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Date: Wed, 12 Jul 2023 13:29:34 -0700
From: Ian Rogers <irogers@...gle.com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
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>,
Kan Liang <kan.liang@...ux.intel.com>,
Zhengjun Xing <zhengjun.xing@...ux.intel.com>,
linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] perf parse-events: Avoid segv if PMU lookup fails for
legacy cache terms
On Wed, Jul 12, 2023 at 12:27 PM Arnaldo Carvalho de Melo
<acme@...nel.org> wrote:
>
> Em Tue, Jul 11, 2023 at 11:52:50PM -0700, Ian Rogers escreveu:
> > libfuzzer found the following command could segv:
> > ```
> > $ perf stat -e cpu/L2,L2/ true
> > ```
> > This is because the L2 term rewrites the perf_event_attr type to
> > PERF_TYPE_HW_CACHE which then fails the PMU lookup for the second
> > legacy cache term.
> >
> > The new failure is consistent with repeated hardware terms:
> > ```
> > $ perf stat -e cpu/L2,L2/ true
> > event syntax error: 'cpu/L2,L2/'
> > \___ Failed to find PMU for type 3
> >
> > Initial error:
> > event syntax error: 'cpu/L2,L2/'
> > \___ Failed to find PMU for type 3
> > Run 'perf list' for a list of valid events
> >
> > Usage: perf stat [<options>] [<command>]
> >
> > -e, --event <event> event selector. use 'perf list' to list available events
> > $ perf stat -e cpu/cycles,cycles/ true
> > event syntax error: 'cpu/cycles,cycles/'
> > \___ Failed to find PMU for type 0
> >
> > Initial error:
> > event syntax error: 'cpu/cycles,cycles/'
> > \___ Failed to find PMU for type 0
> > Run 'perf list' for a list of valid events
> >
> > Usage: perf stat [<options>] [<command>]
> >
> > -e, --event <event> event selector. use 'perf list' to list available events
> > ```
>
> I added the Fixes as requested:
>
> Fixes: 6fd1e5191591f9d5 ("perf parse-events: Support PMUs for legacy cache events")
>
> Please check if the patch below helps a bit giving more info to the
> user, but still a bit cryptic:
>
> ⬢[acme@...lbox perf-tools]$ perf stat -e cpu/L2,L2/ true
> event syntax error: 'cpu/L2,L2/'
> \___ Failed to find PMU for perf_event_attr.type 3 (PERF_TYPE_HW_CACHE)
>
> Initial error:
> event syntax error: 'cpu/L2,L2/'
> \___ Failed to find PMU for perf_event_attr.type 3 (PERF_TYPE_HW_CACHE)
> Run 'perf list' for a list of valid events
>
> Usage: perf stat [<options>] [<command>]
>
> -e, --event <event> event selector. use 'perf list' to list available events
> ⬢[acme@...lbox perf-tools]$
>
> And the other case is needs more patching, so better leave this for 6.6.
>
>
> ⬢[acme@...lbox perf-tools]$ perf stat -e cpu/cycles,cycles/ true
> event syntax error: 'cpu/cycles,cycles/'
> \___ Failed to find PMU for type 0
>
> Initial error:
> event syntax error: 'cpu/cycles,cycles/'
> \___ Failed to find PMU for type 0
> Run 'perf list' for a list of valid events
>
> Usage: perf stat [<options>] [<command>]
>
> -e, --event <event> event selector. use 'perf list' to list available events
> ⬢[acme@...lbox perf-tools]$
The stringify looks good. Something strange is the value there is a
u64 by type is a __u32 in the perf_event_attr.
Thanks!
Ian
> - Arnaldo
>
> diff --git a/tools/perf/util/evsel_fprintf.h b/tools/perf/util/evsel_fprintf.h
> index c8a9fac2f2ddc0f2..044612774a962020 100644
> --- a/tools/perf/util/evsel_fprintf.h
> +++ b/tools/perf/util/evsel_fprintf.h
> @@ -4,6 +4,7 @@
>
> #include <stdio.h>
> #include <stdbool.h>
> +#include <linux/types.h>
>
> struct evsel;
>
> @@ -45,6 +46,8 @@ int sample__fprintf_sym(struct perf_sample *sample, struct addr_location *al,
>
> typedef int (*attr__fprintf_f)(FILE *, const char *, const char *, void *);
>
> +const char *stringify_perf_type_id(u64 value);
> +
> int perf_event_attr__fprintf(FILE *fp, struct perf_event_attr *attr,
> attr__fprintf_f attr__fprintf, void *priv);
> #endif // __PERF_EVSEL_H
> diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
> index acde097e327cce8c..8678469cf974070a 100644
> --- a/tools/perf/util/parse-events.c
> +++ b/tools/perf/util/parse-events.c
> @@ -25,6 +25,7 @@
> #include "asm/bug.h"
> #include "util/parse-branch-options.h"
> #include "util/evsel_config.h"
> +#include "util/evsel_fprintf.h"
> #include "util/event.h"
> #include "util/bpf-filter.h"
> #include "util/util.h"
> @@ -1219,9 +1220,11 @@ static int config_term_pmu(struct perf_event_attr *attr,
> if (!pmu) {
> char *err_str;
>
> - if (asprintf(&err_str, "Failed to find PMU for type %d", attr->type) >= 0)
> + if (asprintf(&err_str, "Failed to find PMU for perf_event_attr.type %d (%s)", attr->type,
> + stringify_perf_type_id(attr->type)) >= 0) {
> parse_events_error__handle(err, term->err_term,
> err_str, /*help=*/NULL);
> + }
> return -EINVAL;
> }
> if (perf_pmu__supports_legacy_cache(pmu)) {
> diff --git a/tools/perf/util/perf_event_attr_fprintf.c b/tools/perf/util/perf_event_attr_fprintf.c
> index 2247991451f3aa1b..ce97371eda027271 100644
> --- a/tools/perf/util/perf_event_attr_fprintf.c
> +++ b/tools/perf/util/perf_event_attr_fprintf.c
> @@ -74,7 +74,7 @@ static void __p_read_format(char *buf, size_t size, u64 value)
> }
>
> #define ENUM_ID_TO_STR_CASE(x) case x: return (#x);
> -static const char *stringify_perf_type_id(u64 value)
> +const char *stringify_perf_type_id(u64 value)
> {
> switch (value) {
> ENUM_ID_TO_STR_CASE(PERF_TYPE_HARDWARE)
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