Fix: stream fd leaks on error

Use a regular pattern for all commands:

If the command callback takes ownership of a pointer or file descriptor,
it sets them to NULL or -1. Therefore, the caller can always try to free
the pointer, or close it if it is greater or equal to 0.

This eliminates memory and fd leaks on error.

Change-Id: I447129ab1672ce4fc6cf3c0baf18dbf27bfcfaf8
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: channel leak on error

Use a regular pattern for all commands:

If the command callback takes ownership of a pointer or file descriptor,
it sets them to NULL or -1. Therefore, the caller can always try to free
the pointer, or close it if it is greater or equal to 0.

This eliminates memory and fd leaks on error.

Change-Id: I0f9cba5fc0f4c095c8ec8f3e8970de8a10386876
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: lttng_abi_map_channel should be static

Change-Id: If0434525f083dc20b50a7628926dadb483d30c88
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: Use default visibility for tracepoint provider symbol

When building a probe provider `someprobe` with -fvisibility=hidden into
a shared library, the `__tracepoint_provider_someprobe` symbol is hidden,
which does not allow tracepoint instrumentation to link to it.

Fix this by using the "default" visibility attribute.

For a shared library built with -fvisibility=hidden, this changes the
output of nm for that symbol from:

000000000000417c b __tracepoint_provider_someprobe

(local BSS symbol)

to

000000000000417c B __tracepoint_provider_someprobe

(global (external) BSS symbol)

Fixes: #1296
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I308374f6cac58cca86e8eb19c872286a3da21a75

Fix: configure: support Autoconf 2.70

The newly-released autoconf 2.70 introduces a number of breaking
changes [1] and is being rolled-out by some distros.

Amongst those changes, the AC_PROG_CC_STDC macro is marked as obsolete
and was merged into AC_PROG_CC, which we already use. On 2.70, this
results in a warning which we handle as an error.

A version check is added to invoke the AC_PROG_CC_STDC macro only when
running a pre-2.70 version of autoconf, fixing the issue.

Also, the AX_PTHREAD macro makes use of the $as_echo built-in shell
variable which no longer exists in 2.70. A patch was submitted to the
GNU Autoconf archive in March, but there have been no signs of life
given since then [2].

As such, our local copy is updated to the latest version and the patch
(which looks fairly straight-forward / safe) is applied. This should
minimize changes once we go back to an "official" version of the macro.

[1] https://lwn.net/Articles/839395/
[2] https://savannah.gnu.org/patch/?9906

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I2f4eac788638924aa4960b54374d09de73957925

Fix: event notifier create protocol order issue

sessiond needs to send the additional command payload before awaiting
reply from UST.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I4d046e3fd2f334d728d4310ceb2b003f6bf0abed

Fix: lttng-ust 2.13 should not try to use notifiers from 2.12 or prior probes

Probe providers built against lttng-ust 2.12 or prior do not implement
the event notifier callback, and accessing desc->u.ext.event_notifier_callback
accesses beyond the size of struct lttng_event_desc.

Therefore, skip those older probe providers from the list of providers
considered for event notifications, and print an error when this
situation is encountered.

Currently, the error reporting of lttng-ust is performed through ERR(),
which is only observable on the console of the application when run with
LTTNG_UST_DEBUG=1.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Change-Id: Ia8a9bae1a471ae5d30ff0364b28e1cd3a8b4e396

Fix: UST comm protocol: event notifier command is too large

The event notifier command is larger than the current largest command,
and we don't want to break the protocol between UST and tools
needlessly.

Therefore, pass the struct lttng_ust_event_notifier _after_ struct
ustcomm_ust_msg.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Change-Id: Ief172eaddd113ec9092dd57bad3d73fd4c29fd51

Fix: incorrect parameters passed to vtracelog

The vtracelog APIs should be called from the vtracelog instrumentation
rather than the "tracelog" APIs, because it passes a va_list rather than
a variable argument list (...).

