On Sun, Jun 01, 2025 at 03:44:28PM -0700, Eric Biggers wrote: > This series improves how lib/crc supports arch-optimized code. First, > instead of the arch-optimized CRC code being in arch/$(SRCARCH)/lib/, it > will now be in lib/crc/$(SRCARCH)/. Second, the API functions (e.g. > crc32c()), arch-optimized functions (e.g. crc32c_arch()), and generic > functions (e.g. crc32c_base()) will now be part of a single module for > each CRC type, allowing better inlining and dead code elimination. The > second change is made possible by the first. > > As an example, consider CONFIG_CRC32=m on x86. We'll now have just > crc32.ko instead of both crc32-x86.ko and crc32.ko. The two modules > were already coupled together and always both got loaded together via > direct symbol dependency, so the separation provided no benefit. > > Note: later I'd like to apply the same design to lib/crypto/ too, where > often the API functions are out-of-line so this will work even better. > In those cases, for each algorithm we currently have 3 modules all > coupled together, e.g. libsha256.ko, libsha256-generic.ko, and > sha256-x86.ko. We should have just one, inline things properly, and > rely on the compiler's dead code elimination to decide the inclusion of > the generic code instead of manually setting it via kconfig. > > Having arch-specific code outside arch/ was somewhat controversial when > Zinc proposed it back in 2018. But I don't think the concerns are > warranted. It's better from a technical perspective, as it enables the > improvements mentioned above. This model is already successfully used > in other places in the kernel such as lib/raid6/. The community of each > architecture still remains free to work on the code, even if it's not in > arch/. At the time there was also a desire to put the library code in > the same files as the old-school crypto API, but that was a mistake; now > that the library is separate, that's no longer a constraint either. > > Patches 1 and 2, which I previously sent out by themselves, are > prerequisites because they eliminate the need for the CRC32 library API > to expose the generic functions. > > Eric Biggers (13): > crypto/crc32: register only one shash_alg > crypto/crc32c: register only one shash_alg
Applied the first 2 patches to https://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux.git/log/?h=crc-next The remaining patches have new versions in the v2 series. - Eric
