I realize that this thread is old, but it is still useful to correct an erroneous assertion about inb(), outb(), etc., especially given that Google drops people in here when looking for an answer to why these functions segfault, even when all the advice featured elsewhere is followed.
The truth is that these functions do in fact work, even under the most recent versions of the kernel (as of 8/11/09). However, they will not work from a user mode program unless the program is run as root (sudo...). It is also true that they will segfault if iopl(3) is not used. iopl(2) is not good enough. It is also true that the method of using ioperm() fails, apparently no matter how it is used. This may have worked in older kernels, but it now always gives a segfault. The only means of using these function seems to be calling iopl(3) first. (Ubuntu Interpid, 2.6.28-15-generic, x86_64 GNU/Linux)