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, 34 insertions, 5 deletions

diff --git a/lib/crypto/Makefile b/lib/crypto/Makefile
index 5823137fa5a8..a887bf103bf0 100644
--- a/lib/crypto/Makefile
+++ b/lib/crypto/Makefile
@@ -66,11 +66,39 @@ libpoly1305-generic-y				+= poly1305-generic.o
 obj-$(CONFIG_CRYPTO_LIB_SHA1)			+= libsha1.o
 libsha1-y					:= sha1.o
 
-obj-$(CONFIG_CRYPTO_LIB_SHA256)			+= libsha256.o
-libsha256-y					:= sha256.o
+################################################################################
 
-obj-$(CONFIG_CRYPTO_LIB_SHA256_GENERIC)		+= libsha256-generic.o
-libsha256-generic-y				:= sha256-generic.o
+obj-$(CONFIG_CRYPTO_LIB_SHA256) += libsha256.o
+libsha256-y := sha256.o
+ifeq ($(CONFIG_CRYPTO_LIB_SHA256_ARCH),y)
+CFLAGS_sha256.o += -I$(src)/$(SRCARCH)
+
+ifeq ($(CONFIG_ARM),y)
+libsha256-y += arm/sha256-ce.o arm/sha256-core.o
+$(obj)/arm/sha256-core.S: $(src)/arm/sha256-armv4.pl
+	$(call cmd,perlasm)
+clean-files += arm/sha256-core.S
+AFLAGS_arm/sha256-core.o += $(aflags-thumb2-y)
+endif
+
+ifeq ($(CONFIG_ARM64),y)
+libsha256-y += arm64/sha256-core.o
+$(obj)/arm64/sha256-core.S: $(src)/arm64/sha2-armv8.pl
+	$(call cmd,perlasm_with_args)
+clean-files += arm64/sha256-core.S
+libsha256-$(CONFIG_KERNEL_MODE_NEON) += arm64/sha256-ce.o
+endif
+
+libsha256-$(CONFIG_PPC) += powerpc/sha256-spe-asm.o
+libsha256-$(CONFIG_RISCV) += riscv/sha256-riscv64-zvknha_or_zvknhb-zvkb.o
+libsha256-$(CONFIG_SPARC) += sparc/sha256_asm.o
+libsha256-$(CONFIG_X86) += x86/sha256-ssse3-asm.o \
+			   x86/sha256-avx-asm.o \
+			   x86/sha256-avx2-asm.o \
+			   x86/sha256-ni-asm.o
+endif # CONFIG_CRYPTO_LIB_SHA256_ARCH
+
+################################################################################
 
 obj-$(CONFIG_CRYPTO_LIB_SHA512) += libsha512.o
 libsha512-y := sha512.o
@@ -100,6 +128,8 @@ libsha512-$(CONFIG_X86) += x86/sha512-ssse3-asm.o \
 			   x86/sha512-avx2-asm.o
 endif # CONFIG_CRYPTO_LIB_SHA512_ARCH
 
+################################################################################
+
 obj-$(CONFIG_MPILIB) += mpi/
 
 obj-$(CONFIG_CRYPTO_SELFTESTS_FULL)		+= simd.o
@@ -113,5 +143,4 @@ obj-$(CONFIG_MIPS) += mips/
 obj-$(CONFIG_PPC) += powerpc/
 obj-$(CONFIG_RISCV) += riscv/
 obj-$(CONFIG_S390) += s390/
-obj-$(CONFIG_SPARC) += sparc/
 obj-$(CONFIG_X86) += x86/