#include <linux/module.h>#include <linux/uaccess.h>#include <linux/kernel.h>#include <linux/errno.h> #include <asm/byteorder.h>#include <asm/word-at-a-time.h> #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS#define IS_UNALIGNED(src, dst)	0#else#define IS_UNALIGNED(src, dst)	\	(((long) dst | (long) src) & (sizeof(long) - 1))#endif /* * Do a strncpy, return length of string without final '\0'. * 'count' is the user-supplied count (return 'count' if we * hit it), 'max' is the address space maximum (and we return * -EFAULT if we hit it). */static inline long do_strncpy_from_user(char *dst, const char __user *src, long count, unsigned long max){	const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;	long res = 0; 	/*	 * Truncate 'max' to the user-specified limit, so that	 * we only have one limit we need to check in the loop	 */	if (max > count)		max = count; 	if (IS_UNALIGNED(src, dst))		goto byte_at_a_time; 	while (max >= sizeof(unsigned long)) {		unsigned long c, data; 		/* Fall back to byte-at-a-time if we get a page fault */		if (unlikely(__get_user(c,(unsigned long __user *)(src+res))))			break;		*(unsigned long *)(dst+res) = c;		if (has_zero(c, &data, &constants)) {			data = prep_zero_mask(c, data, &constants);			data = create_zero_mask(data);			return res + find_zero(data);		}		res += sizeof(unsigned long);		max -= sizeof(unsigned long);	} byte_at_a_time:	while (max) {		char c; 		if (unlikely(__get_user(c,src+res)))			return -EFAULT;		dst[res] = c;		if (!c)			return res;		res++;		max--;	} 	/*	 * Uhhuh. We hit 'max'. But was that the user-specified maximum	 * too? If so, that's ok - we got as much as the user asked for.	 */	if (res >= count)		return res; 	/*	 * Nope: we hit the address space limit, and we still had more	 * characters the caller would have wanted. That's an EFAULT.	 */	return -EFAULT;} /** * strncpy_from_user: - Copy a NUL terminated string from userspace. * @dst:   Destination address, in kernel space.  This buffer must be at *         least @count bytes long. * @src:   Source address, in user space. * @count: Maximum number of bytes to copy, including the trailing NUL. * * Copies a NUL-terminated string from userspace to kernel space. * * On success, returns the length of the string (not including the trailing * NUL). * * If access to userspace fails, returns -EFAULT (some data may have been * copied). * * If @count is smaller than the length of the string, copies @count bytes * and returns @count. */long strncpy_from_user(char *dst, const char __user *src, long count){	unsigned long max_addr, src_addr; 	if (unlikely(count <= 0))		return 0; 	max_addr = user_addr_max();	src_addr = (unsigned long)src;	if (likely(src_addr < max_addr)) {		unsigned long max = max_addr - src_addr;		return do_strncpy_from_user(dst, src, count, max);	}	return -EFAULT;}EXPORT_SYMBOL(strncpy_from_user);