gdb/gdbserver/win32-low.c

/* Low level interface to Windows debugging, for gdbserver.
   Copyright (C) 2006, 2007 Free Software Foundation, Inc.

   Contributed by Leo Zayas.  Based on "win32-nat.c" from GDB.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#include "server.h"
#include "regcache.h"
#include "gdb/signals.h"
#include "mem-break.h"
#include "win32-low.h"

#include <windows.h>
#include <winnt.h>
#include <imagehlp.h>
#include <tlhelp32.h>
#include <psapi.h>
#include <sys/param.h>
#include <malloc.h>
#include <process.h>

#ifndef USE_WIN32API
#include <sys/cygwin.h>
#endif

#define LOG 0

#define OUTMSG(X) do { printf X; fflush (stdout); } while (0)
#if LOG
#define OUTMSG2(X) do { printf X; fflush (stdout); } while (0)
#else
#define OUTMSG2(X) do ; while (0)
#endif

#ifndef _T
#define _T(x) TEXT (x)
#endif

#ifndef COUNTOF
#define COUNTOF(STR) (sizeof (STR) / sizeof ((STR)[0]))
#endif

#ifdef _WIN32_WCE
# define GETPROCADDRESS(DLL, PROC) \
  ((winapi_ ## PROC) GetProcAddress (DLL, TEXT (#PROC)))
#else
# define GETPROCADDRESS(DLL, PROC) \
  ((winapi_ ## PROC) GetProcAddress (DLL, #PROC))
#endif

int using_threads = 1;

/* Globals.  */
static HANDLE current_process_handle = NULL;
static DWORD current_process_id = 0;
static enum target_signal last_sig = TARGET_SIGNAL_0;

/* The current debug event from WaitForDebugEvent.  */
static DEBUG_EVENT current_event;

#define NUM_REGS (the_low_target.num_regs)

typedef BOOL WINAPI (*winapi_DebugActiveProcessStop) (DWORD dwProcessId);
typedef BOOL WINAPI (*winapi_DebugSetProcessKillOnExit) (BOOL KillOnExit);
typedef BOOL WINAPI (*winapi_DebugBreakProcess) (HANDLE);
typedef BOOL WINAPI (*winapi_GenerateConsoleCtrlEvent) (DWORD, DWORD);

static DWORD main_thread_id = 0;

static void win32_resume (struct thread_resume *resume_info);

/* Get the thread ID from the current selected inferior (the current
   thread).  */
static DWORD
current_inferior_tid (void)
{
  win32_thread_info *th = inferior_target_data (current_inferior);
  return th->tid;
}

/* Find a thread record given a thread id.  If GET_CONTEXT is set then
   also retrieve the context for this thread.  */
static win32_thread_info *
thread_rec (DWORD id, int get_context)
{
  struct thread_info *thread;
  win32_thread_info *th;

  thread = (struct thread_info *) find_inferior_id (&all_threads, id);
  if (thread == NULL)
    return NULL;

  th = inferior_target_data (thread);
  if (!th->suspend_count && get_context)
    {
      if (id != current_event.dwThreadId)
	th->suspend_count = SuspendThread (th->h) + 1;

      (*the_low_target.get_thread_context) (th, &current_event);
    }

  return th;
}

/* Add a thread to the thread list.  */
static win32_thread_info *
child_add_thread (DWORD tid, HANDLE h)
{
  win32_thread_info *th;

  if ((th = thread_rec (tid, FALSE)))
    return th;

  th = (win32_thread_info *) malloc (sizeof (*th));
  memset (th, 0, sizeof (*th));
  th->tid = tid;
  th->h = h;

  add_thread (tid, th, (unsigned int) tid);
  set_inferior_regcache_data ((struct thread_info *)
			      find_inferior_id (&all_threads, tid),
			      new_register_cache ());

  if (the_low_target.thread_added != NULL)
    (*the_low_target.thread_added) (th);

  return th;
}

/* Delete a thread from the list of threads.  */
static void
delete_thread_info (struct inferior_list_entry *thread)
{
  win32_thread_info *th = inferior_target_data ((struct thread_info *) thread);

  remove_thread ((struct thread_info *) thread);
  CloseHandle (th->h);
  free (th);
}

/* Delete a thread from the list of threads.  */
static void
child_delete_thread (DWORD id)
{
  struct inferior_list_entry *thread;

  /* If the last thread is exiting, just return.  */
  if (all_threads.head == all_threads.tail)
    return;

  thread = find_inferior_id (&all_threads, id);
  if (thread == NULL)
    return;

  delete_thread_info (thread);
}

/* Transfer memory from/to the debugged process.  */
static int
child_xfer_memory (CORE_ADDR memaddr, char *our, int len,
		   int write, struct target_ops *target)
{
  SIZE_T done;
  long addr = (long) memaddr;

  if (write)
    {
      WriteProcessMemory (current_process_handle, (LPVOID) addr,
			  (LPCVOID) our, len, &done);
      FlushInstructionCache (current_process_handle, (LPCVOID) addr, len);
    }
  else
    {
      ReadProcessMemory (current_process_handle, (LPCVOID) addr, (LPVOID) our,
			 len, &done);
    }
  return done;
}

/* Generally, what has the program done?  */
enum target_waitkind
{
  /* The program has exited.  The exit status is in value.integer.  */
  TARGET_WAITKIND_EXITED,

  /* The program has stopped with a signal.  Which signal is in
     value.sig.  */
  TARGET_WAITKIND_STOPPED,

  /* The program is letting us know that it dynamically loaded
     or unloaded something.  */
  TARGET_WAITKIND_LOADED,

  /* The program has exec'ed a new executable file.  The new file's
     pathname is pointed to by value.execd_pathname.  */
  TARGET_WAITKIND_EXECD,

  /* Nothing interesting happened, but we stopped anyway.  We take the
     chance to check if GDB requested an interrupt.  */
  TARGET_WAITKIND_SPURIOUS,
};

struct target_waitstatus
{
  enum target_waitkind kind;

  /* Forked child pid, execd pathname, exit status or signal number.  */
  union
  {
    int integer;
    enum target_signal sig;
    int related_pid;
    char *execd_pathname;
    int syscall_id;
  }
  value;
};

