import gdb-1999-12-21 snapshot

1 files changed, 2140 insertions, 0 deletions

diff --git a/gdb/lin-thread.c b/gdb/lin-thread.c
new file mode 100644
index 0000000..2f255c0
--- /dev/null
+++ b/gdb/lin-thread.c
@@ -0,0 +1,2140 @@
+/* Multi-threaded debugging support for the thread_db interface,
+   used on operating systems such as Solaris and Linux.
+   Copyright 1999 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.  */
+
+/* This module implements a thread_stratum target that sits on top of
+   a normal process_stratum target (such as procfs or ptrace).  The
+   process_stratum target must install this thread_stratum target when
+   it detects the presence of the thread_db shared library.
+
+   This module will then use the thread_db API to add thread-awareness
+   to the functionality provided by the process_stratum target (or in
+   some cases, to add user-level thread awareness on top of the 
+   kernel-level thread awareness that is already provided by the 
+   process_stratum target).
+
+   Solaris threads (for instance) are a multi-level thread implementation;
+   the kernel provides a Light Weight Process (LWP) which the procfs 
+   process_stratum module is aware of.  This module must then mediate
+   the relationship between kernel LWP threads and user (eg. posix)
+   threads.
+
+   Linux threads are likely to be different -- but the thread_db 
+   library API should make the difference largely transparent to GDB.
+
+   */
+
+/* The thread_db API provides a number of functions that give the caller
+   access to the inner workings of the child process's thread library. 
+   We will be using the following (others may be added):
+
+   td_thr_validate		Confirm valid "live" thread
+   td_thr_get_info		Get info about a thread
+   td_thr_getgregs		Get thread's general registers
+   td_thr_getfpregs		Get thread's floating point registers
+   td_thr_setgregs		Set thread's general registers
+   td_thr_setfpregs		Set thread's floating point registers
+   td_ta_map_id2thr		Get thread handle from thread id
+   td_ta_map_lwp2thr		Get thread handle from LWP id
+   td_ta_thr_iter		Iterate over all threads (with callback)
+
+   In return, the debugger has to provide certain services to the 
+   thread_db library.  Some of these aren't actually required to do
+   anything in practice.  For instance, the thread_db expects to be
+   able to stop the child process and start it again: but in our
+   context, the child process will always be stopped already when we
+   invoke the thread_db library, so the functions that we provide for
+   the library to stop and start the child process are no-ops.
+
+   Here is the list of functions which we export to the thread_db
+   library, divided into no-op functions vs. functions that actually
+   have to do something:
+
+   No-op functions:
+
+   ps_pstop			Stop the child process
+   ps_pcontinue			Continue the child process
+   ps_lstop			Stop a specific LWP (kernel thread)
+   ps_lcontinue			Continue an LWP
+   ps_lgetxregsize		Get size of LWP's xregs (sparc)
+   ps_lgetxregs			Get LWP's xregs (sparc)
+   ps_lsetxregs			Set LWP's xregs (sparc)
+
+   Functions that have to do useful work:
+
+   ps_pglobal_lookup		Get the address of a global symbol
+   ps_pdread			Read memory, data segment
+   ps_ptread			Read memory, text segment
+   ps_pdwrite			Write memory, data segment
+   ps_ptwrite			Write memory, text segment
+   ps_lgetregs			Get LWP's general registers
+   ps_lgetfpregs		Get LWP's floating point registers
+   ps_lsetregs			Set LWP's general registers
+   ps_lsetfpregs		Set LWP's floating point registers
+   ps_lgetLDT			Get LWP's Local Descriptor Table (x86)
+   
+   Thus, if we ask the thread_db library to give us the general registers
+   for user thread X, thread_db may figure out that user thread X is 
+   actually mapped onto kernel thread Y.  Thread_db does not know how
+   to obtain the registers for kernel thread Y, but GDB does, so thread_db
+   turns the request right back to us via the ps_lgetregs callback.  */
+
+#include "defs.h"
+#include "gdbthread.h"
+#include "target.h"
+#include "inferior.h"
+#include "gdbcmd.h"
+
+#ifdef HAVE_WAIT_H
+#include <wait.h>
+#else
+#ifdef HAVE_SYS_WAIT_H
+#include <sys/wait.h>
+#endif
+#endif
+
+/* "wait.h" fills in the gaps left by <wait.h> */
+#include "wait.h"
+
+#include <time.h>
+
+#if defined(USE_PROC_FS) || defined(HAVE_GREGSET_T)
+#include <sys/procfs.h>
+#endif
+
+#if defined (HAVE_PROC_SERVICE_H)
+#include <proc_service.h>	/* defines incoming API (ps_* callbacks) */
+#else
+#include "gdb_proc_service.h"
+#endif
+
+#if defined HAVE_STDINT_H	/* Pre-5.2 systems don't have this header */
+#if defined (HAVE_THREAD_DB_H)
+#include <thread_db.h>		/* defines outgoing API (td_thr_* calls) */
+#else
+#include "gdb_thread_db.h"
+#endif
+
+#include <dlfcn.h>		/* dynamic library interface */
+
+#ifndef TIDGET
+#define TIDGET(PID)		(((PID) & 0x7fffffff) >> 16)
+#define PIDGET(PID)		(((PID) & 0xffff))
+#define MERGEPID(PID, TID)	(((PID) & 0xffff) | ((TID) << 16))
+#endif
+
+/* Macros for superimposing PID and TID into inferior_pid.  */
+#define THREAD_FLAG		0x80000000
+#define is_thread(ARG)		(((ARG) & THREAD_FLAG) != 0)
+#define is_lwp(ARG)		(((ARG) & THREAD_FLAG) == 0)
+#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)
+
+/*
+ * target_beneath is a pointer to the target_ops underlying this one.
+ */
+
+static struct target_ops *target_beneath;
+
+
+/*
+ * target vector defined in this module:
+ */
+
+static struct target_ops thread_db_ops;
+
+/*
+ * Typedefs required to resolve differences between the thread_db
+ * and proc_service API defined on different versions of Solaris:
+ */
+
+#if defined(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
+
+/* 
+ * proc_service callback functions, called by thread_db.
+ */
+
+ps_err_e
+ps_pstop (gdb_ps_prochandle_t ph)		/* Process stop */
+{
+  return PS_OK;
+}
+
+ps_err_e
+ps_pcontinue (gdb_ps_prochandle_t ph)		/* Process continue */
+{
+  return PS_OK;
+}
+
+ps_err_e
+ps_lstop (gdb_ps_prochandle_t ph,		/* LWP stop */
+	  lwpid_t lwpid)
+{
+  return PS_OK;
+}
+
+ps_err_e
+ps_lcontinue (gdb_ps_prochandle_t ph,		/* LWP continue */
+	      lwpid_t lwpid)
+{
+  return PS_OK;
+}
+
+ps_err_e
+ps_lgetxregsize (gdb_ps_prochandle_t ph,	/* Get XREG size */
+		 lwpid_t lwpid,
+		 int *xregsize)
+{
+  return PS_OK;
+}
+
+ps_err_e
+ps_lgetxregs (gdb_ps_prochandle_t ph,		/* Get XREGS */
+	      lwpid_t lwpid,
+	      caddr_t xregset)
+{
+  return PS_OK;
+}
+
+ps_err_e
+ps_lsetxregs (gdb_ps_prochandle_t ph,		/* Set XREGS */
+	      lwpid_t lwpid,
+	      caddr_t xregset)
+{
+  return PS_OK;
+}
+
+void
+ps_plog (const char *fmt, ...)
+{
+  va_list args;
+
+  va_start (args, fmt);
+  vfprintf_filtered (gdb_stderr, fmt, args);
+}
+
+/* Look up a symbol in GDB's global symbol table.
+   Return the symbol's address.
