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/debugfs.h>
  10 #include <linux/device.h>
  11 #include <linux/seq_buf.h>
  12
  13 #include <asm/debug.h>
  14 #include <asm/asm-prototypes.h>
  15 #include <asm/code-patching.h>
  16 #include <asm/security_features.h>
  17 #include <asm/setup.h>
  18
  19
  20 unsigned long powerpc_security_features __read_mostly = SEC_FTR_DEFAULT;
  21
  22 enum count_cache_flush_type {
  23         COUNT_CACHE_FLUSH_NONE  = 0x1,
  24         COUNT_CACHE_FLUSH_SW    = 0x2,
  25         COUNT_CACHE_FLUSH_HW    = 0x4,
  26 };
  27 static enum count_cache_flush_type count_cache_flush_type = COUNT_CACHE_FLUSH_NONE;
  28 static bool link_stack_flush_enabled;
  29
  30 bool barrier_nospec_enabled;
  31 static bool no_nospec;
  32 static bool btb_flush_enabled;
  33 #if defined(CONFIG_PPC_FSL_BOOK3E) || defined(CONFIG_PPC_BOOK3S_64)
  34 static bool no_spectrev2;
  35 #endif
  36
  37 static void enable_barrier_nospec(bool enable)
  38 {
  39         barrier_nospec_enabled = enable;
  40         do_barrier_nospec_fixups(enable);
  41 }
  42
  43 void setup_barrier_nospec(void)
  44 {
  45         bool enable;
  46
  47         /*
  48          * It would make sense to check SEC_FTR_SPEC_BAR_ORI31 below as well.
  49          * But there's a good reason not to. The two flags we check below are
  50          * both are enabled by default in the kernel, so if the hcall is not
  51          * functional they will be enabled.
  52          * On a system where the host firmware has been updated (so the ori
  53          * functions as a barrier), but on which the hypervisor (KVM/Qemu) has
  54          * not been updated, we would like to enable the barrier. Dropping the
  55          * check for SEC_FTR_SPEC_BAR_ORI31 achieves that. The only downside is
  56          * we potentially enable the barrier on systems where the host firmware
  57          * is not updated, but that's harmless as it's a no-op.
  58          */
  59         enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) &&
  60                  security_ftr_enabled(SEC_FTR_BNDS_CHK_SPEC_BAR);
  61
  62         if (!no_nospec)
  63                 enable_barrier_nospec(enable);
  64 }
  65
  66 static int __init handle_nospectre_v1(char *p)
  67 {
  68         no_nospec = true;
  69
  70         return 0;
  71 }
  72 early_param("nospectre_v1", handle_nospectre_v1);
  73
  74 #ifdef CONFIG_DEBUG_FS
  75 static int barrier_nospec_set(void *data, u64 val)
  76 {
  77         switch (val) {
  78         case 0:
  79         case 1:
  80                 break;
  81         default:
  82                 return -EINVAL;
  83         }
  84
  85         if (!!val == !!barrier_nospec_enabled)
  86                 return 0;
  87
  88         enable_barrier_nospec(!!val);
  89
  90         return 0;
  91 }
  92
  93 static int barrier_nospec_get(void *data, u64 *val)
  94 {
  95         *val = barrier_nospec_enabled ? 1 : 0;
  96         return 0;
  97 }
  98
  99 DEFINE_SIMPLE_ATTRIBUTE(fops_barrier_nospec,
 100                         barrier_nospec_get, barrier_nospec_set, "%llu\n");
 101
 102 static __init int barrier_nospec_debugfs_init(void)
 103 {
 104         debugfs_create_file("barrier_nospec", 0600, powerpc_debugfs_root, NULL,
 105                             &fops_barrier_nospec);
 106         return 0;
 107 }
 108 device_initcall(barrier_nospec_debugfs_init);
 109 #endif /* CONFIG_DEBUG_FS */
 110
 111 #if defined(CONFIG_PPC_FSL_BOOK3E) || defined(CONFIG_PPC_BOOK3S_64)
 112 static int __init handle_nospectre_v2(char *p)
 113 {
 114         no_spectrev2 = true;
 115
 116         return 0;
 117 }
 118 early_param("nospectre_v2", handle_nospectre_v2);
 119 #endif /* CONFIG_PPC_FSL_BOOK3E || CONFIG_PPC_BOOK3S_64 */
 120
 121 #ifdef CONFIG_PPC_FSL_BOOK3E
 122 void setup_spectre_v2(void)
 123 {
 124         if (no_spectrev2)
 125                 do_btb_flush_fixups();
 126         else
 127                 btb_flush_enabled = true;
