* config/i386/nm-linux.h (PREPARE_TO_PROCEED, ATTCH_LWP,

GET_THREAD_SIGNALS): New defines.
* config/i386/linux.mh (NATDEPFILES): Remove lin-thread.o and
linux-threads.o.  Add proc-service.o, thread-db.o and lin-lwp.o.
* proc-service.c: New file.
* thread-db.c: New file.
* lin-lwp.c: New file.

gdb/ChangeLog

@@ -1,5 +1,13 @@
 2000-09-03  Mark Kettenis  <kettenis@gnu.org>
 
+	* config/i386/nm-linux.h (PREPARE_TO_PROCEED, ATTCH_LWP,
+	GET_THREAD_SIGNALS): New defines.
+	* config/i386/linux.mh (NATDEPFILES): Remove lin-thread.o and
+	linux-threads.o.  Add proc-service.o, thread-db.o and lin-lwp.o.
+	* proc-service.c: New file.
+	* thread-db.c: New file.
+	* lin-lwp.c: New file.
+
 	* gdb_assert.h: New file.
 
 	* gdb_thread_db.h [HAVE_THREAD_DB_H]: Include <thread_db.h>.

gdb/config/i386/linux.mh

@@ -5,7 +5,7 @@ XDEPFILES=
 
 NAT_FILE= nm-linux.h
 NATDEPFILES= infptrace.o solib.o inftarg.o fork-child.o corelow.o \
-	core-aout.o i386v-nat.o i386-linux-nat.o linux-thread.o lin-thread.o \
+	core-aout.o i386v-nat.o i386-linux-nat.o i387-nat.o \
-	i387-nat.o
+	proc-service.o thread-db.o lin-lwp.o
 
 LOADLIBES = -ldl -rdynamic

gdb/config/i386/nm-linux.h

@@ -1,5 +1,5 @@
-/* Native support for GNU/Linux, for GDB, the GNU debugger.
+/* Native support for Linux/x86.
-   Copyright (C) 1986, 1987, 1989, 1992, 1996, 1998, 2000
+   Copyright 1986, 1987, 1989, 1992, 1996, 1998, 2000
    Free Software Foundation, Inc.
 
    This file is part of GDB.
@@ -79,4 +79,18 @@ extern CORE_ADDR i386_stopped_by_watchpoint (int);
 extern int i386_insert_watchpoint (int pid, CORE_ADDR addr, int len, int rw);
 extern int i386_remove_watchpoint (int pid, CORE_ADDR addr, int len);
 
-#endif /* #ifndef NM_LINUX_H */
+/* FIXME: kettenis/2000-09-03: This should be moved to ../nm-linux.h
+   once we have converted all Linux targets to use the new threads
+   stuff (without the #undef of course).  */
+
+extern int lin_lwp_prepare_to_proceed (void);
+#undef PREPARE_TO_PROCEED
+#define PREPARE_TO_PROCEED(select_it) lin_lwp_prepare_to_proceed ()
+
+extern void lin_lwp_attach_lwp (int pid, int verbose);
+#define ATTACH_LWP(pid, verbose) lin_lwp_attach_lwp ((pid), (verbose))
+
+extern void lin_thread_get_thread_signals (sigset_t *mask);
+#define GET_THREAD_SIGNALS(mask) lin_thread_get_thread_signals (mask)
+
+#endif /* nm_linux.h */

