/**
 * This module provides OS specific helper function for DLL support
 *
 * Copyright: Copyright Digital Mars 2010.
 * License:   <a href="http://www.boost.org/LICENSE_1_0.txt">Boost License 1.0</a>.
 * Authors:   Rainer Schuetze
 *
 *          Copyright Digital Mars 2010.
 * Distributed under the Boost Software License, Version 1.0.
 *    (See accompanying file LICENSE_1_0.txt or copy at
 *          http://www.boost.org/LICENSE_1_0.txt)
 */

module core.dll_helper;

version( Windows )
{
    import std.c.windows.windows;
    import core.stdc.string;
    import core.runtime;

    public import core.thread_helper;

    ///////////////////////////////////////////////////////////////////
    // support fixing implicit TLS for dynamically loaded DLLs on Windows XP

    extern (C)
    {
	extern __gshared void* _tlsstart;
	extern __gshared void* _tlsend;
	extern __gshared int   _tls_index;
	extern __gshared void* _tls_callbacks_a;
    }

private:
    struct dll_helper_aux
    {
	// don't let symbols leak into other modules
	struct LdrpTlsListEntry
	{
	    LdrpTlsListEntry* next;
	    LdrpTlsListEntry* prev;
	    void* tlsstart;
	    void* tlsend;
	    void* ptr_tlsindex;
	    void* callbacks;
	    void* zerofill;
	    int   tlsindex;
	}

	alias extern(Windows)
	void* fnRtlAllocateHeap(void* HeapHandle, uint Flags, uint Size);

	// find a code sequence and return the (relative) address that follows
	static void* findCodeReference( void* adr, int len, ref ubyte[] pattern, bool relative )
	{
	    if( !adr )
		return null;

	    ubyte* code = cast(ubyte*) adr;
	    for( int p = 0; p < len; p++ )
	    {
		if( code[ p .. p + pattern.length ] == pattern[ 0 .. $ ] )
		{
		    ubyte* padr = code + p + pattern.length;
		    if( relative )
			return padr + 4 + *cast(int*) padr;
		    return *cast(void**) padr;
		}
	    }
	    return null;
	}

	// crawl through ntdll to find function _LdrpAllocateTls@0 and references
	//  to _LdrpNumberOfTlsEntries, _NtdllBaseTag and _LdrpTlsList
	// LdrInitializeThunk
	// -> _LdrpInitialize@12
	// -> _LdrpInitializeThread@4
	// -> _LdrpAllocateTls@0
	// -> je chunk
	//     _LdrpNumberOfTlsEntries - number of entries in TlsList
	//     _NtdllBaseTag           - tag used for RtlAllocateHeap
	//     _LdrpTlsList            - root of the double linked list with TlsList entries

	static __gshared int* pNtdllBaseTag; // remembered for reusage in addTlsData

	static __gshared ubyte[] jmp_LdrpInitialize = [ 0x33, 0xED, 0xE9 ]; // xor ebp,ebp; jmp _LdrpInitialize
	static __gshared ubyte[] jmp__LdrpInitialize = [ 0x5D, 0xE9 ]; // pop ebp; jmp __LdrpInitialize
	static __gshared ubyte[] call_LdrpInitializeThread = [ 0xFF, 0x75, 0x08, 0xE8 ]; // push [ebp+8]; call _LdrpInitializeThread
	static __gshared ubyte[] call_LdrpAllocateTls = [ 0x00, 0x00, 0xE8 ]; // jne 0xc3; call _LdrpAllocateTls
	static __gshared ubyte[] jne_LdrpAllocateTls = [ 0x0f, 0x85 ]; // jne body_LdrpAllocateTls
	static __gshared ubyte[] mov_LdrpNumberOfTlsEntries = [ 0x8B, 0x0D ]; // mov ecx, _LdrpNumberOfTlsEntries
	static __gshared ubyte[] mov_NtdllBaseTag = [ 0x51, 0x8B, 0x0D ]; // push ecx; mov ecx, _NtdllBaseTag
	static __gshared ubyte[] mov_LdrpTlsList = [ 0x8B, 0x3D ]; // mov edi, _LdrpTlsList

