tools/testing/selftests/x86/test_vsyscall.c

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2
   3 #define _GNU_SOURCE
   4
   5 #include <stdio.h>
   6 #include <sys/time.h>
   7 #include <time.h>
   8 #include <stdlib.h>
   9 #include <sys/syscall.h>
  10 #include <unistd.h>
  11 #include <dlfcn.h>
  12 #include <string.h>
  13 #include <inttypes.h>
  14 #include <signal.h>
  15 #include <sys/ucontext.h>
  16 #include <errno.h>
  17 #include <err.h>
  18 #include <sched.h>
  19 #include <stdbool.h>
  20 #include <setjmp.h>
  21 #include <sys/uio.h>
  22
  23 #include "helpers.h"
  24 #include "../kselftest.h"
  25
  26 #ifdef __x86_64__
  27 #define TOTAL_TESTS 13
  28 #else
  29 #define TOTAL_TESTS 8
  30 #endif
  31
  32 #ifdef __x86_64__
  33 # define VSYS(x) (x)
  34 #else
  35 # define VSYS(x) 0
  36 #endif
  37
  38 #ifndef SYS_getcpu
  39 # ifdef __x86_64__
  40 #  define SYS_getcpu 309
  41 # else
  42 #  define SYS_getcpu 318
  43 # endif
  44 #endif
  45
  46 /* max length of lines in /proc/self/maps - anything longer is skipped here */
  47 #define MAPS_LINE_LEN 128
  48
  49 /* vsyscalls and vDSO */
  50 bool vsyscall_map_r = false, vsyscall_map_x = false;
  51
  52 typedef long (*gtod_t)(struct timeval *tv, struct timezone *tz);
  53 const gtod_t vgtod = (gtod_t)VSYS(0xffffffffff600000);
  54 gtod_t vdso_gtod;
  55
  56 typedef int (*vgettime_t)(clockid_t, struct timespec *);
  57 vgettime_t vdso_gettime;
  58
  59 typedef long (*time_func_t)(time_t *t);
  60 const time_func_t vtime = (time_func_t)VSYS(0xffffffffff600400);
  61 time_func_t vdso_time;
  62
  63 typedef long (*getcpu_t)(unsigned *, unsigned *, void *);
  64 const getcpu_t vgetcpu = (getcpu_t)VSYS(0xffffffffff600800);
  65 getcpu_t vdso_getcpu;
  66
  67 static void init_vdso(void)
  68 {
  69         void *vdso = dlopen("linux-vdso.so.1", RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
  70         if (!vdso)
  71                 vdso = dlopen("linux-gate.so.1", RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
  72         if (!vdso) {
  73                 ksft_print_msg("[WARN] failed to find vDSO\n");
  74                 return;
  75         }
  76
  77         vdso_gtod = (gtod_t)dlsym(vdso, "__vdso_gettimeofday");
  78         if (!vdso_gtod)
  79                 ksft_print_msg("[WARN] failed to find gettimeofday in vDSO\n");
  80
  81         vdso_gettime = (vgettime_t)dlsym(vdso, "__vdso_clock_gettime");
  82         if (!vdso_gettime)
  83                 ksft_print_msg("[WARN] failed to find clock_gettime in vDSO\n");
  84
  85         vdso_time = (time_func_t)dlsym(vdso, "__vdso_time");
  86         if (!vdso_time)
  87                 ksft_print_msg("[WARN] failed to find time in vDSO\n");
  88
  89         vdso_getcpu = (getcpu_t)dlsym(vdso, "__vdso_getcpu");
  90         if (!vdso_getcpu)
  91                 ksft_print_msg("[WARN] failed to find getcpu in vDSO\n");
  92 }
  93
  94 /* syscalls */
  95 static inline long sys_gtod(struct timeval *tv, struct timezone *tz)
  96 {
  97         return syscall(SYS_gettimeofday, tv, tz);
  98 }
  99
 100 static inline long sys_time(time_t *t)
 101 {
 102         return syscall(SYS_time, t);
 103 }
 104
 105 static inline long sys_getcpu(unsigned * cpu, unsigned * node,
 106                               void* cache)
 107 {
 108         return syscall(SYS_getcpu, cpu, node, cache);
 109 }
 110
 111 static double tv_diff(const struct timeval *a, const struct timeval *b)
 112 {
 113         return (double)(a->tv_sec - b->tv_sec) +
 114                 (double)((int)a->tv_usec - (int)b->tv_usec) * 1e-6;
 115 }
 116
 117 static void check_gtod(const struct timeval *tv_sys1,
 118                        const struct timeval *tv_sys2,
 119                        const struct timezone *tz_sys,
 120                        const char *which,
 121                        const struct timeval *tv_other,
 122                        const struct timezone *tz_other)
 123 {
 124         double d1, d2;
 125
 126         if (tz_other && (tz_sys->tz_minuteswest != tz_other->tz_minuteswest ||
