arch/x86/kernel/cpu/bugs.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  Copyright (C) 1994  Linus Torvalds
   4  *
   5  *  Cyrix stuff, June 1998 by:
   6  *      - Rafael R. Reilova (moved everything from head.S),
   7  *        <rreilova@ececs.uc.edu>
   8  *      - Channing Corn (tests & fixes),
   9  *      - Andrew D. Balsa (code cleanup).
  10  */
  11 #include <linux/init.h>
  12 #include <linux/utsname.h>
  13 #include <linux/cpu.h>
  14 #include <linux/module.h>
  15 #include <linux/nospec.h>
  16 #include <linux/prctl.h>
  17
  18 #include <asm/spec-ctrl.h>
  19 #include <asm/cmdline.h>
  20 #include <asm/bugs.h>
  21 #include <asm/processor.h>
  22 #include <asm/processor-flags.h>
  23 #include <asm/fpu/internal.h>
  24 #include <asm/msr.h>
  25 #include <asm/paravirt.h>
  26 #include <asm/alternative.h>
  27 #include <asm/pgtable.h>
  28 #include <asm/set_memory.h>
  29 #include <asm/intel-family.h>
  30
  31 static void __init spectre_v2_select_mitigation(void);
  32 static void __init ssb_select_mitigation(void);
  33
  34 /*
  35  * Our boot-time value of the SPEC_CTRL MSR. We read it once so that any
  36  * writes to SPEC_CTRL contain whatever reserved bits have been set.
  37  */
  38 u64 __ro_after_init x86_spec_ctrl_base;
  39
  40 /*
  41  * The vendor and possibly platform specific bits which can be modified in
  42  * x86_spec_ctrl_base.
  43  */
  44 static u64 __ro_after_init x86_spec_ctrl_mask = ~SPEC_CTRL_IBRS;
  45
  46 /*
  47  * AMD specific MSR info for Speculative Store Bypass control.
  48  * x86_amd_ls_cfg_rds_mask is initialized in identify_boot_cpu().
  49  */
  50 u64 __ro_after_init x86_amd_ls_cfg_base;
  51 u64 __ro_after_init x86_amd_ls_cfg_rds_mask;
  52
  53 void __init check_bugs(void)
  54 {
  55         identify_boot_cpu();
  56
  57         if (!IS_ENABLED(CONFIG_SMP)) {
  58                 pr_info("CPU: ");
  59                 print_cpu_info(&boot_cpu_data);
  60         }
  61
  62         /*
  63          * Read the SPEC_CTRL MSR to account for reserved bits which may
  64          * have unknown values. AMD64_LS_CFG MSR is cached in the early AMD
  65          * init code as it is not enumerated and depends on the family.
  66          */
  67         if (boot_cpu_has(X86_FEATURE_IBRS))
  68                 rdmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
  69
  70         /* Select the proper spectre mitigation before patching alternatives */
  71         spectre_v2_select_mitigation();
  72
  73         /*
  74          * Select proper mitigation for any exposure to the Speculative Store
  75          * Bypass vulnerability.
  76          */
  77         ssb_select_mitigation();
  78
  79 #ifdef CONFIG_X86_32
  80         /*
  81          * Check whether we are able to run this kernel safely on SMP.
  82          *
  83          * - i386 is no longer supported.
  84          * - In order to run on anything without a TSC, we need to be
  85          *   compiled for a i486.
  86          */
  87         if (boot_cpu_data.x86 < 4)
  88                 panic("Kernel requires i486+ for 'invlpg' and other features");
  89
  90         init_utsname()->machine[1] =
  91                 '0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86);
  92         alternative_instructions();
  93
  94         fpu__init_check_bugs();
  95 #else /* CONFIG_X86_64 */
  96         alternative_instructions();
  97
  98         /*
  99          * Make sure the first 2MB area is not mapped by huge pages
 100          * There are typically fixed size MTRRs in there and overlapping
 101          * MTRRs into large pages causes slow downs.
 102          *
 103          * Right now we don't do that with gbpages because there seems
 104          * very little benefit for that case.