	static LdrpTlsListEntry* addTlsListEntry( void** peb, void* tlsstart, void* tlsend, void* tls_callbacks_a, int* tlsindex )
	{
	    HANDLE hnd = GetModuleHandleA( "NTDLL" );
	    assert( hnd, "cannot get module handle for ntdll" );
	    ubyte* fn = cast(ubyte*) GetProcAddress( hnd, "LdrInitializeThunk" );
	    assert( fn, "cannot find LdrInitializeThunk in ntdll" );

	    try
	    {
		void* pLdrpInitialize = findCodeReference( fn, 20, jmp_LdrpInitialize, true );
		void* p_LdrpInitialize = findCodeReference( pLdrpInitialize, 40, jmp__LdrpInitialize, true );
		void* pLdrpInitializeThread = findCodeReference( p_LdrpInitialize, 200, call_LdrpInitializeThread, true );
		void* pLdrpAllocateTls = findCodeReference( pLdrpInitializeThread, 40, call_LdrpAllocateTls, true );
		void* pBodyAllocateTls = findCodeReference( pLdrpAllocateTls, 40, jne_LdrpAllocateTls, true );

		int* pLdrpNumberOfTlsEntries = cast(int*) findCodeReference( pBodyAllocateTls, 20, mov_LdrpNumberOfTlsEntries, false );
		pNtdllBaseTag = cast(int*) findCodeReference( pBodyAllocateTls, 30, mov_NtdllBaseTag, false );
		LdrpTlsListEntry* pLdrpTlsList = cast(LdrpTlsListEntry*)findCodeReference( pBodyAllocateTls, 60, mov_LdrpTlsList, false );

		if( !pLdrpNumberOfTlsEntries || !pNtdllBaseTag || !pLdrpTlsList )
		    return null;

		fnRtlAllocateHeap* fnAlloc = cast(fnRtlAllocateHeap*) GetProcAddress( hnd, "RtlAllocateHeap" );
		if( !fnAlloc )
		    return null;

		// allocate new TlsList entry (adding 0xC0000 to the tag is obviously a flag also usesd by
		//  the nt-loader, could be the result of HEAP_MAKE_TAG_FLAGS(0,HEAP_NO_SERIALIZE|HEAP_GROWABLE)
		//  but this is not documented in the msdn entry for RtlAlloateHeap
		void* heap = peb[6];
		LdrpTlsListEntry* entry = cast(LdrpTlsListEntry*) (*fnAlloc)( heap, *pNtdllBaseTag | 0xc0000, LdrpTlsListEntry.sizeof );
		if( !entry )
		    return null;

		// fill entry
		entry.tlsstart = tlsstart;
		entry.tlsend = tlsend;
		entry.ptr_tlsindex = tlsindex;
		entry.callbacks = tls_callbacks_a;
		entry.zerofill = null;
		entry.tlsindex = *pLdrpNumberOfTlsEntries;

		// and add it to the end of TlsList
		*tlsindex = *pLdrpNumberOfTlsEntries;
		entry.next = pLdrpTlsList;
		entry.prev = pLdrpTlsList.prev;
		pLdrpTlsList.prev.next = entry;
		pLdrpTlsList.prev = entry;
		(*pLdrpNumberOfTlsEntries)++;

		return entry;
	    }
	    catch( Exception e )
	    {
		// assert( false, e.msg );
		return null;
	    }
	}

	// reallocate TLS array and create a copy of the TLS data section
	static bool addTlsData( void** teb, void* tlsstart, void* tlsend, int tlsindex )
	{
	    try
	    {
		HANDLE hnd = GetModuleHandleA( "NTDLL" );
		assert( hnd, "cannot get module handle for ntdll" );

		fnRtlAllocateHeap* fnAlloc = cast(fnRtlAllocateHeap*) GetProcAddress( hnd, "RtlAllocateHeap" );
		if( !fnAlloc || !pNtdllBaseTag )
		    return false;
	
		void** peb = cast(void**) teb[12];
		void* heap = peb[6];

		int sz = tlsend - tlsstart;
		void* tlsdata = cast(void*) (*fnAlloc)( heap, *pNtdllBaseTag | 0xc0000, sz );
		if( !tlsdata )
		    return false;

