libc/winsup/cygwin/dlfcn.cc

/* dlfcn.cc

   Copyright 1998, 2000, 2001, 2002, 2003, 2004, 2008, 2009, 2010,
   2011 Red Hat, Inc.

This file is part of Cygwin.

This software is a copyrighted work licensed under the terms of the
Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
details. */

#include "winsup.h"
#include <psapi.h>
#include <stdlib.h>
#include <ctype.h>
#include "path.h"
#include "perprocess.h"
#include "dlfcn.h"
#include "cygtls.h"
#include "tls_pbuf.h"
#include "ntdll.h"

static void __stdcall
set_dl_error (const char *str)
{
  strcpy (_my_tls.locals.dl_buffer, strerror (get_errno ()));
  _my_tls.locals.dl_error = 1;
}

/* Look for an executable file given the name and the environment
   variable to use for searching (eg., PATH); returns the full
   pathname (static buffer) if found or NULL if not. */
inline const char * __stdcall
check_path_access (const char *mywinenv, const char *name, path_conv& buf)
{
  return find_exec (name, buf, mywinenv, FE_NNF | FE_NATIVE | FE_CWD | FE_DLL);
}

/* Search LD_LIBRARY_PATH for dll, if it exists.  Search /usr/bin and /usr/lib
   by default.  Return valid full path in path_conv real_filename. */
static inline bool
gfpod_helper (const char *name, path_conv &real_filename)
{
  if (isabspath (name))
    real_filename.check (name, PC_SYM_FOLLOW | PC_NULLEMPTY);
  else if (!check_path_access ("LD_LIBRARY_PATH=", name, real_filename))
    check_path_access ("/usr/bin:/usr/lib", name, real_filename);
  if (!real_filename.exists ())
    real_filename.error = ENOENT;
  return !real_filename.error;
}

static bool __stdcall
get_full_path_of_dll (const char* str, path_conv &real_filename)
{
  int len = strlen (str);

  /* empty string? */
  if (len == 0)
    {
      set_errno (EINVAL);
      return false;		/* Yes.  Let caller deal with it. */
    }

  tmp_pathbuf tp;
  char *name = tp.c_get ();

  strcpy (name, str);	/* Put it somewhere where we can manipulate it. */

  char *basename = strrchr (name, '/');
  basename = basename ? basename + 1 : name;
  char *suffix = strrchr (name, '.');
  if (suffix && suffix < basename)
    suffix = NULL;

  /* Is suffix ".so"? */
  if (suffix && !strcmp (suffix, ".so"))
    {
      /* Does the file exist? */
      if (gfpod_helper (name, real_filename))
	return true;
      /* No, replace ".so" with ".dll". */
      strcpy (suffix, ".dll");
    }
  /* Does the filename start with "lib"? */
  if (!strncmp (basename, "lib", 3))
    {
      /* Yes, replace "lib" with "cyg". */
      strncpy (basename, "cyg", 3);
      /* Does the file exist? */
      if (gfpod_helper (name, real_filename))
	return true;
      /* No, revert back to "lib". */
      strncpy (basename, "lib", 3);
    }
  if (gfpod_helper (name, real_filename))
    return true;

  /* If nothing worked, create a relative path from the original incoming
     filename and let LoadLibrary search for it using the system default
     DLL search path. */
  real_filename.check (str, PC_SYM_FOLLOW | PC_NOFULL | PC_NULLEMPTY);
  if (!real_filename.error)
    return true;

  set_errno (real_filename.error);
  return false;
}

extern "C" void *
dlopen (const char *name, int flags)
{
  void *ret = NULL;

  if (name == NULL)
    {
      ret = (void *) GetModuleHandle (NULL); /* handle for the current module */
      if (!ret)
	__seterrno ();
    }
  else
    {
      /* handle for the named library */
      path_conv pc;
      if (get_full_path_of_dll (name, pc))
	{
	  tmp_pathbuf tp;
	  wchar_t *path = tp.w_get ();

	  pc.get_wide_win32_path (path);
	  /* Check if the last path component contains a dot.  If so,
	     leave the filename alone.  Otherwise add a trailing dot
	     to override LoadLibrary's automatic adding of a ".dll" suffix. */
	  wchar_t *last_bs = wcsrchr (path, L'\\');
	  if (last_bs && !wcschr (last_bs, L'.'))
	    wcscat (last_bs, L".");

