linux-kernel - Re: [RFC PATCH 4/7] kconfig: support new special property shell=

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Message-ID: <CAK8P3a3-63He=LPtqyskQn_J-8VKUTpoFXLPjUU7Vjoj1MYfLA@mail.gmail.com>
Date:   Mon, 12 Feb 2018 11:44:26 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Ulf Magnusson <ulfalizer@...il.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Nicolas Pitre <nicolas.pitre@...aro.org>,
        "Luis R . Rodriguez" <mcgrof@...e.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Sam Ravnborg <sam@...nborg.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Pavel Machek <pavel@....cz>,
        linux-s390 <linux-s390@...r.kernel.org>,
        Jiri Kosina <jkosina@...e.cz>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Tejun Heo <tj@...nel.org>, Ingo Molnar <mingo@...nel.org>,
        "Van De Ven, Arjan" <arjan.van.de.ven@...el.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [RFC PATCH 4/7] kconfig: support new special property shell=

On Sun, Feb 11, 2018 at 10:50 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
> On Sun, Feb 11, 2018 at 1:19 PM, Kees Cook <keescook@...omium.org> wrote:
>> On Sun, Feb 11, 2018 at 1:10 PM, Arnd Bergmann <arnd@...db.de> wrote:
>>>
>>> In my tests last year, I identified gcc-4.6 as a nice minimum level, IIRC
>>> gcc-4.5 was unable to build some of the newer ARM targets.
>>
>> But yes, if Linus wants 4.5 over 4.3, I would agree with Arnd: let's
>> take it to 4.6 instead.
>
> So it sounds like Arnd knows what the distros have.
...
> If no distro is on 4.5, then there's no reason to pick that. The
> reason I mentioned 4.5 is because that's the "asm goto" point, afaik,
> and that is likely to be a requirement in the near future.

Looking at old distros with long support cycles:

Red Hat have either gcc-4.1 (EL5, extended support ends 2020) or
gcc-4.4 (EL6, regular support ends 2020, extended support ends 2024):
https://access.redhat.com/solutions/19458
EL7 uses gcc-4.8 and will be supported until 2024 (no extended support
planned)

SUSE have gcc-4.3 (SLES11, extended support ends 2022) or gcc-4.8
(SLES12, support ends 2024, extended support ends 2027):
https://www.suse.com/lifecycle/

Debian Jessie (oldstable) comes with gcc-4.8 and is supported until June 2018,
extended support until 2020
Debian  Wheezy (oldoldstable) uses gcc-4.6 or 4.7 depending on the
architecture, extended support ends May 2018.

Ubuntu 14.04 is supported until 2019 and uses gcc-4.8

The latest Android SDK provides (known broken) versions of gcc-4.8 and
gcc-4.9 as well as clang.

OpenWRT 14.07 Barrier Breaker uses gcc-4.8, 12.07 Attitude
Adjustment 12.09 used gcc-4.6, but it's very unlikely that anyone
cares about building new kernels with either.

Most embedded distros just build everything from source and are
used to adapting to new requirements.

>From that list above, it sounds like going all the way to gcc-4.8 would
be a better candidate than 4.5 or 4.6, if we decide that 4.3 and 4.4 are
both no longer desirable to support.

> If SLES11 is 4.3, that's obviously a concern. Although Arnd seemed to
> imply that that had already caused problems, so...

The problems are mainly an excessive amount of false-positive
warnings, which makes it tricky to new warnings when you make
a mistake.

          Arnd