efivar fails to read variables

[Heinrich Schuchardt]

On riscv64 StarFive VisionFive 2 with U-Boot v2023.10-rc4 and kernel 6.5.0-2-generic we see this output:

root@ubuntu-server:/var# ls /sys/firmware/efi/efivars/
AuditMode-8be4df61-93ca-11d2-aa0d-00e098032b8c
DeployedMode-8be4df61-93ca-11d2-aa0d-00e098032b8c
OsIndicationsSupported-8be4df61-93ca-11d2-aa0d-00e098032b8c
PlatformLang-8be4df61-93ca-11d2-aa0d-00e098032b8c
PlatformLangCodes-8be4df61-93ca-11d2-aa0d-00e098032b8c
SecureBoot-8be4df61-93ca-11d2-aa0d-00e098032b8c
SetupMode-8be4df61-93ca-11d2-aa0d-00e098032b8c
VendorKeys-8be4df61-93ca-11d2-aa0d-00e098032b8c

root@ubuntu-server:/var# efivar -l
efivar: error listing variables: Function not implemented

root@ubuntu-server:/var# efibootmgr -v
EFI variables are not supported on this system.

Expected behavior would be to display the variables.

[Heinrich Schuchardt (xypron)]

The problem is due to the kernel not supporting the deprecated statfs() call on the efivarfs file system.

To demonstrate this I have created the following program (statfs.c):

#include <sys/vfs.h>
#include <stdio.h>

int main(int argc, char *argv[])
{
        struct statfs s;
        int ret;

        if (argc < 2) {
                printf("usage: %s <dirpath>\n", argv[0]);
                return 1;
        }

        ret = statfs(argv[1], &s);
        if (ret == -1) {
                perror("statfs");
                return 1;
        } else {
                printf("%s type: 0x%llx\n", argv[1],
                       (unsigned long long)s.f_type);
        }
        return 0;
}

When I run it I get the following output:

$ ./statfs /sys/firmware/efi
/sys/firmware/efi type: 0x62656572
$ ./statfs /sys/firmware/efi/efivars/
statfs: Invalid argument
$ mount | grep efivarfs
efivarfs on /sys/firmware/efi/efivars type efivarfs (ro,nosuid,nodev,noexec,relatime)

Though efivarfs is mounted on /sys/firmware/efi/efivars the statfs call fails.

[Heinrich Schuchardt (xypron)]

Kernel commit d86ff3333cb1 ("efivarfs: expose used and total size") introduced an EFI runtime call QueryVariableInfo().

[Heinrich Schuchardt (xypron)]

In U-Boot's EFI_RT_PROPERTIES_TABLE_VERSION the flag EFI_RT_SUPPORTED_QUERY_VARIABLE_INFO is not set.

[Heinrich Schuchardt (xypron)]

U-Boot currently does not implement QueryVariableInfo at runtime. This function is not needed for a read only efivarfs. I think it would be more appropriate to check if GetVariable is enabled in efi.runtime_supported_mask.

[Heinrich Schuchardt (xypron)]

Patch sent upstream https://lore<email address hidden>/T/#u

Without this patch the Ubuntu installer on systems using U-Boot (e.g. riscv64) will fail.

[Heinrich Schuchardt (xypron)]

With kernel 6.5.0-6-generic #6.1-Ubuntu SMP Thu Sep 21 12:51:18 from ppa:esmil/ppa efivar works fine.

[Rade0nfighter (rade0nfighter)]

On the off chance that this issue has a broader impact I will leave a reference to https://answers.launchpad.net/ubuntu/+question/708251 wherein similar behaviours are being observed with 6.5.0-9-generic on amd64.

efivar -l returns: "efivar: error listing variables: Function not implemented", yet `ls /sys/firmware/efi` returns entries.

I noticed this after upgrading from Ubuntu 23.04 when efibootmgr stopped working.

Ubuntu 23.10 x86_64, 6.5.0-9-generic (Plasma 5.27.8 if that makes a difference).

Happy to provide any other info on request.

[Olivier Gayot (ogayot)]

Subiquity users trying to install 23.10 on Apple hardware (amd64) have been running into problems as well because of this issue.

Thank you Heinrich for sending the patch upstream!

[Heinrich Schuchardt (xypron)]

Upstream has accepted the patch and added it to the v6.5 stable series.

https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v6.5.9&id=63565e1cbfb59da059dd322054840eb6a0019e65