I think I might have found the "source" of the problem. https://github.com/torvalds/linux/commit/40576e5e63ea5eeab814de7af83ad09dd64134ee
Replacing the gcc-7 version with gcc-8 seems to "fix" the problem root@ubuntu_base:~/builderr# uname -a Linux ubuntu_base 5.4.0-050400rc5-generic #201910271430 SMP Sun Oct 27 18:33:09 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux root@ubuntu_base:~/builderr# gcc --version gcc (Ubuntu 8.3.0-6ubuntu1~18.04.1) 8.3.0 Copyright (C) 2018 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. root@ubuntu_base:~/builderr# make -C /lib/modules/5.4.0-050400rc5-generic/build/ M=$PWD make: Entering directory '/usr/src/linux-headers-5.4.0-050400rc5-generic' AR /root/builderr/built-in.a CC [M] /root/builderr/conftest.o Building modules, stage 2. MODPOST 1 modules CC [M] /root/builderr/conftest.mod.o LD [M] /root/builderr/conftest.ko make: Leaving directory '/usr/src/linux-headers-5.4.0-050400rc5-generic' -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1849348 Title: linux 5.4-rc4 Unable to build simple kernel module Status in linux package in Ubuntu: Confirmed Bug description: Cannot build a kernel module, errors in Linux headers using the current RC4 (also tried RC3, and daily) mainline kernel packages from http://kernel.ubuntu.com/~kernel-ppa/mainline Am able to build against a 5.4-rc4 kernel level directly from upstream kernel git repo (on a different platform). To recreate error: Install linux headers, etc from current 5.4 RC. (used 5.4.0-050400rc4 dated 10/20 for this test) --[/tmp/builderr/Makefile]-- EXTRA_CFLAGS += obj-m += conftest.o -- [EOF] -- --[/tmp/builderr/conftest.c]-- #include <linux/module.h> void conftest(void) { } MODULE_LICENSE("GPL-2"); -- [EOF] -- Command: make -C /lib/modules/5.4.0-050400rc4-generic/build M=/tmp/builderr/ V=2 &> make_err.log make.log is attached. Expected output (using above Makefile and conftest.c, performed a build on a system with 4.15.0-66 linux packages installed): -- [expected output] -- make -C /lib/modules/4.15.0-66-generic/build/ M=/tmp/builderr make: Entering directory '/usr/src/linux-headers-4.15.0-66-generic' CC [M] /tmp/builderr/conftest.o Building modules, stage 2. MODPOST 1 modules CC /tmp/builderr/conftest.mod.o LD [M] /tmp/builderr/conftest.ko make: Leaving directory '/usr/src/linux-headers-4.15.0-66-generic' ---- ========= lsb_release -rd Description: Ubuntu 18.04.3 LTS Release: 18.04 uname -a Linux ubuntu_base 5.4.0-050400rc4-generic #201910202130 SMP Sun Oct 20 21:32:54 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux dpkg -l | grep "linux\-[a-z]*\-" ii linux-headers-5.4.0-050400rc4 5.4.0-050400rc4.201910202130 all Header files related to Linux kernel version 5.4.0 ii linux-headers-5.4.0-050400rc4-generic 5.4.0-050400rc4.201910202130 amd64 Linux kernel headers for version 5.4.0 on 64 bit x86 SMP ii linux-image-unsigned-5.4.0-050400rc4-generic 5.4.0-050400rc4.201910202130 amd64 Linux kernel image for version 5.4.0 on 64 bit x86 SMP ri linux-libc-dev:amd64 4.15.0-65.74 amd64 Linux Kernel Headers for development ii linux-modules-5.4.0-050400rc4-generic 5.4.0-050400rc4.201910202130 amd64 Linux kernel extra modules for version 5.4.0 on 64 bit x86 SMP To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1849348/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
