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/*-
* SPDX-License-Identifier: BSD-3-Clause
*
* Copyright (c) 1990, 1993
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* Posix rand_r function added May 1999 by Wes Peters <wes@softweyr.com>.
*/
#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)rand.c 8.1 (Berkeley) 6/14/93";
#endif /* LIBC_SCCS and not lint */
#include <sys/cdefs.h>
#include "namespace.h"
#include <sys/param.h>
#include <sys/sysctl.h>
#include <assert.h>
#include <pthread.h>
#include <stdbool.h>
#include <stdlib.h>
#include <syslog.h>
#include "un-namespace.h"
#include "libc_private.h"
#include "random.h"
/*
* Implement rand(3), the standard C PRNG API, using the non-standard but
* higher quality random(3) implementation and the same size 128-byte state
* LFSR as the random(3) default.
*
* It turns out there are portable applications that want a PRNG but are too
* lazy to use better-but-nonstandard interfaces like random(3), when
* available, and too lazy to import higher-quality and faster PRNGs into their
* codebase (such as any of SFC, JSF, 128-bit LCGs, PCG, or Splitmix64).
*
* Since we're stuck with rand(3) due to the C standard, we can at least have
* it produce a relatively good PRNG sequence using our existing random(3)
* LFSR. The random(3) design is not particularly fast nor compact, but it has
* the advantage of being the one already in the tree.
*/
static struct __random_state *rand3_state;
static pthread_once_t rand3_state_once = PTHREAD_ONCE_INIT;
static void
initialize_rand3(void)
{
int error;
rand3_state = allocatestate(TYPE_3);
error = initstate_r(rand3_state, 1, rand3_state->rst_randtbl, BREAK_3);
assert(error == 0);
}
int
rand(void)
{
_once(&rand3_state_once, initialize_rand3);
return ((int)random_r(rand3_state));
}
void
srand(unsigned seed)
{
_once(&rand3_state_once, initialize_rand3);
srandom_r(rand3_state, seed);
}
/*
* FreeBSD 12 and prior compatibility implementation of rand(3).
*/
static int
do_rand(unsigned long *ctx)
{
/*
* Compute x = (7^5 * x) mod (2^31 - 1)
* without overflowing 31 bits:
* (2^31 - 1) = 127773 * (7^5) + 2836
* From "Random number generators: good ones are hard to find",
* Park and Miller, Communications of the ACM, vol. 31, no. 10,
* October 1988, p. 1195.
*/
long hi, lo, x;
/* Transform to [1, 0x7ffffffe] range. */
x = (*ctx % 0x7ffffffe) + 1;
hi = x / 127773;
lo = x % 127773;
x = 16807 * lo - 2836 * hi;
if (x < 0)
x += 0x7fffffff;
/* Transform to [0, 0x7ffffffd] range. */
x--;
*ctx = x;
return (x);
}
/*
* Can't fix this garbage; too little state.
*/
int
rand_r(unsigned *ctx)
{
u_long val;
int r;
val = *ctx;
r = do_rand(&val);
*ctx = (unsigned)val;
return (r);
}
static u_long next = 1;
int __rand_fbsd12(void);
int
__rand_fbsd12(void)
{
return (do_rand(&next));
}
__sym_compat(rand, __rand_fbsd12, FBSD_1.0);
void __srand_fbsd12(unsigned seed);
void
__srand_fbsd12(unsigned seed)
{
next = seed;
}
__sym_compat(srand, __srand_fbsd12, FBSD_1.0);
void __sranddev_fbsd12(void);
void
__sranddev_fbsd12(void)
{
static bool warned = false;
if (!warned) {
syslog(LOG_DEBUG, "Deprecated function sranddev() called");
warned = true;
}
}
__sym_compat(sranddev, __sranddev_fbsd12, FBSD_1.0);
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