		// no relocations! not even self-relocations. Windows does not do them.
		core.stdc.string.memcpy( tlsdata, tlsstart, sz ); 

		// create copy of tls pointer array
		void** array = cast(void**) (*fnAlloc)( heap, *pNtdllBaseTag | 0xc0000, (tlsindex + 1) * (void*).sizeof );
		if( !array )
		    return false;

		if( tlsindex > 0 && teb[11] )
		    core.stdc.string.memcpy( array, teb[11], tlsindex * (void*).sizeof);
		array[tlsindex] = tlsdata;
		teb[11] = cast(void*) array;
	    
		// let the old array leak, in case a oncurrent thread is still relying on it
	    }
	    catch( Exception e )
	    {
		// assert( false, e.msg );
		return false;
	    }
	    return true;
	}

	alias bool BOOLEAN;

	struct UNICODE_STRING
	{
	    short Length;
	    short MaximumLength;
	    wchar* Buffer;
	}

	struct LIST_ENTRY
	{
	    LIST_ENTRY* next;
	    LIST_ENTRY* prev;
        }

	// the following structures can be found here: http://undocumented.ntinternals.net/
	struct LDR_MODULE 
	{
	    LIST_ENTRY      InLoadOrderModuleList;
	    LIST_ENTRY      InMemoryOrderModuleList;
	    LIST_ENTRY      InInitializationOrderModuleList;
	    PVOID           BaseAddress;
	    PVOID           EntryPoint;
	    ULONG           SizeOfImage;
	    UNICODE_STRING  FullDllName;
	    UNICODE_STRING  BaseDllName;
	    ULONG           Flags;
	    SHORT           LoadCount;
	    SHORT           TlsIndex;
	    LIST_ENTRY      HashTableEntry;
	    ULONG           TimeDateStamp;
	}

	struct PEB_LDR_DATA 
	{
	    ULONG           Length;
	    BOOLEAN         Initialized;
	    PVOID           SsHandle;
	    LIST_ENTRY      InLoadOrderModuleList;
	    LIST_ENTRY      InMemoryOrderModuleList;
	    LIST_ENTRY      InInitializationOrderModuleList;
	}

	static LDR_MODULE* findLdrModule( HINSTANCE hInstance, void** peb )
	{
	    PEB_LDR_DATA* ldrData = cast(PEB_LDR_DATA*) peb[3];
	    LIST_ENTRY* root = &ldrData.InLoadOrderModuleList;
	    for(LIST_ENTRY* entry = root.next; entry != root; entry = entry.next)
	    {
		LDR_MODULE *ldrMod = cast(LDR_MODULE*) entry;
		if(ldrMod.BaseAddress == hInstance)
		    return ldrMod;
	    }
	    return null;
	}

	static bool setDllTlsUsage( HINSTANCE hInstance, void** peb )
	{
	    try
	    {
		LDR_MODULE *thisMod = findLdrModule( hInstance, peb );
		if( !thisMod )
		    return false;

		thisMod.TlsIndex = -1;  // uses TLS (not the index itself)
		thisMod.LoadCount = -1; // never unload
		return true;
	    }
	    catch( Exception e )
	    {
		// assert( false, e.msg );
		return false;
	    }
	}
    }
    
public:
    /* *****************************************************
     * Fix implicit thread local storage for the case when a DLL is loaded
     * dynamically after process initialization.
     * The link time variables are passed to allow placing this function into
     * an RTL DLL itself.
     * The problem is described in Bugzilla 3342 and
     * http://www.nynaeve.net/?p=187, to quote from the latter:
     *
     * "When a DLL using implicit TLS is loaded, because the loader doesn't process the TLS
     *  directory, the _tls_index value is not initialized by the loader, nor is there space
     *  allocated for module's TLS data in the ThreadLocalStoragePointer arrays of running
     *  threads. The DLL continues to load, however, and things will appear to work... until the
     *  first access to a __declspec(thread) variable occurs, that is."
     *
     * _tls_index is initialized by the compiler to 0, so we can use this as a test.
     */
    bool dll_fixTLS( HINSTANCE hInstance, void* tlsstart, void* tlsend, void* tls_callbacks_a, int* tlsindex )
    {
	/* If the OS has allocated a TLS slot for us, we don't have to do anything
	 * tls_index 0 means: the OS has not done anything, or it has allocated slot 0
	 * Vista and later Windows systems should do this correctly and not need
	 * this function.
	 */
	if( *tlsindex != 0 )
	    return true;

