Hooking thread creation/termination - windows

Question

Is it possible to hook into thread termination on Windows? IOW, I would like to be notified if a thread inside the process (not interested in other processes and their threads) has terminated (either normally or - more important - forcefully).
Alternatively, hooking into thread creation would also do.
Rationale: I have a library that manages some information on per-thread basis (think of it as a process-wide per-thread cache for some information). When a thread is terminated I have to remove all thread-specific information from the cache. [Cache associations are implemented using thread ID which may get reused for future threads.]
There's no problem with "normal" execution order as the library user will detach the current thread from the library which will clear the state. Problems start to appear if somebody kills the thread owning cached resource.

Answer 1

The best way is to call
WaitForSingleObject with the HANDLE of the thread (call OpenThread using the thread id to get the HANDLE).

Answer 2

If your program is in a dll, you can set up to handle the DllMain method. This is called when a thread or process starts/ends.
For example,
library MyDLL;
uses
SysUtils, Windows;
procedure DllMain(reason: integer) ;
var
dyingThreadId: Cardinal;
begin
case reason of
DLL_THREAD_DETACH:
begin
dyingThreadId := GetCurrentThreadId();
// handle thread exit with thread id
end;
end;
end;
begin
DllProc := #DllMain;
end.
EDIT: The call is made in the context of the exiting thread, so you can call GetCurrentThreadId() to get the thread's id.

Answer 3

You can use the Win32_ThreadStopTrace WMI event to detect the termination of any thread in the system.
To start monitoring this event you must write a WQLsentence like this
Select * from Win32_ThreadStopTrace Within 1 Where ProcessID=PID_Of_Your_App
check this sample
uses
Classes;
type
TProcWmiEventThreadeCallBack = procedure(AObject: OleVariant) of object;
TWmiEventThread = class(TThread)
private
Success : HResult;
FSWbemLocator: OleVariant;
FWMIService : OleVariant;
FEventSource : OleVariant;
FWbemObject : OleVariant;
FCallBack : TProcWmiEventThreadeCallBack;
FWQL : string;
FServer : string;
FUser : string;
FPassword : string;
FNameSpace : string;
TimeoutMs : Integer;
procedure RunCallBack;
public
Constructor Create(CallBack : TProcWmiEventThreadeCallBack;const Server,User,PassWord,NameSpace,WQL:string;iTimeoutMs : Integer); overload;
destructor Destroy; override;
procedure Execute; override;
end;
implementation
uses
SysUtils,
ComObj,
Variants,
ActiveX;
constructor TWmiEventThread.Create(CallBack : TProcWmiEventThreadeCallBack;const Server,User,PassWord,NameSpace,WQL:string;iTimeoutMs : Integer);
begin
inherited Create(False);
FreeOnTerminate := True;
FCallBack := CallBack;
FWQL := WQL;
FServer := Server;
FUser := User;
FPassword := PassWord;
FNameSpace := NameSpace;
TimeoutMs := iTimeoutMs;
end;
destructor TWmiEventThread.Destroy;
begin
FSWbemLocator:=Unassigned;
FWMIService :=Unassigned;
FEventSource :=Unassigned;
FWbemObject :=Unassigned;
inherited;
end;
procedure TWmiEventThread.Execute;
const
wbemErrTimedout = $80043001;
begin
Success := CoInitialize(nil); //CoInitializeEx(nil, COINIT_MULTITHREADED);
try
FSWbemLocator := CreateOleObject('WbemScripting.SWbemLocator');
FWMIService := FSWbemLocator.ConnectServer(FServer, FNameSpace, FUser, FPassword);
FEventSource := FWMIService.ExecNotificationQuery(FWQL);
while not Terminated do
begin
try
FWbemObject := FEventSource.NextEvent(TimeoutMs); //set the max time to wait (ms)
except
on E:EOleException do
if EOleException(E).ErrorCode=HRESULT(wbemErrTimedout) then //Check for the timeout exception and ignore if exist
FWbemObject:=Null
else
raise;
end;
if FindVarData(FWbemObject)^.VType <> varNull then
Synchronize(RunCallBack);
FWbemObject:=Unassigned;
end;
finally
case Success of
S_OK, S_FALSE: CoUninitialize;
end;
end;
end;
procedure TWmiEventThread.RunCallBack;
begin
FCallBack(FWbemObject);
end;
Now to use this thread in your app you must call it in this way
WmiThread:=TWmiEventThread.Create(
Log,
'.',
'',
'',
'root\cimv2',
Format('Select * from Win32_ThreadStopTrace Within 1 Where ProcessID=%d',[GetCurrentProcessId]),1);
and in the callback function
procedure TForm1.Log(AObject: OleVariant);
begin
{
The OleVariant parameter has these properties
uint32 ProcessID;
uint8 SECURITY_DESCRIPTOR[];
uint32 ThreadID;
uint64 TIME_CREATED;
}
//do your stuff here
Memo1.Lines.Add(Format('Thread %s terminated ',[AObject.ThreadID]));
end;

