This reverts commit 2beb81fbf0c01a62515a1bcef326168494ee2bd0.

While removing CONFIG_CRYPTO_STATS is a worthy goal, this also
removed unrelated infrastructure such as crypto_comp_alg_common.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

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>

Since crypto_hash_alg_has_setkey() is only called from ahash.c itself,
make it a static function.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Currently, the ahash API checks the alignment of all key and result
buffers against the algorithm's declared alignmask, and for any
unaligned buffers it falls back to manually aligned temporary buffers.

This is virtually useless, however.  First, since it does not apply to
the message, its effect is much more limited than e.g. is the case for
the alignmask for "skcipher".  Second, the key and result buffers are
given as virtual addresses and cannot (in general) be DMA'ed into, so
drivers end up having to copy to/from them in software anyway.  As a
result it's easy to use memcpy() or the unaligned access helpers.

The crypto_hash_walk_*() helper functions do use the alignmask to align
the message.  But with one exception those are only used for shash
algorithms being exposed via the ahash API, not for native ahashes, and
aligning the message is not required in this case, especially now that
alignmask support has been removed from shash.  The exception is the
n2_core driver, which doesn't set an alignmask.

In any case, no ahash algorithms actually set a nonzero alignmask
anymore.  Therefore, remove support for it from ahash.  The benefit is
that all the code to handle "misaligned" buffers in the ahash API goes
away, reducing the overhead of the ahash API.

This follows the same change that was made to shash.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto_shash_ctx_aligned() is no longer used, and it is useless now that
shash algorithms don't support nonzero alignmasks, so remove it.

Also remove crypto_tfm_ctx_aligned() which was only called by
crypto_shash_ctx_aligned().  It's unlikely to be useful again, since it
seems inappropriate to use cra_alignmask to represent alignment for the
tfm context when it already means alignment for inputs/outputs.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

As skcipher spawn users can no longer assume the spawn is of type
struct skcipher_alg, these helpers are no longer used.  Remove them.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

As skcipher spawns can be of two different types (skcipher vs.
lskcipher), only the common fields can be accessed.  Add a helper
to return the common algorithm object.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Add a new API type lskcipher designed for taking straight kernel
pointers instead of SG lists.  Its relationship to skcipher will
be analogous to that between shash and ahash.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Most drivers should not access the internal details of struct
crypto_engine.  Move it into the internal header file.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Create crypto/internal/engine.h to house details that should not
be used by drivers.  It is empty for the time being.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>