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/* GNU/Linux native-dependent code for debugging multiple forks.

   Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010

   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 "arch-utils.h"

#include "inferior.h"

#include "regcache.h"

#include "gdbcmd.h"

#include "infcall.h"

#include "objfiles.h"

#include "gdb_assert.h"

#include "gdb_string.h"

#include "linux-fork.h"

#include "linux-nat.h"

#include <sys/ptrace.h>

#include "gdb_wait.h"

#include <sys/param.h>

#include "gdb_dirent.h"

#include <ctype.h>

struct fork_info *fork_list;

static int highest_fork_num;

/* Prevent warning from -Wmissing-prototypes.  */

extern void _initialize_linux_fork (void);

/* Fork list data structure:  */

struct fork_info

{

  struct fork_info *next;

  ptid_t ptid;

  int num;                      /* Convenient handle (GDB fork id) */

  struct regcache *savedregs;   /* Convenient for info fork, saves

                                   having to actually switch contexts.  */

  int clobber_regs;             /* True if we should restore saved regs.  */

  off_t *filepos;               /* Set of open file descriptors' offsets.  */

  int maxfd;

};

/* Fork list methods:  */

int

forks_exist_p (void)

{

  return (fork_list != NULL);

}

/* Add a fork to the internal fork list.  */

struct fork_info *

add_fork (pid_t pid)

{

  struct fork_info *fp;

  if (fork_list == NULL && pid != PIDGET (inferior_ptid))

    {

      /* Special case -- if this is the first fork in the list

         (the list is hitherto empty), and if this new fork is

         NOT the current inferior_ptid, then add inferior_ptid

         first, as a special zeroeth fork id.  */

      highest_fork_num = -1;

      add_fork (PIDGET (inferior_ptid));        /* safe recursion */

    }

  fp = XZALLOC (struct fork_info);

  fp->ptid = ptid_build (pid, pid, 0);

  fp->num = ++highest_fork_num;

  fp->next = fork_list;

  fork_list = fp;

  return fp;

}

static void

free_fork (struct fork_info *fp)

{

  /* Notes on step-resume breakpoints: since this is a concern for

     threads, let's convince ourselves that it's not a concern for

     forks.  There are two ways for a fork_info to be created.  First,

     by the checkpoint command, in which case we're at a gdb prompt

     and there can't be any step-resume breakpoint.  Second, by a fork

     in the user program, in which case we *may* have stepped into the

     fork call, but regardless of whether we follow the parent or the

     child, we will return to the same place and the step-resume

     breakpoint, if any, will take care of itself as usual.  And

     unlike threads, we do not save a private copy of the step-resume

     breakpoint -- so we're OK.  */

  if (fp)

    {

      if (fp->savedregs)

        regcache_xfree (fp->savedregs);

      if (fp->filepos)

        xfree (fp->filepos);

      xfree (fp);

    }

}

static void

delete_fork (ptid_t ptid)

{

  struct fork_info *fp, *fpprev;

  fpprev = NULL;

  for (fp = fork_list; fp; fpprev = fp, fp = fp->next)

    if (ptid_equal (fp->ptid, ptid))

      break;

  if (!fp)

    return;

  if (fpprev)

    fpprev->next = fp->next;

  else

    fork_list = fp->next;

  free_fork (fp);

  /* Special case: if there is now only one process in the list,

     and if it is (hopefully!) the current inferior_ptid, then

     remove it, leaving the list empty -- we're now down to the

     default case of debugging a single process.  */

  if (fork_list != NULL && fork_list->next == NULL &&

      ptid_equal (fork_list->ptid, inferior_ptid))

    {

      /* Last fork -- delete from list and handle as solo process

         (should be a safe recursion).  */

      delete_fork (inferior_ptid);

    }

}

/* Find a fork_info by matching PTID.  */

static struct fork_info *

find_fork_ptid (ptid_t ptid)

