From mboxrd@z Thu Jan  1 00:00:00 1970
Reply-To: kernel-hardening@lists.openwall.com
Date: Thu, 5 May 2016 20:40:08 +0200
From: Emese Revfy <re.emese@gmail.com>
Message-Id: <20160505204008.863221b34f9b7c6111e4e7f9@gmail.com>
In-Reply-To: <CAK7LNAT7eOHQ94qscQgTDXTBi+NZsE4SQzw=h3xcK9PCRigFag@mail.gmail.com>
References: <20160422201957.97ce16f0e67377d0ce613d19@gmail.com>
	<20160422202138.d50937e812b30aaba4f38a92@gmail.com>
	<CAK7LNAR-+4+Xdhbs6hoPUTYppLqFwY8dxqdSuw_5j6Pge4uYVg@mail.gmail.com>
	<20160502195617.9b2b7e07ced214a8f2136364@gmail.com>
	<CAK7LNATQY7AWjmEEjDFgpLPkO_oQgkNKutgGb17v7=R8RPb5zA@mail.gmail.com>
	<20160503232932.706dd3bb081df5d04a390de9@gmail.com>
	<CAK7LNAT7eOHQ94qscQgTDXTBi+NZsE4SQzw=h3xcK9PCRigFag@mail.gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Subject: [kernel-hardening] Re: [PATCH v7 1/6] Shared library support
To: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>, PaX Team <pageexec@freemail.hu>, Brad Spengler <spender@grsecurity.net>, kernel-hardening@lists.openwall.com, Michal Marek <mmarek@suse.com>, Kees Cook <keescook@chromium.org>, Rasmus Villemoes <linux@rasmusvillemoes.dk>, Fengguang Wu <fengguang.wu@intel.com>, Dmitry Vyukov <dvyukov@google.com>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, David Brown <david.brown@linaro.org>
List-ID: <kernel-hardening.lists.openwall.com>

On Wed, 4 May 2016 13:09:05 +0900
Masahiro Yamada <yamada.masahiro@socionext.com> wrote:

> Hi Emese,
> 
> 
> 2016-05-04 6:29 GMT+09:00 Emese Revfy <re.emese@gmail.com>:
> > On Tue, 3 May 2016 11:00:56 +0900
> > Masahiro Yamada <yamada.masahiro@socionext.com> wrote:
> >
> > Hi,
> >
> >> # Compile .c file, create position independent .o file
> >> # host-cxxshobjs -> .o
> >> quiet_cmd_host-cxxshobjs = HOSTCXX -fPIC $@
> >>       cmd_host-cxxshobjs = $(HOSTCXX) $(hostcxx_flags) -fPIC -c -o $@ $<
> >>                            $(host-cxxshobjs): $(obj)/%.o: $(src)/%.c FORCE
> >>                            $(call if_changed_dep,host-cxxshobjs)
> >>
> >>
> >>
> >>
> >> We generally use HOSTCC to compile *.c files,
> >> and HOSTCXX to compile *.cc files.
> >>
> >>
> >> But, here, you mention to use HOSTCXX to compile .c files
> >> such as cyc_complexity_plugin.c, sancov_plugin.c, etc.
> >>
> >> This is not straight-forward.  It is worthwhile to comment the reason.
> >
> > I wrote a comment about it here:
> > https://github.com/ephox-gcc-plugins/gcc-plugins_linux-next/commit/74f6343a7f13c071e00c417332051e25f15009ea
> >
> 
> 
> 
> +# Note that plugin capable gcc versions can be either C or C++ based
> +# therefore plugin source files have to be compilable in both C and C++ mode.
> +# This is why a C++ compiler is invoked on a .c file.
> 
> Thanks.
> 
> Please let me confirm if I understood correctly.
> 
> 
> We generally have to do something with the name-space conflict
> (with 'extern "C"') in the mixture of C/C++.
> 
> Depending on the GCC version,
> GCC-plugin-related libraries could be built for C or C++.
> 
> So, we need to check the GCC version and choose correct one
> from C or C++.

The plugin source files have to be compilable by both versions
because gcc versions 4.5 and 4.6 are compiled by a C compiler,
gcc-4.7 can be compiled by a C or a C++ compiler,
and versions 4.8+ can only be compiled by a C++ compiler.

-- 
Emese