Hi Ard,
On Sat, Oct 03, 2020 at 10:56:04AM +0200, Ard Biesheuvel wrote:
> 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 arch_get_random_seed_long(), which is implemented
> in terms of RNDR currently, and will be alternatively backed by a SMC
> call to the secure firmware using same interface after a future patch.
> If neither are available, the kernel's entropy pool is used instead.
>
> Cc: Marc Zyngier <m...@kernel.org>
> Cc: James Morse <james.mo...@arm.com>
> Cc: Julien Thierry <julien.thierry.k...@gmail.com>
> Cc: Suzuki K Poulose <suzuki.poul...@arm.com>
> Cc: Catalin Marinas <catalin.mari...@arm.com>
> Cc: Will Deacon <w...@kernel.org>
> Cc: Mark Rutland <mark.rutl...@arm.com>
> Cc: Lorenzo Pieralisi <lorenzo.pieral...@arm.com>
> Cc: Sudeep Holla <sudeep.ho...@arm.com>
> Cc: Sami Mujawar <sami.muja...@arm.com>
> Cc: Andre Przywara <andre.przyw...@arm.com>
> Cc: Alexandru Elisei <alexandru.eli...@arm.com>
> Cc: Laszlo Ersek <ler...@redhat.com>
> Cc: Leif Lindholm <l...@nuviainc.com>
> Signed-off-by: Ard Biesheuvel <a...@kernel.org>
> ---
> arch/arm64/include/asm/kvm_host.h | 2 +
> arch/arm64/kvm/Makefile | 2 +-
> arch/arm64/kvm/hypercalls.c | 6 ++
> arch/arm64/kvm/trng.c | 91 ++++++++++++++++++++
> include/linux/arm-smccc.h | 31 +++++++
> 5 files changed, 131 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/include/asm/kvm_host.h
> b/arch/arm64/include/asm/kvm_host.h
> index 65568b23868a..f76164d390ea 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -688,4 +688,6 @@ bool kvm_arm_vcpu_is_finalized(struct kvm_vcpu *vcpu);
> #define kvm_arm_vcpu_sve_finalized(vcpu) \
> ((vcpu)->arch.flags & KVM_ARM64_VCPU_SVE_FINALIZED)
>
> +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 99977c1972cc..e117d7086500 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 regmap.o va_layout.o hyp.o handle_exit.o \
> guest.o debug.o reset.o sys_regs.o \
> vgic-sys-reg-v3.o fpsimd.o pmu.o \
> - aarch32.o arch_timer.o \
> + aarch32.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 550dfa3e53cd..70c5e815907d 100644
> --- a/arch/arm64/kvm/hypercalls.c
> +++ b/arch/arm64/kvm/hypercalls.c
> @@ -62,6 +62,12 @@ 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_RND:
> + 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..71f704075e4a
> --- /dev/null
> +++ b/arch/arm64/kvm/trng.c
> @@ -0,0 +1,91 @@
> +// 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
> +
> +#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 MAX_BITS32 96
> +#define MAX_BITS64 192
> +
> +static const uuid_t arm_smc_trng_uuid __aligned(4) = UUID_INIT(
> + 0x023534a2, 0xe0bc, 0x45ec, 0x95, 0xdd, 0x33, 0x34, 0xc1, 0xcc, 0x31,
> 0x89);
Where does this UUID come from?
> +
> +static int kvm_trng_do_rnd(struct kvm_vcpu *vcpu, int size)
> +{
> + u32 num_bits = smccc_get_arg1(vcpu);
> + u64 bits[3];
> + int i;
> +
> + if (num_bits > 3 * size) {
> + smccc_set_retval(vcpu, TRNG_NOT_SUPPORTED, 0, 0, 0);
The spec says we should return "INVALID_PARAMETERS" when N > MAX_BITS.
Of course "INVALID_PARAMETERS", with the 'S', doesn't exist in "Return
codes", but I guess they meant "INVALID_PARAMETER", not NOT_SUPPORTED.
> + return 1;
> + }
> +
> + /* get as many bits as we need to fulfil the request */
> + for (i = 0; i < DIV_ROUND_UP(num_bits, 64); i++)
> + /* use the arm64 specific backend directly if one exists */
> + if (!arch_get_random_seed_long((unsigned long *)&bits[i]))
> + bits[i] = get_random_long();
> +
> + if (num_bits % 64)
> + bits[i - 1] &= U64_MAX >> (64 - (num_bits % 64));
> +
> + while (i < ARRAY_SIZE(bits))
> + bits[i++] = 0;
> +
> + 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 __be32 *u = (__be32 *)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_RND:
> + case ARM_SMCCC_TRNG_RND64:
> + val = TRNG_SUCCESS;
> + }
> + break;
> + case ARM_SMCCC_TRNG_GET_UUID:
> + smccc_set_retval(vcpu, be32_to_cpu(u[3]), be32_to_cpu(u[2]),
> + be32_to_cpu(u[1]), be32_to_cpu(u[0]));
What if our host CPU is BE? We need to return these words in LE according
to 5.3 of DEN0028C.
> + return 1;
> + case ARM_SMCCC_TRNG_RND:
> + 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;
> +}
> diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
> index 15c706fb0a37..9c9decd329b7 100644
> --- a/include/linux/arm-smccc.h
> +++ b/include/linux/arm-smccc.h
> @@ -99,6 +99,37 @@
> ARM_SMCCC_OWNER_STANDARD_HYP, \
> 0x21)
>
> +/* TRNG entropy source calls (defined by ARM DEN0098) */
> +#define ARM_SMCCC_TRNG_VERSION \
> + ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \
> + ARM_SMCCC_SMC_32, \
> + ARM_SMCCC_OWNER_STANDARD, \
> + 0x50)
> +
> +#define ARM_SMCCC_TRNG_FEATURES \
> + ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \
> + ARM_SMCCC_SMC_32, \
> + ARM_SMCCC_OWNER_STANDARD, \
> + 0x51)
> +
> +#define ARM_SMCCC_TRNG_GET_UUID \
> + ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \
> + ARM_SMCCC_SMC_32, \
> + ARM_SMCCC_OWNER_STANDARD, \
> + 0x52)
> +
> +#define ARM_SMCCC_TRNG_RND \
> + ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \
> + ARM_SMCCC_SMC_32, \
> + ARM_SMCCC_OWNER_STANDARD, \
> + 0x53)
> +
> +#define ARM_SMCCC_TRNG_RND64 \
> + ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \
> + ARM_SMCCC_SMC_64, \
> + ARM_SMCCC_OWNER_STANDARD, \
> + 0x53)
> +
> /*
> * Return codes defined in ARM DEN 0070A
> * ARM DEN 0070A is now merged/consolidated into ARM DEN 0028 C
> --
> 2.17.1
>
> _______________________________________________
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> kvmarm@lists.cs.columbia.edu
> https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
>
Thanks,
drew
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