From 3631c545b8e3256c5aba2269491912e3f568cd99 Mon Sep 17 00:00:00 2001
From: Tom Cherry <tomcherry@google.com>
Date: Mon, 18 Sep 2017 12:16:27 -0700
Subject: [PATCH] init: add exec_background command

This command functions similarly to `exec` except that it does not
cause init to halt executing commands until the process has
terminated.  It is useful for launching simple one time background
tasks.

Bug: 65736247
Test: create an exec_background service and see it function properly
Change-Id: I719c8b85479b65201770aedc0a13191303007c11
---
 init/README.md    |  5 +++++
 init/builtins.cpp | 14 ++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/init/README.md b/init/README.md
index 7df37ff62..d7edf21ac 100644
--- a/init/README.md
+++ b/init/README.md
@@ -381,6 +381,11 @@ Commands
   within _argument_.
   Init halts executing commands until the forked process exits.
 
+`exec_background [ <seclabel> [ <user> [ <group>\* ] ] ] -- <command> [ <argument>\* ]`
+> Fork and execute command with the given arguments. This is handled similarly
+  to the `exec` command. The difference is that init does not halt executing
+  commands until the process exits for `exec_background`.
+
 `exec_start <service>`
 > Start a given service and halt the processing of additional init commands
   until it returns.  The command functions similarly to the `exec` command,
diff --git a/init/builtins.cpp b/init/builtins.cpp
index 886c57240..269e5561e 100644
--- a/init/builtins.cpp
+++ b/init/builtins.cpp
@@ -148,6 +148,19 @@ static Result<Success> do_exec(const std::vector<std::string>& args) {
     return Success();
 }
 
+static Result<Success> do_exec_background(const std::vector<std::string>& args) {
+    auto service = Service::MakeTemporaryOneshotService(args);
+    if (!service) {
+        return Error() << "Could not create exec background service";
+    }
+    if (auto result = service->Start(); !result) {
+        return Error() << "Could not start exec background service: " << result.error();
+    }
+
+    ServiceList::GetInstance().AddService(std::move(service));
+    return Success();
+}
+
 static Result<Success> do_exec_start(const std::vector<std::string>& args) {
     Service* service = ServiceList::GetInstance().FindService(args[1]);
     if (!service) {
@@ -959,6 +972,7 @@ const BuiltinFunctionMap::Map& BuiltinFunctionMap::map() const {
         {"domainname",              {1,     1,    do_domainname}},
         {"enable",                  {1,     1,    do_enable}},
         {"exec",                    {1,     kMax, do_exec}},
+        {"exec_background",         {1,     kMax, do_exec_background}},
         {"exec_start",              {1,     1,    do_exec_start}},
         {"export",                  {2,     2,    do_export}},
         {"hostname",                {1,     1,    do_hostname}},