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-rw-r--r--arch/arm64/kernel/proton-pack.c1171
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diff --git a/arch/arm64/kernel/proton-pack.c b/arch/arm64/kernel/proton-pack.c
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+++ b/arch/arm64/kernel/proton-pack.c
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+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Handle detection, reporting and mitigation of Spectre v1, v2, v3a and v4, as
+ * detailed at:
+ *
+ * https://developer.arm.com/support/arm-security-updates/speculative-processor-vulnerability
+ *
+ * This code was originally written hastily under an awful lot of stress and so
+ * aspects of it are somewhat hacky. Unfortunately, changing anything in here
+ * instantly makes me feel ill. Thanks, Jann. Thann.
+ *
+ * Copyright (C) 2018 ARM Ltd, All Rights Reserved.
+ * Copyright (C) 2020 Google LLC
+ *
+ * "If there's something strange in your neighbourhood, who you gonna call?"
+ *
+ * Authors: Will Deacon <will@kernel.org> and Marc Zyngier <maz@kernel.org>
+ */
+
+#include <linux/arm-smccc.h>
+#include <linux/bpf.h>
+#include <linux/cpu.h>
+#include <linux/device.h>
+#include <linux/nospec.h>
+#include <linux/prctl.h>
+#include <linux/sched/task_stack.h>
+
+#include <asm/debug-monitors.h>
+#include <asm/insn.h>
+#include <asm/spectre.h>
+#include <asm/traps.h>
+#include <asm/vectors.h>
+#include <asm/virt.h>
+
+/*
+ * 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;
+
+ /* Userspace almost certainly can't deal with this. */
+ if (WARN_ON(system_capabilities_finalized()))
+ break;
+ } while (cmpxchg_relaxed(oldp, state, new) != state);
+}
+
+/*
+ * Spectre v1.
+ *
+ * The kernel can't protect userspace for this one: it's each person for
+ * themselves. Advertise what we're doing and be done with it.
+ */
+ssize_t cpu_show_spectre_v1(struct device *dev, struct device_attribute *attr,
+ char *buf)
+{
+ return sprintf(buf, "Mitigation: __user pointer sanitization\n");
+}
+
+/*
+ * Spectre v2.
+ *
+ * This one sucks. A CPU is either:
+ *
+ * - Mitigated in hardware and advertised by ID_AA64PFR0_EL1.CSV2.
+ * - Mitigated in hardware and listed in our "safe list".
+ * - Mitigated in software by firmware.
+ * - Mitigated in software by a CPU-specific dance in the kernel and a
+ * firmware call at EL2.
+ * - Vulnerable.
+ *
+ * It's not unlikely for different CPUs in a big.LITTLE system to fall into
+ * different camps.
+ */
+static enum mitigation_state spectre_v2_state;
+
+static bool __read_mostly __nospectre_v2;
+static int __init parse_spectre_v2_param(char *str)
+{
+ __nospectre_v2 = true;
+ return 0;
+}
+early_param("nospectre_v2", parse_spectre_v2_param);
+
+static bool spectre_v2_mitigations_off(void)
+{
+ bool ret = __nospectre_v2 || cpu_mitigations_off();
+
+ if (ret)
+ pr_info_once("spectre-v2 mitigation disabled by command line option\n");
+
+ return ret;
+}
+
+static const char *get_bhb_affected_string(enum mitigation_state bhb_state)
+{
+ switch (bhb_state) {
+ case SPECTRE_UNAFFECTED:
+ return "";
+ default:
+ case SPECTRE_VULNERABLE:
+ return ", but not BHB";
+ case SPECTRE_MITIGATED:
+ return ", BHB";
+ }
+}
+
+static bool _unprivileged_ebpf_enabled(void)
+{
+#ifdef CONFIG_BPF_SYSCALL
+ return !sysctl_unprivileged_bpf_disabled;
+#else
+ return false;
+#endif
+}
+
+ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr,
+ char *buf)
+{
+ enum mitigation_state bhb_state = arm64_get_spectre_bhb_state();
+ const char *bhb_str = get_bhb_affected_string(bhb_state);
+ const char *v2_str = "Branch predictor hardening";
+
+ switch (spectre_v2_state) {
+ case SPECTRE_UNAFFECTED:
+ if (bhb_state == SPECTRE_UNAFFECTED)
+ return sprintf(buf, "Not affected\n");
+
+ /*
+ * Platforms affected by Spectre-BHB can't report
+ * "Not affected" for Spectre-v2.
