diff --git a/.gitattributes b/.gitattributes
index 39e2684c8..512faf1f9 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -5,4 +5,5 @@ src/kxos-user/execve/execve filter=lfs diff=lfs merge=lfs -text
 src/kxos-user/execve/hello filter=lfs diff=lfs merge=lfs -text
 src/kxos-user/fork_c/fork filter=lfs diff=lfs merge=lfs -text
 src/kxos-user/signal_c/divide_zero filter=lfs diff=lfs merge=lfs -text
-src/kxos-user/signal_c/sig_procmask filter=lfs diff=lfs merge=lfs -text
\ No newline at end of file
+src/kxos-user/signal_c/sig_procmask filter=lfs diff=lfs merge=lfs -text
+src/kxos-user/signal_c/sig_action filter=lfs diff=lfs merge=lfs -text
\ No newline at end of file
diff --git a/src/Cargo.lock b/src/Cargo.lock
index 6d3c457b8..1f64b119b 100644
--- a/src/Cargo.lock
+++ b/src/Cargo.lock
@@ -4,9 +4,9 @@ version = 3
 
 [[package]]
 name = "anyhow"
-version = "1.0.63"
+version = "1.0.32"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a26fa4d7e3f2eebadf743988fc8aec9fa9a9e82611acafd77c1462ed6262440a"
+checksum = "6b602bfe940d21c130f3895acd65221e8a61270debe89d628b9cb4e3ccb8569b"
 
 [[package]]
 name = "autocfg"
diff --git a/src/kxos-frame/src/lib.rs b/src/kxos-frame/src/lib.rs
index f59e5c414..be481f248 100644
--- a/src/kxos-frame/src/lib.rs
+++ b/src/kxos-frame/src/lib.rs
@@ -23,7 +23,7 @@ pub mod prelude;
 pub mod sync;
 pub mod task;
 pub mod timer;
-pub(crate) mod trap;
+pub mod trap;
 pub mod user;
 mod util;
 #[macro_use]
diff --git a/src/kxos-frame/src/trap/handler.rs b/src/kxos-frame/src/trap/handler.rs
index d7e30cee1..c6fbf5cbc 100644
--- a/src/kxos-frame/src/trap/handler.rs
+++ b/src/kxos-frame/src/trap/handler.rs
@@ -19,24 +19,29 @@ pub(crate) extern "C" fn syscall_handler(f: &'static mut SyscallFrame) -> isize
     -1
 }
 
-const DIVIDE_BY_ZERO: usize = 0;
-const INVALID_OPCODE: usize = 6;
-const SEGMENT_NOT_PRESENT: usize = 11;
-const STACK_SEGMENT_FAULT: usize = 12;
-const GENERAL_PROTECTION_FAULT: usize = 13;
-const PAGE_FAULT: usize = 14;
-const TIMER: usize = 32;
-
 #[no_mangle]
 pub(crate) extern "C" fn trap_handler(f: &'static mut TrapFrame) {
     if !is_from_kernel(f.cs) {
         let current = Task::current();
         current.inner_exclusive_access().is_from_trap = true;
-    }
-    let irq_line = IRQ_LIST.get(f.id as usize).unwrap();
-    let callback_functions = irq_line.callback_list();
-    for callback_function in callback_functions.iter() {
-        callback_function.call(f.clone());
+        *current.trap_frame() = *SWITCH_TO_USER_SPACE_TASK.trap_frame();
+        if is_cpu_fault(current.trap_frame()) {
+            // if is cpu fault, we will pass control to trap handler in kxos std
+            unsafe {
+                context_switch(
+                    get_idle_task_cx_ptr() as *mut TaskContext,
+                    &Task::current().inner_ctx() as *const TaskContext,
+                )
+            }
+        } else {
+            let irq_line = IRQ_LIST.get(f.id as usize).unwrap();
+            let callback_functions = irq_line.callback_list();
+            for callback_function in callback_functions.iter() {
+                callback_function.call(f.clone());
+            }
+        }
+    } else {
+        panic!("cannot handle kernel exception now");
     }
 }
 
@@ -47,3 +52,36 @@ fn is_from_kernel(cs: u64) -> bool {
         false
     }
 }
+
+/// As Osdev Wiki defines(https://wiki.osdev.org/Exceptions):
+/// CPU exceptions are classified as:
+
+/// Faults: These can be corrected and the program may continue as if nothing happened.
+/// Traps: Traps are reported immediately after the execution of the trapping instruction.
+/// Aborts: Some severe unrecoverable error.
+
+/// This function will determine a trap is a CPU faults.
+/// We will pass control to kxos-std if the trap is **faults**.
+pub fn is_cpu_fault(trap_frame: &TrapFrame) -> bool {
+    match trap_frame.id {
+        DIVIDE_BY_ZERO
+        | DEBUG
+        | BOUND_RANGE_EXCEEDED
+        | INVALID_OPCODE
+        | DEVICE_NOT_AVAILABLE
+        | INVAILD_TSS
+        | SEGMENT_NOT_PRESENT
+        | STACK_SEGMENT_FAULT
+        | GENERAL_PROTECTION_FAULT
+        | PAGE_FAULT
+        | X87_FLOATING_POINT_EXCEPTION
+        | ALIGNMENT_CHECK
+        | SIMD_FLOATING_POINT_EXCEPTION
+        | VIRTUALIZATION_EXCEPTION
+        | CONTROL_PROTECTION_EXCEPTION
+        | HYPERVISOR_INJECTION_EXCEPTION
+        | VMM_COMMUNICATION_EXCEPTION
+        | SECURITY_EXCEPTION => true,
+        _ => false,
+    }
+}
diff --git a/src/kxos-frame/src/trap/mod.rs b/src/kxos-frame/src/trap/mod.rs
index 1d3ebf954..453cb151f 100644
--- a/src/kxos-frame/src/trap/mod.rs
+++ b/src/kxos-frame/src/trap/mod.rs
@@ -144,3 +144,40 @@ pub(crate) fn init() {
         })
     }
 }
+
+macro_rules! define_cpu_exception {
+    ( $( $name: ident = $exception_num: expr ),* ) => {
+        $(
+            pub const $name : u64 = $exception_num;
+        )*
+    }
+}
+
+define_cpu_exception!(
+    DIVIDE_BY_ZERO = 0,
+    DEBUG = 1,
+    NON_MASKABLE_INTERRUPT = 2,
+    BREAKPOINT = 3,
+    OVERFLOW = 4,
+    BOUND_RANGE_EXCEEDED = 5,
+    INVALID_OPCODE = 6,
+    DEVICE_NOT_AVAILABLE = 7,
+    DOUBLE_FAULT = 8,
+    COPROCESSOR_SEGMENT_OVERRUN = 9,
+    INVAILD_TSS = 10,
+    SEGMENT_NOT_PRESENT = 11,
+    STACK_SEGMENT_FAULT = 12,
+    GENERAL_PROTECTION_FAULT = 13,
+    PAGE_FAULT = 14,
+    // 15 reserved
+    X87_FLOATING_POINT_EXCEPTION = 16,
+    ALIGNMENT_CHECK = 17,
+    MACHINE_CHECK = 18,
+    SIMD_FLOATING_POINT_EXCEPTION = 19,
+    VIRTUALIZATION_EXCEPTION = 20,
+    CONTROL_PROTECTION_EXCEPTION = 21,
+    // 22-27 reserved
+    HYPERVISOR_INJECTION_EXCEPTION = 28,
+    VMM_COMMUNICATION_EXCEPTION = 29,
+    SECURITY_EXCEPTION = 30 // 31 reserved
+);
diff --git a/src/kxos-std/src/process/exception.rs b/src/kxos-std/src/process/exception.rs
new file mode 100644
index 000000000..86cd1a4ca
--- /dev/null
+++ b/src/kxos-std/src/process/exception.rs
@@ -0,0 +1,13 @@
+use kxos_frame::cpu::CpuContext;
+
+use crate::{prelude::*, process::signal::signals::fault::FaultSignal};
+
+/// We can't handle most exceptions, just send self a signal to force the process exit before return to user space.
+pub fn handle_exception(context: &mut CpuContext) {
+    let trap_info = context.trap_information.clone();
+    let current = current!();
+    let pid = current.pid();
+    debug!("trap info = {:x?}", trap_info);
+    let signal = Box::new(FaultSignal::new(&trap_info));
+    current.sig_queues().lock().enqueue(signal);
+}
diff --git a/src/kxos-std/src/process/mod.rs b/src/kxos-std/src/process/mod.rs
index b34fca73c..05187c07d 100644
--- a/src/kxos-std/src/process/mod.rs
+++ b/src/kxos-std/src/process/mod.rs
@@ -9,14 +9,17 @@ use self::process_group::ProcessGroup;
 use self::process_vm::mmap_area::MmapArea;
 use self::process_vm::user_heap::UserHeap;
 use self::process_vm::UserVm;
+use self::signal::constants::SIGCHLD;
 use self::signal::sig_disposition::SigDispositions;
 use self::signal::sig_mask::SigMask;
 use self::signal::sig_queues::SigQueues;
+use self::signal::signals::kernel::KernelSignal;
 use self::status::ProcessStatus;
 use self::task::create_user_task_from_elf;
 
