[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <ZUSwOlsOyJdDT1ls@gentoo.org>
Date: Fri, 3 Nov 2023 09:32:58 +0100
From: Guilherme Amadio <amadio@...too.org>
To: Ian Rogers <irogers@...gle.com>
Cc: Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...nel.org>,
Namhyung Kim <namhyung@...nel.org>,
Adrian Hunter <adrian.hunter@...el.com>,
Nick Terrell <terrelln@...com>,
Kan Liang <kan.liang@...ux.intel.com>,
Andi Kleen <ak@...ux.intel.com>,
Kajol Jain <kjain@...ux.ibm.com>,
Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
Huacai Chen <chenhuacai@...nel.org>,
Masami Hiramatsu <mhiramat@...nel.org>,
Vincent Whitchurch <vincent.whitchurch@...s.com>,
"Steinar H. Gunderson" <sesse@...gle.com>,
Liam Howlett <liam.howlett@...cle.com>,
Miguel Ojeda <ojeda@...nel.org>,
Colin Ian King <colin.i.king@...il.com>,
Dmitrii Dolgov <9erthalion6@...il.com>,
Yang Jihong <yangjihong1@...wei.com>,
Ming Wang <wangming01@...ngson.cn>,
James Clark <james.clark@....com>,
K Prateek Nayak <kprateek.nayak@....com>,
Sean Christopherson <seanjc@...gle.com>,
Leo Yan <leo.yan@...aro.org>,
Ravi Bangoria <ravi.bangoria@....com>,
German Gomez <german.gomez@....com>,
Changbin Du <changbin.du@...wei.com>,
Paolo Bonzini <pbonzini@...hat.com>, Li Dong <lidong@...o.com>,
Sandipan Das <sandipan.das@....com>,
liuwenyu <liuwenyu7@...wei.com>, linux-kernel@...r.kernel.org,
linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v4 03/53] libperf: Lazily allocate mmap event copy
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@...gle.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) {
...
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
>
>
Powered by blists - more mailing lists