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Date: Wed, 24 Jun 2020 14:13:46 -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 08/22] kbuild: lto: remove duplicate dependencies from
.mod files
On Wed, Jun 24, 2020 at 1:33 PM Sami Tolvanen <samitolvanen@...gle.com> wrote:
>
> With LTO, llvm-nm prints out symbols for each archive member
> separately, which results in a lot of duplicate dependencies in the
> .mod file when CONFIG_TRIM_UNUSED_SYMS is enabled. When a module
> consists of several compilation units, the output can exceed the
> default xargs command size limit and split the dependency list to
> multiple lines, which results in used symbols getting trimmed.
>
> This change removes duplicate dependencies, which will reduce the
> probability of this happening and makes .mod files smaller and
> easier to read.
>
> Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
> ---
> scripts/Makefile.build | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 82977350f5a6..82b465ce3ca0 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -291,7 +291,7 @@ endef
>
> # List module undefined symbols (or empty line if not enabled)
> ifdef CONFIG_TRIM_UNUSED_KSYMS
> -cmd_undef_syms = $(NM) $< | sed -n 's/^ *U //p' | xargs echo
> +cmd_undef_syms = $(NM) $< | sed -n 's/^ *U //p' | sort -u | xargs echo
> else
> cmd_undef_syms = echo
> endif
> --
> 2.27.0.212.ge8ba1cc988-goog
>
--
Thanks,
~Nick Desaulniers
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