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Diffstat (limited to 'third_party/linux/overflow.h')
| -rw-r--r-- | third_party/linux/overflow.h | 343 |
1 files changed, 0 insertions, 343 deletions
diff --git a/third_party/linux/overflow.h b/third_party/linux/overflow.h deleted file mode 100644 index caa720e6ad..0000000000 --- a/third_party/linux/overflow.h +++ /dev/null @@ -1,343 +0,0 @@ -/* SPDX-License-Identifier: GPL-2.0 OR MIT */ -#ifndef __LINUX_OVERFLOW_H -#define __LINUX_OVERFLOW_H - -#include <stddef.h> -#include <stdint.h> - -/* - * In the fallback code below, we need to compute the minimum and - * maximum values representable in a given type. These macros may also - * be useful elsewhere, so we provide them outside the - * COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW block. - * - * It would seem more obvious to do something like - * - * #define type_min(T) (T)(is_signed_type(T) ? (T)1 << (8*sizeof(T)-1) : 0) - * #define type_max(T) (T)(is_signed_type(T) ? ((T)1 << (8*sizeof(T)-1)) - 1 : ~(T)0) - * - * Unfortunately, the middle expressions, strictly speaking, have - * undefined behaviour, and at least some versions of gcc warn about - * the type_max expression (but not if -fsanitize=undefined is in - * effect; in that case, the warning is deferred to runtime...). - * - * The slightly excessive casting in type_min is to make sure the - * macros also produce sensible values for the exotic type _Bool. [The - * overflow checkers only almost work for _Bool, but that's - * a-feature-not-a-bug, since people shouldn't be doing arithmetic on - * _Bools. Besides, the gcc builtins don't allow _Bool* as third - * argument.] - * - * Idea stolen from - * https://mail-index.netbsd.org/tech-misc/2007/02/05/0000.html - - * credit to Christian Biere. - */ -#define is_signed_type(type) (((type)(-1)) < (type)1) -#define __type_half_max(type) ((type)1 << (8*sizeof(type) - 1 - is_signed_type(type))) -#define type_max(T) ((T)((__type_half_max(T) - 1) + __type_half_max(T))) -#define type_min(T) ((T)((T)-type_max(T)-(T)1)) - -/* - * Avoids triggering -Wtype-limits compilation warning, - * while using unsigned data types to check a < 0. - */ -#define is_non_negative(a) ((a) > 0 || (a) == 0) -#define is_negative(a) (!(is_non_negative(a))) - -#ifdef COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW -/* - * For simplicity and code hygiene, the fallback code below insists on - * a, b and *d having the same type (similar to the min() and max() - * macros), whereas gcc's type-generic overflow checkers accept - * different types. Hence we don't just make check_add_overflow an - * alias for __builtin_add_overflow, but add type checks similar to - * below. - */ -#define check_add_overflow(a, b, d) ({ \ - typeof(a) __a = (a); \ - typeof(b) __b = (b); \ - typeof(d) __d = (d); \ - (void) (&__a == &__b); \ - (void) (&__a == __d); \ - __builtin_add_overflow(__a, __b, __d); \ -}) - -#define check_sub_overflow(a, b, d) ({ \ - typeof(a) __a = (a); \ - typeof(b) __b = (b); \ - typeof(d) __d = (d); \ - (void) (&__a == &__b); \ - (void) (&__a == __d); \ - __builtin_sub_overflow(__a, __b, __d); \ -}) - -#define check_mul_overflow(a, b, d) ({ \ - typeof(a) __a = (a); \ - typeof(b) __b = (b); \ - typeof(d) __d = (d); \ - (void) (&__a == &__b); \ - (void) (&__a == __d); \ - __builtin_mul_overflow(__a, __b, __d); \ -}) - -#else - - -/* Checking for unsigned overflow is relatively easy without causing UB. */ -#define __unsigned_add_overflow(a, b, d) ({ \ - typeof(a) __a = (a); \ - typeof(b) __b = (b); \ - typeof(d) __d = (d); \ - (void) (&__a == &__b); \ - (void) (&__a == __d); \ - *__d = __a + __b; \ - *__d < __a; \ -}) -#define __unsigned_sub_overflow(a, b, d) ({ \ - typeof(a) __a = (a); \ - typeof(b) __b = (b); \ - typeof(d) __d = (d); \ - (void) (&__a == &__b); \ - (void) (&__a == __d); \ - *__d = __a - __b; \ - __a < __b; \ -}) -/* - * If one of a or b is a compile-time constant, this avoids a division. - */ -#define __unsigned_mul_overflow(a, b, d) ({ \ - typeof(a) __a = (a); \ - typeof(b) __b = (b); \ - typeof(d) __d = (d); \ - (void) (&__a == &__b); \ - (void) (&__a == __d); \ - *__d = __a * __b; \ - __builtin_constant_p(__b) ? \ - __b > 0 && __a > type_max(typeof(__a)) / __b : \ - __a > 0 && __b > type_max(typeof(__b)) / __a; \ -}) - -/* - * For signed types, detecting overflow is much harder, especially if - * we want to avoid UB. But the interface of these macros is such that - * we must provide a result in *d, and in fact we must produce the - * result promised by gcc's builtins, which is simply the possibly - * wrapped-around value. Fortunately, we can just formally do the - * operations in the widest relevant unsigned type (uint64_t) and then - * truncate the result - gcc is smart enough to generate the same code - * with and without the (uint64_t) casts. - */ - -/* - * Adding two signed integers can overflow only if they have the same - * sign, and overflow has happened iff the result has the opposite - * sign. - */ -#define __signed_add_overflow(a, b, d) ({ \ - typeof(a) __a = (a); \ - typeof(b) __b = (b); \ - typeof(d) __d = (d); \ - (void) (&__a == &__b); \ - (void) (&__a == __d); \ - *__d = (uint64_t)__a + (uint64_t)__b; \ - (((~(__a ^ __b)) & (*__d ^ __a)) \ - & type_min(typeof(__a))) != 0; \ -}) - -/* - * Subtraction is similar, except that overflow can now happen only - * when the signs are opposite. In this case, overflow has happened if - * the result has the opposite sign of a. - */ -#define __signed_sub_overflow(a, b, d) ({ \ - typeof(a) __a = (a); \ - typeof(b) __b = (b); \ - typeof(d) __d = (d); \ - (void) (&__a == &__b); \ - (void) (&__a == __d); \ - *__d = (uint64_t)__a - (uint64_t)__b; \ - ((((__a ^ __b)) & (*__d ^ __a)) \ - & type_min(typeof(__a))) != 0; \ -}) - -/* - * Signed multiplication is rather hard. gcc always follows C99, so - * division is truncated towards 0. This means that we can write the - * overflow check like this: - * - * (a > 0 && (b > MAX/a || b < MIN/a)) || - * (a < -1 && (b > MIN/a || b < MAX/a) || - * (a == -1 && b == MIN) - * - * The redundant casts of -1 are to silence an annoying -Wtype-limits - * (included in -Wextra) warning: When the type is u8 or u16, the - * __b_c_e in check_mul_overflow obviously selects - * __unsigned_mul_overflow, but unfortunately gcc still parses this - * code and warns about the limited range of __b. - */ - -#define __signed_mul_overflow(a, b, d) ({ \ - typeof(a) __a = (a); \ - typeof(b) __b = (b); \ - typeof(d) __d = (d); \ - typeof(a) __tmax = type_max(typeof(a)); \ - typeof(a) __tmin = type_min(typeof(a)); \ - (void) (&__a == &__b); \ - (void) (&__a == __d); \ - *__d = (uint64_t)__a * (uint64_t)__b; \ - (__b > 0 && (__a > __tmax/__b || __a < __tmin/__b)) || \ - (__b < (typeof(__b))-1 && (__a > __tmin/__b || __a < __tmax/__b)) || \ - (__b == (typeof(__b))-1 && __a == __tmin); \ -}) - - -#define check_add_overflow(a, b, d) \ - __builtin_choose_expr(is_signed_type(typeof(a)), \ - __signed_add_overflow(a, b, d), \ - __unsigned_add_overflow(a, b, d)) - -#define check_sub_overflow(a, b, d) \ - __builtin_choose_expr(is_signed_type(typeof(a)), \ - __signed_sub_overflow(a, b, d), \ - __unsigned_sub_overflow(a, b, d)) - -#define check_mul_overflow(a, b, d) \ - __builtin_choose_expr(is_signed_type(typeof(a)), \ - __signed_mul_overflow(a, b, d), \ - __unsigned_mul_overflow(a, b, d)) - - -#endif /* COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW */ - -/** check_shl_overflow() - Calculate a left-shifted value and check overflow - * - * @a: Value to be shifted - * @s: How many bits left to shift - * @d: Pointer to where to store the result - * - * Computes *@d = (@a << @s) - * - * Returns true if '*d' cannot hold the result or when 'a << s' doesn't - * make sense. Example conditions: - * - 'a << s' causes bits to be lost when stored in *d. - * - 's' is garbage (e.g. negative) or so large that the result of - * 'a << s' is guaranteed to be 0. - * - 'a' is negative. - * - 'a << s' sets the sign bit, if any, in '*d'. - * - * '*d' will hold the results of the attempted shift, but is not - * considered "safe for use" if false is returned. - */ -#define check_shl_overflow(a, s, d) ({ \ - typeof(a) _a = a; \ - typeof(s) _s = s; \ - typeof(d) _d = d; \ - uint64_t _a_full = _a; \ - unsigned int _to_shift = \ - is_non_negative(_s) && _s < 8 * sizeof(*d) ? _s : 0; \ - *_d = (_a_full << _to_shift); \ - (_to_shift != _s || is_negative(*_d) || is_negative(_a) || \ - (*_d >> _to_shift) != _a); \ -}) - -/* - * Disabling for EC since we don't currently have SIZE_MAX defined in our - * stdint.h. - */ -#if 0 -/** - * array_size() - Calculate size of 2-dimensional array. - * - * @a: dimension one - * @b: dimension two - * - * Calculates size of 2-dimensional array: @a * @b. - * - * Returns: number of bytes needed to represent the array or SIZE_MAX on - * overflow. - */ -static inline /*__must_check*/ size_t array_size(size_t a, size_t b) -{ - size_t bytes; - - if (check_mul_overflow(a, b, &bytes)) - return SIZE_MAX; - - return bytes; -} - -/** - * array3_size() - Calculate size of 3-dimensional array. - * - * @a: dimension one - * @b: dimension two - * @c: dimension three - * - * Calculates size of 3-dimensional array: @a * @b * @c. - * - * Returns: number of bytes needed to represent the array or SIZE_MAX on - * overflow. - */ -static inline /*__must_check*/ size_t array3_size(size_t a, size_t b, size_t c) -{ - size_t bytes; - - if (check_mul_overflow(a, b, &bytes)) - return SIZE_MAX; - if (check_mul_overflow(bytes, c, &bytes)) - return SIZE_MAX; - - return bytes; -} - -/* - * Compute a*b+c, returning SIZE_MAX on overflow. Internal helper for - * struct_size() below. - */ -static inline /*__must_check*/ size_t __ab_c_size(size_t a, size_t b, size_t c) -{ - size_t bytes; - - if (check_mul_overflow(a, b, &bytes)) - return SIZE_MAX; - if (check_add_overflow(bytes, c, &bytes)) - return SIZE_MAX; - - return bytes; -} -#endif - -/** - * struct_size() - Calculate size of structure with trailing array. - * @p: Pointer to the structure. - * @member: Name of the array member. - * @count: Number of elements in the array. - * - * Calculates size of memory needed for structure @p followed by an - * array of @count number of @member elements. - * - * Return: number of bytes needed or SIZE_MAX on overflow. - */ -#define struct_size(p, member, count) \ - __ab_c_size(count, \ - sizeof(*(p)->member) + __must_be_array((p)->member),\ - sizeof(*(p))) - -/** - * flex_array_size() - Calculate size of a flexible array member - * within an enclosing structure. - * - * @p: Pointer to the structure. - * @member: Name of the flexible array member. - * @count: Number of elements in the array. - * - * Calculates size of a flexible array of @count number of @member - * elements, at the end of structure @p. - * - * Return: number of bytes needed or SIZE_MAX on overflow. - */ -#define flex_array_size(p, member, count) \ - array_size(count, \ - sizeof(*(p)->member) + __must_be_array((p)->member)) - -#endif /* __LINUX_OVERFLOW_H */ |