gdb/inf-ptrace.c

   1 /* Low-level child interface to ptrace.
   2
   3    Copyright 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
   4    1998, 1999, 2000, 2001, 2002, 2004 Free Software Foundation, Inc.
   5
   6    This file is part of GDB.
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 2 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program; if not, write to the Free Software
  20    Foundation, Inc., 59 Temple Place - Suite 330,
  21    Boston, MA 02111-1307, USA.  */
  22
  23 #include "defs.h"
  24 #include "command.h"
  25 #include "inferior.h"
  26 #include "inflow.h"
  27 #include "gdbcore.h"
  28 #include "observer.h"
  29
  30 #include "gdb_string.h"
  31 #include "gdb_ptrace.h"
  32 #include "gdb_wait.h"
  33 #include <signal.h>
  34
  35 #include "inf-child.h"
  36
  37 /* HACK: Save the ptrace ops returned by inf_ptrace_target.  */
  38 static struct target_ops *ptrace_ops_hack;
  39
  40 static void
  41 inf_ptrace_kill_inferior (void)
  42 {
  43   int status;
  44   int pid = PIDGET (inferior_ptid);
  45
  46   if (pid == 0)
  47     return;
  48
  49   /* This once used to call "kill" to kill the inferior just in case
  50      the inferior was still running.  As others have noted in the past
  51      (kingdon) there shouldn't be any way to get here if the inferior
  52      is still running -- else there's a major problem elsewere in GDB
  53      and it needs to be fixed.
  54
  55      The kill call causes problems under HP-UX 10, so it's been
  56      removed; if this causes problems we'll deal with them as they
  57      arise.  */
  58   ptrace (PT_KILL, pid, (PTRACE_TYPE_ARG3) 0, 0);
  59   wait (&status);
  60   target_mourn_inferior ();
  61 }
  62
  63 /* Resume execution of the inferior process.  If STEP is nonzero,
  64    single-step it.  If SIGNAL is nonzero, give it that signal.  */
  65
  66 static void
  67 inf_ptrace_resume (ptid_t ptid, int step, enum target_signal signal)
  68 {
  69   int request = PT_CONTINUE;
  70   int pid = PIDGET (ptid);
  71
  72   if (pid == -1)
  73     /* Resume all threads.  */
  74     /* I think this only gets used in the non-threaded case, where
  75        "resume all threads" and "resume inferior_ptid" are the
  76        same.  */
  77     pid = PIDGET (inferior_ptid);
  78
  79   if (step)
  80     {
  81       /* If this system does not support PT_STEP, a higher level
  82          function will have called single_step() to transmute the step
  83          request into a continue request (by setting breakpoints on
  84          all possible successor instructions), so we don't have to
  85          worry about that here.  */
  86       request = PT_STEP;
  87     }
  88
  89   /* An address of (PTRACE_TYPE_ARG3)1 tells ptrace to continue from
  90      where it was.  If GDB wanted it to start some other way, we have
  91      already written a new PC value to the child.  */
  92   errno = 0;
  93   ptrace (request, pid, (PTRACE_TYPE_ARG3) 1, target_signal_to_host (signal));
  94   if (errno != 0)
  95     perror_with_name ("ptrace");
  96 }
  97
  98 /* Wait for child to do something.  Return pid of child, or -1 in case
  99    of error; store status through argument pointer OURSTATUS.  */
 100
 101 static ptid_t
 102 inf_ptrace_wait (ptid_t ptid, struct target_waitstatus *ourstatus)
 103 {
 104   int save_errno;
 105   int status;
 106   char *execd_pathname = NULL;
 107   int exit_status;
 108   int related_pid;
 109   int syscall_id;
 110   enum target_waitkind kind;
 111   int pid;
 112
 113   do
 114     {
