arch/arm64/kernel/proton-pack.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Handle detection, reporting and mitigation of Spectre v1, v2, v3a and v4, as
   4  * detailed at:
   5  *
   6  *   https://developer.arm.com/support/arm-security-updates/speculative-processor-vulnerability
   7  *
   8  * This code was originally written hastily under an awful lot of stress and so
   9  * aspects of it are somewhat hacky. Unfortunately, changing anything in here
  10  * instantly makes me feel ill. Thanks, Jann. Thann.
  11  *
  12  * Copyright (C) 2018 ARM Ltd, All Rights Reserved.
  13  * Copyright (C) 2020 Google LLC
  14  *
  15  * "If there's something strange in your neighbourhood, who you gonna call?"
  16  *
  17  * Authors: Will Deacon <will@kernel.org> and Marc Zyngier <maz@kernel.org>
  18  */
  19
  20 #include <linux/arm-smccc.h>
  21 #include <linux/bpf.h>
  22 #include <linux/cpu.h>
  23 #include <linux/device.h>
  24 #include <linux/nospec.h>
  25 #include <linux/prctl.h>
  26 #include <linux/sched/task_stack.h>
  27
  28 #include <asm/debug-monitors.h>
  29 #include <asm/insn.h>
  30 #include <asm/spectre.h>
  31 #include <asm/traps.h>
  32 #include <asm/vectors.h>
  33 #include <asm/virt.h>
  34
  35 /*
  36  * We try to ensure that the mitigation state can never change as the result of
  37  * onlining a late CPU.
  38  */
  39 static void update_mitigation_state(enum mitigation_state *oldp,
  40                                     enum mitigation_state new)
  41 {
  42         enum mitigation_state state;
  43
  44         do {
  45                 state = READ_ONCE(*oldp);
  46                 if (new <= state)
  47                         break;
  48
  49                 /* Userspace almost certainly can't deal with this. */
  50                 if (WARN_ON(system_capabilities_finalized()))
  51                         break;
  52         } while (cmpxchg_relaxed(oldp, state, new) != state);
  53 }
  54
  55 /*
  56  * Spectre v1.
  57  *
  58  * The kernel can't protect userspace for this one: it's each person for
  59  * themselves. Advertise what we're doing and be done with it.
  60  */
  61 ssize_t cpu_show_spectre_v1(struct device *dev, struct device_attribute *attr,
  62                             char *buf)
  63 {
  64         return sprintf(buf, "Mitigation: __user pointer sanitization\n");
  65 }
  66
  67 /*
  68  * Spectre v2.
  69  *
  70  * This one sucks. A CPU is either:
  71  *
  72  * - Mitigated in hardware and advertised by ID_AA64PFR0_EL1.CSV2.
  73  * - Mitigated in hardware and listed in our "safe list".
  74  * - Mitigated in software by firmware.
  75  * - Mitigated in software by a CPU-specific dance in the kernel and a
  76  *   firmware call at EL2.
  77  * - Vulnerable.
  78  *
  79  * It's not unlikely for different CPUs in a big.LITTLE system to fall into
  80  * different camps.
  81  */
  82 static enum mitigation_state spectre_v2_state;
  83
  84 static bool __read_mostly __nospectre_v2;
  85 static int __init parse_spectre_v2_param(char *str)
  86 {
  87         __nospectre_v2 = true;
  88         return 0;
  89 }
  90 early_param("nospectre_v2", parse_spectre_v2_param);
  91
  92 static bool spectre_v2_mitigations_off(void)
  93 {
  94         bool ret = __nospectre_v2 || cpu_mitigations_off();
  95
  96         if (ret)
  97                 pr_info_once("spectre-v2 mitigation disabled by command line option\n");
  98
  99         return ret;
 100 }
 101
 102 static const char *get_bhb_affected_string(enum mitigation_state bhb_state)
 103 {
 104         switch (bhb_state) {
 105         case SPECTRE_UNAFFECTED:
 106                 return "";
 107         default:
 108         case SPECTRE_VULNERABLE:
 109                 return ", but not BHB";
 110         case SPECTRE_MITIGATED:
 111                 return ", BHB";
 112         }
 113 }
 114
 115 static bool _unprivileged_ebpf_enabled(void)
 116 {
 117 #ifdef CONFIG_BPF_SYSCALL
 118         return !sysctl_unprivileged_bpf_disabled;
 119 #else
 120         return false;
 121 #endif
 122 }
 123
 124 ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr,
 125                             char *buf)
 126 {
 127         enum mitigation_state bhb_state = arm64_get_spectre_bhb_state();
 128         const char *bhb_str = get_bhb_affected_string(bhb_state);
 129         const char *v2_str = "Branch predictor hardening";
 130
 131         switch (spectre_v2_state) {
 132         case SPECTRE_UNAFFECTED:
 133                 if (bhb_state == SPECTRE_UNAFFECTED)
 134                         return sprintf(buf, "Not affected\n");
 135
 136                 /*
 137                  * Platforms affected by Spectre-BHB can't report
 138                  * "Not affected" for Spectre-v2.
