s390/string: provide asm lib functions for memcpy and memcmp

Our memcpy and memcmp variants were implemented by calling the corresponding
gcc builtin variants.
However gcc is free to replace a call to __builtin_memcmp with a call to memcmp
which, when called, will result in an endless recursion within memcmp.
So let's provide asm variants and also fix the variants that are used for
uncompressing the kernel image.
In addition remove all other occurences of builtin function calls.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/lib/string.c

@@ -43,11 +43,7 @@ static inline char *__strnend(const char *s, size_t n)
  */
 size_t strlen(const char *s)
 {
-#if __GNUC__ < 4
 	return __strend(s) - s;
-#else
-	return __builtin_strlen(s);
-#endif
 }
 EXPORT_SYMBOL(strlen);
 
@@ -73,7 +69,6 @@ EXPORT_SYMBOL(strnlen);
  */
 char *strcpy(char *dest, const char *src)
 {
-#if __GNUC__ < 4
 	register int r0 asm("0") = 0;
 	char *ret = dest;
 
@@ -82,9 +77,6 @@ char *strcpy(char *dest, const char *src)
 		      : "+&a" (dest), "+&a" (src) : "d" (r0)
 		      : "cc", "memory" );
 	return ret;
-#else
-	return __builtin_strcpy(dest, src);
-#endif
 }
 EXPORT_SYMBOL(strcpy);
 
@@ -106,7 +98,7 @@ size_t strlcpy(char *dest, const char *src, size_t size)
 	if (size) {
 		size_t len = (ret >= size) ? size-1 : ret;
 		dest[len] = '\0';
-		__builtin_memcpy(dest, src, len);
+		memcpy(dest, src, len);
 	}
 	return ret;
 }
@@ -124,8 +116,8 @@ EXPORT_SYMBOL(strlcpy);
 char *strncpy(char *dest, const char *src, size_t n)
 {
 	size_t len = __strnend(src, n) - src;
-	__builtin_memset(dest + len, 0, n - len);
-	__builtin_memcpy(dest, src, len);
+	memset(dest + len, 0, n - len);
+	memcpy(dest, src, len);
 	return dest;
 }
 EXPORT_SYMBOL(strncpy);
@@ -171,7 +163,7 @@ size_t strlcat(char *dest, const char *src, size_t n)
 		if (len >= n)
 			len = n - 1;
 		dest[len] = '\0';
-		__builtin_memcpy(dest, src, len);
+		memcpy(dest, src, len);
 	}
 	return res;
 }
@@ -194,7 +186,7 @@ char *strncat(char *dest, const char *src, size_t n)
 	char *p = __strend(dest);
 
 	p[len] = '\0';
-	__builtin_memcpy(p, src, len);
+	memcpy(p, src, len);
 	return dest;
 }
 EXPORT_SYMBOL(strncat);
@@ -348,41 +340,3 @@ void *memscan(void *s, int c, size_t n)
 	return (void *) ret;
 }
 EXPORT_SYMBOL(memscan);
-
-/**
- * memcpy - Copy one area of memory to another
- * @dest: Where to copy to
- * @src: Where to copy from
- * @n: The size of the area.
- *
- * returns a pointer to @dest
- */
-void *memcpy(void *dest, const void *src, size_t n)
-{
-	return __builtin_memcpy(dest, src, n);
-}
-EXPORT_SYMBOL(memcpy);
-
-/**
- * memset - Fill a region of memory with the given value
- * @s: Pointer to the start of the area.
- * @c: The byte to fill the area with
- * @n: The size of the area.
- *
- * returns a pointer to @s
- */
-void *memset(void *s, int c, size_t n)
-{
-	char *xs;
-
-	if (c == 0)
-		return __builtin_memset(s, 0, n);
-
-	xs = (char *) s;
-	if (n > 0)
-		do {
-			*xs++ = c;
-		} while (--n > 0);
-	return s;
-}
-EXPORT_SYMBOL(memset);