 115       set_sigint_trap ();       /* Causes SIGINT to be passed on to the
 116                                    attached process. */
 117       set_sigio_trap ();
 118
 119       pid = wait (&status);
 120
 121       save_errno = errno;
 122
 123       clear_sigio_trap ();
 124
 125       clear_sigint_trap ();
 126
 127       if (pid == -1)
 128         {
 129           if (save_errno == EINTR)
 130             continue;
 131
 132           fprintf_unfiltered (gdb_stderr,
 133                               "Child process unexpectedly missing: %s.\n",
 134                               safe_strerror (save_errno));
 135
 136           /* Claim it exited with unknown signal.  */
 137           ourstatus->kind = TARGET_WAITKIND_SIGNALLED;
 138           ourstatus->value.sig = TARGET_SIGNAL_UNKNOWN;
 139           return pid_to_ptid (-1);
 140         }
 141
 142       /* Did it exit?  */
 143       if (target_has_exited (pid, status, &exit_status))
 144         {
 145           /* ??rehrauer: For now, ignore this. */
 146           continue;
 147         }
 148
 149       if (!target_thread_alive (pid_to_ptid (pid)))
 150         {
 151           ourstatus->kind = TARGET_WAITKIND_SPURIOUS;
 152           return pid_to_ptid (pid);
 153         }
 154     }
 155   while (pid != PIDGET (inferior_ptid)); /* Some other child died or
 156                                             stopped.  */
 157
 158   store_waitstatus (ourstatus, status);
 159   return pid_to_ptid (pid);
 160 }
 161
 162 /* Check to see if the given thread is alive.
 163
 164    FIXME: Is kill() ever the right way to do this?  I doubt it, but
 165    for now we're going to try and be compatable with the old thread
 166    code.  */
 167
 168 static int
 169 inf_ptrace_thread_alive (ptid_t ptid)
 170 {
 171   pid_t pid = PIDGET (ptid);
 172
 173   return (kill (pid, 0) != -1);
 174 }
 175
 176 /* Attach to process PID, then initialize for debugging it.  */
 177
 178 static void
 179 inf_ptrace_attach (char *args, int from_tty)
 180 {
 181   char *exec_file;
 182   int pid;
 183   char *dummy;
 184
 185   if (!args)
 186     error_no_arg ("process-id to attach");
 187
 188   dummy = args;
 189   pid = strtol (args, &dummy, 0);
 190   /* Some targets don't set errno on errors, grrr!  */
 191   if (pid == 0 && args == dummy)
 192     error ("Illegal process-id: %s\n", args);
 193
 194   if (pid == getpid ())         /* Trying to masturbate?  */
 195     error ("I refuse to debug myself!");
 196
 197   if (from_tty)
 198     {
 199       exec_file = (char *) get_exec_file (0);
 200
 201       if (exec_file)
 202         printf_unfiltered ("Attaching to program: %s, %s\n", exec_file,
 203                            target_pid_to_str (pid_to_ptid (pid)));
 204       else
 205         printf_unfiltered ("Attaching to %s\n",
 206                            target_pid_to_str (pid_to_ptid (pid)));
 207
 208       gdb_flush (gdb_stdout);
 209     }
 210
 211 #ifdef PT_ATTACH
 212   errno = 0;
 213   ptrace (PT_ATTACH, pid, (PTRACE_TYPE_ARG3) 0, 0);
 214   if (errno != 0)
 215     perror_with_name ("ptrace");
 216   attach_flag = 1;
 217 #else
 218   error ("This system does not support attaching to a process");
 219 #endif
 220
 221   inferior_ptid = pid_to_ptid (pid);
 222   push_target (ptrace_ops_hack);
 223
 224   /* Do this first, before anything has had a chance to query the
 225      inferior's symbol table or similar.  */
 226   observer_notify_inferior_created (&current_target, from_tty);
 227 }
 228
 229 static void
 230 inf_ptrace_post_attach (int pid)
 231 {
