diff --git a/bootloader/rustsbi-k210.bin b/bootloader/rustsbi-k210.bin
index 5a9fa7d1..7e07391d 100755
Binary files a/bootloader/rustsbi-k210.bin and b/bootloader/rustsbi-k210.bin differ
diff --git a/os/build.rs b/os/build.rs
index 389587aa..2c006876 100644
--- a/os/build.rs
+++ b/os/build.rs
@@ -47,6 +47,7 @@ _app_names:"#)?;
     .section .data
     .global app_{0}_start
     .global app_{0}_end
+    .align 12
 app_{0}_start:
     .incbin "{2}{1}"
 app_{0}_end:"#, idx, app, TARGET_PATH)?;
diff --git a/os/src/main.rs b/os/src/main.rs
index 3b3eef9f..aa21a5e2 100644
--- a/os/src/main.rs
+++ b/os/src/main.rs
@@ -43,6 +43,7 @@ pub fn rust_main() -> ! {
     mm::init();
     mm::remap_test();
     task::add_initproc();
+    println!("after initproc!");
     trap::init();
     trap::enable_timer_interrupt();
     timer::set_next_trigger();
diff --git a/user/src/bin/00power_3.rs b/user/src/bin/00power_3.rs
deleted file mode 100644
index 532829da..00000000
--- a/user/src/bin/00power_3.rs
+++ /dev/null
@@ -1,29 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-
-const LEN: usize = 100;
-
-static mut S: [u64; LEN] = [0u64; LEN];
-
-#[no_mangle]
-unsafe fn main() -> i32 {
-    let p = 3u64;
-    let m = 998244353u64;
-    let iter: usize = 300000;
-    let mut cur = 0usize;
-    S[cur] = 1;
-    for i in 1..=iter {
-        let next = if cur + 1 == LEN { 0 } else { cur + 1 };
-        S[next] = S[cur] * p % m;
-        cur = next;
-        if i % 10000 == 0 {
-            println!("power_3 [{}/{}]", i, iter);
-        }
-    }
-    println!("{}^{} = {}(mod {})", p, iter, S[cur], m);
-    println!("Test power_3 OK!");
-    0
-}
\ No newline at end of file
diff --git a/user/src/bin/01power_5.rs b/user/src/bin/01power_5.rs
deleted file mode 100644
index f23e3b84..00000000
--- a/user/src/bin/01power_5.rs
+++ /dev/null
@@ -1,29 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-
-const LEN: usize = 100;
-
-static mut S: [u64; LEN] = [0u64; LEN];
-
-#[no_mangle]
-unsafe fn main() -> i32 {
-    let p = 5u64;
-    let m = 998244353u64;
-    let iter: usize = 210000;
-    let mut cur = 0usize;
-    S[cur] = 1;
-    for i in 1..=iter {
-        let next = if cur + 1 == LEN { 0 } else { cur + 1 };
-        S[next] = S[cur] * p % m;
-        cur = next;
-        if i % 10000 == 0 {
-            println!("power_5 [{}/{}]", i, iter);
-        }
-    }
-    println!("{}^{} = {}(mod {})", p, iter, S[cur], m);
-    println!("Test power_5 OK!");
-    0
-}
diff --git a/user/src/bin/02power_7.rs b/user/src/bin/02power_7.rs
deleted file mode 100644
index 35bada18..00000000
--- a/user/src/bin/02power_7.rs
+++ /dev/null
@@ -1,29 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-
-const LEN: usize = 100;
-
-static mut S: [u64; LEN] = [0u64; LEN];
-
-#[no_mangle]
-unsafe fn main() -> i32 {
-    let p = 7u64;
-    let m = 998244353u64;
-    let iter: usize = 240000;
-    let mut cur = 0usize;
-    S[cur] = 1;
-    for i in 1..=iter {
-        let next = if cur + 1 == LEN { 0 } else { cur + 1 };
-        S[next] = S[cur] * p % m;
-        cur = next;
-        if i % 10000 == 0 {
-            println!("power_7 [{}/{}]", i, iter);
-        }
-    }
-    println!("{}^{} = {}(mod {})", p, iter, S[cur], m);
-    println!("Test power_7 OK!");
-    0
-}
diff --git a/user/src/bin/03sleep.rs b/user/src/bin/03sleep.rs
