1*f7c14bbaSAndroid Build Coastguard Worker /* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */ 2*f7c14bbaSAndroid Build Coastguard Worker 3*f7c14bbaSAndroid Build Coastguard Worker #ifndef __LINUX_OVERFLOW_H 4*f7c14bbaSAndroid Build Coastguard Worker #define __LINUX_OVERFLOW_H 5*f7c14bbaSAndroid Build Coastguard Worker 6*f7c14bbaSAndroid Build Coastguard Worker #define is_signed_type(type) (((type)(-1)) < (type)1) 7*f7c14bbaSAndroid Build Coastguard Worker #define __type_half_max(type) ((type)1 << (8*sizeof(type) - 1 - is_signed_type(type))) 8*f7c14bbaSAndroid Build Coastguard Worker #define type_max(T) ((T)((__type_half_max(T) - 1) + __type_half_max(T))) 9*f7c14bbaSAndroid Build Coastguard Worker #define type_min(T) ((T)((T)-type_max(T)-(T)1)) 10*f7c14bbaSAndroid Build Coastguard Worker 11*f7c14bbaSAndroid Build Coastguard Worker #ifndef unlikely 12*f7c14bbaSAndroid Build Coastguard Worker #define unlikely(x) __builtin_expect(!!(x), 0) 13*f7c14bbaSAndroid Build Coastguard Worker #endif 14*f7c14bbaSAndroid Build Coastguard Worker 15*f7c14bbaSAndroid Build Coastguard Worker #ifdef __GNUC__ 16*f7c14bbaSAndroid Build Coastguard Worker #define GCC_VERSION (__GNUC__ * 10000 \ 17*f7c14bbaSAndroid Build Coastguard Worker + __GNUC_MINOR__ * 100 \ 18*f7c14bbaSAndroid Build Coastguard Worker + __GNUC_PATCHLEVEL__) 19*f7c14bbaSAndroid Build Coastguard Worker #if GCC_VERSION >= 50100 20*f7c14bbaSAndroid Build Coastguard Worker #define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1 21*f7c14bbaSAndroid Build Coastguard Worker #endif 22*f7c14bbaSAndroid Build Coastguard Worker #endif 23*f7c14bbaSAndroid Build Coastguard Worker 24*f7c14bbaSAndroid Build Coastguard Worker #ifdef COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 25*f7c14bbaSAndroid Build Coastguard Worker 26*f7c14bbaSAndroid Build Coastguard Worker #define check_mul_overflow(a, b, d) ({ \ 27*f7c14bbaSAndroid Build Coastguard Worker typeof(a) __a = (a); \ 28*f7c14bbaSAndroid Build Coastguard Worker typeof(b) __b = (b); \ 29*f7c14bbaSAndroid Build Coastguard Worker typeof(d) __d = (d); \ 30*f7c14bbaSAndroid Build Coastguard Worker (void) (&__a == &__b); \ 31*f7c14bbaSAndroid Build Coastguard Worker (void) (&__a == __d); \ 32*f7c14bbaSAndroid Build Coastguard Worker __builtin_mul_overflow(__a, __b, __d); \ 33*f7c14bbaSAndroid Build Coastguard Worker }) 34*f7c14bbaSAndroid Build Coastguard Worker 35*f7c14bbaSAndroid Build Coastguard Worker #else 36*f7c14bbaSAndroid Build Coastguard Worker 37*f7c14bbaSAndroid Build Coastguard Worker /* 38*f7c14bbaSAndroid Build Coastguard Worker * If one of a or b is a compile-time constant, this avoids a division. 39*f7c14bbaSAndroid Build Coastguard Worker */ 40*f7c14bbaSAndroid Build Coastguard Worker #define __unsigned_mul_overflow(a, b, d) ({ \ 41*f7c14bbaSAndroid Build Coastguard Worker typeof(a) __a = (a); \ 42*f7c14bbaSAndroid Build Coastguard Worker typeof(b) __b = (b); \ 43*f7c14bbaSAndroid Build Coastguard Worker typeof(d) __d = (d); \ 44*f7c14bbaSAndroid Build Coastguard Worker (void) (&__a == &__b); \ 45*f7c14bbaSAndroid Build Coastguard Worker (void) (&__a == __d); \ 46*f7c14bbaSAndroid Build Coastguard Worker *__d = __a * __b; \ 47*f7c14bbaSAndroid Build Coastguard Worker __builtin_constant_p(__b) ? \ 