harvest.c revision 74914 
1/*-
2 * Copyright (c) 2000 Mark R V Murray
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer
10 *    in this position and unchanged.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 *
26 * $FreeBSD: head/sys/dev/random/harvest.c 74914 2001-03-28 09:17:56Z jhb $
27 */
28
29#include <sys/param.h>
30#include <sys/systm.h>
31#include <sys/types.h>
32#include <sys/queue.h>
33#include <sys/kthread.h>
34#include <sys/lock.h>
35#include <sys/mutex.h>
36#include <sys/poll.h>
37#include <sys/selinfo.h>
38#include <sys/sysctl.h>
39#include <sys/random.h>
40
41#include <machine/cpu.h>
42
43#include <dev/random/randomdev.h>
44
45static u_int read_random_phony(void *, u_int);
46
47/* Structure holding the desired entropy sources */
48struct harvest_select harvest = { 0, 0, 0 };
49
50/* hold the address of the routine which is actually called if
51 * the randomdev is loaded
52 */
53static void (*reap_func)(u_int64_t, void *, u_int, u_int, u_int, u_int) = NULL;
54static u_int (*read_func)(void *, u_int) = read_random_phony;
55
56/* Initialise the harvester at load time */
57void
58random_init_harvester(void (*reaper)(u_int64_t, void *, u_int, u_int, u_int, u_int), u_int (*reader)(void *, u_int))
59{
60	reap_func = reaper;
61	read_func = reader;
62}
63
64/* Deinitialise the harvester at unload time */
65void
66random_deinit_harvester(void)
67{
68	reap_func = NULL;
69	read_func = read_random_phony;
70}
71
72/* Entropy harvesting routine. This is supposed to be fast; do
73 * not do anything slow in here!
74 * Implemented as in indirect call to allow non-inclusion of
75 * the entropy device.
76 */
77void
78random_harvest(void *entropy, u_int count, u_int bits, u_int frac, u_int origin)
79{
80	if (reap_func)
81		(*reap_func)(get_cyclecount(), entropy, count, bits, frac, origin);
82}
83
84/* Userland-visible version of read_random */
85u_int
86read_random(void *buf, u_int count)
87{
88	return (*read_func)(buf, count);
89}
90
91/* If the entropy device is not loaded, make a token effort to
92 * provide _some_ kind of randomness. This should only be used
93 * inside other RNG's, like arc4random(9).
94 */
95static u_int
96read_random_phony(void *buf, u_int count)
97{
98	u_long randval;
99	int size, i;
100	static int initialised = 0;
101
102	/* Try to give random(9) a half decent initialisation
103	 * DO NOT make the mistake of thinking this is secure!!
104	 */
105	if (!initialised)
106		srandom((u_long)get_cyclecount());
107
108	/* Fill buf[] with random(9) output */
109	for (i = 0; i < count; i+= sizeof(u_long)) {
110		randval = random();
111		size = (count - i) < sizeof(u_long) ? (count - i) : sizeof(u_long);
112		memcpy(&((char *)buf)[i], &randval, size);
113	}
114
115	return count;
116}
117
118/* Helper routine to enable kthread_exit() to work while the module is
119 * being (or has been) unloaded.
120 * This routine is in this file because it is always linked into the kernel,
121 * and will thus never be unloaded. This is critical for unloadable modules
122 * that have threads.
123 */
124void
125random_set_wakeup_exit(void *control)
126{
127	wakeup(control);
128	mtx_lock(&Giant);
129	kthread_exit(0);
130	/* NOTREACHED */
131}
132