linux-kernel - Re: [PATCH] Split executable and non-executable mmap tracking

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Date:	Mon, 17 May 2010 15:21:15 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Eric B Munson <ebmunson@...ibm.com>
Cc:	mingo@...e.hu, acme@...hat.com, arjan@...ux.intel.com,
	anton@...ba.org, riel@...hat.com, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [PATCH] Split executable and non-executable mmap tracking

On Fri, 2010-05-07 at 10:05 +0100, Eric B Munson wrote:
> This patch splits tracking of executable and non-executable mmaps.
> Executable mmaps are tracked normally and non-executable are
> tracked when --data is used.
> 
> Signed-off-by: Anton Blanchard <anton@...ba.org>
> 
> Updated code for stable perf ABI
> Signed-off-by: Eric B Munson <ebmunson@...ibm.com>

> +++ b/include/linux/perf_event.h
> @@ -197,6 +197,7 @@ struct perf_event_attr {
>  				exclude_hv     :  1, /* ditto hypervisor      */
>  				exclude_idle   :  1, /* don't count when idle */
>  				mmap           :  1, /* include mmap data     */
> +				mmap_exec      :  1, /* include exec mmap data*/
>  				comm	       :  1, /* include comm data     */
>  				freq           :  1, /* use freq, not period  */
>  				inherit_stat   :  1, /* per task counts       */

You cannot add a field in the middle, that breaks ABI.

> -static inline void perf_event_mmap(struct vm_area_struct *vma)
> -{
> -	if (vma->vm_flags & VM_EXEC)
> -		__perf_event_mmap(vma);
> -}

Also, the current behaviour of perf_event_attr::mmap() is to trace
VM_EXEC maps only, apps relying on that will be broken after this patch
because they'd have to set mmap_exec.

If you want to do this, you'll have to add mmap_data (to the tail of the
bitfield) and have that add !VM_EXEC mmap() tracing.




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