From: Andi Kleen <ak@linux•intel.com>
To: Randy Dunlap <rdunlap@infradead•org>
Cc: akpm@linux-foundation•org, linux-kernel@vger•kernel.org,
linux-next@vger•kernel.org, sfr@canb•auug.org.au, mhocko@suse•cz
Subject: Re: mmotm 2014-07-02-15-07 uploaded (stack protector)
Date: Wed, 2 Jul 2014 17:22:31 -0700 [thread overview]
Message-ID: <20140703002231.GR19781@tassilo.jf.intel.com> (raw)
In-Reply-To: <53B493E2.2030905@infradead.org>
On Wed, Jul 02, 2014 at 04:21:06PM -0700, Randy Dunlap wrote:
> On 07/02/14 15:08, akpm@linux-foundation•org wrote:
> > The mm-of-the-moment snapshot 2014-07-02-15-07 has been uploaded to
> >
> > http://www.ozlabs.org/~akpm/mmotm/
> >
> > mmotm-readme.txt says
> >
> > README for mm-of-the-moment:
> >
> > http://www.ozlabs.org/~akpm/mmotm/
> >
> > This is a snapshot of my -mm patch queue. Uploaded at random hopefully
> > more than once a week.
>
> Hi Andi,
>
> Here is an extract from 10 randconfig builds:
>
>
> $ grep STACKPROTECTOR_STRONG config-r*
> config-r8735:CONFIG_CC_STACKPROTECTOR_STRONG=y
> config-r8736:CONFIG_CC_STACKPROTECTOR_STRONG=y
> config-r8737:# CONFIG_CC_STACKPROTECTOR_STRONG is not set
> config-r8738:# CONFIG_CC_STACKPROTECTOR_STRONG is not set
> config-r8739:CONFIG_CC_STACKPROTECTOR_STRONG=y
> config-r8740:CONFIG_CC_STACKPROTECTOR_STRONG=y
> config-r8741:CONFIG_CC_STACKPROTECTOR_STRONG=y
> config-r8742:# CONFIG_CC_STACKPROTECTOR_STRONG is not set
> config-r8743:# CONFIG_CC_STACKPROTECTOR_STRONG is not set
> config-r8744:# CONFIG_CC_STACKPROTECTOR_STRONG is not set
>
>
> but the captured output for each one says:
>
> grep STACKPROTECTOR_STRONG build*.out
> build-r8735.out:/local/lnx/MM/mmotm-2014-0702-1507/Makefile:662: Cannot use CONFIG_CC_STACKPROTECTOR_STRONG: -fstack-protector-strong not supported by compiler
> build-r8736.out:/local/lnx/MM/mmotm-2014-0702-1507/Makefile:662: Cannot use CONFIG_CC_STACKPROTECTOR_STRONG: -fstack-protector-strong not supported by compiler
> build-r8736.out:/local/lnx/MM/mmotm-2014-0702-1507/Makefile:662: Cannot use CONFIG_CC_STACKPROTECTOR_STRONG: -fstack-protector-strong not supported by compiler
> build-r8737.out:/local/lnx/MM/mmotm-2014-0702-1507/Makefile:662: Cannot use CONFIG_CC_STACKPROTECTOR_STRONG: -fstack-protector-strong not supported by compiler
> build-r8739.out:/local/lnx/MM/mmotm-2014-0702-1507/Makefile:662: Cannot use CONFIG_CC_STACKPROTECTOR_STRONG: -fstack-protector-strong not supported by compiler
> build-r8740.out:/local/lnx/MM/mmotm-2014-0702-1507/Makefile:662: Cannot use CONFIG_CC_STACKPROTECTOR_STRONG: -fstack-protector-strong not supported by compiler
> build-r8740.out:/local/lnx/MM/mmotm-2014-0702-1507/Makefile:662: Cannot use CONFIG_CC_STACKPROTECTOR_STRONG: -fstack-protector-strong not supported by compiler
> build-r8741.out:/local/lnx/MM/mmotm-2014-0702-1507/Makefile:662: Cannot use CONFIG_CC_STACKPROTECTOR_STRONG: -fstack-protector-strong not supported by compiler
> build-r8741.out:/local/lnx/MM/mmotm-2014-0702-1507/Makefile:662: Cannot use CONFIG_CC_STACKPROTECTOR_STRONG: -fstack-protector-strong not supported by compiler
> build-r8742.out:/local/lnx/MM/mmotm-2014-0702-1507/Makefile:662: Cannot use CONFIG_CC_STACKPROTECTOR_STRONG: -fstack-protector-strong not supported by compiler
>
>
> then the build goes on to produce many errors like this one:
>
> CC init/do_mounts.o
> gcc: error: unrecognized command line option '-fstack-protector-strong'
>
>
> Can you explain this, please? or even better yet, fix it.
That's the code
ifdef CONFIG_CC_STACKPROTECTOR_STRONG
stackp-flag := -fstack-protector-strong
ifeq ($(call cc-option, $(stackp-flag)),)
$(warning Cannot use CONFIG_CC_STACKPROTECTOR_STRONG: \
-fstack-protector-strong not supported by compiler)
endif
else
# Force off for distro compilers that enable stack protector by default.
stackp-flag := $(call cc-option, -fno-stack-protector)
endif
endif
KBUILD_CFLAGS += $(stackp-flag)
So -fstack-protector-strong itself is never protected by a cc-option call.
You could add it to the stack-flag line, then it would only warn.
stackp-flag := $(call cc-option, -fstack-protector-strong)
It's hard to tell what the original author wanted, perhaps they wanted
it to error out. It looks intentional. Clearly they didn't think of randconfig
though.
Or get a compiler that supports stack protection?
-Andi
next prev parent reply other threads:[~2014-07-03 0:22 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-02 22:08 mmotm 2014-07-02-15-07 uploaded akpm
2014-07-02 23:21 ` mmotm 2014-07-02-15-07 uploaded (stack protector) Randy Dunlap
2014-07-03 0:22 ` Andi Kleen [this message]
2014-07-03 0:37 ` Randy Dunlap
2014-07-03 0:51 ` Kees Cook
2014-07-03 0:56 ` Andrew Morton
2014-07-03 1:10 ` [PATCH] kbuild: explain stack-protector-strong CONFIG logic Kees Cook
2014-07-03 1:00 ` mmotm 2014-07-02-15-07 uploaded (stack protector) Andi Kleen
2014-07-03 1:13 ` Kees Cook
2014-07-03 0:57 ` Kees Cook
2014-07-03 1:42 ` Randy Dunlap
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