linux-kernel - Re: [PATCH v17 6/9] x86/xen: Add xen

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Message-ID: <20160225075404.GB2354@gmail.com>
Date:	Thu, 25 Feb 2016 08:54:04 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Josh Poimboeuf <jpoimboe@...hat.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, live-patching@...r.kernel.org,
	Michal Marek <mmarek@...e.cz>,
	Peter Zijlstra <peterz@...radead.org>,
	Andy Lutomirski <luto@...nel.org>,
	Borislav Petkov <bp@...en8.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	Pedro Alves <palves@...hat.com>,
	Namhyung Kim <namhyung@...il.com>,
	Bernd Petrovitsch <bernd@...rovitsch.priv.at>,
	Chris J Arges <chris.j.arges@...onical.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jiri Slaby <jslaby@...e.cz>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	David Vrabel <david.vrabel@...rix.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>
Subject: Re: [PATCH v17 6/9] x86/xen: Add xen_cpuid() to objtool whitelist


* Josh Poimboeuf <jpoimboe@...hat.com> wrote:

> 'objtool check' reports the following false positive warning:
> 
>   objtool: arch/x86/xen/enlighten.o: xen_cpuid()+0x41: can't find jump dest instruction at .text+0x108
> 
> The warning is due to xen_cpuid()'s use of XEN_EMULATE_PREFIX to insert
> some fake instructions which objtool doesn't know how to decode.
> 
> Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
> Cc: David Vrabel <david.vrabel@...rix.com>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
> ---
>  arch/x86/xen/enlighten.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index d09e4c9..b7f5909 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -32,6 +32,7 @@
>  #include <linux/gfp.h>
>  #include <linux/memblock.h>
>  #include <linux/edd.h>
> +#include <linux/objtool.h>
>  
>  #ifdef CONFIG_KEXEC_CORE
>  #include <linux/kexec.h>
> @@ -351,8 +352,8 @@ static void xen_cpuid(unsigned int *ax, unsigned int *bx,
>  	*cx &= maskecx;
>  	*cx |= setecx;
>  	*dx &= maskedx;
> -
>  }
> +STACK_FRAME_NON_STANDARD(xen_cpuid); /* XEN_EMULATE_PREFIX */

Could you please change the title and changelog of all such annotation patches to 
say something like:

  x86/xen: Mark xen_cpuid() stack frame as non-standard

?

It's not an objtool whitelist anymore, but a more generic annotation that objtool 
uses.

Thanks,

	Ingo