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 u64 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_DEBUGFS_ATTRIBUTE(fops_barrier_nospec, barrier_nospec_get,
  99                          barrier_nospec_set, "%llu\n");
 100
 101 static __init int barrier_nospec_debugfs_init(void)
 102 {
 103         debugfs_create_file_unsafe("barrier_nospec", 0600,
 104                                    powerpc_debugfs_root, NULL,
 105                                    &fops_barrier_nospec);
 106         return 0;
 107 }
 108 device_initcall(barrier_nospec_debugfs_init);
 109
 110 static __init int security_feature_debugfs_init(void)
 111 {
 112         debugfs_create_x64("security_features", 0400, powerpc_debugfs_root,
 113                            &powerpc_security_features);
 114         return 0;
 115 }
 116 device_initcall(security_feature_debugfs_init);
 117 #endif /* CONFIG_DEBUG_FS */
 118
 119 #if defined(CONFIG_PPC_FSL_BOOK3E) || defined(CONFIG_PPC_BOOK3S_64)
 120 static int __init handle_nospectre_v2(char *p)
 121 {
 122         no_spectrev2 = true;
 123
 124         return 0;
 125 }
 126 early_param("nospectre_v2", handle_nospectre_v2);
 127 #endif /* CONFIG_PPC_FSL_BOOK3E || CONFIG_PPC_BOOK3S_64 */
 128
 129 #ifdef CONFIG_PPC_FSL_BOOK3E
 130 void setup_spectre_v2(void)
 131 {
 132         if (no_spectrev2 || cpu_mitigations_off())
 133                 do_btb_flush_fixups();
 134         else
 135                 btb_flush_enabled = true;
 136 }
 137 #endif /* CONFIG_PPC_FSL_BOOK3E */
 138
 139 #ifdef CONFIG_PPC_BOOK3S_64
 140 ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, char *buf)
 141 {
 142         bool thread_priv;
 143
 144         thread_priv = security_ftr_enabled(SEC_FTR_L1D_THREAD_PRIV);
 145
 146         if (rfi_flush) {
 147                 struct seq_buf s;
 148                 seq_buf_init(&s, buf, PAGE_SIZE - 1);
 149
 150                 seq_buf_printf(&s, "Mitigation: RFI Flush");
 151                 if (thread_priv)
 152                         seq_buf_printf(&s, ", L1D private per thread");
 153
 154                 seq_buf_printf(&s, "\n");
 155
 156                 return s.len;
 157         }
 158
 159         if (thread_priv)
 160                 return sprintf(buf, "Vulnerable: L1D private per thread\n");
 161
 162         if (!security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV) &&
 163             !security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR))
 164                 return sprintf(buf, "Not affected\n");
 165
 166         return sprintf(buf, "Vulnerable\n");
 167 }
 168
 169 ssize_t cpu_show_l1tf(struct device *dev, struct device_attribute *attr, char *buf)
 170 {
 171         return cpu_show_meltdown(dev, attr, buf);
 172 }
 173 #endif
 174
 175 ssize_t cpu_show_spectre_v1(struct device *dev, struct device_attribute *attr, char *buf)
 176 {
 177         struct seq_buf s;
 178
 179         seq_buf_init(&s, buf, PAGE_SIZE - 1);
 180
 181         if (security_ftr_enabled(SEC_FTR_BNDS_CHK_SPEC_BAR)) {
 182                 if (barrier_nospec_enabled)
 183                         seq_buf_printf(&s, "Mitigation: __user pointer sanitization");
 184                 else
 185                         seq_buf_printf(&s, "Vulnerable");
 186
 187                 if (security_ftr_enabled(SEC_FTR_SPEC_BAR_ORI31))
 188                         seq_buf_printf(&s, ", ori31 speculation barrier enabled");
 189
 190                 seq_buf_printf(&s, "\n");
 191         } else
 192                 seq_buf_printf(&s, "Not affected\n");
 193
 194         return s.len;
 195 }
 196
 197 ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr, char *buf)
 198 {
 199         struct seq_buf s;
 200         bool bcs, ccd;
 201
 202         seq_buf_init(&s, buf, PAGE_SIZE - 1);
 203
 204         bcs = security_ftr_enabled(SEC_FTR_BCCTRL_SERIALISED);
