From a8e190cdae1bf8e9e490776b8179babc1962bb25 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Wed, 6 Jan 2021 10:34:53 +0000 Subject: [PATCH] KVM: arm64: Implement the TRNG hypervisor call 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 [Andre: minor fixes, drop arch_get_random() usage] Signed-off-by: Andre Przywara Signed-off-by: Marc Zyngier Link: https://lore.kernel.org/r/20210106103453.152275-6-andre.przywara@arm.com --- arch/arm64/include/asm/kvm_host.h | 2 + arch/arm64/kvm/Makefile | 2 +- arch/arm64/kvm/hypercalls.c | 6 +++ arch/arm64/kvm/trng.c | 85 +++++++++++++++++++++++++++++++ 4 files changed, 94 insertions(+), 1 deletion(-) create mode 100644 arch/arm64/kvm/trng.c diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index 8fcfab0c2567..084d11a2768c 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -771,4 +771,6 @@ bool kvm_arm_vcpu_is_finalized(struct kvm_vcpu *vcpu); #define kvm_vcpu_has_pmu(vcpu) \ (test_bit(KVM_ARM_VCPU_PMU_V3, (vcpu)->arch.features)) +int kvm_trng_call(struct kvm_vcpu *vcpu); + #endif /* __ARM64_KVM_HOST_H__ */ diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile index 13b017284bf9..589921392cb1 100644 --- a/arch/arm64/kvm/Makefile +++ b/arch/arm64/kvm/Makefile @@ -16,7 +16,7 @@ kvm-y := $(KVM)/kvm_main.o $(KVM)/coalesced_mmio.o $(KVM)/eventfd.o \ inject_fault.o va_layout.o handle_exit.o \ guest.o debug.o reset.o sys_regs.o \ vgic-sys-reg-v3.o fpsimd.o pmu.o \ - arch_timer.o \ + arch_timer.o trng.o\ vgic/vgic.o vgic/vgic-init.o \ vgic/vgic-irqfd.o vgic/vgic-v2.o \ vgic/vgic-v3.o vgic/vgic-v4.o \ diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c index 25ea4ecb6449..ead21b98b620 100644 --- a/arch/arm64/kvm/hypercalls.c +++ b/arch/arm64/kvm/hypercalls.c @@ -71,6 +71,12 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu) if (gpa != GPA_INVALID) val = gpa; break; + 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: + return kvm_trng_call(vcpu); default: return kvm_psci_call(vcpu); } diff --git a/arch/arm64/kvm/trng.c b/arch/arm64/kvm/trng.c new file mode 100644 index 000000000000..99bdd7103c9c --- /dev/null +++ b/arch/arm64/kvm/trng.c @@ -0,0 +1,85 @@ +// SPDX-License-Identifier: GPL-2.0 +// Copyright (C) 2020 Arm Ltd. + +#include +#include + +#include + +#include + +#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; +}