Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

MFC r270247: MFV r270195:

Illumos issue:
5045 use atomic_{inc,dec}_* instead of atomic_add_*

MFC r264434:
DTrace's pid provider works by inserting breakpoint instructions at probe
sites and installing a hook at the kernel's trap handler. The fasttrap code
will emulate the overwritten instruction in some common cases, but otherwise
copies it out into some scratch space in the traced process' address space
and ensures that it's executed after returning from the trap.

In Solaris and illumos, this (per-thread) scratch space comes from some
reserved space in TLS, accessible via the fs segment register. This
approach is somewhat unappealing on FreeBSD since it would require some
modifications to rtld and jemalloc (for static TLS) to ensure that TLS is
executable, and would thus introduce dependencies on their implementation
details. I think it would also be impossible to safely trace static binaries
compiled without these modifications.

This change implements the functionality in a different way, by having
fasttrap map pages into the target process' address space on demand. Each
page is divided into 64-byte chunks for use by individual threads, and
fasttrap's process descriptor struct has been extended to keep track of
any scratch space allocated for the corresponding process.

With this change it's possible to trace all libc functions in a program,
e.g. with

pid$target:libc.so.*::entry {@[probefunc] = count();}

Previously this would generally cause the victim process to crash, as
tracing memcpy on amd64 requires the functionality described above.

MFC r268097:

MFV r260708
4427 pid provider rejects probes with valid UTF-8 names

This make use of Solaris' u8_validate() which we happen to
use since r185029 for ZFS.
Use of u8_textprep.c required -Wno-cast-qual for powerpc.

Illumos Revision: 1444d846b126463eb1059a572ff114d51f7562e5

Reference:
https://www.illumos.org/issues/4427

Obtained from: Illumos

MFC r268130, r268224, r268230, r268231:

Various DTrace Merges from OpenSolaris/Illumos:

15-Sep-2008:
6735480 race between probe enabling and provider registration

20-Apr-2008:
6822482 DOF validation needs to handle loadable sections flagged as unloadable

22-Apr-2009:
6823388 DTrace ioctl handlers must validate all structure members

30-Jun-2009:
6851093 system drops to kmdb with anonymous dtrace probes + kmdb

Obtained from: OpenSolaris

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

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

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

fasttrap_fork(): unlock the processes before removing the tracepoints.

In the future, we'll need to come up with new proc_*() functions that accept
locked processes. For now, this prevents postgresql + DTrace from crashing the
system.

MFC after: 1 month

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

Sponsored by: HybridCluster
MFC after: 7 days

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

Reviewed by: rpaulo
MFC after: 1 month

Dtrace: enablings on defunct providers prevent providers from unregistering

Merge change from illumos:

1368 enablings on defunct providers prevent providers from unregistering

We try to address some underlying differences between the Solaris
and FreeBSD implementations: dtrace_attach() / dtrace_detach() are
currently unimplemented in FreeBSD but the new code from illumos
makes use of taskq so some adaptations were made to dtrace_open()
and dtrace_close() to handle them appropriately.

Illumos Revision: r13430:8e6add739e38

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

Reviewed by: gnn
Tested by: Fabian Keil
Obtained from: Illumos
MFC after: 3 weeks

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.

Sponsored by: Spectra Logic Corporation
Reviewed by: rpaulo, gnn
MFC after: 1 week

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.