deleted file mode 100644
index d500f5af..00000000
--- a/user/src/bin/03sleep.rs
+++ /dev/null
@@ -1,18 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-
-use user_lib::{get_time, yield_};
-
-#[no_mangle]
-fn main() -> i32 {
-    let current_timer = get_time();
-    let wait_for = current_timer + 10000000;
-    while get_time() < wait_for {
-        yield_();
-    }
-    println!("Test sleep OK!");
-    0
-}
\ No newline at end of file
diff --git a/user/src/bin/matrix.rs b/user/src/bin/matrix.rs
new file mode 100644
index 00000000..729625e0
--- /dev/null
+++ b/user/src/bin/matrix.rs
@@ -0,0 +1,68 @@
+#![no_std]
+#![no_main]
+
+#[macro_use]
+extern crate user_lib;
+
+use user_lib::{fork, wait, yield_, exit, getpid, get_time, wait_once};
+
+static NUM: usize = 13;
+const N: usize = 10;
+static P: i32 = 10007;
+type Arr = [[i32; N]; N];
+
+fn work(times: isize) {
+    let mut a: Arr = Default::default();
+    let mut b: Arr = Default::default();
+    let mut c: Arr = Default::default();
+    for i in 0..N {
+        for j in 0..N {
+            a[i][j] = 1;
+            b[i][j] = 1;
+        }
+    }
+    yield_();
+    println!("pid {} is running ({} times)!.", getpid(), times);
+    for _ in 0..times {
+        for i in 0..N {
+            for j in 0..N {
+                c[i][j] = 0;
+                for k in 0..N {
+                    c[i][j] = (c[i][j] + a[i][k] * b[k][j]) % P;
+                }
+            }
+        }
+        for i in 0..N {
+            for j in 0..N {
+                a[i][j] = c[i][j];
+                b[i][j] = c[i][j];
+            }
+        }
+    }
+    println!("pid {} done!.", getpid());
+    exit(0);
+}
+
+#[no_mangle]
+pub fn main() -> i32 {
+    for _ in 0..NUM {
+        let pid = fork();
+        if pid == 0 {
+            let current_time = get_time();
+            let times = (current_time as i32 as isize) * (current_time as i32 as isize) % 1000;
+            work(times * 40);
+        }
+    }
+
+    println!("fork ok.");
+
+    let mut xstate: i32 = 0;
+    for _ in 0..NUM {
+        if wait(&mut xstate) < 0 {
+            panic!("wait failed.");
+        }
+    }
+    assert!(wait_once(&mut xstate) < 0);
+    println!("matrix passed.");
+    0
+}
\ No newline at end of file
diff --git a/user/src/lib.rs b/user/src/lib.rs
index 995bb36c..8f3c77da 100644
--- a/user/src/lib.rs
+++ b/user/src/lib.rs
@@ -48,7 +48,22 @@ pub fn get_time() -> isize { sys_get_time() }
 pub fn getpid() -> isize { sys_getpid() }
 pub fn fork() -> isize { sys_fork() }
 pub fn exec(path: &str) -> isize { sys_exec(path) }
-pub fn wait(xstate: &mut i32) -> isize { sys_waitpid(-1, xstate as *mut _) }
-pub fn waitpid(pid: usize, xstate: &mut i32) -> isize {
-    sys_waitpid(pid as isize, xstate as *mut _)
+pub fn wait(exit_code: &mut i32) -> isize {
+    loop {
+        match sys_waitpid(-1, exit_code as *mut _) {
+            -1 => { yield_(); }
+            exit_pid => return exit_pid,
+        }
+    }
+}
+pub fn wait_once(exit_code: &mut i32) -> isize {
+    sys_waitpid(-1, exit_code as *mut _)
+}
+pub fn waitpid(pid: usize, exit_code: &mut i32) -> isize {
+    loop {
+        match sys_waitpid(pid as isize, exit_code as *mut _) {
+            -1 => { yield_(); }
+            exit_pid => return exit_pid,
+        }
+    }
 }
\ No newline at end of file