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/* Low-level child interface to ptrace.

   Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,

   1999, 2000, 2001, 2002, 2004, 2005, 2006, 2007, 2008

   Free Software Foundation, Inc.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify

   it under the terms of the GNU General Public License as published by

   the Free Software Foundation; either version 3 of the License, or

   (at your option) any later version.

   This program is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License

   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#include "defs.h"

#include "command.h"

#include "inferior.h"

#include "inflow.h"

#include "gdbcore.h"

#include "regcache.h"

#include "gdb_stdint.h"

#include "gdb_assert.h"

#include "gdb_string.h"

#include "gdb_ptrace.h"

#include "gdb_wait.h"

#include <signal.h>

#include "inf-child.h"

/* HACK: Save the ptrace ops returned by inf_ptrace_target.  */

static struct target_ops *ptrace_ops_hack;

#ifdef PT_GET_PROCESS_STATE

static int

inf_ptrace_follow_fork (struct target_ops *ops, int follow_child)

{

  pid_t pid, fpid;

  ptrace_state_t pe;

  /* FIXME: kettenis/20050720: This stuff should really be passed as

     an argument by our caller.  */

  {

    ptid_t ptid;

    struct target_waitstatus status;

    get_last_target_status (&ptid, &status);

    gdb_assert (status.kind == TARGET_WAITKIND_FORKED);

    pid = ptid_get_pid (ptid);

  }

  if (ptrace (PT_GET_PROCESS_STATE, pid,

               (PTRACE_TYPE_ARG3)&pe, sizeof pe) == -1)

    perror_with_name (("ptrace"));

  gdb_assert (pe.pe_report_event == PTRACE_FORK);

  fpid = pe.pe_other_pid;

  if (follow_child)

    {

      inferior_ptid = pid_to_ptid (fpid);

      detach_breakpoints (pid);

      /* Reset breakpoints in the child as appropriate.  */

      follow_inferior_reset_breakpoints ();

      if (ptrace (PT_DETACH, pid, (PTRACE_TYPE_ARG3)1, 0) == -1)

        perror_with_name (("ptrace"));

    }

  else

    {

      inferior_ptid = pid_to_ptid (pid);

      detach_breakpoints (fpid);

      if (ptrace (PT_DETACH, fpid, (PTRACE_TYPE_ARG3)1, 0) == -1)

        perror_with_name (("ptrace"));

    }

  return 0;

}

#endif /* PT_GET_PROCESS_STATE */

/* Prepare to be traced.  */

static void

inf_ptrace_me (void)

{

  /* "Trace me, Dr. Memory!"  */

  ptrace (PT_TRACE_ME, 0, (PTRACE_TYPE_ARG3)0, 0);

}

/* Start tracing PID.  */

static void

inf_ptrace_him (int pid)

{

  push_target (ptrace_ops_hack);

  /* On some targets, there must be some explicit synchronization

     between the parent and child processes after the debugger

     forks, and before the child execs the debuggee program.  This

     call basically gives permission for the child to exec.  */

  target_acknowledge_created_inferior (pid);

  /* START_INFERIOR_TRAPS_EXPECTED is defined in inferior.h, and will

     be 1 or 2 depending on whether we're starting without or with a

     shell.  */

  startup_inferior (START_INFERIOR_TRAPS_EXPECTED);

  /* On some targets, there must be some explicit actions taken after

     the inferior has been started up.  */

  target_post_startup_inferior (pid_to_ptid (pid));

}

/* Start a new inferior Unix child process.  EXEC_FILE is the file to

   run, ALLARGS is a string containing the arguments to the program.

   ENV is the environment vector to pass.  If FROM_TTY is non-zero, be

   chatty about it.  */

static void

inf_ptrace_create_inferior (char *exec_file, char *allargs, char **env,

                            int from_tty)

{

  fork_inferior (exec_file, allargs, env, inf_ptrace_me, inf_ptrace_him,

                 NULL, NULL);

}

#ifdef PT_GET_PROCESS_STATE

static void

inf_ptrace_post_startup_inferior (ptid_t pid)

{

  ptrace_event_t pe;

  /* Set the initial event mask.  */

  memset (&pe, 0, sizeof pe);

  pe.pe_set_event |= PTRACE_FORK;

  if (ptrace (PT_SET_EVENT_MASK, ptid_get_pid (pid),

              (PTRACE_TYPE_ARG3)&pe, sizeof pe) == -1)

    perror_with_name (("ptrace"));

}

#endif

/* Clean up a rotting corpse of an inferior after it died.  */

static void

inf_ptrace_mourn_inferior (void)

{

  int status;

  /* Wait just one more time to collect the inferior's exit status.

