linux-kernel - Re: [RFC][PATCH 07/11] perf: Provide PERF_SAMPLE

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Date:	Wed, 3 Mar 2010 09:30:31 -0800
From:	Stephane Eranian <eranian@...gle.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	mingo@...e.hu, linux-kernel@...r.kernel.org, paulus@...ba.org,
	robert.richter@....com, fweisbec@...il.com,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [RFC][PATCH 07/11] perf: Provide PERF_SAMPLE_REGS

This assumes struct pt_regs is somehow exported to userland.
Is that the case?

I would clearly spell out that the REGS are the interrupted REGS,
not the overflow REGS. Maybe PERF_SAMPLE_IREGS.

On Wed, Mar 3, 2010 at 8:39 AM, Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:
> Simply copy out the provided pt_regs in a u64 aligned fashion.
>
> XXX: do task_pt_regs() and get_irq_regs() always clear everything or
>     are we now leaking data?
>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> ---
>  include/linux/perf_event.h |    5 ++++-
>  kernel/perf_event.c        |   17 +++++++++++++++++
>  2 files changed, 21 insertions(+), 1 deletion(-)
>
> Index: linux-2.6/include/linux/perf_event.h
> ===================================================================
> --- linux-2.6.orig/include/linux/perf_event.h
> +++ linux-2.6/include/linux/perf_event.h
> @@ -125,8 +125,9 @@ enum perf_event_sample_format {
>        PERF_SAMPLE_PERIOD                      = 1U << 8,
>        PERF_SAMPLE_STREAM_ID                   = 1U << 9,
>        PERF_SAMPLE_RAW                         = 1U << 10,
> +       PERF_SAMPLE_REGS                        = 1U << 11,
>
> -       PERF_SAMPLE_MAX = 1U << 11,             /* non-ABI */
> +       PERF_SAMPLE_MAX = 1U << 12,             /* non-ABI */
>  };
>
>  /*
> @@ -392,6 +393,7 @@ enum perf_event_type {
>         *      { u64                   period;   } && PERF_SAMPLE_PERIOD
>         *
>         *      { struct read_format    values;   } && PERF_SAMPLE_READ
> +        *      { struct pt_regs        regs;     } && PERF_SAMPLE_REGS
>         *
>         *      { u64                   nr,
>         *        u64                   ips[nr];  } && PERF_SAMPLE_CALLCHAIN
> @@ -800,6 +802,7 @@ struct perf_sample_data {
>        u64                             period;
>        struct perf_callchain_entry     *callchain;
>        struct perf_raw_record          *raw;
> +       struct pt_regs                  *regs;
>  };
>
>  static inline
> Index: linux-2.6/kernel/perf_event.c
> ===================================================================
> --- linux-2.6.orig/kernel/perf_event.c
> +++ linux-2.6/kernel/perf_event.c
> @@ -3176,6 +3176,17 @@ void perf_output_sample(struct perf_outp
>        if (sample_type & PERF_SAMPLE_READ)
>                perf_output_read(handle, event);
>
> +       if (sample_type & PERF_SAMPLE_REGS) {
> +               int size = DIV_ROUND_UP(sizeof(struct pt_regs), sizeof(u64)) -
> +                          sizeof(struct pt_regs);
> +
> +               perf_output_put(handle, *data->regs);
> +               if (size) {
> +                       u64 zero = 0;
> +                       perf_output_copy(handle, &zero, size);
> +               }
> +       }
> +
>        if (sample_type & PERF_SAMPLE_CALLCHAIN) {
>                if (data->callchain) {
>                        int size = 1;
> @@ -3273,6 +3284,12 @@ void perf_prepare_sample(struct perf_eve
>        if (sample_type & PERF_SAMPLE_READ)
>                header->size += perf_event_read_size(event);
>
> +       if (sample_type & PERF_SAMPLE_REGS) {
> +               data->regs = regs;
> +               header->size += DIV_ROUND_UP(sizeof(struct pt_regs),
> +                                            sizeof(u64));
> +       }
> +
>        if (sample_type & PERF_SAMPLE_CALLCHAIN) {
>                int size = 1;
>
>
> --
>
>



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