gdb/proc-service.c

@@ -0,0 +1,333 @@
+/* <proc_service.h> implementation.
+   Copyright 1999, 2000 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 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.  */
+
+#include "defs.h"
+
+#include "gdb_proc_service.h"
+#include <sys/procfs.h>
+
+#include "inferior.h"
+#include "symtab.h"
+#include "target.h"
+
+/* Prototypes for supply_gregset etc.  */
+#include "gregset.h"
+
+
+/* Fix-up some broken systems.  */
+
+/* The prototypes in <proc_service.h> are slightly different on older
+   systems.  Compensate for the discrepancies.  */
+
+#ifdef PROC_SERVICE_IS_OLD
+typedef const struct ps_prochandle *gdb_ps_prochandle_t;
+typedef char *gdb_ps_read_buf_t;
+typedef char *gdb_ps_write_buf_t;
+typedef int gdb_ps_size_t;
+#else
+typedef struct ps_prochandle *gdb_ps_prochandle_t;
+typedef void *gdb_ps_read_buf_t;
+typedef const void *gdb_ps_write_buf_t;
+typedef size_t gdb_ps_size_t;
+#endif
+
+
+/* Building process ids.  */
+
+#ifndef MERGEPID
+#define MERGEPID(PID, TID)	(((PID) & 0xffff) | ((TID) << 16))
+#endif
+
+#define BUILD_LWP(tid, pid)	MERGEPID (pid, tid)
+
+
+/* Helper functions.  */
+
+static void
+restore_inferior_pid (void *arg)
+{
+  int *saved_pid_ptr = arg;
+  inferior_pid = *saved_pid_ptr;
+  free (arg);
+}
+
+static struct cleanup *
+save_inferior_pid (void)
+{
+  int *saved_pid_ptr;
+
+  saved_pid_ptr = xmalloc (sizeof (int));
+  *saved_pid_ptr = inferior_pid;
+  return make_cleanup (restore_inferior_pid, saved_pid_ptr);
+}
+
+/* Transfer LEN bytes of memory between BUF and address ADDR in the
+   process specified by PH.  If WRITE, transfer them to the process,
+   else transfer them from the process.  Returns PS_OK for success,
+   PS_ERR on failure.
+
+   This is a helper function for ps_pdread, ps_pdwrite, ps_ptread and
+   ps_ptwrite.  */
+
+static ps_err_e
+ps_xfer_memory (const struct ps_prochandle *ph, paddr_t addr,
+		char *buf, size_t len, int write)
+{
+  struct cleanup *old_chain = save_inferior_pid ();
+  int ret;
+
+  inferior_pid = ph->pid;
+
+  if (write)
+    ret = target_write_memory (addr, buf, len);
+  else
+    ret = target_read_memory (addr, buf, len);
+
+  do_cleanups (old_chain);
+
+  return (ret == 0 ? PS_OK : PS_ERR);
+}
+
+
+/* Stop the target process PH.  */
+
+ps_err_e
+ps_pstop (gdb_ps_prochandle_t ph)
+{
+  /* The process is always stopped when under control of GDB.  */
+  return PS_OK;
+}
+
+/* Resume the target process PH.  */
+
+ps_err_e
+ps_pcontinue (gdb_ps_prochandle_t ph)
+{
+  /* Pretend we did successfully continue the process.  GDB will take
+     care of it later on.  */
+  return PS_OK;
+}
+
+/* Stop the lightweight process LWPID within the target process PH.  */
+
+ps_err_e
+ps_lstop (gdb_ps_prochandle_t ph, lwpid_t lwpid)
+{
+  /* All lightweight processes are stopped when under control of GDB.  */
+  return PS_OK;
+}
+
+/* Resume the lightweight process (LWP) LWPID within the target
+   process PH.  */
+
+ps_err_e
+ps_lcontinue (gdb_ps_prochandle_t ph, lwpid_t lwpid)
+{
+  /* Pretend we did successfully continue LWPID.  GDB will take care
+     of it later on.  */
+  return PS_OK;
+}
+
+/* Get the size of the architecture-dependent extra state registers
+   for LWP LWPID within the target process PH and return it in
+   *XREGSIZE.  */
+
+ps_err_e
+ps_lgetxregsize (gdb_ps_prochandle_t ph, lwpid_t lwpid, int *xregsize)
+{
+  /* FIXME: Not supported yet.  */
+  return PS_OK;
+}
+
+/* Get the extra state registers of LWP LWPID within the target
+   process PH and store them in XREGSET.  */
+
+ps_err_e
+ps_lgetxregs (gdb_ps_prochandle_t ph, lwpid_t lwpid, caddr_t xregset)
+{
+  /* FIXME: Not supported yet.  */
+  return PS_OK;
+}
+
+/* Set the extra state registers of LWP LWPID within the target
+   process PH from XREGSET.  */
+
+ps_err_e
+ps_lsetxregs (gdb_ps_prochandle_t ph, lwpid_t lwpid, caddr_t xregset)
+{
+  /* FIXME: Not supported yet.  */
+  return PS_OK;
+}
+
+/* Log (additional) diognostic information.  */
