linux-kernel - Re: [PATCH 06/17] x86, mpx: trace attempts to find bounds tables

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Message-ID: <20150327123248.GE18927@pd.tnic>
Date:	Fri, 27 Mar 2015 13:32:48 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Dave Hansen <dave@...1.net>
Cc:	linux-kernel@...r.kernel.org, x86@...nel.org, tglx@...utronix.de,
	dave.hansen@...ux.intel.com
Subject: Re: [PATCH 06/17] x86, mpx: trace attempts to find bounds tables

On Thu, Mar 26, 2015 at 11:33:41AM -0700, Dave Hansen wrote:
> 
> From: Dave Hansen <dave.hansen@...ux.intel.com>
> 
> This event traces any time we go looking to unmap a bounds table
> for a given virtual address range.  This is useful to ensure
> that the kernel actually "tried" to free a bounds table versus
> times it succeeded.
> 
> It might try and fail if it realized that a table was shared
> with an adjacent VMA which is not being unmapped.

Would it make sense to extend this tracepoint to also dump the error
values returned from unmap_edge_bts() and unmap_single_bt() inside
mpx_unmap_tables()?

> Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
> ---
> 
>  b/arch/x86/include/asm/trace/mpx.h |   22 ++++++++++++++++++++++
>  b/arch/x86/mm/mpx.c                |    1 +
>  2 files changed, 23 insertions(+)
> 
> diff -puN arch/x86/include/asm/trace/mpx.h~mpx-trace_unmap_search arch/x86/include/asm/trace/mpx.h
> --- a/arch/x86/include/asm/trace/mpx.h~mpx-trace_unmap_search	2015-03-26 11:27:06.684292099 -0700
> +++ b/arch/x86/include/asm/trace/mpx.h	2015-03-26 11:27:06.689292324 -0700
> @@ -75,6 +75,28 @@ TRACE_EVENT(mpx_unmap_zap,
>  	)
>  );
>  
> +TRACE_EVENT(mpx_unmap_search,
> +
> +	TP_PROTO(unsigned long start,
> +		 unsigned long end),
> +	TP_ARGS(start, end),
> +
> +	TP_STRUCT__entry(
> +		__field(unsigned long, start)
> +		__field(unsigned long, end)
> +	),
> +
> +	TP_fast_assign(
> +		__entry->start = start;
> +		__entry->end   = end;
> +	),
> +
> +	TP_printk("0x%p -> 0x%p",

Interval?

> +		(void *)__entry->start,
> +		(void *)__entry->end
> +	)
> +);
> +
>  #else

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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