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/asm-prototypes.h>
  14 #include <asm/code-patching.h>
  15 #include <asm/debug.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_300))
 295                 type = STF_BARRIER_EIEIO;
 296         else if (cpu_has_feature(CPU_FTR_ARCH_207S))
 297                 type = STF_BARRIER_SYNC_ORI;
 298         else if (cpu_has_feature(CPU_FTR_ARCH_206))
 299                 type = STF_BARRIER_FALLBACK;
 300         else
 301                 type = STF_BARRIER_NONE;
 302
 303         enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) &&
 304                 (security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR) ||
 305                  (security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV) && hv));
 306
 307         if (type == STF_BARRIER_FALLBACK) {
 308                 pr_info("stf-barrier: fallback barrier available\n");
 309         } else if (type == STF_BARRIER_SYNC_ORI) {
 310                 pr_info("stf-barrier: hwsync barrier available\n");
 311         } else if (type == STF_BARRIER_EIEIO) {
 312                 pr_info("stf-barrier: eieio barrier available\n");
 313         }
 314
 315         stf_enabled_flush_types = type;
 316
 317         if (!no_stf_barrier)
 318                 stf_barrier_enable(enable);
 319 }
 320
 321 ssize_t cpu_show_spec_store_bypass(struct device *dev, struct device_attribute *attr, char *buf)
 322 {
 323         if (stf_barrier && stf_enabled_flush_types != STF_BARRIER_NONE) {
 324                 const char *type;
 325                 switch (stf_enabled_flush_types) {
 326                 case STF_BARRIER_EIEIO:
 327                         type = "eieio";
 328                         break;
 329                 case STF_BARRIER_SYNC_ORI:
 330                         type = "hwsync";
 331                         break;
 332                 case STF_BARRIER_FALLBACK:
 333                         type = "fallback";
 334                         break;
 335                 default:
 336                         type = "unknown";
 337                 }
 338                 return sprintf(buf, "Mitigation: Kernel entry/exit barrier (%s)\n", type);
 339         }
 340
 341         if (!security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV) &&
 342             !security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR))
 343                 return sprintf(buf, "Not affected\n");
 344
 345         return sprintf(buf, "Vulnerable\n");
 346 }
 347
 348 #ifdef CONFIG_DEBUG_FS
 349 static int stf_barrier_set(void *data, u64 val)
 350 {
 351         bool enable;
 352
 353         if (val == 1)
 354                 enable = true;
 355         else if (val == 0)
 356                 enable = false;
 357         else
 358                 return -EINVAL;
 359
 360         /* Only do anything if we're changing state */
 361         if (enable != stf_barrier)
 362                 stf_barrier_enable(enable);
 363
 364         return 0;
 365 }
 366
 367 static int stf_barrier_get(void *data, u64 *val)
 368 {
 369         *val = stf_barrier ? 1 : 0;
 370         return 0;
 371 }
 372
 373 DEFINE_SIMPLE_ATTRIBUTE(fops_stf_barrier, stf_barrier_get, stf_barrier_set, "%llu\n");
 374
 375 static __init int stf_barrier_debugfs_init(void)
 376 {
 377         debugfs_create_file("stf_barrier", 0600, powerpc_debugfs_root, NULL, &fops_stf_barrier);
 378         return 0;
 379 }
 380 device_initcall(stf_barrier_debugfs_init);
 381 #endif /* CONFIG_DEBUG_FS */
 382
 383 static void no_count_cache_flush(void)
 384 {
 385         count_cache_flush_type = COUNT_CACHE_FLUSH_NONE;
 386         pr_info("count-cache-flush: software flush disabled.\n");
 387 }
 388
 389 static void toggle_count_cache_flush(bool enable)
 390 {
 391         if (!security_ftr_enabled(SEC_FTR_FLUSH_COUNT_CACHE) &&
 392             !security_ftr_enabled(SEC_FTR_FLUSH_LINK_STACK))
 393                 enable = false;
 394
 395         if (!enable) {
 396                 patch_instruction_site(&patch__call_flush_count_cache, PPC_INST_NOP);