This can be verified by tracing the demo program doc/examples/demo-tracelog/demo-vtracelog:

Issue (corrupted trace output):

16:17:26.686073539] (+0.000000530) thinkos lttng_ust_tracelog:TRACE_ERR: { cpu_id = 2 }, { line = 31, file = "demo-vtracelog.c", func = "print_err", _msg_length = 49, msg = "This is a \"\b\" formatted 638975520 error event d68" }

Fixed:

[16:23:33.538189343] (+0.000000600) thinkos lttng_ust_tracelog:TRACE_ERR: { cpu_id = 3 }, { line = 31, file = "demo-vtracelog.c", func = "print_err", _msg_length = 52, msg = "This is a \"mystring test\" formatted 4 error event 42" }

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I330e339a3bf68fb8d9779bbc71b08c3bc033ac4e

event-notifier: Initialize `_notifier_notification` struct to zero

Valgrind reports the following use of uninitialized bytes:

  ==2233138== Syscall param writev(vector[...]) points to uninitialised byte(s)
  ==2233138==    at 0x4EA161D: __writev (writev.c:26)
  ==2233138==    by 0x4EA161D: writev (writev.c:24)
  ==2233138==    by 0x489A9EC: patient_writev (in /usr/local/lib/liblttng-ust.so.0.0.0)
  ==2233138==    by 0x48C2D5F: lttng_event_notifier_notification_send (in /usr/local/lib/liblttng-ust.so.0.0.0)
  ==2233138==    by 0x4033F3: __event_notifier_probe__tp___tptest (in /home/frdeso/projets/lttng/tools/tests/utils/testapp/gen-ust-events/gen-ust-events)
  ==2233138==    by 0x401D6E: main (in /home/frdeso/projets/lttng/tools/tests/utils/testapp/gen-ust-events/gen-ust-events)
  ==2233138==  Address 0x1ffeffedda is on thread 1's stack
  ==2233138==  in frame #2, created by lttng_event_notifier_notification_send (???:)
  ==2233138==

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I49ac4b440df61b322ac9614b09c32d1f69beedd0

Add tests/unit/libmsgpack/test_msgpack to gitignore

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I8d838f961414ee996a4a63c9270fd26ef8ba0e02

ustctl.h: use enumeration values 0, 1 for bitness

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I915d3bad476f1b11b3c972f6bb60162f3f93d519

ust-abi: use 0, 1 for counter enumerations

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Cleanup: ust-abi: BITNESS_{32,64}BITS -> BITNESS_{32,64}

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I5175116ec93d61fe55d1c17e2e2b99b02a0e73a9

Cleanup: use tabs in ust-abi.h

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I62dcdf8bd833a04501b1088c397ca42999cf8d61

Fix: add struct lttng_event_notifier forward declaration

Add struct lttng_event_notifier forward declaration in
lttng-tracer-core.h.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I1904be0b9170979c0e3c53ce4b8dbd966a8dd04d

Fix: event notifier: notification send should be a callback

Turn notification send into a callback so probes compiled against
lttng-ust 2.13+ but executed in an environment with lttng-ust 2.12 or
prior don't trigger linker error due to missing
lttng_event_notifier_notification_send symbol.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ib51fdc09865f8ae158129417b9e26e86221881b0

Fix: ust-urcu: allow legacy applications without _LGPL_SOURCE

Allow legacy instrumented applications without _LGPL_SOURCE to
use the legacy v1 tracepoint registration API without requiring
the liburcu-bp symbols to be present in the symbol table.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Iaa574647442254b34682ea36b858a30e2ecdf98e

Fix: ust-tracepoint: make sure to expand tracepoint provider token

Using a #defined TRACEPOINT_PROVIDER with the
TRACEPOINT_EVENT_{CLASS,INSTANCE}() macros led to compilation errors,
e.g.:

gcc -I/home/chris/lttng-mwe/app/../lib -c myapp.c
gcc -o myapp myapp.o -L/home/chris/lttng-mwe/app/../lib -Wl,-rpath=/home/chris/lttng-mwe/app/../lib -lmytps -ldl
/usr/bin/ld: /home/chris/lttng-mwe/app/../lib/libmytps.so: undefined reference to `__tracepoint_provider_mismatch_TRACEPOINT_PROVIDER'
collect2: error: ld returned 1 exit status
make: *** [Makefile:9: myapp] Error 1

Use intermediate TRACEPOINT_EVENT_{CLASS,INSTANCE}() macros to make sure
that the tracepoint provider name token gets expanded.

[ Mathieu: Adapt event notifier probes as well. ]

Fixes: #1273
Signed-off-by: Christophe Bedard <bedard.christophe@gmail.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I68550a510c809f1d5f86a7e1d966dcecc3780dda

Fix: notifier: use store-release/load-acquire for error counter

The "record_error" operation is executed concurrently with setting the
error counter in the notifier group without locking, so we need to
explicitly provide existance guarantees.

