看板FB_security
标 题Re: Collecting entropy from device_attach() times.
发信站NCTU CS FreeBSD Server (Wed Oct 3 03:22:40 2012)
转信站ptt!csnews.cs.nctu!news.cs.nctu!FreeBSD.cs.nctu!freebsd.org!owner-free
Dag-Erling Sm=C3=B8rgrav <
[email protected]> writes:
> http://people.freebsd.org/~des/attachtimes-text.txz
1) There is a bug in the program - I made a couple of changes which I
didn't like but didn't fully revert. The (argc !=3D 0) in main()
should actually be (argc =3D=3D 0).
2) I modified the program to create a histogram of the lower bits and
looked at that in gnuplot. It was immediately obvious that the
distribution is extremely non-uniform. I suspect that this is - at
least in part - due to the weird way get_cyclecount() computes the
value it returns. We should either rewrite it to return something
sensible or nuke it and use binuptime() instead.
I uploaded a new tarball with the improved program and the histogram:
http://people.freebsd.org/~des/attachtimes-total.txz
DES
--=20
Dag-Erling Sm=C3=B8rgrav -
[email protected]
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