Re: [RFC][PATCH 07/11] perf: Provide PERF_SAMPLE_REGS

Frederic Weisbecker
2010-03-03T22:03:01Z

On Wed, Mar 03, 2010 at 05:39:43PM +0100, Peter Zijlstra 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?

It looks like there is a leak in case of non trace syscalls.
where we don't appear to save r12-15.

Then task_pt_regs() may leak the top of a process stack...?

>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.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;
>
>
> --
>