 127                          tz_sys->tz_dsttime != tz_other->tz_dsttime))
 128                 ksft_print_msg("%s tz mismatch\n", which);
 129
 130         d1 = tv_diff(tv_other, tv_sys1);
 131         d2 = tv_diff(tv_sys2, tv_other);
 132
 133         ksft_print_msg("%s time offsets: %lf %lf\n", which, d1, d2);
 134
 135         ksft_test_result(!(d1 < 0 || d2 < 0), "%s gettimeofday()'s timeval\n", which);
 136 }
 137
 138 static void test_gtod(void)
 139 {
 140         struct timeval tv_sys1, tv_sys2, tv_vdso, tv_vsys;
 141         struct timezone tz_sys, tz_vdso, tz_vsys;
 142         long ret_vdso = -1;
 143         long ret_vsys = -1;
 144
 145         ksft_print_msg("test gettimeofday()\n");
 146
 147         if (sys_gtod(&tv_sys1, &tz_sys) != 0)
 148                 ksft_exit_fail_msg("syscall gettimeofday: %s\n", strerror(errno));
 149         if (vdso_gtod)
 150                 ret_vdso = vdso_gtod(&tv_vdso, &tz_vdso);
 151         if (vsyscall_map_x)
 152                 ret_vsys = vgtod(&tv_vsys, &tz_vsys);
 153         if (sys_gtod(&tv_sys2, &tz_sys) != 0)
 154                 ksft_exit_fail_msg("syscall gettimeofday: %s\n", strerror(errno));
 155
 156         if (vdso_gtod) {
 157                 if (ret_vdso == 0)
 158                         check_gtod(&tv_sys1, &tv_sys2, &tz_sys, "vDSO", &tv_vdso, &tz_vdso);
 159                 else
 160                         ksft_test_result_fail("vDSO gettimeofday() failed: %ld\n", ret_vdso);
 161         } else {
 162                 ksft_test_result_skip("vdso_gtod isn't set\n");
 163         }
 164
 165         if (vsyscall_map_x) {
 166                 if (ret_vsys == 0)
 167                         check_gtod(&tv_sys1, &tv_sys2, &tz_sys, "vsyscall", &tv_vsys, &tz_vsys);
 168                 else
 169                         ksft_test_result_fail("vsys gettimeofday() failed: %ld\n", ret_vsys);
 170         } else {
 171                 ksft_test_result_skip("vsyscall_map_x isn't set\n");
 172         }
 173 }
 174
 175 static void test_time(void)
 176 {
 177         long t_sys1, t_sys2, t_vdso = 0, t_vsys = 0;
 178         long t2_sys1 = -1, t2_sys2 = -1, t2_vdso = -1, t2_vsys = -1;
 179
 180         ksft_print_msg("test time()\n");
 181         t_sys1 = sys_time(&t2_sys1);
 182         if (vdso_time)
 183                 t_vdso = vdso_time(&t2_vdso);
 184         if (vsyscall_map_x)
 185                 t_vsys = vtime(&t2_vsys);
 186         t_sys2 = sys_time(&t2_sys2);
 187         if (t_sys1 < 0 || t_sys1 != t2_sys1 || t_sys2 < 0 || t_sys2 != t2_sys2) {
 188                 ksft_print_msg("syscall failed (ret1:%ld output1:%ld ret2:%ld output2:%ld)\n",
 189                                t_sys1, t2_sys1, t_sys2, t2_sys2);
 190                 ksft_test_result_skip("vdso_time\n");
 191                 ksft_test_result_skip("vdso_time\n");
 192                 return;
 193         }
 194
 195         if (vdso_time) {
 196                 if (t_vdso < 0 || t_vdso != t2_vdso)
 197                         ksft_test_result_fail("vDSO failed (ret:%ld output:%ld)\n",
 198                                               t_vdso, t2_vdso);
 199                 else if (t_vdso < t_sys1 || t_vdso > t_sys2)
 200                         ksft_test_result_fail("vDSO returned the wrong time (%ld %ld %ld)\n",
 201                                               t_sys1, t_vdso, t_sys2);
 202                 else
 203                         ksft_test_result_pass("vDSO time() is okay\n");
 204         } else {
 205                 ksft_test_result_skip("vdso_time isn't set\n");
 206         }
 207
 208         if (vsyscall_map_x) {
 209                 if (t_vsys < 0 || t_vsys != t2_vsys)
 210                         ksft_test_result_fail("vsyscall failed (ret:%ld output:%ld)\n",
 211                                               t_vsys, t2_vsys);
 212                 else if (t_vsys < t_sys1 || t_vsys > t_sys2)
 213                         ksft_test_result_fail("vsyscall returned the wrong time (%ld %ld %ld)\n",
 214                                               t_sys1, t_vsys, t_sys2);
