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) {
 194                 seq_buf_printf(&s, "Mitigation: ");
 195
 196                 if (bcs)
 197                         seq_buf_printf(&s, "Indirect branch serialisation (kernel only)");
 198
 199                 if (bcs && ccd)
 200                         seq_buf_printf(&s, ", ");
 201
 202                 if (ccd)
 203                         seq_buf_printf(&s, "Indirect branch cache disabled");
 204         } else if (count_cache_flush_type != COUNT_CACHE_FLUSH_NONE) {
 205                 seq_buf_printf(&s, "Mitigation: Software count cache flush");
 206
 207                 if (count_cache_flush_type == COUNT_CACHE_FLUSH_HW)
 208                         seq_buf_printf(&s, " (hardware accelerated)");
 209         } else if (btb_flush_enabled) {
 210                 seq_buf_printf(&s, "Mitigation: Branch predictor state flush");
 211         } else {
 212                 seq_buf_printf(&s, "Vulnerable");
 213         }
 214
 215         seq_buf_printf(&s, "\n");
 216
 217         return s.len;
 218 }
 219
 220 #ifdef CONFIG_PPC_BOOK3S_64
 221 /*
 222  * Store-forwarding barrier support.
 223  */
 224
 225 static enum stf_barrier_type stf_enabled_flush_types;
 226 static bool no_stf_barrier;
 227 bool stf_barrier;
 228
 229 static int __init handle_no_stf_barrier(char *p)
 230 {
 231         pr_info("stf-barrier: disabled on command line.");
 232         no_stf_barrier = true;
 233         return 0;
 234 }
 235
 236 early_param("no_stf_barrier", handle_no_stf_barrier);
 237
 238 /* This is the generic flag used by other architectures */
 239 static int __init handle_ssbd(char *p)
 240 {
 241         if (!p || strncmp(p, "auto", 5) == 0 || strncmp(p, "on", 2) == 0 ) {
 242                 /* Until firmware tells us, we have the barrier with auto */
 243                 return 0;
 244         } else if (strncmp(p, "off", 3) == 0) {
 245                 handle_no_stf_barrier(NULL);
 246                 return 0;
 247         } else
 248                 return 1;
 249
 250         return 0;
 251 }
 252 early_param("spec_store_bypass_disable", handle_ssbd);
 253
 254 /* This is the generic flag used by other architectures */
 255 static int __init handle_no_ssbd(char *p)
 256 {
 257         handle_no_stf_barrier(NULL);
 258         return 0;
 259 }
 260 early_param("nospec_store_bypass_disable", handle_no_ssbd);
 261
 262 static void stf_barrier_enable(bool enable)
 263 {
 264         if (enable)
 265                 do_stf_barrier_fixups(stf_enabled_flush_types);
 266         else
 267                 do_stf_barrier_fixups(STF_BARRIER_NONE);
 268
 269         stf_barrier = enable;
 270 }
 271
 272 void setup_stf_barrier(void)
 273 {
 274         enum stf_barrier_type type;
 275         bool enable, hv;
 276
 277         hv = cpu_has_feature(CPU_FTR_HVMODE);
 278
 279         /* Default to fallback in case fw-features are not available */
 280         if (cpu_has_feature(CPU_FTR_ARCH_300))
 281                 type = STF_BARRIER_EIEIO;
 282         else if (cpu_has_feature(CPU_FTR_ARCH_207S))
 283                 type = STF_BARRIER_SYNC_ORI;
 284         else if (cpu_has_feature(CPU_FTR_ARCH_206))
 285                 type = STF_BARRIER_FALLBACK;
 286         else
 287                 type = STF_BARRIER_NONE;
 288
 289         enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) &&
 290                 (security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR) ||
 291                  (security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV) && hv));
 292
 293         if (type == STF_BARRIER_FALLBACK) {
 294                 pr_info("stf-barrier: fallback barrier available\n");
 295         } else if (type == STF_BARRIER_SYNC_ORI) {
 296                 pr_info("stf-barrier: hwsync barrier available\n");
 297         } else if (type == STF_BARRIER_EIEIO) {
 298                 pr_info("stf-barrier: eieio barrier available\n");
 299         }
 300
 301         stf_enabled_flush_types = type;
 302
 303         if (!no_stf_barrier)
 304                 stf_barrier_enable(enable);
 305 }
 306
 307 ssize_t cpu_show_spec_store_bypass(struct device *dev, struct device_attribute *attr, char *buf)
 308 {
 309         if (stf_barrier && stf_enabled_flush_types != STF_BARRIER_NONE) {
 310                 const char *type;
