x86: introduce ELFNOTE macro

It is needed later for introducing PVH entry point.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>

xen/include/asm-x86/asm_defns.h

@@ -374,4 +374,16 @@ static always_inline void stac(void)
 #define REX64_PREFIX "rex64/"
 #endif
 
+#define ELFNOTE(name, type, desc)           \
+    .pushsection .note.name, "a", @note   ; \
+    .p2align 2                            ; \
+    .long 2f - 1f       /* namesz */      ; \
+    .long 4f - 3f       /* descsz */      ; \
+    .long type          /* type   */      ; \
+1:  .asciz #name        /* name   */      ; \
+2:  .p2align 2                            ; \
+3:  desc                /* desc   */      ; \
+4:  .p2align 2                            ; \
+    .popsection
+
 #endif /* __X86_ASM_DEFNS_H__ */