K 10
svn:author
V 3
cem
K 8
svn:date
V 27
2019-12-26T19:32:11.016283Z
K 7
svn:log
V 1728
random(4): Simplify RANDOM_LOADABLE

Simplify RANDOM_LOADABLE by removing the ability to unload a LOADABLE
random(4) implementation.  This allows one-time random module selection
at boot, by loader(8).  Swapping modules on the fly doesn't seem
especially useful.

This removes the need to hold a lock over the sleepable module calls
read_random and read_random_uio.

init/deinit have been pulled out of random_algorithm entirely.  Algorithms
can run their own sysinits to initialize; deinit is removed entirely, as
algorithms can not be unloaded.  Algorithms should initialize at
SI_SUB_RANDOM:SI_ORDER_SECOND.  In LOADABLE systems, algorithms install
a pointer to their local random_algorithm context in p_random_alg_context at
that time.

Go ahead and const'ify random_algorithm objects; there is no need to mutate
them at runtime.

LOADABLE kernel NULL checks are removed from random_harvestq by ordering
random_harvestq initialization at SI_SUB_RANDOM:SI_ORDER_THIRD, after
algorithm init.  Prior to random_harvestq init, hc_harvest_mask is zero and
no events are forwarded to algorithms; after random_harvestq init, the
relevant pointers will already have been installed.

Remove the bulk of random_infra shim wrappers and instead expose the bare
function pointers in sys/random.h.  In LOADABLE systems, read_random(9) et
al are just thin shim macros around invoking the associated function
pointer.  We do not provide a registration system but instead expect
LOADABLE modules to register themselves at SI_SUB_RANDOM:SI_ORDER_SECOND.
An example is provided in randomdev.c, as used in the random_fortuna.ko
module.

Approved by:	csprng(markm)
Discussed with:	gordon
Differential Revision:	https://reviews.freebsd.org/D22512

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