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

[Frederic Weisbecker <fweisbec@gmail.com>]

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;
>  
> 
> -- 
>