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 #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 /* This is the generic flag used by other architectures */
 252 static int __init handle_ssbd(char *p)
 253 {
 254         if (!p || strncmp(p, "auto", 5) == 0 || strncmp(p, "on", 2) == 0 ) {
 255                 /* Until firmware tells us, we have the barrier with auto */
 256                 return 0;
 257         } else if (strncmp(p, "off", 3) == 0) {
 258                 handle_no_stf_barrier(NULL);
 259                 return 0;
 260         } else
 261                 return 1;
 262
 263         return 0;
 264 }
 265 early_param("spec_store_bypass_disable", handle_ssbd);
 266
 267 /* This is the generic flag used by other architectures */
 268 static int __init handle_no_ssbd(char *p)
 269 {
 270         handle_no_stf_barrier(NULL);
 271         return 0;
 272 }
 273 early_param("nospec_store_bypass_disable", handle_no_ssbd);
 274
 275 static void stf_barrier_enable(bool enable)
 276 {
 277         if (enable)
 278                 do_stf_barrier_fixups(stf_enabled_flush_types);
 279         else
 280                 do_stf_barrier_fixups(STF_BARRIER_NONE);
 281
 282         stf_barrier = enable;
 283 }
 284
 285 void setup_stf_barrier(void)
 286 {
 287         enum stf_barrier_type type;
 288         bool enable, hv;
 289
 290         hv = cpu_has_feature(CPU_FTR_HVMODE);
 291
 292         /* Default to fallback in case fw-features are not available */
 293         if (cpu_has_feature(CPU_FTR_ARCH_207S))
 294                 type = STF_BARRIER_SYNC_ORI;
 295         else if (cpu_has_feature(CPU_FTR_ARCH_206))
 296                 type = STF_BARRIER_FALLBACK;
 297         else
 298                 type = STF_BARRIER_NONE;
 299
 300         enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) &&
 301                 (security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR) ||
 302                  (security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV) && hv));
 303
 304         if (type == STF_BARRIER_FALLBACK) {
 305                 pr_info("stf-barrier: fallback barrier available\n");
 306         } else if (type == STF_BARRIER_SYNC_ORI) {
 307                 pr_info("stf-barrier: hwsync barrier available\n");
 308         } else if (type == STF_BARRIER_EIEIO) {
 309                 pr_info("stf-barrier: eieio barrier available\n");
 310         }
 311
 312         stf_enabled_flush_types = type;
 313
 314         if (!no_stf_barrier)
 315                 stf_barrier_enable(enable);
 316 }
 317
 318 ssize_t cpu_show_spec_store_bypass(struct device *dev, struct device_attribute *attr, char *buf)
 319 {
 320         if (stf_barrier && stf_enabled_flush_types != STF_BARRIER_NONE) {
 321                 const char *type;
 322                 switch (stf_enabled_flush_types) {
 323                 case STF_BARRIER_EIEIO:
 324                         type = "eieio";
 325                         break;
 326                 case STF_BARRIER_SYNC_ORI:
 327                         type = "hwsync";
 328                         break;
 329                 case STF_BARRIER_FALLBACK:
 330                         type = "fallback";
 331                         break;
 332                 default:
 333                         type = "unknown";
 334                 }
 335                 return sprintf(buf, "Mitigation: Kernel entry/exit barrier (%s)\n", type);
 336         }
 337
 338         if (!security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV) &&
 339             !security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR))
 340                 return sprintf(buf, "Not affected\n");
 341
 342         return sprintf(buf, "Vulnerable\n");
 343 }
 344
 345 #ifdef CONFIG_DEBUG_FS
 346 static int stf_barrier_set(void *data, u64 val)
 347 {
 348         bool enable;
 349
 350         if (val == 1)
 351                 enable = true;
 352         else if (val == 0)
 353                 enable = false;
 354         else
 355                 return -EINVAL;
 356
 357         /* Only do anything if we're changing state */
 358         if (enable != stf_barrier)
 359                 stf_barrier_enable(enable);
 360
 361         return 0;
 362 }
 363
 364 static int stf_barrier_get(void *data, u64 *val)
 365 {
 366         *val = stf_barrier ? 1 : 0;
 367         return 0;
 368 }
 369
 370 DEFINE_SIMPLE_ATTRIBUTE(fops_stf_barrier, stf_barrier_get, stf_barrier_set, "%llu\n");
