Re: [PATCH v3 12/13] arm64: Implement branch predictor hardening for Falkor
From: Shanker Donthineni
Date: Fri Jan 12 2018 - 12:59:06 EST
Hi Will,
This patch is the right one for variant2, checks QDF2400 part numbers QCOM_FALKOR and FALKOR_V1
but unfortunately it got modified and merged to linux-next branch causing confusion.Please revert
and merge [V2] patch to fix the problem.
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/arch/arm64?h=next-20180112&id=ec82b567a74fbdffdf418d4bb381d55f6a9096af
[v2] https://www.spinics.net/lists/arm-kernel/msg627364.html
Thanks,
Shanker
On 01/08/2018 11:32 AM, Will Deacon wrote:
> From: Shanker Donthineni <shankerd@xxxxxxxxxxxxxx>
>
> Falkor is susceptible to branch predictor aliasing and can
> theoretically be attacked by malicious code. This patch
> implements a mitigation for these attacks, preventing any
> malicious entries from affecting other victim contexts.
>
> Signed-off-by: Shanker Donthineni <shankerd@xxxxxxxxxxxxxx>
> [will: fix label name when !CONFIG_KVM]
> Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
> ---
> arch/arm64/include/asm/cpucaps.h | 3 ++-
> arch/arm64/include/asm/kvm_asm.h | 2 ++
> arch/arm64/kernel/bpi.S | 8 +++++++
> arch/arm64/kernel/cpu_errata.c | 49 ++++++++++++++++++++++++++++++++++++++--
> arch/arm64/kvm/hyp/entry.S | 12 ++++++++++
> arch/arm64/kvm/hyp/switch.c | 10 ++++++++
> 6 files changed, 81 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
> index 51616e77fe6b..7049b4802587 100644
> --- a/arch/arm64/include/asm/cpucaps.h
> +++ b/arch/arm64/include/asm/cpucaps.h
> @@ -43,7 +43,8 @@
> #define ARM64_SVE 22
> #define ARM64_UNMAP_KERNEL_AT_EL0 23
> #define ARM64_HARDEN_BRANCH_PREDICTOR 24
> +#define ARM64_HARDEN_BP_POST_GUEST_EXIT 25
>
> -#define ARM64_NCAPS 25
> +#define ARM64_NCAPS 26
>
> #endif /* __ASM_CPUCAPS_H */
> diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
> index ab4d0a926043..24961b732e65 100644
> --- a/arch/arm64/include/asm/kvm_asm.h
> +++ b/arch/arm64/include/asm/kvm_asm.h
> @@ -68,6 +68,8 @@ extern u32 __kvm_get_mdcr_el2(void);
>
> extern u32 __init_stage2_translation(void);
>
> +extern void __qcom_hyp_sanitize_btac_predictors(void);
> +
> #endif
>
> #endif /* __ARM_KVM_ASM_H__ */
> diff --git a/arch/arm64/kernel/bpi.S b/arch/arm64/kernel/bpi.S
> index dec95bd82e31..76225c2611ea 100644
> --- a/arch/arm64/kernel/bpi.S
> +++ b/arch/arm64/kernel/bpi.S
> @@ -77,3 +77,11 @@ ENTRY(__psci_hyp_bp_inval_start)
> ldp x0, x1, [sp, #(16 * 8)]
> add sp, sp, #(8 * 18)
> ENTRY(__psci_hyp_bp_inval_end)
> +
> +ENTRY(__qcom_hyp_sanitize_link_stack_start)
> + stp x29, x30, [sp, #-16]!
