Fix: event-notifier: do not flush packet if it only contains subbuf header

This poll behavior returns POLLIN in situations where there is
actually no event to read, which causes read to block when it
should not.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I59e56cd4da9907b6f9ccdc14c6037f0f72e4505e

Implement lttng_event_notifier_group_notif_fops read, poll, open, release ABI

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ia95c67306226202cfd10f3745ddeecb76b1ef1a7

Implement event notifier send notification

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Change-Id: Ibdab5a25439da7d4c26e480c41cdd655a7d58d82

Add event notifier and event notifier enabler

Idea
====
The purpose of the event notifiers is to allow the session daemon to
react to events in the tracer. For example, the user will be able to
start or stop tracing on a session when a specific tracepoint is fired.

An event notifier is really similar to a regular event. The main
difference is that when the tracepoint is fired the action of the event
notifier is to notify the session daemon about it. This mechanism will
use a special purpose ring buffer to expose these notifications to
userspace.

Unlike regular events, there are no claim on the timeliness of such
notifications.

Implementation
==============
This commit adds structures and functions related to event notifiers
mimicking what we currently do with regular events.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I962e6c7051693d6e4a79f89758f8bf1ebda6c148

Implement event notifier group create

Event notifier groups will contain the event notifiers.
All event notifiers of a group will share the same ring buffer to save
the tracer notifications.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I7c38fbfd26517d00c8de38ca1981da623d570529

Add token to `struct lttng_kernel_event`

This token is provided by the user when registering an event rule to the
kernel. It is going to used to identify messages from event notifiers, and
counter bucket owners in the upcoming event notifier and map counter
features.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I58cd6b6e33b97cc21e50cc0b36bef4b9e4224423

lttng-events: move lttng_transport_find earlier in source file

Will be used by upcoming event notifier code which is earlier in source
file.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Idb7be8c682258195166f3b513fee2aa98656de35

lib ring buffer: move subbuffer_consume_record into LTTNG_RING_BUFFER_COUNT_EVENTS ifdef

When event accounting is disabled, counting of event records consumed by
the iterator should be disabled as well, otherwise it triggers
CHAN_WARN_ON() because the accounting of events produced is not
performed.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Id8b9e657ee420886b409be1f05ef08a0807fefdc

lib ring buffer iterator: introduce lib_ring_buffer_put_current_record

Ensure that the current subbuffer is put after client code has read the
payload of the current record.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Id2173ea67213f7ef8e7395b49c5aa8fff0aefffc

Introduce event notifier lib ring buffer client

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I89da147ee956f5759c49bd992bf33fe760d79591

lttng_abi_create_stream_fd: expect fd name as parameter

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ic9711863b58307d3ed6cc782efc78e4f59345950

LTTng ring buffer clients: expect void pointer as private data to create channel

Triggers will create a channel without using the lttng_channel objects,
so allow any type of private data.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I0725616c84e401c9fcbf00a405a2e2d0f1078979

lib ring buffer: use irq_work for wakeup by writer

Using irq_work (like perf does) allows using an interrupt handler
firing soon after the instrumentation execution to issue the wakeups.

This allows the RING_BUFFER_WAKEUP_BY_WRITER ring buffer configuration
to be entirely lock-free, which allows using it in NMI context for
general tracing purposes.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I842ff15736f53d1283cf953804d803f70779652b

Rename `lttng_event_{get,put}()` to `lttng_event_desc_{get,put}()`

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I99a8b4cdf191555c28da5a38a1e65661421fd7fc

Cleanup: extract function to borrow hashlist bucket

This is going to reused by the trigger system.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ie6d032374c3991d0a75ad4737e7f082fbc1a74b1

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()`).

Considering that only these two field 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: If569b7d315700660aa84241d112668f2451b715a

Rename `lttng_create_*_if_missing()` in anticipation of event notifiers

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I58a799f992a53215ff04896b783e7ebe31965b7c

Extract event enabler fields to specialized struct

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I356d9b91c6e20c288ca931a4d449a54b67f3937c

Docs: explain why unused `lttng_enabler::ctx` is kept around

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: If2c6b9203ea324bb1ff4051b0a705e7303dbf3a6

Rename `enum lttng_enabler_type` to `_format_type`

This will avoid confusion between the different types of enablers
(event notifier enablers and event enablers).

- Enabler format types describe the way the event name matching is done.

- Enabler types will describe the type of enablers (event
  notifier vs event)

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ic71d05159c5f244d0b1ad74f9c0ee6247fcdfbbb

Test: add signed value and enum for testings of event notifier capture

Signed-off-by: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I4be725e3ed1e2f94420f4cdcf5ab6ac7962e2464

Cleanup: remove usage of enum in ABI structures

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I3730f7c0341028b25231c368166ee6e5fd74fa5d

Fix: type mismatch in clone instrumentation

The data and metadata types should all agree to use "unsigned long",
else it triggers babeltrace trace parsing errors.

