From ebc610fcb365dd0f62800ddbb9e1c4c9cc379a66 Mon Sep 17 00:00:00 2001
From: Miroslav Lichvar <mlichvar@redhat.com>
Date: Tue, 7 Dec 2021 11:32:54 +0100
Subject: [PATCH] sys_solaris: disable kernel dosynctodr

The dosynctodr kernel variable needs to be set to 0 to block automatic
synchronization of the system clock to the hardware clock. chronyd used
to disable dosynctodr on Solaris versions before 2.6, but it seems it is
now needed even on current versions as the clock driver sets frequency
only without calling adjtime() or setting the ntp_adjtime() PLL offset.

This issue was reproduced and fix tested on current OpenIndiana.

Fixes: 8feb37df2b48 ("sys_solaris: use timex driver")
---
 configure     |  2 +-
 sys_solaris.c | 31 +++++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/configure b/configure
index fad03fd..ac6939c 100755
--- a/configure
+++ b/configure
@@ -467,7 +467,7 @@ case $OPERATINGSYSTEM in
     ;;
     SunOS)
         EXTRA_OBJECTS="sys_generic.o sys_solaris.o sys_timex.o sys_posix.o"
-        LIBS="$LIBS -lsocket -lnsl -lresolv"
+        LIBS="$LIBS -lsocket -lnsl -lkvm -lelf -lresolv"
         try_setsched=1
         try_lockmem=1
         add_def SOLARIS
diff --git a/sys_solaris.c b/sys_solaris.c
index ba86c11..24949cb 100644
--- a/sys_solaris.c
+++ b/sys_solaris.c
@@ -28,16 +28,47 @@
 
 #include "sysincl.h"
 
+#include "logging.h"
 #include "privops.h"
 #include "sys_solaris.h"
 #include "sys_timex.h"
 #include "util.h"
 
+#include <kvm.h>
+#include <nlist.h>
+
+/* ================================================== */
+
+static void
+set_dosynctodr(int on_off)
+{
+  struct nlist nl[] = { {"dosynctodr"}, {NULL} };
+  kvm_t *kt;
+
+  kt = kvm_open(NULL, NULL, NULL, O_RDWR, NULL);
+  if (!kt)
+    LOG_FATAL("Could not open kvm");
+
+  if (kvm_nlist(kt, nl) < 0 || !nl[0].n_value)
+    LOG_FATAL("Could not get dosynctodr address");
+
+  if (kvm_kwrite(kt, nl[0].n_value, &on_off, sizeof (on_off)) < 0)
+    LOG_FATAL("Could not write to dosynctodr");
+
+  kvm_close(kt);
+}
+
 /* ================================================== */
 
 void
 SYS_Solaris_Initialise(void)
 {
+  /* The kernel keeps the system clock and hardware clock synchronised to each
+     other.  The dosynctodr variable needs to be set to zero to prevent the
+     the system clock from following the hardware clock when the system clock
+     is not adjusted by adjtime() or ntp_adjtime(modes=MOD_OFFSET). */
+  set_dosynctodr(0);
+
   /* The kernel allows the frequency to be set in the full range off int32_t */
   SYS_Timex_InitialiseWithFunctions(32500, 1.0 / 100, NULL, NULL, NULL,
                                     0.0, 0.0, NULL, NULL);