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
  25 #ifdef __x86_64__
  26 # define VSYS(x) (x)
  27 #else
  28 # define VSYS(x) 0
  29 #endif
  30
  31 #ifndef SYS_getcpu
  32 # ifdef __x86_64__
  33 #  define SYS_getcpu 309
  34 # else
  35 #  define SYS_getcpu 318
  36 # endif
  37 #endif
  38
  39 /* max length of lines in /proc/self/maps - anything longer is skipped here */
  40 #define MAPS_LINE_LEN 128
  41
  42 static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
  43                        int flags)
  44 {
  45         struct sigaction sa;
  46         memset(&sa, 0, sizeof(sa));
  47         sa.sa_sigaction = handler;
  48         sa.sa_flags = SA_SIGINFO | flags;
  49         sigemptyset(&sa.sa_mask);
  50         if (sigaction(sig, &sa, 0))
  51                 err(1, "sigaction");
  52 }
  53
  54 /* vsyscalls and vDSO */
  55 bool vsyscall_map_r = false, vsyscall_map_x = false;
  56
  57 typedef long (*gtod_t)(struct timeval *tv, struct timezone *tz);
  58 const gtod_t vgtod = (gtod_t)VSYS(0xffffffffff600000);
  59 gtod_t vdso_gtod;
  60
  61 typedef int (*vgettime_t)(clockid_t, struct timespec *);
  62 vgettime_t vdso_gettime;
  63
  64 typedef long (*time_func_t)(time_t *t);
  65 const time_func_t vtime = (time_func_t)VSYS(0xffffffffff600400);
  66 time_func_t vdso_time;
  67
  68 typedef long (*getcpu_t)(unsigned *, unsigned *, void *);
  69 const getcpu_t vgetcpu = (getcpu_t)VSYS(0xffffffffff600800);
  70 getcpu_t vdso_getcpu;
  71
  72 static void init_vdso(void)
  73 {
  74         void *vdso = dlopen("linux-vdso.so.1", RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
  75         if (!vdso)
  76                 vdso = dlopen("linux-gate.so.1", RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
  77         if (!vdso) {
  78                 printf("[WARN]\tfailed to find vDSO\n");
  79                 return;
  80         }
  81
  82         vdso_gtod = (gtod_t)dlsym(vdso, "__vdso_gettimeofday");
  83         if (!vdso_gtod)
  84                 printf("[WARN]\tfailed to find gettimeofday in vDSO\n");
  85
  86         vdso_gettime = (vgettime_t)dlsym(vdso, "__vdso_clock_gettime");
  87         if (!vdso_gettime)
  88                 printf("[WARN]\tfailed to find clock_gettime in vDSO\n");
  89
  90         vdso_time = (time_func_t)dlsym(vdso, "__vdso_time");
  91         if (!vdso_time)
  92                 printf("[WARN]\tfailed to find time in vDSO\n");
  93
  94         vdso_getcpu = (getcpu_t)dlsym(vdso, "__vdso_getcpu");
  95         if (!vdso_getcpu) {
  96                 /* getcpu() was never wired up in the 32-bit vDSO. */
  97                 printf("[%s]\tfailed to find getcpu in vDSO\n",
  98                        sizeof(long) == 8 ? "WARN" : "NOTE");
  99         }
 100 }
 101
 102 static int init_vsys(void)
 103 {
 104 #ifdef __x86_64__
 105         int nerrs = 0;
 106         FILE *maps;
 107         char line[MAPS_LINE_LEN];
 108         bool found = false;
 109
 110         maps = fopen("/proc/self/maps", "r");
 111         if (!maps) {
 112                 printf("[WARN]\tCould not open /proc/self/maps -- assuming vsyscall is r-x\n");
 113                 vsyscall_map_r = true;
 114                 return 0;
 115         }
 116
 117         while (fgets(line, MAPS_LINE_LEN, maps)) {
 118                 char r, x;
 119                 void *start, *end;
 120                 char name[MAPS_LINE_LEN];
 121
 122                 /* sscanf() is safe here as strlen(name) >= strlen(line) */
 123                 if (sscanf(line, "%p-%p %c-%cp %*x %*x:%*x %*u %s",
 124                            &start, &end, &r, &x, name) != 5)
 125                         continue;
 126
 127                 if (strcmp(name, "[vsyscall]"))
 128                         continue;
 129
 130                 printf("\tvsyscall map: %s", line);
 131
 132                 if (start != (void *)0xffffffffff600000 ||
 133                     end != (void *)0xffffffffff601000) {
 134                         printf("[FAIL]\taddress range is nonsense\n");
 135                         nerrs++;
 136                 }