+ */
+ v2_str = "CSV2";
+ fallthrough;
+ case SPECTRE_MITIGATED:
+ if (bhb_state == SPECTRE_MITIGATED && _unprivileged_ebpf_enabled())
+ return sprintf(buf, "Vulnerable: Unprivileged eBPF enabled\n");
+
+ return sprintf(buf, "Mitigation: %s%s\n", v2_str, bhb_str);
+ case SPECTRE_VULNERABLE:
+ fallthrough;
+ default:
+ return sprintf(buf, "Vulnerable\n");
+ }
+}
+
+static enum mitigation_state spectre_v2_get_cpu_hw_mitigation_state(void)
+{
+ u64 pfr0;
+ static const struct midr_range spectre_v2_safe_list[] = {
+ MIDR_ALL_VERSIONS(MIDR_CORTEX_A35),
+ MIDR_ALL_VERSIONS(MIDR_CORTEX_A53),
+ MIDR_ALL_VERSIONS(MIDR_CORTEX_A55),
+ MIDR_ALL_VERSIONS(MIDR_BRAHMA_B53),
+ MIDR_ALL_VERSIONS(MIDR_HISI_TSV110),
+ MIDR_ALL_VERSIONS(MIDR_QCOM_KRYO_2XX_SILVER),
+ MIDR_ALL_VERSIONS(MIDR_QCOM_KRYO_3XX_SILVER),
+ MIDR_ALL_VERSIONS(MIDR_QCOM_KRYO_4XX_SILVER),
+ { /* sentinel */ }
+ };
+
+ /* If the CPU has CSV2 set, we're safe */
+ pfr0 = read_cpuid(ID_AA64PFR0_EL1);
+ if (cpuid_feature_extract_unsigned_field(pfr0, ID_AA64PFR0_EL1_CSV2_SHIFT))
+ return SPECTRE_UNAFFECTED;
+
+ /* Alternatively, we have a list of unaffected CPUs */
+ if (is_midr_in_range_list(read_cpuid_id(), spectre_v2_safe_list))
+ return SPECTRE_UNAFFECTED;
+
+ return SPECTRE_VULNERABLE;
+}
+
+static enum mitigation_state spectre_v2_get_cpu_fw_mitigation_state(void)
+{
+ int ret;
+ struct arm_smccc_res res;
+
+ arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
+ ARM_SMCCC_ARCH_WORKAROUND_1, &res);
+
+ ret = res.a0;
+ switch (ret) {
+ case SMCCC_RET_SUCCESS:
+ return SPECTRE_MITIGATED;
+ case SMCCC_ARCH_WORKAROUND_RET_UNAFFECTED:
+ return SPECTRE_UNAFFECTED;
+ default:
+ fallthrough;
+ case SMCCC_RET_NOT_SUPPORTED:
+ return SPECTRE_VULNERABLE;
+ }
+}
+
+bool has_spectre_v2(const struct arm64_cpu_capabilities *entry, int scope)
+{
+ WARN_ON(scope != SCOPE_LOCAL_CPU || preemptible());
+
+ if (spectre_v2_get_cpu_hw_mitigation_state() == SPECTRE_UNAFFECTED)
+ return false;
+
+ if (spectre_v2_get_cpu_fw_mitigation_state() == SPECTRE_UNAFFECTED)
+ return false;
+
+ return true;
+}
+
+enum mitigation_state arm64_get_spectre_v2_state(void)
+{
+ return spectre_v2_state;
+}
+
+DEFINE_PER_CPU_READ_MOSTLY(struct bp_hardening_data, bp_hardening_data);
+
+static void install_bp_hardening_cb(bp_hardening_cb_t fn)
+{
+ __this_cpu_write(bp_hardening_data.fn, fn);
+
+ /*
+ * Vinz Clortho takes the hyp_vecs start/end "keys" at
+ * the door when we're a guest. Skip the hyp-vectors work.