 205         ccd = security_ftr_enabled(SEC_FTR_COUNT_CACHE_DISABLED);
 206
 207         if (bcs || ccd) {
 208                 seq_buf_printf(&s, "Mitigation: ");
 209
 210                 if (bcs)
 211                         seq_buf_printf(&s, "Indirect branch serialisation (kernel only)");
 212
 213                 if (bcs && ccd)
 214                         seq_buf_printf(&s, ", ");
 215
 216                 if (ccd)
 217                         seq_buf_printf(&s, "Indirect branch cache disabled");
 218
 219                 if (link_stack_flush_enabled)
 220                         seq_buf_printf(&s, ", Software link stack flush");
 221
 222         } else if (count_cache_flush_type != COUNT_CACHE_FLUSH_NONE) {
 223                 seq_buf_printf(&s, "Mitigation: Software count cache flush");
 224
 225                 if (count_cache_flush_type == COUNT_CACHE_FLUSH_HW)
 226                         seq_buf_printf(&s, " (hardware accelerated)");
 227
 228                 if (link_stack_flush_enabled)
 229                         seq_buf_printf(&s, ", Software link stack flush");
 230
 231         } else if (btb_flush_enabled) {
 232                 seq_buf_printf(&s, "Mitigation: Branch predictor state flush");
 233         } else {
 234                 seq_buf_printf(&s, "Vulnerable");
 235         }
 236
 237         seq_buf_printf(&s, "\n");
 238
 239         return s.len;
 240 }
 241
 242 #ifdef CONFIG_PPC_BOOK3S_64
 243 /*
 244  * Store-forwarding barrier support.
 245  */
 246
 247 static enum stf_barrier_type stf_enabled_flush_types;
 248 static bool no_stf_barrier;
 249 bool stf_barrier;
 250
 251 static int __init handle_no_stf_barrier(char *p)
 252 {
 253         pr_info("stf-barrier: disabled on command line.");
 254         no_stf_barrier = true;
 255         return 0;
 256 }
 257
 258 early_param("no_stf_barrier", handle_no_stf_barrier);
 259
 260 /* This is the generic flag used by other architectures */
 261 static int __init handle_ssbd(char *p)
 262 {
 263         if (!p || strncmp(p, "auto", 5) == 0 || strncmp(p, "on", 2) == 0 ) {
 264                 /* Until firmware tells us, we have the barrier with auto */
 265                 return 0;
 266         } else if (strncmp(p, "off", 3) == 0) {
 267                 handle_no_stf_barrier(NULL);
 268                 return 0;
 269         } else
 270                 return 1;
 271
 272         return 0;
 273 }
 274 early_param("spec_store_bypass_disable", handle_ssbd);
 275
 276 /* This is the generic flag used by other architectures */
 277 static int __init handle_no_ssbd(char *p)
 278 {
 279         handle_no_stf_barrier(NULL);
 280         return 0;
 281 }
 282 early_param("nospec_store_bypass_disable", handle_no_ssbd);
 283
 284 static void stf_barrier_enable(bool enable)
 285 {
 286         if (enable)
 287                 do_stf_barrier_fixups(stf_enabled_flush_types);
 288         else
 289                 do_stf_barrier_fixups(STF_BARRIER_NONE);
 290
 291         stf_barrier = enable;
 292 }
 293
 294 void setup_stf_barrier(void)
 295 {
 296         enum stf_barrier_type type;
 297         bool enable, hv;
 298
 299         hv = cpu_has_feature(CPU_FTR_HVMODE);
 300
 301         /* Default to fallback in case fw-features are not available */
 302         if (cpu_has_feature(CPU_FTR_ARCH_300))
 303                 type = STF_BARRIER_EIEIO;
 304         else if (cpu_has_feature(CPU_FTR_ARCH_207S))
 305                 type = STF_BARRIER_SYNC_ORI;
 306         else if (cpu_has_feature(CPU_FTR_ARCH_206))
 307                 type = STF_BARRIER_FALLBACK;
 308         else
 309                 type = STF_BARRIER_NONE;
 310
 311         enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) &&
 312                 (security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR) ||