 232   /* This version of Unix doesn't require a meaningful "post attach"
 233      operation by a debugger.  */
 234 }
 235
 236 /* Take a program previously attached to and detaches it.  The program
 237    resumes execution and will no longer stop on signals, etc.  We'd
 238    better not have left any breakpoints in the program or it'll die
 239    when it hits one.  For this to work, it may be necessary for the
 240    process to have been previously attached.  It *might* work if the
 241    program was started via the normal ptrace (PTRACE_TRACEME).  */
 242
 243 static void
 244 inf_ptrace_detach (char *args, int from_tty)
 245 {
 246   int sig = 0;
 247   int pid = PIDGET (inferior_ptid);
 248
 249   if (from_tty)
 250     {
 251       char *exec_file = get_exec_file (0);
 252       if (exec_file == 0)
 253         exec_file = "";
 254       printf_unfiltered ("Detaching from program: %s, %s\n", exec_file,
 255                          target_pid_to_str (pid_to_ptid (pid)));
 256       gdb_flush (gdb_stdout);
 257     }
 258   if (args)
 259     sig = atoi (args);
 260
 261 #ifdef PT_DETACH
 262   errno = 0;
 263   ptrace (PT_DETACH, pid, (PTRACE_TYPE_ARG3) 1, sig);
 264   if (errno != 0)
 265     perror_with_name ("ptrace");
 266   attach_flag = 0;
 267 #else
 268   error ("This system does not support detaching from a process");
 269 #endif
 270
 271   inferior_ptid = null_ptid;
 272   unpush_target (ptrace_ops_hack);
 273 }
 274
 275 /* Get ready to modify the registers array.  On machines which store
 276    individual registers, this doesn't need to do anything.  On
 277    machines which store all the registers in one fell swoop, this
 278    makes sure that registers contains all the registers from the
 279    program being debugged.  */
 280
 281 static void
 282 inf_ptrace_prepare_to_store (void)
 283 {
 284 }
 285
 286 /* Print status information about what we're accessing.  */
 287
 288 static void
 289 inf_ptrace_files_info (struct target_ops *ignore)
 290 {
 291   printf_unfiltered ("\tUsing the running image of %s %s.\n",
 292                      attach_flag ? "attached" : "child",
 293                      target_pid_to_str (inferior_ptid));
 294 }
 295
 296 static void
 297 inf_ptrace_open (char *arg, int from_tty)
 298 {
 299   error ("Use the \"run\" command to start a Unix child process.");
 300 }
 301
 302 /* Stub function which causes the inferior that runs it, to be ptrace-able
 303    by its parent process.  */
 304
 305 static void
 306 inf_ptrace_me (void)
 307 {
 308   /* "Trace me, Dr. Memory!"  */
 309   ptrace (0, 0, (PTRACE_TYPE_ARG3) 0, 0);
 310 }
 311
 312 /* Stub function which causes the GDB that runs it, to start ptrace-ing
 313    the child process.  */
 314
 315 static void
 316 inf_ptrace_him (int pid)
 317 {
 318   push_target (ptrace_ops_hack);
 319
 320   /* On some targets, there must be some explicit synchronization
 321      between the parent and child processes after the debugger
 322      forks, and before the child execs the debuggee program.  This
 323      call basically gives permission for the child to exec.  */
 324
 325   target_acknowledge_created_inferior (pid);
 326
 327   /* START_INFERIOR_TRAPS_EXPECTED is defined in inferior.h, and will
 328      be 1 or 2 depending on whether we're starting without or with a
 329      shell.  */
 330   startup_inferior (START_INFERIOR_TRAPS_EXPECTED);
 331
 332   /* On some targets, there must be some explicit actions taken after
 333      the inferior has been started up.  */
 334   target_post_startup_inferior (pid_to_ptid (pid));
