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SubjectRe: [PATCH] perf inject jit: Ignore memfd mmap events if jitdump present
Em Thu, Aug 04, 2022 at 08:22:14AM -0700, Ian Rogers escreveu:
> On Tue, Aug 2, 2022 at 11:25 AM Brian Robbins
> <brianrob@linux.microsoft.com> wrote:
> >
> > 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>
>
> Acked-by: Ian Rogers <irogers@google.com>

CC /tmp/build/perf/util/jitdump.o
CC /tmp/build/perf/pmu-events/pmu-events.o
LD /tmp/build/perf/pmu-events/pmu-events-in.o
util/jitdump.c: In function ‘jit_process’:
util/jitdump.c:853:65: error: expected ‘)’ before ‘return’
853 | (strncmp(filename, "/memfd:", 7) == 0))
| ^
| )
854 | return 1;
| ~~~~~~
util/jitdump.c:851:20: note: to match this ‘(’
851 | if (jit_has_pid(machine, pid) &&
| ^
util/jitdump.c:857:9: error: expected expression before ‘}’ token
857 | }
| ^
make[4]: *** [/var/home/acme/git/perf/tools/build/Makefile.build:96: /tmp/build/perf/util/jitdump.o] Error 1
make[4]: *** Waiting for unfinished jobs....
make[3]: *** [/var/home/acme/git/perf/tools/build/Makefile.build:139: util] Error 2


Trying to fix now.

- Arnaldo

> > ---
> > 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))
>
> Related to this there is the prctl PR_SET_VMA_ANON_NAME which will
> name mapping to start with "[anon:"
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/filesystems/proc.rst#n434
> I wonder also we should be checking the pages are executable.
>
> Thanks,
> Ian
>
> > return 1;
> >
> > return 0;
> > --
> > 2.25.1
> >

--

- Arnaldo

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