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/* Low level interface for debugging UnixWare user-mode threads for

   GDB, the GNU debugger.

   Copyright 1999, 2000 Free Software Foundation, Inc.

   Written by Nick Duffek <nsd@cygnus.com>.

   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 2 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, write to the Free Software

   Foundation, Inc., 59 Temple Place - Suite 330,

   Boston, MA 02111-1307, USA.  */

/* Like many systems, UnixWare implements two classes of threads:

   kernel-mode threads, which are scheduled by the kernel; and

   user-mode threads, which are scheduled by a library.  UnixWare

   calls these two classes lightweight processes (LWPs) and threads,

   respectively.

   This module deals with user-mode threads.  It calls procfs_ops

   functions to deal with LWPs and processes and core_ops functions to

   deal with core files.

   As of this writing, the user-mode thread debugging interface is not

   documented beyond the comments in <thread.h>.  The following

   description has been gleaned from experience and from information

   provided by SCO.

   libthread.so, against which all UnixWare user-mode thread programs

   link, provides a global thread_debug structure named _thr_debug.

   It has three fields:

     (1) thr_map is a pointer to a pointer to an element of a

         thread_map ring.  A thread_map contains a single thread's id

         number, state, LWP pointer, recent register state, and other

         useful information.

     (2) thr_brk is a pointer to a stub function that libthread.so

         calls when it changes a thread's state, e.g. by creating it,

         switching it to an LWP, or causing it to exit.

     (3) thr_debug_on controls whether libthread.so calls thr_brk().

   Debuggers are able to track thread activity by setting a private

   breakpoint on thr_brk() and setting thr_debug_on to 1.

   thr_brk() receives two arguments:

     (1) a pointer to a thread_map describing the thread being

         changed; and

     (2) an enum thread_change specifying one of the following

         changes:

         invalid                 unknown

         thread_create           thread has just been created

         thread_exit             thread has just exited

         switch_begin            thread will be switched to an LWP

         switch_complete         thread has been switched to an LWP

         cancel_complete         thread wasn't switched to an LWP

         thread_suspend          thread has been thr_suspend()ed

         thread_suspend_pending  thread will be thr_suspend()ed

         thread_continue         thread has been thr_continue()d

   The thread_map argument to thr_brk() is NULL under the following

   circumstances:

     - The main thread is being acted upon.  The main thread always

       has id 1, so its thread_map is easy to find by scanning through

       _thr_debug.thr_map.

     - A "switch_complete" change is occurring, which means that the

       thread specified in the most recent "switch_begin" change has

       moved to an LWP.

     - A "cancel_complete" change is occurring, which means that the

       thread specified in the most recent "switch_begin" change has

       not moved to an LWP after all.

     - A spurious "switch_begin" change is occurring after a

       "thread_exit" change.

   Between switch_begin and switch_complete or cancel_complete, the

   affected thread's LWP pointer is not reliable.  It is possible that

   other parts of the thread's thread_map are also unreliable during

   that time. */

#include "defs.h"

#include "gdbthread.h"

#include "target.h"

#include "inferior.h"

#include <fcntl.h>

/* <thread.h> includes <sys/priocntl.h>, which requires boolean_t from

   <sys/types.h>, which doesn't typedef boolean_t with gcc. */

#define boolean_t int

#include <thread.h>

#undef boolean_t

#include <synch.h>              /* for UnixWare 2.x */

/* Whether to emit debugging output. */

#define DEBUG 0

/* Default debugging output file, overridden by envvar UWTHR_DEBUG. */

#define DEBUG_FILE "/dev/tty"

/* #if DEBUG, write string S to the debugging output channel. */

#if !DEBUG

# define DBG(fmt_and_args)

# define DBG2(fmt_and_args)

#else

# define DBG(fmt_and_args) dbg fmt_and_args

# define DBG2(fmt_and_args)

#endif

/* Back end to CALL_BASE() and TRY_BASE(): evaluate CALL, then convert

   inferior_pid to a composite thread/process id. */

#define CALL_BASE_1(call)               \

do {                                    \

  DBG2(("CALL_BASE(" #call ")"));       \

  call;                                 \

  do_cleanups (infpid_cleanup);         \

} while (0)

/* If inferior_pid can be converted to a composite lwp/process id, do so,

   evaluate base_ops function CALL, and then convert inferior_pid back to a

   composite thread/process id.