     Do not check whether this succeeds though, since we may be

     dealing with a process that we attached to.  Such a process will

     only report its exit status to its original parent.  */

  waitpid (ptid_get_pid (inferior_ptid), &status, 0);

  unpush_target (ptrace_ops_hack);

  generic_mourn_inferior ();

}

/* Attach to the process specified by ARGS.  If FROM_TTY is non-zero,

   be chatty about it.  */

static void

inf_ptrace_attach (char *args, int from_tty)

{

  char *exec_file;

  pid_t pid;

  char *dummy;

  if (!args)

    error_no_arg (_("process-id to attach"));

  dummy = args;

  pid = strtol (args, &dummy, 0);

  /* Some targets don't set errno on errors, grrr!  */

  if (pid == 0 && args == dummy)

    error (_("Illegal process-id: %s."), args);

  if (pid == getpid ())         /* Trying to masturbate?  */

    error (_("I refuse to debug myself!"));

  if (from_tty)

    {

      exec_file = get_exec_file (0);

      if (exec_file)

        printf_unfiltered (_("Attaching to program: %s, %s\n"), exec_file,

                           target_pid_to_str (pid_to_ptid (pid)));

      else

        printf_unfiltered (_("Attaching to %s\n"),

                           target_pid_to_str (pid_to_ptid (pid)));

      gdb_flush (gdb_stdout);

    }

#ifdef PT_ATTACH

  errno = 0;

  ptrace (PT_ATTACH, pid, (PTRACE_TYPE_ARG3)0, 0);

  if (errno != 0)

    perror_with_name (("ptrace"));

  attach_flag = 1;

#else

  error (_("This system does not support attaching to a process"));

#endif

  inferior_ptid = pid_to_ptid (pid);

  push_target (ptrace_ops_hack);

}

#ifdef PT_GET_PROCESS_STATE

void

inf_ptrace_post_attach (int pid)

{

  ptrace_event_t pe;

  /* Set the initial event mask.  */

  memset (&pe, 0, sizeof pe);

  pe.pe_set_event |= PTRACE_FORK;

  if (ptrace (PT_SET_EVENT_MASK, pid,

              (PTRACE_TYPE_ARG3)&pe, sizeof pe) == -1)

    perror_with_name (("ptrace"));

}

#endif

/* Detach from the inferior, optionally passing it the signal

   specified by ARGS.  If FROM_TTY is non-zero, be chatty about it.  */

static void

inf_ptrace_detach (char *args, int from_tty)

{

  pid_t pid = ptid_get_pid (inferior_ptid);

  int sig = 0;

  if (from_tty)

    {

      char *exec_file = get_exec_file (0);

      if (exec_file == 0)

        exec_file = "";

      printf_unfiltered (_("Detaching from program: %s, %s\n"), exec_file,

                         target_pid_to_str (pid_to_ptid (pid)));

      gdb_flush (gdb_stdout);

    }

  if (args)

    sig = atoi (args);

#ifdef PT_DETACH

  /* We'd better not have left any breakpoints in the program or it'll

     die when it hits one.  Also note that this may only work if we

     previously attached to the inferior.  It *might* work if we

     started the process ourselves.  */

  errno = 0;

  ptrace (PT_DETACH, pid, (PTRACE_TYPE_ARG3)1, sig);

  if (errno != 0)

    perror_with_name (("ptrace"));

  attach_flag = 0;

#else

  error (_("This system does not support detaching from a process"));

#endif

  inferior_ptid = null_ptid;

  unpush_target (ptrace_ops_hack);

}

/* Kill the inferior.  */

static void

inf_ptrace_kill (void)

{

  pid_t pid = ptid_get_pid (inferior_ptid);

  int status;

  if (pid == 0)

    return;

  ptrace (PT_KILL, pid, (PTRACE_TYPE_ARG3)0, 0);

  waitpid (pid, &status, 0);

  target_mourn_inferior ();

}

/* Stop the inferior.  */

static void

inf_ptrace_stop (void)

{

  /* Send a SIGINT to the process group.  This acts just like the user

     typed a ^C on the controlling terminal.  Note that using a

     negative process number in kill() is a System V-ism.  The proper

     BSD interface is killpg().  However, all modern BSDs support the

     System V interface too.  */

  kill (-inferior_process_group, SIGINT);

}

/* Resume execution of thread PTID, or all threads if PTID is -1.  If

   STEP is nonzero, single-step it.  If SIGNAL is nonzero, give it

   that signal.  */

static void

inf_ptrace_resume (ptid_t ptid, int step, enum target_signal signal)

