tools/testing/selftests/x86/ldt_gdt.c

   1 /*
   2  * ldt_gdt.c - Test cases for LDT and GDT access
   3  * Copyright (c) 2015 Andrew Lutomirski
   4  */
   5
   6 #define _GNU_SOURCE
   7 #include <err.h>
   8 #include <stdio.h>
   9 #include <stdint.h>
  10 #include <signal.h>
  11 #include <setjmp.h>
  12 #include <stdlib.h>
  13 #include <string.h>
  14 #include <errno.h>
  15 #include <unistd.h>
  16 #include <sys/syscall.h>
  17 #include <asm/ldt.h>
  18 #include <sys/types.h>
  19 #include <sys/wait.h>
  20 #include <stdbool.h>
  21 #include <pthread.h>
  22 #include <sched.h>
  23 #include <linux/futex.h>
  24 #include <sys/mman.h>
  25 #include <asm/prctl.h>
  26 #include <sys/prctl.h>
  27
  28 #define AR_ACCESSED             (1<<8)
  29
  30 #define AR_TYPE_RODATA          (0 * (1<<9))
  31 #define AR_TYPE_RWDATA          (1 * (1<<9))
  32 #define AR_TYPE_RODATA_EXPDOWN  (2 * (1<<9))
  33 #define AR_TYPE_RWDATA_EXPDOWN  (3 * (1<<9))
  34 #define AR_TYPE_XOCODE          (4 * (1<<9))
  35 #define AR_TYPE_XRCODE          (5 * (1<<9))
  36 #define AR_TYPE_XOCODE_CONF     (6 * (1<<9))
  37 #define AR_TYPE_XRCODE_CONF     (7 * (1<<9))
  38
  39 #define AR_DPL3                 (3 * (1<<13))
  40
  41 #define AR_S                    (1 << 12)
  42 #define AR_P                    (1 << 15)
  43 #define AR_AVL                  (1 << 20)
  44 #define AR_L                    (1 << 21)
  45 #define AR_DB                   (1 << 22)
  46 #define AR_G                    (1 << 23)
  47
  48 #ifdef __x86_64__
  49 # define INT80_CLOBBERS "r8", "r9", "r10", "r11"
  50 #else
  51 # define INT80_CLOBBERS
  52 #endif
  53
  54 static int nerrs;
  55
  56 /* Points to an array of 1024 ints, each holding its own index. */
  57 static const unsigned int *counter_page;
  58 static struct user_desc *low_user_desc;
  59 static struct user_desc *low_user_desc_clear;  /* Use to delete GDT entry */
  60 static int gdt_entry_num;
  61
  62 static void check_invalid_segment(uint16_t index, int ldt)
  63 {
  64         uint32_t has_limit = 0, has_ar = 0, limit, ar;
  65         uint32_t selector = (index << 3) | (ldt << 2) | 3;
  66
  67         asm ("lsl %[selector], %[limit]\n\t"
  68              "jnz 1f\n\t"
  69              "movl $1, %[has_limit]\n\t"
  70              "1:"
  71              : [limit] "=r" (limit), [has_limit] "+rm" (has_limit)
  72              : [selector] "r" (selector));
  73         asm ("larl %[selector], %[ar]\n\t"
  74              "jnz 1f\n\t"
  75              "movl $1, %[has_ar]\n\t"
  76              "1:"
  77              : [ar] "=r" (ar), [has_ar] "+rm" (has_ar)
  78              : [selector] "r" (selector));
  79
  80         if (has_limit || has_ar) {
  81                 printf("[FAIL]\t%s entry %hu is valid but should be invalid\n",
  82                        (ldt ? "LDT" : "GDT"), index);
  83                 nerrs++;
  84         } else {
  85                 printf("[OK]\t%s entry %hu is invalid\n",
  86                        (ldt ? "LDT" : "GDT"), index);
  87         }
  88 }
  89
  90 static void check_valid_segment(uint16_t index, int ldt,
  91                                 uint32_t expected_ar, uint32_t expected_limit,
  92                                 bool verbose)
  93 {
  94         uint32_t has_limit = 0, has_ar = 0, limit, ar;
  95         uint32_t selector = (index << 3) | (ldt << 2) | 3;
  96
  97         asm ("lsl %[selector], %[limit]\n\t"
  98              "jnz 1f\n\t"
  99              "movl $1, %[has_limit]\n\t"
 100              "1:"
 101              : [limit] "=r" (limit), [has_limit] "+rm" (has_limit)
 102              : [selector] "r" (selector));
 103         asm ("larl %[selector], %[ar]\n\t"
 104              "jnz 1f\n\t"
 105              "movl $1, %[has_ar]\n\t"
 106              "1:"
 107              : [ar] "=r" (ar), [has_ar] "+rm" (has_ar)
 108              : [selector] "r" (selector));