/* Clear out any old thread list and reinitialize it to a pristine
   state. */
static void
child_init_thread_list (void)
{
  for_each_inferior (&all_threads, delete_thread_info);
}

static void
do_initial_child_stuff (DWORD pid)
{
  last_sig = TARGET_SIGNAL_0;

  memset (&current_event, 0, sizeof (current_event));

  child_init_thread_list ();

  if (the_low_target.initial_stuff != NULL)
    (*the_low_target.initial_stuff) ();
}

/* Resume all artificially suspended threads if we are continuing
   execution.  */
static int
continue_one_thread (struct inferior_list_entry *this_thread, void *id_ptr)
{
  struct thread_info *thread = (struct thread_info *) this_thread;
  int thread_id = * (int *) id_ptr;
  win32_thread_info *th = inferior_target_data (thread);
  int i;

  if ((thread_id == -1 || thread_id == th->tid)
      && th->suspend_count)
    {
      if (th->context.ContextFlags)
	{
	  (*the_low_target.set_thread_context) (th, &current_event);
	  th->context.ContextFlags = 0;
	}

      for (i = 0; i < th->suspend_count; i++)
	(void) ResumeThread (th->h);
      th->suspend_count = 0;
    }

  return 0;
}

static BOOL
child_continue (DWORD continue_status, int thread_id)
{
  BOOL res;

  res = ContinueDebugEvent (current_event.dwProcessId,
			    current_event.dwThreadId, continue_status);
  if (res)
    find_inferior (&all_threads, continue_one_thread, &thread_id);

  return res;
}

/* Fetch register(s) from the current thread context.  */
static void
child_fetch_inferior_registers (int r)
{
  int regno;
  win32_thread_info *th = thread_rec (current_inferior_tid (), TRUE);
  if (r == -1 || r == 0 || r > NUM_REGS)
    child_fetch_inferior_registers (NUM_REGS);
  else
    for (regno = 0; regno < r; regno++)
      (*the_low_target.fetch_inferior_register) (th, regno);
}

/* Store a new register value into the current thread context.  We don't
   change the program's context until later, when we resume it.  */
static void
child_store_inferior_registers (int r)
{
  int regno;
  win32_thread_info *th = thread_rec (current_inferior_tid (), TRUE);
  if (r == -1 || r == 0 || r > NUM_REGS)
    child_store_inferior_registers (NUM_REGS);
  else
    for (regno = 0; regno < r; regno++)
      (*the_low_target.store_inferior_register) (th, regno);
}

/* Map the Windows error number in ERROR to a locale-dependent error
   message string and return a pointer to it.  Typically, the values
   for ERROR come from GetLastError.

   The string pointed to shall not be modified by the application,
   but may be overwritten by a subsequent call to strwinerror

   The strwinerror function does not change the current setting
   of GetLastError.  */

char *
strwinerror (DWORD error)
{
  static char buf[1024];
  TCHAR *msgbuf;
  DWORD lasterr = GetLastError ();
  DWORD chars = FormatMessage (FORMAT_MESSAGE_FROM_SYSTEM
			       | FORMAT_MESSAGE_ALLOCATE_BUFFER,
			       NULL,
			       error,
			       0, /* Default language */
			       (LPVOID)&msgbuf,
			       0,
			       NULL);
  if (chars != 0)
    {
      /* If there is an \r\n appended, zap it.  */
      if (chars >= 2
	  && msgbuf[chars - 2] == '\r'
	  && msgbuf[chars - 1] == '\n')
	{
	  chars -= 2;
	  msgbuf[chars] = 0;
	}

      if (chars > ((COUNTOF (buf)) - 1))
	{
	  chars = COUNTOF (buf) - 1;
	  msgbuf [chars] = 0;
	}

#ifdef UNICODE
      wcstombs (buf, msgbuf, chars + 1);
#else
      strncpy (buf, msgbuf, chars + 1);
#endif
      LocalFree (msgbuf);
    }
  else
    sprintf (buf, "unknown win32 error (%ld)", error);

  SetLastError (lasterr);
  return buf;
}

static BOOL
create_process (const char *program, char *args,
		DWORD flags, PROCESS_INFORMATION *pi)
{
  BOOL ret;

#ifdef _WIN32_WCE
  wchar_t *p, *wprogram, *wargs;
  size_t argslen;

  wprogram = alloca ((strlen (program) + 1) * sizeof (wchar_t));
  mbstowcs (wprogram, program, strlen (program) + 1);

  for (p = wprogram; *p; ++p)
    if (L'/' == *p)
      *p = L'\\';

  argslen = strlen (args);
  wargs = alloca ((argslen + 1) * sizeof (wchar_t));
  mbstowcs (wargs, args, argslen + 1);

  ret = CreateProcessW (wprogram, /* image name */
                        wargs,    /* command line */
                        NULL,     /* security, not supported */
                        NULL,     /* thread, not supported */
                        FALSE,    /* inherit handles, not supported */
                        flags,    /* start flags */
                        NULL,     /* environment, not supported */
                        NULL,     /* current directory, not supported */
                        NULL,     /* start info, not supported */
                        pi);      /* proc info */
#else
  STARTUPINFOA si = { sizeof (STARTUPINFOA) };

  ret = CreateProcessA (program,  /* image name */
			args,     /* command line */
			NULL,     /* security */
			NULL,     /* thread */
			TRUE,     /* inherit handles */
			flags,    /* start flags */
			NULL,     /* environment */
			NULL,     /* current directory */
			&si,      /* start info */
			pi);      /* proc info */
#endif

  return ret;
}

/* Start a new process.
   PROGRAM is a path to the program to execute.
   ARGS is a standard NULL-terminated array of arguments,
   to be passed to the inferior as ``argv''.
   Returns the new PID on success, -1 on failure.  Registers the new
   process with the process list.  */
static int
win32_create_inferior (char *program, char **program_args)
{
#ifndef USE_WIN32API
  char real_path[MAXPATHLEN];
  char *orig_path, *new_path, *path_ptr;
#endif
  BOOL ret;
  DWORD flags;
  char *args;
  int argslen;
  int argc;
  PROCESS_INFORMATION pi;
  DWORD err;

  if (!program)
    error ("No executable specified, specify executable to debug.\n");

  flags = DEBUG_PROCESS | DEBUG_ONLY_THIS_PROCESS;

