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29ce50e078
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>
127 lines
3.3 KiB
C
127 lines
3.3 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later */
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/*
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* Synchronous Compression operations
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*
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* Copyright 2015 LG Electronics Inc.
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* Copyright (c) 2016, Intel Corporation
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* Author: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
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*/
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#ifndef _CRYPTO_SCOMP_INT_H
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#define _CRYPTO_SCOMP_INT_H
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#include <crypto/acompress.h>
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#include <crypto/algapi.h>
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#define SCOMP_SCRATCH_SIZE 131072
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struct acomp_req;
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struct crypto_scomp {
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struct crypto_tfm base;
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};
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/**
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* struct scomp_alg - synchronous compression algorithm
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*
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* @alloc_ctx: Function allocates algorithm specific context
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* @free_ctx: Function frees context allocated with alloc_ctx
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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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* @base: Common crypto API algorithm data structure
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* @calg: Cmonn algorithm data structure shared with acomp
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*/
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struct scomp_alg {
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void *(*alloc_ctx)(struct crypto_scomp *tfm);
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void (*free_ctx)(struct crypto_scomp *tfm, void *ctx);
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int (*compress)(struct crypto_scomp *tfm, const u8 *src,
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unsigned int slen, u8 *dst, unsigned int *dlen,
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void *ctx);
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int (*decompress)(struct crypto_scomp *tfm, const u8 *src,
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unsigned int slen, u8 *dst, unsigned int *dlen,
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void *ctx);
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union {
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struct COMP_ALG_COMMON;
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struct comp_alg_common calg;
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};
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};
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static inline struct scomp_alg *__crypto_scomp_alg(struct crypto_alg *alg)
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{
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return container_of(alg, struct scomp_alg, base);
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}
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static inline struct crypto_scomp *__crypto_scomp_tfm(struct crypto_tfm *tfm)
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{
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return container_of(tfm, struct crypto_scomp, base);
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}
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static inline struct crypto_tfm *crypto_scomp_tfm(struct crypto_scomp *tfm)
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{
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return &tfm->base;
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}
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static inline void crypto_free_scomp(struct crypto_scomp *tfm)
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{
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crypto_destroy_tfm(tfm, crypto_scomp_tfm(tfm));
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}
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static inline struct scomp_alg *crypto_scomp_alg(struct crypto_scomp *tfm)
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{
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return __crypto_scomp_alg(crypto_scomp_tfm(tfm)->__crt_alg);
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}
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static inline void *crypto_scomp_alloc_ctx(struct crypto_scomp *tfm)
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{
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return crypto_scomp_alg(tfm)->alloc_ctx(tfm);
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}
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static inline void crypto_scomp_free_ctx(struct crypto_scomp *tfm,
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void *ctx)
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{
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return crypto_scomp_alg(tfm)->free_ctx(tfm, ctx);
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}
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static inline int crypto_scomp_compress(struct crypto_scomp *tfm,
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const u8 *src, unsigned int slen,
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u8 *dst, unsigned int *dlen, void *ctx)
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{
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return crypto_scomp_alg(tfm)->compress(tfm, src, slen, dst, dlen, ctx);
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}
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static inline int crypto_scomp_decompress(struct crypto_scomp *tfm,
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const u8 *src, unsigned int slen,
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u8 *dst, unsigned int *dlen,
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void *ctx)
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{
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return crypto_scomp_alg(tfm)->decompress(tfm, src, slen, dst, dlen,
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ctx);
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}
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/**
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* crypto_register_scomp() -- Register synchronous compression algorithm
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*
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* Function registers an implementation of a synchronous
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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_scomp(struct scomp_alg *alg);
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/**
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* crypto_unregister_scomp() -- Unregister synchronous compression algorithm
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*
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* Function unregisters an implementation of a synchronous
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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_scomp(struct scomp_alg *alg);
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int crypto_register_scomps(struct scomp_alg *algs, int count);
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void crypto_unregister_scomps(struct scomp_alg *algs, int count);
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#endif
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