+ */
+ if (!is_hyp_mode_available())
+ return;
+
+ __this_cpu_write(bp_hardening_data.slot, HYP_VECTOR_SPECTRE_DIRECT);
+}
+
+/* Called during entry so must be noinstr */
+static noinstr void call_smc_arch_workaround_1(void)
+{
+ arm_smccc_1_1_smc(ARM_SMCCC_ARCH_WORKAROUND_1, NULL);
+}
+
+/* Called during entry so must be noinstr */
+static noinstr void call_hvc_arch_workaround_1(void)
+{
+ arm_smccc_1_1_hvc(ARM_SMCCC_ARCH_WORKAROUND_1, NULL);
+}
+
+/* Called during entry so must be noinstr */
+static noinstr void qcom_link_stack_sanitisation(void)
+{
+ u64 tmp;
+
+ asm volatile("mov %0, x30 \n"
+ ".rept 16 \n"
+ "bl . + 4 \n"
+ ".endr \n"
+ "mov x30, %0 \n"
+ : "=&r" (tmp));
+}
+
+static bp_hardening_cb_t spectre_v2_get_sw_mitigation_cb(void)
+{
+ u32 midr = read_cpuid_id();
+ if (((midr & MIDR_CPU_MODEL_MASK) != MIDR_QCOM_FALKOR) &&
+ ((midr & MIDR_CPU_MODEL_MASK) != MIDR_QCOM_FALKOR_V1))
+ return NULL;
+
+ return qcom_link_stack_sanitisation;
+}
+
+static enum mitigation_state spectre_v2_enable_fw_mitigation(void)
+{
+ bp_hardening_cb_t cb;
+ enum mitigation_state state;
+
+ state = spectre_v2_get_cpu_fw_mitigation_state();
+ if (state != SPECTRE_MITIGATED)
+ return state;
+
+ if (spectre_v2_mitigations_off())
+ return SPECTRE_VULNERABLE;
+
+ switch (arm_smccc_1_1_get_conduit()) {
+ case SMCCC_CONDUIT_HVC:
+ cb = call_hvc_arch_workaround_1;
+ break;
+
+ case SMCCC_CONDUIT_SMC:
+ cb = call_smc_arch_workaround_1;
+ break;
+
+ default:
+ return SPECTRE_VULNERABLE;
+ }
+
+ /*
+ * Prefer a CPU-specific workaround if it exists. Note that we
+ * still rely on firmware for the mitigation at EL2.
+ */
+ cb = spectre_v2_get_sw_mitigation_cb() ?: cb;
+ install_bp_hardening_cb(cb);
+ return SPECTRE_MITIGATED;
+}
+
+void spectre_v2_enable_mitigation(const struct arm64_cpu_capabilities *__unused)
+{
+ enum mitigation_state state;
+
+ WARN_ON(preemptible());
+
+ state = spectre_v2_get_cpu_hw_mitigation_state();
+ if (state == SPECTRE_VULNERABLE)
+ state = spectre_v2_enable_fw_mitigation();
+
+ update_mitigation_state(&spectre_v2_state, state);
+}
+
+/*
+ * Spectre-v3a.
+ *
+ * Phew, there's not an awful lot to do here! We just instruct EL2 to use
+ * an indirect trampoline for the hyp vectors so that guests can't read
+ * VBAR_EL2 to defeat randomisation of the hypervisor VA layout.
+ */
+bool has_spectre_v3a(const struct arm64_cpu_capabilities *entry, int scope)
+{
+ static const struct midr_range spectre_v3a_unsafe_list[] = {
+ MIDR_ALL_VERSIONS(MIDR_CORTEX_A57),
+ MIDR_ALL_VERSIONS(MIDR_CORTEX_A72),
+ {},
+ };
+
+ WARN_ON(scope != SCOPE_LOCAL_CPU || preemptible());
+ return is_midr_in_range_list(read_cpuid_id(), spectre_v3a_unsafe_list);
+}
+
+void spectre_v3a_enable_mitigation(const struct arm64_cpu_capabilities *__unused)
+{
+ struct bp_hardening_data *data = this_cpu_ptr(&bp_hardening_data);
+
+ if (this_cpu_has_cap(ARM64_SPECTRE_V3A))
+ data->slot += HYP_VECTOR_INDIRECT;
+}
+
+/*
+ * Spectre v4.
+ *
+ * If you thought Spectre v2 was nasty, wait until you see this mess. A CPU is
+ * either:
+ *
+ * - Mitigated in hardware and listed in our "safe list".
+ * - Mitigated in hardware via PSTATE.SSBS.
+ * - Mitigated in software by firmware (sometimes referred to as SSBD).
+ *
+ * Wait, that doesn't sound so bad, does it? Keep reading...
+ *
+ * A major source of headaches is that the software mitigation is enabled both
+ * on a per-task basis, but can also be forced on for the kernel, necessitating
+ * both context-switch *and* entry/exit hooks. To make it even worse, some CPUs
+ * allow EL0 to toggle SSBS directly, which can end up with the prctl() state
+ * being stale when re-entering the kernel. The usual big.LITTLE caveats apply,
+ * so you can have systems that have both firmware and SSBS mitigations. This
+ * means we actually have to reject late onlining of CPUs with mitigations if
+ * all of the currently onlined CPUs are safelisted, as the mitigation tends to
+ * be opt-in for userspace. Yes, really, the cure is worse than the disease.
+ *
+ * The only good part is that if the firmware mitigation is present, then it is
+ * present for all CPUs, meaning we don't have to worry about late onlining of a
+ * vulnerable CPU if one of the boot CPUs is using the firmware mitigation.
