@@ -872,6 +872,16 @@ config ARM64_SSBD
If unsure, say Y.
+config MITIGATE_SPECTRE_BRANCH_HISTORY
+ bool "Mitigate Spectre style attacks against branch history" if EXPERT
+ default y
+ depends on HARDEN_BRANCH_PREDICTOR || !KVM
+ help
+ Speculation attacks against some high-performance processors can
+ make use of branch history to influence future speculation.
+ When taking an exception from user-space, a sequence of branches
+ or a firmware call overwrites the branch history.
+
menuconfig ARMV8_DEPRECATED
bool "Emulate deprecated/obsolete ARMv8 instructions"
depends on COMPAT
@@ -551,7 +551,9 @@ alternative_endif
.macro __mitigate_spectre_bhb_loop tmp
#ifdef CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY
- mov \tmp, #32
+alternative_cb spectre_bhb_patch_loop_iter
+ mov \tmp, #32 // Patched to correct the immediate
+alternative_cb_end
.Lspectre_bhb_loop\@:
b . + 4
subs \tmp, \tmp, #1
@@ -456,6 +456,21 @@ static inline bool cpu_supports_mixed_endian_el0(void)
return id_aa64mmfr0_mixed_endian_el0(read_cpuid(ID_AA64MMFR0_EL1));
}
+static inline bool supports_csv2p3(int scope)
+{
+ u64 pfr0;
+ u8 csv2_val;
+
+ if (scope == SCOPE_LOCAL_CPU)
+ pfr0 = read_sysreg_s(SYS_ID_AA64PFR0_EL1);
+ else
+ pfr0 = read_sanitised_ftr_reg(SYS_ID_AA64PFR0_EL1);
+
+ csv2_val = cpuid_feature_extract_unsigned_field(pfr0,
+ ID_AA64PFR0_CSV2_SHIFT);
+ return csv2_val == 3;
+}
+
static inline bool system_supports_32bit_el0(void)
{
return cpus_have_const_cap(ARM64_HAS_32BIT_EL0);
@@ -503,6 +518,9 @@ enum mitigation_state {
};
enum mitigation_state arm64_get_spectre_bhb_state(void);
+bool is_spectre_bhb_affected(const struct arm64_cpu_capabilities *entry, int scope);
+u8 spectre_bhb_loop_affected(int scope);
+void spectre_bhb_enable_mitigation(const struct arm64_cpu_capabilities *__unused);
#endif /* __ASSEMBLY__ */
#endif
@@ -90,9 +90,13 @@
#define ARM_CPU_PART_CORTEX_A76 0xD0B
#define ARM_CPU_PART_NEOVERSE_N1 0xD0C
#define ARM_CPU_PART_CORTEX_A77 0xD0D
+#define ARM_CPU_PART_NEOVERSE_V1 0xD40
+#define ARM_CPU_PART_CORTEX_A78 0xD41
+#define ARM_CPU_PART_CORTEX_X1 0xD44
#define ARM_CPU_PART_CORTEX_A710 0xD47
#define ARM_CPU_PART_CORTEX_X2 0xD48
#define ARM_CPU_PART_NEOVERSE_N2 0xD49
+#define ARM_CPU_PART_CORTEX_A78C 0xD4B
#define APM_CPU_PART_POTENZA 0x000
@@ -121,9 +125,13 @@
#define MIDR_CORTEX_A76 MIDR_CPU_MODEL(ARM_CPU_IMP_ARM, ARM_CPU_PART_CORTEX_A76)
#define MIDR_NEOVERSE_N1 MIDR_CPU_MODEL(ARM_CPU_IMP_ARM, ARM_CPU_PART_NEOVERSE_N1)
#define MIDR_CORTEX_A77 MIDR_CPU_MODEL(ARM_CPU_IMP_ARM, ARM_CPU_PART_CORTEX_A77)
+#define MIDR_NEOVERSE_V1 MIDR_CPU_MODEL(ARM_CPU_IMP_ARM, ARM_CPU_PART_NEOVERSE_V1)
+#define MIDR_CORTEX_A78 MIDR_CPU_MODEL(ARM_CPU_IMP_ARM, ARM_CPU_PART_CORTEX_A78)
+#define MIDR_CORTEX_X1 MIDR_CPU_MODEL(ARM_CPU_IMP_ARM, ARM_CPU_PART_CORTEX_X1)
#define MIDR_CORTEX_A710 MIDR_CPU_MODEL(ARM_CPU_IMP_ARM, ARM_CPU_PART_CORTEX_A710)
