crypto: Add generic 64-bit carry-less multiply routine

Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Richard Henderson 2023-07-11 10:10:47 +01:00
parent f56d3c1a14
commit 00f463b38a
3 changed files with 51 additions and 0 deletions

View file

@ -92,3 +92,20 @@ uint64_t clmul_32(uint32_t n, uint32_t m32)
}
return r;
}
Int128 clmul_64_gen(uint64_t n, uint64_t m)
{
uint64_t rl = 0, rh = 0;
/* Bit 0 can only influence the low 64-bit result. */
if (n & 1) {
rl = m;
}
for (int i = 1; i < 64; ++i) {
uint64_t mask = -((n >> i) & 1);
rl ^= (m << i) & mask;
rh ^= (m >> (64 - i)) & mask;
}
return int128_make128(rl, rh);
}