This is a note to let you know that I've just added the patch titled
x86: Ignore trap bits on single step exceptions
to the 2.6.36-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-ignore-trap-bits-on-single-step-exceptions.patch
and it can be found in the queue-2.6.36 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 6c0aca288e726405b01dacb12cac556454d34b2a Mon Sep 17 00:00:00 2001
From: Frederic Weisbecker <[email protected]>
Date: Thu, 11 Nov 2010 21:18:43 +0100
Subject: x86: Ignore trap bits on single step exceptions
From: Frederic Weisbecker <[email protected]>
commit 6c0aca288e726405b01dacb12cac556454d34b2a upstream.
When a single step exception fires, the trap bits, used to
signal hardware breakpoints, are in a random state.
These trap bits might be set if another exception will follow,
like a breakpoint in the next instruction, or a watchpoint in the
previous one. Or there can be any junk there.
So if we handle these trap bits during the single step exception,
we are going to handle an exception twice, or we are going to
handle junk.
Just ignore them in this case.
This fixes https://bugzilla.kernel.org/show_bug.cgi?id=21332
Reported-by: Michael Stefaniuc <[email protected]>
Signed-off-by: Frederic Weisbecker <[email protected]>
Cc: Rafael J. Wysocki <[email protected]>
Cc: Maciej Rutecki <[email protected]>
Cc: Alexandre Julliard <[email protected]>
Cc: Jason Wessel <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
arch/x86/kernel/hw_breakpoint.c | 4 ++++
1 file changed, 4 insertions(+)
--- a/arch/x86/kernel/hw_breakpoint.c
+++ b/arch/x86/kernel/hw_breakpoint.c
@@ -433,6 +433,10 @@ static int __kprobes hw_breakpoint_handl
dr6_p = (unsigned long *)ERR_PTR(args->err);
dr6 = *dr6_p;
+ /* If it's a single step, TRAP bits are random */
+ if (dr6 & DR_STEP)
+ return NOTIFY_DONE;
+
/* Do an early return if no trap bits are set in DR6 */
if ((dr6 & DR_TRAP_BITS) == 0)
return NOTIFY_DONE;
Patches currently in stable-queue which might be from [email protected] are
queue-2.6.36/reiserfs-fix-inode-mutex-reiserfs-lock-misordering.patch
queue-2.6.36/reiserfs-don-t-acquire-lock-recursively-in-reiserfs_acl_chmod.patch
queue-2.6.36/x86-ignore-trap-bits-on-single-step-exceptions.patch
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