Re: [PATCH v1 2/7] bpf: Add bpf_perf_event_aux_pause kfunc

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On 12/15/24 11:34 AM, Leo Yan wrote:
The bpf_perf_event_aux_pause kfunc will be used to control the Perf AUX
area to pause or resume.

An example use-case is attaching eBPF to Ftrace tracepoints.  When a
tracepoint is hit, the associated eBPF program will be executed.  The
eBPF program can invoke bpf_perf_event_aux_pause() to pause or resume
AUX trace.  This is useful for fine-grained tracing by combining
Perf and eBPF.

This commit implements the bpf_perf_event_aux_pause kfunc, and make it
pass the eBPF verifier.

The subject and commit message mentions to implement a kfunc,
but actually you implemented a uapi helper. Please implement a kfunc
instead (searching __bpf_kfunc in kernel/bpf directory).


Signed-off-by: Leo Yan <leo.yan@xxxxxxx>
---
  include/uapi/linux/bpf.h | 21 ++++++++++++++++
  kernel/bpf/verifier.c    |  2 ++
  kernel/trace/bpf_trace.c | 52 ++++++++++++++++++++++++++++++++++++++++
  3 files changed, 75 insertions(+)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 4162afc6b5d0..678278c91ce2 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -5795,6 +5795,26 @@ union bpf_attr {
   *		0 on success.
   *
   *		**-ENOENT** if the bpf_local_storage cannot be found.
+ *
+ * long bpf_perf_event_aux_pause(struct bpf_map *map, u64 flags, u32 pause)
+ *	Description
+ *		Pause or resume an AUX area trace associated to the perf event.
+ *
+ *		The *flags* argument is specified as the key value for
+ *		retrieving event pointer from the passed *map*.
+ *
+ *		The *pause* argument controls AUX trace pause or resume.
+ *		Non-zero values (true) are to pause the AUX trace and the zero
+ *		value (false) is for re-enabling the AUX trace.
+ *	Return
+ *		0 on success.
+ *
+ *		**-ENOENT** if not found event in the events map.
+ *
+ *		**-E2BIG** if the event index passed in the *flags* parameter
+ *		is out-of-range of the map.
+ *
+ *		**-EINVAL** if the flags passed is an invalid value.
   */
  #define ___BPF_FUNC_MAPPER(FN, ctx...)			\
  	FN(unspec, 0, ##ctx)				\
@@ -6009,6 +6029,7 @@ union bpf_attr {
  	FN(user_ringbuf_drain, 209, ##ctx)		\
  	FN(cgrp_storage_get, 210, ##ctx)		\
  	FN(cgrp_storage_delete, 211, ##ctx)		\
+	FN(perf_event_aux_pause, 212, ##ctx)		\
  	/* */
/* backwards-compatibility macros for users of __BPF_FUNC_MAPPER that don't

[...]




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