lib/crypto: sha256: Consolidate into single module

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>

1 files changed, 10 insertions, 16 deletions

diff --git a/lib/crypto/Kconfig b/lib/crypto/Kconfig
index 9bd740475a89..3305c6908581 100644
--- a/lib/crypto/Kconfig
+++ b/lib/crypto/Kconfig
@@ -144,20 +144,17 @@ config CRYPTO_LIB_SHA256
 	  by either the generic implementation or an arch-specific one, if one
 	  is available and enabled.
 
-config CRYPTO_ARCH_HAVE_LIB_SHA256
+config CRYPTO_LIB_SHA256_ARCH
 	bool
-	help
-	  Declares whether the architecture provides an arch-specific
-	  accelerated implementation of the SHA-256 library interface.
-
-config CRYPTO_LIB_SHA256_GENERIC
-	tristate
-	default CRYPTO_LIB_SHA256 if !CRYPTO_ARCH_HAVE_LIB_SHA256
-	help
-	  This symbol can be selected by arch implementations of the SHA-256
-	  library interface that require the generic code as a fallback, e.g.,
-	  for SIMD implementations. If no arch specific implementation is
-	  enabled, this implementation serves the users of CRYPTO_LIB_SHA256.
+	depends on CRYPTO_LIB_SHA256 && !UML
+	default y if ARM && !CPU_V7M
+	default y if ARM64
+	default y if MIPS && CPU_CAVIUM_OCTEON
+	default y if PPC && SPE
+	default y if RISCV && 64BIT && RISCV_ISA_V && TOOLCHAIN_HAS_VECTOR_CRYPTO
+	default y if S390
+	default y if SPARC64
+	default y if X86_64
 
 config CRYPTO_LIB_SHA512
 	tristate
@@ -199,9 +196,6 @@ endif
 if S390
 source "lib/crypto/s390/Kconfig"
 endif
-if SPARC
-source "lib/crypto/sparc/Kconfig"
-endif
 if X86
 source "lib/crypto/x86/Kconfig"
 endif