Version

7.2.8

Host OS Type

macOS

Host OS name + version

macOS Tahoe 26.5.0 (Darwin 25.5.0)

Host Architecture

x86

Guest OS Type

Linux

Guest Architecture

x86

Guest OS name + version

Red Hat Enterprise Linux 9.8

Component

Guest Additions/Installer

What happened?

VBoxGuestAdditions 7.2.8 fails to build the vboxguest kernel module on RHEL 9.8 with kernel 5.14.0-687.10.1.el9_8.x86_64. The build reaches the vboxguest module compile and fails in r0drv/linux/timer-r0drv-linux.c due to from_timer() being undeclared — consistent with a RHEL 9.8 backported timer API change.

Note: the VirtualBox machine log is not available for this report. The relevant build failure is captured below from /var/log/vboxadd-setup.log.

Relevant log excerpt (vboxadd-setup.log):

/tmp/vbox.0/r0drv/linux/timer-r0drv-linux.c:754:37: error: implicit declaration of function 'from_timer'; did you mean 'mod_timer'? [-Werror=implicit-function-declaration]
  754 |     PRTTIMERLNXSUBTIMER pSubTimer = from_timer(pSubTimer, pLnxTimer, u.Std.LnxTimer);
      |                                     ^~~~~~~~~~
      |                                     mod_timer
/tmp/vbox.0/r0drv/linux/timer-r0drv-linux.c:754:70: error: 'u' undeclared (first use in this function); did you mean 'up'?
  754 |     PRTTIMERLNXSUBTIMER pSubTimer = from_timer(pSubTimer, pLnxTimer, u.Std.LnxTimer);
      |                                                           ^
      |                                                           up
cc1: some warnings being treated as errors
make[2]: *** [scripts/Makefile.build:250: /tmp/vbox.0/combined-os-specific.o] Error 1
make[1]: *** [Makefile:1968: /tmp/vbox.0] Error 2
make: *** [/tmp/vbox.0/Makefile-footer.gmk:146: vboxguest] Error 2

Expected result:
Guest Additions kernel modules build successfully.

Actual result:
vboxguest fails to build due to from_timer() being undeclared on the RHEL 9.8 kernel stream.

Notes:
The same VBoxGuestAdditions 7.2.8 ISO builds and runs correctly on a RHEL 9.7 guest with kernel 5.14.0-611.55.1.el9_7.x86_64 on the same host. The failure is specific to the RHEL 9.8 / 5.14.0-687 kernel stream. Workaround: pin guest to RHEL 9.7 via subscription-manager release --set=9.7.

How can we reproduce this?

1. Create RHEL 9.8 guest VM in VirtualBox 7.2.8
2. Ensure kernel-devel matching running kernel is installed
3. Mount VBoxGuestAdditions 7.2.8 ISO
4. Run: sudo sh ./VBoxLinuxAdditions.run
5. Check /var/log/vboxadd-setup.log — vboxguest build fails

Did you upload all of your necessary log files, screenshots, etc.?

• Yes, I've uploaded all pertinent files to this issue.