tools/testing/selftests/x86/ptrace_syscall.c

   1 #define _GNU_SOURCE
   2
   3 #include <sys/ptrace.h>
   4 #include <sys/types.h>
   5 #include <sys/wait.h>
   6 #include <sys/syscall.h>
   7 #include <sys/user.h>
   8 #include <unistd.h>
   9 #include <errno.h>
  10 #include <stddef.h>
  11 #include <stdio.h>
  12 #include <err.h>
  13 #include <string.h>
  14 #include <asm/ptrace-abi.h>
  15 #include <sys/auxv.h>
  16
  17 /* Bitness-agnostic defines for user_regs_struct fields. */
  18 #ifdef __x86_64__
  19 # define user_syscall_nr        orig_rax
  20 # define user_arg0              rdi
  21 # define user_arg1              rsi
  22 # define user_arg2              rdx
  23 # define user_arg3              r10
  24 # define user_arg4              r8
  25 # define user_arg5              r9
  26 # define user_ip                rip
  27 # define user_ax                rax
  28 #else
  29 # define user_syscall_nr        orig_eax
  30 # define user_arg0              ebx
  31 # define user_arg1              ecx
  32 # define user_arg2              edx
  33 # define user_arg3              esi
  34 # define user_arg4              edi
  35 # define user_arg5              ebp
  36 # define user_ip                eip
  37 # define user_ax                eax
  38 #endif
  39
  40 static int nerrs = 0;
  41
  42 struct syscall_args32 {
  43         uint32_t nr, arg0, arg1, arg2, arg3, arg4, arg5;
  44 };
  45
  46 #ifdef __i386__
  47 extern void sys32_helper(struct syscall_args32 *, void *);
  48 extern void int80_and_ret(void);
  49 #endif
  50
  51 /*
  52  * Helper to invoke int80 with controlled regs and capture the final regs.
  53  */
  54 static void do_full_int80(struct syscall_args32 *args)
  55 {
  56 #ifdef __x86_64__
  57         register unsigned long bp asm("bp") = args->arg5;
  58         asm volatile ("int $0x80"
  59                       : "+a" (args->nr),
  60                         "+b" (args->arg0), "+c" (args->arg1), "+d" (args->arg2),
  61                         "+S" (args->arg3), "+D" (args->arg4), "+r" (bp)
  62                         : : "r8", "r9", "r10", "r11");
  63         args->arg5 = bp;
  64 #else
  65         sys32_helper(args, int80_and_ret);
  66 #endif
  67 }
  68
  69 #ifdef __i386__
  70 static void (*vsyscall32)(void);
  71
  72 /*
  73  * Nasty helper to invoke AT_SYSINFO (i.e. __kernel_vsyscall) with
  74  * controlled regs and capture the final regs.  This is so nasty that it
  75  * crashes my copy of gdb :)
  76  */
  77 static void do_full_vsyscall32(struct syscall_args32 *args)
  78 {
  79         sys32_helper(args, vsyscall32);
  80 }
  81 #endif
  82
  83 static siginfo_t wait_trap(pid_t chld)
  84 {
  85         siginfo_t si;
  86         if (waitid(P_PID, chld, &si, WEXITED|WSTOPPED) != 0)
  87                 err(1, "waitid");
  88         if (si.si_pid != chld)
  89                 errx(1, "got unexpected pid in event\n");
  90         if (si.si_code != CLD_TRAPPED)
  91                 errx(1, "got unexpected event type %d\n", si.si_code);
  92         return si;
  93 }
  94
  95 static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
  96                        int flags)
  97 {
  98         struct sigaction sa;
  99         memset(&sa, 0, sizeof(sa));
 100         sa.sa_sigaction = handler;
 101         sa.sa_flags = SA_SIGINFO | flags;
