Re: [PATCH v2 16/16] arm64: Add ARM_SMCCC_ARCH_WORKAROUND_1 BP hardening support

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

On 29 January 2018 at 17:45, Marc Zyngier <marc.zyngier@arm.com> wrote:
> Add the detection and runtime code for ARM_SMCCC_ARCH_WORKAROUND_1.
> It is lovely. Really.
>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> ---
>  arch/arm64/include/asm/kvm_psci.h | 63 ++++++++++++++++++++++++++++++++++++
>  arch/arm64/kernel/bpi.S           | 20 ++++++++++++
>  arch/arm64/kernel/cpu_errata.c    | 68 ++++++++++++++++++++++++++++++++++++++-
>  3 files changed, 150 insertions(+), 1 deletion(-)
>  create mode 100644 arch/arm64/include/asm/kvm_psci.h
>
> diff --git a/arch/arm64/include/asm/kvm_psci.h b/arch/arm64/include/asm/kvm_psci.h

Did you mean to add this file? It is mostly identical to include/kvm/arm_psci.h

> new file mode 100644
> index 000000000000..f553e3795a4e
> --- /dev/null
> +++ b/arch/arm64/include/asm/kvm_psci.h
> @@ -0,0 +1,63 @@
> +/*
> + * Copyright (C) 2012,2013 - ARM Ltd
> + * Author: Marc Zyngier <marc.zyngier@arm.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program.  If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#ifndef __ARM64_KVM_PSCI_H__
> +#define __ARM64_KVM_PSCI_H__
> +
> +#include <linux/kvm_host.h>
> +
> +#define PSCI_VERSION(x,y)      ((((x) & 0x7fff) << 16) | ((y) & 0xffff))
> +#define KVM_ARM_PSCI_0_1       PSCI_VERSION(0, 1)
> +#define KVM_ARM_PSCI_0_2       PSCI_VERSION(0, 2)
> +#define KVM_ARM_PSCI_1_0       PSCI_VERSION(1, 0)
> +
> +#define KVM_ARM_PSCI_LATEST    KVM_ARM_PSCI_1_0
> +
> +/*
> + * We need the KVM pointer independently from the vcpu as we can call
> + * this from HYP, and need to apply kern_hyp_va on it...
> + */
> +static inline int kvm_psci_version(struct kvm_vcpu *vcpu, struct kvm *kvm)
> +{
> +       /*
> +        * Our PSCI implementation stays the same across versions from
> +        * v0.2 onward, only adding the few mandatory functions (such
> +        * as FEATURES with 1.0) that are required by newer
> +        * revisions. It is thus safe to return the latest, unless
> +        * userspace has instructed us otherwise.
> +        */
> +       if (test_bit(KVM_ARM_VCPU_PSCI_0_2, vcpu->arch.features)) {
> +               if (kvm->arch.psci_version)
> +                       return kvm->arch.psci_version;
> +
> +               return KVM_ARM_PSCI_LATEST;
> +       }
> +
> +       return KVM_ARM_PSCI_0_1;
> +}
> +
> +
> +int kvm_hvc_call_handler(struct kvm_vcpu *vcpu);
> +
> +struct kvm_one_reg;
> +
> +int kvm_arm_get_fw_num_regs(struct kvm_vcpu *vcpu);
> +int kvm_arm_copy_fw_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices);
> +int kvm_arm_get_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg);
> +int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg);
> +
> +#endif /* __ARM64_KVM_PSCI_H__ */
> diff --git a/arch/arm64/kernel/bpi.S b/arch/arm64/kernel/bpi.S
> index 76225c2611ea..fdeed629f2c6 100644
> --- a/arch/arm64/kernel/bpi.S
> +++ b/arch/arm64/kernel/bpi.S
> @@ -17,6 +17,7 @@
>   */
>
>  #include <linux/linkage.h>
> +#include <linux/arm-smccc.h>
>
>  .macro ventry target
>         .rept 31
> @@ -85,3 +86,22 @@ ENTRY(__qcom_hyp_sanitize_link_stack_start)
>         .endr
>         ldp     x29, x30, [sp], #16
>  ENTRY(__qcom_hyp_sanitize_link_stack_end)
> +
> +.macro smccc_workaround_1 inst
> +       sub     sp, sp, #(8 * 4)
> +       stp     x2, x3, [sp, #(8 * 0)]
> +       stp     x0, x1, [sp, #(8 * 2)]
> +       mov     w0, #ARM_SMCCC_ARCH_WORKAROUND_1
> +       \inst   #0
> +       ldp     x2, x3, [sp, #(8 * 0)]
> +       ldp     x0, x1, [sp, #(8 * 2)]
> +       add     sp, sp, #(8 * 4)
> +.endm
> +
> +ENTRY(__smccc_workaround_1_smc_start)
> +       smccc_workaround_1      smc
> +ENTRY(__smccc_workaround_1_smc_end)
> +
> +ENTRY(__smccc_workaround_1_hvc_start)
> +       smccc_workaround_1      hvc
> +ENTRY(__smccc_workaround_1_hvc_end)
> diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