 109
 110         if (!has_limit || !has_ar) {
 111                 printf("[FAIL]\t%s entry %hu is invalid but should be valid\n",
 112                        (ldt ? "LDT" : "GDT"), index);
 113                 nerrs++;
 114                 return;
 115         }
 116
 117         if (ar != expected_ar) {
 118                 printf("[FAIL]\t%s entry %hu has AR 0x%08X but expected 0x%08X\n",
 119                        (ldt ? "LDT" : "GDT"), index, ar, expected_ar);
 120                 nerrs++;
 121         } else if (limit != expected_limit) {
 122                 printf("[FAIL]\t%s entry %hu has limit 0x%08X but expected 0x%08X\n",
 123                        (ldt ? "LDT" : "GDT"), index, limit, expected_limit);
 124                 nerrs++;
 125         } else if (verbose) {
 126                 printf("[OK]\t%s entry %hu has AR 0x%08X and limit 0x%08X\n",
 127                        (ldt ? "LDT" : "GDT"), index, ar, limit);
 128         }
 129 }
 130
 131 static bool install_valid_mode(const struct user_desc *desc, uint32_t ar,
 132                                bool oldmode)
 133 {
 134         int ret = syscall(SYS_modify_ldt, oldmode ? 1 : 0x11,
 135                           desc, sizeof(*desc));
 136         if (ret < -1)
 137                 errno = -ret;
 138         if (ret == 0) {
 139                 uint32_t limit = desc->limit;
 140                 if (desc->limit_in_pages)
 141                         limit = (limit << 12) + 4095;
 142                 check_valid_segment(desc->entry_number, 1, ar, limit, true);
 143                 return true;
 144         } else if (errno == ENOSYS) {
 145                 printf("[OK]\tmodify_ldt returned -ENOSYS\n");
 146                 return false;
 147         } else {
 148                 if (desc->seg_32bit) {
 149                         printf("[FAIL]\tUnexpected modify_ldt failure %d\n",
 150                                errno);
 151                         nerrs++;
 152                         return false;
 153                 } else {
 154                         printf("[OK]\tmodify_ldt rejected 16 bit segment\n");
 155                         return false;
 156                 }
 157         }
 158 }
 159
 160 static bool install_valid(const struct user_desc *desc, uint32_t ar)
 161 {
 162         return install_valid_mode(desc, ar, false);
 163 }
 164
 165 static void install_invalid(const struct user_desc *desc, bool oldmode)
 166 {
 167         int ret = syscall(SYS_modify_ldt, oldmode ? 1 : 0x11,
 168                           desc, sizeof(*desc));
 169         if (ret < -1)
 170                 errno = -ret;
 171         if (ret == 0) {
 172                 check_invalid_segment(desc->entry_number, 1);
 173         } else if (errno == ENOSYS) {
 174                 printf("[OK]\tmodify_ldt returned -ENOSYS\n");
 175         } else {
 176                 if (desc->seg_32bit) {
 177                         printf("[FAIL]\tUnexpected modify_ldt failure %d\n",
 178                                errno);
 179                         nerrs++;
 180                 } else {
 181                         printf("[OK]\tmodify_ldt rejected 16 bit segment\n");
 182                 }
 183         }
 184 }
 185
 186 static int safe_modify_ldt(int func, struct user_desc *ptr,
 187                            unsigned long bytecount)
 188 {
 189         int ret = syscall(SYS_modify_ldt, 0x11, ptr, bytecount);
 190         if (ret < -1)
 191                 errno = -ret;
 192         return ret;
 193 }
 194
 195 static void fail_install(struct user_desc *desc)
 196 {
 197         if (safe_modify_ldt(0x11, desc, sizeof(*desc)) == 0) {
 198                 printf("[FAIL]\tmodify_ldt accepted a bad descriptor\n");
 199                 nerrs++;
 200         } else if (errno == ENOSYS) {
 201                 printf("[OK]\tmodify_ldt returned -ENOSYS\n");
 202         } else {