 371
 372 static __init int stf_barrier_debugfs_init(void)
 373 {
 374         debugfs_create_file("stf_barrier", 0600, powerpc_debugfs_root, NULL, &fops_stf_barrier);
 375         return 0;
 376 }
 377 device_initcall(stf_barrier_debugfs_init);
 378 #endif /* CONFIG_DEBUG_FS */
 379
 380 static void no_count_cache_flush(void)
 381 {
 382         count_cache_flush_type = COUNT_CACHE_FLUSH_NONE;
 383         pr_info("count-cache-flush: software flush disabled.\n");
 384 }
 385
 386 static void toggle_count_cache_flush(bool enable)
 387 {
 388         if (!security_ftr_enabled(SEC_FTR_FLUSH_COUNT_CACHE) &&
 389             !security_ftr_enabled(SEC_FTR_FLUSH_LINK_STACK))
 390                 enable = false;
 391
 392         if (!enable) {
 393                 patch_instruction_site(&patch__call_flush_count_cache, PPC_INST_NOP);
 394                 pr_info("link-stack-flush: software flush disabled.\n");
 395                 link_stack_flush_enabled = false;
 396                 no_count_cache_flush();
 397                 return;
 398         }
 399
 400         // This enables the branch from _switch to flush_count_cache
 401         patch_branch_site(&patch__call_flush_count_cache,
 402                           (u64)&flush_count_cache, BRANCH_SET_LINK);
 403
 404         pr_info("link-stack-flush: software flush enabled.\n");
 405         link_stack_flush_enabled = true;
 406
 407         // If we just need to flush the link stack, patch an early return
 408         if (!security_ftr_enabled(SEC_FTR_FLUSH_COUNT_CACHE)) {
 409                 patch_instruction_site(&patch__flush_link_stack_return, PPC_INST_BLR);
 410                 no_count_cache_flush();
 411                 return;
 412         }
 413
 414         if (!security_ftr_enabled(SEC_FTR_BCCTR_FLUSH_ASSIST)) {
 415                 count_cache_flush_type = COUNT_CACHE_FLUSH_SW;
 416                 pr_info("count-cache-flush: full software flush sequence enabled.\n");
 417                 return;
 418         }
 419
 420         patch_instruction_site(&patch__flush_count_cache_return, PPC_INST_BLR);
 421         count_cache_flush_type = COUNT_CACHE_FLUSH_HW;
 422         pr_info("count-cache-flush: hardware assisted flush sequence enabled\n");
 423 }
 424
 425 void setup_count_cache_flush(void)
 426 {
 427         bool enable = true;
 428
 429         if (no_spectrev2 || cpu_mitigations_off()) {
 430                 if (security_ftr_enabled(SEC_FTR_BCCTRL_SERIALISED) ||
 431                     security_ftr_enabled(SEC_FTR_COUNT_CACHE_DISABLED))
 432                         pr_warn("Spectre v2 mitigations not fully under software control, can't disable\n");
 433
 434                 enable = false;
 435         }
 436
 437         /*
 438          * There's no firmware feature flag/hypervisor bit to tell us we need to
 439          * flush the link stack on context switch. So we set it here if we see
 440          * either of the Spectre v2 mitigations that aim to protect userspace.
 441          */
 442         if (security_ftr_enabled(SEC_FTR_COUNT_CACHE_DISABLED) ||
 443             security_ftr_enabled(SEC_FTR_FLUSH_COUNT_CACHE))
 444                 security_ftr_set(SEC_FTR_FLUSH_LINK_STACK);
 445
 446         toggle_count_cache_flush(enable);
 447 }
 448
 449 #ifdef CONFIG_DEBUG_FS
 450 static int count_cache_flush_set(void *data, u64 val)
 451 {
 452         bool enable;
 453
 454         if (val == 1)
 455                 enable = true;
 456         else if (val == 0)
 457                 enable = false;
 458         else
 459                 return -EINVAL;
 460
 461         toggle_count_cache_flush(enable);
 462
 463         return 0;
 464 }
 465
 466 static int count_cache_flush_get(void *data, u64 *val)
 467 {
 468         if (count_cache_flush_type == COUNT_CACHE_FLUSH_NONE)
 469                 *val = 0;
 470         else
 471                 *val = 1;
 472
 473         return 0;
 474 }
 475
 476 DEFINE_SIMPLE_ATTRIBUTE(fops_count_cache_flush, count_cache_flush_get,
 477                         count_cache_flush_set, "%llu\n");
 478
 479 static __init int count_cache_flush_debugfs_init(void)
 480 {
 481         debugfs_create_file("count_cache_flush", 0600, powerpc_debugfs_root,
 482                             NULL, &fops_count_cache_flush);
 483         return 0;
 484 }
 485 device_initcall(count_cache_flush_debugfs_init);
 486 #endif /* CONFIG_DEBUG_FS */
 487 #endif /* CONFIG_PPC_BOOK3S_64 */