Because limit gives the address of the last addressable
byte in the segment, the limit argument to SEG16 and SEG
needs to have 1 subtracted from it.

bug in proc_wait

lots of cleanup

idecref cwd in exit

delete unused functions
a few comments

test malloc

nit in sbrk
indirect block
fix dup to share fd struct

better parsing of sh commands (copied from jos sh)
cat: read from 1 if no args
sbrk system call, but untested
getpid system call
moved locks in keyboard intr, but why do we get intr w. null characters from keyboard?

cd in shell
nits in mkdir, ls, etc.

each cpu[] has its own gdt and tss
no per-proc gdt or tss, re-write cpu's in scheduler (you win, cliff)
main0() switches to cpu[0].mpstack

so fast interrupts overflow the kernel stack
fix: cli() before lapic_eoi()

give cpu1 a TSS and gdt for when it enters scheduler()
and a pseudo proc[] entry for each cpu
cpu0 waits for each other cpu to start up
read() for files