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From:   Masahiro Yamada <masahiroy@kernel.org>
Date:   Wed, 15 Sep 2021 19:00:51 +0900
Message-ID: <CAK7LNATqqSRSnDmsNnbPdp5_gmAvSWTShWJaqWaE362n64yh3A@mail.gmail.com>
Subject: Re: [PATCH] [RFC] Add additional include path for gcc plugins
To:     Dan Li <ashimida@linux.alibaba.com>
Cc:     Michal Marek <michal.lkml@markovi.net>,
        Kees Cook <keescook@chromium.org>,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-hardening@vger.kernel.org
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On Wed, Sep 15, 2021 at 6:23 PM Dan Li <ashimida@linux.alibaba.com> wrote:
>
> When kernel enables gcc plugin, some header files are missing in some
> tool chains (as in the following example)
>
> These header files can be found in other toolchains, and sometimes
> the md5hash of these files are same(in most versions).
>
> Should we add a parameter to plugin to allow users to import their own
> header file directories?
>
> ---
>   HOSTCXX scripts/gcc-plugins/stackleak_plugin.so
> In file included from scripts/gcc-plugins/gcc-common.h:103:0,
>                  from scripts/gcc-plugins/stackleak_plugin.c:30:
> /workspace/gcc-arm-9.2-2019.12-x86_64-aarch64-none-linux-gnu/bin/../
> lib/gcc/aarch64-none-linux-gnu/9.2.1/plugin/include/builtins.h:23:17:
>  fatal error: mpc.h: No such file or directory
>  #include <mpc.h>


gcc-plugins are compiled by the host compiler (usually g++).
Kbuild already provides 'HOSTCXXFLAGS'
to pass-in additional flags to it.

But, if you need to tweak include paths, you are already screwed up, maybe.

Some time ago, I got a question about plugin builds failing due to missing gmp.h
but it was solvable by installing a package.

https://lore.kernel.org/all/CAK7LNART2qQBY7Vc8rhMiXS_Fwty7qpWjwwfPrUegTb-gjy6sA@mail.gmail.com/


> Signed-off-by: Dan Li <ashimida@linux.alibaba.com>
> ---
>  Makefile                     | 3 +++
>  scripts/gcc-plugins/Makefile | 2 +-
>  2 files changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/Makefile b/Makefile
> index 09bb314..e6134f3 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1036,6 +1036,9 @@ include-$(CONFIG_UBSAN)           += scripts/Makefile.ubsan
>  include-$(CONFIG_KCOV)         += scripts/Makefile.kcov
>  include-$(CONFIG_GCC_PLUGINS)  += scripts/Makefile.gcc-plugins
>
> +GCC_PLUGINS_EXT_CFLAGS=
> +export GCC_PLUGINS_EXT_CFLAGS
> +
>  include $(addprefix $(srctree)/, $(include-y))
>
>  # scripts/Makefile.gcc-plugins is intentionally included last.
> diff --git a/scripts/gcc-plugins/Makefile b/scripts/gcc-plugins/Makefile
> index 1952d3b..0b3e27a 100644
> --- a/scripts/gcc-plugins/Makefile
> +++ b/scripts/gcc-plugins/Makefile
> @@ -23,7 +23,7 @@ GCC_PLUGINS_DIR = $(shell $(CC) -print-file-name=plugin)
>
>  plugin_cxxflags        = -Wp,-MMD,$(depfile) $(KBUILD_HOSTCXXFLAGS) -fPIC \
>                   -include $(srctree)/include/linux/compiler-version.h \
> -                  -I $(GCC_PLUGINS_DIR)/include -I $(obj) -std=gnu++11 \
> +                  -I $(GCC_PLUGINS_DIR)/include -I $(obj) $(GCC_PLUGINS_EXT_CFLAGS) -std=gnu++11 \
>                    -fno-rtti -fno-exceptions -fasynchronous-unwind-tables \
>                    -ggdb -Wno-narrowing -Wno-unused-variable \
>                    -Wno-format-diag
> --
> 2.7.4
>


-- 
Best Regards
Masahiro Yamada