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/kernel.h>
   8 #include <linux/device.h>
   9 #include <linux/seq_buf.h>
  10
  11 #include <asm/asm-prototypes.h>
  12 #include <asm/code-patching.h>
  13 #include <asm/debugfs.h>
  14 #include <asm/security_features.h>
  15 #include <asm/setup.h>
  16
  17
  18 unsigned long powerpc_security_features __read_mostly = SEC_FTR_DEFAULT;
  19
  20 enum count_cache_flush_type {
  21         COUNT_CACHE_FLUSH_NONE  = 0x1,
  22         COUNT_CACHE_FLUSH_SW    = 0x2,
  23         COUNT_CACHE_FLUSH_HW    = 0x4,
  24 };
  25 static enum count_cache_flush_type count_cache_flush_type = COUNT_CACHE_FLUSH_NONE;
  26
  27 bool barrier_nospec_enabled;
  28 static bool no_nospec;
  29 static bool btb_flush_enabled;
  30 #ifdef CONFIG_PPC_FSL_BOOK3E
  31 static bool no_spectrev2;
  32 #endif
  33
  34 static void enable_barrier_nospec(bool enable)
  35 {
  36         barrier_nospec_enabled = enable;
  37         do_barrier_nospec_fixups(enable);
  38 }
  39
  40 void setup_barrier_nospec(void)
  41 {
  42         bool enable;
  43
  44         /*
  45          * It would make sense to check SEC_FTR_SPEC_BAR_ORI31 below as well.
  46          * But there's a good reason not to. The two flags we check below are
  47          * both are enabled by default in the kernel, so if the hcall is not
  48          * functional they will be enabled.
  49          * On a system where the host firmware has been updated (so the ori
  50          * functions as a barrier), but on which the hypervisor (KVM/Qemu) has
  51          * not been updated, we would like to enable the barrier. Dropping the
  52          * check for SEC_FTR_SPEC_BAR_ORI31 achieves that. The only downside is
  53          * we potentially enable the barrier on systems where the host firmware
  54          * is not updated, but that's harmless as it's a no-op.
  55          */
  56         enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) &&
  57                  security_ftr_enabled(SEC_FTR_BNDS_CHK_SPEC_BAR);
  58
  59         if (!no_nospec)
  60                 enable_barrier_nospec(enable);
  61 }
  62
  63 static int __init handle_nospectre_v1(char *p)
  64 {
  65         no_nospec = true;
  66
  67         return 0;
  68 }
  69 early_param("nospectre_v1", handle_nospectre_v1);
  70
  71 #ifdef CONFIG_DEBUG_FS
  72 static int barrier_nospec_set(void *data, u64 val)
  73 {
  74         switch (val) {
  75         case 0:
  76         case 1:
  77                 break;
  78         default:
  79                 return -EINVAL;
  80         }
  81
  82         if (!!val == !!barrier_nospec_enabled)
  83                 return 0;
  84
  85         enable_barrier_nospec(!!val);
  86
  87         return 0;
  88 }
  89
  90 static int barrier_nospec_get(void *data, u64 *val)
  91 {
  92         *val = barrier_nospec_enabled ? 1 : 0;
  93         return 0;
  94 }
  95
  96 DEFINE_SIMPLE_ATTRIBUTE(fops_barrier_nospec,
  97                         barrier_nospec_get, barrier_nospec_set, "%llu\n");
  98
  99 static __init int barrier_nospec_debugfs_init(void)
 100 {
 101         debugfs_create_file("barrier_nospec", 0600, powerpc_debugfs_root, NULL,
 102                             &fops_barrier_nospec);
 103         return 0;
 104 }
 105 device_initcall(barrier_nospec_debugfs_init);
 106 #endif /* CONFIG_DEBUG_FS */
 107
 108 #ifdef CONFIG_PPC_FSL_BOOK3E
 109 static int __init handle_nospectre_v2(char *p)
 110 {
 111         no_spectrev2 = true;
 112
 113         return 0;
 114 }
 115 early_param("nospectre_v2", handle_nospectre_v2);
 116 void setup_spectre_v2(void)
 117 {
 118         if (no_spectrev2)
 119                 do_btb_flush_fixups();