   Otherwise, issue an error message and return nonlocally. */

#define CALL_BASE(call)                 \

do {                                    \

  if (!lwp_infpid ())                   \

    error ("uw-thread: no lwp");        \

  CALL_BASE_1 (call);                   \

} while (0)

/* Like CALL_BASE(), but instead of returning nonlocally on error, set

   *CALLED to whether the inferior_pid conversion was successful. */

#define TRY_BASE(call, called)          \

do {                                    \

  if ((*(called) = lwp_infpid ()))      \

    CALL_BASE_1 (call);                 \

} while (0)

/* Information passed by thread_iter() to its callback parameter. */

typedef struct {

  struct thread_map map;

  __lwp_desc_t lwp;

  CORE_ADDR mapp;

} iter_t;

/* Private thread data for the thread_info struct. */

struct private_thread_info {

  int stable;           /* 0 if libthread.so is modifying thread map */

  int thrid;            /* thread id assigned by libthread.so */

  int lwpid;            /* thread's lwp if .stable, 0 means no lwp */

  CORE_ADDR mapp;       /* address of thread's map structure */

};

/* procfs.c's target-specific operations. */

extern struct target_ops procfs_ops;

/* Flag to prevent procfs.c from starting inferior processes. */

extern int procfs_suppress_run;

/* This module's target-specific operations. */

static struct target_ops uw_thread_ops;

/* Copy of the target over which uw_thread_ops is pushed.  This is

   more convenient than a pointer to procfs_ops or core_ops, because

   they lack current_target's default callbacks. */

static struct target_ops base_ops;

/* Saved pointer to previous owner of target_new_objfile_hook. */

static void (*target_new_objfile_chain)(struct objfile *);

/* Whether we are debugging a user-space thread program.  This isn't

   set until after libthread.so is loaded by the program being

   debugged.

   Except for module one-time intialization and where otherwise

   documented, no functions in this module get called when

   !uw_thread_active. */

static int uw_thread_active;

/* For efficiency, cache the addresses of libthread.so's _thr_debug

   structure, its thr_brk stub function, and the main thread's map. */

static CORE_ADDR thr_debug_addr;

static CORE_ADDR thr_brk_addr;

static CORE_ADDR thr_map_main;

/* Remember the thread most recently marked as switching.  Necessary because

   libthread.so passes null map when calling stub with tc_*_complete. */

static struct thread_info *switchto_thread;

/* Cleanup chain for safely restoring inferior_pid after CALL_BASE. */

static struct cleanup *infpid_cleanup;

#if DEBUG

/* Helper function for DBG() macro: if printf-style FMT is non-null, format it

   with args and display the result on the debugging output channel. */

static void

dbg (char *fmt, ...)

{

  static int fd = -1, len;

  va_list args;

  char buf[1024];

  char *path;

  if (!fmt)

    return;

  if (fd < 0)

    {

      path = getenv ("UWTHR_DEBUG");

      if (!path)

        path = DEBUG_FILE;

      if ((fd = open (path, O_WRONLY | O_CREAT | O_TRUNC, 0664)) < 0)

        error ("can't open %s\n", path);

    }

  va_start (args, fmt);

  vsprintf (buf, fmt, args);

  va_end (args);

  len = strlen (buf);

  buf[len] = '\n';

  (void)write (fd, buf, len + 1);

}

#if 0

/* Return a string representing composite PID's components. */

static char *

dbgpid (int pid)

{

  static char *buf, buf1[80], buf2[80];

  if (!buf || buf == buf2)

    buf = buf1;

  else

    buf = buf2;

  if (pid <= 0)

    sprintf (buf, "%d", pid);

  else

    sprintf (buf, "%s %d/%d", ISTID (pid) ? "thr" : "lwp",

             TIDGET (pid), PIDGET (pid));

  return buf;

}

/* Return a string representing thread state CHANGE. */

static char *

dbgchange (enum thread_change change)

