Remove unnecessary NULL assignment int create_new_subsystem().

Link: https://lkml.kernel.org/r/20221123065124.3982439-1-bobo.shaobowang@huawei.comSigned-off-by: Wang ShaoBo <bobo.shaobowang@huawei.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

In the case of keeping the system running, the preferred method for
tracing the kernel is dynamic tracing (kprobe), but the drawback of
this method is that events are lost, especially when tracing packages
in the network stack.

Livepatching provides a potential solution, which is to reimplement the
function you want to replace and insert a static tracepoint.
In such a way, custom stable static tracepoints can be expanded without
rebooting the system.

Link: https://lkml.kernel.org/r/20221102160236.11696-1-iecedge@gmail.comSigned-off-by: Jianlin Lv <iecedge@gmail.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

The canonical location for the tracefs filesystem is at /sys/kernel/tracing.

But, from Documentation/trace/ftrace.rst:

  Before 4.1, all ftrace tracing control files were within the debugfs
  file system, which is typically located at /sys/kernel/debug/tracing.
  For backward compatibility, when mounting the debugfs file system,
  the tracefs file system will be automatically mounted at:

  /sys/kernel/debug/tracing

Many comments and Kconfig help messages in the tracing code still refer
to this older debugfs path, so let's update them to avoid confusion.

Link: https://lore.kernel.org/linux-trace-kernel/20230215223350.2658616-2-zwisler@google.comAcked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: Mukesh Ojha <quic_mojha@quicinc.com>
Signed-off-by: Ross Zwisler <zwisler@google.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Fix a small problem with the histogram specification in the
Documentation, and change the example to show output using a
stacktrace field rather than the global stacktrace.

Link: https://lkml.kernel.org/r/f75f807dd4998249e513515f703a2ff7407605f4.1676063532.git.zanussi@kernel.orgSigned-off-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

The current code will always use the current stacktrace as a key even
if a stacktrace contained in a specific event field was specified.

For example, we expect to use the 'unsigned long[] stack' field in the
below event in the histogram:

  # echo 's:block_lat pid_t pid; u64 delta; unsigned long[] stack;' > /sys/kernel/debug/tracing/dynamic_events
  # echo 'hist:keys=delta.buckets=100,stack.stacktrace:sort=delta' > /sys/kernel/debug/tracing/events/synthetic/block_lat/trigger

But in fact, when we type out the trigger, we see that it's using the
plain old global 'stacktrace' as the key, which is just the stacktrace
when the event was hit and not the stacktrace contained in the event,
which is what we want:

  # cat /sys/kernel/debug/tracing/events/synthetic/block_lat/trigger
  hist:keys=delta.buckets=100,stacktrace:vals=hitcount:sort=delta.buckets=100:size=2048 [active]

And in fact, there's no code to actually retrieve it from the event,
so we need to add HIST_FIELD_FN_STACK and hist_field_stack() to get it
and hook it into the trigger code.  For now, since the stack is just
using dynamic strings, this could just use the dynamic string
function, but it seems cleaner to have a dedicated function an be able
to tweak independently as necessary.

Link: https://lkml.kernel.org/r/11aa614c82976adbfa4ea763dbe885b5fb01d59c.1676063532.git.zanussi@kernel.orgSigned-off-by: Tom Zanussi <zanussi@kernel.org>
[ Fixed 32bit build warning reported by kernel test robot <lkp@intel.com> ]
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Currently, there are a few problems when printing hist triggers and
trace output when using stacktrace variables.  This fixes the problems
seen below:

  # echo 'hist:keys=delta.buckets=100,stack.stacktrace:sort=delta' > /sys/kernel/debug/tracing/events/synthetic/block_lat/trigger
  # cat /sys/kernel/debug/tracing/events/synthetic/block_lat/trigger
  hist:keys=delta.buckets=100,stacktrace:vals=hitcount:sort=delta.buckets=100:size=2048 [active]

  # echo 'hist:keys=next_pid:ts=common_timestamp.usecs,st=stacktrace  if prev_state == 2' >> /sys/kernel/debug/tracing/events/sched/sched_switch/trigger
  # cat /sys/kernel/debug/tracing/events/sched/sched_switch/trigger
  hist:keys=next_pid:vals=hitcount:ts=common_timestamp.usecs,st=stacktrace.stacktrace:sort=hitcount:size=2048:clock=global if prev_state == 2 [active]

and also in the trace output (should be stack.stacktrace):

