SystemServer: Add WorkingDirectory support

Services can now have their initial working directory
configured via `SystemServer.ini`.

This commit also configures Terminal's working directory
to be /home/anon

Base/etc/SystemServer.ini

@@ -70,3 +70,4 @@ User=anon
 
 [Terminal]
 User=anon
+WorkingDirectory=/home/anon

Base/usr/share/man/man5/SystemServer.md

@@ -25,6 +25,7 @@ describing how to launch and manage this service.
 * `Socket` - a path to a socket to create on behalf of the service. For lazy services, SystemServer will actually watch the socket for new connection attempts. An open file descriptor to this socket will be passed as fd 3 to the service.
 * `SocketPermissions` - (octal) file system permissions for the socket file. The default permissions are 0600.
 * `User` - a name of the user to run the service as. This impacts what UID, GID (and extra GIDs) the service processes have. By default, services are run as root.
+* `WorkingDirectory` - The working directory in which the service is spawned. By Default, services are spawned in the root (`"/"`) directory.
 
 ## Environment
 

Servers/SystemServer/Service.cpp

@@ -188,6 +188,13 @@ void Service::spawn()
     } else if (m_pid == 0) {
         // We are the child.
 
+        if (!m_working_directory.is_null()) {
+            if (chdir(m_working_directory.characters()) < 0) {
+                perror("chdir");
+                ASSERT_NOT_REACHED();
+            }
+        }
+
         struct sched_param p;
         p.sched_priority = m_priority;
         int rc = sched_setparam(0, &p);
@@ -320,6 +327,8 @@ Service::Service(const Core::ConfigFile& config, const StringView& name)
         m_socket_permissions = strtol(socket_permissions_string.characters(), nullptr, 8) & 04777;
         setup_socket();
     }
+
+    m_working_directory = config.read_entry(name, "WorkingDirectory");
 }
 
 void Service::save_to(JsonObject& json)
@@ -352,4 +361,5 @@ void Service::save_to(JsonObject& json)
         json.set("pid", nullptr);
 
     json.set("restart_attempts", m_restart_attempts);
+    json.set("working_directory", m_working_directory);
 }

Servers/SystemServer/Service.h

@@ -81,6 +81,9 @@ private:
     // times where it has exited unsuccessfully and too quickly.
     int m_restart_attempts { 0 };
 
+    // The working directory in which to spawn the service
+    String m_working_directory;
+
     void resolve_user();
     void setup_socket();
     void setup_notifier();