[PATCH 1/2] bitops: Avoid integer overflow warning in GENMASK_ULL

From	Matthias Kaehlcke <mka@chromium.org>
Newsgroups	linux.kernel
Subject	[PATCH 1/2] bitops: Avoid integer overflow warning in GENMASK_ULL
Date	2017-08-03 01:00 +0200
Message-ID	<uaaMq-7QI-5@gated-at.bofh.it> (permalink)
Organization	linux.* mail to news gateway

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GENMASK_ULL performs a left-shift of (~0ULL), which technically
results in an integer overflow. clang raises a warning about
this if the overflow occurs in a preprocessor expression. To
avoid the overflow first perform a right-shift to clear the
bits that are shifted out.

Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
---
 include/linux/bitops.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index a83c822c35c2..21dfe63001e3 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -22,7 +22,7 @@
 	(((~0UL) << (l)) & (~0UL >> (BITS_PER_LONG - 1 - (h))))
 
 #define GENMASK_ULL(h, l) \
-	(((~0ULL) << (l)) & (~0ULL >> (BITS_PER_LONG_LONG - 1 - (h))))
+	((((~0ULL) >> (l)) << (l)) & (~0ULL >> (BITS_PER_LONG_LONG - 1 - (h))))
 
 extern unsigned int __sw_hweight8(unsigned int w);
 extern unsigned int __sw_hweight16(unsigned int w);
-- 
2.14.0.rc1.383.gd1ce394fe2-goog

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[PATCH 1/2] bitops: Avoid integer overflow warning in GENMASK_ULL Matthias Kaehlcke <mka@chromium.org> - 2017-08-03 01:00 +0200
  [PATCH 2/2] arm64: Define PAGE_OFFSET using GENMASK_ULL Matthias Kaehlcke <mka@chromium.org> - 2017-08-03 01:00 +0200
    Re: [PATCH 2/2] arm64: Define PAGE_OFFSET using GENMASK_ULL Nick Desaulniers <ndesaulniers@google.com> - 2017-08-03 01:20 +0200
      Re: [PATCH 2/2] arm64: Define PAGE_OFFSET using GENMASK_ULL Matthias Kaehlcke <mka@chromium.org> - 2017-08-03 01:50 +0200
    Re: [PATCH 2/2] arm64: Define PAGE_OFFSET using GENMASK_ULL Nick Desaulniers <ndesaulniers@google.com> - 2017-08-03 01:20 +0200
  Re: [PATCH 1/2] bitops: Avoid integer overflow warning in GENMASK_ULL Matthias Kaehlcke <mka@chromium.org> - 2017-08-03 19:10 +0200

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