perf/x86: Annotate struct bts_buffer::buf with __counted_by()

Add the __counted_by() compiler attribute to the flexible array member
buf to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and
CONFIG_FORTIFY_SOURCE.

No functional changes intended.

Signed-off-by: Thorsten Blum <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: toblux

arch/x86/events/intel/bts.c

@@ -58,7 +58,7 @@ struct bts_buffer {
 	local_t		head;
 	unsigned long	end;
 	void		**data_pages;
-	struct bts_phys	buf[];
+	struct bts_phys	buf[] __counted_by(nr_bufs);
 };
 
 static struct pmu bts_pmu;