 139                  */
 140                 v2_str = "CSV2";
 141                 fallthrough;
 142         case SPECTRE_MITIGATED:
 143                 if (bhb_state == SPECTRE_MITIGATED && _unprivileged_ebpf_enabled())
 144                         return sprintf(buf, "Vulnerable: Unprivileged eBPF enabled\n");
 145
 146                 return sprintf(buf, "Mitigation: %s%s\n", v2_str, bhb_str);
 147         case SPECTRE_VULNERABLE:
 148                 fallthrough;
 149         default:
 150                 return sprintf(buf, "Vulnerable\n");
 151         }
 152 }
 153
 154 static enum mitigation_state spectre_v2_get_cpu_hw_mitigation_state(void)
 155 {
 156         u64 pfr0;
 157         static const struct midr_range spectre_v2_safe_list[] = {
 158                 MIDR_ALL_VERSIONS(MIDR_CORTEX_A35),
 159                 MIDR_ALL_VERSIONS(MIDR_CORTEX_A53),
 160                 MIDR_ALL_VERSIONS(MIDR_CORTEX_A55),
 161                 MIDR_ALL_VERSIONS(MIDR_BRAHMA_B53),
 162                 MIDR_ALL_VERSIONS(MIDR_HISI_TSV110),
 163                 MIDR_ALL_VERSIONS(MIDR_QCOM_KRYO_2XX_SILVER),
 164                 MIDR_ALL_VERSIONS(MIDR_QCOM_KRYO_3XX_SILVER),
 165                 MIDR_ALL_VERSIONS(MIDR_QCOM_KRYO_4XX_SILVER),
 166                 { /* sentinel */ }
 167         };
 168
 169         /* If the CPU has CSV2 set, we're safe */
 170         pfr0 = read_cpuid(ID_AA64PFR0_EL1);
 171         if (cpuid_feature_extract_unsigned_field(pfr0, ID_AA64PFR0_CSV2_SHIFT))
 172                 return SPECTRE_UNAFFECTED;
 173
 174         /* Alternatively, we have a list of unaffected CPUs */
 175         if (is_midr_in_range_list(read_cpuid_id(), spectre_v2_safe_list))
 176                 return SPECTRE_UNAFFECTED;
 177
 178         return SPECTRE_VULNERABLE;
 179 }
 180
 181 static enum mitigation_state spectre_v2_get_cpu_fw_mitigation_state(void)
 182 {
 183         int ret;
 184         struct arm_smccc_res res;
 185
 186         arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
 187                              ARM_SMCCC_ARCH_WORKAROUND_1, &res);
 188
 189         ret = res.a0;
 190         switch (ret) {
 191         case SMCCC_RET_SUCCESS:
 192                 return SPECTRE_MITIGATED;
 193         case SMCCC_ARCH_WORKAROUND_RET_UNAFFECTED:
 194                 return SPECTRE_UNAFFECTED;
 195         default:
 196                 fallthrough;
 197         case SMCCC_RET_NOT_SUPPORTED:
 198                 return SPECTRE_VULNERABLE;
 199         }
 200 }
 201
 202 bool has_spectre_v2(const struct arm64_cpu_capabilities *entry, int scope)
 203 {
 204         WARN_ON(scope != SCOPE_LOCAL_CPU || preemptible());
 205
 206         if (spectre_v2_get_cpu_hw_mitigation_state() == SPECTRE_UNAFFECTED)
 207                 return false;
 208
 209         if (spectre_v2_get_cpu_fw_mitigation_state() == SPECTRE_UNAFFECTED)
 210                 return false;
 211
 212         return true;
 213 }
 214
 215 enum mitigation_state arm64_get_spectre_v2_state(void)
 216 {
 217         return spectre_v2_state;
 218 }
 219
 220 DEFINE_PER_CPU_READ_MOSTLY(struct bp_hardening_data, bp_hardening_data);
 221
 222 static void install_bp_hardening_cb(bp_hardening_cb_t fn)
 223 {
 224         __this_cpu_write(bp_hardening_data.fn, fn);
 225
 226         /*
 227          * Vinz Clortho takes the hyp_vecs start/end "keys" at
 228          * the door when we're a guest. Skip the hyp-vectors work.
 229          */
 230         if (!is_hyp_mode_available())
 231                 return;
 232
 233         __this_cpu_write(bp_hardening_data.slot, HYP_VECTOR_SPECTRE_DIRECT);
 234 }
 235
 236 /* Called during entry so must be noinstr */
 237 static noinstr void call_smc_arch_workaround_1(void)
 238 {
 239         arm_smccc_1_1_smc(ARM_SMCCC_ARCH_WORKAROUND_1, NULL);
 240 }
 241
 242 /* Called during entry so must be noinstr */
 243 static noinstr void call_hvc_arch_workaround_1(void)
 244 {
 245         arm_smccc_1_1_hvc(ARM_SMCCC_ARCH_WORKAROUND_1, NULL);
 246 }
 247
 248 /* Called during entry so must be noinstr */
 249 static noinstr void qcom_link_stack_sanitisation(void)
 250 {
 251         u64 tmp;
 252
 253         asm volatile("mov       %0, x30         \n"
 254                      ".rept     16              \n"
 255                      "bl        . + 4           \n"
 256                      ".endr                     \n"
 257                      "mov       x30, %0         \n"
 258                      : "=&r" (tmp));
 259 }
 260
 261 static bp_hardening_cb_t spectre_v2_get_sw_mitigation_cb(void)
 262 {
 263         u32 midr = read_cpuid_id();
 264         if (((midr & MIDR_CPU_MODEL_MASK) != MIDR_QCOM_FALKOR) &&
 265             ((midr & MIDR_CPU_MODEL_MASK) != MIDR_QCOM_FALKOR_V1))
 266                 return NULL;
 267
 268         return qcom_link_stack_sanitisation;
 269 }
 270
 271 static enum mitigation_state spectre_v2_enable_fw_mitigation(void)
 272 {
 273         bp_hardening_cb_t cb;
 274         enum mitigation_state state;
 275
 276         state = spectre_v2_get_cpu_fw_mitigation_state();
 277         if (state != SPECTRE_MITIGATED)
 278                 return state;
 279
 280         if (spectre_v2_mitigations_off())
 281                 return SPECTRE_VULNERABLE;
 282
 283         switch (arm_smccc_1_1_get_conduit()) {
 284         case SMCCC_CONDUIT_HVC:
 285                 cb = call_hvc_arch_workaround_1;
 286                 break;
 287
 288         case SMCCC_CONDUIT_SMC:
 289                 cb = call_smc_arch_workaround_1;
 290                 break;
 291
 292         default:
 293                 return SPECTRE_VULNERABLE;
 294         }
 295
 296         /*
 297          * Prefer a CPU-specific workaround if it exists. Note that we
 298          * still rely on firmware for the mitigation at EL2.
