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Date: Wed, 14 Oct 2020 15:50:28 -0700
From: Kees Cook <keescook@...omium.org>
To: Masahiro Yamada <masahiroy@...nel.org>
Cc: Sami Tolvanen <samitolvanen@...gle.com>,
Steven Rostedt <rostedt@...dmis.org>, Will Deacon <will@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"Paul E. McKenney" <paulmck@...nel.org>,
Nick Desaulniers <ndesaulniers@...gle.com>,
clang-built-linux@...glegroups.com,
kernel-hardening@...ts.openwall.com, linux-arch@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-kbuild@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
x86@...nel.org
Subject: Re: [PATCH v6 14/25] kbuild: lto: remove duplicate dependencies from
.mod files
On Mon, Oct 12, 2020 at 05:31:52PM -0700, Sami Tolvanen 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: Kees Cook <keescook@...omium.org>
Hi Masahiro,
This appears to be a general improvement as well. This looks like it can
land without depending on the rest of the series.
-Kees
> ---
> scripts/Makefile.build | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index ab0ddf4884fd..96d6c9e18901 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -266,7 +266,7 @@ 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
> --
> 2.28.0.1011.ga647a8990f-goog
>
--
Kees Cook
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