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Message-ID: <CAM9d7cjoDXmQ=6B3zMfq_+0QNyTc-r5nBCJoKJBx98JrJjv-YA@mail.gmail.com>
Date: Fri, 20 May 2022 11:59:35 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Shunsuke Nakamura <nakamura.shun@...itsu.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@...hat.com>,
linux-kernel <linux-kernel@...r.kernel.org>,
linux-perf-users <linux-perf-users@...r.kernel.org>
Subject: Re: [PATCH 2/7] libperf: Introduce perf_{evsel, evlist}__open_opt
with extensible struct opts
Hello,
On Fri, Apr 22, 2022 at 2:44 AM Shunsuke Nakamura
<nakamura.shun@...itsu.com> wrote:
>
> Introduce perf_{evsel, evlist}__open_opt with extensible structure opts.
> The mechanism of the extensible structure opts imitates
> tools/lib/bpf/libbpf.h. Currently, only open_flags is supported for the
> opts structure.
>
> Signed-off-by: Shunsuke Nakamura <nakamura.shun@...itsu.com>
> ---
[SNIP]
> diff --git a/tools/lib/perf/evsel.c b/tools/lib/perf/evsel.c
> index 210ea7c06ce8..00c0cea43b52 100644
> --- a/tools/lib/perf/evsel.c
> +++ b/tools/lib/perf/evsel.c
> @@ -16,8 +16,12 @@
> #include <internal/lib.h>
> #include <linux/string.h>
> #include <sys/ioctl.h>
> +#include <signal.h>
> +#include <fcntl.h>
> +#include <sys/types.h>
> #include <sys/mman.h>
> #include <asm/bug.h>
> +#include "internal.h"
>
> void perf_evsel__init(struct perf_evsel *evsel, struct perf_event_attr *attr,
> int idx)
> @@ -26,6 +30,7 @@ void perf_evsel__init(struct perf_evsel *evsel, struct perf_event_attr *attr,
> evsel->attr = *attr;
> evsel->idx = idx;
> evsel->leader = evsel;
> + evsel->open_flags = 0;
In general, you don't need to reset it to zero as it's allocated with
zalloc().
> }
>
[SNIP]
> diff --git a/tools/lib/perf/internal.h b/tools/lib/perf/internal.h
> index 2c27e158de6b..4b91a087ed62 100644
> --- a/tools/lib/perf/internal.h
> +++ b/tools/lib/perf/internal.h
> @@ -20,4 +20,48 @@ do { \
> #define pr_debug2(fmt, ...) __pr(LIBPERF_DEBUG2, fmt, ##__VA_ARGS__)
> #define pr_debug3(fmt, ...) __pr(LIBPERF_DEBUG3, fmt, ##__VA_ARGS__)
>
> +static inline bool libperf_is_mem_zeroed(const char *p, ssize_t len)
> +{
> + while (len > 0) {
> + if (*p)
> + return false;
> + p++;
> + len--;
> + }
> + return true;
> +}
> +
> +static inline bool libperf_validate_opts(const char *opts,
> + size_t opts_sz, size_t user_sz,
> + const char *type_name)
> +{
> + if (user_sz < sizeof(size_t)) {
> + pr_warning("%s size (%zu) is too small\n", type_name, user_sz);
> + return false;
> + }
> + if (!libperf_is_mem_zeroed(opts + opts_sz, (ssize_t)user_sz - opts_sz)) {
I don't think the cast is necessary since it'll be promoted again
to size_t due to opts_sz. Instead, we can check if user_sz is
greater than opts_sz explicitly and call the function.
> + pr_warning("%s has non-zero extra bytes\n", type_name);
> + return false;
> + }
> + return true;
> +}
> +
> +#define offsetofend(TYPE, FIELD) \
> + (offsetof(TYPE, FIELD) + sizeof(((TYPE *)0)->FIELD))
> +
> +#define OPTS_VALID(opts, type) \
> + (!(opts) || libperf_validate_opts((const char *)opts, \
> + offsetofend(struct type, \
> + type##__last_field), \
> + (opts)->sz, #type))
> +#define OPTS_HAS(opts, field) \
> + ((opts) && opts->sz >= offsetofend(typeof(*(opts)), field))
> +#define OPTS_GET(opts, field, fallback_value) \
> + (OPTS_HAS(opts, field) ? (opts)->field : fallback_value)
It'd be nice if you add a blank line between the macros.
Thanks,
Namhyung
> +#define OPTS_SET(opts, field, value) \
> + do { \
> + if (OPTS_HAS(opts, field)) \
> + (opts)->field = value; \
> + } while (0)
> +
> #endif /* __LIBPERF_INTERNAL_H */
> diff --git a/tools/lib/perf/libperf.map b/tools/lib/perf/libperf.map
> index 190b56ae923a..eeeb3075e092 100644
> --- a/tools/lib/perf/libperf.map
> +++ b/tools/lib/perf/libperf.map
> @@ -25,6 +25,7 @@ LIBPERF_0.0.1 {
> perf_evsel__enable;
> perf_evsel__disable;
> perf_evsel__open;
> + perf_evsel__open_opts;
> perf_evsel__close;
> perf_evsel__mmap;
> perf_evsel__munmap;
> @@ -36,6 +37,7 @@ LIBPERF_0.0.1 {
> perf_evlist__new;
> perf_evlist__delete;
> perf_evlist__open;
> + perf_evlist__open_opts;
> perf_evlist__close;
> perf_evlist__enable;
> perf_evlist__disable;
> --
> 2.25.1
>
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