+   FIXME: it would be more correct to look up the symbol in the context 
+   of the LD_OBJECT_NAME provided.  However we're probably fairly safe 
+   as long as there aren't name conflicts with other libraries.  */
+
+ps_err_e
+ps_pglobal_lookup (gdb_ps_prochandle_t ph,
+		   const char *ld_object_name,	/* the library name */
+		   const char *ld_symbol_name,	/* the symbol name */
+		   paddr_t    *ld_symbol_addr)	/* return the symbol addr */
+{
+  struct minimal_symbol *ms;
+
+  ms = lookup_minimal_symbol (ld_symbol_name, NULL, NULL);
+
+  if (!ms)
+    return PS_NOSYM;
+
+  *ld_symbol_addr = SYMBOL_VALUE_ADDRESS (ms);
+
+  return PS_OK;
+}
+
+/* Worker function for all memory reads and writes: */
+static ps_err_e rw_common (const struct ps_prochandle *ph, 
+			   paddr_t addr,
+			   char *buf, 
+			   int size, 
+			   int write_p);
+
+/* target_xfer_memory direction consts */
+enum {PS_READ = 0, PS_WRITE = 1};
+
+ps_err_e
+ps_pdread (gdb_ps_prochandle_t ph, 	/* read from data segment */
+	   paddr_t             addr,
+	   gdb_ps_read_buf_t   buf,
+	   gdb_ps_size_t       size)
+{
+  return rw_common (ph, addr, buf, size, PS_READ);
+}
+
+ps_err_e
+ps_pdwrite (gdb_ps_prochandle_t ph,	/* write to data segment */
+	    paddr_t             addr,
+	    gdb_ps_write_buf_t  buf,
+	    gdb_ps_size_t       size)
+{
+  return rw_common (ph, addr, (char *) buf, size, PS_WRITE);
+}
+
+ps_err_e
+ps_ptread (gdb_ps_prochandle_t ph,	/* read from text segment */
+	   paddr_t             addr,
+	   gdb_ps_read_buf_t   buf,
+	   gdb_ps_size_t       size)
+{
+  return rw_common (ph, addr, buf, size, PS_READ);
+}
+
+ps_err_e
+ps_ptwrite (gdb_ps_prochandle_t ph,	/* write to text segment */
+	    paddr_t             addr,
+	    gdb_ps_write_buf_t  buf,
+	    gdb_ps_size_t       size)
+{
+  return rw_common (ph, addr, (char *) buf, size, PS_WRITE);
+}
+
+static struct cleanup *save_inferior_pid    (void);
+static void            restore_inferior_pid (void *saved_pid);
+static char *thr_err_string   (td_err_e);
+static char *thr_state_string (td_thr_state_e);
+
+struct ps_prochandle {
+  int pid;
+};
+
+struct ps_prochandle main_prochandle;
+td_thragent_t *      main_threadagent;
+
+/* 
+ * Common proc_service routine for reading and writing memory.  
+ */
+
+/* FIXME: once we've munged the inferior_pid, why can't we
+   simply call target_read/write_memory and return?  */
+
+
+static ps_err_e
+rw_common (const struct ps_prochandle *ph,
+	   paddr_t addr,
+	   char   *buf,
+	   int     size,
+	   int     write_p)
+{
+  struct cleanup *old_chain = save_inferior_pid ();
+  int to_do = size;
+  int done  = 0;
+
+  inferior_pid = main_prochandle.pid;
+
+  while (to_do > 0)
+    {
+      done = current_target.to_xfer_memory (addr, buf, size, write_p, 
+					    &current_target);
+      if (done <= 0)
+	{
+	  if (write_p == PS_READ)
+	    print_sys_errmsg ("rw_common (): read", errno);
+	  else
+	    print_sys_errmsg ("rw_common (): write", errno);
+
+	  return PS_ERR;
+	}
+      to_do -= done;
+      buf   += done;
+    }
+  do_cleanups (old_chain);
+  return PS_OK;
+}
+
+/* Cleanup functions used by the register callbacks
+   (which have to manipulate the global inferior_pid).  */
+
+ps_err_e
+ps_lgetregs (gdb_ps_prochandle_t ph,		/* Get LWP general regs */
+	     lwpid_t     lwpid,
+	     prgregset_t gregset)
+{
+  struct cleanup *old_chain = save_inferior_pid ();
+
+  inferior_pid = BUILD_LWP (lwpid, main_prochandle.pid);
+  current_target.to_fetch_registers (-1);
+
+  fill_gregset (gregset, -1);
+  do_cleanups (old_chain);
+
+  return PS_OK;
+}
+
+ps_err_e
+ps_lsetregs (gdb_ps_prochandle_t ph,		/* Set LWP general regs */
+	     lwpid_t           lwpid,
+	     const prgregset_t gregset)
+{
+  struct cleanup *old_chain = save_inferior_pid ();
+
+  inferior_pid = BUILD_LWP (lwpid, main_prochandle.pid);
+  supply_gregset (gregset);
+  current_target.to_store_registers (-1);
+  do_cleanups (old_chain);
+  return PS_OK;
+}
+
+ps_err_e
+ps_lgetfpregs (gdb_ps_prochandle_t ph,		/* Get LWP float regs */
+	       lwpid_t       lwpid,
+	       prfpregset_t *fpregset)
+{
+  struct cleanup *old_chain = save_inferior_pid ();
+
+  inferior_pid = BUILD_LWP (lwpid, main_prochandle.pid);
+  current_target.to_fetch_registers (-1);
+  fill_fpregset (fpregset, -1);
+  do_cleanups (old_chain);
+  return PS_OK;
+}
+
+ps_err_e
+ps_lsetfpregs (gdb_ps_prochandle_t ph,		/* Set LWP float regs */
+	       lwpid_t             lwpid,
+	       const prfpregset_t *fpregset)
+{
+  struct cleanup *old_chain = save_inferior_pid ();
+
+  inferior_pid = BUILD_LWP (lwpid, main_prochandle.pid);
+  supply_fpregset (fpregset);
+  current_target.to_store_registers (-1);
+  do_cleanups (old_chain);
+  return PS_OK;
+}
+
+/*
+ * ps_getpid
+ *
+ * return the main pid for the child process
+ * (special for Linux -- not used on Solaris)
+ */
+
+pid_t
+ps_getpid (gdb_ps_prochandle_t ph)
+{
+  return ph->pid;
+}
+
+#ifdef TM_I386SOL2_H
+
+/* Reads the local descriptor table of a LWP.  */
+
+ps_err_e
+ps_lgetLDT (gdb_ps_prochandle_t ph, lwpid_t lwpid,
+	    struct ssd *pldt)
+{
+  /* NOTE: only used on Solaris, therefore OK to refer to procfs.c */
+  extern struct ssd *procfs_find_LDT_entry (int);
+  struct ssd *ret;
+
+  ret = procfs_find_LDT_entry (BUILD_LWP (lwpid, 
+					  PIDGET (main_prochandle.pid)));
+  if (ret)
+    {
+      memcpy (pldt, ret, sizeof (struct ssd));
+      return PS_OK;
+    }
+  else	/* LDT not found. */
+    return PS_ERR;
+}
+#endif /* TM_I386SOL2_H */
+
+/*
+ * Pointers to thread_db functions:
+ *
+ * These are a dynamic library mechanism.
+ * The dlfcn.h interface will be used to initialize these 
+ * so that they point to the appropriate functions in the
+ * thread_db dynamic library.  This is done dynamically 
+ * so that GDB can still run on systems that lack thread_db.  
+ */
+
+static td_err_e (*p_td_init)              (void);
+
+static td_err_e (*p_td_ta_new)            (const struct ps_prochandle *ph_p, 
+					   td_thragent_t **ta_pp);
+
+static td_err_e (*p_td_ta_delete)         (td_thragent_t *ta_p);
+
+static td_err_e (*p_td_ta_get_nthreads)   (const td_thragent_t *ta_p,
+					   int *nthread_p);
+
+
+static td_err_e (*p_td_ta_thr_iter)       (const td_thragent_t *ta_p,
+					   td_thr_iter_f *cb,
+					   void *cbdata_p,
+					   td_thr_state_e state,
+					   int ti_pri, 
+					   sigset_t *ti_sigmask_p,
+					   unsigned ti_user_flags);
+
+static td_err_e (*p_td_ta_event_addr)     (const td_thragent_t *ta_p,
+					   u_long event,
+					   td_notify_t *notify_p);
+
+static td_err_e (*p_td_ta_event_getmsg)   (const td_thragent_t *ta_p,
+					   td_event_msg_t *msg);
+
+static td_err_e (*p_td_ta_set_event)      (const td_thragent_t *ta_p,
+					   td_thr_events_t *events);
+
+static td_err_e (*p_td_thr_validate)      (const td_thrhandle_t *th_p);
+
+static td_err_e (*p_td_thr_event_enable)  (const td_thrhandle_t *th_p,
+					   int on_off);
+
+static td_err_e (*p_td_thr_get_info)      (const td_thrhandle_t *th_p,
+					   td_thrinfo_t *ti_p);
+
+static td_err_e (*p_td_thr_getgregs)      (const td_thrhandle_t *th_p,
+					   prgregset_t regset);
+
+static td_err_e (*p_td_thr_setgregs)      (const td_thrhandle_t *th_p,
+					   const prgregset_t regset);
+
+static td_err_e (*p_td_thr_getfpregs)     (const td_thrhandle_t *th_p,
+					   prfpregset_t *fpregset);
+
+static td_err_e (*p_td_thr_setfpregs)     (const td_thrhandle_t *th_p,
+					   const prfpregset_t *fpregset);
+
+static td_err_e (*p_td_ta_map_id2thr)     (const td_thragent_t *ta_p,
+					   thread_t tid,
+					   td_thrhandle_t *th_p);
+
+static td_err_e (*p_td_ta_map_lwp2thr)    (const td_thragent_t *ta_p,
+					   lwpid_t lwpid,
+					   td_thrhandle_t *th_p);
+
+/*
+ * API and target vector initialization function: thread_db_initialize.