 105          */
 106         if (!direct_gbpages)
 107                 set_memory_4k((unsigned long)__va(0), 1);
 108 #endif
 109 }
 110
 111 /* The kernel command line selection */
 112 enum spectre_v2_mitigation_cmd {
 113         SPECTRE_V2_CMD_NONE,
 114         SPECTRE_V2_CMD_AUTO,
 115         SPECTRE_V2_CMD_FORCE,
 116         SPECTRE_V2_CMD_RETPOLINE,
 117         SPECTRE_V2_CMD_RETPOLINE_GENERIC,
 118         SPECTRE_V2_CMD_RETPOLINE_AMD,
 119 };
 120
 121 static const char *spectre_v2_strings[] = {
 122         [SPECTRE_V2_NONE]                       = "Vulnerable",
 123         [SPECTRE_V2_RETPOLINE_MINIMAL]          = "Vulnerable: Minimal generic ASM retpoline",
 124         [SPECTRE_V2_RETPOLINE_MINIMAL_AMD]      = "Vulnerable: Minimal AMD ASM retpoline",
 125         [SPECTRE_V2_RETPOLINE_GENERIC]          = "Mitigation: Full generic retpoline",
 126         [SPECTRE_V2_RETPOLINE_AMD]              = "Mitigation: Full AMD retpoline",
 127 };
 128
 129 #undef pr_fmt
 130 #define pr_fmt(fmt)     "Spectre V2 : " fmt
 131
 132 static enum spectre_v2_mitigation spectre_v2_enabled __ro_after_init =
 133         SPECTRE_V2_NONE;
 134
 135 void x86_spec_ctrl_set(u64 val)
 136 {
 137         if (val & x86_spec_ctrl_mask)
 138                 WARN_ONCE(1, "SPEC_CTRL MSR value 0x%16llx is unknown.\n", val);
 139         else
 140                 wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base | val);
 141 }
 142 EXPORT_SYMBOL_GPL(x86_spec_ctrl_set);
 143
 144 u64 x86_spec_ctrl_get_default(void)
 145 {
 146         u64 msrval = x86_spec_ctrl_base;
 147
 148         if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)
 149                 msrval |= rds_tif_to_spec_ctrl(current_thread_info()->flags);
 150         return msrval;
 151 }
 152 EXPORT_SYMBOL_GPL(x86_spec_ctrl_get_default);
 153
 154 void x86_spec_ctrl_set_guest(u64 guest_spec_ctrl)
 155 {
 156         u64 host = x86_spec_ctrl_base;
 157
 158         if (!boot_cpu_has(X86_FEATURE_IBRS))
 159                 return;
 160
 161         if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)
 162                 host |= rds_tif_to_spec_ctrl(current_thread_info()->flags);
 163
 164         if (host != guest_spec_ctrl)
 165                 wrmsrl(MSR_IA32_SPEC_CTRL, guest_spec_ctrl);
 166 }
 167 EXPORT_SYMBOL_GPL(x86_spec_ctrl_set_guest);
 168
 169 void x86_spec_ctrl_restore_host(u64 guest_spec_ctrl)
 170 {
 171         u64 host = x86_spec_ctrl_base;
 172
 173         if (!boot_cpu_has(X86_FEATURE_IBRS))
 174                 return;
 175
 176         if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)
 177                 host |= rds_tif_to_spec_ctrl(current_thread_info()->flags);
 178
 179         if (host != guest_spec_ctrl)
 180                 wrmsrl(MSR_IA32_SPEC_CTRL, host);
 181 }
 182 EXPORT_SYMBOL_GPL(x86_spec_ctrl_restore_host);
 183
 184 static void x86_amd_rds_enable(void)
 185 {
 186         u64 msrval = x86_amd_ls_cfg_base | x86_amd_ls_cfg_rds_mask;
 187
 188         if (boot_cpu_has(X86_FEATURE_AMD_RDS))
 189                 wrmsrl(MSR_AMD64_LS_CFG, msrval);
 190 }
 191
 192 #ifdef RETPOLINE
 193 static bool spectre_v2_bad_module;
 194
 195 bool retpoline_module_ok(bool has_retpoline)
 196 {
 197         if (spectre_v2_enabled == SPECTRE_V2_NONE || has_retpoline)
 198                 return true;
 199
 200         pr_err("System may be vulnerable to spectre v2\n");
 201         spectre_v2_bad_module = true;
 202         return false;
 203 }
 204
 205 static inline const char *spectre_v2_module_string(void)
 206 {
 207         return spectre_v2_bad_module ? " - vulnerable module loaded" : "";
 208 }
 209 #else
 210 static inline const char *spectre_v2_module_string(void) { return ""; }
 211 #endif
 212
 213 static void __init spec2_print_if_insecure(const char *reason)
 214 {
 215         if (boot_cpu_has_bug(X86_BUG_SPECTRE_V2))
 216                 pr_info("%s selected on command line.\n", reason);
 217 }
 218
 219 static void __init spec2_print_if_secure(const char *reason)
 220 {
 221         if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2))