{

  struct fork_info *fp;

  for (fp = fork_list; fp; fp = fp->next)

    if (ptid_equal (fp->ptid, ptid))

      return fp;

  return NULL;

}

/* Find a fork_info by matching ID.  */

static struct fork_info *

find_fork_id (int num)

{

  struct fork_info *fp;

  for (fp = fork_list; fp; fp = fp->next)

    if (fp->num == num)

      return fp;

  return NULL;

}

/* Find a fork_info by matching pid.  */

extern struct fork_info *

find_fork_pid (pid_t pid)

{

  struct fork_info *fp;

  for (fp = fork_list; fp; fp = fp->next)

    if (pid == ptid_get_pid (fp->ptid))

      return fp;

  return NULL;

}

static ptid_t

fork_id_to_ptid (int num)

{

  struct fork_info *fork = find_fork_id (num);

  if (fork)

    return fork->ptid;

  else

    return pid_to_ptid (-1);

}

static void

init_fork_list (void)

{

  struct fork_info *fp, *fpnext;

  if (!fork_list)

    return;

  for (fp = fork_list; fp; fp = fpnext)

    {

      fpnext = fp->next;

      free_fork (fp);

    }

  fork_list = NULL;

}

/* Fork list <-> gdb interface.  */

/* Utility function for fork_load/fork_save.

   Calls lseek in the (current) inferior process.  */

static off_t

call_lseek (int fd, off_t offset, int whence)

{

  char exp[80];

  snprintf (&exp[0], sizeof (exp), "lseek (%d, %ld, %d)",

            fd, (long) offset, whence);

  return (off_t) parse_and_eval_long (&exp[0]);

}

/* Load infrun state for the fork PTID.  */

static void

fork_load_infrun_state (struct fork_info *fp)

{

  extern void nullify_last_target_wait_ptid ();

  int i;

  linux_nat_switch_fork (fp->ptid);

  if (fp->savedregs && fp->clobber_regs)

    regcache_cpy (get_current_regcache (), fp->savedregs);

  registers_changed ();

  reinit_frame_cache ();

  stop_pc = regcache_read_pc (get_current_regcache ());

  nullify_last_target_wait_ptid ();

  /* Now restore the file positions of open file descriptors.  */

  if (fp->filepos)

    {

      for (i = 0; i <= fp->maxfd; i++)

        if (fp->filepos[i] != (off_t) -1)

          call_lseek (i, fp->filepos[i], SEEK_SET);

      /* NOTE: I can get away with using SEEK_SET and SEEK_CUR because

         this is native-only.  If it ever has to be cross, we'll have

         to rethink this.  */

    }

}

/* Save infrun state for the fork PTID.

   Exported for use by linux child_follow_fork.  */

static void

fork_save_infrun_state (struct fork_info *fp, int clobber_regs)

{

  char path[MAXPATHLEN];

  struct dirent *de;

  DIR *d;

  if (fp->savedregs)

    regcache_xfree (fp->savedregs);

  fp->savedregs = regcache_dup (get_current_regcache ());

  fp->clobber_regs = clobber_regs;

  if (clobber_regs)

    {

      /* Now save the 'state' (file position) of all open file descriptors.

         Unfortunately fork does not take care of that for us...  */

      snprintf (path, MAXPATHLEN, "/proc/%ld/fd", (long) PIDGET (fp->ptid));

      if ((d = opendir (path)) != NULL)

        {

          long tmp;

          fp->maxfd = 0;

          while ((de = readdir (d)) != NULL)

            {

              /* Count open file descriptors (actually find highest

                 numbered).  */

              tmp = strtol (&de->d_name[0], NULL, 10);

              if (fp->maxfd < tmp)

                fp->maxfd = tmp;

            }

          /* Allocate array of file positions.  */

          fp->filepos = xrealloc (fp->filepos,

                                  (fp->maxfd + 1) * sizeof (*fp->filepos));

          /* Initialize to -1 (invalid).  */

          for (tmp = 0; tmp <= fp->maxfd; tmp++)

            fp->filepos[tmp] = -1;