The only visible transition is from NULL -> !NULL, because the only
situation reverting the error counter back to NULL is on destruction of
the notification group, after an RCU synchronisation guarantees that no
record_error can observe this pointer anymore.

Use the stronger "cmm_smp_mb()" to provide store-release/load-acquire
semantics because the explicit store-release and load-acquire are not
implemented in the CMM model yet.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I3bbeecc00ff33c5d8ad1e3fd41c8a0dc866f1943

Fix: event-notifier: Groups may not have an error counter

Issue
=====
If no error counter is attached to an event notifier group, calling
the `record_error()` function leads to a NULL pointer dereference.

Solution
========
Check if the error_counter field is allocated before dereferencing it.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I124519d37efe8eb20296cfd74027642c8e8162a5

ustctl: Initialize counter_conf struct to zero

Issue
=====
This struct is not initialize explicitly and is copied and sent through
a Unix socket to the application. This means we are currently sending
uninitialized data.

Valgrind reports the following:
  ==939806== Syscall param sendmsg(msg.msg_iov[0]) points to uninitialised byte(s)
  ==939806==    at 0x519412D: __libc_sendmsg (sendmsg.c:28)
  ==939806==    by 0x519412D: sendmsg (sendmsg.c:25)
  ==939806==    by 0x514D2BF: ustcomm_send_unix_sock (in /usr/local/lib/liblttng-ust-ctl.so.4.0.0)
  ==939806==    by 0x514C0BC: ustctl_send_counter_data_to_ust (in /usr/local/lib/liblttng-ust-ctl.so.4.0.0)
  ==939806==    by 0x4A0B14: send_counter_data_to_ust (event-notifier-error-accounting.c:237)
  ==939806==    by 0x4A046D: event_notifier_error_accounting_register_app (event-notifier-error-accounting.c:311)
  ==939806==    by 0x4B0831: ust_app_setup_event_notifier_group (ust-app.c:3956)
  ==939806==    by 0x495603: thread_dispatch_ust_registration (dispatch.c:394)
  ==939806==    by 0x487552: launch_thread (thread.c:66)
  ==939806==    by 0x5188608: start_thread (pthread_create.c:477)
  ==939806==    by 0x52E2292: clone (clone.S:95)
  ==939806==  Address 0x750fb8e is 46 bytes inside a block of size 228 alloc'd
  ==939806==    at 0x483DD99: calloc (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
  ==939806==    by 0x514988C: ustctl_duplicate_ust_object_data (in /usr/local/lib/liblttng-ust-ctl.so.4.0.0)
  ==939806==    by 0x4A0426: event_notifier_error_accounting_register_app (event-notifier-error-accounting.c:307)
  ==939806==    by 0x4B0831: ust_app_setup_event_notifier_group (ust-app.c:3956)
  ==939806==    by 0x495603: thread_dispatch_ust_registration (dispatch.c:394)
  ==939806==    by 0x487552: launch_thread (thread.c:66)
  ==939806==    by 0x5188608: start_thread (pthread_create.c:477)
  ==939806==    by 0x52E2292: clone (clone.S:95)

Fix
===
Initialize it to zero.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I8ce4753858a3ab3e12b94f26b94a200cef15cb06

cleanup: use <sys/syscall.h>

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I82f783fa131aa6337bc1cd7111bcd5ac85ec4d02

port: fix futex_async wrapper namespacing on FreeBSD

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I5db3fe8a596d273e6a693f3e89e26719c552f027

port: use ust-endian.h compat

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Id76539961e28a90bb7083a7a83eafd6d966cfb39

Fix: event-notifier: not propagating error counter indexes

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ie2936cd59e81410891c0fa87602d1b24132d1e35

fix: undefined symbols for tracepoints in lgpl source

Move the new internal 'urcu-ust' urcu flavor symbols to a separate
library named 'liblttng-ust-common.so' and link 'liblttng-ust.so' and
'liblttng-ust-tracepoint.so' on it.

Add this common library to the pkgconfig file which should handle the
transition for client code using it in its build system.

LGPL_SOURCE client code which doesn't use pkgconfig in its build system
will need to link with '-llttng-ust-common' instead of '-lurcu-bp' like
prior ust versions.

Change-Id: I807f997a2a94cb4f8d1bdf72002c1ae1b9fedf8d
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Remove runtime dependency on liburcu shared objects

Remove the runtime dependency on:

- liblurcu-bp.so
- liblurcu-cds.so
- compat futex code.

By integrating those into the lttng-ust project.

