gdb/inf-ptrace.c

   1 /* Low level Unix child interface to ptrace, for GDB when running under Unix.
   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 "observer.h"
  25 #include "gdb_ptrace.h"
  26 #include "inflow.h"
  27 #include "inferior.h"
  28 #include "regcache.h"
  29 #include "command.h"
  30 #include "gdbcore.h"
  31 #include "inf-child.h"
  32 #include "gdbcmd.h"
  33 #include "gdb_string.h"
  34
  35 #include "gdb_wait.h"
  36 #include <signal.h>
  37
  38 /* HACK: Save the ptrace ops returned by ptrace_target.  */
  39 static struct target_ops *ptrace_ops_hack;
  40
  41 static void
  42 inf_ptrace_kill_inferior (void)
  43 {
  44   int status;
  45   int pid = PIDGET (inferior_ptid);
  46
  47   if (pid == 0)
  48     return;
  49
  50   /* This once used to call "kill" to kill the inferior just in case
  51      the inferior was still running.  As others have noted in the past
  52      (kingdon) there shouldn't be any way to get here if the inferior
  53      is still running -- else there's a major problem elsewere in GDB
  54      and it needs to be fixed.
  55
  56      The kill call causes problems under HP-UX 10, so it's been
  57      removed; if this causes problems we'll deal with them as they
  58      arise.  */
  59   ptrace (PT_KILL, pid, (PTRACE_TYPE_ARG3) 0, 0);
  60   wait (&status);
  61   target_mourn_inferior ();
  62 }
  63
  64 /* Resume execution of the inferior process.  If STEP is nonzero,
  65    single-step it.  If SIGNAL is nonzero, give it that signal.  */
  66
  67 static void
  68 inf_ptrace_resume (ptid_t ptid, int step, enum target_signal signal)
  69 {
  70   int request = PT_CONTINUE;
  71   int pid = PIDGET (ptid);
  72
  73   if (pid == -1)
  74     /* Resume all threads.  */
  75     /* I think this only gets used in the non-threaded case, where
  76        "resume all threads" and "resume inferior_ptid" are the
  77        same.  */
  78     pid = PIDGET (inferior_ptid);
  79
  80   if (step)
  81     {
  82       /* If this system does not support PT_STEP, a higher level
  83          function will have called single_step() to transmute the step
  84          request into a continue request (by setting breakpoints on
  85          all possible successor instructions), so we don't have to
  86          worry about that here.  */
  87       request = PT_STEP;
  88     }
  89
  90   /* An address of (PTRACE_TYPE_ARG3)1 tells ptrace to continue from
  91      where it was.  If GDB wanted it to start some other way, we have
  92      already written a new PC value to the child.  */
  93   errno = 0;
  94   ptrace (request, pid, (PTRACE_TYPE_ARG3) 1, target_signal_to_host (signal));
  95   if (errno != 0)
  96     perror_with_name ("ptrace");
  97 }
  98
  99 /* Wait for child to do something.  Return pid of child, or -1 in case
 100    of error; store status through argument pointer OURSTATUS.  */
 101
 102 static ptid_t
 103 inf_ptrace_wait (ptid_t ptid, struct target_waitstatus *ourstatus)
 104 {
 105   int save_errno;
 106   int status;
 107   char *execd_pathname = NULL;
 108   int exit_status;
 109   int related_pid;
 110   int syscall_id;
 111   enum target_waitkind kind;
 112   int pid;
 113
 114   do
 115     {
 116       set_sigint_trap ();       /* Causes SIGINT to be passed on to the
 117                                    attached process. */
 118       set_sigio_trap ();
 119
 120       pid = wait (&status);
 121
 122       save_errno = errno;
 123
 124       clear_sigio_trap ();
 125
 126       clear_sigint_trap ();
 127
 128       if (pid == -1)
 129         {
 130           if (save_errno == EINTR)
 131             continue;
 132
 133           fprintf_unfiltered (gdb_stderr,
 134                               "Child process unexpectedly missing: %s.\n",
 135                               safe_strerror (save_errno));
 136
 137           /* Claim it exited with unknown signal.  */
 138           ourstatus->kind = TARGET_WAITKIND_SIGNALLED;
 139           ourstatus->value.sig = TARGET_SIGNAL_UNKNOWN;
 140           return pid_to_ptid (-1);
 141         }
 142
 143       /* Did it exit?  */
 144       if (target_has_exited (pid, status, &exit_status))
 145         {
 146           /* ??rehrauer: For now, ignore this. */
 147           continue;
 148         }
 149
 150       if (!target_thread_alive (pid_to_ptid (pid)))
 151         {
 152           ourstatus->kind = TARGET_WAITKIND_SPURIOUS;
 153           return pid_to_ptid (pid);
 154         }
 155     }
 156   while (pid != PIDGET (inferior_ptid)); /* Some other child died or
 157                                             stopped.  */
 158
 159   store_waitstatus (ourstatus, status);
 160   return pid_to_ptid (pid);
 161 }
 162
 163 /* Check to see if the given thread is alive.
