MFC r326276:

various: general adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

No functional change intended.

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

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

Fix conditional expression: previously a bit vector was being operated
on by a logical not instead of the entire expression.

Approved by: cperciva
MFC after: 3 days

Mark global functions and/or variables in memcontrol(8) static where possible.

This allows compilers and static analyzers to do more thorough analysis.

Correct formatting of pointers in the listing by using "0x%" PRIx64 instead of
"%" PRIu64 "x".

WARNS=6 cleanup. This includes:
- Apply __unused on unused parameters
- Use const where suitable
- Use PRIu64 instead of the deprecated %q
- Bump WARNS to 6

Some BIOSs are using MTRR values that are only documented under NDA
to control the mapping of things like the ACPI and APM into memory.

The problem is that starting X changes these values, so if something
was using the bits of BIOS mapped into memory (say ACPI or APM),
then next time they access this memory the machine would hang.

This patch refuse to change MTRR values it doesn't understand,
unless a new "force" option is given. This means X doesn't change
them by accident but someone can override that if they really want
to.

PR: 28418
Tested by: Christopher Masto <chris@netmonger.net>,
David Bushong <david@bushong.net>,
Santos <casd@myrealbox.com>
MFC after: 1 week

Make the MTRR code a bit more defensive - this should help people
trying to run X on some Athlon systems where the BIOS does odd things
(mines an ASUS A7A266, but it seems to also help on other systems).

Here's a description of the problem and my fix:

The problem with the old MTRR code is that it only expects
to find documented values in the bytes of MTRR registers.
To convert the MTRR byte into a FreeBSD "Memory Range Type"
(mrt) it uses the byte value and looks it up in an array.
If the value is not in range then the mrt value ends up
containing random junk.

This isn't an immediate problem. The mrt value is only used
later when rewriting the MTRR registers. When we finally
go to write a value back again, the function i686_mtrrtype()
searches for the junk value and returns -1 when it fails
to find it. This is converted to a byte (0xff) and written
back to the register, causing a GPF as 0xff is an illegal
value for a MTRR byte.

To work around this problem I've added a new mrt flag
MDF_UNKNOWN. We set this when we read a MTRR byte which
we do not understand. If we try to convert a MDF_UNKNOWN
back into a MTRR value, then the new function, i686_mrt2mtrr,
just returns the old value of the MTRR byte. This leaves
the memory range type unchanged.

I have seen one side effect of the fix, which is that ACPI calls
after X has been run seem to hang my machine. As running X would
previously panic the machine, this is still an improvement ;-)

I'd like to MFC this before the 4.6 code freeze - please let me
know if it causes any problems.

PR: 28418, 25958
Tested by: jkh, Christopher Masto <chris@netmonger.net>
MFC after: 2 weeks

Nuke unused variables.

Add `_PATH_DEVZERO'.
Use _PATH_* where where possible.

Make memcontrol(8) able to delete the segments starting at a base of 0
which it can create..

$Id$ -> $FreeBSD$

Make memcontrol's internal help actually work. No substitute for a real
manpage, but at least now you can get syntax help without resorting
to reading the source.

This commit was generated by cvs2svn to compensate for changes in r45410,
which included commits to RCS files with non-trunk default branches.

Commandline tool for manipulating memory range attributes.