Following the standardization on crc32c() as the lib entry point for the
Castagnoli CRC32 instead of the previous mix of crc32c(), crc32c_le(),
and __crc32c_le(), make the same change to the underlying base and arch
functions that implement it.

Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250208024911.14936-7-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>

Since the Castagnoli CRC32 is now always just crc32c(), rename
__crc32c_le_combine() and __crc32c_le_shift() accordingly.

Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250208024911.14936-6-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>

Drop the use of __pure and __attribute_const__ from the CRC32 library
functions that had them.  Both of these are unusual optimizations that
don't help properly written code.  They seem more likely to cause
problems than have any real benefit.

Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250208024911.14936-4-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>

Now that we've standardized on the byte-by-byte implementation of CRC32
as the only generic implementation (see previous commit for the
rationale), remove the code for the other implementations.

Tested with crc_kunit.

Link: https://lore.kernel.org/r/20250123212904.118683-3-ebiggers@kernel.org
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>

Currently the CRC32 library functions are defined as weak symbols, and
the arm64 and riscv architectures override them.

This method of arch-specific overrides has the limitation that it only
works when both the base and arch code is built-in.  Also, it makes the
arch-specific code be silently not used if it is accidentally built with
lib-y instead of obj-y; unfortunately the RISC-V code does this.

This commit reorganizes the code to have explicit *_arch() functions
that are called when they are enabled, similar to how some of the crypto
library code works (e.g. chacha_crypt() calls chacha_crypt_arch()).

Make the existing kconfig choice for the CRC32 implementation also
control whether the arch-optimized implementation (if one is available)
is enabled or not.  Make it enabled by default if CRC32 is also enabled.

The result is that arch-optimized CRC32 library functions will be
included automatically when appropriate, but it is now possible to
disable them.  They can also now be built as a loadable module if the
CRC32 library functions happen to be used only by loadable modules, in
which case the arch and base CRC32 modules will be automatically loaded
via direct symbol dependency when appropriate.

Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20241202010844.144356-3-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>

Remove the leading underscores from __crc32c_le_base().

This is in preparation for adding crc32c_le_arch() and eventually
renaming __crc32c_le() to crc32c_le().

Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20241202010844.144356-2-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>

crc32c-generic is currently backed by the architecture's CRC-32c library
code, which may offer a variety of implementations depending on the
capabilities of the platform. These are not covered by the crypto
subsystem's fuzz testing capabilities because crc32c-generic is the
reference driver that the fuzzing logic uses as a source of truth.

Fix this by providing a crc32c-arch implementation which is based on the
arch library code if available, and modify crc32c-generic so it is
always based on the generic C implementation. If the arch has no CRC-32c
library code, this change does nothing.

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

crc32-generic is currently backed by the architecture's CRC-32 library
code, which may offer a variety of implementations depending on the
capabilities of the platform. These are not covered by the crypto
subsystem's fuzz testing capabilities because crc32-generic is the
reference driver that the fuzzing logic uses as a source of truth.

Fix this by providing a crc32-arch implementation which is based on the
arch library code if available, and modify crc32-generic so it is
always based on the generic C implementation. If the arch has no CRC-32
library code, this change does nothing.

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

crc32_le and __crc32c_le can be overridden - extend this to crc32_be.

Signed-off-by: Kevin Bracey <kevin@bracey.fi>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Casts were added in commit 8f243af42ade ("sections: fix const sections
for crc32 table") to cope with the tables not being const. They are no
longer required since commit f5e38b9284e1 ("lib: crc32: constify crc32
lookup table").

Signed-off-by: Kevin Bracey <kevin@bracey.fi>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>