  {  delta: ~ 100-199, stacktrace         __schedule+0xa19/0x1520

Link: https://lkml.kernel.org/r/60bebd4e546728e012a7a2bcbf58716d48ba6edb.1676063532.git.zanussi@kernel.orgSigned-off-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

The max string length for a histogram variable is 256 bytes. The max depth
of a stacktrace is 16. With 8byte words, that's 16 * 8 = 128. Which can
easily fit in the string variable. The histogram stacktrace is being
stored in the string value (with the given max length), with the
assumption it will fit. To make sure that this is always the case (in the
case that the stack trace depth increases), add a BUILD_BUG_ON() to test
this.

Link: https://lore.kernel.org/linux-trace-kernel/20230214002418.0103b9e765d3e5c374d2aa7d@kernel.org/Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Because stacktraces are saved in dynamic strings,
trace_event_raw_event_synth() uses strlen to determine the length of
the stack.  Stacktraces may contain 0-bytes, though, in the saved
addresses, so the length found and passed to reserve() will be too
small.

Fix this by using the first unsigned long in the stack variables to
store the actual number of elements in the stack and have
trace_event_raw_event_synth() use that to determine the length of the
stack.

Link: https://lkml.kernel.org/r/1ed6906cd9d6477ef2bd8e63c61de20a9ffe64d7.1676063532.git.zanussi@kernel.orgSigned-off-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Add to ftrace_boot_snapshot, "=<instance>" name, where the instance will
get a snapshot buffer, and will take a snapshot at the end of boot (which
will save the boot traces).

Link: https://lkml.kernel.org/r/20230207173026.792774721@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>

Add a generic trace_array_puts() that can be used to "trace_puts()" into
an allocated trace_array instance. This is just another variant of
trace_array_printk().

Link: https://lkml.kernel.org/r/20230207173026.584717290@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>

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>

Add kernel command line to add tracing instances. This only creates
instances at boot but still does not enable any events to them. Later
changes will extend this command line to add enabling of events, filters,
and triggers. As well as possibly redirecting trace_printk()!

Link: https://lkml.kernel.org/r/20230207173026.186210158@goodmis.org

Cc: Randy Dunlap <rdunlap@infradead.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>

The test to check if the field is a stack is to be done if it is not a
string. But the code had:

    } if (event->fields[i]->is_stack) {

and not

   } else if (event->fields[i]->is_stack) {

which would cause it to always be tested. Worse yet, this also included an
"else" statement that was only to be called if the field was not a string
and a stack, but this code allows it to be called if it was a string (and
not a stack).

Also fixed some whitespace issues.

Link: https://lore.kernel.org/all/202301302110.mEtNwkBD-lkp@intel.com/
Link: https://lore.kernel.org/linux-trace-kernel/20230131095237.63e3ca8d@gandalf.local.home

Cc: Tom Zanussi <zanussi@kernel.org>
Fixes: 00cf3d67 ("tracing: Allow synthetic events to pass around stacktraces")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

smatch reports this representative issue
samples/ftrace/ftrace-ops.c:15:14: warning: symbol 'nr_function_calls' was not declared. Should it be static?

The nr_functions_calls and several other global variables are only
used in ftrace-ops.c, so they should be static.
Remove the instances of initializing static int to 0.

Link: https://lore.kernel.org/linux-trace-kernel/20230130193708.1378108-1-trix@redhat.comSigned-off-by: Tom Rix <trix@redhat.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Calculating the average period requires a 64-bit division that leads
to a link failure on 32-bit architectures:

x86_64-linux-ld: samples/ftrace/ftrace-ops.o: in function `ftrace_ops_sample_init':
ftrace-ops.c:(.init.text+0x23b): undefined reference to `__udivdi3'

Use the div_u64() helper to do this instead. Since this is an init function that
is not called frequently, the runtime overhead is going to be acceptable.

Link: https://lore.kernel.org/linux-trace-kernel/20230130130246.247537-1-arnd@kernel.org

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Fixes: b56c68f7 ("ftrace: Add sample with custom ops")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

When other architectures without the nospec functionality write their
direct-call functions of samples/ftrace/*.c, the including of
asm/nospec-branch.h must be taken care to fix the no header file found
error in building process.

