tools: add access macros for unaligned data

Add the basic access macros for unaligned data to common-macros.h.

Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Anthony PERARD <anthony.perard@citrix.com>

tools/include/xen-tools/common-macros.h

@@ -79,6 +79,10 @@
 #define __must_check __attribute__((__warn_unused_result__))
 #endif
 
+#ifndef __packed
+#define __packed __attribute__((__packed__))
+#endif
+
 #define container_of(ptr, type, member) ({              \
     typeof(((type *)0)->member) *mptr__ = (ptr);        \
     (type *)((char *)mptr__ - offsetof(type, member));  \
@@ -87,4 +91,17 @@
 #define __AC(X, Y)   (X ## Y)
 #define _AC(X, Y)    __AC(X, Y)
 
+#define get_unaligned_t(type, ptr) ({                               \
+    const struct { type x; } __packed *ptr_ = (typeof(ptr_))(ptr);  \
+    ptr_->x;                                                        \
+})
+
+#define put_unaligned_t(type, val, ptr) do {                        \
+    struct { type x; } __packed *ptr_ = (typeof(ptr_))(ptr);        \
+    ptr_->x = val;                                                  \
+} while (0)
+
+#define get_unaligned(ptr)      get_unaligned_t(typeof(*(ptr)), ptr)
+#define put_unaligned(val, ptr) put_unaligned_t(typeof(*(ptr)), val, ptr)
+
 #endif	/* __XEN_TOOLS_COMMON_MACROS__ */