	  /* Workaround for broken DLLs built against Cygwin versions 1.7.0-49
	     up to 1.7.0-57.  They override the cxx_malloc pointer in their
	     DLL initialization code even if loaded dynamically.  This is a
	     no-no since a later dlclose lets cxx_malloc point into nirvana.
	     The below kludge "fixes" that by reverting the original cxx_malloc
	     pointer after LoadLibrary.  This implies that their overrides
	     won't be applied; that's OK.  All overrides should be present at
	     final link time, as Windows doesn't allow undefined references;
	     it would actually be wrong for a dlopen'd DLL to opportunistically
	     override functions in a way that wasn't known then.  We're not
	     going to try and reproduce the full ELF dynamic loader here!  */

	  /* Store original cxx_malloc pointer. */
	  struct per_process_cxx_malloc *tmp_malloc;
	  tmp_malloc = __cygwin_user_data.cxx_malloc;

	  if (!(flags & RTLD_NOLOAD)
	      || (ret = GetModuleHandleW (path)) != NULL)
	    {
	      ret = (void *) LoadLibraryW (path);
	      if (ret && (flags & RTLD_NODELETE)
		  && !GetModuleHandleExW (GET_MODULE_HANDLE_EX_FLAG_PIN, path,
					  (HMODULE *) &ret))
		{
		  /* Windows 2000 is missing the GetModuleHandleEx call, so we
		     use a non-documented way to set the DLL to "don't free".
		     This is how it works:  Fetch the Windows Loader data from
		     the PEB.  Iterate backwards through the list of loaded
		     DLLs and compare the DllBase address with the address
		     returned by LoadLibrary.  If they are equal we found the
		     right entry.  Now set the LoadCount to -1, which is the
		     marker for a DLL which should never be free'd. */
		  PPEB_LDR_DATA ldr = NtCurrentTeb ()->Peb->Ldr;

		  for (PLDR_DATA_TABLE_ENTRY entry = (PLDR_DATA_TABLE_ENTRY)
					     ldr->InLoadOrderModuleList.Blink;
		       entry && entry->DllBase;
		       entry = (PLDR_DATA_TABLE_ENTRY)
			       entry->InLoadOrderLinks.Blink)
		    {
		      if (entry->DllBase == ret)
			{
			  entry->LoadCount = (WORD) -1;
			  break;
			}
		    }
		}
	    }

	  /* Restore original cxx_malloc pointer. */
	  __cygwin_user_data.cxx_malloc = tmp_malloc;

	  if (!ret)
	    __seterrno ();
	}
    }

  if (!ret)
    set_dl_error ("dlopen");
  debug_printf ("ret %p", ret);

  return ret;
}

extern "C" void *
dlsym (void *handle, const char *name)
{
  void *ret = NULL;

  if (handle == RTLD_DEFAULT)
    { /* search all modules */
      PDEBUG_BUFFER buf;
      NTSTATUS status;

      buf = RtlCreateQueryDebugBuffer (0, FALSE);
      if (!buf)
	{
	  set_errno (ENOMEM);
	  set_dl_error ("dlsym");
	  return NULL;
	}
      status = RtlQueryProcessDebugInformation (GetCurrentProcessId (),
						PDI_MODULES, buf);
      if (!NT_SUCCESS (status))
	__seterrno_from_nt_status (status);
      else
	{
	  PDEBUG_MODULE_ARRAY mods = (PDEBUG_MODULE_ARRAY)
				     buf->ModuleInformation;
	  for (ULONG i = 0; i < mods->Count; ++i)
	    if ((ret = (void *)
		       GetProcAddress ((HMODULE) mods->Modules[i].Base, name)))
	      break;
	  if (!ret)
	    set_errno (ENOENT);
	}
      RtlDestroyQueryDebugBuffer (buf);
    }
  else
    {
      ret = (void *) GetProcAddress ((HMODULE) handle, name);
      if (!ret)
	__seterrno ();
    }
  if (!ret)
    set_dl_error ("dlsym");
  debug_printf ("ret %p", ret);
  return ret;
}

extern "C" int
dlclose (void *handle)
{
  int ret;
  if (handle == GetModuleHandle (NULL))
    ret = 0;
  else if (FreeLibrary ((HMODULE) handle))
    ret = 0;
  else
    ret = -1;
  if (ret)
    set_dl_error ("dlclose");
  return ret;
}

extern "C" char *
dlerror ()
{
  char *res;
  if (!_my_tls.locals.dl_error)
    res = NULL;
  else
    {
      _my_tls.locals.dl_error = 0;
      res = _my_tls.locals.dl_buffer;
    }
  return res;
}