linux-kernel - Re: [PATCH v2] Makefile: Improve compressed debug info support detection

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Message-ID: <CAK7LNAQAZ3PFvvj7M_AYZKo4uwui1DaJyjebWLmpnp-ism_=mQ@mail.gmail.com>
Date:   Sun, 14 Jun 2020 11:21:07 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Arvind Sankar <nivedita@...m.mit.edu>
Cc:     Fangrui Song <maskray@...gle.com>,
        Rong Chen <rong.a.chen@...el.com>,
        kernel test robot <lkp@...el.com>, kbuild-all@...ts.01.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] Makefile: Improve compressed debug info support detection

On Fri, Jun 12, 2020 at 8:39 AM Nick Desaulniers
<ndesaulniers@...gle.com> wrote:
>
> On Thu, Jun 11, 2020 at 3:03 PM Arvind Sankar <nivedita@...m.mit.edu> wrote:
> >
> > Commit
> >   10e68b02c861 ("Makefile: support compressed debug info")
> > added support for compressed debug sections.
> >
> > Support is detected by checking
> > - does the compiler support -gz=zlib
> > - does the assembler support --compressed-debug-sections=zlib
> > - does the linker support --compressed-debug-sections=zlib
> >
> > However, the gcc driver's support for this option is somewhat
> > convoluted. The driver's builtin specs are set based on the version of
> > binutils that it was configured with. It reports an error if the
> > configure-time linker/assembler (i.e., not necessarily the actual
> > assembler that will be run) do not support the option, but only if the
> > assembler (or linker) is actually invoked when -gz=zlib is passed.
> >
> > The cc-option check in scripts/Kconfig.include does not invoke the
> > assembler, so the gcc driver reports success even if it does not support
> > the option being passed to the assembler.
> >
> > Because the as-option check passes the option directly to the assembler
> > via -Wa,--compressed-debug-sections=zlib, the gcc driver does not see
> > this option and will never report an error.
>
> Thanks for expanding on the failure.
> Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
>


Applied to linux-kbuild/fixes.
Thanks.





-- 
Best Regards
Masahiro Yamada