Hi,
Here is a series of patches to introduce more typecast features
to probe events, which includes 1. expanding BTF typecast to
fprobe and kprobe events, 2. introducing container_of like typecst
option, 3. supporting nested typecast, 4. adding $current special
variable support, 5. adding per-cpu dereference support, 6. adding
a testcase to check typecasts.
Steve introduced BTF typecast feature for eprobe[1].
This series extends it 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.
+CPU(VAR) is the same as this_cpu_read(VAR), and
+PCPU(VAR) is the same as this_cpu_ptr(VAR).
Also, "this_cpu_ptr(VAR)" is available. This is good
with nesting expression.
(STRUCT)(this_cpu_ptr(VAR))->MEMBER
(However, it might be better to allow a special way to omit
parentheses for thi_cpu_ptr())
And added a test script to test part of them.
[1] https://lore.kernel.org/all/[email protected]/
---
Masami Hiramatsu (Google) (7):
tracing/probes: Support typecast for various probe events
tracing/probes: Support nested typecast
tracing/probes: Support field specifier option for typecast
tracing/probes: Add $current variable support
tracing/probes: Add +CPU() and +PCPU() dereference method to fetcharg
tracing/probes: Support reserved this_cpu_ptr() method
tracing/probes: Add a new testcase for BTF typecasts
Documentation/trace/eprobetrace.rst | 11 +
Documentation/trace/fprobetrace.rst | 11 +
Documentation/trace/kprobetrace.rst | 12 +
kernel/trace/trace.c | 6
kernel/trace/trace_probe.c | 312 +++++++++++++++-----
kernel/trace/trace_probe.h | 12 +
kernel/trace/trace_probe_tmpl.h | 33 ++
samples/trace_events/trace-events-sample.c | 38 ++
samples/trace_events/trace-events-sample.h | 34 ++
.../ftrace/test.d/dynevent/btf_probe_event.tc | 52 +++
10 files changed, 422 insertions(+), 99 deletions(-)
create mode 100644
tools/testing/selftests/ftrace/test.d/dynevent/btf_probe_event.tc
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