mirror of
https://gitee.com/openharmony/third_party_libbpf
synced 2024-10-07 06:23:25 +00:00
8acf2635c3
add missing macros, static inline functions, etc. add README to illustrate the purpose of this repo. Signed-off-by: Yonghong Song <yhs@fb.com>
91 lines
2.7 KiB
C
91 lines
2.7 KiB
C
/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
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#ifndef __LINUX_OVERFLOW_H
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#define __LINUX_OVERFLOW_H
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#define is_signed_type(type) (((type)(-1)) < (type)1)
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#define __type_half_max(type) ((type)1 << (8*sizeof(type) - 1 - is_signed_type(type)))
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#define type_max(T) ((T)((__type_half_max(T) - 1) + __type_half_max(T)))
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#define type_min(T) ((T)((T)-type_max(T)-(T)1))
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#ifndef unlikely
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#define unlikely(x) __builtin_expect(!!(x), 0)
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#endif
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#ifdef __GNUC__
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#define GCC_VERSION (__GNUC__ * 10000 \
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+ __GNUC_MINOR__ * 100 \
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+ __GNUC_PATCHLEVEL__)
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#if GCC_VERSION >= 50100
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#define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
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#endif
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#endif
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#ifdef COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW
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#define check_mul_overflow(a, b, d) ({ \
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typeof(a) __a = (a); \
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typeof(b) __b = (b); \
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typeof(d) __d = (d); \
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(void) (&__a == &__b); \
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(void) (&__a == __d); \
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__builtin_mul_overflow(__a, __b, __d); \
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})
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#else
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/*
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* If one of a or b is a compile-time constant, this avoids a division.
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*/
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#define __unsigned_mul_overflow(a, b, d) ({ \
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typeof(a) __a = (a); \
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typeof(b) __b = (b); \
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typeof(d) __d = (d); \
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(void) (&__a == &__b); \
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(void) (&__a == __d); \
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*__d = __a * __b; \
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__builtin_constant_p(__b) ? \
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__b > 0 && __a > type_max(typeof(__a)) / __b : \
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__a > 0 && __b > type_max(typeof(__b)) / __a; \
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})
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/*
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* Signed multiplication is rather hard. gcc always follows C99, so
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* division is truncated towards 0. This means that we can write the
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* overflow check like this:
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*
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* (a > 0 && (b > MAX/a || b < MIN/a)) ||
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* (a < -1 && (b > MIN/a || b < MAX/a) ||
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* (a == -1 && b == MIN)
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*
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* The redundant casts of -1 are to silence an annoying -Wtype-limits
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* (included in -Wextra) warning: When the type is u8 or u16, the
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* __b_c_e in check_mul_overflow obviously selects
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* __unsigned_mul_overflow, but unfortunately gcc still parses this
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* code and warns about the limited range of __b.
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*/
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#define __signed_mul_overflow(a, b, d) ({ \
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typeof(a) __a = (a); \
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typeof(b) __b = (b); \
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typeof(d) __d = (d); \
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typeof(a) __tmax = type_max(typeof(a)); \
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typeof(a) __tmin = type_min(typeof(a)); \
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(void) (&__a == &__b); \
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(void) (&__a == __d); \
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*__d = (__u64)__a * (__u64)__b; \
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(__b > 0 && (__a > __tmax/__b || __a < __tmin/__b)) || \
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(__b < (typeof(__b))-1 && (__a > __tmin/__b || __a < __tmax/__b)) || \
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(__b == (typeof(__b))-1 && __a == __tmin); \
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})
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#define check_mul_overflow(a, b, d) \
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__builtin_choose_expr(is_signed_type(typeof(a)), \
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__signed_mul_overflow(a, b, d), \
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__unsigned_mul_overflow(a, b, d))
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#endif /* COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW */
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#endif
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