For rculfhash, only the minimum pieces needed by lttng-ust are
integrated (no auto-resize, no accounting).

lttng-ust still requires liburcu at build time for header dependencies.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Idffb205b27b1bb0f972523c3ce3bdaf25bfe1710

Fix: handle default switch case with -EINVAL in __lttng_counter_add

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ie7cb76725789a75cfd7cf2bdb3031a81983ad146

Bump LTTNG_UST_EVENT_NOTIFIER_PADDING to 32 bytes

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Iad5de41f09c373cf1069e81996b1201e3c02e572

Fix: memory leak in apply_context_reloc

Fixes commit b77aaa1b8edf2 ("Decouple `struct lttng_session` from filter code")

lttng_ust_add_app_context_to_ctx_rcu should be able to update the
session ctx field and not only the local ctx pointer.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I1bfdc7a1a2b6f9c579206e996572e36bf30d60e7

Fix: libcounter bad compare

Identified by Coverity.

>>>     CID 1437325:  Incorrect expression  (BAD_COMPARE)
>>>     Comparing pointer "counter_cpu_fds" against "NULL" using anything besides "==" or "!=" is likely to be incorrect.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I0d21112a0266d67fafde7a6b81e0062a7a43dce0

Fix: remove dead code in msgpack.c

Identified by Coverity. Comparing unsigned types < 0 is never true.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ic623a5b15c7053844c8e3a0b374ac3b9b929c050

Fix: counter: cast UINT*_MAX to 64-bit signed type before negative

(long long)-UINT32_MAX leads to value 1 which is not what we expect.
This is due to implicit type promotion from unsigned to signed 32-bit
integer.

Apply this to 8-bit and 16-bit types as well even though they are
not affected by this issue to keep things regular.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I8e05f270eae71cb15848075c4dfae80e8070fd80

Fix: libcounter: use LTTNG_UST_ALIGN

ALIGN() on FreeBSD does not expect the same number of arguments.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I8ce4cc94bc840a11dc30ae0679f6b2c41e11bc12

Fix: ust-abi: clarify which command is used on which object descriptor

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: If0c874ec7c8061422706582fdb66838659f7b890

Implement event notifier error counter

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ia8008a162a1e4c881fdc948a390847cb5258e4f7

Implement libcounter

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I7bc2707e8bdea712addc84d90329486cda1a24e1

Implement capturing payload on event notifiers

This commit allows the user to request a subset of payload fields of the
tracepoint to be captured when a event notifier is fired and sent back
the session daemon as part of the notification.

Captures are really similar to filter in the way they work. Like with
filters, the sessiond attaches to a event notifier one bytecode program
per field it wants to capture using the following function:

  int ustctl_set_capture(int sock, struct lttng_ust_capture_bytecode *bytecode,
         struct lttng_ust_object_data *obj_data);

The capture bytecode program is then validated and specialized for its
target tracepoint just like filter bytecode programs.

The major difference between filters and captures is with what they
return. Filters can only return _RECORD or _DISCARD for match and
no-match respectively. Captures also need to return captured values. For
this reason, we added an output parameter to the capture interpreter
function that value can be extracted.

Here is the signature of the capture interpreter function:
  uint64_t lttng_bytecode_capture_interpret(void *capture_data,
         const char *capture_stack_data,
         void *output)

When comes the time to send the notification, every capture bytecode
program is executed in turns and its output value is recorded to the
capture buffer to be sent back to the sessiond.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ia3023a4f5c0aec014b37b72f92d1a924c7eff6a2

bytecode: handle all integer types of dynamic contexts

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I86d24abd87bc6ed3fb2fbe659bc2bab877017c08

bytecode: initialize all contexts on event notifier group creation

Rename `lttng_session_context_init()` to `lttng_context_init_all()` so
to reuse the code.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: If80745677db993c1b38e158785886180d2e60d26

bytecode: Add `OBJECT_TYPE_{UN,}SIGNED_ENUM` type

Enumerations are currently converted to their integer counterparts as
soon as they are encountered.

In order to use them in captures, we need to differentiate the
enumerations from integers for the entirety of the interpretation.

This commit adds the `OBJECT_TYPE_SIGNED_ENUM` and
`OBJECT_TYPE_UNSIGNED_ENUM` to keep track of these objects.