 164
 165    FIXME: Is kill() ever the right way to do this?  I doubt it, but
 166    for now we're going to try and be compatable with the old thread
 167    code.  */
 168
 169 static int
 170 inf_ptrace_thread_alive (ptid_t ptid)
 171 {
 172   pid_t pid = PIDGET (ptid);
 173
 174   return (kill (pid, 0) != -1);
 175 }
 176
 177 /* Attach to process PID, then initialize for debugging it.  */
 178
 179 static void
 180 inf_ptrace_attach (char *args, int from_tty)
 181 {
 182   char *exec_file;
 183   int pid;
 184   char *dummy;
 185
 186   if (!args)
 187     error_no_arg ("process-id to attach");
 188
 189   dummy = args;
 190   pid = strtol (args, &dummy, 0);
 191   /* Some targets don't set errno on errors, grrr!  */
 192   if (pid == 0 && args == dummy)
 193     error ("Illegal process-id: %s\n", args);
 194
 195   if (pid == getpid ())         /* Trying to masturbate?  */
 196     error ("I refuse to debug myself!");
 197
 198   if (from_tty)
 199     {
 200       exec_file = (char *) get_exec_file (0);
 201
 202       if (exec_file)
 203         printf_unfiltered ("Attaching to program: %s, %s\n", exec_file,
 204                            target_pid_to_str (pid_to_ptid (pid)));
 205       else
 206         printf_unfiltered ("Attaching to %s\n",
 207                            target_pid_to_str (pid_to_ptid (pid)));
 208
 209       gdb_flush (gdb_stdout);
 210     }
 211
 212 #ifdef PT_ATTACH
 213   errno = 0;
 214   ptrace (PT_ATTACH, pid, (PTRACE_TYPE_ARG3) 0, 0);
 215   if (errno != 0)
 216     perror_with_name ("ptrace");
 217   attach_flag = 1;
 218 #else
 219   error ("This system does not support attaching to a process");
 220 #endif
 221
 222   inferior_ptid = pid_to_ptid (pid);
 223   push_target (ptrace_ops_hack);
 224
 225   /* Do this first, before anything has had a chance to query the
 226      inferior's symbol table or similar.  */
 227   observer_notify_inferior_created (&current_target, from_tty);
 228 }
 229
 230 static void
 231 inf_ptrace_post_attach (int pid)
 232 {
 233   /* This version of Unix doesn't require a meaningful "post attach"
 234      operation by a debugger.  */
 235 }
 236
 237 /* Take a program previously attached to and detaches it.  The program
 238    resumes execution and will no longer stop on signals, etc.  We'd
 239    better not have left any breakpoints in the program or it'll die
 240    when it hits one.  For this to work, it may be necessary for the
 241    process to have been previously attached.  It *might* work if the
 242    program was started via the normal ptrace (PTRACE_TRACEME).  */
 243
 244 static void
 245 inf_ptrace_detach (char *args, int from_tty)
 246 {
 247   int sig = 0;
 248   int pid = PIDGET (inferior_ptid);
 249
 250   if (from_tty)
 251     {
 252       char *exec_file = get_exec_file (0);
 253       if (exec_file == 0)
 254         exec_file = "";
 255       printf_unfiltered ("Detaching from program: %s, %s\n", exec_file,
 256                          target_pid_to_str (pid_to_ptid (pid)));
 257       gdb_flush (gdb_stdout);
 258     }
 259   if (args)
 260     sig = atoi (args);
 261
 262 #ifdef PT_DETACH
 263   errno = 0;
 264   ptrace (PT_DETACH, pid, (PTRACE_TYPE_ARG3) 1, sig);
 265   if (errno != 0)
 266     perror_with_name ("ptrace");
 267   attach_flag = 0;
 268 #else
 269   error ("This system does not support detaching from a process");
 270 #endif
 271
 272   inferior_ptid = null_ptid;
 273   unpush_target (ptrace_ops_hack);
 274 }
 275
 276 /* Get ready to modify the registers array.  On machines which store
 277    individual registers, this doesn't need to do anything.  On
 278    machines which store all the registers in one fell swoop, this
 279    makes sure that registers contains all the registers from the
 280    program being debugged.  */
 281
 282 static void
 283 inf_ptrace_prepare_to_store (void)
 284 {
 285 }
 286
 287 /* Print status information about what we're accessing.  */
 288
 289 static void
 290 inf_ptrace_files_info (struct target_ops *ignore)
 291 {
 292   printf_unfiltered ("\tUsing the running image of %s %s.\n",
 293                      attach_flag ? "attached" : "child",
 294                      target_pid_to_str (inferior_ptid));
 295 }
 296
 297 static void
 298 inf_ptrace_open (char *arg, int from_tty)
 299 {
 300   error ("Use the \"run\" command to start a Unix child process.");
