1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (c) 2022, Linaro Limited
4 */
5
6 #define LOG_CATEGORY UCLASS_RNG
7
8 #include <dm.h>
9 #include <linker_lists.h>
10 #include <log.h>
11 #include <rng.h>
12 #include <dm/device_compat.h>
13 #include <linux/arm-smccc.h>
14 #include <linux/bitops.h>
15 #include <linux/kernel.h>
16 #include <linux/psci.h>
17
18 #define DRIVER_NAME "smccc-trng"
19
20 /**
21 * Arm SMCCC TRNG firmware interface specification:
22 * https://developer.arm.com/documentation/den0098/latest/
23 */
24 #define ARM_SMCCC_TRNG_VERSION 0x84000050
25 #define ARM_SMCCC_TRNG_FEATURES 0x84000051
26 #define ARM_SMCCC_TRNG_GET_UUID 0x84000052
27 #define ARM_SMCCC_TRNG_RND_32 0x84000053
28 #define ARM_SMCCC_TRNG_RND_64 0xC4000053
29
30 #define ARM_SMCCC_RET_TRNG_SUCCESS ((ulong)0)
31 #define ARM_SMCCC_RET_TRNG_NOT_SUPPORTED ((ulong)-1)
32 #define ARM_SMCCC_RET_TRNG_INVALID_PARAMETER ((ulong)-2)
33 #define ARM_SMCCC_RET_TRNG_NO_ENTROPY ((ulong)-3)
34
35 #define TRNG_MAJOR_MASK GENMASK(30, 16)
36 #define TRNG_MAJOR_SHIFT 16
37 #define TRNG_MINOR_MASK GENMASK(15, 0)
38 #define TRNG_MINOR_SHIFT 0
39
40 #define TRNG_MAX_RND_64 (192 / 8)
41 #define TRNG_MAX_RND_32 (96 / 8)
42
43 /**
44 * struct smccc_trng_priv - Private data for SMCCC TRNG support
45 *
46 * @smc64 - True if TRNG_RND_64 is supported, false if TRNG_RND_32 is supported
47 */
48 struct smccc_trng_priv {
49 bool smc64;
50 };
51
52 /*
53 * Copy random bytes from ulong SMCCC output register to target buffer
54 * Defines 2 function flavors for whether ARM_SMCCC_TRNG_RND_32 or
55 * ARM_SMCCC_TRNG_RND_64 was used to invoke the service.
56 */
smc32_copy_sample(u8 ** ptr,size_t size,ulong * rnd)57 static size_t smc32_copy_sample(u8 **ptr, size_t size, ulong *rnd)
58 {
59 size_t len = min(size, sizeof(u32));
60 u32 sample = *rnd;
61
62 memcpy(*ptr, &sample, len);
63 *ptr += len;
64
65 return size - len;
66 }
67
smc64_copy_sample(u8 ** ptr,size_t size,ulong * rnd)68 static size_t smc64_copy_sample(u8 **ptr, size_t size, ulong *rnd)
69 {
70 size_t len = min(size, sizeof(u64));
71 u64 sample = *rnd;
72
73 memcpy(*ptr, &sample, len);
74 *ptr += len;
75
76 return size - len;
77 }
78
smccc_trng_read(struct udevice * dev,void * data,size_t len)79 static int smccc_trng_read(struct udevice *dev, void *data, size_t len)
80 {
81 struct psci_plat_data *smccc = dev_get_parent_plat(dev);
82 struct smccc_trng_priv *priv = dev_get_priv(dev);
83 struct arm_smccc_res res;
84 u32 func_id;
85 u8 *ptr = data;
86 size_t rem = len;
87 size_t max_sz;
88 size_t (*copy_sample)(u8 **ptr, size_t size, ulong *rnd);
89
90 if (priv->smc64) {
91 copy_sample = smc64_copy_sample;
92 func_id = ARM_SMCCC_TRNG_RND_64;
93 max_sz = TRNG_MAX_RND_64;
94 } else {
95 copy_sample = smc32_copy_sample;
96 func_id = ARM_SMCCC_TRNG_RND_32;
97 max_sz = TRNG_MAX_RND_32;
98 }
99
100 while (rem) {
101 size_t sz = min(rem, max_sz);
102
103 smccc->invoke_fn(func_id, sz * 8, 0, 0, 0, 0, 0, 0, &res);
104
105 switch (res.a0) {
106 case ARM_SMCCC_RET_TRNG_SUCCESS:
107 break;
108 case ARM_SMCCC_RET_TRNG_NO_ENTROPY:
