On Tue, Sep 27, 2022 at 8:35 AM Dominik Brodowski linux@dominikbrodowski.net wrote:
#if defined(LATENT_ENTROPY_PLUGIN) static const u8 compiletime_seed[BLAKE2S_BLOCK_SIZE] __initconst __latent_entropy; @@ -803,34 +798,46 @@ int __init random_init(const char *command_line) i += longs; continue; }
entropy[0] = random_get_entropy();_mix_pool_bytes(entropy, sizeof(*entropy)); arch_bits -= sizeof(*entropy) * 8; ++i; }Previously, random_get_entropy() was mixed into the pool ARRAY_SIZE(entropy) times.
+/*
- This is called a little bit after the prior function, and now there is
- access to timestamps counters. Interrupts are not yet enabled.
- */
+void __init random_init(void) +{
unsigned long entropy = random_get_entropy();ktime_t now = ktime_get_real();_mix_pool_bytes(utsname(), sizeof(*(utsname())));But now, it's only mixed into the pool once. Is this change on purpose?
Yea, it is. I don't think it's really doing much of use. Before we did it because it was convenient -- because we simply could. But in reality mostly what we care about is capturing when it gets to that point in the execution. For jitter, the actual jitter function (try_to_generate_entropy()) is better here.
However, before feeling too sad about it, remember that extract_entropy() is still filling a block with rdtsc when rdrand fails, the same way as this function was. So it's still in there anyway.
Jason