3a57f08b50
Before this patch there was a chance for thread that called rand(3) slightly later to see rand3_state already allocated, but not yet initialized. While this API is not expected to be thread-safe, it is not expected to crash. ztest on 64-thread system reproduced it reliably for me. Submitted by: avg@ MFC after: 1 month
169 lines
4.7 KiB
C
169 lines
4.7 KiB
C
/*-
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* SPDX-License-Identifier: BSD-3-Clause
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*
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* Copyright (c) 1990, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* Posix rand_r function added May 1999 by Wes Peters <wes@softweyr.com>.
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*/
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#if defined(LIBC_SCCS) && !defined(lint)
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static char sccsid[] = "@(#)rand.c 8.1 (Berkeley) 6/14/93";
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#endif /* LIBC_SCCS and not lint */
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include "namespace.h"
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#include <sys/param.h>
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#include <sys/sysctl.h>
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#include <assert.h>
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#include <pthread.h>
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#include <stdbool.h>
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#include <stdlib.h>
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#include <syslog.h>
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#include "un-namespace.h"
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#include "libc_private.h"
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#include "random.h"
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/*
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* Implement rand(3), the standard C PRNG API, using the non-standard but
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* higher quality random(3) implementation and the same size 128-byte state
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* LFSR as the random(3) default.
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*
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* It turns out there are portable applications that want a PRNG but are too
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* lazy to use better-but-nonstandard interfaces like random(3), when
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* available, and too lazy to import higher-quality and faster PRNGs into their
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* codebase (such as any of SFC, JSF, 128-bit LCGs, PCG, or Splitmix64).
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*
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* Since we're stuck with rand(3) due to the C standard, we can at least have
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* it produce a relatively good PRNG sequence using our existing random(3)
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* LFSR. The random(3) design is not particularly fast nor compact, but it has
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* the advantage of being the one already in the tree.
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*/
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static struct __random_state *rand3_state;
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static pthread_once_t rand3_state_once = PTHREAD_ONCE_INIT;
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static void
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initialize_rand3(void)
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{
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int error;
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rand3_state = allocatestate(TYPE_3);
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error = initstate_r(rand3_state, 1, rand3_state->rst_randtbl, BREAK_3);
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assert(error == 0);
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}
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int
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rand(void)
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{
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_once(&rand3_state_once, initialize_rand3);
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return ((int)random_r(rand3_state));
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}
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void
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srand(unsigned seed)
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{
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_once(&rand3_state_once, initialize_rand3);
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srandom_r(rand3_state, seed);
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}
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/*
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* FreeBSD 12 and prior compatibility implementation of rand(3).
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*/
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static int
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do_rand(unsigned long *ctx)
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{
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/*
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* Compute x = (7^5 * x) mod (2^31 - 1)
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* without overflowing 31 bits:
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* (2^31 - 1) = 127773 * (7^5) + 2836
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* From "Random number generators: good ones are hard to find",
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* Park and Miller, Communications of the ACM, vol. 31, no. 10,
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* October 1988, p. 1195.
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*/
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long hi, lo, x;
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/* Transform to [1, 0x7ffffffe] range. */
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x = (*ctx % 0x7ffffffe) + 1;
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hi = x / 127773;
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lo = x % 127773;
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x = 16807 * lo - 2836 * hi;
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if (x < 0)
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x += 0x7fffffff;
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/* Transform to [0, 0x7ffffffd] range. */
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x--;
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*ctx = x;
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return (x);
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}
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/*
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* Can't fix this garbage; too little state.
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*/
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int
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rand_r(unsigned *ctx)
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{
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u_long val;
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int r;
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val = *ctx;
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r = do_rand(&val);
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*ctx = (unsigned)val;
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return (r);
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}
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static u_long next = 1;
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int __rand_fbsd12(void);
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int
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__rand_fbsd12(void)
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{
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return (do_rand(&next));
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}
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__sym_compat(rand, __rand_fbsd12, FBSD_1.0);
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void __srand_fbsd12(unsigned seed);
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void
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__srand_fbsd12(unsigned seed)
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{
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next = seed;
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}
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__sym_compat(srand, __srand_fbsd12, FBSD_1.0);
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void __sranddev_fbsd12(void);
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void
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__sranddev_fbsd12(void)
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{
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static bool warned = false;
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if (!warned) {
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syslog(LOG_DEBUG, "Deprecated function sranddev() called");
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warned = true;
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}
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}
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__sym_compat(sranddev, __sranddev_fbsd12, FBSD_1.0);
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