linux-toradex.git/kernel/trace/trace_events_hist.c, branch v4.17-rc1

tracing: Uninitialized variable in create_tracing_map_fields()

2018-04-06T12:56:50+00:00

Smatch complains that idx can be used uninitialized when we check if
(idx < 0).  It has to be the first iteration through the loop and the
HIST_FIELD_FL_STACKTRACE bit has to be clear and the HIST_FIELD_FL_VAR
bit has to be set to reach the bug.

Link: http://lkml.kernel.org/r/20180328114815.GC29050@mwanda

Fixes: 30350d65ac56 ("tracing: Add variable support to hist triggers")
Acked-by: Tom Zanussi 
Signed-off-by: Dan Carpenter 
Signed-off-by: Steven Rostedt (VMware)

tracing: Make sure variable string fields are NULL-terminated

2018-04-06T12:56:50+00:00

The strncpy() currently being used for variable string fields can
result in a lack of termination if the string length is equal to the
field size.  Use the safer strscpy() instead, which will guarantee
termination.

Link: http://lkml.kernel.org/r/fb97c1e518fb358c12a4057d7445ba2c46956cd7.1522256721.git.tom.zanussi@linux.intel.com

Signed-off-by: Tom Zanussi 
Signed-off-by: Steven Rostedt (VMware)

tracing: Add action comparisons when testing matching hist triggers

2018-04-06T12:56:49+00:00

Actions also need to be considered when checking for matching triggers
- triggers differing only by action should be allowed, but currently
aren't because the matching check ignores the action and erroneously
returns -EEXIST.

Add and call an actions_match() function to address that.

Here's an example using onmatch() actions.  The first -EEXIST shouldn't
occur because the onmatch() is different in the second wakeup_latency()
param.  The second -EEXIST shouldn't occur because it's a different
action (in this case, it doesn't have an action, so shouldn't be seen
as being the same and therefore rejected).

In the after case, both are correctly accepted (and trying to add one of
them again returns -EEXIST as it should).

before:

  # echo 'wakeup_latency u64 lat; pid_t pid' >> /sys/kernel/debug/tracing/synthetic_events
  # echo 'hist:keys=pid:ts0=common_timestamp.usecs if comm=="cyclictest"' >> /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
  # echo 'hist:keys=next_pid:wakeup_lat=common_timestamp.usecs-$ts0 if next_comm=="cyclictest"' >> /sys/kernel/debug/tracing/events/sched/sched_switch/trigger
  # echo 'hist:keys=next_pid:onmatch(sched.sched_wakeup).wakeup_latency(sched.sched_switch.$wakeup_lat,next_pid) if next_comm=="cyclictest"' >> /sys/kernel/debug/tracing/events/sched/sched_switch/trigger
  # echo 'hist:keys=next_pid:onmatch(sched.sched_wakeup).wakeup_latency(sched.sched_switch.$wakeup_lat,prev_pid) if next_comm=="cyclictest"' >> /sys/kernel/debug/tracing/events/sched/sched_switch/trigger
-su: echo: write error: File exists
  # echo 'hist:keys=next_pid if next_comm=="cyclictest"' >> /sys/kernel/debug/tracing/events/sched/sched_switch/trigger
-su: echo: write error: File exists

after:

  # echo 'wakeup_latency u64 lat; pid_t pid' >> /sys/kernel/debug/tracing/synthetic_events
  # echo 'hist:keys=pid:ts0=common_timestamp.usecs if comm=="cyclictest"' >> /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
  # echo 'hist:keys=next_pid:wakeup_lat=common_timestamp.usecs-$ts0 if next_comm=="cyclictest"' >> /sys/kernel/debug/tracing/events/sched/sched_switch/trigger
  # echo 'hist:keys=next_pid:onmatch(sched.sched_wakeup).wakeup_latency(sched.sched_switch.$wakeup_lat,next_pid) if next_comm=="cyclictest"' >> /sys/kernel/debug/tracing/events/sched/sched_switch/trigger
  # echo 'hist:keys=next_pid:onmatch(sched.sched_wakeup).wakeup_latency(sched.sched_switch.$wakeup_lat,prev_pid) if next_comm=="cyclictest"' >> /sys/kernel/debug/tracing/events/sched/sched_switch/trigger
  # echo 'hist:keys=next_pid if next_comm=="cyclictest"' >> /sys/kernel/debug/tracing/events/sched/sched_switch/trigger

Link: http://lkml.kernel.org/r/a7fd668b87ec10736c8f016ac4279c8480d50c2b.1522256721.git.tom.zanussi@linux.intel.com

Tested-by: Masami Hiramatsu 
Signed-off-by: Tom Zanussi 
Signed-off-by: Steven Rostedt (VMware)

tracing: Don't add flag strings when displaying variable references

2018-04-06T12:56:49+00:00

Variable references should never have flags appended when displayed -
prevent that from happening.

Before:

  # cat /sys/kernel/debug/tracing/events/sched/sched_switch/trigger
  hist:keys=next_pid:vals=hitcount:wakeup_lat=common_timestamp.usecs-$ts0.usecs:...

