diff --git a/src/arch/x86_64/gdt.rs b/src/arch/x86_64/gdt.rs
index a3095ae..76292f3 100644
--- a/src/arch/x86_64/gdt.rs
+++ b/src/arch/x86_64/gdt.rs
@@ -58,7 +58,7 @@ static mut TSS_PTR: Unique<TaskStateSegment> = unsafe{ Unique::new_unchecked(0 a
 ///
 /// 每次进入用户态前，都要调用此函数，才能保证正确返回内核态
 pub fn set_ring0_rsp(rsp: usize) {
-    debug!("gdt.set_ring0_rsp: {:#x}", rsp);
+//    debug!("gdt.set_ring0_rsp: {:#x}", rsp);
     unsafe {
         TSS_PTR.as_mut().privilege_stack_table[0] = VirtualAddress(rsp);
 //        debug!("TSS:\n{:?}", TSS_PTR.as_ref());
diff --git a/src/arch/x86_64/interrupt/handler.rs b/src/arch/x86_64/interrupt/handler.rs
index 2e3797d..bb280ea 100644
--- a/src/arch/x86_64/interrupt/handler.rs
+++ b/src/arch/x86_64/interrupt/handler.rs
@@ -75,7 +75,7 @@ use spin::Mutex;
 // FIXME: Deadlock
 //static TICK: Mutex<usize> = Mutex::new(0);
 
-interrupt_switch!(timer, rsp, {
+interrupt_switch!(timer, stack, rsp, {
 //    let mut tick = TICK.lock();
 //    *tick += 1;
 //    let tick = *tick;
@@ -107,16 +107,16 @@ interrupt_stack_p!(to_kernel, stack, {
     stack.iret.ss = gdt::KDATA_SELECTOR.0 as usize;
 });
 
-interrupt_stack_p!(syscall, stack, {
+interrupt_switch!(syscall, stack, rsp, {
     println!("\nInterupt: Syscall {:#x?}", stack.scratch.rax);
     use syscall::syscall;
-    let ret = syscall(stack, false);
+    let ret = syscall(stack, rsp, false);
     stack.scratch.rax = ret as usize;
 });
 
-interrupt_stack_p!(syscall32, stack, {
-    println!("\nInterupt: Syscall {:#x?}", stack.scratch.rax);
+interrupt_switch!(syscall32, stack, rsp, {
+//    println!("\nInterupt: Syscall {:#x?}", stack.scratch.rax);
     use syscall::syscall;
-    let ret = syscall(stack, true);
+    let ret = syscall(stack, rsp, true);
     stack.scratch.rax = ret as usize;
 });
\ No newline at end of file
diff --git a/src/arch/x86_64/interrupt/template.rs b/src/arch/x86_64/interrupt/template.rs
index 873a995..33480b2 100644
--- a/src/arch/x86_64/interrupt/template.rs
+++ b/src/arch/x86_64/interrupt/template.rs
@@ -315,11 +315,11 @@ impl Debug for InterruptStackP {
 }
 
 macro_rules! interrupt_switch {
-    ($name:ident, $rsp: ident, $func:block) => {
+    ($name:ident, $stack: ident, $rsp: ident, $func:block) => {
         #[naked]
         pub unsafe extern fn $name () {
             #[inline(never)]
-            unsafe fn inner($rsp: &mut usize) {
+            unsafe fn inner($stack: &mut InterruptStackP, $rsp: &mut usize) {
                 $func
             }
 
@@ -333,7 +333,7 @@ macro_rules! interrupt_switch {
             asm!("" : "={rsp}"(rsp) : : : "intel", "volatile");
 
             // Call inner rust function
-            inner(&mut rsp);
+            inner(&mut *(rsp as *mut InterruptStackP), &mut rsp);
 
             // Set return rsp if to user
             use arch::gdt;
diff --git a/src/consts.rs b/src/consts.rs
index a267e79..5567824 100644
--- a/src/consts.rs
+++ b/src/consts.rs
@@ -26,7 +26,7 @@ pub const MAX_CPU_NUM: usize = 8;
     pub const KERNEL_HEAP_OFFSET: usize = KERNEL_OFFSET - PML4_SIZE;
     pub const KERNEL_HEAP_PML4: usize = (KERNEL_HEAP_OFFSET & PML4_MASK)/PML4_SIZE;
     /// Size of kernel heap
-    pub const KERNEL_HEAP_SIZE: usize = 2 * 1024 * 1024; // 1 MB
+    pub const KERNEL_HEAP_SIZE: usize = 8 * 1024 * 1024; // 8 MB
 