 215                 else
 216                         ksft_test_result_pass("vsyscall time() is okay\n");
 217         } else {
 218                 ksft_test_result_skip("vsyscall_map_x isn't set\n");
 219         }
 220 }
 221
 222 static void test_getcpu(int cpu)
 223 {
 224         unsigned int cpu_sys, cpu_vdso, cpu_vsys, node_sys, node_vdso, node_vsys;
 225         long ret_sys, ret_vdso = -1, ret_vsys = -1;
 226         unsigned int node = 0;
 227         bool have_node = false;
 228         cpu_set_t cpuset;
 229
 230         ksft_print_msg("getcpu() on CPU %d\n", cpu);
 231
 232         CPU_ZERO(&cpuset);
 233         CPU_SET(cpu, &cpuset);
 234         if (sched_setaffinity(0, sizeof(cpuset), &cpuset) != 0) {
 235                 ksft_print_msg("failed to force CPU %d\n", cpu);
 236                 ksft_test_result_skip("vdso_getcpu\n");
 237                 ksft_test_result_skip("vsyscall_map_x\n");
 238
 239                 return;
 240         }
 241
 242         ret_sys = sys_getcpu(&cpu_sys, &node_sys, 0);
 243         if (vdso_getcpu)
 244                 ret_vdso = vdso_getcpu(&cpu_vdso, &node_vdso, 0);
 245         if (vsyscall_map_x)
 246                 ret_vsys = vgetcpu(&cpu_vsys, &node_vsys, 0);
 247
 248         if (ret_sys == 0) {
 249                 if (cpu_sys != cpu)
 250                         ksft_print_msg("syscall reported CPU %u but should be %d\n",
 251                                        cpu_sys, cpu);
 252
 253                 have_node = true;
 254                 node = node_sys;
 255         }
 256
 257         if (vdso_getcpu) {
 258                 if (ret_vdso) {
 259                         ksft_test_result_fail("vDSO getcpu() failed\n");
 260                 } else {
 261                         if (!have_node) {
 262                                 have_node = true;
 263                                 node = node_vdso;
 264                         }
 265
 266                         if (cpu_vdso != cpu || node_vdso != node) {
 267                                 if (cpu_vdso != cpu)
 268                                         ksft_print_msg("vDSO reported CPU %u but should be %d\n",
 269                                                        cpu_vdso, cpu);
 270                                 if (node_vdso != node)
 271                                         ksft_print_msg("vDSO reported node %u but should be %u\n",
 272                                                        node_vdso, node);
 273                                 ksft_test_result_fail("Wrong values\n");
 274                         } else {
 275                                 ksft_test_result_pass("vDSO reported correct CPU and node\n");
 276                         }
 277                 }
 278         } else {
 279                 ksft_test_result_skip("vdso_getcpu isn't set\n");
 280         }
 281
 282         if (vsyscall_map_x) {
 283                 if (ret_vsys) {
 284                         ksft_test_result_fail("vsyscall getcpu() failed\n");
 285                 } else {
 286                         if (!have_node) {
 287                                 have_node = true;
 288                                 node = node_vsys;
 289                         }
 290
 291                         if (cpu_vsys != cpu || node_vsys != node) {
 292                                 if (cpu_vsys != cpu)
 293                                         ksft_print_msg("vsyscall reported CPU %u but should be %d\n",
 294                                                        cpu_vsys, cpu);
 295                                 if (node_vsys != node)
 296                                         ksft_print_msg("vsyscall reported node %u but should be %u\n",
 297                                                        node_vsys, node);
 298                                 ksft_test_result_fail("Wrong values\n");
 299                         } else {
 300                                 ksft_test_result_pass("vsyscall reported correct CPU and node\n");
 301                         }
