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Left-shifting past the size of your datatype is undefined behaviour in C. The literal 34 gets the type `int`, and that one is not big enough to be left shifted by 26 bits. An `unsigned` is long enough (on any machine that has at least 32 bits for their ints.) For uniformity, we mark all the literals as unsigned. But it's only really needed for HUGETLB_FLAG_ENCODE_16GB. Thanks to Randy Dunlap for an initial review and suggestion. Link: https://lkml.kernel.org/r/20220905031904.150925-1-matthias.goergens@gmail.com Signed-off-by: Matthias Goergens <matthias.goergens@gmail.com> Acked-by: Randy Dunlap <rdunlap@infradead.org> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Muchun Song <songmuchun@bytedance.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
38 lines
1.8 KiB
C
38 lines
1.8 KiB
C
#ifndef _ASM_GENERIC_HUGETLB_ENCODE_H_
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#define _ASM_GENERIC_HUGETLB_ENCODE_H_
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/*
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* Several system calls take a flag to request "hugetlb" huge pages.
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* Without further specification, these system calls will use the
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* system's default huge page size. If a system supports multiple
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* huge page sizes, the desired huge page size can be specified in
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* bits [26:31] of the flag arguments. The value in these 6 bits
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* will encode the log2 of the huge page size.
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*
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* The following definitions are associated with this huge page size
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* encoding in flag arguments. System call specific header files
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* that use this encoding should include this file. They can then
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* provide definitions based on these with their own specific prefix.
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* for example:
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* #define MAP_HUGE_SHIFT HUGETLB_FLAG_ENCODE_SHIFT
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*/
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#define HUGETLB_FLAG_ENCODE_SHIFT 26
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#define HUGETLB_FLAG_ENCODE_MASK 0x3f
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#define HUGETLB_FLAG_ENCODE_16KB (14U << HUGETLB_FLAG_ENCODE_SHIFT)
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#define HUGETLB_FLAG_ENCODE_64KB (16U << HUGETLB_FLAG_ENCODE_SHIFT)
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#define HUGETLB_FLAG_ENCODE_512KB (19U << HUGETLB_FLAG_ENCODE_SHIFT)
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#define HUGETLB_FLAG_ENCODE_1MB (20U << HUGETLB_FLAG_ENCODE_SHIFT)
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#define HUGETLB_FLAG_ENCODE_2MB (21U << HUGETLB_FLAG_ENCODE_SHIFT)
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#define HUGETLB_FLAG_ENCODE_8MB (23U << HUGETLB_FLAG_ENCODE_SHIFT)
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#define HUGETLB_FLAG_ENCODE_16MB (24U << HUGETLB_FLAG_ENCODE_SHIFT)
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#define HUGETLB_FLAG_ENCODE_32MB (25U << HUGETLB_FLAG_ENCODE_SHIFT)
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#define HUGETLB_FLAG_ENCODE_256MB (28U << HUGETLB_FLAG_ENCODE_SHIFT)
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#define HUGETLB_FLAG_ENCODE_512MB (29U << HUGETLB_FLAG_ENCODE_SHIFT)
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#define HUGETLB_FLAG_ENCODE_1GB (30U << HUGETLB_FLAG_ENCODE_SHIFT)
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#define HUGETLB_FLAG_ENCODE_2GB (31U << HUGETLB_FLAG_ENCODE_SHIFT)
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#define HUGETLB_FLAG_ENCODE_16GB (34U << HUGETLB_FLAG_ENCODE_SHIFT)
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#endif /* _ASM_GENERIC_HUGETLB_ENCODE_H_ */
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