock>>,
@@ -30,9 +30,7 @@ impl Processor {
 }
 
 lazy_static! {
-    pub static ref PROCESSOR: UPSafeCell<Processor> = unsafe {
-        UPSafeCell::new(Processor::new())
-    };
+    pub static ref PROCESSOR: UPSafeCell<Processor> = unsafe { UPSafeCell::new(Processor::new()) };
 }
 
 pub fn run_tasks() {
@@ -50,10 +48,7 @@ pub fn run_tasks() {
             // release processor manually
             drop(processor);
             unsafe {
-                __switch(
-                    idle_task_cx_ptr,
-                    next_task_cx_ptr,
-                );
+                __switch(idle_task_cx_ptr, next_task_cx_ptr);
             }
         }
     }
@@ -74,7 +69,10 @@ pub fn current_user_token() -> usize {
 }
 
 pub fn current_trap_cx() -> &'static mut TrapContext {
-    current_task().unwrap().inner_exclusive_access().get_trap_cx()
+    current_task()
+        .unwrap()
+        .inner_exclusive_access()
+        .get_trap_cx()
 }
 
 pub fn schedule(switched_task_cx_ptr: *mut TaskContext) {
@@ -82,9 +80,6 @@ pub fn schedule(switched_task_cx_ptr: *mut TaskContext) {
     let idle_task_cx_ptr = processor.get_idle_task_cx_ptr();
     drop(processor);
     unsafe {
-        __switch(
-            switched_task_cx_ptr,
-            idle_task_cx_ptr,
-        );
+        __switch(switched_task_cx_ptr, idle_task_cx_ptr);
     }
 }
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 8108ea88..cd346d59 100644
--- a/os/src/task/task.rs
+++ b/os/src/task/task.rs
@@ -1,12 +1,12 @@
-use crate::mm::{MemorySet, PhysPageNum, KERNEL_SPACE, VirtAddr};
-use crate::trap::{TrapContext, trap_handler};
-use crate::config::TRAP_CONTEXT;
-use crate::sync::UPSafeCell;
-use core::cell::RefMut;
 use super::TaskContext;
-use super::{PidHandle, pid_alloc, KernelStack};
-use alloc::sync::{Weak, Arc};
+use super::{pid_alloc, KernelStack, PidHandle};
+use crate::config::TRAP_CONTEXT;
+use crate::mm::{MemorySet, PhysPageNum, VirtAddr, KERNEL_SPACE};
+use crate::sync::UPSafeCell;
+use crate::trap::{trap_handler, TrapContext};
+use alloc::sync::{Arc, Weak};
 use alloc::vec::Vec;
+use core::cell::RefMut;
 
 pub struct TaskControlBlock {
     // immutable
@@ -66,16 +66,18 @@ impl TaskControlBlock {
         let task_control_block = Self {
             pid: pid_handle,
             kernel_stack,
-            inner: unsafe { UPSafeCell::new(TaskControlBlockInner {
-                trap_cx_ppn,
-                base_size: user_sp,
-                task_cx: TaskContext::goto_trap_return(kernel_stack_top),
-                task_status: TaskStatus::Ready,
-                memory_set,
-                parent: None,
-                children: Vec::new(),
-                exit_code: 0,
-            })},
+            inner: unsafe {
+                UPSafeCell::new(TaskControlBlockInner {
+                    trap_cx_ppn,
+                    base_size: user_sp,
+                    task_cx: TaskContext::goto_trap_return(kernel_stack_top),
+                    task_status: TaskStatus::Ready,
+                    memory_set,
+                    parent: None,
+                    children: Vec::new(),
+                    exit_code: 0,
+                })
+            },
         };
         // prepare TrapContext in user space
         let trap_cx = task_control_block.inner_exclusive_access().get_trap_cx();
@@ -117,9 +119,7 @@ impl TaskControlBlock {
         // ---- access parent PCB exclusively
         let mut parent_inner = self.inner_exclusive_access();
         // copy user space(include trap context)
-        let memory_set = MemorySet::from_existed_user(
-            &parent_inner.memory_set
-        );
+        let memory_set = MemorySet::from_existed_user(&parent_inner.memory_set);
         let trap_cx_ppn = memory_set
             .translate(VirtAddr::from(TRAP_CONTEXT).into())
             .unwrap()
@@ -131,16 +131,18 @@ impl TaskControlBlock {
         let task_control_block = Arc::new(TaskControlBlock {
             pid: pid_handle,
             kernel_stack,
-            inner: unsafe { UPSafeCell::new(TaskControlBlockInner {
-                trap_cx_ppn,
-                base_size: parent_inner.base_size,
-                task_cx: TaskContext::goto_trap_return(kernel_stack_top),
-                task_status: TaskStatus::Ready,
-                memory_set,
-                parent: Some(Arc::downgrade(self)),
-                children: Vec::new(),
-                exit_code: 0,
-            })},
+            inner: unsafe {
+                UPSafeCell::new(TaskControlBlockInner {
+                    trap_cx_ppn,
+                    base_size: parent_inner.base_size,
+                    task_cx: TaskContext::goto_trap_return(kernel_stack_top),
+                    task_status: TaskStatus::Ready,
+                    memory_set,
+                    parent: Some(Arc::downgrade(self)),
+                    children: Vec::new(),
+                    exit_code: 0,
+                })
+            },
         });
         // add child
         parent_inner.children.push(task_control_block.clone());
@@ -163,4 +165,4 @@ pub enum TaskStatus {
     Ready,
     Running,
     Zombie,
-}
\ No newline at end of file
+}
diff --git a/os/src/timer.rs b/os/src/timer.rs
index 92d50e3a..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;
@@ -15,4 +15,4 @@ pub fn get_time_ms() -> usize {
 
