Quelle  bugs.c   Sprache: C

// SPDX-License-Identifier: GPL-2.0
/*
 *  Copyright (C) 1994  Linus Torvalds
 *
 *  Cyrix stuff, June 1998 by:
 * - Rafael R. Reilova (moved everything from head.S),
 *        <rreilova@ececs.uc.edu>
 * - Channing Corn (tests & fixes),
 * - Andrew D. Balsa (code cleanup).
 */
#include <linux/init.h>
#include <linux/cpu.h>
#include <linux/module.h>
#include <linux/nospec.h>
#include <linux/prctl.h>
#include <linux/sched/smt.h>
#include <linux/pgtable.h>
#include <linux/bpf.h>

#include <asm/spec-ctrl.h>
#include <asm/cmdline.h>
#include <asm/bugs.h>
#include <asm/processor.h>
#include <asm/processor-flags.h>
#include <asm/fpu/api.h>
#include <asm/msr.h>
#include <asm/vmx.h>
#include <asm/paravirt.h>
#include <asm/cpu_device_id.h>
#include <asm/e820/api.h>
#include <asm/hypervisor.h>
#include <asm/tlbflush.h>
#include <asm/cpu.h>

#include "cpu.h"

/*
 * Speculation Vulnerability Handling
 *
 * Each vulnerability is handled with the following functions:
 *   <vuln>_select_mitigation() -- Selects a mitigation to use.  This should
 *    take into account all relevant command line
 *    options.
 *   <vuln>_update_mitigation() -- This is called after all vulnerabilities have
 *    selected a mitigation, in case the selection
 *    may want to change based on other choices
 *    made.  This function is optional.
 *   <vuln>_apply_mitigation() -- Enable the selected mitigation.
 *
 * The compile-time mitigation in all cases should be AUTO.  An explicit
 * command-line option can override AUTO.  If no such option is
 * provided, <vuln>_select_mitigation() will override AUTO to the best
 * mitigation option.
 */

static void __init spectre_v1_select_mitigation(void);
static void __init spectre_v1_apply_mitigation(void);
static void __init spectre_v2_select_mitigation(void);
static void __init spectre_v2_update_mitigation(void);
static void __init spectre_v2_apply_mitigation(void);
static void __init retbleed_select_mitigation(void);
static void __init retbleed_update_mitigation(void);
static void __init retbleed_apply_mitigation(void);
static void __init spectre_v2_user_select_mitigation(void);
static void __init spectre_v2_user_update_mitigation(void);
static void __init spectre_v2_user_apply_mitigation(void);
static void __init ssb_select_mitigation(void);
static void __init ssb_apply_mitigation(void);
static void __init l1tf_select_mitigation(void);
static void __init l1tf_apply_mitigation(void);
static void __init mds_select_mitigation(void);
static void __init mds_update_mitigation(void);
static void __init mds_apply_mitigation(void);
static void __init taa_select_mitigation(void);
static void __init taa_update_mitigation(void);
static void __init taa_apply_mitigation(void);
static void __init mmio_select_mitigation(void);
static void __init mmio_update_mitigation(void);
static void __init mmio_apply_mitigation(void);
static void __init rfds_select_mitigation(void);
static void __init rfds_update_mitigation(void);
static void __init rfds_apply_mitigation(void);
static void __init srbds_select_mitigation(void);
static void __init srbds_apply_mitigation(void);
static void __init l1d_flush_select_mitigation(void);
static void __init srso_select_mitigation(void);
static void __init srso_update_mitigation(void);
static void __init srso_apply_mitigation(void);
static void __init gds_select_mitigation(void);
static void __init gds_apply_mitigation(void);
static void __init bhi_select_mitigation(void);
static void __init bhi_update_mitigation(void);
static void __init bhi_apply_mitigation(void);
static void __init its_select_mitigation(void);
static void __init its_update_mitigation(void);
static void __init its_apply_mitigation(void);
static void __init tsa_select_mitigation(void);
static void __init tsa_apply_mitigation(void);
static void __init vmscape_select_mitigation(void);
static void __init vmscape_update_mitigation(void);
static void __init vmscape_apply_mitigation(void);

/* The base value of the SPEC_CTRL MSR without task-specific bits set */
u64 x86_spec_ctrl_base;
EXPORT_SYMBOL_GPL(x86_spec_ctrl_base);

/* The current value of the SPEC_CTRL MSR with task-specific bits set */
DEFINE_PER_CPU(u64, x86_spec_ctrl_current);
EXPORT_PER_CPU_SYMBOL_GPL(x86_spec_ctrl_current);

/*
 * Set when the CPU has run a potentially malicious guest. An IBPB will
 * be needed to before running userspace. That IBPB will flush the branch
 * predictor content.
 */
DEFINE_PER_CPU(bool, x86_ibpb_exit_to_user);
EXPORT_PER_CPU_SYMBOL_GPL(x86_ibpb_exit_to_user);

u64 x86_pred_cmd __ro_after_init = PRED_CMD_IBPB;

static u64 __ro_after_init x86_arch_cap_msr;

static DEFINE_MUTEX(spec_ctrl_mutex);

void (*x86_return_thunk)(void) __ro_after_init = __x86_return_thunk;

static void __init set_return_thunk(void *thunk)
{
 x86_return_thunk = thunk;

 pr_info("active return thunk: %ps\n", thunk);
}

/* Update SPEC_CTRL MSR and its cached copy unconditionally */
static void update_spec_ctrl(u64 val)
{
 this_cpu_write(x86_spec_ctrl_current, val);
 wrmsrq(MSR_IA32_SPEC_CTRL, val);
}

/*
 * Keep track of the SPEC_CTRL MSR value for the current task, which may differ
 * from x86_spec_ctrl_base due to STIBP/SSB in __speculation_ctrl_update().
 */
void update_spec_ctrl_cond(u64 val)
{
 if (this_cpu_read(x86_spec_ctrl_current) == val)
  return;

 this_cpu_write(x86_spec_ctrl_current, val);

 /*
 * When KERNEL_IBRS this MSR is written on return-to-user, unless
 * forced the update can be delayed until that time.
 */
 if (!cpu_feature_enabled(X86_FEATURE_KERNEL_IBRS))
  wrmsrq(MSR_IA32_SPEC_CTRL, val);
}

noinstr u64 spec_ctrl_current(void)
{
 return this_cpu_read(x86_spec_ctrl_current);
}
EXPORT_SYMBOL_GPL(spec_ctrl_current);

/*
 * AMD specific MSR info for Speculative Store Bypass control.
 * x86_amd_ls_cfg_ssbd_mask is initialized in identify_boot_cpu().
 */
u64 __ro_after_init x86_amd_ls_cfg_base;
u64 __ro_after_init x86_amd_ls_cfg_ssbd_mask;

/* Control conditional STIBP in switch_to() */
DEFINE_STATIC_KEY_FALSE(switch_to_cond_stibp);
/* Control conditional IBPB in switch_mm() */
DEFINE_STATIC_KEY_FALSE(switch_mm_cond_ibpb);
/* Control unconditional IBPB in switch_mm() */
DEFINE_STATIC_KEY_FALSE(switch_mm_always_ibpb);

/* Control IBPB on vCPU load */
DEFINE_STATIC_KEY_FALSE(switch_vcpu_ibpb);
EXPORT_SYMBOL_GPL(switch_vcpu_ibpb);

/* Control CPU buffer clear before idling (halt, mwait) */
DEFINE_STATIC_KEY_FALSE(cpu_buf_idle_clear);
EXPORT_SYMBOL_GPL(cpu_buf_idle_clear);

/*
 * Controls whether l1d flush based mitigations are enabled,
 * based on hw features and admin setting via boot parameter
 * defaults to false
 */
DEFINE_STATIC_KEY_FALSE(switch_mm_cond_l1d_flush);

/*
 * Controls CPU Fill buffer clear before VMenter. This is a subset of
 * X86_FEATURE_CLEAR_CPU_BUF, and should only be enabled when KVM-only
 * mitigation is required.
 */
DEFINE_STATIC_KEY_FALSE(cpu_buf_vm_clear);
EXPORT_SYMBOL_GPL(cpu_buf_vm_clear);

#undef pr_fmt
#define pr_fmt(fmt) "mitigations: " fmt

static void __init cpu_print_attack_vectors(void)
{
 pr_info("Enabled attack vectors: ");

 if (cpu_attack_vector_mitigated(CPU_MITIGATE_USER_KERNEL))
  pr_cont("user_kernel, ");

 if (cpu_attack_vector_mitigated(CPU_MITIGATE_USER_USER))
  pr_cont("user_user, ");

 if (cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_HOST))
  pr_cont("guest_host, ");

 if (cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_GUEST))
  pr_cont("guest_guest, ");

 pr_cont("SMT mitigations: ");

 switch (smt_mitigations) {
 case SMT_MITIGATIONS_OFF:
  pr_cont("off\n");
  break;
 case SMT_MITIGATIONS_AUTO:
  pr_cont("auto\n");
  break;
 case SMT_MITIGATIONS_ON:
  pr_cont("on\n");
 }
}

void __init cpu_select_mitigations(void)
{
 /*
 * Read the SPEC_CTRL MSR to account for reserved bits which may
 * have unknown values. AMD64_LS_CFG MSR is cached in the early AMD
 * init code as it is not enumerated and depends on the family.
 */
 if (cpu_feature_enabled(X86_FEATURE_MSR_SPEC_CTRL)) {
  rdmsrq(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);

  /*
 * Previously running kernel (kexec), may have some controls
 * turned ON. Clear them and let the mitigations setup below
 * rediscover them based on configuration.
 */
  x86_spec_ctrl_base &= ~SPEC_CTRL_MITIGATIONS_MASK;
 }

 x86_arch_cap_msr = x86_read_arch_cap_msr();

 cpu_print_attack_vectors();

 /* Select the proper CPU mitigations before patching alternatives: */
 spectre_v1_select_mitigation();
 spectre_v2_select_mitigation();
 retbleed_select_mitigation();
 spectre_v2_user_select_mitigation();
 ssb_select_mitigation();
 l1tf_select_mitigation();
 mds_select_mitigation();
 taa_select_mitigation();
 mmio_select_mitigation();
 rfds_select_mitigation();
 srbds_select_mitigation();
 l1d_flush_select_mitigation();
 srso_select_mitigation();
 gds_select_mitigation();
 its_select_mitigation();
 bhi_select_mitigation();
 tsa_select_mitigation();
 vmscape_select_mitigation();

 /*
 * After mitigations are selected, some may need to update their
 * choices.
 */
 spectre_v2_update_mitigation();
 /*
 * retbleed_update_mitigation() relies on the state set by
 * spectre_v2_update_mitigation(); specifically it wants to know about
 * spectre_v2=ibrs.
 */
 retbleed_update_mitigation();
 /*
 * its_update_mitigation() depends on spectre_v2_update_mitigation()
 * and retbleed_update_mitigation().
 */
 its_update_mitigation();

