1 /* $NetBSD: overflow.h,v 1.2 2021/12/19 12:20:53 riastradh Exp $ */ 2 3 /*- 4 * Copyright (c) 2018 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Taylor R. Campbell. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29 * POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32 #ifndef _LINUX_OVERFLOW_H_ 33 #define _LINUX_OVERFLOW_H_ 34 35 #include <sys/types.h> 36 37 #include <lib/libkern/libkern.h> /* offsetof */ 38 39 #define check_mul_overflow(a, b, res) __builtin_mul_overflow(a, b, res) 40 #define check_add_overflow(a, b, res) __builtin_add_overflow(a, b, res) 41 42 /* return x*y saturated at SIZE_MAX */ 43 static inline size_t 44 array_size(size_t x, size_t y) 45 { 46 size_t xy; 47 48 if (check_mul_overflow(x, y, &xy)) 49 return SIZE_MAX; 50 return xy; 51 } 52 53 /* return x*y*z saturated at SIZE_MAX */ 54 static inline size_t 55 array3_size(size_t x, size_t y, size_t z) 56 { 57 size_t xy, xyz; 58 59 if (check_mul_overflow(x, y, &xy)) 60 return SIZE_MAX; 61 if (check_mul_overflow(xy, z, &xyz)) 62 return SIZE_MAX; 63 return xyz; 64 } 65 66 /* return basesize + elemsize*nelem saturated at SIZE_MAX */ 67 static inline size_t 68 __struct_size(size_t basesize, size_t elemsize, size_t nelem) 69 { 70 size_t arraysize, totalsize; 71 72 KASSERT(elemsize); 73 if ((arraysize = array_size(elemsize, nelem)) == SIZE_MAX) 74 return SIZE_MAX; 75 if (check_add_overflow(basesize, arraysize, &totalsize)) 76 return SIZE_MAX; 77 return totalsize; 78 } 79 80 #define struct_size(p, member, n) \ 81 ({ \ 82 CTASSERT(sizeof(*(p)) >= offsetof(__typeof__(*(p)), member)); \ 83 __struct_size(sizeof(*(p)), sizeof((p)->member[0]), (n)); \ 84 }) 85 86 #endif /* _LINUX_OVERFLOW_H_ */ 87