 pub fn set_next_trigger() {
     set_timer(get_time() + CLOCK_FREQ / TICKS_PER_SEC);
-}
\ No newline at end of file
+}
diff --git a/os/src/trap/context.rs b/os/src/trap/context.rs
index 8c5175f7..2f6084f0 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 {
@@ -11,7 +11,9 @@ 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,
diff --git a/os/src/trap/mod.rs b/os/src/trap/mod.rs
index 541ff305..7fa1dd7f 100644
--- a/os/src/trap/mod.rs
+++ b/os/src/trap/mod.rs
@@ -1,27 +1,17 @@
 mod context;
 
-use riscv::register::{
-    mtvec::TrapMode,
-    stvec,
-    scause::{
-        self,
-        Trap,
-        Exception,
-        Interrupt,
-    },
-    stval,
-    sie,
-};
+use crate::config::{TRAMPOLINE, TRAP_CONTEXT};
 use crate::syscall::syscall;
 use crate::task::{
-    exit_current_and_run_next,
-    suspend_current_and_run_next,
-    current_user_token,
-    current_trap_cx,
+    current_trap_cx, current_user_token, exit_current_and_run_next, suspend_current_and_run_next,
 };
 use crate::timer::set_next_trigger;
-use crate::config::{TRAP_CONTEXT, TRAMPOLINE};
-use core::arch::{global_asm, asm};
+use core::arch::{asm, global_asm};
+use riscv::register::{
+    mtvec::TrapMode,
+    scause::{self, Exception, Interrupt, Trap},
+    sie, stval, stvec,
+};
 
 global_asm!(include_str!("trap.S"));
 
@@ -42,7 +32,9 @@ fn set_user_trap_entry() {
 }
 
 pub fn enable_timer_interrupt() {
-    unsafe { sie::set_stimer(); }
+    unsafe {
+        sie::set_stimer();
+    }
 }
 
 #[no_mangle]
@@ -61,12 +53,12 @@ pub fn trap_handler() -> ! {
             cx = current_trap_cx();
             cx.x[10] = result as usize;
         }
-        Trap::Exception(Exception::StoreFault) |
-        Trap::Exception(Exception::StorePageFault) |
-        Trap::Exception(Exception::InstructionFault) |
-        Trap::Exception(Exception::InstructionPageFault) |
-        Trap::Exception(Exception::LoadFault) |
-        Trap::Exception(Exception::LoadPageFault) => {
+        Trap::Exception(Exception::StoreFault)
+        | Trap::Exception(Exception::StorePageFault)
+        | Trap::Exception(Exception::InstructionFault)
+        | Trap::Exception(Exception::InstructionPageFault)
+        | Trap::Exception(Exception::LoadFault)
+        | Trap::Exception(Exception::LoadPageFault) => {
             println!(
                 "[kernel] {:?} in application, bad addr = {:#x}, bad instruction = {:#x}, kernel killed it.",
                 scause.cause(),
@@ -86,7 +78,11 @@ pub fn trap_handler() -> ! {
             suspend_current_and_run_next();
         }
         _ => {
-            panic!("Unsupported trap {:?}, stval = {:#x}!", scause.cause(), stval);
+            panic!(
+                "Unsupported trap {:?}, stval = {:#x}!",
+                scause.cause(),
+                stval
+            );
         }
     }
     trap_return();
@@ -119,4 +115,4 @@ pub fn trap_from_kernel() -> ! {
     panic!("a trap {:?} from kernel!", scause::read().cause());
 }
 
