linux-kernel - Re: [PATCH] Coresight: tpda/tpdm: remove incorrect _

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Date:   Fri, 27 Jan 2023 17:12:55 +0000
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     Arnd Bergmann <arnd@...db.de>, Arnd Bergmann <arnd@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Tao Zhang <quic_taozha@...cinc.com>,
        Mao Jinlong <quic_jinlmao@...cinc.com>,
        Will Deacon <will@...nel.org>
Cc:     Mike Leach <mike.leach@...aro.org>, Leo Yan <leo.yan@...aro.org>,
        coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Coresight: tpda/tpdm: remove incorrect __exit annotation

On 27/01/2023 17:00, Arnd Bergmann wrote:
> On Fri, Jan 27, 2023, at 17:46, Suzuki K Poulose wrote:
>> On 26/01/2023 20:37, Arnd Bergmann wrote:
>>> On Thu, Jan 26, 2023, at 19:02, Suzuki K Poulose wrote:
>>>> On 26/01/2023 16:35, Arnd Bergmann wrote:
>>>>> From: Arnd Bergmann <arnd@...db.de>
>>>> Thanks for the fix, I will queue this. Btw, I did try to
>>>> reproduce it locally, but couldn't trigger the warnings,
>>>> even with
>>>>
>>>> CONFIG_WERROR=y
>>>>
>>>> and all CORESIGHT configs builtin. I see other drivers doing the
>>>> same outside coresight too. Just curious to know why is this
>>>> any different. Is it specific to "bus" driver (e.g. AMBA) ?
>>>
>>> The warning comes from postprocessing the object file, it's got
>>> nothing to do with the bus type, only with a symbol in .data
>>> referencing a symbol in .init.text. Maybe there are some
>>> config options that keep the section from getting discarded?
>>> Or possibly you only built the files in this directory, but did
>>> not get to the final link?
>>
>> I did a full kernel build. Also, I see a similar issue with the
>> coresight-etm4x (by code inspection) driver. Did you not hit that ?
>>
>> May be there is a config option that is masking it on my end. But
>> the case of etm4x driver is puzzling.
>>
>> $ git grep etm4_remove_amba
>> drivers/hwtracing/coresight/coresight-etm4x-core.c
>> drivers/hwtracing/coresight/coresight-etm4x-core.c:static void __exit
>> etm4_remove_amba(struct amba_device *adev)
>> drivers/hwtracing/coresight/coresight-etm4x-core.c:     .remove
>> = etm4_remove_amba,
> 
> Indeed, that one clearly has the same but, but I have never
> observed a warning for it.
> 
> I checked one more thing and found that I only get the warning
> for 32-bit Arm builds, but not arm64. Since the etm4x driver
> 'depends on ARM64' for its use of asm/sysreg.h,
> I never test-built it on 32-bit arm.
> 
>  From the git history of arch/arm64/kernel/vmlinux.lds.S,
> I can see that arm64 never discards the .exit section, see
> commit 07c802bd7c39 ("arm64: vmlinux.lds.S: don't discard
> .exit.* sections at link-time").

That makes sense, thanks for getting to the bottom of this. I
have pushed it to coresight next.

https://git.kernel.org/coresight/c/0c1ccc158bbc

Kind regards
Suzuki



> 
>       Arnd