Use strsep() to parse init_path in start_init().

[brooks]

Summary

This simplifies the use of the path variable by making it NUL
terminated. This is a prerequisite for further cleanups.

[brooks]

Developed on CheriBSD (mips64), testing in an amd64 VM including verifying that single user mode works.

Once this and D15468 are in, I have another change to remove the temporary mapping in the stack region and just construct a struct image_args here for kern_execve().

[imp]

Despite a couple grumbles, this looks good to my eye.

sys/kern/init_main.c

734

We don't have strdup?

769–770

are there any alignment requirements for ucp?

803

Kinda lame to free something just before panic :)

[brooks]

sys/kern/init_main.c

734

Hmm, I was sure we didn't, but we do. I'll switch.

769–770

Nope, it's just a bunch of strings in a row.

803

I debated this, but concluded that leak checkers would probably be happier without a path with no free.

[brooks]

• Use strdup().

[imp]

OK. Can't find anything else to argue with :)