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

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

- Add minidump support for FreeBSD/mips

PowerPC, meet kernel core dumps. The support is based
on a generic dumper that creates an ELF core file and
uses PMAP functions to scan and iterate over memory
chunks, as well as handle memory mappings used during
dumping.
the PMAP layer can choose to return physical memory
chunks or virtual memory chunks. For minidumps, the
chunks should be virtual.

The default MMU I/F implementation for the scan_md()
method returns NULL. Thus, when a PMAP implementation
does not implement the required methods, an empty
core file is created. Here, empty means having an ELF
header only.

Obtained from: Juniper Networks

Collect N identical (or near identical) mkdumpheader() implementations into
one, as threatened in the comment. Textdump magic can be passed in.

Define a new kernel dump "architecture", TEXTDUMPMAGIC, which is used
to identify textdumps in the swap/dump partition. While textdumps
aren't really an architecture, they are architecture-neutral and so
don't really correspond to any existing architecture.

Define a version number for textdumps, KERNELDUMP_TEXT_VERSION, of 1.

MFC after: 3 months

Minor style consistency improvements.

Define KERNELDUMP_ARM_VERSION.

Switch AMD64 and i386 platforms to using ELF as their kernel crash
dump format. The key reason to do this is so that we can dump sparse
address space. For example, we need to be able to skip the PCI hole
just below the 4GB boundary. Trying to destructively dump MMIO device
registers is Really Bad(TM). The frequent result of trying to do a
crash dump on a machine with 4GB or more ram was ugly (lockup or reboot).

This code has been taken directly from the IA64 dump_machdep.c code,
with just a few (mostly minor) mods.

Introduce a dump_avail[] array in the machdep.c code so that we have a
source of truth for what memory is present in a machine that needs to be
dumped. We can't use phys_avail[] because all sorts of things slice
memory out of it that we really need to dump. eg: the vm page array
and the dmesg buffer. dump_avail[] is pretty much an unmolested version
of phys_avail[]. It does have Maxmem correction.

Bump the i386 and amd64 dump format to version 2, but nothing actually
uses this. amd64 was actually using the i386 dump version number.

libkvm support to follow.

Approved by: re

Add kernel dump support, based on the ia64 version (which was committed
as sparc64/sparc64/dump_machdep.c a while back).
Other than ia64 (which uses ELF), sparc64 uses a homegrown format for
the dumps (headers are required because the physical address and size of
the tsb must be noted, and because physical memory may be discontiguous);
ELF would not offer any advantages here.

Reviewed by: jake

Restore the ability to take crashdumps on alpha. This was cut and pasted
nearly in its entirety from i386, so it retains the phk/nati copyright.

Savecore likes the results, but I have no way to test it as gdb is
still broken.

Add a KERNELDUMPMAGIC_CLEARED macro to unbreak savecore. Since
it is a "magic" value, what it expands to is not really important.
I set it to "Cleared Kernel Dump", but that can be changed later
if someone thinks it's not good enough.

Pointy hat to: fenner

Make the kernel dump header endianness invariant by always dumping
in dump byte order (=network byte order). Swap blocksize and dumptime
to avoid extraneous padding on 64-bit architectures. Use CTASSERT
instead of runtime checks to make sure the header is 512 bytes large.
Various style(9) fixes.

Reviewed by: phk, bde, mike

o Add header version for ia64,
o Make it compile with GCC 3.x.

Add a new #include which describes the common header format for kerneldumps.

This design is my best effort and it is quite likely that people more used
to kernel dumps may want to change this subsequently so two levels of
version numbers are provided: one for the common header and one per
architecture.

Sponsored by: DARPA & NAI Labs.