linux-kernel - Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array

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Message-ID: <CACT4Y+bRWePGuZB-HCGBhHuENHAM=uDDv3i81fwZjNUKhNY2UA@mail.gmail.com>
Date:   Fri, 24 Mar 2017 14:50:24 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Borislav Petkov <bp@...en8.de>,
        Alexander Potapenko <glider@...gle.com>,
        Michael Davidson <md@...gle.com>,
        Michal Marek <mmarek@...e.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Shaohua Li <shli@...nel.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "open list:KERNEL BUILD + fi..." <linux-kbuild@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-crypto@...r.kernel.org, linux-raid@...r.kernel.org,
        kbuild-all@...org, Fengguang Wu <fengguang.wu@...el.com>
Subject: Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array

On Fri, Mar 17, 2017 at 8:29 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Fri, Mar 17, 2017 at 08:26:42PM +0100, Peter Zijlstra wrote:
>> On Fri, Mar 17, 2017 at 08:05:16PM +0100, Dmitry Vyukov wrote:
>> > You can also find some reasons in the Why section of LLVM-Linux project:
>> > http://llvm.linuxfoundation.org/index.php/Main_Page
>>
>> From that:
>>
>>  - LLVM/Clang is a fast moving project with many things fixed quickly
>>    and features added.
>>
>> So what's the deal with that 5 year old bug you want us to work around?
>>
>> Also, clang doesn't support asm cc flags output and a few other
>> extensions last time I checked.
>>
>
> Another great one:
>
>  - BSD License (some people prefer this license to the GPL)
>
> Seems a very weak argument to make when talking about the Linux Kernel
> which is very explicitly GPLv2 (and not later).

OK, I guess should not have referenced the llvm-linux page.
So here are reasons on our side that I am ready to vouch:

 - clang make it possible to implement KMSAN (dynamic detection of
uses of uninit memory)
 - better code coverage for fuzzing
 - why simpler and faster development (e.g. we can port our user-space
hardening technologies -- CFI and SafeStack)

Michael is on a different team and has own reasons to do this.