 222                 pr_info("%s selected on command line.\n", reason);
 223 }
 224
 225 static inline bool retp_compiler(void)
 226 {
 227         return __is_defined(RETPOLINE);
 228 }
 229
 230 static inline bool match_option(const char *arg, int arglen, const char *opt)
 231 {
 232         int len = strlen(opt);
 233
 234         return len == arglen && !strncmp(arg, opt, len);
 235 }
 236
 237 static const struct {
 238         const char *option;
 239         enum spectre_v2_mitigation_cmd cmd;
 240         bool secure;
 241 } mitigation_options[] = {
 242         { "off",               SPECTRE_V2_CMD_NONE,              false },
 243         { "on",                SPECTRE_V2_CMD_FORCE,             true },
 244         { "retpoline",         SPECTRE_V2_CMD_RETPOLINE,         false },
 245         { "retpoline,amd",     SPECTRE_V2_CMD_RETPOLINE_AMD,     false },
 246         { "retpoline,generic", SPECTRE_V2_CMD_RETPOLINE_GENERIC, false },
 247         { "auto",              SPECTRE_V2_CMD_AUTO,              false },
 248 };
 249
 250 static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)
 251 {
 252         char arg[20];
 253         int ret, i;
 254         enum spectre_v2_mitigation_cmd cmd = SPECTRE_V2_CMD_AUTO;
 255
 256         if (cmdline_find_option_bool(boot_command_line, "nospectre_v2"))
 257                 return SPECTRE_V2_CMD_NONE;
 258         else {
 259                 ret = cmdline_find_option(boot_command_line, "spectre_v2", arg, sizeof(arg));
 260                 if (ret < 0)
 261                         return SPECTRE_V2_CMD_AUTO;
 262
 263                 for (i = 0; i < ARRAY_SIZE(mitigation_options); i++) {
 264                         if (!match_option(arg, ret, mitigation_options[i].option))
 265                                 continue;
 266                         cmd = mitigation_options[i].cmd;
 267                         break;
 268                 }
 269
 270                 if (i >= ARRAY_SIZE(mitigation_options)) {
 271                         pr_err("unknown option (%s). Switching to AUTO select\n", arg);
 272                         return SPECTRE_V2_CMD_AUTO;
 273                 }
 274         }
 275
 276         if ((cmd == SPECTRE_V2_CMD_RETPOLINE ||
 277              cmd == SPECTRE_V2_CMD_RETPOLINE_AMD ||
 278              cmd == SPECTRE_V2_CMD_RETPOLINE_GENERIC) &&
 279             !IS_ENABLED(CONFIG_RETPOLINE)) {
 280                 pr_err("%s selected but not compiled in. Switching to AUTO select\n", mitigation_options[i].option);
 281                 return SPECTRE_V2_CMD_AUTO;
 282         }
 283
 284         if (cmd == SPECTRE_V2_CMD_RETPOLINE_AMD &&
 285             boot_cpu_data.x86_vendor != X86_VENDOR_AMD) {
 286                 pr_err("retpoline,amd selected but CPU is not AMD. Switching to AUTO select\n");
 287                 return SPECTRE_V2_CMD_AUTO;
 288         }
 289
 290         if (mitigation_options[i].secure)
 291                 spec2_print_if_secure(mitigation_options[i].option);
 292         else
 293                 spec2_print_if_insecure(mitigation_options[i].option);
 294
 295         return cmd;
 296 }
 297
 298 /* Check for Skylake-like CPUs (for RSB handling) */
 299 static bool __init is_skylake_era(void)
 300 {
 301         if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
 302             boot_cpu_data.x86 == 6) {
 303                 switch (boot_cpu_data.x86_model) {
 304                 case INTEL_FAM6_SKYLAKE_MOBILE:
 305                 case INTEL_FAM6_SKYLAKE_DESKTOP:
 306                 case INTEL_FAM6_SKYLAKE_X:
 307                 case INTEL_FAM6_KABYLAKE_MOBILE:
 308                 case INTEL_FAM6_KABYLAKE_DESKTOP:
 309                         return true;
 310                 }
 311         }
 312         return false;
 313 }
 314
 315 static void __init spectre_v2_select_mitigation(void)
 316 {
 317         enum spectre_v2_mitigation_cmd cmd = spectre_v2_parse_cmdline();
 318         enum spectre_v2_mitigation mode = SPECTRE_V2_NONE;
 319
 320         /*
 321          * If the CPU is not affected and the command line mode is NONE or AUTO
 322          * then nothing to do.
