From time to time a buddy of mine who's not a professional software developer asks questions that are interesting albeit they go against the grain of UN*X programming.
This time he asked whether printk is accessible to user-mode applications. As per entry.S it does not but the guy is stubborn so I got bored explaining the impossibility I got to work and wrote a Linux kernel module that allows him to fulfill his fantasy.
The technical article is here: http://spamchk.no-ip.org/uprintk.html. The source code is here.