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From:   =?utf-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn@kernel.org>
To:     "liaochang (A)" <liaochang1@huawei.com>,
        Chen Guokai <chenguokai17@mails.ucas.ac.cn>,
        paul.walmsley@sifive.com, palmer@dabbelt.com,
        aou@eecs.berkeley.edu, rostedt@goodmis.org, mingo@redhat.com,
        sfr@canb.auug.org.au
Cc:     linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 0/9] Add OPTPROBES feature on RISCV
In-Reply-To: <f2e121f3-2bb7-5389-79e3-91edbebe60b8@huawei.com>
References: <20221224114315.850130-1-chenguokai17@mails.ucas.ac.cn>
 <87y1qkvmpf.fsf@all.your.base.are.belong.to.us>
 <f2e121f3-2bb7-5389-79e3-91edbebe60b8@huawei.com>
Date:   Wed, 04 Jan 2023 09:53:01 +0100
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"liaochang (A)" <liaochang1@huawei.com> writes:

> Hi=EF=BC=8CBj=C3=B6rn=EF=BC=8Cappreciate for your review and testing abou=
t this feature.

Thank you for the hard work!

> =E5=9C=A8 2023/1/3 2:02, Bj=C3=B6rn T=C3=B6pel =E5=86=99=E9=81=93:
>> Chen Guokai <chenguokai17@mails.ucas.ac.cn> writes:
>>=20
>>> Add jump optimization support for RISC-V.
>>=20
>> Thank you for continuing to work on the series! I took the series for a
>> spin, and ran into a number of issues that makes me wonder how you test
>> the series, and how the testing is different from my runs.
>
> I have pick some kernel functions to test this series, which means all op=
tprobe
> are install at entry of function, i guess the instruction pattern is not =
versatile
> enough for my testcases leads to some bugs are not discovered.
>
> Do you think it is good idea to test this feature via binary ftracetest a=
nd the
> kprobe related tc scripts in tools/testing/ftrace directory?

Definitely! Both running all tests in tools/testing/selftests/ftrace and
with the CONFIG_KPROBES_SANITY_TEST module.

[...]

>> 4. Lockdep splat

[...]

> Need to study this backtrace further, but at first glance, i guess CONFIG=
_DYNAMIC_FTRACE is enabled on your kernel, right?
> If so, all krpobe is installed via ftrace stub, then kprobe optimiztion o=
ccur in the ftrace trampoline code, and it also
> a corner case to current optprobe implementation.

Yes, CONFIG_DYNAMIC_FTRACE is on. My kernel config was simply:
  make ARCH=3Driscv CROSS_COMPILE=3Driscv64-linux-gnu- defconfig
  make ARCH=3Driscv CROSS_COMPILE=3Driscv64-linux-gnu- kselftest-merge


Thanks,
Bj=C3=B6rn