Date: Fri, 4 Dec 2020 02:59:31 +0900 From: Masahiro Yamada <masahiroy@...nel.org> To: Kees Cook <keescook@...omium.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 <clang-built-linux@...glegroups.com>, Kernel Hardening <kernel-hardening@...ts.openwall.com>, linux-arch <linux-arch@...r.kernel.org>, linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>, Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, linux-pci@...r.kernel.org, X86 ML <x86@...nel.org> Subject: Re: [PATCH v6 14/25] kbuild: lto: remove duplicate dependencies from .mod files On Thu, Oct 15, 2020 at 7:50 AM Kees Cook <keescook@...omium.org> wrote: > > 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. It cannot. Adding "sort -u" is pointless without the rest of the series since the symbol duplication happens only with Clang LTO. This is not a solution. "reduce the probability of this happening" well describes it. I wrote a different patch. > -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 > > -- > > 18.104.22.1681.ga647a8990f-goog > > > > -- > Kees Cook > > -- > You received this message because you are subscribed to the Google Groups "Clang Built Linux" group. > To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@...glegroups.com. > To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/202010141549.412F2BF0%40keescook. -- Best Regards Masahiro Yamada
Powered by blists - more mailing lists
Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.