Signed-off-by: Francis Deslauriers <fdeslaur@gmail.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I4b3ec8187a578ddc6c9d87f72d462441ba5e4a1e

Generalize `lttng_enabler_link_bytecode()` bytecode list

So it can be used for both filter and capture bytecode runtimes

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I61ac07545f8db2964f8ea0a7d40ec7be306efe90

Cleanup: rename `_lttng_filter_link_bytecode()` -> `link_bytecode()`

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ia4416b46b05869bb7ad4c754e8ff302762bfffb2

Add `interpreter_funcs` to `lttng_bytecode_runtime`

Background
==========
The current filter interpreter function signature looks like this:

  uint64_t lttng_bytecode_filter_interpret(void *filter_data,
                  const char *filter_stack_data);

The upcoming capture interpreter function will need an output parameter
to extract the top of stack register. It will look like this:

  uint64_t lttng_bytecode_capture_interpret(void *capture_data,
                  const char *capture_stack_data,
                  struct output_register *output);

Problems
========
We can't reuse the same function pointer field in `struct
lttng_bytecode_runtime` as the two interpreter functions will have
different signatures.

We can't change the signature of this existing filter function because
it's used in the tracepoint probes.

Solution
========
Add a union of callbacks to hold both interpreter functions. This also
doesn't change the layout of the `struct lttng_bytecode_runtime`
objects.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I9fcd6def9ce7783087b9648ddbf5ec71fb7b997a

bytecode: rename `lttng_filter_sync_state()` -> `lttng_bytecode_filter_sync_state()`

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I8d6386a087d5df1844bd157af571c08f41d54a9b

Implement enum and sequence capture serialization functions

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I9dff84b7213c68fbef1be582301d834720706726

Extract `handle_bytecode_recv()` function

A lot of this code will be reused for capture bytecode.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ib095033ae2b9dae6e8284ea4def0f7c69f688c63

Rename filter bytecode types and files

File renames:
- filter-bytecode.h -> bytecode.h
- lttng-filter-interpreter.c -> lttng-bytecode-interpreter.c
- lttng-filter-specialize.c -> lttng-bytecode-specialize.c
- lttng-filter-validator.c -> lttng-bytecode-validator.c
- lttng-filter.c -> lttng-bytecode.c
- lttng-filter.h -> lttng-bytecode.h

Function renames:
- `lttng_filter_interpret_bytecode_false()` -> `lttng_bytecode_filter_interpret_false()`
- `lttng_filter_interpret_bytecode()` -> `lttng_bytecode_filter_interpret()`
- `lttng_filter_specialize_bytecode()` -> `lttng_bytecode_specialize()`
- `lttng_filter_validate_bytecode()` -> `lttng_bytecode_validate()`

Type renames
- `filter_opcode_t` to `bytecode_opcode_t`

Enum renames:
- `enum filter_op` to `enum bytecode_op`
  - `FILTER_OP_*` to `BYTECODE_OP_*`
- `enum lttng_filter_ret` -> `enum lttng_bytecode_interpreter_ret`
  - `LTTNG_FILTER_DISCARD` -> `LTTNG_INTERPRETER_DISCARD`
  - `LTTNG_FILTER_RECORD_FLAG` -> `LTTNG_INTERPRETER_RECORD_FLAG`

Define renames:
- `FILTER_STACK_EMPTY` -> `INTERPRETER_STACK_EMPTY`
- `FILTER_STACK_LEN`-> `INTERPRETER_STACK_LEN`
- `FILTER_MAX_DATA_LEN` -> `BYTECODE_MAX_DATA_LEN`

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Iaab55116da5a3a8562b0f9e5b6033b556292f55b

bytecode: generalize `struct lttng_ust_filter_bytecode_node`

Rename `struct lttng_ust_filter_bytecode_node` to `struct
lttng_ust_bytecode_node` so it can be used by capture bytecode as well.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I0bb4ba4962601f1c83bf92494be4c47032f47db3

Cleanup: Rename filter functions/fields to mention "filter"

This will be cleaner when we introduce the capture bytecode functions
and fields.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I81a986386908212bf7a6814413204b54da6950c8

Add `patient_writev()` function

This function wraps the `writev()` function to make it EINTR-aware.

We are going to use this function to send multiple structs in a single
call when dealing with event notifier captures.

This function also supports partial writes even though this should never
happen with event notifier notification. We assert that the data sent is less
then PIPE_BUF in size so to take advantage of the POSIX guarantee for
write atomicity as explained in pipe(7).

