diff --git a/os/src/gui/graphic.rs b/os/src/gui/graphic.rs
index d13ad61..4c18a26 100644
--- a/os/src/gui/graphic.rs
+++ b/os/src/gui/graphic.rs
@@ -27,6 +27,10 @@ impl Graphics {
         let fb = self.drv.get_framebuffer();
         fb.fill(0u8);
     }
+
+    pub fn get_framebuffer(&self)-> &mut [u8] {
+        self.drv.get_framebuffer()
+    }
 }
 
 impl OriginDimensions for Graphics {
diff --git a/os/src/mm/address.rs b/os/src/mm/address.rs
index cf147a0..8792f62 100644
--- a/os/src/mm/address.rs
+++ b/os/src/mm/address.rs
@@ -260,3 +260,4 @@ where
     }
 }
 pub type VPNRange = SimpleRange<VirtPageNum>;
+pub type PPNRange = SimpleRange<PhysPageNum>;
diff --git a/os/src/mm/frame_allocator.rs b/os/src/mm/frame_allocator.rs
index 1ecfe99..a280379 100644
--- a/os/src/mm/frame_allocator.rs
+++ b/os/src/mm/frame_allocator.rs
@@ -18,6 +18,9 @@ impl FrameTracker {
         }
         Self { ppn }
     }
+    pub fn new_nowrite(ppn: PhysPageNum) -> Self {
+        Self { ppn }
+    }
 }
 
 impl Debug for FrameTracker {
diff --git a/os/src/mm/memory_set.rs b/os/src/mm/memory_set.rs
index 663b68d..8875617 100644
--- a/os/src/mm/memory_set.rs
+++ b/os/src/mm/memory_set.rs
@@ -1,7 +1,7 @@
 use super::{frame_alloc, FrameTracker};
 use super::{PTEFlags, PageTable, PageTableEntry};
 use super::{PhysAddr, PhysPageNum, VirtAddr, VirtPageNum};
-use super::{StepByOne, VPNRange};
+use super::{StepByOne, VPNRange, PPNRange};
 use crate::config::{MEMORY_END, MMIO, PAGE_SIZE, TRAMPOLINE};
 use crate::sync::UPIntrFreeCell;
 use alloc::collections::BTreeMap;
@@ -78,6 +78,10 @@ impl MemorySet {
         }
         self.areas.push(map_area);
     }
+    pub fn push_noalloc(&mut self, mut map_area: MapArea, ppn_range: PPNRange) {
+        map_area.map_noalloc(&mut self.page_table, ppn_range);
+        self.areas.push(map_area);
+    }    
     /// Mention that trampoline is not collected by areas.
     fn map_trampoline(&mut self) {
         self.page_table.map(
@@ -301,6 +305,14 @@ impl MapArea {
             self.map_one(page_table, vpn);
         }
     }
+    pub fn map_noalloc(&mut self, page_table: &mut PageTable,ppn_range:PPNRange) {
+        for (vpn,ppn) in core::iter::zip(self.vpn_range,ppn_range) {
+            self.data_frames.insert(vpn, FrameTracker::new_nowrite(ppn));
+            let pte_flags = PTEFlags::from_bits(self.map_perm.bits).unwrap();
+            page_table.map(vpn, ppn, pte_flags);
+        }
+    }
+
     pub fn unmap(&mut self, page_table: &mut PageTable) {
         for vpn in self.vpn_range {
             self.unmap_one(page_table, vpn);
diff --git a/os/src/mm/mod.rs b/os/src/mm/mod.rs
index 34220c4..9482a30 100644
--- a/os/src/mm/mod.rs
+++ b/os/src/mm/mod.rs
@@ -4,11 +4,11 @@ mod heap_allocator;
 mod memory_set;
 mod page_table;
 
