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 unsigned long 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
  28 bool barrier_nospec_enabled;
  29 static bool no_nospec;
  30 static bool btb_flush_enabled;
  31 #ifdef CONFIG_PPC_FSL_BOOK3E
  32 static bool no_spectrev2;
  33 #endif
  34
  35 static void enable_barrier_nospec(bool enable)
  36 {
  37         barrier_nospec_enabled = enable;
  38         do_barrier_nospec_fixups(enable);
  39 }
  40
  41 void setup_barrier_nospec(void)
  42 {
  43         bool enable;
  44
  45         /*
  46          * It would make sense to check SEC_FTR_SPEC_BAR_ORI31 below as well.
  47          * But there's a good reason not to. The two flags we check below are
  48          * both are enabled by default in the kernel, so if the hcall is not
  49          * functional they will be enabled.
  50          * On a system where the host firmware has been updated (so the ori
  51          * functions as a barrier), but on which the hypervisor (KVM/Qemu) has
  52          * not been updated, we would like to enable the barrier. Dropping the
  53          * check for SEC_FTR_SPEC_BAR_ORI31 achieves that. The only downside is
  54          * we potentially enable the barrier on systems where the host firmware
  55          * is not updated, but that's harmless as it's a no-op.
  56          */
  57         enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) &&
  58                  security_ftr_enabled(SEC_FTR_BNDS_CHK_SPEC_BAR);
  59
  60         if (!no_nospec)
  61                 enable_barrier_nospec(enable);
  62 }
  63
  64 static int __init handle_nospectre_v1(char *p)
  65 {
  66         no_nospec = true;
  67
  68         return 0;
  69 }
  70 early_param("nospectre_v1", handle_nospectre_v1);
  71
  72 #ifdef CONFIG_DEBUG_FS
  73 static int barrier_nospec_set(void *data, u64 val)
  74 {
  75         switch (val) {
  76         case 0:
  77         case 1:
  78                 break;
  79         default:
  80                 return -EINVAL;
  81         }
  82
  83         if (!!val == !!barrier_nospec_enabled)
  84                 return 0;
  85
  86         enable_barrier_nospec(!!val);
  87
  88         return 0;
  89 }
  90
  91 static int barrier_nospec_get(void *data, u64 *val)
  92 {
  93         *val = barrier_nospec_enabled ? 1 : 0;
  94         return 0;
  95 }
  96
  97 DEFINE_SIMPLE_ATTRIBUTE(fops_barrier_nospec,
  98                         barrier_nospec_get, barrier_nospec_set, "%llu\n");
  99
 100 static __init int barrier_nospec_debugfs_init(void)
 101 {
 102         debugfs_create_file("barrier_nospec", 0600, powerpc_debugfs_root, NULL,
 103                             &fops_barrier_nospec);
 104         return 0;
 105 }
 106 device_initcall(barrier_nospec_debugfs_init);
 107 #endif /* CONFIG_DEBUG_FS */
 108
 109 #ifdef CONFIG_PPC_FSL_BOOK3E
 110 static int __init handle_nospectre_v2(char *p)
 111 {
 112         no_spectrev2 = true;
 113
 114         return 0;
 115 }
 116 early_param("nospectre_v2", handle_nospectre_v2);
 117 void setup_spectre_v2(void)
 118 {
 119         if (no_spectrev2)
 120                 do_btb_flush_fixups();
 121         else
 122                 btb_flush_enabled = true;
 123 }
 124 #endif /* CONFIG_PPC_FSL_BOOK3E */
 125
 126 #ifdef CONFIG_PPC_BOOK3S_64
 127 ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, char *buf)
 128 {
 129         bool thread_priv;
 130
 131         thread_priv = security_ftr_enabled(SEC_FTR_L1D_THREAD_PRIV);
 132
 133         if (rfi_flush || thread_priv) {
 134                 struct seq_buf s;
 135                 seq_buf_init(&s, buf, PAGE_SIZE - 1);
 136
 137                 seq_buf_printf(&s, "Mitigation: ");
 138
 139                 if (rfi_flush)
 140                         seq_buf_printf(&s, "RFI Flush");
 141
 142                 if (rfi_flush && thread_priv)
 143                         seq_buf_printf(&s, ", ");
 144
 145                 if (thread_priv)
 146                         seq_buf_printf(&s, "L1D private per thread");
 147
 148                 seq_buf_printf(&s, "\n");
 149
 150                 return s.len;
 151         }
 152
 153         if (!security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV) &&
 154             !security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR))
 155                 return sprintf(buf, "Not affected\n");
 156
 157         return sprintf(buf, "Vulnerable\n");
 158 }
 159 #endif
 160
 161 ssize_t cpu_show_spectre_v1(struct device *dev, struct device_attribute *attr, char *buf)
 162 {
 163         struct seq_buf s;
 164
 165         seq_buf_init(&s, buf, PAGE_SIZE - 1);
 166
 167         if (security_ftr_enabled(SEC_FTR_BNDS_CHK_SPEC_BAR)) {
 168                 if (barrier_nospec_enabled)
 169                         seq_buf_printf(&s, "Mitigation: __user pointer sanitization");