 128 }
 129 #endif /* CONFIG_PPC_FSL_BOOK3E */
 130
 131 #ifdef CONFIG_PPC_BOOK3S_64
 132 ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, char *buf)
 133 {
 134         bool thread_priv;
 135
 136         thread_priv = security_ftr_enabled(SEC_FTR_L1D_THREAD_PRIV);
 137
 138         if (rfi_flush || thread_priv) {
 139                 struct seq_buf s;
 140                 seq_buf_init(&s, buf, PAGE_SIZE - 1);
 141
 142                 seq_buf_printf(&s, "Mitigation: ");
 143
 144                 if (rfi_flush)
 145                         seq_buf_printf(&s, "RFI Flush");
 146
 147                 if (rfi_flush && thread_priv)
 148                         seq_buf_printf(&s, ", ");
 149
 150                 if (thread_priv)
 151                         seq_buf_printf(&s, "L1D private per thread");
 152
 153                 seq_buf_printf(&s, "\n");
 154
 155                 return s.len;
 156         }
 157
 158         if (!security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV) &&
 159             !security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR))
 160                 return sprintf(buf, "Not affected\n");
 161
 162         return sprintf(buf, "Vulnerable\n");
 163 }
 164
 165 ssize_t cpu_show_l1tf(struct device *dev, struct device_attribute *attr, char *buf)
 166 {
 167         return cpu_show_meltdown(dev, attr, buf);
 168 }
 169 #endif
 170
 171 ssize_t cpu_show_spectre_v1(struct device *dev, struct device_attribute *attr, char *buf)
 172 {
 173         struct seq_buf s;
 174
 175         seq_buf_init(&s, buf, PAGE_SIZE - 1);
 176
 177         if (security_ftr_enabled(SEC_FTR_BNDS_CHK_SPEC_BAR)) {
 178                 if (barrier_nospec_enabled)
 179                         seq_buf_printf(&s, "Mitigation: __user pointer sanitization");
 180                 else
 181                         seq_buf_printf(&s, "Vulnerable");
 182
 183                 if (security_ftr_enabled(SEC_FTR_SPEC_BAR_ORI31))
 184                         seq_buf_printf(&s, ", ori31 speculation barrier enabled");
 185
 186                 seq_buf_printf(&s, "\n");
 187         } else
 188                 seq_buf_printf(&s, "Not affected\n");
 189
 190         return s.len;
 191 }
 192
 193 ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr, char *buf)
 194 {
 195         struct seq_buf s;
 196         bool bcs, ccd;
 197
 198         seq_buf_init(&s, buf, PAGE_SIZE - 1);
 199
 200         bcs = security_ftr_enabled(SEC_FTR_BCCTRL_SERIALISED);
 201         ccd = security_ftr_enabled(SEC_FTR_COUNT_CACHE_DISABLED);
 202
 203         if (bcs || ccd) {
 204                 seq_buf_printf(&s, "Mitigation: ");
 205
 206                 if (bcs)
 207                         seq_buf_printf(&s, "Indirect branch serialisation (kernel only)");
 208
 209                 if (bcs && ccd)
 210                         seq_buf_printf(&s, ", ");
 211
 212                 if (ccd)
 213                         seq_buf_printf(&s, "Indirect branch cache disabled");
 214
 215                 if (link_stack_flush_enabled)
 216                         seq_buf_printf(&s, ", Software link stack flush");
 217
 218         } else if (count_cache_flush_type != COUNT_CACHE_FLUSH_NONE) {
 219                 seq_buf_printf(&s, "Mitigation: Software count cache flush");
 220
 221                 if (count_cache_flush_type == COUNT_CACHE_FLUSH_HW)
 222                         seq_buf_printf(&s, " (hardware accelerated)");
 223
 224                 if (link_stack_flush_enabled)
 225                         seq_buf_printf(&s, ", Software link stack flush");
 226
 227         } else if (btb_flush_enabled) {
 228                 seq_buf_printf(&s, "Mitigation: Branch predictor state flush");
 229         } else {
 230                 seq_buf_printf(&s, "Vulnerable");
 231         }
 232
 233         seq_buf_printf(&s, "\n");
 234
 235         return s.len;
 236 }
 237
 238 #ifdef CONFIG_PPC_BOOK3S_64
 239 /*
 240  * Store-forwarding barrier support.
