LXR linux/arch/arm64/kvm/trng.c

   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