#define MIDR_CORTEX_X2 MIDR_CPU_MODEL(ARM_CPU_IMP_ARM, ARM_CPU_PART_CORTEX_X2)
#define MIDR_NEOVERSE_N2 MIDR_CPU_MODEL(ARM_CPU_IMP_ARM, ARM_CPU_PART_NEOVERSE_N2)
+#define MIDR_CORTEX_A78C MIDR_CPU_MODEL(ARM_CPU_IMP_ARM, ARM_CPU_PART_CORTEX_A78C)
#define MIDR_THUNDERX MIDR_CPU_MODEL(ARM_CPU_IMP_CAVIUM, CAVIUM_CPU_PART_THUNDERX)
#define MIDR_THUNDERX_81XX MIDR_CPU_MODEL(ARM_CPU_IMP_CAVIUM, CAVIUM_CPU_PART_THUNDERX_81XX)
#define MIDR_THUNDERX_83XX MIDR_CPU_MODEL(ARM_CPU_IMP_CAVIUM, CAVIUM_CPU_PART_THUNDERX_83XX)
@@ -448,6 +448,7 @@
#define ID_AA64MMFR0_TGRAN16_SUPPORTED 0x1
/* id_aa64mmfr1 */
+#define ID_AA64MMFR1_ECBHB_SHIFT 60
#define ID_AA64MMFR1_PAN_SHIFT 20
#define ID_AA64MMFR1_LOR_SHIFT 16
#define ID_AA64MMFR1_HPD_SHIFT 12
@@ -9,6 +9,7 @@
#include <linux/percpu.h>
#include <asm/fixmap.h>
+#include <asm/mmu.h>
extern char vectors[];
extern char tramp_vectors[];
@@ -40,6 +41,11 @@ enum arm64_bp_harden_el1_vectors {
EL1_VECTOR_KPTI,
};
+#ifndef CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY
+#define EL1_VECTOR_BHB_LOOP -1
+#define EL1_VECTOR_BHB_FW -1
+#endif /* !CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY */
+
/* The vectors to use on return from EL0. e.g. to remap the kernel */
DECLARE_PER_CPU_READ_MOSTLY(const char *, this_cpu_vector);
@@ -23,6 +23,7 @@
#include <asm/cpu.h>
#include <asm/cputype.h>
#include <asm/cpufeature.h>
+#include <asm/vectors.h>
static bool __maybe_unused
is_affected_midr_range(const struct arm64_cpu_capabilities *entry, int scope)
@@ -731,6 +732,13 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
ERRATA_MIDR_RANGE(MIDR_CORTEX_A76, 0, 0, 2, 0),
},
#endif
+ {
+ .desc = "Spectre-BHB",
+ .capability = ARM64_SPECTRE_BHB,
+ .type = ARM64_CPUCAP_LOCAL_CPU_ERRATUM,
+ .matches = is_spectre_bhb_affected,
+ .cpu_enable = spectre_bhb_enable_mitigation,
+ },
{
}
};
@@ -795,6 +803,33 @@ ssize_t cpu_show_spec_store_bypass(struct device *dev,
return sprintf(buf, "Vulnerable\n");
}
+/*
+ * We try to ensure that the mitigation state can never change as the result of
+ * onlining a late CPU.
+ */
+static void update_mitigation_state(enum mitigation_state *oldp,
+ enum mitigation_state new)
+{
+ enum mitigation_state state;
+
+ do {
+ state = READ_ONCE(*oldp);
+ if (new <= state)
+ break;
+ } while (cmpxchg_relaxed(oldp, state, new) != state);
+}
+
+/*
+ * Spectre BHB.
+ *
+ * A CPU is either:
+ * - 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 'Exception Clears Branch History Buffer' (ECBHB) feature, so no
+ * software mitigation in the vectors is needed.
+ * - Has CSV2.3, so is unaffected.
+ */
static enum mitigation_state spectre_bhb_state;
enum mitigation_state arm64_get_spectre_bhb_state(void)
@@ -802,6 +837,163 @@ enum mitigation_state arm64_get_spectre_bhb_state(void)
return spectre_bhb_state;
}
+/*
+ * This must be called with SCOPE_LOCAL_CPU for each type of CPU, before any
+ * SCOPE_SYSTEM call will give the right answer.
