[uaccess] Add memcmp_user()

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/arch/i386/include/librm.h

 	trivial_memmove_user ( dest, dest_off, src, src_off, len );
 }
 
+static inline __always_inline int
+UACCESS_INLINE ( librm, memcmp_user ) ( userptr_t first, off_t first_off,
+					userptr_t second, off_t second_off,
+					size_t len ) {
+	return trivial_memcmp_user ( first, first_off, second, second_off, len);
+}
+
 static inline __always_inline void
 UACCESS_INLINE ( librm, memset_user ) ( userptr_t buffer, off_t offset,
 					int c, size_t len ) {

src/include/ipxe/efi/efi_uaccess.h

 	trivial_memmove_user ( dest, dest_off, src, src_off, len );
 }
 
+static inline __always_inline int
+UACCESS_INLINE ( efi, memcmp_user ) ( userptr_t first, off_t first_off,
+				      userptr_t second, off_t second_off,
+				      size_t len ) {
+	return trivial_memcmp_user ( first, first_off, second, second_off, len);
+}
+
 static inline __always_inline void
 UACCESS_INLINE ( efi, memset_user ) ( userptr_t buffer, off_t offset,
 					int c, size_t len ) {

src/include/ipxe/linux/linux_uaccess.h

 	trivial_memmove_user(dest, dest_off, src, src_off, len);
 }
 
+static inline __always_inline int
+UACCESS_INLINE(linux, memcmp_user)(userptr_t first, off_t first_off, userptr_t second, off_t second_off, size_t len)
+{
+	return trivial_memcmp_user(first, first_off, second, second_off, len);
+}
+
 static inline __always_inline void
 UACCESS_INLINE(linux, memset_user)(userptr_t buffer, off_t offset, int c, size_t len)
 {

src/include/ipxe/uaccess.h

 		  ( ( void * ) src + src_off ), len );
 }
 
+/**
+ * Compare data between user buffers
+ *
+ * @v first		First buffer
+ * @v first_off		First buffer offset
+ * @v second		Second buffer
+ * @v second_off	Second buffer offset
+ * @v len		Length
+ * @ret diff		Difference
+ */
+static inline __always_inline int
+trivial_memcmp_user ( userptr_t first, off_t first_off,
+		      userptr_t second, off_t second_off, size_t len ) {
+	return memcmp ( ( ( void * ) first + first_off ),
+			( ( void * ) second + second_off ), len );
+}
+
 /**
  * Fill user buffer with a constant byte
  *
 void memmove_user ( userptr_t dest, off_t dest_off,
 		    userptr_t src, off_t src_off, size_t len );
 
+/**
+ * Compare data between user buffers
+ *
+ * @v first		First buffer
+ * @v first_off		First buffer offset
+ * @v second		Second buffer
+ * @v second_off	Second buffer offset
+ * @v len		Length
+ * @ret diff		Difference
+ */
+int memcmp_user ( userptr_t first, off_t first_off,
+		  userptr_t second, off_t second_off, size_t len );
+
 /**
  * Fill user buffer with a constant byte
  *