renumber system calls (run gmake clean!)
skeleton for dup system call

don't hold fd table lock across idecref() (latter does block i/o)
idecref calls iput() in case last ref -> freeing inode
dir size is 512 * # blocks, so readi/writei &c work
unlink deletes dirent even if ip->nlink > 0

primitive ls

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

convert userfs to use printf
bfree
ifree
writei
start on unlink

checkpoint: write(fd,"hello\n",6) where fd is a console dev almost works

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

Rename fd_reference to more suggestive fd_incref.
(Fd_reference sounds like it might just return the ref count.)

succeeds at usertests.c pipe test

swtch idles on per-CPU stack, not on calling process's stack
fix pipe bugs
usertest.c tests pipes, fork, exit, close

pipes