 /*
 * spectre_v2_user_update_mitigation() depends on
 * retbleed_update_mitigation(), specifically the STIBP
 * selection is forced for UNRET or IBPB.
 */
 spectre_v2_user_update_mitigation();
 mds_update_mitigation();
 taa_update_mitigation();
 mmio_update_mitigation();
 rfds_update_mitigation();
 bhi_update_mitigation();
 /* srso_update_mitigation() depends on retbleed_update_mitigation(). */
 srso_update_mitigation();
 vmscape_update_mitigation();

 spectre_v1_apply_mitigation();
 spectre_v2_apply_mitigation();
 retbleed_apply_mitigation();
 spectre_v2_user_apply_mitigation();
 ssb_apply_mitigation();
 l1tf_apply_mitigation();
 mds_apply_mitigation();
 taa_apply_mitigation();
 mmio_apply_mitigation();
 rfds_apply_mitigation();
 srbds_apply_mitigation();
 srso_apply_mitigation();
 gds_apply_mitigation();
 its_apply_mitigation();
 bhi_apply_mitigation();
 tsa_apply_mitigation();
 vmscape_apply_mitigation();
}

/*
 * NOTE: This function is *only* called for SVM, since Intel uses
 * MSR_IA32_SPEC_CTRL for SSBD.
 */
void
x86_virt_spec_ctrl(u64 guest_virt_spec_ctrl, bool setguest)
{
 u64 guestval, hostval;
 struct thread_info *ti = current_thread_info();

 /*
 * If SSBD is not handled in MSR_SPEC_CTRL on AMD, update
 * MSR_AMD64_L2_CFG or MSR_VIRT_SPEC_CTRL if supported.
 */
 if (!static_cpu_has(X86_FEATURE_LS_CFG_SSBD) &&
     !static_cpu_has(X86_FEATURE_VIRT_SSBD))
  return;

 /*
 * If the host has SSBD mitigation enabled, force it in the host's
 * virtual MSR value. If its not permanently enabled, evaluate
 * current's TIF_SSBD thread flag.
 */
 if (static_cpu_has(X86_FEATURE_SPEC_STORE_BYPASS_DISABLE))
  hostval = SPEC_CTRL_SSBD;
 else
  hostval = ssbd_tif_to_spec_ctrl(ti->flags);

 /* Sanitize the guest value */
 guestval = guest_virt_spec_ctrl & SPEC_CTRL_SSBD;

 if (hostval != guestval) {
  unsigned long tif;

  tif = setguest ? ssbd_spec_ctrl_to_tif(guestval) :
     ssbd_spec_ctrl_to_tif(hostval);

  speculation_ctrl_update(tif);
 }
}
EXPORT_SYMBOL_GPL(x86_virt_spec_ctrl);

static void x86_amd_ssb_disable(void)
{
 u64 msrval = x86_amd_ls_cfg_base | x86_amd_ls_cfg_ssbd_mask;

 if (boot_cpu_has(X86_FEATURE_VIRT_SSBD))
  wrmsrq(MSR_AMD64_VIRT_SPEC_CTRL, SPEC_CTRL_SSBD);
 else if (boot_cpu_has(X86_FEATURE_LS_CFG_SSBD))
  wrmsrq(MSR_AMD64_LS_CFG, msrval);
}

#undef pr_fmt
#define pr_fmt(fmt) "MDS: " fmt

/*
 * Returns true if vulnerability should be mitigated based on the
 * selected attack vector controls.
 *
 * See Documentation/admin-guide/hw-vuln/attack_vector_controls.rst
 */
static bool __init should_mitigate_vuln(unsigned int bug)
{
 switch (bug) {
 /*
 * The only runtime-selected spectre_v1 mitigations in the kernel are
 * related to SWAPGS protection on kernel entry.  Therefore, protection
 * is only required for the user->kernel attack vector.
 */
 case X86_BUG_SPECTRE_V1:
  return cpu_attack_vector_mitigated(CPU_MITIGATE_USER_KERNEL);

 case X86_BUG_SPECTRE_V2:
 case X86_BUG_RETBLEED:
 case X86_BUG_L1TF:
 case X86_BUG_ITS:
  return cpu_attack_vector_mitigated(CPU_MITIGATE_USER_KERNEL) ||
         cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_HOST);

 case X86_BUG_SPECTRE_V2_USER:
  return cpu_attack_vector_mitigated(CPU_MITIGATE_USER_USER) ||
         cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_GUEST);

 /*
 * All the vulnerabilities below allow potentially leaking data
 * across address spaces.  Therefore, mitigation is required for
 * any of these 4 attack vectors.
 */
 case X86_BUG_MDS:
 case X86_BUG_TAA:
 case X86_BUG_MMIO_STALE_DATA:
 case X86_BUG_RFDS:
 case X86_BUG_SRBDS:
  return cpu_attack_vector_mitigated(CPU_MITIGATE_USER_KERNEL) ||
         cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_HOST) ||
         cpu_attack_vector_mitigated(CPU_MITIGATE_USER_USER) ||
         cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_GUEST);

 case X86_BUG_GDS:
  return cpu_attack_vector_mitigated(CPU_MITIGATE_USER_KERNEL) ||
         cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_HOST) ||
         cpu_attack_vector_mitigated(CPU_MITIGATE_USER_USER) ||
         cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_GUEST) ||
         (smt_mitigations != SMT_MITIGATIONS_OFF);

 case X86_BUG_SPEC_STORE_BYPASS:
  return cpu_attack_vector_mitigated(CPU_MITIGATE_USER_USER);

 case X86_BUG_VMSCAPE:
  return cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_HOST);

 default:
  WARN(1, "Unknown bug %x\n", bug);
  return false;
 }
}

/* Default mitigation for MDS-affected CPUs */
static enum mds_mitigations mds_mitigation __ro_after_init =
 IS_ENABLED(CONFIG_MITIGATION_MDS) ? MDS_MITIGATION_AUTO : MDS_MITIGATION_OFF;
static bool mds_nosmt __ro_after_init = false;

static const char * const mds_strings[] = {
 [MDS_MITIGATION_OFF] = "Vulnerable",
 [MDS_MITIGATION_FULL] = "Mitigation: Clear CPU buffers",
 [MDS_MITIGATION_VMWERV] = "Vulnerable: Clear CPU buffers attempted, no microcode",
};

enum taa_mitigations {
 TAA_MITIGATION_OFF,
 TAA_MITIGATION_AUTO,
 TAA_MITIGATION_UCODE_NEEDED,
 TAA_MITIGATION_VERW,
 TAA_MITIGATION_TSX_DISABLED,
};

/* Default mitigation for TAA-affected CPUs */
static enum taa_mitigations taa_mitigation __ro_after_init =
 IS_ENABLED(CONFIG_MITIGATION_TAA) ? TAA_MITIGATION_AUTO : TAA_MITIGATION_OFF;

enum mmio_mitigations {
 MMIO_MITIGATION_OFF,
 MMIO_MITIGATION_AUTO,
 MMIO_MITIGATION_UCODE_NEEDED,
 MMIO_MITIGATION_VERW,
};

/* Default mitigation for Processor MMIO Stale Data vulnerabilities */
static enum mmio_mitigations mmio_mitigation __ro_after_init =
 IS_ENABLED(CONFIG_MITIGATION_MMIO_STALE_DATA) ? MMIO_MITIGATION_AUTO : MMIO_MITIGATION_OFF;

enum rfds_mitigations {
 RFDS_MITIGATION_OFF,
 RFDS_MITIGATION_AUTO,
 RFDS_MITIGATION_VERW,
 RFDS_MITIGATION_UCODE_NEEDED,
};

/* Default mitigation for Register File Data Sampling */
static enum rfds_mitigations rfds_mitigation __ro_after_init =
 IS_ENABLED(CONFIG_MITIGATION_RFDS) ? RFDS_MITIGATION_AUTO : RFDS_MITIGATION_OFF;

/*
 * Set if any of MDS/TAA/MMIO/RFDS are going to enable VERW clearing
 * through X86_FEATURE_CLEAR_CPU_BUF on kernel and guest entry.
 */
static bool verw_clear_cpu_buf_mitigation_selected __ro_after_init;

static void __init mds_select_mitigation(void)
{
 if (!boot_cpu_has_bug(X86_BUG_MDS)) {
  mds_mitigation = MDS_MITIGATION_OFF;
  return;
 }

 if (mds_mitigation == MDS_MITIGATION_AUTO) {
  if (should_mitigate_vuln(X86_BUG_MDS))
   mds_mitigation = MDS_MITIGATION_FULL;
  else
   mds_mitigation = MDS_MITIGATION_OFF;
 }

 if (mds_mitigation == MDS_MITIGATION_OFF)
  return;

 verw_clear_cpu_buf_mitigation_selected = true;
}

static void __init mds_update_mitigation(void)
{
 if (!boot_cpu_has_bug(X86_BUG_MDS))
  return;

 /* If TAA, MMIO, or RFDS are being mitigated, MDS gets mitigated too. */
 if (verw_clear_cpu_buf_mitigation_selected)
  mds_mitigation = MDS_MITIGATION_FULL;

 if (mds_mitigation == MDS_MITIGATION_FULL) {
  if (!boot_cpu_has(X86_FEATURE_MD_CLEAR))
   mds_mitigation = MDS_MITIGATION_VMWERV;
 }

 pr_info("%s\n", mds_strings[mds_mitigation]);
}

static void __init mds_apply_mitigation(void)
{
 if (mds_mitigation == MDS_MITIGATION_FULL ||
     mds_mitigation == MDS_MITIGATION_VMWERV) {
  setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF);
  if (!boot_cpu_has(X86_BUG_MSBDS_ONLY) &&
      (mds_nosmt || smt_mitigations == SMT_MITIGATIONS_ON))
   cpu_smt_disable(false);
 }
}

static int __init mds_cmdline(char *str)
{
 if (!boot_cpu_has_bug(X86_BUG_MDS))
  return 0;

 if (!str)
  return -EINVAL;

 if (!strcmp(str, "off"))
  mds_mitigation = MDS_MITIGATION_OFF;
 else if (!strcmp(str, "full"))
  mds_mitigation = MDS_MITIGATION_FULL;
 else if (!strcmp(str, "full,nosmt")) {
  mds_mitigation = MDS_MITIGATION_FULL;
  mds_nosmt = true;
 }

 return 0;
}
early_param("mds", mds_cmdline);

#undef pr_fmt
#define pr_fmt(fmt) "TAA: " fmt

static bool taa_nosmt __ro_after_init;

static const char * const taa_strings[] = {
 [TAA_MITIGATION_OFF]  = "Vulnerable",
 [TAA_MITIGATION_UCODE_NEEDED] = "Vulnerable: Clear CPU buffers attempted, no microcode",
 [TAA_MITIGATION_VERW]  = "Mitigation: Clear CPU buffers",
 [TAA_MITIGATION_TSX_DISABLED] = "Mitigation: TSX disabled",
};

static bool __init taa_vulnerable(void)
{
 return boot_cpu_has_bug(X86_BUG_TAA) && boot_cpu_has(X86_FEATURE_RTM);
}

static void __init taa_select_mitigation(void)
{
 if (!boot_cpu_has_bug(X86_BUG_TAA)) {
  taa_mitigation = TAA_MITIGATION_OFF;
  return;
 }