 120         else
 121                 btb_flush_enabled = true;
 122 }
 123 #endif /* CONFIG_PPC_FSL_BOOK3E */
 124
 125 #ifdef CONFIG_PPC_BOOK3S_64
 126 ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, char *buf)
 127 {
 128         bool thread_priv;
 129
 130         thread_priv = security_ftr_enabled(SEC_FTR_L1D_THREAD_PRIV);
 131
 132         if (rfi_flush || thread_priv) {
 133                 struct seq_buf s;
 134                 seq_buf_init(&s, buf, PAGE_SIZE - 1);
 135
 136                 seq_buf_printf(&s, "Mitigation: ");
 137
 138                 if (rfi_flush)
 139                         seq_buf_printf(&s, "RFI Flush");
 140
 141                 if (rfi_flush && thread_priv)
 142                         seq_buf_printf(&s, ", ");
 143
 144                 if (thread_priv)
 145                         seq_buf_printf(&s, "L1D private per thread");
 146
 147                 seq_buf_printf(&s, "\n");
 148
 149                 return s.len;
 150         }
 151
 152         if (!security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV) &&
 153             !security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR))
 154                 return sprintf(buf, "Not affected\n");
 155
 156         return sprintf(buf, "Vulnerable\n");
 157 }
 158 #endif
 159
 160 ssize_t cpu_show_spectre_v1(struct device *dev, struct device_attribute *attr, char *buf)
 161 {
 162         struct seq_buf s;
 163
 164         seq_buf_init(&s, buf, PAGE_SIZE - 1);
 165
 166         if (security_ftr_enabled(SEC_FTR_BNDS_CHK_SPEC_BAR)) {
 167                 if (barrier_nospec_enabled)
 168                         seq_buf_printf(&s, "Mitigation: __user pointer sanitization");
 169                 else
 170                         seq_buf_printf(&s, "Vulnerable");
 171
 172                 if (security_ftr_enabled(SEC_FTR_SPEC_BAR_ORI31))
 173                         seq_buf_printf(&s, ", ori31 speculation barrier enabled");
 174
 175                 seq_buf_printf(&s, "\n");
 176         } else
 177                 seq_buf_printf(&s, "Not affected\n");
 178
 179         return s.len;
 180 }
 181
 182 ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr, char *buf)
 183 {
 184         struct seq_buf s;
 185         bool bcs, ccd;
 186
 187         seq_buf_init(&s, buf, PAGE_SIZE - 1);
 188
 189         bcs = security_ftr_enabled(SEC_FTR_BCCTRL_SERIALISED);
 190         ccd = security_ftr_enabled(SEC_FTR_COUNT_CACHE_DISABLED);
 191
 192         if (bcs || ccd || count_cache_flush_type != COUNT_CACHE_FLUSH_NONE) {
 193                 bool comma = false;
 194                 seq_buf_printf(&s, "Mitigation: ");
 195
 196                 if (bcs) {
 197                         seq_buf_printf(&s, "Indirect branch serialisation (kernel only)");
 198                         comma = true;
 199                 }
 200
 201                 if (ccd) {
 202                         if (comma)
 203                                 seq_buf_printf(&s, ", ");
 204                         seq_buf_printf(&s, "Indirect branch cache disabled");
 205                         comma = true;
 206                 }
 207
 208                 if (comma)
 209                         seq_buf_printf(&s, ", ");
 210
 211                 seq_buf_printf(&s, "Software count cache flush");
 212
 213                 if (count_cache_flush_type == COUNT_CACHE_FLUSH_HW)
 214                         seq_buf_printf(&s, "(hardware accelerated)");
 215         } else
 216                 seq_buf_printf(&s, "Vulnerable");
 217
 218         seq_buf_printf(&s, "\n");
 219
 220         return s.len;
 221 }
 222
 223 #ifdef CONFIG_PPC_BOOK3S_64
 224 /*
 225  * Store-forwarding barrier support.