+ *
+ * Give me a VAX-11/780 any day of the week...
+ */
+static enum mitigation_state spectre_v4_state;
+
+/* This is the per-cpu state tracking whether we need to talk to firmware */
+DEFINE_PER_CPU_READ_MOSTLY(u64, arm64_ssbd_callback_required);
+
+enum spectre_v4_policy {
+ SPECTRE_V4_POLICY_MITIGATION_DYNAMIC,
+ SPECTRE_V4_POLICY_MITIGATION_ENABLED,
+ SPECTRE_V4_POLICY_MITIGATION_DISABLED,
+};
+
+static enum spectre_v4_policy __read_mostly __spectre_v4_policy;
+
+static const struct spectre_v4_param {
+ const char *str;
+ enum spectre_v4_policy policy;
+} spectre_v4_params[] = {
+ { "force-on", SPECTRE_V4_POLICY_MITIGATION_ENABLED, },
+ { "force-off", SPECTRE_V4_POLICY_MITIGATION_DISABLED, },
+ { "kernel", SPECTRE_V4_POLICY_MITIGATION_DYNAMIC, },
+};
+static int __init parse_spectre_v4_param(char *str)
+{
+ int i;
+
+ if (!str || !str[0])
+ return -EINVAL;
+
+ for (i = 0; i < ARRAY_SIZE(spectre_v4_params); i++) {
+ const struct spectre_v4_param *param = &spectre_v4_params[i];
+
+ if (strncmp(str, param->str, strlen(param->str)))
+ continue;
+
+ __spectre_v4_policy = param->policy;
+ return 0;
+ }
+
+ return -EINVAL;
+}
+early_param("ssbd", parse_spectre_v4_param);
+
+/*
+ * Because this was all written in a rush by people working in different silos,
+ * we've ended up with multiple command line options to control the same thing.
+ * Wrap these up in some helpers, which prefer disabling the mitigation if faced
+ * with contradictory parameters. The mitigation is always either "off",
+ * "dynamic" or "on".
+ */
+static bool spectre_v4_mitigations_off(void)
+{
+ bool ret = cpu_mitigations_off() ||
+ __spectre_v4_policy == SPECTRE_V4_POLICY_MITIGATION_DISABLED;
+
+ if (ret)
+ pr_info_once("spectre-v4 mitigation disabled by command-line option\n");
+
+ return ret;
+}
+
+/* Do we need to toggle the mitigation state on entry to/exit from the kernel? */
+static bool spectre_v4_mitigations_dynamic(void)
+{
+ return !spectre_v4_mitigations_off() &&
+ __spectre_v4_policy == SPECTRE_V4_POLICY_MITIGATION_DYNAMIC;
+}
+
+static bool spectre_v4_mitigations_on(void)
+{
+ return !spectre_v4_mitigations_off() &&
+ __spectre_v4_policy == SPECTRE_V4_POLICY_MITIGATION_ENABLED;
+}
+
+ssize_t cpu_show_spec_store_bypass(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ switch (spectre_v4_state) {
+ case SPECTRE_UNAFFECTED:
+ return sprintf(buf, "Not affected\n");
+ case SPECTRE_MITIGATED:
+ return sprintf(buf, "Mitigation: Speculative Store Bypass disabled via prctl\n");
+ case SPECTRE_VULNERABLE:
+ fallthrough;
+ default:
+ return sprintf(buf, "Vulnerable\n");
+ }
+}
+
+enum mitigation_state arm64_get_spectre_v4_state(void)
+{
+ return spectre_v4_state;
+}
+
+static enum mitigation_state spectre_v4_get_cpu_hw_mitigation_state(void)
+{
+ static const struct midr_range spectre_v4_safe_list[] = {
+ MIDR_ALL_VERSIONS(MIDR_CORTEX_A35),
+ MIDR_ALL_VERSIONS(MIDR_CORTEX_A53),
+ MIDR_ALL_VERSIONS(MIDR_CORTEX_A55),
+ MIDR_ALL_VERSIONS(MIDR_BRAHMA_B53),
+ MIDR_ALL_VERSIONS(MIDR_QCOM_KRYO_3XX_SILVER),
+ MIDR_ALL_VERSIONS(MIDR_QCOM_KRYO_4XX_SILVER),
+ { /* sentinel */ },
+ };
+
