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Subject[PATCH] perf inject jit: Ignore memfd mmap events if jitdump present
Date
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@linux.microsoft.com>
---
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
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