lib/crypto: blake2b: Roll up BLAKE2b round loop on 32-bit

2025-12-09T23:10:21+00:00

BLAKE2b has a state of 16 64-bit words. Add the message data in and there are 32 64-bit words. With the current code where all the rounds are unrolled to enable constant-folding of the blake2b_sigma values, this results in a very large code size on 32-bit kernels, including a recurring issue where gcc uses a large amount of stack. There's just not much benefit to this unrolling when the code is already so large. Let's roll up the rounds when !CONFIG_64BIT. To avoid having to duplicate the code, just write the code once using a loop, and conditionally use 'unrolled_full' from . Then, fold the now-unneeded ROUND() macro into the loop. Finally, also remove the now-unneeded override of the stack frame size warning. Code size improvements for blake2b_compress_generic(): Size before (bytes) Size after (bytes) ------------------- ------------------ i386, gcc 27584 3632 i386, clang 18208 3248 arm32, gcc 19912 2860 arm32, clang 21336 3344 Running the BLAKE2b benchmark on a !CONFIG_64BIT kernel on an x86_64 processor shows a 16384B throughput change of 351 => 340 MB/s (gcc) or 442 MB/s => 375 MB/s (clang). So clearly not much of a slowdown either. But also that microbenchmark also effectively disregards cache usage, which is important in practice and is far better in the smaller code. Note: If we rolled up the loop on x86_64 too, the change would be 7024 bytes => 1584 bytes and 1960 MB/s => 1396 MB/s (gcc), or 6848 bytes => 1696 bytes and 1920 MB/s => 1263 MB/s (clang). Maybe still worth it, though not quite as clearly beneficial. Fixes: 91d689337fe8 ("crypto: blake2b - add blake2b generic implementation") Reviewed-by: Ard Biesheuvel Link: https://lore.kernel.org/r/20251205050330.89704-1-ebiggers@kernel.org Signed-off-by: Eric Biggers

lib/crypto: blake2b: Add BLAKE2b library functions

2025-10-30T05:04:24+00:00

Add a library API for BLAKE2b, closely modeled after the BLAKE2s API. This will allow in-kernel users such as btrfs to use BLAKE2b without going through the generic crypto layer. In addition, as usual the BLAKE2b crypto_shash algorithms will be reimplemented on top of this. Note: to create lib/crypto/blake2b.c I made a copy of lib/crypto/blake2s.c and made the updates from BLAKE2s => BLAKE2b. This way, the BLAKE2s and BLAKE2b code is kept consistent. Therefore, it borrows the SPDX-License-Identifier and Copyright from lib/crypto/blake2s.c rather than crypto/blake2b_generic.c. The library API uses 'struct blake2b_ctx', consistent with other lib/crypto/ APIs. The existing 'struct blake2b_state' will be removed once the blake2b crypto_shash algorithms are updated to stop using it. Reviewed-by: Ard Biesheuvel Link: https://lore.kernel.org/r/20251018043106.375964-7-ebiggers@kernel.org Signed-off-by: Eric Biggers

kernel/linux.git/lib/crypto/blake2b.c, branch v6.19.11

lib/crypto: blake2b: Roll up BLAKE2b round loop on 32-bit

lib/crypto: blake2b: Add BLAKE2b library functions