 /* TSX previously disabled by tsx=off */
 if (!boot_cpu_has(X86_FEATURE_RTM)) {
  taa_mitigation = TAA_MITIGATION_TSX_DISABLED;
  return;
 }

 /* Microcode will be checked in taa_update_mitigation(). */
 if (taa_mitigation == TAA_MITIGATION_AUTO) {
  if (should_mitigate_vuln(X86_BUG_TAA))
   taa_mitigation = TAA_MITIGATION_VERW;
  else
   taa_mitigation = TAA_MITIGATION_OFF;
 }

 if (taa_mitigation != TAA_MITIGATION_OFF)
  verw_clear_cpu_buf_mitigation_selected = true;
}

static void __init taa_update_mitigation(void)
{
 if (!taa_vulnerable())
  return;

 if (verw_clear_cpu_buf_mitigation_selected)
  taa_mitigation = TAA_MITIGATION_VERW;

 if (taa_mitigation == TAA_MITIGATION_VERW) {
  /* Check if the requisite ucode is available. */
  if (!boot_cpu_has(X86_FEATURE_MD_CLEAR))
   taa_mitigation = TAA_MITIGATION_UCODE_NEEDED;

  /*
 * VERW doesn't clear the CPU buffers when MD_CLEAR=1 and MDS_NO=1.
 * A microcode update fixes this behavior to clear CPU buffers. It also
 * adds support for MSR_IA32_TSX_CTRL which is enumerated by the
 * ARCH_CAP_TSX_CTRL_MSR bit.
 *
 * On MDS_NO=1 CPUs if ARCH_CAP_TSX_CTRL_MSR is not set, microcode
 * update is required.
 */
  if ((x86_arch_cap_msr & ARCH_CAP_MDS_NO) &&
     !(x86_arch_cap_msr & ARCH_CAP_TSX_CTRL_MSR))
   taa_mitigation = TAA_MITIGATION_UCODE_NEEDED;
 }

 pr_info("%s\n", taa_strings[taa_mitigation]);
}

static void __init taa_apply_mitigation(void)
{
 if (taa_mitigation == TAA_MITIGATION_VERW ||
     taa_mitigation == TAA_MITIGATION_UCODE_NEEDED) {
  /*
 * TSX is enabled, select alternate mitigation for TAA which is
 * the same as MDS. Enable MDS static branch to clear CPU buffers.
 *
 * For guests that can't determine whether the correct microcode is
 * present on host, enable the mitigation for UCODE_NEEDED as well.
 */
  setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF);

  if (taa_nosmt || smt_mitigations == SMT_MITIGATIONS_ON)
   cpu_smt_disable(false);
 }
}

static int __init tsx_async_abort_parse_cmdline(char *str)
{
 if (!boot_cpu_has_bug(X86_BUG_TAA))
  return 0;

 if (!str)
  return -EINVAL;

 if (!strcmp(str, "off")) {
  taa_mitigation = TAA_MITIGATION_OFF;
 } else if (!strcmp(str, "full")) {
  taa_mitigation = TAA_MITIGATION_VERW;
 } else if (!strcmp(str, "full,nosmt")) {
  taa_mitigation = TAA_MITIGATION_VERW;
  taa_nosmt = true;
 }

 return 0;
}
early_param("tsx_async_abort", tsx_async_abort_parse_cmdline);

#undef pr_fmt
#define pr_fmt(fmt) "MMIO Stale Data: " fmt

static bool mmio_nosmt __ro_after_init = false;

static const char * const mmio_strings[] = {
 [MMIO_MITIGATION_OFF]  = "Vulnerable",
 [MMIO_MITIGATION_UCODE_NEEDED] = "Vulnerable: Clear CPU buffers attempted, no microcode",
 [MMIO_MITIGATION_VERW]  = "Mitigation: Clear CPU buffers",
};

static void __init mmio_select_mitigation(void)
{
 if (!boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA) ||
      cpu_mitigations_off()) {
  mmio_mitigation = MMIO_MITIGATION_OFF;
  return;
 }

 /* Microcode will be checked in mmio_update_mitigation(). */
 if (mmio_mitigation == MMIO_MITIGATION_AUTO) {
  if (should_mitigate_vuln(X86_BUG_MMIO_STALE_DATA))
   mmio_mitigation = MMIO_MITIGATION_VERW;
  else
   mmio_mitigation = MMIO_MITIGATION_OFF;
 }

 if (mmio_mitigation == MMIO_MITIGATION_OFF)
  return;

 /*
 * Enable CPU buffer clear mitigation for host and VMM, if also affected
 * by MDS or TAA.
 */
 if (boot_cpu_has_bug(X86_BUG_MDS) || taa_vulnerable())
  verw_clear_cpu_buf_mitigation_selected = true;
}

static void __init mmio_update_mitigation(void)
{
 if (!boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA))
  return;

 if (verw_clear_cpu_buf_mitigation_selected)
  mmio_mitigation = MMIO_MITIGATION_VERW;

 if (mmio_mitigation == MMIO_MITIGATION_VERW) {
  /*
 * Check if the system has the right microcode.
 *
 * CPU Fill buffer clear mitigation is enumerated by either an explicit
 * FB_CLEAR or by the presence of both MD_CLEAR and L1D_FLUSH on MDS
 * affected systems.
 */
  if (!((x86_arch_cap_msr & ARCH_CAP_FB_CLEAR) ||
        (boot_cpu_has(X86_FEATURE_MD_CLEAR) &&
         boot_cpu_has(X86_FEATURE_FLUSH_L1D) &&
       !(x86_arch_cap_msr & ARCH_CAP_MDS_NO))))
   mmio_mitigation = MMIO_MITIGATION_UCODE_NEEDED;
 }

 pr_info("%s\n", mmio_strings[mmio_mitigation]);
}

static void __init mmio_apply_mitigation(void)
{
 if (mmio_mitigation == MMIO_MITIGATION_OFF)
  return;

 /*
 * Only enable the VMM mitigation if the CPU buffer clear mitigation is
 * not being used.
 */
 if (verw_clear_cpu_buf_mitigation_selected) {
  setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF);
  static_branch_disable(&cpu_buf_vm_clear);
 } else {
  static_branch_enable(&cpu_buf_vm_clear);
 }

 /*
 * If Processor-MMIO-Stale-Data bug is present and Fill Buffer data can
 * be propagated to uncore buffers, clearing the Fill buffers on idle
 * is required irrespective of SMT state.
 */
 if (!(x86_arch_cap_msr & ARCH_CAP_FBSDP_NO))
  static_branch_enable(&cpu_buf_idle_clear);

 if (mmio_nosmt || smt_mitigations == SMT_MITIGATIONS_ON)
  cpu_smt_disable(false);
}

static int __init mmio_stale_data_parse_cmdline(char *str)
{
 if (!boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA))
  return 0;

 if (!str)
  return -EINVAL;

 if (!strcmp(str, "off")) {
  mmio_mitigation = MMIO_MITIGATION_OFF;
 } else if (!strcmp(str, "full")) {
  mmio_mitigation = MMIO_MITIGATION_VERW;
 } else if (!strcmp(str, "full,nosmt")) {
  mmio_mitigation = MMIO_MITIGATION_VERW;
  mmio_nosmt = true;
 }

 return 0;
}
early_param("mmio_stale_data", mmio_stale_data_parse_cmdline);

#undef pr_fmt
#define pr_fmt(fmt) "Register File Data Sampling: " fmt

static const char * const rfds_strings[] = {
 [RFDS_MITIGATION_OFF]   = "Vulnerable",
 [RFDS_MITIGATION_VERW]   = "Mitigation: Clear Register File",
 [RFDS_MITIGATION_UCODE_NEEDED]  = "Vulnerable: No microcode",
};

static inline bool __init verw_clears_cpu_reg_file(void)
{
 return (x86_arch_cap_msr & ARCH_CAP_RFDS_CLEAR);
}

static void __init rfds_select_mitigation(void)
{
 if (!boot_cpu_has_bug(X86_BUG_RFDS)) {
  rfds_mitigation = RFDS_MITIGATION_OFF;
  return;
 }

 if (rfds_mitigation == RFDS_MITIGATION_AUTO) {
  if (should_mitigate_vuln(X86_BUG_RFDS))
   rfds_mitigation = RFDS_MITIGATION_VERW;
  else
   rfds_mitigation = RFDS_MITIGATION_OFF;
 }

 if (rfds_mitigation == RFDS_MITIGATION_OFF)
  return;

 if (verw_clears_cpu_reg_file())
  verw_clear_cpu_buf_mitigation_selected = true;
}

static void __init rfds_update_mitigation(void)
{
 if (!boot_cpu_has_bug(X86_BUG_RFDS))
  return;

 if (verw_clear_cpu_buf_mitigation_selected)
  rfds_mitigation = RFDS_MITIGATION_VERW;

 if (rfds_mitigation == RFDS_MITIGATION_VERW) {
  if (!verw_clears_cpu_reg_file())
   rfds_mitigation = RFDS_MITIGATION_UCODE_NEEDED;
 }

 pr_info("%s\n", rfds_strings[rfds_mitigation]);
}

static void __init rfds_apply_mitigation(void)
{
 if (rfds_mitigation == RFDS_MITIGATION_VERW)
  setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF);
}

static __init int rfds_parse_cmdline(char *str)
{
 if (!str)
  return -EINVAL;

 if (!boot_cpu_has_bug(X86_BUG_RFDS))
  return 0;

 if (!strcmp(str, "off"))
  rfds_mitigation = RFDS_MITIGATION_OFF;
 else if (!strcmp(str, "on"))
  rfds_mitigation = RFDS_MITIGATION_VERW;

 return 0;
}
early_param("reg_file_data_sampling", rfds_parse_cmdline);

#undef pr_fmt
#define pr_fmt(fmt) "SRBDS: " fmt

enum srbds_mitigations {
 SRBDS_MITIGATION_OFF,
 SRBDS_MITIGATION_AUTO,
 SRBDS_MITIGATION_UCODE_NEEDED,
 SRBDS_MITIGATION_FULL,
 SRBDS_MITIGATION_TSX_OFF,
 SRBDS_MITIGATION_HYPERVISOR,
};

static enum srbds_mitigations srbds_mitigation __ro_after_init =
 IS_ENABLED(CONFIG_MITIGATION_SRBDS) ? SRBDS_MITIGATION_AUTO : SRBDS_MITIGATION_OFF;

static const char * const srbds_strings[] = {
 [SRBDS_MITIGATION_OFF]  = "Vulnerable",
 [SRBDS_MITIGATION_UCODE_NEEDED] = "Vulnerable: No microcode",
 [SRBDS_MITIGATION_FULL]  = "Mitigation: Microcode",
 [SRBDS_MITIGATION_TSX_OFF] = "Mitigation: TSX disabled",
 [SRBDS_MITIGATION_HYPERVISOR] = "Unknown: Dependent on hypervisor status",
};

static bool srbds_off;

void update_srbds_msr(void)
{
 u64 mcu_ctrl;

 if (!boot_cpu_has_bug(X86_BUG_SRBDS))
  return;

 if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
  return;

 if (srbds_mitigation == SRBDS_MITIGATION_UCODE_NEEDED)
  return;