 299          */
 300         cb = spectre_v2_get_sw_mitigation_cb() ?: cb;
 301         install_bp_hardening_cb(cb);
 302         return SPECTRE_MITIGATED;
 303 }
 304
 305 void spectre_v2_enable_mitigation(const struct arm64_cpu_capabilities *__unused)
 306 {
 307         enum mitigation_state state;
 308
 309         WARN_ON(preemptible());
 310
 311         state = spectre_v2_get_cpu_hw_mitigation_state();
 312         if (state == SPECTRE_VULNERABLE)
 313                 state = spectre_v2_enable_fw_mitigation();
 314
 315         update_mitigation_state(&spectre_v2_state, state);
 316 }
 317
 318 /*
 319  * Spectre-v3a.
 320  *
 321  * Phew, there's not an awful lot to do here! We just instruct EL2 to use
 322  * an indirect trampoline for the hyp vectors so that guests can't read
 323  * VBAR_EL2 to defeat randomisation of the hypervisor VA layout.
 324  */
 325 bool has_spectre_v3a(const struct arm64_cpu_capabilities *entry, int scope)
 326 {
 327         static const struct midr_range spectre_v3a_unsafe_list[] = {
 328                 MIDR_ALL_VERSIONS(MIDR_CORTEX_A57),
 329                 MIDR_ALL_VERSIONS(MIDR_CORTEX_A72),
 330                 {},
 331         };
 332
 333         WARN_ON(scope != SCOPE_LOCAL_CPU || preemptible());
 334         return is_midr_in_range_list(read_cpuid_id(), spectre_v3a_unsafe_list);
 335 }
 336
 337 void spectre_v3a_enable_mitigation(const struct arm64_cpu_capabilities *__unused)
 338 {
 339         struct bp_hardening_data *data = this_cpu_ptr(&bp_hardening_data);
 340
 341         if (this_cpu_has_cap(ARM64_SPECTRE_V3A))
 342                 data->slot += HYP_VECTOR_INDIRECT;
 343 }
 344
 345 /*
 346  * Spectre v4.
 347  *
 348  * If you thought Spectre v2 was nasty, wait until you see this mess. A CPU is
 349  * either:
 350  *
 351  * - Mitigated in hardware and listed in our "safe list".
 352  * - Mitigated in hardware via PSTATE.SSBS.
 353  * - Mitigated in software by firmware (sometimes referred to as SSBD).
 354  *
 355  * Wait, that doesn't sound so bad, does it? Keep reading...
 356  *
 357  * A major source of headaches is that the software mitigation is enabled both
 358  * on a per-task basis, but can also be forced on for the kernel, necessitating
 359  * both context-switch *and* entry/exit hooks. To make it even worse, some CPUs
 360  * allow EL0 to toggle SSBS directly, which can end up with the prctl() state
 361  * being stale when re-entering the kernel. The usual big.LITTLE caveats apply,
 362  * so you can have systems that have both firmware and SSBS mitigations. This
 363  * means we actually have to reject late onlining of CPUs with mitigations if
 364  * all of the currently onlined CPUs are safelisted, as the mitigation tends to
 365  * be opt-in for userspace. Yes, really, the cure is worse than the disease.
 366  *
 367  * The only good part is that if the firmware mitigation is present, then it is
 368  * present for all CPUs, meaning we don't have to worry about late onlining of a
 369  * vulnerable CPU if one of the boot CPUs is using the firmware mitigation.
 370  *
 371  * Give me a VAX-11/780 any day of the week...
 372  */
 373 static enum mitigation_state spectre_v4_state;
 374
 375 /* This is the per-cpu state tracking whether we need to talk to firmware */
 376 DEFINE_PER_CPU_READ_MOSTLY(u64, arm64_ssbd_callback_required);
 377
 378 enum spectre_v4_policy {
 379         SPECTRE_V4_POLICY_MITIGATION_DYNAMIC,
 380         SPECTRE_V4_POLICY_MITIGATION_ENABLED,
 381         SPECTRE_V4_POLICY_MITIGATION_DISABLED,
 382 };
 383
 384 static enum spectre_v4_policy __read_mostly __spectre_v4_policy;
 385
 386 static const struct spectre_v4_param {
 387         const char              *str;
 388         enum spectre_v4_policy  policy;
 389 } spectre_v4_params[] = {
 390         { "force-on",   SPECTRE_V4_POLICY_MITIGATION_ENABLED, },
 391         { "force-off",  SPECTRE_V4_POLICY_MITIGATION_DISABLED, },
 392         { "kernel",     SPECTRE_V4_POLICY_MITIGATION_DYNAMIC, },
 393 };
 394 static int __init parse_spectre_v4_param(char *str)
 395 {
 396         int i;
 397
 398         if (!str || !str[0])
 399                 return -EINVAL;
 400
 401         for (i = 0; i < ARRAY_SIZE(spectre_v4_params); i++) {
 402                 const struct spectre_v4_param *param = &spectre_v4_params[i];
 403
 404                 if (strncmp(str, param->str, strlen(param->str)))
 405                         continue;
 406
 407                 __spectre_v4_policy = param->policy;
 408                 return 0;
 409         }
 410
 411         return -EINVAL;
 412 }
 413 early_param("ssbd", parse_spectre_v4_param);
 414
 415 /*
 416  * Because this was all written in a rush by people working in different silos,
 417  * we've ended up with multiple command line options to control the same thing.
 418  * Wrap these up in some helpers, which prefer disabling the mitigation if faced
 419  * with contradictory parameters. The mitigation is always either "off",
 420  * "dynamic" or "on".
