x86_64: Put allocated ELF notes in read-only data segment

This changes the x86_64 linker script to use the asm-generic NOTES macro so
that ELF note sections with SHF_ALLOC set are linked into the kernel image
along with other read-only data.  The PT_NOTE also points to their location.

This paves the way for putting useful build-time information into ELF notes
that can be found easily later in a kernel memory dump.

Signed-off-by: Roland McGrath <roland@redhat.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/x86_64/kernel/vmlinux.lds.S

@@ -48,7 +48,9 @@ SECTIONS
   __ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) { *(__ex_table) }
   __stop___ex_table = .;
 
-  BUG_TABLE
+  NOTES :text :note
+
+  BUG_TABLE :text
 
   RODATA