{

  pid_t pid = ptid_get_pid (ptid);

  int request = PT_CONTINUE;

  if (pid == -1)

    /* Resume all threads.  Traditionally ptrace() only supports

       single-threaded processes, so simply resume the inferior.  */

    pid = ptid_get_pid (inferior_ptid);

  if (step)

    {

      /* If this system does not support PT_STEP, a higher level

         function will have called single_step() to transmute the step

         request into a continue request (by setting breakpoints on

         all possible successor instructions), so we don't have to

         worry about that here.  */

      request = PT_STEP;

    }

  /* An address of (PTRACE_TYPE_ARG3)1 tells ptrace to continue from

     where it was.  If GDB wanted it to start some other way, we have

     already written a new program counter value to the child.  */

  errno = 0;

  ptrace (request, pid, (PTRACE_TYPE_ARG3)1, target_signal_to_host (signal));

  if (errno != 0)

    perror_with_name (("ptrace"));

}

/* Wait for the child specified by PTID to do something.  Return the

   process ID of the child, or MINUS_ONE_PTID in case of error; store

   the status in *OURSTATUS.  */

static ptid_t

inf_ptrace_wait (ptid_t ptid, struct target_waitstatus *ourstatus)

{

  pid_t pid;

  int status, save_errno;

  do

    {

      set_sigint_trap ();

      set_sigio_trap ();

      do

        {

          pid = waitpid (ptid_get_pid (ptid), &status, 0);

          save_errno = errno;

        }

      while (pid == -1 && errno == EINTR);

      clear_sigio_trap ();

      clear_sigint_trap ();

      if (pid == -1)

        {

          fprintf_unfiltered (gdb_stderr,

                              _("Child process unexpectedly missing: %s.\n"),

                              safe_strerror (save_errno));

          /* Claim it exited with unknown signal.  */

          ourstatus->kind = TARGET_WAITKIND_SIGNALLED;

          ourstatus->value.sig = TARGET_SIGNAL_UNKNOWN;

          return minus_one_ptid;

        }

      /* Ignore terminated detached child processes.  */

      if (!WIFSTOPPED (status) && pid != ptid_get_pid (inferior_ptid))

        pid = -1;

    }

  while (pid == -1);

#ifdef PT_GET_PROCESS_STATE

  if (WIFSTOPPED (status))

    {

      ptrace_state_t pe;

      pid_t fpid;

      if (ptrace (PT_GET_PROCESS_STATE, pid,

                  (PTRACE_TYPE_ARG3)&pe, sizeof pe) == -1)

        perror_with_name (("ptrace"));

      switch (pe.pe_report_event)

        {

        case PTRACE_FORK:

          ourstatus->kind = TARGET_WAITKIND_FORKED;

          ourstatus->value.related_pid = pe.pe_other_pid;

          /* Make sure the other end of the fork is stopped too.  */

          fpid = waitpid (pe.pe_other_pid, &status, 0);

          if (fpid == -1)

            perror_with_name (("waitpid"));

          if (ptrace (PT_GET_PROCESS_STATE, fpid,

                      (PTRACE_TYPE_ARG3)&pe, sizeof pe) == -1)

            perror_with_name (("ptrace"));

          gdb_assert (pe.pe_report_event == PTRACE_FORK);

          gdb_assert (pe.pe_other_pid == pid);

          if (fpid == ptid_get_pid (inferior_ptid))

            {

              ourstatus->value.related_pid = pe.pe_other_pid;

              return pid_to_ptid (fpid);

            }

          return pid_to_ptid (pid);

        }

    }

#endif

  store_waitstatus (ourstatus, status);

  return pid_to_ptid (pid);

}

/* Attempt a transfer all LEN bytes starting at OFFSET between the

   inferior's OBJECT:ANNEX space and GDB's READBUF/WRITEBUF buffer.

