libc/winsup/cygwin/dlfcn.cc

/* dlfcn.cc

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 <wctype.h>
#include "path.h"
#include "fhandler.h"
#include "dtable.h"
#include "cygheap.h"
#include "perprocess.h"
#include "dlfcn.h"
#include "cygtls.h"
#include "tls_pbuf.h"
#include "ntdll.h"

static void
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 *
check_path_access (const char *mywinenv, const char *name, path_conv& buf)
{
  return find_exec (name, buf, mywinenv, FE_NNF | 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 (strchr (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
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'\\') ?: path;
	  if (last_bs && !wcschr (last_bs, L'.'))
	    wcscat (last_bs, L".");

#ifndef __x86_64__
	  /* 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;
#endif

	  if (flags & RTLD_NOLOAD)
	    GetModuleHandleExW (0, path, (HMODULE *) &ret);
	  else
	    ret = (void *) LoadLibraryW (path);
	  if (ret && (flags & RTLD_NODELETE))
	    GetModuleHandleExW (GET_MODULE_HANDLE_EX_FLAG_PIN, path,
				(HMODULE *) &ret);

#ifndef __x86_64__
	  /* Restore original cxx_malloc pointer. */
	  __cygwin_user_data.cxx_malloc = tmp_malloc;
#endif

	  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;
}