diff --git a/.github/workflows/rust-test.yml b/.github/workflows/rust-test.yml
index 3da7c1e..05f6aee 100644
--- a/.github/workflows/rust-test.yml
+++ b/.github/workflows/rust-test.yml
@@ -11,6 +11,8 @@ on:
       - "**.ps1"
       - "**.yml"
       - "**.toml"
+      - "**.S"
+      - "**.ld"
       - "!**.md"
   pull_request:
     types: [opened, synchronize]
@@ -21,6 +23,8 @@ on:
       - "**.ps1"
       - "**.yml"
       - "**.toml"
+      - "**.S"
+      - "**.ld"
       - "!**.md"
 
 env:
diff --git a/crates/rkos-arch/src/x86/head_64.S b/crates/rkos-arch/src/x86/head_64.S
new file mode 100644
index 0000000..e7df2fa
--- /dev/null
+++ b/crates/rkos-arch/src/x86/head_64.S
@@ -0,0 +1,154 @@
+/*
+    Bootstrapping x86_64 kernel
+    see also: https://wiki.osdev.org/Entering_Long_Mode
+*/
+    /* prepare space for 4-level paging to entering long mode 
+        .bss: | PML4 | PML3 | PML2 | Kernel_Stack(.bss.stack)|
+              | 4kb  | 4kb  | 4kb  | 16kb                 |
+    */
+    .section .bss
+    .align 4096
+p4_table:
+    .skip 4096
+p3_table:
+    .skip 4096
+p2_table:
+    .skip 4096
+
+    /* Kernel Stack */
+    .section .bss.stack
+    .align 16
+stack_bottom:
+    .skip 16384
+stack_top:
+
+    /*  
+        64-bit Global Descriptor Table (GDT) 
+        see also: https://wiki.osdev.org/Global_Descriptor_Table
+    */
+
+    /* because of .rodata is read only now,when adding more features,we should move it to .data */
+    .section .rodata 
+    /* every items in gdt64 is 8 bytes */
+    .align 8
+gdt64:
+    /* the first item is null */
+    .quad 0x0000000000000000  
+    
+    /* the second item is 64-bit code segment 
+        Base 63:56 0x00000000
+        G 55 0
+        D/B 54 0
+        L 53 1 (64-bit code segment)
+        AVL 52 0
+        Limit 51:48 0x0000
+        P 47 1
+        DPL 46:45 0x00
+        S 44 1
+        Type 43:40 0x10
+        Base 39:16 0x000000
+        Limit 15:0 0x0000
+    */
+    .quad 0x0020980000000000  
+gdt64_pointer:
+    /* length of gdt64 minus 1 */
+    .word 15    
+    /* pointer to gdt64 */              
+    .quad gdt64 
+
+    /* 
+        multiboot header
+        see also: https://wiki.osdev.org/Multiboot_Specification
+    */
+    .section .text.entry
+    .align 4
+    
+    .global multiboot_header
+multiboot_header:
+    /* 0x1badb002: magic number for multiboot protocol*/
+    .long 0x1badb002
+    /* 0x00010000: flags */
+    .long 0x00010000
+    /* checksum */
+    .long -(0x1badb002 + 0x00010000)
+
+    /* pointer to multiboot_header */
+    .long multiboot_header
+    .long stext
+    .long edata
+    .long ebss
+    .long _start
+
+    /* 
+        start of 32-bit code
+    */
+    .global _start
+_start:
+    .code32
+    /* set stack pointer */
+    mov esp, offset stack_top
+
+    /* 
+        set up temporary page table
+        map first 2MB of physical memory to virtual memory
+    */
+    mov eax, offset p3_table
+    or eax, 0b11          /* 0b11 means present and writable */
+    mov dword ptr [p4_table], eax
+
+    /* p3_table[0] -> p2_table */
+    mov eax, offset p2_table
+    or eax, 0b11
+    mov dword ptr [p3_table], eax
+
+    /* map first 2MB of physical memory to virtual memory as huge page */
+    mov eax, 0x83         /* 0x80 (Huge) + 0x02 (Writable) + 0x01 (Present) */
+    mov dword ptr [p2_table], eax
+
+    /* into long mode */
+    /* step 1: set CR3 to p4_table */
+    mov eax, offset p4_table
+    mov cr3, eax
+
+    /* step 2: enable PAE in CR4 */
+    mov eax, cr4
+    or eax, 1 << 5
+    mov cr4, eax
+
+    /* step 3: enable LME in EFER */
+    mov ecx, 0xC0000080
+    rdmsr
+    or eax, 1 << 8
+    wrmsr
+
+    /* step 4: enable paging in CR0 */
+    mov eax, cr0
+    or eax, 1 << 31
+    mov cr0, eax
+
+    /* step 5: load gdt64 */
+    lgdt [gdt64_pointer]
+
+    /* jump to 64-bit code */
+    push 8                     /* push 64-bit code segment */
+    mov eax, offset long_mode_start
+    push eax                   /* push 64-bit code entry point */
+    retf                       /* retf to long mode */
+
+    .code64
+long_mode_start:
+    /* first thing: set all data segment registers to 0 */
+    mov ax, 0
+    mov ss, ax
+    mov ds, ax
+    mov es, ax
+    mov fs, ax
+    mov gs, ax
+
+    /* call _main */
+    call _main
+
+    /* if _main returns, loop forever */
+.loop64:
+    hlt
+    jmp .loop64
\ No newline at end of file
diff --git a/crates/rkos-arch/src/x86/link.ld b/crates/rkos-arch/src/x86/link.ld
index ade506b..f59116d 100644
--- a/crates/rkos-arch/src/x86/link.ld
+++ b/crates/rkos-arch/src/x86/link.ld
@@ -1,3 +1,7 @@
+/* 
+    linker script for x86_64 kernel
+    see also: https://wiki.osdev.org/Linker_Scripts
+*/
 OUTPUT_ARCH(i386:x86-64)
 ENTRY(_start)
 
