Rump (Runnable Userspace Meta Program) is a mechanism for running kernel code
as part of a user program's address space. As opposed to executing system calls
for requesting kernel services, rump programs do a library call into the kernel
code for equivalent functionality. Kernel code is simply recompiled as a
userspace shared library from the kernel sources instead of being rewritten,
so services imitate the same services being provided by the kernel. Select
architectures such as i386 and amd64 also support directly linking binary
kernel modules against rump programs.

WWW: http://www.rumpkernel.org