v4.19.13 snapshot.
diff --git a/fs/proc/uptime.c b/fs/proc/uptime.c
new file mode 100644
index 0000000..a4c2791
--- /dev/null
+++ b/fs/proc/uptime.c
@@ -0,0 +1,38 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/proc_fs.h>
+#include <linux/sched.h>
+#include <linux/seq_file.h>
+#include <linux/time.h>
+#include <linux/kernel_stat.h>
+
+static int uptime_proc_show(struct seq_file *m, void *v)
+{
+ struct timespec64 uptime;
+ struct timespec64 idle;
+ u64 nsec;
+ u32 rem;
+ int i;
+
+ nsec = 0;
+ for_each_possible_cpu(i)
+ nsec += (__force u64) kcpustat_cpu(i).cpustat[CPUTIME_IDLE];
+
+ ktime_get_boottime_ts64(&uptime);
+ idle.tv_sec = div_u64_rem(nsec, NSEC_PER_SEC, &rem);
+ idle.tv_nsec = rem;
+ seq_printf(m, "%lu.%02lu %lu.%02lu\n",
+ (unsigned long) uptime.tv_sec,
+ (uptime.tv_nsec / (NSEC_PER_SEC / 100)),
+ (unsigned long) idle.tv_sec,
+ (idle.tv_nsec / (NSEC_PER_SEC / 100)));
+ return 0;
+}
+
+static int __init proc_uptime_init(void)
+{
+ proc_create_single("uptime", 0, NULL, uptime_proc_show);
+ return 0;
+}
+fs_initcall(proc_uptime_init);