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
  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 }