Commit ec82b567 authored by Shanker Donthineni's avatar Shanker Donthineni Committed by Catalin Marinas

arm64: Implement branch predictor hardening for Falkor

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: default avatarShanker Donthineni <shankerd@codeaurora.org>
[will: fix label name when !CONFIG_KVM and remove references to MIDR_FALKOR]
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent aa6acde6
......@@ -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 */
......@@ -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__ */
......@@ -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)
......@@ -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 +329,15 @@ 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_BP_POST_GUEST_EXIT,
MIDR_ALL_VERSIONS(MIDR_QCOM_FALKOR_V1),
},
#endif
{
}
......
......@@ -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)
......@@ -406,6 +406,14 @@ 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_V1)
__qcom_hyp_sanitize_btac_predictors();
}
fp_enabled = __fpsimd_enabled();
__sysreg_save_guest_state(guest_ctxt);
......
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