Re: [DRAFT PATCH] random32: make prandom_u32() output unpredictable

+ CC:netdev

( Just FYI: Build and boot on bare metal. )

- Sedat -

On Sun, Aug 9, 2020 at 11:01 PM Sedat Dilek [off-list ref] wrote:

Hi George,

I have tried your patch on top of Linux v5.8 with...

commit f227e3ec3b5c ("random32: update the net random state on
interrupt and activity")

...reverted.
This was a bit tricky - what was your base?

Applied the typo fix from Randy - will a v2 follow?

Why DRAFT and not RFC?

Please drop the CC:stable - it's a DRAFT.

Other Linux stable like linux-5.7.y include...

commit c0842fbc1b18c7a044e6ff3e8fa78bfa822c7d1a
random32: move the pseudo-random 32-bit definitions to prandom.h

commit 585524081ecdcde1c719e63916c514866d898217
random: random.h should include archrandom.h, not the other way around

...linux-5.8.y stable will follow.

Isn't the move to prandom.h making your patch easier to apply?

In a second build I applied the snippet from Willy.

What do you mean by...?

[ quote ]
I wonder if, on general principles, it would be better to use a more
SipHash style mixing in of the sample:
    m = get_cycles();
    v3 ^= m;
    SIPROUND(v0, v1, v2, v3);
    SIPROUND(v0, v1, v2, v3);
    v0 ^= m;

Not sure if it's worth the extra register (and associated spill/fill).
[ /quote ]

Have you a snippet for testing?

Thanks.

Regards,
- Sedat -