1 files changed, 129 insertions, 116 deletions

diff --git a/dlfcn.c b/dlfcn.c
index b356558..8d3c793 100644
--- a/dlfcn.c
+++ b/dlfcn.c
@@ -2,6 +2,7 @@
  * dlfcn-win32

  * Copyright (c) 2007 Ramiro Polla

  * Copyright (c) 2015 Tiancheng "Timothy" Gu

+ * Copyright (c) 2019 Pali Rohár <pali.rohar@gmail.com>

  *

  * dlfcn-win32 is free software; you can redistribute it and/or

  * modify it under the terms of the GNU Lesser General Public

@@ -29,6 +30,17 @@
 #include <stdio.h>

 #include <stdlib.h>

 

+#ifdef _MSC_VER

+/* https://docs.microsoft.com/en-us/cpp/intrinsics/returnaddress */

+#include <intrin.h>

+#pragma intrinsic(_ReturnAddress)

+#else

+/* https://gcc.gnu.org/onlinedocs/gcc/Return-Address.html */

+#ifndef _ReturnAddress

+#define _ReturnAddress() (__builtin_extract_return_addr(__builtin_return_address(0)))

+#endif

+#endif

+

 #ifdef SHARED

 #define DLFCN_WIN32_EXPORTS

 #endif

@@ -52,57 +64,48 @@
  * any kind of thread safety.

  */

 

-typedef struct global_object {

+typedef struct local_object {

     HMODULE hModule;

-    struct global_object *previous;

-    struct global_object *next;

-} global_object;

+    struct local_object *previous;

+    struct local_object *next;

+} local_object;

 

-static global_object first_object;

-static global_object first_automatic_object;

-static int auto_ref_count = 0;

+static local_object first_object;

 

-/* These functions implement a double linked list for the global objects. */

-static global_object *global_search( global_object *start, HMODULE hModule )

+/* These functions implement a double linked list for the local objects. */

+static local_object *local_search( HMODULE hModule )

 {

-    global_object *pobject;

+    local_object *pobject;

 

     if( hModule == NULL )

         return NULL;

 

-    for( pobject = start; pobject; pobject = pobject->next )

+    for( pobject = &first_object; pobject; pobject = pobject->next )

         if( pobject->hModule == hModule )

             return pobject;

 

     return NULL;

 }

 

-static void global_add( global_object *start, HMODULE hModule )

+static void local_add( HMODULE hModule )

 {

-    global_object *pobject;

-    global_object *nobject;

+    local_object *pobject;

+    local_object *nobject;

 

     if( hModule == NULL )

         return;

 

-    pobject = global_search( start, hModule );

+    pobject = local_search( hModule );

 

     /* Do not add object again if it's already on the list */

     if( pobject )

         return;

 

-    if( start == &first_automatic_object )

-    {

-        pobject = global_search( &first_object, hModule );

-        if( pobject )

-            return;

-    }

-

-    for( pobject = start; pobject->next; pobject = pobject->next );

+    for( pobject = &first_object; pobject->next; pobject = pobject->next );

 

-    nobject = (global_object*) malloc( sizeof( global_object ) );

+    nobject = (local_object*) malloc( sizeof( local_object ) );

 

-    /* Should this be enough to fail global_add, and therefore also fail

+    /* Should this be enough to fail local_add, and therefore also fail

      * dlopen?

      */

     if( !nobject )

@@ -114,14 +117,14 @@ static void global_add( global_object *start, HMODULE hModule )
     nobject->hModule = hModule;

 }

 

-static void global_rem( global_object *start, HMODULE hModule )

+static void local_rem( HMODULE hModule )

 {

-    global_object *pobject;

+    local_object *pobject;

 

     if( hModule == NULL )

         return;

 

-    pobject = global_search( start, hModule );

+    pobject = local_search( hModule );

 

     if( !pobject )

         return;

@@ -224,10 +227,6 @@ void *dlopen( const char *file, int mode )
 

     if( file == 0 )

     {

-        HMODULE hAddtnlMods[1024]; // Already loaded modules

-        HANDLE hCurrentProc = GetCurrentProcess( );

-        DWORD cbNeeded;

-

         /* POSIX says that if the value of file is 0, a handle on a global

          * symbol object must be provided. That object must be able to access

          * all symbols from the original program file, and any objects loaded

@@ -242,27 +241,13 @@ void *dlopen( const char *file, int mode )
 

         if( !hModule )

             save_err_ptr_str( file );

-

-

-        /* GetModuleHandle( NULL ) only returns the current program file. So

-         * if we want to get ALL loaded module including those in linked DLLs,

-         * we have to use EnumProcessModules( ).

