Next up in Linux's boot sequence is a few things relating to processing the commandline args bootloaders like GRUB might give it.
The 1st of these is a routine for outputting those commandline arguments to the ringbuffer, possibly adding a relatively simple line-wrapping algorithm looking for whitespace.
The 2nd (via a call-once, arg-duplicating wrapper) parses certain commandline flags according to (via a callback) a compile-time generated lookuptable of options.
1/2?
I've described Linux's parser for commandline arguments earlier.
That parser's called again with callback that checks (via wrappers) a lookuptable for aliases, restores envvar syntax (via a helper), ignores the bootloader's prefixes, ignores anything with a "." in it, ignores if a `panic_later` flag's set, & appends to the appropriate array.
Then it might (if `panic_later`'s unset) sum up how much memory it needs & temporarily allocates it, concatenates those unknown options, & outputs them.