gcov: support GCC 7.1

Starting from GCC 7.1, __gcov_exit is a new symbol expected to be
implemented in a profiling runtime.

[akpm@linux-foundation.org: coding-style fixes]
[mliska@suse.cz: v2]
  Link: http://lkml.kernel.org/r/e63a3c59-0149-c97e-4084-20ca8f146b26@suse.cz
Link: http://lkml.kernel.org/r/8c4084fa-3885-29fe-5fc4-0d4ca199c785@suse.czSigned-off-by: Martin Liska <mliska@suse.cz>
Acked-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/gcov/base.c

@@ -98,6 +98,12 @@ void __gcov_merge_icall_topn(gcov_type *counters, unsigned int n_counters)
 }
 EXPORT_SYMBOL(__gcov_merge_icall_topn);
 
+void __gcov_exit(void)
+{
+	/* Unused. */
+}
+EXPORT_SYMBOL(__gcov_exit);
+
 /**
  * gcov_enable_events - enable event reporting through gcov_event()
  *

kernel/gcov/gcc_4_7.c

@@ -18,7 +18,9 @@
 #include <linux/vmalloc.h>
 #include "gcov.h"
 
-#if (__GNUC__ > 5) || (__GNUC__ == 5 && __GNUC_MINOR__ >= 1)
+#if (__GNUC__ >= 7)
+#define GCOV_COUNTERS			9
+#elif (__GNUC__ > 5) || (__GNUC__ == 5 && __GNUC_MINOR__ >= 1)
 #define GCOV_COUNTERS			10
 #elif __GNUC__ == 4 && __GNUC_MINOR__ >= 9
 #define GCOV_COUNTERS			9