forked from mirrors/linux
f747e6667e
GENMASK() has an input check which uses __builtin_choose_expr() to enable a compile time sanity check of its inputs if they are known at compile time. However, it turns out that __builtin_constant_p() does not always return a compile time constant [0]. It was thought this problem was fixed with gcc 4.9 [1], but apparently this is not the case [2]. Switch to use __is_constexpr() instead which always returns a compile time constant, regardless of its inputs. Link: https://lore.kernel.org/lkml/42b4342b-aefc-a16a-0d43-9f9c0d63ba7a@rasmusvillemoes.dk [0] Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=19449 [1] Link: https://lore.kernel.org/lkml/1ac7bbc2-45d9-26ed-0b33-bf382b8d858b@I-love.SAKURA.ne.jp [2] Link: https://lkml.kernel.org/r/20210511203716.117010-1-rikard.falkeborn@gmail.com Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com> Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Acked-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com> Cc: Ard Biesheuvel <ardb@kernel.org> Cc: Yury Norov <yury.norov@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
46 lines
1.4 KiB
C
46 lines
1.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __LINUX_BITS_H
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#define __LINUX_BITS_H
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#include <linux/const.h>
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#include <vdso/bits.h>
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#include <asm/bitsperlong.h>
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#define BIT_ULL(nr) (ULL(1) << (nr))
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#define BIT_MASK(nr) (UL(1) << ((nr) % BITS_PER_LONG))
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#define BIT_WORD(nr) ((nr) / BITS_PER_LONG)
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#define BIT_ULL_MASK(nr) (ULL(1) << ((nr) % BITS_PER_LONG_LONG))
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#define BIT_ULL_WORD(nr) ((nr) / BITS_PER_LONG_LONG)
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#define BITS_PER_BYTE 8
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/*
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* Create a contiguous bitmask starting at bit position @l and ending at
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* position @h. For example
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* GENMASK_ULL(39, 21) gives us the 64bit vector 0x000000ffffe00000.
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*/
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#if !defined(__ASSEMBLY__)
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#include <linux/build_bug.h>
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#define GENMASK_INPUT_CHECK(h, l) \
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(BUILD_BUG_ON_ZERO(__builtin_choose_expr( \
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__is_constexpr((l) > (h)), (l) > (h), 0)))
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#else
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/*
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* BUILD_BUG_ON_ZERO is not available in h files included from asm files,
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* disable the input check if that is the case.
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*/
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#define GENMASK_INPUT_CHECK(h, l) 0
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#endif
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#define __GENMASK(h, l) \
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(((~UL(0)) - (UL(1) << (l)) + 1) & \
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(~UL(0) >> (BITS_PER_LONG - 1 - (h))))
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#define GENMASK(h, l) \
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(GENMASK_INPUT_CHECK(h, l) + __GENMASK(h, l))
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#define __GENMASK_ULL(h, l) \
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(((~ULL(0)) - (ULL(1) << (l)) + 1) & \
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(~ULL(0) >> (BITS_PER_LONG_LONG - 1 - (h))))
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#define GENMASK_ULL(h, l) \
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(GENMASK_INPUT_CHECK(h, l) + __GENMASK_ULL(h, l))
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#endif /* __LINUX_BITS_H */
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