 pub mod clone;
 pub mod elf;
+pub mod exception;
 pub mod fifo_scheduler;
 pub mod process_filter;
 pub mod process_group;
@@ -272,8 +275,11 @@ impl Process {
             }
         }
 
-        // wake up parent waiting children, if any
         if let Some(parent) = current_process.parent() {
+            // set parent sig child
+            let signal = Box::new(KernelSignal::new(SIGCHLD));
+            parent.sig_queues().lock().enqueue(signal);
+            // wake up parent waiting children, if any
             parent
                 .waiting_children()
                 .wake_all_on_condition(&current_process.pid(), |filter, pid| {
@@ -341,12 +347,17 @@ impl Process {
         None
     }
 
-    /// free zombie child with pid, returns the exit code of child process
-    /// We current just remove the child from the children map.
+    /// free zombie child with pid, returns the exit code of child process.
+    /// remove process from process group.
     pub fn reap_zombie_child(&self, pid: Pid) -> i32 {
         let child_process = self.children.lock().remove(&pid).unwrap();
         assert!(child_process.status().lock().is_zombie());
         table::remove_process(child_process.pid());
+        if let Some(process_group) = child_process.process_group().lock().as_ref() {
+            if let Some(process_group) = process_group.upgrade() {
+                process_group.remove_process(child_process.pid);
+            }
+        }
         child_process.exit_code()
     }
 
diff --git a/src/kxos-std/src/process/process_group.rs b/src/kxos-std/src/process/process_group.rs
index 8444fe683..1a422f692 100644
--- a/src/kxos-std/src/process/process_group.rs
+++ b/src/kxos-std/src/process/process_group.rs
@@ -1,4 +1,4 @@
-use super::{Pgid, Pid, Process};
+use super::{table, Pgid, Pid, Process};
 use crate::prelude::*;
 
 pub struct ProcessGroup {
@@ -44,7 +44,15 @@ impl ProcessGroup {
     }
 
     pub fn remove_process(&self, pid: Pid) {
-        self.inner.lock().processes.remove(&pid);
+        let mut inner_lock = self.inner.lock();
+        inner_lock.processes.remove(&pid);
+        let len = inner_lock.processes.len();
+        let pgid = inner_lock.pgid;
+        // if self contains no process, remove self from table
+        if len == 0 {
+            // this must be the last statement
+            table::remove_process_group(pgid);
+        }
     }
 
     pub fn pgid(&self) -> Pgid {
diff --git a/src/kxos-std/src/process/signal/constants.rs b/src/kxos-std/src/process/signal/constants.rs
index 7f2a3752c..9c4593e1a 100644
--- a/src/kxos-std/src/process/signal/constants.rs
+++ b/src/kxos-std/src/process/signal/constants.rs
@@ -55,3 +55,49 @@ define_std_signums! {
     SIGPWR    = 30, // Power failure (System V)
     SIGSYS    = 31, // Bad system call (SVr4); see also seccomp(2)
 }
+
+pub const SI_ASYNCNL: i32 = -60;
+pub const SI_TKILL: i32 = -6;
+pub const SI_SIGIO: i32 = -5;
+pub const SI_ASYNCIO: i32 = -4;
+pub const SI_MESGQ: i32 = -3;
+pub const SI_TIMER: i32 = -2;
+pub const SI_QUEUE: i32 = -1;
+pub const SI_USER: i32 = 0;
+pub const SI_KERNEL: i32 = 128;
+
+pub const FPE_INTDIV: i32 = 1;
+pub const FPE_INTOVF: i32 = 2;
+pub const FPE_FLTDIV: i32 = 3;
+pub const FPE_FLTOVF: i32 = 4;
+pub const FPE_FLTUND: i32 = 5;
+pub const FPE_FLTRES: i32 = 6;
+pub const FPE_FLTINV: i32 = 7;
+pub const FPE_FLTSUB: i32 = 8;
+
+pub const ILL_ILLOPC: i32 = 1;
+pub const ILL_ILLOPN: i32 = 2;
+pub const ILL_ILLADR: i32 = 3;
+pub const ILL_ILLTRP: i32 = 4;
+pub const ILL_PRVOPC: i32 = 5;
+pub const ILL_PRVREG: i32 = 6;
+pub const ILL_COPROC: i32 = 7;
+pub const ILL_BADSTK: i32 = 8;
+
+pub const SEGV_MAPERR: i32 = 1;
+pub const SEGV_ACCERR: i32 = 2;
+pub const SEGV_BNDERR: i32 = 3;
+pub const SEGV_PKUERR: i32 = 4;
+
+pub const BUS_ADRALN: i32 = 1;
+pub const BUS_ADRERR: i32 = 2;
+pub const BUS_OBJERR: i32 = 3;
+pub const BUS_MCEERR_AR: i32 = 4;
+pub const BUS_MCEERR_AO: i32 = 5;
+
+pub const CLD_EXITED: i32 = 1;
+pub const CLD_KILLED: i32 = 2;
+pub const CLD_DUMPED: i32 = 3;
+pub const CLD_TRAPPED: i32 = 4;
+pub const CLD_STOPPED: i32 = 5;
+pub const CLD_CONTINUED: i32 = 6;
diff --git a/src/kxos-std/src/process/signal/mod.rs b/src/kxos-std/src/process/signal/mod.rs
index 2743e79b3..bacf7daab 100644
--- a/src/kxos-std/src/process/signal/mod.rs
+++ b/src/kxos-std/src/process/signal/mod.rs
@@ -6,6 +6,8 @@ pub mod sig_num;
 pub mod sig_queues;
 pub mod signals;
 
