2011-02-20 18:26:36

by Marcin Slusarz

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

2011-02-21 03:41:28

by Nicolas Pitre

Subject: Re: bug in arm_kprobe_decode_insn

On Sun, 20 Feb 2011, Marcin Slusarz wrote:

> 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.

Good catch, thanks.


Nicolas