Update comment to reflect xv6 doesn't have per-cpu segments anymore

Eliminate code for gs trick to track per-cpu state. We rely on lapiccpunum()
to find a per-cpu id with which we locate a cpu's cpu struct.

One definition of several macros and constants

initproc, usegment, swtch tweaks

clean up %fs %gs use

sync with c; .text is implied

always save and restore %fs, %gs to ensure old segment entries are never
accessible to user from the hidden CPU segment registers.

nits

Replace yield system call with sleep.

formatting, fix comment

PDF at http://am.lcs.mit.edu/~rsc/xv6.pdf

Various changes made while offline.

+ bwrite sector argument is redundant; use b->sector.
+ reformatting of files for nicer PDF page breaks
+ distinguis

PDF at http://am.lcs.mit.edu/~rsc/xv6.pdf

Various changes made while offline.

+ bwrite sector argument is redundant; use b->sector.
+ reformatting of files for nicer PDF page breaks
+ distinguish between locked, unlocked inodes in type signatures
+ change FD_FILE to FD_INODE
+ move userinit (nee proc0init) to proc.c
+ move ROOTDEV to param.h
+ always parenthesize sizeof argument

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standardize various * conventions

spacing fixes: no tabs, 2-space indents (for rtm)

prune unneeded panics and debug output

Attempt to clean up newproc somewhat.

Also remove all calls to memcpy in favor of
memmove, which has defined semantics when
the ranges overlap. The fact that memcpy was
working in console.c to scro

Attempt to clean up newproc somewhat.

Also remove all calls to memcpy in favor of
memmove, which has defined semantics when
the ranges overlap. The fact that memcpy was
working in console.c to scroll the screen is not
guaranteed by all implementations.

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New scheduler.

Removed cli and sti stack in favor of tracking
number of locks held on each CPU and explicit
conditionals in spinlock.c.

no more big kernel lock
succeeds at usertests.c pipe test

Changes to allow use of native x86 ELF compilers, which on my
Linux 2.4 box using gcc 3.4.6 don't seem to follow the same
conventions as the i386-jos-elf-gcc compilers.
Can run make 'TOOLPREFIX=' or

Changes to allow use of native x86 ELF compilers, which on my
Linux 2.4 box using gcc 3.4.6 don't seem to follow the same
conventions as the i386-jos-elf-gcc compilers.
Can run make 'TOOLPREFIX=' or edit the Makefile.

curproc[cpu()] can now be NULL, indicating that no proc is running.
This seemed safer to me than having curproc[0] and curproc[1]
both pointing at proc[0] potentially.

The old implementation of swtch depended on the stack frame layout
used inside swtch being okay to return from on the other stack
(exactly the V6 you are not expected to understand this).
It also could be called in two contexts: at boot time, to schedule
the very first process, and later, on behalf of a process, to sleep
or schedule some other process.

I split this into two functions: scheduler and swtch.

The scheduler is now a separate never-returning function, invoked
by each cpu once set up. The scheduler looks like:

scheduler() {
setjmp(cpu.context);

pick proc to schedule
blah blah blah

longjmp(proc.context)
}

The new swtch is intended to be called only when curproc[cpu()] is not NULL,
that is, only on behalf of a user proc. It does:

swtch() {
if(setjmp(proc.context) == 0)
longjmp(cpu.context)
}

to save the current proc context and then jump over to the scheduler,
running on the cpu stack.

Similarly the system call stubs are now in assembly in usys.S to avoid
needing to know the details of stack frame layout used by the compiler.

Also various changes in the debugging prints.

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bug in trapret

compile "user programs"
curproc array

checkpoint. booting second processor. stack is messed up, but thanks to cliff
and plan 9 code, at least boots and gets into C code.

primitive fork and exit system calls

more or less take traps/interrupts

import