Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

MFC r230426:
Add support for the extended FPU states on amd64, both for native
64bit and 32bit ABIs. As a side-effect, it enables AVX on capable
CPUs.

MFC r230765:
Synchronize the struct sigcontext definitions on x86 with mcontext_t.

MFC r227399:
Attempt to improve formatting and content of several comments for
amd64 and i386 MD code.

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Add all segment registers for the amd64 CPU to struct reg and mcontext.
To keep these structures ABI-compatible, half the size of r_trapno,
r_err, mc_trapno, mc_flags.

Add fsbase and gsbase to mcontext on both amd64 and i386.
Add flags to amd64 mcontext to indicate that it contains valid segments
or bases.

In collaboration with: pho
Discussed with: peter
Reviewed by: jhb

Update the graffiti.

Rename npx* to fpu*. I haven't done the flags/function names yet.

Pull the tier-2 card one last time and break the get/setcontext and
sigreturn() ABI and the signal context on the stack.

Make the trapframe (and its shadows in the ucontext and sigframe etc)
8 bytes larger in order to preserve 16 byte stack alignment for the
following C code calls. I could have done some padding after the
trapframe was saved, but some of the C code still expects an argument of
'struct trapframe'. Anyway, this gives me a spare field that can be used
to store things like 'partial trapframe' status or something else in
the future.

The runtime impact is fairly small, *except* for threaded apps and things
that decode contexts and the signal stack (eg: cvsup binary). Signal
delivery isn't too badly affected because the kernel generates the
sigframe that sigreturn uses after the handler has been called.

The size of mcontext_t and struct sigframe hasn't changed. Only
the last few fields (sc_eip etc) got moved a little and I eliminated
a spare field. mc_len/sc_len did change location though so the
sanity checks there will still trap it.

Use __register_t instead of register_t, otherwise <sys/types.h> is a
prerequisite for <ucontext.h> on amd64. Oops.

Oops. sizeof(long) = 8, not 4. Get the fxsave buffer inside mcontext
the right size. I'm planning on *possibly* stealing the two 'spare'
variables on either side for botched alignment correction.

For the page fault handler, save %cr2 in the outer trap handler so that
we do not have to run so long with interrupts disabled. This involved
creating tf_addr in the trapframe. Reorganize the trap stubs so that
they consistently reserve the stack space and initialize any missing
bits.

Approved by: re (amd64 stuff)

Sync ucontext with reality. The struct trapframe changes need to be
reflected here.

Approved by: re (blanket amd64/*)

Commit MD parts of a loosely functional AMD64 port. This is based on
a heavily stripped down FreeBSD/i386 (brutally stripped down actually) to
attempt to get a stable base to start from. There is a lot missing still.
Worth noting:
- The kernel runs at 1GB in order to cheat with the pmap code. pmap uses
a variation of the PAE code in order to avoid having to worry about 4
levels of page tables yet.
- It boots in 64 bit "long mode" with a tiny trampoline embedded in the
i386 loader. This simplifies locore.s greatly.
- There are still quite a few fragments of i386-specific code that have
not been translated yet, and some that I cheated and wrote dumb C
versions of (bcopy etc).
- It has both int 0x80 for syscalls (but using registers for argument
passing, as is native on the amd64 ABI), and the 'syscall' instruction
for syscalls. int 0x80 preserves all registers, 'syscall' does not.
- I have tried to minimize looking at the NetBSD code, except in a couple
of places (eg: to find which register they use to replace the trashed
%rcx register in the syscall instruction). As a result, there is not a
lot of similarity. I did look at NetBSD a few times while debugging to
get some ideas about what I might have done wrong in my first attempt.

Align the FPU state in the ucontext and sigcontext to 16 bytes
to accomodate the new SSE/XMM floating point save/restore
instructions.

This commit is mostly from bde and includes some style nits.

Approved by: re (jhb)

Add getcontext, setcontext, and swapcontext as system calls.
Previously these were libc functions but were requested to
be made into system calls for atomicity and to coalesce what
might be two entrances into the kernel (signal mask setting
and floating point trap) into one.

A few style nits and comments from bde are also included.

Tested on alpha by: gallatin

Split 4.x and 5.x signal handling so that we can keep 4.x signal
handling clean and functional as 5.x evolves. This allows some of the
nasty bandaids in the 5.x codepaths to be unwound.