+use kxos_frame::task::Task;
+
 use crate::{
     prelude::*,
     process::signal::sig_action::{SigAction, SigDefaultAction},
@@ -14,13 +16,16 @@ use crate::{
 /// Handle pending signal for current process
 pub fn handle_pending_signal() {
     let current = current!();
+    let pid = current.pid();
+    let process_name = current.filename().unwrap();
     let sig_queues = current.sig_queues();
     let mut sig_queues_guard = sig_queues.lock();
     let sig_mask = current.sig_mask().lock().clone();
     if let Some(signal) = sig_queues_guard.dequeue(&sig_mask) {
         let sig_num = signal.num();
-        debug!("sig_num = {:?}", sig_num);
+        debug!("sig_num = {:?}, sig_name = {}", sig_num, sig_num.sig_name());
         let sig_action = current.sig_dispositions().lock().get(sig_num);
+        debug!("sig action: {:?}", sig_action);
         match sig_action {
             SigAction::Ign => {
                 debug!("Ignore signal {:?}", sig_num);
@@ -28,10 +33,18 @@ pub fn handle_pending_signal() {
             SigAction::User { .. } => todo!(),
             SigAction::Dfl => {
                 let sig_default_action = SigDefaultAction::from_signum(sig_num);
+                debug!("sig_default_action: {:?}", sig_default_action);
                 match sig_default_action {
                     SigDefaultAction::Core | SigDefaultAction::Term => {
+                        error!(
+                            "{:?}: terminating on signal {}",
+                            process_name,
+                            sig_num.sig_name()
+                        );
                         // FIXME: How to set correct status if process is terminated
                         current.exit(1);
+                        // We should exit current here, since we cannot restore a valid status from trap now.
+                        Task::current().exit();
                     }
                     SigDefaultAction::Ign => {}
                     SigDefaultAction::Stop => {
diff --git a/src/kxos-std/src/process/signal/sig_mask.rs b/src/kxos-std/src/process/signal/sig_mask.rs
index 301cc9f90..d80f971bc 100644
--- a/src/kxos-std/src/process/signal/sig_mask.rs
+++ b/src/kxos-std/src/process/signal/sig_mask.rs
@@ -40,7 +40,7 @@ impl SigMask {
         self.bits &= !unblock_sets;
     }
 
-    pub fn set(&mut self, new_set:u64) {
+    pub fn set(&mut self, new_set: u64) {
         self.bits = new_set;
     }
 
diff --git a/src/kxos-std/src/process/signal/sig_num.rs b/src/kxos-std/src/process/signal/sig_num.rs
index 27963f9ee..2c7329fc0 100644
--- a/src/kxos-std/src/process/signal/sig_num.rs
+++ b/src/kxos-std/src/process/signal/sig_num.rs
@@ -37,4 +37,41 @@ impl SigNum {
     pub fn is_real_time(&self) -> bool {
         self.sig_num >= MIN_RT_SIG_NUM
     }
+
+    pub const fn sig_name(&self) -> &'static str {
+        match *self {
+            SIGHUP => "SIGHUP",
+            SIGINT => "SIGINT",
+            SIGQUIT => "SIGQUIT",
+            SIGILL => "SIGILL",
+            SIGTRAP => "SIGTRAP",
+            SIGABRT => "SIGABRT",
+            SIGBUS => "SIGBUS",
+            SIGFPE => "SIGFPE",
+            SIGKILL => "SIGKILL",
+            SIGUSR1 => "SIGUSR1",
+            SIGSEGV => "SIGSEGV",
+            SIGUSR2 => "SIGUSR2",
+            SIGPIPE => "SIGPIPE",
+            SIGALRM => "SIGALRM",
+            SIGTERM => "SIGTERM",
+            SIGSTKFLT => "SIGSTKFLT",
+            SIGCHLD => "SIGCHLD",
+            SIGCONT => "SIGCONT",
+            SIGSTOP => "SIGSTOP",
+            SIGTSTP => "SIGTSTP",
+            SIGTTIN => "SIGTTIN",
+            SIGTTOU => "SIGTTOU",
+            SIGURG => "SIGURG",
+            SIGXCPU => "SIGXCPU",
+            SIGXFSZ => "SIGXFSZ",
+            SIGVTALRM => "SIGVTALRM",
+            SIGPROF => "SIGPROF",
+            SIGWINCH => "SIGWINCH",
+            SIGIO => "SIGIO",
+            SIGPWR => "SIGPWR",
+            SIGSYS => "SIGSYS",
+            _ => "Realtime Signal",
+        }
+    }
 }
diff --git a/src/kxos-std/src/process/signal/signals/fault.rs b/src/kxos-std/src/process/signal/signals/fault.rs
new file mode 100644
index 000000000..71477cb65
--- /dev/null
+++ b/src/kxos-std/src/process/signal/signals/fault.rs
@@ -0,0 +1,51 @@
+use kxos_frame::cpu::TrapInformation;
+use kxos_frame::trap::{
+    ALIGNMENT_CHECK, BOUND_RANGE_EXCEEDED, DIVIDE_BY_ZERO, GENERAL_PROTECTION_FAULT,
+    INVALID_OPCODE, PAGE_FAULT, SIMD_FLOATING_POINT_EXCEPTION, X87_FLOATING_POINT_EXCEPTION,
+};
+
+use crate::prelude::*;
+use crate::process::signal::constants::*;
+use crate::process::signal::sig_num::SigNum;
+
+use super::Signal;
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub struct FaultSignal {
+    num: SigNum,
+    code: i32,
+    addr: Option<u64>,
+}
+
+impl FaultSignal {
+    pub fn new(trap_info: &TrapInformation) -> FaultSignal {
+        debug!("Trap id: {}", trap_info.id);
+        let (num, code, addr) = match trap_info.id {
+            DIVIDE_BY_ZERO => (SIGFPE, FPE_INTDIV, None),
+            X87_FLOATING_POINT_EXCEPTION | SIMD_FLOATING_POINT_EXCEPTION => {
+                (SIGFPE, FPE_FLTDIV, None)
+            }
+            BOUND_RANGE_EXCEEDED => (SIGSEGV, SEGV_BNDERR, None),
+            ALIGNMENT_CHECK => (SIGBUS, BUS_ADRALN, None),
+            INVALID_OPCODE => (SIGILL, ILL_ILLOPC, None),
+            GENERAL_PROTECTION_FAULT => (SIGBUS, BUS_ADRERR, None),
+            PAGE_FAULT => {
+                const PF_ERR_FLAG_PRESENT: u64 = 1u64 << 0;
+                let code = if trap_info.err & PF_ERR_FLAG_PRESENT != 0 {
+                    SEGV_ACCERR
+                } else {
+                    SEGV_MAPERR
+                };
+                let addr = Some(trap_info.cr2);
+                (SIGSEGV, code, addr)
+            }
+            _ => panic!("Exception cannnot be a signal"),
+        };
+        FaultSignal { num, code, addr }
+    }
+}
+
+impl Signal for FaultSignal {
+    fn num(&self) -> SigNum {
+        self.num
+    }
+}
diff --git a/src/kxos-std/src/process/signal/signals/kernel.rs b/src/kxos-std/src/process/signal/signals/kernel.rs
new file mode 100644
index 000000000..c0cec7527
--- /dev/null
+++ b/src/kxos-std/src/process/signal/signals/kernel.rs
@@ -0,0 +1,20 @@
+use crate::process::signal::sig_num::SigNum;
+
+use super::Signal;
+
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub struct KernelSignal {
+    num: SigNum,
+}
+
+impl KernelSignal {
+    pub const fn new(num: SigNum) -> Self {
+        Self { num }
+    }
+}
+
+impl Signal for KernelSignal {
+    fn num(&self) -> SigNum {
+        self.num
+    }
+}
diff --git a/src/kxos-std/src/process/signal/signals/mod.rs b/src/kxos-std/src/process/signal/signals/mod.rs
index 064f1c127..71452ea2b 100644
--- a/src/kxos-std/src/process/signal/signals/mod.rs
+++ b/src/kxos-std/src/process/signal/signals/mod.rs
@@ -1,3 +1,5 @@
+pub mod fault;
+pub mod kernel;
 pub mod user;
 
 use core::fmt::Debug;
diff --git a/src/kxos-std/src/process/task.rs b/src/kxos-std/src/process/task.rs
index 286e4eea6..8c6b886d9 100644
--- a/src/kxos-std/src/process/task.rs
+++ b/src/kxos-std/src/process/task.rs
@@ -7,9 +7,12 @@ use kxos_frame::{
     vm::VmSpace,
 };
 
-use crate::{prelude::*, process::signal::handle_pending_signal};
+use crate::{
+    prelude::*,
+    process::{exception::handle_exception, signal::handle_pending_signal},
+};
 
-use crate::syscall::syscall_handler;
+use crate::syscall::handle_syscall;
 
 use super::{elf::load_elf_to_vm_space, Process};
 
