From: Andrew Morton <akpm@linux-foundation.org>
To: Kees Cook <kees@outflux.net>
Cc: Andi Kleen <ak@linux.intel.com>,
Randy Dunlap <rdunlap@infradead.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 17:56:35 -0700 [thread overview]
Message-ID: <20140702175635.79d54c44.akpm@linux-foundation.org> (raw)
In-Reply-To: <20140703005100.GI5412@outflux.net>
On Wed, 2 Jul 2014 17:51:00 -0700 Kees Cook <kees@outflux.net> wrote:
> > 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.
>
> The problem is that if you make kbuild hard-fail when selecting this missing
> compiler option, you can never switch it back because "make menuconfig" will
> refuse to build since the compiler option would be missing. Being silent
> about the missing option (and/or falling back to other options) means that
> you could get two different kernel features selection with the same CONFIG_*
> set, depending on the kernel, which is extremely bad ("I selected
> stack-protector-strong but it built without it?!").
>
> So, the middle ground was to warn about it during the kbuild logic so
> you could find the source of the problem, but ultimately fail the build
> when the compiler doesn't support it so there weren't any silent failure
> modes.
--- a/Makefile~a
+++ a/Makefile
@@ -630,6 +630,9 @@ KBUILD_CFLAGS += $(call cc-option,-Wfram
endif
# Handle stack protector mode.
+#
+# This space reserved for Kees
+#
ifdef CONFIG_CC_STACKPROTECTOR_REGULAR
stackp-flag := -fstack-protector
ifeq ($(call cc-option, $(stackp-flag)),)
_
next prev parent reply other threads:[~2014-07-03 0:57 UTC|newest]
Thread overview: 12+ 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 22:08 ` akpm
2014-07-02 23:21 ` mmotm 2014-07-02-15-07 uploaded (stack protector) Randy Dunlap
2014-07-03 0:22 ` Andi Kleen
2014-07-03 0:37 ` Randy Dunlap
2014-07-03 0:51 ` Kees Cook
2014-07-03 0:56 ` Andrew Morton [this message]
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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