+ if (is_midr_in_range_list(read_cpuid_id(), spectre_v4_safe_list))
+ return SPECTRE_UNAFFECTED;
+
+ /* CPU features are detected first */
+ if (this_cpu_has_cap(ARM64_SSBS))
+ return SPECTRE_MITIGATED;
+
+ return SPECTRE_VULNERABLE;
+}
+
+static enum mitigation_state spectre_v4_get_cpu_fw_mitigation_state(void)
+{
+ int ret;
+ struct arm_smccc_res res;
+
+ arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
+ ARM_SMCCC_ARCH_WORKAROUND_2, &res);
+
+ ret = res.a0;
+ switch (ret) {
+ case SMCCC_RET_SUCCESS:
+ return SPECTRE_MITIGATED;
+ case SMCCC_ARCH_WORKAROUND_RET_UNAFFECTED:
+ fallthrough;
+ case SMCCC_RET_NOT_REQUIRED:
+ return SPECTRE_UNAFFECTED;
+ default:
+ fallthrough;
+ case SMCCC_RET_NOT_SUPPORTED:
+ return SPECTRE_VULNERABLE;
+ }
+}
+
+bool has_spectre_v4(const struct arm64_cpu_capabilities *cap, int scope)
+{
+ enum mitigation_state state;
+
+ WARN_ON(scope != SCOPE_LOCAL_CPU || preemptible());
+
+ state = spectre_v4_get_cpu_hw_mitigation_state();
+ if (state == SPECTRE_VULNERABLE)
+ state = spectre_v4_get_cpu_fw_mitigation_state();
+
+ return state != SPECTRE_UNAFFECTED;
+}
+
+static int ssbs_emulation_handler(struct pt_regs *regs, u32 instr)
+{
+ if (user_mode(regs))
+ return 1;
+
+ if (instr & BIT(PSTATE_Imm_shift))
+ regs->pstate |= PSR_SSBS_BIT;
+ else
+ regs->pstate &= ~PSR_SSBS_BIT;
+
+ arm64_skip_faulting_instruction(regs, 4);
+ return 0;
+}
+
+static struct undef_hook ssbs_emulation_hook = {
+ .instr_mask = ~(1U << PSTATE_Imm_shift),
+ .instr_val = 0xd500401f | PSTATE_SSBS,
+ .fn = ssbs_emulation_handler,
+};
+
+static enum mitigation_state spectre_v4_enable_hw_mitigation(void)
+{
+ static bool undef_hook_registered = false;
+ static DEFINE_RAW_SPINLOCK(hook_lock);
+ enum mitigation_state state;
+
+ /*
+ * If the system is mitigated but this CPU doesn't have SSBS, then
+ * we must be on the safelist and there's nothing more to do.
+ */
+ state = spectre_v4_get_cpu_hw_mitigation_state();
+ if (state != SPECTRE_MITIGATED || !this_cpu_has_cap(ARM64_SSBS))
+ return state;
+
+ raw_spin_lock(&hook_lock);
+ if (!undef_hook_registered) {
+ register_undef_hook(&ssbs_emulation_hook);
+ undef_hook_registered = true;
+ }
+ raw_spin_unlock(&hook_lock);
+
+ if (spectre_v4_mitigations_off()) {
+ sysreg_clear_set(sctlr_el1, 0, SCTLR_ELx_DSSBS);
+ set_pstate_ssbs(1);
+ return SPECTRE_VULNERABLE;
+ }
+
+ /* SCTLR_EL1.DSSBS was initialised to 0 during boot */
+ set_pstate_ssbs(0);
+ return SPECTRE_MITIGATED;
+}
+
+/*
+ * Patch a branch over the Spectre-v4 mitigation code with a NOP so that
+ * we fallthrough and check whether firmware needs to be called on this CPU.
+ */
+void __init spectre_v4_patch_fw_mitigation_enable(struct alt_instr *alt,
+ __le32 *origptr,
+ __le32 *updptr, int nr_inst)
+{
+ BUG_ON(nr_inst != 1); /* Branch -> NOP */
+
+ if (spectre_v4_mitigations_off())
+ return;
+
+ if (cpus_have_cap(ARM64_SSBS))
+ return;
+
+ if (spectre_v4_mitigations_dynamic())
+ *updptr = cpu_to_le32(aarch64_insn_gen_nop());
+}
+
+/*
+ * Patch a NOP in the Spectre-v4 mitigation code with an SMC/HVC instruction
+ * to call into firmware to adjust the mitigation state.
