[PATCH v5 4/5] perf evsel: don't set PERF_SAMPLE_IP for unprivileged tracepoints

[Anubhav Shelat]

For tracepoint events the IP is a static kernel address.
It doesn't vary by sample and provides no useful information for
unprivileged users. Skipping setting PERF_SAMPLE_IP for unprivileged
tracepoints avoids exposing a kernel address that reveals the KASLR base
offset.

Make an exception for uprobes, which are registered as
PERF_TYPE_TRACEPOINT, because the IP is important for their
functionality and is a safe userspace address. Detect them with
__probe_ip (entry) and __probe_ret_ip (return) using evsel__field().

Assisted-by: CLAUDE:claude-opus-4 Apogee
Signed-off-by: Anubhav Shelat <ashelat@xxxxxxxxxx>
---
 tools/perf/util/evsel.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index ea9fa04429f0..1d85e5503cf3 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -1571,7 +1571,19 @@ void evsel__config(struct evsel *evsel, const struct record_opts *opts,
 	attr->write_backward = opts->overwrite ? 1 : 0;
 	attr->read_format   = PERF_FORMAT_LOST;
 
-	evsel__set_sample_bit(evsel, IP);
+	/*
+	 * Don't set PERF_SAMPLE_IP for unprivileged kernel tracepoints to
+	 * avoid exposing kernel addresses. Uprobes expose only userspace
+	 * addresses so they're safe. Detect both entry and return uprobes.
+	 */
+	if (attr->type != PERF_TYPE_TRACEPOINT || perf_event_paranoid_check(1)
+#ifdef HAVE_LIBTRACEEVENT
+	    || evsel__field(evsel, "__probe_ip")
+	    || evsel__field(evsel, "__probe_ret_ip")
+#endif
+	    )
+		evsel__set_sample_bit(evsel, IP);
+
 	evsel__set_sample_bit(evsel, TID);
 
 	if (evsel->sample_read) {
-- 
2.54.0