 203                 printf("[OK]\tmodify_ldt failure %d\n", errno);
 204         }
 205 }
 206
 207 static void do_simple_tests(void)
 208 {
 209         struct user_desc desc = {
 210                 .entry_number    = 0,
 211                 .base_addr       = 0,
 212                 .limit           = 10,
 213                 .seg_32bit       = 1,
 214                 .contents        = 2, /* Code, not conforming */
 215                 .read_exec_only  = 0,
 216                 .limit_in_pages  = 0,
 217                 .seg_not_present = 0,
 218                 .useable         = 0
 219         };
 220         install_valid(&desc, AR_DPL3 | AR_TYPE_XRCODE | AR_S | AR_P | AR_DB);
 221
 222         desc.limit_in_pages = 1;
 223         install_valid(&desc, AR_DPL3 | AR_TYPE_XRCODE |
 224                       AR_S | AR_P | AR_DB | AR_G);
 225
 226         check_invalid_segment(1, 1);
 227
 228         desc.entry_number = 2;
 229         install_valid(&desc, AR_DPL3 | AR_TYPE_XRCODE |
 230                       AR_S | AR_P | AR_DB | AR_G);
 231
 232         check_invalid_segment(1, 1);
 233
 234         desc.base_addr = 0xf0000000;
 235         install_valid(&desc, AR_DPL3 | AR_TYPE_XRCODE |
 236                       AR_S | AR_P | AR_DB | AR_G);
 237
 238         desc.useable = 1;
 239         install_valid(&desc, AR_DPL3 | AR_TYPE_XRCODE |
 240                       AR_S | AR_P | AR_DB | AR_G | AR_AVL);
 241
 242         desc.seg_not_present = 1;
 243         install_valid(&desc, AR_DPL3 | AR_TYPE_XRCODE |
 244                       AR_S | AR_DB | AR_G | AR_AVL);
 245
 246         desc.seg_32bit = 0;
 247         install_valid(&desc, AR_DPL3 | AR_TYPE_XRCODE |
 248                       AR_S | AR_G | AR_AVL);
 249
 250         desc.seg_32bit = 1;
 251         desc.contents = 0;
 252         install_valid(&desc, AR_DPL3 | AR_TYPE_RWDATA |
 253                       AR_S | AR_DB | AR_G | AR_AVL);
 254
 255         desc.read_exec_only = 1;
 256         install_valid(&desc, AR_DPL3 | AR_TYPE_RODATA |
 257                       AR_S | AR_DB | AR_G | AR_AVL);
 258
 259         desc.contents = 1;
 260         install_valid(&desc, AR_DPL3 | AR_TYPE_RODATA_EXPDOWN |
 261                       AR_S | AR_DB | AR_G | AR_AVL);
 262
 263         desc.read_exec_only = 0;
 264         desc.limit_in_pages = 0;
 265         install_valid(&desc, AR_DPL3 | AR_TYPE_RWDATA_EXPDOWN |
 266                       AR_S | AR_DB | AR_AVL);
 267
 268         desc.contents = 3;
 269         install_valid(&desc, AR_DPL3 | AR_TYPE_XRCODE_CONF |
 270                       AR_S | AR_DB | AR_AVL);
 271
 272         desc.read_exec_only = 1;
 273         install_valid(&desc, AR_DPL3 | AR_TYPE_XOCODE_CONF |
 274                       AR_S | AR_DB | AR_AVL);
 275
 276         desc.read_exec_only = 0;
 277         desc.contents = 2;
 278         install_valid(&desc, AR_DPL3 | AR_TYPE_XRCODE |
 279                       AR_S | AR_DB | AR_AVL);
 280
 281         desc.read_exec_only = 1;
 282
 283 #ifdef __x86_64__
 284         desc.lm = 1;
 285         install_valid(&desc, AR_DPL3 | AR_TYPE_XOCODE |
 286                       AR_S | AR_DB | AR_AVL);
 287         desc.lm = 0;
 288 #endif
 289
 290         bool entry1_okay = install_valid(&desc, AR_DPL3 | AR_TYPE_XOCODE |
 291                                          AR_S | AR_DB | AR_AVL);
 292
 293         if (entry1_okay) {
 294                 printf("[RUN]\tTest fork\n");
 295                 pid_t child = fork();
 296                 if (child == 0) {
 297                         nerrs = 0;
 298                         check_valid_segment(desc.entry_number, 1,
 299                                             AR_DPL3 | AR_TYPE_XOCODE |
 300                                             AR_S | AR_DB | AR_AVL, desc.limit,
 301                                             true);
 302                         check_invalid_segment(1, 1);
