1 // SPDX-License-Identifier: GPL-2.0 2 #define _GNU_SOURCE 3 4 #include <sys/ptrace.h> 5 #include <sys/types.h> 6 #include <sys/wait.h> 7 #include <sys/syscall.h> 8 #include <sys/user.h> 9 #include <unistd.h> 10 #include <errno.h> 11 #include <stddef.h> 12 #include <stdio.h> 13 #include <err.h> 14 #include <string.h> 15 #include <asm/ptrace-abi.h> 16 #include <sys/auxv.h> 17 18 /* Bitness-agnostic defines for user_regs_struct fields. */ 19 #ifdef __x86_64__ 20 # define user_syscall_nr orig_rax 21 # define user_arg0 rdi 22 # define user_arg1 rsi 23 # define user_arg2 rdx 24 # define user_arg3 r10 25 # define user_arg4 r8 26 # define user_arg5 r9 27 # define user_ip rip 28 # define user_ax rax 29 #else 30 # define user_syscall_nr orig_eax 31 # define user_arg0 ebx 32 # define user_arg1 ecx 33 # define user_arg2 edx 34 # define user_arg3 esi 35 # define user_arg4 edi 36 # define user_arg5 ebp 37 # define user_ip eip 38 # define user_ax eax 39 #endif 40 41 static int nerrs = 0; 42 43 struct syscall_args32 { 44 uint32_t nr, arg0, arg1, arg2, arg3, arg4, arg5; 45 }; 46 47 #ifdef __i386__ 48 extern void sys32_helper(struct syscall_args32 *, void *); 49 extern void int80_and_ret(void); 50 #endif 51 52 /* 53 * Helper to invoke int80 with controlled regs and capture the final regs. 54 */ 55 static void do_full_int80(struct syscall_args32 *args) 56 { 57 #ifdef __x86_64__ 58 register unsigned long bp asm("bp") = args->arg5; 59 asm volatile ("int $0x80" 60 : "+a" (args->nr), 61 "+b" (args->arg0), "+c" (args->arg1), "+d" (args->arg2), 62 "+S" (args->arg3), "+D" (args->arg4), "+r" (bp) 63 : : "r8", "r9", "r10", "r11"); 64 args->arg5 = bp; 65 #else 66 sys32_helper(args, int80_and_ret); 67 #endif 68 } 69 70 #ifdef __i386__ 71 static void (*vsyscall32)(void); 72 73 /* 74 * Nasty helper to invoke AT_SYSINFO (i.e. __kernel_vsyscall) with 75 * controlled regs and capture the final regs. This is so nasty that it 76 * crashes my copy of gdb :) 77 */ 78 static void do_full_vsyscall32(struct syscall_args32 *args) 79 { 80 sys32_helper(args, vsyscall32); 81 } 82 #endif 83 84 static siginfo_t wait_trap(pid_t chld) 85 { 86 siginfo_t si; 87 if (waitid(P_PID, chld, &si, WEXITED|WSTOPPED) != 0) 88 err(1, "waitid"); 89 if (si.si_pid != chld) 90 errx(1, "got unexpected pid in event\n"); 91 if (si.si_code != CLD_TRAPPED) 92 errx(1, "got unexpected event type %d\n", si.si_code); 93 return si; 94 } 95 96 static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *), 97 int flags) 98 { 99 struct sigaction sa; 100 memset(&sa, 0, sizeof(sa)); 101 sa.sa_sigaction = handler; 102 sa.sa_flags = SA_SIGINFO | flags; 103 sigemptyset(&sa.sa_mask); 104 if (sigaction(sig, &sa, 0)) 105 err(1, "sigaction"); 106 } 107 108 static void setsigign(int sig, int flags) 109 { 110 struct sigaction sa; 111 memset(&sa, 0, sizeof(sa)); 112 sa.sa_sigaction = (void *)SIG_IGN; 113 sa.sa_flags = flags; 114 sigemptyset(&sa.sa_mask); 