linux-kernel - Re: [PATCH 0/5 v2] [GIT PULL] x86/jump label: Paranoid checks and 2 or 5 byte nops

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Message-ID: <20120201080539.GA11770@elte.hu>
Date:	Wed, 1 Feb 2012 09:05:40 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jason Baron <jbaron@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH 0/5 v2] [GIT PULL] x86/jump label: Paranoid checks and 2
 or 5 byte nops


* Steven Rostedt <rostedt@...dmis.org> wrote:

> On Tue, 2012-01-31 at 20:48 +0100, Ingo Molnar wrote:
> 
> > Attached. (you need to run it through make oldconfig and use the 
> > defaults.)
> 
> Hmm, I'm not able to reproduce it.
> 
> Could you apply this patch and run it again. I'm interested in what was
> at the location when it tried to do the conversion.
> 
> Thanks!
> 
> -- Steve
> 
> diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
> index 6173ca6..da12264 100644
> --- a/arch/x86/kernel/jump_label.c
> +++ b/arch/x86/kernel/jump_label.c
> @@ -58,13 +58,17 @@ static void __jump_label_transform(struct jump_entry *entry,
>  			size = JUMP_LABEL_NOP_SIZE;
>  			code.jump = 0xe9;
>  			code.offset = entry->target - (entry->code + size);
> -		} else
> +		} else {
> +			unsigned char *ins = ip;
>  			/*
>  			 * The location is not a nop that we were expecting,
>  			 * something went wrong. Crash the box, as something could be
>  			 * corrupting the kernel.
>  			 */
> +			printk("Unknown op at %pS (%02x:%02x:%02x:%02x:%02x)\n",
> +			       ip, ins[0], ins[1], ins[2], ins[3], ins[4]);
>  			BUG();
> +		}

It would be better to make this a regular commit, this kind of 
diagnostics obviously makes sense. That way i could pull in your 
updated branch for more testing.

Thanks,

	Ingo
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