+
+void
+ps_plog (const char *fmt, ...)
+{
+  va_list args;
+
+  va_start (args, fmt);
+  vfprintf_filtered (gdb_stderr, fmt, args);
+}
+
+/* Search for the symbol named NAME within the object named OBJ within
+   the target process PH.  If the symbol is found the address of the
+   symbol is stored in SYM_ADDR.  */
+
+ps_err_e
+ps_pglobal_lookup (gdb_ps_prochandle_t ph, const char *obj,
+		   const char *name, paddr_t *sym_addr)
+{
+  struct minimal_symbol *ms;
+
+  /* FIXME: kettenis/2000-09-03: What should we do with OBJ?  */
+  ms = lookup_minimal_symbol (name, NULL, NULL);
+  if (ms == NULL)
+    return PS_NOSYM;
+
+  *sym_addr = SYMBOL_VALUE_ADDRESS (ms);
+  return PS_OK;
+}
+
+/* Read SIZE bytes from the target process PH at address ADDR and copy
+   them into BUF.  */
+
+ps_err_e
+ps_pdread (gdb_ps_prochandle_t ph, paddr_t addr,
+	   gdb_ps_read_buf_t buf, gdb_ps_size_t size)
+{
+  return ps_xfer_memory (ph, addr, buf, size, 0);
+}
+
+/* Write SIZE bytes from BUF into the target process PH at address ADDR.  */
+
+ps_err_e
+ps_pdwrite (gdb_ps_prochandle_t ph, paddr_t addr,
+	    gdb_ps_write_buf_t buf, gdb_ps_size_t size)
+{
+  return ps_xfer_memory (ph, addr, (char *) buf, size, 1);
+}
+
+/* Read SIZE bytes from the target process PH at address ADDR and copy
+   them into BUF.  */
+
+ps_err_e
+ps_ptread (gdb_ps_prochandle_t ph, paddr_t addr,
+	   gdb_ps_read_buf_t buf, gdb_ps_size_t size)
+{
+  return ps_xfer_memory (ph, addr, buf, size, 0);
+}
+
+/* Write SIZE bytes from BUF into the target process PH at address ADDR.  */
+
+ps_err_e
+ps_ptwrite (gdb_ps_prochandle_t ph, paddr_t addr,
+	    gdb_ps_write_buf_t buf, gdb_ps_size_t size)
+{
+  return ps_xfer_memory (ph, addr, (char *) buf, size, 1);
+}
+
+/* Get the general registers of LWP LWPID within the target process PH
+   and store them in GREGSET.  */
+
+ps_err_e
+ps_lgetregs (gdb_ps_prochandle_t ph, lwpid_t lwpid, prgregset_t gregset)
+{
+  struct cleanup *old_chain = save_inferior_pid ();
+
+  inferior_pid = BUILD_LWP (lwpid, ph->pid);
+
+  target_fetch_registers (-1);
+  fill_gregset ((gdb_gregset_t *) gregset, -1);
+
+  do_cleanups (old_chain);
+  return PS_OK;
+}
+
+/* Set the general registers of LWP LWPID within the target process PH
+   from GREGSET.  */
+
+ps_err_e
+ps_lsetregs (gdb_ps_prochandle_t ph, lwpid_t lwpid, const prgregset_t gregset)
+{
+  struct cleanup *old_chain = save_inferior_pid ();
+
+  inferior_pid = BUILD_LWP (lwpid, ph->pid);
+
+  /* FIXME: We should really make supply_gregset const-correct.  */
+  supply_gregset ((gdb_gregset_t *) gregset);
+  target_store_registers (-1);
+
+  do_cleanups (old_chain);
+  return PS_OK;
+}
+
+/* Get the floating-point registers of LWP LWPID within the target
+   process PH and store them in FPREGSET.  */
+
+ps_err_e
+ps_lgetfpregs (gdb_ps_prochandle_t ph, lwpid_t lwpid,
+	       gdb_prfpregset_t *fpregset)
+{
+  struct cleanup *old_chain = save_inferior_pid ();
+
+  inferior_pid = BUILD_LWP (lwpid, ph->pid);
+
+  target_fetch_registers (-1);
+  fill_fpregset ((gdb_fpregset_t *) fpregset, -1);
+
+  do_cleanups (old_chain);
+  return PS_OK;
+}
+
+/* Set the floating-point registers of LWP LWPID within the target
+   process PH from FPREGSET.  */
+
+ps_err_e
+ps_lsetfpregs (gdb_ps_prochandle_t ph, lwpid_t lwpid,
+	       const gdb_prfpregset_t *fpregset)
+{
+  struct cleanup *old_chain = save_inferior_pid ();
+
+  inferior_pid = BUILD_LWP (lwpid, ph->pid);
+
+  /* FIXME: We should really make supply_fpregset const-correct.  */
+  supply_fpregset ((gdb_fpregset_t *) fpregset);
+  target_store_registers (-1);
+
+  do_cleanups (old_chain);
+  return PS_OK;
+}
+
+/* Return overall process id of the target PH.
+   Special for Linux -- not used on Solaris.  */
+
+pid_t
+ps_getpid (gdb_ps_prochandle_t ph)
+{
+  return ph->pid;
+}
+
+void
+_initialize_proc_service (void)
+{
+  /* This function solely exists to make sure this module is linked
+     into the final binary.  */
+}