 303                         exit(nerrs ? 1 : 0);
 304                 } else {
 305                         int status;
 306                         if (waitpid(child, &status, 0) != child ||
 307                             !WIFEXITED(status)) {
 308                                 printf("[FAIL]\tChild died\n");
 309                                 nerrs++;
 310                         } else if (WEXITSTATUS(status) != 0) {
 311                                 printf("[FAIL]\tChild failed\n");
 312                                 nerrs++;
 313                         } else {
 314                                 printf("[OK]\tChild succeeded\n");
 315                         }
 316                 }
 317
 318                 printf("[RUN]\tTest size\n");
 319                 int i;
 320                 for (i = 0; i < 8192; i++) {
 321                         desc.entry_number = i;
 322                         desc.limit = i;
 323                         if (safe_modify_ldt(0x11, &desc, sizeof(desc)) != 0) {
 324                                 printf("[FAIL]\tFailed to install entry %d\n", i);
 325                                 nerrs++;
 326                                 break;
 327                         }
 328                 }
 329                 for (int j = 0; j < i; j++) {
 330                         check_valid_segment(j, 1, AR_DPL3 | AR_TYPE_XOCODE |
 331                                             AR_S | AR_DB | AR_AVL, j, false);
 332                 }
 333                 printf("[DONE]\tSize test\n");
 334         } else {
 335                 printf("[SKIP]\tSkipping fork and size tests because we have no LDT\n");
 336         }
 337
 338         /* Test entry_number too high. */
 339         desc.entry_number = 8192;
 340         fail_install(&desc);
 341
 342         /* Test deletion and actions mistakeable for deletion. */
 343         memset(&desc, 0, sizeof(desc));
 344         install_valid(&desc, AR_DPL3 | AR_TYPE_RWDATA | AR_S | AR_P);
 345
 346         desc.seg_not_present = 1;
 347         install_valid(&desc, AR_DPL3 | AR_TYPE_RWDATA | AR_S);
 348
 349         desc.seg_not_present = 0;
 350         desc.read_exec_only = 1;
 351         install_valid(&desc, AR_DPL3 | AR_TYPE_RODATA | AR_S | AR_P);
 352
 353         desc.read_exec_only = 0;
 354         desc.seg_not_present = 1;
 355         install_valid(&desc, AR_DPL3 | AR_TYPE_RWDATA | AR_S);
 356
 357         desc.read_exec_only = 1;
 358         desc.limit = 1;
 359         install_valid(&desc, AR_DPL3 | AR_TYPE_RODATA | AR_S);
 360
 361         desc.limit = 0;
 362         desc.base_addr = 1;
 363         install_valid(&desc, AR_DPL3 | AR_TYPE_RODATA | AR_S);
 364
 365         desc.base_addr = 0;
 366         install_invalid(&desc, false);
 367
 368         desc.seg_not_present = 0;
 369         desc.read_exec_only = 0;
 370         desc.seg_32bit = 1;
 371         install_valid(&desc, AR_DPL3 | AR_TYPE_RWDATA | AR_S | AR_P | AR_DB);
 372         install_invalid(&desc, true);
 373 }
 374
 375 /*
 376  * 0: thread is idle
 377  * 1: thread armed
 378  * 2: thread should clear LDT entry 0
 379  * 3: thread should exit
 380  */
 381 static volatile unsigned int ftx;
 382
 383 static void *threadproc(void *ctx)
 384 {
 385         cpu_set_t cpuset;
 386         CPU_ZERO(&cpuset);
 387         CPU_SET(1, &cpuset);
 388         if (sched_setaffinity(0, sizeof(cpuset), &cpuset) != 0)
 389                 err(1, "sched_setaffinity to CPU 1");   /* should never fail */
 390
 391         while (1) {
 392                 syscall(SYS_futex, &ftx, FUTEX_WAIT, 0, NULL, NULL, 0);
 393                 while (ftx != 2) {
 394                         if (ftx >= 3)
 395                                 return NULL;
 396                 }
 397
 398                 /* clear LDT entry 0 */
 399                 const struct user_desc desc = {};