The implementation was inspired by this stackoverflow.com post:
https://stackoverflow.com/questions/5853675/techniques-for-handling-short-reads-writes-with-scatter-gather

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ifd1def23f38ab95411fd4550858466451d0468ea

Add `libmsgpack` for serializing captures

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ice8ed791a0452ea9e659ffcaf9e081f47288e8d5

bytecode: allow interpreter to return any type

The bytecode interpreter when used by capture bytecode needs to return
types other than an integer or dynamic type.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ib93aaa8285ddd615b16dd6ebbf038f79880e25e8

bytecode: propagate `rev_bo` of element

When specializing and executing bytecode.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I9fc7381b397acdae02f87e941128ed89e12f7350

bytecode: set register type to `REG_PTR` even if not used

There was no need to set the field when using filter as the next
instruction would assume that the top of stack is a `REG_PTR`.

With the upcoming capture feature, we need to ensure this field is
consistent for extraction.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I8790618ddde23b29ef2a55698524c45b39ef4793

Add `lttng_bytecode_interpret_format_output()` for top of stack extraction

This new static function will be used to extract the register on the top of
stack after the execution of the bytecode. This is currently not used by the
filter bytecode but will be used by capture bytecode in the future.

The returned value is saved in a tagged union struct named `struct
lttng_interpreter_output` and can be used by the caller of the interpreter
function.

Typically, this struct will be allocated on the stack to avoid dynamic
allocation inside the tracepoint probes.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Id8a64d55f2bfb1af1657634a36d34dba5325777f

bytecode: add `REG_U64` interpreter register type

This will be used by the capture bytecode for unsigned integer
extraction.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I8ff7ec22eddcf3acb4a359ad398f97476dd079f2

Implement event notifier

The event notifier feature allows the user to get notify through a pipe
that an callsite was reached. It's really similar to a regular UST event
in that firing can be controlled by filters and exclusions. It diverges
because firing a event notifier does not end up writing to the tracing
buffers. In fact, event notifiers live outside of any sessions (i.e. no
session is needed).

Definitions
===========
A `Event notifier` is defined as an event description (event name, log level,
etc.) and a unique event notifier token.

A `Event notifier group` is a set of event notifiers sharing the same
pipe to the liblttng-ust-ctl user.

Sequence of operations
======================
  event_notifier_group_handle = ustctl_create_event_notifier_group(notification_fd)
  event_notifier_handle = ustctl_create_event_notifier(event_notifier_group_handle, event_notifier_id);
  ustctl_set_filter(event_notifier_handle, filter)
  ustctl_set_exclusion(event_notifier_handle, exclusion)
  ustctl_enable(event_notifier_handle)
  ...
  ustctl_disable(event_notifier_handle)
  ustctl_release_object(event_notifier_handle)
  ustctl_release_object(event_notifier_group_handle)

Highlevel changes
=================
- Add the event notifier probe generation macros,
- Add event notifier enabling/disabling machinery,
- Add event notifier filter machinery,
- Add event notifier exclusion machinery,
- Expose ABI structures
- Expose ABI enums
- Expose ABI cmds
- Expose ustctl functions

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I493d784cc6830cd6c7979f6f08b209521676f05c

Add token to `struct lttng_ust_event`

This token is provided by the user when registering an event rule to
UST. It is going to used to identify messages from event notifiers in
the upcoming event notifier feature.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I780c681a6775cf61a2f805b7c6aed6ff2e321ea9

Create `_for_each` function to unregister probe providers

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ic09169fb81c6ee420c60a63045532831efaa0806

Cleanup: extract function to borrow hashlist bucket

This is going to reused by the event notifier system.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I5132273ae79a84afdfbf0f88c8042c2b3828d782

Decouple `struct lttng_event` from filter code

The filter infrastructure will be used by event notifiers and decoupling
this will allow for massive code reuse.

Of all `struct lttng_event`'s fields, filter code needs:
  1. The `const struct lttng_event_desc *desc` field,
  2. The `struct cds_list_head bytecode_runtime_head` list.

These fields are used to do the tracepoint field relocation
(`apply_field_reloc()` and `specialize_event_payload_lookup()`).

Given that only these two fields are needed, we can pass them directly
to these functions.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I25cb6fba5ba3cb74dbc4ee9f1fa1026171a6599a

Cleanup: hide `lttng_ust_{filter_bytecode,excluder}_node`

Those two structs are not used in the external API so we better hide
them in internal files.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I9fee32ab4cc4ac7a440ad57d344b1a369a121313

Abstract base `lttng_enabler` to support other types of enablers

Future commits will introduce the concept of event notifier enablers
which are similar to the event enablers already present with a few
differences.