-pub use context::{TrapContext};
+pub use context::TrapContext;
diff --git a/user/src/bin/exit.rs b/user/src/bin/exit.rs
index 5bde550b..60510c90 100644
--- a/user/src/bin/exit.rs
+++ b/user/src/bin/exit.rs
@@ -3,7 +3,7 @@
 
 #[macro_use]
 extern crate user_lib;
-use user_lib::{fork, yield_, waitpid, exit, wait};
+use user_lib::{exit, fork, wait, waitpid, yield_};
 
 const MAGIC: i32 = -0x10384;
 
@@ -13,7 +13,9 @@ pub fn main() -> i32 {
     let pid = fork();
     if pid == 0 {
         println!("I am the child.");
-        for _ in 0..7 { yield_(); }
+        for _ in 0..7 {
+            yield_();
+        }
         exit(MAGIC);
     } else {
         println!("I am parent, fork a child pid {}", pid);
@@ -26,4 +28,3 @@ pub fn main() -> i32 {
     println!("exit pass.");
     0
 }
-
diff --git a/user/src/bin/fantastic_text.rs b/user/src/bin/fantastic_text.rs
index bb51db30..a3402ff6 100644
--- a/user/src/bin/fantastic_text.rs
+++ b/user/src/bin/fantastic_text.rs
@@ -41,4 +41,4 @@ pub fn main() -> i32 {
         println!("{}", color_text!(text, i));
     }
     0
-}
\ No newline at end of file
+}
diff --git a/user/src/bin/forktest.rs b/user/src/bin/forktest.rs
index a7d523a8..5374a56c 100644
--- a/user/src/bin/forktest.rs
+++ b/user/src/bin/forktest.rs
@@ -4,7 +4,7 @@
 #[macro_use]
 extern crate user_lib;
 
-use user_lib::{fork, wait, exit};
+use user_lib::{exit, fork, wait};
 
 const MAX_CHILD: usize = 30;
 
diff --git a/user/src/bin/forktest2.rs b/user/src/bin/forktest2.rs
index d08a4120..c91ce152 100644
--- a/user/src/bin/forktest2.rs
+++ b/user/src/bin/forktest2.rs
@@ -4,7 +4,7 @@
 #[macro_use]
 extern crate user_lib;
 
-use user_lib::{fork, wait, getpid, exit, sleep, get_time};
+use user_lib::{exit, fork, get_time, getpid, sleep, wait};
 
 static NUM: usize = 30;
 
@@ -14,7 +14,8 @@ pub fn main() -> i32 {
         let pid = fork();
         if pid == 0 {
             let current_time = get_time();
-            let sleep_length = (current_time as i32 as isize) * (current_time as i32 as isize) % 1000 + 1000;
+            let sleep_length =
+                (current_time as i32 as isize) * (current_time as i32 as isize) % 1000 + 1000;
             println!("pid {} sleep for {} ms", getpid(), sleep_length);
             sleep(sleep_length as usize);
             println!("pid {} OK!", getpid());
@@ -30,4 +31,4 @@ pub fn main() -> i32 {
     assert!(wait(&mut exit_code) < 0);
     println!("forktest2 test passed!");
     0
-}
\ No newline at end of file
+}
diff --git a/user/src/bin/forktest_simple.rs b/user/src/bin/forktest_simple.rs
index 821fba64..29a624b4 100644
--- a/user/src/bin/forktest_simple.rs
+++ b/user/src/bin/forktest_simple.rs
@@ -25,4 +25,4 @@ pub fn main() -> i32 {
         println!("child process pid = {}, exit code = {}", pid, exit_code);
         0
     }
-}
\ No newline at end of file
+}
diff --git a/user/src/bin/forktree.rs b/user/src/bin/forktree.rs
index 2debf6c5..bfcfc4ca 100644
--- a/user/src/bin/forktree.rs
+++ b/user/src/bin/forktree.rs
@@ -4,7 +4,7 @@
 #[macro_use]
 extern crate user_lib;
 
-use user_lib::{sleep, getpid, fork, exit, yield_};
+use user_lib::{exit, fork, getpid, sleep, yield_};
 
 const DEPTH: usize = 4;
 
diff --git a/user/src/bin/hello_world.rs b/user/src/bin/hello_world.rs
index de4a6a92..10d3f26c 100644
--- a/user/src/bin/hello_world.rs
+++ b/user/src/bin/hello_world.rs
@@ -8,4 +8,4 @@ extern crate user_lib;
 pub fn main() -> i32 {
     println!("Hello world from user mode program!");
     0
-}
\ No newline at end of file
+}
diff --git a/user/src/bin/initproc.rs b/user/src/bin/initproc.rs
index 6d30fdb6..71bed27e 100644
--- a/user/src/bin/initproc.rs
+++ b/user/src/bin/initproc.rs
@@ -4,12 +4,7 @@
 #[macro_use]
 extern crate user_lib;
 
