sdk/lib/freestanding/memcpy.c

/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1990, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Chris Torek.
 *
 * 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.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
 */
/*
 * CHERI CHANGES START
 * {
 *   "updated": 20181121,
 *   "target_type": "lib",
 *   "changes": [
 *     "integer_provenance"
 *   ]
 * }
 * CHERI CHANGES END
 */

#include <cdefs.h>
#include <stddef.h>
#include <string.h>

typedef void *word;

#define wsize sizeof(word)
_Static_assert(wsize != 0);
_Static_assert((wsize & (wsize - 1)) == 0);

#define wmask (wsize - 1)

void *memcpy(void *dst0, const void *src0, size_t length)
{
	char *      dst = dst0;
	const char *src = src0;
	size_t      t;

	if (length == 0 || dst == src)
		goto done;

		// Macros: loop-t-times; and loop-t-times, t>0.
#define TLOOP(s)                                                               \
	if (t)                                                                     \
	TLOOP1(s)
#define TLOOP1(s)                                                              \
	do                                                                         \
	{                                                                          \
		s;                                                                     \
	} while (--t)

	if (dst < src)
	{
		t = (__cheri_addr size_t)src;
		if ((t | (__cheri_addr size_t)dst) & wmask)
		{
			// Try to align operands.  This cannot be done unless the low bits
			// match.
			if ((t ^ (__cheri_addr size_t)dst) & wmask || length < wsize)
				t = length;
			else
				t = wsize - (t & wmask);
			length -= t;
			TLOOP1(*dst++ = *src++);
		}
		// Copy whole words, then mop up any trailing bytes.
		t = length / wsize;
		TLOOP(*(word *)dst = *(const word *)src; src += wsize; dst += wsize);
		t = length & wmask;
		TLOOP(*dst++ = *src++);
	}
	else
	{
		// Copy backwards. Otherwise essentially the same.
		// Alignment works as before, except that it takes (t&wmask) bytes to
		// align, not wsize-(t&wmask).
		src += length;
		dst += length;
		t = (__cheri_addr size_t)src;
		if ((t | (__cheri_addr size_t)dst) & wmask)
		{
			if ((t ^ (__cheri_addr size_t)dst) & wmask || length <= wsize)
				t = length;
			else
				t &= wmask;
			length -= t;
			TLOOP1(*--dst = *--src);
		}
		t = length / wsize;
		TLOOP(src -= wsize; dst -= wsize; *(word *)dst = *(const word *)src);
		t = length & wmask;
		TLOOP(*--dst = *--src);
	}
done:
	return (dst0);
}

void *memmove(void *dst0, const void *src0, size_t length)
{
	return memcpy(dst0, src0, length);
}