To prepare the ground, this commit moves event dependent fields from the
`struct lttng_enabler` struct to a specialized `struct
lttng_event_enabler`.

The `lttng_enabler_*()` functions cannot be renamed because they are
currently exported. These are only used internally, so we can stop using
them and add new `lttng_event_enabler_*()` functions marked as hidden
which won't be exported (see liblttng-ust/ust-events-internal.h).
`lttng_enabler_*()` functions are kept in the ust-events.h file but
moved to the bottom of the file with other deprecated symbols.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I6d0af091c257a9ad297d17fca8993956279eb848

Rename `enum lttng_enabler_type` to `_format_type`

Currently, the `_type` field is used to express in what format the event
rule was provided, either the full event name or a glob pattern.

Future commit will introduce the concept event notifier enabler that
will be along side regular event enabler.
The use of the `_type` suffix might become confusing with this new class
of enablers.

So this commit rename the  `_type` field to `_format_type`.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I4d1e97da03df3983cba8b65c35d42818e0a967a5

Decouple `struct lttng_session` from filter code

Use `struct lttng_ctx` directly so that the future event notifier
infrastructure, which will be outside any session, can use it.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I84109a0c01636bc5206f43e7abdceee27124c520

port: FreeBSD 12.2 added pthread_setname_np

With a minor difference that it doesn't return an error when the name is
too long, add this check in the wrapper to have the same behavior on
all platforms.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Id6fa0970b011867424a215e5d7ba69e9fe617389

port: tests: Add a simple unit test for shm operations

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Idf347eb2985cac2216da0bb13aee5b09884c8b48

port: fsync(2) on a POSIX shm fd returns EINVAL on FreeBSD

The POSIX shared memory object implementation on FreeBSD is not file
based and doesn't support fsync(2).

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ie170254122aeab858a12c0522dc4e78075f243f9

port: set shm size with ftruncate before writing

According to POSIX, the size of shared memory object must be set with
ftruncate before writing to it. This happenen to work on Linux because
the implementation simply creates files on a tmpfs but on FreeBSD it is
implemented using actual shared memory objects and as such requires the
size to be set first.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I048f65104d7c34142025337ec1f6777650bfd62f

fix: pass the detected CFLAGS to the C++ compiler

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I8f76c87c1acb772d93292ca36bd9b7d56a147b5e

Cleanup: silent rules are always available in automake >= 1.12

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ib0acb195594e1b788c8c6d1b2cd879c3c271aef3

Cleanup: Use pkg-config to detect liburcu

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Iddfc721318e3ac06f2403876c1aa196da797d113

tests: Move tap-driver.sh out of the autotools aux directory

We have made local modifications to this script, move it to the test
suite directory so it doesn't get overwritten by an updated version from
autotools.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ie46f0c39fe4d196b2bab3978ac02c2b1fed883c7

Enable autotools warnings as errors

Enable all autotools warnings and error out to help catch all the
wonderful, shall we say, pecularities of M4sh.

And fix some associated errors in configure.ac.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Icc693a1913a003f2c5b299e82084252c5735603f

Cleanup: separate tests between 'unit' and 'compile'

Change-Id: Ib4326540609dc464b9a89ba9b891cf9c410d902b
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Cleanup: Bump autoconf required version to 2.69

We already depend on automake 1.12 released in 2012, set the minimum
autoconf version to 2.69 which was released on the same year.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ib3c8bb5fccca3eacb80e78f361bc1b3fddbe00e1

Cleanup: Remove obsolete and unused tests

These tests have not been built in years and are not compatible with the
current API.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I6e18ba701d5deec72102e9b652ec9dfc9f08a9c2

fix: pthread_setname_np tests to match compat behavior

Adjust the test to expect an error when setting a thread name of more
than 16 bytes. Also don't override global AM_CPPFLAGS in
pthread_name/Makefile.am so that we get the proper include
configuration.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Iee41d8ea845836d273f01e890ea4196ae2ed43ef

fix: pthread_setname_np fails on longer tread names

When supplied with a thread name of more than 16 bytes including the
null terminating byte pthread_setname_np will fail with ERANGE,
replicate this behavior in the compat wrappers.

Change-Id: I91ac35a400a39c297e49fcab83b4f345b7ad92d0
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Namespace lttng/align.h macros

These macros are part of the API and should have been namespaced
initialy. Namespace them and add backwards compatibility defines, make
sure to include the relevant system headers first for platforms that
have conflicting defines.

