Date: Thu, 27 Sep 2012 16:34:23 +0200 From: =?utf-8?Q?Dag-Erling_Sm=C3=B8rgrav?= <des@des.no> To: RW <rwmaillists@googlemail.com> Cc: freebsd-security@freebsd.org Subject: Re: Collecting entropy from device_attach() times. Message-ID: <86pq57o7ps.fsf@ds4.des.no> In-Reply-To: <20120927125956.0594fa73@gumby.homeunix.com> (RW's message of "Thu, 27 Sep 2012 12:59:56 %2B0100") References: <20120918211422.GA1400@garage.freebsd.pl> <20120919192836.3a60cdfd@gumby.homeunix.com> <863923pzgi.fsf@ds4.des.no> <CAG5KPzwhq4UzPxbx74vX5KKtqC4tWkTsKAHjGDsdD8MqJVVkRg@mail.gmail.com> <20120927125956.0594fa73@gumby.homeunix.com>
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RW <rwmaillists@googlemail.com> writes:
> static __inline uint64_t
> get_cyclecount(void)
> {
> struct bintime bt;
>
> binuptime(&bt);
> return (bt.frac ^ bt.sec);
>=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
> }
Why the heck does it xor the integer and fractional parts together?
That makes no sense at all. I would have used ((uint64_t)bt.sec << 32 |
bt.frac >> 32). It wraps around after 136 years' uptime, but hey, you
can't win them all.
DES
--=20
Dag-Erling Sm=C3=B8rgrav - des@des.no
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