48*f7c14bbaSAndroid Build Coastguard Worker __b > 0 && __a > type_max(typeof(__a)) / __b : \ 49*f7c14bbaSAndroid Build Coastguard Worker __a > 0 && __b > type_max(typeof(__b)) / __a; \ 50*f7c14bbaSAndroid Build Coastguard Worker }) 51*f7c14bbaSAndroid Build Coastguard Worker 52*f7c14bbaSAndroid Build Coastguard Worker /* 53*f7c14bbaSAndroid Build Coastguard Worker * Signed multiplication is rather hard. gcc always follows C99, so 54*f7c14bbaSAndroid Build Coastguard Worker * division is truncated towards 0. This means that we can write the 55*f7c14bbaSAndroid Build Coastguard Worker * overflow check like this: 56*f7c14bbaSAndroid Build Coastguard Worker * 57*f7c14bbaSAndroid Build Coastguard Worker * (a > 0 && (b > MAX/a || b < MIN/a)) || 58*f7c14bbaSAndroid Build Coastguard Worker * (a < -1 && (b > MIN/a || b < MAX/a) || 59*f7c14bbaSAndroid Build Coastguard Worker * (a == -1 && b == MIN) 60*f7c14bbaSAndroid Build Coastguard Worker * 61*f7c14bbaSAndroid Build Coastguard Worker * The redundant casts of -1 are to silence an annoying -Wtype-limits 62*f7c14bbaSAndroid Build Coastguard Worker * (included in -Wextra) warning: When the type is u8 or u16, the 63*f7c14bbaSAndroid Build Coastguard Worker * __b_c_e in check_mul_overflow obviously selects 64*f7c14bbaSAndroid Build Coastguard Worker * __unsigned_mul_overflow, but unfortunately gcc still parses this 65*f7c14bbaSAndroid Build Coastguard Worker * code and warns about the limited range of __b. 66*f7c14bbaSAndroid Build Coastguard Worker */ 67*f7c14bbaSAndroid Build Coastguard Worker 68*f7c14bbaSAndroid Build Coastguard Worker #define __signed_mul_overflow(a, b, d) ({ \ 69*f7c14bbaSAndroid Build Coastguard Worker typeof(a) __a = (a); \ 70*f7c14bbaSAndroid Build Coastguard Worker typeof(b) __b = (b); \ 71*f7c14bbaSAndroid Build Coastguard Worker typeof(d) __d = (d); \ 72*f7c14bbaSAndroid Build Coastguard Worker typeof(a) __tmax = type_max(typeof(a)); \ 73*f7c14bbaSAndroid Build Coastguard Worker typeof(a) __tmin = type_min(typeof(a)); \ 74*f7c14bbaSAndroid Build Coastguard Worker (void) (&__a == &__b); \ 75*f7c14bbaSAndroid Build Coastguard Worker (void) (&__a == __d); \ 76*f7c14bbaSAndroid Build Coastguard Worker *__d = (__u64)__a * (__u64)__b; \ 77*f7c14bbaSAndroid Build Coastguard Worker (__b > 0 && (__a > __tmax/__b || __a < __tmin/__b)) || \ 78*f7c14bbaSAndroid Build Coastguard Worker (__b < (typeof(__b))-1 && (__a > __tmin/__b || __a < __tmax/__b)) || \ 79*f7c14bbaSAndroid Build Coastguard Worker (__b == (typeof(__b))-1 && __a == __tmin); \ 80*f7c14bbaSAndroid Build Coastguard Worker }) 81*f7c14bbaSAndroid Build Coastguard Worker 82*f7c14bbaSAndroid Build Coastguard Worker #define check_mul_overflow(a, b, d) \ 83*f7c14bbaSAndroid Build Coastguard Worker __builtin_choose_expr(is_signed_type(typeof(a)), \ 84*f7c14bbaSAndroid Build Coastguard Worker __signed_mul_overflow(a, b, d), \ 85*f7c14bbaSAndroid Build Coastguard Worker __unsigned_mul_overflow(a, b, d)) 86*f7c14bbaSAndroid Build Coastguard Worker 87*f7c14bbaSAndroid Build Coastguard Worker 88*f7c14bbaSAndroid Build Coastguard Worker #endif /* COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW */ 89*f7c14bbaSAndroid Build Coastguard Worker 90*f7c14bbaSAndroid Build Coastguard Worker #endif 91