Add grpc service to shim

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

utils/reaper.go

@@ -0,0 +1,49 @@
+package utils
+
+import "syscall"
+
+// Exit is the wait4 information from an exited process
+type Exit struct {
+	Pid    int
+	Status int
+}
+
+// Reap reaps all child processes for the calling process and returns their
+// exit information
+func Reap(wait bool) (exits []Exit, err error) {
+	var (
+		ws  syscall.WaitStatus
+		rus syscall.Rusage
+	)
+	flag := syscall.WNOHANG
+	if wait {
+		flag = 0
+	}
+	for {
+		pid, err := syscall.Wait4(-1, &ws, flag, &rus)
+		if err != nil {
+			if err == syscall.ECHILD {
+				return exits, nil
+			}
+			return exits, err
+		}
+		if pid <= 0 {
+			return exits, nil
+		}
+		exits = append(exits, Exit{
+			Pid:    pid,
+			Status: ExitStatus(ws),
+		})
+	}
+}
+
+const exitSignalOffset = 128
+
+// ExitStatus returns the correct exit status for a process based on if it
+// was signaled or exited cleanly
+func ExitStatus(status syscall.WaitStatus) int {
+	if status.Signaled() {
+		return exitSignalOffset + int(status.Signal())
+	}
+	return status.ExitStatus()
+}