exec: Add SELinuxContext configuration item

This permit to let system administrators decide of the domain of a service.
This can be used with templated units to have each service in a différent
domain ( for example, a per customer database, using MLS or anything ),
or can be used to force a non selinux enabled system (jvm, erlang, etc)
to start in a different domain for each service.

src/shared/exit-status.c

@@ -130,6 +130,9 @@ const char* exit_status_to_string(ExitStatus status, ExitStatusLevel level) {
 
                 case EXIT_SECCOMP:
                         return "SECCOMP";
+
+                case EXIT_SELINUX_CONTEXT:
+                        return "SELINUX_CONTEXT";
                 }
         }
 

src/shared/exit-status.h

@@ -67,7 +67,8 @@ typedef enum ExitStatus {
         EXIT_NETWORK,
         EXIT_NAMESPACE,
         EXIT_NO_NEW_PRIVILEGES,
-        EXIT_SECCOMP
+        EXIT_SECCOMP,
+        EXIT_SELINUX_CONTEXT
 } ExitStatus;
 
 typedef enum ExitStatusLevel {