 /*
 * A MDS_NO CPU for which SRBDS mitigation is not needed due to TSX
 * being disabled and it hasn't received the SRBDS MSR microcode.
 */
 if (!boot_cpu_has(X86_FEATURE_SRBDS_CTRL))
  return;

 rdmsrq(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl);

 switch (srbds_mitigation) {
 case SRBDS_MITIGATION_OFF:
 case SRBDS_MITIGATION_TSX_OFF:
  mcu_ctrl |= RNGDS_MITG_DIS;
  break;
 case SRBDS_MITIGATION_FULL:
  mcu_ctrl &= ~RNGDS_MITG_DIS;
  break;
 default:
  break;
 }

 wrmsrq(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl);
}

static void __init srbds_select_mitigation(void)
{
 if (!boot_cpu_has_bug(X86_BUG_SRBDS)) {
  srbds_mitigation = SRBDS_MITIGATION_OFF;
  return;
 }

 if (srbds_mitigation == SRBDS_MITIGATION_AUTO) {
  if (should_mitigate_vuln(X86_BUG_SRBDS))
   srbds_mitigation = SRBDS_MITIGATION_FULL;
  else {
   srbds_mitigation = SRBDS_MITIGATION_OFF;
   return;
  }
 }

 /*
 * Check to see if this is one of the MDS_NO systems supporting TSX that
 * are only exposed to SRBDS when TSX is enabled or when CPU is affected
 * by Processor MMIO Stale Data vulnerability.
 */
 if ((x86_arch_cap_msr & ARCH_CAP_MDS_NO) && !boot_cpu_has(X86_FEATURE_RTM) &&
     !boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA))
  srbds_mitigation = SRBDS_MITIGATION_TSX_OFF;
 else if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
  srbds_mitigation = SRBDS_MITIGATION_HYPERVISOR;
 else if (!boot_cpu_has(X86_FEATURE_SRBDS_CTRL))
  srbds_mitigation = SRBDS_MITIGATION_UCODE_NEEDED;
 else if (srbds_off)
  srbds_mitigation = SRBDS_MITIGATION_OFF;

 pr_info("%s\n", srbds_strings[srbds_mitigation]);
}

static void __init srbds_apply_mitigation(void)
{
 update_srbds_msr();
}

static int __init srbds_parse_cmdline(char *str)
{
 if (!str)
  return -EINVAL;

 if (!boot_cpu_has_bug(X86_BUG_SRBDS))
  return 0;

 srbds_off = !strcmp(str, "off");
 return 0;
}
early_param("srbds", srbds_parse_cmdline);

#undef pr_fmt
#define pr_fmt(fmt)     "L1D Flush : " fmt

enum l1d_flush_mitigations {
 L1D_FLUSH_OFF = 0,
 L1D_FLUSH_ON,
};

static enum l1d_flush_mitigations l1d_flush_mitigation __initdata = L1D_FLUSH_OFF;

static void __init l1d_flush_select_mitigation(void)
{
 if (!l1d_flush_mitigation || !boot_cpu_has(X86_FEATURE_FLUSH_L1D))
  return;

 static_branch_enable(&switch_mm_cond_l1d_flush);
 pr_info("Conditional flush on switch_mm() enabled\n");
}

static int __init l1d_flush_parse_cmdline(char *str)
{
 if (!strcmp(str, "on"))
  l1d_flush_mitigation = L1D_FLUSH_ON;

 return 0;
}
early_param("l1d_flush", l1d_flush_parse_cmdline);

#undef pr_fmt
#define pr_fmt(fmt) "GDS: " fmt

enum gds_mitigations {
 GDS_MITIGATION_OFF,
 GDS_MITIGATION_AUTO,
 GDS_MITIGATION_UCODE_NEEDED,
 GDS_MITIGATION_FORCE,
 GDS_MITIGATION_FULL,
 GDS_MITIGATION_FULL_LOCKED,
 GDS_MITIGATION_HYPERVISOR,
};

static enum gds_mitigations gds_mitigation __ro_after_init =
 IS_ENABLED(CONFIG_MITIGATION_GDS) ? GDS_MITIGATION_AUTO : GDS_MITIGATION_OFF;

static const char * const gds_strings[] = {
 [GDS_MITIGATION_OFF]  = "Vulnerable",
 [GDS_MITIGATION_UCODE_NEEDED] = "Vulnerable: No microcode",
 [GDS_MITIGATION_FORCE]  = "Mitigation: AVX disabled, no microcode",
 [GDS_MITIGATION_FULL]  = "Mitigation: Microcode",
 [GDS_MITIGATION_FULL_LOCKED] = "Mitigation: Microcode (locked)",
 [GDS_MITIGATION_HYPERVISOR] = "Unknown: Dependent on hypervisor status",
};

bool gds_ucode_mitigated(void)
{
 return (gds_mitigation == GDS_MITIGATION_FULL ||
  gds_mitigation == GDS_MITIGATION_FULL_LOCKED);
}
EXPORT_SYMBOL_GPL(gds_ucode_mitigated);

void update_gds_msr(void)
{
 u64 mcu_ctrl_after;
 u64 mcu_ctrl;

 switch (gds_mitigation) {
 case GDS_MITIGATION_OFF:
  rdmsrq(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl);
  mcu_ctrl |= GDS_MITG_DIS;
  break;
 case GDS_MITIGATION_FULL_LOCKED:
  /*
 * The LOCKED state comes from the boot CPU. APs might not have
 * the same state. Make sure the mitigation is enabled on all
 * CPUs.
 */
 case GDS_MITIGATION_FULL:
  rdmsrq(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl);
  mcu_ctrl &= ~GDS_MITG_DIS;
  break;
 case GDS_MITIGATION_FORCE:
 case GDS_MITIGATION_UCODE_NEEDED:
 case GDS_MITIGATION_HYPERVISOR:
 case GDS_MITIGATION_AUTO:
  return;
 }

 wrmsrq(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl);

 /*
 * Check to make sure that the WRMSR value was not ignored. Writes to
 * GDS_MITG_DIS will be ignored if this processor is locked but the boot
 * processor was not.
 */
 rdmsrq(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl_after);
 WARN_ON_ONCE(mcu_ctrl != mcu_ctrl_after);
}

static void __init gds_select_mitigation(void)
{
 u64 mcu_ctrl;

 if (!boot_cpu_has_bug(X86_BUG_GDS))
  return;

 if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) {
  gds_mitigation = GDS_MITIGATION_HYPERVISOR;
  return;
 }

 /* Will verify below that mitigation _can_ be disabled */
 if (gds_mitigation == GDS_MITIGATION_AUTO) {
  if (should_mitigate_vuln(X86_BUG_GDS))
   gds_mitigation = GDS_MITIGATION_FULL;
  else
   gds_mitigation = GDS_MITIGATION_OFF;
 }

 /* No microcode */
 if (!(x86_arch_cap_msr & ARCH_CAP_GDS_CTRL)) {
  if (gds_mitigation != GDS_MITIGATION_FORCE)
   gds_mitigation = GDS_MITIGATION_UCODE_NEEDED;
  return;
 }

 /* Microcode has mitigation, use it */
 if (gds_mitigation == GDS_MITIGATION_FORCE)
  gds_mitigation = GDS_MITIGATION_FULL;

 rdmsrq(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl);
 if (mcu_ctrl & GDS_MITG_LOCKED) {
  if (gds_mitigation == GDS_MITIGATION_OFF)
   pr_warn("Mitigation locked. Disable failed.\n");

  /*
 * The mitigation is selected from the boot CPU. All other CPUs
 * _should_ have the same state. If the boot CPU isn't locked
 * but others are then update_gds_msr() will WARN() of the state
 * mismatch. If the boot CPU is locked update_gds_msr() will
 * ensure the other CPUs have the mitigation enabled.
 */
  gds_mitigation = GDS_MITIGATION_FULL_LOCKED;
 }
}

static void __init gds_apply_mitigation(void)
{
 if (!boot_cpu_has_bug(X86_BUG_GDS))
  return;

 /* Microcode is present */
 if (x86_arch_cap_msr & ARCH_CAP_GDS_CTRL)
  update_gds_msr();
 else if (gds_mitigation == GDS_MITIGATION_FORCE) {
  /*
 * This only needs to be done on the boot CPU so do it
 * here rather than in update_gds_msr()
 */
  setup_clear_cpu_cap(X86_FEATURE_AVX);
  pr_warn("Microcode update needed! Disabling AVX as mitigation.\n");
 }

 pr_info("%s\n", gds_strings[gds_mitigation]);
}

static int __init gds_parse_cmdline(char *str)
{
 if (!str)
  return -EINVAL;

 if (!boot_cpu_has_bug(X86_BUG_GDS))
  return 0;

 if (!strcmp(str, "off"))
  gds_mitigation = GDS_MITIGATION_OFF;
 else if (!strcmp(str, "force"))
  gds_mitigation = GDS_MITIGATION_FORCE;

 return 0;
}
early_param("gather_data_sampling", gds_parse_cmdline);

#undef pr_fmt
#define pr_fmt(fmt)     "Spectre V1 : " fmt

enum spectre_v1_mitigation {
 SPECTRE_V1_MITIGATION_NONE,
 SPECTRE_V1_MITIGATION_AUTO,
};

static enum spectre_v1_mitigation spectre_v1_mitigation __ro_after_init =
 IS_ENABLED(CONFIG_MITIGATION_SPECTRE_V1) ?
  SPECTRE_V1_MITIGATION_AUTO : SPECTRE_V1_MITIGATION_NONE;

static const char * const spectre_v1_strings[] = {
 [SPECTRE_V1_MITIGATION_NONE] = "Vulnerable: __user pointer sanitization and usercopy barriers only; no swapgs barriers",
 [SPECTRE_V1_MITIGATION_AUTO] = "Mitigation: usercopy/swapgs barriers and __user pointer sanitization",
};

/*
 * Does SMAP provide full mitigation against speculative kernel access to
 * userspace?
 */
static bool smap_works_speculatively(void)
{
 if (!boot_cpu_has(X86_FEATURE_SMAP))
  return false;