+ */
+void __init smccc_patch_fw_mitigation_conduit(struct alt_instr *alt,
+ __le32 *origptr,
+ __le32 *updptr, int nr_inst)
+{
+ u32 insn;
+
+ BUG_ON(nr_inst != 1); /* NOP -> HVC/SMC */
+
+ switch (arm_smccc_1_1_get_conduit()) {
+ case SMCCC_CONDUIT_HVC:
+ insn = aarch64_insn_get_hvc_value();
+ break;
+ case SMCCC_CONDUIT_SMC:
+ insn = aarch64_insn_get_smc_value();
+ break;
+ default:
+ return;
+ }
+
+ *updptr = cpu_to_le32(insn);
+}
+
+static enum mitigation_state spectre_v4_enable_fw_mitigation(void)
+{
+ enum mitigation_state state;
+
+ state = spectre_v4_get_cpu_fw_mitigation_state();
+ if (state != SPECTRE_MITIGATED)
+ return state;
+
+ if (spectre_v4_mitigations_off()) {
+ arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_WORKAROUND_2, false, NULL);
+ return SPECTRE_VULNERABLE;
+ }
+
+ arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_WORKAROUND_2, true, NULL);
+
+ if (spectre_v4_mitigations_dynamic())
+ __this_cpu_write(arm64_ssbd_callback_required, 1);
+
+ return SPECTRE_MITIGATED;
+}
+
+void spectre_v4_enable_mitigation(const struct arm64_cpu_capabilities *__unused)
+{
+ enum mitigation_state state;
+
+ WARN_ON(preemptible());
+
+ state = spectre_v4_enable_hw_mitigation();
+ if (state == SPECTRE_VULNERABLE)
+ state = spectre_v4_enable_fw_mitigation();
+
+ update_mitigation_state(&spectre_v4_state, state);
+}
+
+static void __update_pstate_ssbs(struct pt_regs *regs, bool state)
+{
+ u64 bit = compat_user_mode(regs) ? PSR_AA32_SSBS_BIT : PSR_SSBS_BIT;
+
+ if (state)
+ regs->pstate |= bit;
+ else
+ regs->pstate &= ~bit;
+}
+
+void spectre_v4_enable_task_mitigation(struct task_struct *tsk)
+{
+ struct pt_regs *regs = task_pt_regs(tsk);
+ bool ssbs = false, kthread = tsk->flags & PF_KTHREAD;
+
+ if (spectre_v4_mitigations_off())
+ ssbs = true;
+ else if (spectre_v4_mitigations_dynamic() && !kthread)
+ ssbs = !test_tsk_thread_flag(tsk, TIF_SSBD);
+
+ __update_pstate_ssbs(regs, ssbs);
+}
+
+/*
+ * The Spectre-v4 mitigation can be controlled via a prctl() from userspace.
+ * This is interesting because the "speculation disabled" behaviour can be
+ * configured so that it is preserved across exec(), which means that the
+ * prctl() may be necessary even when PSTATE.SSBS can be toggled directly
+ * from userspace.
+ */
+static void ssbd_prctl_enable_mitigation(struct task_struct *task)
+{
+ task_clear_spec_ssb_noexec(task);
+ task_set_spec_ssb_disable(task);
+ set_tsk_thread_flag(task, TIF_SSBD);
+}
+
+static void ssbd_prctl_disable_mitigation(struct task_struct *task)
+{
+ task_clear_spec_ssb_noexec(task);
+ task_clear_spec_ssb_disable(task);
+ clear_tsk_thread_flag(task, TIF_SSBD);
+}
+
+static int ssbd_prctl_set(struct task_struct *task, unsigned long ctrl)
+{
+ switch (ctrl) {
+ case PR_SPEC_ENABLE:
+ /* Enable speculation: disable mitigation */
+ /*
+ * Force disabled speculation prevents it from being
+ * re-enabled.
+ */
+ if (task_spec_ssb_force_disable(task))
+ return -EPERM;
+
+ /*
+ * If the mitigation is forced on, then speculation is forced
+ * off and we again prevent it from being re-enabled.
+ */
+ if (spectre_v4_mitigations_on())
+ return -EPERM;
+
+ ssbd_prctl_disable_mitigation(task);
+ break;
+ case PR_SPEC_FORCE_DISABLE:
+ /* Force disable speculation: force enable mitigation */
+ /*
+ * If the mitigation is forced off, then speculation is forced
+ * on and we prevent it from being disabled.
+ */
+ if (spectre_v4_mitigations_off())
+ return -EPERM;
+
+ task_set_spec_ssb_force_disable(task);
+ fallthrough;
+ case PR_SPEC_DISABLE:
+ /* Disable speculation: enable mitigation */
+ /* Same as PR_SPEC_FORCE_DISABLE */
+ if (spectre_v4_mitigations_off())
+ return -EPERM;
+
+ ssbd_prctl_enable_mitigation(task);
+ break;
+ case PR_SPEC_DISABLE_NOEXEC:
+ /* Disable speculation until execve(): enable mitigation */
+ /*
+ * If the mitigation state is forced one way or the other, then
+ * we must fail now before we try to toggle it on execve().