	void** peb;
	asm 
	{
	    mov EAX,FS:[0x30]; 
	    mov peb, EAX; 
	}
	dll_helper_aux.LDR_MODULE *ldrMod = dll_helper_aux.findLdrModule( hInstance, peb );
	if( !ldrMod )
	    return false; // not in module list, bail out
	if( ldrMod.TlsIndex != 0 )
	    return true;  // the OS has already setup TLS
	    
	dll_helper_aux.LdrpTlsListEntry* entry = dll_helper_aux.addTlsListEntry( peb, tlsstart, tlsend, tls_callbacks_a, tlsindex );
	if( !entry )
	    return false;

	if( !enumProcessThreads( 
	    function (uint id, void* context) {
		dll_helper_aux.LdrpTlsListEntry* entry = cast(dll_helper_aux.LdrpTlsListEntry*) context;
		return dll_helper_aux.addTlsData( getTEB( id ), entry.tlsstart, entry.tlsend, entry.tlsindex );
	    }, entry ) )
	    return false;

	ldrMod.TlsIndex = -1;  // flag TLS usage (not the index itself)
	ldrMod.LoadCount = -1; // prevent unloading of the DLL,
			       // since XP does not keep track of used TLS entries
	return true;
    }

    // fixup TLS storage, initialize runtime and attach to threads
    // to be called from DllMain with reason DLL_PROCESS_ATTACH
    bool dll_process_attach( HINSTANCE hInstance, bool attach_threads,
                             void* tlsstart, void* tlsend, void* tls_callbacks_a, int* tlsindex )
    {
	if( !dll_fixTLS( hInstance, tlsstart, tlsend, tls_callbacks_a, tlsindex ) )
	    return false;

	thread_setNeedLock(true);
	Runtime.initialize();

	if( !attach_threads )
	    return true;
	    
	// attach to all other threads
	return enumProcessThreads(
	    function (uint id, void* context) { 
		if( !Thread.findThread( id ) )
		{
		    thread_attach( id );
		    thread_moduleTlsCtor( id );
		}
		return true; 
	    }, null );
    }

    // same as above, but only usable if druntime is linked statically
    bool dll_process_attach( HINSTANCE hInstance, bool attach_threads = true )
    {
	return dll_process_attach( hInstance, attach_threads,
	                           &_tlsstart, &_tlsend, &_tls_callbacks_a, &_tls_index );
    }
    
    // to be called from DllMain with reason DLL_PROCESS_DETACH
    void dll_process_detach( HINSTANCE hInstance, bool detach_threads = true )
    {
	// detach from all other threads
	if( detach_threads )
	    enumProcessThreads( 
		function (uint id, void* context) { 
		    if( id != GetCurrentThreadId() && Thread.findThread( id ) ) 
		    {
			thread_moduleTlsDtor( id );
			thread_detach( id ); 
		    }
		    return true; 
		}, null );

	Runtime.terminate();
    }

    // to be called from DllMain with reason DLL_THREAD_ATTACH
    void dll_thread_attach( bool attach_thread = true, bool initTls = true )
    {
	if( attach_thread && !Thread.findThread( GetCurrentThreadId() ) )
	    thread_attachThis(); 
	if( initTls && !_moduleinfo_tlsdtors_i ) // avoid duplicate calls
	    _moduleTlsCtor();
    }

    // to be called from DllMain with reason DLL_THREAD_DETACH
    void dll_thread_detach( bool detach_thread = true, bool exitTls = true )
    {
	if( exitTls )
	    _moduleTlsDtor();
	if( detach_thread )
	    thread_detachThis(); 
    }
}
