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#include <linux/module.h>
#include <linux/uaccess.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <asm/byteorder.h>
static inline long find_zero(unsigned long mask)
{
long byte = 0;
#ifdef __BIG_ENDIAN
#ifdef CONFIG_64BIT
if (mask >> 32)
mask >>= 32;
else
byte = 4;
#endif
if (mask >> 16)
mask >>= 16;
else
byte += 2;
return (mask >> 8) ? byte : byte + 1;
#else
#ifdef CONFIG_64BIT
if (!((unsigned int) mask)) {
mask >>= 32;
byte = 4;
}
#endif
if (!(mask & 0xffff)) {
mask >>= 16;
byte += 2;
}
return (mask & 0xff) ? byte : byte + 1;
#endif
}
#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 unsigned long high_bits = REPEAT_BYTE(0xfe) + 1;
const unsigned long low_bits = REPEAT_BYTE(0x7f);
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, v, rhs;
/* Fall back to byte-at-a-time if we get a page fault */
if (unlikely(__get_user(c,(unsigned long __user *)(src+res))))
break;
rhs = c | low_bits;
v = (c + high_bits) & ~rhs;
*(unsigned long *)(dst+res) = c;
if (v) {
v = (c & low_bits) + low_bits;
v = ~(v | rhs);
return res + find_zero(v);
}
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);
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