linux-kernel - Re: [PATCH 13/22] scripts/mod: disable LTO for empty.c

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Date:   Wed, 24 Jun 2020 13:57:11 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Sami Tolvanen <samitolvanen@...gle.com>
Cc:     Masahiro Yamada <masahiroy@...nel.org>,
        Will Deacon <will@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        linux-arch <linux-arch@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, linux-pci@...r.kernel.org,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>
Subject: Re: [PATCH 13/22] scripts/mod: disable LTO for empty.c

On Wed, Jun 24, 2020 at 1:33 PM Sami Tolvanen <samitolvanen@...gle.com> wrote:
>
> With CONFIG_LTO_CLANG, clang generates LLVM IR instead of ELF object
> files. As empty.o is used for probing target properties, disable LTO
> for it to produce an object file instead.
>
> Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>

Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

> ---
>  scripts/mod/Makefile | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/scripts/mod/Makefile b/scripts/mod/Makefile
> index 296b6a3878b2..b6e3b40c6eeb 100644
> --- a/scripts/mod/Makefile
> +++ b/scripts/mod/Makefile
> @@ -1,5 +1,6 @@
>  # SPDX-License-Identifier: GPL-2.0
>  OBJECT_FILES_NON_STANDARD := y
> +CFLAGS_REMOVE_empty.o += $(CC_FLAGS_LTO)
>
>  hostprogs      := modpost mk_elfconfig
>  always-y       := $(hostprogs) empty.o
> --
> 2.27.0.212.ge8ba1cc988-goog
>


-- 
Thanks,
~Nick Desaulniers