 226  */
 227
 228 static enum stf_barrier_type stf_enabled_flush_types;
 229 static bool no_stf_barrier;
 230 bool stf_barrier;
 231
 232 static int __init handle_no_stf_barrier(char *p)
 233 {
 234         pr_info("stf-barrier: disabled on command line.");
 235         no_stf_barrier = true;
 236         return 0;
 237 }
 238
 239 early_param("no_stf_barrier", handle_no_stf_barrier);
 240
 241 /* This is the generic flag used by other architectures */
 242 static int __init handle_ssbd(char *p)
 243 {
 244         if (!p || strncmp(p, "auto", 5) == 0 || strncmp(p, "on", 2) == 0 ) {
 245                 /* Until firmware tells us, we have the barrier with auto */
 246                 return 0;
 247         } else if (strncmp(p, "off", 3) == 0) {
 248                 handle_no_stf_barrier(NULL);
 249                 return 0;
 250         } else
 251                 return 1;
 252
 253         return 0;
 254 }
 255 early_param("spec_store_bypass_disable", handle_ssbd);
 256
 257 /* This is the generic flag used by other architectures */
 258 static int __init handle_no_ssbd(char *p)
 259 {
 260         handle_no_stf_barrier(NULL);
 261         return 0;
 262 }
 263 early_param("nospec_store_bypass_disable", handle_no_ssbd);
 264
 265 static void stf_barrier_enable(bool enable)
 266 {
 267         if (enable)
 268                 do_stf_barrier_fixups(stf_enabled_flush_types);
 269         else
 270                 do_stf_barrier_fixups(STF_BARRIER_NONE);
 271
 272         stf_barrier = enable;
 273 }
 274
 275 void setup_stf_barrier(void)
 276 {
 277         enum stf_barrier_type type;
 278         bool enable, hv;
 279
 280         hv = cpu_has_feature(CPU_FTR_HVMODE);
 281
 282         /* Default to fallback in case fw-features are not available */
 283         if (cpu_has_feature(CPU_FTR_ARCH_300))
 284                 type = STF_BARRIER_EIEIO;
 285         else if (cpu_has_feature(CPU_FTR_ARCH_207S))
 286                 type = STF_BARRIER_SYNC_ORI;
 287         else if (cpu_has_feature(CPU_FTR_ARCH_206))
 288                 type = STF_BARRIER_FALLBACK;
 289         else
 290                 type = STF_BARRIER_NONE;
 291
 292         enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) &&
 293                 (security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR) ||
 294                  (security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV) && hv));
 295
 296         if (type == STF_BARRIER_FALLBACK) {
 297                 pr_info("stf-barrier: fallback barrier available\n");
 298         } else if (type == STF_BARRIER_SYNC_ORI) {
 299                 pr_info("stf-barrier: hwsync barrier available\n");
 300         } else if (type == STF_BARRIER_EIEIO) {
 301                 pr_info("stf-barrier: eieio barrier available\n");
 302         }
 303
 304         stf_enabled_flush_types = type;
 305
 306         if (!no_stf_barrier)
 307                 stf_barrier_enable(enable);
 308 }
 309
 310 ssize_t cpu_show_spec_store_bypass(struct device *dev, struct device_attribute *attr, char *buf)
 311 {
 312         if (stf_barrier && stf_enabled_flush_types != STF_BARRIER_NONE) {
 313                 const char *type;
 314                 switch (stf_enabled_flush_types) {
 315                 case STF_BARRIER_EIEIO:
 316                         type = "eieio";
 317                         break;
 318                 case STF_BARRIER_SYNC_ORI:
 319                         type = "hwsync";
 320                         break;
 321                 case STF_BARRIER_FALLBACK:
 322                         type = "fallback";
 323                         break;
 324                 default:
 325                         type = "unknown";
 326                 }