This commit (ee3e2469 "x86/ftrace: Make it call depth tracking aware")
file-globally includes asm/nospec-branch.h providing CALL_DEPTH_ACCOUNT
for only x86 direct-call functions.

It seems better to move the including to `#ifdef CONFIG_X86_64`.

Link: https://lore.kernel.org/linux-trace-kernel/20230130085954.647845-1-suagrfillet@gmail.comSigned-off-by: Song Shuai <suagrfillet@gmail.com>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

there is one dwc3 trace event declare as below,
DECLARE_EVENT_CLASS(dwc3_log_event,
	TP_PROTO(u32 event, struct dwc3 *dwc),
	TP_ARGS(event, dwc),
	TP_STRUCT__entry(
		__field(u32, event)
		__field(u32, ep0state)
		__dynamic_array(char, str, DWC3_MSG_MAX)
	),
	TP_fast_assign(
		__entry->event = event;
		__entry->ep0state = dwc->ep0state;
	),
	TP_printk("event (%08x): %s", __entry->event,
			dwc3_decode_event(__get_str(str), DWC3_MSG_MAX,
				__entry->event, __entry->ep0state))
);
the problem is when trace function called, it will allocate up to
DWC3_MSG_MAX bytes from trace event buffer, but never fill the buffer
during fast assignment, it only fill the buffer when output function are
called, so this means if output function are not called, the buffer will
never used.

add __get_buf(len) which acquiree buffer from iter->tmp_seq when trace
output function called, it allow user write string to acquired buffer.

the mentioned dwc3 trace event will changed as below,
DECLARE_EVENT_CLASS(dwc3_log_event,
	TP_PROTO(u32 event, struct dwc3 *dwc),
	TP_ARGS(event, dwc),
	TP_STRUCT__entry(
		__field(u32, event)
		__field(u32, ep0state)
	),
	TP_fast_assign(
		__entry->event = event;
		__entry->ep0state = dwc->ep0state;
	),
	TP_printk("event (%08x): %s", __entry->event,
		dwc3_decode_event(__get_buf(DWC3_MSG_MAX), DWC3_MSG_MAX,
				__entry->event, __entry->ep0state))
);.

Link: https://lore.kernel.org/linux-trace-kernel/1675065249-23368-1-git-send-email-quic_linyyuan@quicinc.com

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Linyu Yuan <quic_linyyuan@quicinc.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Most shell command snippets (echo/cat) and their output are already in
literal code blocks. However a few still isn't wrapped, in which the
htmldocs output is ugly.

Wrap the remaining unwrapped snippets, while also fix recent kernel test
robot warnings.

Link: https://lore.kernel.org/linux-trace-kernel/20230129031402.47420-1-bagasdotme@gmail.com

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/linux-doc/202301290253.LU5yIxcJ-lkp@intel.com/
Fixes: 88238513 ("tracing/histogram: Document variable stacktrace")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

No slack time is being passed, just use schedule_hrtimeout().

Link: https://lore.kernel.org/linux-trace-kernel/20230123234649.17968-1-dave@stgolabs.netSigned-off-by: Davidlohr Bueso <dave@stgolabs.net>
Acked-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

The bpf events are created by the same macro magic as tracefs trace
events are. But to hook into bpf, it has its own code. It duplicates many
of the same macros as the tracefs macros and this is an issue because it
misses bug fixes as well as any new enhancements that come with the other
trace macros.

As the trace macros have been put into their own staging files, have bpf
take advantage of this and use the tracefs stage 6 macros that the "fast
ssign" portion of the trace event macro uses.

Link: https://lkml.kernel.org/r/20230124202515.873075730@goodmis.org
Link: https://lore.kernel.org/lkml/1671181385-5719-1-git-send-email-quic_linyyuan@quicinc.com/

Cc: bpf@vger.kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Reported-by: Linyu Yuan <quic_linyyuan@quicinc.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

The perf events are created by the same macro magic as tracefs trace
events are. But to hook into perf, it has its own code. It duplicates many
of the same macros as the tracefs macros and this is an issue because it
misses bug fixes as well as any new enhancements that come with the other
trace macros.

As the trace macros have been put into their own staging files, have perf
take advantage of this and use the tracefs stage 6 macros that the "fast
assign" portion of the trace event macro uses.

