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 r262661:
Fix emulation of call and jmp instructions on i386 and for 32-bit processes
on amd64.

MFC r262542:
Move some files that are identical on i386 and amd64 to an x86 subdirectory
rather than keeping duplicate copies.

MFC r259535:
The fasttrap fork handler is responsible for removing tracepoints in the
child process that were inherited from its parent. However, this should
not be done in the case of a vfork, since the fork handler ends up removing
the tracepoints from the shared vm space, and userland DTrace probes in the
parent will no longer fire as a result.

Now the child of a vfork may trigger userland DTrace probes enabled in its
parent, so modify the fasttrap probe handler to handle this case and handle
the child process in the same way that it would handle the traced process.
In particular, if once traces function foo() in a process that vforks, and
the child calls foo(), fasttrap will treat this call as having come from the
parent. This is the behaviour of the upstream code.

While here, add #ifdef guards to some code that isn't present upstream.

MFC r257679: Use suword32 and suword64 instead of copyout(9) in fasttrap

MFC r257143: Fix a couple of bugs in the fasttrap emulation of a "push
%rbp" instruction

MFC kernel fixes to userland dtrace support.

r247049
-------
Avoid panic when tearing down the DTrace pid provider for a
process that has crashed.

sys/cddl/contrib/opensolaris/uts/common/dtrace/fasttrap.c:
In fasttrap_pid_disable(), we cannot PHOLD the proc
structure for a process that no longer exists, but
we still have other, fasttrap specific, state that
must be cleaned up for probes that existed in the
dead process. Instead of returning early if the
process related to our probes isn't found,
conditionalize the locking and carry on with a NULL
proc pointer. The rest of the fasttrap code already
understands that a NULL proc is possible and does
the right things in this case.

r247820
-------
Fix assertion failure when using userland DTrace probes from
the pid provider on a kernel compiled with INVARIANTS.

sys/cddl/contrib/opensolaris/uts/intel/dtrace/fasttrap_isa.c:
In fasttrap_probe_pid(), attempts to write to the
address space of the thread that fired the probe
must be performed with the process of the thread
held. Use _PHOLD() to ensure this is the case.

In fasttrap_probe_pid(), use proc_write_regs() instead
of calling set_regs() directly. proc_write_regs()
performs invariant checks to verify the calling
environment of set_regs(). PROC_LOCK()/UNLOCK() around
the call to proc_write_regs() so that it's invariants
are satisfied.

Sponsored by: Spectra Logic Corporation

MFC r227290 and r227291:

r227290:
Fix the DTrace pid return trap interrupt vector. Previously we were using
31, but that vector is reserved.

Without this fix, running dtrace -p <pid> would either cause the target
process to crash or the kernel to page fault

r227291:
Replace fasttrap_copyout() with uwrite(). FreeBSD copyout() is not able to
write to the .text section of a process.

Approved by: re (kib)

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

Approved by: re (implicit)

Revamp locking a bit. This fixes three problems:
* processes now can't go away while we are inserting probes (fixes a panic)
* if a trap happens, we won't be holding the process lock (fixes a hang)
* fix a LOR between the process lock and the fasttrap bucket list lock

Thanks to kib for pointing some problems.
Sponsored by: The FreeBSD Foundation

Remove debugging.

Sponsored by: The FreeBSD Foundation

MD fasttrap implementation.

Sponsored by: The FreeBSD Foundation

Merge from vendor-sys/opensolaris:
* add fasttrap files

Import fasttrap_isa.c from OpenSolaris.