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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
	Nick Desaulniers <ndesaulniers@google.com>,
	linux-arch <linux-arch@vger.kernel.org>,
	Kees Cook <keescook@chromium.org>,
	"the arch/x86 maintainers" <x86@kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	Luis Chamberlain <mcgrof@kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
	Christoph Hellwig <hch@lst.de>
Subject: Re: remove the last set_fs() in common code, and remove it for x86 and powerpc v3
Date: Wed, 9 Sep 2020 14:33:36 -0700	[thread overview]
Message-ID: <CAHk-=whu19Du_rZ-zBtGsXAB-Qo7NtoJjQjd-Sa9OB5u1Cq_Zw@mail.gmail.com> (raw)
In-Reply-To: <20200909184001.GB28786@gate.crashing.org>

On Wed, Sep 9, 2020 at 11:42 AM Segher Boessenkool
<segher@kernel.crashing.org> 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

  reply	other threads:[~2020-09-09 21:34 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-03 14:22 remove the last set_fs() in common code, and remove it for x86 and powerpc v3 Christoph Hellwig
2020-09-03 14:22 ` [PATCH 01/14] proc: remove a level of indentation in proc_get_inode Christoph Hellwig
2020-09-03 14:22 ` [PATCH 02/14] proc: cleanup the compat vs no compat file ops Christoph Hellwig
2020-09-03 14:22 ` [PATCH 03/14] proc: add a read_iter method to proc proc_ops Christoph Hellwig
2020-09-03 14:22 ` [PATCH 04/14] sysctl: Convert to iter interfaces Christoph Hellwig
2020-09-03 14:22 ` [PATCH 05/14] fs: don't allow kernel reads and writes without iter ops Christoph Hellwig
2020-10-01 22:38   ` Eric Biggers
2020-10-01 22:40     ` Al Viro
2020-10-02 16:27       ` Linus Torvalds
2020-10-09 22:06         ` Eric Biggers
2020-10-10  1:03           ` Linus Torvalds
2020-10-10  1:19             ` Eric Biggers
2020-10-10  1:29               ` Linus Torvalds
2020-10-10  1:55                 ` Alexander Viro
2020-10-14  5:51                   ` Christoph Hellwig
2020-09-03 14:22 ` [PATCH 06/14] fs: don't allow splice read/write without explicit ops Christoph Hellwig
2020-09-03 14:22 ` [PATCH 07/14] uaccess: add infrastructure for kernel builds with set_fs() Christoph Hellwig
2020-09-03 14:22 ` [PATCH 08/14] test_bitmap: remove user bitmap tests Christoph Hellwig
2020-09-03 14:22 ` [PATCH 09/14] lkdtm: remove set_fs-based tests Christoph Hellwig
2020-09-03 14:22 ` [PATCH 10/14] x86: move PAGE_OFFSET, TASK_SIZE & friends to page_{32,64}_types.h Christoph Hellwig
2020-09-03 14:22 ` [PATCH 11/14] x86: make TASK_SIZE_MAX usable from assembly code Christoph Hellwig
2020-09-03 14:22 ` [PATCH 12/14] x86: remove address space overrides using set_fs() Christoph Hellwig
2020-09-03 21:30   ` David Laight
2020-09-03 23:25     ` Linus Torvalds
2020-09-04  7:59       ` David Laight
2020-09-04  2:55   ` Al Viro
2020-09-04  4:41     ` Al Viro
2020-09-04  6:38     ` Christoph Hellwig
2020-09-04  7:47       ` Christoph Hellwig
2020-09-03 14:22 ` [PATCH 13/14] powerpc: use non-set_fs based maccess routines Christoph Hellwig
2020-09-03 14:22 ` [PATCH 14/14] powerpc: remove address space overrides using set_fs() Christoph Hellwig
2020-09-03 15:43   ` Christophe Leroy
2020-09-03 15:49     ` Christoph Hellwig
2020-09-03 15:56       ` Christoph Hellwig
2020-09-03 16:03         ` Christophe Leroy
2020-09-03 14:28 ` remove the last set_fs() in common code, and remove it for x86 and powerpc v3 Al Viro
2020-09-03 14:30   ` Christoph Hellwig
2020-09-03 14:36     ` Al Viro
2020-09-03 14:40       ` Christoph Hellwig
2020-09-09 17:31   ` Linus Torvalds
2020-09-09 18:40     ` Segher Boessenkool
2020-09-09 21:33       ` Linus Torvalds [this message]
2020-09-10  8:04         ` David Laight
2020-09-10  8:13           ` Christophe Leroy
2020-09-10  9:26             ` David Laight
2020-09-10 12:26               ` David Laight
2020-09-10 15:20                 ` Segher Boessenkool
2020-09-10 15:31                   ` David Laight
2020-09-10 17:15                     ` Segher Boessenkool
2020-09-10 15:16               ` Segher Boessenkool
2020-09-10 15:44         ` Segher Boessenkool
2020-09-03 15:49 ` Linus Torvalds
2020-09-04  6:00 ` Ingo Molnar
2020-09-04 17:58   ` Alexey Dobriyan
2020-09-04 18:42     ` Linus Torvalds
2020-09-04 21:01     ` David Laight
2020-09-05  7:16       ` Christophe Leroy
2020-09-05 10:13         ` David Laight

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