From: Kees Cook <keescook@google.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matthias Kaehlcke <mka@chromium.org>,
Arnd Bergmann <arnd@arndb.de>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Andrew Morton <akpm@linux-foundation.org>,
James Y Knight <jyknight@google.com>,
Chandler Carruth <chandlerc@google.com>,
Stephen Hines <srhines@google.com>,
Nick Desaulniers <ndesaulniers@google.com>,
Guenter Roeck <groeck@chromium.org>,
Greg Hackmann <ghackmann@google.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [GIT PULL] x86/build changes for v4.17
Date: Wed, 4 Apr 2018 17:20:14 -0700 [thread overview]
Message-ID: <CAGXu5jLebFAFTmu0r4jZLUvWi_6ki2JL598M-tCXeTnWo5vWPQ@mail.gmail.com> (raw)
In-Reply-To: <CA+55aFyHzKg3GzTdW4Z+xC5u2FZ8HnduNFi3PYVTGoKCqpR6Dg@mail.gmail.com>
On Wed, Apr 4, 2018 at 5:05 PM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> On Wed, Apr 4, 2018 at 4:31 PM, Matthias Kaehlcke <mka@chromium.org> wrote:
>>
>> From some experiments it looks like clang, in difference to gcc, does
>> not treat constant values passed as parameters to inline function as
>> constants.
>
> Yeah, I think gcc used to have those semantics a long time ago too.
>
> Many of our __builtin_constant_p() uses are indeed just in macros, but
> certainly not all.
>
> Other examples are found in our "fortified" string functions.
>
> There a clang build will likely simply miss some of the build-time
> fortification checks, and trigger them at runtime instead.
>
> Of course, we hopefully don't *have* any build-time failures, because
> gcc will have caught them, so you won't care as long as clang is a
> secondary compiler, but long-term they'd be good.
Yeah, it's used in inline functions in a lot of places. Some quickly
jump out: kmalloc, crypto, bitmaps, networking, uaccess, kvm, etc from
doing a dumb grep as:
git grep -B5 __builtin_constant_p | grep -A5 inline
FWIW, I prefer inline functions over macros just to keep type checking
a some level of sanity when reading build warnings/errors. ;)
-Kees
--
Kees Cook
Pixel Security
next prev parent reply other threads:[~2018-04-05 0:20 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-02 9:50 [GIT PULL] x86/build changes for v4.17 Ingo Molnar
2018-04-02 21:44 ` Linus Torvalds
2018-04-02 22:38 ` Matthias Kaehlcke
2018-04-03 1:26 ` Matthias Kaehlcke
2018-04-03 8:59 ` Peter Zijlstra
2018-04-03 9:51 ` Ingo Molnar
2018-04-03 12:09 ` Peter Zijlstra
2018-04-03 18:06 ` Matthias Kaehlcke
2018-04-03 21:58 ` Nick Desaulniers
2018-04-04 9:19 ` Peter Zijlstra
2018-04-04 9:38 ` Greg KH
2018-04-04 16:49 ` Nick Desaulniers
2018-04-04 17:13 ` Linus Torvalds
2018-04-04 17:46 ` Nick Desaulniers
2018-04-04 23:10 ` Nick Desaulniers
2018-04-04 16:53 ` Nick Desaulniers
2018-04-04 16:59 ` Greg KH
2018-04-04 19:26 ` James Y Knight
2018-04-04 19:42 ` Linus Torvalds
2018-04-04 22:21 ` James Y Knight
2018-04-04 22:29 ` Linus Torvalds
2018-04-05 7:08 ` Peter Zijlstra
2018-04-05 16:21 ` James Y Knight
2018-04-04 19:32 ` Josh Poimboeuf
2018-06-07 19:23 ` Nick Desaulniers
2018-06-07 20:11 ` Greg KH
2018-04-04 9:30 ` Peter Zijlstra
2018-04-04 19:17 ` Matthias Kaehlcke
2018-04-04 20:33 ` Arnd Bergmann
2018-04-04 20:58 ` Matthias Kaehlcke
2018-04-04 21:11 ` Arnd Bergmann
2018-04-04 21:46 ` Matthias Kaehlcke
2018-04-04 21:59 ` Linus Torvalds
2018-04-04 22:17 ` Matthias Kaehlcke
2018-04-04 22:39 ` Linus Torvalds
2018-04-04 23:31 ` Matthias Kaehlcke
2018-04-05 0:05 ` Linus Torvalds
2018-04-05 0:20 ` Kees Cook [this message]
2018-04-05 7:24 ` Peter Zijlstra
2018-04-05 8:04 ` Ingo Molnar
2018-04-05 8:24 ` Peter Zijlstra
2018-04-05 16:43 ` Linus Torvalds
2018-04-05 7:20 ` Peter Zijlstra
2018-04-05 17:46 ` James Y Knight
2018-04-05 18:06 ` Linus Torvalds
2018-04-05 20:51 ` James Y Knight
2018-04-05 21:13 ` Linus Torvalds
2018-04-05 22:51 ` James Y Knight
2018-04-06 2:02 ` Linus Torvalds
2018-04-05 17:47 ` James Y Knight
2018-04-04 23:04 ` Nick Desaulniers
2018-04-03 17:36 ` Linus Torvalds
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