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 
kvm_trng_do_rnd(struct kvm_vcpu * vcpu,int size)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 
kvm_trng_call(struct kvm_vcpu * vcpu)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