+ *
+ * NOTE: this function is deliberately NOT named with the GDB convention
+ * of module initializer function names that begin with "_initialize".
+ * This module is NOT intended to be auto-initialized at GDB startup.
+ * Rather, it will only be initialized when a multi-threaded child
+ * process is detected.
+ *
+ */
+
+/* 
+ * Initializer for thread_db library interface.
+ * This function does the dynamic library stuff (dlopen, dlsym), 
+ * and then calls the thread_db library's one-time initializer 
+ * function (td_init).  If everything succeeds, this function
+ * returns true; otherwise it returns false, and this module
+ * cannot be used.
+ */
+
+static int
+init_thread_db_library ()
+{
+  void *dlhandle;
+  td_err_e ret;
+
+  /* Open a handle to the "thread_db" dynamic library.  */
+  if ((dlhandle = dlopen ("libthread_db.so.1", RTLD_NOW)) == NULL)
+    return 0;			/* fail */
+
+  /* Initialize pointers to the dynamic library functions we will use.
+   * Note that we are not calling the functions here -- we are only
+   * establishing pointers to them.
+   */
+
+  /* td_init: initialize thread_db library. */
+  if ((p_td_init = dlsym (dlhandle, "td_init")) == NULL)
+    return 0;			/* fail */
+  /* td_ta_new: register a target process with thread_db.  */
+  if ((p_td_ta_new = dlsym (dlhandle, "td_ta_new")) == NULL)
+    return 0;			/* fail */
+  /* td_ta_delete: un-register a target process with thread_db.  */
+  if ((p_td_ta_delete = dlsym (dlhandle, "td_ta_delete")) == NULL)
+    return 0;			/* fail */
+
+  /* td_ta_map_id2thr: get thread handle from thread id.  */
+  if ((p_td_ta_map_id2thr = dlsym (dlhandle, "td_ta_map_id2thr")) == NULL)
+    return 0;			/* fail */
+  /* td_ta_map_lwp2thr: get thread handle from lwp id.  */
+  if ((p_td_ta_map_lwp2thr = dlsym (dlhandle, "td_ta_map_lwp2thr")) == NULL)
+    return 0;			/* fail */
+  /* td_ta_get_nthreads: get number of threads in target process.  */
+  if ((p_td_ta_get_nthreads = dlsym (dlhandle, "td_ta_get_nthreads")) == NULL)
+    return 0;			/* fail */
+  /* td_ta_thr_iter: iterate over all thread handles.  */
+  if ((p_td_ta_thr_iter = dlsym (dlhandle, "td_ta_thr_iter")) == NULL)
+    return 0;			/* fail */
+
+  /* td_thr_validate: make sure a thread handle is real and alive.  */
+  if ((p_td_thr_validate = dlsym (dlhandle, "td_thr_validate")) == NULL)
+    return 0;			/* fail */
+  /* td_thr_get_info: get a bunch of info about a thread.  */
+  if ((p_td_thr_get_info = dlsym (dlhandle, "td_thr_get_info")) == NULL)
+    return 0;			/* fail */
+  /* td_thr_getgregs: get general registers for thread.  */
+  if ((p_td_thr_getgregs = dlsym (dlhandle, "td_thr_getgregs")) == NULL)
+    return 0;			/* fail */
+  /* td_thr_setgregs: set general registers for thread.  */
+  if ((p_td_thr_setgregs = dlsym (dlhandle, "td_thr_setgregs")) == NULL)
+    return 0;			/* fail */
+  /* td_thr_getfpregs: get floating point registers for thread.  */
+  if ((p_td_thr_getfpregs = dlsym (dlhandle, "td_thr_getfpregs")) == NULL)
+    return 0;			/* fail */
+  /* td_thr_setfpregs: set floating point registers for thread.  */
+  if ((p_td_thr_setfpregs = dlsym (dlhandle, "td_thr_setfpregs")) == NULL)
+    return 0;			/* fail */
+  
+  ret = p_td_init ();
+  if (ret != TD_OK)
+    {
+      warning ("init_thread_db: td_init: %s", thr_err_string (ret));
+      return 0;
+    }
+
+  /* Optional functions:
+     We can still debug even if the following functions are not found.  */
+
+  /* td_ta_event_addr: get the breakpoint address for specified event.  */
+  p_td_ta_event_addr = dlsym (dlhandle, "td_ta_event_addr");
+
+  /* td_ta_event_getmsg: get the next event message for the process.  */
+  p_td_ta_event_getmsg = dlsym (dlhandle, "td_ta_event_getmsg");
+
+  /* td_ta_set_event: request notification of an event.  */
+  p_td_ta_set_event = dlsym (dlhandle, "td_ta_set_event");
+
+  /* td_thr_event_enable: enable event reporting in a thread.  */
+  p_td_thr_event_enable = dlsym (dlhandle, "td_thr_event_enable");
+
+  return 1;			/* success */
+}
+
+/*
+ * Local utility functions:
+ */
+
+
+/*
+
+   LOCAL FUNCTION
+
+   save_inferior_pid - Save inferior_pid on the cleanup list
+   restore_inferior_pid - Restore inferior_pid from the cleanup list
+
+   SYNOPSIS
+
+   struct cleanup *save_inferior_pid (void);
+   void            restore_inferior_pid (void *saved_pid);
+
+   DESCRIPTION
+
+   These two functions act in unison to restore inferior_pid in
+   case of an error.
+
+   NOTES
+
+   inferior_pid is a global variable that needs to be changed by many
+   of these routines before calling functions in procfs.c.  In order
+   to guarantee that inferior_pid gets restored (in case of errors),
+   you need to call save_inferior_pid before changing it.  At the end
+   of the function, you should invoke do_cleanups to restore it.
+
+ */
+
+static struct cleanup *
+save_inferior_pid (void)
+{
+#if TARGET_PTR_BIT > TARGET_INT_BIT
+  return make_cleanup (restore_inferior_pid, (void *) ((long) inferior_pid));
+#else
+  return make_cleanup (restore_inferior_pid, (void *) inferior_pid);
+#endif
+}
+
+static void
+restore_inferior_pid (void *saved_pid)
+{
+#if TARGET_PTR_BIT > TARGET_INT_BIT
+  inferior_pid = (int) ((long) saved_pid);
+#else
+  inferior_pid = (int) saved_pid;
+#endif
+}
+
+/*
+
+   LOCAL FUNCTION
+
+   thr_err_string - Convert a thread_db error code to a string
+
+   SYNOPSIS
+
+   char * thr_err_string (errcode)
+
+   DESCRIPTION
+
+   Return a string description of the thread_db errcode.  If errcode
+   is unknown, then return an <unknown> message.
+
+ */
+
+static char *
+thr_err_string (errcode)
+     td_err_e errcode;
+{
+  static char buf[50];
+
+  switch (errcode) {
+  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:
+    sprintf (buf, "unknown thread_db error '%d'", errcode);
+    return buf;
+  }
+}
+
+/*
+
+   LOCAL FUNCTION
+
+   thr_state_string - Convert a thread_db state code to a string
+
+   SYNOPSIS
+
+   char *thr_state_string (statecode)
+
+   DESCRIPTION
+
+   Return the thread_db state string associated with statecode.  
+   If statecode is unknown, then return an <unknown> message.
+
+ */
+
+static char *
+thr_state_string (statecode)
+     td_thr_state_e statecode;
+{
+  static char buf[50];
+
+  switch (statecode) {
+  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:
+    sprintf (buf, "unknown thread_db state %d", statecode);
+    return buf;
+  }
+}
+
+/*
+ * Local thread/event list.
+ * This data structure will be used to hold a list of threads and 
+ * pending/deliverable events.
