Warning happened in trace_buffered_event_disable() at
  WARN_ON_ONCE(!trace_buffered_event_ref)

  Call Trace:
   ? __warn+0xa5/0x1b0
   ? trace_buffered_event_disable+0x189/0x1b0
   __ftrace_event_enable_disable+0x19e/0x3e0
   free_probe_data+0x3b/0xa0
   unregister_ftrace_function_probe_func+0x6b8/0x800
   event_enable_func+0x2f0/0x3d0
   ftrace_process_regex.isra.0+0x12d/0x1b0
   ftrace_filter_write+0xe6/0x140
   vfs_write+0x1c9/0x6f0
   [...]

The cause of the warning is in __ftrace_event_enable_disable(),
trace_buffered_event_enable() was called once while
trace_buffered_event_disable() was called twice.
Reproduction script show as below, for analysis, see the comments:
 ```
 #!/bin/bash

 cd /sys/kernel/tracing/

 # 1. Register a 'disable_event' command, then:
 #    1) SOFT_DISABLED_BIT was set;
 #    2) trace_buffered_event_enable() was called first time;
 echo 'cmdline_proc_show:disable_event:initcall:initcall_finish' > \
     set_ftrace_filter

 # 2. Enable the event registered, then:
 #    1) SOFT_DISABLED_BIT was cleared;
 #    2) trace_buffered_event_disable() was called first time;
 echo 1 > events/initcall/initcall_finish/enable

 # 3. Try to call into cmdline_proc_show(), then SOFT_DISABLED_BIT was
 #    set again!!!
 cat /proc/cmdline

 # 4. Unregister the 'disable_event' command, then:
 #    1) SOFT_DISABLED_BIT was cleared again;
 #    2) trace_buffered_event_disable() was called second time!!!
 echo '!cmdline_proc_show:disable_event:initcall:initcall_finish' > \
     set_ftrace_filter
 ```

To fix it, IIUC, we can change to call trace_buffered_event_enable() at
fist time soft-mode enabled, and call trace_buffered_event_disable() at
last time soft-mode disabled.

Link: https://lore.kernel.org/linux-trace-kernel/20230726095804.920457-1-zhengyejian1@huawei.com

Cc: <mhiramat@kernel.org>
Fixes: 0fc1b09ff1ff ("tracing: Use temp buffer when filtering events")
Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Pull hardening updates from Kees Cook:
 "There are three areas of note:

  A bunch of strlcpy()->strscpy() conversions ended up living in my tree
  since they were either Acked by maintainers for me to carry, or got
  ignored for multiple weeks (and were trivial changes).

  The compiler option '-fstrict-flex-arrays=3' has been enabled
  globally, and has been in -next for the entire devel cycle. This
  changes compiler diagnostics (though mainly just -Warray-bounds which
  is disabled) and potential UBSAN_BOUNDS and FORTIFY _warning_
  coverage. In other words, there are no new restrictions, just
  potentially new warnings. Any new FORTIFY warnings we've seen have
  been fixed (usually in their respective subsystem trees). For more
  details, see commit df8fc4e934c12b.

  The under-development compiler attribute __counted_by has been added
  so that we can start annotating flexible array members with their
  associated structure member that tracks the count of flexible array
  elements at run-time. It is possible (likely?) that the exact syntax
  of the attribute will change before it is finalized, but GCC and Clang
  are working together to sort it out. Any changes can be made to the
  macro while we continue to add annotations.

  As an example of that last case, I have a treewide commit waiting with
  such annotations found via Coccinelle:

    https://git.kernel.org/linus/adc5b3cb48a049563dc673f348eab7b6beba8a9b

  Also see commit dd06e72e68bcb4 for more details.

  Summary:

   - Fix KMSAN vs FORTIFY in strlcpy/strlcat (Alexander Potapenko)

   - Convert strreplace() to return string start (Andy Shevchenko)

   - Flexible array conversions (Arnd Bergmann, Wyes Karny, Kees Cook)

   - Add missing function prototypes seen with W=1 (Arnd Bergmann)

   - Fix strscpy() kerndoc typo (Arne Welzel)

   - Replace strlcpy() with strscpy() across many subsystems which were
     either Acked by respective maintainers or were trivial changes that
     went ignored for multiple weeks (Azeem Shaikh)

   - Remove unneeded cc-option test for UBSAN_TRAP (Nick Desaulniers)

   - Add KUnit tests for strcat()-family

   - Enable KUnit tests of FORTIFY wrappers under UML

   - Add more complete FORTIFY protections for strlcat()

   - Add missed disabling of FORTIFY for all arch purgatories.