 137
 138                 printf("\tvsyscall permissions are %c-%c\n", r, x);
 139                 vsyscall_map_r = (r == 'r');
 140                 vsyscall_map_x = (x == 'x');
 141
 142                 found = true;
 143                 break;
 144         }
 145
 146         fclose(maps);
 147
 148         if (!found) {
 149                 printf("\tno vsyscall map in /proc/self/maps\n");
 150                 vsyscall_map_r = false;
 151                 vsyscall_map_x = false;
 152         }
 153
 154         return nerrs;
 155 #else
 156         return 0;
 157 #endif
 158 }
 159
 160 /* syscalls */
 161 static inline long sys_gtod(struct timeval *tv, struct timezone *tz)
 162 {
 163         return syscall(SYS_gettimeofday, tv, tz);
 164 }
 165
 166 static inline int sys_clock_gettime(clockid_t id, struct timespec *ts)
 167 {
 168         return syscall(SYS_clock_gettime, id, ts);
 169 }
 170
 171 static inline long sys_time(time_t *t)
 172 {
 173         return syscall(SYS_time, t);
 174 }
 175
 176 static inline long sys_getcpu(unsigned * cpu, unsigned * node,
 177                               void* cache)
 178 {
 179         return syscall(SYS_getcpu, cpu, node, cache);
 180 }
 181
 182 static jmp_buf jmpbuf;
 183 static volatile unsigned long segv_err;
 184
 185 static void sigsegv(int sig, siginfo_t *info, void *ctx_void)
 186 {
 187         ucontext_t *ctx = (ucontext_t *)ctx_void;
 188
 189         segv_err =  ctx->uc_mcontext.gregs[REG_ERR];
 190         siglongjmp(jmpbuf, 1);
 191 }
 192
 193 static double tv_diff(const struct timeval *a, const struct timeval *b)
 194 {
 195         return (double)(a->tv_sec - b->tv_sec) +
 196                 (double)((int)a->tv_usec - (int)b->tv_usec) * 1e-6;
 197 }
 198
 199 static int check_gtod(const struct timeval *tv_sys1,
 200                       const struct timeval *tv_sys2,
 201                       const struct timezone *tz_sys,
 202                       const char *which,
 203                       const struct timeval *tv_other,
 204                       const struct timezone *tz_other)
 205 {
 206         int nerrs = 0;
 207         double d1, d2;
 208
 209         if (tz_other && (tz_sys->tz_minuteswest != tz_other->tz_minuteswest || tz_sys->tz_dsttime != tz_other->tz_dsttime)) {
 210                 printf("[FAIL] %s tz mismatch\n", which);
 211                 nerrs++;
 212         }
 213
 214         d1 = tv_diff(tv_other, tv_sys1);
 215         d2 = tv_diff(tv_sys2, tv_other);
 216         printf("\t%s time offsets: %lf %lf\n", which, d1, d2);
 217
 218         if (d1 < 0 || d2 < 0) {
 219                 printf("[FAIL]\t%s time was inconsistent with the syscall\n", which);
 220                 nerrs++;
 221         } else {
 222                 printf("[OK]\t%s gettimeofday()'s timeval was okay\n", which);
 223         }
 224
 225         return nerrs;
 226 }
 227
 228 static int test_gtod(void)
 229 {
 230         struct timeval tv_sys1, tv_sys2, tv_vdso, tv_vsys;
 231         struct timezone tz_sys, tz_vdso, tz_vsys;
 232         long ret_vdso = -1;
 233         long ret_vsys = -1;
 234         int nerrs = 0;
 235
 236         printf("[RUN]\ttest gettimeofday()\n");
 237
 238         if (sys_gtod(&tv_sys1, &tz_sys) != 0)
 239                 err(1, "syscall gettimeofday");
 240         if (vdso_gtod)
 241                 ret_vdso = vdso_gtod(&tv_vdso, &tz_vdso);
 242         if (vsyscall_map_x)
 243                 ret_vsys = vgtod(&tv_vsys, &tz_vsys);
 244         if (sys_gtod(&tv_sys2, &tz_sys) != 0)
 245                 err(1, "syscall gettimeofday");
 246
 247         if (vdso_gtod) {
 248                 if (ret_vdso == 0) {
 249                         nerrs += check_gtod(&tv_sys1, &tv_sys2, &tz_sys, "vDSO", &tv_vdso, &tz_vdso);
 250                 } else {
 251                         printf("[FAIL]\tvDSO gettimeofday() failed: %ld\n", ret_vdso);
 252                         nerrs++;
 253                 }
 254         }
 255
 256         if (vsyscall_map_x) {
 257                 if (ret_vsys == 0) {