 327                 return sprintf(buf, "Mitigation: Kernel entry/exit barrier (%s)\n", type);
 328         }
 329
 330         if (!security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV) &&
 331             !security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR))
 332                 return sprintf(buf, "Not affected\n");
 333
 334         return sprintf(buf, "Vulnerable\n");
 335 }
 336
 337 #ifdef CONFIG_DEBUG_FS
 338 static int stf_barrier_set(void *data, u64 val)
 339 {
 340         bool enable;
 341
 342         if (val == 1)
 343                 enable = true;
 344         else if (val == 0)
 345                 enable = false;
 346         else
 347                 return -EINVAL;
 348
 349         /* Only do anything if we're changing state */
 350         if (enable != stf_barrier)
 351                 stf_barrier_enable(enable);
 352
 353         return 0;
 354 }
 355
 356 static int stf_barrier_get(void *data, u64 *val)
 357 {
 358         *val = stf_barrier ? 1 : 0;
 359         return 0;
 360 }
 361
 362 DEFINE_SIMPLE_ATTRIBUTE(fops_stf_barrier, stf_barrier_get, stf_barrier_set, "%llu\n");
 363
 364 static __init int stf_barrier_debugfs_init(void)
 365 {
 366         debugfs_create_file("stf_barrier", 0600, powerpc_debugfs_root, NULL, &fops_stf_barrier);
 367         return 0;
 368 }
 369 device_initcall(stf_barrier_debugfs_init);
 370 #endif /* CONFIG_DEBUG_FS */
 371
 372 static void toggle_count_cache_flush(bool enable)
 373 {
 374         if (!enable || !security_ftr_enabled(SEC_FTR_FLUSH_COUNT_CACHE)) {
 375                 patch_instruction_site(&patch__call_flush_count_cache, PPC_INST_NOP);
 376                 count_cache_flush_type = COUNT_CACHE_FLUSH_NONE;
 377                 pr_info("count-cache-flush: software flush disabled.\n");
 378                 return;
 379         }
 380
 381         patch_branch_site(&patch__call_flush_count_cache,
 382                           (u64)&flush_count_cache, BRANCH_SET_LINK);
 383
 384         if (!security_ftr_enabled(SEC_FTR_BCCTR_FLUSH_ASSIST)) {
 385                 count_cache_flush_type = COUNT_CACHE_FLUSH_SW;
 386                 pr_info("count-cache-flush: full software flush sequence enabled.\n");
 387                 return;
 388         }
 389
 390         patch_instruction_site(&patch__flush_count_cache_return, PPC_INST_BLR);
 391         count_cache_flush_type = COUNT_CACHE_FLUSH_HW;
 392         pr_info("count-cache-flush: hardware assisted flush sequence enabled\n");
 393 }
 394
 395 void setup_count_cache_flush(void)
 396 {
 397         toggle_count_cache_flush(true);
 398 }
 399
 400 #ifdef CONFIG_DEBUG_FS
 401 static int count_cache_flush_set(void *data, u64 val)
 402 {
 403         bool enable;
 404
 405         if (val == 1)
 406                 enable = true;
 407         else if (val == 0)
 408                 enable = false;
 409         else
 410                 return -EINVAL;
 411
 412         toggle_count_cache_flush(enable);
 413
 414         return 0;
 415 }
 416
 417 static int count_cache_flush_get(void *data, u64 *val)
 418 {
 419         if (count_cache_flush_type == COUNT_CACHE_FLUSH_NONE)
 420                 *val = 0;
 421         else
 422                 *val = 1;
 423
 424         return 0;
 425 }
 426
 427 DEFINE_SIMPLE_ATTRIBUTE(fops_count_cache_flush, count_cache_flush_get,
 428                         count_cache_flush_set, "%llu\n");
 429
 430 static __init int count_cache_flush_debugfs_init(void)
 431 {
 432         debugfs_create_file("count_cache_flush", 0600, powerpc_debugfs_root,
 433                             NULL, &fops_count_cache_flush);
 434         return 0;
 435 }
 436 device_initcall(count_cache_flush_debugfs_init);
 437 #endif /* CONFIG_DEBUG_FS */
 438 #endif /* CONFIG_PPC_BOOK3S_64 */