+ */
+u8 spectre_bhb_loop_affected(int scope)
+{
+ u8 k = 0;
+ static u8 max_bhb_k;
+
+ if (scope == SCOPE_LOCAL_CPU) {
+ static const struct midr_range spectre_bhb_k32_list[] = {
+ MIDR_ALL_VERSIONS(MIDR_CORTEX_A78),
+ MIDR_ALL_VERSIONS(MIDR_CORTEX_A78C),
+ MIDR_ALL_VERSIONS(MIDR_CORTEX_X1),
+ MIDR_ALL_VERSIONS(MIDR_CORTEX_A710),
+ MIDR_ALL_VERSIONS(MIDR_CORTEX_X2),
+ MIDR_ALL_VERSIONS(MIDR_NEOVERSE_N2),
+ MIDR_ALL_VERSIONS(MIDR_NEOVERSE_V1),
+ {},
+ };
+ static const struct midr_range spectre_bhb_k24_list[] = {
+ MIDR_ALL_VERSIONS(MIDR_CORTEX_A77),
+ MIDR_ALL_VERSIONS(MIDR_CORTEX_A76),
+ MIDR_ALL_VERSIONS(MIDR_NEOVERSE_N1),
+ {},
+ };
+ static const struct midr_range spectre_bhb_k8_list[] = {
+ MIDR_ALL_VERSIONS(MIDR_CORTEX_A72),
+ MIDR_ALL_VERSIONS(MIDR_CORTEX_A57),
+ {},
+ };
+
+ if (is_midr_in_range_list(read_cpuid_id(), spectre_bhb_k32_list))
+ k = 32;
+ else if (is_midr_in_range_list(read_cpuid_id(), spectre_bhb_k24_list))
+ k = 24;
+ else if (is_midr_in_range_list(read_cpuid_id(), spectre_bhb_k8_list))
+ k = 8;
+
+ max_bhb_k = max(max_bhb_k, k);
+ } else {
+ k = max_bhb_k;
+ }
+
+ return k;
+}
+
+static enum mitigation_state spectre_bhb_get_cpu_fw_mitigation_state(void)
+{
+ int ret;
+ struct arm_smccc_res res;
+
+ if (psci_ops.smccc_version == SMCCC_VERSION_1_0)
+ return SPECTRE_VULNERABLE;
+
+ switch (psci_ops.conduit) {
+ case PSCI_CONDUIT_HVC:
+ arm_smccc_1_1_hvc(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
+ ARM_SMCCC_ARCH_WORKAROUND_3, &res);
+ break;
+
+ case PSCI_CONDUIT_SMC:
+ arm_smccc_1_1_smc(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
+ ARM_SMCCC_ARCH_WORKAROUND_3, &res);
+ break;
+
+ default:
+ return SPECTRE_VULNERABLE;
+ }
+
+ ret = res.a0;
+ switch (ret) {
+ case SMCCC_RET_SUCCESS:
+ return SPECTRE_MITIGATED;
+ case SMCCC_ARCH_WORKAROUND_RET_UNAFFECTED:
+ return SPECTRE_UNAFFECTED;
+ default:
+ case SMCCC_RET_NOT_SUPPORTED:
+ return SPECTRE_VULNERABLE;
+ }
+}
+
+static bool is_spectre_bhb_fw_affected(int scope)
+{
+ static bool system_affected;
+ enum mitigation_state fw_state;
+ bool has_smccc = (psci_ops.smccc_version >= SMCCC_VERSION_1_1);
+ static const struct midr_range spectre_bhb_firmware_mitigated_list[] = {
+ MIDR_ALL_VERSIONS(MIDR_CORTEX_A73),
+ MIDR_ALL_VERSIONS(MIDR_CORTEX_A75),
+ {},
+ };
+ bool cpu_in_list = is_midr_in_range_list(read_cpuid_id(),
+ spectre_bhb_firmware_mitigated_list);
+
+ if (scope != SCOPE_LOCAL_CPU)
+ return system_affected;
+
+ fw_state = spectre_bhb_get_cpu_fw_mitigation_state();
+ if (cpu_in_list || (has_smccc && fw_state == SPECTRE_MITIGATED)) {
+ system_affected = true;
+ return true;
+ }
+
+ return false;
+}
+
+static bool supports_ecbhb(int scope)
+{
+ u64 mmfr1;
+
+ if (scope == SCOPE_LOCAL_CPU)
+ mmfr1 = read_sysreg_s(SYS_ID_AA64MMFR1_EL1);
+ else
+ mmfr1 = read_sanitised_ftr_reg(SYS_ID_AA64MMFR1_EL1);
+
+ return cpuid_feature_extract_unsigned_field(mmfr1,
+ ID_AA64MMFR1_ECBHB_SHIFT);
+}
+
+bool is_spectre_bhb_affected(const struct arm64_cpu_capabilities *entry,
+ int scope)
+{
+ WARN_ON(scope != SCOPE_LOCAL_CPU || preemptible());
+
+ if (supports_csv2p3(scope))
+ return false;
+
+ if (spectre_bhb_loop_affected(scope))
+ return true;
+
+ if (is_spectre_bhb_fw_affected(scope))
+ return true;
+
+ return false;
+}
+
+static void this_cpu_set_vectors(enum arm64_bp_harden_el1_vectors slot)
+{
+ const char *v = arm64_get_bp_hardening_vector(slot);
+
+ if (slot < 0)
+ return;
+
+ __this_cpu_write(this_cpu_vector, v);
+
+ /*
+ * When KPTI is in use, the vectors are switched when exiting to
+ * user-space.
