linux-kernel - Re: [PATCH] kbuild: modpost: Warn about references from rodata to _

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Date:   Sat, 22 Jul 2017 00:57:44 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Stephen Boyd <sboyd@...eaurora.org>
Cc:     Rob Clark <robdclark@...il.com>, Michal Marek <mmarek@...e.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Subject: Re: [PATCH] kbuild: modpost: Warn about references from rodata to
 __init text

Hi Stephen,


2017-07-21 2:52 GMT+09:00 Stephen Boyd <sboyd@...eaurora.org>:
> On 07/20, Masahiro Yamada wrote:
>> Hi Stephen, Rob,
>>
>> 2017-07-01 8:59 GMT+09:00 Rob Clark <robdclark@...il.com>:
>> > On Fri, Jun 30, 2017 at 6:58 PM, Stephen Boyd <sboyd@...eaurora.org> wrote:
>> >> If we have a structure that's marked const it will be placed
>> >> into the .rodata section but it could reference an init section
>> >> function. Include the read only data section in the check we have
>> >> for read/write data sections referencing init sections so we can
>> >> find this class of problems. This exposes quite a few places
>> >> where const marked structures are referencing __init functions and
>> >> __init data that we were previously ignoring.
>> >>
>> >> Cc: Rob Clark <robdclark@...il.com>
>> >> Cc: Bjorn Andersson <bjorn.andersson@...aro.org>
>> >> Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
>> >> ---
>> >>
>> >> Making this change leads to quite a few other errors even on the
>> >> multi_v7_defconfig for ARM[1]. I still need to do a build of the
>> >> allmodconfig to see how many other errors there, but it seems to
>> >> be quite a few. I suppose those will need to be fixed before we can
>> >> merge this?
>> >
>> > thanks.. the explosions you get with these mistakes when building
>> > drivers as modules in a distro kernel config are quite "fun" to
>> > debug..
>> >
>> > I'm not quite sure about the rules for whether merging this would
>> > count as a regression, but I would argue those drivers are already
>> > broken, just no one noticed yet.  Similar to when a new gcc gets more
>> > clever about detecting bugs.  So I wouldn't be against merging this
>> > first to force drivers to fix their crap ;-)
>>
>> I applied this, but this way seems unacceptable.
>> I cannot send a pull-req for this
>> unless most of the warnings are fixed.
>>
>> Is there any activity for driver fixes?
>
> Sorry, no. I've only had a little time to look at the errors
> reported. Some of them seem to be noise, because there are
> structures that have a handful of members where one of the
> members points to an __init function or piece of data that is
> only used in __init code. We would need to mark these structures
> as __ref or write more complicated section mismatch checking code
> to be silent in these cases.

OK.  I will drop this patch for now.



-- 
Best Regards
Masahiro Yamada