src/dynlib.c

   1 /* Portable API for dynamic loading.
   2
   3 Copyright 2015-2016 Free Software Foundation, Inc.
   4
   5 This file is part of GNU Emacs.
   6
   7 GNU Emacs is free software: you can redistribute it and/or modify
   8 it under the terms of the GNU General Public License as published by
   9 the Free Software Foundation, either version 3 of the License, or (at
  10 your option) any later version.
  11
  12 GNU Emacs is distributed in the hope that it will be useful,
  13 but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 GNU General Public License for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20
  21 /* Assume modules are enabled on modern systems...  *Yes*, the
  22    preprocessor macro checks could be more precise.  I don't care.
  23
  24    If you think the abstraction is too leaky use libltdl (libtool),
  25    don't reinvent the wheel by fixing this one.  */
  26
  27 #include <config.h>
  28
  29 #include "dynlib.h"
  30
  31 #ifdef WINDOWSNT
  32
  33 /* MS-Windows systems.  */
  34
  35 #include <errno.h>
  36 #include "lisp.h"
  37 #include "w32common.h"  /* for os_subtype */
  38 #include "w32.h"
  39
  40 static BOOL g_b_init_get_module_handle_ex;
  41 static DWORD dynlib_last_err;
  42
  43 /* Some versions of w32api headers only expose the following when
  44    _WIN32_WINNT is set to higher values that we use.  */
  45 typedef BOOL (WINAPI *GetModuleHandleExA_Proc) (DWORD,LPCSTR,HMODULE*);
  46 #ifndef GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS
  47 # define GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS 4
  48 #endif
  49 #ifndef GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT
  50 # define GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT 2
  51 #endif
  52
  53 /* This needs to be called at startup to countermand any non-zero
  54    values recorded by temacs.  */
  55 void
  56 dynlib_reset_last_error (void)
  57 {
  58   g_b_init_get_module_handle_ex = 0;
  59   dynlib_last_err = 0;
  60 }
  61
  62 dynlib_handle_ptr
  63 dynlib_open (const char *dll_fname)
  64 {
  65   HMODULE hdll;
  66   char dll_fname_local[MAX_UTF8_PATH];
  67
  68   if (!dll_fname)
  69     {
  70       errno = ENOTSUP;
  71       return NULL;
  72     }
  73
  74   if (!dll_fname)
  75     hdll = GetModuleHandle (NULL);
  76   else
  77     {
  78       /* LoadLibrary wants backslashes.  */
  79       strcpy (dll_fname_local, dll_fname);
  80       unixtodos_filename (dll_fname_local);
  81
  82       if (w32_unicode_filenames)
  83         {
  84           wchar_t dll_fname_w[MAX_PATH];
  85
  86           filename_to_utf16 (dll_fname_local, dll_fname_w);
  87           hdll = LoadLibraryW (dll_fname_w);
  88         }
  89       else
  90         {
  91           char dll_fname_a[MAX_PATH];
  92
  93           filename_to_ansi (dll_fname_local, dll_fname_a);
  94           hdll = LoadLibraryA (dll_fname_a);
  95         }
  96     }
  97
  98   if (!hdll)
  99     dynlib_last_err = GetLastError ();
 100
 101   return (dynlib_handle_ptr) hdll;
 102 }
 103
 104 void *
 105 dynlib_sym (dynlib_handle_ptr h, const char *sym)
 106 {
 107   FARPROC sym_addr = NULL;
 108
 109   if (!h || h == INVALID_HANDLE_VALUE || !sym)
 110     {
 111       dynlib_last_err = ERROR_INVALID_PARAMETER;
 112       return NULL;
 113     }
 114
 115   sym_addr = GetProcAddress ((HMODULE) h, sym);
 116   if (!sym_addr)
 117     dynlib_last_err = GetLastError ();
 118
 119   return (void *)sym_addr;
 120 }
 121
 122 bool
 123 dynlib_addr (void *addr, const char **fname, const char **symname)
 124 {
 125   static char dll_filename[MAX_UTF8_PATH];
 126   static char addr_str[22];
 127   static GetModuleHandleExA_Proc s_pfn_Get_Module_HandleExA = NULL;
 128   char *dll_fn = NULL;
 129   HMODULE hm_kernel32 = NULL;
 130   bool result = false;
 131   HMODULE hm_dll = NULL;
 132   wchar_t mfn_w[MAX_PATH];
 133   char mfn_a[MAX_PATH];
 134
 135   /* Step 1: Find the handle of the module where ADDR lives.  */
 136   if (os_subtype == OS_9X
 137       /* Windows NT family version before XP (v5.1).  */
 138       || ((w32_major_version + (w32_minor_version > 0)) < 6))
 139     {
 140       MEMORY_BASIC_INFORMATION mbi;
 141
 142       /* According to Matt Pietrek, the module handle is just the base
 143          address where it's loaded in memory.  */
 144       if (VirtualQuery (addr, &mbi, sizeof(mbi)))
 145         hm_dll = (HMODULE)mbi.AllocationBase;
 146     }
 147   else
 148     {
 149       /* Use the documented API when available (XP and later).  */
 150       if (g_b_init_get_module_handle_ex == 0)
 151         {
 152           g_b_init_get_module_handle_ex = 1;
 153           hm_kernel32 = LoadLibrary ("kernel32.dll");
 154           /* We load the ANSI version of the function because the
 155              address we pass to it is not an address of a string, but
 156              an address of a function.  So we don't care about the
 157              Unicode version.  */
 158           s_pfn_Get_Module_HandleExA =
 159             (GetModuleHandleExA_Proc) GetProcAddress (hm_kernel32,