 170                 else
 171                         seq_buf_printf(&s, "Vulnerable");
 172
 173                 if (security_ftr_enabled(SEC_FTR_SPEC_BAR_ORI31))
 174                         seq_buf_printf(&s, ", ori31 speculation barrier enabled");
 175
 176                 seq_buf_printf(&s, "\n");
 177         } else
 178                 seq_buf_printf(&s, "Not affected\n");
 179
 180         return s.len;
 181 }
 182
 183 ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr, char *buf)
 184 {
 185         struct seq_buf s;
 186         bool bcs, ccd;
 187
 188         seq_buf_init(&s, buf, PAGE_SIZE - 1);
 189
 190         bcs = security_ftr_enabled(SEC_FTR_BCCTRL_SERIALISED);
 191         ccd = security_ftr_enabled(SEC_FTR_COUNT_CACHE_DISABLED);
 192
 193         if (bcs || ccd || count_cache_flush_type != COUNT_CACHE_FLUSH_NONE) {
 194                 bool comma = false;
 195                 seq_buf_printf(&s, "Mitigation: ");
 196
 197                 if (bcs) {
 198                         seq_buf_printf(&s, "Indirect branch serialisation (kernel only)");
 199                         comma = true;
 200                 }
 201
 202                 if (ccd) {
 203                         if (comma)
 204                                 seq_buf_printf(&s, ", ");
 205                         seq_buf_printf(&s, "Indirect branch cache disabled");
 206                         comma = true;
 207                 }
 208
 209                 if (comma)
 210                         seq_buf_printf(&s, ", ");
 211
 212                 seq_buf_printf(&s, "Software count cache flush");
 213
 214                 if (count_cache_flush_type == COUNT_CACHE_FLUSH_HW)
 215                         seq_buf_printf(&s, "(hardware accelerated)");
 216         } else if (btb_flush_enabled) {
 217                 seq_buf_printf(&s, "Mitigation: Branch predictor state flush");
 218         } else {
 219                 seq_buf_printf(&s, "Vulnerable");
 220         }
 221
 222         seq_buf_printf(&s, "\n");
 223
 224         return s.len;
 225 }
 226
 227 #ifdef CONFIG_PPC_BOOK3S_64
 228 /*
 229  * Store-forwarding barrier support.
 230  */
 231
 232 static enum stf_barrier_type stf_enabled_flush_types;
 233 static bool no_stf_barrier;
 234 bool stf_barrier;
 235
 236 static int __init handle_no_stf_barrier(char *p)
 237 {
 238         pr_info("stf-barrier: disabled on command line.");
 239         no_stf_barrier = true;
 240         return 0;
 241 }
 242
 243 early_param("no_stf_barrier", handle_no_stf_barrier);
 244
 245 /* This is the generic flag used by other architectures */
 246 static int __init handle_ssbd(char *p)
 247 {
 248         if (!p || strncmp(p, "auto", 5) == 0 || strncmp(p, "on", 2) == 0 ) {
 249                 /* Until firmware tells us, we have the barrier with auto */
 250                 return 0;
 251         } else if (strncmp(p, "off", 3) == 0) {
 252                 handle_no_stf_barrier(NULL);
 253                 return 0;
 254         } else
 255                 return 1;
 256
 257         return 0;
 258 }
 259 early_param("spec_store_bypass_disable", handle_ssbd);
 260
 261 /* This is the generic flag used by other architectures */
 262 static int __init handle_no_ssbd(char *p)
 263 {
 264         handle_no_stf_barrier(NULL);
 265         return 0;
 266 }
 267 early_param("nospec_store_bypass_disable", handle_no_ssbd);
 268
 269 static void stf_barrier_enable(bool enable)
 270 {
 271         if (enable)
 272                 do_stf_barrier_fixups(stf_enabled_flush_types);
 273         else
 274                 do_stf_barrier_fixups(STF_BARRIER_NONE);
 275
 276         stf_barrier = enable;
 277 }
 278
 279 void setup_stf_barrier(void)
 280 {
 281         enum stf_barrier_type type;
 282         bool enable, hv;
 283
 284         hv = cpu_has_feature(CPU_FTR_HVMODE);
 285
 286         /* Default to fallback in case fw-features are not available */
 287         if (cpu_has_feature(CPU_FTR_ARCH_300))
 288                 type = STF_BARRIER_EIEIO;
 289         else if (cpu_has_feature(CPU_FTR_ARCH_207S))
 290                 type = STF_BARRIER_SYNC_ORI;
 291         else if (cpu_has_feature(CPU_FTR_ARCH_206))
 292                 type = STF_BARRIER_FALLBACK;
 293         else
 294                 type = STF_BARRIER_NONE;
 295
 296         enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) &&
 297                 (security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR) ||
 298                  (security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV) && hv));
 299
 300         if (type == STF_BARRIER_FALLBACK) {
 301                 pr_info("stf-barrier: fallback barrier available\n");
 302         } else if (type == STF_BARRIER_SYNC_ORI) {
 303                 pr_info("stf-barrier: hwsync barrier available\n");
