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