From: Arnd Bergmann <arnd@kernel.org>
To: Sedat Dilek <sedat.dilek@gmail.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
Ionela Voinescu <ionela.voinescu@arm.com>,
Kees Cook <keescook@chromium.org>, Arnd Bergmann <arnd@arndb.de>,
Catalin Marinas <catalin.marinas@arm.com>,
Nick Desaulniers <ndesaulniers@google.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Kristina Martsenko <kristina.martsenko@arm.com>,
Ard Biesheuvel <ardb@kernel.org>,
Nathan Chancellor <nathan@kernel.org>,
Clang-Built-Linux ML <clang-built-linux@googlegroups.com>,
Mark Brown <broonie@kernel.org>, Andrew Scull <ascull@google.com>,
Marc Zyngier <maz@kernel.org>,
Geert Uytterhoeven <geert+renesas@glider.be>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
Will Deacon <will@kernel.org>,
David Brazdil <dbrazdil@google.com>,
Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] [RFC] arm64: enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION
Date: Fri, 26 Feb 2021 10:51:40 +0100 [thread overview]
Message-ID: <CAK8P3a0cyAYqdPg_OoaVVY2Gjn=vtwAyfsVPjZ5qYddiOOc-eA@mail.gmail.com> (raw)
In-Reply-To: <CA+icZUW9Hzm_ZZtLiJu8pVeOmYJMOaXkV4Om_u4yZKYRVWNddA@mail.gmail.com>
On Fri, Feb 26, 2021 at 10:05 AM Sedat Dilek <sedat.dilek@gmail.com> wrote:
> On Fri, Feb 26, 2021 at 9:14 AM Arnd Bergmann <arnd@kernel.org> wrote:
>
> > > BTW, is CONFIG_LD_DEAD_CODE_DATA_ELIMINATION=y setable for x86 (64bit)?
> > > ( Did not look or check for it. )
> >
> > No, in mainline, HAVE_LD_DEAD_CODE_DATA_ELIMINATION is currently
> > only selected on MIPS and PowerPC. I only sent experimental patches to
> > enable it on arm64 and m68k, but have not tried booting them. If you
> > select the symbol on x86, you should see similar results.
> >
>
> OK, i see:
>
> $ git grep HAVE_LD_DEAD_CODE_DATA_ELIMINATION arch/mips/
> arch/mips/Kconfig: select HAVE_LD_DEAD_CODE_DATA_ELIMINATION
>
> $ git grep HAVE_LD_DEAD_CODE_DATA_ELIMINATION arch/powerpc/
> arch/powerpc/Kconfig: select HAVE_LD_DEAD_CODE_DATA_ELIMINATION
>
> So, I need to add this to arch/x86/Kconfig.
>
> You happen to know if changes to arch/x86/kernel/vmlinux.lds.S
> (sections) are needed?
No idea. I'm still debugging a possible regression on arm64, but both
issues I found for arm64 are specific to that architecture and won't
happen on x86. It's likely that something else breaks though.
> Last question:
> The last days I see a lot of fixes touching inlining with LLVM/Clang v13-git.
> What git tag are you using?
> What are your experiences?
> Pending patches (kernel-side)?
>
> I use:
> $ /opt/llvm-toolchain/bin/clang --version
> dileks clang version 13.0.0 (https://github.com/llvm/llvm-project.git
> c465429f286f50e52a8d2b3b39f38344f3381cce)
This is what I have on the build box:
Ubuntu clang version
13.0.0-++20210223104451+ebca13c66504-1~exp1~20210223095200.234
Arnd
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next prev parent reply other threads:[~2021-02-26 9:53 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-25 11:20 [PATCH] [RFC] arm64: enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION Arnd Bergmann
2021-02-25 20:16 ` Kees Cook
2021-02-26 0:36 ` Sedat Dilek
2021-02-26 8:14 ` Arnd Bergmann
2021-02-26 9:05 ` Sedat Dilek
2021-02-26 9:51 ` Arnd Bergmann [this message]
2021-02-26 10:02 ` Sedat Dilek
2021-02-26 21:13 ` Fangrui Song
2021-02-27 9:49 ` Arnd Bergmann
2021-03-01 1:11 ` Nicholas Piggin
2021-03-10 20:49 ` Masahiro Yamada
2021-03-10 21:08 ` Arnd Bergmann
2021-03-10 21:24 ` Sedat Dilek
2021-03-10 21:47 ` Nicolas Pitre
2021-03-10 21:57 ` Sedat Dilek
2021-03-10 22:02 ` Nick Desaulniers
2021-03-10 22:08 ` Nicolas Pitre
2021-03-10 22:29 ` Fangrui Song
2021-03-10 21:45 ` Rasmus Villemoes
2021-03-10 21:19 ` Nicolas Pitre
2021-03-10 22:42 ` Fangrui Song
2021-03-17 14:37 ` Catalin Marinas
2021-03-17 16:18 ` Catalin Marinas
2021-03-18 8:41 ` Arnd Bergmann
2021-03-19 12:25 ` Catalin Marinas
2021-03-19 14:01 ` Arnd Bergmann
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