[patch] [virtualbox-host-dkms] Suggestion: Build host modules only for GCC compiled kernels, since it makes CLANG compiled kernels freezing and upstream only supports GCC compiled kernels.

This is not a bug report, but a feature suggestion, and includes a patch which tries to implement the feature. It fixes possible system freezes.

Note also that I report a "feature request" here because on the site "Bug reporting guidelines" in the Arch Linux wiki it seems to me that feature suggestions are also going to this issue tracker: "When you are sure it is a bug or a feature […], then you are ready to open a […] feature request." So forgive me if this tracker is only for bugs, and then please point me to the correct place and maybe correct the wiki.

---

Ahoj,

according to this comment from VirtualBox upstream:

We do not officially support CLANG on Linux host (only GCC is supported).

clang compiled Linux kernels are not supported by the VirtualBox host kernel modules.
And I experience kernel freeze when I actually do that.

So I suggest to add some logic to the virtualbox PKGBUILD that the package virtualbox-host-dkms only compiles a module for Linux kernels compiled with gcc, not with clang.

The issue happens when someone has a custom compiled kernel, and has it compiled using CLANG.
And then install virtualbox-host-dkms.

DKMS then, after installing the package virtualbox-host-dkms, builds VirtualBox host modules via DKMS also for CLANG compiled kernels, and it builds them with CLANG.

And when I then launch a VirtualBox VM, the system hard-freezes.

Attached (and below in plaintext) is a patch suggestion to this package which adds checks and maked DKMS abort if the kernel it is building for is not compiled with gcc:

virtualbox_arch_linux_package_build_host_modules_only_for_gcc-kernels.patch:

diff -rNU1 virtualbox.orig/dkms_check_kernel_cc_make_wrapper.sh virtualbox/dkms_check_kernel_cc_make_wrapper.sh
--- virtualbox.orig/dkms_check_kernel_cc_make_wrapper.sh	1970-01-01 01:00:00.000000000 +0100
+++ virtualbox/dkms_check_kernel_cc_make_wrapper.sh	2024-11-24 14:26:27.940099446 +0100
@@ -0,0 +1,20 @@
+#!/bin/sh
+
+_msg() {
+  printf '%s\n' "$@"
+}
+
+if [ "${KERNEL_CC}" == "gcc" ]; then
+  make "$@"
+else
+  _msg ""
+  _msg "ERROR building VirtualBox host modules:"
+  _msg ""
+  _msg "Build of VirtualBox host drivers is only supported for Linux kernels compiled with GCC."
+  _msg "Experience shows that using VirtualBox on CLANG compiled kernels leads to system freeze."
+  _msg "This kernel for which the modules now should be compiled was compiled with '${KERNEL_CC}'."
+  _msg "(For background, see e.g. https://www.virtualbox.org/ticket/22064)"
+  _msg ""
+  _msg "Aborting."
+  exit 99
+fi
diff -rNU1 virtualbox.orig/dkms_inform_about_cc.sh virtualbox/dkms_inform_about_cc.sh
--- virtualbox.orig/dkms_inform_about_cc.sh	1970-01-01 01:00:00.000000000 +0100
+++ virtualbox/dkms_inform_about_cc.sh	2024-11-24 14:26:01.943432530 +0100
@@ -0,0 +1,24 @@
+#!/bin/sh
+
+_msg() {
+  printf '%s\n' "$@"
+}
+
+_msg ""
+_msg "== Information about compiler and linker to be used =="
+_msg "KERNEL_CC: ${KERNEL_CC:-(unset)}"
+_msg "CC:        ${CC:-(unset)}"
+_msg "LD:        ${LD:-(unset)}"
+
+if [ "${KERNEL_CC}" != "gcc" ]; then
+  _msg ""
+  _msg "ERROR building VirtualBox host modules:"
+  _msg ""
+  _msg "Build of VirtualBox host drivers is only supported for Linux kernels compiled with GCC."
+  _msg "Experience shows that using VirtualBox on CLANG compiled kernels leads to system freeze."
+  _msg "This kernel for which the modules now should be compiled was compiled with '${KERNEL_CC}'."
+  _msg "(For background, see e.g. https://www.virtualbox.org/ticket/22064)"
+  _msg ""
+  _msg "Build process will be aborted to prevent those modules from beeing installed."
+  ## Note: Exiting the PRE_BUILD script with a non-zero exitcode makes `dkms` _not_ aborting the build process. So we have a wrapper arounf `make` which does the check again and aborts. But the output of this is not printed to the terminal, so we have this block here to inform the user.
+fi
diff -rNU1 virtualbox.orig/PKGBUILD virtualbox/PKGBUILD
--- virtualbox.orig/PKGBUILD	2024-11-22 16:47:36.750020729 +0100
+++ virtualbox/PKGBUILD	2024-11-24 15:04:12.506787865 +0100
@@ -56,2 +56,4 @@
         'virtualbox-host-dkms.conf'
+        'dkms_inform_about_cc.sh'
+        'dkms_check_kernel_cc_make_wrapper.sh'
         'virtualbox.sysusers'
@@ -76,3 +78,5 @@
 sha256sums=('872e7a42b41f8558abbf887f1bdc7aac932bb88b2764d07cbce270cab57e3b5e'
-            '76d98ea062fcad9e5e3fa981d046a6eb12a3e718a296544a68b66f4b65cb56db'
+            '7790b2752f209abb194d597a35b4d0828dd1703a7c4169736a38a752bc0aa3ea' # 'virtualbox-host-dkms.conf'
+            'fbfc010246e0a31be26bc971650f85ff7d607a00cc5f6bdcdb77df7a9aa200a5' # 'dkms_inform_about_cc.sh'
+            'b497d03341766cfe9294f8df73625f40e9eb53f0c8c3574edf9ff9612bb47f39' # 'dkms_check_kernel_cc_make_wrapper.sh'
             '2101ebb58233bbfadf3aa74381f22f7e7e508559d2b46387114bc2d8e308554c'
@@ -282,2 +286,3 @@
     sed -i "s,@VERSION@,${pkgver}," "${_p}"
+    install -D -m0755 -t "${pkgdir}/usr/src/vboxhost-${pkgver}_OSE" "${srcdir}"/{dkms_inform_about_cc.sh,dkms_check_kernel_cc_make_wrapper.sh}
 }
diff -rNU1 virtualbox.orig/virtualbox-host-dkms.conf virtualbox/virtualbox-host-dkms.conf
--- virtualbox.orig/virtualbox-host-dkms.conf	2024-11-22 16:47:36.750020729 +0100
+++ virtualbox/virtualbox-host-dkms.conf	2024-11-24 13:05:09.250052599 +0100
@@ -31 +31,7 @@
 DEST_MODULE_LOCATION[2]="/kernel/misc"
+
+## clang compiled kernel is not supported and leads to system freeze, so do not build modules for that. See https://www.virtualbox.org/ticket/22064#comment:10.
+# Inform the user about kernel compiler and possible abort if it is not GCC:
+PRE_BUILD="dkms_inform_about_cc.sh"            # Needs to be relative to `dkms.conf`.
+# Check if the kernel compiler is GCC, and abort if not:
+MAKE="./dkms_check_kernel_cc_make_wrapper.sh"  # Is a system command, prepend `./` if it is relative to `dkms.conf`.

Regards!