diff --git a/kernel/src/arch/mipsel/boot/context.S b/kernel/src/arch/mipsel/boot/context.S
index 86c9a85..6a3975a 100644
--- a/kernel/src/arch/mipsel/boot/context.S
+++ b/kernel/src/arch/mipsel/boot/context.S
@@ -5,7 +5,7 @@
 
 .section .text.context
 .globl switch_context
-.extern root_page_table_ptr
+.extern _root_page_table_ptr
 
 switch_context:
 	// save from's registers
@@ -25,7 +25,7 @@ switch_context:
 	sw ra, 12*4(sp)
 	sw sp, 13*4(sp)
 
-	la s0, root_page_table_ptr
+	la s0, _root_page_table_ptr
 	lw AT, 0(s0)
 	sw AT, 4(sp)
 
diff --git a/kernel/src/arch/mipsel/boot/trap.S b/kernel/src/arch/mipsel/boot/trap.S
index 513b9cd..04cf983 100644
--- a/kernel/src/arch/mipsel/boot/trap.S
+++ b/kernel/src/arch/mipsel/boot/trap.S
@@ -158,9 +158,9 @@ kernel_stack:
 kernel_stack_top:
 
     .align 12  #PGSHIFT
-    .global root_page_table_buffer
-root_page_table_buffer:
+    .global _root_page_table_buffer
+_root_page_table_buffer:
     .space 1024 * 4 # 4KB
-    .global root_page_table_ptr
-root_page_table_ptr:
+    .global _root_page_table_ptr
+_root_page_table_ptr:
     .space 4 # 4bytes
diff --git a/kernel/src/arch/mipsel/context.rs b/kernel/src/arch/mipsel/context.rs
index 372a186..4d20869 100644
--- a/kernel/src/arch/mipsel/context.rs
+++ b/kernel/src/arch/mipsel/context.rs
@@ -1,9 +1,5 @@
 use mips::registers::cp0;
 
-extern {
-    static root_page_table_ptr : *mut usize;
-}
-
 /// Saved registers on a trap.
 #[derive(Clone)]
 #[repr(C)]
diff --git a/kernel/src/arch/mipsel/interrupt.rs b/kernel/src/arch/mipsel/interrupt.rs
index fc59fae..bf6256b 100644
--- a/kernel/src/arch/mipsel/interrupt.rs
+++ b/kernel/src/arch/mipsel/interrupt.rs
@@ -5,6 +5,7 @@ use crate::drivers::DRIVERS;
 use mips::paging::{PageTable as MIPSPageTable, PageTableEntry, PageTableFlags as EF, TwoLevelPageTable};
 use mips::addr::*;
 pub use self::context::*;
+use crate::arch::paging::get_root_page_table_ptr;
 use log::*;
 
 #[path = "context.rs"]
@@ -131,10 +132,6 @@ fn syscall(tf: &mut TrapFrame) {
     tf.v0 = ret as usize;
 }
 
-extern {
-    static root_page_table_ptr : *mut usize;
-}
-
 fn page_fault(tf: &mut TrapFrame) {
     // TODO: set access/dirty bit
     let addr = tf.vaddr;
@@ -146,7 +143,7 @@ fn page_fault(tf: &mut TrapFrame) {
 
     let virt_addr = VirtAddr::new(addr);
     let root_table = unsafe {
-        &mut *(root_page_table_ptr as *mut MIPSPageTable)
+        &mut *(get_root_page_table_ptr() as *mut MIPSPageTable)
     };
     let tlb_entry = root_table.lookup(addr);
     tlb::write_tlb_random(tlb_entry);
diff --git a/kernel/src/arch/mipsel/memory.rs b/kernel/src/arch/mipsel/memory.rs
index a1f09f9..67ff901 100644
--- a/kernel/src/arch/mipsel/memory.rs
+++ b/kernel/src/arch/mipsel/memory.rs
@@ -3,12 +3,21 @@ use rcore_memory::PAGE_SIZE;
 use log::*;
 use crate::memory::{FRAME_ALLOCATOR, init_heap, MemoryAttr, MemorySet, Linear};
 use crate::consts::{MEMORY_OFFSET, MEMORY_END, KERNEL_OFFSET};
+use crate::arch::paging::*;
 
 /// Initialize the memory management module
 pub fn init() {
     // initialize heap and Frame allocator
     init_frame_allocator();
     init_heap();
+
+    set_root_page_table_ptr(0xFFFF_FFFF);
+    extern "C" {
+        fn _root_page_table_buffer();
+        fn _root_page_table_ptr();
+    }
+
+    println!("_root_page_table_ptr {:x}", _root_page_table_ptr as usize);
 }
 
 pub fn init_other() {
diff --git a/kernel/src/arch/mipsel/paging.rs b/kernel/src/arch/mipsel/paging.rs
index 772cea3..47c2899 100644
--- a/kernel/src/arch/mipsel/paging.rs
+++ b/kernel/src/arch/mipsel/paging.rs
@@ -6,8 +6,6 @@ use mips::paging::{Mapper, PageTable as MIPSPageTable, PageTableEntry, PageTable
 use mips::paging::{FrameAllocator, FrameDeallocator};
 use rcore_memory::paging::*;
 use log::*;
-#[cfg(target_arch = "riscv32")]
-use crate::consts::KERNEL_P2_INDEX;
 
 pub struct ActivePageTable(TwoLevelPageTable<'static>, PageEntry);
 
@@ -46,18 +44,38 @@ impl PageTable for ActivePageTable {
     }
 }
 
+extern "C" {
+    fn _root_page_table_buffer();
+    fn _root_page_table_ptr();
+}
+
+pub fn set_root_page_table_ptr(ptr : usize) {
+    unsafe {
+        *(_root_page_table_ptr as *mut usize) = ptr;
+    }
+}
+
+pub fn get_root_page_table_ptr() -> usize {
+    unsafe {
+        *(_root_page_table_ptr as *mut usize)
+    }
+}
+
+pub fn root_page_table_buffer() -> &'static mut MIPSPageTable {
+    unsafe {
+        &mut *(_root_page_table_ptr as *mut MIPSPageTable)
+    }
+}
+
+
 impl PageTableExt for ActivePageTable {}
 
 /// The virtual address of root page table
-extern {
-    static root_page_table_buffer : *mut MIPSPageTable;
-    static root_page_table_ptr : *mut usize;
-}
 
 impl ActivePageTable {
     pub unsafe fn new() -> Self {
         ActivePageTable(
-            TwoLevelPageTable::new(&mut *(root_page_table_buffer as *mut MIPSPageTable)),
+            TwoLevelPageTable::new(root_page_table_buffer()),
             ::core::mem::uninitialized()
         )
     }
@@ -123,11 +141,11 @@ impl InactivePageTable for InactivePageTable0 {
     }
 
     unsafe fn set_token(token: usize) {
-        *root_page_table_ptr = token;
+        set_root_page_table_ptr(token);
     }
 
     fn active_token() -> usize {
-        unsafe { *root_page_table_ptr }
+        get_root_page_table_ptr()
     }
 
     fn flush_tlb() {