          /* Now find actual file positions.  */

          rewinddir (d);

          while ((de = readdir (d)) != NULL)

            if (isdigit (de->d_name[0]))

              {

                tmp = strtol (&de->d_name[0], NULL, 10);

                fp->filepos[tmp] = call_lseek (tmp, 0, SEEK_CUR);

              }

          closedir (d);

        }

    }

}

/* Kill 'em all, let God sort 'em out...  */

void

linux_fork_killall (void)

{

  /* Walk list and kill every pid.  No need to treat the

     current inferior_ptid as special (we do not return a

     status for it) -- however any process may be a child

     or a parent, so may get a SIGCHLD from a previously

     killed child.  Wait them all out.  */

  struct fork_info *fp;

  pid_t pid, ret;

  int status;

  for (fp = fork_list; fp; fp = fp->next)

    {

      pid = PIDGET (fp->ptid);

      do {

        /* Use SIGKILL instead of PTRACE_KILL because the former works even

           if the thread is running, while the later doesn't.  */

        kill (pid, SIGKILL);

        ret = waitpid (pid, &status, 0);

        /* We might get a SIGCHLD instead of an exit status.  This is

         aggravated by the first kill above - a child has just

         died.  MVS comment cut-and-pasted from linux-nat.  */

      } while (ret == pid && WIFSTOPPED (status));

    }

  init_fork_list ();    /* Clear list, prepare to start fresh.  */

}

/* The current inferior_ptid has exited, but there are other viable

   forks to debug.  Delete the exiting one and context-switch to the

   first available.  */

void

linux_fork_mourn_inferior (void)

{

  /* 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.  */

  int status;

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

  /* OK, presumably inferior_ptid is the one who has exited.

     We need to delete that one from the fork_list, and switch

     to the next available fork.  */

  delete_fork (inferior_ptid);

  /* There should still be a fork - if there's only one left,

     delete_fork won't remove it, because we haven't updated

     inferior_ptid yet.  */

  gdb_assert (fork_list);

  fork_load_infrun_state (fork_list);

  printf_filtered (_("[Switching to %s]\n"),

                   target_pid_to_str (inferior_ptid));

  /* If there's only one fork, switch back to non-fork mode.  */

  if (fork_list->next == NULL)

    delete_fork (inferior_ptid);

}

/* The current inferior_ptid is being detached, but there are other

   viable forks to debug.  Detach and delete it and context-switch to

   the first available.  */

void

linux_fork_detach (char *args, int from_tty)

{

  /* OK, inferior_ptid is the one we are detaching from.  We need to

     delete it from the fork_list, and switch to the next available

     fork.  */

  if (ptrace (PTRACE_DETACH, PIDGET (inferior_ptid), 0, 0))

    error (_("Unable to detach %s"), target_pid_to_str (inferior_ptid));

  delete_fork (inferior_ptid);

  /* There should still be a fork - if there's only one left,

     delete_fork won't remove it, because we haven't updated

     inferior_ptid yet.  */

  gdb_assert (fork_list);

  fork_load_infrun_state (fork_list);

  if (from_tty)

    printf_filtered (_("[Switching to %s]\n"),

                     target_pid_to_str (inferior_ptid));

  /* If there's only one fork, switch back to non-fork mode.  */

  if (fork_list->next == NULL)

    delete_fork (inferior_ptid);

}

/* Fork list <-> user interface.  */

static void

delete_checkpoint_command (char *args, int from_tty)

{

  ptid_t ptid;

  if (!args || !*args)

    error (_("Requires argument (checkpoint id to delete)"));

  ptid = fork_id_to_ptid (parse_and_eval_long (args));

  if (ptid_equal (ptid, minus_one_ptid))

    error (_("No such checkpoint id, %s"), args);

  if (ptid_equal (ptid, inferior_ptid))

    error (_("\

Please switch to another checkpoint before deleting the current one"));

  if (ptrace (PTRACE_KILL, PIDGET (ptid), 0, 0))

    error (_("Unable to kill pid %s"), target_pid_to_str (ptid));

  if (from_tty)

    printf_filtered (_("Killed %s\n"), target_pid_to_str (ptid));

  delete_fork (ptid);