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

syscalls: Make clone()'s `flags` field a 2 enum struct.

The clone system call has a flags field, whose values are defined in
uapi/linux/sched.h file. This field is now a struct made of 2
enumerations to make the values more readable/meaningful.

The `flags` field has two parts:
  1. exit signal: the least significant byte of the `unsigned long` is
      the signal the kernel need to send to the parent process on child
      exit,
  2. clone options: the remaining bytes of the `unsigned long` is used a
      bitwise flag for the clone options.

Those 2-in-1 fields should be printed using two different CTF fields.

Here's an example babeltrace output of the clone system call:
  syscall_entry_clone: { cpu_id = 2 }, { flags = { exit_signal = ( "SIGCHLD" : container = 0x11 ), options = ( "CLONE_CHILD_CLEARTID" | "CLONE_CHILD_SETTID" : container = 0x12000 ) }

Change-Id: Ic375b59fb3b6564f036e1af24d66c0c7069b47d6
Signed-off-by: Geneviève Bastien <gbastien@versatic.net>
Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

fix: strncpy equals destination size warning

Some versions of GCC when called with -Wstringop-truncation will warn
when doing a copy of the same size as the destination buffer with
strncpy :

  ‘strncpy’ specified bound 256 equals destination size [-Werror=stringop-truncation]

Since we unconditionally write '\0' in the last byte, reduce the copy
size by one.

Change-Id: Idb907c9550817a06fc0dffc489740f63d440e7d4
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>

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: I4124a7d9d9c2f7a36816b7e498ffd37ae27da604

Cleanup: lttng-syscalls: silence warning about uninitialized bitmap variable

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

Add 'kernel_read' wrapper for kernels < v4.14

See upstream commit:

  commit bdd1d2d3d251c65b74ac4493e08db18971c09240
  Author: Christoph Hellwig <hch@lst.de>
  Date:   Fri Sep 1 17:39:13 2017 +0200

    fs: fix kernel_read prototype

    Use proper ssize_t and size_t types for the return value and count
    argument, move the offset last and make it an in/out argument like
    all other read/write helpers, and make the buf argument a void pointer
    to get rid of lots of casts in the callers.

Change-Id: I825c3fcbcc17e9b46e2a661fadc66b52a94eb2da
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

fix: Use 'kernel_read' to read from procfs

Use the 'kernel_read' helper to read files in procfs, it's present in
the kernel since the 2.6 series and does the right thing on kernels that
require the set_fs dance and newer one which don't.

Change-Id: I1a53fda379e0bb9acc79331626925bbdba63d727
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

fix: don't allow userspace copy to read kernel memory

This patch fixes a security issue which allows the root user to read
arbitrary kernel memory. Considering the security model used in LTTng
userspace tooling for kernel tracing, this bug also allows members of
the 'tracing' group to read arbitrary kernel memory.

Calls to __copy_from_user_inatomic() where wrongly enclosed in
set_fs(KERNEL_DS) defeating the access_ok() calls and allowing to read
from kernel memory if a kernel address is provided.

Remove all set_fs() calls around __copy_from_user_inatomic().

As a side effect this will allow us to support v5.10 which should remove
set_fs().

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I35e4562c835217352c012ed96a7b8f93e941381e

fix: Add a 1MB limit to lttng_strlen_user_inatomic

The previous implementation was unbounded which could result in long
loops with preemption turned off.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I85afcd879258735bb2e7502f6016fcb2d3974cf7

fix: Adjust ranges for Ubuntu 4.15.0-119 kernel

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ie32f70f810c8fc756fbd31ab129aeb35500790f7

fix: Adjust ranges for Ubuntu HWE 5.0 kernels

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I36f2c3485dcc6ccb74ea86a7ce66fcb1662d060b

Fix: system call filter table

The system call filter table has effectively been unused for a long
time due to system call name prefix mismatch. This means the overhead of
selective system call tracing was larger than it should have been because
the event payload preparation would be done for all system calls as soon
as a single system call is traced.

However, fixing this underlying issue unearths several issues that crept
unnoticed when the "enabler" concept was introduced (after the original
implementation of the system call filter table).

Here is a list of the issues which are resolved here:

- Split lttng_syscalls_unregister into an unregister and destroy
  function, thus awaiting for a grace period (and therefore quiescence
  of the users) after unregistering the system call tracepoints before
  freeing the system call filter data structures. This effectively fixes
  a use-after-free.