 421  */
 422 static bool spectre_v4_mitigations_off(void)
 423 {
 424         bool ret = cpu_mitigations_off() ||
 425                    __spectre_v4_policy == SPECTRE_V4_POLICY_MITIGATION_DISABLED;
 426
 427         if (ret)
 428                 pr_info_once("spectre-v4 mitigation disabled by command-line option\n");
 429
 430         return ret;
 431 }
 432
 433 /* Do we need to toggle the mitigation state on entry to/exit from the kernel? */
 434 static bool spectre_v4_mitigations_dynamic(void)
 435 {
 436         return !spectre_v4_mitigations_off() &&
 437                __spectre_v4_policy == SPECTRE_V4_POLICY_MITIGATION_DYNAMIC;
 438 }
 439
 440 static bool spectre_v4_mitigations_on(void)
 441 {
 442         return !spectre_v4_mitigations_off() &&
 443                __spectre_v4_policy == SPECTRE_V4_POLICY_MITIGATION_ENABLED;
 444 }
 445
 446 ssize_t cpu_show_spec_store_bypass(struct device *dev,
 447                                    struct device_attribute *attr, char *buf)
 448 {
 449         switch (spectre_v4_state) {
 450         case SPECTRE_UNAFFECTED:
 451                 return sprintf(buf, "Not affected\n");
 452         case SPECTRE_MITIGATED:
 453                 return sprintf(buf, "Mitigation: Speculative Store Bypass disabled via prctl\n");
 454         case SPECTRE_VULNERABLE:
 455                 fallthrough;
 456         default:
 457                 return sprintf(buf, "Vulnerable\n");
 458         }
 459 }
 460
 461 enum mitigation_state arm64_get_spectre_v4_state(void)
 462 {
 463         return spectre_v4_state;
 464 }
 465
 466 static enum mitigation_state spectre_v4_get_cpu_hw_mitigation_state(void)
 467 {
 468         static const struct midr_range spectre_v4_safe_list[] = {
 469                 MIDR_ALL_VERSIONS(MIDR_CORTEX_A35),
 470                 MIDR_ALL_VERSIONS(MIDR_CORTEX_A53),
 471                 MIDR_ALL_VERSIONS(MIDR_CORTEX_A55),
 472                 MIDR_ALL_VERSIONS(MIDR_BRAHMA_B53),
 473                 MIDR_ALL_VERSIONS(MIDR_QCOM_KRYO_3XX_SILVER),
 474                 MIDR_ALL_VERSIONS(MIDR_QCOM_KRYO_4XX_SILVER),
 475                 { /* sentinel */ },
 476         };
 477
 478         if (is_midr_in_range_list(read_cpuid_id(), spectre_v4_safe_list))
 479                 return SPECTRE_UNAFFECTED;
 480
 481         /* CPU features are detected first */
 482         if (this_cpu_has_cap(ARM64_SSBS))
 483                 return SPECTRE_MITIGATED;
 484
 485         return SPECTRE_VULNERABLE;
 486 }
 487
 488 static enum mitigation_state spectre_v4_get_cpu_fw_mitigation_state(void)
 489 {
 490         int ret;
 491         struct arm_smccc_res res;
 492
 493         arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
 494                              ARM_SMCCC_ARCH_WORKAROUND_2, &res);
 495
 496         ret = res.a0;
 497         switch (ret) {
 498         case SMCCC_RET_SUCCESS:
 499                 return SPECTRE_MITIGATED;
 500         case SMCCC_ARCH_WORKAROUND_RET_UNAFFECTED:
 501                 fallthrough;
 502         case SMCCC_RET_NOT_REQUIRED:
 503                 return SPECTRE_UNAFFECTED;
 504         default:
 505                 fallthrough;
 506         case SMCCC_RET_NOT_SUPPORTED:
 507                 return SPECTRE_VULNERABLE;
 508         }
 509 }
 510
 511 bool has_spectre_v4(const struct arm64_cpu_capabilities *cap, int scope)
 512 {
 513         enum mitigation_state state;
 514
 515         WARN_ON(scope != SCOPE_LOCAL_CPU || preemptible());
 516
 517         state = spectre_v4_get_cpu_hw_mitigation_state();
 518         if (state == SPECTRE_VULNERABLE)
 519                 state = spectre_v4_get_cpu_fw_mitigation_state();
 520
 521         return state != SPECTRE_UNAFFECTED;
 522 }
 523
 524 bool try_emulate_el1_ssbs(struct pt_regs *regs, u32 instr)
 525 {
 526         const u32 instr_mask = ~(1U << PSTATE_Imm_shift);
 527         const u32 instr_val = 0xd500401f | PSTATE_SSBS;
 528
 529         if ((instr & instr_mask) != instr_val)
 530                 return false;
 531
 532         if (instr & BIT(PSTATE_Imm_shift))
 533                 regs->pstate |= PSR_SSBS_BIT;
 534         else
 535                 regs->pstate &= ~PSR_SSBS_BIT;
 536
 537         arm64_skip_faulting_instruction(regs, 4);
 538         return true;
 539 }
 540
 541 static enum mitigation_state spectre_v4_enable_hw_mitigation(void)
 542 {
 543         enum mitigation_state state;
 544
 545         /*
 546          * If the system is mitigated but this CPU doesn't have SSBS, then
 547          * we must be on the safelist and there's nothing more to do.
 548          */
 549         state = spectre_v4_get_cpu_hw_mitigation_state();
 550         if (state != SPECTRE_MITIGATED || !this_cpu_has_cap(ARM64_SSBS))
 551                 return state;
 552
 553         if (spectre_v4_mitigations_off()) {
 554                 sysreg_clear_set(sctlr_el1, 0, SCTLR_ELx_DSSBS);
 555                 set_pstate_ssbs(1);
 556                 return SPECTRE_VULNERABLE;
 557         }
 558
 559         /* SCTLR_EL1.DSSBS was initialised to 0 during boot */
 560         set_pstate_ssbs(0);
 561         return SPECTRE_MITIGATED;
 562 }
 563
 564 /*
 565  * Patch a branch over the Spectre-v4 mitigation code with a NOP so that
 566  * we fallthrough and check whether firmware needs to be called on this CPU.
 567  */
 568 void __init spectre_v4_patch_fw_mitigation_enable(struct alt_instr *alt,
 569                                                   __le32 *origptr,
 570                                                   __le32 *updptr, int nr_inst)
 571 {
 572         BUG_ON(nr_inst != 1); /* Branch -> NOP */
 573
 574         if (spectre_v4_mitigations_off())
 575                 return;
 576
 577         if (cpus_have_final_cap(ARM64_SSBS))
 578                 return;
 579
 580         if (spectre_v4_mitigations_dynamic())
 581                 *updptr = cpu_to_le32(aarch64_insn_gen_nop());
 582 }
 583
 584 /*
 585  * Patch a NOP in the Spectre-v4 mitigation code with an SMC/HVC instruction
 586  * to call into firmware to adjust the mitigation state.
