Re: [PATCH v5 0/6] enable creating [k,u]probe with perf_event_open

On Dec 8, 2017, at 11:57 AM, Daniel Borkmann [off-list ref] wrote:

On 12/06/2017 11:45 PM, Song Liu wrote:

quoted

Changes PATCH v4 to PATCH v5:
 Remove PERF_PROBE_CONFIG_IS_RETPROBE from uapi, use PMU_FORMAT_ATTR
 instead.

Changes PATCH v3 to PATCH v4:
 Remove uapi define MAX_PROBE_FUNC_NAME_LEN, use KSYM_NAME_LEN instead.
 Add flag PERF_PROBE_CONFIG_IS_RETPROBE for config field of [k,u]probe.
 Optimize ifdef's of CONFIG_KPROBE_EVENTS and CONFIG_UPROBE_EVENTS.
 Optimize checks in perf_event_is_tracing().
 Optimize perf_tp_register().

Changes PATCH v2 to PATCH v3:
 Remove fixed type PERF_TYPE_KPROBE and PERF_TYPE_UPROBE, use dynamic
 type instead.
 Update userspace (samples/bpf, bcc) to look up type from sysfs.
 Change License info in test_many_kprobe_user.c as Philippe Ombredanne
 suggested.

Changes PATCH v1 to PATCH v2:
 Split PERF_TYPE_PROBE into PERF_TYPE_KPROBE and PERF_TYPE_UPROBE.
 Split perf_probe into perf_kprobe and perf_uprobe.
 Remove struct probe_desc, use config1 and config2 instead.

Changes RFC v2 to PATCH v1:
 Check type PERF_TYPE_PROBE in perf_event_set_filter().
 Rebase on to tip perf/core.

Changes RFC v1 to RFC v2:
 Fix build issue reported by kbuild test bot by adding ifdef of
 CONFIG_KPROBE_EVENTS, and CONFIG_UPROBE_EVENTS.

RFC v1 cover letter:

This is to follow up the discussion over "new kprobe api" at Linux
Plumbers 2017:

https://urldefense.proofpoint.com/v2/url?u=https-3A__www.linuxplumbersconf.org_2017_ocw_proposals_4808&d=DwICaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=dR8692q0_uaizy0jkrBJQM5k2hfm4CiFxYT8KaysFrg&m=iAtBi3jXPYfFgvhHTsv8oWyUKiyEwnGZ34-4jniREz4&s=87sxRxoRkJJenQjCtFLJFXkMLvd_rHkY8ZGON9em1Jc&e=

With current kernel, user space tools can only create/destroy [k,u]probes
with a text-based API (kprobe_events and uprobe_events in tracefs). This
approach relies on user space to clean up the [k,u]probe after using them.
However, this is not easy for user space to clean up properly.

To solve this problem, we introduce a file descriptor based API.
Specifically, we extended perf_event_open to create [k,u]probe, and attach
this [k,u]probe to the file descriptor created by perf_event_open. These
[k,u]probe are associated with this file descriptor, so they are not
available in tracefs.

We reuse large portion of existing trace_kprobe and trace_uprobe code.
Currently, the file descriptor API does not support arguments as the
text-based API does. This should not be a problem, as user of the file
decriptor based API read data through other methods (bpf, etc.).

I also include a patch to to bcc, and a patch to man-page perf_even_open.
Please see the list below. A fork of bcc with this patch is also available
on github:

 https://github.com/liu-song-6/bcc/tree/perf_event_open

Peter / Stephen, I presume this will be routed through one of you, if
not please yell.

Thanks,
Daniel

Dear Peter, 

Do you have further feedbacks/comments on these patches? If not, could you 
please confirm they are ready for merge?

Thanks and Best Regards,
Song