speculation.h

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/*
 * Copyright (c) 2019 Intel Corporation.
 *
 * SPDX-License-Identifier: Apache-2.0
 */
 
#ifndef ZEPHYR_MISC_SPECULATION_H
#define ZEPHYR_MISC_SPECULATION_H
 
#include <zephyr/types.h>
 
static inline uint32_t k_array_index_sanitize(uint32_t index, uint32_t array_size)
{
#ifdef CONFIG_BOUNDS_CHECK_BYPASS_MITIGATION
        int32_t signed_index = index, signed_array_size = array_size;
 
        /* Take the difference between index and max.
         * A proper value will result in a negative result. We also AND in
         * the complement of index, so that we automatically reject any large
         * indexes which would wrap around the difference calculation.
         *
         * Sign-extend just the sign bit to produce a mask of all 1s (accept)
         * or all 0s (truncate).
         */
        uint32_t mask = ((signed_index - signed_array_size) & ~signed_index) >> 31;
 
        return index & mask;
#else
        ARG_UNUSED(array_size);
 
        return index;
#endif /* CONFIG_BOUNDS_CHECK_BYPASS_MITIGATION */
}
#endif /* ZEPHYR_MISC_SPECULATION_H */