From 6407d676d62906e10ad81cfd4d301e9ba24e8f6e Mon Sep 17 00:00:00 2001
From: radeon92 <caoruidong@huawei.com>
Date: Tue, 2 Nov 2021 20:43:10 +0800
Subject: [PATCH] Init sends signal about exit of child to real process1

---
 .gitignore           |  2 +-
 src/init/src/main.rs | 73 ++++++++++++++++++++++++++++++--------------
 src/systemd/demo.c   | 24 +++++++++++++++
 3 files changed, 75 insertions(+), 24 deletions(-)
 create mode 100644 src/systemd/demo.c

diff --git a/.gitignore b/.gitignore
index 3e573d31..a36d0931 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,3 @@
 target
 .vscode
-.Cargo.lock
+Cargo.lock
diff --git a/src/init/src/main.rs b/src/init/src/main.rs
index 1d794b70..99867e08 100644
--- a/src/init/src/main.rs
+++ b/src/init/src/main.rs
@@ -1,13 +1,19 @@
-use std::io::Error;
+use std::fs::write;
+use std::io::{self, Error};
+use std::mem::MaybeUninit;
 use std::path::Path;
-use std::process::Command;
+use std::process::{Child, Command};
 
-use nix::unistd::Pid;
+use libc::{siginfo_t, waitid};
+use nix::libc;
 use nix::sys::wait::waitpid;
-use nix::sys::wait::WaitPidFlag;
+use nix::unistd::Pid;
 
 const PROCESS1_PATH: &'static str = "/usr/lib/process1/process1";
 const SYSTEMD_PATH: &'static str = "/usr/lib/systemd/systemd";
+const PIDFILE: &'static str = "/.init.pid";
+const SELF_CODE_OFFSET: i32 = 14;
+const SELF_SIG_OFFSET: i32 = 7;
 
 fn main() {
     let cmd = match get_command() {
@@ -23,8 +29,8 @@ fn main() {
 }
 
 fn get_command() -> Option<String> {
-    if std::env::args().count() > 2 { 
-        panic!("More than one para, panic!!!"); 
+    if std::env::args().count() > 2 {
+        panic!("More than one para, panic!!!");
     }
 
     std::env::args().nth(1)
@@ -43,31 +49,52 @@ fn detect_init() -> String {
 fn execute_mode(s: &String) -> Result<(), Error> {
     println!("Running to execute command : {:?}", s);
 
-    let mut command = Command::new(s);
-    let mut child = command.spawn()?;
+    let mut error_count = 0;
+    let mut child = create_init(s)?;
     loop {
-        let result = child.try_wait();
-        match result {
-            Ok(Some(status)) => {
-                if status.success() {
-                    println!("Successfully finished");  // shutdown
-                    break;
-                } else {
+        let mut siginfo = MaybeUninit::<siginfo_t>::zeroed();
+        let pid = unsafe {
+            if waitid(libc::P_ALL, 0, siginfo.as_mut_ptr(),
+                      libc::WEXITED | libc::WNOWAIT) < 0 {
+                continue;
+            };
+            siginfo.assume_init().si_pid()
+        };
+        if pid <= 0 {
+            continue;
+        } else if pid == child.id() as i32 {
+            if let Ok(status) = child.wait() {
+                if !status.success() {
+                    error_count += 1;
+                    if error_count >= 3 {
+                        break;
+                    }
                     println!("Exited with error, Again");
-                    child = command.spawn()?;
+                    child = create_init(s)?;
                 }
             }
-            _ => {}
+        } else {
+            println!("Receiving {} exited", pid);
+            send_signal(child.id(), siginfo);
+            let _result = waitpid(Pid::from_raw(pid), None);
+            println!("Reaped {}", pid);
         }
-        reap_zombie()
     }
     Ok(())
 }
 
-fn reap_zombie() {
-    let _result = waitpid(Pid::from_raw(-1),
-                                Some(WaitPidFlag::WNOHANG));
-    send_signal()
+fn create_init(s: &String) -> io::Result<Child> {
+    let child = Command::new(s).spawn()?;
+    let _ = write(String::from(PIDFILE), child.id().to_string());
+    Ok(child)
 }
 
-fn send_signal() {}
+fn send_signal(pid: u32, mut siginfo: MaybeUninit<siginfo_t>) {
+    unsafe {
+        siginfo.assume_init_mut().si_code -= SELF_CODE_OFFSET;
+        if libc::syscall(libc::SYS_rt_sigqueueinfo, pid, libc::SIGRTMIN() + SELF_SIG_OFFSET,
+                         siginfo.as_mut_ptr()) < 0 {
+            println!("send signal error:{}", Error::last_os_error())
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/systemd/demo.c b/src/systemd/demo.c
new file mode 100644
index 00000000..041e71b5
--- /dev/null
+++ b/src/systemd/demo.c
@@ -0,0 +1,24 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <signal.h>
+
+void handler(int signum, siginfo_t *siginfo, void *ucontext){
+    siginfo->si_code+=14;
+    // follow systemd function
+}
+
+void install_handler(){
+    struct sigaction act;
+    act.sa_sigaction = handler;
+    act.sa_flags = SA_SIGINFO;
+    sigemptyset(&act.sa_mask);
+    sigaction(SIGRTMIN+7, &act, NULL);
+}
+
+int main(){
+    install_handler();
+    for(int i=0;i<10;i++){
+        sleep(100);
+    }
+}
+
-- 
Gitee