+ */
+
+typedef struct THREADINFO {
+  thread_t       tid;		/* thread ID */
+  pid_t          lid;		/* process/lwp ID */
+  td_thr_state_e state;		/* thread state (a la thread_db) */
+  td_thr_type_e  type;		/* thread type (a la thread_db) */
+  int            pending;	/* true if holding a pending event */
+  int            status;	/* wait status of any interesting event */
+} threadinfo;
+
+threadinfo * threadlist;
+int threadlist_max = 0;		/* current size of table */
+int threadlist_top = 0;		/* number of threads now in table */
+#define THREADLIST_ALLOC 100	/* chunk size by which to expand table */
+
+static threadinfo *
+insert_thread (tid, lid, state, type)
+     int            tid;
+     int            lid;
+     td_thr_state_e state;
+     td_thr_type_e  type;
+{
+  if (threadlist_top >= threadlist_max)
+    {
+      threadlist_max += THREADLIST_ALLOC;
+      threadlist      = realloc (threadlist, 
+				 threadlist_max * sizeof (threadinfo));
+      if (threadlist == NULL)
+	return NULL;
+    }
+  threadlist[threadlist_top].tid     = tid;
+  threadlist[threadlist_top].lid     = lid;
+  threadlist[threadlist_top].state   = state;
+  threadlist[threadlist_top].type    = type;
+  threadlist[threadlist_top].pending = 0;
+  threadlist[threadlist_top].status  = 0;
+
+  return &threadlist[threadlist_top++];
+}
+
+static void
+empty_threadlist ()
+{
+  threadlist_top = 0;
+}
+
+static threadinfo *
+next_pending_event ()
+{
+  int i;
+
+  for (i = 0; i < threadlist_top; i++)
+    if (threadlist[i].pending)
+      return &threadlist[i];
+
+  return NULL;
+}
+
+static void
+threadlist_iter (func, data, state, type)
+     int (*func) ();
+     void *data;
+     td_thr_state_e state;
+     td_thr_type_e  type;
+{
+  int i;
+
+  for (i = 0; i < threadlist_top; i++)
+    if ((state == TD_THR_ANY_STATE || state == threadlist[i].state) &&
+	(type  == TD_THR_ANY_TYPE  || type  == threadlist[i].type))
+      if ((*func) (&threadlist[i], data) != 0)
+	break;
+
+  return;
+}     
+
+/*
+ * Global state
+ * 
+ * Here we keep state information all collected in one place.
+ */
+
+/* This flag is set when we activate, so that we don't do it twice. 
+   Defined in linux-thread.c and used for inter-target syncronization.  */
+extern int using_thread_db;
+
+/* The process id for which we've stopped.
+ * This is only set when we actually stop all threads.
+ * Otherwise it's zero.
+ */
+static int event_pid;
+
+/*
+ * The process id for a new thread to which we've just attached.
+ * This process needs special handling at resume time.
+ */
+static int attach_pid;
+
+
+/*
+ * thread_db event handling:
+ *
+ * The mechanism for event notification via the thread_db API.
+ * These events are implemented as breakpoints.  The thread_db
+ * library gives us an address where we can set a breakpoint.
+ * When the breakpoint is hit, it represents an event of interest
+ * such as:
+ *   Thread creation
+ *   Thread death
+ *   Thread reap
+ */
+
+/* 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 thread_creation_bkpt_address;
+
+/* Location of the thread death event breakpoint.  The code at this
+   location in the child process will be called by the pthread library
+   whenever a thread is destroyed.  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 thread_death_bkpt_address;
+
+/* This function handles the global parts of enabling thread events.
+   The thread-specific enabling is handled per-thread elsewhere.  */
+
+static void
+enable_thread_event_reporting (ta)
+     td_thragent_t *ta;
+{
+  td_thr_events_t events;
+  td_notify_t     notify;
+  CORE_ADDR       addr;
+
+  if (p_td_ta_set_event     == NULL ||
+      p_td_ta_event_addr    == NULL ||
+      p_td_ta_event_getmsg  == NULL ||
+      p_td_thr_event_enable == NULL)
+    return;	/* can't do thread event reporting without these funcs */
+
+  /* set process wide mask saying which events we are interested in */
+  td_event_emptyset (&events);
+  td_event_addset (&events, TD_CREATE);
+  td_event_addset (&events, TD_DEATH);
+
+  if (p_td_ta_set_event (ta, &events) != TD_OK)
+    {
+      warning ("unable to set global thread event mask");
+      return;
+    }
+
+  /* Delete previous thread event breakpoints, if any.  */
+  remove_thread_event_breakpoints ();
+
+  /* create breakpoints -- thread creation and death */
+  /* thread creation */
+  /* get breakpoint location */
+  if (p_td_ta_event_addr (ta, TD_CREATE, &notify) != TD_OK)
+    {
+      warning ("unable to get location for thread creation breakpoint");
+      return;
+    }
+
+  /* Set up the breakpoint. */
+  create_thread_event_breakpoint (notify.u.bptaddr);
+
+  /* Save it's location. */
+  thread_creation_bkpt_address = notify.u.bptaddr;
+
+  /* thread death */
+  /* get breakpoint location */
+  if (p_td_ta_event_addr (ta, TD_DEATH, &notify) != TD_OK)
+    {
+      warning ("unable to get location for thread death breakpoint");
+      return;
+    }
+  /* Set up the breakpoint. */
+  create_thread_event_breakpoint (notify.u.bptaddr);
+
+  /* Save it's location. */
+  thread_death_bkpt_address = notify.u.bptaddr;
+}
+
+/* This function handles the global parts of disabling thread events.
+   The thread-specific enabling is handled per-thread elsewhere.  */
+
+static void
+disable_thread_event_reporting (ta)
+     td_thragent_t *ta;
+{
+  td_thr_events_t events;
+
+  /* set process wide mask saying we aren't interested in any events */
+  td_event_emptyset (&events);
+  p_td_ta_set_event (main_threadagent, &events);
+
+  /* Delete thread event breakpoints, if any.  */
+  remove_thread_event_breakpoints ();
+  thread_creation_bkpt_address = 0;
+  thread_death_bkpt_address = 0;
+}
+
+/* check_for_thread_event
+   
+   if it's a thread event we recognize (currently
+   we only recognize creation and destruction
+   events), return 1; else return 0.  */
+
+
+static int
+check_for_thread_event (struct target_waitstatus *tws, int event_pid)
+{
+  /* FIXME: to be more efficient, we should keep a static 
+     list of threads, and update it only here (with td_ta_thr_iter). */
+}
+
+static void
+thread_db_push_target (void)
+{
+  /* Called ONLY from thread_db_new_objfile after td_ta_new call succeeds. */
+
+  /* Push this target vector */
+  push_target (&thread_db_ops);
+  /* Find the underlying process-layer target for calling later.  */
+  target_beneath = find_target_beneath (&thread_db_ops);
+  using_thread_db = 1;
+  /* Turn on thread_db event-reporting API.  */
+  enable_thread_event_reporting (main_threadagent);
+}
+
+static void
+thread_db_unpush_target (void)
+{
+  /* Must be called whenever we remove ourself from the target stack! */
+
+  using_thread_db = 0;
+  target_beneath = NULL;
+
+  /* delete local list of threads */
+  empty_threadlist ();
+  /* Turn off the thread_db API.  */
+  p_td_ta_delete (main_threadagent);
+  /* Unpush this target vector */
+  unpush_target (&thread_db_ops);
+  /* Reset linuxthreads module.  */
+  linuxthreads_discard_global_state ();
+}
+
+/*
+ * New objfile hook function:
+ * Called for each new objfile (image, shared lib) in the target process.
+ *
+ * The purpose of this function is to detect that the target process
+ * is linked with the (appropriate) thread library.  So every time a
+ * new target shared library is detected, we will call td_ta_new.
+ * If it succeeds, we know we have a multi-threaded target process
+ * that we can debug using the thread_db API.
+ */
+
+/* 
+ * new_objfile function:
+ *
+ * connected to target_new_objfile_hook, this function gets called
+ * every time a new binary image is loaded.
+ *
+ * At each call, we attempt to open the thread_db connection to the
+ * child process.  If it succeeds, we know we have a libthread process
+ * and we can debug it with this target vector.  Therefore we push
+ * ourself onto the target stack.
+ */
+
+static void (*target_new_objfile_chain)   (struct objfile *objfile);
+static int stop_or_attach_thread_callback (const td_thrhandle_t *th, 
+					   void *data);
+static int wait_thread_callback           (const td_thrhandle_t *th, 
+					   void *data);
+
+static void
+thread_db_new_objfile (struct objfile *objfile)
+{
+  td_err_e   ret;
+  
+  if (using_thread_db)			/* libthread already detected, and */
+    goto quit;				/* thread target vector activated. */
+
+  if (objfile == NULL)
+    goto quit;	/* un-interesting object file */
+
+  /* Initialize our "main prochandle" with the main inferior pid.  */
+  main_prochandle.pid = PIDGET (inferior_pid);
+
+  /* Now attempt to open a thread_db connection to the 
+     thread library running in the child process.  */
+  ret = p_td_ta_new (&main_prochandle, &main_threadagent);
+  switch (ret) {
+  default:
+    warning ("Unexpected error initializing thread_db: %s", 
+	     thr_err_string (ret));
+    break;
+  case TD_NOLIBTHREAD:	/* expected: no libthread in child process (yet) */
+    break;	
+  case TD_OK:		/* libthread detected in child: we go live now! */
+    thread_db_push_target ();
+    event_pid = inferior_pid;	/* for resume */
+
+    /* Now stop everyone else, and attach any new threads you find.  */
+    p_td_ta_thr_iter (main_threadagent, 
+		      stop_or_attach_thread_callback,
+		      (void *) 0,
+		      TD_THR_ANY_STATE,
+		      TD_THR_LOWEST_PRIORITY,
+		      TD_SIGNO_MASK,
+		      TD_THR_ANY_USER_FLAGS);
+
+    /* Now go call wait on all the threads you've stopped:
+       This allows us to absorb the SIGKILL event, and to make sure
+       that the thread knows that it is stopped (Linux peculiarity).  */
+    p_td_ta_thr_iter (main_threadagent, 
+		      wait_thread_callback,
+		      (void *) 0,
+		      TD_THR_ANY_STATE,
+		      TD_THR_LOWEST_PRIORITY,
+		      TD_SIGNO_MASK,
+		      TD_THR_ANY_USER_FLAGS);
+
+    break;
+  }
+quit:
+  if (target_new_objfile_chain)
+    target_new_objfile_chain (objfile);
+}
+
+
+/* 
+
+   LOCAL FUNCTION
+
+   thread_db_alive     - test thread for "aliveness"
+
+   SYNOPSIS
+
+   static bool thread_db_alive (int pid);
+
+   DESCRIPTION
+
+   returns true if thread still active in inferior.