- The state for enabling "all" system calls vs enabling specific system
  calls (and sequences of enable-disable) was incorrect with respect to
  the "enablers" semantic. This is solved by always tracking the
  bitmap of enabled system calls, and keeping this bitmap even when
  enabling all system calls. The sc_filter is now always allocated
  before system call tracing is registered to tracepoints, which means
  it does not need to be RCU dereferenced anymore.

Padding fields in the ABI are reserved to select whether to:

- Trace either native or compat system call (or both, which is the
  behavior currently implemented),
- Trace either system call entry or exit (or both, which is the
  behavior currently implemented),
- Select the system call to trace by name (behavior currently
  implemented) or by system call number,

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

fix: version ranges for ext4_discard_preallocations and writeback_queue_io

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Id4fa53cb2e713cbda651e1a75deed91013115592

fix: writeback: Fix sync livelock due to b_dirty_time processing (v5.9)

See upstream commit:

  commit f9cae926f35e8230330f28c7b743ad088611a8de
  Author: Jan Kara <jack@suse.cz>
  Date:   Fri May 29 16:08:58 2020 +0200

    writeback: Fix sync livelock due to b_dirty_time processing

    When we are processing writeback for sync(2), move_expired_inodes()
    didn't set any inode expiry value (older_than_this). This can result in
    writeback never completing if there's steady stream of inodes added to
    b_dirty_time list as writeback rechecks dirty lists after each writeback
    round whether there's more work to be done. Fix the problem by using
    sync(2) start time is inode expiry value when processing b_dirty_time
    list similarly as for ordinarily dirtied inodes. This requires some
    refactoring of older_than_this handling which simplifies the code
    noticeably as a bonus.

Change-Id: I8b894b13ccc14d9b8983ee4c2810a927c319560b
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

fix: writeback: Drop I_DIRTY_TIME_EXPIRE (v5.9)

See upstream commit:

  commit 5fcd57505c002efc5823a7355e21f48dd02d5a51
  Author: Jan Kara <jack@suse.cz>
  Date:   Fri May 29 16:24:43 2020 +0200

    writeback: Drop I_DIRTY_TIME_EXPIRE

    The only use of I_DIRTY_TIME_EXPIRE is to detect in
    __writeback_single_inode() that inode got there because flush worker
    decided it's time to writeback the dirty inode time stamps (either
    because we are syncing or because of age). However we can detect this
    directly in __writeback_single_inode() and there's no need for the
    strange propagation with I_DIRTY_TIME_EXPIRE flag.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I92e37c2ff3ec36d431e8f9de5c8e37c5a2da55ea

fix: removal of [smp_]read_barrier_depends (v5.9)

See upstream commits:

  commit 76ebbe78f7390aee075a7f3768af197ded1bdfbb
  Author: Will Deacon <will@kernel.org>
  Date:   Tue Oct 24 11:22:47 2017 +0100

    locking/barriers: Add implicit smp_read_barrier_depends() to READ_ONCE()

    In preparation for the removal of lockless_dereference(), which is the
    same as READ_ONCE() on all architectures other than Alpha, add an
    implicit smp_read_barrier_depends() to READ_ONCE() so that it can be
    used to head dependency chains on all architectures.

  commit 76ebbe78f7390aee075a7f3768af197ded1bdfbb
  Author: Will Deacon <will.deacon@arm.com>
  Date:   Tue Oct 24 11:22:47 2017 +0100

    locking/barriers: Add implicit smp_read_barrier_depends() to READ_ONCE()

    In preparation for the removal of lockless_dereference(), which is the
    same as READ_ONCE() on all architectures other than Alpha, add an
    implicit smp_read_barrier_depends() to READ_ONCE() so that it can be
    used to head dependency chains on all architectures.

Change-Id: Ife8880bd9378dca2972da8838f40fc35ccdfaaac
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

fix: ext4: indicate via a block bitmap read is prefetched… (v5.9)

See upstream commit:

  commit ab74c7b23f3770935016e3eb3ecdf1e42b73efaa
  Author: Theodore Ts'o <tytso@mit.edu>
  Date:   Wed Jul 15 11:48:55 2020 -0400

    ext4: indicate via a block bitmap read is prefetched via a tracepoint

    Modify the ext4_read_block_bitmap_load tracepoint so that it tells us
    whether a block bitmap is being prefetched.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I0e5e2c5b8004223d0928235c092449ee16a940e1

fix: ext4: limit the length of per-inode prealloc list (v5.9)

See upstream commit:

  commit 27bc446e2def38db3244a6eb4bb1d6312936610a
  Author: brookxu <brookxu.cn@gmail.com>
  Date:   Mon Aug 17 15:36:15 2020 +0800

    ext4: limit the length of per-inode prealloc list

    In the scenario of writing sparse files, the per-inode prealloc list may
    be very long, resulting in high overhead for ext4_mb_use_preallocated().
    To circumvent this problem, we limit the maximum length of per-inode
    prealloc list to 512 and allow users to modify it.

