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         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, &regs) != 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, &regs) != 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, &regs) != 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, &regs) != 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, &regs) != 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 }