diff --git a/user/Makefile b/user/Makefile
index eabb4b2750804fb9372589f1aec977504919ea82..5e0f87c39060e50ddde9c0585887e2f1ecdec53e 100644
--- a/user/Makefile
+++ b/user/Makefile
@@ -1,5 +1,5 @@
 TARGET := riscv64gc-unknown-none-elf
-MODE := debug
+MODE := release
 APP_DIR := src/bin
 TARGET_DIR := target/$(TARGET)/$(MODE)
 APPS := $(wildcard $(APP_DIR)/*.rs)
@@ -10,7 +10,7 @@ OBJDUMP := rust-objdump --arch-name=riscv64
 OBJCOPY := rust-objcopy --binary-architecture=riscv64
 
 elf: $(APPS)
-	@python3 build.py
+	@cargo build --release
 
 binary: elf
 	$(foreach elf, $(ELFS), $(OBJCOPY) $(elf) --strip-all -O binary $(patsubst $(TARGET_DIR)/%, $(TARGET_DIR)/%.bin, $(elf));)
diff --git a/user/build.py b/user/build.py
deleted file mode 100644
index 1a220881568856a37da3371ed4a6d51cee4a6693..0000000000000000000000000000000000000000
--- a/user/build.py
+++ /dev/null
@@ -1,25 +0,0 @@
-import os
-
-base_address = 0x80100000
-step = 0x20000
-linker = 'src/linker.ld'
-
-app_id = 0
-apps = os.listdir('src/bin')
-apps.sort()
-for app in apps:
-    app = app[:app.find('.')]
-    lines = []
-    lines_before = []
-    with open(linker, 'r') as f:
-        for line in f.readlines():
-            lines_before.append(line)
-            line = line.replace(hex(base_address), hex(base_address+step*app_id))
-            lines.append(line)
-    with open(linker, 'w+') as f:
-        f.writelines(lines)
-    os.system('cargo build --bin %s' % app)
-    print('[build.py] application %s start with address %s' %(app, hex(base_address+step*app_id)))
-    with open(linker, 'w+') as f:
-        f.writelines(lines_before)
-    app_id = app_id + 1
diff --git a/user/src/lib.rs b/user/src/lib.rs
index fdcb6d56deb60482aab4fa6c65e1f5ea7b612c5a..c072ef498056ebf08bb900c9ba9cea9a1b2500ba 100644
--- a/user/src/lib.rs
+++ b/user/src/lib.rs
@@ -11,7 +11,6 @@ mod lang_items;
 #[no_mangle]
 #[link_section = ".text.entry"]
 pub extern "C" fn _start() -> ! {
-    clear_bss();
     syscall::sys_exit(main());
     panic!("unreachable after sys_exit!");
 }
@@ -22,14 +21,5 @@ fn main() -> i32 {
     panic!("Cannot find main!");
 }
 
-fn clear_bss() {
-    extern "C" {
-        fn start_bss();
-        fn end_bss();
-    }
-    (start_bss as usize..end_bss as usize).for_each(|addr| {
-        unsafe { (addr as *mut u8).write_volatile(0); }
-    });
-}
 
 pub use syscall::*;
\ No newline at end of file
diff --git a/user/src/linker.ld b/user/src/linker.ld
index 1c64a19b2ed1d6ab00831e6798e69813646a75a5..db314ce32eda682d110416b309537397e6014fa9 100644
--- a/user/src/linker.ld
+++ b/user/src/linker.ld
@@ -2,7 +2,7 @@
 OUTPUT_ARCH(riscv)
 ENTRY(_start)
 
-BASE_ADDRESS = 0x80100000;
+BASE_ADDRESS = 0x0;
 
 SECTIONS
 {
@@ -18,9 +18,7 @@ SECTIONS
         *(.data .data.*)
     }
     .bss : {
-        start_bss = .;
         *(.bss .bss.*)
-        end_bss = .;
     }
     /DISCARD/ : {
         *(.eh_frame)