 /*
 * On CPUs which are vulnerable to Meltdown, SMAP does not
 * prevent speculative access to user data in the L1 cache.
 * Consider SMAP to be non-functional as a mitigation on these
 * CPUs.
 */
 if (boot_cpu_has(X86_BUG_CPU_MELTDOWN))
  return false;

 return true;
}

static void __init spectre_v1_select_mitigation(void)
{
 if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V1))
  spectre_v1_mitigation = SPECTRE_V1_MITIGATION_NONE;

 if (!should_mitigate_vuln(X86_BUG_SPECTRE_V1))
  spectre_v1_mitigation = SPECTRE_V1_MITIGATION_NONE;
}

static void __init spectre_v1_apply_mitigation(void)
{
 if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V1))
  return;

 if (spectre_v1_mitigation == SPECTRE_V1_MITIGATION_AUTO) {
  /*
 * With Spectre v1, a user can speculatively control either
 * path of a conditional swapgs with a user-controlled GS
 * value.  The mitigation is to add lfences to both code paths.
 *
 * If FSGSBASE is enabled, the user can put a kernel address in
 * GS, in which case SMAP provides no protection.
 *
 * If FSGSBASE is disabled, the user can only put a user space
 * address in GS.  That makes an attack harder, but still
 * possible if there's no SMAP protection.
 */
  if (boot_cpu_has(X86_FEATURE_FSGSBASE) ||
      !smap_works_speculatively()) {
   /*
 * Mitigation can be provided from SWAPGS itself or
 * PTI as the CR3 write in the Meltdown mitigation
 * is serializing.
 *
 * If neither is there, mitigate with an LFENCE to
 * stop speculation through swapgs.
 */
   if (boot_cpu_has_bug(X86_BUG_SWAPGS) &&
       !boot_cpu_has(X86_FEATURE_PTI))
    setup_force_cpu_cap(X86_FEATURE_FENCE_SWAPGS_USER);

   /*
 * Enable lfences in the kernel entry (non-swapgs)
 * paths, to prevent user entry from speculatively
 * skipping swapgs.
 */
   setup_force_cpu_cap(X86_FEATURE_FENCE_SWAPGS_KERNEL);
  }
 }

 pr_info("%s\n", spectre_v1_strings[spectre_v1_mitigation]);
}

static int __init nospectre_v1_cmdline(char *str)
{
 spectre_v1_mitigation = SPECTRE_V1_MITIGATION_NONE;
 return 0;
}
early_param("nospectre_v1", nospectre_v1_cmdline);

enum spectre_v2_mitigation spectre_v2_enabled __ro_after_init = SPECTRE_V2_NONE;

/* Depends on spectre_v2 mitigation selected already */
static inline bool cdt_possible(enum spectre_v2_mitigation mode)
{
 if (!IS_ENABLED(CONFIG_MITIGATION_CALL_DEPTH_TRACKING) ||
     !IS_ENABLED(CONFIG_MITIGATION_RETPOLINE))
  return false;

 if (mode == SPECTRE_V2_RETPOLINE ||
     mode == SPECTRE_V2_EIBRS_RETPOLINE)
  return true;

 return false;
}

#undef pr_fmt
#define pr_fmt(fmt)     "RETBleed: " fmt

enum its_mitigation {
 ITS_MITIGATION_OFF,
 ITS_MITIGATION_AUTO,
 ITS_MITIGATION_VMEXIT_ONLY,
 ITS_MITIGATION_ALIGNED_THUNKS,
 ITS_MITIGATION_RETPOLINE_STUFF,
};

static enum its_mitigation its_mitigation __ro_after_init =
 IS_ENABLED(CONFIG_MITIGATION_ITS) ? ITS_MITIGATION_AUTO : ITS_MITIGATION_OFF;

enum retbleed_mitigation {
 RETBLEED_MITIGATION_NONE,
 RETBLEED_MITIGATION_AUTO,
 RETBLEED_MITIGATION_UNRET,
 RETBLEED_MITIGATION_IBPB,
 RETBLEED_MITIGATION_IBRS,
 RETBLEED_MITIGATION_EIBRS,
 RETBLEED_MITIGATION_STUFF,
};

static const char * const retbleed_strings[] = {
 [RETBLEED_MITIGATION_NONE] = "Vulnerable",
 [RETBLEED_MITIGATION_UNRET] = "Mitigation: untrained return thunk",
 [RETBLEED_MITIGATION_IBPB] = "Mitigation: IBPB",
 [RETBLEED_MITIGATION_IBRS] = "Mitigation: IBRS",
 [RETBLEED_MITIGATION_EIBRS] = "Mitigation: Enhanced IBRS",
 [RETBLEED_MITIGATION_STUFF] = "Mitigation: Stuffing",
};

static enum retbleed_mitigation retbleed_mitigation __ro_after_init =
 IS_ENABLED(CONFIG_MITIGATION_RETBLEED) ? RETBLEED_MITIGATION_AUTO : RETBLEED_MITIGATION_NONE;

static int __ro_after_init retbleed_nosmt = false;

enum srso_mitigation {
 SRSO_MITIGATION_NONE,
 SRSO_MITIGATION_AUTO,
 SRSO_MITIGATION_UCODE_NEEDED,
 SRSO_MITIGATION_SAFE_RET_UCODE_NEEDED,
 SRSO_MITIGATION_MICROCODE,
 SRSO_MITIGATION_NOSMT,
 SRSO_MITIGATION_SAFE_RET,
 SRSO_MITIGATION_IBPB,
 SRSO_MITIGATION_IBPB_ON_VMEXIT,
 SRSO_MITIGATION_BP_SPEC_REDUCE,
};

static enum srso_mitigation srso_mitigation __ro_after_init = SRSO_MITIGATION_AUTO;

static int __init retbleed_parse_cmdline(char *str)
{
 if (!str)
  return -EINVAL;

 while (str) {
  char *next = strchr(str, ',');
  if (next) {
   *next = 0;
   next++;
  }

  if (!strcmp(str, "off")) {
   retbleed_mitigation = RETBLEED_MITIGATION_NONE;
  } else if (!strcmp(str, "auto")) {
   retbleed_mitigation = RETBLEED_MITIGATION_AUTO;
  } else if (!strcmp(str, "unret")) {
   retbleed_mitigation = RETBLEED_MITIGATION_UNRET;
  } else if (!strcmp(str, "ibpb")) {
   retbleed_mitigation = RETBLEED_MITIGATION_IBPB;
  } else if (!strcmp(str, "stuff")) {
   retbleed_mitigation = RETBLEED_MITIGATION_STUFF;
  } else if (!strcmp(str, "nosmt")) {
   retbleed_nosmt = true;
  } else if (!strcmp(str, "force")) {
   setup_force_cpu_bug(X86_BUG_RETBLEED);
  } else {
   pr_err("Ignoring unknown retbleed option (%s).", str);
  }

  str = next;
 }

 return 0;
}
early_param("retbleed", retbleed_parse_cmdline);

#define RETBLEED_UNTRAIN_MSG "WARNING: BTB untrained return thunk mitigation is only effective on AMD/Hygon!\n"
#define RETBLEED_INTEL_MSG "WARNING: Spectre v2 mitigation leaves CPU vulnerable to RETBleed attacks, data leaks possible!\n"

static void __init retbleed_select_mitigation(void)
{
 if (!boot_cpu_has_bug(X86_BUG_RETBLEED)) {
  retbleed_mitigation = RETBLEED_MITIGATION_NONE;
  return;
 }

 switch (retbleed_mitigation) {
 case RETBLEED_MITIGATION_UNRET:
  if (!IS_ENABLED(CONFIG_MITIGATION_UNRET_ENTRY)) {
   retbleed_mitigation = RETBLEED_MITIGATION_AUTO;
   pr_err("WARNING: kernel not compiled with MITIGATION_UNRET_ENTRY.\n");
  }
  break;
 case RETBLEED_MITIGATION_IBPB:
  if (!boot_cpu_has(X86_FEATURE_IBPB)) {
   pr_err("WARNING: CPU does not support IBPB.\n");
   retbleed_mitigation = RETBLEED_MITIGATION_AUTO;
  } else if (!IS_ENABLED(CONFIG_MITIGATION_IBPB_ENTRY)) {
   pr_err("WARNING: kernel not compiled with MITIGATION_IBPB_ENTRY.\n");
   retbleed_mitigation = RETBLEED_MITIGATION_AUTO;
  }
  break;
 case RETBLEED_MITIGATION_STUFF:
  if (!IS_ENABLED(CONFIG_MITIGATION_CALL_DEPTH_TRACKING)) {
   pr_err("WARNING: kernel not compiled with MITIGATION_CALL_DEPTH_TRACKING.\n");
   retbleed_mitigation = RETBLEED_MITIGATION_AUTO;
  } else if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) {
   pr_err("WARNING: retbleed=stuff only supported for Intel CPUs.\n");
   retbleed_mitigation = RETBLEED_MITIGATION_AUTO;
  }
  break;
 default:
  break;
 }

 if (retbleed_mitigation != RETBLEED_MITIGATION_AUTO)
  return;

 if (!should_mitigate_vuln(X86_BUG_RETBLEED)) {
  retbleed_mitigation = RETBLEED_MITIGATION_NONE;
  return;
 }

 /* Intel mitigation selected in retbleed_update_mitigation() */
 if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
     boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) {
  if (IS_ENABLED(CONFIG_MITIGATION_UNRET_ENTRY))
   retbleed_mitigation = RETBLEED_MITIGATION_UNRET;
  else if (IS_ENABLED(CONFIG_MITIGATION_IBPB_ENTRY) &&
    boot_cpu_has(X86_FEATURE_IBPB))
   retbleed_mitigation = RETBLEED_MITIGATION_IBPB;
  else
   retbleed_mitigation = RETBLEED_MITIGATION_NONE;
 } else if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) {
  /* Final mitigation depends on spectre-v2 selection */
  if (boot_cpu_has(X86_FEATURE_IBRS_ENHANCED))
   retbleed_mitigation = RETBLEED_MITIGATION_EIBRS;
  else if (boot_cpu_has(X86_FEATURE_IBRS))
   retbleed_mitigation = RETBLEED_MITIGATION_IBRS;
  else
   retbleed_mitigation = RETBLEED_MITIGATION_NONE;
 }
}

static void __init retbleed_update_mitigation(void)
{
 if (!boot_cpu_has_bug(X86_BUG_RETBLEED))
  return;

  /* ITS can also enable stuffing */
 if (its_mitigation == ITS_MITIGATION_RETPOLINE_STUFF)
  retbleed_mitigation = RETBLEED_MITIGATION_STUFF;

 /* If SRSO is using IBPB, that works for retbleed too */
 if (srso_mitigation == SRSO_MITIGATION_IBPB)
  retbleed_mitigation = RETBLEED_MITIGATION_IBPB;

 if (retbleed_mitigation == RETBLEED_MITIGATION_STUFF &&
     !cdt_possible(spectre_v2_enabled)) {
  pr_err("WARNING: retbleed=stuff depends on retpoline\n");
  retbleed_mitigation = RETBLEED_MITIGATION_NONE;
 }