 302                 }
 303         } else {
 304                 ksft_test_result_skip("vsyscall_map_x isn't set\n");
 305         }
 306 }
 307
 308 #ifdef __x86_64__
 309
 310 static jmp_buf jmpbuf;
 311 static volatile unsigned long segv_err;
 312
 313 static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
 314                        int flags)
 315 {
 316         struct sigaction sa;
 317
 318         memset(&sa, 0, sizeof(sa));
 319         sa.sa_sigaction = handler;
 320         sa.sa_flags = SA_SIGINFO | flags;
 321         sigemptyset(&sa.sa_mask);
 322         if (sigaction(sig, &sa, 0))
 323                 ksft_exit_fail_msg("sigaction failed\n");
 324 }
 325
 326 static void sigsegv(int sig, siginfo_t *info, void *ctx_void)
 327 {
 328         ucontext_t *ctx = (ucontext_t *)ctx_void;
 329
 330         segv_err =  ctx->uc_mcontext.gregs[REG_ERR];
 331         siglongjmp(jmpbuf, 1);
 332 }
 333
 334 static void test_vsys_r(void)
 335 {
 336         ksft_print_msg("Checking read access to the vsyscall page\n");
 337         bool can_read;
 338         if (sigsetjmp(jmpbuf, 1) == 0) {
 339                 *(volatile int *)0xffffffffff600000;
 340                 can_read = true;
 341         } else {
 342                 can_read = false;
 343         }
 344
 345         if (can_read && !vsyscall_map_r)
 346                 ksft_test_result_fail("We have read access, but we shouldn't\n");
 347         else if (!can_read && vsyscall_map_r)
 348                 ksft_test_result_fail("We don't have read access, but we should\n");
 349         else if (can_read)
 350                 ksft_test_result_pass("We have read access\n");
 351         else
 352                 ksft_test_result_pass("We do not have read access: #PF(0x%lx)\n", segv_err);
 353 }
 354
 355 static void test_vsys_x(void)
 356 {
 357         if (vsyscall_map_x) {
 358                 /* We already tested this adequately. */
 359                 ksft_test_result_pass("vsyscall_map_x is true\n");
 360                 return;
 361         }
 362
 363         ksft_print_msg("Make sure that vsyscalls really page fault\n");
 364
 365         bool can_exec;
 366         if (sigsetjmp(jmpbuf, 1) == 0) {
 367                 vgtod(NULL, NULL);
 368                 can_exec = true;
 369         } else {
 370                 can_exec = false;
 371         }
 372
 373         if (can_exec)
 374                 ksft_test_result_fail("Executing the vsyscall did not page fault\n");
 375         else if (segv_err & (1 << 4)) /* INSTR */
 376                 ksft_test_result_pass("Executing the vsyscall page failed: #PF(0x%lx)\n",
 377                                       segv_err);
 378         else
 379                 ksft_test_result_fail("Execution failed with the wrong error: #PF(0x%lx)\n",
 380                                       segv_err);
 381 }
 382
 383 /*
 384  * Debuggers expect ptrace() to be able to peek at the vsyscall page.
 385  * Use process_vm_readv() as a proxy for ptrace() to test this.  We
 386  * want it to work in the vsyscall=emulate case and to fail in the
 387  * vsyscall=xonly case.
 388  *
 389  * It's worth noting that this ABI is a bit nutty.  write(2) can't
 390  * read from the vsyscall page on any kernel version or mode.  The
 391  * fact that ptrace() ever worked was a nice courtesy of old kernels,
 392  * but the code to support it is fairly gross.
 393  */
 394 static void test_process_vm_readv(void)
 395 {
 396         char buf[4096];
 397         struct iovec local, remote;
 398         int ret;
 399
 400         ksft_print_msg("process_vm_readv() from vsyscall page\n");
 401
 402         local.iov_base = buf;
 403         local.iov_len = 4096;
 404         remote.iov_base = (void *)0xffffffffff600000;
 405         remote.iov_len = 4096;
 406         ret = process_vm_readv(getpid(), &local, 1, &remote, 1, 0);
 407         if (ret != 4096) {
 408                 /*
 409                  * We expect process_vm_readv() to work if and only if the
 410                  * vsyscall page is readable.