 313                  (security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV) && hv));
 314
 315         if (type == STF_BARRIER_FALLBACK) {
 316                 pr_info("stf-barrier: fallback barrier available\n");
 317         } else if (type == STF_BARRIER_SYNC_ORI) {
 318                 pr_info("stf-barrier: hwsync barrier available\n");
 319         } else if (type == STF_BARRIER_EIEIO) {
 320                 pr_info("stf-barrier: eieio barrier available\n");
 321         }
 322
 323         stf_enabled_flush_types = type;
 324
 325         if (!no_stf_barrier && !cpu_mitigations_off())
 326                 stf_barrier_enable(enable);
 327 }
 328
 329 ssize_t cpu_show_spec_store_bypass(struct device *dev, struct device_attribute *attr, char *buf)
 330 {
 331         if (stf_barrier && stf_enabled_flush_types != STF_BARRIER_NONE) {
 332                 const char *type;
 333                 switch (stf_enabled_flush_types) {
 334                 case STF_BARRIER_EIEIO:
 335                         type = "eieio";
 336                         break;
 337                 case STF_BARRIER_SYNC_ORI:
 338                         type = "hwsync";
 339                         break;
 340                 case STF_BARRIER_FALLBACK:
 341                         type = "fallback";
 342                         break;
 343                 default:
 344                         type = "unknown";
 345                 }
 346                 return sprintf(buf, "Mitigation: Kernel entry/exit barrier (%s)\n", type);
 347         }
 348
 349         if (!security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV) &&
 350             !security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR))
 351                 return sprintf(buf, "Not affected\n");
 352
 353         return sprintf(buf, "Vulnerable\n");
 354 }
 355
 356 #ifdef CONFIG_DEBUG_FS
 357 static int stf_barrier_set(void *data, u64 val)
 358 {
 359         bool enable;
 360
 361         if (val == 1)
 362                 enable = true;
 363         else if (val == 0)
 364                 enable = false;
 365         else
 366                 return -EINVAL;
 367
 368         /* Only do anything if we're changing state */
 369         if (enable != stf_barrier)
 370                 stf_barrier_enable(enable);
 371
 372         return 0;
 373 }
 374
 375 static int stf_barrier_get(void *data, u64 *val)
 376 {
 377         *val = stf_barrier ? 1 : 0;
 378         return 0;
 379 }
 380
 381 DEFINE_DEBUGFS_ATTRIBUTE(fops_stf_barrier, stf_barrier_get, stf_barrier_set,
 382                          "%llu\n");
 383
 384 static __init int stf_barrier_debugfs_init(void)
 385 {
 386         debugfs_create_file_unsafe("stf_barrier", 0600, powerpc_debugfs_root,
 387                                    NULL, &fops_stf_barrier);
 388         return 0;
 389 }
 390 device_initcall(stf_barrier_debugfs_init);
 391 #endif /* CONFIG_DEBUG_FS */
 392
 393 static void no_count_cache_flush(void)
 394 {
 395         count_cache_flush_type = COUNT_CACHE_FLUSH_NONE;
 396         pr_info("count-cache-flush: software flush disabled.\n");
 397 }
 398
 399 static void toggle_count_cache_flush(bool enable)
 400 {
 401         if (!security_ftr_enabled(SEC_FTR_FLUSH_COUNT_CACHE) &&
 402             !security_ftr_enabled(SEC_FTR_FLUSH_LINK_STACK))
 403                 enable = false;
 404
 405         if (!enable) {
 406                 patch_instruction_site(&patch__call_flush_count_cache, PPC_INST_NOP);
 407 #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
 408                 patch_instruction_site(&patch__call_kvm_flush_link_stack, PPC_INST_NOP);
 409 #endif
 410                 pr_info("link-stack-flush: software flush disabled.\n");
 411                 link_stack_flush_enabled = false;