 /*
 * Let IBRS trump all on Intel without affecting the effects of the
 * retbleed= cmdline option except for call depth based stuffing
 */
 if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) {
  switch (spectre_v2_enabled) {
  case SPECTRE_V2_IBRS:
   retbleed_mitigation = RETBLEED_MITIGATION_IBRS;
   break;
  case SPECTRE_V2_EIBRS:
  case SPECTRE_V2_EIBRS_RETPOLINE:
  case SPECTRE_V2_EIBRS_LFENCE:
   retbleed_mitigation = RETBLEED_MITIGATION_EIBRS;
   break;
  default:
   if (retbleed_mitigation != RETBLEED_MITIGATION_STUFF) {
    if (retbleed_mitigation != RETBLEED_MITIGATION_NONE)
     pr_err(RETBLEED_INTEL_MSG);

    retbleed_mitigation = RETBLEED_MITIGATION_NONE;
   }
  }
 }

 pr_info("%s\n", retbleed_strings[retbleed_mitigation]);
}

static void __init retbleed_apply_mitigation(void)
{
 bool mitigate_smt = false;

 switch (retbleed_mitigation) {
 case RETBLEED_MITIGATION_NONE:
  return;

 case RETBLEED_MITIGATION_UNRET:
  setup_force_cpu_cap(X86_FEATURE_RETHUNK);
  setup_force_cpu_cap(X86_FEATURE_UNRET);

  set_return_thunk(retbleed_return_thunk);

  if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD &&
      boot_cpu_data.x86_vendor != X86_VENDOR_HYGON)
   pr_err(RETBLEED_UNTRAIN_MSG);

  mitigate_smt = true;
  break;

 case RETBLEED_MITIGATION_IBPB:
  setup_force_cpu_cap(X86_FEATURE_ENTRY_IBPB);
  setup_force_cpu_cap(X86_FEATURE_IBPB_ON_VMEXIT);
  mitigate_smt = true;

  /*
 * IBPB on entry already obviates the need for
 * software-based untraining so clear those in case some
 * other mitigation like SRSO has selected them.
 */
  setup_clear_cpu_cap(X86_FEATURE_UNRET);
  setup_clear_cpu_cap(X86_FEATURE_RETHUNK);

  /*
 * There is no need for RSB filling: write_ibpb() ensures
 * all predictions, including the RSB, are invalidated,
 * regardless of IBPB implementation.
 */
  setup_clear_cpu_cap(X86_FEATURE_RSB_VMEXIT);

  break;

 case RETBLEED_MITIGATION_STUFF:
  setup_force_cpu_cap(X86_FEATURE_RETHUNK);
  setup_force_cpu_cap(X86_FEATURE_CALL_DEPTH);

  set_return_thunk(call_depth_return_thunk);
  break;

 default:
  break;
 }

 if (mitigate_smt && !boot_cpu_has(X86_FEATURE_STIBP) &&
     (retbleed_nosmt || smt_mitigations == SMT_MITIGATIONS_ON))
  cpu_smt_disable(false);
}

#undef pr_fmt
#define pr_fmt(fmt)     "ITS: " fmt

static const char * const its_strings[] = {
 [ITS_MITIGATION_OFF]   = "Vulnerable",
 [ITS_MITIGATION_VMEXIT_ONLY]  = "Mitigation: Vulnerable, KVM: Not affected",
 [ITS_MITIGATION_ALIGNED_THUNKS]  = "Mitigation: Aligned branch/return thunks",
 [ITS_MITIGATION_RETPOLINE_STUFF] = "Mitigation: Retpolines, Stuffing RSB",
};

static int __init its_parse_cmdline(char *str)
{
 if (!str)
  return -EINVAL;

 if (!IS_ENABLED(CONFIG_MITIGATION_ITS)) {
  pr_err("Mitigation disabled at compile time, ignoring option (%s)", str);
  return 0;
 }

 if (!strcmp(str, "off")) {
  its_mitigation = ITS_MITIGATION_OFF;
 } else if (!strcmp(str, "on")) {
  its_mitigation = ITS_MITIGATION_ALIGNED_THUNKS;
 } else if (!strcmp(str, "force")) {
  its_mitigation = ITS_MITIGATION_ALIGNED_THUNKS;
  setup_force_cpu_bug(X86_BUG_ITS);
 } else if (!strcmp(str, "vmexit")) {
  its_mitigation = ITS_MITIGATION_VMEXIT_ONLY;
 } else if (!strcmp(str, "stuff")) {
  its_mitigation = ITS_MITIGATION_RETPOLINE_STUFF;
 } else {
  pr_err("Ignoring unknown indirect_target_selection option (%s).", str);
 }

 return 0;
}
early_param("indirect_target_selection", its_parse_cmdline);

static void __init its_select_mitigation(void)
{
 if (!boot_cpu_has_bug(X86_BUG_ITS)) {
  its_mitigation = ITS_MITIGATION_OFF;
  return;
 }

 if (its_mitigation == ITS_MITIGATION_AUTO) {
  if (should_mitigate_vuln(X86_BUG_ITS))
   its_mitigation = ITS_MITIGATION_ALIGNED_THUNKS;
  else
   its_mitigation = ITS_MITIGATION_OFF;
 }

 if (its_mitigation == ITS_MITIGATION_OFF)
  return;

 if (!IS_ENABLED(CONFIG_MITIGATION_RETPOLINE) ||
     !IS_ENABLED(CONFIG_MITIGATION_RETHUNK)) {
  pr_err("WARNING: ITS mitigation depends on retpoline and rethunk support\n");
  its_mitigation = ITS_MITIGATION_OFF;
  return;
 }

 if (IS_ENABLED(CONFIG_DEBUG_FORCE_FUNCTION_ALIGN_64B)) {
  pr_err("WARNING: ITS mitigation is not compatible with CONFIG_DEBUG_FORCE_FUNCTION_ALIGN_64B\n");
  its_mitigation = ITS_MITIGATION_OFF;
  return;
 }

 if (its_mitigation == ITS_MITIGATION_RETPOLINE_STUFF &&
     !IS_ENABLED(CONFIG_MITIGATION_CALL_DEPTH_TRACKING)) {
  pr_err("RSB stuff mitigation not supported, using default\n");
  its_mitigation = ITS_MITIGATION_ALIGNED_THUNKS;
 }

 if (its_mitigation == ITS_MITIGATION_VMEXIT_ONLY &&
     !boot_cpu_has_bug(X86_BUG_ITS_NATIVE_ONLY))
  its_mitigation = ITS_MITIGATION_ALIGNED_THUNKS;
}

static void __init its_update_mitigation(void)
{
 if (!boot_cpu_has_bug(X86_BUG_ITS))
  return;

 switch (spectre_v2_enabled) {
 case SPECTRE_V2_NONE:
  if (its_mitigation != ITS_MITIGATION_OFF)
   pr_err("WARNING: Spectre-v2 mitigation is off, disabling ITS\n");
  its_mitigation = ITS_MITIGATION_OFF;
  break;
 case SPECTRE_V2_RETPOLINE:
 case SPECTRE_V2_EIBRS_RETPOLINE:
  /* Retpoline+CDT mitigates ITS */
  if (retbleed_mitigation == RETBLEED_MITIGATION_STUFF)
   its_mitigation = ITS_MITIGATION_RETPOLINE_STUFF;
  break;
 case SPECTRE_V2_LFENCE:
 case SPECTRE_V2_EIBRS_LFENCE:
  pr_err("WARNING: ITS mitigation is not compatible with lfence mitigation\n");
  its_mitigation = ITS_MITIGATION_OFF;
  break;
 default:
  break;
 }

 if (its_mitigation == ITS_MITIGATION_RETPOLINE_STUFF &&
     !cdt_possible(spectre_v2_enabled))
  its_mitigation = ITS_MITIGATION_ALIGNED_THUNKS;

 pr_info("%s\n", its_strings[its_mitigation]);
}

static void __init its_apply_mitigation(void)
{
 switch (its_mitigation) {
 case ITS_MITIGATION_OFF:
 case ITS_MITIGATION_AUTO:
 case ITS_MITIGATION_VMEXIT_ONLY:
  break;
 case ITS_MITIGATION_ALIGNED_THUNKS:
  if (!boot_cpu_has(X86_FEATURE_RETPOLINE))
   setup_force_cpu_cap(X86_FEATURE_INDIRECT_THUNK_ITS);

  setup_force_cpu_cap(X86_FEATURE_RETHUNK);
  set_return_thunk(its_return_thunk);
  break;
 case ITS_MITIGATION_RETPOLINE_STUFF:
  setup_force_cpu_cap(X86_FEATURE_RETHUNK);
  setup_force_cpu_cap(X86_FEATURE_CALL_DEPTH);
  set_return_thunk(call_depth_return_thunk);
  break;
 }
}

#undef pr_fmt
#define pr_fmt(fmt) "Transient Scheduler Attacks: " fmt

enum tsa_mitigations {
 TSA_MITIGATION_NONE,
 TSA_MITIGATION_AUTO,
 TSA_MITIGATION_UCODE_NEEDED,
 TSA_MITIGATION_USER_KERNEL,
 TSA_MITIGATION_VM,
 TSA_MITIGATION_FULL,
};

static const char * const tsa_strings[] = {
 [TSA_MITIGATION_NONE]  = "Vulnerable",
 [TSA_MITIGATION_UCODE_NEEDED] = "Vulnerable: No microcode",
 [TSA_MITIGATION_USER_KERNEL] = "Mitigation: Clear CPU buffers: user/kernel boundary",
 [TSA_MITIGATION_VM]  = "Mitigation: Clear CPU buffers: VM",
 [TSA_MITIGATION_FULL]  = "Mitigation: Clear CPU buffers",
};

static enum tsa_mitigations tsa_mitigation __ro_after_init =
 IS_ENABLED(CONFIG_MITIGATION_TSA) ? TSA_MITIGATION_AUTO : TSA_MITIGATION_NONE;

static int __init tsa_parse_cmdline(char *str)
{
 if (!str)
  return -EINVAL;

 if (!strcmp(str, "off"))
  tsa_mitigation = TSA_MITIGATION_NONE;
 else if (!strcmp(str, "on"))
  tsa_mitigation = TSA_MITIGATION_FULL;
 else if (!strcmp(str, "user"))
  tsa_mitigation = TSA_MITIGATION_USER_KERNEL;
 else if (!strcmp(str, "vm"))
  tsa_mitigation = TSA_MITIGATION_VM;
 else
  pr_err("Ignoring unknown tsa=%s option.\n", str);

 return 0;
}
early_param("tsa", tsa_parse_cmdline);

static void __init tsa_select_mitigation(void)
{
 if (!boot_cpu_has_bug(X86_BUG_TSA)) {
  tsa_mitigation = TSA_MITIGATION_NONE;
  return;
 }

 if (tsa_mitigation == TSA_MITIGATION_AUTO) {
  bool vm = false, uk = false;

  tsa_mitigation = TSA_MITIGATION_NONE;

  if (cpu_attack_vector_mitigated(CPU_MITIGATE_USER_KERNEL) ||
      cpu_attack_vector_mitigated(CPU_MITIGATE_USER_USER)) {
   tsa_mitigation = TSA_MITIGATION_USER_KERNEL;
   uk = true;
  }

  if (cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_HOST) ||
      cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_GUEST)) {
   tsa_mitigation = TSA_MITIGATION_VM;
   vm = true;
  }

  if (uk && vm)
   tsa_mitigation = TSA_MITIGATION_FULL;
 }

 if (tsa_mitigation == TSA_MITIGATION_NONE)
  return;

 if (!boot_cpu_has(X86_FEATURE_VERW_CLEAR))
  tsa_mitigation = TSA_MITIGATION_UCODE_NEEDED;