 323          */
 324         if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2) &&
 325             (cmd == SPECTRE_V2_CMD_NONE || cmd == SPECTRE_V2_CMD_AUTO))
 326                 return;
 327
 328         switch (cmd) {
 329         case SPECTRE_V2_CMD_NONE:
 330                 return;
 331
 332         case SPECTRE_V2_CMD_FORCE:
 333         case SPECTRE_V2_CMD_AUTO:
 334                 if (IS_ENABLED(CONFIG_RETPOLINE))
 335                         goto retpoline_auto;
 336                 break;
 337         case SPECTRE_V2_CMD_RETPOLINE_AMD:
 338                 if (IS_ENABLED(CONFIG_RETPOLINE))
 339                         goto retpoline_amd;
 340                 break;
 341         case SPECTRE_V2_CMD_RETPOLINE_GENERIC:
 342                 if (IS_ENABLED(CONFIG_RETPOLINE))
 343                         goto retpoline_generic;
 344                 break;
 345         case SPECTRE_V2_CMD_RETPOLINE:
 346                 if (IS_ENABLED(CONFIG_RETPOLINE))
 347                         goto retpoline_auto;
 348                 break;
 349         }
 350         pr_err("Spectre mitigation: kernel not compiled with retpoline; no mitigation available!");
 351         return;
 352
 353 retpoline_auto:
 354         if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) {
 355         retpoline_amd:
 356                 if (!boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) {
 357                         pr_err("Spectre mitigation: LFENCE not serializing, switching to generic retpoline\n");
 358                         goto retpoline_generic;
 359                 }
 360                 mode = retp_compiler() ? SPECTRE_V2_RETPOLINE_AMD :
 361                                          SPECTRE_V2_RETPOLINE_MINIMAL_AMD;
 362                 setup_force_cpu_cap(X86_FEATURE_RETPOLINE_AMD);
 363                 setup_force_cpu_cap(X86_FEATURE_RETPOLINE);
 364         } else {
 365         retpoline_generic:
 366                 mode = retp_compiler() ? SPECTRE_V2_RETPOLINE_GENERIC :
 367                                          SPECTRE_V2_RETPOLINE_MINIMAL;
 368                 setup_force_cpu_cap(X86_FEATURE_RETPOLINE);
 369         }
 370
 371         spectre_v2_enabled = mode;
 372         pr_info("%s\n", spectre_v2_strings[mode]);
 373
 374         /*
 375          * If neither SMEP nor PTI are available, there is a risk of
 376          * hitting userspace addresses in the RSB after a context switch
 377          * from a shallow call stack to a deeper one. To prevent this fill
 378          * the entire RSB, even when using IBRS.
 379          *
 380          * Skylake era CPUs have a separate issue with *underflow* of the
 381          * RSB, when they will predict 'ret' targets from the generic BTB.
 382          * The proper mitigation for this is IBRS. If IBRS is not supported
 383          * or deactivated in favour of retpolines the RSB fill on context
 384          * switch is required.
 385          */
 386         if ((!boot_cpu_has(X86_FEATURE_PTI) &&
 387              !boot_cpu_has(X86_FEATURE_SMEP)) || is_skylake_era()) {
 388                 setup_force_cpu_cap(X86_FEATURE_RSB_CTXSW);
 389                 pr_info("Spectre v2 mitigation: Filling RSB on context switch\n");
 390         }
 391
 392         /* Initialize Indirect Branch Prediction Barrier if supported */
 393         if (boot_cpu_has(X86_FEATURE_IBPB)) {
 394                 setup_force_cpu_cap(X86_FEATURE_USE_IBPB);
 395                 pr_info("Spectre v2 mitigation: Enabling Indirect Branch Prediction Barrier\n");
 396         }
 397
 398         /*
 399          * Retpoline means the kernel is safe because it has no indirect
 400          * branches. But firmware isn't, so use IBRS to protect that.