-use address::VPNRange;
+pub use address::{VPNRange, PPNRange};
 pub use address::{PhysAddr, PhysPageNum, StepByOne, VirtAddr, VirtPageNum};
 pub use frame_allocator::{frame_alloc, frame_dealloc, FrameTracker};
 pub use memory_set::remap_test;
-pub use memory_set::{kernel_token, MapPermission, MemorySet, KERNEL_SPACE};
+pub use memory_set::{kernel_token, MapPermission, MemorySet, MapArea, MapType, KERNEL_SPACE};
 use page_table::PTEFlags;
 pub use page_table::{
     translated_byte_buffer, translated_ref, translated_refmut, translated_str, PageTable,
diff --git a/os/src/syscall/gui.rs b/os/src/syscall/gui.rs
new file mode 100644
index 0000000..0018604
--- /dev/null
+++ b/os/src/syscall/gui.rs
@@ -0,0 +1,37 @@
+use crate::mm::{MapArea, MapPermission, MapType, PPNRange, PhysAddr};
+use crate::task::current_process;
+
+//use crate::gui::*;
+use crate::drivers::GPU_DEVICE;
+
+const FB_VADDR: usize = 0x10000000;
+
+pub fn sys_framebuffer() -> isize {
+    let gpu = GPU_DEVICE.clone();
+    let fb = gpu.get_framebuffer();
+    let len = fb.len();
+    println!("[kernel] FrameBuffer: addr 0x{:X}, len {}", fb.as_ptr() as usize , len);
+    let fb_ppn = PhysAddr::from(fb.as_ptr() as usize).floor();
+    let fb_end_ppn = PhysAddr::from(fb.as_ptr() as usize + len).ceil();
+
+    let current_process = current_process();
+    let mut inner = current_process.inner_exclusive_access();
+    let mem_set = &mut inner.memory_set;
+
+    mem_set.push_noalloc(
+        MapArea::new(
+            (FB_VADDR as usize).into(),
+            (FB_VADDR + len as usize).into(),
+            MapType::Framed,
+            MapPermission::R | MapPermission::W | MapPermission::U,
+        ),
+        PPNRange::new(fb_ppn, fb_end_ppn),
+    );
+    FB_VADDR as isize
+}
+
+pub fn sys_framebuffer_flush() -> isize {
+    let gpu = GPU_DEVICE.clone();
+    gpu.flush();
+    0
+}
\ No newline at end of file
diff --git a/os/src/syscall/mod.rs b/os/src/syscall/mod.rs
index fa4a4cf..3f95b94 100644
--- a/os/src/syscall/mod.rs
+++ b/os/src/syscall/mod.rs
@@ -25,16 +25,20 @@ const SYSCALL_SEMAPHORE_DOWN: usize = 1022;
 const SYSCALL_CONDVAR_CREATE: usize = 1030;
 const SYSCALL_CONDVAR_SIGNAL: usize = 1031;
 const SYSCALL_CONDVAR_WAIT: usize = 1032;
+const SYSCALL_FRAMEBUFFER: usize = 2000;
+const SYSCALL_FRAMEBUFFER_FLUSH: usize = 2001;
 
 mod fs;
 mod process;
 mod sync;
 mod thread;
+mod gui;
 
 use fs::*;
 use process::*;
 use sync::*;
 use thread::*;
+use gui::*;
 
 pub fn syscall(syscall_id: usize, args: [usize; 3]) -> isize {
     match syscall_id {
@@ -65,6 +69,8 @@ pub fn syscall(syscall_id: usize, args: [usize; 3]) -> isize {
         SYSCALL_CONDVAR_CREATE => sys_condvar_create(args[0]),
         SYSCALL_CONDVAR_SIGNAL => sys_condvar_signal(args[0]),
         SYSCALL_CONDVAR_WAIT => sys_condvar_wait(args[0], args[1]),
+        SYSCALL_FRAMEBUFFER => sys_framebuffer(),
+        SYSCALL_FRAMEBUFFER_FLUSH => sys_framebuffer_flush(),
         _ => panic!("Unsupported syscall_id: {}", syscall_id),
     }
 }
diff --git a/user/Cargo.toml b/user/Cargo.toml
index a609f4d..d8d10cc 100644
--- a/user/Cargo.toml
+++ b/user/Cargo.toml
@@ -10,6 +10,7 @@ edition = "2018"
 buddy_system_allocator = "0.6"
 bitflags = "1.2.1"
 riscv = { git = "https://github.com/rcore-os/riscv", features = ["inline-asm"] }
+embedded-graphics = "0.7.1"
 
