linux-kernel - Re: [PATCH 1/3] kbuild: Add cc-option-no-kbuild macro

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Message-ID: <20170613164552.GK141096@google.com>
Date:   Tue, 13 Jun 2017 09:45:52 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     Arnd Bergmann <arnd@...db.de>, Michal Marek <mmarek@...e.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        "H . J . Lu" <hjl.tools@...il.com>,
        David Woodhouse <dwmw2@...radead.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Michael Davidson <md@...gle.com>,
        Greg Hackmann <ghackmann@...gle.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Stephen Hines <srhines@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Bernhard.Rosenkranzer@...aro.org,
        Peter Foley <pefoley2@...oley.com>,
        Behan Webster <behanw@...verseincode.com>,
        Douglas Anderson <dianders@...omium.org>
Subject: Re: [PATCH 1/3] kbuild: Add cc-option-no-kbuild macro

El Tue, Jun 13, 2017 at 07:13:55PM +0900 Masahiro Yamada ha dit:

> 2017-06-13 17:31 GMT+09:00 Arnd Bergmann <arnd@...db.de>:
> > On Tue, Jun 13, 2017 at 9:49 AM, Michal Marek <mmarek@...e.com> wrote:
> >> On 2017-06-13 02:55, Matthias Kaehlcke wrote:
> >>> cc-option uses KBUILD_CFLAGS and KBUILD_CPPFLAGS when it determines
> >>> whether an option is supported or not. This is fine for options used to
> >>> build the kernel itself, however some components like the x86 boot code
> >>> use a different set of flags.
> >>>
> >>> Add the new macro cc-option-no-kbuild which does the same as cc-option
> >>> except that it has an additional parameter with the compiler options
> >>> which are used instead of KBUILD_CFLAGS and KBUILD_CPPFLAGS.
> >>>
> >>> Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
> >>> ---
> >>>  scripts/Kbuild.include | 5 +++++
> >>>  1 file changed, 5 insertions(+)
> >>>
> >>> diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
> >>> index 61f87a99bf0a..d9fdc740105f 100644
> >>> --- a/scripts/Kbuild.include
> >>> +++ b/scripts/Kbuild.include
> >>> @@ -128,6 +128,11 @@ cc-option-yn = $(call try-run,\
> >>>  cc-option-align = $(subst -functions=0,,\
> >>>       $(call cc-option,-falign-functions=0,-malign-functions=0))
> >>>
> >>> +# cc-option-no-kbuild
> >>> +# Usage: cflags-no-kbuild-y += $(call cc-option-no-kbuild,<other flags>,-march=winchip-c6,-march=i586)
> >>> +cc-option-no-kbuild = $(call try-run,\
> >>> +     $(CC) -Werror $(filter-out $(GCC_PLUGINS_CFLAGS),$(1)) $(2) -c -x c /dev/null -o "$$TMP",$(2),$(3))
> >>
> >> As this is a version of cc-option with an extrra argument, how about
> >> implementing cc-option as a shorthand for cc-option-no-kbuild? It would
> >> make it more obvious what cc-option-no-kbuild does differently (it's
> >> probably just me, but I was unable to infer the semantics from its name).
> >
> > Agreed, also the hostcc-option could be based on the same I think, if we
> > also make the $(CC) an argument of the low-level helper.
> >
> 
> Agree.  One possible implementation:
> 
> cc-option-raw = $(call try-run,\
>              $(1) -Werror $(2) $(3) -c -x c /dev/null -o "$$TMP",$(3),$(4))
> 
> cc-option = $(call cc-option-raw, $(CC), $(KBUILD_CPPFLAGS)
> $(CC_OPTION_CFLAGS),\
>                                                                 $(1), $(2))
> 
> This will allow us to do:
> hostcc-option = $(call cc-option-raw, $(HOSTCC), $(HOSTCFLAGS), $(1), $(2))

Looks good, thanks all for the suggestions.

> Suggestion for a better name is welcome...

Yeah, this tends to be the difficult part, I didn't like
the initial 'cc-option-no-kbuild' either ... 'cc-option-raw' seems
ok if nothing better pops up.