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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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lib/crypto: x86/blake2s: Avoid writing back unchanged 'f' value

Just before returning, blake2s_compress_ssse3() and
blake2s_compress_avx512() store updated values to the 'h', 't', and 'f'
fields of struct blake2s_ctx. But 'f' is always unchanged (which is
correct; only the C code changes it). So, there's no need to write to
'f'. Use 64-bit stores (movq and vmovq) instead of 128-bit stores
(movdqu and vmovdqu) so that only 't' is written.

Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20251102234209.62133-6-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>

Eric Biggers cd552862 a7acd77e

+2 -2
+2 -2
lib/crypto/x86/blake2s-core.S
··· 193 193 194 194 movdqu %xmm0,(CTX) // Store new h[0..3] 195 195 movdqu %xmm1,16(CTX) // Store new h[4..7] 196 - movdqu %xmm14,32(CTX) // Store new t and f 196 + movq %xmm14,32(CTX) // Store new t (f is unchanged) 197 197 RET 198 198 SYM_FUNC_END(blake2s_compress_ssse3) 199 199 ··· 287 287 288 288 vmovdqu %xmm0,(CTX) // Store new h[0..3] 289 289 vmovdqu %xmm1,16(CTX) // Store new h[4..7] 290 - vmovdqu %xmm4,32(CTX) // Store new t and f 290 + vmovq %xmm4,32(CTX) // Store new t (f is unchanged) 291 291 vzeroupper 292 292 RET 293 293 SYM_FUNC_END(blake2s_compress_avx512)