linux-kernel - [PATCH 74/74] lto, workaround: Mark do_futex noinline to prevent clobbering ebp

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Message-Id: <1345345030-22211-75-git-send-email-andi@firstfloor.org>
Date:	Sat, 18 Aug 2012 19:57:10 -0700
From:	Andi Kleen <andi@...stfloor.org>
To:	linux-kernel@...r.kernel.org
Cc:	x86@...nel.org, mmarek@...e.cz, linux-kbuild@...r.kernel.org,
	JBeulich@...e.com, akpm@...ux-foundation.org,
	Andi Kleen <ak@...ux.intel.com>
Subject: [PATCH 74/74] lto, workaround: Mark do_futex noinline to prevent clobbering ebp

From: Andi Kleen <ak@...ux.intel.com>

On a 32bit build gcc 4.7 with LTO decides to clobber the 6th argument on the
stack.  Unfortunately this corrupts the user EBP and leads to later crashes.
For now mark do_futex noinline to prevent this.

I wish there was a generic way to handle this. Seems like a ticking time
bomb problem.

Signed-off-by: Andi Kleen <ak@...ux.intel.com>
---
 kernel/futex.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index 3717e7b..48b5a07 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2620,7 +2620,7 @@ void exit_robust_list(struct task_struct *curr)
 				   curr, pip);
 }
 
-long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
+noinline long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
 		u32 __user *uaddr2, u32 val2, u32 val3)
 {
 	int cmd = op & FUTEX_CMD_MASK;
-- 
1.7.7.6

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