 160                                                       "GetModuleHandleExA");
 161         }
 162       if (s_pfn_Get_Module_HandleExA)
 163         {
 164           DWORD flags = (GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS
 165                          /* We don't want to call FreeLibrary at the
 166                             end, because then we'd need to remember
 167                             whether we obtained the handle by this
 168                             method or the above one.  */
 169                          | GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT);
 170
 171           if (!s_pfn_Get_Module_HandleExA (flags, addr, &hm_dll))
 172             {
 173               dynlib_last_err = GetLastError ();
 174               hm_dll = NULL;
 175             }
 176         }
 177     }
 178
 179   /* Step 2: Find the absolute file name of the module corresponding
 180      to the hm_dll handle.  */
 181   if (hm_dll)
 182     {
 183       DWORD retval;
 184
 185       if (w32_unicode_filenames)
 186         {
 187           retval = GetModuleFileNameW (hm_dll, mfn_w, MAX_PATH);
 188           if (retval > 0 && retval < MAX_PATH
 189               && filename_from_utf16 (mfn_w, dll_filename) == 0)
 190             dll_fn = dll_filename;
 191           else if (retval == MAX_PATH)
 192             dynlib_last_err = ERROR_INSUFFICIENT_BUFFER;
 193           else
 194             dynlib_last_err = GetLastError ();
 195         }
 196       else
 197         {
 198           retval = GetModuleFileNameA (hm_dll, mfn_a, MAX_PATH);
 199           if (retval > 0 && retval < MAX_PATH
 200               && filename_from_ansi (mfn_a, dll_filename) == 0)
 201             dll_fn = dll_filename;
 202           else if (retval == MAX_PATH)
 203             dynlib_last_err = ERROR_INSUFFICIENT_BUFFER;
 204           else
 205             dynlib_last_err = GetLastError ();
 206         }
 207       if (dll_fn)
 208         {
 209           dostounix_filename (dll_fn);
 210           /* We cannot easily produce the function name, since
 211              typically all of the module functions will be unexported,
 212              and probably even static, which means the symbols can be
 213              obtained only if we link against libbfd (and the DLL can
 214              be stripped anyway).  So we just show the address and the
 215              file name; they can use that with addr2line or GDB to
 216              recover the symbolic name.  */
 217           sprintf (addr_str, "at 0x%x", (DWORD_PTR)addr);
 218           *symname = addr_str;
 219           result = true;
 220         }
 221     }
 222
 223   *fname = dll_fn;
 224   return result;
 225 }
 226
 227 const char *
 228 dynlib_error (void)
 229 {
 230   char *error_string = NULL;
 231
 232   if (dynlib_last_err)
 233     {
 234       error_string = w32_strerror (dynlib_last_err);
 235       dynlib_last_err = 0;
 236     }
 237
 238   return error_string;
 239 }
 240
 241 int
 242 dynlib_close (dynlib_handle_ptr h)
 243 {
 244   if (!h || h == INVALID_HANDLE_VALUE)
 245     {
 246       dynlib_last_err = ERROR_INVALID_PARAMETER;
 247       return -1;
 248     }
 249   /* If the handle is for the main module (the .exe file), it
 250      shouldn't be passed to FreeLibrary, because GetModuleHandle
 251      doesn't increment the refcount, but FreeLibrary does decrement
 252      it.  I don't think this should matter for the main module, but
 253      just in case, we avoid the call here, relying on another call to
 254      GetModuleHandle to return the same value.  */
 255   if (h == GetModuleHandle (NULL))
 256     return 0;
 257
 258   if (!FreeLibrary ((HMODULE) h))
 259     {
 260       dynlib_last_err = GetLastError ();
 261       return -1;
 262     }
 263
 264   return 0;
 265 }
 266
 267 #elif defined HAVE_UNISTD_H
 268
 269 /* POSIX systems.  */
 270
 271 #include <dlfcn.h>
 272
 273 dynlib_handle_ptr
 274 dynlib_open (const char *path)
 275 {
 276   return dlopen (path, RTLD_LAZY);
 277 }
 278
 279 void *
 280 dynlib_sym (dynlib_handle_ptr h, const char *sym)
 281 {
 282   return dlsym (h, sym);
 283 }
 284
 285 bool
 286 dynlib_addr (void *ptr, const char **path, const char **sym)
 287 {
 288 #ifdef HAVE_DLADDR
 289   Dl_info info;
 290   if (dladdr (ptr, &info) && info.dli_fname && info.dli_sname)
 291     {
 292       *path = info.dli_fname;
 293       *sym = info.dli_sname;
 294       return true;
 295     }
 296 #endif
 297   return false;
 298 }
 299
 300 const char *
 301 dynlib_error (void)
 302 {
 303   return dlerror ();
 304 }
 305
 306 /* FIXME: Currently there is no way to unload a module, so this
 307    function is never used.  */
 308 #if false
 309 int
 310 dynlib_close (dynlib_handle_ptr h)
 311 {
 312   return dlclose (h) == 0;
 313 }
 314 #endif
 315
 316 #else
 317
 318 #error "No dynamic loading for this system"
 319
 320 #endif
 321
 322 #if !HAVE_DLFUNC
 323 # define dlfunc dynlib_sym
 324 #endif
 325
 326 dynlib_function_ptr
 327 dynlib_func (dynlib_handle_ptr h, const char *sym)
 328 {
 329   return (dynlib_function_ptr) dlfunc (h, sym);
 330 }