@@ -56,6 +59,7 @@ pub fn create_new_task(userspace: Arc<UserSpace>, parent: Weak<Process>) -> Arc<
             }
             handle_pending_signal();
             if current.status().lock().is_zombie() {
+                debug!("exit due to signal");
                 break;
             }
             // If current is suspended, wait for a signal to wake up self
@@ -65,6 +69,7 @@ pub fn create_new_task(userspace: Arc<UserSpace>, parent: Weak<Process>) -> Arc<
                 handle_pending_signal();
             }
         }
+        debug!("exit user loop");
     }
 
     Task::new(user_task_entry, parent, Some(userspace)).expect("spawn task failed")
@@ -72,8 +77,8 @@ pub fn create_new_task(userspace: Arc<UserSpace>, parent: Weak<Process>) -> Arc<
 
 fn handle_user_event(user_event: UserEvent, context: &mut CpuContext) {
     match user_event {
-        UserEvent::Syscall => syscall_handler(context),
+        UserEvent::Syscall => handle_syscall(context),
         UserEvent::Fault => todo!(),
-        UserEvent::Exception => todo!(),
+        UserEvent::Exception => handle_exception(context),
     }
 }
diff --git a/src/kxos-std/src/syscall/access.rs b/src/kxos-std/src/syscall/access.rs
index 452fb65e9..cc066ecb1 100644
--- a/src/kxos-std/src/syscall/access.rs
+++ b/src/kxos-std/src/syscall/access.rs
@@ -1,13 +1,12 @@
 use super::constants::*;
-use super::SyscallResult;
 use crate::{memory::read_bytes_from_user, prelude::*, syscall::SYS_ACCESS};
 
-pub fn sys_access(filename_ptr: Vaddr, file_mode: u64) -> SyscallResult {
+pub fn sys_access(filename_ptr: Vaddr, file_mode: u64) -> Result<isize> {
     debug!("[syscall][id={}][SYS_ACCESS]", SYS_ACCESS);
     let mut filename_buffer = vec![0u8; MAX_FILENAME_LEN];
     read_bytes_from_user(filename_ptr, &mut filename_buffer);
     let filename = CString::from(CStr::from_bytes_until_nul(&filename_buffer).unwrap());
     debug!("filename: {:?}", filename);
     warn!("access currenly does not check and just return success");
-    SyscallResult::Return(0)
+    Ok(0)
 }
diff --git a/src/kxos-std/src/syscall/arch_prctl.rs b/src/kxos-std/src/syscall/arch_prctl.rs
index 09accf2a4..8aeccbcb2 100644
--- a/src/kxos-std/src/syscall/arch_prctl.rs
+++ b/src/kxos-std/src/syscall/arch_prctl.rs
@@ -1,7 +1,7 @@
 use kxos_frame::cpu::CpuContext;
 
 use crate::prelude::*;
-use crate::syscall::{SyscallResult, SYS_ARCH_PRCTL};
+use crate::syscall::SYS_ARCH_PRCTL;
 
 #[allow(non_camel_case_types)]
 #[derive(Debug)]
@@ -26,17 +26,19 @@ impl TryFrom<u64> for ArchPrctlCode {
     }
 }
 
-pub fn sys_arch_prctl(code: u64, addr: u64, context: &mut CpuContext) -> SyscallResult {
+pub fn sys_arch_prctl(code: u64, addr: u64, context: &mut CpuContext) -> Result<isize> {
     debug!("[syscall][id={}][SYS_ARCH_PRCTL]", SYS_ARCH_PRCTL);
-    let arch_prctl_code = ArchPrctlCode::try_from(code);
+    let arch_prctl_code = ArchPrctlCode::try_from(code)?;
     debug!("arch_prctl_code: {:?}", arch_prctl_code);
-    match arch_prctl_code {
-        Err(_) => SyscallResult::Return(-1),
-        Ok(code) => {
-            let res = do_arch_prctl(code, addr, context).unwrap();
-            SyscallResult::Return(res as _)
-        }
-    }
+    let res = do_arch_prctl(arch_prctl_code, addr, context).unwrap();
+    Ok(res as _)
+    // match arch_prctl_code {
+    //     Err(_) => SyscallResult::Return(-1),
+    //     Ok(code) => {
+    //         let res = do_arch_prctl(code, addr, context).unwrap();
+    //         SyscallResult::Return(res as _)
+    //     }
+    // }
 }
 
 pub fn do_arch_prctl(code: ArchPrctlCode, addr: u64, context: &mut CpuContext) -> Result<u64> {
diff --git a/src/kxos-std/src/syscall/brk.rs b/src/kxos-std/src/syscall/brk.rs
index 906570377..b9dd71e53 100644
--- a/src/kxos-std/src/syscall/brk.rs
+++ b/src/kxos-std/src/syscall/brk.rs
@@ -1,12 +1,9 @@
 use crate::prelude::*;
 
-use crate::{
-    process::Process,
-    syscall::{SyscallResult, SYS_BRK},
-};
+use crate::{process::Process, syscall::SYS_BRK};
 
 /// expand the user heap to new heap end, returns the new heap end if expansion succeeds.
-pub fn sys_brk(heap_end: u64) -> SyscallResult {
+pub fn sys_brk(heap_end: u64) -> Result<isize> {
     debug!("[syscall][id={}][SYS_BRK]", SYS_BRK);
     let current = Process::current();
     let new_heap_end = if heap_end == 0 {
@@ -23,5 +20,5 @@ pub fn sys_brk(heap_end: u64) -> SyscallResult {
         .expect("brk should work on process with user space");
     let new_heap_end = user_heap.brk(new_heap_end, vm_space);
 
-    SyscallResult::Return(new_heap_end as _)
+    Ok(new_heap_end as _)
 }
diff --git a/src/kxos-std/src/syscall/clone.rs b/src/kxos-std/src/syscall/clone.rs
index f52fbefc1..e60b0b4bf 100644
--- a/src/kxos-std/src/syscall/clone.rs
+++ b/src/kxos-std/src/syscall/clone.rs
@@ -1,6 +1,5 @@
 use kxos_frame::cpu::CpuContext;
 
-use super::SyscallResult;
 use crate::process::clone::{clone_child, CloneArgs, CloneFlags};
 use crate::{prelude::*, syscall::SYS_CLONE};
 
@@ -13,7 +12,7 @@ pub fn sys_clone(
     child_tidptr: Vaddr,
     tls: usize,
     parent_context: CpuContext,
-) -> SyscallResult {
+) -> Result<isize> {
     debug!("[syscall][id={}][SYS_CLONE]", SYS_CLONE);
     debug!("flags = {}", clone_flags);
     let clone_flags = CloneFlags::from(clone_flags);
@@ -29,5 +28,5 @@ pub fn sys_clone(
     debug!("*********schedule child process, pid = {}**********", pid);
     child_process.send_to_scheduler();
     debug!("*********return to parent process, pid = {}*********", pid);
-    SyscallResult::Return(child_pid as _)
+    Ok(child_pid as _)
 }
diff --git a/src/kxos-std/src/syscall/execve.rs b/src/kxos-std/src/syscall/execve.rs
index fb2f6e1d1..240dbff2f 100644
--- a/src/kxos-std/src/syscall/execve.rs
+++ b/src/kxos-std/src/syscall/execve.rs
@@ -1,7 +1,6 @@
 use kxos_frame::cpu::CpuContext;
 
 use super::constants::*;
-use super::SyscallResult;
 use crate::process::elf::load_elf_to_vm_space;
 use crate::{memory::read_bytes_from_user, prelude::*, process::Process, syscall::SYS_EXECVE};
 
