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