Answer 4

You could use something like Detours to do API-level hooking of Win32 APIs like TerminateThread.
I'm not seeing why you need to do this, though. It sounds like you need to clear the thread's associated cache when the thread dies so you can re-use that slot if another thread with the same ID comes along. Is this correct?
If so, couldn't you just clear the cache association in DllMain when you get the DLL_THREAD_ATTACH event? This is essentially your new thread notification. At this point, you know you have a new thread, so isn't it safe to clear the existing associated cache?
The other alternative that might work is thread-local storage (TLS). You can use Win32 APIs like TlsAlloc/TlsSetValue to store thread-specific information. You could also define a variable with __declspec(thread) to have the compiler manage the TLS for you. This way, each thread maintains its own cache. The code remains the same for each thread, but the data accesses are relative to the thread.

Answer 5

program ThreadExitHook;
{$APPTYPE CONSOLE}
uses
Windows,
Classes,
madCodeHook;
type
TLdrShutdownThread = procedure; stdcall;
var
LdrShutdownThreadNext : TLdrShutdownThread;
procedure LdrShutdownThreadCallback; stdcall;
begin
WriteLn('Thread terminating:', GetCurrentThreadId);
LdrShutdownThreadNext;
end;
begin
HookAPI('ntdll.dll', 'LdrShutdownThread', #LdrShutdownThreadCallback, #LdrShutdownThreadNext);
TThread.CreateAnonymousThread(procedure begin
WriteLn('Hello from Thread');
Sleep(1000);
end).Start;
ReadLn;
UnhookAPI(#LdrShutdownThreadNext);
end.
Here is a version that does not depend on any external library:
program Project7;
{$APPTYPE CONSOLE}
uses
Windows,
Classes;
{==============================================================================}
function IsWin9x: Boolean;
asm
MOV EAX, FS:[030H]
TEST EAX, EAX
SETS AL
end;
{------------------------------------------------------------------------------}
function CalcJump(Src, Dest: DWORD): DWORD;
begin
if (Dest < Src) then begin
Result := Src - Dest;
Result := $FFFFFFFF - Result;
Result := Result - 4;
end else begin
Result := Dest - Src;
Result := Result - 5;
end;
end;
{------------------------------------------------------------------------------}
function OpCodeLength(Address: DWORD): DWORD; cdecl; assembler;
const
O_UNIQUE = 0;
O_PREFIX = 1;
O_IMM8 = 2;
O_IMM16 = 3;
O_IMM24 = 4;
O_IMM32 = 5;
O_IMM48 = 6;
O_MODRM = 7;
O_MODRM8 = 8;
O_MODRM32 = 9;
O_EXTENDED = 10;
O_WEIRD = 11;
O_ERROR = 12;
asm
pushad
cld
xor edx, edx
mov esi, Address
mov ebp, esp
push 1097F71Ch
push 0F71C6780h
push 17389718h
push 101CB718h
push 17302C17h
push 18173017h
push 0F715F547h
push 4C103748h
push 272CE7F7h
push 0F7AC6087h
push 1C121C52h
push 7C10871Ch
push 201C701Ch
push 4767602Bh
push 20211011h
push 40121625h
push 82872022h
push 47201220h
push 13101419h
push 18271013h
push 28858260h
push 15124045h
push 5016A0C7h
push 28191812h
push 0F2401812h
push 19154127h
push 50F0F011h
mov ecx, 15124710h
push ecx
push 11151247h
push 10111512h
push 47101115h
mov eax, 12472015h
push eax
push eax
push 12471A10h
add cl, 10h
push ecx
sub cl, 20h
push ecx
xor ecx, ecx
dec ecx
##ps:
inc ecx
mov edi, esp
