fixed some omitted merge
ex1 mark
find a bug in user_mem_check and try getting fixed
ex2 mark
ex3 mark
tmp mark
ex4 mark
ex5 mark
fixed a bug in user_mem_check
ex6 mark
ex8 mark, part B finished
fixed bug in SETGATE while I don't know why.
lab4 finished (in hurry)
Merge branch 'lab4'