Your parent needs a ROMFile capability to run your program. Ask it for that capability to read your own file. You can call that RPC getexecname or whatever strikes your fancy.
the question is what path for open() call I should use for ROMfile?
Not sure if that's relevant to the discussion as I'm jumping in mid-stream, but in my Genode run scenarios I use the following, in order to access data files (not exe files) :
<start name="my_application"> <config> <vfs> <rom name="background.jpeg"/> ..etc
And then I can use Genode's libc POSIX functions (open() or fopen() etc) with the above "files", as they are located at the very top root of the VFS, i.e. "/background.jpeg" (just prepended with a slash)
Cedric