#ifndef USE_WIN32API
  orig_path = NULL;
  path_ptr = getenv ("PATH");
  if (path_ptr)
    {
      orig_path = alloca (strlen (path_ptr) + 1);
      new_path = alloca (cygwin_posix_to_win32_path_list_buf_size (path_ptr));
      strcpy (orig_path, path_ptr);
      cygwin_posix_to_win32_path_list (path_ptr, new_path);
      setenv ("PATH", new_path, 1);
    }
  cygwin_conv_to_win32_path (program, real_path);
  program = real_path;
#endif

  argslen = 1;
  for (argc = 1; program_args[argc]; argc++)
    argslen += strlen (program_args[argc]) + 1;
  args = alloca (argslen);
  args[0] = '\0';
  for (argc = 1; program_args[argc]; argc++)
    {
      /* FIXME: Can we do better about quoting?  How does Cygwin
         handle this?  */
      strcat (args, " ");
      strcat (args, program_args[argc]);
    }
  OUTMSG2 (("Command line is \"%s\"\n", args));

#ifdef CREATE_NEW_PROCESS_GROUP
  flags |= CREATE_NEW_PROCESS_GROUP;
#endif

  ret = create_process (program, args, flags, &pi);
  err = GetLastError ();
  if (!ret && err == ERROR_FILE_NOT_FOUND)
    {
      char *exename = alloca (strlen (program) + 5);
      strcat (strcpy (exename, program), ".exe");
      ret = create_process (exename, args, flags, &pi);
      err = GetLastError ();
    }

#ifndef USE_WIN32API
  if (orig_path)
    setenv ("PATH", orig_path, 1);
#endif

  if (!ret)
    {
      error ("Error creating process \"%s%s\", (error %d): %s\n",
	     program, args, (int) err, strwinerror (err));
    }
  else
    {
      OUTMSG2 (("Process created: %s\n", (char *) args));
    }

#ifndef _WIN32_WCE
  /* On Windows CE this handle can't be closed.  The OS reuses
     it in the debug events, while the 9x/NT versions of Windows
     probably use a DuplicateHandle'd one.  */
  CloseHandle (pi.hThread);
#endif

  current_process_handle = pi.hProcess;
  current_process_id = pi.dwProcessId;

  do_initial_child_stuff (current_process_id);

  return current_process_id;
}

/* Attach to a running process.
   PID is the process ID to attach to, specified by the user
   or a higher layer.  */
static int
win32_attach (unsigned long pid)
{
  winapi_DebugActiveProcessStop DebugActiveProcessStop = NULL;
  winapi_DebugSetProcessKillOnExit DebugSetProcessKillOnExit = NULL;
#ifdef _WIN32_WCE
  HMODULE dll = GetModuleHandle (_T("COREDLL.DLL"));
#else
  HMODULE dll = GetModuleHandle (_T("KERNEL32.DLL"));
#endif
  DebugActiveProcessStop = GETPROCADDRESS (dll, DebugActiveProcessStop);
  DebugSetProcessKillOnExit = GETPROCADDRESS (dll, DebugSetProcessKillOnExit);

  if (DebugActiveProcess (pid))
    {
      if (DebugSetProcessKillOnExit != NULL)
 	DebugSetProcessKillOnExit (FALSE);

      current_process_handle = OpenProcess (PROCESS_ALL_ACCESS, FALSE, pid);

      if (current_process_handle != NULL)
 	{
 	  current_process_id = pid;
 	  do_initial_child_stuff (pid);
 	  return 0;
 	}
      if (DebugActiveProcessStop != NULL)
	DebugActiveProcessStop (current_process_id);
    }

  error ("Attach to process failed.");
}

/* Handle OUTPUT_DEBUG_STRING_EVENT from child process.  */
static void
handle_output_debug_string (struct target_waitstatus *ourstatus)
{
#define READ_BUFFER_LEN 1024
  CORE_ADDR addr;
  char s[READ_BUFFER_LEN + 1] = { 0 };
  DWORD nbytes = current_event.u.DebugString.nDebugStringLength;

  if (nbytes == 0)
    return;

  if (nbytes > READ_BUFFER_LEN)
    nbytes = READ_BUFFER_LEN;

  addr = (CORE_ADDR) (size_t) current_event.u.DebugString.lpDebugStringData;

  if (current_event.u.DebugString.fUnicode)
    {
      /* The event tells us how many bytes, not chars, even
         in Unicode.  */
      WCHAR buffer[(READ_BUFFER_LEN + 1) / sizeof (WCHAR)] = { 0 };
      if (read_inferior_memory (addr, (unsigned char *) buffer, nbytes) != 0)
	return;
      wcstombs (s, buffer, (nbytes + 1) / sizeof (WCHAR));
    }
  else
    {
      if (read_inferior_memory (addr, (unsigned char *) s, nbytes) != 0)
	return;
    }

  if (strncmp (s, "cYg", 3) != 0)
    {
      if (!server_waiting)
	{
	  OUTMSG2(("%s", s));
	  return;
	}

      monitor_output (s);
    }
#undef READ_BUFFER_LEN
}

/* Kill all inferiors.  */
static void
win32_kill (void)
{
  win32_thread_info *current_thread;

  if (current_process_handle == NULL)
    return;

  TerminateProcess (current_process_handle, 0);
  for (;;)
    {
      if (!child_continue (DBG_CONTINUE, -1))
	break;
      if (!WaitForDebugEvent (&current_event, INFINITE))
	break;
      if (current_event.dwDebugEventCode == EXIT_PROCESS_DEBUG_EVENT)
	break;
      else if (current_event.dwDebugEventCode == OUTPUT_DEBUG_STRING_EVENT)
	{
  	  struct target_waitstatus our_status = { 0 };
	  handle_output_debug_string (&our_status);
  	}
    }

  CloseHandle (current_process_handle);

  current_thread = inferior_target_data (current_inferior);
  if (current_thread && current_thread->h)
    {
      /* This may fail in an attached process, so don't check.  */
      (void) CloseHandle (current_thread->h);
    }
}

