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2beb81fbf0
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 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. Cc: Corentin Labbe <clabbe@baylibre.com> Signed-off-by: Eric Biggers <ebiggers@google.com> Acked-by: Ard Biesheuvel <ardb@kernel.org> Acked-by: Corentin Labbe <clabbe@baylibre.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
107 lines
3 KiB
C
107 lines
3 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later */
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/*
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* Asynchronous Compression operations
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*
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* Copyright (c) 2016, Intel Corporation
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* Authors: Weigang Li <weigang.li@intel.com>
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* Giovanni Cabiddu <giovanni.cabiddu@intel.com>
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*/
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#ifndef _CRYPTO_ACOMP_INT_H
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#define _CRYPTO_ACOMP_INT_H
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#include <crypto/acompress.h>
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#include <crypto/algapi.h>
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/**
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* struct acomp_alg - asynchronous compression algorithm
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*
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* @compress: Function performs a compress operation
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* @decompress: Function performs a de-compress operation
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* @dst_free: Frees destination buffer if allocated inside the algorithm
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* @init: Initialize the cryptographic transformation object.
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* This function is used to initialize the cryptographic
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* transformation object. This function is called only once at
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* the instantiation time, right after the transformation context
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* was allocated. In case the cryptographic hardware has some
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* special requirements which need to be handled by software, this
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* function shall check for the precise requirement of the
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* transformation and put any software fallbacks in place.
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* @exit: Deinitialize the cryptographic transformation object. This is a
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* counterpart to @init, used to remove various changes set in
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* @init.
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*
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* @reqsize: Context size for (de)compression requests
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* @base: Common crypto API algorithm data structure
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*/
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struct acomp_alg {
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int (*compress)(struct acomp_req *req);
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int (*decompress)(struct acomp_req *req);
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void (*dst_free)(struct scatterlist *dst);
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int (*init)(struct crypto_acomp *tfm);
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void (*exit)(struct crypto_acomp *tfm);
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unsigned int reqsize;
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struct crypto_alg base;
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};
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/*
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* Transform internal helpers.
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*/
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static inline void *acomp_request_ctx(struct acomp_req *req)
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{
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return req->__ctx;
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}
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static inline void *acomp_tfm_ctx(struct crypto_acomp *tfm)
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{
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return tfm->base.__crt_ctx;
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}
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static inline void acomp_request_complete(struct acomp_req *req,
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int err)
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{
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crypto_request_complete(&req->base, err);
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}
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static inline struct acomp_req *__acomp_request_alloc(struct crypto_acomp *tfm)
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{
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struct acomp_req *req;
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req = kzalloc(sizeof(*req) + crypto_acomp_reqsize(tfm), GFP_KERNEL);
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if (likely(req))
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acomp_request_set_tfm(req, tfm);
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return req;
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}
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static inline void __acomp_request_free(struct acomp_req *req)
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{
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kfree_sensitive(req);
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}
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/**
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* crypto_register_acomp() -- Register asynchronous compression algorithm
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*
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* Function registers an implementation of an asynchronous
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* compression algorithm
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*
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* @alg: algorithm definition
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*
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* Return: zero on success; error code in case of error
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*/
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int crypto_register_acomp(struct acomp_alg *alg);
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/**
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* crypto_unregister_acomp() -- Unregister asynchronous compression algorithm
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*
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* Function unregisters an implementation of an asynchronous
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* compression algorithm
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*
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* @alg: algorithm definition
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*/
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void crypto_unregister_acomp(struct acomp_alg *alg);
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int crypto_register_acomps(struct acomp_alg *algs, int count);
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void crypto_unregister_acomps(struct acomp_alg *algs, int count);
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#endif
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