   - Enable -fstrict-flex-arrays=3 globally

   - Tightening UBSAN_BOUNDS when using GCC

   - Improve checkpatch to check for strcpy, strncpy, and fake flex
     arrays

   - Improve use of const variables in FORTIFY

   - Add requested struct_size_t() helper for types not pointers

   - Add __counted_by macro for annotating flexible array size members"

* tag 'hardening-v6.5-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: (54 commits)
  netfilter: ipset: Replace strlcpy with strscpy
  uml: Replace strlcpy with strscpy
  um: Use HOST_DIR for mrproper
  kallsyms: Replace all non-returning strlcpy with strscpy
  sh: Replace all non-returning strlcpy with strscpy
  of/flattree: Replace all non-returning strlcpy with strscpy
  sparc64: Replace all non-returning strlcpy with strscpy
  Hexagon: Replace all non-returning strlcpy with strscpy
  kobject: Use return value of strreplace()
  lib/string_helpers: Change returned value of the strreplace()
  jbd2: Avoid printing outside the boundary of the buffer
  checkpatch: Check for 0-length and 1-element arrays
  riscv/purgatory: Do not use fortified string functions
  s390/purgatory: Do not use fortified string functions
  x86/purgatory: Do not use fortified string functions
  acpi: Replace struct acpi_table_slit 1-element array with flex-array
  clocksource: Replace all non-returning strlcpy with strscpy
  string: use __builtin_memcpy() in strlcpy/strlcat
  staging: most: Replace all non-returning strlcpy with strscpy
  drm/i2c: tda998x: Replace all non-returning strlcpy with strscpy
  ...

strlcpy() reads the entire source buffer first.
This read may exceed the destination size limit.
This is both inefficient and can lead to linear read
overflows if a source string is not NUL-terminated [1].
In an effort to remove strlcpy() completely [2], replace
strlcpy() here with strscpy().

No return values were used, so direct replacement with strlcpy is safe.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
[2] https://github.com/KSPP/linux/issues/89

Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20230516143956.1367827-1-azeemshaikh38@gmail.com

The histogram and synthetic events can use a pseudo event called
"stacktrace" that will create a stacktrace at the time of the event and
use it just like it was a normal field. We have other pseudo events such
as "common_cpu" and "common_timestamp". To stay consistent with that,
convert "stacktrace" to "common_stacktrace". As this was used in older
kernels, to keep backward compatibility, this will act just like
"common_cpu" did with "cpu". That is, "cpu" will be the same as
"common_cpu" unless the event has a "cpu" field. In which case, the
event's field is used. The same is true with "stacktrace".

Also update the documentation to reflect this change.

Link: https://lore.kernel.org/linux-trace-kernel/20230523230913.6860e28d@rorschach.local.home

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Tom Zanussi <zanussi@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Pull tracing updates from Steven Rostedt:

 - Add function names as a way to filter function addresses

 - Add sample module to test ftrace ops and dynamic trampolines

 - Allow stack traces to be passed from beginning event to end event for
   synthetic events. This will allow seeing the stack trace of when a
   task is scheduled out and recorded when it gets scheduled back in.

 - Add trace event helper __get_buf() to use as a temporary buffer when
   printing out trace event output.

 - Add kernel command line to create trace instances on boot up.

 - Add enabling of events to instances created at boot up.

 - Add trace_array_puts() to write into instances.

 - Allow boot instances to take a snapshot at the end of boot up.