/* Detach from all inferiors.  */
static int
win32_detach (void)
{
  HANDLE h;

  winapi_DebugActiveProcessStop DebugActiveProcessStop = NULL;
  winapi_DebugSetProcessKillOnExit DebugSetProcessKillOnExit = NULL;
#ifdef _WIN32_WCE
  HMODULE dll = GetModuleHandle (_T("COREDLL.DLL"));
#else
  HMODULE dll = GetModuleHandle (_T("KERNEL32.DLL"));
#endif
  DebugActiveProcessStop = GETPROCADDRESS (dll, DebugActiveProcessStop);
  DebugSetProcessKillOnExit = GETPROCADDRESS (dll, DebugSetProcessKillOnExit);

  if (DebugSetProcessKillOnExit == NULL
      || DebugActiveProcessStop == NULL)
    return -1;

  /* We need a new handle, since DebugActiveProcessStop
     closes all the ones that came through the events.  */
  if ((h = OpenProcess (PROCESS_ALL_ACCESS,
			FALSE,
			current_process_id)) == NULL)
    {
      /* The process died.  */
      return -1;
    }

  {
    struct thread_resume resume;
    resume.thread = -1;
    resume.step = 0;
    resume.sig = 0;
    resume.leave_stopped = 0;
    win32_resume (&resume);
  }

  if (!DebugActiveProcessStop (current_process_id))
    {
      CloseHandle (h);
      return -1;
    }
  DebugSetProcessKillOnExit (FALSE);

  current_process_handle = h;
  return 0;
}

/* Wait for inferiors to end.  */
static void
win32_join (void)
{
  if (current_process_id == 0
      || current_process_handle == NULL)
    return;

  WaitForSingleObject (current_process_handle, INFINITE);
  CloseHandle (current_process_handle);

  current_process_handle = NULL;
  current_process_id = 0;
}

/* Return 1 iff the thread with thread ID TID is alive.  */
static int
win32_thread_alive (unsigned long tid)
{
  int res;

  /* Our thread list is reliable; don't bother to poll target
     threads.  */
  if (find_inferior_id (&all_threads, tid) != NULL)
    res = 1;
  else
    res = 0;
  return res;
}

/* Resume the inferior process.  RESUME_INFO describes how we want
   to resume.  */
static void
win32_resume (struct thread_resume *resume_info)
{
  DWORD tid;
  enum target_signal sig;
  int step;
  win32_thread_info *th;
  DWORD continue_status = DBG_CONTINUE;

  /* This handles the very limited set of resume packets that GDB can
     currently produce.  */

  if (resume_info[0].thread == -1)
    tid = -1;
  else if (resume_info[1].thread == -1 && !resume_info[1].leave_stopped)
    tid = -1;
  else
    /* Yes, we're ignoring resume_info[0].thread.  It'd be tricky to make
       the Windows resume code do the right thing for thread switching.  */
    tid = current_event.dwThreadId;

  if (resume_info[0].thread != -1)
    {
      sig = resume_info[0].sig;
      step = resume_info[0].step;
    }
  else
    {
      sig = 0;
      step = 0;
    }

  if (sig != TARGET_SIGNAL_0)
    {
      if (current_event.dwDebugEventCode != EXCEPTION_DEBUG_EVENT)
	{
	  OUTMSG (("Cannot continue with signal %d here.\n", sig));
	}
      else if (sig == last_sig)
	continue_status = DBG_EXCEPTION_NOT_HANDLED;
      else
	OUTMSG (("Can only continue with recieved signal %d.\n", last_sig));
    }

  last_sig = TARGET_SIGNAL_0;

  /* Get context for the currently selected thread.  */
  th = thread_rec (current_event.dwThreadId, FALSE);
  if (th)
    {
      if (th->context.ContextFlags)
	{
	  /* Move register values from the inferior into the thread
	     context structure.  */
	  regcache_invalidate ();

	  if (step)
	    {
	      if (the_low_target.single_step != NULL)
		(*the_low_target.single_step) (th);
	      else
		error ("Single stepping is not supported "
		       "in this configuration.\n");
	    }

	  (*the_low_target.set_thread_context) (th, &current_event);
	  th->context.ContextFlags = 0;
	}
    }

  /* Allow continuing with the same signal that interrupted us.
     Otherwise complain.  */

  child_continue (continue_status, tid);
}

static void
win32_add_one_solib (const char *name, CORE_ADDR load_addr)
{
  char buf[MAX_PATH + 1];
  char buf2[MAX_PATH + 1];

#ifdef _WIN32_WCE
  WIN32_FIND_DATA w32_fd;
  WCHAR wname[MAX_PATH + 1];
  mbstowcs (wname, name, MAX_PATH);
  HANDLE h = FindFirstFile (wname, &w32_fd);
#else
  WIN32_FIND_DATAA w32_fd;
  HANDLE h = FindFirstFileA (name, &w32_fd);
#endif

  if (h == INVALID_HANDLE_VALUE)
    strcpy (buf, name);
  else
    {
      FindClose (h);
      strcpy (buf, name);
#ifndef _WIN32_WCE
      {
	char cwd[MAX_PATH + 1];
	char *p;
	if (GetCurrentDirectoryA (MAX_PATH + 1, cwd))
	  {
	    p = strrchr (buf, '\\');
	    if (p)
	      p[1] = '\0';
	    SetCurrentDirectoryA (buf);
	    GetFullPathNameA (w32_fd.cFileName, MAX_PATH, buf, &p);
	    SetCurrentDirectoryA (cwd);
	  }
      }
#endif
    }

#ifdef __CYGWIN__
  cygwin_conv_to_posix_path (buf, buf2);
#else
  strcpy (buf2, buf);
#endif

  loaded_dll (buf2, load_addr);
}

static char *
get_image_name (HANDLE h, void *address, int unicode)
{
  static char buf[(2 * MAX_PATH) + 1];
  DWORD size = unicode ? sizeof (WCHAR) : sizeof (char);
  char *address_ptr;
  int len = 0;
  char b[2];
  DWORD done;

  /* Attempt to read the name of the dll that was detected.
     This is documented to work only when actively debugging
     a program.  It will not work for attached processes. */
  if (address == NULL)
    return NULL;