    After patching, we observed that the sys ratio of cpu has dropped, and
    the system throughput has increased significantly. We created a process
    to write the sparse file, and the running time of the process on the
    fixed kernel was significantly reduced, as follows:

    Running time on unfixed kernel：
    [root@TENCENT64 ~]# time taskset 0x01 ./sparse /data1/sparce.dat
    real    0m2.051s
    user    0m0.008s
    sys     0m2.026s

    Running time on fixed kernel：
    [root@TENCENT64 ~]# time taskset 0x01 ./sparse /data1/sparce.dat
    real    0m0.471s
    user    0m0.004s
    sys     0m0.395s

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I5169cb24853d4da32e2862a6626f1f058689b053

fix: KVM: x86/mmu: Make kvm_mmu_page definition and accessor internal-only (v5.9)

  commit 985ab2780164698ec6e7d73fad523d50449261dd
  Author: Sean Christopherson <sean.j.christopherson@intel.com>
  Date:   Mon Jun 22 13:20:32 2020 -0700

    KVM: x86/mmu: Make kvm_mmu_page definition and accessor internal-only

    Make 'struct kvm_mmu_page' MMU-only, nothing outside of the MMU should
    be poking into the gory details of shadow pages.

Change-Id: Ia5c1b9c49c2b00dad1d5b17c50c3dc730dafda20
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

fix: Move mmutrace.h into the mmu/ sub-directory (v5.9)

  commit 33e3042dac6bcc33b80835f7d7b502b1d74c457c
  Author: Sean Christopherson <sean.j.christopherson@intel.com>
  Date:   Mon Jun 22 13:20:29 2020 -0700

    KVM: x86/mmu: Move mmu_audit.c and mmutrace.h into the mmu/ sub-directory

    Move mmu_audit.c and mmutrace.h under mmu/ where they belong.

Change-Id: I582525ccca34e1e3bd62870364108a7d3e9df2e4
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Namespace all logging statements

Add the 'LTTng:' prefix to all our logging statements to easily
distinguish them from other kernel messages.

Change-Id: I90fb4f4c75ce195734ec82946827bcf78e03429a
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Kconfig: fix dependency issue when building in-tree without CONFIG_FTRACE

When building in-tree, one could disable CONFIG_FTRACE from kernel
config which will leave CONFIG_TRACEPOINTS selected by LTTNG modules,
but generate a lot of linker errors like below because it leaves out
other stuff, e.g.:

trace.c:(.text+0xd86b): undefined reference to `trace_event_buffer_reserve'
ld: trace.c:(.text+0xd8de): undefined reference to `trace_event_buffer_commit'
ld: trace.c:(.text+0xd926): undefined reference to `event_triggers_call'
ld: trace.c:(.text+0xd942): undefined reference to `trace_event_ignore_this_pid'
ld: net/mac80211/trace.o: in function `trace_event_raw_event_drv_tdls_cancel_channel_switch':

It appears to be caused by the fact that TRACE_EVENT macros in the Linux
kernel depend on the Ftrace ring buffer as soon as CONFIG_TRACEPOINTS is
enabled.

Steps to reproduce:

- Get a clone of an upstream stable kernel and use scripts/built-in.sh on it

- Configure a standard x86-64 build, enable built-in LTTNG but disable
  CONFIG_FTRACE from Kernel Hacking-->Tracers using menuconfig

- Build will fail at linking stage

Signed-off-by: Beniamin Sandu <beniaminsandu@gmail.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: mmap enum flags build failures

Some of the mmap option flags are not available on all architectures and
are defined to zero by include/linux/mman.h. This is probably done as a
way to no-op the use of these flags on configurations that don't support
them.
To fix this, only define these flags in our enumeration if they are
defined and non-zero.

Also, the MAP_HUGE_{2MB,1GB} labels were mistakingly named
MAP_HUGETLB_{2MB,1GB}.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I778a52a0da9da6e04231a52c7f68a22d122dfb83

syscalls: Make mmap()'s fields `prot` and `flags` enums

The `prot` flags is a simple CTF enumeration.

The `flags` field is a CTF struct of 2 CTF enumerations (`type` and
`options`). This is needed to express the two parts of this integer
flag. The 4 least significant bits of the integer are reserved to
express the type of the mapping (MAP_SHARED=0x1, MAP_PRIVATE=0x2, and
MAP_SHARED_VALIDATE=0x3).

