lib: Sparc's strncpy_from_user is generic enough, move under lib/

To use this, an architecture simply needs to:

1) Provide a user_addr_max() implementation via asm/uaccess.h

2) Add "select GENERIC_STRNCPY_FROM_USER" to their arch Kcnfig

3) Remove the existing strncpy_from_user() implementation and symbol
   exports their architecture had.

Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: David Howells <dhowells@redhat.com>

2 files changed, 1 insertions, 144 deletions

diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
index 051af37f2b49..22474233205b 100644
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -32,6 +32,7 @@ config SPARC
 	select HAVE_NMI_WATCHDOG if SPARC64
 	select HAVE_BPF_JIT
 	select GENERIC_SMP_IDLE_THREAD
+	select GENERIC_STRNCPY_FROM_USER
 
 config SPARC32
 	def_bool !64BIT
diff --git a/arch/sparc/lib/usercopy.c b/arch/sparc/lib/usercopy.c
index 0b12e91d6ccc..5c4284ce1c03 100644
--- a/arch/sparc/lib/usercopy.c
+++ b/arch/sparc/lib/usercopy.c
@@ -1,153 +1,9 @@
 #include <linux/module.h>
-#include <linux/uaccess.h>
 #include <linux/kernel.h>
-#include <linux/errno.h>
 #include <linux/bug.h>
 
-#include <asm/byteorder.h>
-
 void copy_from_user_overflow(void)
 {
 	WARN(1, "Buffer overflow detected!\n");
 }
 EXPORT_SYMBOL(copy_from_user_overflow);
-
-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);