-use user_lib::{
-    fork,
-    wait,
-    exec,
-    yield_,
-};
+use user_lib::{exec, fork, wait, yield_};
 
 #[no_mangle]
 fn main() -> i32 {
@@ -25,10 +20,9 @@ fn main() -> i32 {
             }
             println!(
                 "[initproc] Released a zombie process, pid={}, exit_code={}",
-                pid,
-                exit_code,
+                pid, exit_code,
             );
         }
     }
     0
-}
\ No newline at end of file
+}
diff --git a/user/src/bin/matrix.rs b/user/src/bin/matrix.rs
index 8f1357ea..b282d58f 100644
--- a/user/src/bin/matrix.rs
+++ b/user/src/bin/matrix.rs
@@ -1,10 +1,11 @@
 #![no_std]
 #![no_main]
+#![allow(clippy::needless_range_loop)]
 
 #[macro_use]
 extern crate user_lib;
 
-use user_lib::{fork, wait, yield_, exit, getpid, get_time};
+use user_lib::{exit, fork, get_time, getpid, wait, yield_};
 
 static NUM: usize = 30;
 const N: usize = 10;
@@ -27,6 +28,7 @@ fn work(times: isize) {
         for i in 0..N {
             for j in 0..N {
                 c[i][j] = 0;
+                #[allow(clippy::needless_range_loop)]
                 for k in 0..N {
                     c[i][j] = (c[i][j] + a[i][k] * b[k][j]) % P;
                 }
diff --git a/user/src/bin/sleep.rs b/user/src/bin/sleep.rs
index beba78c6..641a4f9d 100644
--- a/user/src/bin/sleep.rs
+++ b/user/src/bin/sleep.rs
@@ -4,7 +4,7 @@
 #[macro_use]
 extern crate user_lib;
 
-use user_lib::{sleep, exit, get_time, fork, waitpid};
+use user_lib::{exit, fork, get_time, sleep, waitpid};
 
 fn sleepy() {
     let time: usize = 100;
@@ -27,4 +27,4 @@ pub fn main() -> i32 {
     println!("use {} msecs.", get_time() - current_time);
     println!("sleep pass.");
     0
-}
\ No newline at end of file
+}
diff --git a/user/src/bin/sleep_simple.rs b/user/src/bin/sleep_simple.rs
index 4c058f87..7015a3d4 100644
--- a/user/src/bin/sleep_simple.rs
+++ b/user/src/bin/sleep_simple.rs
@@ -13,7 +13,11 @@ pub fn main() -> i32 {
     println!("current time_msec = {}", start);
     sleep(100);
     let end = get_time();
-    println!("time_msec = {} after sleeping 100 ticks, delta = {}ms!", end, end - start);
+    println!(
+        "time_msec = {} after sleeping 100 ticks, delta = {}ms!",
+        end,
+        end - start
+    );
     println!("r_sleep passed!");
     0
-}
\ No newline at end of file
+}
diff --git a/user/src/bin/stack_overflow.rs b/user/src/bin/stack_overflow.rs
index e0ea471d..5d365f5d 100644
--- a/user/src/bin/stack_overflow.rs
+++ b/user/src/bin/stack_overflow.rs
@@ -5,7 +5,7 @@
 extern crate user_lib;
 
 fn f(d: usize) {
-    println!("d = {}",d);
+    println!("d = {}", d);
     f(d + 1);
 }
 
@@ -14,4 +14,4 @@ pub fn main() -> i32 {
     println!("It should trigger segmentation fault!");
     f(0);
     0
-}
\ No newline at end of file
+}
diff --git a/user/src/bin/user_shell.rs b/user/src/bin/user_shell.rs
index 796bddb5..cdcb9721 100644
--- a/user/src/bin/user_shell.rs
+++ b/user/src/bin/user_shell.rs
@@ -1,5 +1,6 @@
 #![no_std]
 #![no_main]
+#![allow(clippy::println_empty_string)]
 
 extern crate alloc;
 
@@ -12,8 +13,8 @@ const DL: u8 = 0x7fu8;
 const BS: u8 = 0x08u8;
 
 use alloc::string::String;
-use user_lib::{fork, exec, waitpid};
 use user_lib::console::getchar;
+use user_lib::{exec, fork, waitpid};
 