##go:
lodsb
mov bh, al
##ft:
mov ah, [edi]
inc edi
shr ah, 4
sub al, ah
jnc ##ft
mov al, [edi-1]
and al, 0Fh
cmp al, O_ERROR
jnz ##i7
pop edx
not edx
##i7:
inc edx
cmp al, O_UNIQUE
jz ##t_exit
cmp al, O_PREFIX
jz ##ps
add edi, 51h
cmp al, O_EXTENDED
jz ##go
mov edi, [ebp+((1+8)*4)+4]
##i6:
inc edx
cmp al, O_IMM8
jz ##t_exit
cmp al, O_MODRM
jz ##t_modrm
cmp al, O_WEIRD
jz ##t_weird
##i5:
inc edx
cmp al, O_IMM16
jz ##t_exit
cmp al, O_MODRM8
jz ##t_modrm
##i4:
inc edx
cmp al, O_IMM24
jz ##t_exit
##i3:
inc edx
##i2:
inc edx
pushad
mov al, 66h
repnz scasb
popad
jnz ##c32
##d2:
dec edx
dec edx
##c32:
cmp al, O_MODRM32
jz ##t_modrm
sub al, O_IMM32
jz ##t_imm32
##i1:
inc edx
##t_exit:
jmp ##ASMEnded
##t_modrm:
lodsb
mov ah, al
shr al, 7
jb ##prmk
jz ##prm
add dl, 4
pushad
mov al, 67h
repnz scasb
popad
jnz ##prm
##d3: sub dl, 3
dec al
##prmk:jnz ##t_exit
inc edx
inc eax
##prm:
and ah, 00000111b
pushad
mov al, 67h
repnz scasb
popad
jz ##prm67chk
cmp ah, 04h
jz ##prmsib
cmp ah, 05h
jnz ##t_exit
##prm5chk:
dec al
jz ##t_exit
##i42: add dl, 4
jmp ##t_exit
##prm67chk:
cmp ax, 0600h
jnz ##t_exit
inc edx
jmp ##i1
##prmsib:
cmp al, 00h
jnz ##i1
lodsb
and al, 00000111b
sub al, 05h
jnz ##i1
inc edx
jmp ##i42
##t_weird:
test byte ptr [esi], 00111000b
jnz ##t_modrm
mov al, O_MODRM8
shr bh, 1
adc al, 0
jmp ##i5
##t_imm32:
sub bh, 0A0h
cmp bh, 04h
jae ##d2
pushad
mov al, 67h
repnz scasb
popad
jnz ##chk66t
##d4: dec edx
dec edx
##chk66t:
pushad
mov al, 66h
repnz scasb
popad
jz ##i1
jnz ##d2
##ASMEnded:
mov esp, ebp
mov [result+(9*4)], edx
popad
end;
{------------------------------------------------------------------------------}
function ApiHook(ModName, ApiName: PChar; FuncAddr, HookedApi: Pointer; var MainApi: Pointer): Boolean;
var
dwCount, Cnt, i, jmp: DWORD;
P: Pointer;
hMod, OldP, TMP: Cardinal;
begin
Result := False;
if IsWin9x then
Exit;
P := FuncAddr;
if P = nil then begin
hMod := GetModuleHandle(ModName);
if hMod = 0 then
hMod := LoadLibrary(ModName);
P := GetProcAddress(hMod, ApiName);
end;
if (P = nil) or (HookedApi = nil) then
Exit;
if not VirtualProtect(P, $40, PAGE_EXECUTE_READWRITE, #OldP) then
Exit;
if ((Byte(P^) = $68) and (DWORD(Pointer(DWORD(P) + 1)^) = DWORD(HookedApi))) then
Exit;
MainApi := VirtualAlloc(nil, $1000, MEM_COMMIT, PAGE_EXECUTE_READWRITE);
if MainApi = nil then
Exit;
Cnt := 0;
for dwCount := 0 to $3F do begin
Inc(Cnt, OpCodeLength(DWORD(P) + Cnt));
for i := 0 to Cnt - 1 do
PByte(MainApi)[i] := PByte(P)[i];
if Cnt > 5 then
Break;
end;
PByte(MainApi)[Cnt] := $68;
DWORD(Pointer(DWORD(MainApi) + Cnt + 1)^) := DWORD(P) + Cnt;
PByte(MainApi)[Cnt + 5] := $C3;
PByte(MainApi)[Cnt + 6] := $99;
if (OpCodeLength(DWORD(MainApi)) = 5) and
((Byte(MainApi^) = $E8) or (Byte(MainApi^) = $E9)) then
begin
jmp := DWORD(P) + DWORD(Pointer(DWORD(MainApi) + 1)^) + 5;
DWORD(Pointer(DWORD(MainApi) + 1)^) := CalcJump(DWORD(MainApi), jmp);
end;
PByte(P)[0] := $68;
DWORD(Pointer(DWORD(P) + 1)^) := DWORD(HookedApi);
PByte(P)[5] := $C3;
VirtualProtect(P, $40, OldP, #TMP);
Result := True;
end;
{------------------------------------------------------------------------------}
