coredump: Use 64bit time for unix time of coredump

struct timeval on 32-bit systems will have its tv_sec
value overflow in year 2038 and beyond.
Use a 64 bit value to print time of the coredump in seconds.
ktime_get_real_seconds is chosen here for efficiency reasons.

Suggested by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Tina Ruchandani <ruchandani.tina@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/coredump.c

@@ -32,6 +32,7 @@
 #include <linux/pipe_fs_i.h>
 #include <linux/oom.h>
 #include <linux/compat.h>
+#include <linux/timekeeping.h>
 
 #include <asm/uaccess.h>
 #include <asm/mmu_context.h>
@@ -232,9 +233,10 @@ static int format_corename(struct core_name *cn, struct coredump_params *cprm)
 				break;
 			/* UNIX time of coredump */
 			case 't': {
-				struct timeval tv;
-				do_gettimeofday(&tv);
-				err = cn_printf(cn, "%lu", tv.tv_sec);
+				time64_t time;
+
+				time = ktime_get_real_seconds();
+				err = cn_printf(cn, "%lld", time);
 				break;
 			}
 			/* hostname */