Subject: [PATCH] tools/perf: Disable perf probe when libtraceevent is missing

From: Athira Rajeev <[email-masked]>
Date: Fri, 20 Jan 2023 17:32:56 +0530

While parsing the tracepoint events in parse_events_add_tracepoint()
function, code checks for HAVE_LIBTRACEEVENT support. This is needed
since libtraceevent is necessary for tracepoint. But while adding
probe points, check for LIBTRACEEVENT is not done in case of perf probe.
Hence, in environment with missing libtraceevent-devel, it is
observed that adding a probe point works even though its not
supported.

Example:
Adding probe point:
	./perf probe 'vfs_getname=getname_flags:72 pathname=result->name:string'
	Added new event:
	  probe:vfs_getname    (on getname_flags:72 with pathname=result->name:string)

	You can now use it in all perf tools, such as:

		perf record -e probe:vfs_getname -aR sleep 1

But trying perf record:
	./perf  record -e probe:vfs_getname -aR sleep 1
	event syntax error: 'probe:vfs_getname'
				\___ unsupported tracepoint
	libtraceevent is necessary for tracepoint support
	Run 'perf list' for a list of valid events

Fix this by wrapping "builtin-probe" compilation and
"perf probe" usage under "CONFIG_LIBTRACEEVENT" check.

Signed-off-by: Athira Rajeev <[email-masked]>
---
 tools/perf/Build  | 4 +++-
 tools/perf/perf.c | 2 ++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/tools/perf/Build b/tools/perf/Build
index 6dd67e502295..a138a2304929 100644
--- a/tools/perf/Build
+++ b/tools/perf/Build
@@ -33,7 +33,9 @@ ifeq ($(CONFIG_LIBTRACEEVENT),y)
   perf-$(CONFIG_TRACE) += trace/beauty/
 endif
 
-perf-$(CONFIG_LIBELF) += builtin-probe.o
+ifeq ($(CONFIG_LIBTRACEEVENT),y)
+  perf-$(CONFIG_LIBELF) += builtin-probe.o
+endif
 
 perf-y += bench/
 perf-y += tests/
diff --git a/tools/perf/perf.c b/tools/perf/perf.c
index 82bbe0ca858b..7b0d79284d5a 100644
--- a/tools/perf/perf.c
+++ b/tools/perf/perf.c
@@ -80,9 +80,11 @@ static struct cmd_struct commands[] = {
 #ifdef HAVE_LIBTRACEEVENT
 	{ "sched",	cmd_sched,	0 },
 #endif
+#ifdef HAVE_LIBTRACEEVENT
 #ifdef HAVE_LIBELF_SUPPORT
 	{ "probe",	cmd_probe,	0 },
 #endif
+#endif
 #ifdef HAVE_LIBTRACEEVENT
 	{ "kmem",	cmd_kmem,	0 },
 	{ "lock",	cmd_lock,	0 },
-- 
2.39.0