alert(Cc["@mozilla.org/file/directory_service;1"].getService(Ci.nsIProperties).get("CurProcD", Ci.nsIFile).path)
//returns C:Program FilesAurorabrowser

var process = Cc["@mozilla.org/process/util;1"].createInstance(Ci.nsIProcess);
process.init(execFile);
var args = ["-safe-mode"];
process.run(false, args, args.length);