{

  switch (change) {

  case tc_invalid:                      return "invalid";

  case tc_thread_create:                return "thread_create";

  case tc_thread_exit:                  return "thread_exit";

  case tc_switch_begin:                 return "switch_begin";

  case tc_switch_complete:              return "switch_complete";

  case tc_cancel_complete:              return "cancel_complete";

  case tc_thread_suspend:               return "thread_suspend";

  case tc_thread_suspend_pending:       return "thread_suspend_pending";

  case tc_thread_continue:              return "thread_continue";

  default:                              return "unknown";

  }

}

/* Return a string representing thread STATE. */

static char *

dbgstate (int state)

{

  switch (state) {

  case TS_ONPROC:       return "running";

  case TS_SLEEP:        return "sleeping";

  case TS_RUNNABLE:     return "runnable";

  case TS_ZOMBIE:       return "zombie";

  case TS_SUSPENDED:    return "suspended";

#ifdef TS_FORK

  case TS_FORK:         return "forking";

#endif

  default:              return "confused";

  }

}

#endif  /* 0 */

#endif  /* DEBUG */

/* Read the contents of _thr_debug into *DEBUGP.  Return success. */

static int

read_thr_debug (struct thread_debug *debugp)

{

  return base_ops.to_xfer_memory (thr_debug_addr, (char *)debugp,

                                  sizeof (*debugp), 0, &base_ops);

}

/* Read into MAP the contents of the thread map at inferior process address

   MAPP.  Return success. */

static int

read_map (CORE_ADDR mapp, struct thread_map *map)

{

  return base_ops.to_xfer_memory ((CORE_ADDR)THR_MAP (mapp), (char *)map,

                                  sizeof (*map), 0, &base_ops);

}

/* Read into LWP the contents of the lwp decriptor at inferior process address

   LWPP.  Return success. */

static int

read_lwp (CORE_ADDR lwpp, __lwp_desc_t *lwp)

{

  return base_ops.to_xfer_memory (lwpp, (char *)lwp,

                                  sizeof (*lwp), 0, &base_ops);

}

/* Iterate through all user threads, applying FUNC(<map>, <lwp>, DATA) until

     (a) FUNC returns nonzero,

     (b) FUNC has been applied to all threads, or

     (c) an error occurs,

   where <map> is the thread's struct thread_map and <lwp> if non-null is the

   thread's current __lwp_desc_t.

   If a call to FUNC returns nonzero, return that value; otherwise, return 0. */

static int

thread_iter (int (*func)(iter_t *, void *), void *data)

{

  struct thread_debug debug;

  CORE_ADDR first, mapp;

  iter_t iter;

  int ret;

  if (!read_thr_debug (&debug))

    return 0;

  if (!base_ops.to_xfer_memory ((CORE_ADDR)debug.thr_map, (char *)&mapp,

                                sizeof (mapp), 0, &base_ops))

    return 0;

  if (!mapp)

    return 0;

  for (first = mapp;;)

    {

      if (!read_map (mapp, &iter.map))

        return 0;

      if (iter.map.thr_lwpp)

        if (!read_lwp ((CORE_ADDR)iter.map.thr_lwpp, &iter.lwp))

          return 0;

      iter.mapp = mapp;

      if ((ret = func (&iter, data)))

        return ret;

      mapp = (CORE_ADDR)iter.map.thr_next;

      if (mapp == first)

        return 0;

    }

}

/* Deactivate user-mode thread support. */

static void

deactivate_uw_thread (void)

{

  remove_thread_event_breakpoints ();

  uw_thread_active = 0;

  unpush_target (&uw_thread_ops);

}

/* Return the composite lwp/process id corresponding to composite

   id PID.  If PID is a thread with no lwp, return 0. */

static int

thr_to_lwp (int pid)

{

  struct thread_info *info;

  int lid;

  if (!ISTID (pid))

    lid = pid;

  else if (!(info = find_thread_pid (pid)))

    lid = 0;

  else if (!info->private->lwpid)

    lid = 0;

  else

    lid = MKLID (pid, info->private->lwpid);

  DBG2(("  thr_to_lwp(%s) = %s", dbgpid (pid), dbgpid (lid)));

  return lid;

}

/* find_thread_lwp() callback: return whether TP describes a thread

   associated with lwp id DATA. */

static int

find_thread_lwp_callback (struct thread_info *tp, void *data)