 102         sigemptyset(&sa.sa_mask);
 103         if (sigaction(sig, &sa, 0))
 104                 err(1, "sigaction");
 105 }
 106
 107 static void setsigign(int sig, int flags)
 108 {
 109         struct sigaction sa;
 110         memset(&sa, 0, sizeof(sa));
 111         sa.sa_sigaction = (void *)SIG_IGN;
 112         sa.sa_flags = flags;
 113         sigemptyset(&sa.sa_mask);
 114         if (sigaction(sig, &sa, 0))
 115                 err(1, "sigaction");
 116 }
 117
 118 static void clearhandler(int sig)
 119 {
 120         struct sigaction sa;
 121         memset(&sa, 0, sizeof(sa));
 122         sa.sa_handler = SIG_DFL;
 123         sigemptyset(&sa.sa_mask);
 124         if (sigaction(sig, &sa, 0))
 125                 err(1, "sigaction");
 126 }
 127
 128 #ifdef __x86_64__
 129 # define REG_BP REG_RBP
 130 #else
 131 # define REG_BP REG_EBP
 132 #endif
 133
 134 static void empty_handler(int sig, siginfo_t *si, void *ctx_void)
 135 {
 136 }
 137
 138 static void test_sys32_regs(void (*do_syscall)(struct syscall_args32 *))
 139 {
 140         struct syscall_args32 args = {
 141                 .nr = 224,      /* gettid */
 142                 .arg0 = 10, .arg1 = 11, .arg2 = 12,
 143                 .arg3 = 13, .arg4 = 14, .arg5 = 15,
 144         };
 145
 146         do_syscall(&args);
 147
 148         if (args.nr != getpid() ||
 149             args.arg0 != 10 || args.arg1 != 11 || args.arg2 != 12 ||
 150             args.arg3 != 13 || args.arg4 != 14 || args.arg5 != 15) {
 151                 printf("[FAIL]\tgetpid() failed to preserve regs\n");
 152                 nerrs++;
 153         } else {
 154                 printf("[OK]\tgetpid() preserves regs\n");
 155         }
 156
 157         sethandler(SIGUSR1, empty_handler, 0);
 158
 159         args.nr = 37;   /* kill */
 160         args.arg0 = getpid();
 161         args.arg1 = SIGUSR1;
 162         do_syscall(&args);
 163         if (args.nr != 0 ||
 164             args.arg0 != getpid() || args.arg1 != SIGUSR1 || args.arg2 != 12 ||
 165             args.arg3 != 13 || args.arg4 != 14 || args.arg5 != 15) {
 166                 printf("[FAIL]\tkill(getpid(), SIGUSR1) failed to preserve regs\n");
 167                 nerrs++;
 168         } else {
 169                 printf("[OK]\tkill(getpid(), SIGUSR1) preserves regs\n");
 170         }
 171         clearhandler(SIGUSR1);
 172 }
 173
 174 static void test_ptrace_syscall_restart(void)
 175 {
 176         printf("[RUN]\tptrace-induced syscall restart\n");
 177         pid_t chld = fork();
 178         if (chld < 0)
 179                 err(1, "fork");
 180
 181         if (chld == 0) {
 182                 if (ptrace(PTRACE_TRACEME, 0, 0, 0) != 0)
 183                         err(1, "PTRACE_TRACEME");
 184
 185                 printf("\tChild will make one syscall\n");
 186                 raise(SIGSTOP);
 187
 188                 syscall(SYS_gettid, 10, 11, 12, 13, 14, 15);
 189                 _exit(0);
 190         }
 191
 192         int status;
 193
 194         /* Wait for SIGSTOP. */
 195         if (waitpid(chld, &status, 0) != chld || !WIFSTOPPED(status))
 196                 err(1, "waitpid");
 197
 198         struct user_regs_struct regs;
 199
 200         printf("[RUN]\tSYSEMU\n");
 201         if (ptrace(PTRACE_SYSEMU, chld, 0, 0) != 0)
 202                 err(1, "PTRACE_SYSEMU");