After:

  hist:keys=next_pid:vals=hitcount:wakeup_lat=common_timestamp.usecs-$ts0:...

Link: http://lkml.kernel.org/r/913318a5610ef6b24af2522575f671fa6ee19b6b.1522256721.git.tom.zanussi@linux.intel.com

Signed-off-by: Tom Zanussi 
Signed-off-by: Steven Rostedt (VMware)

tracing: Fix display of hist trigger expressions containing timestamps

2018-04-06T12:56:48+00:00

When displaying hist triggers, variable references that have the
timestamp field flag set are erroneously displayed as common_timestamp
rather than the variable reference.  Additionally, timestamp
expressions are displayed in the same way.  Fix this by forcing the
timestamp flag handling to follow variable reference and expression
handling.

Before:

  # cat /sys/kernel/debug/tracing/events/sched/sched_switch/trigger
  hist:keys=next_pid:vals=hitcount:wakeup_lat=common_timestamp.usecs:...

After:

  # cat /sys/kernel/debug/tracing/events/sched/sched_switch/trigger
  hist:keys=next_pid:vals=hitcount:wakeup_lat=common_timestamp.usecs-$ts0.usecs:...

Link: http://lkml.kernel.org/r/92746b06be67499c2a6217bd55395b350ad18fad.1522256721.git.tom.zanussi@linux.intel.com

Signed-off-by: Tom Zanussi 
Signed-off-by: Steven Rostedt (VMware)

tracing: Fix a potential NULL dereference

2018-03-23T15:15:20+00:00

We forgot to set the error code on this path so we return ERR_PTR(0)
which is NULL.  It results in a NULL dereference in the caller.

Link: http://lkml.kernel.org/r/20180323113735.GC28518@mwanda

Fixes: 100719dcef44 ("tracing: Add simple expression support to hist triggers")
Acked-by: Tom Zanussi 
Signed-off-by: Dan Carpenter 
Signed-off-by: Steven Rostedt (VMware)

tracing: Use the ring-buffer nesting to allow synthetic events to be traced

2018-03-10T21:06:04+00:00

Synthetic events can be done within the recording of other events. Notify
the ring buffer via ring_buffer_nest_start() and ring_buffer_nest_end() that
this is intended and not to block it due to its recursion protection.

Signed-off-by: Steven Rostedt (VMware)

tracing: Add a clock attribute for hist triggers

2018-03-10T21:06:03+00:00

The default clock if timestamps are used in a histogram is "global".
If timestamps aren't used, the clock is irrelevant.

Use the "clock=" param only if you want to override the default
"global" clock for a histogram with timestamps.

Link: http://lkml.kernel.org/r/427bed1389c5d22aa40c3e0683e30cc3d151e260.1516069914.git.tom.zanussi@linux.intel.com

Signed-off-by: Tom Zanussi 
Signed-off-by: Rajvi Jingar 
Signed-off-by: Steven Rostedt (VMware)

tracing: Add 'last error' error facility for hist triggers

2018-03-10T21:06:02+00:00

With the addition of variables and actions, it's become necessary to
provide more detailed error information to users about syntax errors.

Add a 'last error' facility accessible via the erroring event's 'hist'
file.  Reading the hist file after an error will display more detailed
information about what went wrong, if information is available.  This
extended error information will be available until the next hist
trigger command for that event.

  # echo xxx > /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
  echo: write error: Invalid argument

  # cat /sys/kernel/debug/tracing/events/sched/sched_wakeup/hist

  ERROR: Couldn't yyy: zzz
  Last command: xxx

Also add specific error messages for variable and action errors.

Link: http://lkml.kernel.org/r/64e9c422fc8aeafcc2f7a3b4328c0cffe7969129.1516069914.git.tom.zanussi@linux.intel.com

Signed-off-by: Tom Zanussi 
Signed-off-by: Steven Rostedt (VMware)

tracing: Add hist trigger support for variable reference aliases

2018-03-10T21:06:01+00:00

Add support for alias=$somevar where alias can be used as
onmatch.xxx($alias).

Aliases are a way of creating a new name for an existing variable, for
flexibly in making naming more clear in certain cases.  For example in
the below the user perhaps feels that using $new_lat in the synthetic
event invocation is opaque or doesn't fit well stylistically with
previous triggers, so creates an alias of $new_lat named $latency and
uses that in the call instead:

  # echo 'hist:keys=next_pid:new_lat=common_timestamp.usecs' >
    /sys/kernel/debug/tracing/events/sched/sched_switch/trigger

  # echo 'hist:keys=pid:latency=$new_lat:
    onmatch(sched.sched_switch).wake2($latency,pid)' >
    /sys/kernel/debug/tracing/events/synthetic/wake1/trigger

Link: http://lkml.kernel.org/r/ef20a65d921af3a873a6f1e8c71407c926d5586f.1516069914.git.tom.zanussi@linux.intel.com

Signed-off-by: Tom Zanussi 
Signed-off-by: Steven Rostedt (VMware)