infix/package/finit/0004-Fix-418-support-systems-with-a-broken-RTC.patch

From bc8118d515839dc598f437aa01f07a771646968d Mon Sep 17 00:00:00 2001
From: Joachim Wiberg <troglobit@gmail.com>
Date: Sun, 3 Nov 2024 09:47:16 +0100
Subject: [PATCH 4/6] Fix #418: support systems with a broken RTC
Organization: Addiva Elektronik

This patch introduces a new configure option --with-rtc-file=FILE.  When
enabled the RTC plugin detects missing RTC device and falls back to save
and restore system time from a file instead.  When --with-rtc-file is
used without an argument the default file is /var/lib/misc/rtc, but the
feature itself is disabled by default.

The usefulness of this feature may not be obvious at first, but some
systems are equipped with an RTC that resets to a random date at power
on.  This can be really bad in the case the date is far in the future,
because an NTP sync would then cause time skips backwards, which shows
up in logs and causes a whole lot of pain in alarm systems.

The solution is to disable the RTC driver or device tree node, and when
Finit starts up, the RTC plugin detects a the device node and instead
restores time from the last save game.  Meaning time will always only
move forwards.

NOTE: when Finit is built --with-rtc-file we always save to disk, but
      only restore from the "save game" if restoring from RTC fails.
      If the system has no RTC we always restore from disk.

      As an added bonus, this change also makes sure to periodically
      sync also the RTC with the system clock.  Useful for systems
      that do not run an NTP client.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
---
 configure.ac  |  12 ++++++
 plugins/rtc.c | 105 ++++++++++++++++++++++++++++++++++++++++++++++----
 2 files changed, 110 insertions(+), 7 deletions(-)

diff --git a/configure.ac b/configure.ac
index 483457f..ae7cd23 100644
--- a/configure.ac
+++ b/configure.ac
@@ -180,6 +180,10 @@ AC_ARG_WITH(rtc-date,
 	AS_HELP_STRING([--with-rtc-date=DATE], [If RTC date/time is too old, restore to DATE, format "YYYY-MM-DD HH:MM", default "2000-01-01 00:00"]),
 	[rtc_date=$withval], [rtc_date=no])
 
+AC_ARG_WITH(rtc-file,
+        AS_HELP_STRING([--with-rtc-file=FILE], [If RTC is missing, save and restore system clock from this file, default: no]),
+	[rtc_file=$withval], [rtc_file=no])
+
 ### Enable features ###########################################################################
 
 # Create config.h from selected features and fallback defaults
@@ -281,6 +285,13 @@ AS_IF([test "x$rtc_date" != "xno"], [
 	AC_DEFINE(RTC_TIMESTAMP_CUSTOM, "$rtc_date", [Custom RTC restore date, default: 2000-01-01 00:00])], [
 	rtc_date=""])
 
+AS_IF([test "x$rtc_file" != "xno"], [
+	AS_IF([test "x$rtc_file" = "xyes"], [
+		rtc_file=/var/lib/misc/rtc])
+	AC_EXPAND_DIR(rtcfile_path, "$rtc_file")
+	AC_DEFINE_UNQUOTED(RTC_FILE, "$rtcfile_path", [Save and restore system time from this file if /dev/rtc is missing.])],[
+	AC_DEFINE_UNQUOTED(RTC_FILE, NULL)])
+
 AS_IF([test "x$with_keventd" != "xno"], [with_keventd=yes])
 
 AS_IF([test "x$with_sulogin" != "xno"], [
@@ -387,6 +398,7 @@ Behavior:
   Boot heading..........: $heading
   Plugins...............: $plugins
   RTC restore date......: $RTC_DATE
+  RTC fallback file.....: $rtc_file
 
 Optional features:
   Install doc/..........: $enable_doc
diff --git a/plugins/rtc.c b/plugins/rtc.c
index 9520c7d..9b4eeae 100644
--- a/plugins/rtc.c
+++ b/plugins/rtc.c
@@ -36,8 +36,15 @@
 #include "helpers.h"
 #include "plugin.h"
 
