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Date:   Wed, 12 Oct 2022 15:22:51 +0530
From:   "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Subject: Re: [PATCH] powerpc/kprobes: Fix null pointer reference in
 arch_prepare_kprobe()
To:     jniethe5@gmail.com, Li Huafei <lihuafei1@huawei.com>,
        mpe@ellerman.id.au
Cc:     christophe.leroy@csgroup.eu, linux-kernel@vger.kernel.org,
        linuxppc-dev@lists.ozlabs.org, mhiramat@kernel.org,
        npiggin@gmail.com, peterz@infradead.org, rostedt@goodmis.org
References: <20220923093253.177298-1-lihuafei1@huawei.com>
        <1664530538.ke6dp49pwh.naveen@linux.ibm.com>
        <de8e524d-02b3-c2d0-45c3-5cc1e5556660@huawei.com>
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Li Huafei wrote:
>>>
>>> =C2=A0 # echo 'p cmdline_proc_show' > kprobe_events
>>> =C2=A0 # echo 'p cmdline_proc_show+16' >> kprobe_events
>>=20
>> I think we should extend multiple_kprobes selftest to also place
>> contiguous probes to catch such errors.
>>=20
> Yes. But each architecture implementation is different and it looks a
> little difficult to decide which offsets need to be tested.

I don't think we need to be accurate here. A test to simply try putting=20
a probe at every byte within the first 256 bytes of a kernel function=20
should help catch many such issues. Some of those probes will be=20
rejected, but we can ignore errors.


- Naveen