arch/powerpc/kernel/security.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 //
   3 // Security related flags and so on.
   4 //
   5 // Copyright 2018, Michael Ellerman, IBM Corporation.
   6
   7 #include <linux/cpu.h>
   8 #include <linux/kernel.h>
   9 #include <linux/device.h>
  10 #include <linux/seq_buf.h>
  11
  12 #include <asm/asm-prototypes.h>
  13 #include <asm/code-patching.h>
  14 #include <asm/debugfs.h>
  15 #include <asm/security_features.h>
  16 #include <asm/setup.h>
  17
  18
  19 unsigned long powerpc_security_features __read_mostly = SEC_FTR_DEFAULT;
  20
  21 enum count_cache_flush_type {
  22         COUNT_CACHE_FLUSH_NONE  = 0x1,
  23         COUNT_CACHE_FLUSH_SW    = 0x2,
  24         COUNT_CACHE_FLUSH_HW    = 0x4,
  25 };
  26 static enum count_cache_flush_type count_cache_flush_type = COUNT_CACHE_FLUSH_NONE;
  27 static bool link_stack_flush_enabled;
  28
  29 bool barrier_nospec_enabled;
  30 static bool no_nospec;
  31 static bool btb_flush_enabled;
  32 #if defined(CONFIG_PPC_FSL_BOOK3E) || defined(CONFIG_PPC_BOOK3S_64)
  33 static bool no_spectrev2;
  34 #endif
  35
  36 static void enable_barrier_nospec(bool enable)
  37 {
  38         barrier_nospec_enabled = enable;
  39         do_barrier_nospec_fixups(enable);
  40 }
  41
  42 void setup_barrier_nospec(void)
  43 {
  44         bool enable;
  45
  46         /*
  47          * It would make sense to check SEC_FTR_SPEC_BAR_ORI31 below as well.
  48          * But there's a good reason not to. The two flags we check below are
  49          * both are enabled by default in the kernel, so if the hcall is not
  50          * functional they will be enabled.
  51          * On a system where the host firmware has been updated (so the ori
  52          * functions as a barrier), but on which the hypervisor (KVM/Qemu) has
  53          * not been updated, we would like to enable the barrier. Dropping the
  54          * check for SEC_FTR_SPEC_BAR_ORI31 achieves that. The only downside is
  55          * we potentially enable the barrier on systems where the host firmware
  56          * is not updated, but that's harmless as it's a no-op.
  57          */
  58         enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) &&
  59                  security_ftr_enabled(SEC_FTR_BNDS_CHK_SPEC_BAR);
  60
  61         if (!no_nospec && !cpu_mitigations_off())
  62                 enable_barrier_nospec(enable);
  63 }
  64
  65 static int __init handle_nospectre_v1(char *p)
  66 {
  67         no_nospec = true;
  68
  69         return 0;
  70 }
  71 early_param("nospectre_v1", handle_nospectre_v1);
  72
  73 #ifdef CONFIG_DEBUG_FS
  74 static int barrier_nospec_set(void *data, u64 val)
  75 {
  76         switch (val) {
  77         case 0:
  78         case 1:
  79                 break;
  80         default:
  81                 return -EINVAL;
  82         }
  83
  84         if (!!val == !!barrier_nospec_enabled)
  85                 return 0;
  86
  87         enable_barrier_nospec(!!val);
  88
  89         return 0;
  90 }
  91
  92 static int barrier_nospec_get(void *data, u64 *val)
  93 {
  94         *val = barrier_nospec_enabled ? 1 : 0;
  95         return 0;
  96 }
  97
  98 DEFINE_SIMPLE_ATTRIBUTE(fops_barrier_nospec,
  99                         barrier_nospec_get, barrier_nospec_set, "%llu\n");
 100
 101 static __init int barrier_nospec_debugfs_init(void)
 102 {
 103         debugfs_create_file("barrier_nospec", 0600, powerpc_debugfs_root, NULL,
 104                             &fops_barrier_nospec);
 105         return 0;
 106 }