 241  */
 242
 243 static enum stf_barrier_type stf_enabled_flush_types;
 244 static bool no_stf_barrier;
 245 bool stf_barrier;
 246
 247 static int __init handle_no_stf_barrier(char *p)
 248 {
 249         pr_info("stf-barrier: disabled on command line.");
 250         no_stf_barrier = true;
 251         return 0;
 252 }
 253
 254 early_param("no_stf_barrier", handle_no_stf_barrier);
 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_207S))
 299                 type = STF_BARRIER_SYNC_ORI;
 300         else if (cpu_has_feature(CPU_FTR_ARCH_206))
 301                 type = STF_BARRIER_FALLBACK;
 302         else
 303                 type = STF_BARRIER_NONE;
 304
 305         enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) &&
 306                 (security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR) ||
 307                  (security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV) && hv));
 308
 309         if (type == STF_BARRIER_FALLBACK) {
 310                 pr_info("stf-barrier: fallback barrier available\n");
 311         } else if (type == STF_BARRIER_SYNC_ORI) {
 312                 pr_info("stf-barrier: hwsync barrier available\n");
 313         } else if (type == STF_BARRIER_EIEIO) {
 314                 pr_info("stf-barrier: eieio barrier available\n");
 315         }
 316
 317         stf_enabled_flush_types = type;
 318
 319         if (!no_stf_barrier)
 320                 stf_barrier_enable(enable);
 321 }
 322
 323 ssize_t cpu_show_spec_store_bypass(struct device *dev, struct device_attribute *attr, char *buf)
 324 {
 325         if (stf_barrier && stf_enabled_flush_types != STF_BARRIER_NONE) {
 326                 const char *type;
 327                 switch (stf_enabled_flush_types) {
 328                 case STF_BARRIER_EIEIO:
 329                         type = "eieio";
 330                         break;
 331                 case STF_BARRIER_SYNC_ORI:
 332                         type = "hwsync";
 333                         break;
 334                 case STF_BARRIER_FALLBACK:
 335                         type = "fallback";
 336                         break;
 337                 default:
 338                         type = "unknown";
 339                 }
 340                 return sprintf(buf, "Mitigation: Kernel entry/exit barrier (%s)\n", type);
 341         }
 342
 343         if (!security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV) &&
 344             !security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR))
 345                 return sprintf(buf, "Not affected\n");
 346
 347         return sprintf(buf, "Vulnerable\n");
 348 }
 349
 350 #ifdef CONFIG_DEBUG_FS
 351 static int stf_barrier_set(void *data, u64 val)
 352 {
 353         bool enable;
 354
 355         if (val == 1)
 356                 enable = true;
 357         else if (val == 0)
 358                 enable = false;
 359         else
 360                 return -EINVAL;
 361
 362         /* Only do anything if we're changing state */
 363         if (enable != stf_barrier)
 364                 stf_barrier_enable(enable);
 365
 366         return 0;
 367 }
 368
 369 static int stf_barrier_get(void *data, u64 *val)
 370 {
 371         *val = stf_barrier ? 1 : 0;
 372         return 0;
 373 }
 374
 375 DEFINE_SIMPLE_ATTRIBUTE(fops_stf_barrier, stf_barrier_get, stf_barrier_set, "%llu\n");
 376
 377 static __init int stf_barrier_debugfs_init(void)
 378 {
 379         debugfs_create_file("stf_barrier", 0600, powerpc_debugfs_root, NULL, &fops_stf_barrier);
 380         return 0;
 381 }
 382 device_initcall(stf_barrier_debugfs_init);
 383 #endif /* CONFIG_DEBUG_FS */
 384
 385 static void no_count_cache_flush(void)
 386 {
 387         count_cache_flush_type = COUNT_CACHE_FLUSH_NONE;
 388         pr_info("count-cache-flush: software flush disabled.\n");
 389 }
 390
 391 static void toggle_count_cache_flush(bool enable)
 392 {
 393         if (!security_ftr_enabled(SEC_FTR_FLUSH_COUNT_CACHE) &&
 394             !security_ftr_enabled(SEC_FTR_FLUSH_LINK_STACK))
 395                 enable = false;
 396
 397         if (!enable) {