 - Allow live patch modules to include trace events

 - Minor fixes and clean ups

* tag 'trace-v6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (31 commits)
  tracing: Remove unnecessary NULL assignment
  tracepoint: Allow livepatch module add trace event
  tracing: Always use canonical ftrace path
  tracing/histogram: Fix stacktrace histogram Documententation
  tracing/histogram: Fix stacktrace key
  tracing/histogram: Fix a few problems with stacktrace variable printing
  tracing: Add BUILD_BUG() to make sure stacktrace fits in strings
  tracing/histogram: Don't use strlen to find length of stacktrace variables
  tracing: Allow boot instances to have snapshot buffers
  tracing: Add trace_array_puts() to write into instance
  tracing: Add enabling of events to boot instances
  tracing: Add creation of instances at boot command line
  tracing: Fix trace_event_raw_event_synth() if else statement
  samples: ftrace: Make some global variables static
  ftrace: sample: avoid open-coded 64-bit division
  samples: ftrace: Include the nospec-branch.h only for x86
  tracing: Acquire buffer from temparary trace sequence
  tracing/histogram: Wrap remaining shell snippets in code blocks
  tracing/osnoise: No need for schedule_hrtimeout range
  bpf/tracing: Use stage6 of tracing to not duplicate macros
  ...

Remove unnecessary NULL assignment int create_new_subsystem().

Link: https://lkml.kernel.org/r/20221123065124.3982439-1-bobo.shaobowang@huawei.com

Signed-off-by: Wang ShaoBo <bobo.shaobowang@huawei.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

trace_define_field_ext() is not used outside of trace_events.c, it should
be static.

Link: https://lore.kernel.org/oe-kbuild-all/202302130750.679RaRog-lkp@intel.com/

Fixes: b6c7abd1c28a ("tracing: Fix TASK_COMM_LEN in trace event format file")
Reported-by: Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

After commit 3087c61ed2c4 ("tools/testing/selftests/bpf: replace open-coded 16 with TASK_COMM_LEN"),
the content of the format file under
/sys/kernel/tracing/events/task/task_newtask was changed from
  field:char comm[16];    offset:12;    size:16;    signed:0;
to
  field:char comm[TASK_COMM_LEN];    offset:12;    size:16;    signed:0;

John reported that this change breaks older versions of perfetto.
Then Mathieu pointed out that this behavioral change was caused by the
use of __stringify(_len), which happens to work on macros, but not on enum
labels. And he also gave the suggestion on how to fix it:
  :One possible solution to make this more robust would be to extend
  :struct trace_event_fields with one more field that indicates the length
  :of an array as an actual integer, without storing it in its stringified
  :form in the type, and do the formatting in f_show where it belongs.

The result as follows after this change,
$ cat /sys/kernel/tracing/events/task/task_newtask/format
        field:char comm[16];    offset:12;      size:16;        signed:0;

Link: https://lore.kernel.org/lkml/Y+QaZtz55LIirsUO@google.com/
Link: https://lore.kernel.org/linux-trace-kernel/20230210155921.4610-1-laoar.shao@gmail.com/
Link: https://lore.kernel.org/linux-trace-kernel/20230212151303.12353-1-laoar.shao@gmail.com

Cc: stable@vger.kernel.org
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Kajetan Puchalski <kajetan.puchalski@arm.com>
CC: Qais Yousef <qyousef@layalina.io>
Fixes: 3087c61ed2c4 ("tools/testing/selftests/bpf: replace open-coded 16 with TASK_COMM_LEN")
Reported-by: John Stultz <jstultz@google.com>
Debugged-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Suggested-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Add the format of:

  trace_instance=foo,sched:sched_switch,irq_handler_entry,initcall

That will create the "foo" instance and enable the sched_switch event
(here were the "sched" system is explicitly specified), the
irq_handler_entry event, and all events under the system initcall.

Link: https://lkml.kernel.org/r/20230207173026.386114535@goodmis.org

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Ross Zwisler <zwisler@google.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

There's been several times where an event records a function address in
its field and I needed to filter on that address for a specific function
name. It required looking up the function in kallsyms, finding its size,
and doing a compare of "field >= function_start && field < function_end".

But this would change from boot to boot and is unreliable in scripts.
Also, it is useful to have this at boot up, where the addresses will not
be known. For example, on the boot command line:

  trace_trigger="initcall_finish.traceoff if func.function == acpi_init"

To implement this, add a ".function" prefix, that will check that the
field is of size long, and the only operations allowed (so far) are "=="
and "!=".

Link: https://lkml.kernel.org/r/20221219183213.916833763@goodmis.org

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Tom Zanussi <zanussi@kernel.org>
Cc: Zheng Yejian <zhengyejian1@huawei.com>
Reviewed-by: Ross Zwisler <zwisler@google.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>