 258                         nerrs += check_gtod(&tv_sys1, &tv_sys2, &tz_sys, "vsyscall", &tv_vsys, &tz_vsys);
 259                 } else {
 260                         printf("[FAIL]\tvsys gettimeofday() failed: %ld\n", ret_vsys);
 261                         nerrs++;
 262                 }
 263         }
 264
 265         return nerrs;
 266 }
 267
 268 static int test_time(void) {
 269         int nerrs = 0;
 270
 271         printf("[RUN]\ttest time()\n");
 272         long t_sys1, t_sys2, t_vdso = 0, t_vsys = 0;
 273         long t2_sys1 = -1, t2_sys2 = -1, t2_vdso = -1, t2_vsys = -1;
 274         t_sys1 = sys_time(&t2_sys1);
 275         if (vdso_time)
 276                 t_vdso = vdso_time(&t2_vdso);
 277         if (vsyscall_map_x)
 278                 t_vsys = vtime(&t2_vsys);
 279         t_sys2 = sys_time(&t2_sys2);
 280         if (t_sys1 < 0 || t_sys1 != t2_sys1 || t_sys2 < 0 || t_sys2 != t2_sys2) {
 281                 printf("[FAIL]\tsyscall failed (ret1:%ld output1:%ld ret2:%ld output2:%ld)\n", t_sys1, t2_sys1, t_sys2, t2_sys2);
 282                 nerrs++;
 283                 return nerrs;
 284         }
 285
 286         if (vdso_time) {
 287                 if (t_vdso < 0 || t_vdso != t2_vdso) {
 288                         printf("[FAIL]\tvDSO failed (ret:%ld output:%ld)\n", t_vdso, t2_vdso);
 289                         nerrs++;
 290                 } else if (t_vdso < t_sys1 || t_vdso > t_sys2) {
 291                         printf("[FAIL]\tvDSO returned the wrong time (%ld %ld %ld)\n", t_sys1, t_vdso, t_sys2);
 292                         nerrs++;
 293                 } else {
 294                         printf("[OK]\tvDSO time() is okay\n");
 295                 }
 296         }
 297
 298         if (vsyscall_map_x) {
 299                 if (t_vsys < 0 || t_vsys != t2_vsys) {
 300                         printf("[FAIL]\tvsyscall failed (ret:%ld output:%ld)\n", t_vsys, t2_vsys);
 301                         nerrs++;
 302                 } else if (t_vsys < t_sys1 || t_vsys > t_sys2) {
 303                         printf("[FAIL]\tvsyscall returned the wrong time (%ld %ld %ld)\n", t_sys1, t_vsys, t_sys2);
 304                         nerrs++;
 305                 } else {
 306                         printf("[OK]\tvsyscall time() is okay\n");
 307                 }
 308         }
 309
 310         return nerrs;
 311 }
 312
 313 static int test_getcpu(int cpu)
 314 {
 315         int nerrs = 0;
 316         long ret_sys, ret_vdso = -1, ret_vsys = -1;
 317
 318         printf("[RUN]\tgetcpu() on CPU %d\n", cpu);
 319
 320         cpu_set_t cpuset;
 321         CPU_ZERO(&cpuset);
 322         CPU_SET(cpu, &cpuset);
 323         if (sched_setaffinity(0, sizeof(cpuset), &cpuset) != 0) {
 324                 printf("[SKIP]\tfailed to force CPU %d\n", cpu);
 325                 return nerrs;
 326         }
 327
 328         unsigned cpu_sys, cpu_vdso, cpu_vsys, node_sys, node_vdso, node_vsys;
 329         unsigned node = 0;
 330         bool have_node = false;
 331         ret_sys = sys_getcpu(&cpu_sys, &node_sys, 0);
 332         if (vdso_getcpu)
 333                 ret_vdso = vdso_getcpu(&cpu_vdso, &node_vdso, 0);
 334         if (vsyscall_map_x)
 335                 ret_vsys = vgetcpu(&cpu_vsys, &node_vsys, 0);
 336
 337         if (ret_sys == 0) {
 338                 if (cpu_sys != cpu) {
 339                         printf("[FAIL]\tsyscall reported CPU %hu but should be %d\n", cpu_sys, cpu);
 340                         nerrs++;
 341                 }
 342
 343                 have_node = true;
 344                 node = node_sys;
 345         }
 346
 347         if (vdso_getcpu) {
 348                 if (ret_vdso) {
 349                         printf("[FAIL]\tvDSO getcpu() failed\n");
 350                         nerrs++;
 351                 } else {
 352                         if (!have_node) {
 353                                 have_node = true;
 354                                 node = node_vdso;
 355                         }
 356
 357                         if (cpu_vdso != cpu) {
 358                                 printf("[FAIL]\tvDSO reported CPU %hu but should be %d\n", cpu_vdso, cpu);