 304         } else if (type == STF_BARRIER_EIEIO) {
 305                 pr_info("stf-barrier: eieio barrier available\n");
 306         }
 307
 308         stf_enabled_flush_types = type;
 309
 310         if (!no_stf_barrier)
 311                 stf_barrier_enable(enable);
 312 }
 313
 314 ssize_t cpu_show_spec_store_bypass(struct device *dev, struct device_attribute *attr, char *buf)
 315 {
 316         if (stf_barrier && stf_enabled_flush_types != STF_BARRIER_NONE) {
 317                 const char *type;
 318                 switch (stf_enabled_flush_types) {
 319                 case STF_BARRIER_EIEIO:
 320                         type = "eieio";
 321                         break;
 322                 case STF_BARRIER_SYNC_ORI:
 323                         type = "hwsync";
 324                         break;
 325                 case STF_BARRIER_FALLBACK:
 326                         type = "fallback";
 327                         break;
 328                 default:
 329                         type = "unknown";
 330                 }
 331                 return sprintf(buf, "Mitigation: Kernel entry/exit barrier (%s)\n", type);
 332         }
 333
 334         if (!security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV) &&
 335             !security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR))
 336                 return sprintf(buf, "Not affected\n");
 337
 338         return sprintf(buf, "Vulnerable\n");
 339 }
 340
 341 #ifdef CONFIG_DEBUG_FS
 342 static int stf_barrier_set(void *data, u64 val)
 343 {
 344         bool enable;
 345
 346         if (val == 1)
 347                 enable = true;
 348         else if (val == 0)
 349                 enable = false;
 350         else
 351                 return -EINVAL;
 352
 353         /* Only do anything if we're changing state */
 354         if (enable != stf_barrier)
 355                 stf_barrier_enable(enable);
 356
 357         return 0;
 358 }
 359
 360 static int stf_barrier_get(void *data, u64 *val)
 361 {
 362         *val = stf_barrier ? 1 : 0;
 363         return 0;
 364 }
 365
 366 DEFINE_SIMPLE_ATTRIBUTE(fops_stf_barrier, stf_barrier_get, stf_barrier_set, "%llu\n");
 367
 368 static __init int stf_barrier_debugfs_init(void)
 369 {
 370         debugfs_create_file("stf_barrier", 0600, powerpc_debugfs_root, NULL, &fops_stf_barrier);
 371         return 0;
 372 }
 373 device_initcall(stf_barrier_debugfs_init);
 374 #endif /* CONFIG_DEBUG_FS */
 375
 376 static void toggle_count_cache_flush(bool enable)
 377 {
 378         if (!enable || !security_ftr_enabled(SEC_FTR_FLUSH_COUNT_CACHE)) {
 379                 patch_instruction_site(&patch__call_flush_count_cache, PPC_INST_NOP);
 380                 count_cache_flush_type = COUNT_CACHE_FLUSH_NONE;
 381                 pr_info("count-cache-flush: software flush disabled.\n");
 382                 return;
 383         }
 384
 385         patch_branch_site(&patch__call_flush_count_cache,
 386                           (u64)&flush_count_cache, BRANCH_SET_LINK);
 387
 388         if (!security_ftr_enabled(SEC_FTR_BCCTR_FLUSH_ASSIST)) {
 389                 count_cache_flush_type = COUNT_CACHE_FLUSH_SW;
 390                 pr_info("count-cache-flush: full software flush sequence enabled.\n");
 391                 return;
 392         }
 393
 394         patch_instruction_site(&patch__flush_count_cache_return, PPC_INST_BLR);
 395         count_cache_flush_type = COUNT_CACHE_FLUSH_HW;
 396         pr_info("count-cache-flush: hardware assisted flush sequence enabled\n");
 397 }
 398
 399 void setup_count_cache_flush(void)
 400 {
 401         toggle_count_cache_flush(true);
 402 }
 403
 404 #ifdef CONFIG_DEBUG_FS
 405 static int count_cache_flush_set(void *data, u64 val)
 406 {
 407         bool enable;
 408
 409         if (val == 1)
 410                 enable = true;
 411         else if (val == 0)
 412                 enable = false;
 413         else
 414                 return -EINVAL;
 415
 416         toggle_count_cache_flush(enable);
 417
 418         return 0;
 419 }
 420
 421 static int count_cache_flush_get(void *data, u64 *val)
 422 {
 423         if (count_cache_flush_type == COUNT_CACHE_FLUSH_NONE)
 424                 *val = 0;
 425         else
 426                 *val = 1;
 427
 428         return 0;
 429 }
 430
 431 DEFINE_SIMPLE_ATTRIBUTE(fops_count_cache_flush, count_cache_flush_get,
 432                         count_cache_flush_set, "%llu\n");
 433
 434 static __init int count_cache_flush_debugfs_init(void)
 435 {
 436         debugfs_create_file("count_cache_flush", 0600, powerpc_debugfs_root,
 437                             NULL, &fops_count_cache_flush);
 438         return 0;
 439 }
 440 device_initcall(count_cache_flush_debugfs_init);
 441 #endif /* CONFIG_DEBUG_FS */
 442 #endif /* CONFIG_PPC_BOOK3S_64 */