linux-kernel - Re: [kernel-hardening] Re: [PATCH v7 2/6] GCC plugin infrastructure

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Message-Id: <20160502195903.8a07c51ebf1cce1c0a1ccd6f@gmail.com>
Date:	Mon, 2 May 2016 19:59:03 +0200
From:	Emese Revfy <re.emese@...il.com>
To:	kernel-hardening@...ts.openwall.com
Cc:	Masahiro Yamada <yamada.masahiro@...ionext.com>,
	Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
	PaX Team <pageexec@...email.hu>,
	Brad Spengler <spender@...ecurity.net>,
	Michal Marek <mmarek@...e.com>,
	Kees Cook <keescook@...omium.org>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Fengguang Wu <fengguang.wu@...el.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	David Brown <david.brown@...aro.org>
Subject: Re: [kernel-hardening] Re: [PATCH v7 2/6] GCC plugin infrastructure

On Mon, 2 May 2016 14:07:35 +0900
Masahiro Yamada <yamada.masahiro@...ionext.com> wrote:

Hi,

> > diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
> > index 253b72e..f912316 100644
> > --- a/arch/x86/entry/vdso/Makefile
> > +++ b/arch/x86/entry/vdso/Makefile
> > @@ -75,7 +75,7 @@ CFL := $(PROFILING) -mcmodel=small -fPIC -O2 -fasynchronous-unwind-tables -m64 \
> >         -fno-omit-frame-pointer -foptimize-sibling-calls \
> >         -DDISABLE_BRANCH_PROFILING -DBUILD_VDSO
> >
> > -$(vobjs): KBUILD_CFLAGS += $(CFL)
> > +$(vobjs): KBUILD_CFLAGS := $(filter-out $(GCC_PLUGINS_CFLAGS),$(KBUILD_CFLAGS)) $(CFL)
> >
> >  #
> >  # vDSO code runs in userspace and -pg doesn't help with profiling anyway.
> > @@ -145,6 +145,7 @@ KBUILD_CFLAGS_32 := $(filter-out -m64,$(KBUILD_CFLAGS))
> >  KBUILD_CFLAGS_32 := $(filter-out -mcmodel=kernel,$(KBUILD_CFLAGS_32))
> >  KBUILD_CFLAGS_32 := $(filter-out -fno-pic,$(KBUILD_CFLAGS_32))
> >  KBUILD_CFLAGS_32 := $(filter-out -mfentry,$(KBUILD_CFLAGS_32))
> > +KBUILD_CFLAGS_32 := $(filter-out $(GCC_PLUGINS_CFLAGS),$(KBUILD_CFLAGS_32))
> >  KBUILD_CFLAGS_32 += -m32 -msoft-float -mregparm=0 -fpic
> >  KBUILD_CFLAGS_32 += $(call cc-option, -fno-stack-protector)
> >  KBUILD_CFLAGS_32 += $(call cc-option, -foptimize-sibling-calls)
> 
> 
> Looks like gcc-plugins should be omitted only for this directory.
> Please tell me why.
> I am not familiar with x86 architecture, so this is not clear to me.

The vdso is userland code so in general kernel instrumentation/analysis doesn't apply to it.

-- 
Emese