 311                 switch (stf_enabled_flush_types) {
 312                 case STF_BARRIER_EIEIO:
 313                         type = "eieio";
 314                         break;
 315                 case STF_BARRIER_SYNC_ORI:
 316                         type = "hwsync";
 317                         break;
 318                 case STF_BARRIER_FALLBACK:
 319                         type = "fallback";
 320                         break;
 321                 default:
 322                         type = "unknown";
 323                 }
 324                 return sprintf(buf, "Mitigation: Kernel entry/exit barrier (%s)\n", type);
 325         }
 326
 327         if (!security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV) &&
 328             !security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR))
 329                 return sprintf(buf, "Not affected\n");
 330
 331         return sprintf(buf, "Vulnerable\n");
 332 }
 333
 334 #ifdef CONFIG_DEBUG_FS
 335 static int stf_barrier_set(void *data, u64 val)
 336 {
 337         bool enable;
 338
 339         if (val == 1)
 340                 enable = true;
 341         else if (val == 0)
 342                 enable = false;
 343         else
 344                 return -EINVAL;
 345
 346         /* Only do anything if we're changing state */
 347         if (enable != stf_barrier)
 348                 stf_barrier_enable(enable);
 349
 350         return 0;
 351 }
 352
 353 static int stf_barrier_get(void *data, u64 *val)
 354 {
 355         *val = stf_barrier ? 1 : 0;
 356         return 0;
 357 }
 358
 359 DEFINE_SIMPLE_ATTRIBUTE(fops_stf_barrier, stf_barrier_get, stf_barrier_set, "%llu\n");
 360
 361 static __init int stf_barrier_debugfs_init(void)
 362 {
 363         debugfs_create_file("stf_barrier", 0600, powerpc_debugfs_root, NULL, &fops_stf_barrier);
 364         return 0;
 365 }
 366 device_initcall(stf_barrier_debugfs_init);
 367 #endif /* CONFIG_DEBUG_FS */
 368
 369 static void toggle_count_cache_flush(bool enable)
 370 {
 371         if (!enable || !security_ftr_enabled(SEC_FTR_FLUSH_COUNT_CACHE)) {
 372                 patch_instruction_site(&patch__call_flush_count_cache, PPC_INST_NOP);
 373                 count_cache_flush_type = COUNT_CACHE_FLUSH_NONE;
 374                 pr_info("count-cache-flush: software flush disabled.\n");
 375                 return;
 376         }
 377
 378         patch_branch_site(&patch__call_flush_count_cache,
 379                           (u64)&flush_count_cache, BRANCH_SET_LINK);
 380
 381         if (!security_ftr_enabled(SEC_FTR_BCCTR_FLUSH_ASSIST)) {
 382                 count_cache_flush_type = COUNT_CACHE_FLUSH_SW;
 383                 pr_info("count-cache-flush: full software flush sequence enabled.\n");
 384                 return;
 385         }
 386
 387         patch_instruction_site(&patch__flush_count_cache_return, PPC_INST_BLR);
 388         count_cache_flush_type = COUNT_CACHE_FLUSH_HW;
 389         pr_info("count-cache-flush: hardware assisted flush sequence enabled\n");
 390 }
 391
 392 void setup_count_cache_flush(void)
 393 {
 394         toggle_count_cache_flush(true);
 395 }
 396
 397 #ifdef CONFIG_DEBUG_FS
 398 static int count_cache_flush_set(void *data, u64 val)
 399 {
 400         bool enable;
 401
 402         if (val == 1)
 403                 enable = true;
 404         else if (val == 0)
 405                 enable = false;
 406         else
 407                 return -EINVAL;
 408
 409         toggle_count_cache_flush(enable);
 410
 411         return 0;
 412 }
 413
 414 static int count_cache_flush_get(void *data, u64 *val)
 415 {
 416         if (count_cache_flush_type == COUNT_CACHE_FLUSH_NONE)
 417                 *val = 0;
 418         else
 419                 *val = 1;
 420
 421         return 0;
 422 }
 423
 424 DEFINE_SIMPLE_ATTRIBUTE(fops_count_cache_flush, count_cache_flush_get,
 425                         count_cache_flush_set, "%llu\n");
 426
 427 static __init int count_cache_flush_debugfs_init(void)
 428 {
 429         debugfs_create_file("count_cache_flush", 0600, powerpc_debugfs_root,
 430                             NULL, &fops_count_cache_flush);
 431         return 0;
 432 }
 433 device_initcall(count_cache_flush_debugfs_init);
 434 #endif /* CONFIG_DEBUG_FS */
 435 #endif /* CONFIG_PPC_BOOK3S_64 */