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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Sun, 11 Feb 2018 11:53:12 -0800
Message-ID: <CA+55aFwWQ4nL2Asmzn0NSsw=w-tX5hAM9bFiOZhxehnhWH+wkw@mail.gmail.com>
Subject: Re: [RFC PATCH 4/7] kconfig: support new special property shell=
To:     Kees Cook <keescook@chromium.org>
Cc:     Ulf Magnusson <ulfalizer@gmail.com>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Nicolas Pitre <nicolas.pitre@linaro.org>,
        "Luis R . Rodriguez" <mcgrof@suse.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        Sam Ravnborg <sam@ravnborg.org>,
        Michal Marek <michal.lkml@markovi.net>,
        Martin Schwidefsky <schwidefsky@de.ibm.com>,
        Pavel Machek <pavel@ucw.cz>,
        linux-s390 <linux-s390@vger.kernel.org>,
        Jiri Kosina <jkosina@suse.cz>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Tejun Heo <tj@kernel.org>, Ingo Molnar <mingo@kernel.org>,
        "Van De Ven, Arjan" <arjan.van.de.ven@intel.com>,
        Arnd Bergmann <arnd@arndb.de>
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On Sun, Feb 11, 2018 at 11:39 AM, Kees Cook <keescook@chromium.org> wrote:
>>
>>  (a) make gcc 4.5 be the minimum required version
>
> I love bumping minimum for so many reason more than just stack protector. :)

Well, it's still not a very *big* bump. With modern distros being at
7.3, and people testing pre-releases of gcc-8, something like gcc-4.5
is still pretty darn ancient.

But it would be good to be able to rely on asm goto rather than have
completely different logic for "have to do it by hand". And I do
wonder how many of our "let's test if gcc supports this option" are
completely out-dated.

And in <linux/compiler-gcc.h> we still have tests for truly ancient garbage.

> This made akpm and Arnd very very grumpy as it regressed their builds.
> That's why I had to deal with the condition very carefully for _AUTO.

Well, Arnd build new cross-tools last week, probably because you
really need new tools for other reasons anyway (ie all the spectre
mitigation). So I think Arnd is set.

And akpm being on some ancient stone age system has been an issue
before. The only way to fix it is to break it.

What I would worry about primarily is not one of the odd developers
who can upgrade, but random people in the wild. I don't want to lose
the occasional odd tester that does things nobody else does.

But with gcc-4.5 being 7+ years old, I can't imagine it's a huge issue.

              Linus