 301 }
 302
 303 /* Stub function which causes the inferior that runs it, to be ptrace-able
 304    by its parent process.  */
 305
 306 static void
 307 inf_ptrace_me (void)
 308 {
 309   /* "Trace me, Dr. Memory!"  */
 310   ptrace (0, 0, (PTRACE_TYPE_ARG3) 0, 0);
 311 }
 312
 313 /* Stub function which causes the GDB that runs it, to start ptrace-ing
 314    the child process.  */
 315
 316 static void
 317 inf_ptrace_him (int pid)
 318 {
 319   push_target (ptrace_ops_hack);
 320
 321   /* On some targets, there must be some explicit synchronization
 322      between the parent and child processes after the debugger
 323      forks, and before the child execs the debuggee program.  This
 324      call basically gives permission for the child to exec.  */
 325
 326   target_acknowledge_created_inferior (pid);
 327
 328   /* START_INFERIOR_TRAPS_EXPECTED is defined in inferior.h, and will
 329      be 1 or 2 depending on whether we're starting without or with a
 330      shell.  */
 331   startup_inferior (START_INFERIOR_TRAPS_EXPECTED);
 332
 333   /* On some targets, there must be some explicit actions taken after
 334      the inferior has been started up.  */
 335   target_post_startup_inferior (pid_to_ptid (pid));
 336 }
 337
 338 /* Start an inferior Unix child process and sets inferior_ptid to its
 339    pid.  EXEC_FILE is the file to run.  ALLARGS is a string containing
 340    the arguments to the program.  ENV is the environment vector to
 341    pass.  Errors reported with error().  */
 342
 343 static void
 344 inf_ptrace_create_inferior (char *exec_file, char *allargs, char **env,
 345                             int from_tty)
 346 {
 347   fork_inferior (exec_file, allargs, env, inf_ptrace_me, inf_ptrace_him,
 348                  NULL, NULL);
 349   /* We are at the first instruction we care about.  */
 350   observer_notify_inferior_created (&current_target, from_tty);
 351   /* Pedal to the metal...  */
 352   proceed ((CORE_ADDR) -1, TARGET_SIGNAL_0, 0);
 353 }
 354
 355 static void
 356 inf_ptrace_post_startup_inferior (ptid_t ptid)
 357 {
 358   /* This version of Unix doesn't require a meaningful "post startup
 359      inferior" operation by a debugger.  */
 360 }
 361
 362 static void
 363 inf_ptrace_acknowledge_created_inferior (int pid)
 364 {
 365   /* This version of Unix doesn't require a meaningful "acknowledge
 366      created inferior" operation by a debugger.  */
 367 }
 368
 369 static int
 370 inf_ptrace_insert_fork_catchpoint (int pid)
 371 {
 372   /* This version of Unix doesn't support notification of fork events.  */
 373   return 0;
 374 }
 375
 376 static int
 377 inf_ptrace_remove_fork_catchpoint (int pid)
 378 {
 379   /* This version of Unix doesn't support notification of fork events.  */
 380   return 0;
 381 }
 382
 383 static int
 384 inf_ptrace_insert_vfork_catchpoint (int pid)
 385 {
 386   /* This version of Unix doesn't support notification of vfork events.  */
 387   return 0;
 388 }
 389
 390 static int
 391 inf_ptrace_remove_vfork_catchpoint (int pid)
 392 {
 393   /* This version of Unix doesn't support notification of vfork events.  */
 394   return 0;
 395 }
 396
 397 static int
 398 inf_ptrace_follow_fork (int follow_child)
 399 {
 400   /* This version of Unix doesn't support following fork or vfork events.  */
 401   return 0;
 402 }
 403
 404 static int
 405 inf_ptrace_insert_exec_catchpoint (int pid)
 406 {
 407   /* This version of Unix doesn't support notification of exec events.  */
 408   return 0;
 409 }
 410
 411 static int
 412 inf_ptrace_remove_exec_catchpoint (int pid)
 413 {
 414   /* This version of Unix doesn't support notification of exec events.  */
 415   return 0;
 416 }
 417
 418 static int
 419 inf_ptrace_reported_exec_events_per_exec_call (void)
 420 {
 421   /* This version of Unix doesn't support notification of exec events.  */
 422   return 1;
 423 }
 424
 425 static int
 426 inf_ptrace_has_exited (int pid, int wait_status, int *exit_status)
 427 {
 428   if (WIFEXITED (wait_status))
 429     {
 430       *exit_status = WEXITSTATUS (wait_status);
 431       return 1;
 432     }
 433
 434   if (WIFSIGNALED (wait_status))
 435     {
 436       *exit_status = 0;         /* ?? Don't know what else to say here. */
 437       return 1;
 438     }
 439
 440   /* ??? Do we really need to consult the event state, too?