   Return the number of bytes actually transferred.  */

static LONGEST

inf_ptrace_xfer_partial (struct target_ops *ops, enum target_object object,

                         const char *annex, gdb_byte *readbuf,

                         const gdb_byte *writebuf,

                         ULONGEST offset, LONGEST len)

{

  pid_t pid = ptid_get_pid (inferior_ptid);

  switch (object)

    {

    case TARGET_OBJECT_MEMORY:

#ifdef PT_IO

      /* OpenBSD 3.1, NetBSD 1.6 and FreeBSD 5.0 have a new PT_IO

         request that promises to be much more efficient in reading

         and writing data in the traced process's address space.  */

      {

        struct ptrace_io_desc piod;

        /* NOTE: We assume that there are no distinct address spaces

           for instruction and data.  However, on OpenBSD 3.9 and

           later, PIOD_WRITE_D doesn't allow changing memory that's

           mapped read-only.  Since most code segments will be

           read-only, using PIOD_WRITE_D will prevent us from

           inserting breakpoints, so we use PIOD_WRITE_I instead.  */

        piod.piod_op = writebuf ? PIOD_WRITE_I : PIOD_READ_D;

        piod.piod_addr = writebuf ? (void *) writebuf : readbuf;

        piod.piod_offs = (void *) (long) offset;

        piod.piod_len = len;

        errno = 0;

        if (ptrace (PT_IO, pid, (caddr_t)&piod, 0) == 0)

          /* Return the actual number of bytes read or written.  */

          return piod.piod_len;

        /* If the PT_IO request is somehow not supported, fallback on

           using PT_WRITE_D/PT_READ_D.  Otherwise we will return zero

           to indicate failure.  */

        if (errno != EINVAL)

          return 0;

      }

#endif

      {

        union

        {

          PTRACE_TYPE_RET word;

          gdb_byte byte[sizeof (PTRACE_TYPE_RET)];

        } buffer;

        ULONGEST rounded_offset;

        LONGEST partial_len;

        /* Round the start offset down to the next long word

           boundary.  */

        rounded_offset = offset & -(ULONGEST) sizeof (PTRACE_TYPE_RET);

        /* Since ptrace will transfer a single word starting at that

           rounded_offset the partial_len needs to be adjusted down to

           that (remember this function only does a single transfer).

           Should the required length be even less, adjust it down

           again.  */

        partial_len = (rounded_offset + sizeof (PTRACE_TYPE_RET)) - offset;

        if (partial_len > len)

          partial_len = len;

        if (writebuf)

          {

            /* If OFFSET:PARTIAL_LEN is smaller than

               ROUNDED_OFFSET:WORDSIZE then a read/modify write will

               be needed.  Read in the entire word.  */

            if (rounded_offset < offset

                || (offset + partial_len

                    < rounded_offset + sizeof (PTRACE_TYPE_RET)))

              /* Need part of initial word -- fetch it.  */

              buffer.word = ptrace (PT_READ_I, pid,

                                    (PTRACE_TYPE_ARG3)(uintptr_t)

                                    rounded_offset, 0);

            /* Copy data to be written over corresponding part of

               buffer.  */

            memcpy (buffer.byte + (offset - rounded_offset),

                    writebuf, partial_len);

            errno = 0;

            ptrace (PT_WRITE_D, pid,

                    (PTRACE_TYPE_ARG3)(uintptr_t)rounded_offset,

                    buffer.word);

            if (errno)

              {

                /* Using the appropriate one (I or D) is necessary for

                   Gould NP1, at least.  */

                errno = 0;

                ptrace (PT_WRITE_I, pid,

                        (PTRACE_TYPE_ARG3)(uintptr_t)rounded_offset,

                        buffer.word);

                if (errno)

                  return 0;

              }

          }

        if (readbuf)

          {

            errno = 0;

            buffer.word = ptrace (PT_READ_I, pid,

                                  (PTRACE_TYPE_ARG3)(uintptr_t)rounded_offset,

                                  0);

            if (errno)

              return 0;

            /* Copy appropriate bytes out of the buffer.  */

            memcpy (readbuf, buffer.byte + (offset - rounded_offset),

                    partial_len);

          }

        return partial_len;

      }

    case TARGET_OBJECT_UNWIND_TABLE:

      return -1;

    case TARGET_OBJECT_AUXV:

      return -1;

    case TARGET_OBJECT_WCOOKIE:

      return -1;

    default:

      return -1;

    }

}

/* Return non-zero if the thread specified by PTID is alive.  */

static int

inf_ptrace_thread_alive (ptid_t ptid)

{

  /* ??? Is kill the right way to do this?  */

  return (kill (ptid_get_pid (ptid), 0) != -1);

}

/* Print status information about what we're accessing.  */

static void

inf_ptrace_files_info (struct target_ops *ignore)

{

  printf_filtered (_("\tUsing the running image of %s %s.\n"),

                   attach_flag ? "attached" : "child",

                   target_pid_to_str (inferior_ptid));

}

/* Create a prototype ptrace target.  The client can override it with

   local methods.  */

struct target_ops *

inf_ptrace_target (void)

