linux/arch/x86/boot/compressed/string.c

// SPDX-License-Identifier: GPL-2.0
/*
 * This provides an optimized implementation of memcpy, and a simplified
 * implementation of memset and memmove. These are used here because the
 * standard kernel runtime versions are not yet available and we don't
 * trust the gcc built-in implementations as they may do unexpected things
 * (e.g. FPU ops) in the minimal decompression stub execution environment.
 */
#include "error.h"

#include "../string.c"

#ifdef CONFIG_X86_32
static void *____memcpy(void *dest, const void *src, size_t n)
{
	int d0, d1, d2;
	asm volatile(
		"rep ; movsl\n\t"
		"movl %4,%%ecx\n\t"
		"rep ; movsb\n\t"
		: "=&c" (d0), "=&D" (d1), "=&S" (d2)
		: "0" (n >> 2), "g" (n & 3), "1" (dest), "2" (src)
		: "memory");

	return dest;
}
#else
static void *____memcpy(void *dest, const void *src, size_t n)
{ … }
#endif

void *memset(void *s, int c, size_t n)
{ … }

void *memmove(void *dest, const void *src, size_t n)
{ … }

/* Detect and warn about potential overlaps, but handle them with memmove. */
void *memcpy(void *dest, const void *src, size_t n)
{ … }

#ifdef CONFIG_KASAN
extern void *__memset(void *s, int c, size_t n) __alias(memset);
extern void *__memmove(void *dest, const void *src, size_t n) __alias(memmove);
extern void *__memcpy(void *dest, const void *src, size_t n) __alias(memcpy);
#endif