From: Rikard Falkeborn <rikard.falkeborn@gmail.com>
To: Joe Perches <joe@perches.com>
Cc: Rikard Falkeborn <rikard.falkeborn@gmail.com>,
Masahiro Yamada <yamada.masahiro@socionext.com>,
Andrew Morton <akpm@linux-foundation.org>,
Johannes Berg <johannes@sipsolutions.net>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] linux/bits.h: Add compile time sanity check of GENMASK inputs
Date: Wed, 7 Aug 2019 22:53:02 +0200 [thread overview]
Message-ID: <20190807205302.GB14779@rikard> (raw)
In-Reply-To: <a687a6d29d4cc928a6aa128bcada5f55b26f41a4.camel@perches.com>
On Tue, Aug 06, 2019 at 02:15:54PM -0700, Joe Perches wrote:
> On Tue, 2019-08-06 at 21:27 +0200, Rikard Falkeborn wrote:
> > On Wed, Aug 07, 2019 at 12:19:36AM +0900, Masahiro Yamada wrote:
> > > How about this?
> > > #define GENMASK_INPUT_CHECK(high, low) \
> > > BUILD_BUG_ON_ZERO(__builtin_choose_expr( \
> > > __builtin_constant_p((low) > (high)), (low) > (high), 0))
> > Thanks for the feedback, your version looks much cleaner than mine. I
> > *think* I had a reason for using __is_constexpr() instead of
> > __builtin_constant_p but I'll try a full rebuild to see if something
> > comes up.
>
> Perhaps a statement expression so high and low aren't possibly
> evaluated multiple times?
>
> #define GENMASK_INPUT_CHECK(high, low) \
> ({ \
> typeof(high) _high = high; \
> typeof(low) _low = low; \
> BUILD_BUG_ON_ZERO(__builtin_constant_p(_low > _high, \
> _low > _high, \
> 0)) \
> })
>
>
That doesn't work I think (even after adding __builtin_choose_expr).
Even so, high and low are not evaluated multiple times (they're not
evaluated at all in GENMASK_INPUT_CHECK, if they were, the arguments
would be evaluated twice since they're evaluated in __GENMASK as well.
__builtin_constant_p does not seem to evaluate it's expression (even
though I didn't manage to find that spelled out in the docs, but since
__builtin_constant_p is evaluated at compile time it makes sense that it
doesn't), and __builtin_choose_expr does not evaluate the operand that
is not chosen (this is actually in the docs). Even if it was,
BUIlD_BUG_ON_ZERO uses sizeof its argument, which is evaluated at compile
time (unless the argument is a VLA).
So this should be safe.
next prev parent reply other threads:[~2019-08-07 20:53 UTC|newest]
Thread overview: 176+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20190710050444epcas1p250f7aa0f8798a7757df51d66f5970c2a@epcas1p2.samsung.com>
2019-07-10 5:04 ` [PATCH 00/12] treewide: Fix GENMASK misuses Joe Perches
2019-07-10 5:04 ` Joe Perches
2019-07-10 5:04 ` Joe Perches
2019-07-10 5:04 ` Joe Perches
2019-07-10 5:04 ` Joe Perches
2019-07-10 5:04 ` [PATCH 01/12] checkpatch: Add GENMASK tests Joe Perches
2019-07-24 18:03 ` Joe Perches
2019-07-10 5:04 ` [PATCH 02/12] clocksource/drivers/npcm: Fix misuse of GENMASK macro Joe Perches
2019-07-10 9:10 ` [tip:timers/urgent] " tip-bot for Joe Perches
2019-07-15 10:00 ` [PATCH 02/12] " Avi Fishman
2019-07-15 10:00 ` Avi Fishman
2019-07-10 5:04 ` [PATCH 03/12] drm: aspeed_gfx: " Joe Perches
2019-07-10 5:04 ` Joe Perches
2019-07-10 5:04 ` Joe Perches
2019-07-24 17:16 ` Joe Perches
2019-07-24 17:16 ` Joe Perches
2019-07-25 1:10 ` Andrew Jeffery
2019-07-25 1:10 ` Andrew Jeffery
2019-07-25 1:10 ` Andrew Jeffery