Link: https://lkml.kernel.org/r/20230124202515.716458410@goodmis.org
Link: https://lore.kernel.org/lkml/1671181385-5719-1-git-send-email-quic_linyyuan@quicinc.com/

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reported-by: Linyu Yuan <quic_linyyuan@quicinc.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Update the selftests to include a test of passing a stacktrace between the
events of a synthetic event.

Link: https://lkml.kernel.org/r/20230117152236.475439286@goodmis.org

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

Add a little documentation (and a useful example) of how a stacktrace can
be used within a histogram variable and synthetic event.

Link: https://lkml.kernel.org/r/20230117152236.320181354@goodmis.org

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

Now that stacktraces can be part of synthetic events, allow a key to be
typed as a stacktrace.

  # cd /sys/kernel/tracing
  # echo 's:block_lat u64 delta; unsigned long stack[];' >> dynamic_events
  # echo 'hist:keys=next_pid:ts=common_timestamp.usecs,st=stacktrace if prev_state == 2' >> events/sched/sched_switch/trigger
  # echo 'hist:keys=prev_pid:delta=common_timestamp.usecs-$ts,st2=$st:onmatch(sched.sched_switch).trace(block_lat,$delta,$st2)' >> events/sched/sched_switch/trigger
  # echo 'hist:keys=delta.buckets=100,stack.stacktrace:sort=delta' > events/synthetic/block_lat/trigger

  # cat events/synthetic/block_lat/hist

  # event histogram
  #
  # trigger info: hist:keys=delta.buckets=100,stacktrace:vals=hitcount:sort=delta.buckets=100:size=2048 [active]
  #

  { delta: ~ 0-99, stacktrace:
           event_hist_trigger+0x464/0x480
           event_triggers_call+0x52/0xe0
           trace_event_buffer_commit+0x193/0x250
           trace_event_raw_event_sched_switch+0xfc/0x150
           __traceiter_sched_switch+0x41/0x60
           __schedule+0x448/0x7b0
           schedule_idle+0x26/0x40
           cpu_startup_entry+0x19/0x20
           start_secondary+0xed/0xf0
           secondary_startup_64_no_verify+0xe0/0xeb
  } hitcount:          6
  { delta: ~ 0-99, stacktrace:
           event_hist_trigger+0x464/0x480
           event_triggers_call+0x52/0xe0
           trace_event_buffer_commit+0x193/0x250
           trace_event_raw_event_sched_switch+0xfc/0x150
           __traceiter_sched_switch+0x41/0x60
           __schedule+0x448/0x7b0
           schedule_idle+0x26/0x40
           cpu_startup_entry+0x19/0x20
           __pfx_kernel_init+0x0/0x10
           arch_call_rest_init+0xa/0x24
           start_kernel+0x964/0x98d
           secondary_startup_64_no_verify+0xe0/0xeb
  } hitcount:          3
  { delta: ~ 0-99, stacktrace:
           event_hist_trigger+0x464/0x480
           event_triggers_call+0x52/0xe0
           trace_event_buffer_commit+0x193/0x250
           trace_event_raw_event_sched_switch+0xfc/0x150
           __traceiter_sched_switch+0x41/0x60
           __schedule+0x448/0x7b0
           schedule+0x5a/0xb0
           worker_thread+0xaf/0x380
           kthread+0xe9/0x110
           ret_from_fork+0x2c/0x50
  } hitcount:          1
  { delta: ~ 100-199, stacktrace:
           event_hist_trigger+0x464/0x480
           event_triggers_call+0x52/0xe0
           trace_event_buffer_commit+0x193/0x250
           trace_event_raw_event_sched_switch+0xfc/0x150
           __traceiter_sched_switch+0x41/0x60
           __schedule+0x448/0x7b0
           schedule_idle+0x26/0x40
           cpu_startup_entry+0x19/0x20
           start_secondary+0xed/0xf0
           secondary_startup_64_no_verify+0xe0/0xeb
  } hitcount:         15
  [..]
  { delta: ~ 8500-8599, stacktrace:
           event_hist_trigger+0x464/0x480
           event_triggers_call+0x52/0xe0
           trace_event_buffer_commit+0x193/0x250
           trace_event_raw_event_sched_switch+0xfc/0x150
           __traceiter_sched_switch+0x41/0x60
           __schedule+0x448/0x7b0
           schedule_idle+0x26/0x40
           cpu_startup_entry+0x19/0x20
           start_secondary+0xed/0xf0
           secondary_startup_64_no_verify+0xe0/0xeb
  } hitcount:          1

  Totals:
      Hits: 89
      Entries: 11
      Dropped: 0

Link: https://lkml.kernel.org/r/20230117152236.167046397@goodmis.org

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

Allow a stacktrace from one event to be displayed by the end event of a
synthetic event. This is very useful when looking for the longest latency
of a sleep or something blocked on I/O.