 335 }
 336
 337 /* Start an inferior Unix child process and sets inferior_ptid to its
 338    pid.  EXEC_FILE is the file to run.  ALLARGS is a string containing
 339    the arguments to the program.  ENV is the environment vector to
 340    pass.  Errors reported with error().  */
 341
 342 static void
 343 inf_ptrace_create_inferior (char *exec_file, char *allargs, char **env,
 344                             int from_tty)
 345 {
 346   fork_inferior (exec_file, allargs, env, inf_ptrace_me, inf_ptrace_him,
 347                  NULL, NULL);
 348   /* We are at the first instruction we care about.  */
 349   observer_notify_inferior_created (&current_target, from_tty);
 350   /* Pedal to the metal...  */
 351   proceed ((CORE_ADDR) -1, TARGET_SIGNAL_0, 0);
 352 }
 353
 354 static void
 355 inf_ptrace_post_startup_inferior (ptid_t ptid)
 356 {
 357   /* This version of Unix doesn't require a meaningful "post startup
 358      inferior" operation by a debugger.  */
 359 }
 360
 361 static void
 362 inf_ptrace_acknowledge_created_inferior (int pid)
 363 {
 364   /* This version of Unix doesn't require a meaningful "acknowledge
 365      created inferior" operation by a debugger.  */
 366 }
 367
 368 static int
 369 inf_ptrace_insert_fork_catchpoint (int pid)
 370 {
 371   /* This version of Unix doesn't support notification of fork events.  */
 372   return 0;
 373 }
 374
 375 static int
 376 inf_ptrace_remove_fork_catchpoint (int pid)
 377 {
 378   /* This version of Unix doesn't support notification of fork events.  */
 379   return 0;
 380 }
 381
 382 static int
 383 inf_ptrace_insert_vfork_catchpoint (int pid)
 384 {
 385   /* This version of Unix doesn't support notification of vfork events.  */
 386   return 0;
 387 }
 388
 389 static int
 390 inf_ptrace_remove_vfork_catchpoint (int pid)
 391 {
 392   /* This version of Unix doesn't support notification of vfork events.  */
 393   return 0;
 394 }
 395
 396 static int
 397 inf_ptrace_follow_fork (int follow_child)
 398 {
 399   /* This version of Unix doesn't support following fork or vfork events.  */
 400   return 0;
 401 }
 402
 403 static int
 404 inf_ptrace_insert_exec_catchpoint (int pid)
 405 {
 406   /* This version of Unix doesn't support notification of exec events.  */
 407   return 0;
 408 }
 409
 410 static int
 411 inf_ptrace_remove_exec_catchpoint (int pid)
 412 {
 413   /* This version of Unix doesn't support notification of exec events.  */
 414   return 0;
 415 }
 416
 417 static int
 418 inf_ptrace_reported_exec_events_per_exec_call (void)
 419 {
 420   /* This version of Unix doesn't support notification of exec events.  */
 421   return 1;
 422 }
 423
 424 static int
 425 inf_ptrace_has_exited (int pid, int wait_status, int *exit_status)
 426 {
 427   if (WIFEXITED (wait_status))
 428     {
 429       *exit_status = WEXITSTATUS (wait_status);
 430       return 1;
 431     }
 432
 433   if (WIFSIGNALED (wait_status))
 434     {
 435       *exit_status = 0;         /* ?? Don't know what else to say here. */
 436       return 1;
 437     }
 438
 439   /* ??? Do we really need to consult the event state, too?
 440      Assume the wait_state alone suffices.  */
 441   return 0;
 442 }
 443
 444 static void
 445 inf_ptrace_mourn_inferior (void)
 446 {
 447   unpush_target (ptrace_ops_hack);
 448   generic_mourn_inferior ();
 449 }
 450
 451 static int
 452 inf_ptrace_can_run (void)
 453 {
 454   return 1;
 455 }
 456
 457 /* Send a SIGINT to the process group.  This acts just like the user
 458    typed a ^C on the controlling terminal.
