p_flag bits?

[Mouse <mouse%Rodents-Montreal.ORG@localhost>]

Looking at sys/proc.h, the PK_* bits are scattered around oddly within
the p_flag field (true of 5.2 and 9.1; since the two use the same set
of names with the same values, I suspect also true of everything in
between).

But I also haven't been able to find anything that uses the p_flag bits
other than the 0x800e4307 bits.

Are the other 22 bits unused?  If not, what am I missing?

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