[PATCH] perf inject jit: Ignore memfd mmap events if jitdump present

[Brian Robbins]

Some processes store jitted code in memfd mappings to avoid having rwx
mappings.  These processes map the code with a writeable mapping and a
read-execute mapping.  They write the code using the writeable mapping
and then unmap the writeable mapping.  All subsequent execution is
through the read-execute mapping.

perf inject --jit ignores //anon* mappings for each process where a
jitdump is present because it expects to inject mmap events for each
jitted code range, and said jitted code ranges will overlap with the
//anon* mappings.

Ignore /memfd: mappings so that jitted code contained in /memfd:
mappings is treated the same way as jitted code contained in //anon*
mappings.

Signed-off-by: Brian Robbins <brianrob@xxxxxxxxxxxxxxxxxxx>
---
 tools/perf/util/jitdump.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/jitdump.c b/tools/perf/util/jitdump.c
index a23255773c60..335a3c61940b 100644
--- a/tools/perf/util/jitdump.c
+++ b/tools/perf/util/jitdump.c
@@ -845,8 +845,12 @@ jit_process(struct perf_session *session,
 	if (jit_detect(filename, pid, nsi)) {
 		nsinfo__put(nsi);
 
-		// Strip //anon* mmaps if we processed a jitdump for this pid
-		if (jit_has_pid(machine, pid) && (strncmp(filename, "//anon", 6) == 0))
+		/*
+		 * Strip //anon* and /memfd:* mmaps if we processed a jitdump for this pid
+		 */
+		if (jit_has_pid(machine, pid) &&
+			((strncmp(filename, "//anon", 6) == 0) ||
+			 (strncmp(filename, "/memfd:", 7) == 0))
 			return 1;
 
 		return 0;
-- 
2.25.1