6.1 Backport request: fbf5892df21a ("kbuild: Use CRC32 and a 1MiB dictionary for XZ compressed modules")

6.1 Backport request: fbf5892df21a ("kbuild: Use CRC32 and a 1MiB dictionary for XZ compressed modules")

[Christoph Biedl]

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Hello,

please backport

commit fbf5892df21a8ccfcb2fda0fd65bc3169c89ed28
Author: Martin Nybo Andersen <tweek@tweek.dk>
Date:   Fri Sep 15 12:15:39 2023 +0200

    kbuild: Use CRC32 and a 1MiB dictionary for XZ compressed modules

    Kmod is now (since kmod commit 09c9f8c5df04 ("libkmod: Use kernel
    decompression when available")) using the kernel decompressor, when
    loading compressed modules.

    However, the kernel XZ decompressor is XZ Embedded, which doesn't
    handle CRC64 and dictionaries larger than 1MiB.

    Use CRC32 and 1MiB dictionary when XZ compressing and installing
    kernel modules.

to the 6.1 stable kernel, and possibly older ones as well.

The commit message actually has it all, so just my story: There's a
hardware that has or had issues with never kernels (no time to check),
my kernel for this board is usually static. But after building a kernel
with xz-compressed modules, they wouldn't load but trigger
"decompression failed with status 6". Investigation led to a CRC64 check
for these files, and eventually to the above commit.

The commit applies (with an offset), the resulting modules work as
expected.

Kernel 6.6 and newer already have that commit. Older kernels could
possibly benefit from this as well, I haven't checked.

Kind regards,

    Christoph

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