Re: [linux-next:master 12136/12319] drivers/firmware/dmi_scan.c:692: undefined reference to `efi'

[Kees Cook <kees@kernel.org>]

On Sun, Jul 27, 2025 at 03:04:55AM +0800, kernel test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
> head:   d7af19298454ed155f5cf67201a70f5cf836c842
> commit: 1ad483981776ff67e2b37bb6951412e608c55adb [12136/12319] init.h: Disable sanitizer coverage for __init and __head
> config: x86_64-randconfig-077-20250726 (https://download.01.org/0day-ci/archive/20250727/202507270258.neWuiXLd-lkp@intel.com/config)
> compiler: gcc-12 (Debian 12.2.0-14+deb12u1) 12.2.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250727/202507270258.neWuiXLd-lkp@intel.com/reproduce)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202507270258.neWuiXLd-lkp@intel.com/
> 
> All errors (new ones prefixed by >>):
> 
>    ld: vmlinux.o: in function `setup_arch':
>    arch/x86/kernel/setup.c:987: undefined reference to `efi_init'
>    ld: arch/x86/kernel/setup.c:971: undefined reference to `efi_memblock_x86_reserve_range'
>    ld: vmlinux.o: in function `ms_hyperv_init_platform':
>    arch/x86/kernel/cpu/mshyperv.c:496: undefined reference to `isolation_type_tdx'
>    ld: arch/x86/kernel/cpu/mshyperv.c:494: undefined reference to `isolation_type_snp'
>    ld: vmlinux.o: in function `acpi_os_get_root_pointer':
>    drivers/acpi/osl.c:210: undefined reference to `efi'
>    ld: drivers/acpi/osl.c:210: undefined reference to `efi'
>    ld: drivers/acpi/osl.c:212: undefined reference to `efi'
>    ld: drivers/acpi/osl.c:212: undefined reference to `efi'
>    ld: vmlinux.o: in function `dmi_scan_machine':
> >> drivers/firmware/dmi_scan.c:692: undefined reference to `efi'
>    ld: vmlinux.o:drivers/firmware/dmi_scan.c:692: more undefined references to `efi' follow

This looks like a GCC bug that was fixed after GCC 12.

All the efi references are present even though CONFIG_EFI is not set in
the .config (all the checks are already wrapped in efi_enabled() calls,
which _should_ get DCEd by the compiler and leave no references to "efi"
nor "efi_init" behind.

i.e., with gcc 12:

$ nm gcc-bug/drivers/firmware/dmi_scan.o |grep efi
                 U efi

with gcc (Ubuntu 14.2.0-19ubuntu2) 14.2.0:

$ nm gcc-bug/drivers/firmware/dmi_scan.o |grep efi | wc -l
0


-- 
Kees Cook