 400                 if (syscall(SYS_modify_ldt, 1, &desc, sizeof(desc)) != 0)
 401                         err(1, "modify_ldt");
 402
 403                 /* If ftx == 2, set it to zero.  If ftx == 100, quit. */
 404                 unsigned int x = -2;
 405                 asm volatile ("lock xaddl %[x], %[ftx]" :
 406                               [x] "+r" (x), [ftx] "+m" (ftx));
 407                 if (x != 2)
 408                         return NULL;
 409         }
 410 }
 411
 412 static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
 413                        int flags)
 414 {
 415         struct sigaction sa;
 416         memset(&sa, 0, sizeof(sa));
 417         sa.sa_sigaction = handler;
 418         sa.sa_flags = SA_SIGINFO | flags;
 419         sigemptyset(&sa.sa_mask);
 420         if (sigaction(sig, &sa, 0))
 421                 err(1, "sigaction");
 422
 423 }
 424
 425 static jmp_buf jmpbuf;
 426
 427 static void sigsegv(int sig, siginfo_t *info, void *ctx_void)
 428 {
 429         siglongjmp(jmpbuf, 1);
 430 }
 431
 432 static void do_multicpu_tests(void)
 433 {
 434         cpu_set_t cpuset;
 435         pthread_t thread;
 436         int failures = 0, iters = 5, i;
 437         unsigned short orig_ss;
 438
 439         CPU_ZERO(&cpuset);
 440         CPU_SET(1, &cpuset);
 441         if (sched_setaffinity(0, sizeof(cpuset), &cpuset) != 0) {
 442                 printf("[SKIP]\tCannot set affinity to CPU 1\n");
 443                 return;
 444         }
 445
 446         CPU_ZERO(&cpuset);
 447         CPU_SET(0, &cpuset);
 448         if (sched_setaffinity(0, sizeof(cpuset), &cpuset) != 0) {
 449                 printf("[SKIP]\tCannot set affinity to CPU 0\n");
 450                 return;
 451         }
 452
 453         sethandler(SIGSEGV, sigsegv, 0);
 454 #ifdef __i386__
 455         /* True 32-bit kernels send SIGILL instead of SIGSEGV on IRET faults. */
 456         sethandler(SIGILL, sigsegv, 0);
 457 #endif
 458
 459         printf("[RUN]\tCross-CPU LDT invalidation\n");
 460
 461         if (pthread_create(&thread, 0, threadproc, 0) != 0)
 462                 err(1, "pthread_create");
 463
 464         asm volatile ("mov %%ss, %0" : "=rm" (orig_ss));
 465
 466         for (i = 0; i < 5; i++) {
 467                 if (sigsetjmp(jmpbuf, 1) != 0)
 468                         continue;
 469
 470                 /* Make sure the thread is ready after the last test. */
 471                 while (ftx != 0)
 472                         ;
 473
 474                 struct user_desc desc = {
 475                         .entry_number    = 0,
 476                         .base_addr       = 0,
 477                         .limit           = 0xfffff,
 478                         .seg_32bit       = 1,
 479                         .contents        = 0, /* Data */
 480                         .read_exec_only  = 0,
 481                         .limit_in_pages  = 1,
 482                         .seg_not_present = 0,
 483                         .useable         = 0
 484                 };
 485
 486                 if (safe_modify_ldt(0x11, &desc, sizeof(desc)) != 0) {
 487                         if (errno != ENOSYS)
 488                                 err(1, "modify_ldt");
 489                         printf("[SKIP]\tmodify_ldt unavailable\n");
 490                         break;
 491                 }
 492
 493                 /* Arm the thread. */
 494                 ftx = 1;
 495                 syscall(SYS_futex, &ftx, FUTEX_WAKE, 0, NULL, NULL, 0);
 496
 497                 asm volatile ("mov %0, %%ss" : : "r" (0x7));
 498
 499                 /* Go! */
 500                 ftx = 2;
 501
 502                 while (ftx != 0)
 503                         ;
 504
 505                 /*
 506                  * On success, modify_ldt will segfault us synchronously,
 507                  * and we'll escape via siglongjmp.
