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>

arch/h8300/Kconfig

@@ -23,6 +23,7 @@ config H8300
 	select HAVE_ARCH_KGDB
 	select HAVE_ARCH_HASH
 	select CPU_NO_EFFICIENT_FFS
+	select UACCESS_MEMCPY
 
 config CPU_BIG_ENDIAN
 	def_bool y

arch/h8300/include/asm/Kbuild

@@ -46,6 +46,7 @@ generic-y += timex.h
 generic-y += tlbflush.h
 generic-y += topology.h
 generic-y += trace_clock.h
+generic-y += uaccess.h
 generic-y += unaligned.h
 generic-y += vga.h
 generic-y += word-at-a-time.h

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

lib/Kconfig

@@ -591,6 +591,10 @@ config ARCH_NO_SG_CHAIN
 config ARCH_HAS_PMEM_API
 	bool
 
+# use memcpy to implement user copies for nommu architectures
+config UACCESS_MEMCPY
+	bool
+
 config ARCH_HAS_UACCESS_FLUSHCACHE
 	bool