The remaining 28 bits are used to specify optional configurations on the
mapping. As opposed to the type part, the options part is bit flag
field where all values are power of 2. This part can be expressed as
ORed bit flag values.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I5ae78754b5863b31d9a3ba1b1173502e1ae284d3

x86: add error code enum to pagefault tracepoints

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ia939eccd1a918958f6a281595e447f33da2d64f7

Fix: TAINT_UNSAFE_SMP renamed to TAINT_CPU_OUT_OF_SPEC in v3.15

See upstream commit:

  commit 8c90487cdc64847b4fdd812ab3047f426fec4d13
  Author: Dave Jones <davej@redhat.com>
  Date:   Wed Feb 26 10:49:49 2014 -0500

    Rename TAINT_UNSAFE_SMP to TAINT_CPU_OUT_OF_SPEC

    Rename TAINT_UNSAFE_SMP to TAINT_CPU_OUT_OF_SPEC, so we can repurpose
    the flag to encompass a wider range of pushing the CPU beyond its
    warrany.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I3e91df01bfbfaa6fab4e3904e59317022a9ec0f8

module_load: change `taints` field to `ctf_enum`

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I67b5aad0bd2bc43e06a5708f0f5e1fea56f31436

Fix: Lock metadata cache on session destroy

commit 92143b2c5656 ("Fix: metadata stream leak, missing list removal and locking")
missed taking a lock protecting the metadata stream list iteration on
session destroy. This opens a race window between iteration and item
removal/free which triggers kernel OOPS.

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

Fix: metadata stream leak, missing list removal and locking

The metadata stream is part of a list of metadata streams in the
metadata cache. Its addition to the list should be protected by
the metadata cache lock. It needs to be paired with protection
of list iteration with the same lock.

Removal from the list is entirely missing, and should be added
to lttng_metadata_ring_buffer_release (with proper locking).

This missing list removal was probably not causing issues because the
metadata stream structure was leaked: a kfree() is missing from
lttng_metadata_ring_buffer_release as well.

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

Fix: coherent state not changed atomically with metadata written

commit 122c63cb4310 ("Fix: Implement RING_BUFFER_GET_NEXT_SUBBUF_METADATA_CHECK")
introduces a new ioctl which returns a flag indicating whether the
metadata is in consistent state at the end of the sub-buffer.

That commit is meant to address metadata consistency issues observable
in live sessions.

However, the "consistent" state is false as soon as a producer is
active (between an outermost metadata_begin/end pair). Unfortunately,
if the last "RING_BUFFER_GET_NEXT_SUBBUF_METADATA_CHECK" operation is
done between the last metadata printf and "end" of the transaction, the
last consistency state will be false, and the consumer daemon will never
send metadata to the relay daemon. This in turn causes a live viewer to
wait for metadata endlessly.

This issue can be reproduced by running lttng-tools:
tests/regression/tools/live/test_kernel

as root in a loop.

We observe two things:
1) the poll operation blocks when there is no more metadata to send,
   which means there is no mean to unblock when the consistency state
   changes back to "true" without producing additional metadata,

2) Even if (1) was fixed, the expectation from an ABI perspective is
   that the "coherent" state is only populated when
   RING_BUFFER_GET_NEXT_SUBBUF_METADATA_CHECK succeeds. Therefore,
   there is no way to let user-space know about conherency transition
   unless additional metadata is generated.

Fixing this requires to hold the metadata cache lock across the entire
production of a coherent metadata transaction. This simpler scheme is
possible because the metadata is generated in a reallocated memory area
and not directly into a ring buffer anymore. This was not the case in
earlier lttng-modules versions, when the metadata was generated directly
into a ring buffer, which explains why this simpler scheme was not
implemented.

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

fix: include module.h for EXPORT_SYMBOL_GPL

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ic337e1eb375791ace08560555dd02b37cbefcf25

fix: __lttng_vmalloc_node_range const caller introduced in v3.6

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ib13cf03b5ab11830a8732318a12713720cf1b3e3

fix: version range for overflow_callback

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I1b8f1d59552a1723d3f4ed74780a2b57d13d0e52

fix: global_dirty_limit was introduced in v3.1

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Id97dbb2d0181a45c45cfed36c4be8753cabac283

fix: wrapper_uprobe_unregister is a void function

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ib4438da02aac3defd1245324d1b48f400f806d58

fix: prior to v4.0, __vmalloc_node_range had no vm_flags param

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ib476e32d109298d9ca3e6b6ab7ac8f63c50fb09f

fix: vmalloc on v5.8 without KALLSYMS

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ic945dad92e78a5bc2895a969a10c527e1349decf

Detect missing symbols used with kallsyms_lookup at compile time

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I19a9a31c386196899517899d861fe63611272139

Add time namespace context

Add a context for the new time namespace introduced in v5.6.