 508                  */
 509
 510                 failures++;
 511                 asm volatile ("mov %0, %%ss" : : "rm" (orig_ss));
 512         };
 513
 514         ftx = 100;  /* Kill the thread. */
 515         syscall(SYS_futex, &ftx, FUTEX_WAKE, 0, NULL, NULL, 0);
 516
 517         if (pthread_join(thread, NULL) != 0)
 518                 err(1, "pthread_join");
 519
 520         if (failures) {
 521                 printf("[FAIL]\t%d of %d iterations failed\n", failures, iters);
 522                 nerrs++;
 523         } else {
 524                 printf("[OK]\tAll %d iterations succeeded\n", iters);
 525         }
 526 }
 527
 528 static int finish_exec_test(void)
 529 {
 530         /*
 531          * In a sensible world, this would be check_invalid_segment(0, 1);
 532          * For better or for worse, though, the LDT is inherited across exec.
 533          * We can probably change this safely, but for now we test it.
 534          */
 535         check_valid_segment(0, 1,
 536                             AR_DPL3 | AR_TYPE_XRCODE | AR_S | AR_P | AR_DB,
 537                             42, true);
 538
 539         return nerrs ? 1 : 0;
 540 }
 541
 542 static void do_exec_test(void)
 543 {
 544         printf("[RUN]\tTest exec\n");
 545
 546         struct user_desc desc = {
 547                 .entry_number    = 0,
 548                 .base_addr       = 0,
 549                 .limit           = 42,
 550                 .seg_32bit       = 1,
 551                 .contents        = 2, /* Code, not conforming */
 552                 .read_exec_only  = 0,
 553                 .limit_in_pages  = 0,
 554                 .seg_not_present = 0,
 555                 .useable         = 0
 556         };
 557         install_valid(&desc, AR_DPL3 | AR_TYPE_XRCODE | AR_S | AR_P | AR_DB);
 558
 559         pid_t child = fork();
 560         if (child == 0) {
 561                 execl("/proc/self/exe", "ldt_gdt_test_exec", NULL);
 562                 printf("[FAIL]\tCould not exec self\n");
 563                 exit(1);        /* exec failed */
 564         } else {
 565                 int status;
 566                 if (waitpid(child, &status, 0) != child ||
 567                     !WIFEXITED(status)) {
 568                         printf("[FAIL]\tChild died\n");
 569                         nerrs++;
 570                 } else if (WEXITSTATUS(status) != 0) {
 571                         printf("[FAIL]\tChild failed\n");
 572                         nerrs++;
 573                 } else {
 574                         printf("[OK]\tChild succeeded\n");
 575                 }
 576         }
 577 }
 578
 579 static void setup_counter_page(void)
 580 {
 581         unsigned int *page = mmap(NULL, 4096, PROT_READ | PROT_WRITE,
 582                          MAP_ANONYMOUS | MAP_PRIVATE | MAP_32BIT, -1, 0);
 583         if (page == MAP_FAILED)
 584                 err(1, "mmap");
 585
 586         for (int i = 0; i < 1024; i++)
 587                 page[i] = i;
 588         counter_page = page;
 589 }
 590
 591 static int invoke_set_thread_area(void)
 592 {
 593         int ret;
 594         asm volatile ("int $0x80"
 595                       : "=a" (ret), "+m" (low_user_desc) :
 596                         "a" (243), "b" (low_user_desc)
 597                       : INT80_CLOBBERS);
 598         return ret;
 599 }
 600
 601 static void setup_low_user_desc(void)
 602 {
 603         low_user_desc = mmap(NULL, 2 * sizeof(struct user_desc),
 604                              PROT_READ | PROT_WRITE,
 605                              MAP_ANONYMOUS | MAP_PRIVATE | MAP_32BIT, -1, 0);
 606         if (low_user_desc == MAP_FAILED)
 607                 err(1, "mmap");
 608
 609         low_user_desc->entry_number     = -1;
 610         low_user_desc->base_addr        = (unsigned long)&counter_page[1];
 611         low_user_desc->limit            = 0xfffff;
 612         low_user_desc->seg_32bit        = 1;
 613         low_user_desc->contents         = 0; /* Data, grow-up*/