 # cd /sys/kernel/tracing/
 # echo 's:block_lat pid_t pid; u64 delta; unsigned long[] stack;' > dynamic_events
 # echo 'hist:keys=next_pid:ts=common_timestamp.usecs,st=stacktrace  if prev_state == 1||prev_state == 2' > events/sched/sched_switch/trigger
 # echo 'hist:keys=prev_pid:delta=common_timestamp.usecs-$ts,s=$st:onmax($delta).trace(block_lat,prev_pid,$delta,$s)' >> events/sched/sched_switch/trigger

The above creates a "block_lat" synthetic event that take the stacktrace of
when a task schedules out in either the interruptible or uninterruptible
states, and on a new per process max $delta (the time it was scheduled
out), will print the process id and the stacktrace.

  # echo 1 > events/synthetic/block_lat/enable
  # cat trace
 #           TASK-PID     CPU#  |||||  TIMESTAMP  FUNCTION
 #              | |         |   |||||     |         |
    kworker/u16:0-767     [006] d..4.   560.645045: block_lat: pid=767 delta=66 stack=STACK:
 => __schedule
 => schedule
 => pipe_read
 => vfs_read
 => ksys_read
 => do_syscall_64
 => 0x966000aa

           <idle>-0       [003] d..4.   561.132117: block_lat: pid=0 delta=413787 stack=STACK:
 => __schedule
 => schedule
 => schedule_hrtimeout_range_clock
 => do_sys_poll
 => __x64_sys_poll
 => do_syscall_64
 => 0x966000aa

            <...>-153     [006] d..4.   562.068407: block_lat: pid=153 delta=54 stack=STACK:
 => __schedule
 => schedule
 => io_schedule
 => rq_qos_wait
 => wbt_wait
 => __rq_qos_throttle
 => blk_mq_submit_bio
 => submit_bio_noacct_nocheck
 => ext4_bio_write_page
 => mpage_submit_page
 => mpage_process_page_bufs
 => mpage_prepare_extent_to_map
 => ext4_do_writepages
 => ext4_writepages
 => do_writepages
 => __writeback_single_inode

Link: https://lkml.kernel.org/r/20230117152236.010941267@goodmis.org

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

Allow to save stacktraces into a histogram variable. This will be used by
synthetic events to allow a stacktrace from one event to be passed and
displayed by another event.

The special keyword "stacktrace" is to be used to trigger a stack
trace for the event that the histogram trigger is attached to.

  echo 'hist:keys=pid:st=stacktrace" > events/sched/sched_waking/trigger

Currently nothing can get access to the "$st" variable above that contains
the stack trace, but that will soon change.

Link: https://lkml.kernel.org/r/20230117152235.856323729@goodmis.org

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

When tracing a dynamic string field for a synthetic event, the offset
calculation for where to write the next event can use struct_size() to
find what the current size of the structure is.

This simplifies the code and makes it less error prone.

Link: https://lkml.kernel.org/r/20230117152235.698632147@goodmis.org

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

In a previous commit 7433632c, buffer, buffer->buffers and
buffer->buffers[cpu] in ring_buffer_wake_waiters() can be NULL,
and thus the related checks are added.

However, in the same call stack, these variables are also used in
ring_buffer_free_read_page():

tracing_buffers_release()
  ring_buffer_wake_waiters(iter->array_buffer->buffer)
    cpu_buffer = buffer->buffers[cpu] -> Add checks by previous commit
  ring_buffer_free_read_page(iter->array_buffer->buffer)
    cpu_buffer = buffer->buffers[cpu] -> No check

Thus, to avod possible null-pointer derefernces, the related checks
should be added.

These results are reported by a static tool designed by myself.