 398                 patch_instruction_site(&patch__call_flush_count_cache, PPC_INST_NOP);
 399 #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
 400                 patch_instruction_site(&patch__call_kvm_flush_link_stack, PPC_INST_NOP);
 401 #endif
 402                 pr_info("link-stack-flush: software flush disabled.\n");
 403                 link_stack_flush_enabled = false;
 404                 no_count_cache_flush();
 405                 return;
 406         }
 407
 408         // This enables the branch from _switch to flush_count_cache
 409         patch_branch_site(&patch__call_flush_count_cache,
 410                           (u64)&flush_count_cache, BRANCH_SET_LINK);
 411
 412 #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
 413         // This enables the branch from guest_exit_cont to kvm_flush_link_stack
 414         patch_branch_site(&patch__call_kvm_flush_link_stack,
 415                           (u64)&kvm_flush_link_stack, BRANCH_SET_LINK);
 416 #endif
 417
 418         pr_info("link-stack-flush: software flush enabled.\n");
 419         link_stack_flush_enabled = true;
 420
 421         // If we just need to flush the link stack, patch an early return
 422         if (!security_ftr_enabled(SEC_FTR_FLUSH_COUNT_CACHE)) {
 423                 patch_instruction_site(&patch__flush_link_stack_return, PPC_INST_BLR);
 424                 no_count_cache_flush();
 425                 return;
 426         }
 427
 428         if (!security_ftr_enabled(SEC_FTR_BCCTR_FLUSH_ASSIST)) {
 429                 count_cache_flush_type = COUNT_CACHE_FLUSH_SW;
 430                 pr_info("count-cache-flush: full software flush sequence enabled.\n");
 431                 return;
 432         }
 433
 434         patch_instruction_site(&patch__flush_count_cache_return, PPC_INST_BLR);
 435         count_cache_flush_type = COUNT_CACHE_FLUSH_HW;
 436         pr_info("count-cache-flush: hardware assisted flush sequence enabled\n");
 437 }
 438
 439 void setup_count_cache_flush(void)
 440 {
 441         bool enable = true;
 442
 443         if (no_spectrev2 || cpu_mitigations_off()) {
 444                 if (security_ftr_enabled(SEC_FTR_BCCTRL_SERIALISED) ||
 445                     security_ftr_enabled(SEC_FTR_COUNT_CACHE_DISABLED))
 446                         pr_warn("Spectre v2 mitigations not fully under software control, can't disable\n");
 447
 448                 enable = false;
 449         }
 450
 451         /*
 452          * There's no firmware feature flag/hypervisor bit to tell us we need to
 453          * flush the link stack on context switch. So we set it here if we see
 454          * either of the Spectre v2 mitigations that aim to protect userspace.
 455          */
 456         if (security_ftr_enabled(SEC_FTR_COUNT_CACHE_DISABLED) ||
 457             security_ftr_enabled(SEC_FTR_FLUSH_COUNT_CACHE))
 458                 security_ftr_set(SEC_FTR_FLUSH_LINK_STACK);
 459
 460         toggle_count_cache_flush(enable);
 461 }
 462
 463 #ifdef CONFIG_DEBUG_FS
 464 static int count_cache_flush_set(void *data, u64 val)
 465 {
 466         bool enable;
 467
 468         if (val == 1)
 469                 enable = true;
 470         else if (val == 0)
 471                 enable = false;
 472         else
 473                 return -EINVAL;
 474
 475         toggle_count_cache_flush(enable);
 476
 477         return 0;
 478 }
 479
 480 static int count_cache_flush_get(void *data, u64 *val)
 481 {
 482         if (count_cache_flush_type == COUNT_CACHE_FLUSH_NONE)
 483                 *val = 0;
 484         else
 485                 *val = 1;
 486
 487         return 0;
 488 }
 489
 490 DEFINE_SIMPLE_ATTRIBUTE(fops_count_cache_flush, count_cache_flush_get,
 491                         count_cache_flush_set, "%llu\n");
 492
 493 static __init int count_cache_flush_debugfs_init(void)
 494 {
 495         debugfs_create_file("count_cache_flush", 0600, powerpc_debugfs_root,
 496                             NULL, &fops_count_cache_flush);
 497         return 0;
 498 }
 499 device_initcall(count_cache_flush_debugfs_init);
 500 #endif /* CONFIG_DEBUG_FS */
 501 #endif /* CONFIG_PPC_BOOK3S_64 */