Change-Id: Ic3393f65702b80c87670bb21049ee2a19413111d
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Use exported symbol bdevname() instead of disk_name()

bdevname() is a simple wrapper over disk_name() but has the honor to be
exported. Using it removes the need for a kallsym wrapper.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ic2b2233c4db7826175c68edea69751ddcb17a5e6

Add git-review config

Add .gitreview for contributors wishing to use gerrit for patch
reviews.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I663e66a433ddb645f580c4b9f885db9c3a08e02f

fix: mm: remove vmalloc_sync_(un)mappings() (v5.8)

See upstream commit:

  commit 73f693c3a705756032c2863bfb37570276902d7d
  Author: Joerg Roedel <jroedel@suse.de>
  Date:   Mon Jun 1 21:52:36 2020 -0700

    mm: remove vmalloc_sync_(un)mappings()

    These functions are not needed anymore because the vmalloc and ioremap
    mappings are now synchronized when they are created or torn down.

    Remove all callers and function definitions.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ifdefa35b25b4906cde407360e608b77e47cc3808

Update design document

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

Add lttng-modules design document

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

Fix: callstack: initialize nested sequence length field name

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

Fix: callstack: NULL pointer dereference: length field also need fdata

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

Fix: callstack context memory corruption

commit ceabb767180e "tracepoint: Refactor representation of nested types"
introduces two context fields for callstack contexts. Keeping a pointer
to the first field is not valid when adding the second context field to
the array, because the array is reallocated.

Fix this by introducing new context APIs which operate on indexes rather
than pointers:
- lttng_append_context_index,
- lttng_get_context_field_from_index,
- lttng_remove_context_field_index.

Add a NULL check to lttng_find_context so it can be used before adding
the first context.

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

fix: mm/writeback: discard NR_UNSTABLE_NFS, use NR_WRITEBACK (v5.8)

See upstream commit:

  commit 8d92890bd6b8502d6aee4b37430ae6444ade7a8c
  Author: NeilBrown <neilb@suse.de>
  Date:   Mon Jun 1 21:48:21 2020 -0700

    mm/writeback: discard NR_UNSTABLE_NFS, use NR_WRITEBACK instead

    After an NFS page has been written it is considered "unstable" until a
    COMMIT request succeeds.  If the COMMIT fails, the page will be
    re-written.

    These "unstable" pages are currently accounted as "reclaimable", either
    in WB_RECLAIMABLE, or in NR_UNSTABLE_NFS which is included in a
    'reclaimable' count.  This might have made sense when sending the COMMIT
    required a separate action by the VFS/MM (e.g.  releasepage() used to
    send a COMMIT).  However now that all writes generated by ->writepages()
    will automatically be followed by a COMMIT (since commit 919e3bd9a875
    ("NFS: Ensure we commit after writeback is complete")) it makes more
    sense to treat them as writeback pages.

    So this patch removes NR_UNSTABLE_NFS and accounts unstable pages in
    NR_WRITEBACK and WB_WRITEBACK.

    A particular effect of this change is that when
    wb_check_background_flush() calls wb_over_bg_threshold(), the latter
    will report 'true' a lot less often as the 'unstable' pages are no
    longer considered 'dirty' (as there is nothing that writeback can do
    about them anyway).

    Currently wb_check_background_flush() will trigger writeback to NFS even
    when there are relatively few dirty pages (if there are lots of unstable
    pages), this can result in small writes going to the server (10s of
    Kilobytes rather than a Megabyte) which hurts throughput.  With this
    patch, there are fewer writes which are each larger on average.

    Where the NR_UNSTABLE_NFS count was included in statistics
    virtual-files, the entry is retained, but the value is hard-coded as
    zero.  static trace points and warning printks which mentioned this
    counter no longer report it.

Change-Id: I18080ca62bc6c1cd7d6da4cb27cc1521fbdca5e1
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

fix: block: remove the error argument to the block_bio_complete (v5.8)

See upstream commit:

  commit d24de76af836260a99ca2ba281a937bd5bc55591
  Author: Christoph Hellwig <hch@lst.de>
  Date:   Wed Jun 3 07:14:43 2020 +0200

    block: remove the error argument to the block_bio_complete tracepoint

    The status can be trivially derived from the bio itself.  That also avoid
    callers like NVMe to incorrectly pass a blk_status_t instead of the errno,
    and the overhead of translating the blk_status_t to the errno in the I/O
    completion fast path when no tracing is enabled.

Fixes: 35fe0d12c8a3 ("nvme: trace bio completion")
Change-Id: I8d1463184d79bfab418a1755bfc6a0200170fff3
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

fix: pipe_buf_operations rework (v5.8)

See upstream commits:

  commit c928f642c29a5ffb02e16f2430b42b876dde69de
  Author: Christoph Hellwig <hch@lst.de>
  Date:   Wed May 20 17:58:16 2020 +0200

    fs: rename pipe_buf ->steal to ->try_steal

    And replace the arcane return value convention with a simple bool
    where true means success and false means failure.