gdb/thread-db.c

@@ -0,0 +1,992 @@
+/* libthread_db assisted debugging support, generic parts.
+   Copyright 1999, 2000 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 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.  */
+
+#include "defs.h"
+
+#include "gdb_assert.h"
+#include <dlfcn.h>
+#include "gdb_proc_service.h"
+#include "gdb_thread_db.h"
+
+#include "gdbthread.h"
+#include "inferior.h"
+#include "target.h"
+
+#ifndef LIBTHREAD_DB_SO
+#define LIBTHREAD_DB_SO "libthread_db.so.1"
+#endif
+
+/* If we're running on Linux, we must explicitly attach to any new threads.  */
+
+/* FIXME: There is certainly some room for improvements:
+   - Cache LWP ids.
+   - Bypass libthread_db when fetching or storing registers for
+   threads bound to a LWP.  */
+
+/* This module's target vector.  */
+static struct target_ops thread_db_ops;
+
+/* The target vector that we call for things this module can't handle.  */
+static struct target_ops *target_beneath;
+
+/* Pointer to the next function on the objfile event chain.  */
+static void (*target_new_objfile_chain) (struct objfile *objfile);
+
+/* Non-zero if we're using this module's target vector.  */
+static int using_thread_db;
+
+/* Non-zero if we have determined the signals used by the threads
+   library.  */
+static int thread_signals;
+static sigset_t thread_stop_set;
+static sigset_t thread_print_set;
+
+/* Structure that identifies the child process for the
+   <proc_service.h> interface.  */
+static struct ps_prochandle proc_handle;
+
+/* Connection to the libthread_db library.  */
+static td_thragent_t *thread_agent;
+
+/* Pointers to the libthread_db functions.  */
+
+static td_err_e (*td_init_p) (void);
+
+static td_err_e (*td_ta_new_p) (struct ps_prochandle *ps, td_thragent_t **ta);
+static td_err_e (*td_ta_map_id2thr_p) (const td_thragent_t *ta, thread_t pt,
+				       td_thrhandle_t *__th);
+static td_err_e (*td_ta_map_lwp2thr_p) (const td_thragent_t *ta, lwpid_t lwpid,
+					td_thrhandle_t *th);
+static td_err_e (*td_ta_thr_iter_p) (const td_thragent_t *ta,
+				     td_thr_iter_f *callback,
+				     void *cbdata_p, td_thr_state_e state,
+				     int ti_pri, sigset_t *ti_sigmask_p,
+				     unsigned int ti_user_flags);
+static td_err_e (*td_ta_event_addr_p) (const td_thragent_t *ta,
+				       td_event_e event, td_notify_t *ptr);
+static td_err_e (*td_ta_set_event_p) (const td_thragent_t *ta,
+				      td_thr_events_t *event);
+static td_err_e (*td_ta_event_getmsg_p) (const td_thragent_t *ta,
+					 td_event_msg_t *msg);
+
+static td_err_e (*td_thr_validate_p) (const td_thrhandle_t *th);
+static td_err_e (*td_thr_get_info_p) (const td_thrhandle_t *th,
+				      td_thrinfo_t *infop);
+static td_err_e (*td_thr_getfpregs_p) (const td_thrhandle_t *th,
+				       gdb_prfpregset_t *regset);
+static td_err_e (*td_thr_getgregs_p) (const td_thrhandle_t *th,
+				      prgregset_t gregs);
+static td_err_e (*td_thr_setfpregs_p) (const td_thrhandle_t *th,
+				       const gdb_prfpregset_t *fpregs);
+static td_err_e (*td_thr_setgregs_p) (const td_thrhandle_t *th,
+				      prgregset_t gregs);
+static td_err_e (*td_thr_event_enable_p) (const td_thrhandle_t *th, int event);
+
+/* Location of the thread creation event breakpoint.  The code at this
+   location in the child process will be called by the pthread library
+   whenever a new thread is created.  By setting a special breakpoint
+   at this location, GDB can detect when a new thread is created.  We
+   obtain this location via the td_ta_event_addr call.  */
+static CORE_ADDR td_create_bp_addr;
+
+/* Location of the thread death event breakpoint.  */
+static CORE_ADDR td_death_bp_addr;
+
+/* Prototypes for local functions.  */
+static int find_new_threads_callback (const td_thrhandle_t *th_p, void *data);
+
+
+/* Building process ids.  */
+
+#ifndef TIDGET
+#define TIDGET(PID)		(((PID) & 0x7fffffff) >> 16)
+#define PIDGET(PID)		(((PID) & 0xffff))
+#define MERGEPID(PID, TID)	(((PID) & 0xffff) | ((TID) << 16))
+#endif
+
+#define THREAD_FLAG		0x80000000
+
+#define is_lwp(pid)		(((pid) & THREAD_FLAG) == 0 && TIDGET (pid))
+#define is_thread(pid)		((pid) & THREAD_FLAG)
+
+#define GET_PID(pid)		PIDGET (pid)
+#define GET_LWP(pid)		TIDGET (pid)
+#define GET_THREAD(pid)		TIDGET (pid)
+
+#define BUILD_LWP(tid, pid)	MERGEPID (pid, tid)
+#define BUILD_THREAD(tid, pid)	(MERGEPID (pid, tid) | THREAD_FLAG)
+
+
+struct private_thread_info
+{
+  /* Cached LWP id.  Must come first, see lin-lwp.c.  */
+  lwpid_t lwpid;
+};
+
+
+/* Helper functions.  */
+
+static void
+restore_inferior_pid (void *arg)
+{
+  int *saved_pid_ptr = arg;
+  inferior_pid = *saved_pid_ptr;
+  free (arg);
+}
+
+static struct cleanup *
+save_inferior_pid (void)
+{
+  int *saved_pid_ptr;
+
+  saved_pid_ptr = xmalloc (sizeof (int));
+  *saved_pid_ptr = inferior_pid;
+  return make_cleanup (restore_inferior_pid, saved_pid_ptr);
+}
+
+
+static char *
+thread_db_err_str (td_err_e err)
+{
+  static char buf[64];
+
+  switch (err)
+    {
+    case TD_OK:
+      return "generic 'call succeeded'";
+    case TD_ERR:
+      return "generic error";
+    case TD_NOTHR:
+      return "no thread to satisfy query";
+    case TD_NOSV:
+      return "no sync handle to satisfy query";
+    case TD_NOLWP:
+      return "no LWP to satisfy query";
+    case TD_BADPH:
+      return "invalid process handle";
+    case TD_BADTH:
+      return "invalid thread handle";
+    case TD_BADSH:
+      return "invalid synchronization handle";
+    case TD_BADTA:
+      return "invalid thread agent";
+    case TD_BADKEY:
+      return "invalid key";
+    case TD_NOMSG:
+      return "no event message for getmsg";
+    case TD_NOFPREGS:
+      return "FPU register set not available";
+    case TD_NOLIBTHREAD:
+      return "application not linked with libthread";
+    case TD_NOEVENT:
+      return "requested event is not supported";
+    case TD_NOCAPAB:
+      return "capability not available";
+    case TD_DBERR:
+      return "debugger service failed";
+    case TD_NOAPLIC:
+      return "operation not applicable to";
+    case TD_NOTSD:
+      return "no thread-specific data for this thread";
+    case TD_MALLOC:
+      return "malloc failed";
+    case TD_PARTIALREG:
+      return "only part of register set was written/read";
+    case TD_NOXREGS:
+      return "X register set not available for this thread";
+    default:
+      snprintf (buf, sizeof (buf), "unknown thread_db error '%d'", err);
+      return buf;
+    }
+}
+
+static char *
+thread_db_state_str (td_thr_state_e state)
+{
+  static char buf[64];
+
+  switch (state)
+    {
+    case TD_THR_STOPPED:
+      return "stopped by debugger";
+    case TD_THR_RUN:
+      return "runnable";
+    case TD_THR_ACTIVE:
+      return "active";
+    case TD_THR_ZOMBIE:
+      return "zombie";
+    case TD_THR_SLEEP:
+      return "sleeping";
+    case TD_THR_STOPPED_ASLEEP:
+      return "stopped by debugger AND blocked";
+    default:
+      snprintf (buf, sizeof (buf), "unknown thread_db state %d", state);
+      return buf;
+    }
+}
+
+
+/* Convert between user-level thread ids and LWP ids.  */
+
+static int
+thread_from_lwp (int pid)
+{
+  td_thrinfo_t ti;
+  td_thrhandle_t th;
+  td_err_e err;
+
+  if (GET_LWP (pid) == 0)
+    pid = BUILD_LWP (pid, pid);
+
+  gdb_assert (is_lwp (pid));
+
+  err = td_ta_map_lwp2thr_p (thread_agent, GET_LWP (pid), &th);
+  if (err != TD_OK)
+    error ("Cannot find user-level thread for LWP %d: %s",
+	   GET_LWP (pid), thread_db_err_str (err));
+
+  err = td_thr_get_info_p (&th, &ti);
+  if (err != TD_OK)
+    error ("Cannot get thread info: %s", thread_db_err_str (err));
+
+  return BUILD_THREAD (ti.ti_tid, GET_PID (pid));
+}
+
+static int
+lwp_from_thread (int pid)
+{
+  td_thrinfo_t ti;
+  td_thrhandle_t th;
+  td_err_e err;
+
+  if (! is_thread (pid))
+    return pid;
+
+  err = td_ta_map_id2thr_p (thread_agent, GET_THREAD (pid), &th);
+  if (err != TD_OK)
+    error ("Cannot find thread %ld: %s",
+	   (long) GET_THREAD (pid), thread_db_err_str (err));
+
+  err = td_thr_get_info_p (&th, &ti);
+  if (err != TD_OK)
+    error ("Cannot get thread info: %s", thread_db_err_str (err));
+
+  return BUILD_LWP (ti.ti_lid, GET_PID (pid));
+}
+
+
+void
+thread_db_init (struct target_ops *target)
+{
+  target_beneath = target;
+}
+
+static int
+thread_db_load (void)
+{
+  void *handle;
+  td_err_e err;
+
+  handle = dlopen (LIBTHREAD_DB_SO, RTLD_NOW);
+  if (handle == NULL)
+    return 0;
+
+  /* Initialize pointers to the dynamic library functions we will use.
+     Essential functions first.  */
+
+  td_init_p = dlsym (handle, "td_init");
+  if (td_init_p == NULL)
+    return 0;
+
+  td_ta_new_p = dlsym (handle, "td_ta_new");
+  if (td_ta_new_p == NULL)
+    return 0;
+
+  td_ta_map_id2thr_p = dlsym (handle, "td_ta_map_id2thr");
+  if (td_ta_map_id2thr_p == NULL)
+    return 0;
+
+  td_ta_map_lwp2thr_p = dlsym (handle, "td_ta_map_lwp2thr");
+  if (td_ta_map_lwp2thr_p == NULL)
+    return 0;
+
+  td_ta_thr_iter_p = dlsym (handle, "td_ta_thr_iter");
+  if (td_ta_thr_iter_p == NULL)
+    return 0;
+
+  td_thr_validate_p = dlsym (handle, "td_thr_validate");
+  if (td_thr_validate_p == NULL)
+    return 0;
+
+  td_thr_get_info_p = dlsym (handle, "td_thr_get_info");
+  if (td_thr_get_info_p == NULL)
+    return 0;
+
+  td_thr_getfpregs_p = dlsym (handle, "td_thr_getfpregs");
+  if (td_thr_getfpregs_p == NULL)
+    return 0;
+
+  td_thr_getgregs_p = dlsym (handle, "td_thr_getgregs");
+  if (td_thr_getgregs_p == NULL)
+    return 0;
+
+  td_thr_setfpregs_p = dlsym (handle, "td_thr_setfpregs");
+  if (td_thr_setfpregs_p == NULL)
+    return 0;
+
+  td_thr_setgregs_p = dlsym (handle, "td_thr_setgregs");
+  if (td_thr_setgregs_p == NULL)
+    return 0;
+
+  /* Initialize the library.  */
+  err = td_init_p ();
+  if (err != TD_OK)
+    {
+      warning ("Cannot initialize libthread_db: %s", thread_db_err_str (err));
+      return 0;
+    }
+
+  /* These are not essential.  */
+  td_ta_event_addr_p = dlsym (handle, "td_ta_event_addr");
+  td_ta_set_event_p = dlsym (handle, "td_ta_set_event");
+  td_ta_event_getmsg_p = dlsym (handle, "td_ta_event_getmsg");
+  td_thr_event_enable_p = dlsym (handle, "td_thr_event_enable");
+
+  return 1;
+}
+
+static void
+enable_thread_event_reporting (void)
+{
+  td_thr_events_t events;
+  td_notify_t notify;
+  td_err_e err;
+
+  /* We cannot use the thread event reporting facility if these
+     functions aren't available.  */
+  if (td_ta_event_addr_p == NULL || td_ta_set_event_p == NULL
+      || td_ta_event_getmsg_p == NULL || td_thr_event_enable_p == NULL)
+    return;
+
+  /* Set the process wide mask saying which events we're interested in.  */
+  td_event_emptyset (&events);
+  td_event_addset (&events, TD_CREATE);
+#if 0
