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From: Kees Cook <keescook@chromium.org>
To: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Ulf Magnusson <ulfalizer@gmail.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Nicolas Pitre <nicolas.pitre@linaro.org>,
	"Luis R . Rodriguez" <mcgrof@suse.com>,
	Randy Dunlap <rdunlap@infradead.org>,
	Sam Ravnborg <sam@ravnborg.org>,
	Michal Marek <michal.lkml@markovi.net>,
	Martin Schwidefsky <schwidefsky@de.ibm.com>,
	Pavel Machek <pavel@ucw.cz>,
	linux-s390 <linux-s390@vger.kernel.org>,
	Jiri Kosina <jkosina@suse.cz>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Tejun Heo <tj@kernel.org>, Ingo Molnar <mingo@kernel.org>,
	"Van De Ven, Arjan" <arjan.van.de.ven@intel.com>,
	Arnd Bergmann <arnd@arndb.de>
Subject: Re: [RFC PATCH 4/7] kconfig: support new special property shell=
Date: Mon, 12 Feb 2018 07:24:45 -0800	[thread overview]
Message-ID: <CAGXu5j+7kv=jrg2u7jaxFEXwHoyzDXP_jyKHYA682_BrYuHwQQ@mail.gmail.com> (raw)
In-Reply-To: <CAK7LNAQpS6dYBnt_PjL5zrX1=eccSg80khu=WYCjnHNvDiKa3w@mail.gmail.com>

On Mon, Feb 12, 2018 at 6:39 AM, Masahiro Yamada
<yamada.masahiro@socionext.com> wrote:
> 2018-02-12 2:56 GMT+09:00 Kees Cook <keescook@chromium.org>:
>> I think it would work to skip KBUILD_CPPFLAGS right up until it
>> didn't. Since we have the arch split, we can already add -m32 to the
>> 32-bit case, etc. However, I worry about interaction with other
>> selected build options. For example, while retpoline doesn't interact
>> stack-protector, it's easy to imagine things that might.

I want to be sure I clarify: I'm not aware of any negative interaction
between stack-protector and other options at present. I was just
trying to think of an illustrative example. I do know we're about to
get some per-architecture stack protector options (e.g. arm64 using a
per-process canary instead of global), but I *think* that can be
handled in the new Kconfig too.

> One ugly solution could be
> to add one more CC_HAS_ for the combination of the two ?

Yeah, that seems reasonable, but it's a fix after the fact. I guess
we'll have to see.

>> (And in thinking about this, does Kconfig know the true $CC in use?
>> i.e. the configured cross compiler, etc?)
>
> I was thinking of removing CONFIG_CROSS_COMPILE.
>
> A user can dynamically change CROSS_COMPILE from
> "make menuconfig".

Most builds I've seen implement cross compilers as an environment
variable during all "make" invocations.

> If we continue to support this, $CC changes
> according to CONFIG_CROSS_COMPILE.
> Then, compiler flags must be re-evaluated
> every time a user changes a compiler in use.
> It will introduce much more complexity.

Right now, this is just handled in the Makefile: all the right
variables exist, etc.

-Kees

-- 
Kees Cook
Pixel Security

  reply	other threads:[~2018-02-12 15:24 UTC|newest]

