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
21static const uuid_t arm_smc_trng_uuid __aligned(4) = UUID_INIT(
22	0x0d21e000, 0x4384, 0x11eb, 0x80, 0x70, 0x52, 0x44, 0x55, 0x4e, 0x5a, 0x4c);
23
24static 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
51int 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