 /*
 * No need to set verw_clear_cpu_buf_mitigation_selected - it
 * doesn't fit all cases here and it is not needed because this
 * is the only VERW-based mitigation on AMD.
 */
 pr_info("%s\n", tsa_strings[tsa_mitigation]);
}

static void __init tsa_apply_mitigation(void)
{
 switch (tsa_mitigation) {
 case TSA_MITIGATION_USER_KERNEL:
  setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF);
  break;
 case TSA_MITIGATION_VM:
  setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF_VM);
  break;
 case TSA_MITIGATION_FULL:
  setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF);
  setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF_VM);
  break;
 default:
  break;
 }
}

#undef pr_fmt
#define pr_fmt(fmt)     "Spectre V2 : " fmt

static enum spectre_v2_user_mitigation spectre_v2_user_stibp __ro_after_init =
 SPECTRE_V2_USER_NONE;
static enum spectre_v2_user_mitigation spectre_v2_user_ibpb __ro_after_init =
 SPECTRE_V2_USER_NONE;

#ifdef CONFIG_MITIGATION_RETPOLINE
static bool spectre_v2_bad_module;

bool retpoline_module_ok(bool has_retpoline)
{
 if (spectre_v2_enabled == SPECTRE_V2_NONE || has_retpoline)
  return true;

 pr_err("System may be vulnerable to spectre v2\n");
 spectre_v2_bad_module = true;
 return false;
}

static inline const char *spectre_v2_module_string(void)
{
 return spectre_v2_bad_module ? " - vulnerable module loaded" : "";
}
#else
static inline const char *spectre_v2_module_string(void) { return ""; }
#endif

#define SPECTRE_V2_LFENCE_MSG "WARNING: LFENCE mitigation is not recommended for this CPU, data leaks possible!\n"
#define SPECTRE_V2_EIBRS_EBPF_MSG "WARNING: Unprivileged eBPF is enabled with eIBRS on, data leaks possible via Spectre v2 BHB attacks!\n"
#define SPECTRE_V2_EIBRS_LFENCE_EBPF_SMT_MSG "WARNING: Unprivileged eBPF is enabled with eIBRS+LFENCE mitigation and SMT, data leaks possible via Spectre v2 BHB attacks!\n"
#define SPECTRE_V2_IBRS_PERF_MSG "WARNING: IBRS mitigation selected on Enhanced IBRS CPU, this may cause unnecessary performance loss\n"

#ifdef CONFIG_BPF_SYSCALL
void unpriv_ebpf_notify(int new_state)
{
 if (new_state)
  return;

 /* Unprivileged eBPF is enabled */

 switch (spectre_v2_enabled) {
 case SPECTRE_V2_EIBRS:
  pr_err(SPECTRE_V2_EIBRS_EBPF_MSG);
  break;
 case SPECTRE_V2_EIBRS_LFENCE:
  if (sched_smt_active())
   pr_err(SPECTRE_V2_EIBRS_LFENCE_EBPF_SMT_MSG);
  break;
 default:
  break;
 }
}
#endif

static inline bool match_option(const char *arg, int arglen, const char *opt)
{
 int len = strlen(opt);

 return len == arglen && !strncmp(arg, opt, len);
}

/* The kernel command line selection for spectre v2 */
enum spectre_v2_mitigation_cmd {
 SPECTRE_V2_CMD_NONE,
 SPECTRE_V2_CMD_AUTO,
 SPECTRE_V2_CMD_FORCE,
 SPECTRE_V2_CMD_RETPOLINE,
 SPECTRE_V2_CMD_RETPOLINE_GENERIC,
 SPECTRE_V2_CMD_RETPOLINE_LFENCE,
 SPECTRE_V2_CMD_EIBRS,
 SPECTRE_V2_CMD_EIBRS_RETPOLINE,
 SPECTRE_V2_CMD_EIBRS_LFENCE,
 SPECTRE_V2_CMD_IBRS,
};

static enum spectre_v2_mitigation_cmd spectre_v2_cmd __ro_after_init = SPECTRE_V2_CMD_AUTO;

enum spectre_v2_user_cmd {
 SPECTRE_V2_USER_CMD_NONE,
 SPECTRE_V2_USER_CMD_AUTO,
 SPECTRE_V2_USER_CMD_FORCE,
 SPECTRE_V2_USER_CMD_PRCTL,
 SPECTRE_V2_USER_CMD_PRCTL_IBPB,
 SPECTRE_V2_USER_CMD_SECCOMP,
 SPECTRE_V2_USER_CMD_SECCOMP_IBPB,
};

static const char * const spectre_v2_user_strings[] = {
 [SPECTRE_V2_USER_NONE]   = "User space: Vulnerable",
 [SPECTRE_V2_USER_STRICT]  = "User space: Mitigation: STIBP protection",
 [SPECTRE_V2_USER_STRICT_PREFERRED] = "User space: Mitigation: STIBP always-on protection",
 [SPECTRE_V2_USER_PRCTL]   = "User space: Mitigation: STIBP via prctl",
 [SPECTRE_V2_USER_SECCOMP]  = "User space: Mitigation: STIBP via seccomp and prctl",
};

static const struct {
 const char   *option;
 enum spectre_v2_user_cmd cmd;
 bool    secure;
} v2_user_options[] __initconst = {
 { "auto",  SPECTRE_V2_USER_CMD_AUTO,  false },
 { "off",  SPECTRE_V2_USER_CMD_NONE,  false },
 { "on",   SPECTRE_V2_USER_CMD_FORCE,  true  },
 { "prctl",  SPECTRE_V2_USER_CMD_PRCTL,  false },
 { "prctl,ibpb",  SPECTRE_V2_USER_CMD_PRCTL_IBPB,  false },
 { "seccomp",  SPECTRE_V2_USER_CMD_SECCOMP,  false },
 { "seccomp,ibpb", SPECTRE_V2_USER_CMD_SECCOMP_IBPB, false },
};

static void __init spec_v2_user_print_cond(const char *reason, bool secure)
{
 if (boot_cpu_has_bug(X86_BUG_SPECTRE_V2) != secure)
  pr_info("spectre_v2_user=%s forced on command line.\n", reason);
}

static enum spectre_v2_user_cmd __init spectre_v2_parse_user_cmdline(void)
{
 char arg[20];
 int ret, i;

 if (!IS_ENABLED(CONFIG_MITIGATION_SPECTRE_V2))
  return SPECTRE_V2_USER_CMD_NONE;

 ret = cmdline_find_option(boot_command_line, "spectre_v2_user",
      arg, sizeof(arg));
 if (ret < 0)
  return SPECTRE_V2_USER_CMD_AUTO;

 for (i = 0; i < ARRAY_SIZE(v2_user_options); i++) {
  if (match_option(arg, ret, v2_user_options[i].option)) {
   spec_v2_user_print_cond(v2_user_options[i].option,
      v2_user_options[i].secure);
   return v2_user_options[i].cmd;
  }
 }

 pr_err("Unknown user space protection option (%s). Switching to default\n", arg);
 return SPECTRE_V2_USER_CMD_AUTO;
}

static inline bool spectre_v2_in_ibrs_mode(enum spectre_v2_mitigation mode)
{
 return spectre_v2_in_eibrs_mode(mode) || mode == SPECTRE_V2_IBRS;
}

static void __init spectre_v2_user_select_mitigation(void)
{
 if (!boot_cpu_has(X86_FEATURE_IBPB) && !boot_cpu_has(X86_FEATURE_STIBP))
  return;

 switch (spectre_v2_parse_user_cmdline()) {
 case SPECTRE_V2_USER_CMD_NONE:
  return;
 case SPECTRE_V2_USER_CMD_FORCE:
  spectre_v2_user_ibpb  = SPECTRE_V2_USER_STRICT;
  spectre_v2_user_stibp = SPECTRE_V2_USER_STRICT;
  break;
 case SPECTRE_V2_USER_CMD_AUTO:
  if (!should_mitigate_vuln(X86_BUG_SPECTRE_V2_USER))
   break;
  spectre_v2_user_ibpb = SPECTRE_V2_USER_PRCTL;
  if (smt_mitigations == SMT_MITIGATIONS_OFF)
   break;
  spectre_v2_user_stibp = SPECTRE_V2_USER_PRCTL;
  break;
 case SPECTRE_V2_USER_CMD_PRCTL:
  spectre_v2_user_ibpb  = SPECTRE_V2_USER_PRCTL;
  spectre_v2_user_stibp = SPECTRE_V2_USER_PRCTL;
  break;
 case SPECTRE_V2_USER_CMD_PRCTL_IBPB:
  spectre_v2_user_ibpb  = SPECTRE_V2_USER_STRICT;
  spectre_v2_user_stibp = SPECTRE_V2_USER_PRCTL;
  break;
 case SPECTRE_V2_USER_CMD_SECCOMP:
  if (IS_ENABLED(CONFIG_SECCOMP))
   spectre_v2_user_ibpb = SPECTRE_V2_USER_SECCOMP;
  else
   spectre_v2_user_ibpb = SPECTRE_V2_USER_PRCTL;
  spectre_v2_user_stibp = spectre_v2_user_ibpb;
  break;
 case SPECTRE_V2_USER_CMD_SECCOMP_IBPB:
  spectre_v2_user_ibpb = SPECTRE_V2_USER_STRICT;
  if (IS_ENABLED(CONFIG_SECCOMP))
   spectre_v2_user_stibp = SPECTRE_V2_USER_SECCOMP;
  else
   spectre_v2_user_stibp = SPECTRE_V2_USER_PRCTL;
  break;
 }

 /*
 * At this point, an STIBP mode other than "off" has been set.
 * If STIBP support is not being forced, check if STIBP always-on
 * is preferred.
 */
 if ((spectre_v2_user_stibp == SPECTRE_V2_USER_PRCTL ||
      spectre_v2_user_stibp == SPECTRE_V2_USER_SECCOMP) &&
     boot_cpu_has(X86_FEATURE_AMD_STIBP_ALWAYS_ON))
  spectre_v2_user_stibp = SPECTRE_V2_USER_STRICT_PREFERRED;

 if (!boot_cpu_has(X86_FEATURE_IBPB))
  spectre_v2_user_ibpb = SPECTRE_V2_USER_NONE;

 if (!boot_cpu_has(X86_FEATURE_STIBP))
  spectre_v2_user_stibp = SPECTRE_V2_USER_NONE;
}

static void __init spectre_v2_user_update_mitigation(void)
{
 if (!boot_cpu_has(X86_FEATURE_IBPB) && !boot_cpu_has(X86_FEATURE_STIBP))
  return;

 /* The spectre_v2 cmd line can override spectre_v2_user options */
 if (spectre_v2_cmd == SPECTRE_V2_CMD_NONE) {
  spectre_v2_user_ibpb = SPECTRE_V2_USER_NONE;
  spectre_v2_user_stibp = SPECTRE_V2_USER_NONE;
 } else if (spectre_v2_cmd == SPECTRE_V2_CMD_FORCE) {
  spectre_v2_user_ibpb = SPECTRE_V2_USER_STRICT;
  spectre_v2_user_stibp = SPECTRE_V2_USER_STRICT;
 }

