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[209.85.208.177]) by smtp.gmail.com with ESMTPSA id t19sm1021808ljj.100.2020.09.09.14.33.52 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 09 Sep 2020 14:33:52 -0700 (PDT) Received: by mail-lj1-f177.google.com with SMTP id y4so5449561ljk.8 for ; Wed, 09 Sep 2020 14:33:52 -0700 (PDT) X-Received: by 2002:a2e:84d6:: with SMTP id q22mr2679648ljh.70.1599687232145; Wed, 09 Sep 2020 14:33:52 -0700 (PDT) MIME-Version: 1.0 References: <20200903142242.925828-1-hch@lst.de> <20200903142803.GM1236603@ZenIV.linux.org.uk> <20200909184001.GB28786@gate.crashing.org> In-Reply-To: <20200909184001.GB28786@gate.crashing.org> From: Linus Torvalds Date: Wed, 9 Sep 2020 14:33:36 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: remove the last set_fs() in common code, and remove it for x86 and powerpc v3 To: Segher Boessenkool Cc: Al Viro , Nick Desaulniers , linux-arch , Kees Cook , "the arch/x86 maintainers" , Linux Kernel Mailing List , Alexey Dobriyan , Luis Chamberlain , linux-fsdevel , linuxppc-dev , Christoph Hellwig Content-Type: text/plain; charset="UTF-8" Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Wed, Sep 9, 2020 at 11:42 AM Segher Boessenkool wrote: > > It will not work like this in GCC, no. The LLVM people know about that. > I do not know why they insist on pushing this, being incompatible and > everything. Umm. Since they'd be the ones supporting this, *gcc* would be the incompatible one, not clang. Like it or not, clang is becoming a major kernel compiler. It's already basically used for all android uses afaik. So I'd phrase it differently. If gcc is planning on doing some different model for asm goto with outputs, that would be the incompatible case. I'm not sure how gcc could do it differently. The only possible difference I see is (a) not doing it at all (b) doing the "all goto targets have the outputs" case and honestly, (b) is actually inferior for the error cases, even if to a compiler person it might feel like the "RightThing(tm)" to do. Because when an exception happens, the outputs simply won't be initialized. Anyway, for either of those cases, the kernel won't care either way. We'll have to support the non-goto case for many years even if everybody were to magically implement it today, so it's not like this is a "you have to do it" thing. Linus