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 args->arg5 = bp; 63 #else 64 sys32_helper(args, int80_and_ret); 65 #endif 66 } 67 68 #ifdef __i386__ 69 static void (*vsyscall32)(void); 70 71 /* 72 * Nasty helper to invoke AT_SYSINFO (i.e. __kernel_vsyscall) with 73 * controlled regs and capture the final regs. This is so nasty that it 74 * crashes my copy of gdb :) 75 */ 76 static void do_full_vsyscall32(struct syscall_args32 *args) 77 { 78 sys32_helper(args, vsyscall32); 79 } 80 #endif 81 82 static siginfo_t wait_trap(pid_t chld) 83 { 84 siginfo_t si; 85 if (waitid(P_PID, chld, &si, WEXITED|WSTOPPED) != 0) 86 err(1, "waitid"); 87 if (si.si_pid != chld) 88 errx(1, "got unexpected pid in event\n"); 89 if (si.si_code != CLD_TRAPPED) 90 errx(1, "got unexpected event type %d\n", si.si_code); 91 return si; 92 } 93 94 static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *), 95 int flags) 96 { 97 struct sigaction sa; 98 memset(&sa, 0, sizeof(sa)); 99 sa.sa_sigaction = handler; 100 sa.sa_flags = SA_SIGINFO | flags; 101 sigemptyset(&sa.sa_mask); 102 if (sigaction(sig, &sa, 0)) 103 err(1, "sigaction"); 104 } 105 106 static void clearhandler(int sig) 107 { 108 struct sigaction sa; 109 memset(&sa, 0, sizeof(sa)); 110 sa.sa_handler = SIG_DFL; 111 sigemptyset(&sa.sa_mask); 112 if (sigaction(sig, &sa, 0)) 113 err(1, "sigaction"); 114 } 115 116 #ifdef __x86_64__ 117 # define REG_BP REG_RBP 118 #else 119 # define REG_BP REG_EBP 120 #endif 121 122 static void empty_handler(int sig, siginfo_t *si, void *ctx_void) 123 { 124 } 125 126 static void test_sys32_regs(void (*do_syscall)(struct syscall_args32 *)) 127 { 128 struct syscall_args32 args = { 129 .nr = 224, /* gettid */ 130 .arg0 = 10, .arg1 = 11, .arg2 = 12, 131 .arg3 = 13, .arg4 = 14, .arg5 = 15, 132 }; 133 134 do_syscall(&args); 135 136 if (args.nr != getpid() || 137 args.arg0 != 10 || args.arg1 != 11 || args.arg2 != 12 || 138 args.arg3 != 13 || args.arg4 != 14 || args.arg5 != 15) { 139 printf("[FAIL]\tgetpid() failed to preseve regs\n"); 140 nerrs++; 141 } else { 142 printf("[OK]\tgetpid() preserves regs\n"); 143 } 144 145 sethandler(SIGUSR1, empty_handler, 0); 146 147 args.nr = 37; /* kill */ 148 args.arg0 = getpid(); 149 args.arg1 = SIGUSR1; 150 do_syscall(&args); 151 if (args.nr != 0 || 152 args.arg0 != getpid() || args.arg1 != SIGUSR1 || args.arg2 != 12 || 153 args.arg3 != 13 || args.arg4 != 14 || args.arg5 != 15) { 154 printf("[FAIL]\tkill(getpid(), SIGUSR1) failed to preseve regs\n"); 155 nerrs++; 156 } else { 157 printf("[OK]\tkill(getpid(), SIGUSR1) preserves regs\n"); 158 } 159 clearhandler(SIGUSR1); 160 } 161 162 static void test_ptrace_syscall_restart(void) 163 { 164 printf("[RUN]\tptrace-induced syscall restart\n"); 165 pid_t chld = fork(); 166 if (chld < 0) 167 err(1, "fork"); 168 169 if (chld == 0) { 170 if (ptrace(PTRACE_TRACEME, 0, 0, 0) != 0) 171 err(1, "PTRACE_TRACEME"); 172 173 printf("\tChild will make one syscall\n"); 174 raise(SIGSTOP); 175 176 syscall(SYS_gettid, 10, 11, 12, 13, 14, 15); 177 _exit(0); 178 } 179 180 int status; 181 182 /* Wait for SIGSTOP. */ 183 if (waitpid(chld, &status, 0) != chld || !WIFSTOPPED(status)) 184 err(1, "waitpid"); 185 186 struct user_regs_struct regs; 187 188 printf("[RUN]\tSYSEMU\n"); 189 if (ptrace(PTRACE_SYSEMU, chld, 0, 0) != 0) 190 err(1, "PTRACE_SYSCALL"); 191 wait_trap(chld); 192 193 if (ptrace(PTRACE_GETREGS, chld, 0, ®s) != 0) 194 err(1, "PTRACE_GETREGS"); 195 196 if (regs.user_syscall_nr != SYS_gettid || 197 regs.user_arg0 != 10 || regs.user_arg1 != 11 || 198 regs.user_arg2 != 12 || regs.user_arg3 != 13 || 199 regs.user_arg4 != 14 || regs.user_arg5 != 15) { 200 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); 201 nerrs++; 202 } else { 203 printf("[OK]\tInitial nr and args are correct\n"); 204 } 205 206 printf("[RUN]\tRestart the syscall (ip = 0x%lx)\n", 207 (unsigned long)regs.user_ip); 208 209 /* 210 * This does exactly what it appears to do if syscall is int80 or 211 * SYSCALL64. For SYSCALL32 or SYSENTER, though, this is highly 212 * magical. It needs to work so that ptrace and syscall restart 213 * work as expected. 214 */ 215 regs.user_ax = regs.user_syscall_nr; 216 regs.user_ip -= 2; 217 if (ptrace(PTRACE_SETREGS, chld, 0, ®s) != 0) 218 err(1, "PTRACE_SETREGS"); 219 220 if (ptrace(PTRACE_SYSEMU, chld, 0, 0) != 0) 221 err(1, "PTRACE_SYSCALL"); 222 wait_trap(chld); 223 224 if (ptrace(PTRACE_GETREGS, chld, 0, ®s) != 0) 225 err(1, "PTRACE_GETREGS"); 226 227 if (regs.user_syscall_nr != SYS_gettid || 228 regs.user_arg0 != 10 || regs.user_arg1 != 11 || 229 regs.user_arg2 != 12 || regs.user_arg3 != 13 || 230 regs.user_arg4 != 14 || regs.user_arg5 != 15) { 231 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); 232 nerrs++; 233 } else { 234 printf("[OK]\tRestarted nr and args are correct\n"); 235 } 236 237 printf("[RUN]\tChange nr and args and restart the syscall (ip = 0x%lx)\n", 238 (unsigned long)regs.user_ip); 239 240 regs.user_ax = SYS_getpid; 241 regs.user_arg0 = 20; 242 regs.user_arg1 = 21; 243 regs.user_arg2 = 22; 244 regs.user_arg3 = 23; 245 regs.user_arg4 = 24; 246 regs.user_arg5 = 25; 247 regs.user_ip -= 2; 248 249 if (ptrace(PTRACE_SETREGS, chld, 0, ®s) != 0) 250 err(1, "PTRACE_SETREGS"); 251 252 if (ptrace(PTRACE_SYSEMU, chld, 0, 0) != 0) 253 err(1, "PTRACE_SYSCALL"); 254 wait_trap(chld); 255 256 if (ptrace(PTRACE_GETREGS, chld, 0, ®s) != 0) 257 err(1, "PTRACE_GETREGS"); 258 259 if (regs.user_syscall_nr != SYS_getpid || 260 regs.user_arg0 != 20 || regs.user_arg1 != 21 || regs.user_arg2 != 22 || 261 regs.user_arg3 != 23 || regs.user_arg4 != 24 || regs.user_arg5 != 25) { 262 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); 263 nerrs++; 264 } else { 265 printf("[OK]\tReplacement nr and args are correct\n"); 266 } 267 268 if (ptrace(PTRACE_CONT, chld, 0, 0) != 0) 269 err(1, "PTRACE_CONT"); 270 if (waitpid(chld, &status, 0) != chld) 271 err(1, "waitpid"); 272 if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) { 273 printf("[FAIL]\tChild failed\n"); 274 nerrs++; 275 } else { 276 printf("[OK]\tChild exited cleanly\n"); 277 } 278 } 279 280 int main() 281 { 282 printf("[RUN]\tCheck int80 return regs\n"); 283 test_sys32_regs(do_full_int80); 284 285 #if defined(__i386__) && (!defined(__GLIBC__) || __GLIBC__ > 2 || __GLIBC_MINOR__ >= 16) 286 vsyscall32 = (void *)getauxval(AT_SYSINFO); 287 printf("[RUN]\tCheck AT_SYSINFO return regs\n"); 288 test_sys32_regs(do_full_vsyscall32); 289 #endif 290 291 test_ptrace_syscall_restart(); 292 293 return 0; 294 } 295