#ifdef _WIN32_WCE
  /* Windows CE reports the address of the image name,
     instead of an address of a pointer into the image name.  */
  address_ptr = address;
#else
  /* See if we could read the address of a string, and that the
     address isn't null. */
  if (!ReadProcessMemory (h, address,  &address_ptr,
			  sizeof (address_ptr), &done)
      || done != sizeof (address_ptr)
      || !address_ptr)
    return NULL;
#endif

  /* Find the length of the string */
  while (ReadProcessMemory (h, address_ptr + len++ * size, &b, size, &done)
	 && (b[0] != 0 || b[size - 1] != 0) && done == size)
    continue;

  if (!unicode)
    ReadProcessMemory (h, address_ptr, buf, len, &done);
  else
    {
      WCHAR *unicode_address = (WCHAR *) alloca (len * sizeof (WCHAR));
      ReadProcessMemory (h, address_ptr, unicode_address, len * sizeof (WCHAR),
			 &done);

      WideCharToMultiByte (CP_ACP, 0, unicode_address, len, buf, len, 0, 0);
    }

  return buf;
}

typedef BOOL (WINAPI *winapi_EnumProcessModules) (HANDLE, HMODULE *,
						  DWORD, LPDWORD);
typedef BOOL (WINAPI *winapi_GetModuleInformation) (HANDLE, HMODULE,
						    LPMODULEINFO, DWORD);
typedef DWORD (WINAPI *winapi_GetModuleFileNameExA) (HANDLE, HMODULE,
						     LPSTR, DWORD);

static winapi_EnumProcessModules win32_EnumProcessModules;
static winapi_GetModuleInformation win32_GetModuleInformation;
static winapi_GetModuleFileNameExA win32_GetModuleFileNameExA;

static BOOL
load_psapi (void)
{
  static int psapi_loaded = 0;
  static HMODULE dll = NULL;

  if (!psapi_loaded)
    {
      psapi_loaded = 1;
      dll = LoadLibrary (TEXT("psapi.dll"));
      if (!dll)
	return FALSE;
      win32_EnumProcessModules =
	      GETPROCADDRESS (dll, EnumProcessModules);
      win32_GetModuleInformation =
	      GETPROCADDRESS (dll, GetModuleInformation);
      win32_GetModuleFileNameExA =
	      GETPROCADDRESS (dll, GetModuleFileNameExA);
    }

  return (win32_EnumProcessModules != NULL
	  && win32_GetModuleInformation != NULL
	  && win32_GetModuleFileNameExA != NULL);
}

static int
psapi_get_dll_name (DWORD BaseAddress, char *dll_name_ret)
{
  DWORD len;
  MODULEINFO mi;
  size_t i;
  HMODULE dh_buf[1];
  HMODULE *DllHandle = dh_buf;
  DWORD cbNeeded;
  BOOL ok;

  if (!load_psapi ())
    goto failed;

  cbNeeded = 0;
  ok = (*win32_EnumProcessModules) (current_process_handle,
				    DllHandle,
				    sizeof (HMODULE),
				    &cbNeeded);

  if (!ok || !cbNeeded)
    goto failed;

  DllHandle = (HMODULE *) alloca (cbNeeded);
  if (!DllHandle)
    goto failed;

  ok = (*win32_EnumProcessModules) (current_process_handle,
				    DllHandle,
				    cbNeeded,
				    &cbNeeded);
  if (!ok)
    goto failed;

  for (i = 0; i < ((size_t) cbNeeded / sizeof (HMODULE)); i++)
    {
      if (!(*win32_GetModuleInformation) (current_process_handle,
					  DllHandle[i],
					  &mi,
					  sizeof (mi)))
	{
	  DWORD err = GetLastError ();
	  error ("Can't get module info: (error %d): %s\n",
		 (int) err, strwinerror (err));
	}

      if ((DWORD) (mi.lpBaseOfDll) == BaseAddress)
	{
	  len = (*win32_GetModuleFileNameExA) (current_process_handle,
					       DllHandle[i],
					       dll_name_ret,
					       MAX_PATH);
	  if (len == 0)
	    {
	      DWORD err = GetLastError ();
	      error ("Error getting dll name: (error %d): %s\n",
		     (int) err, strwinerror (err));
	    }
	  return 1;
	}
    }

failed:
  dll_name_ret[0] = '\0';
  return 0;
}

typedef HANDLE (WINAPI *winapi_CreateToolhelp32Snapshot) (DWORD, DWORD);
typedef BOOL (WINAPI *winapi_Module32First) (HANDLE, LPMODULEENTRY32);
typedef BOOL (WINAPI *winapi_Module32Next) (HANDLE, LPMODULEENTRY32);

static winapi_CreateToolhelp32Snapshot win32_CreateToolhelp32Snapshot;
static winapi_Module32First win32_Module32First;
static winapi_Module32Next win32_Module32Next;
#ifdef _WIN32_WCE
typedef BOOL (WINAPI *winapi_CloseToolhelp32Snapshot) (HANDLE);
static winapi_CloseToolhelp32Snapshot win32_CloseToolhelp32Snapshot;
#endif

static BOOL
load_toolhelp (void)
{
  static int toolhelp_loaded = 0;
  static HMODULE dll = NULL;

  if (!toolhelp_loaded)
    {
      toolhelp_loaded = 1;
#ifndef _WIN32_WCE
      dll = GetModuleHandle (_T("KERNEL32.DLL"));
#else
      dll = LoadLibrary (L"TOOLHELP.DLL");
#endif
      if (!dll)
	return FALSE;

      win32_CreateToolhelp32Snapshot =
	GETPROCADDRESS (dll, CreateToolhelp32Snapshot);
      win32_Module32First = GETPROCADDRESS (dll, Module32First);
      win32_Module32Next = GETPROCADDRESS (dll, Module32Next);
#ifdef _WIN32_WCE
      win32_CloseToolhelp32Snapshot =
	GETPROCADDRESS (dll, CloseToolhelp32Snapshot);
#endif
    }

  return (win32_CreateToolhelp32Snapshot != NULL
	  && win32_Module32First != NULL
	  && win32_Module32Next != NULL
#ifdef _WIN32_WCE
	  && win32_CloseToolhelp32Snapshot != NULL
#endif
	  );
}

static int
toolhelp_get_dll_name (DWORD BaseAddress, char *dll_name_ret)
{
  HANDLE snapshot_module;
  MODULEENTRY32 modEntry = { sizeof (MODULEENTRY32) };
  int found = 0;

  if (!load_toolhelp ())
    return 0;

  snapshot_module = win32_CreateToolhelp32Snapshot (TH32CS_SNAPMODULE,
						    current_event.dwProcessId);
  if (snapshot_module == INVALID_HANDLE_VALUE)
    return 0;