-         */

-        if( EnumProcessModules( hCurrentProc, hAddtnlMods,

-            sizeof( hAddtnlMods ), &cbNeeded ) != 0 )

-        {

-            DWORD i;

-            for( i = 0; i < cbNeeded / sizeof( HMODULE ); i++ )

-            {

-                global_add( &first_automatic_object, hAddtnlMods[i] );

-            }

-        }

-        auto_ref_count++;

     }

     else

     {

+        HANDLE hCurrentProc;

+        DWORD dwProcModsBefore, dwProcModsAfter;

         CHAR lpFileName[MAX_PATH];

-        int i;

+        size_t i;

 

         /* MSDN says backslashes *must* be used instead of forward slashes. */

         for( i = 0 ; i < sizeof(lpFileName) - 1 ; i ++ )

@@ -276,6 +261,11 @@ void *dlopen( const char *file, int mode )
         }

         lpFileName[i] = '\0';

 

+        hCurrentProc = GetCurrentProcess( );

+

+        if( EnumProcessModules( hCurrentProc, NULL, 0, &dwProcModsBefore ) == 0 )

+            dwProcModsBefore = 0;

+

         /* POSIX says the search path is implementation-defined.

          * LOAD_WITH_ALTERED_SEARCH_PATH is used to make it behave more closely

          * to UNIX's search paths (start with system folders instead of current

@@ -284,17 +274,24 @@ void *dlopen( const char *file, int mode )
         hModule = LoadLibraryEx(lpFileName, NULL, 

                                 LOAD_WITH_ALTERED_SEARCH_PATH );

 

-        /* If the object was loaded with RTLD_GLOBAL, add it to list of global

-         * objects, so that its symbols may be retrieved even if the handle for

+        if( EnumProcessModules( hCurrentProc, NULL, 0, &dwProcModsAfter ) == 0 )

+            dwProcModsAfter = 0;

+

+        /* If the object was loaded with RTLD_LOCAL, add it to list of local

+         * objects, so that its symbols cannot be retrieved even if the handle for

          * the original program file is passed. POSIX says that if the same

          * file is specified in multiple invocations, and any of them are

          * RTLD_GLOBAL, even if any further invocations use RTLD_LOCAL, the

-         * symbols will remain global.

+         * symbols will remain global. If number of loaded modules was not

+         * changed after calling LoadLibraryEx(), it means that library was

+         * already loaded.

          */

         if( !hModule )

             save_err_str( lpFileName );

-        else if( (mode & RTLD_GLOBAL) )

-            global_add( &first_object, hModule );

+        else if( (mode & RTLD_LOCAL) && dwProcModsBefore != dwProcModsAfter )

+            local_add( hModule );

+        else if( !(mode & RTLD_LOCAL) && dwProcModsBefore == dwProcModsAfter )

+            local_rem( hModule );

     }

 

     /* Return to previous state of the error-mode bit flags. */

@@ -303,21 +300,6 @@ void *dlopen( const char *file, int mode )
     return (void *) hModule;

 }

 

-static void free_auto( )

-{

-    global_object *pobject = first_automatic_object.next;

-    if( pobject )

-    {

-        global_object *next;

-        for ( ; pobject; pobject = next )

-        {

-            next = pobject->next;

-            free( pobject );

-        }

-        first_automatic_object.next = NULL;

-    }

-}

-

 int dlclose( void *handle )

 {

     HMODULE hModule = (HMODULE) handle;

@@ -327,22 +309,11 @@ int dlclose( void *handle )
 

     ret = FreeLibrary( hModule );

 

-    /* If the object was loaded with RTLD_GLOBAL, remove it from list of global

+    /* If the object was loaded with RTLD_LOCAL, remove it from list of local

      * objects.

      */

     if( ret )

-    {

-        HMODULE cur = GetModuleHandle( NULL );

-        global_rem( &first_object, hModule );

-        if( hModule == cur )

-        {

-            auto_ref_count--;

-            if( auto_ref_count < 0 )

-                auto_ref_count = 0;

-            if( !auto_ref_count )

-                free_auto( );

-        }

-    }

+        local_rem( hModule );

     else

         save_err_ptr_str( handle );

 

@@ -352,10 +323,13 @@ int dlclose( void *handle )
     return (int) ret;

 }

 

+__declspec(noinline) /* Needed for _ReturnAddress() */

 void *dlsym( void *handle, const char *name )

 {

     FARPROC symbol;

+    HMODULE hCaller;

     HMODULE hModule;

+    HANDLE hCurrentProc;

 

 #ifdef UNICODE

     wchar_t namew[MAX_PATH];

@@ -363,39 +337,88 @@ void *dlsym( void *handle, const char *name )
 #endif

 

     current_error = NULL;

+    symbol = NULL;

+    hCaller = NULL;

+    hModule = GetModuleHandle( NULL );

+    hCurrentProc = GetCurrentProcess( );

 

-    symbol = GetProcAddress( (HMODULE) handle, name );

+    if( handle == RTLD_DEFAULT )

+    {

+        /* The symbol lookup happens in the normal global scope; that is,

+         * a search for a symbol using this handle would find the same

+         * definition as a direct use of this symbol in the program code.

