[PATCH v8 00/10] tracing/probes: Add more typecast features

[Masami Hiramatsu (Google)]

Hi,

Here is the 8th version of series to introduce more typecast features
to probe events. The previous version is here:

 https://lore.kernel.org/all/178217904992.643090.15726197350652241270.stgit@devnote2/

In this version, I removed already picked 2 patches and add 2 new
fix and feature patches. The previous BTF typecast patch allows
`(STRUCT)FIELD->MEMBER` without $ prefix for eprobes, but it also
allows user to use COMM/comm instead of FIELD. $COMM/$comm are special
variables, so it should not skip $ prefix[1/10]. However, accessing
event fields without $ prefix itself is acceptable, it is generically
allowed without typecast[2/10].
Other patches have small fixes according to Julian and Sashiko's
comments and are rebased on top of probes/core branch.

This series extends BTF typecast feature and add more options:

1. Expanding BTF typecast to kprobe and fprobe.
   (currently only function entry/exit)

2. Introduce container_of like typecast. This adds a "assigned
   member" option to the typecast.

   (STRUCT,MEMBER)VAR->ANOTHER_MEMBER

   This casts VAR to STRUCT type but the VAR is as the address
   of STRUCT.MEMBER. In C, it is:

   container_of(VAR, STRUCT, MEMBER)->ANOTHER_MEMBER

3. Support nested typecast, e.g.

   (STRUCT)((STRUCT2)VAR->MEMBER2)->MEMBER

   the nest level must be smaller than 3.

4. Add $current variable to point "current" task_struct.
   This is useful with typecast, e.g.

   (task_struct)$current->pid

5. per-cpu dereference support.

   Intrdouce this_cpu_read(VAR) and this_cpu_ptr(VAR) to
   access per-cpu data on the current CPU (accessing other CPU
   data is not stable, because it can be changed.)

   You can access the member of per-cpu data structure using
   typecast like:

   (STRUCT)this_cpu_ptr(VAR)->MEMBER

6. Support event fields without $ prefix on eprobes.

   Now eprobe events can access its event fields.

And added fetcharg dump feature (for debug) and updated test scripts
to test part of them.

Thanks,

---
base-commit: 18dfb4703cd6af27deb30d628dac2e7db2b24e6a

Masami Hiramatsu (Google) (10):
      tracing/probes: Make the $ prefix mandatory for comm access
      tracing/probes: Allow eprobe to use variable without $ prefix
      tracing/probes: Support dumping fetcharg program for debugging dynamic events
      tracing/probes: Support typecast for various probe events
      tracing/probes: Support nested typecast
      tracing/probes: Type casting always involves nested calls
      tracing/probes: Support field specifier option for typecast
      tracing/probes: Add $current variable support
      tracing/probes: Add this_cpu_read() and this_cpu_ptr() dereference method to fetcharg
      tracing/probes: Add a new testcase for BTF typecasts


 Documentation/trace/eprobetrace.rst                |    9 
 Documentation/trace/fprobetrace.rst                |   10 
 Documentation/trace/kprobetrace.rst                |   11 
 kernel/trace/Kconfig                               |   12 
 kernel/trace/trace.c                               |    8 
 kernel/trace/trace_eprobe.c                        |    2 
 kernel/trace/trace_fprobe.c                        |    2 
 kernel/trace/trace_kprobe.c                        |    2 
 kernel/trace/trace_probe.c                         |  586 ++++++++++++++++----
 kernel/trace/trace_probe.h                         |   99 ++-
 kernel/trace/trace_probe_tmpl.h                    |   25 +
 kernel/trace/trace_uprobe.c                        |    3 
 samples/trace_events/trace-events-sample.c         |   40 +
 samples/trace_events/trace-events-sample.h         |   34 +
 .../ftrace/test.d/dynevent/btf_probe_event.tc      |   51 ++
 .../test.d/dynevent/eprobes_syntax_errors.tc       |    6 
 .../ftrace/test.d/dynevent/fprobe_syntax_errors.tc |   12 
 .../ftrace/test.d/kprobe/kprobe_syntax_errors.tc   |   12 
 .../ftrace/test.d/kprobe/uprobe_syntax_errors.tc   |    5 
 19 files changed, 770 insertions(+), 159 deletions(-)
 create mode 100644 tools/testing/selftests/ftrace/test.d/dynevent/btf_probe_event.tc

--
Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>