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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Ilya Leoshkevich <iii@linux.ibm.com>,
        Alexander Gordeev <agordeev@linux.ibm.com>,
        Heiko Carstens <hca@linux.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>
Subject: [PATCH 5.15 201/262] s390/extable: fix exception table sorting
Date:   Mon,  7 Mar 2022 10:19:05 +0100
Message-Id: <20220307091708.365171874@linuxfoundation.org>
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From: Heiko Carstens <hca@linux.ibm.com>

commit c194dad21025dfd043210912653baab823bdff67 upstream.

s390 has a swap_ex_entry_fixup function, however it is not being used
since common code expects a swap_ex_entry_fixup define. If it is not
defined the default implementation will be used. So fix this by adding
a proper define.
However also the implementation of the function must be fixed, since a
NULL value for handler has a special meaning and must not be adjusted.

Luckily all of this doesn't fix a real bug currently: the main extable
is correctly sorted during build time, and for runtime sorting there
is currently no case where the handler field is not NULL.

Fixes: 05a68e892e89 ("s390/kernel: expand exception table logic to allow new handling options")
Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/s390/include/asm/extable.h |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

--- a/arch/s390/include/asm/extable.h
+++ b/arch/s390/include/asm/extable.h
@@ -69,8 +69,13 @@ static inline void swap_ex_entry_fixup(s
 {
 	a->fixup = b->fixup + delta;
 	b->fixup = tmp.fixup - delta;
-	a->handler = b->handler + delta;
-	b->handler = tmp.handler - delta;
+	a->handler = b->handler;
+	if (a->handler)
+		a->handler += delta;
+	b->handler = tmp.handler;
+	if (b->handler)
+		b->handler -= delta;
 }
+#define swap_ex_entry_fixup swap_ex_entry_fixup
 
 #endif