 412                 no_count_cache_flush();
 413                 return;
 414         }
 415
 416         // This enables the branch from _switch to flush_count_cache
 417         patch_branch_site(&patch__call_flush_count_cache,
 418                           (u64)&flush_count_cache, BRANCH_SET_LINK);
 419
 420 #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
 421         // This enables the branch from guest_exit_cont to kvm_flush_link_stack
 422         patch_branch_site(&patch__call_kvm_flush_link_stack,
 423                           (u64)&kvm_flush_link_stack, BRANCH_SET_LINK);
 424 #endif
 425
 426         pr_info("link-stack-flush: software flush enabled.\n");
 427         link_stack_flush_enabled = true;
 428
 429         // If we just need to flush the link stack, patch an early return
 430         if (!security_ftr_enabled(SEC_FTR_FLUSH_COUNT_CACHE)) {
 431                 patch_instruction_site(&patch__flush_link_stack_return, PPC_INST_BLR);
 432                 no_count_cache_flush();
 433                 return;
 434         }
 435
 436         if (!security_ftr_enabled(SEC_FTR_BCCTR_FLUSH_ASSIST)) {
 437                 count_cache_flush_type = COUNT_CACHE_FLUSH_SW;
 438                 pr_info("count-cache-flush: full software flush sequence enabled.\n");
 439                 return;
 440         }
 441
 442         patch_instruction_site(&patch__flush_count_cache_return, PPC_INST_BLR);
 443         count_cache_flush_type = COUNT_CACHE_FLUSH_HW;
 444         pr_info("count-cache-flush: hardware assisted flush sequence enabled\n");
 445 }
 446
 447 void setup_count_cache_flush(void)
 448 {
 449         bool enable = true;
 450
 451         if (no_spectrev2 || cpu_mitigations_off()) {
 452                 if (security_ftr_enabled(SEC_FTR_BCCTRL_SERIALISED) ||
 453                     security_ftr_enabled(SEC_FTR_COUNT_CACHE_DISABLED))
 454                         pr_warn("Spectre v2 mitigations not fully under software control, can't disable\n");
 455
 456                 enable = false;
 457         }
 458
 459         /*
 460          * There's no firmware feature flag/hypervisor bit to tell us we need to
 461          * flush the link stack on context switch. So we set it here if we see
 462          * either of the Spectre v2 mitigations that aim to protect userspace.
 463          */
 464         if (security_ftr_enabled(SEC_FTR_COUNT_CACHE_DISABLED) ||
 465             security_ftr_enabled(SEC_FTR_FLUSH_COUNT_CACHE))
 466                 security_ftr_set(SEC_FTR_FLUSH_LINK_STACK);
 467
 468         toggle_count_cache_flush(enable);
 469 }
 470
 471 #ifdef CONFIG_DEBUG_FS
 472 static int count_cache_flush_set(void *data, u64 val)
 473 {
 474         bool enable;
 475
 476         if (val == 1)
 477                 enable = true;
 478         else if (val == 0)
 479                 enable = false;
 480         else
 481                 return -EINVAL;
 482
 483         toggle_count_cache_flush(enable);
 484
 485         return 0;
 486 }
 487
 488 static int count_cache_flush_get(void *data, u64 *val)
 489 {
 490         if (count_cache_flush_type == COUNT_CACHE_FLUSH_NONE)
 491                 *val = 0;
 492         else
 493                 *val = 1;
 494
 495         return 0;
 496 }
 497
 498 DEFINE_DEBUGFS_ATTRIBUTE(fops_count_cache_flush, count_cache_flush_get,
 499                          count_cache_flush_set, "%llu\n");
 500
 501 static __init int count_cache_flush_debugfs_init(void)
 502 {
 503         debugfs_create_file_unsafe("count_cache_flush", 0600,
 504                                    powerpc_debugfs_root, NULL,
 505                                    &fops_count_cache_flush);
 506         return 0;
 507 }
 508 device_initcall(count_cache_flush_debugfs_init);
 509 #endif /* CONFIG_DEBUG_FS */
 510 #endif /* CONFIG_PPC_BOOK3S_64 */