Change-Id: If2929ec2202dbde896614a25440ab200514ef4ad
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: remove redefinition of _GNU_SOURCE

Now that _GNU_SOURCE is defined by the compiler command line, no need to
redefine it.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I5a02dd945f0dfec778779a8c5806cc9f45960520

Add pthread_setname_np tests

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I5999ecddf62be9ad25cd67a61ff7315b48f3306a

port: fix pthread_setname_np integration

The detection was broken and initialy went undetected because of the
failover code. Replace it with a hard fail and fix the detection for
each platform.

Also, replace the private LTTNG_UST_PROCNAME_LEN with
LTTNG_UST_ABI_PROCNAME_LEN from the public headers. The limit of 16
bytes does in fact include the terminating null byte contrary to what
was defined in LTTNG_UST_PROCNAME_LEN. This was not catched before since
the string is silently truncated if it exceeds 16 bytes.

Change-Id: I1ea95dfd882dfeb80fdc3d71ebec6618b1324a79
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Cleanup: standardise include path

Use the same include setup as our other projects, set the default
includes globally in configure.ac by exporting AM_CPPFLAGS. Move the
local config.h to the include directory and include it by default on the
command line.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I28b48dc47cfc923d588a0033b97c2917a9c893a5

port: no libnuma on FreeBSD

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I1c5b376de188a8f23ae90c2a6ab72fb1ecc42ace

port: use /bin/sh in test_ust_elf

The script doesn't use any bash extensions, use the default shell.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I7f7c843087400938f1e4d0de140d5deaff4efcd9

port: fix typo 'lttng_ust_safe_closefrom' -> 'lttng_ust_safe_closefrom_fd'

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I6f9ddd4b46e83c379ed76dd435ce44c49393f7cf

port: include limits.h first for CHAR_BIT

On FreeBSD, CHAR_BIT is defined in limits.h, include it first so we
don't get redifinition errors.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I694cc906d801bcd9b1e82dcbcf1163cdb3c41100

port: fix endian and byteswap compat on FreeBSD

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I8edd89df2c99406b10b846eb1a8bcf959e8bbde4

port: Silence macro redefinition warnings on FreeBSD

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I32473a65116fd9e4120a852a8cbc5c145e9609f7

port: fix pthread autoconf detection to support FreeBSD

Use the same autoconf pthread code as lttng-tools to handle pthread
compat on FreeBSD.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I713446b1f5ec2eaab96cdfc7e9888ab543e8a67f

Set version to 2.13-pre

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Id17c197aa437f0cf7a5d489f62f5f6b5cffb22e0

Fix: ustctl_release_object: eliminate double-close/free on error

When ustctl_release_object returns an error, it is unclear to the caller
what close/free side effects were effectively performed and which were
not. So the only courses of action are to either leak file descriptors
or memory, or call ustctl_release_object again which can trigger double
close or double free.

Fix this by setting the file descriptors to -1 after successful close,
and pointers to NULL after successful free.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

tests: return the proper TAP exit code

The C TAP library provides the 'exit_status()' function that will return
the proper exit code according to the number of tests that succeeded or
failed.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I786527dfa9cfe2d1a7c8bc80086d54186f60b4d9

Add userspace time namespace context

This was introduced in kernel v5.6.0, on a system running an older kernel,
zero will be returned.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I1ea66a98c96a4de084c02521f6982e8c7d1b53bb

Use libtool syntax in LDADD

Use .la files to add link dependencies between libraries, linking
directly to the content of '.libs' is relying on an implementation
detail of libtool.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I6fe0157e23f13cd69c436111a2e743fa1c763d64

Add missing files to distribution

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I5b0be9c7c87dc7fef1c6f46f15091d4e3c2a09a8

Fix: python agent: 'time' has no attribute 'clock'

The time.clock() function was removed in python 3.8 and is marked as
deprecated since python 3.3. See PEP 418 for more details [1].

Solution
=====

When the python version is greater than 3.2 use the
`time.perf_counter()` function [2]. Otherwise, fall back to
`time.clock()`.

Introduce a compat module to the lttngust agent package providing the
`_clock` function.

[1] https://www.python.org/dev/peps/pep-0418/
[2] https://docs.python.org/3/library/time.html#time.perf_counter

Signed-off-by: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I3d6d8b24309d45d43b634dc2a6b4d5dbc12da3aa