Failed to insert openafs module on ARM platform: Exec format error

[Chengen Du]

[Impact]
The openafs module cannot be installed on the ARM platform, resulting in the following error:
insmod /lib/modules/6.5.0-1025-gcp/updates/dkms/openafs.ko
modprobe: ERROR: could not insert 'openafs': Exec format error

[Fix]
There is an upstream commit that addresses this issue:

commit 2f260825b96b76556aba82fc364c841357a23a7d
Author: Cheyenne Wills <email address hidden>
Date: Thu Mar 28 12:51:46 2024 -0400

    Linux: Remove weak attribute for key_type_keyring

    The reference to the Linux symbol key_type_keyring uses a weak
    attribute to assist in determining if the symbol is exported. This
    method was introduced in commit: 'keyring-updated-20080310' (b7fb842b1c)
    as a way to detect if the symbol was exported by the Linux kernel. A
    later commit: 'linux-keyring-export-check-20090701' (4ca66112c2)
    introduced an autoconf test that eliminated the need for using the weak
    attribute, but the commit did not remove the attribute.

    On a Debian-12 system on ARM64 the use of the weak attribute in this
    case causes an error when loading the kernel module:
      "ERROR: could not insert 'openafs': Exec format error".
    The error is due to the Linux module loader not supporting the
    relocation entry type in the openafs kernel module for the
    key_type_keyring. Further investigation showed that this problem could
    occur with gcc-12 on a ARM64 system (see below for additional
    information).

    The code in osi_groups.c uses a pointer, __key_type_keyring, to the
    key_type_keyring. When this symbol is exported by the Linux kernel, the
    loader would resolve the address and __key_type_keyring would contain
    the address. If the key_type_keyring symbol was not exported,
    __key_type_keyring would be set to NULL (due to the weak attribute
    associated with key_type_keyring).

    Remove the weak attribute for key_type_keyring when the configure
    test, introduced in the 4ca66112c2 commit, determines that the symbol
    is exported (EXPORTED_KEY_TYPE_KEYRING is defined). When the symbol
    isn't exported (pre Linux 2.6.22), just set the pointer,
    __key_type_keyring to NULL.

    NOTE:

    The load error was reported on the openafs IRC channel by "clarkb"

    The problem of loading the openafs kernel module was also observed
    on a NixOS system as well, and is described in the NixOS ticket

      https://github.com/NixOS/nixpkgs/issues/284501

    A Debian-11 system did not have a problem loading the openafs kernel
    module. Investigation of the differences between Debian-11 and Debian-12
    showed that the problem is due to a series of fixes in the toolchain
    (in particular gcc-12) to address 'Cortex-A53 erratum #843419', which
    deals with how the ARM64 ADRP instruction is used. With gcc-12, the
    code generated uses a R_AARCH64_ADR_GOT for this particular case (which
    isn't supported by the Linux kernel module loader). Gcc-11 created a
    R_AARCH64_ABS64 relocation entry type for the symbol.

[Test Plan]
1. Install the OpenAFS client using the command `sudo apt install openafs-client`.
2. Load the kernel module by running `sudo modprobe --verbose openafs`.
3. Confirm that the module loads successfully without any errors.

[Where problems could occur]
The patch removed the weak attribute from key_type_keyring.
Previously, commit #4ca66112c2 (linux-keyring-export-check-20090701) introduced an autoconf test that made the weak attribute unnecessary, but the attribute was not removed at that time.
If the patch causes a regression, it might prevent the openafs module from being installed successfully.

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