Messages in this thread | | | From | Ian Rogers <> | Date | Fri, 3 Nov 2023 08:48:56 -0700 | Subject | Re: [PATCH v4 03/53] libperf: Lazily allocate mmap event copy |
| |
On Fri, Nov 3, 2023 at 1:33 AM Guilherme Amadio <amadio@gentoo.org> wrote: > > Hi, > > On Thu, Nov 02, 2023 at 10:56:45AM -0700, Ian Rogers wrote: > > The event copy in the mmap is used to have storage to a read > > event. Not all users of mmaps read the events, such as perf record, so > > switch the allocation to being on first read rather than being > > embedded within the perf_mmap. > > > > Signed-off-by: Ian Rogers <irogers@google.com> > > --- > > tools/lib/perf/include/internal/mmap.h | 2 +- > > tools/lib/perf/mmap.c | 9 +++++++++ > > 2 files changed, 10 insertions(+), 1 deletion(-) > > > > diff --git a/tools/lib/perf/include/internal/mmap.h b/tools/lib/perf/include/internal/mmap.h > > index 5a062af8e9d8..b11aaf5ed645 100644 > > --- a/tools/lib/perf/include/internal/mmap.h > > +++ b/tools/lib/perf/include/internal/mmap.h > > @@ -33,7 +33,7 @@ struct perf_mmap { > > bool overwrite; > > u64 flush; > > libperf_unmap_cb_t unmap_cb; > > - char event_copy[PERF_SAMPLE_MAX_SIZE] __aligned(8); > > + void *event_copy; > > struct perf_mmap *next; > > }; > > > > diff --git a/tools/lib/perf/mmap.c b/tools/lib/perf/mmap.c > > index 2184814b37dd..91ae46aac378 100644 > > --- a/tools/lib/perf/mmap.c > > +++ b/tools/lib/perf/mmap.c > > @@ -51,6 +51,8 @@ int perf_mmap__mmap(struct perf_mmap *map, struct perf_mmap_param *mp, > > > > void perf_mmap__munmap(struct perf_mmap *map) > > { > > + free(map->event_copy); > > + map->event_copy = NULL; > > if (map && map->base != NULL) { > > If map can be NULL as the if statement above suggests, then there is a > potential a null pointer dereference bug here. Suggestion: > > if (!map) > return; > > free(map->event_copy); > map->event_copy = NULL; > if (map->base != NULL) { > > ...
Makes sense, will fix in v5. Waiting to get additional feedback to avoid too much email.
Thanks, Ian
> Cheers, > -Guilherme > > > munmap(map->base, perf_mmap__mmap_len(map)); > > map->base = NULL; > > @@ -226,6 +228,13 @@ static union perf_event *perf_mmap__read(struct perf_mmap *map, > > unsigned int len = min(sizeof(*event), size), cpy; > > void *dst = map->event_copy; > > > > + if (!dst) { > > + dst = malloc(PERF_SAMPLE_MAX_SIZE); > > + if (!dst) > > + return NULL; > > + map->event_copy = dst; > > + } > > + > > do { > > cpy = min(map->mask + 1 - (offset & map->mask), len); > > memcpy(dst, &data[offset & map->mask], cpy); > > -- > > 2.42.0.869.gea05f2083d-goog > > > >
| |