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.

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