7

The Thread Local Storage (TLS) contains static or global values for a thread. Those values can be very important to find reliable references to memory structures when the memory locations are not static.

I would like to get the Thread Local Storage of another process.

The TLS should be at [FS:0x2C] in the Thread Information Block (TIB). Though I quite don't understand how the FS register works. I guess I have to find the TIB Base address first? I think I can find it in the Thread Context I can get with WINAPI GetThreadContext, but I am a little bit overwhelmed.

|improve this question
  • Are you looking for ways to access it in the same process? different process? Clarify your situation and what exactly you need to do. – Igor Skochinsky♦ Dec 7 '13 at 0:36
  • I try to do it for a different process. I will update my question for clarification. – samuirai Dec 7 '13 at 0:49
7

You need to use GetThreadSelectorEntry().

Pseudocode:

GetThreadContext(hThread, &context);
GetThreadSelectorEntry(hThread, context.SegFs, &selectorEntry);
ReadProcessMemory(hProcess, (selectorEntry.BaseLow | (selectorEntry.HighWord.Bytes.BaseMid << 0x10) | (selectorEntry.HighWord.Bytes.BaseHi << 0x18)) + 0x2C, &pTLS, sizeof(pTLS), &numberOfBytesRead);

You can see the function GetProcessEntryPointAddress() here for some sample code that does something similar.

|improve this answer
  • thank you, it worked like a charm :) I didn't know GetThreadSelectorEntry() – samuirai Dec 7 '13 at 20:00

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.