 /*
 * If no STIBP, Intel enhanced IBRS is enabled, or SMT impossible, STIBP
 * is not required.
 *
 * Intel's Enhanced IBRS also protects against cross-thread branch target
 * injection in user-mode as the IBRS bit remains always set which
 * implicitly enables cross-thread protections.  However, in legacy IBRS
 * mode, the IBRS bit is set only on kernel entry and cleared on return
 * to userspace.  AMD Automatic IBRS also does not protect userspace.
 * These modes therefore disable the implicit cross-thread protection,
 * so allow for STIBP to be selected in those cases.
 */
 if (!boot_cpu_has(X86_FEATURE_STIBP) ||
     !cpu_smt_possible() ||
     (spectre_v2_in_eibrs_mode(spectre_v2_enabled) &&
      !boot_cpu_has(X86_FEATURE_AUTOIBRS))) {
  spectre_v2_user_stibp = SPECTRE_V2_USER_NONE;
  return;
 }

 if (spectre_v2_user_stibp != SPECTRE_V2_USER_NONE &&
     (retbleed_mitigation == RETBLEED_MITIGATION_UNRET ||
      retbleed_mitigation == RETBLEED_MITIGATION_IBPB)) {
  if (spectre_v2_user_stibp != SPECTRE_V2_USER_STRICT &&
      spectre_v2_user_stibp != SPECTRE_V2_USER_STRICT_PREFERRED)
   pr_info("Selecting STIBP always-on mode to complement retbleed mitigation\n");
  spectre_v2_user_stibp = SPECTRE_V2_USER_STRICT_PREFERRED;
 }
 pr_info("%s\n", spectre_v2_user_strings[spectre_v2_user_stibp]);
}

static void __init spectre_v2_user_apply_mitigation(void)
{
 /* Initialize Indirect Branch Prediction Barrier */
 if (spectre_v2_user_ibpb != SPECTRE_V2_USER_NONE) {
  static_branch_enable(&switch_vcpu_ibpb);

  switch (spectre_v2_user_ibpb) {
  case SPECTRE_V2_USER_STRICT:
   static_branch_enable(&switch_mm_always_ibpb);
   break;
  case SPECTRE_V2_USER_PRCTL:
  case SPECTRE_V2_USER_SECCOMP:
   static_branch_enable(&switch_mm_cond_ibpb);
   break;
  default:
   break;
  }

  pr_info("mitigation: Enabling %s Indirect Branch Prediction Barrier\n",
   static_key_enabled(&switch_mm_always_ibpb) ?
   "always-on" : "conditional");
 }
}

static const char * const spectre_v2_strings[] = {
 [SPECTRE_V2_NONE]   = "Vulnerable",
 [SPECTRE_V2_RETPOLINE]   = "Mitigation: Retpolines",
 [SPECTRE_V2_LFENCE]   = "Vulnerable: LFENCE",
 [SPECTRE_V2_EIBRS]   = "Mitigation: Enhanced / Automatic IBRS",
 [SPECTRE_V2_EIBRS_LFENCE]  = "Mitigation: Enhanced / Automatic IBRS + LFENCE",
 [SPECTRE_V2_EIBRS_RETPOLINE]  = "Mitigation: Enhanced / Automatic IBRS + Retpolines",
 [SPECTRE_V2_IBRS]   = "Mitigation: IBRS",
};

static const struct {
 const char *option;
 enum spectre_v2_mitigation_cmd cmd;
 bool secure;
} mitigation_options[] __initconst = {
 { "off",  SPECTRE_V2_CMD_NONE,    false },
 { "on",   SPECTRE_V2_CMD_FORCE,    true  },
 { "retpoline",  SPECTRE_V2_CMD_RETPOLINE,   false },
 { "retpoline,amd", SPECTRE_V2_CMD_RETPOLINE_LFENCE,  false },
 { "retpoline,lfence", SPECTRE_V2_CMD_RETPOLINE_LFENCE,  false },
 { "retpoline,generic", SPECTRE_V2_CMD_RETPOLINE_GENERIC, false },
 { "eibrs",  SPECTRE_V2_CMD_EIBRS,    false },
 { "eibrs,lfence", SPECTRE_V2_CMD_EIBRS_LFENCE,   false },
 { "eibrs,retpoline", SPECTRE_V2_CMD_EIBRS_RETPOLINE,   false },
 { "auto",  SPECTRE_V2_CMD_AUTO,    false },
 { "ibrs",  SPECTRE_V2_CMD_IBRS,              false },
};

static void __init spec_v2_print_cond(const char *reason, bool secure)
{
 if (boot_cpu_has_bug(X86_BUG_SPECTRE_V2) != secure)
  pr_info("%s selected on command line.\n", reason);
}

static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)
{
 enum spectre_v2_mitigation_cmd cmd;
 char arg[20];
 int ret, i;

 cmd = IS_ENABLED(CONFIG_MITIGATION_SPECTRE_V2) ?  SPECTRE_V2_CMD_AUTO : SPECTRE_V2_CMD_NONE;
 if (cmdline_find_option_bool(boot_command_line, "nospectre_v2"))
  return SPECTRE_V2_CMD_NONE;

 ret = cmdline_find_option(boot_command_line, "spectre_v2", arg, sizeof(arg));
 if (ret < 0)
  return cmd;

 for (i = 0; i < ARRAY_SIZE(mitigation_options); i++) {
  if (!match_option(arg, ret, mitigation_options[i].option))
   continue;
  cmd = mitigation_options[i].cmd;
  break;
 }

 if (i >= ARRAY_SIZE(mitigation_options)) {
  pr_err("unknown option (%s). Switching to default mode\n", arg);
  return cmd;
 }

 if ((cmd == SPECTRE_V2_CMD_RETPOLINE ||
      cmd == SPECTRE_V2_CMD_RETPOLINE_LFENCE ||
      cmd == SPECTRE_V2_CMD_RETPOLINE_GENERIC ||
      cmd == SPECTRE_V2_CMD_EIBRS_LFENCE ||
      cmd == SPECTRE_V2_CMD_EIBRS_RETPOLINE) &&
     !IS_ENABLED(CONFIG_MITIGATION_RETPOLINE)) {
  pr_err("%s selected but not compiled in. Switching to AUTO select\n",
         mitigation_options[i].option);
  return SPECTRE_V2_CMD_AUTO;
 }

 if ((cmd == SPECTRE_V2_CMD_EIBRS ||
      cmd == SPECTRE_V2_CMD_EIBRS_LFENCE ||
      cmd == SPECTRE_V2_CMD_EIBRS_RETPOLINE) &&
     !boot_cpu_has(X86_FEATURE_IBRS_ENHANCED)) {
  pr_err("%s selected but CPU doesn't have Enhanced or Automatic IBRS. Switching to AUTO select\n",
         mitigation_options[i].option);
  return SPECTRE_V2_CMD_AUTO;
 }

 if ((cmd == SPECTRE_V2_CMD_RETPOLINE_LFENCE ||
      cmd == SPECTRE_V2_CMD_EIBRS_LFENCE) &&
     !boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) {
  pr_err("%s selected, but CPU doesn't have a serializing LFENCE. Switching to AUTO select\n",
         mitigation_options[i].option);
  return SPECTRE_V2_CMD_AUTO;
 }

 if (cmd == SPECTRE_V2_CMD_IBRS && !IS_ENABLED(CONFIG_MITIGATION_IBRS_ENTRY)) {
  pr_err("%s selected but not compiled in. Switching to AUTO select\n",
         mitigation_options[i].option);
  return SPECTRE_V2_CMD_AUTO;
 }

 if (cmd == SPECTRE_V2_CMD_IBRS && boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) {
  pr_err("%s selected but not Intel CPU. Switching to AUTO select\n",
         mitigation_options[i].option);
  return SPECTRE_V2_CMD_AUTO;
 }

 if (cmd == SPECTRE_V2_CMD_IBRS && !boot_cpu_has(X86_FEATURE_IBRS)) {
  pr_err("%s selected but CPU doesn't have IBRS. Switching to AUTO select\n",
         mitigation_options[i].option);
  return SPECTRE_V2_CMD_AUTO;
 }

 if (cmd == SPECTRE_V2_CMD_IBRS && cpu_feature_enabled(X86_FEATURE_XENPV)) {
  pr_err("%s selected but running as XenPV guest. Switching to AUTO select\n",
         mitigation_options[i].option);
  return SPECTRE_V2_CMD_AUTO;
 }

 spec_v2_print_cond(mitigation_options[i].option,
      mitigation_options[i].secure);
 return cmd;
}

static enum spectre_v2_mitigation __init spectre_v2_select_retpoline(void)
{
 if (!IS_ENABLED(CONFIG_MITIGATION_RETPOLINE)) {
  pr_err("Kernel not compiled with retpoline; no mitigation available!");
  return SPECTRE_V2_NONE;
 }

 return SPECTRE_V2_RETPOLINE;
}

static bool __ro_after_init rrsba_disabled;

/* Disable in-kernel use of non-RSB RET predictors */
static void __init spec_ctrl_disable_kernel_rrsba(void)
{
 if (rrsba_disabled)
  return;

 if (!(x86_arch_cap_msr & ARCH_CAP_RRSBA)) {
  rrsba_disabled = true;
  return;
 }

 if (!boot_cpu_has(X86_FEATURE_RRSBA_CTRL))
  return;

 x86_spec_ctrl_base |= SPEC_CTRL_RRSBA_DIS_S;
 update_spec_ctrl(x86_spec_ctrl_base);
 rrsba_disabled = true;
}

static void __init spectre_v2_select_rsb_mitigation(enum spectre_v2_mitigation mode)
{
 /*
 * WARNING! There are many subtleties to consider when changing *any*
 * code related to RSB-related mitigations.  Before doing so, carefully
 * read the following document, and update if necessary:
 *
 *   Documentation/admin-guide/hw-vuln/rsb.rst
 *
 * In an overly simplified nutshell:
 *
 *   - User->user RSB attacks are conditionally mitigated during
 *     context switches by cond_mitigation -> write_ibpb().
 *
 *   - User->kernel and guest->host attacks are mitigated by eIBRS or
 *     RSB filling.
 *
 *     Though, depending on config, note that other alternative
 *     mitigations may end up getting used instead, e.g., IBPB on
 *     entry/vmexit, call depth tracking, or return thunks.
 */

 switch (mode) {
 case SPECTRE_V2_NONE:
  break;

 case SPECTRE_V2_EIBRS:
 case SPECTRE_V2_EIBRS_LFENCE:
 case SPECTRE_V2_EIBRS_RETPOLINE:
  if (boot_cpu_has_bug(X86_BUG_EIBRS_PBRSB)) {
   pr_info("Spectre v2 / PBRSB-eIBRS: Retire a single CALL on VMEXIT\n");
   setup_force_cpu_cap(X86_FEATURE_RSB_VMEXIT_LITE);
  }
  break;

 case SPECTRE_V2_RETPOLINE:
--> --------------------

--> maximum size reached

--> --------------------