115 if (sigaction(sig, &sa, 0)) 116 err(1, "sigaction"); 117 } 118 119 static void clearhandler(int sig) 120 { 121 struct sigaction sa; 122 memset(&sa, 0, sizeof(sa)); 123 sa.sa_handler = SIG_DFL; 124 sigemptyset(&sa.sa_mask); 125 if (sigaction(sig, &sa, 0)) 126 err(1, "sigaction"); 127 } 128 129 #ifdef __x86_64__ 130 # define REG_BP REG_RBP 131 #else 132 # define REG_BP REG_EBP 133 #endif 134 135 static void empty_handler(int sig, siginfo_t *si, void *ctx_void) 136 { 137 } 138 139 static void test_sys32_regs(void (*do_syscall)(struct syscall_args32 *)) 140 { 141 struct syscall_args32 args = { 142 .nr = 224, /* gettid */ 143 .arg0 = 10, .arg1 = 11, .arg2 = 12, 144 .arg3 = 13, .arg4 = 14, .arg5 = 15, 145 }; 146 147 do_syscall(&args); 148 149 if (args.nr != getpid() || 150 args.arg0 != 10 || args.arg1 != 11 || args.arg2 != 12 || 151 args.arg3 != 13 || args.arg4 != 14 || args.arg5 != 15) { 152 printf("[FAIL]\tgetpid() failed to preserve regs\n"); 153 nerrs++; 154 } else { 155 printf("[OK]\tgetpid() preserves regs\n"); 156 } 157 158 sethandler(SIGUSR1, empty_handler, 0); 159 160 args.nr = 37; /* kill */ 161 args.arg0 = getpid(); 162 args.arg1 = SIGUSR1; 163 do_syscall(&args); 164 if (args.nr != 0 || 165 args.arg0 != getpid() || args.arg1 != SIGUSR1 || args.arg2 != 12 || 166 args.arg3 != 13 || args.arg4 != 14 || args.arg5 != 15) { 167 printf("[FAIL]\tkill(getpid(), SIGUSR1) failed to preserve regs\n"); 168 nerrs++; 169 } else { 170 printf("[OK]\tkill(getpid(), SIGUSR1) preserves regs\n"); 171 } 172 clearhandler(SIGUSR1); 173 } 174 175 static void test_ptrace_syscall_restart(void) 176 { 177 printf("[RUN]\tptrace-induced syscall restart\n"); 178 pid_t chld = fork(); 179 if (chld < 0) 180 err(1, "fork"); 181 182 if (chld == 0) { 183 if (ptrace(PTRACE_TRACEME, 0, 0, 0) != 0) 184 err(1, "PTRACE_TRACEME"); 185 186 printf("\tChild will make one syscall\n"); 187 raise(SIGSTOP); 188 189 syscall(SYS_gettid, 10, 11, 12, 13, 14, 15); 190 _exit(0); 191 } 192 193 int status; 194 195 /* Wait for SIGSTOP. */ 196 if (waitpid(chld, &status, 0) != chld || !WIFSTOPPED(status)) 197 err(1, "waitpid"); 198 199 struct user_regs_struct regs; 200 201 printf("[RUN]\tSYSEMU\n"); 202 if (ptrace(PTRACE_SYSEMU, chld, 0, 0) != 0) 203 err(1, "PTRACE_SYSEMU"); 204 wait_trap(chld); 205 206 if (ptrace(PTRACE_GETREGS, chld, 0, ®s) != 0) 207 err(1, "PTRACE_GETREGS"); 208 209 if (regs.user_syscall_nr != SYS_gettid || 210 regs.user_arg0 != 10 || regs.user_arg1 != 11 || 211 regs.user_arg2 != 12 || regs.user_arg3 != 13 || 212 regs.user_arg4 != 14 || regs.user_arg5 != 15) { 213 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); 214 nerrs++; 215 } else { 216 printf("[OK]\tInitial nr and args are correct\n"); 217 } 218 219 printf("[RUN]\tRestart the syscall (ip = 0x%lx)\n", 220 (unsigned long)regs.user_ip); 221 222 /* 223 * This does exactly what it appears to do if syscall is int80 or 224 * SYSCALL64. For SYSCALL32 or SYSENTER, though, this is highly 225 * magical. It needs to work so that ptrace and syscall restart 226 * work as expected. 