2019-07-25 1:18 ` Joe Perches
2019-07-25 1:18 ` Joe Perches
2019-07-25 1:18 ` Joe Perches
2019-07-25 2:52 ` Joel Stanley
2019-07-25 2:52 ` Joel Stanley
2019-07-25 14:37 ` Joe Perches
2019-07-25 14:37 ` Joe Perches
2019-07-25 14:37 ` Joe Perches
2019-07-10 5:04 ` [PATCH 04/12] iio: adc: max9611: " Joe Perches
2019-07-14 11:54 ` Jonathan Cameron
2019-07-14 12:19 ` Joe Perches
2019-07-14 14:37 ` Jacopo Mondi
2019-07-29 21:52 ` Jacopo Mondi
2019-07-31 8:37 ` Jonathan Cameron
2019-07-10 5:04 ` [PATCH 05/12] irqchip/gic-v3-its: " Joe Perches
2019-07-10 8:28 ` Marc Zyngier
2019-07-10 9:07 ` [tip:irq/urgent] " tip-bot for Joe Perches
2019-07-10 5:04 ` [PATCH 06/12] mmc: meson-mx-sdio: " Joe Perches
2019-07-10 5:04 ` Joe Perches
2019-07-10 5:04 ` Joe Perches
2019-07-22 7:23 ` Neil Armstrong
2019-07-22 7:23 ` Neil Armstrong
2019-07-22 7:23 ` Neil Armstrong
2019-07-22 13:43 ` Ulf Hansson
2019-07-22 13:43 ` Ulf Hansson
2019-07-22 13:43 ` Ulf Hansson
2019-07-10 5:04 ` [PATCH 07/12] net: ethernet: mediatek: Fix misuses " Joe Perches
2019-07-10 5:04 ` Joe Perches
2019-07-10 5:04 ` [PATCH 08/12] net: stmmac: " Joe Perches
2019-07-10 5:04 ` Joe Perches
2019-07-10 10:33 ` Jose Abreu
2019-07-10 10:33 ` Jose Abreu
2019-07-10 5:04 ` [PATCH 09/12] rtw88: Fix misuse " Joe Perches
2019-07-10 5:07 ` Tony Chuang
2019-07-24 11:48 ` Kalle Valo
2019-07-10 5:04 ` [PATCH 10/12] phy: amlogic: G12A: " Joe Perches
2019-07-10 5:04 ` Joe Perches
2019-07-10 5:04 ` Joe Perches
2019-07-22 7:23 ` Neil Armstrong
2019-07-22 7:23 ` Neil Armstrong
2019-07-22 7:23 ` Neil Armstrong
2019-08-23 2:41 ` Kishon Vijay Abraham I
2019-08-23 2:41 ` Kishon Vijay Abraham I
2019-08-23 2:41 ` Kishon Vijay Abraham I
2019-08-23 4:59 ` Joe Perches
2019-08-23 4:59 ` Joe Perches
2019-08-23 4:59 ` Joe Perches
2019-07-10 5:04 ` [PATCH 11/12] staging: media: cedrus: " Joe Perches
2019-07-10 5:04 ` Joe Perches
2019-07-10 5:04 ` Joe Perches
2019-07-10 7:23 ` Paul Kocialkowski
2019-07-10 7:23 ` Paul Kocialkowski
2019-07-10 7:23 ` Paul Kocialkowski
2019-07-24 17:09 ` Joe Perches
2019-07-24 17:09 ` Joe Perches
2019-07-24 18:35 ` Greg Kroah-Hartman
2019-07-24 18:35 ` Greg Kroah-Hartman
2019-07-24 18:39 ` Joe Perches
2019-07-24 18:39 ` Joe Perches
2019-07-24 18:55 ` Greg Kroah-Hartman
2019-07-24 18:55 ` Greg Kroah-Hartman
2019-07-25 6:46 ` Hans Verkuil
2019-07-25 6:46 ` Hans Verkuil
2019-07-10 5:04 ` Joe Perches
2019-07-10 5:04 ` [PATCH 12/12] ASoC: wcd9335: " Joe Perches
2019-07-22 12:22 ` Applied "ASoC: wcd9335: Fix misuse of GENMASK macro" to the asoc tree Mark Brown
2019-07-22 12:22 ` Mark Brown
2019-07-10 9:17 ` [PATCH 00/12] treewide: Fix GENMASK misuses Johannes Berg
2019-07-10 9:17 ` Johannes Berg
2019-07-10 9:17 ` Johannes Berg
2019-07-10 9:17 ` Johannes Berg
2019-07-10 9:17 ` Johannes Berg
2019-07-10 9:43 ` Russell King - ARM Linux admin
2019-07-10 9:43 ` Russell King - ARM Linux admin
2019-07-10 9:43 ` Russell King - ARM Linux admin
2019-07-10 9:43 ` Russell King - ARM Linux admin
2019-07-10 9:43 ` Russell King - ARM Linux admin
2019-07-10 15:45 ` Joe Perches
2019-07-10 15:45 ` Joe Perches
2019-07-10 15:45 ` Joe Perches
2019-07-10 15:45 ` Joe Perches
2019-07-10 15:45 ` Joe Perches
2019-07-10 16:01 ` Joe Perches
2019-07-10 16:01 ` Joe Perches
2019-07-10 16:01 ` Joe Perches