function ApiUnHook(ModName, ApiName: PChar; FuncAddr, HookedApi: Pointer; var MainApi: Pointer): Boolean;
var
dwCount, Cnt, i, jmp: DWORD;
P: Pointer;
hMod, OldP, TMP: Cardinal;
begin
Result := False;
if IsWin9x then
Exit;
P := FuncAddr;
if P = nil then begin
hMod := GetModuleHandle(ModName);
P := GetProcAddress(hMod, ApiName);
end;
if (P = nil) or (MainApi = nil) or (HookedApi = nil) then
Exit;
if not VirtualProtect(P, $40, PAGE_EXECUTE_READWRITE, #OldP) then
Exit;
if ((Byte(P^) <> $68) or (DWORD(Pointer(DWORD(P) + 1)^) <> DWORD(HookedApi))) then
Exit;
Cnt := 0;
for dwCount := 0 to $3F do begin
Inc(Cnt, OpCodeLength(DWORD(MainApi) + Cnt));
if (Byte(Pointer(DWORD(MainApi) + Cnt)^) = $C3) and
(Byte(Pointer(DWORD(MainApi) + Cnt + 1)^) = $99) then
Break;
for i := 0 to Cnt - 1 do
PByte(P)[i] := PByte(MainApi)[i];
end;
if (OpCodeLength(DWORD(P)) = 5) and ((Byte(P^) = $E8) or (byte(P^) = $E9)) then begin
jmp := DWORD(MainApi) + DWORD(Pointer(DWORD(MainApi) + 1)^) + 5;
DWORD(Pointer(DWORD(P) + 1)^) := CalcJump(DWORD(P), jmp);
end;
VirtualProtect(P, $40, OldP, #TMP);
VirtualFree(MainApi, 0, MEM_RELEASE);
Result := True;
end;
{==============================================================================}
type
TLdrShutdownThread = procedure; stdcall;
var
LdrShutdownThreadNext : TLdrShutdownThread;
procedure LdrShutdownThreadCallback; stdcall;
begin
WriteLn('Thread terminating:', GetCurrentThreadId);
LdrShutdownThreadNext;
end;
begin
ApiHook('ntdll.dll', 'LdrShutdownThread', nil, #LdrShutdownThreadCallback, #LdrShutdownThreadNext);
TThread.CreateAnonymousThread(procedure begin
WriteLn('Hello from Thread');
Sleep(1000);
WriteLn('Waking up');
end).Start;
ReadLn;
ApiUnHook('ntdll.dll', 'LdrShutdownThread', nil, #LdrShutdownThreadCallback, #LdrShutdownThreadNext);
TThread.CreateAnonymousThread(procedure begin
WriteLn('Hello from Thread');
Sleep(1000);
WriteLn('Waking up');
end).Start;
ReadLn;
end.

Answer 6

Chris' mention of DLL_THREAD_ATTACH gave me an idea ...
Basically, associating cache with thread ID is a bad thing. I have to rework my library so that a thread will initially establish some kind of handle and then manage associations using this handle.

Answer 7

I guess if you really want to badly enough, you could use the debugging API (e.g., WaitForDebugEvent, ContinueDebugEvent), . You'll get an EXIT_THREAD_DEBUG_EVENT when a thread exits.
I can't say that's exactly a straightforward or clean way to do it, but if you can't come up with anything else, it's probably better than nothing.

Answer 8

Boost provides boost::this_thread::at_thread_exit() which allows you to provide arbitrary code to run when the current thread exits. If you call this on each thread then when it exits normally the code will be run. If a thread is terminated forcibly with TerminateThread then no more code is run on that thread, so the at_thread_exit functions are not called. The only way to handle such cases would be to hook TerminateThread, though this won't necessarily handle the case that another process terminates your threads.

Answer 9

The only way to reliably do this is in a DLL that hooks DLL_THREAD_ATTACH and DLL_THREAD_DETACH. See previous discussion here.