> index ed6881882231..36cff870d5d7 100644
> --- a/arch/arm64/kernel/cpu_errata.c
> +++ b/arch/arm64/kernel/cpu_errata.c
> @@ -70,6 +70,10 @@ DEFINE_PER_CPU_READ_MOSTLY(struct bp_hardening_data, bp_hardening_data);
>  extern char __psci_hyp_bp_inval_start[], __psci_hyp_bp_inval_end[];
>  extern char __qcom_hyp_sanitize_link_stack_start[];
>  extern char __qcom_hyp_sanitize_link_stack_end[];
> +extern char __smccc_workaround_1_smc_start[];
> +extern char __smccc_workaround_1_smc_end[];
> +extern char __smccc_workaround_1_hvc_start[];
> +extern char __smccc_workaround_1_hvc_end[];
>
>  static void __copy_hyp_vect_bpi(int slot, const char *hyp_vecs_start,
>                                 const char *hyp_vecs_end)
> @@ -116,6 +120,10 @@ static void __install_bp_hardening_cb(bp_hardening_cb_t fn,
>  #define __psci_hyp_bp_inval_end                        NULL
>  #define __qcom_hyp_sanitize_link_stack_start   NULL
>  #define __qcom_hyp_sanitize_link_stack_end     NULL
> +#define __smccc_workaround_1_smc_start         NULL
> +#define __smccc_workaround_1_smc_end           NULL
> +#define __smccc_workaround_1_hvc_start         NULL
> +#define __smccc_workaround_1_hvc_end           NULL
>
>  static void __install_bp_hardening_cb(bp_hardening_cb_t fn,
>                                       const char *hyp_vecs_start,
> @@ -142,17 +150,75 @@ static void  install_bp_hardening_cb(const struct arm64_cpu_capabilities *entry,
>         __install_bp_hardening_cb(fn, hyp_vecs_start, hyp_vecs_end);
>  }
>
> +#include <uapi/linux/psci.h>
> +#include <linux/arm-smccc.h>
>  #include <linux/psci.h>
>
> +static void call_smc_arch_workaround_1(void)
> +{
> +       arm_smccc_1_1_smc(ARM_SMCCC_ARCH_WORKAROUND_1, NULL);
> +}
> +
> +static void call_hvc_arch_workaround_1(void)
> +{
> +       arm_smccc_1_1_hvc(ARM_SMCCC_ARCH_WORKAROUND_1, NULL);
> +}
> +
> +static bool check_smccc_arch_workaround_1(const struct arm64_cpu_capabilities *entry)
> +{
> +       bp_hardening_cb_t cb;
> +       void *smccc_start, *smccc_end;
> +       struct arm_smccc_res res;
> +
> +       if (!entry->matches(entry, SCOPE_LOCAL_CPU))
> +               return false;
> +
> +       if (psci_ops.variant == SMCCC_VARIANT_1_0)
> +               return false;
> +
> +       switch (psci_ops.conduit) {
> +       case PSCI_CONDUIT_HVC:
> +               arm_smccc_1_1_hvc(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
> +                                 ARM_SMCCC_ARCH_WORKAROUND_1, &res);
> +               if (res.a0)
> +                       return false;
> +               cb = call_hvc_arch_workaround_1;
> +               smccc_start = __smccc_workaround_1_hvc_start;
> +               smccc_end = __smccc_workaround_1_hvc_end;
> +               break;
> +
> +       case PSCI_CONDUIT_SMC:
> +               arm_smccc_1_1_smc(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
> +                                 ARM_SMCCC_ARCH_WORKAROUND_1, &res);
> +               if (res.a0)
> +                       return false;
> +               cb = call_smc_arch_workaround_1;
> +               smccc_start = __smccc_workaround_1_smc_start;
> +               smccc_end = __smccc_workaround_1_smc_end;
> +               break;
> +
> +       default:
> +               return false;
> +       }
> +
> +       install_bp_hardening_cb(entry, cb, smccc_start, smccc_end);
> +
> +       return true;
> +}
> +
>  static int enable_psci_bp_hardening(void *data)
>  {
>         const struct arm64_cpu_capabilities *entry = data;
>
> -       if (psci_ops.get_version)
> +       if (psci_ops.get_version) {
> +               if (check_smccc_arch_workaround_1(entry))
> +                       return 0;
> +
>                 install_bp_hardening_cb(entry,
>                                        (bp_hardening_cb_t)psci_ops.get_version,
>                                        __psci_hyp_bp_inval_start,
>                                        __psci_hyp_bp_inval_end);
> +       }
>
>         return 0;
>  }
> --
> 2.14.2
>