  /* Ignore the first module, which is the exe.  */
  if (win32_Module32First (snapshot_module, &modEntry))
    while (win32_Module32Next (snapshot_module, &modEntry))
      if ((DWORD) modEntry.modBaseAddr == BaseAddress)
	{
#ifdef UNICODE
	  wcstombs (dll_name_ret, modEntry.szExePath, MAX_PATH + 1);
#else
	  strcpy (dll_name_ret, modEntry.szExePath);
#endif
	  found = 1;
	  break;
	}

#ifdef _WIN32_WCE
  win32_CloseToolhelp32Snapshot (snapshot_module);
#else
  CloseHandle (snapshot_module);
#endif
  return found;
}

static void
handle_load_dll (void)
{
  LOAD_DLL_DEBUG_INFO *event = &current_event.u.LoadDll;
  char dll_buf[MAX_PATH + 1];
  char *dll_name = NULL;
  DWORD load_addr;

  dll_buf[0] = dll_buf[sizeof (dll_buf) - 1] = '\0';

  /* Windows does not report the image name of the dlls in the debug
     event on attaches.  We resort to iterating over the list of
     loaded dlls looking for a match by image base.  */
  if (!psapi_get_dll_name ((DWORD) event->lpBaseOfDll, dll_buf))
    {
      if (!server_waiting)
	/* On some versions of Windows and Windows CE, we can't create
	   toolhelp snapshots while the inferior is stopped in a
	   LOAD_DLL_DEBUG_EVENT due to a dll load, but we can while
	   Windows is reporting the already loaded dlls.  */
	toolhelp_get_dll_name ((DWORD) event->lpBaseOfDll, dll_buf);
    }

  dll_name = dll_buf;

  if (*dll_name == '\0')
    dll_name = get_image_name (current_process_handle,
			       event->lpImageName, event->fUnicode);
  if (!dll_name)
    return;

  /* The symbols in a dll are offset by 0x1000, which is the
     the offset from 0 of the first byte in an image - because
     of the file header and the section alignment. */

  load_addr = (DWORD) event->lpBaseOfDll + 0x1000;
  win32_add_one_solib (dll_name, load_addr);
}

static void
handle_unload_dll (void)
{
  CORE_ADDR load_addr =
	  (CORE_ADDR) (DWORD) current_event.u.UnloadDll.lpBaseOfDll;
  load_addr += 0x1000;
  unloaded_dll (NULL, load_addr);
}

static void
handle_exception (struct target_waitstatus *ourstatus)
{
  DWORD code = current_event.u.Exception.ExceptionRecord.ExceptionCode;

  ourstatus->kind = TARGET_WAITKIND_STOPPED;

  switch (code)
    {
    case EXCEPTION_ACCESS_VIOLATION:
      OUTMSG2 (("EXCEPTION_ACCESS_VIOLATION"));
      ourstatus->value.sig = TARGET_SIGNAL_SEGV;
      break;
    case STATUS_STACK_OVERFLOW:
      OUTMSG2 (("STATUS_STACK_OVERFLOW"));
      ourstatus->value.sig = TARGET_SIGNAL_SEGV;
      break;
    case STATUS_FLOAT_DENORMAL_OPERAND:
      OUTMSG2 (("STATUS_FLOAT_DENORMAL_OPERAND"));
      ourstatus->value.sig = TARGET_SIGNAL_FPE;
      break;
    case EXCEPTION_ARRAY_BOUNDS_EXCEEDED:
      OUTMSG2 (("EXCEPTION_ARRAY_BOUNDS_EXCEEDED"));
      ourstatus->value.sig = TARGET_SIGNAL_FPE;
      break;
    case STATUS_FLOAT_INEXACT_RESULT:
      OUTMSG2 (("STATUS_FLOAT_INEXACT_RESULT"));
      ourstatus->value.sig = TARGET_SIGNAL_FPE;
      break;
    case STATUS_FLOAT_INVALID_OPERATION:
      OUTMSG2 (("STATUS_FLOAT_INVALID_OPERATION"));
      ourstatus->value.sig = TARGET_SIGNAL_FPE;
      break;
    case STATUS_FLOAT_OVERFLOW:
      OUTMSG2 (("STATUS_FLOAT_OVERFLOW"));
      ourstatus->value.sig = TARGET_SIGNAL_FPE;
      break;
    case STATUS_FLOAT_STACK_CHECK:
      OUTMSG2 (("STATUS_FLOAT_STACK_CHECK"));
      ourstatus->value.sig = TARGET_SIGNAL_FPE;
      break;
    case STATUS_FLOAT_UNDERFLOW:
      OUTMSG2 (("STATUS_FLOAT_UNDERFLOW"));
      ourstatus->value.sig = TARGET_SIGNAL_FPE;
      break;
    case STATUS_FLOAT_DIVIDE_BY_ZERO:
      OUTMSG2 (("STATUS_FLOAT_DIVIDE_BY_ZERO"));
      ourstatus->value.sig = TARGET_SIGNAL_FPE;
      break;
    case STATUS_INTEGER_DIVIDE_BY_ZERO:
      OUTMSG2 (("STATUS_INTEGER_DIVIDE_BY_ZERO"));
      ourstatus->value.sig = TARGET_SIGNAL_FPE;
      break;
    case STATUS_INTEGER_OVERFLOW:
      OUTMSG2 (("STATUS_INTEGER_OVERFLOW"));
      ourstatus->value.sig = TARGET_SIGNAL_FPE;
      break;
    case EXCEPTION_BREAKPOINT:
      OUTMSG2 (("EXCEPTION_BREAKPOINT"));
      ourstatus->value.sig = TARGET_SIGNAL_TRAP;
#ifdef _WIN32_WCE
      /* Remove the initial breakpoint.  */
      check_breakpoints ((CORE_ADDR) (long) current_event
                         .u.Exception.ExceptionRecord.ExceptionAddress);
#endif
      break;
    case DBG_CONTROL_C:
      OUTMSG2 (("DBG_CONTROL_C"));
      ourstatus->value.sig = TARGET_SIGNAL_INT;
      break;
    case DBG_CONTROL_BREAK:
      OUTMSG2 (("DBG_CONTROL_BREAK"));
      ourstatus->value.sig = TARGET_SIGNAL_INT;
      break;
    case EXCEPTION_SINGLE_STEP:
      OUTMSG2 (("EXCEPTION_SINGLE_STEP"));
      ourstatus->value.sig = TARGET_SIGNAL_TRAP;
      break;
    case EXCEPTION_ILLEGAL_INSTRUCTION:
      OUTMSG2 (("EXCEPTION_ILLEGAL_INSTRUCTION"));
      ourstatus->value.sig = TARGET_SIGNAL_ILL;
      break;
    case EXCEPTION_PRIV_INSTRUCTION:
      OUTMSG2 (("EXCEPTION_PRIV_INSTRUCTION"));
      ourstatus->value.sig = TARGET_SIGNAL_ILL;
      break;
    case EXCEPTION_NONCONTINUABLE_EXCEPTION:
      OUTMSG2 (("EXCEPTION_NONCONTINUABLE_EXCEPTION"));
      ourstatus->value.sig = TARGET_SIGNAL_ILL;
      break;
    default:
      if (current_event.u.Exception.dwFirstChance)
	{
	  ourstatus->kind = TARGET_WAITKIND_SPURIOUS;
	  return;
	}
      OUTMSG2 (("gdbserver: unknown target exception 0x%08lx at 0x%08lx",
		current_event.u.Exception.ExceptionRecord.ExceptionCode,
		(DWORD) current_event.u.Exception.ExceptionRecord.
		ExceptionAddress));
      ourstatus->value.sig = TARGET_SIGNAL_UNKNOWN;
      break;
    }
  OUTMSG2 (("\n"));
  last_sig = ourstatus->value.sig;
}

