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 r258291: change the ioctl definition so that the fasttrap ioctl
handler is responsible for copying in userland data

MFC r258311

opensolaris/uts/common/dtrace/fasttrap.c
Fix several problems that can cause panics on kldload and kldunload.

* kproc_create(fasttrap_pid_cleanup_cb, ...) gets called before
fasttrap_provs.fth_table gets allocated. This can lead to a panic
on module load, because fasttrap_pid_cleanup_cb references
fasttrap_provs.fth_table. Move kproc_create down after the point
that fasttrap_provs.fth_table gets allocated, and modify the error
handling accordingly.

* dtrace_fasttrap_{fork,exec,exit} weren't getting NULLed until
after fasttrap_provs.fth_table got freed. That caused panics on
module unload because fasttrap_exec_exit calls
fasttrap_provider_retire, which references
fasttrap_provs.fth_table. NULL those function pointers earlier.

* There wasn't any code to destroy the
fasttrap_{tpoints,provs,procs}.fth_table mutexes on module unload,
leading to a resource leak when WITNESS is enabled. Destroy those
mutexes during fasttrap_unload().

Sponsored by: Spectra Logic Corporation

MFC r250953:
The fasttrap provider cleans up probes asynchronously when a process with
USDT probes exits. This was previously done with a callout; however, it is
possible to sleep while holding the DTrace mutexes, so a panic will occur
on INVARIANTS kernels if the callout handler can't immediately acquire one
of these mutexes. This panic will be frequently triggered on systems where
a USDT-enabled program (perl, for instance) is often run.

This revision changes the fasttrap cleanup mechanism so that a dedicated
thread is used instead of a callout. The old behaviour is otherwise
preserved.

MFC r252493:
Be sure to destory the fasttrap cleanup mutex when unloading the fasttrap
module. This should be MFCed with r250953.

MFC r253079: dtrace/fasttrap: install hook functions only after all data
is initialized

Approved by: re (marius)

MFC r248983:
Dtrace: enablings on defunct providers prevent providers from unregistering

Merge change from illumos:

1368 enablings on defunct providers prevent providers from unregistering

Illumos Revision: 13430:8e6add739e38

Reference:
https://www.illumos.org/issues/1368

Reviewed by: gnn
Tested by: Fabian Keil
Obtained from: Illumos

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

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

Avoid a LOR (sleepable after non-sleepable) in
fasttrap_tracepoint_enable().

Sponsored by: The FreeBSD Foundation

Fix two bugs in DTrace:
* when the process exits, remove the associated USDT probes
* when the process forks, duplicate the USDT probes.

Sponsored by: The FreeBSD Foundation

Replace a memory barrier with a mutex barrier.

Sponsored by: The FreeBSD Foundation

Replace a pksignal() call with tdksignal().

Pointed out by: kib

Port the fasttrap provider to FreeBSD. This provider is responsible for
injecting debugging probes in the userland programs and is the basis for
the pid provider and the usdt provider.

Sponsored by: The FreeBSD Foundation

Merge latest DTrace changes from Perforce.

FreeBSD changes to vendor source.

This commit was generated by cvs2svn to compensate for changes in r179193,
which included commits to RCS files with non-trunk default branches.

Vendor import of the src/sys OpenSolaris bits for DTrace.