1 /*
2 * Copyright (c) 2018 Oticon A/S
3 *
4 * SPDX-License-Identifier: Apache-2.0
5 *
6 * Pseudo-random entropy generator for the ARCH_POSIX architecture:
7 * Following the principle of reproducibility of the native_posix board
8 * this entropy device will always generate the same random sequence when
9 * initialized with the same seed
10 *
11 * This entropy source should only be used for testing.
12 */
13
14 #define DT_DRV_COMPAT zephyr_native_posix_rng
15
16 #include <zephyr/device.h>
17 #include <zephyr/drivers/entropy.h>
18 #include <zephyr/init.h>
19 #include <zephyr/sys/util.h>
20 #include <stdlib.h>
21 #include <string.h>
22 #include <zephyr/arch/posix/posix_trace.h>
23 #include "soc.h"
24 #include "cmdline.h" /* native_posix command line options header */
25 #include "nsi_host_trampolines.h"
26
27 static unsigned int seed = 0x5678;
28
entropy_native_posix_get_entropy(const struct device * dev,uint8_t * buffer,uint16_t length)29 static int entropy_native_posix_get_entropy(const struct device *dev,
30 uint8_t *buffer,
31 uint16_t length)
32 {
33 ARG_UNUSED(dev);
34
35 while (length) {
36 /*
37 * Note that only 1 thread (Zephyr thread or HW models), runs at
38 * a time, therefore there is no need to use random_r()
39 */
40 long value = nsi_host_random();
41
42 size_t to_copy = MIN(length, sizeof(long int));
43
44 memcpy(buffer, &value, to_copy);
45 buffer += to_copy;
46 length -= to_copy;
47 }
48
49 return 0;
50 }
51
entropy_native_posix_get_entropy_isr(const struct device * dev,uint8_t * buf,uint16_t len,uint32_t flags)52 static int entropy_native_posix_get_entropy_isr(const struct device *dev,
53 uint8_t *buf,
54 uint16_t len, uint32_t flags)
55 {
56 ARG_UNUSED(flags);
57
58 /*
59 * entropy_native_posix_get_entropy() is also safe for ISRs
60 * and always produces data.
61 */
62 entropy_native_posix_get_entropy(dev, buf, len);
63
64 return len;
65 }
66
entropy_native_posix_init(const struct device * dev)67 static int entropy_native_posix_init(const struct device *dev)
68 {
69 ARG_UNUSED(dev);
70 nsi_host_srandom(seed);
71 posix_print_warning("WARNING: "
72 "Using a test - not safe - entropy source\n");
73 return 0;
74 }
75
76 static const struct entropy_driver_api entropy_native_posix_api_funcs = {
77 .get_entropy = entropy_native_posix_get_entropy,
78 .get_entropy_isr = entropy_native_posix_get_entropy_isr
79 };
80
81 DEVICE_DT_INST_DEFINE(0,
82 entropy_native_posix_init, NULL,
83 NULL, NULL,
84 PRE_KERNEL_1, CONFIG_ENTROPY_INIT_PRIORITY,
85 &entropy_native_posix_api_funcs);
86
add_fake_entropy_option(void)87 static void add_fake_entropy_option(void)
88 {
89 static struct args_struct_t entropy_options[] = {
90 /*
91 * Fields:
92 * manual, mandatory, switch,
93 * option_name, var_name ,type,
94 * destination, callback,
95 * description
96 */
97 {false, false, false,
98 "seed", "r_seed", 'u',
99 (void *)&seed, NULL,
100 "A 32-bit integer seed value for the entropy device, such as "
101 "97229 (decimal), 0x17BCD (hex), or 0275715 (octal)"},
102 ARG_TABLE_ENDMARKER
103 };
104
105 native_add_command_line_opts(entropy_options);
106 }
107
108 NATIVE_TASK(add_fake_entropy_option, PRE_BOOT_1, 10);
109
