When debugging use-after-free(UAF) bugs, knowing when the object reaches 0 references and enters final release can significantly aid the debugging process.
There is currently no universal way to trace this information. This patch series implements tracing of the final puts in the most widely used refcounting implementations, refcount_t(and thus kref which uses it), and percpu-ref. The tracepoint records three fields: - caller: function that called the refcounting function(refcount_sub_and_test, percpu_ref_put_many) - fn: refcounting function(eg refcount_sub_and_test) - obj: refcount object(struct percpu_ref, refcount_t) Signed-off-by: Eugene Mavick <[email protected]> --- Changes in v2: -include/linux/ref_trace.h: change macro name, use direct tracepoint call in macro to avoid double check -add tracepoint to refcount_dec_if_one -kunit: make significant improvements to design, fix critical bug, add test case for refcount_dec_if_one() -Link to v1: https://lore.kernel.org/r/[email protected] --- Eugene Mavick (5): tracing: add ref_trace_final_put tracepoint refcount: add ref_trace_final_put tracepoint percpu-refcount: add ref_trace_final_put trace kunit: add test for ref_trace_final_put MAINTAINERS: add entries for ref_trace_final_put MAINTAINERS | 3 + include/linux/percpu-refcount.h | 5 +- include/linux/ref_trace.h | 26 ++++++++ include/linux/refcount.h | 2 + include/trace/events/ref_trace.h | 46 +++++++++++++ lib/Kconfig | 10 +++ lib/Makefile | 2 + lib/ref_trace.c | 12 ++++ lib/refcount.c | 8 ++- lib/tests/Makefile | 1 + lib/tests/ref_trace_kunit.c | 136 +++++++++++++++++++++++++++++++++++++++ 11 files changed, 249 insertions(+), 2 deletions(-) --- base-commit: df685633c3dbc67441cc86f1c3fee58de4652ba2 change-id: 20260624-refcount-final-put-trace-49bd7c39bd5a Best regards, -- Eugene Mavick <[email protected]>
