Consolidate the CPU-based SHA-256 code into a single module, following
what I did with SHA-512:
- Each arch now provides a header file lib/crypto/$(SRCARCH)/sha256.h,
replacing lib/crypto/$(SRCARCH)/sha256.c. The header defines
sha256_blocks() and optionally sha256_mod_init_arch(). It is included
by lib/crypto/sha256.c, and thus the code gets built into the single
libsha256 module, with proper inlining and dead code elimination.
- sha256_blocks_generic() is moved from lib/crypto/sha256-generic.c into
lib/crypto/sha256.c. It's now a static function marked with
__maybe_unused, so the compiler automatically eliminates it in any
cases where it's not used.
- Whether arch-optimized SHA-256 is buildable is now controlled
centrally by lib/crypto/Kconfig instead of by
lib/crypto/$(SRCARCH)/Kconfig. The conditions for enabling it remain
the same as before, and it remains enabled by default.
- Any additional arch-specific translation units for the optimized
SHA-256 code (such as assembly files) are now compiled by
lib/crypto/Makefile instead of lib/crypto/$(SRCARCH)/Makefile.
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250630160645.3198-13-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Instead of having both sha256_blocks_arch() and sha256_blocks_simd(),
instead have just sha256_blocks_arch() which uses the most efficient
implementation that is available in the calling context.
This is simpler, as it reduces the API surface. It's also safer, since
sha256_blocks_arch() just works in all contexts, including contexts
where the FPU/SIMD/vector registers cannot be used. This doesn't mean
that SHA-256 computations *should* be done in such contexts, but rather
we should just do the right thing instead of corrupting a random task's
registers. Eliminating this footgun and simplifying the code is well
worth the very small performance cost of doing the check.
Note: in the case of arm and arm64, what used to be sha256_blocks_arch()
is renamed back to its original name of sha256_block_data_order().
sha256_blocks_arch() is now used for the higher-level dispatch function.
This renaming also required an update to lib/crypto/arm64/sha512.h,
since sha2-armv8.pl is shared by both SHA-256 and SHA-512.
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250630160645.3198-5-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Move the contents of arch/x86/lib/crypto/ into lib/crypto/x86/.
The new code organization makes a lot more sense for how this code
actually works and is developed. In particular, it makes it possible to
build each algorithm as a single module, with better inlining and dead
code elimination. For a more detailed explanation, see the patchset
which did this for the CRC library code:
https://lore.kernel.org/r/20250607200454.73587-1-ebiggers@kernel.org/.
Also see the patchset which did this for SHA-512:
https://lore.kernel.org/linux-crypto/20250616014019.415791-1-ebiggers@kernel.org/
This is just a preparatory commit, which does the move to get the files
into their new location but keeps them building the same way as before.
Later commits will make the actual improvements to the way the
arch-optimized code is integrated for each algorithm.
Add a gitignore entry for the removed directory arch/x86/lib/crypto/ so
that people don't accidentally commit leftover generated files.
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Sohil Mehta <sohil.mehta@intel.com>
Link: https://lore.kernel.org/r/20250619191908.134235-9-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
