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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Peter Anvin <hpa@zytor.com>
Cc: namit@vmware.com, Peter Zijlstra <peterz@infradead.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	"the arch/x86 maintainers" <x86@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	Josh Poimboeuf <jpoimboe@redhat.com>
Subject: Re: [PATCH 2/6] x86: bug: prevent gcc distortions
Date: Fri, 18 May 2018 11:50:12 -0700	[thread overview]
Message-ID: <CA+55aFzLhG1L0WXvJiUSWrAN5ghzn4XFAK64wgFoyVAHTHZH-A@mail.gmail.com> (raw)
In-Reply-To: <BF0C5636-3EFC-4D57-9019-3EB209E56D2C@zytor.com>

On Fri, May 18, 2018 at 11:34 AM <hpa@zytor.com> wrote:

> On May 18, 2018 11:25:32 AM PDT, Linus Torvalds <
torvalds@linux-foundation.org> wrote:

> Unfortunately gcc doesn't guarantee that global assembly inlines will
appear at the top of the file.

Yeah. It really would be better to do the "asm version of -inline".

We already do something like that for real *.S files on some architectures
(because their assembly really wants it, eg

  arch/arm/Makefile:
    KBUILD_AFLAGS +=$(CFLAGS_ABI) $(AFLAGS_ISA) $(arch-y) $(tune-y) -include
asm/unified.h -msoft-float

but I do want to point out that KBUILD_AFLAGS is *not* used for
compiler-generated assembly, only for actual *.S files.

Sadly, I don't actually know any way to make gcc call the 'as' phase with
particular options. We can use "-Wa,xyzzy" to pass in xyzzy to the
assembler, but there is no "-include" option for GNU as afaik.

Can you perhaps define a macro symbol for "--defsym"? Probably not.

                       Linus

  reply	other threads:[~2018-05-18 18:50 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-17 16:13 [PATCH 0/6] Macrofying inline assembly for better compilation Nadav Amit
2018-05-17 16:13 ` Nadav Amit
2018-05-17 16:13 ` [PATCH 1/6] x86: objtool: use asm macro for better compiler decisions Nadav Amit
2018-05-17 16:13   ` Nadav Amit
2018-05-17 16:13 ` [PATCH 2/6] x86: bug: prevent gcc distortions Nadav Amit
2018-05-18  7:58   ` Peter Zijlstra
2018-05-18  8:13     ` Ingo Molnar
2018-05-18 10:11       ` Borislav Petkov
2018-05-18 14:36         ` Nadav Amit
2018-05-18 15:40           ` Borislav Petkov
2018-05-18 15:46             ` Nadav Amit
2018-05-18 15:53               ` Borislav Petkov
2018-05-18 16:29                 ` Nadav Amit
2018-05-18 17:41                   ` Boris Petkov
2018-05-18 14:30       ` Nadav Amit
2018-05-18 14:22     ` Nadav Amit
2018-05-18 17:52       ` Joe Perches
2018-05-18 16:24     ` Linus Torvalds
2018-05-18 17:24       ` Nadav Amit
2018-05-18 18:25         ` Linus Torvalds
2018-05-18 18:33           ` hpa
2018-05-18 18:50             ` Linus Torvalds [this message]
2018-05-18 18:53               ` hpa
2018-05-18 19:02                 ` Nadav Amit
2018-05-18 19:05                   ` hpa
2018-05-18 19:11                   ` Linus Torvalds
2018-05-18 19:18                     ` Nadav Amit
2018-05-18 19:21                       ` Linus Torvalds
2018-05-18 19:22                         ` hpa
2018-05-18 19:36                           ` Nadav Amit
2018-05-18 19:41                             ` hpa
2018-05-17 16:13 ` [PATCH 3/6] x86: alternative: macrofy locks for better inlining Nadav Amit
2018-05-17 16:14 ` [PATCH 4/6] x86: prevent inline distortion by paravirt ops Nadav Amit
2018-05-17 16:14 ` [PATCH 5/6] x86: refcount: prevent gcc distortions Nadav Amit
2018-05-19  4:27   ` kbuild test robot
2018-05-17 16:14 ` [PATCH 6/6] x86: removing unneeded new-lines Nadav Amit
2018-05-18  9:20 ` [PATCH 0/6] Macrofying inline assembly for better compilation David Laight
2018-05-18  9:20 ` David Laight
2018-05-18 14:15   ` Nadav Amit

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