linux-kernel - Re: [PATCH] kbuild: fix Clang LTO with CONFIG

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Message-ID: <f8759dae-ec1c-4f3c-a44a-dbd22d7964e4@linux.dev>
Date: Fri, 31 Jan 2025 08:58:21 -0800
From: Yonghong Song <yonghong.song@...ux.dev>
To: Masahiro Yamada <masahiroy@...nel.org>, linux-kbuild@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, Bill Wendling <morbo@...gle.com>,
 Justin Stitt <justinstitt@...gle.com>, Nathan Chancellor
 <nathan@...nel.org>, Nick Desaulniers <ndesaulniers@...gle.com>,
 Nicolas Schier <nicolas@...sle.eu>, llvm@...ts.linux.dev
Subject: Re: [PATCH] kbuild: fix Clang LTO with CONFIG_OBJTOOL=n




On 1/31/25 6:04 AM, Masahiro Yamada wrote:
> Since commit bede169618c6 ("kbuild: enable objtool for *.mod.o and
> additional kernel objects"), Clang LTO builds do not perform any
> optimizations when CONFIG_OBJTOOL is disable (e.g., for ARCH=arm64).
> This is because every LLVM bitcode file is immediately converted to
> ELF format before the object files are linked together.
>
> This commit fixes the breakage.
>
> Fixes: bede169618c6 ("kbuild: enable objtool for *.mod.o and additional kernel objects")
> Reported-by: Yonghong Song <yonghong.song@...ux.dev>
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>

Thanks for the fix!

I tested x86_64 and arm64 for with and without lto, everything works fine. So

Tested-by: Yonghong Song <yonghong.song@...ux.dev>