227 */ 228 regs.user_ax = regs.user_syscall_nr; 229 regs.user_ip -= 2; 230 if (ptrace(PTRACE_SETREGS, chld, 0, ®s) != 0) 231 err(1, "PTRACE_SETREGS"); 232 233 if (ptrace(PTRACE_SYSEMU, chld, 0, 0) != 0) 234 err(1, "PTRACE_SYSEMU"); 235 wait_trap(chld); 236 237 if (ptrace(PTRACE_GETREGS, chld, 0, ®s) != 0) 238 err(1, "PTRACE_GETREGS"); 239 240 if (regs.user_syscall_nr != SYS_gettid || 241 regs.user_arg0 != 10 || regs.user_arg1 != 11 || 242 regs.user_arg2 != 12 || regs.user_arg3 != 13 || 243 regs.user_arg4 != 14 || regs.user_arg5 != 15) { 244 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); 245 nerrs++; 246 } else { 247 printf("[OK]\tRestarted nr and args are correct\n"); 248 } 249 250 printf("[RUN]\tChange nr and args and restart the syscall (ip = 0x%lx)\n", 251 (unsigned long)regs.user_ip); 252 253 regs.user_ax = SYS_getpid; 254 regs.user_arg0 = 20; 255 regs.user_arg1 = 21; 256 regs.user_arg2 = 22; 257 regs.user_arg3 = 23; 258 regs.user_arg4 = 24; 259 regs.user_arg5 = 25; 260 regs.user_ip -= 2; 261 262 if (ptrace(PTRACE_SETREGS, chld, 0, ®s) != 0) 263 err(1, "PTRACE_SETREGS"); 264 265 if (ptrace(PTRACE_SYSEMU, chld, 0, 0) != 0) 266 err(1, "PTRACE_SYSEMU"); 267 wait_trap(chld); 268 269 if (ptrace(PTRACE_GETREGS, chld, 0, ®s) != 0) 270 err(1, "PTRACE_GETREGS"); 271 272 if (regs.user_syscall_nr != SYS_getpid || 273 regs.user_arg0 != 20 || regs.user_arg1 != 21 || regs.user_arg2 != 22 || 274 regs.user_arg3 != 23 || regs.user_arg4 != 24 || regs.user_arg5 != 25) { 275 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); 276 nerrs++; 277 } else { 278 printf("[OK]\tReplacement nr and args are correct\n"); 279 } 280 281 if (ptrace(PTRACE_CONT, chld, 0, 0) != 0) 282 err(1, "PTRACE_CONT"); 283 if (waitpid(chld, &status, 0) != chld) 284 err(1, "waitpid"); 285 if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) { 286 printf("[FAIL]\tChild failed\n"); 287 nerrs++; 288 } else { 289 printf("[OK]\tChild exited cleanly\n"); 290 } 291 } 292 293 static void test_restart_under_ptrace(void) 294 { 295 printf("[RUN]\tkernel syscall restart under ptrace\n"); 296 pid_t chld = fork(); 297 if (chld < 0) 298 err(1, "fork"); 299 300 if (chld == 0) { 301 if (ptrace(PTRACE_TRACEME, 0, 0, 0) != 0) 302 err(1, "PTRACE_TRACEME"); 303 304 printf("\tChild will take a nap until signaled\n"); 305 setsigign(SIGUSR1, SA_RESTART); 306 raise(SIGSTOP); 307 308 syscall(SYS_pause, 0, 0, 0, 0, 0, 0); 309 _exit(0); 310 } 311 312 int status; 313 314 /* Wait for SIGSTOP. */ 315 if (waitpid(chld, &status, 0) != chld || !WIFSTOPPED(status)) 316 err(1, "waitpid"); 317 318 struct user_regs_struct regs; 319 320 printf("[RUN]\tSYSCALL\n"); 321 if (ptrace(PTRACE_SYSCALL, chld, 0, 0) != 0) 322 err(1, "PTRACE_SYSCALL"); 323 wait_trap(chld); 324 325 /* We should be stopped at