 587  */
 588 void __init smccc_patch_fw_mitigation_conduit(struct alt_instr *alt,
 589                                                __le32 *origptr,
 590                                                __le32 *updptr, int nr_inst)
 591 {
 592         u32 insn;
 593
 594         BUG_ON(nr_inst != 1); /* NOP -> HVC/SMC */
 595
 596         switch (arm_smccc_1_1_get_conduit()) {
 597         case SMCCC_CONDUIT_HVC:
 598                 insn = aarch64_insn_get_hvc_value();
 599                 break;
 600         case SMCCC_CONDUIT_SMC:
 601                 insn = aarch64_insn_get_smc_value();
 602                 break;
 603         default:
 604                 return;
 605         }
 606
 607         *updptr = cpu_to_le32(insn);
 608 }
 609
 610 static enum mitigation_state spectre_v4_enable_fw_mitigation(void)
 611 {
 612         enum mitigation_state state;
 613
 614         state = spectre_v4_get_cpu_fw_mitigation_state();
 615         if (state != SPECTRE_MITIGATED)
 616                 return state;
 617
 618         if (spectre_v4_mitigations_off()) {
 619                 arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_WORKAROUND_2, false, NULL);
 620                 return SPECTRE_VULNERABLE;
 621         }
 622
 623         arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_WORKAROUND_2, true, NULL);
 624
 625         if (spectre_v4_mitigations_dynamic())
 626                 __this_cpu_write(arm64_ssbd_callback_required, 1);
 627
 628         return SPECTRE_MITIGATED;
 629 }
 630
 631 void spectre_v4_enable_mitigation(const struct arm64_cpu_capabilities *__unused)
 632 {
 633         enum mitigation_state state;
 634
 635         WARN_ON(preemptible());
 636
 637         state = spectre_v4_enable_hw_mitigation();
 638         if (state == SPECTRE_VULNERABLE)
 639                 state = spectre_v4_enable_fw_mitigation();
 640
 641         update_mitigation_state(&spectre_v4_state, state);
 642 }
 643
 644 static void __update_pstate_ssbs(struct pt_regs *regs, bool state)
 645 {
 646         u64 bit = compat_user_mode(regs) ? PSR_AA32_SSBS_BIT : PSR_SSBS_BIT;
 647
 648         if (state)
 649                 regs->pstate |= bit;
 650         else
 651                 regs->pstate &= ~bit;
 652 }
 653
 654 void spectre_v4_enable_task_mitigation(struct task_struct *tsk)
 655 {
 656         struct pt_regs *regs = task_pt_regs(tsk);
 657         bool ssbs = false, kthread = tsk->flags & PF_KTHREAD;
 658
 659         if (spectre_v4_mitigations_off())
 660                 ssbs = true;
 661         else if (spectre_v4_mitigations_dynamic() && !kthread)
 662                 ssbs = !test_tsk_thread_flag(tsk, TIF_SSBD);
 663
 664         __update_pstate_ssbs(regs, ssbs);
 665 }
 666
 667 /*
 668  * The Spectre-v4 mitigation can be controlled via a prctl() from userspace.
 669  * This is interesting because the "speculation disabled" behaviour can be
 670  * configured so that it is preserved across exec(), which means that the
 671  * prctl() may be necessary even when PSTATE.SSBS can be toggled directly
 672  * from userspace.
 673  */
 674 static void ssbd_prctl_enable_mitigation(struct task_struct *task)
 675 {
 676         task_clear_spec_ssb_noexec(task);
 677         task_set_spec_ssb_disable(task);
 678         set_tsk_thread_flag(task, TIF_SSBD);
 679 }
 680
 681 static void ssbd_prctl_disable_mitigation(struct task_struct *task)
 682 {
 683         task_clear_spec_ssb_noexec(task);
 684         task_clear_spec_ssb_disable(task);
 685         clear_tsk_thread_flag(task, TIF_SSBD);
 686 }
 687
 688 static int ssbd_prctl_set(struct task_struct *task, unsigned long ctrl)
 689 {
 690         switch (ctrl) {
 691         case PR_SPEC_ENABLE:
 692                 /* Enable speculation: disable mitigation */
 693                 /*
 694                  * Force disabled speculation prevents it from being
 695                  * re-enabled.
 696                  */
 697                 if (task_spec_ssb_force_disable(task))
 698                         return -EPERM;
 699
 700                 /*
 701                  * If the mitigation is forced on, then speculation is forced
 702                  * off and we again prevent it from being re-enabled.
 703                  */
 704                 if (spectre_v4_mitigations_on())
 705                         return -EPERM;
 706
 707                 ssbd_prctl_disable_mitigation(task);
 708                 break;
 709         case PR_SPEC_FORCE_DISABLE:
 710                 /* Force disable speculation: force enable mitigation */
 711                 /*
 712                  * If the mitigation is forced off, then speculation is forced
 713                  * on and we prevent it from being disabled.
 714                  */
 715                 if (spectre_v4_mitigations_off())
 716                         return -EPERM;
 717
 718                 task_set_spec_ssb_force_disable(task);
 719                 fallthrough;
 720         case PR_SPEC_DISABLE:
 721                 /* Disable speculation: enable mitigation */
 722                 /* Same as PR_SPEC_FORCE_DISABLE */
 723                 if (spectre_v4_mitigations_off())
 724                         return -EPERM;
 725
 726                 ssbd_prctl_enable_mitigation(task);
 727                 break;
 728         case PR_SPEC_DISABLE_NOEXEC:
 729                 /* Disable speculation until execve(): enable mitigation */
 730                 /*
 731                  * If the mitigation state is forced one way or the other, then
 732                  * we must fail now before we try to toggle it on execve().