{

  int lwpid = (int)data;

  if (!ISTID (tp->pid))

    return 0;

  if (!tp->private->stable)

    return 0;

  if (lwpid != tp->private->lwpid)

    return 0;

  /* match */

  return 1;

}

/* If a thread is associated with lwp id LWPID, return the corresponding

   member of the global thread list; otherwise, return null. */

static struct thread_info *

find_thread_lwp (int lwpid)

{

  return iterate_over_threads (find_thread_lwp_callback, (void *)lwpid);

}

/* Return the composite thread/process id corresponding to composite

   id PID.  If PID is an lwp with no thread, return PID. */

static int

lwp_to_thr (int pid)

{

  struct thread_info *info;

  int tid = pid, lwpid;

  if (ISTID (pid))

    goto done;

  if (!(lwpid = LIDGET (pid)))

    goto done;

  if (!(info = find_thread_lwp (lwpid)))

    goto done;

  tid = MKTID (pid, info->private->thrid);

 done:

  DBG2((ISTID (tid) ? NULL : "lwp_to_thr: no thr for %s", dbgpid (pid)));

  return tid;

}

/* do_cleanups() callback: convert inferior_pid to a composite

   thread/process id after having made a procfs call. */

static void

thr_infpid (void *unused)

{

  int pid = lwp_to_thr (inferior_pid);

  DBG2((" inferior_pid from procfs: %s => %s",

        dbgpid (inferior_pid), dbgpid (pid)));

  inferior_pid = pid;

}

/* If possible, convert inferior_pid to a composite lwp/process id in

   preparation for making a procfs call.  Return success. */

static int

lwp_infpid (void)

{

  int pid = thr_to_lwp (inferior_pid);

  DBG2((" inferior_pid to procfs: %s => %s",

        dbgpid (inferior_pid), dbgpid (pid)));

  if (!pid)

    return 0;

  inferior_pid = pid;

  infpid_cleanup = make_cleanup (thr_infpid, NULL);

  return 1;

}

/* Add to the global thread list a new user-mode thread with system id THRID,

   lwp id LWPID, map address MAPP, and composite thread/process PID. */

static void

add_thread_uw (int thrid, int lwpid, CORE_ADDR mapp, int pid)

{

  struct thread_info *newthread;

  if ((newthread = add_thread (pid)) == NULL)

    error ("failed to create new thread structure");

  newthread->private = xmalloc (sizeof (struct private_thread_info));

  newthread->private->stable = 1;

  newthread->private->thrid = thrid;

  newthread->private->lwpid = lwpid;

  newthread->private->mapp = mapp;

  if (target_has_execution)

    printf_unfiltered ("[New %s]\n", target_pid_to_str (pid));

}

/* notice_threads() and find_main() callback: if the thread list doesn't

   already contain the thread described by ITER, add it if it's the main

   thread or if !DATA. */

static int

notice_thread (iter_t *iter, void *data)

{

  int thrid = iter->map.thr_tid;

  int lwpid = !iter->map.thr_lwpp ? 0 : iter->lwp.lwp_id;

  int pid = MKTID (inferior_pid, thrid);

  if (!find_thread_pid (pid) && (!data || thrid == 1))

    add_thread_uw (thrid, lwpid, iter->mapp, pid);

  return 0;

}

/* Add to the thread list any threads it doesn't already contain. */

static void

notice_threads (void)

{

  thread_iter (notice_thread, NULL);

}

/* Return the address of the main thread's map.  On error, return 0. */

static CORE_ADDR

find_main (void)

{

  if (!thr_map_main)

    {

      struct thread_info *info;

      thread_iter (notice_thread, (void *)1);

      if ((info = find_thread_pid (MKTID (inferior_pid, 1))))

        thr_map_main = info->private->mapp;

    }

  return thr_map_main;

}

/* Attach to process specified by ARGS, then initialize for debugging it

   and wait for the trace-trap that results from attaching.