}

static void

detach_checkpoint_command (char *args, int from_tty)

{

  ptid_t ptid;

  if (!args || !*args)

    error (_("Requires argument (checkpoint id to detach)"));

  ptid = fork_id_to_ptid (parse_and_eval_long (args));

  if (ptid_equal (ptid, minus_one_ptid))

    error (_("No such checkpoint id, %s"), args);

  if (ptid_equal (ptid, inferior_ptid))

    error (_("\

Please switch to another checkpoint before detaching the current one"));

  if (ptrace (PTRACE_DETACH, PIDGET (ptid), 0, 0))

    error (_("Unable to detach %s"), target_pid_to_str (ptid));

  if (from_tty)

    printf_filtered (_("Detached %s\n"), target_pid_to_str (ptid));

  delete_fork (ptid);

}

/* Print information about currently known checkpoints.  */

static void

info_checkpoints_command (char *arg, int from_tty)

{

  struct gdbarch *gdbarch = get_current_arch ();

  struct frame_info *cur_frame;

  struct symtab_and_line sal;

  struct symtab *cur_symtab;

  struct fork_info *fp;

  int cur_line;

  ULONGEST pc;

  int requested = -1;

  struct fork_info *printed = NULL;

  if (arg && *arg)

    requested = (int) parse_and_eval_long (arg);

  for (fp = fork_list; fp; fp = fp->next)

    {

      if (requested > 0 && fp->num != requested)

        continue;

      printed = fp;

      if (ptid_equal (fp->ptid, inferior_ptid))

        {

          printf_filtered ("* ");

          pc = regcache_read_pc (get_current_regcache ());

        }

      else

        {

          printf_filtered ("  ");

          pc = regcache_read_pc (fp->savedregs);

        }

      printf_filtered ("%d %s", fp->num, target_pid_to_str (fp->ptid));

      if (fp->num == 0)

        printf_filtered (_(" (main process)"));

      printf_filtered (_(" at "));

      fputs_filtered (paddress (gdbarch, pc), gdb_stdout);

      sal = find_pc_line (pc, 0);

      if (sal.symtab)

        {

          char *tmp = strrchr (sal.symtab->filename, '/');

          if (tmp)

            printf_filtered (_(", file %s"), tmp + 1);

          else

            printf_filtered (_(", file %s"), sal.symtab->filename);

        }

      if (sal.line)

        printf_filtered (_(", line %d"), sal.line);

      if (!sal.symtab && !sal.line)

        {

          struct minimal_symbol *msym;

          msym = lookup_minimal_symbol_by_pc (pc);

          if (msym)

            printf_filtered (", <%s>", SYMBOL_LINKAGE_NAME (msym));

        }

      putchar_filtered ('\n');

    }

  if (printed == NULL)

    {

      if (requested > 0)

        printf_filtered (_("No checkpoint number %d.\n"), requested);

      else

        printf_filtered (_("No checkpoints.\n"));

    }

}

/* The PID of the process we're checkpointing.  */

static int checkpointing_pid = 0;

int

linux_fork_checkpointing_p (int pid)

{

  return (checkpointing_pid == pid);

}

static void

checkpoint_command (char *args, int from_tty)

{

  struct objfile *fork_objf;

  struct gdbarch *gdbarch;

  struct target_waitstatus last_target_waitstatus;

  ptid_t last_target_ptid;

  struct value *fork_fn = NULL, *ret;

  struct fork_info *fp;

  pid_t retpid;

  struct cleanup *old_chain;

  long i;