 459
 460    FIXME: This may not be correct for all systems.  Some may want to
 461    use killpg() instead of kill (-pgrp).  */
 462
 463 static void
 464 inf_ptrace_stop (void)
 465 {
 466   kill (-inferior_process_group, SIGINT);
 467 }
 468
 469 /* Perform a partial transfer to/from the specified object.  For
 470    memory transfers, fall back to the old memory xfer functions.  */
 471
 472 static LONGEST
 473 inf_ptrace_xfer_partial (struct target_ops *ops, enum target_object object,
 474                          const char *annex, void *readbuf,
 475                          const void *writebuf, ULONGEST offset, LONGEST len)
 476 {
 477   switch (object)
 478     {
 479     case TARGET_OBJECT_MEMORY:
 480 #ifdef PT_IO
 481       /* OpenBSD 3.1, NetBSD 1.6 and FreeBSD 5.0 have a new PT_IO
 482          request that promises to be much more efficient in reading
 483          and writing data in the traced process's address space.  */
 484       {
 485         struct ptrace_io_desc piod;
 486
 487         /* NOTE: We assume that there are no distinct address spaces
 488            for instruction and data.  */
 489         piod.piod_op = writebuf ? PIOD_WRITE_D : PIOD_READ_D;
 490         piod.piod_addr = writebuf ? (void *) writebuf : readbuf;
 491         piod.piod_offs = (void *) (long) offset;
 492         piod.piod_len = len;
 493
 494         errno = 0;
 495         if (ptrace (PT_IO, PIDGET (inferior_ptid), (caddr_t) &piod, 0) == 0)
 496           /* Return the actual number of bytes read or written.  */
 497           return piod.piod_len;
 498         /* If the PT_IO request is somehow not supported, fallback on
 499            using PT_WRITE_D/PT_READ_D.  Otherwise we will return zero
 500            to indicate failure.  */
 501         if (errno != EINVAL)
 502           return 0;
 503       }
 504 #endif
 505       {
 506         union
 507         {
 508           PTRACE_TYPE_RET word;
 509           unsigned char byte[sizeof (PTRACE_TYPE_RET)];
 510         } buffer;
 511         ULONGEST rounded_offset;
 512         LONGEST partial_len;
 513
 514         /* Round the start offset down to the next long word
 515            boundary.  */
 516         rounded_offset = offset & -(ULONGEST) sizeof (PTRACE_TYPE_RET);
 517
 518         /* Since ptrace will transfer a single word starting at that
 519            rounded_offset the partial_len needs to be adjusted down to
 520            that (remember this function only does a single transfer).
 521            Should the required length be even less, adjust it down
 522            again.  */
 523         partial_len = (rounded_offset + sizeof (PTRACE_TYPE_RET)) - offset;
 524         if (partial_len > len)
 525           partial_len = len;
 526
 527         if (writebuf)
 528           {
 529             /* If OFFSET:PARTIAL_LEN is smaller than
 530                ROUNDED_OFFSET:WORDSIZE then a read/modify write will
 531                be needed.  Read in the entire word.  */
 532             if (rounded_offset < offset
 533                 || (offset + partial_len
 534                     < rounded_offset + sizeof (PTRACE_TYPE_RET)))
 535               /* Need part of initial word -- fetch it.  */
 536               buffer.word = ptrace (PT_READ_I, PIDGET (inferior_ptid),
 537                                     (PTRACE_TYPE_ARG3) (long) rounded_offset,
 538                                     0);
 539
 540             /* Copy data to be written over corresponding part of
 541                buffer.  */
 542             memcpy (buffer.byte + (offset - rounded_offset),
