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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Sat, 10 Feb 2018 20:46:02 -0800
Message-ID: <CA+55aFxdx3FYE6YGifRR=BSG9QzXwgThj5z7RmV5P5+RpNXSiQ@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>
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On Sat, Feb 10, 2018 at 8:13 PM, Kees Cook <keescook@chromium.org> wrote:
>
> It's been there since the very beginning when Arjan added it to
> validate that the compiler actually produces a stack protector when
> you give it -fstack-protector. Older gccs broke this entirely, more
> recent misconfigurations (as seen with some of Arnd's local gcc
> builds) did similar, and there have been regressions in some versions
> where gcc's x86 support flipped to the global canary instead of the
> %gs-offset canary.

Argh. I wanted to get rid of all that entirely, and simplify this all.
The mentioned script (and bugzilla) was from 2006, I assumed this was
all historical.

But if it has broken again since, I guess we need to have a silly script. Grr.

But yes, I also reacted to your earlier " It can't silently rewrite it
to _REGULAR because the compiler support for _STRONG regressed."
Because it damn well can. If the compiler doesn't support
-fstack-protector-strong, we can just fall back on -fstack-protector.
Silently. No extra crazy complex logic for that either.

                 Linus