 203         wait_trap(chld);
 204
 205         if (ptrace(PTRACE_GETREGS, chld, 0, &regs) != 0)
 206                 err(1, "PTRACE_GETREGS");
 207
 208         if (regs.user_syscall_nr != SYS_gettid ||
 209             regs.user_arg0 != 10 || regs.user_arg1 != 11 ||
 210             regs.user_arg2 != 12 || regs.user_arg3 != 13 ||
 211             regs.user_arg4 != 14 || regs.user_arg5 != 15) {
 212                 printf("[FAIL]\tInitial args are wrong (nr=%lu, args=%lu %lu %lu %lu %lu %lu)\n", (unsigned long)regs.user_syscall_nr, (unsigned long)regs.user_arg0, (unsigned long)regs.user_arg1, (unsigned long)regs.user_arg2, (unsigned long)regs.user_arg3, (unsigned long)regs.user_arg4, (unsigned long)regs.user_arg5);
 213                 nerrs++;
 214         } else {
 215                 printf("[OK]\tInitial nr and args are correct\n");
 216         }
 217
 218         printf("[RUN]\tRestart the syscall (ip = 0x%lx)\n",
 219                (unsigned long)regs.user_ip);
 220
 221         /*
 222          * This does exactly what it appears to do if syscall is int80 or
 223          * SYSCALL64.  For SYSCALL32 or SYSENTER, though, this is highly
 224          * magical.  It needs to work so that ptrace and syscall restart
 225          * work as expected.
 226          */
 227         regs.user_ax = regs.user_syscall_nr;
 228         regs.user_ip -= 2;
 229         if (ptrace(PTRACE_SETREGS, chld, 0, &regs) != 0)
 230                 err(1, "PTRACE_SETREGS");
 231
 232         if (ptrace(PTRACE_SYSEMU, chld, 0, 0) != 0)
 233                 err(1, "PTRACE_SYSEMU");
 234         wait_trap(chld);
 235
 236         if (ptrace(PTRACE_GETREGS, chld, 0, &regs) != 0)
 237                 err(1, "PTRACE_GETREGS");
 238
 239         if (regs.user_syscall_nr != SYS_gettid ||
 240             regs.user_arg0 != 10 || regs.user_arg1 != 11 ||
 241             regs.user_arg2 != 12 || regs.user_arg3 != 13 ||
 242             regs.user_arg4 != 14 || regs.user_arg5 != 15) {
 243                 printf("[FAIL]\tRestart nr or args are wrong (nr=%lu, args=%lu %lu %lu %lu %lu %lu)\n", (unsigned long)regs.user_syscall_nr, (unsigned long)regs.user_arg0, (unsigned long)regs.user_arg1, (unsigned long)regs.user_arg2, (unsigned long)regs.user_arg3, (unsigned long)regs.user_arg4, (unsigned long)regs.user_arg5);
 244                 nerrs++;
 245         } else {
 246                 printf("[OK]\tRestarted nr and args are correct\n");
 247         }
 248
 249         printf("[RUN]\tChange nr and args and restart the syscall (ip = 0x%lx)\n",
 250                (unsigned long)regs.user_ip);
 251
 252         regs.user_ax = SYS_getpid;
 253         regs.user_arg0 = 20;
 254         regs.user_arg1 = 21;
 255         regs.user_arg2 = 22;
 256         regs.user_arg3 = 23;
 257         regs.user_arg4 = 24;
 258         regs.user_arg5 = 25;
 259         regs.user_ip -= 2;
 260
 261         if (ptrace(PTRACE_SETREGS, chld, 0, &regs) != 0)
 262                 err(1, "PTRACE_SETREGS");
 263
 264         if (ptrace(PTRACE_SYSEMU, chld, 0, 0) != 0)
 265                 err(1, "PTRACE_SYSEMU");
 266         wait_trap(chld);
 267
 268         if (ptrace(PTRACE_GETREGS, chld, 0, &regs) != 0)
 269                 err(1, "PTRACE_GETREGS");
 270
 271         if (regs.user_syscall_nr != SYS_getpid ||
 272             regs.user_arg0 != 20 || regs.user_arg1 != 21 || regs.user_arg2 != 22 ||