 543                     writebuf, partial_len);
 544
 545             errno = 0;
 546             ptrace (PT_WRITE_D, PIDGET (inferior_ptid),
 547                     (PTRACE_TYPE_ARG3) (long) rounded_offset,
 548                     buffer.word);
 549             if (errno)
 550               {
 551                 /* Using the appropriate one (I or D) is necessary for
 552                    Gould NP1, at least.  */
 553                 errno = 0;
 554                 ptrace (PT_WRITE_I, PIDGET (inferior_ptid),
 555                         (PTRACE_TYPE_ARG3) (long) rounded_offset,
 556                         buffer.word);
 557                 if (errno)
 558                   return 0;
 559               }
 560           }
 561         if (readbuf)
 562           {
 563             errno = 0;
 564             buffer.word = ptrace (PT_READ_I, PIDGET (inferior_ptid),
 565                                   (PTRACE_TYPE_ARG3) (long) rounded_offset, 0);
 566             if (errno)
 567               return 0;
 568             /* Copy appropriate bytes out of the buffer.  */
 569             memcpy (readbuf, buffer.byte + (offset - rounded_offset),
 570                     partial_len);
 571           }
 572         return partial_len;
 573       }
 574
 575     case TARGET_OBJECT_UNWIND_TABLE:
 576       return -1;
 577
 578     case TARGET_OBJECT_AUXV:
 579       return -1;
 580
 581     case TARGET_OBJECT_WCOOKIE:
 582       return -1;
 583
 584     default:
 585       return -1;
 586     }
 587 }
 588
 589 static char *
 590 inf_ptrace_pid_to_str (ptid_t ptid)
 591 {
 592   return normal_pid_to_str (ptid);
 593 }
 594
 595 struct target_ops *
 596 inf_ptrace_target (void)
 597 {
 598   struct target_ops *t = inf_child_target ();
 599   t->to_open = inf_ptrace_open;
 600   t->to_attach = inf_ptrace_attach;
 601   t->to_post_attach = inf_ptrace_post_attach;
 602   t->to_detach = inf_ptrace_detach;
 603   t->to_resume = inf_ptrace_resume;
 604   t->to_wait = inf_ptrace_wait;
 605   t->to_prepare_to_store = inf_ptrace_prepare_to_store;
 606   t->to_xfer_partial = inf_ptrace_xfer_partial;
 607   t->to_files_info = inf_ptrace_files_info;
 608   t->to_kill = inf_ptrace_kill_inferior;
 609   t->to_create_inferior = inf_ptrace_create_inferior;
 610   t->to_post_startup_inferior = inf_ptrace_post_startup_inferior;
 611   t->to_acknowledge_created_inferior =
 612     inf_ptrace_acknowledge_created_inferior;
 613   t->to_insert_fork_catchpoint = inf_ptrace_insert_fork_catchpoint;
 614   t->to_remove_fork_catchpoint = inf_ptrace_remove_fork_catchpoint;
 615   t->to_insert_vfork_catchpoint = inf_ptrace_insert_vfork_catchpoint;
 616   t->to_remove_vfork_catchpoint = inf_ptrace_remove_vfork_catchpoint;
 617   t->to_follow_fork = inf_ptrace_follow_fork;
 618   t->to_insert_exec_catchpoint = inf_ptrace_insert_exec_catchpoint;
 619   t->to_remove_exec_catchpoint = inf_ptrace_remove_exec_catchpoint;
 620   t->to_reported_exec_events_per_exec_call =
 621     inf_ptrace_reported_exec_events_per_exec_call;
 622   t->to_has_exited = inf_ptrace_has_exited;
 623   t->to_mourn_inferior = inf_ptrace_mourn_inferior;
 624   t->to_can_run = inf_ptrace_can_run;
 625   t->to_thread_alive = inf_ptrace_thread_alive;
 626   t->to_pid_to_str = inf_ptrace_pid_to_str;
 627   t->to_stop = inf_ptrace_stop;
 628   t->to_stratum = process_stratum;
 629   t->to_has_all_memory = 1;
 630   t->to_has_memory = 1;
 631   t->to_has_stack = 1;
 632   t->to_has_registers = 1;
 633   t->to_has_execution = 1;
 634   t->to_magic = OPS_MAGIC;
 635   ptrace_ops_hack = t;
 636   return t;
 637 }