linux-kernel - [PATCH] Fix broken mmiotrace due to dr6 by reference change

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Message-Id: <1263634770-14578-1-git-send-email-luca@luca-barbieri.com>
Date:	Sat, 16 Jan 2010 10:39:30 +0100
From:	Luca Barbieri <luca@...a-barbieri.com>
To:	Ingo Molnar <mingo@...hat.com>
Cc:	"K.Prasad" <prasad@...ux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	linux-kernel@...r.kernel.org,
	Luca Barbieri <luca@...a-barbieri.com>
Subject: [PATCH] Fix broken mmiotrace due to dr6 by reference change

Commit 62edab9056a6cf0c9207339c8892c923a5217e45 (from June 2009 but merged
in 2.6.33) changes notify_die to pass dr6 by reference.

However, it forgets to fix the check for DR_STEP in kmmio.c, breaking
mmiotrace. It also passes a wrong value to the post handler.

This simple fix makes mmiotrace work again.

Please send to Linus for inclusion in 2.6.33

Signed-off-by: Luca Barbieri <luca@...a-barbieri.com>
---
 arch/x86/mm/kmmio.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/x86/mm/kmmio.c b/arch/x86/mm/kmmio.c
index c0f6198..536fb68 100644
--- a/arch/x86/mm/kmmio.c
+++ b/arch/x86/mm/kmmio.c
@@ -538,14 +538,15 @@ static int
 kmmio_die_notifier(struct notifier_block *nb, unsigned long val, void *args)
 {
 	struct die_args *arg = args;
+	unsigned long* dr6_p = (unsigned long *)ERR_PTR(arg->err);
 
-	if (val == DIE_DEBUG && (arg->err & DR_STEP))
-		if (post_kmmio_handler(arg->err, arg->regs) == 1) {
+	if (val == DIE_DEBUG && (*dr6_p & DR_STEP))
+		if (post_kmmio_handler(*dr6_p, arg->regs) == 1) {
 			/*
 			 * Reset the BS bit in dr6 (pointed by args->err) to
 			 * denote completion of processing
 			 */
-			(*(unsigned long *)ERR_PTR(arg->err)) &= ~DR_STEP;
+			*dr6_p &= ~DR_STEP;
 			return NOTIFY_STOP;
 		}
 
-- 
1.6.3.3

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