@@ -10,7 +9,7 @@ pub fn sys_execve(
     argv_ptr_ptr: Vaddr,
     envp_ptr_ptr: Vaddr,
     context: &mut CpuContext,
-) -> SyscallResult {
+) -> Result<isize> {
     debug!("[syscall][id={}][SYS_EXECVE]", SYS_EXECVE);
     let mut filename_buffer = vec![0u8; MAX_FILENAME_LEN];
     read_bytes_from_user(filename_ptr, &mut filename_buffer);
@@ -47,5 +46,5 @@ pub fn sys_execve(
     // set new user stack top
     context.gp_regs.rsp = elf_load_info.user_stack_top();
     debug!("user stack top: 0x{:x}", elf_load_info.user_stack_top());
-    SyscallResult::Return(0)
+    Ok(0)
 }
diff --git a/src/kxos-std/src/syscall/exit.rs b/src/kxos-std/src/syscall/exit.rs
index 3d0682ff6..3c8a11c0c 100644
--- a/src/kxos-std/src/syscall/exit.rs
+++ b/src/kxos-std/src/syscall/exit.rs
@@ -2,10 +2,8 @@ use crate::prelude::*;
 
 use crate::syscall::SYS_EXIT;
 
-use super::SyscallResult;
-
-pub fn sys_exit(exit_code: i32) -> SyscallResult {
+pub fn sys_exit(exit_code: i32) -> Result<isize> {
     debug!("[syscall][id={}][SYS_EXIT]", SYS_EXIT);
     current!().exit(exit_code);
-    SyscallResult::NotReturn
+    Ok(0)
 }
diff --git a/src/kxos-std/src/syscall/exit_group.rs b/src/kxos-std/src/syscall/exit_group.rs
index 1ac7bd7cb..0d8ee732a 100644
--- a/src/kxos-std/src/syscall/exit_group.rs
+++ b/src/kxos-std/src/syscall/exit_group.rs
@@ -1,9 +1,9 @@
 use crate::prelude::*;
 
-use crate::syscall::{SyscallResult, SYS_EXIT_GROUP};
+use crate::syscall::SYS_EXIT_GROUP;
 
-pub fn sys_exit_group(exit_code: u64) -> SyscallResult {
+pub fn sys_exit_group(exit_code: u64) -> Result<isize> {
     debug!("[syscall][id={}][SYS_EXIT_GROUP]", SYS_EXIT_GROUP);
     current!().exit(exit_code as _);
-    SyscallResult::NotReturn
+    Ok(0)
 }
diff --git a/src/kxos-std/src/syscall/fork.rs b/src/kxos-std/src/syscall/fork.rs
index 6a8ac24d5..37fe5961b 100644
--- a/src/kxos-std/src/syscall/fork.rs
+++ b/src/kxos-std/src/syscall/fork.rs
@@ -6,12 +6,10 @@ use kxos_frame::cpu::CpuContext;
 
 use crate::{process::Process, syscall::SYS_FORK};
 
-use super::SyscallResult;
-
-pub fn sys_fork(parent_context: CpuContext) -> SyscallResult {
+pub fn sys_fork(parent_context: CpuContext) -> Result<isize> {
     debug!("[syscall][id={}][SYS_FORK]", SYS_FORK);
     let child_process = fork(parent_context);
-    SyscallResult::Return(child_process.pid() as _)
+    Ok(child_process.pid() as _)
 }
 
 /// Fork a child process
diff --git a/src/kxos-std/src/syscall/fstat.rs b/src/kxos-std/src/syscall/fstat.rs
index 1581ad7c4..934e7cac9 100644
--- a/src/kxos-std/src/syscall/fstat.rs
+++ b/src/kxos-std/src/syscall/fstat.rs
@@ -3,9 +3,9 @@ use kxos_frame::vm::VmIo;
 use crate::fs::stat::Stat;
 use crate::prelude::*;
 
-use crate::syscall::{SyscallResult, SYS_FSTAT};
+use crate::syscall::SYS_FSTAT;
 
-pub fn sys_fstat(fd: u64, stat_buf_ptr: Vaddr) -> SyscallResult {
+pub fn sys_fstat(fd: u64, stat_buf_ptr: Vaddr) -> Result<isize> {
     debug!("[syscall][id={}][SYS_FSTAT]", SYS_FSTAT);
     debug!("fd = {}", fd);
     debug!("stat_buf_addr = 0x{:x}", stat_buf_ptr);
@@ -19,8 +19,8 @@ pub fn sys_fstat(fd: u64, stat_buf_ptr: Vaddr) -> SyscallResult {
         vm_space
             .write_val(stat_buf_ptr, &stat)
             .expect("Write value failed");
-        return SyscallResult::Return(0);
+        return Ok(0);
     }
     warn!("TODO: fstat only returns fake result now.");
-    SyscallResult::Return(0)
+    Ok(0)
 }
diff --git a/src/kxos-std/src/syscall/futex.rs b/src/kxos-std/src/syscall/futex.rs
index 9f4aa452a..b71f153e4 100644
--- a/src/kxos-std/src/syscall/futex.rs
+++ b/src/kxos-std/src/syscall/futex.rs
@@ -1,6 +1,5 @@
 use crate::{memory::read_val_from_user, syscall::SYS_FUTEX};
 
-use super::SyscallResult;
 use crate::prelude::*;
 use kxos_frame::{cpu::num_cpus, sync::WaitQueue};
 
@@ -18,7 +17,7 @@ pub fn sys_futex(
     utime_addr: u64,
     futex_new_addr: u64,
     bitset: u64,
-) -> SyscallResult {
+) -> Result<isize> {
     debug!("[syscall][id={}][SYS_FUTEX]", SYS_FUTEX);
     // FIXME: we current ignore futex flags
     let (futex_op, futex_flags) = futex_op_and_flags_from_u32(futex_op as _).unwrap();
@@ -70,7 +69,7 @@ pub fn sys_futex(
     }
     .unwrap();
 
-    SyscallResult::Return(res as _)
+    Ok(res as _)
 }
 
 /// do futex wait
diff --git a/src/kxos-std/src/syscall/getpid.rs b/src/kxos-std/src/syscall/getpid.rs
index 136760824..1b5ab04d6 100644
--- a/src/kxos-std/src/syscall/getpid.rs
+++ b/src/kxos-std/src/syscall/getpid.rs
@@ -2,11 +2,9 @@ use crate::prelude::*;
 
 use crate::{process::Process, syscall::SYS_GETPID};
 
-use super::SyscallResult;
-
-pub fn sys_getpid() -> SyscallResult {
+pub fn sys_getpid() -> Result<isize> {
     debug!("[syscall][id={}][SYS_GETPID]", SYS_GETPID);
     let pid = Process::current().pid();
     info!("[sys_getpid]: pid = {}", pid);
-    SyscallResult::Return(pid as _)
+    Ok(pid as _)
 }
diff --git a/src/kxos-std/src/syscall/gettid.rs b/src/kxos-std/src/syscall/gettid.rs
index 1f5b7bd7d..c1d8e9622 100644
--- a/src/kxos-std/src/syscall/gettid.rs
+++ b/src/kxos-std/src/syscall/gettid.rs
@@ -2,11 +2,9 @@ use crate::prelude::*;
 
 use crate::{process::Process, syscall::SYS_GETTID};
 
-use super::SyscallResult;
-
-pub fn sys_gettid() -> SyscallResult {
+pub fn sys_gettid() -> Result<isize> {
     debug!("[syscall][id={}][SYS_GETTID]", SYS_GETTID);
     // For single-thread process, tid is equal to pid
     let tid = Process::current().pid();
-    SyscallResult::Return(tid as _)
+    Ok(tid as _)
 }
diff --git a/src/kxos-std/src/syscall/kill.rs b/src/kxos-std/src/syscall/kill.rs
index 96ab2bac3..90e347c4e 100644
--- a/src/kxos-std/src/syscall/kill.rs
+++ b/src/kxos-std/src/syscall/kill.rs
@@ -7,14 +7,12 @@ use crate::{
     syscall::SYS_KILL,
 };
 