-/* Kernel RTC driver validates against this date for sanity check */
+/*
+ * Kernel RTC driver validates against this date for sanity check.  The
+ * on NTP sync the driver can also update the RTC every 11 mins.  We use
+ * the same update interval to handle manual time set and file save.
+ */
 #define RTC_TIMESTAMP_BEGIN_2000 "2000-01-01 00:00:00"
+#define RTC_FMT                  "%Y-%m-%d %H:%M:%S"
+#define RTC_PERIOD               (11 * 60 * 1000)
+
 #ifdef  RTC_TIMESTAMP_CUSTOM
 static char  *rtc_timestamp     = RTC_TIMESTAMP_CUSTOM;
 #else
@@ -45,6 +52,10 @@ static char  *rtc_timestamp     = RTC_TIMESTAMP_BEGIN_2000;
 #endif
 static time_t rtc_date_fallback = 946684800LL;
 
+static char  *rtc_file          = RTC_FILE;
+static uev_t  rtc_timer;
+
+
 static void tz_set(char *tz, size_t len)
 {
 	char *ptr;
@@ -122,6 +133,68 @@ static int time_get(struct tm *tm)
 	return rc;
 }
 
+static void file_save(void *arg)
+{
+	struct tm tm = { 0 };
+	int rc = 0;
+	FILE *fp;
+
+	fp = fopen(rtc_file, "w");
+	if (!fp) {
+		logit(LOG_WARNING, "Failed saving system clock to %s, code %d: %s",
+		      rtc_file, errno, strerror(errno));
+		return;
+	}
+
+	if ((rc = time_get(&tm))) {
+		logit(LOG_ERR, "System clock invalid, before %s, not saving", rtc_timestamp);
+		print_desc(NULL, "System clock invalid, skipping");
+	} else {
+		char buf[32] = { 0 };
+
+		print_desc(NULL, "Saving system clock to file");
+		strftime(buf, sizeof(buf), RTC_FMT, &tm);
+		fprintf(fp, "%s\n", buf);
+	}
+
+	print(rc, NULL);
+	fclose(fp);
+}
+
+static void file_restore(void *arg)
+{
+	struct tm tm = { 0 };
+	int rc = 1;
+	FILE *fp;
+
+	if (!rtc_file) {
+		logit(LOG_NOTICE, "System has no RTC (missing driver?), skipping restore.");
+		return;
+	}
+
+	print_desc(NULL, "Restoring system clock from backup");
+
+	fp = fopen(rtc_file, "r");
+	if (fp) {
+		char buf[32];
+
+		if (fgets(buf, sizeof(buf), fp)) {
+			chomp(buf);
+			strptime(buf, RTC_FMT, &tm);
+			rc = time_set(&tm);
+		}
+		fclose(fp);
+	} else
+		logit(LOG_WARNING, "Missing %s", rtc_file);
+
+	if (rc) {
+		time_set(NULL);
+		rc = 2;
+	}
+
+	print(rc, NULL);
+}
+
 static int rtc_open(void)
 {
 	char *alt[] = {
@@ -185,7 +258,7 @@ static void rtc_restore(void *arg)
 
 	fd = rtc_open();
 	if (fd < 0) {
-		logit(LOG_NOTICE, "System has no RTC (missing driver?), skipping restore.");
+		file_restore(arg);
 		return;
 	}
 
@@ -210,21 +283,37 @@ static void rtc_restore(void *arg)
 		else
 			logit(LOG_ERR, "RTC error code %d: %s", errno, strerror(errno));
 
-		time_set(NULL);
-		rc = 2;
-	}
+		print(2, NULL);
+
+		/* Try restoring from last save game */
+		if (rtc_file)
+			file_restore(arg);
+	} else
+		print(0, NULL);
 
-	print(rc, NULL);
 	close(fd);
 }
 
+
+static void save(void *arg)
+{
+	rtc_save(arg);
+	file_save(arg);
+}
+
+static void update(uev_t *w, void *arg, int events)
+{
+	save(arg);
+}
+
+
 static plugin_t plugin = {
 	.name = __FILE__,
 	.hook[HOOK_BASEFS_UP] = {
 		.cb  = rtc_restore
 	},
 	.hook[HOOK_SHUTDOWN] = {
-		.cb  = rtc_save
+		.cb  = save
 	}
 };
 
@@ -237,6 +326,8 @@ PLUGIN_INIT(plugin_init)
 	else
 		rtc_timestamp = RTC_TIMESTAMP_BEGIN_2000;
 
+	uev_timer_init(ctx, &rtc_timer, update, NULL, RTC_PERIOD, RTC_PERIOD);
+
 	plugin_register(&plugin);
 }
 
-- 
2.43.0