linux-kernel - [PATCH] bitops.h: Widen BIT macro to support 64-bit types

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Date:	Thu, 14 Oct 2010 12:58:55 +0200
From:	Borislav Petkov <bp@...64.org>
To:	Randy Dunlap <randy.dunlap@...cle.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Doug Thompson <dougthompson@...ssion.com>,
	akpm <akpm@...ux-foundation.org>, linux-arch@...r.kernel.org
Subject: [PATCH] bitops.h: Widen BIT macro to support 64-bit types

> From: Randy Dunlap <randy.dunlap@...cle.com>
> Date: Wed, Oct 13, 2010 at 04:10:57PM -0400
> 
> > The BIT() macro works on unsigned longs, but this warning happens
> > on i386 (X86_32), where UL is 32 bits and this value needs to be
> > 64 bits, so use open-coded ULL.
> > 
> > drivers/edac/mce_amd.c:262: warning: left shift count >= width of type
> 
> Ok, so BIT() should be fixed to work with the largest type available,
> IMHO. Let me cook up something.

Maybe something like the following. Build-tested with the crosstool
(http://www.kernel.org/pub/tools/crosstool) on the following arches:
alpha blackfin cris hppa64 ia64 mips64 sparc.

Any objections?

--
From: Borislav Petkov <Borislav.Petkov@....com>
Date: Thu, 14 Oct 2010 12:00:17 +0200
Subject: [PATCH] bitops.h: Widen BIT macro to support 64-bit types

Nowadays, every arch defines an unsigned 64-bit type using either one
of the include/asm-generic/int-l{,l}64.h headers. Thus, make the BIT()
macro return that 64-bit type by default. This makes sense on x86 when
manipulating MSR values and prevents overflow errors on 32-bit arches,
for example.

Signed-off-by: Borislav Petkov <borislav.petkov@....com>
---
 include/linux/bitops.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index fc68053..7b9170b 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -3,7 +3,7 @@
 #include <asm/types.h>
 
 #ifdef	__KERNEL__
-#define BIT(nr)			(1UL << (nr))
+#define BIT(nr)			(U64_C(1) << (nr))
 #define BIT_MASK(nr)		(1UL << ((nr) % BITS_PER_LONG))
 #define BIT_WORD(nr)		((nr) / BITS_PER_LONG)
 #define BITS_PER_BYTE		8
-- 
1.7.3.1.50.g1e633

-- 
Regards/Gruss,
Boris.

Advanced Micro Devices GmbH
Einsteinring 24, 85609 Dornach
General Managers: Alberto Bozzo, Andrew Bowd
Registration: Dornach, Gemeinde Aschheim, Landkreis Muenchen
Registergericht Muenchen, HRB Nr. 43632
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