-use super::SyscallResult;
-
-pub fn sys_kill(process_filter: u64, sig_num: u64) -> SyscallResult {
+pub fn sys_kill(process_filter: u64, sig_num: u64) -> Result<isize> {
     debug!("[syscall][id={}][SYS_KILL]", SYS_KILL);
     let process_filter = ProcessFilter::from_id(process_filter as _);
     let sig_num = SigNum::try_from(sig_num as u8).unwrap();
-    let _ = do_sys_kill(process_filter, sig_num);
-    SyscallResult::Return(0)
+    do_sys_kill(process_filter, sig_num)?;
+    Ok(0)
 }
 
 pub fn do_sys_kill(process_filter: ProcessFilter, sig_num: SigNum) -> Result<()> {
diff --git a/src/kxos-std/src/syscall/mmap.rs b/src/kxos-std/src/syscall/mmap.rs
index 64fad283b..073862b82 100644
--- a/src/kxos-std/src/syscall/mmap.rs
+++ b/src/kxos-std/src/syscall/mmap.rs
@@ -6,8 +6,6 @@ use kxos_frame::vm::VmPerm;
 
 use crate::{process::Process, syscall::SYS_MMAP};
 
-use super::SyscallResult;
-
 pub fn sys_mmap(
     addr: u64,
     len: u64,
@@ -15,7 +13,7 @@ pub fn sys_mmap(
     flags: u64,
     fd: u64,
     offset: u64,
-) -> SyscallResult {
+) -> Result<isize> {
     debug!("[syscall][id={}][SYS_MMAP]", SYS_MMAP);
     let perms = VmPerm::try_from(perms).unwrap();
     let flags = MMapFlags::try_from(flags).unwrap();
@@ -27,7 +25,7 @@ pub fn sys_mmap(
         fd as usize,
         offset as usize,
     );
-    SyscallResult::Return(res as _)
+    Ok(res as _)
 }
 
 pub fn do_sys_mmap(
diff --git a/src/kxos-std/src/syscall/mod.rs b/src/kxos-std/src/syscall/mod.rs
index 1c17291a0..bf62fa450 100644
--- a/src/kxos-std/src/syscall/mod.rs
+++ b/src/kxos-std/src/syscall/mod.rs
@@ -46,6 +46,7 @@ mod kill;
 mod mmap;
 mod mprotect;
 mod readlink;
+mod rt_sigprocmask;
 mod sched_yield;
 mod tgkill;
 mod uname;
@@ -53,7 +54,6 @@ mod wait4;
 mod waitid;
 mod write;
 mod writev;
-mod rt_sigprocmask;
 
 const SYS_WRITE: u64 = 1;
 const SYS_FSTAT: u64 = 5;
@@ -90,11 +90,6 @@ pub struct SyscallArgument {
     args: [u64; 6],
 }
 
-pub enum SyscallResult {
-    Return(i32),
-    NotReturn,
-}
-
 impl SyscallArgument {
     fn new_from_context(context: &CpuContext) -> Self {
         let syscall_number = context.gp_regs.rax;
@@ -112,22 +107,31 @@ impl SyscallArgument {
     }
 }
 
-pub fn syscall_handler(context: &mut CpuContext) {
+pub fn handle_syscall(context: &mut CpuContext) {
     let syscall_frame = SyscallArgument::new_from_context(context);
     let syscall_return =
         syscall_dispatch(syscall_frame.syscall_number, syscall_frame.args, context);
 
-    if let SyscallResult::Return(return_value) = syscall_return {
-        // FIXME: set return value?
-        context.gp_regs.rax = return_value as u64;
+    match syscall_return {
+        Ok(return_value) => {
+            context.gp_regs.rax = return_value as u64;
+        }
+        Err(err) => {
+            let errno = err.error() as i32;
+            context.gp_regs.rax = (-errno) as u64
+        }
     }
+    // if let Syscal(return_value) = syscall_return {
+    //     // FIXME: set return value?
+    //     context.gp_regs.rax = return_value as u64;
+    // }
 }
 
 pub fn syscall_dispatch(
     syscall_number: u64,
     args: [u64; 6],
     context: &mut CpuContext,
-) -> SyscallResult {
+) -> Result<isize> {
     match syscall_number {
         SYS_WRITE => sys_write(args[0], args[1], args[2]),
         SYS_FSTAT => sys_fstat(args[0], args[1] as _),
@@ -135,7 +139,9 @@ pub fn syscall_dispatch(
         SYS_MPROTECT => sys_mprotect(args[0], args[1], args[2]),
         SYS_BRK => sys_brk(args[0]),
         SYS_RT_SIGACTION => sys_rt_sigaction(),
-        SYS_RT_SIGPROCMASK => sys_rt_sigprocmask(args[0] as _, args[1] as _, args[2] as _, args[3] as _),
+        SYS_RT_SIGPROCMASK => {
+            sys_rt_sigprocmask(args[0] as _, args[1] as _, args[2] as _, args[3] as _)
+        }
         SYS_WRITEV => sys_writev(args[0], args[1], args[2]),
         SYS_ACCESS => sys_access(args[0] as _, args[1]),
         SYS_GETPID => sys_getpid(),
@@ -168,32 +174,32 @@ pub fn syscall_dispatch(
     }
 }
 
-pub fn sys_rt_sigaction() -> SyscallResult {
+pub fn sys_rt_sigaction() -> Result<isize> {
     debug!("[syscall][id={}][SYS_RT_SIGACTION]", SYS_RT_SIGACTION);
     warn!("TODO: rt_sigaction only return a fake result");
-    SyscallResult::Return(0)
+    Ok(0)
 }
 
-pub fn sys_getuid() -> SyscallResult {
+pub fn sys_getuid() -> Result<isize> {
     debug!("[syscall][id={}][SYS_GETUID]", SYS_GETUID);
     warn!("TODO: getuid only return a fake uid now");
-    SyscallResult::Return(0)
+    Ok(0)
 }
 
-pub fn sys_getgid() -> SyscallResult {
-    debug!("[syscall][id={}][SYS_GETGID]", SYS_GETUID);
+pub fn sys_getgid() -> Result<isize> {
+    debug!("[syscall][id={}][SYS_GETGID]", SYS_GETGID);
     warn!("TODO: getgid only return a fake gid now");
-    SyscallResult::Return(0)
+    Ok(0)
 }
 
-pub fn sys_geteuid() -> SyscallResult {
+pub fn sys_geteuid() -> Result<isize> {
     debug!("[syscall][id={}][SYS_GETEUID]", SYS_GETEUID);
     warn!("TODO: geteuid only return a fake euid now");
-    SyscallResult::Return(0)
+    Ok(0)
 }
 
-pub fn sys_getegid() -> SyscallResult {
+pub fn sys_getegid() -> Result<isize> {
     debug!("[syscall][id={}][SYS_GETEGID]", SYS_GETEGID);
     warn!("TODO: getegid only return a fake egid now");
-    SyscallResult::Return(0)
+    Ok(0)
 }
diff --git a/src/kxos-std/src/syscall/mprotect.rs b/src/kxos-std/src/syscall/mprotect.rs
index 259f10a53..23b101858 100644
--- a/src/kxos-std/src/syscall/mprotect.rs
+++ b/src/kxos-std/src/syscall/mprotect.rs
@@ -4,13 +4,11 @@ use crate::prelude::*;
 
 use crate::syscall::SYS_MPROTECT;
 
-use super::SyscallResult;
-
-pub fn sys_mprotect(vaddr: u64, len: u64, perms: u64) -> SyscallResult {
+pub fn sys_mprotect(vaddr: u64, len: u64, perms: u64) -> Result<isize> {
     debug!("[syscall][id={}][SYS_MPROTECT]", SYS_MPROTECT);
     let perms = VmPerm::try_from(perms).unwrap();
     do_sys_mprotect(vaddr as Vaddr, len as usize, perms);
-    SyscallResult::Return(0)
+    Ok(0)
 }
 
 pub fn do_sys_mprotect(addr: Vaddr, len: usize, perms: VmPerm) -> isize {
diff --git a/src/kxos-std/src/syscall/readlink.rs b/src/kxos-std/src/syscall/readlink.rs
index c9ae7da13..de76fca8e 100644
--- a/src/kxos-std/src/syscall/readlink.rs
+++ b/src/kxos-std/src/syscall/readlink.rs
@@ -6,18 +6,16 @@ use crate::{
     syscall::SYS_READLINK,
 };
 