 733                  */
 734                 if (task_spec_ssb_force_disable(task) ||
 735                     spectre_v4_mitigations_off() ||
 736                     spectre_v4_mitigations_on()) {
 737                         return -EPERM;
 738                 }
 739
 740                 ssbd_prctl_enable_mitigation(task);
 741                 task_set_spec_ssb_noexec(task);
 742                 break;
 743         default:
 744                 return -ERANGE;
 745         }
 746
 747         spectre_v4_enable_task_mitigation(task);
 748         return 0;
 749 }
 750
 751 int arch_prctl_spec_ctrl_set(struct task_struct *task, unsigned long which,
 752                              unsigned long ctrl)
 753 {
 754         switch (which) {
 755         case PR_SPEC_STORE_BYPASS:
 756                 return ssbd_prctl_set(task, ctrl);
 757         default:
 758                 return -ENODEV;
 759         }
 760 }
 761
 762 static int ssbd_prctl_get(struct task_struct *task)
 763 {
 764         switch (spectre_v4_state) {
 765         case SPECTRE_UNAFFECTED:
 766                 return PR_SPEC_NOT_AFFECTED;
 767         case SPECTRE_MITIGATED:
 768                 if (spectre_v4_mitigations_on())
 769                         return PR_SPEC_NOT_AFFECTED;
 770
 771                 if (spectre_v4_mitigations_dynamic())
 772                         break;
 773
 774                 /* Mitigations are disabled, so we're vulnerable. */
 775                 fallthrough;
 776         case SPECTRE_VULNERABLE:
 777                 fallthrough;
 778         default:
 779                 return PR_SPEC_ENABLE;
 780         }
 781
 782         /* Check the mitigation state for this task */
 783         if (task_spec_ssb_force_disable(task))
 784                 return PR_SPEC_PRCTL | PR_SPEC_FORCE_DISABLE;
 785
 786         if (task_spec_ssb_noexec(task))
 787                 return PR_SPEC_PRCTL | PR_SPEC_DISABLE_NOEXEC;
 788
 789         if (task_spec_ssb_disable(task))
 790                 return PR_SPEC_PRCTL | PR_SPEC_DISABLE;
 791
 792         return PR_SPEC_PRCTL | PR_SPEC_ENABLE;
 793 }
 794
 795 int arch_prctl_spec_ctrl_get(struct task_struct *task, unsigned long which)
 796 {
 797         switch (which) {
 798         case PR_SPEC_STORE_BYPASS:
 799                 return ssbd_prctl_get(task);
 800         default:
 801                 return -ENODEV;
 802         }
 803 }
 804
 805 /*
 806  * Spectre BHB.
 807  *
 808  * A CPU is either:
 809  * - Mitigated by a branchy loop a CPU specific number of times, and listed
 810  *   in our "loop mitigated list".
 811  * - Mitigated in software by the firmware Spectre v2 call.
 812  * - Has the ClearBHB instruction to perform the mitigation.
 813  * - Has the 'Exception Clears Branch History Buffer' (ECBHB) feature, so no
 814  *   software mitigation in the vectors is needed.
 815  * - Has CSV2.3, so is unaffected.
 816  */
 817 static enum mitigation_state spectre_bhb_state;
 818
 819 enum mitigation_state arm64_get_spectre_bhb_state(void)
 820 {
 821         return spectre_bhb_state;
 822 }
 823
 824 enum bhb_mitigation_bits {
 825         BHB_LOOP,
 826         BHB_FW,
 827         BHB_HW,
 828         BHB_INSN,
 829 };
 830 static unsigned long system_bhb_mitigations;
 831
 832 /*
 833  * This must be called with SCOPE_LOCAL_CPU for each type of CPU, before any
 834  * SCOPE_SYSTEM call will give the right answer.
 835  */
 836 u8 spectre_bhb_loop_affected(int scope)
 837 {
 838         u8 k = 0;
 839         static u8 max_bhb_k;
 840
 841         if (scope == SCOPE_LOCAL_CPU) {
 842                 static const struct midr_range spectre_bhb_k32_list[] = {
 843                         MIDR_ALL_VERSIONS(MIDR_CORTEX_A78),
 844                         MIDR_ALL_VERSIONS(MIDR_CORTEX_A78AE),
 845                         MIDR_ALL_VERSIONS(MIDR_CORTEX_A78C),
 846                         MIDR_ALL_VERSIONS(MIDR_CORTEX_X1),
 847                         MIDR_ALL_VERSIONS(MIDR_CORTEX_A710),
 848                         MIDR_ALL_VERSIONS(MIDR_CORTEX_X2),
 849                         MIDR_ALL_VERSIONS(MIDR_NEOVERSE_N2),
 850                         MIDR_ALL_VERSIONS(MIDR_NEOVERSE_V1),
 851                         {},
 852                 };
 853                 static const struct midr_range spectre_bhb_k24_list[] = {
 854                         MIDR_ALL_VERSIONS(MIDR_CORTEX_A76),
 855                         MIDR_ALL_VERSIONS(MIDR_CORTEX_A77),
 856                         MIDR_ALL_VERSIONS(MIDR_NEOVERSE_N1),
 857                         {},
 858                 };
 859                 static const struct midr_range spectre_bhb_k11_list[] = {
 860                         MIDR_ALL_VERSIONS(MIDR_AMPERE1),
 861                         {},
 862                 };
 863                 static const struct midr_range spectre_bhb_k8_list[] = {
 864                         MIDR_ALL_VERSIONS(MIDR_CORTEX_A72),
 865                         MIDR_ALL_VERSIONS(MIDR_CORTEX_A57),
 866                         {},
 867                 };
 868
 869                 if (is_midr_in_range_list(read_cpuid_id(), spectre_bhb_k32_list))
 870                         k = 32;
 871                 else if (is_midr_in_range_list(read_cpuid_id(), spectre_bhb_k24_list))
 872                         k = 24;
 873                 else if (is_midr_in_range_list(read_cpuid_id(), spectre_bhb_k11_list))
 874                         k = 11;
 875                 else if (is_midr_in_range_list(read_cpuid_id(), spectre_bhb_k8_list))