 107 device_initcall(barrier_nospec_debugfs_init);
 108 #endif /* CONFIG_DEBUG_FS */
 109
 110 #if defined(CONFIG_PPC_FSL_BOOK3E) || defined(CONFIG_PPC_BOOK3S_64)
 111 static int __init handle_nospectre_v2(char *p)
 112 {
 113         no_spectrev2 = true;
 114
 115         return 0;
 116 }
 117 early_param("nospectre_v2", handle_nospectre_v2);
 118 #endif /* CONFIG_PPC_FSL_BOOK3E || CONFIG_PPC_BOOK3S_64 */
 119
 120 #ifdef CONFIG_PPC_FSL_BOOK3E
 121 void setup_spectre_v2(void)
 122 {
 123         if (no_spectrev2 || cpu_mitigations_off())
 124                 do_btb_flush_fixups();
 125         else
 126                 btb_flush_enabled = true;
 127 }
 128 #endif /* CONFIG_PPC_FSL_BOOK3E */
 129
 130 #ifdef CONFIG_PPC_BOOK3S_64
 131 ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, char *buf)
 132 {
 133         bool thread_priv;
 134
 135         thread_priv = security_ftr_enabled(SEC_FTR_L1D_THREAD_PRIV);
 136
 137         if (rfi_flush) {
 138                 struct seq_buf s;
 139                 seq_buf_init(&s, buf, PAGE_SIZE - 1);
 140
 141                 seq_buf_printf(&s, "Mitigation: RFI Flush");
 142                 if (thread_priv)
 143                         seq_buf_printf(&s, ", L1D private per thread");
 144
 145                 seq_buf_printf(&s, "\n");
 146
 147                 return s.len;
 148         }
 149
 150         if (thread_priv)
 151                 return sprintf(buf, "Vulnerable: L1D private per thread\n");
 152
 153         if (!security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV) &&
 154             !security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR))
 155                 return sprintf(buf, "Not affected\n");
 156
 157         return sprintf(buf, "Vulnerable\n");
 158 }
 159
 160 ssize_t cpu_show_l1tf(struct device *dev, struct device_attribute *attr, char *buf)
 161 {
 162         return cpu_show_meltdown(dev, attr, buf);
 163 }
 164 #endif
 165
 166 ssize_t cpu_show_spectre_v1(struct device *dev, struct device_attribute *attr, char *buf)
 167 {
 168         struct seq_buf s;
 169
 170         seq_buf_init(&s, buf, PAGE_SIZE - 1);
 171
 172         if (security_ftr_enabled(SEC_FTR_BNDS_CHK_SPEC_BAR)) {
 173                 if (barrier_nospec_enabled)
 174                         seq_buf_printf(&s, "Mitigation: __user pointer sanitization");
 175                 else
 176                         seq_buf_printf(&s, "Vulnerable");
 177
 178                 if (security_ftr_enabled(SEC_FTR_SPEC_BAR_ORI31))
 179                         seq_buf_printf(&s, ", ori31 speculation barrier enabled");
 180
 181                 seq_buf_printf(&s, "\n");
 182         } else
 183                 seq_buf_printf(&s, "Not affected\n");
 184
 185         return s.len;
 186 }
 187
 188 ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr, char *buf)
 189 {
 190         struct seq_buf s;
 191         bool bcs, ccd;
 192
 193         seq_buf_init(&s, buf, PAGE_SIZE - 1);
 194
 195         bcs = security_ftr_enabled(SEC_FTR_BCCTRL_SERIALISED);
 196         ccd = security_ftr_enabled(SEC_FTR_COUNT_CACHE_DISABLED);
 197
 198         if (bcs || ccd) {
 199                 seq_buf_printf(&s, "Mitigation: ");
 200
 201                 if (bcs)
 202                         seq_buf_printf(&s, "Indirect branch serialisation (kernel only)");
 203
 204                 if (bcs && ccd)
 205                         seq_buf_printf(&s, ", ");
 206
 207                 if (ccd)
 208                         seq_buf_printf(&s, "Indirect branch cache disabled");
 209
 210                 if (link_stack_flush_enabled)
