Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

According to a clarification at http://austingroupbugs.net/view.php?id=503
ptsname may set errno, so avoid saving and restoring errno across the
function.

PR: standards/171572

mdoc: order prologue macros consistently by Dd/Dt/Os

Although groff_mdoc(7) gives another impression, this is the ordering
most widely used and also required by mdocml/mandoc.

Reviewed by: ru
Approved by: philip, ed (mentors)

Our implementation of granpt(3) could be valid in the future.

When I wrote the pseudo-terminal driver for the MPSAFE TTY code, Robert
Watson and I agreed the best way to implement this, would be to let
posix_openpt() create a pseudo-terminal with proper permissions in place
and let grantpt() and unlockpt() be no-ops.

This isn't valid behaviour when looking at the spec. Because I thought
it was an elegant solution, I filed a bug report at the Austin Group
about this. In their last teleconference, they agreed on this subject.
This means that future revisions of POSIX may allow grantpt() and
unlockpt() to be no-ops if an open() on /dev/ptmx (if the implementation
has such a device) and posix_openpt() already do the right thing.

I'd rather put this in the manpage, because simply mentioning we don't
comply to any standard makes it look worse than it is. Right now we
don't, but at least we took care of it.

Approved by: re (kib)
MFC after: 3 days

Our grantpt(3) and unlockpt(3) don't comply with POSIX.

Clean out some empty mergeinfo records, presumably by people doing local
cp/mv operations. The full repo-relative URL should be specified for the
source in these cases.

Integrate the new MPSAFE TTY layer to the FreeBSD operating system.

The last half year I've been working on a replacement TTY layer for the
FreeBSD kernel. The new TTY layer was designed to improve the following:

- Improved driver model:

The old TTY layer has a driver model that is not abstract enough to
make it friendly to use. A good example is the output path, where the
device drivers directly access the output buffers. This means that an
in-kernel PPP implementation must always convert network buffers into
TTY buffers.

If a PPP implementation would be built on top of the new TTY layer
(still needs a hooks layer, though), it would allow the PPP
implementation to directly hand the data to the TTY driver.

- Improved hotplugging:

With the old TTY layer, it isn't entirely safe to destroy TTY's from
the system. This implementation has a two-step destructing design,
where the driver first abandons the TTY. After all threads have left
the TTY, the TTY layer calls a routine in the driver, which can be
used to free resources (unit numbers, etc).

The pts(4) driver also implements this feature, which means
posix_openpt() will now return PTY's that are created on the fly.

- Improved performance:

One of the major improvements is the per-TTY mutex, which is expected
to improve scalability when compared to the old Giant locking.
Another change is the unbuffered copying to userspace, which is both
used on TTY device nodes and PTY masters.

Upgrading should be quite straightforward. Unlike previous versions,
existing kernel configuration files do not need to be changed, except
when they reference device drivers that are listed in UPDATING.

Obtained from: //depot/projects/mpsafetty/...
Approved by: philip (ex-mentor)
Discussed: on the lists, at BSDCan, at the DevSummit
Sponsored by: Snow B.V., the Netherlands
dcons(4) fixed by: kan

Get rid of duplicates.

Assorted mdoc(7) fixes.

Implement POSIX grantpt(3) functionality, and add a pt_chown utility (akin
to Solaris, it is in /usr/libexec) to perform the handing over of tty nodes
to the user being granted the pty.

Submitted by: Ryan Younce <ryany@pobox.com>
Reviewed by: security-officer@, standards@, mike@