Messages in this thread | | | Date | Mon, 11 Nov 2019 17:07:38 +0100 | From | Jiri Olsa <> | Subject | Re: [RFC] perf session: Fix compression processing |
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On Mon, Nov 11, 2019 at 06:53:35PM +0300, Alexey Budankov wrote: > On 11.11.2019 18:46, Jiri Olsa wrote: > > On Mon, Nov 11, 2019 at 06:41:47PM +0300, Alexey Budankov wrote: > >> On 11.11.2019 17:56, Jiri Olsa wrote: > >>> On Mon, Nov 11, 2019 at 05:38:49PM +0300, Alexey Budankov wrote: > >>>> > >>>> On 04.11.2019 1:24, Jiri Olsa wrote: > >>>>> hi, > >>>> <SNIP> > >>>>> --- > >>>>> The compressed data processing occasionally fails with: > >>>>> $ perf report --stdio -vv > >>>>> decomp (B): 44519 to 163000 > >>>>> decomp (B): 48119 to 174800 > >>>>> decomp (B): 65527 to 131072 > >>>>> fetch_mmaped_event: head=0x1ffe0 event->header_size=0x28, mmap_size=0x20000: fuzzed perf.data? > >>>>> Error: > >>>>> failed to process sample > >>>>> ... > >>>>> > >>>>> It's caused by recent fuzzer fix that does not take into account > >>>>> that compressed data do not need to by fully present in the buffer, > >>>>> so it's ok to just return NULL and not to fail. > >>>>> > >>>>> Fixes: 57fc032ad643 ("perf session: Avoid infinite loop when seeing invalid header.size") > >>>>> Link: http://lkml.kernel.org/n/tip-q1biqscs4stcmc9bs1iokfro@git.kernel.org > >>>>> Signed-off-by: Jiri Olsa <jolsa@kernel.org> > >>>>> --- > >>>>> tools/perf/util/session.c | 8 +++++--- > >>>>> 1 file changed, 5 insertions(+), 3 deletions(-) > >>>>> > >>>>> diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c > >>>>> index f07b8ecb91bc..3589ed14a629 100644 > >>>>> --- a/tools/perf/util/session.c > >>>>> +++ b/tools/perf/util/session.c > >>>>> @@ -1959,7 +1959,7 @@ static int __perf_session__process_pipe_events(struct perf_session *session) > >>>>> > >>>>> static union perf_event * > >>>>> fetch_mmaped_event(struct perf_session *session, > >>>>> - u64 head, size_t mmap_size, char *buf) > >>>>> + u64 head, size_t mmap_size, char *buf, bool decomp) > >>>> > >>>> bools in interface make code less transparent. > >>>> > >>>>> { > >>>>> union perf_event *event; > >>>>> > >>>>> @@ -1979,6 +1979,8 @@ fetch_mmaped_event(struct perf_session *session, > >>>>> /* We're not fetching the event so swap back again */ > >>>>> if (session->header.needs_swap) > >>>>> perf_event_header__bswap(&event->header); > >>>>> + if (decomp) > >>>>> + return NULL; > >>>>> pr_debug("%s: head=%#" PRIx64 " event->header_size=%#x, mmap_size=%#zx: fuzzed perf.data?\n", > >>>>> __func__, head, event->header.size, mmap_size); > >>>>> return ERR_PTR(-EINVAL); > >>>>> @@ -1997,7 +1999,7 @@ static int __perf_session__process_decomp_events(struct perf_session *session) > >>>>> return 0; > >>>>> > >>>>> while (decomp->head < decomp->size && !session_done()) { > >>>>> - union perf_event *event = fetch_mmaped_event(session, decomp->head, decomp->size, decomp->data); > >>>>> + union perf_event *event = fetch_mmaped_event(session, decomp->head, decomp->size, decomp->data, true); > >>>> > >>>> It looks like this call can be skipped, at all, in this case. > >>> > >>> not sure what you mean, we are in decomp code no? > >> > >> Ok, it is inside "not fetching" branch. > >> NULL return value means to proceed getting further over the trace. > >> Checking record type == COMPRESSED at the higher level could > >> probably be cleaner fix and also work faster. > > > > any chance you could post the fix? the patch I did was a > > quick fix to get the feature working for presentation ;-) > > you're probably thinking of the proper approach > > Please share the exact reproducing steps > so I could come up with something.
'perf record -z' for longer workloads
jirka
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