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-rw-r--r--arch/arm64/kvm/trng.c85
1 files changed, 85 insertions, 0 deletions
diff --git a/arch/arm64/kvm/trng.c b/arch/arm64/kvm/trng.c
new file mode 100644
index 0000000000..99bdd7103c
--- /dev/null
+++ b/arch/arm64/kvm/trng.c
@@ -0,0 +1,85 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2020 Arm Ltd.
+
+#include <linux/arm-smccc.h>
+#include <linux/kvm_host.h>
+
+#include <asm/kvm_emulate.h>
+
+#include <kvm/arm_hypercalls.h>
+
+#define ARM_SMCCC_TRNG_VERSION_1_0 0x10000UL
+
+/* Those values are deliberately separate from the generic SMCCC definitions. */
+#define TRNG_SUCCESS 0UL
+#define TRNG_NOT_SUPPORTED ((unsigned long)-1)
+#define TRNG_INVALID_PARAMETER ((unsigned long)-2)
+#define TRNG_NO_ENTROPY ((unsigned long)-3)
+
+#define TRNG_MAX_BITS64 192
+
+static const uuid_t arm_smc_trng_uuid __aligned(4) = UUID_INIT(
+ 0x0d21e000, 0x4384, 0x11eb, 0x80, 0x70, 0x52, 0x44, 0x55, 0x4e, 0x5a, 0x4c);
+
+static int kvm_trng_do_rnd(struct kvm_vcpu *vcpu, int size)
+{
+ DECLARE_BITMAP(bits, TRNG_MAX_BITS64);
+ u32 num_bits = smccc_get_arg1(vcpu);
+ int i;
+
+ if (num_bits > 3 * size) {
+ smccc_set_retval(vcpu, TRNG_INVALID_PARAMETER, 0, 0, 0);
+ return 1;
+ }
+
+ /* get as many bits as we need to fulfil the request */
+ for (i = 0; i < DIV_ROUND_UP(num_bits, BITS_PER_LONG); i++)
+ bits[i] = get_random_long();
+
+ bitmap_clear(bits, num_bits, TRNG_MAX_BITS64 - num_bits);
+
+ if (size == 32)
+ smccc_set_retval(vcpu, TRNG_SUCCESS, lower_32_bits(bits[1]),
+ upper_32_bits(bits[0]), lower_32_bits(bits[0]));
+ else
+ smccc_set_retval(vcpu, TRNG_SUCCESS, bits[2], bits[1], bits[0]);
+
+ memzero_explicit(bits, sizeof(bits));
+ return 1;
+}
+
+int kvm_trng_call(struct kvm_vcpu *vcpu)
+{
+ const __le32 *u = (__le32 *)arm_smc_trng_uuid.b;
+ u32 func_id = smccc_get_function(vcpu);
+ unsigned long val = TRNG_NOT_SUPPORTED;
+ int size = 64;
+
+ switch (func_id) {
+ case ARM_SMCCC_TRNG_VERSION:
+ val = ARM_SMCCC_TRNG_VERSION_1_0;
+ break;
+ case ARM_SMCCC_TRNG_FEATURES:
+ switch (smccc_get_arg1(vcpu)) {
+ case ARM_SMCCC_TRNG_VERSION:
+ case ARM_SMCCC_TRNG_FEATURES:
+ case ARM_SMCCC_TRNG_GET_UUID:
+ case ARM_SMCCC_TRNG_RND32:
+ case ARM_SMCCC_TRNG_RND64:
+ val = TRNG_SUCCESS;
+ }
+ break;
+ case ARM_SMCCC_TRNG_GET_UUID:
+ smccc_set_retval(vcpu, le32_to_cpu(u[0]), le32_to_cpu(u[1]),
+ le32_to_cpu(u[2]), le32_to_cpu(u[3]));
+ return 1;
+ case ARM_SMCCC_TRNG_RND32:
+ size = 32;
+ fallthrough;
+ case ARM_SMCCC_TRNG_RND64:
+ return kvm_trng_do_rnd(vcpu, size);
+ }
+
+ smccc_set_retval(vcpu, val, 0, 0, 0);
+ return 1;
+}