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

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Message-ID: <CAPhsuW5GsWe-hV7MwMPbFMDK24W5OAPzjE+HJQjNKQ4CKtKqqA@mail.gmail.com>
Date: Fri, 31 Jan 2025 13:41:29 -0800
From: Song Liu <song@...nel.org>
To: Masahiro Yamada <masahiroy@...nel.org>
Cc: linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Yonghong Song <yonghong.song@...ux.dev>, 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 Fri, Jan 31, 2025 at 6:04 AM Masahiro Yamada <masahiroy@...nel.org> 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>

Tested-by: Song Liu <song@...nel.org>