+
+ */
+
+static int
+thread_db_alive (pid)
+     int pid;
+{
+  if (is_thread (pid))		/* user-space (non-kernel) thread */
+    {
+      td_thrhandle_t th;
+      td_err_e ret;
+
+      pid = GET_THREAD (pid);
+      if ((ret = p_td_ta_map_id2thr (main_threadagent, pid, &th)) != TD_OK)
+	return 0;		/* thread not found */
+      if ((ret = p_td_thr_validate (&th)) != TD_OK)
+	return 0;		/* thread not valid */
+      return 1;			/* known thread: return true */
+    }
+  else if (target_beneath->to_thread_alive)
+    return target_beneath->to_thread_alive (pid);
+  else
+    return 0;		/* default to "not alive" (shouldn't happen anyway) */
+}
+
+/*
+ * get_lwp_from_thread_handle
+ */
+
+static int	/* lwpid_t or pid_t */
+get_lwp_from_thread_handle (th)
+     td_thrhandle_t *th;
+{
+  td_thrinfo_t ti;
+  td_err_e     ret;
+
+  if ((ret = p_td_thr_get_info (th, &ti)) != TD_OK)
+    error ("get_lwp_from_thread_handle: thr_get_info failed: %s", 
+	   thr_err_string (ret));
+
+  return ti.ti_lid;
+}
+
+/*
+ * get_lwp_from_thread_id
+ */
+
+static int	/* lwpid_t or pid_t */
+get_lwp_from_thread_id (tid)
+     int tid;	/* thread_t? */
+{
+  td_thrhandle_t th;
+  td_err_e       ret;
+
+  if ((ret = p_td_ta_map_id2thr (main_threadagent, tid, &th)) != TD_OK)
+    error ("get_lwp_from_thread_id: map_id2thr failed: %s", 
+	   thr_err_string (ret));
+
+  return get_lwp_from_thread_handle (&th);
+}
+
+/* 
+ * pid_to_str has to handle user-space threads.
+ * If not a user-space thread, then pass the request on to the 
+ * underlying stratum if it can handle it: else call normal_pid_to_str.
+ */
+
+static char *
+thread_db_pid_to_str (int pid)
+{
+  static char buf[100];
+  td_thrhandle_t th;
+  td_thrinfo_t ti;
+  td_err_e ret;
+
+  if (is_thread (pid))
+    {
+      if ((ret = p_td_ta_map_id2thr (main_threadagent, 
+				     GET_THREAD (pid),
+				     &th)) != TD_OK)
+	error ("thread_db: map_id2thr failed: %s", thr_err_string (ret));
+
+      if ((ret = p_td_thr_get_info (&th, &ti)) != TD_OK)
+	error ("thread_db: thr_get_info failed: %s", thr_err_string (ret));
+
+      if (ti.ti_state == TD_THR_ACTIVE &&
+	  ti.ti_lid != 0)
+	sprintf (buf, "Thread %d (LWP %d)", ti.ti_tid, ti.ti_lid);
+      else
+	sprintf (buf, "Thread %d (%s)", ti.ti_tid,
+		 thr_state_string (ti.ti_state));
+    }
+  else if (GET_LWP (pid))
+    sprintf (buf, "LWP %d", GET_LWP (pid));
+  else return normal_pid_to_str (pid);
+
+  return buf;
+}
+
+/* 
+ * thread_db target vector functions:
+ */
+
+static void
+thread_db_files_info (struct target_ops *tgt_vector)
+{
+  /* This function will be unnecessary in real life.  */
+  printf_filtered ("thread_db stratum:\n");
+  target_beneath->to_files_info (tgt_vector);
+}
+
+/* 
+ * xfer_memory has to munge the inferior_pid before passing the call
+ * down to the target layer.  
+ */
+
+static int
+thread_db_xfer_memory (memaddr, myaddr, len, dowrite, target)
+     CORE_ADDR memaddr;
+     char *myaddr;
+     int len;
+     int dowrite;
+     struct target_ops *target;	/* ignored */
+{
+  struct cleanup *old_chain;
+  int ret;
+
+  old_chain = save_inferior_pid ();
+
+  if (is_thread (inferior_pid) ||
+      !target_thread_alive (inferior_pid))
+    {
+      /* FIXME: use the LID/LWP, so that underlying process layer
+	 can read memory from specific threads?  */
+      inferior_pid = main_prochandle.pid;
+    }
+
+  ret = target_beneath->to_xfer_memory (memaddr, myaddr, len,
+					   dowrite, target);
+  do_cleanups (old_chain);
+  return ret;
+}
+
+/* 
+ * fetch_registers has to determine if inferior_pid is a user-space thread.
+ * If so, we use the thread_db API to get the registers.
+ * And if not, we call the underlying process stratum.
+ */
+
+static void
+thread_db_fetch_registers (regno)
+     int regno;
+{
+  td_thrhandle_t thandle;
+  prfpregset_t fpregset;
+  prgregset_t gregset;
+  thread_t thread;
+  td_err_e ret;
+
+  if (!is_thread (inferior_pid))	/* kernel thread */
+    {			/* pass the request on to the target underneath.  */
+      target_beneath->to_fetch_registers (regno);
+      return;
+    }
+
+  /* convert inferior_pid into a td_thrhandle_t */
+
+  if ((thread = GET_THREAD (inferior_pid)) == 0)
+    error ("fetch_registers:  thread == 0");
+
+  if ((ret = p_td_ta_map_id2thr (main_threadagent, thread, &thandle)) != TD_OK)
+    error ("fetch_registers: td_ta_map_id2thr: %s", thr_err_string (ret));
+
+  /* Get the integer regs: 
+     For the sparc, TD_PARTIALREG means that only i0->i7, l0->l7, 
+     pc and sp are saved (by a thread context switch).  */
+  if ((ret = p_td_thr_getgregs (&thandle, gregset)) != TD_OK &&
+      ret != TD_PARTIALREG)
+    error ("fetch_registers: td_thr_getgregs %s", thr_err_string (ret));
+
+  /* And, now the fp regs */
+  if ((ret = p_td_thr_getfpregs (&thandle, &fpregset)) != TD_OK &&
+      ret != TD_NOFPREGS)
+    error ("fetch_registers: td_thr_getfpregs %s", thr_err_string (ret));
+
+/* Note that we must call supply_{g fp}regset *after* calling the td routines
+   because the td routines call ps_lget* which affect the values stored in the
+   registers array.  */
+
+  supply_gregset (gregset);
+  supply_fpregset (&fpregset);
+
+}
+
+/* 
+ * store_registers has to determine if inferior_pid is a user-space thread.
+ * If so, we use the thread_db API to get the registers.
+ * And if not, we call the underlying process stratum.