    [AV: braino fix folded in]

  commit b8d9e7f2411b0744df2ec33e80d7698180fef21a
  Author: Christoph Hellwig <hch@lst.de>
  Date:   Wed May 20 17:58:15 2020 +0200

    fs: make the pipe_buf_operations ->confirm operation optional

    Just return 0 for success if it is not present.

  commit 76887c256744740d6121af9bc4aa787712a1f694
  Author: Christoph Hellwig <hch@lst.de>
  Date:   Wed May 20 17:58:14 2020 +0200

    fs: make the pipe_buf_operations ->steal operation optional

    Just return 1 for failure if it is not present.

Change-Id: Ic185632202470db1eb5b012e95e793ff2cb26be7
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: syscalls: Ignore fcntl cmd specific to 32-bit in 64-bit only config

When CONFIG_64BIT is defined and CONFIG_COMPAT is not defined, the fcntl system call
"F_GETLK64", "F_SETLK64" and "F_SETLKW64" should be ignored.

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

Fix: Implement RING_BUFFER_GET_NEXT_SUBBUF_METADATA_CHECK

Get next metadata subbuffer, returning a flag indicating whether the
metadata is guaranteed to be in a consistent state at the end of this
sub-buffer (can be parsed).

This can be used by the consumer to know whether the metadata can be
parsed at the end of this sub-buffer, which is useful to distinguish
between errors and incomplete metadata in live tracing.

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

fix: vmalloc_sync_mappings was backported to v5.5.12

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ie554d9c956afc2a8e114fe41e4b3c225d8af40a1

Update: Additional kernel ranges for vmalloc_sync_mappings

Some Ubuntu kernels cannot be directly mapped to an upstream stable
version. Define distro specific ranges for those (4.15, 5.0, 5.3).

Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Update: Use vmalloc_sync_mappings for stable kernels

Starting from v5.4.28/v5.2.37/v4.19.113/v4.14.175/v4.9.218/v4.4.218, stable
kernel branches backported v5.6 upstream commit [1], causing the following
warnings:
...
[  483.242037] LTTng: vmalloc_sync_all symbol lookup failed.
[  483.257056] Page fault handler and NMI tracing might trigger faults.
...

Extend check for vmalloc_sync_mappings for stable kernels as well.

[1] https://github.com/torvalds/linux/commit/763802b53a427ed3cbd419dbba255c414fdd9e7c

[ Edit: minor coding style fix by Mathieu Desnoyers. ]

Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Fix: Use vmalloc_sync_mappings on kernel 5.6 as well

Upstream commit [1], that got rid of vmalloc_sync_all and introduced
vmalloc_sync_mappings, is a v5.6 commit:
$ git tag --contains 763802b53a427ed3cbd419dbba255c414fdd9e7c
v5.6
v5.6-rc7
v5.7-rc1
v5.7-rc2
v5.7-rc3

Extend the LINUX_VERSION_CODE check to v5.6 to fix the following warnings:
...
[  483.242037] LTTng: vmalloc_sync_all symbol lookup failed.
[  483.257056] Page fault handler and NMI tracing might trigger faults.
...

[1] https://github.com/torvalds/linux/commit/763802b53a427ed3cbd419dbba255c414fdd9e7c

Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Cleanup: remove unsupported `ctf_float()` macros

Tracing floats is not supported for the kernel tracer. Disallow building
kernel probes with those fields, rather than silently ignoring them.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I1cf9751df96d2af3b54f725797bd20d7b05f2b38

Cleanup: have interpreter functions return _DISCARD instead of 0

It's easier to understand the meaning of the zero return value of these
function using the enum. It makes it obvious.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I1df8f704fa9f6768f413c12c3c1de61a94b3aff8

Cleanup: bytecode: typo: "s16" -> "u16"

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I68901ca2d89d08f2cb69853816e0214c588aa7f8

Cleanup: Rename patches.i to patches.h

This generated header file contains a list of patches applied on the
lttng-modules tree. Based on the C99 specification, ".i" files are not
supposed to be preprocessed, although this header header file is
expected to be preprocessed.

Rename it from ".i" to ".h" to convey that it is a C header meant to be
preprocessed.

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

Cleanup: Move all source files to src/

This includes *.c, lib/*/*.c, probes/*.c, wrapper/*.c.

Adapt Makefile and Kbuild accordingly. Introduce src/Kbuild.