 211                         seq_buf_printf(&s, ", Software link stack flush");
 212
 213         } else if (count_cache_flush_type != COUNT_CACHE_FLUSH_NONE) {
 214                 seq_buf_printf(&s, "Mitigation: Software count cache flush");
 215
 216                 if (count_cache_flush_type == COUNT_CACHE_FLUSH_HW)
 217                         seq_buf_printf(&s, " (hardware accelerated)");
 218
 219                 if (link_stack_flush_enabled)
 220                         seq_buf_printf(&s, ", Software link stack flush");
 221
 222         } else if (btb_flush_enabled) {
 223                 seq_buf_printf(&s, "Mitigation: Branch predictor state flush");
 224         } else {
 225                 seq_buf_printf(&s, "Vulnerable");
 226         }
 227
 228         seq_buf_printf(&s, "\n");
 229
 230         return s.len;
 231 }
 232
 233 #ifdef CONFIG_PPC_BOOK3S_64
 234 /*
 235  * Store-forwarding barrier support.
 236  */
 237
 238 static enum stf_barrier_type stf_enabled_flush_types;
 239 static bool no_stf_barrier;
 240 bool stf_barrier;
 241
 242 static int __init handle_no_stf_barrier(char *p)
 243 {
 244         pr_info("stf-barrier: disabled on command line.");
 245         no_stf_barrier = true;
 246         return 0;
 247 }
 248
 249 early_param("no_stf_barrier", handle_no_stf_barrier);
 250
 251 enum stf_barrier_type stf_barrier_type_get(void)
 252 {
 253         return stf_enabled_flush_types;
 254 }
 255
 256 /* This is the generic flag used by other architectures */
 257 static int __init handle_ssbd(char *p)
 258 {
 259         if (!p || strncmp(p, "auto", 5) == 0 || strncmp(p, "on", 2) == 0 ) {
 260                 /* Until firmware tells us, we have the barrier with auto */
 261                 return 0;
 262         } else if (strncmp(p, "off", 3) == 0) {
 263                 handle_no_stf_barrier(NULL);
 264                 return 0;
 265         } else
 266                 return 1;
 267
 268         return 0;
 269 }
 270 early_param("spec_store_bypass_disable", handle_ssbd);
 271
 272 /* This is the generic flag used by other architectures */
 273 static int __init handle_no_ssbd(char *p)
 274 {
 275         handle_no_stf_barrier(NULL);
 276         return 0;
 277 }
 278 early_param("nospec_store_bypass_disable", handle_no_ssbd);
 279
 280 static void stf_barrier_enable(bool enable)
 281 {
 282         if (enable)
 283                 do_stf_barrier_fixups(stf_enabled_flush_types);
 284         else
 285                 do_stf_barrier_fixups(STF_BARRIER_NONE);
 286
 287         stf_barrier = enable;
 288 }
 289
 290 void setup_stf_barrier(void)
 291 {
 292         enum stf_barrier_type type;
 293         bool enable, hv;
 294
 295         hv = cpu_has_feature(CPU_FTR_HVMODE);
 296
 297         /* Default to fallback in case fw-features are not available */
 298         if (cpu_has_feature(CPU_FTR_ARCH_300))
 299                 type = STF_BARRIER_EIEIO;
 300         else if (cpu_has_feature(CPU_FTR_ARCH_207S))
 301                 type = STF_BARRIER_SYNC_ORI;
 302         else if (cpu_has_feature(CPU_FTR_ARCH_206))
 303                 type = STF_BARRIER_FALLBACK;
 304         else
 305                 type = STF_BARRIER_NONE;
 306
 307         enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) &&
 308                 (security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR) ||
 309                  (security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV) && hv));
 310
 311         if (type == STF_BARRIER_FALLBACK) {
 312                 pr_info("stf-barrier: fallback barrier available\n");
 313         } else if (type == STF_BARRIER_SYNC_ORI) {