     /// Offset to kernel percpu variables
     //TODO: Use 64-bit fs offset to enable this pub const KERNEL_PERCPU_OFFSET: usize = KERNEL_HEAP_OFFSET - PML4_SIZE;
diff --git a/src/io/mod.rs b/src/io/mod.rs
index 0ce8438..3944f05 100644
--- a/src/io/mod.rs
+++ b/src/io/mod.rs
@@ -49,10 +49,32 @@ pub fn debug(args: fmt::Arguments) {
     print_in_color(args, Color::LightRed);
 }
 
-pub fn write(fd: usize, base: *const u8, len: usize) {
-    //    debug!("write: fd: {}, base: {:?}, len: {:#x}", fd, base, len);
+pub fn write(fd: usize, base: *const u8, len: usize) -> i32 {
+    debug!("write: fd: {}, base: {:?}, len: {:#x}", fd, base, len);
     use core::slice;
     use core::str;
     let slice = unsafe { slice::from_raw_parts(base, len) };
     print!("{}", str::from_utf8(slice).unwrap());
+    0
+}
+
+pub fn open(path: *const u8, flags: usize) -> i32 {
+    let path = unsafe { from_cstr(path) };
+    debug!("open: path: {:?}, flags: {:?}", path, flags);
+    match path {
+        "stdin:" => 0,
+        "stdout:" => 1,
+        _ => -1,
+    }
+}
+
+pub fn close(fd: usize) -> i32 {
+    debug!("close: fd: {:?}", fd);
+    0
+}
+
+pub unsafe fn from_cstr(s: *const u8) -> &'static str {
+    use core::{str, slice};
+    let len = (0usize..).find(|&i| *s.offset(i as isize) == 0).unwrap();
+    str::from_utf8(slice::from_raw_parts(s, len)).unwrap()
 }
\ No newline at end of file
diff --git a/src/process/mod.rs b/src/process/mod.rs
index cea83b8..a838c6b 100644
--- a/src/process/mod.rs
+++ b/src/process/mod.rs
@@ -76,6 +76,27 @@ extern fn idle_thread() {
 }
 
 /// Fork the current process
-pub fn fork(tf: &TrapFrame) {
+pub fn sys_fork(tf: &TrapFrame) -> i32 {
     PROCESSOR.try().unwrap().lock().fork(tf);
+    0
+}
+
+/// Kill the process
+pub fn sys_kill(pid: usize) -> i32 {
+    PROCESSOR.try().unwrap().lock().kill(pid);
+    0
+}
+
+/// Get the current process id
+pub fn sys_getpid() -> i32 {
+    PROCESSOR.try().unwrap().lock().current().pid as i32
+}
+
+/// Exit the current process
+pub fn sys_exit(rsp: &mut usize, error_code: usize) -> i32 {
+    let mut processor = PROCESSOR.try().unwrap().lock();
+    let pid = processor.current().pid;
+    processor.schedule(rsp);
+    processor.exit(pid, error_code);
+    0
 }
\ No newline at end of file
diff --git a/src/process/process.rs b/src/process/process.rs
index aba7267..03291ef 100644
--- a/src/process/process.rs
+++ b/src/process/process.rs
@@ -19,7 +19,7 @@ pub struct Process {
 
 pub type Pid = usize;
 
-#[derive(Debug)]
+#[derive(Debug, Eq, PartialEq)]
 pub enum Status {
     Ready, Running, Sleeping(usize), Exited
 }
diff --git a/src/process/processor.rs b/src/process/processor.rs
index 8f29793..90cb017 100644
--- a/src/process/processor.rs
+++ b/src/process/processor.rs
@@ -43,7 +43,8 @@ impl Processor {
 
     fn find_next(&self) -> Pid {
         *self.procs.keys()
-            .find(|&&i| i > self.current_pid)
+            .find(|&&i| i > self.current_pid
+                && self.get(i).status != Status::Exited)
             .unwrap_or(self.procs.keys().nth(0).unwrap())
     }
 
@@ -76,8 +77,12 @@ impl Processor {
         debug!("Processor: switch from {} to {}\n  rsp: {:#x} -> {:#x}", pid0, pid, rsp0, rsp);
     }
 