 401          */
 402         if (boot_cpu_has(X86_FEATURE_IBRS)) {
 403                 setup_force_cpu_cap(X86_FEATURE_USE_IBRS_FW);
 404                 pr_info("Enabling Restricted Speculation for firmware calls\n");
 405         }
 406 }
 407
 408 #undef pr_fmt
 409 #define pr_fmt(fmt)     "Speculative Store Bypass: " fmt
 410
 411 static enum ssb_mitigation ssb_mode __ro_after_init = SPEC_STORE_BYPASS_NONE;
 412
 413 /* The kernel command line selection */
 414 enum ssb_mitigation_cmd {
 415         SPEC_STORE_BYPASS_CMD_NONE,
 416         SPEC_STORE_BYPASS_CMD_AUTO,
 417         SPEC_STORE_BYPASS_CMD_ON,
 418         SPEC_STORE_BYPASS_CMD_PRCTL,
 419         SPEC_STORE_BYPASS_CMD_SECCOMP,
 420 };
 421
 422 static const char *ssb_strings[] = {
 423         [SPEC_STORE_BYPASS_NONE]        = "Vulnerable",
 424         [SPEC_STORE_BYPASS_DISABLE]     = "Mitigation: Speculative Store Bypass disabled",
 425         [SPEC_STORE_BYPASS_PRCTL]       = "Mitigation: Speculative Store Bypass disabled via prctl",
 426         [SPEC_STORE_BYPASS_SECCOMP]     = "Mitigation: Speculative Store Bypass disabled via prctl and seccomp",
 427 };
 428
 429 static const struct {
 430         const char *option;
 431         enum ssb_mitigation_cmd cmd;
 432 } ssb_mitigation_options[] = {
 433         { "auto",       SPEC_STORE_BYPASS_CMD_AUTO },    /* Platform decides */
 434         { "on",         SPEC_STORE_BYPASS_CMD_ON },      /* Disable Speculative Store Bypass */
 435         { "off",        SPEC_STORE_BYPASS_CMD_NONE },    /* Don't touch Speculative Store Bypass */
 436         { "prctl",      SPEC_STORE_BYPASS_CMD_PRCTL },   /* Disable Speculative Store Bypass via prctl */
 437         { "seccomp",    SPEC_STORE_BYPASS_CMD_SECCOMP }, /* Disable Speculative Store Bypass via prctl and seccomp */
 438 };
 439
 440 static enum ssb_mitigation_cmd __init ssb_parse_cmdline(void)
 441 {
 442         enum ssb_mitigation_cmd cmd = SPEC_STORE_BYPASS_CMD_AUTO;
 443         char arg[20];
 444         int ret, i;
 445
 446         if (cmdline_find_option_bool(boot_command_line, "nospec_store_bypass_disable")) {
 447                 return SPEC_STORE_BYPASS_CMD_NONE;
 448         } else {
 449                 ret = cmdline_find_option(boot_command_line, "spec_store_bypass_disable",
 450                                           arg, sizeof(arg));
 451                 if (ret < 0)
 452                         return SPEC_STORE_BYPASS_CMD_AUTO;
 453
 454                 for (i = 0; i < ARRAY_SIZE(ssb_mitigation_options); i++) {
 455                         if (!match_option(arg, ret, ssb_mitigation_options[i].option))
 456                                 continue;
 457
 458                         cmd = ssb_mitigation_options[i].cmd;
 459                         break;
 460                 }
 461
 462                 if (i >= ARRAY_SIZE(ssb_mitigation_options)) {
 463                         pr_err("unknown option (%s). Switching to AUTO select\n", arg);
 464                         return SPEC_STORE_BYPASS_CMD_AUTO;
 465                 }
 466         }
 467
 468         return cmd;
 469 }
 470
 471 static enum ssb_mitigation_cmd __init __ssb_select_mitigation(void)
 472 {
 473         enum ssb_mitigation mode = SPEC_STORE_BYPASS_NONE;
 474         enum ssb_mitigation_cmd cmd;
 475
 476         if (!boot_cpu_has(X86_FEATURE_RDS))
 477                 return mode;
 478
 479         cmd = ssb_parse_cmdline();
 480         if (!boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS) &&
 481             (cmd == SPEC_STORE_BYPASS_CMD_NONE ||
 482              cmd == SPEC_STORE_BYPASS_CMD_AUTO))
 483                 return mode;
 484
 485         switch (cmd) {
 486         case SPEC_STORE_BYPASS_CMD_AUTO:
 487         case SPEC_STORE_BYPASS_CMD_SECCOMP:
 488                 /*
 489                  * Choose prctl+seccomp as the default mode if seccomp is
 490                  * enabled.