 614         low_user_desc->read_exec_only   = 0;
 615         low_user_desc->limit_in_pages   = 1;
 616         low_user_desc->seg_not_present  = 0;
 617         low_user_desc->useable          = 0;
 618
 619         if (invoke_set_thread_area() == 0) {
 620                 gdt_entry_num = low_user_desc->entry_number;
 621                 printf("[NOTE]\tset_thread_area is available; will use GDT index %d\n", gdt_entry_num);
 622         } else {
 623                 printf("[NOTE]\tset_thread_area is unavailable\n");
 624         }
 625
 626         low_user_desc_clear = low_user_desc + 1;
 627         low_user_desc_clear->entry_number = gdt_entry_num;
 628         low_user_desc_clear->read_exec_only = 1;
 629         low_user_desc_clear->seg_not_present = 1;
 630 }
 631
 632 static void test_gdt_invalidation(void)
 633 {
 634         if (!gdt_entry_num)
 635                 return; /* 64-bit only system -- we can't use set_thread_area */
 636
 637         unsigned short prev_sel;
 638         unsigned short sel;
 639         unsigned int eax;
 640         const char *result;
 641 #ifdef __x86_64__
 642         unsigned long saved_base;
 643         unsigned long new_base;
 644 #endif
 645
 646         /* Test DS */
 647         invoke_set_thread_area();
 648         eax = 243;
 649         sel = (gdt_entry_num << 3) | 3;
 650         asm volatile ("movw %%ds, %[prev_sel]\n\t"
 651                       "movw %[sel], %%ds\n\t"
 652 #ifdef __i386__
 653                       "pushl %%ebx\n\t"
 654 #endif
 655                       "movl %[arg1], %%ebx\n\t"
 656                       "int $0x80\n\t"   /* Should invalidate ds */
 657 #ifdef __i386__
 658                       "popl %%ebx\n\t"
 659 #endif
 660                       "movw %%ds, %[sel]\n\t"
 661                       "movw %[prev_sel], %%ds"
 662                       : [prev_sel] "=&r" (prev_sel), [sel] "+r" (sel),
 663                         "+a" (eax)
 664                       : "m" (low_user_desc_clear),
 665                         [arg1] "r" ((unsigned int)(unsigned long)low_user_desc_clear)
 666                       : INT80_CLOBBERS);
 667
 668         if (sel != 0) {
 669                 result = "FAIL";
 670                 nerrs++;
 671         } else {
 672                 result = "OK";
 673         }
 674         printf("[%s]\tInvalidate DS with set_thread_area: new DS = 0x%hx\n",
 675                result, sel);
 676
 677         /* Test ES */
 678         invoke_set_thread_area();
 679         eax = 243;
 680         sel = (gdt_entry_num << 3) | 3;
 681         asm volatile ("movw %%es, %[prev_sel]\n\t"
 682                       "movw %[sel], %%es\n\t"
 683 #ifdef __i386__
 684                       "pushl %%ebx\n\t"
 685 #endif
 686                       "movl %[arg1], %%ebx\n\t"
 687                       "int $0x80\n\t"   /* Should invalidate es */
 688 #ifdef __i386__
 689                       "popl %%ebx\n\t"
 690 #endif
 691                       "movw %%es, %[sel]\n\t"
 692                       "movw %[prev_sel], %%es"
 693                       : [prev_sel] "=&r" (prev_sel), [sel] "+r" (sel),
 694                         "+a" (eax)
 695                       : "m" (low_user_desc_clear),
 696                         [arg1] "r" ((unsigned int)(unsigned long)low_user_desc_clear)
 697                       : INT80_CLOBBERS);
 698
 699         if (sel != 0) {
 700                 result = "FAIL";
 701                 nerrs++;
 702         } else {
 703                 result = "OK";
 704         }
 705         printf("[%s]\tInvalidate ES with set_thread_area: new ES = 0x%hx\n",
 706                result, sel);
 707
 708         /* Test FS */
 709         invoke_set_thread_area();
 710         eax = 243;
 711         sel = (gdt_entry_num << 3) | 3;
 712 #ifdef __x86_64__
 713         syscall(SYS_arch_prctl, ARCH_GET_FS, &saved_base);
 714 #endif
 715         asm volatile ("movw %%fs, %[prev_sel]\n\t"
