Re: [PATCH v7 perf, bpf-next 8/8] perf tools: synthesize PERF_RECORD_* for loaded BPF programs

On Jan 11, 2019, at 10:44 AM, Arnaldo Carvalho de Melo [off-list ref] wrote:

Em Thu, Jan 10, 2019 at 04:19:33PM -0800, Song Liu escreveu:

quoted

This patch synthesize PERF_RECORD_KSYMBOL and PERF_RECORD_BPF_EVENT for
BPF programs loaded before perf-record. This is achieved by gathering
information about all BPF programs via sys_bpf.

Signed-off-by: Song Liu <redacted>
---
tools/perf/builtin-record.c |   6 ++
tools/perf/util/bpf-event.c | 205 ++++++++++++++++++++++++++++++++++++
tools/perf/util/bpf-event.h |   5 +
3 files changed, 216 insertions(+)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index deaf9b902094..88ea11d57c6f 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c

@@ -41,6 +41,7 @@

#include "util/perf-hooks.h"
#include "util/time-utils.h"
#include "util/units.h"
+#include "util/bpf-event.h"
#include "asm/bug.h"

#include <errno.h>

@@ -1082,6 +1083,11 @@ static int record__synthesize(struct record *rec, bool tail)

		return err;
	}

+	err = perf_event__synthesize_bpf_events(tool, process_synthesized_event,
+						machine, opts);
+	if (err < 0)
+		pr_warning("Couldn't synthesize bpf events.\n");
+

There should be no warnings on older systems, I build a kernel and tools
with your changes and then, before rebooting, I tried:

[root@quaco ~]# perf record ls
Couldn't synthesize bpf events.
<SNIP>
[root@quaco ~]# uname -a
Linux quaco 4.19.13-300.fc29.x86_64 #1 SMP Sat Dec 29 22:54:28 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
[root@quaco ~]#

At most this should be a pr_debug(), but then it should check if the
system is bpf capable and if not only warn if the user explicitely asked
for bpf events.

Thanks Arnaldo! I will fix it in the next version. 

Song