foget one thing .
i have done them with no errors . i figure out once in a way that , in my directory kernel 2.6.x , when use the new skas kernel, i can excute "make help" , but out the directory,
excute "make" seems works ,and uml core "linux" can excute without any errors (haven't make "linux" work with rootfs) ,and i tried to download a sourceball , bridge . tried to compile it .
but got segmentation fault too.