1 // SPDX-License-Identifier: GPL-2.0
2 // Copyright (C) 2020 Arm Ltd.
3
4 #include <linux/arm-smccc.h>
5 #include <linux/kvm_host.h>
6
7 #include <asm/kvm_emulate.h>
8
9 #include <kvm/arm_hypercalls.h>
10
11 #define ARM_SMCCC_TRNG_VERSION_1_0 0x10000UL
12
13 /* Those values are deliberately separate from the generic SMCCC definitions. */
14 #define TRNG_SUCCESS 0UL
15 #define TRNG_NOT_SUPPORTED ((unsigned long)-1)
16 #define TRNG_INVALID_PARAMETER ((unsigned long)-2)
17 #define TRNG_NO_ENTROPY ((unsigned long)-3)
18
19 #define TRNG_MAX_BITS64 192
20
21 static const uuid_t arm_smc_trng_uuid __aligned(4) = UUID_INIT(
22 0x0d21e000, 0x4384, 0x11eb, 0x80, 0x70, 0x52, 0x44, 0x55, 0x4e, 0x5a, 0x4c);
23
24 static int kvm_trng_do_rnd(struct kvm_vcpu *vcpu, int size)
25 {
26 DECLARE_BITMAP(bits, TRNG_MAX_BITS64);
27 u32 num_bits = smccc_get_arg1(vcpu);
28 int i;
29
30 if (num_bits > 3 * size) {
31 smccc_set_retval(vcpu, TRNG_INVALID_PARAMETER, 0, 0, 0);
32 return 1;
33 }
34
35 /* get as many bits as we need to fulfil the request */
36 for (i = 0; i < DIV_ROUND_UP(num_bits, BITS_PER_LONG); i++)
37 bits[i] = get_random_long();
38
39 bitmap_clear(bits, num_bits, TRNG_MAX_BITS64 - num_bits);
40
41 if (size == 32)
42 smccc_set_retval(vcpu, TRNG_SUCCESS, lower_32_bits(bits[1]),
43 upper_32_bits(bits[0]), lower_32_bits(bits[0]));
44 else
45 smccc_set_retval(vcpu, TRNG_SUCCESS, bits[2], bits[1], bits[0]);
46
47 memzero_explicit(bits, sizeof(bits));
48 return 1;
49 }
50
51 int kvm_trng_call(struct kvm_vcpu *vcpu)
52 {
53 const __le32 *u = (__le32 *)arm_smc_trng_uuid.b;
54 u32 func_id = smccc_get_function(vcpu);
55 unsigned long val = TRNG_NOT_SUPPORTED;
56 int size = 64;
57
58 switch (func_id) {
59 case ARM_SMCCC_TRNG_VERSION:
60 val = ARM_SMCCC_TRNG_VERSION_1_0;
61 break;
62 case ARM_SMCCC_TRNG_FEATURES:
63 switch (smccc_get_arg1(vcpu)) {
64 case ARM_SMCCC_TRNG_VERSION:
65 case ARM_SMCCC_TRNG_FEATURES:
66 case ARM_SMCCC_TRNG_GET_UUID:
67 case ARM_SMCCC_TRNG_RND32:
68 case ARM_SMCCC_TRNG_RND64:
69 val = TRNG_SUCCESS;
70 }
71 break;
72 case ARM_SMCCC_TRNG_GET_UUID:
73 smccc_set_retval(vcpu, le32_to_cpu(u[0]), le32_to_cpu(u[1]),
74 le32_to_cpu(u[2]), le32_to_cpu(u[3]));
75 return 1;
76 case ARM_SMCCC_TRNG_RND32:
77 size = 32;
78 fallthrough;
79 case ARM_SMCCC_TRNG_RND64:
80 return kvm_trng_do_rnd(vcpu, size);
81 }
82
83 smccc_set_retval(vcpu, val, 0, 0, 0);
84 return 1;
85 }
86
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