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/* $NetBSD: overflow.h,v 1.2 2021/12/19 12:20:53 riastradh Exp $ */
/*-
* Copyright (c) 2018 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Taylor R. Campbell.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef _LINUX_OVERFLOW_H_
#define _LINUX_OVERFLOW_H_
#include <sys/types.h>
#include <lib/libkern/libkern.h> /* offsetof */
#define check_mul_overflow(a, b, res) __builtin_mul_overflow(a, b, res)
#define check_add_overflow(a, b, res) __builtin_add_overflow(a, b, res)
/* return x*y saturated at SIZE_MAX */
static inline size_t
array_size(size_t x, size_t y)
{
size_t xy;
if (check_mul_overflow(x, y, &xy))
return SIZE_MAX;
return xy;
}
/* return x*y*z saturated at SIZE_MAX */
static inline size_t
array3_size(size_t x, size_t y, size_t z)
{
size_t xy, xyz;
if (check_mul_overflow(x, y, &xy))
return SIZE_MAX;
if (check_mul_overflow(xy, z, &xyz))
return SIZE_MAX;
return xyz;
}
/* return basesize + elemsize*nelem saturated at SIZE_MAX */
static inline size_t
__struct_size(size_t basesize, size_t elemsize, size_t nelem)
{
size_t arraysize, totalsize;
KASSERT(elemsize);
if ((arraysize = array_size(elemsize, nelem)) == SIZE_MAX)
return SIZE_MAX;
if (check_add_overflow(basesize, arraysize, &totalsize))
return SIZE_MAX;
return totalsize;
}
#define struct_size(p, member, n) \
({ \
CTASSERT(sizeof(*(p)) >= offsetof(__typeof__(*(p)), member)); \
__struct_size(sizeof(*(p)), sizeof((p)->member[0]), (n)); \
})
#endif /* _LINUX_OVERFLOW_H_ */
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