> + .rept 16
> + bl . + 4
> + .endr
> + ldp x29, x30, [sp], #16
> +ENTRY(__qcom_hyp_sanitize_link_stack_end)
> diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
> index cb0fb3796bb8..7b4efde087fc 100644
> --- a/arch/arm64/kernel/cpu_errata.c
> +++ b/arch/arm64/kernel/cpu_errata.c
> @@ -54,6 +54,8 @@ DEFINE_PER_CPU_READ_MOSTLY(struct bp_hardening_data, bp_hardening_data);
>
> #ifdef CONFIG_KVM
> 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[];
>
> static void __copy_hyp_vect_bpi(int slot, const char *hyp_vecs_start,
> const char *hyp_vecs_end)
> @@ -96,8 +98,10 @@ static void __install_bp_hardening_cb(bp_hardening_cb_t fn,
> spin_unlock(&bp_lock);
> }
> #else
> -#define __psci_hyp_bp_inval_start NULL
> -#define __psci_hyp_bp_inval_end NULL
> +#define __psci_hyp_bp_inval_start NULL
> +#define __psci_hyp_bp_inval_end NULL
> +#define __qcom_hyp_sanitize_link_stack_start NULL
> +#define __qcom_hyp_sanitize_link_stack_end NULL
>
> static void __install_bp_hardening_cb(bp_hardening_cb_t fn,
> const char *hyp_vecs_start,
> @@ -138,6 +142,29 @@ static int enable_psci_bp_hardening(void *data)
>
> return 0;
> }
> +
> +static void qcom_link_stack_sanitization(void)
> +{
> + u64 tmp;
> +
> + asm volatile("mov %0, x30 \n"
> + ".rept 16 \n"
> + "bl . + 4 \n"
> + ".endr \n"
> + "mov x30, %0 \n"
> + : "=&r" (tmp));
> +}
> +
> +static int qcom_enable_link_stack_sanitization(void *data)
> +{
> + const struct arm64_cpu_capabilities *entry = data;
> +
> + install_bp_hardening_cb(entry, qcom_link_stack_sanitization,
> + __qcom_hyp_sanitize_link_stack_start,
> + __qcom_hyp_sanitize_link_stack_end);
> +
> + return 0;
> +}
> #endif /* CONFIG_HARDEN_BRANCH_PREDICTOR */
>
> #define MIDR_RANGE(model, min, max) \
> @@ -302,6 +329,24 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
> MIDR_ALL_VERSIONS(MIDR_CORTEX_A75),
> .enable = enable_psci_bp_hardening,
> },
> + {
> + .capability = ARM64_HARDEN_BRANCH_PREDICTOR,
> + MIDR_ALL_VERSIONS(MIDR_QCOM_FALKOR_V1),
> + .enable = qcom_enable_link_stack_sanitization,
> + },
> + {
> + .capability = ARM64_HARDEN_BRANCH_PREDICTOR,
> + MIDR_ALL_VERSIONS(MIDR_QCOM_FALKOR),
> + .enable = qcom_enable_link_stack_sanitization,
> + },
> + {
> + .capability = ARM64_HARDEN_BP_POST_GUEST_EXIT,
> + MIDR_ALL_VERSIONS(MIDR_QCOM_FALKOR_V1),
> + },
> + {
> + .capability = ARM64_HARDEN_BP_POST_GUEST_EXIT,
> + MIDR_ALL_VERSIONS(MIDR_QCOM_FALKOR),
> + },
> #endif
> {
> }
> diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
> index 12ee62d6d410..9c45c6af1f58 100644
> --- a/arch/arm64/kvm/hyp/entry.S
> +++ b/arch/arm64/kvm/hyp/entry.S
> @@ -196,3 +196,15 @@ alternative_endif
>
> eret
> ENDPROC(__fpsimd_guest_restore)
> +
> +ENTRY(__qcom_hyp_sanitize_btac_predictors)
> + /**
> + * Call SMC64 with Silicon provider serviceID 23<<8 (0xc2001700)
> + * 0xC2000000-0xC200FFFF: assigned to SiP Service Calls
> + * b15-b0: contains SiP functionID
> + */
> + movz x0, #0x1700
> + movk x0, #0xc200, lsl #16
> + smc #0
> + ret
> +ENDPROC(__qcom_hyp_sanitize_btac_predictors)
> diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> index 4d273f6d0e69..7e373791fad1 100644
> --- a/arch/arm64/kvm/hyp/switch.c
> +++ b/arch/arm64/kvm/hyp/switch.c
> @@ -406,6 +406,16 @@ int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu)
> /* 0 falls through to be handled out of EL2 */
> }
>
> + if (cpus_have_const_cap(ARM64_HARDEN_BP_POST_GUEST_EXIT)) {
> + u32 midr = read_cpuid_id();
> +
> + /* Apply BTAC predictors mitigation to all Falkor chips */
> + if (((midr & MIDR_CPU_MODEL_MASK) == MIDR_QCOM_FALKOR) ||
> + ((midr & MIDR_CPU_MODEL_MASK) == MIDR_QCOM_FALKOR_V1)) {
> + __qcom_hyp_sanitize_btac_predictors();
> + }
> + }
> +
> fp_enabled = __fpsimd_enabled();
>
> __sysreg_save_guest_state(guest_ctxt);
>
--
Shanker Donthineni
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.