 359                                 nerrs++;
 360                         } else {
 361                                 printf("[OK]\tvDSO reported correct CPU\n");
 362                         }
 363
 364                         if (node_vdso != node) {
 365                                 printf("[FAIL]\tvDSO reported node %hu but should be %hu\n", node_vdso, node);
 366                                 nerrs++;
 367                         } else {
 368                                 printf("[OK]\tvDSO reported correct node\n");
 369                         }
 370                 }
 371         }
 372
 373         if (vsyscall_map_x) {
 374                 if (ret_vsys) {
 375                         printf("[FAIL]\tvsyscall getcpu() failed\n");
 376                         nerrs++;
 377                 } else {
 378                         if (!have_node) {
 379                                 have_node = true;
 380                                 node = node_vsys;
 381                         }
 382
 383                         if (cpu_vsys != cpu) {
 384                                 printf("[FAIL]\tvsyscall reported CPU %hu but should be %d\n", cpu_vsys, cpu);
 385                                 nerrs++;
 386                         } else {
 387                                 printf("[OK]\tvsyscall reported correct CPU\n");
 388                         }
 389
 390                         if (node_vsys != node) {
 391                                 printf("[FAIL]\tvsyscall reported node %hu but should be %hu\n", node_vsys, node);
 392                                 nerrs++;
 393                         } else {
 394                                 printf("[OK]\tvsyscall reported correct node\n");
 395                         }
 396                 }
 397         }
 398
 399         return nerrs;
 400 }
 401
 402 static int test_vsys_r(void)
 403 {
 404 #ifdef __x86_64__
 405         printf("[RUN]\tChecking read access to the vsyscall page\n");
 406         bool can_read;
 407         if (sigsetjmp(jmpbuf, 1) == 0) {
 408                 *(volatile int *)0xffffffffff600000;
 409                 can_read = true;
 410         } else {
 411                 can_read = false;
 412         }
 413
 414         if (can_read && !vsyscall_map_r) {
 415                 printf("[FAIL]\tWe have read access, but we shouldn't\n");
 416                 return 1;
 417         } else if (!can_read && vsyscall_map_r) {
 418                 printf("[FAIL]\tWe don't have read access, but we should\n");
 419                 return 1;
 420         } else if (can_read) {
 421                 printf("[OK]\tWe have read access\n");
 422         } else {
 423                 printf("[OK]\tWe do not have read access: #PF(0x%lx)\n",
 424                        segv_err);
 425         }
 426 #endif
 427
 428         return 0;
 429 }
 430
 431 static int test_vsys_x(void)
 432 {
 433 #ifdef __x86_64__
 434         if (vsyscall_map_x) {
 435                 /* We already tested this adequately. */
 436                 return 0;
 437         }
 438
 439         printf("[RUN]\tMake sure that vsyscalls really page fault\n");
 440
 441         bool can_exec;
 442         if (sigsetjmp(jmpbuf, 1) == 0) {
 443                 vgtod(NULL, NULL);
 444                 can_exec = true;
 445         } else {
 446                 can_exec = false;
 447         }
 448
 449         if (can_exec) {
 450                 printf("[FAIL]\tExecuting the vsyscall did not page fault\n");
 451                 return 1;
 452         } else if (segv_err & (1 << 4)) { /* INSTR */
 453                 printf("[OK]\tExecuting the vsyscall page failed: #PF(0x%lx)\n",
 454                        segv_err);
 455         } else {
 456                 printf("[FAIL]\tExecution failed with the wrong error: #PF(0x%lx)\n",
 457                        segv_err);
 458                 return 1;
 459         }
 460 #endif
 461
 462         return 0;
 463 }
 464
 465 /*
 466  * Debuggers expect ptrace() to be able to peek at the vsyscall page.