-use super::SyscallResult;
-
 const MAX_FILENAME_LEN: usize = 128;
 
-pub fn sys_readlink(filename_ptr: u64, user_buf_ptr: u64, user_buf_len: u64) -> SyscallResult {
+pub fn sys_readlink(filename_ptr: u64, user_buf_ptr: u64, user_buf_len: u64) -> Result<isize> {
     debug!("[syscall][id={}][SYS_READLINK]", SYS_READLINK);
     let res = do_sys_readlink(
         filename_ptr as Vaddr,
         user_buf_ptr as Vaddr,
         user_buf_len as usize,
     );
-    SyscallResult::Return(res as _)
+    Ok(res as _)
 }
 
 /// do sys readlink
diff --git a/src/kxos-std/src/syscall/rt_sigprocmask.rs b/src/kxos-std/src/syscall/rt_sigprocmask.rs
index 2da276635..ee2052d12 100644
--- a/src/kxos-std/src/syscall/rt_sigprocmask.rs
+++ b/src/kxos-std/src/syscall/rt_sigprocmask.rs
@@ -2,8 +2,12 @@ use kxos_frame::vm::VmIo;
 
 use crate::{prelude::*, syscall::SYS_RT_SIGPROCMASK};
 
-use super::SyscallResult;
-pub fn sys_rt_sigprocmask(how: u32, set_ptr: Vaddr, oldset_ptr: Vaddr, sigset_size: usize) -> SyscallResult {
+pub fn sys_rt_sigprocmask(
+    how: u32,
+    set_ptr: Vaddr,
+    oldset_ptr: Vaddr,
+    sigset_size: usize,
+) -> Result<isize> {
     debug!("[syscall][id={}][SYS_RT_SIGPROCMASK]", SYS_RT_SIGPROCMASK);
     let mask_op = MaskOp::try_from(how).unwrap();
     debug!("mask op = {:?}", mask_op);
@@ -14,10 +18,15 @@ pub fn sys_rt_sigprocmask(how: u32, set_ptr: Vaddr, oldset_ptr: Vaddr, sigset_si
         warn!("sigset size is not equal to 8");
     }
     do_rt_sigprocmask(mask_op, set_ptr, oldset_ptr, sigset_size).unwrap();
-    SyscallResult::Return(0)
+    Ok(0)
 }
 
-fn do_rt_sigprocmask(mask_op: MaskOp, set_ptr: Vaddr, oldset_ptr: Vaddr, sigset_size: usize) -> Result<()>{
+fn do_rt_sigprocmask(
+    mask_op: MaskOp,
+    set_ptr: Vaddr,
+    oldset_ptr: Vaddr,
+    sigset_size: usize,
+) -> Result<()> {
     let current = current!();
     let vm_space = current.vm_space().unwrap();
     let mut sig_mask = current.sig_mask().lock();
@@ -30,7 +39,7 @@ fn do_rt_sigprocmask(mask_op: MaskOp, set_ptr: Vaddr, oldset_ptr: Vaddr, sigset_
         let new_set = vm_space.read_val::<u64>(set_ptr)?;
         debug!("new set = 0x{:x}", new_set);
         match mask_op {
-            MaskOp::Block => sig_mask.block(new_set ),
+            MaskOp::Block => sig_mask.block(new_set),
             MaskOp::Unblock => sig_mask.unblock(new_set),
             MaskOp::SetMask => sig_mask.set(new_set),
         }
@@ -60,4 +69,4 @@ impl TryFrom<u32> for MaskOp {
         };
         Ok(op)
     }
-}
\ No newline at end of file
+}
diff --git a/src/kxos-std/src/syscall/sched_yield.rs b/src/kxos-std/src/syscall/sched_yield.rs
index d58217f84..2768661f3 100644
--- a/src/kxos-std/src/syscall/sched_yield.rs
+++ b/src/kxos-std/src/syscall/sched_yield.rs
@@ -2,10 +2,8 @@ use crate::prelude::*;
 
 use crate::{process::Process, syscall::SYS_SCHED_YIELD};
 
-use super::SyscallResult;
-
-pub fn sys_sched_yield() -> SyscallResult {
+pub fn sys_sched_yield() -> Result<isize> {
     debug!("[syscall][id={}][SYS_SCHED_YIELD]", SYS_SCHED_YIELD);
     Process::yield_now();
-    SyscallResult::Return(0)
+    Ok(0)
 }
diff --git a/src/kxos-std/src/syscall/tgkill.rs b/src/kxos-std/src/syscall/tgkill.rs
index de9e419cc..0bdd713b6 100644
--- a/src/kxos-std/src/syscall/tgkill.rs
+++ b/src/kxos-std/src/syscall/tgkill.rs
@@ -1,11 +1,11 @@
 use crate::prelude::*;
 
-use crate::syscall::{SyscallResult, SYS_TGKILL};
+use crate::syscall::SYS_TGKILL;
 
-pub fn sys_tgkill(tgid: u64, pid: u64, signal: u64) -> SyscallResult {
+pub fn sys_tgkill(tgid: u64, pid: u64, signal: u64) -> Result<isize> {
     debug!("[syscall][id={}][SYS_TGKILL]", SYS_TGKILL);
     debug!("tgid = {}", tgid);
     debug!("pid = {}", pid);
     warn!("TODO: tgkill do nothing now");
-    SyscallResult::Return(0)
+    Ok(0)
 }
diff --git a/src/kxos-std/src/syscall/uname.rs b/src/kxos-std/src/syscall/uname.rs
index 5bcb08eaa..6d6140216 100644
--- a/src/kxos-std/src/syscall/uname.rs
+++ b/src/kxos-std/src/syscall/uname.rs
@@ -1,9 +1,6 @@
 use crate::prelude::*;
 
-use crate::{
-    memory::write_val_to_user,
-    syscall::{SyscallResult, SYS_UNAME},
-};
+use crate::{memory::write_val_to_user, syscall::SYS_UNAME};
 
 // We don't use the real name and version of our os here. Instead, we pick up fake values witch is the same as the ones of linux.
 // The values are used to fool glibc since glibc will check the version and os name.
@@ -59,10 +56,10 @@ fn copy_cstring_to_u8_slice(src: &CStr, dst: &mut [u8]) {
     dst[..len].copy_from_slice(&src[..len]);
 }
 
-pub fn sys_uname(old_uname_addr: u64) -> SyscallResult {
+pub fn sys_uname(old_uname_addr: u64) -> Result<isize> {
     debug!("[syscall][id={}][SYS_UNAME]", SYS_UNAME);
     do_sys_uname(old_uname_addr as Vaddr);
-    SyscallResult::Return(0)
+    Ok(0)
 }
 
 pub fn do_sys_uname(old_uname_addr: Vaddr) -> usize {
diff --git a/src/kxos-std/src/syscall/wait4.rs b/src/kxos-std/src/syscall/wait4.rs
index 71f9d7b87..41dabeebe 100644
--- a/src/kxos-std/src/syscall/wait4.rs
+++ b/src/kxos-std/src/syscall/wait4.rs
@@ -4,11 +4,10 @@ use crate::{
     syscall::SYS_WAIT4,
 };
 
-use super::SyscallResult;
 use crate::prelude::*;
 use crate::process::wait::WaitOptions;
 