   This function only gets called with uw_thread_active == 0. */

static void

uw_thread_attach (char *args, int from_tty)

{

  procfs_ops.to_attach (args, from_tty);

  if (uw_thread_active)

    thr_infpid (NULL);

}

/* Detach from the process attached to by uw_thread_attach(). */

static void

uw_thread_detach (char *args, int from_tty)

{

  deactivate_uw_thread ();

  base_ops.to_detach (args, from_tty);

}

/* Tell the inferior process to continue running thread PID if >= 0

   and all threads otherwise. */

static void

uw_thread_resume (int pid, int step, enum target_signal signo)

{

  if (pid > 0 && !(pid = thr_to_lwp (pid)))

    pid = -1;

  CALL_BASE (base_ops.to_resume (pid, step, signo));

}

/* If the trap we just received from lwp PID was due to a breakpoint

   on the libthread.so debugging stub, update this module's state

   accordingly. */

static void

libthread_stub (int pid)

{

  CORE_ADDR sp, mapp, mapp_main;

  enum thread_change change;

  struct thread_map map;

  __lwp_desc_t lwp;

  int tid = 0, lwpid;

  struct thread_info *info;

  /* Check for stub breakpoint. */

  if (read_pc_pid (pid) - DECR_PC_AFTER_BREAK != thr_brk_addr)

    return;

  /* Retrieve stub args. */

  sp = read_register_pid (SP_REGNUM, pid);

  if (!base_ops.to_xfer_memory (sp + SP_ARG0, (char *)&mapp,

                                sizeof (mapp), 0, &base_ops))

    goto err;

  if (!base_ops.to_xfer_memory (sp + SP_ARG0 + sizeof (mapp), (char *)&change,

                                sizeof (change), 0, &base_ops))

    goto err;

  /* create_inferior() may not have finished yet, so notice the main

     thread to ensure that it's displayed first by add_thread(). */

  mapp_main = find_main ();

  /* Notice thread creation, deletion, or stability change. */

  switch (change) {

  case tc_switch_begin:

    if (!mapp)                          /* usually means main thread */

      mapp = mapp_main;

    /* fall through */

  case tc_thread_create:

  case tc_thread_exit:

    if (!mapp)

      break;

    if (!read_map (mapp, &map))

      goto err;

    tid = MKTID (pid, map.thr_tid);

    switch (change) {

    case tc_thread_create:              /* new thread */

      if (!map.thr_lwpp)

        lwpid = 0;

      else if (!read_lwp ((CORE_ADDR)map.thr_lwpp, &lwp))

        goto err;

      else

        lwpid = lwp.lwp_id;

      add_thread_uw (map.thr_tid, lwpid, mapp, tid);

      break;

    case tc_thread_exit:                /* thread has exited */

      printf_unfiltered ("[Exited %s]\n", target_pid_to_str (tid));

      delete_thread (tid);

      if (tid == inferior_pid)

        inferior_pid = pid;

      break;

    case tc_switch_begin:               /* lwp is switching threads */

      if (switchto_thread)

        goto err;

      if (!(switchto_thread = find_thread_pid (tid)))

        goto err;

      switchto_thread->private->stable = 0;

      break;

    default:

      break;

    }

    break;

  case tc_switch_complete:              /* lwp has switched threads */

  case tc_cancel_complete:              /* lwp didn't switch threads */

    if (!switchto_thread)

      goto err;

    if (change == tc_switch_complete)

      {

        /* If switchto_thread is the main thread, then (a) the corresponding

           tc_switch_begin probably received a null map argument and therefore

           (b) it may have been a spurious switch following a tc_thread_exit.

           Therefore, explicitly query the thread's lwp before caching it in

           its thread list entry. */

        if (!read_map (switchto_thread->private->mapp, &map))

          goto err;

        if (map.thr_lwpp)

          {

            if (!read_lwp ((CORE_ADDR)map.thr_lwpp, &lwp))

              goto err;

            if ((info = find_thread_lwp (lwp.lwp_id)))

              info->private->lwpid = 0;

            switchto_thread->private->lwpid = lwp.lwp_id;

          }

      }

    switchto_thread->private->stable = 1;

    switchto_thread = NULL;

    break;

  case tc_invalid:

  case tc_thread_suspend:

  case tc_thread_suspend_pending:

  case tc_thread_continue:

  err:

    DBG(("unexpected condition in libthread_stub()"));

    break;

  }

  DBG2(("libthread_stub(%s): %s %s %s", dbgpid (pid), dbgpid (tid),

        dbgchange (change), tid ? dbgstate (map.thr_state) : ""));