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: <1328072925.5882.57.camel@gandalf.stny.rr.com>
Date:	Wed, 01 Feb 2012 00:08:45 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Ingo Molnar <mingo@...e.hu>
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

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();
+		}
 	} else {
 		/*
 		 * We are disabling this jump label. If it is not what


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