 716                       "movw %[sel], %%fs\n\t"
 717 #ifdef __i386__
 718                       "pushl %%ebx\n\t"
 719 #endif
 720                       "movl %[arg1], %%ebx\n\t"
 721                       "int $0x80\n\t"   /* Should invalidate fs */
 722 #ifdef __i386__
 723                       "popl %%ebx\n\t"
 724 #endif
 725                       "movw %%fs, %[sel]\n\t"
 726                       : [prev_sel] "=&r" (prev_sel), [sel] "+r" (sel),
 727                         "+a" (eax)
 728                       : "m" (low_user_desc_clear),
 729                         [arg1] "r" ((unsigned int)(unsigned long)low_user_desc_clear)
 730                       : INT80_CLOBBERS);
 731
 732 #ifdef __x86_64__
 733         syscall(SYS_arch_prctl, ARCH_GET_FS, &new_base);
 734 #endif
 735
 736         /* Restore FS/BASE for glibc */
 737         asm volatile ("movw %[prev_sel], %%fs" : : [prev_sel] "rm" (prev_sel));
 738 #ifdef __x86_64__
 739         if (saved_base)
 740                 syscall(SYS_arch_prctl, ARCH_SET_FS, saved_base);
 741 #endif
 742
 743         if (sel != 0) {
 744                 result = "FAIL";
 745                 nerrs++;
 746         } else {
 747                 result = "OK";
 748         }
 749         printf("[%s]\tInvalidate FS with set_thread_area: new FS = 0x%hx\n",
 750                result, sel);
 751
 752 #ifdef __x86_64__
 753         if (sel == 0 && new_base != 0) {
 754                 nerrs++;
 755                 printf("[FAIL]\tNew FSBASE was 0x%lx\n", new_base);
 756         } else {
 757                 printf("[OK]\tNew FSBASE was zero\n");
 758         }
 759 #endif
 760
 761         /* Test GS */
 762         invoke_set_thread_area();
 763         eax = 243;
 764         sel = (gdt_entry_num << 3) | 3;
 765 #ifdef __x86_64__
 766         syscall(SYS_arch_prctl, ARCH_GET_GS, &saved_base);
 767 #endif
 768         asm volatile ("movw %%gs, %[prev_sel]\n\t"
 769                       "movw %[sel], %%gs\n\t"
 770 #ifdef __i386__
 771                       "pushl %%ebx\n\t"
 772 #endif
 773                       "movl %[arg1], %%ebx\n\t"
 774                       "int $0x80\n\t"   /* Should invalidate gs */
 775 #ifdef __i386__
 776                       "popl %%ebx\n\t"
 777 #endif
 778                       "movw %%gs, %[sel]\n\t"
 779                       : [prev_sel] "=&r" (prev_sel), [sel] "+r" (sel),
 780                         "+a" (eax)
 781                       : "m" (low_user_desc_clear),
 782                         [arg1] "r" ((unsigned int)(unsigned long)low_user_desc_clear)
 783                       : INT80_CLOBBERS);
 784
 785 #ifdef __x86_64__
 786         syscall(SYS_arch_prctl, ARCH_GET_GS, &new_base);
 787 #endif
 788
 789         /* Restore GS/BASE for glibc */
 790         asm volatile ("movw %[prev_sel], %%gs" : : [prev_sel] "rm" (prev_sel));
 791 #ifdef __x86_64__
 792         if (saved_base)
 793                 syscall(SYS_arch_prctl, ARCH_SET_GS, saved_base);
 794 #endif
 795
 796         if (sel != 0) {
 797                 result = "FAIL";
 798                 nerrs++;
 799         } else {
 800                 result = "OK";
 801         }
 802         printf("[%s]\tInvalidate GS with set_thread_area: new GS = 0x%hx\n",
 803                result, sel);
 804
 805 #ifdef __x86_64__
 806         if (sel == 0 && new_base != 0) {
 807                 nerrs++;
 808                 printf("[FAIL]\tNew GSBASE was 0x%lx\n", new_base);
 809         } else {
 810                 printf("[OK]\tNew GSBASE was zero\n");
 811         }
 812 #endif
 813 }
 814
 815 int main(int argc, char **argv)
 816 {
 817         if (argc == 1 && !strcmp(argv[0], "ldt_gdt_test_exec"))
 818                 return finish_exec_test();
 819
 820         setup_counter_page();
 821         setup_low_user_desc();
 822
 823         do_simple_tests();
 824
 825         do_multicpu_tests();
 826
 827         do_exec_test();
 828
 829         test_gdt_invalidation();
 830
 831         return nerrs ? 1 : 0;
 832 }