On Sun, Oct 19, 2025 at 11:10:25AM +0300, Askar Safin wrote:
On Sun, Oct 19, 2025 at 9:09 AM Askar Safin safinaskar@gmail.com wrote:
Eric Biggers ebiggers@kernel.org:
Now that the lower level __crc32c_le() library function is optimized for
This patch (i. e. 38a9a5121c3b ("lib/crc32: make crc32c() go directly to lib")) solves actual bug I found in practice. So, please, backport it to stable kernels.
Oops. I just noticed that this patch removes module "libcrc32c". And this breaks build for Debian kernel v6.12.48. Previously I tested minimal build using "make localmodconfig". Now I tried full build of Debian kernel using "dpkg-buildpackage". And it failed, because some of Debian files reference "libcrc32c", which is not available.
So, please, don't backport this patch to stable kernels. I'm sorry.
Right, this commit simplified the CRC library design by removing the libcrc32c module. initramfs build scripts that hard-coded the addition of libcrc32c.ko into the ramdisk (which I don't think was ever necessary in the first place, though it did used to be useful to hard-code some of the *other* CRC modules like crc32c-intel) had to be updated to remove it. It looks like Debian did indeed do that, and they updated it in https://salsa.debian.org/kernel-team/linux/-/commit/6c242c647f84bfdbdc22a6a7...
As for your original problem, I'd glad to see that the simplified design is preventing problems. There's an issue with backporting this commit alone, though. This was patch 15 of a 19-patch series for a good reason: the CRC-32C implementation in lib/ wasn't architecture-optimized until after patches 1-14 of this series. Backporting this commit alone would make crc32c() no longer utilize architecture-optimized code.
Now, it already didn't do so reliably (and this patch series fixed that). However, backporting this commit alone would make it never do so. So it would regress performance in some cases.
Since the errors you're actually getting are:
[ 19.619731] Invalid ELF header magic: != ELF modprobe: can't load module libcrc32c (kernel/lib/libcrc32c.ko.xz): unknown symbol in module, or unknown parameter
I do have to wonder if this is actually a busybox bug or misconfiguration, where it's passing a compressed module to the kernel without decompressing it? And removing the module just hid the problem.
- Eric