Obtain Thread Info from tls callback - c++

Question

So I have a tls callback implemented in a separate dll and I want to retrieve the thread information on thread attach like the entry point,
parameters etc
void NTAPI on_tls_callback(LPVOID dll, DWORD reason, LPVOID reserved)
{
if (reason == DLL_THREAD_ATTACH)
{
//obtain thread info
}
}
#pragma comment (linker, "/INCLUDE:__tls_used")
#pragma comment (linker, "/INCLUDE:__xl_b")
#pragma data_seg(".CRT$XLB")
EXTERN_C
PIMAGE_TLS_CALLBACK _xl_b = on_tls_callback;
#pragma data_seg()
I read here that it's possible
How can DLL injection be detected?

Answer 1

Okay after a bit of further research I found a way here
Thread EntryPoint in TLS callback as AntiDebug technique
typedef NTSTATUS
(NTAPI*NtQueryInformationThread_t)(
IN HANDLE ThreadHandle,
IN THREADINFOCLASS ThreadInformationClass,
OUT PVOID ThreadInformation,
IN ULONG ThreadInformationLength,
OUT PULONG ReturnLength OPTIONAL
);
void NTAPI on_tls_callback(LPVOID dll, DWORD reason, LPVOID reserved)
{
if (reason == DLL_THREAD_ATTACH)
{
DWORD startAddress = 0;
NtQueryInformationThread_t pNtQueryInformationThread =
reinterpret_cast<NtQueryInformationThread_t>(GetProcAddress(
GetModuleHandle("ntdll.dll"), "NtQueryInformationThread"));
pNtQueryInformationThread(GetCurrentThread(), THREADINFOCLASS(9),
&startAddress, sizeof(startAddress), nullptr);
}
}
#pragma comment (linker, "/INCLUDE:__tls_used")
#pragma comment (linker, "/INCLUDE:__xl_b")
#pragma data_seg(".CRT$XLB")
EXTERN_C
PIMAGE_TLS_CALLBACK _xl_b = on_tls_callback;
#pragma data_seg()