Starting a user program from the Pre-loader.

There is common way right? You may bring the path and application name to the kernel as a boot parameter for init, then kernel will only start the init process itself

try look at this(see: http://en.wikipedia.org/wiki/linux_startup_process). Traditionally this application then handles starting daemons, geTTYs, etc.

Most boot loaders allow you to specify a path for the init app as part of the configuration for where to find the kernel.

as example:- /boot/vmlinuz-n.n.n init=/path/to/theapp