+  /* FIXME: kettenis/2000-04-23: The event reporting facility is
+     broken for TD_DEATH events in glibc 2.1.3, so don't enable it for
+     now.  */
+  td_event_addset (&events, TD_DEATH);
+#endif
+
+  err = td_ta_set_event_p (thread_agent, &events);
+  if (err != TD_OK)
+    {
+      warning ("Unable to set global thread event mask: %s",
+	       thread_db_err_str (err));
+      return;
+    }
+
+  /* Delete previous thread event breakpoints, if any.  */
+  remove_thread_event_breakpoints ();
+
+  /* Get address for thread creation breakpoint.  */
+  err = td_ta_event_addr_p (thread_agent, TD_CREATE, &notify);
+  if (err != TD_OK)
+    {
+      warning ("Unable to get location for thread creation breakpoint: %s",
+	       thread_db_err_str (err));
+      return;
+    }
+
+  /* Set up the breakpoint.  */
+  td_create_bp_addr = (CORE_ADDR) notify.u.bptaddr;
+  create_thread_event_breakpoint (td_create_bp_addr);
+
+  /* Get address for thread death breakpoint.  */
+  err = td_ta_event_addr_p (thread_agent, TD_DEATH, &notify);
+  if (err != TD_OK)
+    {
+      warning ("Unable to get location for thread creation breakpoint: %s",
+	       thread_db_err_str (err));
+      return;
+    }
+
+  /* Set up the breakpoint.  */
+  td_death_bp_addr = (CORE_ADDR) notify.u.bptaddr;
+  create_thread_event_breakpoint (td_death_bp_addr);
+}
+
+static void
+disable_thread_event_reporting (void)
+{
+  td_thr_events_t events;
+
+  /* Set the process wide mask saying we aren't interested in any
+     events anymore.  */
+  td_event_emptyset (&events);
+  td_ta_set_event_p (thread_agent, &events);
+
+  /* Delete thread event breakpoints, if any.  */
+  remove_thread_event_breakpoints ();
+  td_create_bp_addr = 0;
+  td_death_bp_addr = 0;
+}
+
+static void
+check_thread_signals (void)
+{
+#ifdef GET_THREAD_SIGNALS
+  if (! thread_signals)
+    {
+      sigset_t mask;
+      int i;
+
+      GET_THREAD_SIGNALS (&mask);
+      sigemptyset (&thread_stop_set);
+      sigemptyset (&thread_print_set);
+
+      for (i = 0; i < NSIG; i++)
+	{
+	  if (sigismember (&mask, i))
+	    {
+	      if (signal_stop_update (target_signal_from_host (i), 0))
+		sigaddset (&thread_stop_set, i);
+	      if (signal_print_update (target_signal_from_host (i), 0))
+		sigaddset (&thread_print_set, i);
+	      thread_signals = 1;
+	    }
+	}
+    }
+#endif
+}
+
+static void
+disable_thread_signals (void)
+{
+#ifdef GET_THREAD_SIGNALS
+  if (thread_signals)
+    {
+      int i;
+
+      for (i = 0; i < NSIG; i++)
+	{
+	  if (sigismember (&thread_stop_set, i))
+	    signal_stop_update (target_signal_from_host (i), 1);
+	  if (sigismember (&thread_print_set, i))
+	    signal_print_update (target_signal_from_host (i), 1);
+	}
+
+      thread_signals = 0;
+    }
+#endif
+}
+
+static void
+thread_db_push_target (void)
+{
+  using_thread_db = 1;
+
+  /* Push this target vector.  */
+  push_target (&thread_db_ops);
+
+  enable_thread_event_reporting ();
+}
+
+static void
+thread_db_unpush_target (void)
+{
+  /* Unpush this target vector.  */
+  unpush_target (&thread_db_ops);
+
+  using_thread_db = 0;
+}
+
+static void
+thread_db_new_objfile (struct objfile *objfile)
+{
+  td_err_e err;
+
+  if (using_thread_db)
+    /* Nothing to do.  The thread library was already detected and the
+       target vector was already activated.  */
+    goto quit;
+
+  if (objfile == NULL)
+    /* Un-interesting object file.  */
+    goto quit;
+
+  /* Initialize the structure that identifies the child process.  */
+  proc_handle.pid = GET_PID (inferior_pid);
+
+  /* Now attempt to open a connection to the thread library running in
+     the child process.  */
+  err = td_ta_new_p (&proc_handle, &thread_agent);
+  switch (err)
+    {
+    case TD_NOLIBTHREAD:
+      /* No thread library found in the child process, probably
+         because the child process isn't running yet.  */
+      break;
+
+    case TD_OK:
+      /* The thread library was detected in the child; we go live now!  */
+      thread_db_push_target ();
+
+      /* Find all user-space threads.  */
+      err = td_ta_thr_iter_p (thread_agent, find_new_threads_callback,
+			      &inferior_pid, TD_THR_ANY_STATE,
+			      TD_THR_LOWEST_PRIORITY, TD_SIGNO_MASK,
+			      TD_THR_ANY_USER_FLAGS);
+      if (err != TD_OK)
+	error ("Finding new threads failed: %s", thread_db_err_str (err));
+      break;
+
+    default:
+      warning ("Cannot initialize thread debugging library: %s",
+	       thread_db_err_str (err));
+      break;
+    }
+
+ quit:
+  if (target_new_objfile_chain)
+    target_new_objfile_chain (objfile);
+}
+
+static void
+attach_thread (int pid, const td_thrhandle_t *th_p,
+	       const td_thrinfo_t *ti_p, int verbose)
+{
+  struct thread_info *tp;
+  td_err_e err;
+
+  check_thread_signals ();
+
+  if (verbose)
+    printf_unfiltered ("[New %s]\n", target_pid_to_str (pid));
+
+  /* Add the thread to GDB's thread list.  */
+  tp = add_thread (pid);
+  tp->private = xmalloc (sizeof (struct private_thread_info));
+  tp->private->lwpid = ti_p->ti_lid;
+
+  /* Under Linux, we have to attach to each and every thread.  */
+#ifdef ATTACH_LWP
+  if (ti_p->ti_lid != GET_PID (pid))
+    ATTACH_LWP (BUILD_LWP (ti_p->ti_lid, GET_PID (pid)), 0);
+#endif
+
+  /* Enable thread event reporting for this thread.  */
+  err = td_thr_event_enable_p (th_p, 1);
+  if (err != TD_OK)
