commit 5361ad3910c257bc327567be76fde532ed238e42
Author: Florian Weimer <fweimer@redhat.com>
Date:   Fri Apr 19 14:38:17 2024 +0200

    login: Use unsigned 32-bit types for seconds-since-epoch
    
    These fields store timestamps when the system was running.  No Linux
    systems existed before 1970, so these values are unused.  Switching
    to unsigned types allows continued use of the existing struct layouts
    beyond the year 2038.
    
    The intent is to give distributions more time to switch to improved
    interfaces that also avoid locking/data corruption issues.
    
    Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

diff --git a/bits/utmp.h b/bits/utmp.h
index f2d1c13d8cd205b2..27cb536800c46d67 100644
--- a/bits/utmp.h
+++ b/bits/utmp.h
@@ -36,7 +36,7 @@
 struct lastlog
   {
 #if __WORDSIZE_TIME64_COMPAT32
-    int32_t ll_time;
+    __uint32_t ll_time;
 #else
     __time_t ll_time;
 #endif
@@ -76,7 +76,7 @@ struct utmp
   int32_t ut_session;		/* Session ID, used for windowing.  */
   struct
   {
-    int32_t tv_sec;		/* Seconds.  */
+    __uint32_t tv_sec;		/* Seconds.  */
     int32_t tv_usec;		/* Microseconds.  */
   } ut_tv;			/* Time entry was made.  */
 #else
diff --git a/login/Makefile b/login/Makefile
index f91190e3dcd1e6c6..84563230ef665f9c 100644
--- a/login/Makefile
+++ b/login/Makefile
@@ -44,9 +44,11 @@ subdir-dirs = programs
 vpath %.c programs
 
 tests := tst-utmp tst-utmpx tst-grantpt tst-ptsname tst-getlogin tst-updwtmpx \
-  tst-pututxline-lockfail tst-pututxline-cache tst-utmp-size tst-utmp-size-64
+  tst-pututxline-lockfail tst-pututxline-cache tst-utmp-size tst-utmp-size-64 \
+  tst-utmp-unsigned tst-utmp-unsigned-64
 
 CFLAGS-tst-utmp-size-64.c += -D_FILE_OFFSET_BITS=64 -D_TIME_BITS=64
+CFLAGS-tst-utmp-unsigned-64.c += -D_FILE_OFFSET_BITS=64 -D_TIME_BITS=64
 
 # Empty compatibility library for old binaries.
 extra-libs      := libutil
diff --git a/login/tst-utmp-unsigned-64.c b/login/tst-utmp-unsigned-64.c
new file mode 100644
index 0000000000000000..940e7654f8dc5fd6
--- /dev/null
+++ b/login/tst-utmp-unsigned-64.c
@@ -0,0 +1 @@
+#include "tst-utmp-unsigned.c"
diff --git a/login/tst-utmp-unsigned.c b/login/tst-utmp-unsigned.c
new file mode 100644
index 0000000000000000..27ad03a7d608e83d
--- /dev/null
+++ b/login/tst-utmp-unsigned.c
@@ -0,0 +1,40 @@
+/* Check that struct utmp, struct utmpx, struct lastlog use unsigned epoch.
+   Copyright (C) 2024 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <utmp.h>
+#include <utmpx.h>
+#include <utmp-size.h>
+
+/* Undefined.  Used to check that the conditions below are optimized away.  */
+void link_failure_utmp (void);
+void link_failure_utmpx (void);
+void link_failure_lastlog (void);
+
+static int
+do_test (void)
+{
+  if ((struct utmp) { .ut_tv = { 0x80000000U, }, }.ut_tv.tv_sec <= 0)
+    link_failure_utmp ();
+  if ((struct utmpx) { .ut_tv = { 0x80000000U, }, }.ut_tv.tv_sec <= 0)
+    link_failure_utmpx ();
+  if ((struct lastlog) { .ll_time = 0x80000000U, }.ll_time <= 0)
+    link_failure_lastlog ();
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/sysdeps/gnu/bits/utmpx.h b/sysdeps/gnu/bits/utmpx.h
index 34b4afbc6ac25968..ed0df9bd8141d4e6 100644
--- a/sysdeps/gnu/bits/utmpx.h
+++ b/sysdeps/gnu/bits/utmpx.h
@@ -74,7 +74,7 @@ struct utmpx
   __int32_t ut_session;		/* Session ID, used for windowing.  */
   struct
   {
-    __int32_t tv_sec;		/* Seconds.  */
+    __uint32_t tv_sec;		/* Seconds.  */
     __int32_t tv_usec;		/* Microseconds.  */
   } ut_tv;			/* Time entry was made.  */
 #else