+ */
+ if (arm64_kernel_unmapped_at_el0())
+ return;
+
+ write_sysreg(v, vbar_el1);
+ isb();
+}
+
#ifdef CONFIG_KVM
static const char *kvm_bhb_get_vecs_end(const char *start)
{
@@ -817,7 +1009,7 @@ static const char *kvm_bhb_get_vecs_end(const char *start)
return NULL;
}
-void kvm_setup_bhb_slot(const char *hyp_vecs_start)
+static void kvm_setup_bhb_slot(const char *hyp_vecs_start)
{
int cpu, slot = -1;
const char *hyp_vecs_end;
@@ -855,5 +1047,77 @@ void kvm_setup_bhb_slot(const char *hyp_vecs_start)
#define __spectre_bhb_loop_k24_start NULL
#define __spectre_bhb_loop_k32_start NULL
-void kvm_setup_bhb_slot(const char *hyp_vecs_start) { };
+static void kvm_setup_bhb_slot(const char *hyp_vecs_start) { };
#endif
+
+void spectre_bhb_enable_mitigation(const struct arm64_cpu_capabilities *entry)
+{
+ enum mitigation_state fw_state, state = SPECTRE_VULNERABLE;
+
+ if (!is_spectre_bhb_affected(entry, SCOPE_LOCAL_CPU))
+ return;
+
+ if (!__spectrev2_safe && !__hardenbp_enab) {
+ /* No point mitigating Spectre-BHB alone. */
+ } else if (!IS_ENABLED(CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY)) {
+ pr_info_once("spectre-bhb mitigation disabled by compile time option\n");
+ } else if (cpu_mitigations_off()) {
+ pr_info_once("spectre-bhb mitigation disabled by command line option\n");
+ } else if (supports_ecbhb(SCOPE_LOCAL_CPU)) {
+ state = SPECTRE_MITIGATED;
+ } else if (spectre_bhb_loop_affected(SCOPE_LOCAL_CPU)) {
+ switch (spectre_bhb_loop_affected(SCOPE_SYSTEM)) {
+ case 8:
+ kvm_setup_bhb_slot(__spectre_bhb_loop_k8_start);
+ break;
+ case 24:
+ kvm_setup_bhb_slot(__spectre_bhb_loop_k24_start);
+ break;
+ case 32:
+ kvm_setup_bhb_slot(__spectre_bhb_loop_k32_start);
+ break;
+ default:
+ WARN_ON_ONCE(1);
+ }
+ this_cpu_set_vectors(EL1_VECTOR_BHB_LOOP);
+
+ state = SPECTRE_MITIGATED;
+ } else if (is_spectre_bhb_fw_affected(SCOPE_LOCAL_CPU)) {
+ fw_state = spectre_bhb_get_cpu_fw_mitigation_state();
+ if (fw_state == SPECTRE_MITIGATED) {
+ kvm_setup_bhb_slot(__smccc_workaround_3_smc_start);
+ this_cpu_set_vectors(EL1_VECTOR_BHB_FW);
+
+ /*
+ * With WA3 in the vectors, the WA1 calls can be
+ * removed.
+ */
+ __this_cpu_write(bp_hardening_data.fn, NULL);
+
+ state = SPECTRE_MITIGATED;
+ }
+ }
+
+ update_mitigation_state(&spectre_bhb_state, state);
+}
+
+/* Patched to correct the immediate */
+void __init spectre_bhb_patch_loop_iter(struct alt_instr *alt,
+ __le32 *origptr, __le32 *updptr, int nr_inst)
+{
+ u8 rd;
+ u32 insn;
+ u16 loop_count = spectre_bhb_loop_affected(SCOPE_SYSTEM);
+
+ BUG_ON(nr_inst != 1); /* MOV -> MOV */
+
+ if (!IS_ENABLED(CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY))
+ return;
+
+ insn = le32_to_cpu(*origptr);
+ rd = aarch64_insn_decode_register(AARCH64_INSN_REGTYPE_RD, insn);
+ insn = aarch64_insn_gen_movewide(rd, loop_count, 0,
+ AARCH64_INSN_VARIANT_64BIT,
+ AARCH64_INSN_MOVEWIDE_ZERO);
+ *updptr++ = cpu_to_le32(insn);
+}
@@ -135,6 +135,10 @@ el1_hvc_guest:
/* ARM_SMCCC_ARCH_WORKAROUND_2 handling */
eor w1, w1, #(ARM_SMCCC_ARCH_WORKAROUND_1 ^ \
ARM_SMCCC_ARCH_WORKAROUND_2)
+ cbz w1, wa_epilogue
+
+ eor w1, w1, #(ARM_SMCCC_ARCH_WORKAROUND_2 ^ \
+ ARM_SMCCC_ARCH_WORKAROUND_3)
cbnz w1, el1_trap
#ifdef CONFIG_ARM64_SSBD