@@ -8,16 +12,20 @@ KERNEL_BASE_ADDRESS = 0x100000;
 SECTIONS {
     . = KERNEL_BASE_ADDRESS;
 
-    /* kernel code */
+    /*  
+        .text: kernel code
+        start at 0x100000
+    */
     .text : {
         stext = .;              
-        *(.text.entry)          
+        *(.text.entry)         
         *(.text .text.*)        
         . = ALIGN(4096);
         etext = .;              
     }
-
-    /* kernel rodata */
+    /* 
+        .rodata: kernel rodata 
+    */
     .rodata : {
         srodata = .;
         *(.rodata .rodata.*)
@@ -25,7 +33,9 @@ SECTIONS {
         erodata = .;
     }
 
-    /* kernel data */
+    /* 
+        .data: kernel data 
+    */
     .data : {
         sdata = .;
         *(.data .data.*)
@@ -33,7 +43,9 @@ SECTIONS {
         edata = .;
     }
 
-    /* kernel bss */
+    /* 
+        .bss: kernel bss 
+    */
     .bss : {
         sbss = .;
         *(.bss.stack)           /* kernel stack */
@@ -43,7 +55,9 @@ SECTIONS {
         ebss = .;
     }
 
-    /* kernel end */
+    /* 
+        kernel end
+    */
     . = ALIGN(4096);
     ekernel = .;
 }
diff --git a/crates/rkos/src/main.rs b/crates/rkos/src/main.rs
index 6e52051..ff7f6b4 100644
--- a/crates/rkos/src/main.rs
+++ b/crates/rkos/src/main.rs
@@ -4,35 +4,34 @@
 use core::arch::global_asm;
 use core::panic::PanicInfo;
 
-global_asm!(
-    r#"
-    .section .text.entry
-    .align 4
-    
-    .global multiboot_header
-    multiboot_header:
-    
-    .long 0x1badb002
-    .long 0x00010000
-    .long -(0x1badb002 + 0x00010000)
-
-    .long multiboot_header
-    .long stext
-    .long edata
-    .long ebss
-    .long _start
-
-    .global _start
-    _start:
-    .code32
-        mov eax, 0x4f4f4f4f
-        mov dword ptr [0xb8000], eax
-        
-    .loop:
-        hlt
-        jmp .loop
-    "#
-);
+#[cfg(target_arch = "x86_64")]
+global_asm!(include_str!("../../rkos-arch/src/x86/head_64.S"));
+
+#[unsafe(no_mangle)]
+pub extern "C" fn _main() {
+    // VGA_BASE: 0xb8000
+    let vga_buffer = 0xb8000 as *mut u8;
+
+    let text = b"[OK] Barrensea rkos has conquered 64-bit Long Mode!!!";
+    let color_byte = 0x0a;
+
+    for (i, &byte) in text.iter().enumerate() {
+        unsafe {
+            *vga_buffer.add(i * 2) = byte;
+            *vga_buffer.add(i * 2 + 1) = color_byte;
+        }
+    }
+
+    unsafe extern "C" {
+        fn stext();
+        fn edata();
+        fn ebss();
+    }
+    let _text_size = edata as *const () as usize - stext as *const () as usize;
+    let _bss_size = ebss as *const () as usize - edata as *const () as usize;
+
+    //loop {}
+}
 
 #[panic_handler]
 fn panic(_info: &PanicInfo) -> ! {