Since we assume the PRNG above is doing "something old, something new"
folding, shortcut and do fewer repeats through the timing loop.
ok beck

ok schwarze@

portable code path must handle that; with brent cook

improve the random stream itself (it doesn't), but to introduce
noise in the arc4random calling pattern. Thanks to matthew@ who
pointed out bias in a previous diff, ok deraadt@ matthew@

mechanism, to aid in portability to other systems as requested.
ok matthew

use the address, not what it points to (which is always the same)
ok deraadt@

ok deraadt@

by getauxval if we have it.
ok deraadt@

we are running supports it.
from enh@google.com

Ben Lovett, simpler diff from aja@

should not know anything about. Verified not to be used in ports; riding upon
the recent libcrypto major bump.

ChaCha context. Other changes will also ride this crank.

RANDOM_UUID is an enum member.

names to shorten line lengths
ok beck

artificially constrain alternative implementations. ok deraadt

Modern compiler toolchains are capable of optimizing even across
translation unit boundaries, so simply moving the memory clearing into
a separate function is not guaranteed to clear memory.
To avoid this, we take advantage of ELF weak symbol semantics, and
insert a call to an empty, weakly named function.  The semantics of
calling this function aren't determinable until load time, so the
compiler and linker need to keep the memset() call.
There are still ways a toolchain might defeat this trick (e.g.,
optimistically expecting the weak symbol to not be overloaded, and
only calling memset() if it is; promoting weak symbols to strong
symbols at link-time when emitting a static binary because they won't
be interposed; implementing load-time optimizations).  But at least
for the foreseeable future, these seem unlikely.
ok deraadt

ok deraadt@ beck@

/dev/urandom. Does well in the fallback case. Get it in tree so
it can be worked on.
ok otto@ deraadt@

Allow other non-zero return values in case we change our mind to
return an ssize_t byte count instead of simple success/fail.
ok deraadt, djm

MAP_INHERIT_ZERO anymore.  This restores arc4random's previous
behavior where fork children would mix in some randomness from the
parent process.
New behavior noticed by deraadt
ok deraadt, tedu

The extra argument doesn't hurt genuine atexit handlers and this fixes a
bug where we didn't provide the argument (effectively passing garbage) for
functions registered with __cxa_atexit in the main executable.
Pointed out by Dmitriy Ivanov <dimitry@google.com> and Elliott Hughes
<enh@google.com>.
ok matthew@

Now instead of calling getpid() each time a user invokes arc4random(),
we're able to rely on the kernel zero'ing out the RNG state if the
process forks.
ok deraadt, djm

discussion with matthew

buffersize is enforced strictly, this supplies sufficient entropy
payload to act as seed material.  Discourage general use of this
API, but lock down this function name as the go-to for userland
PRNG seeding.  Improve documentation.
ok miod matthew

of sysctl().  Mark it with XXX while we consider.

call abort().
this direction discussed at length with miod beck tedu matthew etc

I accepted that he's right (again) to seperate this out from heavy
sysctl API and this will simply a variety of things.  Functionname
is not used by anyone in the ports tree, so we guess we can use it.
Shocking that no application has a function called this.
ok matthew & others who pushed him to start this early on

ok deraadt, jmc, tedu

behavior for certain inputs.  From NetBSD.  OK tedu@

ok beck

From inframare at arachnogoat dot com; OK deraadt@ sthen@

collateral damage.
The syncronous nature of this mechanism has hampered performance for
symmetric crypto relative to brute-force cpu. The assymetric crypto
support never really materialized in drivers.
So abandon the complexity.
ok tedu beck mikeb
some disagrement from djm but if he wants to test /dev/crypto ciphers
he should do it without this this gigantic API in the way

ok aja@ dcoppa@