{

  struct target_ops *t = inf_child_target ();

  t->to_attach = inf_ptrace_attach;

  t->to_detach = inf_ptrace_detach;

  t->to_resume = inf_ptrace_resume;

  t->to_wait = inf_ptrace_wait;

  t->to_files_info = inf_ptrace_files_info;

  t->to_kill = inf_ptrace_kill;

  t->to_create_inferior = inf_ptrace_create_inferior;

#ifdef PT_GET_PROCESS_STATE

  t->to_follow_fork = inf_ptrace_follow_fork;

  t->to_post_startup_inferior = inf_ptrace_post_startup_inferior;

  t->to_post_attach = inf_ptrace_post_attach;

#endif

  t->to_mourn_inferior = inf_ptrace_mourn_inferior;

  t->to_thread_alive = inf_ptrace_thread_alive;

  t->to_pid_to_str = normal_pid_to_str;

  t->to_stop = inf_ptrace_stop;

  t->to_xfer_partial = inf_ptrace_xfer_partial;

  ptrace_ops_hack = t;

  return t;

}

/* Pointer to a function that returns the offset within the user area

   where a particular register is stored.  */

static CORE_ADDR (*inf_ptrace_register_u_offset)(struct gdbarch *, int, int);

/* Fetch register REGNUM from the inferior.  */

static void

inf_ptrace_fetch_register (struct regcache *regcache, int regnum)

{

  struct gdbarch *gdbarch = get_regcache_arch (regcache);

  CORE_ADDR addr;

  size_t size;

  PTRACE_TYPE_RET *buf;

  int pid, i;

  /* This isn't really an address, but ptrace thinks of it as one.  */

  addr = inf_ptrace_register_u_offset (gdbarch, regnum, 0);

  if (addr == (CORE_ADDR)-1

      || gdbarch_cannot_fetch_register (gdbarch, regnum))

    {

      regcache_raw_supply (regcache, regnum, NULL);

      return;

    }

  /* Cater for systems like GNU/Linux, that implement threads as

     separate processes.  */

  pid = ptid_get_lwp (inferior_ptid);

  if (pid == 0)

    pid = ptid_get_pid (inferior_ptid);

  size = register_size (gdbarch, regnum);

  gdb_assert ((size % sizeof (PTRACE_TYPE_RET)) == 0);

  buf = alloca (size);

  /* Read the register contents from the inferior a chunk at a time.  */

  for (i = 0; i < size / sizeof (PTRACE_TYPE_RET); i++)

    {

      errno = 0;

      buf[i] = ptrace (PT_READ_U, pid, (PTRACE_TYPE_ARG3)(uintptr_t)addr, 0);

      if (errno != 0)

        error (_("Couldn't read register %s (#%d): %s."),

               gdbarch_register_name (gdbarch, regnum),

               regnum, safe_strerror (errno));

      addr += sizeof (PTRACE_TYPE_RET);

    }

  regcache_raw_supply (regcache, regnum, buf);

}

/* Fetch register REGNUM from the inferior.  If REGNUM is -1, do this

   for all registers.  */

static void

inf_ptrace_fetch_registers (struct regcache *regcache, int regnum)

{

  if (regnum == -1)

    for (regnum = 0;

         regnum < gdbarch_num_regs (get_regcache_arch (regcache));

         regnum++)

      inf_ptrace_fetch_register (regcache, regnum);

  else

    inf_ptrace_fetch_register (regcache, regnum);

}

/* Store register REGNUM into the inferior.  */

static void

inf_ptrace_store_register (const struct regcache *regcache, int regnum)

{

  struct gdbarch *gdbarch = get_regcache_arch (regcache);

  CORE_ADDR addr;

  size_t size;

  PTRACE_TYPE_RET *buf;

  int pid, i;

  /* This isn't really an address, but ptrace thinks of it as one.  */

  addr = inf_ptrace_register_u_offset (gdbarch, regnum, 1);

  if (addr == (CORE_ADDR)-1

      || gdbarch_cannot_store_register (gdbarch, regnum))

    return;

  /* Cater for systems like GNU/Linux, that implement threads as

     separate processes.  */

  pid = ptid_get_lwp (inferior_ptid);

  if (pid == 0)

    pid = ptid_get_pid (inferior_ptid);

  size = register_size (gdbarch, regnum);

  gdb_assert ((size % sizeof (PTRACE_TYPE_RET)) == 0);

  buf = alloca (size);

  /* Write the register contents into the inferior a chunk at a time.  */

  regcache_raw_collect (regcache, regnum, buf);

  for (i = 0; i < size / sizeof (PTRACE_TYPE_RET); i++)

    {