 314                 pr_info("stf-barrier: hwsync barrier available\n");
 315         } else if (type == STF_BARRIER_EIEIO) {
 316                 pr_info("stf-barrier: eieio barrier available\n");
 317         }
 318
 319         stf_enabled_flush_types = type;
 320
 321         if (!no_stf_barrier && !cpu_mitigations_off())
 322                 stf_barrier_enable(enable);
 323 }
 324
 325 ssize_t cpu_show_spec_store_bypass(struct device *dev, struct device_attribute *attr, char *buf)
 326 {
 327         if (stf_barrier && stf_enabled_flush_types != STF_BARRIER_NONE) {
 328                 const char *type;
 329                 switch (stf_enabled_flush_types) {
 330                 case STF_BARRIER_EIEIO:
 331                         type = "eieio";
 332                         break;
 333                 case STF_BARRIER_SYNC_ORI:
 334                         type = "hwsync";
 335                         break;
 336                 case STF_BARRIER_FALLBACK:
 337                         type = "fallback";
 338                         break;
 339                 default:
 340                         type = "unknown";
 341                 }
 342                 return sprintf(buf, "Mitigation: Kernel entry/exit barrier (%s)\n", type);
 343         }
 344
 345         if (!security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV) &&
 346             !security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR))
 347                 return sprintf(buf, "Not affected\n");
 348
 349         return sprintf(buf, "Vulnerable\n");
 350 }
 351
 352 #ifdef CONFIG_DEBUG_FS
 353 static int stf_barrier_set(void *data, u64 val)
 354 {
 355         bool enable;
 356
 357         if (val == 1)
 358                 enable = true;
 359         else if (val == 0)
 360                 enable = false;
 361         else
 362                 return -EINVAL;
 363
 364         /* Only do anything if we're changing state */
 365         if (enable != stf_barrier)
 366                 stf_barrier_enable(enable);
 367
 368         return 0;
 369 }
 370
 371 static int stf_barrier_get(void *data, u64 *val)
 372 {
 373         *val = stf_barrier ? 1 : 0;
 374         return 0;
 375 }
 376
 377 DEFINE_SIMPLE_ATTRIBUTE(fops_stf_barrier, stf_barrier_get, stf_barrier_set, "%llu\n");
 378
 379 static __init int stf_barrier_debugfs_init(void)
 380 {
 381         debugfs_create_file("stf_barrier", 0600, powerpc_debugfs_root, NULL, &fops_stf_barrier);
 382         return 0;
 383 }
 384 device_initcall(stf_barrier_debugfs_init);
 385 #endif /* CONFIG_DEBUG_FS */
 386
 387 static void no_count_cache_flush(void)
 388 {
 389         count_cache_flush_type = COUNT_CACHE_FLUSH_NONE;
 390         pr_info("count-cache-flush: software flush disabled.\n");
 391 }
 392
 393 static void toggle_count_cache_flush(bool enable)
 394 {
 395         if (!security_ftr_enabled(SEC_FTR_FLUSH_COUNT_CACHE) &&
 396             !security_ftr_enabled(SEC_FTR_FLUSH_LINK_STACK))
 397                 enable = false;
 398
 399         if (!enable) {
 400                 patch_instruction_site(&patch__call_flush_count_cache, PPC_INST_NOP);
 401 #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
 402                 patch_instruction_site(&patch__call_kvm_flush_link_stack, PPC_INST_NOP);
 403 #endif
 404                 pr_info("link-stack-flush: software flush disabled.\n");
 405                 link_stack_flush_enabled = false;
 406                 no_count_cache_flush();
 407                 return;
 408         }
 409
 410         // This enables the branch from _switch to flush_count_cache