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

Cleanup: Move patches.i to include/generated/

Move patches.i from /extra_version to include/generated/ so we
can include them without using relative path includes.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I87927a372ffeb244f3c097c9bb80eeca7d9f99eb

Cleanup: Move lttng-modules instrumentation headers

The directory hierarchy "instrumentation/events/lttng-module/" only
exists for historical reasons and is not needed anymore. Move all
its contents into "instrumentation/events/".

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

Cleanup: Remove toplevel directory from include search path

Now that all include files are moved to include/ (except for those
meant to be included with "#include "...h"), we can remove the toplevel
directory from the include search path.

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

Cleanup: Move blacklist/ headers to include/blacklist/

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

Cleanup: Move wrapper/ headers to include/wrapper/

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

Cleanup: Move instrumentation/ headers to include/instrumentation/

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

Cleanup: Remove deprecated TODO file

All relevant items that were left were moved to
https://bugs.lttng.org/projects/lttng-modules "Feature".

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

fix: add missing guid_t type to wrapper

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I0de39c24a7925b580fabbdaa12dbe05c43cfcd98

Fix: missing wrapper rename to wrapper_vmalloc_sync_mappings

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Idf7082a980c5a604bfef5c69906678b5083a9bbf

Cleanup: Move headers from toplevel to include/lttng/

- Remove extra "lttng-" from filename (now implied by the path).
- Adapt includes accordingly.

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

Cleanup: Move headers from probes/ to include/lttng/

- Remove extra "lttng-" from filename (now implied by the path).
- Adapt includes accordingly.
- Adapt lttng-syscalls-generate-headers.sh header generation script
  accordingly.
- Remove probes/lttng.h, include its PARAMS() define in the two
  user headers.

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

Cleanup: Move headers from lib/ to include/lttng/

Adapt includes accordingly.

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

Cleanup: Move lib/ringbuffer/ headers to include/ringbuffer/

Remove the <wrapper/ringbuffer/...> proxy include files, and add the
include/ directory to the preprocessor include search patch.

Adapt all includes accordingly.

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

Fix: wrapper random documentation

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

Update for kernel 5.7: use vmalloc_sync_mappings on kernels >= 5.7

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

Unbreak LTTng for kernel 5.7

Linux commit 0bd476e6c67190b5eb7b6e105c8db8ff61103281 ("kallsyms:
unexport kallsyms_lookup_name() and kallsyms_on_each_symbol()") breaks
LTTng-modules by removing symbols used by the LTTng-modules out-of-tree
tracer.

I pointed this out when the change was originally considered before the
5.7 merge window. This generated some discussion but it did not lead to
any concrete proposal to fix the issue. [1]

The commit has been merged in the 5.7 merge window. At that point, as
maintainer of LTTng, I immediately raised a flag about this issue,
proposing an alternative approach to solve this: expose the few symbols
needed by LTTng to GPL modules. This was NACKed on the ground that the
Linux kernel cannot export GPL symbols when there are no in-tree
users. [2]

Steven Rostedt has shown interest in merging LTTng-modules upstream.
LTTng-modules being LGPL, this is very much doable. I have prepared a
tree of LTTng-modules "for upstreaming" and sent it to him privately so
he can review it. Even if in an ideal scenario LTTng-modules is merged
for the following merge window, it leaves LTTng-modules broken on the
5.7 kernel.

In order to ensure that the LTTng-modules kernel tracer continues working
for my end users on kernels 5.7 onwards, as a very last resort, this is
with great reluctance that I created this fix for LTTng modules. It
basically uses kprobes to lookup the kallsyms_lookup_name symbol, and
continues using kallsyms_lookup_name as before.

Link: https://lore.kernel.org/r/20200302192811.n6o5645rsib44vco@localhost
Link: https://lore.kernel.org/r/20200409193543.18115-1-mathieu.desnoyers@efficios.com
Link: https://lwn.net/Articles/817988/
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Will Deacon <will@kernel.org>
CC: akpm@linux-foundation.org
CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
CC: Masami Hiramatsu <mhiramat@kernel.org>
CC: rostedt@goodmis.org
CC: Alexei Starovoitov <ast@kernel.org>

Move lttng wrappers into own module

Currently, we only pull the wrapper symbols into a single sub-module,
either:

lttng-tracer.o:
  - wrapper/random.o
  - wrapper/trace-clock.o
  - wrapper/page_alloc.o

or

lttng-statedump.o:
  - wrapper/irqdesc.o
  - wrapper/fdtable.o

Because lttng-tracer depends on lttng-statedump, we cannot just put all
wrappers into lttng-tracer.o, because it would create a circular
dependency. This will be an issue if we introduce common wrappers which
are used in both lttng-tracer.o and in lttng-statedump.o.

Introduce a new lttng-wrapper.o to contain all wrapper symbols for all
lttng modules.

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