linux-kernel - Re: [PATCH 03/17] x86, mpx: trace #BR exceptions

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Message-ID: <20150330212528.GI3042@home.goodmis.org>
Date:	Mon, 30 Mar 2015 17:25:28 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
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 03/17] x86, mpx: trace #BR exceptions

On Fri, Mar 27, 2015 at 02:52:59PM -0700, Dave Hansen wrote:
> 
> --- /dev/null	2014-10-10 16:10:57.316716958 -0700
> +++ b/arch/x86/include/asm/trace/mpx.h	2015-03-27 14:35:04.735760444 -0700
> @@ -0,0 +1,48 @@
> +#undef TRACE_SYSTEM
> +#define TRACE_SYSTEM mpx
> +
> +#if !defined(_TRACE_MPX_H) || defined(TRACE_HEADER_MULTI_READ)
> +#define _TRACE_MPX_H
> +
> +#include <linux/tracepoint.h>
> +
> +#ifdef CONFIG_X86_INTEL_MPX
> +
> +TRACE_EVENT(bounds_exception_mpx,
> +
> +	TP_PROTO(struct bndcsr *bndcsr),
> +	TP_ARGS(bndcsr),
> +
> +	TP_STRUCT__entry(
> +		__field(u64, bndcfgu)
> +		__field(u64, bndstatus)
> +	),
> +
> +	TP_fast_assign(
> +		__entry->bndcfgu   = bndcsr->bndcfgu;
> +		__entry->bndstatus = bndcsr->bndstatus;
> +	),
> +
> +	TP_printk("bndcfgu:0x%llx bndstatus:0x%llx",
> +		__entry->bndcfgu,
> +		__entry->bndstatus)
> +);
> +
> +#else
> +
> +/*
> + * This gets used outside of MPX-specific code, so we need a stub.
> + */

I'm a bit confused by this. What exactly is used outside of MPX-specific code?
Does it break the build without this?

-- Steve

> +static inline void trace_bounds_exception_mpx(struct bndcsr *bndcsr)
> +{
> +}
> +
> +#endif /* CONFIG_X86_INTEL_MPX */
> +
> +#undef TRACE_INCLUDE_PATH
> +#define TRACE_INCLUDE_PATH asm/trace/
> +#define TRACE_INCLUDE_FILE mpx
> +#endif /* _TRACE_MPX_H */
> +
> +/* This part must be outside protection */
> +#include <trace/define_trace.h>
> diff -puN arch/x86/kernel/traps.c~x86-br-exception-trace arch/x86/kernel/traps.c
> --- a/arch/x86/kernel/traps.c~x86-br-exception-trace	2015-03-27 14:35:04.731760263 -0700
> +++ b/arch/x86/kernel/traps.c	2015-03-27 14:35:04.736760489 -0700
> @@ -61,6 +61,7 @@
>  #include <asm/mach_traps.h>
>  #include <asm/alternative.h>
>  #include <asm/mpx.h>
> +#include <asm/trace/mpx.h>
>  #include <asm/xsave.h>
>  
>  #ifdef CONFIG_X86_64
> @@ -401,6 +402,7 @@ dotraplinkage void do_bounds(struct pt_r
>  	if (!bndcsr)
>  		goto exit_trap;
>  
> +	trace_bounds_exception_mpx(bndcsr);
>  	/*
>  	 * The error code field of the BNDSTATUS register communicates status
>  	 * information of a bound range exception #BR or operation involving
> diff -puN arch/x86/mm/mpx.c~x86-br-exception-trace arch/x86/mm/mpx.c
> --- a/arch/x86/mm/mpx.c~x86-br-exception-trace	2015-03-27 14:35:04.732760308 -0700
> +++ b/arch/x86/mm/mpx.c	2015-03-27 14:35:04.736760489 -0700
> @@ -18,6 +18,9 @@
>  #include <asm/processor.h>
>  #include <asm/fpu-internal.h>
>  
> +#define CREATE_TRACE_POINTS
> +#include <asm/trace/mpx.h>
> +
>  static const char *mpx_mapping_name(struct vm_area_struct *vma)
>  {
>  	return "[mpx]";
> _
> --
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