+    fn get(&self, pid: Pid) -> &Process {
+        self.procs.get(&pid).unwrap()
+    }
+
     pub fn current(&self) -> &Process {
-        self.procs.get(&self.current_pid).unwrap()
+        self.get(self.current_pid)
     }
 
     /// Fork the current process
@@ -85,4 +90,15 @@ impl Processor {
         let new = self.current().fork(tf, &mut self.mc.borrow_mut());
         self.add(new);
     }
+
+    pub fn kill(&mut self, pid: Pid) {
+        let process = self.procs.get_mut(&pid).unwrap();
+        process.status = Status::Exited;
+        // TODO: Remove process from set
+    }
+
+    pub fn exit(&mut self, pid: Pid, error_code: usize) {
+        debug!("Processor: {} exit, code: {}", pid, error_code);
+        self.kill(pid);
+    }
 }
\ No newline at end of file
diff --git a/src/syscall.rs b/src/syscall.rs
index 45bd6be..8dc3354 100644
--- a/src/syscall.rs
+++ b/src/syscall.rs
@@ -2,16 +2,10 @@ use super::*;
 use process;
 use arch::interrupt::TrapFrame;
 
-pub unsafe fn syscall(tf: &TrapFrame, is32: bool) -> i32 {
+pub unsafe fn syscall(tf: &TrapFrame, rsp: &mut usize, is32: bool) -> i32 {
     let id = match is32 {
-        false => tf.scratch.rax,
-        true => match tf.scratch.rax {
-            UCORE_SYS_OPEN => SYS_OPEN,
-            UCORE_SYS_CLOSE => SYS_CLOSE,
-            UCORE_SYS_WRITE => SYS_WRITE,
-            UCORE_SYS_READ => SYS_READ,
-            _ => 0,
-        }
+        false => Syscall::Xv6(tf.scratch.rax),
+        true => Syscall::Ucore(tf.scratch.rax),
     };
     let args = match is32 {
         // For ucore x86
@@ -19,24 +13,40 @@ pub unsafe fn syscall(tf: &TrapFrame, is32: bool) -> i32 {
         // For xv6 x86_64
         false => [tf.scratch.rdi, tf.scratch.rsi, tf.scratch.rdx, tf.scratch.rcx, tf.scratch.r8, tf.scratch.r9],
     };
-    debug!("id: {:#x}, args: {:#x?}", id, args);
 
     match id {
-        SYS_FORK => {
-            process::fork(tf);
-            0
-        }
-        SYS_WRITE => {
-            io::write(args[0], args[1] as *const u8, args[2]);
-            0
-        }
+        Syscall::Xv6(SYS_WRITE) | Syscall::Ucore(UCORE_SYS_WRITE) =>
+            io::write(args[0], args[1] as *const u8, args[2]),
+        Syscall::Xv6(SYS_OPEN) | Syscall::Ucore(UCORE_SYS_OPEN) =>
+            io::open(args[0] as *const u8, args[1]),
+        Syscall::Xv6(SYS_CLOSE) | Syscall::Ucore(UCORE_SYS_CLOSE) =>
+            io::close(args[0]),
+        Syscall::Xv6(SYS_FORK) | Syscall::Ucore(UCORE_SYS_FORK) =>
+            process::sys_fork(tf),
+        Syscall::Xv6(SYS_KILL) | Syscall::Ucore(UCORE_SYS_KILL) =>
+            process::sys_kill(args[0]),
+        Syscall::Xv6(SYS_EXIT) | Syscall::Ucore(UCORE_SYS_EXIT) =>
+            process::sys_exit(rsp, args[0]),
+        Syscall::Ucore(UCORE_SYS_GETPID) =>
+            process::sys_getpid(),
+        Syscall::Ucore(UCORE_SYS_PUTC) =>
+            {
+                print!("{}", args[0] as u8 as char);
+                0
+            },
         _ => {
-            debug!("unknown syscall {:#x}", id);
+            debug!("unknown syscall {:#x?}", id);
             -1
-        }
+        },
     }
 }
 
+#[derive(Debug)]
+enum Syscall {
+    Xv6(usize),
+    Ucore(usize),
+}
+
 const SYS_FORK: usize = 1;
 const SYS_EXIT: usize = 2;
 const SYS_WAIT: usize = 3;