csky: use generic strncpy/strnlen from_user

Remove the csky implemenation of strncpy/strnlen and instead use the
generic versions. The csky version is fairly slow because it always does
byte accesses even for aligned data, and it lacks a checks for
user_addr_max().

Reviewed-by: Christoph Hellwig <[e-mail]>
Signed-off-by: Arnd Bergmann <[e-mail]>

arch/csky/Kconfig

···
 	select GENERIC_IRQ_MULTI_HANDLER
 	select GENERIC_SCHED_CLOCK
 	select GENERIC_SMP_IDLE_THREAD
+	select GENERIC_STRNCPY_FROM_USER
+	select GENERIC_STRNLEN_USER
 	select GENERIC_TIME_VSYSCALL
 	select GENERIC_VDSO_32
 	select GENERIC_GETTIMEOFDAY

arch/csky/include/asm/uaccess.h

···
 unsigned long __clear_user(void __user *to, unsigned long n);
 #define __clear_user __clear_user
 
-long strncpy_from_user(char *dst, const char *src, long count);
-#define strncpy_from_user strncpy_from_user
-
-long strnlen_user(const char *s, long n);
-#define strnlen_user strnlen_user
-
 #include <asm/segment.h>
 #include <asm-generic/uaccess.h>
 

arch/csky/lib/usercopy.c

···
 EXPORT_SYMBOL(raw_copy_to_user);
 
 /*
- * __strncpy_from_user: - Copy a NUL terminated string from userspace,
- * with less checking.
- * @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.
- * Caller must check the specified block with access_ok() before calling
- * this function.
- *
- * 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 *src, long count)
-{
-	long res, faultres;
-	int tmp;
-
-	if (!access_ok(s, 1))
-		return -EFAULT;
-
-	__asm__ __volatile__(
-	"       cmpnei  %3, 0           \n"
-	"       bf      4f              \n"
-	"1:     cmpnei  %1, 0          	\n"
-	"       bf      5f              \n"
-	"2:     ldb     %4, (%3, 0)     \n"
-	"       stb     %4, (%2, 0)     \n"
-	"       cmpnei  %4, 0           \n"
-	"       bf      3f              \n"
-	"       addi    %3,  1          \n"
-	"       addi    %2,  1          \n"
-	"       subi    %1,  1          \n"
-	"       br      1b              \n"
-	"3:     subu	%0, %1          \n"
-	"       br      5f              \n"
-	"4:     mov     %0, %5          \n"
-	"       br      5f              \n"
-	".section __ex_table, \"a\"     \n"
-	".align   2                     \n"
-	".long    2b, 4b                \n"
-	".previous                      \n"
-	"5:                             \n"
-	: "=r"(res), "=r"(count), "=r"(dst),
-	  "=r"(src), "=r"(tmp), "=r"(faultres)
-	: "5"(-EFAULT), "0"(count), "1"(count),
-	  "2"(dst), "3"(src)
-	: "memory");
-
-	return res;
-}
-EXPORT_SYMBOL(strncpy_from_user);
-
-/*
- * strnlen_user: - Get the size of a string in user space.
- * @str: The string to measure.
- * @n:   The maximum valid length
- *
- * Get the size of a NUL-terminated string in user space.
- *
- * Returns the size of the string INCLUDING the terminating NUL.
- * On exception, returns 0.
- * If the string is too long, returns a value greater than @n.
- */
-long strnlen_user(const char *s, long n)
-{
-	unsigned long res, tmp;
-
-	if (!access_ok(s, 1))
-		return -EFAULT;
-
-	__asm__ __volatile__(
-	"       cmpnei  %1, 0           \n"
-	"       bf      3f              \n"
-	"1:     cmpnei  %0, 0           \n"
-	"       bf      3f              \n"
-	"2:     ldb     %3, (%1, 0)     \n"
-	"       cmpnei  %3, 0           \n"
-	"       bf      3f              \n"
-	"       subi    %0,  1          \n"
-	"       addi    %1,  1          \n"
-	"       br      1b              \n"
-	"3:     subu    %2, %0          \n"
-	"       addi    %2,  1          \n"
-	"       br      5f              \n"
-	"4:     movi    %0, 0           \n"
-	"       br      5f              \n"
-	".section __ex_table, \"a\"     \n"
-	".align   2                     \n"
-	".long    2b, 4b                \n"
-	".previous                      \n"
-	"5:                             \n"
-	: "=r"(n), "=r"(s), "=r"(res), "=r"(tmp)
-	: "0"(n), "1"(s), "2"(n)
-	: "memory");
-
-	return res;
-}
-EXPORT_SYMBOL(strnlen_user);
-
-/*
  * __clear_user: - Zero a block of memory in user space, with less checking.
  * @to:   Destination address, in user space.
  * @n:    Number of bytes to zero.