 273             regs.user_arg3 != 23 || regs.user_arg4 != 24 || regs.user_arg5 != 25) {
 274                 printf("[FAIL]\tRestart nr or args are wrong (nr=%lu, args=%lu %lu %lu %lu %lu %lu)\n", (unsigned long)regs.user_syscall_nr, (unsigned long)regs.user_arg0, (unsigned long)regs.user_arg1, (unsigned long)regs.user_arg2, (unsigned long)regs.user_arg3, (unsigned long)regs.user_arg4, (unsigned long)regs.user_arg5);
 275                 nerrs++;
 276         } else {
 277                 printf("[OK]\tReplacement nr and args are correct\n");
 278         }
 279
 280         if (ptrace(PTRACE_CONT, chld, 0, 0) != 0)
 281                 err(1, "PTRACE_CONT");
 282         if (waitpid(chld, &status, 0) != chld)
 283                 err(1, "waitpid");
 284         if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
 285                 printf("[FAIL]\tChild failed\n");
 286                 nerrs++;
 287         } else {
 288                 printf("[OK]\tChild exited cleanly\n");
 289         }
 290 }
 291
 292 static void test_restart_under_ptrace(void)
 293 {
 294         printf("[RUN]\tkernel syscall restart under ptrace\n");
 295         pid_t chld = fork();
 296         if (chld < 0)
 297                 err(1, "fork");
 298
 299         if (chld == 0) {
 300                 if (ptrace(PTRACE_TRACEME, 0, 0, 0) != 0)
 301                         err(1, "PTRACE_TRACEME");
 302
 303                 printf("\tChild will take a nap until signaled\n");
 304                 setsigign(SIGUSR1, SA_RESTART);
 305                 raise(SIGSTOP);
 306
 307                 syscall(SYS_pause, 0, 0, 0, 0, 0, 0);
 308                 _exit(0);
 309         }
 310
 311         int status;
 312
 313         /* Wait for SIGSTOP. */
 314         if (waitpid(chld, &status, 0) != chld || !WIFSTOPPED(status))
 315                 err(1, "waitpid");
 316
 317         struct user_regs_struct regs;
 318
 319         printf("[RUN]\tSYSCALL\n");
 320         if (ptrace(PTRACE_SYSCALL, chld, 0, 0) != 0)
 321                 err(1, "PTRACE_SYSCALL");
 322         wait_trap(chld);
 323
 324         /* We should be stopped at pause(2) entry. */
 325
 326         if (ptrace(PTRACE_GETREGS, chld, 0, &regs) != 0)
 327                 err(1, "PTRACE_GETREGS");
 328
 329         if (regs.user_syscall_nr != SYS_pause ||
 330             regs.user_arg0 != 0 || regs.user_arg1 != 0 ||
 331             regs.user_arg2 != 0 || regs.user_arg3 != 0 ||
 332             regs.user_arg4 != 0 || regs.user_arg5 != 0) {
 333                 printf("[FAIL]\tInitial args are wrong (nr=%lu, args=%lu %lu %lu %lu %lu %lu)\n", (unsigned long)regs.user_syscall_nr, (unsigned long)regs.user_arg0, (unsigned long)regs.user_arg1, (unsigned long)regs.user_arg2, (unsigned long)regs.user_arg3, (unsigned long)regs.user_arg4, (unsigned long)regs.user_arg5);
 334                 nerrs++;
 335         } else {
 336                 printf("[OK]\tInitial nr and args are correct\n");
 337         }
 338
 339         /* Interrupt it. */
 340         kill(chld, SIGUSR1);
 341
 342         /* Advance.  We should be stopped at exit. */
 343         printf("[RUN]\tSYSCALL\n");
 344         if (ptrace(PTRACE_SYSCALL, chld, 0, 0) != 0)
 345                 err(1, "PTRACE_SYSCALL");
 346         wait_trap(chld);
 347
 348         if (ptrace(PTRACE_GETREGS, chld, 0, &regs) != 0)