+ */
+
+static void
+thread_db_store_registers (regno)
+     int regno;
+{
+  td_thrhandle_t thandle;
+  prfpregset_t fpregset;
+  prgregset_t  gregset;
+  thread_t thread;
+  td_err_e ret;
+
+  if (!is_thread (inferior_pid))	/* Kernel thread: */
+    {		/* pass the request on to the underlying target vector.  */
+      target_beneath->to_store_registers (regno);
+      return;
+    }
+
+  /* convert inferior_pid into a td_thrhandle_t */
+
+  if ((thread = GET_THREAD (inferior_pid)) == 0)
+    error ("store_registers: thread == 0");
+
+  if ((ret = p_td_ta_map_id2thr (main_threadagent, thread, &thandle)) != TD_OK)
+    error ("store_registers: td_ta_map_id2thr %s", thr_err_string (ret));
+
+  if (regno != -1)
+    {				/* Not writing all the regs */
+      /* save new register value */
+      /* MVS: I don't understand this... */
+      char old_value[REGISTER_SIZE];
+
+      memcpy (old_value, &registers[REGISTER_BYTE (regno)], REGISTER_SIZE);
+
+      if ((ret = p_td_thr_getgregs (&thandle, gregset)) != TD_OK)
+	error ("store_registers: td_thr_getgregs %s", thr_err_string (ret));
+      if ((ret = p_td_thr_getfpregs (&thandle, &fpregset)) != TD_OK)
+	error ("store_registers: td_thr_getfpregs %s", thr_err_string (ret));
+
+      /* restore new register value */
+      memcpy (&registers[REGISTER_BYTE (regno)], old_value, REGISTER_SIZE);
+
+    }
+
+  fill_gregset  (gregset, regno);
+  fill_fpregset (&fpregset, regno);
+
+  if ((ret = p_td_thr_setgregs (&thandle, gregset)) != TD_OK)
+    error ("store_registers: td_thr_setgregs %s", thr_err_string (ret));
+  if ((ret = p_td_thr_setfpregs (&thandle, &fpregset)) != TD_OK &&
+      ret != TD_NOFPREGS)
+    error ("store_registers: td_thr_setfpregs %s", thr_err_string (ret));
+}
+
+static void
+handle_new_thread (tid, lid, verbose)
+     int tid;	/* user thread id */
+     int lid;	/* kernel thread id */
+     int verbose;
+{
+  int gdb_pid = BUILD_THREAD (tid, main_prochandle.pid);
+  int wait_pid, wait_status;
+
+  if (verbose)
+    printf_filtered ("[New %s]\n", target_pid_to_str (gdb_pid));
+  add_thread (gdb_pid);
+
+  if (lid != main_prochandle.pid)
+    {
+      attach_thread (lid);
+      /* According to the Eric Paire model, we now have to send
+	 the restart signal to the new thread -- however, empirically,
+	 I do not find that to be necessary.  */
+      attach_pid = lid;
+    }
+}
+
+static void
+test_for_new_thread (tid, lid, verbose)
+     int tid;
+     int lid;
+     int verbose;
+{
+  if (!in_thread_list (BUILD_THREAD (tid, main_prochandle.pid)))
+    handle_new_thread (tid, lid, verbose);
+}
+
+/* 
+ * Callback function that gets called once per USER thread 
+ * (i.e., not kernel) thread by td_ta_thr_iter.
+ */
+
+static int
+find_new_threads_callback (th, ignored)
+     const td_thrhandle_t *th;
+     void *ignored;
+{
+  td_thrinfo_t ti;
+  td_err_e     ret;
+
+  if ((ret = p_td_thr_get_info (th, &ti)) != TD_OK)
+    {
+      warning ("find_new_threads_callback: %s", thr_err_string (ret));
+      return -1;		/* bail out, get_info failed. */
+    }
+
+  /* FIXME: 
+     As things now stand, this should never detect a new thread.
+     But if it does, we could be in trouble because we aren't calling
+     wait_thread_callback for it.  */
+  test_for_new_thread (ti.ti_tid, ti.ti_lid, 0);
+  return 0;
+}
+
+/* 
+ * find_new_threads uses the thread_db iterator function to discover
+ * user-space threads.  Then if the underlying process stratum has a
+ * find_new_threads method, we call that too.
+ */
+
+static void
+thread_db_find_new_threads ()
+{
+  if (inferior_pid == -1)	/* FIXME: still necessary? */
+    {
+      printf_filtered ("No process.\n");
+      return;
+    }
+  p_td_ta_thr_iter (main_threadagent, 
+		    find_new_threads_callback, 
+		    (void *) 0, 
+		    TD_THR_ANY_STATE, 
+		    TD_THR_LOWEST_PRIORITY,
+		    TD_SIGNO_MASK, 
+		    TD_THR_ANY_USER_FLAGS);
+  if (target_beneath->to_find_new_threads)
+    target_beneath->to_find_new_threads ();
+}
+
+/*
+ * Resume all threads, or resume a single thread.
+ * If step is true, then single-step the appropriate thread
+ * (or single-step inferior_pid, but continue everyone else).
+ * If signo is true, then send that signal to at least one thread.
+ */
+
+/*
+ * This function is called once for each thread before resuming.
+ * It sends continue (no step, and no signal) to each thread except
+ *   the main thread, and
+ *   the event thread (the one that stopped at a breakpoint etc.)
+ *
+ * The event thread is handled separately so that it can be sent
+ * the stepping and signal args with which target_resume was called.
+ *
+ * The main thread is resumed last, so that the thread_db proc_service
+ * callbacks will still work during the iterator function.
+ */
+
+static int
+resume_thread_callback (th, data)
+     const td_thrhandle_t *th;
+     void *data;
+{
+  td_thrinfo_t ti;
+  td_err_e     ret;
+
+  if ((ret = p_td_thr_get_info (th, &ti)) != TD_OK)
+    {
+      warning ("resume_thread_callback: %s", thr_err_string (ret));
+      return -1;		/* bail out, get_info failed. */
+    }
+  /* FIXME: 
+     As things now stand, this should never detect a new thread.
+     But if it does, we could be in trouble because we aren't calling
+     wait_thread_callback for it.  */
+  test_for_new_thread (ti.ti_tid, ti.ti_lid, 1);
+
+  if (ti.ti_lid != main_prochandle.pid &&
+      ti.ti_lid != event_pid)
+    {
+      /* Unconditionally continue the thread with no signal.
+	 Only the event thread will get a signal of any kind.  */
+
+      target_beneath->to_resume (ti.ti_lid, 0, 0);
+    }
+  return 0;
+}
+
+static int
+new_resume_thread_callback (thread, data)
+     threadinfo *thread;
+     void *data;
+{
+  if (thread->lid != event_pid &&
+      thread->lid != main_prochandle.pid)
+    {
+      /* Unconditionally continue the thread with no signal (for now).  */
+
+      target_beneath->to_resume (thread->lid, 0, 0);
+    }
+  return 0;
+}
+
+static int last_resume_pid;
+static int last_resume_step;
+static int last_resume_signo;
+
+static void
+thread_db_resume (pid, step, signo)
+     int pid;
+     int step;
+     enum target_signal signo;
+{
+  last_resume_pid   = pid;
+  last_resume_step  = step;
+  last_resume_signo = signo;
+
+  /* resuming a specific pid? */
+  if (pid != -1)
+    {
+      if (is_thread (pid))
+	pid = get_lwp_from_thread_id (GET_THREAD (pid));
+      else if (GET_LWP (pid))
+	pid = GET_LWP (pid);
+    }
+
+  /* Apparently the interpretation of 'pid' is dependent on 'step':
+     If step is true, then a specific pid means 'step only this pid'.
+     But if step is not true, then pid means 'continue ALL pids, but
+     give the signal only to this one'.  */
+  if (pid != -1 && step)
+    {
+      /* FIXME: is this gonna work in all circumstances? */
+      target_beneath->to_resume (pid, step, signo);
+    }
+  else
+    {
+      /* 1) Continue all threads except the event thread and the main thread.
+	 2) resume the event thread with step and signo.
+	 3) If event thread != main thread, continue the main thread.
+
+	 Note: order of 2 and 3 may need to be reversed.  */
+
+      threadlist_iter (new_resume_thread_callback, 
+			(void *) 0, 
+			TD_THR_ANY_STATE, 
+			TD_THR_ANY_TYPE);
+      /* now resume event thread, and if necessary also main thread. */
+      if (event_pid)
+	{
+	  target_beneath->to_resume (event_pid, step, signo);
+	}
+      if (event_pid != main_prochandle.pid)
+	{
+	  target_beneath->to_resume (main_prochandle.pid, 0, 0);
+	}
+    }
+}
+
+/* All new threads will be attached.
+   All previously known threads will be stopped using kill (SIGKILL).  */
+
+static int
+stop_or_attach_thread_callback (const td_thrhandle_t *th, void *data)
+{
+  td_thrinfo_t ti;
+  td_err_e     ret;
+  int          gdb_pid;
+  int on_off = 1;
+
+  if ((ret = p_td_thr_get_info (th, &ti)) != TD_OK)
+    {
+      warning ("stop_or_attach_thread_callback: %s", thr_err_string (ret));
+      return -1;		/* bail out, get_info failed. */
+    }
+
+  /* First add it to our internal list.  