 411         patch_branch_site(&patch__call_flush_count_cache,
 412                           (u64)&flush_count_cache, BRANCH_SET_LINK);
 413
 414 #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
 415         // This enables the branch from guest_exit_cont to kvm_flush_link_stack
 416         patch_branch_site(&patch__call_kvm_flush_link_stack,
 417                           (u64)&kvm_flush_link_stack, BRANCH_SET_LINK);
 418 #endif
 419
 420         pr_info("link-stack-flush: software flush enabled.\n");
 421         link_stack_flush_enabled = true;
 422
 423         // If we just need to flush the link stack, patch an early return
 424         if (!security_ftr_enabled(SEC_FTR_FLUSH_COUNT_CACHE)) {
 425                 patch_instruction_site(&patch__flush_link_stack_return, PPC_INST_BLR);
 426                 no_count_cache_flush();
 427                 return;
 428         }
 429
 430         if (!security_ftr_enabled(SEC_FTR_BCCTR_FLUSH_ASSIST)) {
 431                 count_cache_flush_type = COUNT_CACHE_FLUSH_SW;
 432                 pr_info("count-cache-flush: full software flush sequence enabled.\n");
 433                 return;
 434         }
 435
 436         patch_instruction_site(&patch__flush_count_cache_return, PPC_INST_BLR);
 437         count_cache_flush_type = COUNT_CACHE_FLUSH_HW;
 438         pr_info("count-cache-flush: hardware assisted flush sequence enabled\n");
 439 }
 440
 441 void setup_count_cache_flush(void)
 442 {
 443         bool enable = true;
 444
 445         if (no_spectrev2 || cpu_mitigations_off()) {
 446                 if (security_ftr_enabled(SEC_FTR_BCCTRL_SERIALISED) ||
 447                     security_ftr_enabled(SEC_FTR_COUNT_CACHE_DISABLED))
 448                         pr_warn("Spectre v2 mitigations not fully under software control, can't disable\n");
 449
 450                 enable = false;
 451         }
 452
 453         /*
 454          * There's no firmware feature flag/hypervisor bit to tell us we need to
 455          * flush the link stack on context switch. So we set it here if we see
 456          * either of the Spectre v2 mitigations that aim to protect userspace.
 457          */
 458         if (security_ftr_enabled(SEC_FTR_COUNT_CACHE_DISABLED) ||
 459             security_ftr_enabled(SEC_FTR_FLUSH_COUNT_CACHE))
 460                 security_ftr_set(SEC_FTR_FLUSH_LINK_STACK);
 461
 462         toggle_count_cache_flush(enable);
 463 }
 464
 465 #ifdef CONFIG_DEBUG_FS
 466 static int count_cache_flush_set(void *data, u64 val)
 467 {
 468         bool enable;
 469
 470         if (val == 1)
 471                 enable = true;
 472         else if (val == 0)
 473                 enable = false;
 474         else
 475                 return -EINVAL;
 476
 477         toggle_count_cache_flush(enable);
 478
 479         return 0;
 480 }
 481
 482 static int count_cache_flush_get(void *data, u64 *val)
 483 {
 484         if (count_cache_flush_type == COUNT_CACHE_FLUSH_NONE)
 485                 *val = 0;
 486         else
 487                 *val = 1;
 488
 489         return 0;
 490 }
 491
 492 DEFINE_SIMPLE_ATTRIBUTE(fops_count_cache_flush, count_cache_flush_get,
 493                         count_cache_flush_set, "%llu\n");
 494
 495 static __init int count_cache_flush_debugfs_init(void)
 496 {
 497         debugfs_create_file("count_cache_flush", 0600, powerpc_debugfs_root,
 498                             NULL, &fops_count_cache_flush);
 499         return 0;
 500 }
 501 device_initcall(count_cache_flush_debugfs_init);
 502 #endif /* CONFIG_DEBUG_FS */
 503 #endif /* CONFIG_PPC_BOOK3S_64 */