 876                         k =  8;
 877
 878                 max_bhb_k = max(max_bhb_k, k);
 879         } else {
 880                 k = max_bhb_k;
 881         }
 882
 883         return k;
 884 }
 885
 886 static enum mitigation_state spectre_bhb_get_cpu_fw_mitigation_state(void)
 887 {
 888         int ret;
 889         struct arm_smccc_res res;
 890
 891         arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
 892                              ARM_SMCCC_ARCH_WORKAROUND_3, &res);
 893
 894         ret = res.a0;
 895         switch (ret) {
 896         case SMCCC_RET_SUCCESS:
 897                 return SPECTRE_MITIGATED;
 898         case SMCCC_ARCH_WORKAROUND_RET_UNAFFECTED:
 899                 return SPECTRE_UNAFFECTED;
 900         default:
 901                 fallthrough;
 902         case SMCCC_RET_NOT_SUPPORTED:
 903                 return SPECTRE_VULNERABLE;
 904         }
 905 }
 906
 907 static bool is_spectre_bhb_fw_affected(int scope)
 908 {
 909         static bool system_affected;
 910         enum mitigation_state fw_state;
 911         bool has_smccc = arm_smccc_1_1_get_conduit() != SMCCC_CONDUIT_NONE;
 912         static const struct midr_range spectre_bhb_firmware_mitigated_list[] = {
 913                 MIDR_ALL_VERSIONS(MIDR_CORTEX_A73),
 914                 MIDR_ALL_VERSIONS(MIDR_CORTEX_A75),
 915                 {},
 916         };
 917         bool cpu_in_list = is_midr_in_range_list(read_cpuid_id(),
 918                                          spectre_bhb_firmware_mitigated_list);
 919
 920         if (scope != SCOPE_LOCAL_CPU)
 921                 return system_affected;
 922
 923         fw_state = spectre_bhb_get_cpu_fw_mitigation_state();
 924         if (cpu_in_list || (has_smccc && fw_state == SPECTRE_MITIGATED)) {
 925                 system_affected = true;
 926                 return true;
 927         }
 928
 929         return false;
 930 }
 931
 932 static bool supports_ecbhb(int scope)
 933 {
 934         u64 mmfr1;
 935
 936         if (scope == SCOPE_LOCAL_CPU)
 937                 mmfr1 = read_sysreg_s(SYS_ID_AA64MMFR1_EL1);
 938         else
 939                 mmfr1 = read_sanitised_ftr_reg(SYS_ID_AA64MMFR1_EL1);
 940
 941         return cpuid_feature_extract_unsigned_field(mmfr1,
 942                                                     ID_AA64MMFR1_ECBHB_SHIFT);
 943 }
 944
 945 bool is_spectre_bhb_affected(const struct arm64_cpu_capabilities *entry,
 946                              int scope)
 947 {
 948         WARN_ON(scope != SCOPE_LOCAL_CPU || preemptible());
 949
 950         if (supports_csv2p3(scope))
 951                 return false;
 952
 953         if (supports_clearbhb(scope))
 954                 return true;
 955
 956         if (spectre_bhb_loop_affected(scope))
 957                 return true;
 958
 959         if (is_spectre_bhb_fw_affected(scope))
 960                 return true;
 961
 962         return false;
 963 }
 964
 965 static void this_cpu_set_vectors(enum arm64_bp_harden_el1_vectors slot)
 966 {
 967         const char *v = arm64_get_bp_hardening_vector(slot);
 968
 969         if (slot < 0)
 970                 return;
 971
 972         __this_cpu_write(this_cpu_vector, v);
 973
 974         /*
 975          * When KPTI is in use, the vectors are switched when exiting to
 976          * user-space.
 977          */
 978         if (arm64_kernel_unmapped_at_el0())
 979                 return;
 980
 981         write_sysreg(v, vbar_el1);
 982         isb();
 983 }
 984
 985 void spectre_bhb_enable_mitigation(const struct arm64_cpu_capabilities *entry)
 986 {
 987         bp_hardening_cb_t cpu_cb;
 988         enum mitigation_state fw_state, state = SPECTRE_VULNERABLE;
 989         struct bp_hardening_data *data = this_cpu_ptr(&bp_hardening_data);
 990
 991         if (!is_spectre_bhb_affected(entry, SCOPE_LOCAL_CPU))
 992                 return;
 993
 994         if (arm64_get_spectre_v2_state() == SPECTRE_VULNERABLE) {
 995                 /* No point mitigating Spectre-BHB alone. */
 996         } else if (!IS_ENABLED(CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY)) {
 997                 pr_info_once("spectre-bhb mitigation disabled by compile time option\n");
 998         } else if (cpu_mitigations_off()) {
 999                 pr_info_once("spectre-bhb mitigation disabled by command line option\n");
1000         } else if (supports_ecbhb(SCOPE_LOCAL_CPU)) {
1001                 state = SPECTRE_MITIGATED;
1002                 set_bit(BHB_HW, &system_bhb_mitigations);
1003         } else if (supports_clearbhb(SCOPE_LOCAL_CPU)) {
1004                 /*
1005                  * Ensure KVM uses the indirect vector which will have ClearBHB
1006                  * added.
1007                  */
1008                 if (!data->slot)
1009                         data->slot = HYP_VECTOR_INDIRECT;
1010
1011                 this_cpu_set_vectors(EL1_VECTOR_BHB_CLEAR_INSN);
1012                 state = SPECTRE_MITIGATED;
1013                 set_bit(BHB_INSN, &system_bhb_mitigations);
1014         } else if (spectre_bhb_loop_affected(SCOPE_LOCAL_CPU)) {
1015                 /*
1016                  * Ensure KVM uses the indirect vector which will have the
1017                  * branchy-loop added. A57/A72-r0 will already have selected
1018                  * the spectre-indirect vector, which is sufficient for BHB
1019                  * too.