 #[no_mangle]
 pub fn main() -> i32 {
@@ -59,4 +60,4 @@ pub fn main() -> i32 {
             }
         }
     }
-}
\ No newline at end of file
+}
diff --git a/user/src/bin/usertests.rs b/user/src/bin/usertests.rs
index 7a4a6d7b..62bc8388 100644
--- a/user/src/bin/usertests.rs
+++ b/user/src/bin/usertests.rs
@@ -32,9 +32,12 @@ pub fn main() -> i32 {
             let mut exit_code: i32 = Default::default();
             let wait_pid = waitpid(pid as usize, &mut exit_code);
             assert_eq!(pid, wait_pid);
-            println!("\x1b[32mUsertests: Test {} in Process {} exited with code {}\x1b[0m", test, pid, exit_code);
+            println!(
+                "\x1b[32mUsertests: Test {} in Process {} exited with code {}\x1b[0m",
+                test, pid, exit_code
+            );
         }
     }
     println!("Usertests passed!");
     0
-}
\ No newline at end of file
+}
diff --git a/user/src/bin/yield.rs b/user/src/bin/yield.rs
index 55032e40..78b1468c 100644
--- a/user/src/bin/yield.rs
+++ b/user/src/bin/yield.rs
@@ -14,4 +14,4 @@ pub fn main() -> i32 {
     }
     println!("yield pass.");
     0
-}
\ 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 378dbca7..be1255db 100644
--- a/user/src/lib.rs
+++ b/user/src/lib.rs
@@ -5,11 +5,11 @@
 
 #[macro_use]
 pub mod console;
-mod syscall;
 mod lang_items;
+mod syscall;
 
-use syscall::*;
 use buddy_system_allocator::LockedHeap;
+use syscall::*;
 
 const USER_HEAP_SIZE: usize = 16384;
 
@@ -39,18 +39,36 @@ fn main() -> i32 {
     panic!("Cannot find main!");
 }
 
-pub fn read(fd: usize, buf: &mut [u8]) -> isize { sys_read(fd, buf) }
-pub fn write(fd: usize, buf: &[u8]) -> isize { sys_write(fd, buf) }
-pub fn exit(exit_code: i32) -> ! { sys_exit(exit_code); }
-pub fn yield_() -> isize { sys_yield() }
-pub fn get_time() -> isize { sys_get_time() }
-pub fn getpid() -> isize { sys_getpid() }
-pub fn fork() -> isize { sys_fork() }
-pub fn exec(path: &str) -> isize { sys_exec(path) }
+pub fn read(fd: usize, buf: &mut [u8]) -> isize {
+    sys_read(fd, buf)
+}
+pub fn write(fd: usize, buf: &[u8]) -> isize {
+    sys_write(fd, buf)
+}
+pub fn exit(exit_code: i32) -> ! {
+    sys_exit(exit_code);
+}
+pub fn yield_() -> isize {
+    sys_yield()
+}
+pub fn get_time() -> isize {
+    sys_get_time()
+}
+pub fn getpid() -> isize {
+    sys_getpid()
+}
+pub fn fork() -> isize {
+    sys_fork()
+}
+pub fn exec(path: &str) -> isize {
+    sys_exec(path)
+}
 pub fn wait(exit_code: &mut i32) -> isize {
     loop {
         match sys_waitpid(-1, exit_code as *mut _) {
-            -2 => { yield_(); }
+            -2 => {
+                yield_();
+            }
             // -1 or a real pid
             exit_pid => return exit_pid,
         }
@@ -60,7 +78,9 @@ pub fn wait(exit_code: &mut i32) -> isize {
 pub fn waitpid(pid: usize, exit_code: &mut i32) -> isize {
     loop {
         match sys_waitpid(pid as isize, exit_code as *mut _) {
-            -2 => { yield_(); }
+            -2 => {
+                yield_();
+            }
             // -1 or a real pid
             exit_pid => return exit_pid,
         }
diff --git a/user/src/syscall.rs b/user/src/syscall.rs
index dfe3966e..a37fadb3 100644
--- a/user/src/syscall.rs
+++ b/user/src/syscall.rs
@@ -25,7 +25,10 @@ fn syscall(id: usize, args: [usize; 3]) -> isize {
 }
 
 pub fn sys_read(fd: usize, buffer: &mut [u8]) -> isize {
-    syscall(SYSCALL_READ, [fd, buffer.as_mut_ptr() as usize, buffer.len()])
+    syscall(
+        SYSCALL_READ,
+        [fd, buffer.as_mut_ptr() as usize, buffer.len()],
+    )
 }
 
 pub fn sys_write(fd: usize, buffer: &[u8]) -> isize {