 441      Assume the wait_state alone suffices.  */
 442   return 0;
 443 }
 444
 445 static void
 446 inf_ptrace_mourn_inferior (void)
 447 {
 448   unpush_target (ptrace_ops_hack);
 449   generic_mourn_inferior ();
 450 }
 451
 452 static int
 453 inf_ptrace_can_run (void)
 454 {
 455   return 1;
 456 }
 457
 458 /* Send a SIGINT to the process group.  This acts just like the user
 459    typed a ^C on the controlling terminal.
 460
 461    FIXME: This may not be correct for all systems.  Some may want to
 462    use killpg() instead of kill (-pgrp).  */
 463
 464 static void
 465 inf_ptrace_stop (void)
 466 {
 467   kill (-inferior_process_group, SIGINT);
 468 }
 469
 470 /* Perform a partial transfer to/from the specified object.  For
 471    memory transfers, fall back to the old memory xfer functions.  */
 472
 473 static LONGEST
 474 inf_ptrace_xfer_partial (struct target_ops *ops, enum target_object object,
 475                          const char *annex, void *readbuf,
 476                          const void *writebuf, ULONGEST offset, LONGEST len)
 477 {
 478   switch (object)
 479     {
 480     case TARGET_OBJECT_MEMORY:
 481 #ifdef PT_IO
 482       /* OpenBSD 3.1, NetBSD 1.6 and FreeBSD 5.0 have a new PT_IO
 483          request that promises to be much more efficient in reading
 484          and writing data in the traced process's address space.  */
 485       {
 486         struct ptrace_io_desc piod;
 487
 488         /* NOTE: We assume that there are no distinct address spaces
 489            for instruction and data.  */
 490         piod.piod_op = writebuf ? PIOD_WRITE_D : PIOD_READ_D;
 491         piod.piod_addr = writebuf ? (void *) writebuf : readbuf;
 492         piod.piod_offs = (void *) (long) offset;
 493         piod.piod_len = len;
 494
 495         errno = 0;
 496         if (ptrace (PT_IO, PIDGET (inferior_ptid), (caddr_t) &piod, 0) == 0)
 497           /* Return the actual number of bytes read or written.  */
 498           return piod.piod_len;
 499         /* If the PT_IO request is somehow not supported, fallback on
 500            using PT_WRITE_D/PT_READ_D.  Otherwise we will return zero
 501            to indicate failure.  */
 502         if (errno != EINVAL)
 503           return 0;
 504       }
 505 #endif
 506       {
 507         union
 508         {
 509           PTRACE_TYPE_RET word;
 510           unsigned char byte[sizeof (PTRACE_TYPE_RET)];
 511         } buffer;
 512         ULONGEST rounded_offset;
 513         LONGEST partial_len;
 514
 515         /* Round the start offset down to the next long word
 516            boundary.  */
 517         rounded_offset = offset & -(ULONGEST) sizeof (PTRACE_TYPE_RET);
 518
 519         /* Since ptrace will transfer a single word starting at that
 520            rounded_offset the partial_len needs to be adjusted down to
 521            that (remember this function only does a single transfer).
