linux-kernel - bug in arm_kprobe_decode

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Date:	Sun, 20 Feb 2011 19:24:37 +0100
From:	Marcin Slusarz <marcin.slusarz@...il.com>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	Quentin Barnes <qbarnes@...il.com>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: bug in arm_kprobe_decode_insn

Hi

In arch/arm/kernel/kprobes-decode.c there's a function arm_kprobe_decode_insn
which does:

} else if ((insn & 0x0e000000) == 0x0c400000) {
...

This is always false, so code below is dead.

I'm not sure about what was intended here, but I think this change might be correct:

diff --git a/arch/arm/kernel/kprobes-decode.c b/arch/arm/kernel/kprobes-decode.c
index 2c1f005..8f6ed43 100644
--- a/arch/arm/kernel/kprobes-decode.c
+++ b/arch/arm/kernel/kprobes-decode.c
@@ -1437,7 +1437,7 @@ arm_kprobe_decode_insn(kprobe_opcode_t insn, struct arch_specific_insn *asi)
 
 		return space_cccc_1100_010x(insn, asi);
 
-	} else if ((insn & 0x0e000000) == 0x0c400000) {
+	} else if ((insn & 0x0e000000) == 0x0c000000) {
 
 		return space_cccc_110x(insn, asi);
 
--


I found this bug by coccinelle (http://coccinelle.lip6.fr/).
(The script is ugly, so I'm not attaching it here)


Marcin Slusarz
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