+    error ("Cannot enable thread event reporting for %s: %s",
+	   target_pid_to_str (pid), thread_db_err_str (err));
+}
+
+static void
+detach_thread (int pid, int verbose)
+{
+  if (verbose)
+    printf_unfiltered ("[%s exited]\n", target_pid_to_str (pid));
+}
+
+static void
+thread_db_detach (char *args, int from_tty)
+{
+  disable_thread_event_reporting ();
+  thread_db_unpush_target ();
+
+  target_beneath->to_detach (args, from_tty);
+}
+
+static void
+thread_db_resume (int pid, int step, enum target_signal signo)
+{
+  struct cleanup *old_chain = save_inferior_pid ();
+
+  if (pid == -1)
+    inferior_pid = lwp_from_thread (inferior_pid);
+  else if (is_thread (pid))
+    pid = lwp_from_thread (pid);
+
+  target_beneath->to_resume (pid, step, signo);
+
+  do_cleanups (old_chain);
+}
+
+/* Check if PID is currently stopped at the location of a thread event
+   breakpoint location.  If it is, read the event message and act upon
+   the event.  */
+
+static void
+check_event (int pid)
+{
+  td_event_msg_t msg;
+  td_thrinfo_t ti;
+  td_err_e err;
+  CORE_ADDR stop_pc;
+
+  /* Bail out early if we're not at a thread event breakpoint.  */
+  stop_pc = read_pc_pid (pid) - DECR_PC_AFTER_BREAK;
+  if (stop_pc != td_create_bp_addr && stop_pc != td_death_bp_addr)
+    return;
+
+  err = td_ta_event_getmsg_p (thread_agent, &msg);
+  if (err != TD_OK)
+    {
+      if (err == TD_NOMSG)
+	return;
+
+      error ("Cannot get thread event message: %s", thread_db_err_str (err));
+    }
+
+  err = td_thr_get_info_p (msg.th_p, &ti);
+  if (err != TD_OK)
+    error ("Cannot get thread info: %s", thread_db_err_str (err));
+
+  pid = BUILD_THREAD (ti.ti_tid, GET_PID (pid));
+
+  switch (msg.event)
+    {
+    case TD_CREATE:
+#if 0
+      /* FIXME: kettenis/2000-08-26: Since we use td_ta_event_getmsg,
+         there is no guarantee that the breakpoint will match the
+         event.  Should we use td_thr_event_getmsg instead?  */
+
+      if (stop_pc != td_create_bp_addr)
+	error ("Thread creation event doesn't match breakpoint.");
+#endif
+
+      if (in_thread_list (pid))
+	error ("Spurious thread creation event.");
+
+      attach_thread (pid, msg.th_p, &ti, 1);
+      return;
+
+    case TD_DEATH:
+#if 0
+      /* FIXME: See TD_CREATE.  */
+
+      if (stop_pc != td_death_bp_addr)
+	error ("Thread death event doesn't match breakpoint.");
+#endif
+
+      if (! in_thread_list (pid))
+	error ("Spurious thread death event.");
+
+      detach_thread (pid, 1);
+      return;
+
+    default:
+      error ("Spurious thread event.");
+    }
+}
+
+static int
+thread_db_wait (int pid, struct target_waitstatus *ourstatus)
+{
+  extern int trap_pid;
+
+  if (pid != -1 && is_thread (pid))
+    pid = lwp_from_thread (pid);
+
+  pid = target_beneath->to_wait (pid, ourstatus);
+
+  if (ourstatus->kind == TARGET_WAITKIND_EXITED)
+    return -1;
+
+  if (ourstatus->kind == TARGET_WAITKIND_STOPPED
+      && ourstatus->value.sig == TARGET_SIGNAL_TRAP)
+    /* Check for a thread event.  */
+    check_event (pid);
+
+  if (trap_pid)
+    trap_pid = thread_from_lwp (trap_pid);
+
+  return thread_from_lwp (pid);
+}
+
+static int
+thread_db_xfer_memory (CORE_ADDR memaddr, char *myaddr, int len, int write,
+		       struct target_ops *target)
+{
+  struct cleanup *old_chain = save_inferior_pid ();
+  int xfer;
+
+  if (is_thread (inferior_pid))
+    {
+      /* FIXME: This seems to be necessary to make sure breakpoints
+         are removed.  */
+      if (! target_thread_alive (inferior_pid))
+	inferior_pid = GET_PID (inferior_pid);
+      else
+	inferior_pid = lwp_from_thread (inferior_pid);
+    }
+
+  xfer = target_beneath->to_xfer_memory (memaddr, myaddr, len, write, target);
+
+  do_cleanups (old_chain);
+  return xfer;
+}
+
+static void
+thread_db_fetch_registers (int regno)
+{
+  td_thrhandle_t th;
+  prgregset_t gregset;
+  gdb_prfpregset_t fpregset;
+  td_err_e err;
+
+  if (! is_thread (inferior_pid))
+    {
+      /* Pass the request to the target beneath us.  */
+      target_beneath->to_fetch_registers (regno);
+      return;
+    }
+
+  err = td_ta_map_id2thr_p (thread_agent, GET_THREAD (inferior_pid), &th);
+  if (err != TD_OK)
+    error ("Cannot find thread %ld: %s",
+	   (long) GET_THREAD (inferior_pid), thread_db_err_str (err));
+
+  err = td_thr_getgregs_p (&th, gregset);
+  if (err != TD_OK)
+    error ("Cannot fetch general-purpose registers for thread %ld: %s",
+	   (long) GET_THREAD (inferior_pid), thread_db_err_str (err));
+
+  err = td_thr_getfpregs_p (&th, &fpregset);
+  if (err != TD_OK)
+    error ("Cannot get floating-point registers for thread %ld: %s",
+	   (long) GET_THREAD (inferior_pid), thread_db_err_str (err));
+
+  /* Note that we must call supply_gregset after calling the thread_db
+     routines because the thread_db routines call ps_lgetgregs and
+     friends which clobber GDB's register cache.  */
+  supply_gregset ((gdb_gregset_t *) gregset);
+  supply_fpregset (&fpregset);
+}
+
+static void
+thread_db_store_registers (int regno)
+{
+  td_thrhandle_t th;
+  prgregset_t gregset;
+  gdb_prfpregset_t fpregset;
+  td_err_e err;
+
+  if (! is_thread (inferior_pid))
+    {
+      /* Pass the request to the target beneath us.  */
+      target_beneath->to_store_registers (regno);
+      return;
+    }
+
+  err = td_ta_map_id2thr_p (thread_agent, GET_THREAD (inferior_pid), &th);
+  if (err != TD_OK)