Link: https://lkml.kernel.org/r/20230113125501.760324-1-baijiaju1990@gmail.comReported-by: TOTE Robot <oslab@tsinghua.edu.cn>
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

When reworking core ftrace code or architectural ftrace code, it's often
necessary to test/analyse/benchmark a number of ftrace_ops
configurations. This patch adds a module which can be used to explore
some of those configurations.

I'm using this to benchmark various options for changing the way
trampolines and handling of ftrace_ops work on arm64, and ensuring other
architectures aren't adversely affected.

For example, in a QEMU+KVM VM running on a 2GHz Xeon E5-2660
workstation, loading the module in various configurations produces:

| # insmod ftrace-ops.ko
| ftrace_ops: registering:
|   relevant ops: 1
|     tracee: tracee_relevant [ftrace_ops]
|     tracer: ops_func_nop [ftrace_ops]
|   irrelevant ops: 0
|     tracee: tracee_irrelevant [ftrace_ops]
|     tracer: ops_func_nop [ftrace_ops]
|   saving registers: NO
|   assist recursion: NO
|   assist RCU: NO
| ftrace_ops: Attempted 100000 calls to tracee_relevant [ftrace_ops] in 1681558ns (16ns / call)

| # insmod ftrace-ops.ko nr_ops_irrelevant=5
| ftrace_ops: registering:
|   relevant ops: 1
|     tracee: tracee_relevant [ftrace_ops]
|     tracer: ops_func_nop [ftrace_ops]
|   irrelevant ops: 5
|     tracee: tracee_irrelevant [ftrace_ops]
|     tracer: ops_func_nop [ftrace_ops]
|   saving registers: NO
|   assist recursion: NO
|   assist RCU: NO
| ftrace_ops: Attempted 100000 calls to tracee_relevant [ftrace_ops] in 1693042ns (16ns / call)

| # insmod ftrace-ops.ko nr_ops_relevant=2
| ftrace_ops: registering:
|   relevant ops: 2
|     tracee: tracee_relevant [ftrace_ops]
|     tracer: ops_func_nop [ftrace_ops]
|   irrelevant ops: 0
|     tracee: tracee_irrelevant [ftrace_ops]
|     tracer: ops_func_nop [ftrace_ops]
|   saving registers: NO
|   assist recursion: NO
|   assist RCU: NO
| ftrace_ops: Attempted 100000 calls to tracee_relevant [ftrace_ops] in 11965582ns (119ns / call)

| # insmod ftrace-ops.ko save_regs=true
| ftrace_ops: registering:
|   relevant ops: 1
|     tracee: tracee_relevant [ftrace_ops]
|     tracer: ops_func_nop [ftrace_ops]
|   irrelevant ops: 0
|     tracee: tracee_irrelevant [ftrace_ops]
|     tracer: ops_func_nop [ftrace_ops]
|   saving registers: YES
|   assist recursion: NO
|   assist RCU: NO
| ftrace_ops: Attempted 100000 calls to tracee_relevant [ftrace_ops] in 4459624ns (44ns / call)

Link: https://lkml.kernel.org/r/20230103124912.2948963-4-mark.rutland@arm.com

Cc: Florent Revest <revest@chromium.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

With the new filter logic of passing in the name of a function to match an
instruction pointer (or the address of the function), add a test to make
sure that it is functional.

This is also the first test to test plain filtering. The filtering has
been tested via the trigger logic, which uses the same code, but there was
nothing to test just the event filter, so this test is the first to add
such a case.

Link: https://lkml.kernel.org/r/20221219183214.075559302@goodmis.org

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Tom Zanussi <zanussi@kernel.org>
Cc: Zheng Yejian <zhengyejian1@huawei.com>
Cc: linux-kselftest@vger.kernel.org
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: Ross Zwisler <zwisler@google.com>
Acked-by: Shuah Khan <skhan@linuxfoundation.org>
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>

The pointer ptr is being initialized with a value that is never read,
it is being updated later on a call to strim. Remove the extraneous
initialization.

Link: https://lkml.kernel.org/r/20230116161612.77192-1-colin.i.king@gmail.com

Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

There's no entry in MAINTAINERS for samples/ftrace. Add one so that the
FTRACE maintainers are kept in the loop.

