exec.c
for merge
update exception write check
for check merged result
Merge branch 'master' of https://github.com/popacai/TQOS

Conflicts:
	code/userprog/exception.cc
Merge branch 'master' of https://github.com/popacai/TQOS

Conflicts:
	code/userprog/exception.cc
exception.cc RW_bufck
Merge branch 'master' of https://github.com/popacai/TQOS