asm-generic: provide entirely generic nommu uaccess

Move the code to implement uaccess using memcpy or direct loads and
stores to asm-generic/uaccess.h and make it selectable kconfig option.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

1 files changed, 48 insertions, 0 deletions

diff --git a/include/asm-generic/uaccess.h b/include/asm-generic/uaccess.h
index aac336831204..3dcabfceb21e 100644
--- a/include/asm-generic/uaccess.h
+++ b/include/asm-generic/uaccess.h
@@ -9,6 +9,54 @@
  */
 #include <linux/string.h>
 
+#ifdef CONFIG_UACCESS_MEMCPY
+static inline __must_check unsigned long
+raw_copy_from_user(void *to, const void __user * from, unsigned long n)
+{
+	if (__builtin_constant_p(n)) {
+		switch(n) {
+		case 1:
+			*(u8 *)to = *(u8 __force *)from;
+			return 0;
+		case 2:
+			*(u16 *)to = *(u16 __force *)from;
+			return 0;
+		case 4:
+			*(u32 *)to = *(u32 __force *)from;
+			return 0;
+		}
+	}
+
+	memcpy(to, (const void __force *)from, n);
+	return 0;
+}
+
+static inline __must_check unsigned long
+raw_copy_to_user(void __user *to, const void *from, unsigned long n)
+{
+	if (__builtin_constant_p(n)) {
+		switch(n) {
+		case 1:
+			*(u8 __force *)to = *(u8 *)from;
+			return 0;
+		case 2:
+			*(u16 __force *)to = *(u16 *)from;
+			return 0;
+		case 4:
+			*(u32 __force *)to = *(u32 *)from;
+			return 0;
+		default:
+			break;
+		}
+	}
+
+	memcpy((void __force *)to, from, n);
+	return 0;
+}
+#define INLINE_COPY_FROM_USER
+#define INLINE_COPY_TO_USER
+#endif /* CONFIG_UACCESS_MEMCPY */
+
 #define MAKE_MM_SEG(s)	((mm_segment_t) { (s) })
 
 #ifndef KERNEL_DS