UNIX for Dummies Questions & Answers

can anyone tell me how loadable kernel modules work. I know they are loaded into the kernel to extend the kernel's functionality but the part that I don't understand is how they are loaded. I thought the kernel was a fixed length after compilation. So what I want to know is the processes the kernel module goes through in order to be loaded.
Thanks.

They reside outside the kernel still, they don't have to be inside the kernel's fixed length. The kernel allocates memory pages outside itself to hold them, and marks them executable so it can run instructions inside them, and keeps pointers so it knows where they are. There's a lot of alignment and fiddly things to consider in order to make sure you're loading the right data into the right memory the right way, but at base that's all it has to do -- put the data in some other memory.