+     We build this list anew at every wait event.  */
+  insert_thread (ti.ti_tid, ti.ti_lid, ti.ti_state, ti.ti_type);
+  /* Now: if we've already seen it, stop it, else add it and attach it.  */
+  gdb_pid = BUILD_THREAD (ti.ti_tid, main_prochandle.pid);
+  if (!in_thread_list (gdb_pid))	/* new thread */
+    {
+      handle_new_thread (ti.ti_tid, ti.ti_lid, 1);
+      /* Enable thread events */
+      if (p_td_thr_event_enable)
+	if ((ret = p_td_thr_event_enable (th, on_off)) != TD_OK)
+	  warning ("stop_or_attach_thread: %s", thr_err_string (ret));
+    }
+  else if (ti.ti_lid != event_pid &&
+	   ti.ti_lid != main_prochandle.pid)
+    {
+      ret = (td_err_e) kill (ti.ti_lid, SIGSTOP);
+    }
+
+  return 0;
+}
+     
+/*
+ * Wait for signal N from pid PID.
+ * If wait returns any other signals, put them back before returning.
+ */
+
+static void
+wait_for_stop (pid)
+     int pid;
+{
+  int i;
+  int retpid;
+  int status;
+
+  /* Array of wait/signal status */
+  /* FIXME: wrong data structure, we need a queue.
+     Realtime signals may be delivered more than once.  
+     And at that, we really can't handle them (see below).  */
+#if defined (NSIG)
+  static int   wstatus [NSIG];
+#elif defined (_NSIG)
+  static int   wstatus [_NSIG];
+#else
+#error No definition for number of signals!
+#endif
+
+  /* clear wait/status list */
+  memset (&wstatus, 0, sizeof (wstatus));
+
+  /* Now look for SIGSTOP event on all threads except event thread.  */
+  do {
+    errno = 0;
+    if (pid == main_prochandle.pid)
+      retpid = waitpid (pid, &status, 0);
+    else
+      retpid = waitpid (pid, &status, __WCLONE);
+
+    if (retpid > 0)
+      if (WSTOPSIG (status) == SIGSTOP)
+	{
+	  /* Got the SIGSTOP event we're looking for.
+	     Throw it away, and throw any other events back!  */
+	  for (i = 0; i < sizeof(wstatus) / sizeof (wstatus[0]); i++)
+	    if (wstatus[i])
+	      if (i != SIGSTOP)
+		{
+		  kill (retpid, i);
+		}
+	  break;	/* all done */
+	}
+      else
+	{
+	  int signo;
+	  /* Oops, got an event other than SIGSTOP.
+	     Save it, and throw it back after we find the SIGSTOP event.  */
+	  
+	  /* FIXME (how?)  This method is going to fail for realtime
+	     signals, which cannot be put back simply by using kill.  */
+
+	  if (WIFEXITED (status))
+	    error ("Ack!  Thread Exited event.  What do I do now???");
+	  else if (WIFSTOPPED (status))
+	    signo = WSTOPSIG (status);
+	  else
+	    signo = WTERMSIG (status);
+	  
+	  /* If a thread other than the event thread has hit a GDB
+	     breakpoint (as opposed to some random trap signal), then
+	     just arrange for it to hit it again later.  Back up the
+	     PC if necessary.  Don't forward the SIGTRAP signal to
+	     the thread.  We will handle the current event, eventually
+	     we will resume all the threads, and this one will get
+	     it's breakpoint trap again.
+
+	     If we do not do this, then we run the risk that the user
+	     will delete or disable the breakpoint, but the thread will
+	     have already tripped on it.  */
+
+	  if (retpid != event_pid &&
+	      signo == SIGTRAP &&
+	      breakpoint_inserted_here_p (read_pc_pid (retpid) - 
+					  DECR_PC_AFTER_BREAK))
+	    {
+	      /* Set the pc to before the trap and DO NOT re-send the signal */
+	      if (DECR_PC_AFTER_BREAK)
+		write_pc_pid (read_pc_pid (retpid) - DECR_PC_AFTER_BREAK,
+			      retpid);
+	    }
+
+	  /* Since SIGINT gets forwarded to the entire process group
+	     (in the case where ^C is typed at the tty / console), 
+	     just ignore all SIGINTs from other than the event thread.  */
+	  else if (retpid != event_pid && signo == SIGINT)
+	    { /* do nothing.  Signal will disappear into oblivion!  */
+	      ;
+	    }
+
+	  else /* This is some random signal other than a breakpoint. */
+	    {
+	      wstatus [signo] = 1;
+	    }
+	  child_resume (retpid, 0, TARGET_SIGNAL_0);
+	  continue;
+	}
+
+  } while (errno == 0 || errno == EINTR);
+}
+
+/*
+ * wait_thread_callback
+ *
+ * Calls waitpid for each thread, repeatedly if necessary, until
+ * SIGSTOP is returned.  Afterward, if any other signals were returned
+ * by waitpid, return them to the thread's pending queue by calling kill.
+ */
+
+static int
+wait_thread_callback (const td_thrhandle_t *th, void *data)
+{
+  td_thrinfo_t ti;
+  td_err_e     ret;
+
+  if ((ret = p_td_thr_get_info (th, &ti)) != TD_OK)
+    {
+      warning ("wait_thread_callback: %s", thr_err_string (ret));
+      return -1;		/* bail out, get_info failed. */
+    }
+
+  /* This callback to act on all threads except the event thread: */
+  if (ti.ti_lid == event_pid || 	/* no need to wait (no sigstop) */
+      ti.ti_lid == main_prochandle.pid)	/* no need to wait (already waited) */
+    return 0;	/* don't wait on the event thread.  */
+
+  wait_for_stop (ti.ti_lid);
+  return 0;	/* finished: next thread. */
+}
+
+static int
+new_wait_thread_callback (thread, data)
+     threadinfo *thread;
+     void *data;
+{
+  /* don't wait on the event thread -- it's already stopped and waited.  
+     Ditto the main thread.  */
+  if (thread->lid != event_pid &&
+      thread->lid != main_prochandle.pid)
+    {
+      wait_for_stop (thread->lid);
+    }
+  return 0;
+}
+
+/* 
+ * Wait for any thread to stop, by calling the underlying wait method.
+ * The PID returned by the underlying target may be a kernel thread,
+ * in which case we will want to convert it to the corresponding
+ * user-space thread.  
+ */
+
+static int
+thread_db_wait (int pid, struct target_waitstatus *ourstatus)
+{
+  td_thrhandle_t thandle;
+  td_thrinfo_t ti;
+  td_err_e ret;
+  lwpid_t lwp;
+  int retpid;
+  int status;
+  int save_errno;
+
+  /* OK, we're about to wait for an event from the running inferior.
+     Make sure we're ignoring the right signals.  */
+
+  check_all_signal_numbers ();	/* see if magic signals changed. */
+
+  event_pid = 0;
+  attach_pid = 0;
+
+  /* FIXME: should I do the wait right here inline?  */
+#if 0
+  if (pid == -1)
+    lwp = -1;
+  else
+    lwp = get_lwp_from_thread_id (GET_THREAD (pid));
+#endif
+
+
+  save_errno = linux_child_wait (-1, &retpid, &status);
+  store_waitstatus (ourstatus, status);
+
+  /* Thread ID is irrelevant if the target process exited.
+     FIXME: do I have any killing to do?
+     Can I get this event mistakenly from a thread?  */
+  if (ourstatus->kind == TARGET_WAITKIND_EXITED)
+    return retpid;
+
+  /* OK, we got an event of interest.
+     Go stop all threads and look for new ones.
+     FIXME: maybe don't do this for the restart signal?  Optimization...  */
+  event_pid = retpid;
+
+  /* If the last call to resume was for a specific thread, then we don't
+     need to stop everyone else: they should already be stopped.  */
+  if (last_resume_step == 0 || last_resume_pid == -1)
+    {
+      /* Main thread must be stopped before calling the iterator.  */
+      if (retpid != main_prochandle.pid)
+	{
+	  kill (main_prochandle.pid, SIGSTOP);
+	  wait_for_stop (main_prochandle.pid);
+	}
+
+      empty_threadlist ();
+      /* Now stop everyone else, and attach any new threads you find.  */
+      p_td_ta_thr_iter (main_threadagent, 
+			stop_or_attach_thread_callback,
+			(void *) 0,
+			TD_THR_ANY_STATE,
+			TD_THR_LOWEST_PRIORITY,
+			TD_SIGNO_MASK,
+			TD_THR_ANY_USER_FLAGS);
+
+      /* Now go call wait on all the threads we've stopped:
+	 This allows us to absorb the SIGKILL event, and to make sure
+	 that the thread knows that it is stopped (Linux peculiarity).  */
+
+      threadlist_iter (new_wait_thread_callback, 
+		       (void *) 0,
+		       TD_THR_ANY_STATE, 
+		       TD_THR_ANY_TYPE);
+    }
+
+  /* Convert the kernel thread id to the corresponding thread id.  */
+
+  /* If the process layer does not furnish an lwp,
+     then perhaps the returned pid IS the lwp... */
+  if ((lwp = GET_LWP (retpid)) == 0)
+    lwp = retpid;
+
+  if ((ret = p_td_ta_map_lwp2thr (main_threadagent, lwp, &thandle)) != TD_OK)
+    return retpid;	/* LWP is not mapped onto a user-space thread. */
+
+  if ((ret = p_td_thr_validate (&thandle)) != TD_OK)
+    return retpid;	/* LWP is not mapped onto a valid thread. */
+
+  if ((ret = p_td_thr_get_info (&thandle, &ti)) != TD_OK)
+    {
+      warning ("thread_db: thr_get_info failed ('%s')", thr_err_string (ret));
+      return retpid;
+    }
+
+  retpid = BUILD_THREAD (ti.ti_tid, main_prochandle.pid);
+  /* If this is a new user thread, notify GDB about it.  */
+  if (!in_thread_list (retpid))
+    {
+      printf_filtered ("[New %s]\n", target_pid_to_str (retpid));
+      add_thread (retpid);
+    }
+
+#if 0
+  /* Now detect if this is a thread creation/deletion event: */
+  check_for_thread_event (ourstatus, retpid);
+#endif
+  return retpid;
+}
+
+/* 
+ * kill has to call the underlying kill.