  /* Make the inferior fork, record its (and gdb's) state.  */

  if (lookup_minimal_symbol ("fork", NULL, NULL) != NULL)

    fork_fn = find_function_in_inferior ("fork", &fork_objf);

  if (!fork_fn)

    if (lookup_minimal_symbol ("_fork", NULL, NULL) != NULL)

      fork_fn = find_function_in_inferior ("fork", &fork_objf);

  if (!fork_fn)

    error (_("checkpoint: can't find fork function in inferior."));

  gdbarch = get_objfile_arch (fork_objf);

  ret = value_from_longest (builtin_type (gdbarch)->builtin_int, 0);

  /* Tell linux-nat.c that we're checkpointing this inferior.  */

  old_chain = make_cleanup_restore_integer (&checkpointing_pid);

  checkpointing_pid = PIDGET (inferior_ptid);

  ret = call_function_by_hand (fork_fn, 0, &ret);

  do_cleanups (old_chain);

  if (!ret)     /* Probably can't happen.  */

    error (_("checkpoint: call_function_by_hand returned null."));

  retpid = value_as_long (ret);

  get_last_target_status (&last_target_ptid, &last_target_waitstatus);

  if (from_tty)

    {

      int parent_pid;

      printf_filtered (_("checkpoint: fork returned pid %ld.\n"),

                       (long) retpid);

      if (info_verbose)

        {

          parent_pid = ptid_get_lwp (last_target_ptid);

          if (parent_pid == 0)

            parent_pid = ptid_get_pid (last_target_ptid);

          printf_filtered (_("   gdb says parent = %ld.\n"),

                           (long) parent_pid);

        }

    }

  fp = find_fork_pid (retpid);

  if (!fp)

    error (_("Failed to find new fork"));

  fork_save_infrun_state (fp, 1);

}

static void

linux_fork_context (struct fork_info *newfp, int from_tty)

{

  /* Now we attempt to switch processes.  */

  struct fork_info *oldfp;

  ptid_t ptid;

  int id, i;

  gdb_assert (newfp != NULL);

  oldfp = find_fork_ptid (inferior_ptid);

  gdb_assert (oldfp != NULL);

  fork_save_infrun_state (oldfp, 1);

  remove_breakpoints ();

  fork_load_infrun_state (newfp);

  insert_breakpoints ();

  printf_filtered (_("Switching to %s\n"),

                   target_pid_to_str (inferior_ptid));

  print_stack_frame (get_selected_frame (NULL), 1, SRC_AND_LOC);

}

/* Switch inferior process (checkpoint) context, by checkpoint id.  */

static void

restart_command (char *args, int from_tty)

{

  struct fork_info *fp;

  if (!args || !*args)

    error (_("Requires argument (checkpoint id to restart)"));

  if ((fp = find_fork_id (parse_and_eval_long (args))) == NULL)

    error (_("Not found: checkpoint id %s"), args);

  linux_fork_context (fp, from_tty);

}

void

_initialize_linux_fork (void)

{

  init_fork_list ();

  /* Checkpoint command: create a fork of the inferior process

     and set it aside for later debugging.  */

  add_com ("checkpoint", class_obscure, checkpoint_command, _("\

Fork a duplicate process (experimental)."));

  /* Restart command: restore the context of a specified checkpoint

     process.  */

  add_com ("restart", class_obscure, restart_command, _("\

restart <n>: restore program context from a checkpoint.\n\

Argument 'n' is checkpoint ID, as displayed by 'info checkpoints'."));

  /* Delete checkpoint command: kill the process and remove it from

     the fork list.  */

  add_cmd ("checkpoint", class_obscure, delete_checkpoint_command, _("\

Delete a checkpoint (experimental)."),

           &deletelist);

  /* Detach checkpoint command: release the process to run independently,

     and remove it from the fork list.  */

  add_cmd ("checkpoint", class_obscure, detach_checkpoint_command, _("\

Detach from a checkpoint (experimental)."),

           &detachlist);

  /* Info checkpoints command: list all forks/checkpoints

     currently under gdb's control.  */

  add_info ("checkpoints", info_checkpoints_command,

            _("IDs of currently known checkpoints."));

}