1020                  */
1021                 if (!data->slot)
1022                         data->slot = HYP_VECTOR_INDIRECT;
1023
1024                 this_cpu_set_vectors(EL1_VECTOR_BHB_LOOP);
1025                 state = SPECTRE_MITIGATED;
1026                 set_bit(BHB_LOOP, &system_bhb_mitigations);
1027         } else if (is_spectre_bhb_fw_affected(SCOPE_LOCAL_CPU)) {
1028                 fw_state = spectre_bhb_get_cpu_fw_mitigation_state();
1029                 if (fw_state == SPECTRE_MITIGATED) {
1030                         /*
1031                          * Ensure KVM uses one of the spectre bp_hardening
1032                          * vectors. The indirect vector doesn't include the EL3
1033                          * call, so needs upgrading to
1034                          * HYP_VECTOR_SPECTRE_INDIRECT.
1035                          */
1036                         if (!data->slot || data->slot == HYP_VECTOR_INDIRECT)
1037                                 data->slot += 1;
1038
1039                         this_cpu_set_vectors(EL1_VECTOR_BHB_FW);
1040
1041                         /*
1042                          * The WA3 call in the vectors supersedes the WA1 call
1043                          * made during context-switch. Uninstall any firmware
1044                          * bp_hardening callback.
1045                          */
1046                         cpu_cb = spectre_v2_get_sw_mitigation_cb();
1047                         if (__this_cpu_read(bp_hardening_data.fn) != cpu_cb)
1048                                 __this_cpu_write(bp_hardening_data.fn, NULL);
1049
1050                         state = SPECTRE_MITIGATED;
1051                         set_bit(BHB_FW, &system_bhb_mitigations);
1052                 }
1053         }
1054
1055         update_mitigation_state(&spectre_bhb_state, state);
1056 }
1057
1058 /* Patched to NOP when enabled */
1059 void noinstr spectre_bhb_patch_loop_mitigation_enable(struct alt_instr *alt,
1060                                                      __le32 *origptr,
1061                                                       __le32 *updptr, int nr_inst)
1062 {
1063         BUG_ON(nr_inst != 1);
1064
1065         if (test_bit(BHB_LOOP, &system_bhb_mitigations))
1066                 *updptr++ = cpu_to_le32(aarch64_insn_gen_nop());
1067 }
1068
1069 /* Patched to NOP when enabled */
1070 void noinstr spectre_bhb_patch_fw_mitigation_enabled(struct alt_instr *alt,
1071                                                    __le32 *origptr,
1072                                                    __le32 *updptr, int nr_inst)
1073 {
1074         BUG_ON(nr_inst != 1);
1075
1076         if (test_bit(BHB_FW, &system_bhb_mitigations))
1077                 *updptr++ = cpu_to_le32(aarch64_insn_gen_nop());
1078 }
1079
1080 /* Patched to correct the immediate */
1081 void noinstr spectre_bhb_patch_loop_iter(struct alt_instr *alt,
1082                                    __le32 *origptr, __le32 *updptr, int nr_inst)
1083 {
1084         u8 rd;
1085         u32 insn;
1086         u16 loop_count = spectre_bhb_loop_affected(SCOPE_SYSTEM);
1087
1088         BUG_ON(nr_inst != 1); /* MOV -> MOV */
1089
1090         if (!IS_ENABLED(CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY))
1091                 return;
1092
1093         insn = le32_to_cpu(*origptr);
1094         rd = aarch64_insn_decode_register(AARCH64_INSN_REGTYPE_RD, insn);
1095         insn = aarch64_insn_gen_movewide(rd, loop_count, 0,
1096                                          AARCH64_INSN_VARIANT_64BIT,
1097                                          AARCH64_INSN_MOVEWIDE_ZERO);
1098         *updptr++ = cpu_to_le32(insn);
1099 }
1100
1101 /* Patched to mov WA3 when supported */
1102 void noinstr spectre_bhb_patch_wa3(struct alt_instr *alt,
1103                                    __le32 *origptr, __le32 *updptr, int nr_inst)
1104 {
1105         u8 rd;
1106         u32 insn;
1107
1108         BUG_ON(nr_inst != 1); /* MOV -> MOV */
1109
1110         if (!IS_ENABLED(CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY) ||
1111             !test_bit(BHB_FW, &system_bhb_mitigations))
1112                 return;
1113
1114         insn = le32_to_cpu(*origptr);
1115         rd = aarch64_insn_decode_register(AARCH64_INSN_REGTYPE_RD, insn);
1116
1117         insn = aarch64_insn_gen_logical_immediate(AARCH64_INSN_LOGIC_ORR,
1118                                                   AARCH64_INSN_VARIANT_32BIT,
1119                                                   AARCH64_INSN_REG_ZR, rd,
1120                                                   ARM_SMCCC_ARCH_WORKAROUND_3);
1121         if (WARN_ON_ONCE(insn == AARCH64_BREAK_FAULT))
1122                 return;
1123
1124         *updptr++ = cpu_to_le32(insn);
1125 }
1126
1127 /* Patched to NOP when not supported */
1128 void __init spectre_bhb_patch_clearbhb(struct alt_instr *alt,
1129                                    __le32 *origptr, __le32 *updptr, int nr_inst)
1130 {
1131         BUG_ON(nr_inst != 2);
1132
1133         if (test_bit(BHB_INSN, &system_bhb_mitigations))
1134                 return;
1135
1136         *updptr++ = cpu_to_le32(aarch64_insn_gen_nop());
1137         *updptr++ = cpu_to_le32(aarch64_insn_gen_nop());
1138 }
1139
1140 #ifdef CONFIG_BPF_SYSCALL
1141 #define EBPF_WARN "Unprivileged eBPF is enabled, data leaks possible via Spectre v2 BHB attacks!\n"
1142 void unpriv_ebpf_notify(int new_state)
1143 {
1144         if (spectre_v2_state == SPECTRE_VULNERABLE ||
1145             spectre_bhb_state != SPECTRE_MITIGATED)
1146                 return;
1147
1148         if (!new_state)
1149                 pr_err("WARNING: %s", EBPF_WARN);
1150 }
1151 #endif