 491                  */
 492                 if (IS_ENABLED(CONFIG_SECCOMP))
 493                         mode = SPEC_STORE_BYPASS_SECCOMP;
 494                 else
 495                         mode = SPEC_STORE_BYPASS_PRCTL;
 496                 break;
 497         case SPEC_STORE_BYPASS_CMD_ON:
 498                 mode = SPEC_STORE_BYPASS_DISABLE;
 499                 break;
 500         case SPEC_STORE_BYPASS_CMD_PRCTL:
 501                 mode = SPEC_STORE_BYPASS_PRCTL;
 502                 break;
 503         case SPEC_STORE_BYPASS_CMD_NONE:
 504                 break;
 505         }
 506
 507         /*
 508          * We have three CPU feature flags that are in play here:
 509          *  - X86_BUG_SPEC_STORE_BYPASS - CPU is susceptible.
 510          *  - X86_FEATURE_RDS - CPU is able to turn off speculative store bypass
 511          *  - X86_FEATURE_SPEC_STORE_BYPASS_DISABLE - engage the mitigation
 512          */
 513         if (mode == SPEC_STORE_BYPASS_DISABLE) {
 514                 setup_force_cpu_cap(X86_FEATURE_SPEC_STORE_BYPASS_DISABLE);
 515                 /*
 516                  * Intel uses the SPEC CTRL MSR Bit(2) for this, while AMD uses
 517                  * a completely different MSR and bit dependent on family.
 518                  */
 519                 switch (boot_cpu_data.x86_vendor) {
 520                 case X86_VENDOR_INTEL:
 521                         x86_spec_ctrl_base |= SPEC_CTRL_RDS;
 522                         x86_spec_ctrl_mask &= ~SPEC_CTRL_RDS;
 523                         x86_spec_ctrl_set(SPEC_CTRL_RDS);
 524                         break;
 525                 case X86_VENDOR_AMD:
 526                         x86_amd_rds_enable();
 527                         break;
 528                 }
 529         }
 530
 531         return mode;
 532 }
 533
 534 static void ssb_select_mitigation()
 535 {
 536         ssb_mode = __ssb_select_mitigation();
 537
 538         if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS))
 539                 pr_info("%s\n", ssb_strings[ssb_mode]);
 540 }
 541
 542 #undef pr_fmt
 543 #define pr_fmt(fmt)     "Speculation prctl: " fmt
 544
 545 static int ssb_prctl_set(struct task_struct *task, unsigned long ctrl)
 546 {
 547         bool update;
 548
 549         if (ssb_mode != SPEC_STORE_BYPASS_PRCTL &&
 550             ssb_mode != SPEC_STORE_BYPASS_SECCOMP)
 551                 return -ENXIO;
 552
 553         switch (ctrl) {
 554         case PR_SPEC_ENABLE:
 555                 /* If speculation is force disabled, enable is not allowed */
 556                 if (task_spec_ssb_force_disable(task))
 557                         return -EPERM;
 558                 task_clear_spec_ssb_disable(task);
 559                 update = test_and_clear_tsk_thread_flag(task, TIF_RDS);
 560                 break;
 561         case PR_SPEC_DISABLE:
 562                 task_set_spec_ssb_disable(task);
 563                 update = !test_and_set_tsk_thread_flag(task, TIF_RDS);
 564                 break;
 565         case PR_SPEC_FORCE_DISABLE:
 566                 task_set_spec_ssb_disable(task);
 567                 task_set_spec_ssb_force_disable(task);
 568                 update = !test_and_set_tsk_thread_flag(task, TIF_RDS);
 569                 break;
 570         default:
 571                 return -ERANGE;
 572         }
 573
 574         /*
 575          * If being set on non-current task, delay setting the CPU
 576          * mitigation until it is next scheduled.
