diff --git a/os/src/loader.rs b/os/src/loader.rs
index d4ae5731..0d0a5774 100644
--- a/os/src/loader.rs
+++ b/os/src/loader.rs
@@ -1,5 +1,6 @@
 use crate::trap::TrapContext;
 use crate::config::*;
+use core::arch::asm;
 
 #[repr(align(4096))]
 #[derive(Copy, Clone)]
diff --git a/os/src/main.rs b/os/src/main.rs
index 608f1b09..c64cece5 100644
--- a/os/src/main.rs
+++ b/os/src/main.rs
@@ -1,9 +1,9 @@
 #![no_std]
 #![no_main]
-#![feature(global_asm)]
-#![feature(asm)]
 #![feature(panic_info_message)]
 
+use core::arch::global_asm;
+
 #[macro_use]
 mod console;
 mod lang_items;
diff --git a/os/src/sbi.rs b/os/src/sbi.rs
index 935fe24e..aa12b7f3 100644
--- a/os/src/sbi.rs
+++ b/os/src/sbi.rs
@@ -1,5 +1,7 @@
 #![allow(unused)]
 
+use core::arch::asm;
+
 const SBI_SET_TIMER: usize = 0;
 const SBI_CONSOLE_PUTCHAR: usize = 1;
 const SBI_CONSOLE_GETCHAR: usize = 2;
diff --git a/os/src/task/switch.rs b/os/src/task/switch.rs
index fa75be1a..dd3a2d3e 100644
--- a/os/src/task/switch.rs
+++ b/os/src/task/switch.rs
@@ -1,6 +1,7 @@
-global_asm!(include_str!("switch.S"));
-
 use super::TaskContext;
+use core::arch::global_asm;
+
+global_asm!(include_str!("switch.S"));
 
 extern "C" {
     pub fn __switch(
diff --git a/os/src/trap/mod.rs b/os/src/trap/mod.rs
index a6288997..d105bb9d 100644
--- a/os/src/trap/mod.rs
+++ b/os/src/trap/mod.rs
@@ -11,6 +11,7 @@ use riscv::register::{
     stval,
 };
 use crate::syscall::syscall;
+use core::arch::global_asm;
 
 global_asm!(include_str!("trap.S"));
 
@@ -48,4 +49,4 @@ pub fn trap_handler(cx: &mut TrapContext) -> &mut TrapContext {
     cx
 }
 
-pub use context::TrapContext;
\ No newline at end of file
+pub use context::TrapContext;
diff --git a/rust-toolchain b/rust-toolchain
index c9f86822..a8a61591 100644
--- a/rust-toolchain
+++ b/rust-toolchain
@@ -1 +1 @@
-nightly-2021-12-15
+nightly-2022-01-01
diff --git a/user/src/lib.rs b/user/src/lib.rs
index 94cce773..c8fabfee 100644
--- a/user/src/lib.rs
+++ b/user/src/lib.rs
@@ -1,5 +1,4 @@
 #![no_std]
-#![feature(asm)]
 #![feature(linkage)]
 #![feature(panic_info_message)]
 
diff --git a/user/src/syscall.rs b/user/src/syscall.rs
index 4a1f781b..30baeba8 100644
--- a/user/src/syscall.rs
+++ b/user/src/syscall.rs
@@ -1,3 +1,5 @@
+use core::arch::asm;
+
 const SYSCALL_WRITE: usize = 64;
 const SYSCALL_EXIT: usize = 93;
 const SYSCALL_YIELD: usize = 124;