+ */
+ if (task_spec_ssb_force_disable(task) ||
+ spectre_v4_mitigations_off() ||
+ spectre_v4_mitigations_on()) {
+ return -EPERM;
+ }
+
+ ssbd_prctl_enable_mitigation(task);
+ task_set_spec_ssb_noexec(task);
+ break;
+ default:
+ return -ERANGE;
+ }
+
+ spectre_v4_enable_task_mitigation(task);
+ return 0;
+}
+
+int arch_prctl_spec_ctrl_set(struct task_struct *task, unsigned long which,
+ unsigned long ctrl)
+{
+ switch (which) {
+ case PR_SPEC_STORE_BYPASS:
+ return ssbd_prctl_set(task, ctrl);
+ default:
+ return -ENODEV;
+ }
+}
+
+static int ssbd_prctl_get(struct task_struct *task)
+{
+ switch (spectre_v4_state) {
+ case SPECTRE_UNAFFECTED:
+ return PR_SPEC_NOT_AFFECTED;
+ case SPECTRE_MITIGATED:
+ if (spectre_v4_mitigations_on())
+ return PR_SPEC_NOT_AFFECTED;
+
+ if (spectre_v4_mitigations_dynamic())
+ break;
+
+ /* Mitigations are disabled, so we're vulnerable. */
+ fallthrough;
+ case SPECTRE_VULNERABLE:
+ fallthrough;
+ default:
+ return PR_SPEC_ENABLE;
+ }
+
+ /* Check the mitigation state for this task */
+ if (task_spec_ssb_force_disable(task))
+ return PR_SPEC_PRCTL | PR_SPEC_FORCE_DISABLE;
+
+ if (task_spec_ssb_noexec(task))
+ return PR_SPEC_PRCTL | PR_SPEC_DISABLE_NOEXEC;
+
+ if (task_spec_ssb_disable(task))
+ return PR_SPEC_PRCTL | PR_SPEC_DISABLE;
+
+ return PR_SPEC_PRCTL | PR_SPEC_ENABLE;
+}
+
+int arch_prctl_spec_ctrl_get(struct task_struct *task, unsigned long which)
+{
+ switch (which) {
+ case PR_SPEC_STORE_BYPASS:
+ return ssbd_prctl_get(task);
+ default:
+ return -ENODEV;
+ }
+}
+
+/*
+ * 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 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.
+ */
+static enum mitigation_state spectre_bhb_state;
+
+enum mitigation_state arm64_get_spectre_bhb_state(void)
+{
+ return spectre_bhb_state;
+}
+
+enum bhb_mitigation_bits {
+ BHB_LOOP,
+ BHB_FW,
+ BHB_HW,
+ BHB_INSN,
+};
+static unsigned long system_bhb_mitigations;
+
+/*
+ * 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_A78AE),
+ 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_A76),
+ MIDR_ALL_VERSIONS(MIDR_CORTEX_A77),
+ MIDR_ALL_VERSIONS(MIDR_NEOVERSE_N1),
+ {},
+ };
+ static const struct midr_range spectre_bhb_k11_list[] = {
+ MIDR_ALL_VERSIONS(MIDR_AMPERE1),
+ {},
+ };
+ 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_k11_list))
+ k = 11;
+ 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;
+
+ arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
+ ARM_SMCCC_ARCH_WORKAROUND_3, &res);
+
+ ret = res.a0;
+ switch (ret) {
+ case SMCCC_RET_SUCCESS:
+ return SPECTRE_MITIGATED;
+ case SMCCC_ARCH_WORKAROUND_RET_UNAFFECTED:
+ return SPECTRE_UNAFFECTED;
+ default:
+ fallthrough;
+ 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 = arm_smccc_1_1_get_conduit() != SMCCC_CONDUIT_NONE;
+ 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_EL1_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 (supports_clearbhb(scope))
+ return true;
+
+ 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();
+}
+
+static bool __read_mostly __nospectre_bhb;
+static int __init parse_spectre_bhb_param(char *str)
+{
+ __nospectre_bhb = true;
+ return 0;
+}
+early_param("nospectre_bhb", parse_spectre_bhb_param);
+
+void spectre_bhb_enable_mitigation(const struct arm64_cpu_capabilities *entry)
+{
+ bp_hardening_cb_t cpu_cb;
+ enum mitigation_state fw_state, state = SPECTRE_VULNERABLE;
+ struct bp_hardening_data *data = this_cpu_ptr(&bp_hardening_data);
+
+ if (!is_spectre_bhb_affected(entry, SCOPE_LOCAL_CPU))
+ return;
+
+ if (arm64_get_spectre_v2_state() == SPECTRE_VULNERABLE) {
+ /* 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() || __nospectre_bhb) {
+ pr_info_once("spectre-bhb mitigation disabled by command line option\n");
+ } 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
+ * branchy-loop added. A57/A72-r0 will already have selected
+ * the spectre-indirect vector, which is sufficient for BHB
+ * too.