2019-07-10 16:01 ` Joe Perches
2019-07-10 16:01 ` Joe Perches
2019-07-10 16:01 ` Joe Perches
2019-07-27 19:54 ` Rikard Falkeborn
2019-07-28 23:45 ` Joe Perches
2019-07-31 19:03 ` [PATCH] linux/bits.h: Add compile time sanity check of GENMASK inputs Rikard Falkeborn
2019-07-31 19:27 ` Joe Perches
2019-08-01 23:03 ` Rikard Falkeborn
2019-08-02 1:40 ` Masahiro Yamada
2019-08-02 3:13 ` Joe Perches
2019-08-02 3:25 ` Masahiro Yamada
2019-08-02 18:18 ` Rikard Falkeborn
2019-08-03 3:03 ` Masahiro Yamada
2019-08-03 3:12 ` Masahiro Yamada
2019-08-03 18:36 ` Rikard Falkeborn
2019-08-04 6:45 ` Masahiro Yamada
2019-08-05 19:55 ` Rikard Falkeborn
2019-08-06 15:19 ` Masahiro Yamada
2019-08-06 19:27 ` Rikard Falkeborn
2019-08-06 21:15 ` Joe Perches
2019-08-07 20:53 ` Rikard Falkeborn [this message]
2019-08-01 2:50 ` Masahiro Yamada
2019-08-01 2:57 ` Joe Perches
2019-08-01 23:03 ` Rikard Falkeborn
2019-08-01 23:03 ` [PATCH v2 1/2] linux/bits.h: Clarify macro argument names Rikard Falkeborn
2019-08-01 23:03 ` [PATCH v2 2/2] linux/bits.h: Add compile time sanity check of GENMASK inputs Rikard Falkeborn
2019-08-01 23:14 ` Joe Perches
2019-08-07 14:27 ` Guenter Roeck
2019-08-07 14:55 ` Masahiro Yamada
2019-08-07 16:52 ` Guenter Roeck
2019-08-07 20:07 ` Rikard Falkeborn
2019-08-08 0:07 ` Joe Perches
2019-08-08 0:58 ` Guenter Roeck
2019-08-08 1:08 ` Joe Perches
2019-08-08 1:53 ` Guenter Roeck
2019-08-08 2:44 ` kbuild test robot
2019-08-08 2:44 ` kbuild test robot
2019-08-08 3:46 ` [PATCH v2 1/2] linux/bits.h: Clarify macro argument names Masahiro Yamada
2019-08-10 18:43 ` Rikard Falkeborn
2019-08-10 19:20 ` Joe Perches
2019-08-11 18:49 ` [PATCH v3 0/3] Add compile time sanity check of GENMASK inputs Rikard Falkeborn
2019-08-11 18:49 ` [PATCH v3 1/3] x86/boot: Use common BUILD_BUG_ON Rikard Falkeborn
2019-08-12 18:19 ` [tip:x86/boot] " tip-bot for Rikard Falkeborn
2019-08-16 12:19 ` tip-bot for Rikard Falkeborn
2019-08-11 18:49 ` [PATCH v3 2/3] linux/build_bug.h: Change type to int Rikard Falkeborn
2019-10-06 2:26 ` Masahiro Yamada
2019-08-11 18:49 ` [PATCH v3 3/3] linux/bits.h: Add compile time sanity check of GENMASK inputs Rikard Falkeborn
2019-10-06 2:30 ` Masahiro Yamada
2019-10-08 7:23 ` Geert Uytterhoeven
2019-10-08 7:44 ` Masahiro Yamada
2019-10-08 7:52 ` Masahiro Yamada
2019-10-08 19:06 ` Rikard Falkeborn
2019-08-12 17:58 ` [PATCH v3 0/3] " Kees Cook
2019-10-05 19:46 ` Rikard Falkeborn
2019-10-09 21:45 ` [Patch v4 0/2] " Rikard Falkeborn
2019-10-09 21:45 ` [Patch v4 1/2] linux/build_bug.h: Change type to int Rikard Falkeborn
2019-10-09 21:45 ` [Patch v4 2/2] linux/bits.h: Add compile time sanity check of GENMASK inputs Rikard Falkeborn
2019-10-10 2:24 ` Masahiro Yamada
2019-10-12 2:27 ` Andrew Morton
2019-10-22 19:53 ` Rikard Falkeborn
2019-11-01 21:28 ` Rikard Falkeborn
2020-03-08 19:39 ` [PATCH v5] " Rikard Falkeborn
2020-03-09 16:40 ` Kees Cook
2019-07-11 21:30 ` [PATCH 00/12] treewide: Fix GENMASK misuses David Miller
2019-07-11 21:30 ` David Miller
2019-07-11 21:30 ` David Miller
2019-07-11 21:30 ` David Miller
2019-07-12 12:54 ` Andrzej Hajda
2019-07-12 12:54 ` Andrzej Hajda
2019-07-12 12:54 ` Andrzej Hajda
2019-07-12 12:54 ` Andrzej Hajda
2019-07-12 12:54 ` Andrzej Hajda
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