.endm
/*
+ * Clear Branch History instruction
+ */
+ .macro clearbhb
+ hint #22
+ .endm
+
+/*
* Speculation barrier
*/
.macro sb
ldp x0, x1, [sp], #16
#endif /* CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY */
.endm
+
+ .macro mitigate_spectre_bhb_clear_insn
+#ifdef CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY
+alternative_cb spectre_bhb_patch_clearbhb
+ /* Patched to NOP when not supported */
+ clearbhb
+ isb
+alternative_cb_end
+#endif /* CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY */
+ .endm
#endif /* __ASM_ASSEMBLER_H */
return csv2_val == 3;
}
+static inline bool supports_clearbhb(int scope)
+{
+ u64 isar2;
+
+ if (scope == SCOPE_LOCAL_CPU)
+ isar2 = read_sysreg_s(SYS_ID_AA64ISAR2_EL1);
+ else
+ isar2 = read_sanitised_ftr_reg(SYS_ID_AA64ISAR2_EL1);
+
+ return cpuid_feature_extract_unsigned_field(isar2,
+ ID_AA64ISAR2_CLEARBHB_SHIFT);
+}
+
const struct cpumask *system_32bit_el0_cpumask(void);
DECLARE_STATIC_KEY_FALSE(arm64_mismatched_32bit_el0);
AARCH64_INSN_HINT_PSB = 0x11 << 5,
AARCH64_INSN_HINT_TSB = 0x12 << 5,
AARCH64_INSN_HINT_CSDB = 0x14 << 5,
+ AARCH64_INSN_HINT_CLEARBHB = 0x16 << 5,
AARCH64_INSN_HINT_BTI = 0x20 << 5,
AARCH64_INSN_HINT_BTIC = 0x22 << 5,
#define ID_AA64ISAR1_GPI_IMP_DEF 0x1
/* id_aa64isar2 */
+#define ID_AA64ISAR2_CLEARBHB_SHIFT 28
#define ID_AA64ISAR2_RPRES_SHIFT 4
#define ID_AA64ISAR2_WFXT_SHIFT 0
* canonical vectors.
*/
EL1_VECTOR_BHB_FW,
+
+ /*
+ * Use the ClearBHB instruction, before branching to the canonical
+ * vectors.
+ */
+ EL1_VECTOR_BHB_CLEAR_INSN,
#endif /* CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY */
/*
#ifndef CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY
#define EL1_VECTOR_BHB_LOOP -1
#define EL1_VECTOR_BHB_FW -1
+#define EL1_VECTOR_BHB_CLEAR_INSN -1
#endif /* !CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY */
/* The vectors to use on return from EL0. e.g. to remap the kernel */
};
static const struct arm64_ftr_bits ftr_id_aa64isar2[] = {
+ ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_HIGHER_SAFE, ID_AA64ISAR2_CLEARBHB_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_VISIBLE, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64ISAR2_RPRES_SHIFT, 4, 0),
ARM64_FTR_END,
};
#define BHB_MITIGATION_NONE 0
#define BHB_MITIGATION_LOOP 1
#define BHB_MITIGATION_FW 2
+#define BHB_MITIGATION_INSN 3
.macro tramp_ventry, vector_start, regsize, kpti, bhb
.align 7
__mitigate_spectre_bhb_loop x30
.endif // \bhb == BHB_MITIGATION_LOOP
+ .if \bhb == BHB_MITIGATION_INSN
+ clearbhb
+ isb
+ .endif // \bhb == BHB_MITIGATION_INSN
+
.if \kpti == 1
/*
* Defend against branch aliasing attacks by pushing a dummy
#ifdef CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY
generate_tramp_vector kpti=1, bhb=BHB_MITIGATION_LOOP
generate_tramp_vector kpti=1, bhb=BHB_MITIGATION_FW
+ generate_tramp_vector kpti=1, bhb=BHB_MITIGATION_INSN
#endif /* CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY */
generate_tramp_vector kpti=1, bhb=BHB_MITIGATION_NONE
SYM_CODE_END(tramp_vectors)
#ifdef CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY
generate_el1_vector bhb=BHB_MITIGATION_LOOP
generate_el1_vector bhb=BHB_MITIGATION_FW
+ generate_el1_vector bhb=BHB_MITIGATION_INSN
#endif /* CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY */
SYM_CODE_END(__bp_harden_el1_vectors)
.popsection
KVM_NVHE_ALIAS(spectre_bhb_patch_loop_iter);
KVM_NVHE_ALIAS(spectre_bhb_patch_loop_mitigation_enable);
KVM_NVHE_ALIAS(spectre_bhb_patch_wa3);
+KVM_NVHE_ALIAS(spectre_bhb_patch_clearbhb);
/* Global kernel state accessed by nVHE hyp code. */
KVM_NVHE_ALIAS(kvm_vgic_global_state);
* - Mitigated by a branchy loop a CPU specific number of times, and listed
* in our "loop mitigated list".
* - Mitigated in software by the firmware Spectre v2 call.
+ * - Has the ClearBHB instruction to perform the mitigation.
* - Has the 'Exception Clears Branch History Buffer' (ECBHB) feature, so no
* software mitigation in the vectors is needed.
* - Has CSV2.3, so is unaffected.
BHB_LOOP,
BHB_FW,
BHB_HW,
+ BHB_INSN,
};
static unsigned long system_bhb_mitigations;
if (supports_csv2p3(scope))
return false;
+ if (supports_clearbhb(scope))
+ return true;
+
if (spectre_bhb_loop_affected(scope))
return true;
} else if (supports_ecbhb(SCOPE_LOCAL_CPU)) {
state = SPECTRE_MITIGATED;
set_bit(BHB_HW, &system_bhb_mitigations);
+ } else if (supports_clearbhb(SCOPE_LOCAL_CPU)) {
+ /*
+ * Ensure KVM uses the indirect vector which will have ClearBHB
+ * added.
+ */
+ if (!data->slot)
+ data->slot = HYP_VECTOR_INDIRECT;
+
+ this_cpu_set_vectors(EL1_VECTOR_BHB_CLEAR_INSN);
+ state = SPECTRE_MITIGATED;
+ set_bit(BHB_INSN, &system_bhb_mitigations);
} else if (spectre_bhb_loop_affected(SCOPE_LOCAL_CPU)) {
/*
* Ensure KVM uses the indirect vector which will have the
*updptr++ = cpu_to_le32(insn);
}
+
+/* Patched to NOP when not supported */
+void __init spectre_bhb_patch_clearbhb(struct alt_instr *alt,
+ __le32 *origptr, __le32 *updptr, int nr_inst)
+{
+ BUG_ON(nr_inst != 2);
+
+ if (test_bit(BHB_INSN, &system_bhb_mitigations))
+ return;
+
+ *updptr++ = cpu_to_le32(aarch64_insn_gen_nop());
+ *updptr++ = cpu_to_le32(aarch64_insn_gen_nop());
+}
.else
stp x0, x1, [sp, #-16]!
mitigate_spectre_bhb_loop x0
+ mitigate_spectre_bhb_clear_insn
.endif
.if \indirect != 0
alternative_cb kvm_patch_vector_branch