 [profile.release]
 debug = true
diff --git a/user/src/bin/gui_simple.rs b/user/src/bin/gui_simple.rs
new file mode 100644
index 0000000..df4cfbb
--- /dev/null
+++ b/user/src/bin/gui_simple.rs
@@ -0,0 +1,35 @@
+#![no_std]
+#![no_main]
+
+use user_lib::{framebuffer, framebuffer_flush};
+
+#[macro_use]
+extern crate user_lib;
+
+// use embedded_graphics::pixelcolor::Rgb888;
+// use embedded_graphics::prelude::{Drawable, Point, RgbColor, Size};
+// use embedded_graphics::primitives::Primitive;
+// use embedded_graphics::primitives::{PrimitiveStyle, Rectangle};
+// use embedded_graphics::{
+//     draw_target::DrawTarget,
+//     prelude::{OriginDimensions},
+// };
+pub const VIRTGPU_XRES: usize = 1280;
+pub const VIRTGPU_YRES: usize = 800;
+
+#[no_mangle]
+pub fn main() -> i32 {
+    let fb_ptr =framebuffer() as *mut u8;
+    println!("Hello world from user mode program! 0x{:X} , len {}", fb_ptr as usize, VIRTGPU_XRES*VIRTGPU_YRES*4);
+    let fb= unsafe {core::slice::from_raw_parts_mut(fb_ptr as *mut u8, VIRTGPU_XRES*VIRTGPU_YRES*4 as usize)};
+    for y in 0..800 {
+        for x in 0..1280 {
+            let idx = (y * 1280 + x) * 4;
+            fb[idx] = x as u8;
+            fb[idx + 1] = y as u8;
+            fb[idx + 2] = (x + y) as u8;
+        }
+    }
+    framebuffer_flush();
+    0
+}
diff --git a/user/src/lib.rs b/user/src/lib.rs
index 729eaef..16d4abd 100644
--- a/user/src/lib.rs
+++ b/user/src/lib.rs
@@ -198,6 +198,12 @@ pub fn condvar_signal(condvar_id: usize) {
 pub fn condvar_wait(condvar_id: usize, mutex_id: usize) {
     sys_condvar_wait(condvar_id, mutex_id);
 }
+pub fn framebuffer() -> isize {
+    sys_framebuffer()
+}
+pub fn framebuffer_flush() -> isize {
+    sys_framebuffer_flush()
+}
 
 #[macro_export]
 macro_rules! vstore {
diff --git a/user/src/syscall.rs b/user/src/syscall.rs
index b4bb67a..330388c 100644
--- a/user/src/syscall.rs
+++ b/user/src/syscall.rs
@@ -25,6 +25,8 @@ const SYSCALL_SEMAPHORE_DOWN: usize = 1022;
 const SYSCALL_CONDVAR_CREATE: usize = 1030;
 const SYSCALL_CONDVAR_SIGNAL: usize = 1031;
 const SYSCALL_CONDVAR_WAIT: usize = 1032;
+const SYSCALL_FRAMEBUFFER: usize = 2000;
+const SYSCALL_FRAMEBUFFER_FLUSH: usize = 2001;
 
 fn syscall(id: usize, args: [usize; 3]) -> isize {
     let mut ret: isize;
@@ -154,3 +156,12 @@ pub fn sys_condvar_signal(condvar_id: usize) -> isize {
 pub fn sys_condvar_wait(condvar_id: usize, mutex_id: usize) -> isize {
     syscall(SYSCALL_CONDVAR_WAIT, [condvar_id, mutex_id, 0])
 }
+
+
+pub fn sys_framebuffer() -> isize {
+    syscall(SYSCALL_FRAMEBUFFER, [0, 0, 0])
+}
+
+pub fn sys_framebuffer_flush() -> isize {
+    syscall(SYSCALL_FRAMEBUFFER_FLUSH, [0, 0, 0])
+}
\ No newline at end of file