Win32 TIB (Thread Information Block)

Win32 TIB 

Win32 TIB (Thread Information Block) is a data struct in wins32 on x86 that stores info about the currently running thread. 

If you have a Process Explorer type application, you can use TIB instead of using APIs to get the thread and process information. 

The TIB can be used to get a lot of information on the process without calling win32 API. Examples include emulating GetLastError(), GetVersion(). Through the pointer to the PEB one can obtain access to the import tables (IAT), process startup arguments, image name, etc.

 How to Access TIB 

The TIB can be accessed as an offset of segment register FS.FS is the  data selector to TIB  for the first thread.

FS maps to a TIB which is embedded in a data block known as the TDB (thread data base). The TIB contains the thread-specific exception handling chain and pointer to the TLS (thread local storage.) The thread local storage is not the same as C local storage.

 TIB Contents: 

Position	Windows Ver.	Description
FS:[0x00]	Win9x and NT
FS:[0x04]	Win9x and NT	Top of stack
FS:[0x08]	Win9x and NT	Current bottom of stack
FS:[0x10]	NT
FS:[0x14]	Win9x and NT	Arbitrary data slot
FS:[0x18]	Win9x and NT	Linear address of TIB
FS:[0x1C]	NT	Environment Pointer
FS:[0x20]	NT	Process ID
FS:[0x24]	NT	Current thread ID
FS:[0x28]	NT	Active RPC Handle
FS:[0x2C]	Win9x and NT	Linear address of the TLS array
FS:[0x30]	NT	Linear address of (PEB)
FS:[0x34]	NT	Last error number
FS:[0x38]	NT	Count of owned critical sections
FS:[0x3C]	NT	Address of CSR Client Thread
FS:[0x40]	NT	Win32 Thread Information
FS:[0x44]	NT,Wine	Win32 client information (NT), user32 private data (Wine), 0x60 = LastError (Win95), 0x74 = LastError (WinME)
FS:[0xC0]	NT	Reserved for Wow32
FS:[0xC4]	NT	Current Locale
FS:[0xC8]	NT	FP Software Status Register
FS:[0xCC]	NT,Wine	Reserved for OS (NT), kernel32 private data (Wine)
FS:[0x124]	NT	Pointer to KTHREAD (ETHREAD) structure
FS:[0x1A4]	NT	Exception code
FS:[0x1A8]	NT	Activation context stack
FS:[0x1BC]	NT,Wine	Spare bytes (NT), ntdll private data (Wine)
FS:[0x1D4]	NT,Wine	Reserved for OS (NT), ntdll private data (Wine)
FS:[0x1FC]	NT,Wine	GDI TEB Batch (OS), vm86 private data (Wine)
FS:[0x6DC]	NT	GDI Region
FS:[0x6E0]	NT	GDI Pen
FS:[0x6E4]	NT	GDI Brush
FS:[0x6E8]	NT	Real Process ID
FS:[0x6EC]	NT	Real Thread ID
FS:[0x6F0]	NT	GDI cached process handle
FS:[0x6F4]	NT	GDI client process ID (PID)
FS:[0x6F8]	NT	GDI client thread ID (TID)
FS:[0x6FC]	NT	GDI thread locale information
FS:[0x700]	NT	Reserved for user application
FS:[0x714]	NT	Reserved for GL
FS:[0xBF4]	NT	Last Status Value
FS:[0xBF8]	NT	Reserved for advapi32
FS:[0xE0C]	NT	Pointer to deallocation stack
FS:[0xE10]	NT	TLS slots, 4 byte per slot
FS:[0xF10]	NT	TLS links (LIST_ENTRY structure)
FS:[0xF18]	NT	VDM
FS:[0xF1C]	NT	Reserved for RPC

Sample Code:

void *pTIB;

__asm

{

mov EAX,FS:[20h]
mov [pTIB],EAX

}

//Here you can see the most recent Process ID in pTIB.

EAX – is a CPU Register (Accumulator Register).

Cheers!!

CMemoryState - Detects memory leaks in your program

Memory leak occurs when memory for an object is allocated on the heap but not deallocated when it is no longer required. Such memory leaks can lead to out-of-memory errors.CMemoryState provides an excellent way to detect memory leaks in your program.

The CMemoryState diagnostics only help to detect memory leaks caused when memory allocated using the new operator is not deallocated using delete.

CMemoryState will not address the leaks caused by malloc , LocalAlloc & GlobalAlloc.

How to Use: 

CMemoryState oldMemState, newMemState, diffMemState;
oldMemState.Checkpoint();
/* Obtains a snapshot or "checkpoint" of the current memory state.*/

/* memory allocation activities go on here */

newMemState.Checkpoint();
if(diffMemState.Difference(oldMemState,newMemState))
{

     TRACE( "Memory leak Detected!\n" );
              diffMemState.DumpAllObjectsSince();

}
/* Difference() - Computes the difference between two objects of type CMemoryState.*/
/* DumpAllObjectsSince() - Dumps a summary of all currently allocated objects since a previous checkpoint.*/

cheers!