 467  * Use process_vm_readv() as a proxy for ptrace() to test this.  We
 468  * want it to work in the vsyscall=emulate case and to fail in the
 469  * vsyscall=xonly case.
 470  *
 471  * It's worth noting that this ABI is a bit nutty.  write(2) can't
 472  * read from the vsyscall page on any kernel version or mode.  The
 473  * fact that ptrace() ever worked was a nice courtesy of old kernels,
 474  * but the code to support it is fairly gross.
 475  */
 476 static int test_process_vm_readv(void)
 477 {
 478 #ifdef __x86_64__
 479         char buf[4096];
 480         struct iovec local, remote;
 481         int ret;
 482
 483         printf("[RUN]\tprocess_vm_readv() from vsyscall page\n");
 484
 485         local.iov_base = buf;
 486         local.iov_len = 4096;
 487         remote.iov_base = (void *)0xffffffffff600000;
 488         remote.iov_len = 4096;
 489         ret = process_vm_readv(getpid(), &local, 1, &remote, 1, 0);
 490         if (ret != 4096) {
 491                 /*
 492                  * We expect process_vm_readv() to work if and only if the
 493                  * vsyscall page is readable.
 494                  */
 495                 printf("[%s]\tprocess_vm_readv() failed (ret = %d, errno = %d)\n", vsyscall_map_r ? "FAIL" : "OK", ret, errno);
 496                 return vsyscall_map_r ? 1 : 0;
 497         }
 498
 499         if (vsyscall_map_r) {
 500                 if (!memcmp(buf, (const void *)0xffffffffff600000, 4096)) {
 501                         printf("[OK]\tIt worked and read correct data\n");
 502                 } else {
 503                         printf("[FAIL]\tIt worked but returned incorrect data\n");
 504                         return 1;
 505                 }
 506         } else {
 507                 printf("[FAIL]\tprocess_rm_readv() succeeded, but it should have failed in this configuration\n");
 508                 return 1;
 509         }
 510 #endif
 511
 512         return 0;
 513 }
 514
 515 #ifdef __x86_64__
 516 static volatile sig_atomic_t num_vsyscall_traps;
 517
 518 static void sigtrap(int sig, siginfo_t *info, void *ctx_void)
 519 {
 520         ucontext_t *ctx = (ucontext_t *)ctx_void;
 521         unsigned long ip = ctx->uc_mcontext.gregs[REG_RIP];
 522
 523         if (((ip ^ 0xffffffffff600000UL) & ~0xfffUL) == 0)
 524                 num_vsyscall_traps++;
 525 }
 526
 527 static int test_emulation(void)
 528 {
 529         time_t tmp;
 530         bool is_native;
 531
 532         if (!vsyscall_map_x)
 533                 return 0;
 534
 535         printf("[RUN]\tchecking that vsyscalls are emulated\n");
 536         sethandler(SIGTRAP, sigtrap, 0);
 537         set_eflags(get_eflags() | X86_EFLAGS_TF);
 538         vtime(&tmp);
 539         set_eflags(get_eflags() & ~X86_EFLAGS_TF);
 540
 541         /*
 542          * If vsyscalls are emulated, we expect a single trap in the
 543          * vsyscall page -- the call instruction will trap with RIP
 544          * pointing to the entry point before emulation takes over.
 545          * In native mode, we expect two traps, since whatever code
 546          * the vsyscall page contains will be more than just a ret
 547          * instruction.
 548          */
 549         is_native = (num_vsyscall_traps > 1);
 550
 551         printf("[%s]\tvsyscalls are %s (%d instructions in vsyscall page)\n",
 552                (is_native ? "FAIL" : "OK"),
 553                (is_native ? "native" : "emulated"),
 554                (int)num_vsyscall_traps);
 555
 556         return is_native;
 557 }
 558 #endif
 559
 560 int main(int argc, char **argv)
 561 {
 562         int nerrs = 0;
 563
 564         init_vdso();
 565         nerrs += init_vsys();
 566
 567         nerrs += test_gtod();
 568         nerrs += test_time();
 569         nerrs += test_getcpu(0);
 570         nerrs += test_getcpu(1);
 571
 572         sethandler(SIGSEGV, sigsegv, 0);
 573         nerrs += test_vsys_r();
 574         nerrs += test_vsys_x();
 575
 576         nerrs += test_process_vm_readv();
 577
 578 #ifdef __x86_64__
 579         nerrs += test_emulation();
 580 #endif
 581
 582         return nerrs ? 1 : 0;
 583 }