/* Get the next event from the child.  */
static void
get_child_debug_event (struct target_waitstatus *ourstatus)
{
  BOOL debug_event;

  last_sig = TARGET_SIGNAL_0;
  ourstatus->kind = TARGET_WAITKIND_SPURIOUS;

  /* Keep the wait time low enough for confortable remote interruption,
     but high enough so gdbserver doesn't become a bottleneck.  */
  if (!(debug_event = WaitForDebugEvent (&current_event, 250)))
    return;

  current_inferior =
    (struct thread_info *) find_inferior_id (&all_threads,
					     current_event.dwThreadId);

  switch (current_event.dwDebugEventCode)
    {
    case CREATE_THREAD_DEBUG_EVENT:
      OUTMSG2 (("gdbserver: kernel event CREATE_THREAD_DEBUG_EVENT "
		"for pid=%d tid=%x)\n",
		(unsigned) current_event.dwProcessId,
		(unsigned) current_event.dwThreadId));

      /* Record the existence of this thread.  */
      child_add_thread (current_event.dwThreadId,
			     current_event.u.CreateThread.hThread);
      break;

    case EXIT_THREAD_DEBUG_EVENT:
      OUTMSG2 (("gdbserver: kernel event EXIT_THREAD_DEBUG_EVENT "
		"for pid=%d tid=%x\n",
		(unsigned) current_event.dwProcessId,
		(unsigned) current_event.dwThreadId));
      child_delete_thread (current_event.dwThreadId);
      break;

    case CREATE_PROCESS_DEBUG_EVENT:
      OUTMSG2 (("gdbserver: kernel event CREATE_PROCESS_DEBUG_EVENT "
		"for pid=%d tid=%x\n",
		(unsigned) current_event.dwProcessId,
		(unsigned) current_event.dwThreadId));
      CloseHandle (current_event.u.CreateProcessInfo.hFile);

      current_process_handle = current_event.u.CreateProcessInfo.hProcess;
      main_thread_id = current_event.dwThreadId;

      ourstatus->kind = TARGET_WAITKIND_EXECD;
      ourstatus->value.execd_pathname = "Main executable";

      /* Add the main thread.  */
      child_add_thread (main_thread_id,
			current_event.u.CreateProcessInfo.hThread);

      ourstatus->value.related_pid = current_event.dwThreadId;
#ifdef _WIN32_WCE
      /* Windows CE doesn't set the initial breakpoint automatically
	 like the desktop versions of Windows do.  We add it explicitly
	 here.  It will be removed as soon as it is hit.  */
      set_breakpoint_at ((CORE_ADDR) (long) current_event.u
			 .CreateProcessInfo.lpStartAddress,
			 delete_breakpoint_at);
#endif
      break;

    case EXIT_PROCESS_DEBUG_EVENT:
      OUTMSG2 (("gdbserver: kernel event EXIT_PROCESS_DEBUG_EVENT "
		"for pid=%d tid=%x\n",
		(unsigned) current_event.dwProcessId,
		(unsigned) current_event.dwThreadId));
      ourstatus->kind = TARGET_WAITKIND_EXITED;
      ourstatus->value.integer = current_event.u.ExitProcess.dwExitCode;
      CloseHandle (current_process_handle);
      current_process_handle = NULL;
      break;

    case LOAD_DLL_DEBUG_EVENT:
      OUTMSG2 (("gdbserver: kernel event LOAD_DLL_DEBUG_EVENT "
		"for pid=%d tid=%x\n",
		(unsigned) current_event.dwProcessId,
		(unsigned) current_event.dwThreadId));
      CloseHandle (current_event.u.LoadDll.hFile);
      handle_load_dll ();

      ourstatus->kind = TARGET_WAITKIND_LOADED;
      ourstatus->value.sig = TARGET_SIGNAL_TRAP;
      break;

    case UNLOAD_DLL_DEBUG_EVENT:
      OUTMSG2 (("gdbserver: kernel event UNLOAD_DLL_DEBUG_EVENT "
		"for pid=%d tid=%x\n",
		(unsigned) current_event.dwProcessId,
		(unsigned) current_event.dwThreadId));
      handle_unload_dll ();
      ourstatus->kind = TARGET_WAITKIND_LOADED;
      ourstatus->value.sig = TARGET_SIGNAL_TRAP;
      break;

