diff -r e70b616a077b -r 89742f1fa6cb rust/chg/src/procutil.rs
--- a/rust/chg/src/procutil.rs	Mon Sep 24 22:19:49 2018 +0900
+++ b/rust/chg/src/procutil.rs	Tue Sep 25 20:55:03 2018 +0900
@@ -5,14 +5,19 @@
 
 //! Low-level utility for signal and process handling.
 
-use libc::{self, c_int, size_t, ssize_t};
+use libc::{self, c_int, pid_t, size_t, ssize_t};
 use std::io;
 use std::os::unix::io::RawFd;
+use std::sync;
 
 #[link(name = "procutil", kind = "static")]
 extern "C" {
     // sendfds.c
     fn sendfds(sockfd: c_int, fds: *const c_int, fdlen: size_t) -> ssize_t;
+
+    // sighandlers.c
+    fn setupsignalhandler(pid: pid_t, pgid: pid_t) -> c_int;
+    fn restoresignalhandler() -> c_int;
 }
 
 /// Returns the effective uid of the current process.
@@ -41,3 +46,42 @@
     }
     Ok(())
 }
+
+static SETUP_SIGNAL_HANDLER: sync::Once = sync::Once::new();
+static RESTORE_SIGNAL_HANDLER: sync::Once = sync::Once::new();
+
+/// Installs signal handlers to forward signals to the server.
+///
+/// # Safety
+///
+/// This touches global states, and thus synchronized as a one-time
+/// initialization function.
+pub fn setup_signal_handler_once(pid: u32, pgid: Option<u32>) -> io::Result<()> {
+    let pid_signed = pid as i32;
+    let pgid_signed = pgid.map(|n| n as i32).unwrap_or(0);
+    let mut r = 0;
+    SETUP_SIGNAL_HANDLER.call_once(|| {
+        r = unsafe { setupsignalhandler(pid_signed, pgid_signed) };
+    });
+    if r < 0 {
+        return Err(io::Error::last_os_error());
+    }
+    Ok(())
+}
+
+/// Restores the original signal handlers.
+///
+/// # Safety
+///
+/// This touches global states, and thus synchronized as a one-time
+/// initialization function.
+pub fn restore_signal_handler_once() -> io::Result<()> {
+    let mut r = 0;
+    RESTORE_SIGNAL_HANDLER.call_once(|| {
+        r = unsafe { restoresignalhandler() };
+    });
+    if r < 0 {
+        return Err(io::Error::last_os_error());
+    }
+    Ok(())
+}