 522            Should the required length be even less, adjust it down
 523            again.  */
 524         partial_len = (rounded_offset + sizeof (PTRACE_TYPE_RET)) - offset;
 525         if (partial_len > len)
 526           partial_len = len;
 527
 528         if (writebuf)
 529           {
 530             /* If OFFSET:PARTIAL_LEN is smaller than
 531                ROUNDED_OFFSET:WORDSIZE then a read/modify write will
 532                be needed.  Read in the entire word.  */
 533             if (rounded_offset < offset
 534                 || (offset + partial_len
 535                     < rounded_offset + sizeof (PTRACE_TYPE_RET)))
 536               /* Need part of initial word -- fetch it.  */
 537               buffer.word = ptrace (PT_READ_I, PIDGET (inferior_ptid),
 538                                     (PTRACE_TYPE_ARG3) (long) rounded_offset,
 539                                     0);
 540
 541             /* Copy data to be written over corresponding part of
 542                buffer.  */
 543             memcpy (buffer.byte + (offset - rounded_offset),
 544                     writebuf, partial_len);
 545
 546             errno = 0;
 547             ptrace (PT_WRITE_D, PIDGET (inferior_ptid),
 548                     (PTRACE_TYPE_ARG3) (long) rounded_offset,
 549                     buffer.word);
 550             if (errno)
 551               {
 552                 /* Using the appropriate one (I or D) is necessary for
 553                    Gould NP1, at least.  */
 554                 errno = 0;
 555                 ptrace (PT_WRITE_I, PIDGET (inferior_ptid),
 556                         (PTRACE_TYPE_ARG3) (long) rounded_offset,
 557                         buffer.word);
 558                 if (errno)
 559                   return 0;
 560               }
 561           }
 562         if (readbuf)
 563           {
 564             errno = 0;
 565             buffer.word = ptrace (PT_READ_I, PIDGET (inferior_ptid),
 566                                   (PTRACE_TYPE_ARG3) (long) rounded_offset, 0);
 567             if (errno)
 568               return 0;
 569             /* Copy appropriate bytes out of the buffer.  */
 570             memcpy (readbuf, buffer.byte + (offset - rounded_offset),
 571                     partial_len);
 572           }
 573         return partial_len;
 574       }
 575
 576     case TARGET_OBJECT_UNWIND_TABLE:
 577       return -1;
 578
 579     case TARGET_OBJECT_AUXV:
 580       return -1;
 581
 582     case TARGET_OBJECT_WCOOKIE:
 583       return -1;
 584
 585     default:
 586       return -1;
 587     }
 588 }
 589
 590 static char *
 591 inf_ptrace_pid_to_str (ptid_t ptid)
 592 {
 593   return normal_pid_to_str (ptid);
 594 }
 595
 596 struct target_ops *
 597 inf_ptrace_target (void)
 598 {
 599   struct target_ops *t = inf_child_target ();
 600   t->to_open = inf_ptrace_open;
 601   t->to_attach = inf_ptrace_attach;
 602   t->to_post_attach = inf_ptrace_post_attach;
 603   t->to_detach = inf_ptrace_detach;
 604   t->to_resume = inf_ptrace_resume;
 605   t->to_wait = inf_ptrace_wait;
 606   t->to_prepare_to_store = inf_ptrace_prepare_to_store;
 607   t->to_xfer_partial = inf_ptrace_xfer_partial;
 608   t->to_files_info = inf_ptrace_files_info;
 609   t->to_kill = inf_ptrace_kill_inferior;
 610   t->to_create_inferior = inf_ptrace_create_inferior;
 611   t->to_post_startup_inferior = inf_ptrace_post_startup_inferior;
 612   t->to_acknowledge_created_inferior =
 613     inf_ptrace_acknowledge_created_inferior;
 614   t->to_insert_fork_catchpoint = inf_ptrace_insert_fork_catchpoint;
 615   t->to_remove_fork_catchpoint = inf_ptrace_remove_fork_catchpoint;
 616   t->to_insert_vfork_catchpoint = inf_ptrace_insert_vfork_catchpoint;
 617   t->to_remove_vfork_catchpoint = inf_ptrace_remove_vfork_catchpoint;
 618   t->to_follow_fork = inf_ptrace_follow_fork;
 619   t->to_insert_exec_catchpoint = inf_ptrace_insert_exec_catchpoint;
 620   t->to_remove_exec_catchpoint = inf_ptrace_remove_exec_catchpoint;
 621   t->to_reported_exec_events_per_exec_call =
 622     inf_ptrace_reported_exec_events_per_exec_call;
 623   t->to_has_exited = inf_ptrace_has_exited;
 624   t->to_mourn_inferior = inf_ptrace_mourn_inferior;
 625   t->to_can_run = inf_ptrace_can_run;
 626   t->to_thread_alive = inf_ptrace_thread_alive;
 627   t->to_pid_to_str = inf_ptrace_pid_to_str;
 628   t->to_stop = inf_ptrace_stop;
 629   t->to_stratum = process_stratum;
 630   t->to_has_all_memory = 1;
 631   t->to_has_memory = 1;
 632   t->to_has_stack = 1;
 633   t->to_has_registers = 1;
 634   t->to_has_execution = 1;
 635   t->to_magic = OPS_MAGIC;
 636   ptrace_ops_hack = t;
 637   return t;
 638 }