Link: https://lkml.kernel.org/r/20230103124912.2948963-2-mark.rutland@arm.comAcked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Use the 'struct' keyword for a struct's kernel-doc notation and
use the correct function parameter name to eliminate kernel-doc
warnings:

kernel/trace/trace_events_filter.c:136: warning: cannot understand function prototype: 'struct prog_entry '
kerne/trace/trace_events_filter.c:155: warning: Excess function parameter 'when_to_branch' description in 'update_preds'

Also correct some trivial punctuation problems.

Link: https://lkml.kernel.org/r/20230108021238.16398-1-rdunlap@infradead.orgSigned-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Fix spelling in lib/ Kconfig files.
(reported by codespell)

Link: https://lkml.kernel.org/r/20230124181655.16269-1-rdunlap@infradead.org

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Marco Elver <elver@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: kasan-dev@googlegroups.com
Reviewed-by: Marco Elver <elver@google.com>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Function 'create_hist_field' is called recursively at
trace_events_hist.c:1954 and can return NULL-value that's why we have
to check it to avoid null pointer dereference.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Link: https://lkml.kernel.org/r/20230111120409.4111-1-n.petrova@fintech.ru

Cc: stable@vger.kernel.org
Fixes: 30350d65 ("tracing: Add variable support to hist triggers")
Signed-off-by: Natalia Petrova <n.petrova@fintech.ru>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

list_for_each_entry_rcu() has built-in RCU and lock checking.

Pass cond argument to list_for_each_entry_rcu() to silence false lockdep
warning when CONFIG_PROVE_RCU_LIST is enabled.

Execute as follow:

 [tracing]# echo osnoise > current_tracer
 [tracing]# echo 1 > tracing_on
 [tracing]# echo 0 > tracing_on

The trace_types_lock is held when osnoise_tracer_stop() or
timerlat_tracer_stop() are called in the non-RCU read side section.
So, pass lockdep_is_held(&trace_types_lock) to silence false lockdep
warning.

Link: https://lkml.kernel.org/r/20221227023036.784337-1-nashuiliang@gmail.com

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Fixes: dae18134 ("tracing/osnoise: Support a list of trace_array *tr")
Acked-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Chuang Wang <nashuiliang@gmail.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Fix some editorial nits in trace Kconfig.

Link: https://lkml.kernel.org/r/20230124181647.15902-1-rdunlap@infradead.orgSigned-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

The instructions for the ftrace-bisect.sh script, which is used to find
what function is being traced that is causing a kernel crash, and possibly
a triple fault reboot, uses the old method. In 5.1, a new feature was
added that let the user write in the index into available_filter_functions
that maps to the function a user wants to set in set_ftrace_filter (or
set_ftrace_notrace). This takes O(1) to set, as suppose to writing a
function name, which takes O(n) (where n is the number of functions in
available_filter_functions).

The ftrace-bisect.sh requires setting half of the functions in
available_filter_functions, which is O(n^2) using the name method to enable
and can take several minutes to complete. The number method is O(n) which
takes less than a second to complete. Using the number method for any
kernel 5.1 and after is the proper way to do the bisect.

Update the usage to reflect the new change, as well as using the
/sys/kernel/tracing path instead of the obsolete debugfs path.

Link: https://lkml.kernel.org/r/20230123112252.022003dd@gandalf.local.home

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Fixes: f79b3f33 ("ftrace: Allow enabling of filters via index of available_filter_functions")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Currently trace_printk() can be used as soon as early_trace_init() is
called from start_kernel(). But if a crash happens, and
"ftrace_dump_on_oops" is set on the kernel command line, all you get will
be:

  [    0.456075]   <idle>-0         0dN.2. 347519us : Unknown type 6
  [    0.456075]   <idle>-0         0dN.2. 353141us : Unknown type 6
  [    0.456075]   <idle>-0         0dN.2. 358684us : Unknown type 6

This is because the trace_printk() event (type 6) hasn't been registered
yet. That gets done via an early_initcall(), which may be early, but not
early enough.

Instead of registering the trace_printk() event (and other ftrace events,
which are not trace events) via an early_initcall(), have them registered at
the same time that trace_printk() can be used. This way, if there is a
crash before early_initcall(), then the trace_printk()s will actually be
useful.

Link: https://lkml.kernel.org/r/20230104161412.019f6c55@gandalf.local.home

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Fixes: e725c731 ("tracing: Split tracing initialization into two for early initialization")
Reported-by: "Joel Fernandes (Google)" <joel@joelfernandes.org>
Tested-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>