109 continue;
110 default:
111 return -EIO;
112 }
113
114 rem -= sz;
115
116 sz = copy_sample(&ptr, sz, &res.a3);
117 if (sz)
118 sz = copy_sample(&ptr, sz, &res.a2);
119 if (sz)
120 sz = copy_sample(&ptr, sz, &res.a1);
121 }
122
123 return 0;
124 }
125
126 static const struct dm_rng_ops smccc_trng_ops = {
127 .read = smccc_trng_read,
128 };
129
smccc_trng_is_supported(void (* invoke_fn)(unsigned long a0,unsigned long a1,unsigned long a2,unsigned long a3,unsigned long a4,unsigned long a5,unsigned long a6,unsigned long a7,struct arm_smccc_res * res))130 static bool smccc_trng_is_supported(void (*invoke_fn)(unsigned long a0, unsigned long a1,
131 unsigned long a2, unsigned long a3,
132 unsigned long a4, unsigned long a5,
133 unsigned long a6, unsigned long a7,
134 struct arm_smccc_res *res))
135 {
136 struct arm_smccc_res res;
137
138 (*invoke_fn)(ARM_SMCCC_TRNG_VERSION, 0, 0, 0, 0, 0, 0, 0, &res);
139 if (res.a0 & BIT(31))
140 return false;
141
142 /* Test 64bit interface and fallback to 32bit interface */
143 invoke_fn(ARM_SMCCC_TRNG_FEATURES, ARM_SMCCC_TRNG_RND_64,
144 0, 0, 0, 0, 0, 0, &res);
145
146 if (res.a0 == ARM_SMCCC_RET_TRNG_NOT_SUPPORTED)
147 invoke_fn(ARM_SMCCC_TRNG_FEATURES, ARM_SMCCC_TRNG_RND_32,
148 0, 0, 0, 0, 0, 0, &res);
149
150 return res.a0 == ARM_SMCCC_RET_TRNG_SUCCESS;
151 }
152
153 ARM_SMCCC_FEATURE_DRIVER(smccc_trng) = {
154 .driver_name = DRIVER_NAME,
155 .is_supported = smccc_trng_is_supported,
156 };
157
smccc_trng_probe(struct udevice * dev)158 static int smccc_trng_probe(struct udevice *dev)
159 {
160 struct psci_plat_data *smccc = dev_get_parent_plat(dev);
161 struct smccc_trng_priv *priv = dev_get_priv(dev);
162 struct arm_smccc_res res;
163
164 if (!smccc || !(smccc_trng_is_supported(smccc->invoke_fn)))
165 return -ENODEV;
166
167 /* At least one of 64bit and 32bit interfaces is available */
168 smccc->invoke_fn(ARM_SMCCC_TRNG_FEATURES, ARM_SMCCC_TRNG_RND_64,
169 0, 0, 0, 0, 0, 0, &res);
170 priv->smc64 = (res.a0 == ARM_SMCCC_RET_TRNG_SUCCESS);
171
172 #ifdef DEBUG
173 smccc->invoke_fn(ARM_SMCCC_TRNG_GET_UUID, 0, 0, 0, 0, 0, 0, 0, &res);
174 if (res.a0 != ARM_SMCCC_RET_TRNG_NOT_SUPPORTED) {
175 unsigned long uuid_a0 = res.a0;
176 unsigned long uuid_a1 = res.a1;
177 unsigned long uuid_a2 = res.a2;
178 unsigned long uuid_a3 = res.a3;
179 unsigned long major, minor;
180
181 smccc->invoke_fn(ARM_SMCCC_TRNG_VERSION, 0, 0, 0, 0, 0, 0, 0, &res);
182 major = (res.a0 & TRNG_MAJOR_MASK) >> TRNG_MAJOR_SHIFT;
183 minor = (res.a0 & TRNG_MINOR_MASK) >> TRNG_MINOR_SHIFT;
184
185 dev_dbg(dev, "Version %lu.%lu, UUID %08lx-%04lx-%04lx-%04lx-%04lx%08lx\n",
186 major, minor, uuid_a0, uuid_a1 >> 16, uuid_a1 & GENMASK(16, 0),
187 uuid_a2 >> 16, uuid_a2 & GENMASK(16, 0), uuid_a3);
188 } else {
189 dev_warn(dev, "Can't get TRNG UUID\n");
190 }
191 #endif
192
193 return 0;
194 }
195
196 U_BOOT_DRIVER(smccc_trng) = {
197 .name = DRIVER_NAME,
198 .id = UCLASS_RNG,
199 .ops = &smccc_trng_ops,
200 .probe = smccc_trng_probe,
201 .priv_auto = sizeof(struct smccc_trng_priv),
202 };
203