 397 #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
 398                 patch_instruction_site(&patch__call_kvm_flush_link_stack, PPC_INST_NOP);
 399 #endif
 400                 pr_info("link-stack-flush: software flush disabled.\n");
 401                 link_stack_flush_enabled = false;
 402                 no_count_cache_flush();
 403                 return;
 404         }
 405
 406         // This enables the branch from _switch to flush_count_cache
 407         patch_branch_site(&patch__call_flush_count_cache,
 408                           (u64)&flush_count_cache, BRANCH_SET_LINK);
 409
 410 #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
 411         // This enables the branch from guest_exit_cont to kvm_flush_link_stack
 412         patch_branch_site(&patch__call_kvm_flush_link_stack,
 413                           (u64)&kvm_flush_link_stack, BRANCH_SET_LINK);
 414 #endif
 415
 416         pr_info("link-stack-flush: software flush enabled.\n");
 417         link_stack_flush_enabled = true;
 418
 419         // If we just need to flush the link stack, patch an early return
 420         if (!security_ftr_enabled(SEC_FTR_FLUSH_COUNT_CACHE)) {
 421                 patch_instruction_site(&patch__flush_link_stack_return, PPC_INST_BLR);
 422                 no_count_cache_flush();
 423                 return;
 424         }
 425
 426         if (!security_ftr_enabled(SEC_FTR_BCCTR_FLUSH_ASSIST)) {
 427                 count_cache_flush_type = COUNT_CACHE_FLUSH_SW;
 428                 pr_info("count-cache-flush: full software flush sequence enabled.\n");
 429                 return;
 430         }
 431
 432         patch_instruction_site(&patch__flush_count_cache_return, PPC_INST_BLR);
 433         count_cache_flush_type = COUNT_CACHE_FLUSH_HW;
 434         pr_info("count-cache-flush: hardware assisted flush sequence enabled\n");
 435 }
 436
 437 void setup_count_cache_flush(void)
 438 {
 439         bool enable = true;
 440
 441         if (no_spectrev2 || cpu_mitigations_off()) {
 442                 if (security_ftr_enabled(SEC_FTR_BCCTRL_SERIALISED) ||
 443                     security_ftr_enabled(SEC_FTR_COUNT_CACHE_DISABLED))
 444                         pr_warn("Spectre v2 mitigations not fully under software control, can't disable\n");
 445
 446                 enable = false;
 447         }
 448
 449         /*
 450          * There's no firmware feature flag/hypervisor bit to tell us we need to
 451          * flush the link stack on context switch. So we set it here if we see
 452          * either of the Spectre v2 mitigations that aim to protect userspace.
 453          */
 454         if (security_ftr_enabled(SEC_FTR_COUNT_CACHE_DISABLED) ||
 455             security_ftr_enabled(SEC_FTR_FLUSH_COUNT_CACHE))
 456                 security_ftr_set(SEC_FTR_FLUSH_LINK_STACK);
 457
 458         toggle_count_cache_flush(enable);
 459 }
 460
 461 #ifdef CONFIG_DEBUG_FS
 462 static int count_cache_flush_set(void *data, u64 val)
 463 {
 464         bool enable;
 465
 466         if (val == 1)
 467                 enable = true;
 468         else if (val == 0)
 469                 enable = false;
 470         else
 471                 return -EINVAL;
 472
 473         toggle_count_cache_flush(enable);
 474
 475         return 0;
 476 }
 477
 478 static int count_cache_flush_get(void *data, u64 *val)
 479 {
 480         if (count_cache_flush_type == COUNT_CACHE_FLUSH_NONE)
 481                 *val = 0;
 482         else
 483                 *val = 1;
 484
 485         return 0;
 486 }
 487
 488 DEFINE_SIMPLE_ATTRIBUTE(fops_count_cache_flush, count_cache_flush_get,
 489                         count_cache_flush_set, "%llu\n");
 490
 491 static __init int count_cache_flush_debugfs_init(void)
 492 {
 493         debugfs_create_file("count_cache_flush", 0600, powerpc_debugfs_root,
 494                             NULL, &fops_count_cache_flush);
 495         return 0;
 496 }
 497 device_initcall(count_cache_flush_debugfs_init);
 498 #endif /* CONFIG_DEBUG_FS */
 499 #endif /* CONFIG_PPC_BOOK3S_64 */