-pub fn sys_wait4(wait_pid: u64, exit_status_ptr: u64, wait_options: u64) -> SyscallResult {
+pub fn sys_wait4(wait_pid: u64, exit_status_ptr: u64, wait_options: u64) -> Result<isize> {
     debug!("[syscall][id={}][SYS_WAIT4]", SYS_WAIT4);
     let wait_options = WaitOptions::from_bits(wait_options as u32).expect("Unknown wait options");
     debug!("pid = {}", wait_pid as isize);
@@ -20,5 +19,5 @@ pub fn sys_wait4(wait_pid: u64, exit_status_ptr: u64, wait_options: u64) -> Sysc
         write_val_to_user(exit_status_ptr as _, &exit_code);
     }
 
-    SyscallResult::Return(return_pid as _)
+    Ok(return_pid as _)
 }
diff --git a/src/kxos-std/src/syscall/waitid.rs b/src/kxos-std/src/syscall/waitid.rs
index f7e1d77f7..04dbc5486 100644
--- a/src/kxos-std/src/syscall/waitid.rs
+++ b/src/kxos-std/src/syscall/waitid.rs
@@ -1,6 +1,6 @@
+use crate::prelude::*;
 use crate::process::{process_filter::ProcessFilter, wait::wait_child_exit};
 
-use super::SyscallResult;
 use crate::process::wait::WaitOptions;
 
 pub fn sys_waitid(
@@ -9,10 +9,10 @@ pub fn sys_waitid(
     infoq_addr: u64,
     options: u64,
     rusage_addr: u64,
-) -> SyscallResult {
+) -> Result<isize> {
     // FIXME: what does infoq and rusage use for?
     let process_filter = ProcessFilter::from_which_and_id(which, upid);
     let wait_options = WaitOptions::from_bits(options as u32).expect("Unknown wait options");
     let (exit_code, pid) = wait_child_exit(process_filter, wait_options);
-    SyscallResult::Return(pid)
+    Ok(pid as _)
 }
diff --git a/src/kxos-std/src/syscall/write.rs b/src/kxos-std/src/syscall/write.rs
index 1d13d2551..f2aed5df6 100644
--- a/src/kxos-std/src/syscall/write.rs
+++ b/src/kxos-std/src/syscall/write.rs
@@ -2,12 +2,10 @@ use crate::prelude::*;
 
 use crate::{memory::read_bytes_from_user, syscall::SYS_WRITE};
 
-use super::SyscallResult;
-
 const STDOUT: u64 = 1;
 const STDERR: u64 = 2;
 
-pub fn sys_write(fd: u64, user_buf_ptr: u64, user_buf_len: u64) -> SyscallResult {
+pub fn sys_write(fd: u64, user_buf_ptr: u64, user_buf_len: u64) -> Result<isize> {
     // only suppprt STDOUT now.
     debug!("[syscall][id={}][SYS_WRITE]", SYS_WRITE);
 
@@ -21,7 +19,7 @@ pub fn sys_write(fd: u64, user_buf_ptr: u64, user_buf_len: u64) -> SyscallResult
             info!("Error message from user mode: {:?}", content);
         }
 
-        SyscallResult::Return(user_buf_len as _)
+        Ok(user_buf_len as _)
     } else {
         panic!("Unsupported fd number {}", fd);
     }
diff --git a/src/kxos-std/src/syscall/writev.rs b/src/kxos-std/src/syscall/writev.rs
index ae3c1d9f9..f70ab37b5 100644
--- a/src/kxos-std/src/syscall/writev.rs
+++ b/src/kxos-std/src/syscall/writev.rs
@@ -5,8 +5,6 @@ use crate::{
     syscall::SYS_WRITEV,
 };
 
-use super::SyscallResult;
-
 const IOVEC_MAX: usize = 256;
 
 #[repr(C)]
@@ -16,10 +14,10 @@ pub struct IoVec {
     len: usize,
 }
 
-pub fn sys_writev(fd: u64, io_vec_ptr: u64, io_vec_count: u64) -> SyscallResult {
+pub fn sys_writev(fd: u64, io_vec_ptr: u64, io_vec_count: u64) -> Result<isize> {
     debug!("[syscall][id={}][SYS_WRITEV]", SYS_WRITEV);
     let res = do_sys_writev(fd, io_vec_ptr as Vaddr, io_vec_count as usize);
-    SyscallResult::Return(res as _)
+    Ok(res as _)
 }
 
 pub fn do_sys_writev(fd: u64, io_vec_ptr: Vaddr, io_vec_count: usize) -> usize {
diff --git a/src/kxos-std/src/user_apps.rs b/src/kxos-std/src/user_apps.rs
index f91fe1360..10ad61f9c 100644
--- a/src/kxos-std/src/user_apps.rs
+++ b/src/kxos-std/src/user_apps.rs
@@ -49,9 +49,17 @@ pub fn get_all_apps() -> Vec<UserApp> {
     res.push(app5);
 
     // Set sig procmask
-    let app6 = UserApp::new("/sig_procmask", read_sig_procmask());
+    let app6 = UserApp::new("/sig_procmask", read_sig_procmask_content());
     res.push(app6);
 
+    // divide zero
+    let app7 = UserApp::new("/divide_zero", read_divide_zero_content());
+    res.push(app7);
+
+    // sig_action
+    let app8 = UserApp::new("/sig_action", read_sig_action_content());
+    res.push(app8);
+
     res
 }
 
@@ -79,6 +87,14 @@ fn read_fork_c_content() -> &'static [u8] {
     include_bytes!("../../kxos-user/fork_c/fork")
 }
 
-fn read_sig_procmask() -> &'static [u8] {
+fn read_sig_procmask_content() -> &'static [u8] {
     include_bytes!("../../kxos-user/signal_c/sig_procmask")
 }
+
+fn read_divide_zero_content() -> &'static [u8] {
+    include_bytes!("../../kxos-user/signal_c/divide_zero")
+}
+
+fn read_sig_action_content() -> &'static [u8] {
+    include_bytes!("../../kxos-user/signal_c/sig_action")
+}
diff --git a/src/kxos-user/signal_c/Makefile b/src/kxos-user/signal_c/Makefile
index bc903b97f..090aaaf3d 100644
--- a/src/kxos-user/signal_c/Makefile
+++ b/src/kxos-user/signal_c/Makefile
@@ -1,9 +1,10 @@
 .PHONY: build clean run
-build: divide_zero.c sig_procmask.c
+build: divide_zero.c sig_procmask.c sig_action.c
 	@gcc -static divide_zero.c -o divide_zero
 	@gcc -static sig_procmask.c -o sig_procmask
+	@gcc -static sig_action.c -o sig_action
 clean:
-	@rm divide_zero sig_procmask
+	@rm divide_zero sig_procmask sig_action
 run: build
 	@./sig_procmask
-	@./divide_zero
+	@./sig_action
diff --git a/src/kxos-user/signal_c/sig_action b/src/kxos-user/signal_c/sig_action
new file mode 100755
index 000000000..42d39e3a8
--- /dev/null
+++ b/src/kxos-user/signal_c/sig_action
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:08b21d340c8d144c1bfb86097e46ceda6d690041269cf56fee5bd8918e8253fa
+size 877544
diff --git a/src/kxos-user/signal_c/sig_action.c b/src/kxos-user/signal_c/sig_action.c
index e69de29bb..c1927c1f7 100644
--- a/src/kxos-user/signal_c/sig_action.c
+++ b/src/kxos-user/signal_c/sig_action.c
@@ -0,0 +1,29 @@
+#include <stdio.h>
+#include <signal.h> 
+#include <unistd.h>
+#include <errno.h>
+#include <sys/wait.h>
+
+int sigchld = 0;
+
+void proc_exit() {
+    sigchld = 999;
+}
+
+int main() {
+    signal(SIGCHLD, proc_exit);
+    printf("Run a parent process has pid = %d\n", getpid());
+    fflush(stdout);
+    int pid = fork();
+    if(pid == 0) {
+        // child process
+        printf("create a new proces successfully (pid = %d)\n", getpid());
+        fflush(stdout);
+    } else {
+        // parent process
+        wait(NULL);
+        printf("sigchld = %d\n", sigchld);
+        fflush(stdout);
+    }
+    return 0;
+}
\ No newline at end of file