diff --git a/kernel/src/arch/x86_64/interrupt/handler.rs b/kernel/src/arch/x86_64/interrupt/handler.rs
index 98e80a3a..39ec86ec 100644
--- a/kernel/src/arch/x86_64/interrupt/handler.rs
+++ b/kernel/src/arch/x86_64/interrupt/handler.rs
@@ -67,7 +67,6 @@
 use super::consts::*;
 use super::TrapFrame;
 use crate::drivers::IRQ_MANAGER;
-use crate::process::current_thread;
 use crate::signal::do_signal;
 use bitflags::*;
 use log::*;
@@ -216,7 +215,7 @@ pub extern "C" fn syscall(tf: &mut TrapFrame) {
     trace!("\nInterupt: Syscall {:#x?}", tf.rax);
     //let ret = crate::syscall::syscall(tf.rax, [tf.rdi, tf.rsi, tf.rdx, tf.r10, tf.r8, tf.r9], tf);
     //tf.rax = ret as usize;
-    do_signal(tf);
+    //do_signal(tf);
 }
 
 fn syscall32(tf: &mut TrapFrame) {
diff --git a/kernel/src/fs/devfs/fbdev.rs b/kernel/src/fs/devfs/fbdev.rs
index 2deb08c7..e4650ac3 100755
--- a/kernel/src/fs/devfs/fbdev.rs
+++ b/kernel/src/fs/devfs/fbdev.rs
@@ -100,6 +100,7 @@ impl INode for Fbdev {
             if area.offset + area.end_vaddr - area.start_vaddr > fb.framebuffer_size() {
                 return Err(FsError::NoDeviceSpace);
             }
+            /*
             let thread = unsafe { crate::process::current_thread() };
             thread.vm.lock().push(
                 area.start_vaddr,
@@ -108,6 +109,7 @@ impl INode for Fbdev {
                 Linear::new((fb.paddr() + area.offset - area.start_vaddr) as isize),
                 "mmap_file",
             );
+            */
             Ok(())
         } else {
             Err(FsError::NoDevice)
diff --git a/kernel/src/fs/file.rs b/kernel/src/fs/file.rs
index 6108b13c..9a9e3d52 100644
--- a/kernel/src/fs/file.rs
+++ b/kernel/src/fs/file.rs
@@ -1,7 +1,7 @@
 //! File handle for process
 
 use crate::memory::GlobalFrameAlloc;
-use crate::process::{current_thread, INodeForMap};
+use crate::process::INodeForMap;
 use crate::syscall::{MmapProt, SysResult, TimeSpec};
 use alloc::{string::String, sync::Arc};
 use core::fmt;
@@ -233,6 +233,7 @@ impl FileHandle {
         match self.inode.metadata()?.type_ {
             FileType::File => {
                 let prot = MmapProt::from_bits_truncate(area.prot);
+                /*
                 let thread = unsafe { current_thread() };
                 thread.vm.lock().push(
                     area.start_vaddr,
@@ -247,6 +248,7 @@ impl FileHandle {
                     },
                     "mmap_file",
                 );
+                */
                 Ok(())
             }
             FileType::CharDevice => self.inode.mmap(area),
diff --git a/kernel/src/lib.rs b/kernel/src/lib.rs
index 40be74e0..07cd8a30 100644
--- a/kernel/src/lib.rs
+++ b/kernel/src/lib.rs
@@ -8,6 +8,7 @@
 #![feature(negative_impls)]
 #![feature(alloc_prelude)]
 #![feature(const_fn)]
+#![feature(const_in_array_repeat_expressions)]
 #![deny(unused_must_use)]
 #![deny(stable_features)]
 #![deny(unused_unsafe)]
diff --git a/kernel/src/memory.rs b/kernel/src/memory.rs
index 5c84e56e..f15b8062 100644
--- a/kernel/src/memory.rs
+++ b/kernel/src/memory.rs
@@ -141,8 +141,9 @@ impl Drop for KernelStack {
 pub fn handle_page_fault(addr: usize) -> bool {
     debug!("page fault @ {:#x}", addr);
 
-    let thread = unsafe { current_thread() };
-    thread.vm.lock().handle_page_fault(addr)
+    let thread = current_thread().unwrap();
+    let mut lock = thread.vm.lock();
+    lock.handle_page_fault(addr)
 }
 
 pub fn init_heap() {
diff --git a/kernel/src/process/mod.rs b/kernel/src/process/mod.rs
index c98b8c6e..94515750 100644
--- a/kernel/src/process/mod.rs
+++ b/kernel/src/process/mod.rs
@@ -38,15 +38,16 @@ pub fn init() {
     info!("process: init end");
 }
 
+static mut THREADS: [Option<Arc<Thread>>; MAX_CPU_NUM] = [None; MAX_CPU_NUM];
+
 /// Get current thread
 ///
 /// `Thread` is a thread-local object.
 /// It is safe to call this once, and pass `&mut Thread` as a function argument.
-pub unsafe fn current_thread() -> &'static mut Thread {
-    // trick: force downcast from trait object
-    //let (process, _): (&mut Thread, *const ()) = core::mem::transmute(processor().context());
-    //process
-    todo!()
+/// Should only be called in kernel trap handler
+pub fn current_thread() -> Option<Arc<Thread>> {
+    let cpu_id = cpu::id();
+    unsafe { THREADS[cpu_id].clone() }
 }
 
 pub fn spawn(thread: Arc<Thread>) {
@@ -109,6 +110,10 @@ impl Future for PageTableSwitchWrapper {
     type Output = ();
     fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
         // vmtoken might change upon sys_exec
+        let cpu_id = cpu::id();
+        unsafe {
+            THREADS[cpu_id] = Some(self.thread.clone());
+        }
         let vmtoken = self.thread.vm.lock().token();
         unsafe {
             Cr3::write(
@@ -116,6 +121,10 @@ impl Future for PageTableSwitchWrapper {
                 Cr3Flags::empty(),
             );
         }
-        self.inner.lock().as_mut().poll(cx)
+        let res = self.inner.lock().as_mut().poll(cx);
+        unsafe {
+            THREADS[cpu_id] = None;
+        }
+        res
     }
 }
diff --git a/kernel/src/signal/mod.rs b/kernel/src/signal/mod.rs
index d4a3a5ef..50b88817 100644
--- a/kernel/src/signal/mod.rs
+++ b/kernel/src/signal/mod.rs
@@ -1,4 +1,4 @@
-use crate::process::{current_thread, process, process_of, Process};
+use crate::process::{process, process_of, Process, Thread};
 use crate::sync::{MutexGuard, SpinNoIrq, SpinNoIrqLock as Mutex};
 use alloc::sync::Arc;
 use bitflags::*;
@@ -132,9 +132,8 @@ pub struct SignalFrame {
     pub ret_code: [u8; 7],           // call sys_sigreturn
 }
 
-pub fn do_signal(tf: &mut TrapFrame) {
-    let thread = unsafe { current_thread() };
-    let mut process = unsafe { current_thread().proc.lock() };
+pub fn do_signal(thread: &Arc<Thread>, tf: &mut TrapFrame) {
+    let mut process = thread.proc.lock();
     while let Some((idx, info)) =
         process
             .sig_queue