linux-kernel - Re: [PATCH] kbuild: introduce ccflags-remove-y and asflags-remove-y

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Date:   Mon, 29 Jun 2020 15:57:11 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Masahiro Yamada <masahiroy@...nel.org>,
        linux-kbuild@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Masahiro Yamada <masahiroy@...nel.org>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Ingo Molnar <mingo@...hat.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        Paul Mackerras <paulus@...ba.org>,
        Rich Felker <dalias@...c.org>,
        Russell King <linux@...linux.org.uk>,
        Steven Rostedt <rostedt@...dmis.org>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        linux-arm-kernel@...ts.infradead.org, linux-sh@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH] kbuild: introduce ccflags-remove-y and asflags-remove-y

Masahiro Yamada <masahiroy@...nel.org> writes:
> CFLAGS_REMOVE_<file>.o works per object, that is, there is no
> convenient way to filter out flags for every object in a directory.
>
> Add ccflags-remove-y and asflags-remove-y to make it easily.
>
> Use ccflags-remove-y to clean up some Makefiles.
>
> Suggested-by: Sami Tolvanen <samitolvanen@...gle.com>
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> ---
>
>  arch/arm/boot/compressed/Makefile | 6 +-----
>  arch/powerpc/xmon/Makefile        | 3 +--
>  arch/sh/boot/compressed/Makefile  | 5 +----
>  kernel/trace/Makefile             | 4 ++--
>  lib/Makefile                      | 5 +----
>  scripts/Makefile.lib              | 4 ++--
>  6 files changed, 8 insertions(+), 19 deletions(-)
>
> diff --git a/arch/powerpc/xmon/Makefile b/arch/powerpc/xmon/Makefile
> index 89c76ca35640..55cbcdd88ac0 100644
> --- a/arch/powerpc/xmon/Makefile
> +++ b/arch/powerpc/xmon/Makefile
> @@ -7,8 +7,7 @@ UBSAN_SANITIZE := n
>  KASAN_SANITIZE := n
>  
>  # Disable ftrace for the entire directory
> -ORIG_CFLAGS := $(KBUILD_CFLAGS)
> -KBUILD_CFLAGS = $(subst $(CC_FLAGS_FTRACE),,$(ORIG_CFLAGS))
> +ccflags-remove-y += $(CC_FLAGS_FTRACE)

This could be:

ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)

Similar to kernel/trace/Makefile below.

I don't mind though.

Acked-by: Michael Ellerman <mpe@...erman.id.au> (powerpc)

cheers

> diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
> index 6575bb0a0434..7492844a8b1b 100644
> --- a/kernel/trace/Makefile
> +++ b/kernel/trace/Makefile
> @@ -2,9 +2,9 @@
>  
>  # Do not instrument the tracer itself:
>  
> +ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
> +
>  ifdef CONFIG_FUNCTION_TRACER
> -ORIG_CFLAGS := $(KBUILD_CFLAGS)
> -KBUILD_CFLAGS = $(subst $(CC_FLAGS_FTRACE),,$(ORIG_CFLAGS))
>  
>  # Avoid recursion due to instrumentation.
>  KCSAN_SANITIZE := n