Encapsulate 4.x signal handling under COMPAT_FREEBSD4 (there is an
anti-foot-shooting measure in place, 5.x folks need this for a while) and
finish encapsulating the older stuff under COMPAT_43. Since the ancient
stuff is required on alpha (longjmp(3) passes a 'struct osigcontext *'
to the current sigreturn(2), instead of the 'ucontext_t *' that sigreturn
is supposed to take), add a compile time check to prevent foot shooting
there too. Add uniform COMPAT_43 stubs for ia64/sparc64/powerpc.

Tested on: i386, alpha, ia64. Compiled on sparc64 (a few days ago).
Approved by: re

Add another temporary hack to allow running older i386 binaries.
This will be removed when new versions of syscalls sigreturn()
and sigaction() are added (mini is working on this but is in
the middle of a move).

This should fix the problem of cvsupd dying.

Add kernel support needed for the KSE-aware libpthread:
- Maintain fpu state across signals.
- Save and restore FPU state properly in ucontext_t's.

Reviewed by: deischen, julian
Approved by: -arch

Use a spare slot in the machine context for a flags word to indicate
whether the machine context is valid and whether the FPU state is
valid (saved).

Mark the machine context valid before copying it out when sending a
signal.

Approved by: -arch

Add a per-signal flag to mark handlers registered with osigaction, so we
can provide the correct context to each signal handler.

Fix broken sigsuspend(): don't use p_oldsigmask as a flag, use SAS_OLDMASK
as we did before the linuxthreads support merge (submitted by bde).

Move ps_sigstk from to p_sigacts to the main proc structure since signal
stack should not be shared among threads.

Move SAS_OLDMASK and SAS_ALTSTACK flags from sigacts::ps_flags to proc::p_flag.
Move PS_NOCLDSTOP and PS_NOCLDWAIT flags from proc::p_flag to procsig::ps_flag.

Reviewed by: marcel, jdp, bde

Simplification of the signal trampoline and other cleanups.

o Remove unused defines from genassym.c that were needed
by the trampoline.
o Add load_gs_param function to support.s that catches
a fault when %gs is loaded with an invalid descriptor.
The function returns EFAULT in that case.
o Remove struct trapframe from mcontext_t and replace it
with the list of registers.
o Modify sendsig and sigreturn accordingly.

This commit contains a patch by bde.

Reviewed by: luoqi, jdp

Re-introduction of sigcontext.

struct sigcontext and ucontext_t/mcontext_t are defined in such
a way that both (ie struct sigcontext and ucontext_t) can be
passed on to sigreturn. The signal handler is still given a
ucontext_t for maximum flexibility.

For backward compatibility sigreturn restores the state for the
alternate signal stack from sigcontext.sc_onstack and not from
ucontext_t.uc_stack. A good way to determine which value the
application has set and thus which value to use, is still open
for discussion.

NOTE: This change should only affect those binaries that use
sigcontext and/or ucontext_t. In the source tree itself
this is only doscmd. Recompilation is required for those
applications.

This commit also fixes a lot of style bugs without hopefully
adding new ones.

NOTE: struct sigaltstack.ss_size now has type size_t again. For
some reason I changed that into unsigned int.

Parts submitted by: bde
sigaltstack bug found by: bde

sigset_t change (part 3 of 5)
-----------------------------

By introducing a new sigframe so that the signal handler operates
on the new siginfo_t and on ucontext_t instead of sigcontext, we
now need two version of sendsig and sigreturn.

A flag in struct proc determines whether the process expects an
old sigframe or a new sigframe. The signal trampoline handles
which sigreturn to call. It does this by testing for a magic
cookie in the frame.

The alpha uses osigreturn to implement longjmp. This means that
osigreturn is not only used for compatibility with existing
binaries. To handle the new sigset_t, setjmp saves it in
sc_reserved (see NOTE).

the struct sigframe has been moved from frame.h to sigframe.h
to handle the complex header dependencies that was caused by
the new sigframe.

NOTE: For the i386, the size of jmp_buf has been increased to hold
the new sigset_t. On the alpha this has been prevented by
using sc_reserved in sigcontext.