+    error ("Cannot find thread %ld: %s",
+	   (long) GET_THREAD (inferior_pid), thread_db_err_str (err));
+
+  if (regno != -1)
+    {
+      char raw[MAX_REGISTER_RAW_SIZE];
+
+      read_register_gen (regno, raw);
+      thread_db_fetch_registers (-1);
+      supply_register (regno, raw);
+    }
+
+  fill_gregset ((gdb_gregset_t *) gregset, -1);
+  fill_fpregset (&fpregset, -1);
+
+  err = td_thr_setgregs_p (&th, gregset);
+  if (err != TD_OK)
+    error ("Cannot store general-purpose registers for thread %ld: %s",
+	   (long) GET_THREAD (inferior_pid), thread_db_err_str (err));
+  err = td_thr_setfpregs_p (&th, &fpregset);
+  if (err != TD_OK)
+    error ("Cannot store floating-point registers  for thread %ld: %s",
+	   (long) GET_THREAD (inferior_pid), thread_db_err_str (err));
+}
+
+static void
+thread_db_kill (void)
+{
+  target_beneath->to_kill ();
+}
+
+static void
+thread_db_create_inferior (char *exec_file, char *allargs, char **env)
+{
+  /* We never want to actually create the inferior!  If this is ever
+     called, it means we were on the target stack when the user said
+     "run".  But we don't want to be on the new inferior's target
+     stack until the libthread_db connection is ready to be made.  So
+     we unpush ourselves from the stack, and then invoke
+     find_default_create_inferior, which will invoke the appropriate
+     process_stratum target to do the create.  */
+
+  thread_db_unpush_target ();
+
+  find_default_create_inferior (exec_file, allargs, env);
+}
+
+static void
+thread_db_mourn_inferior (void)
+{
+  remove_thread_event_breakpoints ();
+  thread_db_unpush_target ();
+
+  target_beneath->to_mourn_inferior ();
+}
+
+static int
+thread_db_thread_alive (int pid)
+{
+  if (is_thread (pid))
+    {
+      td_thrhandle_t th;
+      td_err_e err;
+
+      err = td_ta_map_id2thr_p (thread_agent, GET_THREAD (pid), &th);
+      if (err != TD_OK)
+	return 0;
+
+      err = td_thr_validate_p (&th);
+      if (err != TD_OK)
+	return 0;
+
+      return 1;
+    }
+
+  if (target_beneath->to_thread_alive)
+    return target_beneath->to_thread_alive (pid);
+
+  return 0;
+}
+
+static int
+find_new_threads_callback (const td_thrhandle_t *th_p, void *data)
+{
+  td_thrinfo_t ti;
+  td_err_e err;
+  int pid;
+
+  err = td_thr_get_info_p (th_p, &ti);
+  if (err != TD_OK)
+    error ("Cannot get thread info: %s", thread_db_err_str (err));
+
+  pid = BUILD_THREAD (ti.ti_tid, GET_PID (inferior_pid));
+
+  if (! in_thread_list (pid))
+    attach_thread (pid, th_p, &ti, 1);
+
+  return 0;
+}
+
+static void
+thread_db_find_new_threads (void)
+{
+  td_err_e err;
+
+  /* Iterate over all user-space threads to discover new threads.  */
+  err = td_ta_thr_iter_p (thread_agent, find_new_threads_callback, NULL,
+			  TD_THR_ANY_STATE, TD_THR_LOWEST_PRIORITY,
+			  TD_SIGNO_MASK, TD_THR_ANY_USER_FLAGS);
+  if (err != TD_OK)
+    error ("Cannot find new threads: %s", thread_db_err_str (err));
+}
+
+static char *
+thread_db_pid_to_str (int pid)
+{
+  if (is_thread (pid))
+    {
+      static char buf[64];
+      td_thrhandle_t th;
+      td_thrinfo_t ti;
+      td_err_e err;
+
+      err = td_ta_map_id2thr_p (thread_agent, GET_THREAD (pid), &th);
+      if (err != TD_OK)
+	error ("Cannot find thread %ld: %s",
+	       (long) GET_THREAD (pid), thread_db_err_str (err));
+
+      err = td_thr_get_info_p (&th, &ti);
+      if (err != TD_OK)
+	error ("Cannot get thread info for thread %ld: %s",
+	       (long) GET_THREAD (pid), thread_db_err_str (err));
+
+      if (ti.ti_state == TD_THR_ACTIVE && ti.ti_lid != 0)
+	{
+	  snprintf (buf, sizeof (buf), "Thread %ld (LWP %d)",
+		    (long) ti.ti_tid, ti.ti_lid);
+	}
+      else
+	{
+	  snprintf (buf, sizeof (buf), "Thread %ld (%s)",
+		    (long) ti.ti_tid, thread_db_state_str (ti.ti_state));
+	}
+
+      return buf;
+    }
+
+  if (target_beneath->to_pid_to_str (pid))
+    return target_beneath->to_pid_to_str (pid);
+
+  return normal_pid_to_str (pid);
+}
+
+static void
+init_thread_db_ops (void)
+{
+  thread_db_ops.to_shortname = "multi-thread";
+  thread_db_ops.to_longname = "multi-threaded child process.";
+  thread_db_ops.to_doc = "Threads and pthreads support.";
+  thread_db_ops.to_detach = thread_db_detach;
+  thread_db_ops.to_resume = thread_db_resume;
+  thread_db_ops.to_wait = thread_db_wait;
+  thread_db_ops.to_fetch_registers = thread_db_fetch_registers;
+  thread_db_ops.to_store_registers = thread_db_store_registers;
+  thread_db_ops.to_xfer_memory = thread_db_xfer_memory;
+  thread_db_ops.to_kill = thread_db_kill;
+  thread_db_ops.to_create_inferior = thread_db_create_inferior;
+  thread_db_ops.to_mourn_inferior = thread_db_mourn_inferior;
+  thread_db_ops.to_thread_alive = thread_db_thread_alive;
+  thread_db_ops.to_find_new_threads = thread_db_find_new_threads;
+  thread_db_ops.to_pid_to_str = thread_db_pid_to_str;
+  thread_db_ops.to_stratum = thread_stratum;
+  thread_db_ops.to_has_thread_control = tc_schedlock;
+  thread_db_ops.to_magic = OPS_MAGIC;
+}
+
+void
+_initialize_thread_db (void)
+{
+  /* Only initialize the module if we can load libthread_db.  */
+  if (thread_db_load ())
+    {
+      init_thread_db_ops ();
+      add_target (&thread_db_ops);
+
+      /* Add ourselves to objfile event chain.  */
+      target_new_objfile_chain = target_new_objfile_hook;
+      target_new_objfile_hook = thread_db_new_objfile;
+    }
+}