Add prng(9) API

Add prng(9) as a replacement for random(9) in the kernel.

There are two major differences from random(9) and random(3):

- General prng(9) APIs (prng32(9), etc) do not guarantee an
  implementation or particular sequence; they should not be used for
  repeatable simulations.

- However, specific named API families are also exposed (for now: PCG),
  and those are expected to be repeatable (when so-guaranteed by the named
  algorithm).

Some minor differences from random(3) and earlier random(9):

- PRNG state for the general prng(9) APIs is per-CPU; this eliminates
  contention on PRNG state in SMP workloads.  Each PCPU generator in an
  SMP system produces a unique sequence.

- Better statistical properties than the Park-Miller ("minstd") PRNG
  (longer period, uniform distribution in all bits, passes
  BigCrush/PractRand analysis).

- Faster than Park-Miller ("minstd") PRNG -- no division is required to
  step PCG-family PRNGs.

For now, random(9) becomes a thin shim around prng32().  Eventually I
would like to mechanically switch consumers over to the explicit API.

Reviewed by:	kib, markj (previous version both)
Discussed with:	markm
Differential Revision:	https://reviews.freebsd.org/D25916

1 files changed, 5 insertions, 0 deletions

diff --git a/share/man/man9/Makefile b/share/man/man9/Makefile
index 33e162d5fae0..993f65188543 100644
--- a/share/man/man9/Makefile
+++ b/share/man/man9/Makefile
@@ -272,6 +272,7 @@ MAN=	accept_filter.9 \
 	printf.9 \
 	prison_check.9 \
 	priv.9 \
+	prng.9 \
 	proc_rwmem.9 \
 	pseudofs.9 \
 	psignal.9 \
@@ -1745,6 +1746,10 @@ MLINKS+=printf.9 log.9 \
 	printf.9 uprintf.9
 MLINKS+=priv.9 priv_check.9 \
 	priv.9 priv_check_cred.9
+MLINKS+=prng.9 prng32.9 \
+	prng.9 prng32_bounded.9 \
+	prng.9 prng64.9 \
+	prng.9 prng64_bounded.9
 MLINKS+=proc_rwmem.9 proc_readmem.9 \
 	proc_rwmem.9 proc_writemem.9
 MLINKS+=psignal.9 gsignal.9 \