linux-kernel - Re: [PATCH 4/7] perf: add ability to change event according to sample

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Message-ID: <4EB84A3F.5060501@gmail.com>
Date:	Mon, 07 Nov 2011 14:14:39 -0700
From:	David Ahern <dsahern@...il.com>
To:	Andrew Vagin <avagin@...nvz.org>
CC:	linux-kernel@...r.kernel.org, Arun Sharma <asharma@...com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>, Ingo Molnar <mingo@...e.hu>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	devel@...nvz.org
Subject: Re: [PATCH 4/7] perf: add ability to change event according to sample



On 11/07/2011 05:54 AM, Andrew Vagin wrote:
> It's opposition of perf_session__parse_sample.
> 
> Signed-off-by: Andrew Vagin <avagin@...nvz.org>
> ---
>  tools/perf/util/event.h   |    2 +
>  tools/perf/util/evsel.c   |   74 +++++++++++++++++++++++++++++++++++++++++++++
>  tools/perf/util/session.h |    9 +++++
>  3 files changed, 85 insertions(+), 0 deletions(-)
> 
> diff --git a/tools/perf/util/event.h b/tools/perf/util/event.h
> index 357a85b..0493101 100644
> --- a/tools/perf/util/event.h
> +++ b/tools/perf/util/event.h
> @@ -187,5 +187,7 @@ const char *perf_event__name(unsigned int id);
>  int perf_event__parse_sample(const union perf_event *event, u64 type,
>  			     int sample_size, bool sample_id_all,
>  			     struct perf_sample *sample, bool swapped);
> +int perf_event__change_sample(union perf_event *event, u64 type,
> +			     const struct perf_sample *data, bool swapped);
>  
>  #endif /* __PERF_RECORD_H */
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index b46f6e4..9274e08 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -475,3 +475,77 @@ int perf_event__parse_sample(const union perf_event *event, u64 type,
>  
>  	return 0;
>  }
> +
> +int perf_event__change_sample(union perf_event *event, u64 type,
> +			     const struct perf_sample *data, bool swapped)
> +{
> +	u64 *array;
> +
> +	/*
> +	 * used for cross-endian analysis. See git commit 65014ab3
> +	 * for why this goofiness is needed.
> +	 */
> +	union {
> +		u64 val64;
> +		u32 val32[2];
> +	} u;
> +
> +	array = event->sample.array;
> +
> +	if (type & PERF_SAMPLE_IP) {
> +		event->ip.ip = data->ip;
> +		array++;
> +	}
> +
> +	if (type & PERF_SAMPLE_TID) {
> +		u.val32[0] = data->pid;
> +		u.val32[1] = data->tid;
> +		if (swapped) {
> +			/* undo swap of u64, then swap on individual u32s */
> +			u.val64 = bswap_64(u.val64);
> +			u.val32[0] = bswap_32(u.val32[0]);
> +			u.val32[1] = bswap_32(u.val32[1]);

If this is meant to be the reverse direction of parse_sample then I
think you need the bswap_64 after the bswap_32.


> +		}
> +
> +		*array = u.val64;
> +		array++;
> +	}
> +
> +	if (type & PERF_SAMPLE_TIME) {
> +		*array = data->time;
> +		array++;
> +	}
> +
> +	if (type & PERF_SAMPLE_ADDR) {
> +		*array = data->addr;
> +		array++;
> +	}
> +
> +	if (type & PERF_SAMPLE_ID) {
> +		*array = data->id;
> +		array++;
> +	}
> +
> +	if (type & PERF_SAMPLE_STREAM_ID) {
> +		*array = data->stream_id;
> +		array++;
> +	}
> +
> +	if (type & PERF_SAMPLE_CPU) {
> +		u.val32[0] = data->cpu;
> +		if (swapped) {
> +			/* undo swap of u64, then swap on individual u32s */
> +			u.val64 = bswap_64(u.val64);
> +			u.val32[0] = bswap_32(u.val32[0]);
> +		}

Ditto here too.

This really should be tested for cross-endian analysis to verify it
works properly.

David


> +		*array = u.val64;
> +		array++;
> +	}
> +
> +	if (type & PERF_SAMPLE_PERIOD) {
> +		*array = data->period;
> +		array++;
> +	}
> +
> +	return 0;
> +}
> diff --git a/tools/perf/util/session.h b/tools/perf/util/session.h
> index 514b06d..5a36d10 100644
> --- a/tools/perf/util/session.h
> +++ b/tools/perf/util/session.h
> @@ -166,6 +166,15 @@ static inline int perf_session__parse_sample(struct perf_session *session,
>  					session->header.needs_swap);
>  }
>  
> +static inline int perf_session__change_sample(struct perf_session *session,
> +					     union perf_event *event,
> +					     const struct perf_sample *sample)
> +{
> +	return perf_event__change_sample(event, session->sample_type,
> +					sample,
> +					session->header.needs_swap);
> +}
> +
>  struct perf_evsel *perf_session__find_first_evtype(struct perf_session *session,
>  					    unsigned int type);
>  
--
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