pause(2) entry. */ 326 327 if (ptrace(PTRACE_GETREGS, chld, 0, ®s) != 0) 328 err(1, "PTRACE_GETREGS"); 329 330 if (regs.user_syscall_nr != SYS_pause || 331 regs.user_arg0 != 0 || regs.user_arg1 != 0 || 332 regs.user_arg2 != 0 || regs.user_arg3 != 0 || 333 regs.user_arg4 != 0 || regs.user_arg5 != 0) { 334 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); 335 nerrs++; 336 } else { 337 printf("[OK]\tInitial nr and args are correct\n"); 338 } 339 340 /* Interrupt it. */ 341 kill(chld, SIGUSR1); 342 343 /* Advance. We should be stopped at exit. */ 344 printf("[RUN]\tSYSCALL\n"); 345 if (ptrace(PTRACE_SYSCALL, chld, 0, 0) != 0) 346 err(1, "PTRACE_SYSCALL"); 347 wait_trap(chld); 348 349 if (ptrace(PTRACE_GETREGS, chld, 0, ®s) != 0) 350 err(1, "PTRACE_GETREGS"); 351 352 if (regs.user_syscall_nr != SYS_pause || 353 regs.user_arg0 != 0 || regs.user_arg1 != 0 || 354 regs.user_arg2 != 0 || regs.user_arg3 != 0 || 355 regs.user_arg4 != 0 || regs.user_arg5 != 0) { 356 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); 357 nerrs++; 358 } else { 359 printf("[OK]\tArgs after SIGUSR1 are correct (ax = %ld)\n", 360 (long)regs.user_ax); 361 } 362 363 /* Poke the regs back in. This must not break anything. */ 364 if (ptrace(PTRACE_SETREGS, chld, 0, ®s) != 0) 365 err(1, "PTRACE_SETREGS"); 366 367 /* Catch the (ignored) SIGUSR1. */ 368 if (ptrace(PTRACE_CONT, chld, 0, 0) != 0) 369 err(1, "PTRACE_CONT"); 370 if (waitpid(chld, &status, 0) != chld) 371 err(1, "waitpid"); 372 if (!WIFSTOPPED(status)) { 373 printf("[FAIL]\tChild was stopped for SIGUSR1 (status = 0x%x)\n", status); 374 nerrs++; 375 } else { 376 printf("[OK]\tChild got SIGUSR1\n"); 377 } 378 379 /* The next event should be pause(2) again. */ 380 printf("[RUN]\tStep again\n"); 381 if (ptrace(PTRACE_SYSCALL, chld, 0, 0) != 0) 382 err(1, "PTRACE_SYSCALL"); 383 wait_trap(chld); 384 385 /* We should be stopped at pause(2) entry. */ 386 387 if (ptrace(PTRACE_GETREGS, chld, 0, ®s) != 0) 388 err(1, "PTRACE_GETREGS"); 389 390 if (regs.user_syscall_nr != SYS_pause || 391 regs.user_arg0 != 0 || regs.user_arg1 != 0 || 392 regs.user_arg2 != 0 || regs.user_arg3 != 0 || 393 regs.user_arg4 != 0 || regs.user_arg5 != 0) { 394 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); 395 nerrs++; 396 } else { 397 printf("[OK]\tpause(2) restarted correctly\n"); 398 } 399 400 /* Kill it. */ 401 kill(chld, SIGKILL); 402 if (waitpid(chld, &status, 0) != chld) 403 err(1, "waitpid"); 404 } 405 406 int main() 407 { 408 printf("[RUN]\tCheck int80 return regs\n"); 409 test_sys32_regs(do_full_int80); 410 411 #if defined(__i386__) && (!defined(__GLIBC__) || __GLIBC__ > 2 || __GLIBC_MINOR__ >= 16) 412 vsyscall32 = (void *)getauxval(AT_SYSINFO); 413 printf("[RUN]\tCheck AT_SYSINFO return regs\n"); 414 test_sys32_regs(do_full_vsyscall32); 415 #endif 416 417 test_ptrace_syscall_restart(); 418 419 test_restart_under_ptrace(); 420 421 return 0; 422 } 423