 411                  */
 412                 ksft_test_result(!vsyscall_map_r,
 413                                  "process_vm_readv() failed (ret = %d, errno = %d)\n", ret, errno);
 414                 return;
 415         }
 416
 417         if (vsyscall_map_r)
 418                 ksft_test_result(!memcmp(buf, remote.iov_base, sizeof(buf)), "Read data\n");
 419         else
 420                 ksft_test_result_fail("process_rm_readv() succeeded, but it should have failed in this configuration\n");
 421 }
 422
 423 static void init_vsys(void)
 424 {
 425         int nerrs = 0;
 426         FILE *maps;
 427         char line[MAPS_LINE_LEN];
 428         bool found = false;
 429
 430         maps = fopen("/proc/self/maps", "r");
 431         if (!maps) {
 432                 ksft_test_result_skip("Could not open /proc/self/maps -- assuming vsyscall is r-x\n");
 433                 vsyscall_map_r = true;
 434                 return;
 435         }
 436
 437         while (fgets(line, MAPS_LINE_LEN, maps)) {
 438                 char r, x;
 439                 void *start, *end;
 440                 char name[MAPS_LINE_LEN];
 441
 442                 /* sscanf() is safe here as strlen(name) >= strlen(line) */
 443                 if (sscanf(line, "%p-%p %c-%cp %*x %*x:%*x %*u %s",
 444                            &start, &end, &r, &x, name) != 5)
 445                         continue;
 446
 447                 if (strcmp(name, "[vsyscall]"))
 448                         continue;
 449
 450                 ksft_print_msg("vsyscall map: %s", line);
 451
 452                 if (start != (void *)0xffffffffff600000 ||
 453                     end != (void *)0xffffffffff601000) {
 454                         ksft_print_msg("address range is nonsense\n");
 455                         nerrs++;
 456                 }
 457
 458                 ksft_print_msg("vsyscall permissions are %c-%c\n", r, x);
 459                 vsyscall_map_r = (r == 'r');
 460                 vsyscall_map_x = (x == 'x');
 461
 462                 found = true;
 463                 break;
 464         }
 465
 466         fclose(maps);
 467
 468         if (!found) {
 469                 ksft_print_msg("no vsyscall map in /proc/self/maps\n");
 470                 vsyscall_map_r = false;
 471                 vsyscall_map_x = false;
 472         }
 473
 474         ksft_test_result(!nerrs, "vsyscall map\n");
 475 }
 476
 477 static volatile sig_atomic_t num_vsyscall_traps;
 478
 479 static void sigtrap(int sig, siginfo_t *info, void *ctx_void)
 480 {
 481         ucontext_t *ctx = (ucontext_t *)ctx_void;
 482         unsigned long ip = ctx->uc_mcontext.gregs[REG_RIP];
 483
 484         if (((ip ^ 0xffffffffff600000UL) & ~0xfffUL) == 0)
 485                 num_vsyscall_traps++;
 486 }
 487
 488 static void test_emulation(void)
 489 {
 490         time_t tmp;
 491         bool is_native;
 492
 493         if (!vsyscall_map_x) {
 494                 ksft_test_result_skip("vsyscall_map_x isn't set\n");
 495                 return;
 496         }
 497
 498         ksft_print_msg("checking that vsyscalls are emulated\n");
 499         sethandler(SIGTRAP, sigtrap, 0);
 500         set_eflags(get_eflags() | X86_EFLAGS_TF);
 501         vtime(&tmp);
 502         set_eflags(get_eflags() & ~X86_EFLAGS_TF);
 503
 504         /*
 505          * If vsyscalls are emulated, we expect a single trap in the
 506          * vsyscall page -- the call instruction will trap with RIP
 507          * pointing to the entry point before emulation takes over.
 508          * In native mode, we expect two traps, since whatever code
 509          * the vsyscall page contains will be more than just a ret
 510          * instruction.
 511          */
 512         is_native = (num_vsyscall_traps > 1);
 513
 514         ksft_test_result(!is_native, "vsyscalls are %s (%d instructions in vsyscall page)\n",
 515                          (is_native ? "native" : "emulated"), (int)num_vsyscall_traps);
 516 }
 517 #endif
 518
 519 int main(int argc, char **argv)
 520 {
 521         int total_tests = TOTAL_TESTS;
 522
 523         ksft_print_header();
 524         ksft_set_plan(total_tests);
 525
 526         init_vdso();
 527 #ifdef __x86_64__
 528         init_vsys();
 529 #endif
 530
 531         test_gtod();
 532         test_time();
 533         test_getcpu(0);
 534         test_getcpu(1);
 535
 536 #ifdef __x86_64__
 537         sethandler(SIGSEGV, sigsegv, 0);
 538         test_vsys_r();
 539         test_vsys_x();
 540         test_process_vm_readv();
 541         test_emulation();
 542 #endif
 543
 544         ksft_finished();
 545 }