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) <[email protected]>
