linux-toradex.git/kernel/trace/trace.h, branch v5.19-rc8

tracing: Have existing event_command.parse() implementations use helpers

2022-04-26T21:58:50+00:00

Simplify the existing event_command.parse() implementations by having
them make use of the helper functions previously introduced.

Link: https://lkml.kernel.org/r/b353e3427a81f9d3adafd98fd7d73e78a8209f43.1644010576.git.zanussi@kernel.org

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

tracing: Remove redundant trigger_ops params

2022-04-26T21:58:50+00:00

Since event_trigger_data contains the .ops trigger_ops field, there's
no reason to pass the trigger_ops separately. Remove it as a param
from functions whenever event_trigger_data is passed.

Link: https://lkml.kernel.org/r/9856c9bc81bde57077f5b8d6f8faa47156c6354a.1644010575.git.zanussi@kernel.org

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

tracing: Remove logic for registering multiple event triggers at a time

2022-04-26T21:58:50+00:00

Code for registering triggers assumes it's possible to register more
than one trigger at a time.  In fact, it's unimplemented and there
doesn't seem to be a reason to do that.

Remove the n_registered param from event_trigger_register() and fix up
callers.

Doing so simplifies the logic in event_trigger_register to the point
that it just becomes a wrapper calling event_command.reg().

It also removes the problematic call to event_command.unreg() in case
of failure.  A new function, event_trigger_unregister() is also added
for callers to call themselves.

The changes to trace_events_hist.c simply allow compilation; a
separate patch follows which updates the hist triggers to work
correctly with the new changes.

Link: https://lkml.kernel.org/r/6149fec7a139d93e84fa4535672fb5bef88006b0.1644010575.git.zanussi@kernel.org

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

Merge tag 'trace-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

2022-03-23T18:40:25+00:00

Pull tracing updates from Steven Rostedt:

- New user_events interface. User space can register an event with the
kernel describing the format of the event. Then it will receive a
byte in a page mapping that it can check against. A privileged task
can then enable that event like any other event, which will change
the mapped byte to true, telling the user space application to start
writing the event to the tracing buffer.

- Add new "ftrace_boot_snapshot" kernel command line parameter. When
set, the tracing buffer will be saved in the snapshot buffer at boot
up when the kernel hands things over to user space. This will keep
the traces that happened at boot up available even if user space boot
up has tracing as well.

- Have TRACE_EVENT_ENUM() also update trace event field type
descriptions. Thus if a static array defines its size with an enum,
the user space trace event parsers can still know how to parse that
array.

- Add new TRACE_CUSTOM_EVENT() macro. This acts the same as the
TRACE_EVENT() macro, but will attach to an existing tracepoint. This
will make one tracepoint be able to trace different content and not
be stuck at only what the original TRACE_EVENT() macro exports.

- Fixes to tracing error logging.

- Better saving of cmdlines to PIDs when tracing (use the wakeup events
for mapping).

* tag 'trace-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (30 commits)
tracing: Have type enum modifications copy the strings
user_events: Add trace event call as root for low permission cases
tracing/user_events: Use alloc_pages instead of kzalloc() for register pages
tracing: Add snapshot at end of kernel boot up
tracing: Have TRACE_DEFINE_ENUM affect trace event types as well
tracing: Fix strncpy warning in trace_events_synth.c
user_events: Prevent dyn_event delete racing with ioctl add/delete
tracing: Add TRACE_CUSTOM_EVENT() macro
tracing: Move the defines to create TRACE_EVENTS into their own files
tracing: Add sample code for custom trace events
tracing: Allow custom events to be added to the tracefs directory
tracing: Fix last_cmd_set() string management in histogram code
user_events: Fix potential uninitialized pointer while parsing field
tracing: Fix allocation of last_cmd in last_cmd_set()
user_events: Add documentation file
user_events: Add sample code for typical usage
user_events: Add self-test for validator boundaries
user_events: Add self-test for perf_event integration
user_events: Add self-test for dynamic_events integration
user_events: Add self-test for ftrace integration
...

eprobes: Remove redundant event type information

2022-02-25T17:07:01+00:00

Currently, the event probes save the type of the event they are attached
to when recording the event. For example:

