It seems that Magic Lantern crew are trying to get Linux kernel running on various Canon bodies.
http://www.magiclantern.fm/forum/index.php?topic=14847
https://youtu.be/IcBEG-g5cJg
It is portable, the same binary runs on all ML-enabled cameras (confirmed for 60D, 600D, 7D, 5D2 and 5D3)
allocates all available RAM
prints debug messages on the camera screen
sets up timer interrupts for scheduling
mounts a 8 MiB ext2fs initial ramdisk
starts /bin/init from the initrd
this init process is a self-contained, libc-less hello world
next step: build userspace binaries (GUI, etc)
Lets not have DSLR viruses though!
Good things come to those who wait!