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2024-04-02crypto: remove CONFIG_CRYPTO_STATSEric Biggers1-30/+0
Remove support for the "Crypto usage statistics" feature (CONFIG_CRYPTO_STATS). This feature does not appear to have ever been used, and it is harmful because it significantly reduces performance and is a large maintenance burden. Covering each of these points in detail: 1. Feature is not being used Since these generic crypto statistics are only readable using netlink, it's fairly straightforward to look for programs that use them. I'm unable to find any evidence that any such programs exist. For example, Debian Code Search returns no hits except the kernel header and kernel code itself and translations of the kernel header: https://codesearch.debian.net/search?q=CRYPTOCFGA_STAT&literal=1&perpkg=1 The patch series that added this feature in 2018 (https://lore.kernel.org/linux-crypto/1537351855-16618-1-git-send-email-clabbe@baylibre.com/) said "The goal is to have an ifconfig for crypto device." This doesn't appear to have happened. It's not clear that there is real demand for crypto statistics. Just because the kernel provides other types of statistics such as I/O and networking statistics and some people find those useful does not mean that crypto statistics are useful too. Further evidence that programs are not using CONFIG_CRYPTO_STATS is that it was able to be disabled in RHEL and Fedora as a bug fix (https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/2947). Even further evidence comes from the fact that there are and have been bugs in how the stats work, but they were never reported. For example, before Linux v6.7 hash stats were double-counted in most cases. There has also never been any documentation for this feature, so it might be hard to use even if someone wanted to. 2. CONFIG_CRYPTO_STATS significantly reduces performance Enabling CONFIG_CRYPTO_STATS significantly reduces the performance of the crypto API, even if no program ever retrieves the statistics. This primarily affects systems with a large number of CPUs. For example, https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2039576 reported that Lustre client encryption performance improved from 21.7GB/s to 48.2GB/s by disabling CONFIG_CRYPTO_STATS. It can be argued that this means that CONFIG_CRYPTO_STATS should be optimized with per-cpu counters similar to many of the networking counters. But no one has done this in 5+ years. This is consistent with the fact that the feature appears to be unused, so there seems to be little interest in improving it as opposed to just disabling it. It can be argued that because CONFIG_CRYPTO_STATS is off by default, performance doesn't matter. But Linux distros tend to error on the side of enabling options. The option is enabled in Ubuntu and Arch Linux, and until recently was enabled in RHEL and Fedora (see above). So, even just having the option available is harmful to users. 3. CONFIG_CRYPTO_STATS is a large maintenance burden There are over 1000 lines of code associated with CONFIG_CRYPTO_STATS, spread among 32 files. It significantly complicates much of the implementation of the crypto API. After the initial submission, many fixes and refactorings have consumed effort of multiple people to keep this feature "working". We should be spending this effort elsewhere. Acked-by: Ard Biesheuvel <ardb@kernel.org> Acked-by: Corentin Labbe <clabbe@baylibre.com> Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-10-27crypto: ahash - optimize performance when wrapping shashEric Biggers1-0/+10
The "ahash" API provides access to both CPU-based and hardware offload- based implementations of hash algorithms. Typically the former are implemented as "shash" algorithms under the hood, while the latter are implemented as "ahash" algorithms. The "ahash" API provides access to both. Various kernel subsystems use the ahash API because they want to support hashing hardware offload without using a separate API for it. Yet, the common case is that a crypto accelerator is not actually being used, and ahash is just wrapping a CPU-based shash algorithm. This patch optimizes the ahash API for that common case by eliminating the extra indirect call for each ahash operation on top of shash. It also fixes the double-counting of crypto stats in this scenario (though CONFIG_CRYPTO_STATS should *not* be enabled by anyone interested in performance anyway...), and it eliminates redundant checking of CRYPTO_TFM_NEED_KEY. As a bonus, it also shrinks struct crypto_ahash. Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-10-27crypto: hash - move "ahash wrapping shash" functions to ahash.cEric Biggers1-3/+1
The functions that are involved in implementing the ahash API on top of an shash algorithm belong better in ahash.c, not in shash.c where they currently are. Move them. Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-04-20crypto: hash - Add crypto_clone_ahash/shashHerbert Xu1-0/+4
This patch adds the helpers crypto_clone_ahash and crypto_clone_shash. They are the hash-specific counterparts of crypto_clone_tfm. This allows code paths that cannot otherwise allocate a hash tfm object to do so. Once a new tfm has been obtained its key could then be changed without impacting other users. Note that only algorithms that implement clone_tfm can be cloned. However, all keyless hashes can be cloned by simply reusing the tfm object. Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Reviewed-by: Simon Horman <simon.horman@corigine.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-03-14crypto: hash - Count error stats differentlyHerbert Xu1-0/+36
Move all stat code specific to hash into the hash code. While we're at it, change the stats so that bytes and counts are always incremented even in case of error. This allows the reference counting to be removed as we can now increment the counters prior to the operation. After the operation we simply increase the error count if necessary. This is safe as errors can only occur synchronously (or rather, the existing code already ignored asynchronous errors which are only visible to the callback function). Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>