Thread overview: 89+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-08 16:19 [RFC PATCH 0/7] Kconfig: add new special property shell= to test compiler options in Kconfig Masahiro Yamada
2018-02-08 16:19 ` [RFC PATCH 1/7] kbuild: remove kbuild cache Masahiro Yamada
2018-02-08 16:19 ` [RFC PATCH 2/7] kconfig: add xrealloc() helper Masahiro Yamada
2018-02-08 16:19 ` [RFC PATCH 3/7] kconfig: remove const qualifier from sym_expand_string_value() Masahiro Yamada
2018-02-08 16:19 ` [RFC PATCH 4/7] kconfig: support new special property shell= Masahiro Yamada
2018-02-09  5:30   ` Ulf Magnusson
2018-02-09  9:19     ` Masahiro Yamada
2018-02-09 12:46       ` Ulf Magnusson
2018-02-09 20:46         ` Kees Cook
2018-02-10  5:48           ` Ulf Magnusson
2018-02-10  7:12             ` Masahiro Yamada
2018-02-10  7:49               ` Ulf Magnusson
2018-02-10  8:05                 ` Ulf Magnusson
2018-02-10  8:55                   ` Ulf Magnusson
2018-02-10  9:21                     ` Ulf Magnusson
2018-02-10 18:05                     ` Randy Dunlap
2018-02-11  2:00                       ` Kevin Easton
2018-02-10 19:23                     ` Kees Cook
2018-02-10 20:08                       ` Linus Torvalds
2018-02-11  4:13                         ` Kees Cook
2018-02-11  4:46                           ` Linus Torvalds
2018-02-11  7:28                             ` Linus Torvalds
2018-02-11 10:34                               ` Ulf Magnusson
2018-02-11 17:56                                 ` Kees Cook
2018-02-11 18:13                                   ` Linus Torvalds
2018-02-11 19:39                                     ` Kees Cook
2018-02-11 19:53                                       ` Linus Torvalds
2018-02-11 20:06                                         ` Linus Torvalds
2018-02-11 21:10                                           ` Arnd Bergmann
2018-02-11 21:19                                             ` Kees Cook
2018-02-11 21:50                                               ` Linus Torvalds
2018-02-12 10:44                                                 ` Arnd Bergmann
2018-02-12 10:44                                                   ` Arnd Bergmann
2018-02-11 22:29                                             ` Geert Uytterhoeven
2018-02-15 23:38                                           ` [RFC PATCH 4/7] kconfig: support new special property shell Palmer Dabbelt
2018-02-11 21:11                                         ` [RFC PATCH 4/7] kconfig: support new special property shell= Kees Cook
2018-02-11 19:42                                     ` Linus Torvalds
2018-02-12  8:26                                     ` Peter Zijlstra
2018-02-12 10:27                                       ` Thomas Gleixner
2018-02-12 11:52                                         ` Peter Zijlstra
2018-02-12 16:19                                       ` David Woodhouse
2018-02-12 16:19                                         ` David Woodhouse
2018-02-12 16:56                                         ` Kees Cook
2018-02-12 17:05                                           ` Peter Zijlstra
2018-02-12 17:33                                             ` Kees Cook
2018-02-12 17:36                                               ` David Woodhouse
2018-02-12 17:36                                                 ` David Woodhouse
2018-02-12 17:37                                                 ` Kees Cook
2018-02-12 17:00                                         ` Peter Zijlstra
2018-02-11 18:34                                   ` Ulf Magnusson
2018-02-11 21:05                                     ` Kees Cook
2018-02-11 21:35                                       ` Ulf Magnusson
2018-02-11 20:29                                   ` Ulf Magnusson
2018-02-11 20:42                                     ` Ulf Magnusson
2018-02-12 12:54                                       ` Ulf Magnusson
2018-02-12 14:21                                         ` Masahiro Yamada
2018-02-12 14:23                                           ` Masahiro Yamada
2018-02-12 14:32                                             ` Ulf Magnusson
2018-02-12 14:29                                           ` Ulf Magnusson
2018-02-12 14:53                                           ` Ulf Magnusson
2018-02-12 15:22                                             ` Masahiro Yamada
2018-02-12 15:35                                               ` Ulf Magnusson
2018-02-11 21:22                                   ` Ulf Magnusson
2018-02-12 14:39                                   ` Masahiro Yamada
2018-02-12 15:24                                     ` Kees Cook [this message]
2018-02-12 23:48                                       ` Randy Dunlap
2018-02-13  1:41                                         ` Masahiro Yamada
2018-02-13  1:53                                           ` Randy Dunlap
2018-02-13  8:35                                             ` Arnd Bergmann
2018-02-13  8:59                                               ` Masahiro Yamada
2018-02-12 10:44                                 ` Masahiro Yamada
2018-02-12 11:44                                   ` Ulf Magnusson
2018-02-12 11:49                                     ` Ulf Magnusson
2018-02-12 13:53                                     ` Masahiro Yamada
2018-02-12 14:13                                       ` Ulf Magnusson
2018-02-12 15:46                                   ` Kees Cook
2018-02-12 16:10                                     ` Masahiro Yamada
2018-02-13  8:55                                       ` Ulf Magnusson
2018-02-11 16:54                               ` Kees Cook
2018-02-08 16:19 ` [RFC PATCH 5/7] kconfig: invoke silentoldconfig when compiler is updated Masahiro Yamada
2018-02-08 17:19   ` Masahiro Yamada
2018-02-08 17:45     ` Linus Torvalds
2018-02-08 16:19 ` [RFC PATCH 6/7] kconfig: add basic environments to evaluate C flags in Kconfig Masahiro Yamada
2018-02-08 16:19 ` [RFC PATCH 7/7] Test stackprotector options in Kconfig to kill CC_STACKPROTECTOR_AUTO Masahiro Yamada
2018-02-08 18:30   ` Kees Cook
2018-02-09  4:13     ` Masahiro Yamada
2018-02-08 16:43 ` [RFC PATCH 0/7] Kconfig: add new special property shell= to test compiler options in Kconfig Greg Kroah-Hartman
2018-02-08 17:19 ` Linus Torvalds
2018-02-08 17:39   ` Masahiro Yamada

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