  # echo 'e:switch sched/sched_switch prev_state=$prev_state prev_prio=$prev_prio next_pid=$next_pid next_prio=$next_prio' > dynamic_events
  # cat events/eprobes/switch/format

 name: switch
 ID: 1717
 format:
        field:unsigned short common_type;       offset:0;       size:2; signed:0;
        field:unsigned char common_flags;       offset:2;       size:1; signed:0;
        field:unsigned char common_preempt_count;       offset:3;       size:1; signed:0;
        field:int common_pid;   offset:4;       size:4; signed:1;

        field:unsigned int __probe_type;        offset:8;       size:4; signed:0;
        field:u64 prev_state;   offset:12;      size:8; signed:0;
        field:u64 prev_prio;    offset:20;      size:8; signed:0;
        field:u64 next_pid;     offset:28;      size:8; signed:0;
        field:u64 next_prio;    offset:36;      size:8; signed:0;

 print fmt: "(%u) prev_state=0x%Lx prev_prio=0x%Lx next_pid=0x%Lx next_prio=0x%Lx", REC->__probe_type, REC->prev_state, REC->prev_prio, REC->next_pid, REC->next_prio

The __probe_type adds 4 bytes to every event.

One of the reasons for creating eprobes is to limit what is traced in an
event to be able to limit what is written into the ring buffer. Having
this redundant 4 bytes to every event takes away from this.

The event that is recorded can be retrieved from the event probe itself,
that is available when the trace is happening. For user space tools, it
could simply read the dynamic_event file to find the event they are for.
So there is really no reason to write this information into the ring
buffer for every event.

Link: https://lkml.kernel.org/r/20220218190057.2f5a19a8@gandalf.local.home

Acked-by: Masami Hiramatsu 
Reviewed-by: Joel Fernandes 
Signed-off-by: Steven Rostedt (Google)

tracing: Remove size restriction on tracing_log_err cmd strings

2022-02-11T03:27:17+00:00

Currently, tracing_log_err.cmd strings are restricted to a length of
MAX_FILTER_STR_VAL (256), which is too short for some commands already
seen in the wild (with cmd strings longer than that showing up
truncated).

Remove the restriction so that no command string is ever truncated.

Link: https://lkml.kernel.org/r/ca965f23256b350ebd94b3dc1a319f28e8267f5f.1643319703.git.zanussi@kernel.org

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

tracing: Add helper functions to simplify event_command.parse() callback handling

2022-01-10T16:09:11+00:00

The event_command.parse() callback is responsible for parsing and
registering triggers.  The existing command implementions for this
callback duplicate a lot of the same code, so to clean up and
consolidate those implementations, introduce a handful of helper
functions for implementors to use.

This also makes it easier for new commands to be implemented and
allows them to focus more on the customizations they provide rather
than obscuring and complicating it with boilerplate code.

Link: https://lkml.kernel.org/r/c1ff71f594d45177706571132bd3119491097221.1641823001.git.zanussi@kernel.org

Signed-off-by: Tom Zanussi 
Signed-off-by: Steven Rostedt

tracing: Remove ops param from event_command reg()/unreg() callbacks

2022-01-10T16:09:11+00:00

The event_trigger_ops for an event_command are already accessible via
event_trigger_data.ops so remove the redundant ops from the callback.

Link: https://lkml.kernel.org/r/4c6f2a41820452f9cacddc7634ad442928aa2aa6.1641823001.git.zanussi@kernel.org

Signed-off-by: Tom Zanussi 
Signed-off-by: Steven Rostedt

tracing: Change event_trigger_ops func() to trigger()

2022-01-10T16:09:10+00:00

The name of the func() callback on event_trigger_ops is too generic
and is easily confused with other callbacks with that name, so change
it to something that reflects its actual purpose.

In this case, the main purpose of the callback is to implement an
event trigger, so call it trigger() instead.

Also add some more documentation to event_trigger_ops describing the
callbacks a bit better.

Link: https://lkml.kernel.org/r/36ab812e3ee74ee03ae0043fda41a858ee728c00.1641823001.git.zanussi@kernel.org

Signed-off-by: Tom Zanussi 
Signed-off-by: Steven Rostedt

tracing: Change event_command func() to parse()

2022-01-10T16:09:10+00:00

The name of the func() callback on event_command is too generic and is
easily confused with other callbacks with that name, so change it to
something that reflects its actual purpose.

In this case, the main purpose of the callback is to parse an event
command, so call it parse() instead.

Link: https://lkml.kernel.org/r/7784e321840752ed88aac0b349c0c685fc9247b1.1641823001.git.zanussi@kernel.org

Signed-off-by: Tom Zanussi 
Signed-off-by: Steven Rostedt