How do I compile my own uml?

Step 1: Get the uml patch for the appropriate kernel source you have.
Step 2: patch the kernel with the uml patch
Step3 run make xconfig or make menuconfig with the additional parameter ARCH=uml
Step 4: do a make dep; make ARCH=uml; make modules ARCH=uml

Step 1: Get the uml patch for the appropriate kernel source you have.