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a8e190cdae
Provide a hypervisor implementation of the ARM architected TRNG firmware interface described in ARM spec DEN0098. All function IDs are implemented, including both 32-bit and 64-bit versions of the TRNG_RND service, which is the centerpiece of the API. The API is backed by the kernel's entropy pool only, to avoid guests draining more precious direct entropy sources. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> [Andre: minor fixes, drop arch_get_random() usage] Signed-off-by: Andre Przywara <andre.przywara@arm.com> Signed-off-by: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20210106103453.152275-6-andre.przywara@arm.com
85 lines
2.2 KiB
C
85 lines
2.2 KiB
C
// SPDX-License-Identifier: GPL-2.0
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// Copyright (C) 2020 Arm Ltd.
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#include <linux/arm-smccc.h>
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#include <linux/kvm_host.h>
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#include <asm/kvm_emulate.h>
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#include <kvm/arm_hypercalls.h>
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#define ARM_SMCCC_TRNG_VERSION_1_0 0x10000UL
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/* Those values are deliberately separate from the generic SMCCC definitions. */
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#define TRNG_SUCCESS 0UL
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#define TRNG_NOT_SUPPORTED ((unsigned long)-1)
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#define TRNG_INVALID_PARAMETER ((unsigned long)-2)
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#define TRNG_NO_ENTROPY ((unsigned long)-3)
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#define TRNG_MAX_BITS64 192
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static const uuid_t arm_smc_trng_uuid __aligned(4) = UUID_INIT(
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0x0d21e000, 0x4384, 0x11eb, 0x80, 0x70, 0x52, 0x44, 0x55, 0x4e, 0x5a, 0x4c);
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static int kvm_trng_do_rnd(struct kvm_vcpu *vcpu, int size)
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{
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DECLARE_BITMAP(bits, TRNG_MAX_BITS64);
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u32 num_bits = smccc_get_arg1(vcpu);
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int i;
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if (num_bits > 3 * size) {
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smccc_set_retval(vcpu, TRNG_INVALID_PARAMETER, 0, 0, 0);
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return 1;
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}
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/* get as many bits as we need to fulfil the request */
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for (i = 0; i < DIV_ROUND_UP(num_bits, BITS_PER_LONG); i++)
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bits[i] = get_random_long();
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bitmap_clear(bits, num_bits, TRNG_MAX_BITS64 - num_bits);
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if (size == 32)
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smccc_set_retval(vcpu, TRNG_SUCCESS, lower_32_bits(bits[1]),
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upper_32_bits(bits[0]), lower_32_bits(bits[0]));
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else
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smccc_set_retval(vcpu, TRNG_SUCCESS, bits[2], bits[1], bits[0]);
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memzero_explicit(bits, sizeof(bits));
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return 1;
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}
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int kvm_trng_call(struct kvm_vcpu *vcpu)
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{
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const __le32 *u = (__le32 *)arm_smc_trng_uuid.b;
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u32 func_id = smccc_get_function(vcpu);
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unsigned long val = TRNG_NOT_SUPPORTED;
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int size = 64;
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switch (func_id) {
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case ARM_SMCCC_TRNG_VERSION:
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val = ARM_SMCCC_TRNG_VERSION_1_0;
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break;
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case ARM_SMCCC_TRNG_FEATURES:
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switch (smccc_get_arg1(vcpu)) {
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case ARM_SMCCC_TRNG_VERSION:
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case ARM_SMCCC_TRNG_FEATURES:
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case ARM_SMCCC_TRNG_GET_UUID:
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case ARM_SMCCC_TRNG_RND32:
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case ARM_SMCCC_TRNG_RND64:
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val = TRNG_SUCCESS;
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}
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break;
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case ARM_SMCCC_TRNG_GET_UUID:
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smccc_set_retval(vcpu, le32_to_cpu(u[0]), le32_to_cpu(u[1]),
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le32_to_cpu(u[2]), le32_to_cpu(u[3]));
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return 1;
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case ARM_SMCCC_TRNG_RND32:
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size = 32;
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fallthrough;
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case ARM_SMCCC_TRNG_RND64:
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return kvm_trng_do_rnd(vcpu, size);
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}
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smccc_set_retval(vcpu, val, 0, 0, 0);
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return 1;
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}
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