 349                 err(1, "PTRACE_GETREGS");
 350
 351         if (regs.user_syscall_nr != SYS_pause ||
 352             regs.user_arg0 != 0 || regs.user_arg1 != 0 ||
 353             regs.user_arg2 != 0 || regs.user_arg3 != 0 ||
 354             regs.user_arg4 != 0 || regs.user_arg5 != 0) {
 355                 printf("[FAIL]\tArgs after SIGUSR1 are wrong (nr=%lu, args=%lu %lu %lu %lu %lu %lu)\n", (unsigned long)regs.user_syscall_nr, (unsigned long)regs.user_arg0, (unsigned long)regs.user_arg1, (unsigned long)regs.user_arg2, (unsigned long)regs.user_arg3, (unsigned long)regs.user_arg4, (unsigned long)regs.user_arg5);
 356                 nerrs++;
 357         } else {
 358                 printf("[OK]\tArgs after SIGUSR1 are correct (ax = %ld)\n",
 359                        (long)regs.user_ax);
 360         }
 361
 362         /* Poke the regs back in.  This must not break anything. */
 363         if (ptrace(PTRACE_SETREGS, chld, 0, &regs) != 0)
 364                 err(1, "PTRACE_SETREGS");
 365
 366         /* Catch the (ignored) SIGUSR1. */
 367         if (ptrace(PTRACE_CONT, chld, 0, 0) != 0)
 368                 err(1, "PTRACE_CONT");
 369         if (waitpid(chld, &status, 0) != chld)
 370                 err(1, "waitpid");
 371         if (!WIFSTOPPED(status)) {
 372                 printf("[FAIL]\tChild was stopped for SIGUSR1 (status = 0x%x)\n", status);
 373                 nerrs++;
 374         } else {
 375                 printf("[OK]\tChild got SIGUSR1\n");
 376         }
 377
 378         /* The next event should be pause(2) again. */
 379         printf("[RUN]\tStep again\n");
 380         if (ptrace(PTRACE_SYSCALL, chld, 0, 0) != 0)
 381                 err(1, "PTRACE_SYSCALL");
 382         wait_trap(chld);
 383
 384         /* We should be stopped at pause(2) entry. */
 385
 386         if (ptrace(PTRACE_GETREGS, chld, 0, &regs) != 0)
 387                 err(1, "PTRACE_GETREGS");
 388
 389         if (regs.user_syscall_nr != SYS_pause ||
 390             regs.user_arg0 != 0 || regs.user_arg1 != 0 ||
 391             regs.user_arg2 != 0 || regs.user_arg3 != 0 ||
 392             regs.user_arg4 != 0 || regs.user_arg5 != 0) {
 393                 printf("[FAIL]\tpause did not restart (nr=%lu, args=%lu %lu %lu %lu %lu %lu)\n", (unsigned long)regs.user_syscall_nr, (unsigned long)regs.user_arg0, (unsigned long)regs.user_arg1, (unsigned long)regs.user_arg2, (unsigned long)regs.user_arg3, (unsigned long)regs.user_arg4, (unsigned long)regs.user_arg5);
 394                 nerrs++;
 395         } else {
 396                 printf("[OK]\tpause(2) restarted correctly\n");
 397         }
 398
 399         /* Kill it. */
 400         kill(chld, SIGKILL);
 401         if (waitpid(chld, &status, 0) != chld)
 402                 err(1, "waitpid");
 403 }
 404
 405 int main()
 406 {
 407         printf("[RUN]\tCheck int80 return regs\n");
 408         test_sys32_regs(do_full_int80);
 409
 410 #if defined(__i386__) && (!defined(__GLIBC__) || __GLIBC__ > 2 || __GLIBC_MINOR__ >= 16)
 411         vsyscall32 = (void *)getauxval(AT_SYSINFO);
 412         printf("[RUN]\tCheck AT_SYSINFO return regs\n");
 413         test_sys32_regs(do_full_vsyscall32);
 414 #endif
 415
 416         test_ptrace_syscall_restart();
 417
 418         test_restart_under_ptrace();
 419
 420         return 0;
 421 }