+ * FIXME: I'm not sure if it's necessary to check inferior_pid any more,
+ * but we might need to fix inferior_pid up if it's a user thread.
+ */
+
+static int
+kill_thread_callback (th, data)
+     td_thrhandle_t *th;
+     void *data;
+{
+  td_thrinfo_t ti;
+  td_err_e     ret;
+
+  /* Fixme: 
+     For Linux, threads may need to be waited.  */
+  if ((ret = p_td_thr_get_info (th, &ti)) != TD_OK)
+    {
+      warning ("kill_thread_callback: %s", thr_err_string (ret));
+      return -1;		/* bail out, get_info failed. */
+    }
+
+  if (ti.ti_lid != main_prochandle.pid)
+    {
+      kill (ti.ti_lid, SIGKILL);
+    }
+  return 0;
+}
+
+
+static void thread_db_kill (void)
+{
+  int rpid;
+  int status;
+
+  /* Fixme: 
+     For Linux, threads may need to be waited.  */
+  if (inferior_pid != 0)
+    {
+      /* Go kill the children first.  Save the main thread for last. */
+      p_td_ta_thr_iter (main_threadagent, 
+			kill_thread_callback, 
+			(void *) 0, 
+			TD_THR_ANY_STATE,
+			TD_THR_LOWEST_PRIORITY,
+			TD_SIGNO_MASK,
+			TD_THR_ANY_USER_FLAGS);
+
+      /* Turn off thread_db event-reporting API *before* killing the
+	 main thread, since this operation requires child memory access.
+	 Can't move this into thread_db_unpush target because then 
+	 detach would not work.  */
+      disable_thread_event_reporting (main_threadagent);
+
+      inferior_pid = main_prochandle.pid;
+
+      /* 
+       * Since both procfs_kill and ptrace_kill call target_mourn, 
+       * it should be sufficient for me to call one of them.
+       * That will result in my mourn being called, which will both
+       * unpush me and call the underlying mourn.
+       */
+      target_beneath->to_kill ();
+    }
+
+  /* Wait for all threads. */
+  /* FIXME: need a universal wait_for_signal func? */
+  do
+    {
+      rpid = waitpid (-1, &status, __WCLONE | WNOHANG);
+    }
+  while (rpid > 0 || errno == EINTR);
+
+  do
+    {
+      rpid = waitpid (-1, &status, WNOHANG);
+    }
+  while (rpid > 0 || errno == EINTR);
+}
+
+/* 
+ * Mourn has to remove us from the target stack, 
+ * and then call the underlying mourn.
+ */
+
+static void thread_db_mourn_inferior (void)
+{
+  thread_db_unpush_target ();
+  target_mourn_inferior ();	/* call the underlying mourn */
+}
+
+/* 
+ * Detach has to remove us from the target stack, 
+ * and then call the underlying detach.
+ *
+ * But first, it has to detach all the cloned threads!
+ */
+
+static int
+detach_thread_callback (th, data)
+     td_thrhandle_t *th;
+     void *data;
+{
+  /* Called once per thread.  */
+  td_thrinfo_t ti;
+  td_err_e     ret;
+
+  if ((ret = p_td_thr_get_info (th, &ti)) != TD_OK)
+    {
+      warning ("detach_thread_callback: %s", thr_err_string (ret));
+      return -1;                /* bail out, get_info failed. */
+    }
+
+  if (!in_thread_list (BUILD_THREAD (ti.ti_tid, main_prochandle.pid)))
+    return 0;	/* apparently we don't know this one.  */
+
+  /* Save main thread for last, or the iterator will fail! */
+  if (ti.ti_lid != main_prochandle.pid)
+    {
+      struct cleanup *old_chain;
+      int off = 0;
+
+      /* Time to detach this thread. 
+	 First disable thread_db event reporting for the thread.  */
+      if (p_td_thr_event_enable &&
+	  (ret = p_td_thr_event_enable (th, off)) != TD_OK)
+	{
+	  warning ("detach_thread_callback: %s\n", thr_err_string (ret));
+	  return 0;
+	}
+
+      /* Now cancel any pending SIGTRAPS.  FIXME!  */
+
+      /* Call underlying detach method.  FIXME just detach it.  */
+      old_chain = save_inferior_pid ();
+      inferior_pid = ti.ti_lid;
+      detach (TARGET_SIGNAL_0);
+      do_cleanups (old_chain);
+    }
+  return 0;
+}
+
+static void
+thread_db_detach (char *args, int from_tty)
+{
+  td_err_e ret;
+
+  if ((ret = p_td_ta_thr_iter (main_threadagent, 
+			       detach_thread_callback, 
+			       (void *) 0, 
+			       TD_THR_ANY_STATE,
+			       TD_THR_LOWEST_PRIORITY,
+			       TD_SIGNO_MASK,
+			       TD_THR_ANY_USER_FLAGS))
+      != TD_OK)
+    warning ("detach (thr_iter): %s", thr_err_string (ret));
+
+  /* Turn off thread_db event-reporting API 
+     (before detaching the main thread) */
+  disable_thread_event_reporting (main_threadagent);
+
+  thread_db_unpush_target ();
+
+  /* above call nullifies target_beneath, so don't use that! */
+  inferior_pid = PIDGET (inferior_pid);
+  target_detach (args, from_tty);
+}
+
+
+/* 
+ * 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 thread_db / libthread
+ * connection is ready to be made.
+ *
+ * So, what shall we do?
+ * Unpush ourselves from the stack, and then invoke
+ * find_default_create_inferior, which will invoke the
+ * appropriate process_stratum target to do the create.
+ */
+
+static void
+thread_db_create_inferior (exec_file, allargs, env)
+     char *exec_file;
+     char *allargs;
+     char **env;
+{
+  thread_db_unpush_target ();
+  find_default_create_inferior (exec_file, allargs, env);
+}
+
+/* 
+ * Thread_db target vector initializer.
+ */
+
+void
+init_thread_db_ops ()
+{
+  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_files_info       = thread_db_files_info;
+  thread_db_ops.to_create_inferior  = thread_db_create_inferior;
+  thread_db_ops.to_detach           = thread_db_detach;
+  thread_db_ops.to_wait             = thread_db_wait;
+  thread_db_ops.to_resume           = thread_db_resume;
+  thread_db_ops.to_mourn_inferior   = thread_db_mourn_inferior;
+  thread_db_ops.to_kill             = thread_db_kill;
+  thread_db_ops.to_xfer_memory      = thread_db_xfer_memory;
+  thread_db_ops.to_fetch_registers  = thread_db_fetch_registers;
+  thread_db_ops.to_store_registers  = thread_db_store_registers;
+  thread_db_ops.to_thread_alive     = thread_db_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;
+}
+#endif	/* HAVE_STDINT_H */
+
+/*
+ * Module constructor / initializer function.
+ * If connection to thread_db dynamic library is successful, 
+ * then initialize this module's target vectors and the 
+ * new_objfile hook.
+ */
+
+
+void
+_initialize_thread_db ()
+{
+#ifdef HAVE_STDINT_H	/* stub out entire module, leave initializer empty */
+  if (init_thread_db_library ())
+    {
+      init_thread_db_ops ();
+      add_target (&thread_db_ops);
+      /*
+       * Hook up to the new_objfile event.
+       * If someone is already there, arrange for him to be called
+       * after we are.
+       */
+      target_new_objfile_chain = target_new_objfile_hook;
+      target_new_objfile_hook  = thread_db_new_objfile;
+    }
+#endif	/* HAVE_STDINT_H */
+}
+