 577          */
 578         if (task == current && update)
 579                 speculative_store_bypass_update();
 580
 581         return 0;
 582 }
 583
 584 int arch_prctl_spec_ctrl_set(struct task_struct *task, unsigned long which,
 585                              unsigned long ctrl)
 586 {
 587         switch (which) {
 588         case PR_SPEC_STORE_BYPASS:
 589                 return ssb_prctl_set(task, ctrl);
 590         default:
 591                 return -ENODEV;
 592         }
 593 }
 594
 595 #ifdef CONFIG_SECCOMP
 596 void arch_seccomp_spec_mitigate(struct task_struct *task)
 597 {
 598         if (ssb_mode == SPEC_STORE_BYPASS_SECCOMP)
 599                 ssb_prctl_set(task, PR_SPEC_FORCE_DISABLE);
 600 }
 601 #endif
 602
 603 static int ssb_prctl_get(struct task_struct *task)
 604 {
 605         switch (ssb_mode) {
 606         case SPEC_STORE_BYPASS_DISABLE:
 607                 return PR_SPEC_DISABLE;
 608         case SPEC_STORE_BYPASS_SECCOMP:
 609         case SPEC_STORE_BYPASS_PRCTL:
 610                 if (task_spec_ssb_force_disable(task))
 611                         return PR_SPEC_PRCTL | PR_SPEC_FORCE_DISABLE;
 612                 if (task_spec_ssb_disable(task))
 613                         return PR_SPEC_PRCTL | PR_SPEC_DISABLE;
 614                 return PR_SPEC_PRCTL | PR_SPEC_ENABLE;
 615         default:
 616                 if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS))
 617                         return PR_SPEC_ENABLE;
 618                 return PR_SPEC_NOT_AFFECTED;
 619         }
 620 }
 621
 622 int arch_prctl_spec_ctrl_get(struct task_struct *task, unsigned long which)
 623 {
 624         switch (which) {
 625         case PR_SPEC_STORE_BYPASS:
 626                 return ssb_prctl_get(task);
 627         default:
 628                 return -ENODEV;
 629         }
 630 }
 631
 632 void x86_spec_ctrl_setup_ap(void)
 633 {
 634         if (boot_cpu_has(X86_FEATURE_IBRS))
 635                 x86_spec_ctrl_set(x86_spec_ctrl_base & ~x86_spec_ctrl_mask);
 636
 637         if (ssb_mode == SPEC_STORE_BYPASS_DISABLE)
 638                 x86_amd_rds_enable();
 639 }
 640
 641 #ifdef CONFIG_SYSFS
 642
 643 ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr,
 644                         char *buf, unsigned int bug)
 645 {
 646         if (!boot_cpu_has_bug(bug))
 647                 return sprintf(buf, "Not affected\n");
 648
 649         switch (bug) {
 650         case X86_BUG_CPU_MELTDOWN:
 651                 if (boot_cpu_has(X86_FEATURE_PTI))
 652                         return sprintf(buf, "Mitigation: PTI\n");
 653
 654                 break;
 655
 656         case X86_BUG_SPECTRE_V1:
 657                 return sprintf(buf, "Mitigation: __user pointer sanitization\n");
 658
 659         case X86_BUG_SPECTRE_V2:
 660                 return sprintf(buf, "%s%s%s%s\n", spectre_v2_strings[spectre_v2_enabled],
 661                                boot_cpu_has(X86_FEATURE_USE_IBPB) ? ", IBPB" : "",
 662                                boot_cpu_has(X86_FEATURE_USE_IBRS_FW) ? ", IBRS_FW" : "",
 663                                spectre_v2_module_string());
 664
 665         case X86_BUG_SPEC_STORE_BYPASS:
 666                 return sprintf(buf, "%s\n", ssb_strings[ssb_mode]);
 667
 668         default:
 669                 break;
 670         }
 671
 672         return sprintf(buf, "Vulnerable\n");
 673 }
 674
 675 ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, char *buf)
 676 {
 677         return cpu_show_common(dev, attr, buf, X86_BUG_CPU_MELTDOWN);
 678 }
 679
 680 ssize_t cpu_show_spectre_v1(struct device *dev, struct device_attribute *attr, char *buf)
 681 {
 682         return cpu_show_common(dev, attr, buf, X86_BUG_SPECTRE_V1);
 683 }
 684
 685 ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr, char *buf)
 686 {
 687         return cpu_show_common(dev, attr, buf, X86_BUG_SPECTRE_V2);
 688 }
 689
 690 ssize_t cpu_show_spec_store_bypass(struct device *dev, struct device_attribute *attr, char *buf)
 691 {
 692         return cpu_show_common(dev, attr, buf, X86_BUG_SPEC_STORE_BYPASS);
 693 }
 694 #endif