+         * So use same lookup procedure as when filename is NULL.

+         */

+        handle = hModule;

+    }

+    else if( handle == RTLD_NEXT )

+    {

+        /* Specifies the next object after this one that defines name.

+         * This one refers to the object containing the invocation of dlsym().

+         * The next object is the one found upon the application of a load

+         * order symbol resolution algorithm. To get caller function of dlsym()

+         * use _ReturnAddress() intrinsic. To get HMODULE of caller function

+         * use undocumented hack from https://stackoverflow.com/a/2396380

+         * The HMODULE of a DLL is the same value as the module's base address.

+         */

+        MEMORY_BASIC_INFORMATION info;

+        size_t sLen;

+        sLen = VirtualQueryEx( hCurrentProc, _ReturnAddress(), &info, sizeof( info ) );

+        if( sLen != sizeof( info ) )

+            goto end;

+        hCaller = (HMODULE) info.AllocationBase;

+        if(!hCaller)

+            goto end;

+    }

 

-    if( symbol != NULL )

-        goto end;

+    if( handle != RTLD_NEXT )

+    {

+        symbol = GetProcAddress( (HMODULE) handle, name );

+

+        if( symbol != NULL )

+            goto end;

+    }

 

     /* If the handle for the original program file is passed, also search

      * in all globally loaded objects.

      */

 

-    hModule = GetModuleHandle( NULL );

-

-    if( hModule == handle )

+    if( hModule == handle || handle == RTLD_NEXT )

     {

-        global_object *pobject;

-

-        for( pobject = &first_object; pobject; pobject = pobject->next )

-        {

-            if( pobject->hModule )

-            {

-                symbol = GetProcAddress( pobject->hModule, name );

-                if( symbol != NULL )

-                    goto end;

-            }

-        }

+        HMODULE *modules;

+        DWORD cbNeeded;

+        DWORD dwSize;

+        size_t i;

 

-        for( pobject = &first_automatic_object; pobject; pobject = pobject->next )

+        /* GetModuleHandle( NULL ) only returns the current program file. So

+         * if we want to get ALL loaded module including those in linked DLLs,

+         * we have to use EnumProcessModules( ).

+         */

+        if( EnumProcessModules( hCurrentProc, NULL, 0, &dwSize ) != 0 )

         {

-            if( pobject->hModule )

+            modules = malloc( dwSize );

+            if( modules )

             {

-                symbol = GetProcAddress( pobject->hModule, name );

-                if( symbol != NULL )

-                    goto end;

+                if( EnumProcessModules( hCurrentProc, modules, dwSize, &cbNeeded ) != 0 && dwSize == cbNeeded )

+                {

+                    for( i = 0; i < dwSize / sizeof( HMODULE ); i++ )

+                    {

+                        if( handle == RTLD_NEXT && hCaller )

+                        {

+                            /* Next modules can be used for RTLD_NEXT */

+                            if( hCaller == modules[i] )

+                                hCaller = NULL;

+                            continue;

+                        }

+                        if( local_search( modules[i] ) )

+                            continue;

+                        symbol = GetProcAddress( modules[i], name );

+                        if( symbol != NULL )

+                            goto end;

+                    }

+

+                }

+                free( modules );

             }

         }

     }

@@ -472,18 +495,8 @@ char *dlerror( void )
 BOOL WINAPI DllMain( HINSTANCE hinstDLL, DWORD fdwReason, LPVOID lpvReserved )

 {

     (void) hinstDLL;

-    /*

-     * https://msdn.microsoft.com/en-us/library/windows/desktop/ms682583(v=vs.85).aspx 

-     *

-     *     When handling DLL_PROCESS_DETACH, a DLL should free resources such as heap

-     *     memory only if the DLL is being unloaded dynamically (the lpReserved

-     *     parameter is NULL).

-     */

-    if( fdwReason == DLL_PROCESS_DETACH && !lpvReserved )

-    {

-        auto_ref_count = 0;

-        free_auto( );

-    }

+    (void) fdwReason;

+    (void) lpvReserved;

     return TRUE;

 }

 #endif