Congratulations!
"Segmentation Fault" has gone away:)
Here are my problems:
[1] while compiling Plan9_binary as a module, i got the "undefined reference to" errors but build-in kernel -- no such errors
[2] cat runs smoothly but leaves a small nitpick
$ ./cat test
9load: 1000 5daf 6000 69a0 6cb4 0 926a
9load: Read 3252!
9load: BPRM Value: bffffd8b
9load: Stack start: bffffd40, TOS: bffffd50
Hello, Plan9!
BUG: Bad page state in process swapper pfn:0e962
page: c11d2c40 flags: 40000000 count:0 mapcount:-2 mapping:(null) index:ce962fa3