+ */
+ if (!data->slot)
+ data->slot = HYP_VECTOR_INDIRECT;
+
+ this_cpu_set_vectors(EL1_VECTOR_BHB_LOOP);
+ state = SPECTRE_MITIGATED;
+ set_bit(BHB_LOOP, &system_bhb_mitigations);
+ } else if (is_spectre_bhb_fw_affected(SCOPE_LOCAL_CPU)) {
+ fw_state = spectre_bhb_get_cpu_fw_mitigation_state();
+ if (fw_state == SPECTRE_MITIGATED) {
+ /*
+ * Ensure KVM uses one of the spectre bp_hardening
+ * vectors. The indirect vector doesn't include the EL3
+ * call, so needs upgrading to
+ * HYP_VECTOR_SPECTRE_INDIRECT.
+ */
+ if (!data->slot || data->slot == HYP_VECTOR_INDIRECT)
+ data->slot += 1;
+
+ this_cpu_set_vectors(EL1_VECTOR_BHB_FW);
+
+ /*
+ * The WA3 call in the vectors supersedes the WA1 call
+ * made during context-switch. Uninstall any firmware
+ * bp_hardening callback.
+ */
+ cpu_cb = spectre_v2_get_sw_mitigation_cb();
+ if (__this_cpu_read(bp_hardening_data.fn) != cpu_cb)
+ __this_cpu_write(bp_hardening_data.fn, NULL);
+
+ state = SPECTRE_MITIGATED;
+ set_bit(BHB_FW, &system_bhb_mitigations);
+ }
+ }
+
+ update_mitigation_state(&spectre_bhb_state, state);
+}
+
+/* Patched to NOP when enabled */
+void noinstr spectre_bhb_patch_loop_mitigation_enable(struct alt_instr *alt,
+ __le32 *origptr,
+ __le32 *updptr, int nr_inst)
+{
+ BUG_ON(nr_inst != 1);
+
+ if (test_bit(BHB_LOOP, &system_bhb_mitigations))
+ *updptr++ = cpu_to_le32(aarch64_insn_gen_nop());
+}
+
+/* Patched to NOP when enabled */
+void noinstr spectre_bhb_patch_fw_mitigation_enabled(struct alt_instr *alt,
+ __le32 *origptr,
+ __le32 *updptr, int nr_inst)
+{
+ BUG_ON(nr_inst != 1);
+
+ if (test_bit(BHB_FW, &system_bhb_mitigations))
+ *updptr++ = cpu_to_le32(aarch64_insn_gen_nop());
+}
+
+/* Patched to correct the immediate */
+void noinstr 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);
+}
+
+/* Patched to mov WA3 when supported */
+void noinstr spectre_bhb_patch_wa3(struct alt_instr *alt,
+ __le32 *origptr, __le32 *updptr, int nr_inst)
+{
+ u8 rd;
+ u32 insn;
+
+ BUG_ON(nr_inst != 1); /* MOV -> MOV */
+
+ if (!IS_ENABLED(CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY) ||
+ !test_bit(BHB_FW, &system_bhb_mitigations))
+ return;
+
+ insn = le32_to_cpu(*origptr);
+ rd = aarch64_insn_decode_register(AARCH64_INSN_REGTYPE_RD, insn);
+
+ insn = aarch64_insn_gen_logical_immediate(AARCH64_INSN_LOGIC_ORR,
+ AARCH64_INSN_VARIANT_32BIT,
+ AARCH64_INSN_REG_ZR, rd,
+ ARM_SMCCC_ARCH_WORKAROUND_3);
+ if (WARN_ON_ONCE(insn == AARCH64_BREAK_FAULT))
+ return;
+
+ *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());
+}
+
+#ifdef CONFIG_BPF_SYSCALL
+#define EBPF_WARN "Unprivileged eBPF is enabled, data leaks possible via Spectre v2 BHB attacks!\n"
+void unpriv_ebpf_notify(int new_state)
+{
+ if (spectre_v2_state == SPECTRE_VULNERABLE ||
+ spectre_bhb_state != SPECTRE_MITIGATED)
+ return;
+
+ if (!new_state)
+ pr_err("WARNING: %s", EBPF_WARN);
+}
+#endif