s390/uaccess: Make s390_kernel_write() usable for decompressor

To avoid lots of ifdefs in C code make s390_kernel_write() usable for
the decompressor: simply use memcpy() for this case since there is no
write protection enabled that early.
Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Tested-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/include/asm/uaccess.h

@@ -332,7 +332,14 @@ static inline unsigned long __must_check clear_user(void __user *to, unsigned lo
 	return __clear_user(to, n);
 }
 
-void *s390_kernel_write(void *dst, const void *src, size_t size);
+void *__s390_kernel_write(void *dst, const void *src, size_t size);
+
+static inline void *s390_kernel_write(void *dst, const void *src, size_t size)
+{
+	if (__is_defined(__DECOMPRESSOR))
+		return memcpy(dst, src, size);
+	return __s390_kernel_write(dst, src, size);
+}
 
 int __noreturn __put_kernel_bad(void);
 

arch/s390/mm/maccess.c

@@ -48,7 +48,7 @@ static notrace long s390_kernel_write_odd(void *dst, const void *src, size_t siz
 }
 
 /*
- * s390_kernel_write - write to kernel memory bypassing DAT
+ * __s390_kernel_write - write to kernel memory bypassing DAT
  * @dst: destination address
  * @src: source address
  * @size: number of bytes to copy
@@ -61,7 +61,7 @@ static notrace long s390_kernel_write_odd(void *dst, const void *src, size_t siz
  */
 static DEFINE_SPINLOCK(s390_kernel_write_lock);
 
-notrace void *s390_kernel_write(void *dst, const void *src, size_t size)
+notrace void *__s390_kernel_write(void *dst, const void *src, size_t size)
 {
 	void *tmp = dst;
 	unsigned long flags;