    case EXCEPTION_DEBUG_EVENT:
      OUTMSG2 (("gdbserver: kernel event EXCEPTION_DEBUG_EVENT "
		"for pid=%d tid=%x\n",
		(unsigned) current_event.dwProcessId,
		(unsigned) current_event.dwThreadId));
      handle_exception (ourstatus);
      break;

    case OUTPUT_DEBUG_STRING_EVENT:
      /* A message from the kernel (or Cygwin).  */
      OUTMSG2 (("gdbserver: kernel event OUTPUT_DEBUG_STRING_EVENT "
		"for pid=%d tid=%x\n",
		(unsigned) current_event.dwProcessId,
		(unsigned) current_event.dwThreadId));
      handle_output_debug_string (ourstatus);
      break;

    default:
      OUTMSG2 (("gdbserver: kernel event unknown "
		"for pid=%d tid=%x code=%ld\n",
		(unsigned) current_event.dwProcessId,
		(unsigned) current_event.dwThreadId,
		current_event.dwDebugEventCode));
      break;
    }

  current_inferior =
    (struct thread_info *) find_inferior_id (&all_threads,
					     current_event.dwThreadId);
}

/* Wait for the inferior process to change state.
   STATUS will be filled in with a response code to send to GDB.
   Returns the signal which caused the process to stop. */
static unsigned char
win32_wait (char *status)
{
  struct target_waitstatus our_status;

  *status = 'T';

  while (1)
    {
      /* Check if GDB sent us an interrupt request.  */
      check_remote_input_interrupt_request ();

      get_child_debug_event (&our_status);

      switch (our_status.kind)
	{
	case TARGET_WAITKIND_EXITED:
	  OUTMSG2 (("Child exited with retcode = %x\n",
		    our_status.value.integer));

	  *status = 'W';

	  child_fetch_inferior_registers (-1);

	  return our_status.value.integer;
	case TARGET_WAITKIND_STOPPED:
 	case TARGET_WAITKIND_LOADED:
	  OUTMSG2 (("Child Stopped with signal = %d \n",
		    our_status.value.sig));

	  *status = 'T';

	  child_fetch_inferior_registers (-1);

	  if (our_status.kind == TARGET_WAITKIND_LOADED
	      && !server_waiting)
	    {
	      /* When gdb connects, we want to be stopped at the
		 initial breakpoint, not in some dll load event.  */
	      child_continue (DBG_CONTINUE, -1);
	      break;
	    }

	  return our_status.value.sig;
 	default:
	  OUTMSG (("Ignoring unknown internal event, %d\n", our_status.kind));
 	  /* fall-through */
 	case TARGET_WAITKIND_SPURIOUS:
 	case TARGET_WAITKIND_EXECD:
	  /* do nothing, just continue */
	  child_continue (DBG_CONTINUE, -1);
	  break;
	}
    }
}

/* Fetch registers from the inferior process.
   If REGNO is -1, fetch all registers; otherwise, fetch at least REGNO.  */
static void
win32_fetch_inferior_registers (int regno)
{
  child_fetch_inferior_registers (regno);
}

/* Store registers to the inferior process.
   If REGNO is -1, store all registers; otherwise, store at least REGNO.  */
static void
win32_store_inferior_registers (int regno)
{
  child_store_inferior_registers (regno);
}

/* Read memory from the inferior process.  This should generally be
   called through read_inferior_memory, which handles breakpoint shadowing.
   Read LEN bytes at MEMADDR into a buffer at MYADDR.  */
static int
win32_read_inferior_memory (CORE_ADDR memaddr, unsigned char *myaddr, int len)
{
  return child_xfer_memory (memaddr, (char *) myaddr, len, 0, 0) != len;
}

/* Write memory to the inferior process.  This should generally be
   called through write_inferior_memory, which handles breakpoint shadowing.
   Write LEN bytes from the buffer at MYADDR to MEMADDR.
   Returns 0 on success and errno on failure.  */
static int
win32_write_inferior_memory (CORE_ADDR memaddr, const unsigned char *myaddr,
			     int len)
{
  return child_xfer_memory (memaddr, (char *) myaddr, len, 1, 0) != len;
}

/* Send an interrupt request to the inferior process. */
static void
win32_request_interrupt (void)
{
  winapi_DebugBreakProcess DebugBreakProcess;
  winapi_GenerateConsoleCtrlEvent GenerateConsoleCtrlEvent;

#ifdef _WIN32_WCE
  HMODULE dll = GetModuleHandle (_T("COREDLL.DLL"));
#else
  HMODULE dll = GetModuleHandle (_T("KERNEL32.DLL"));
#endif

  GenerateConsoleCtrlEvent = GETPROCADDRESS (dll, GenerateConsoleCtrlEvent);

  if (GenerateConsoleCtrlEvent != NULL
      && GenerateConsoleCtrlEvent (CTRL_BREAK_EVENT, current_process_id))
    return;

  /* GenerateConsoleCtrlEvent can fail if process id being debugged is
     not a process group id.
     Fallback to XP/Vista 'DebugBreakProcess', which generates a
     breakpoint exception in the interior process.  */

  DebugBreakProcess = GETPROCADDRESS (dll, DebugBreakProcess);

  if (DebugBreakProcess != NULL
      && DebugBreakProcess (current_process_handle))
    return;

  OUTMSG (("Could not interrupt process.\n"));
}

static const char *
win32_arch_string (void)
{
  return the_low_target.arch_string;
}

static struct target_ops win32_target_ops = {
  win32_create_inferior,
  win32_attach,
  win32_kill,
  win32_detach,
  win32_join,
  win32_thread_alive,
  win32_resume,
  win32_wait,
  win32_fetch_inferior_registers,
  win32_store_inferior_registers,
  win32_read_inferior_memory,
  win32_write_inferior_memory,
  NULL,
  win32_request_interrupt,
  NULL,
  NULL,
  NULL,
  NULL,
  NULL,
  NULL,
  NULL,
  win32_arch_string
};

/* Initialize the Win32 backend.  */
void
initialize_low (void)
{
  set_target_ops (&win32_target_ops);
  if (the_low_target.breakpoint != NULL)
    set_breakpoint_data (the_low_target.breakpoint,
			 the_low_target.breakpoint_len);
  init_registers ();
}