GetCsrssPid3

#define echo(x) x
#define label(x) echo(x)__LINE__
#define RTL_CONSTANT_STRINGW(s) { sizeof( s ) - sizeof( (s)[0] ), sizeof( s ),(PWSTR)(s) }
#define STATIC_UNICODE_STRING(name, str) static const WCHAR label(__)[] = L##str; static const UNICODE_STRING name = RTL_CONSTANT_STRINGW(label(__))

NTSTATUS GetCsrssPid(HANDLE* pUniqueProcessId)
{
    NTSTATUS status;
    ULONG cb = 0x10000;
    do
    {
        status = STATUS_INSUFFICIENT_RESOURCES;

        if (PVOID buf = ExAllocatePool(PagedPool, cb))
        {
            if (0 <= (status = NtQuerySystemInformation(SystemProcessInformation, buf, cb, &cb)))
            {
                status = STATUS_NOT_FOUND;

                union {
                    PSYSTEM_PROCESS_INFORMATION pspi;
                    PVOID pv;
                    PUCHAR pb;
                };

                pv = buf;

                ULONG NextEntryOffset = 0;
                do
                {
                    pb += NextEntryOffset;

                    STATIC_UNICODE_STRING(csrss, "csrss.exe");

                    if (pspi->UniqueProcessId)
                        DbgPrint("%p %wZ\n", pspi->UniqueProcessId, &pspi->ImageName);

                    if (RtlEqualUnicodeString(&csrss, &pspi->ImageName, TRUE))
                    {
                        ///////// This part never is executed ///////

                        *pUniqueProcessId = pspi->UniqueProcessId;
                         DbgPrint("%p\n", *pUniqueProcessId);
                        status = STATUS_SUCCESS;
                        break;

                       ////////////////////////////////////////////
                    }

                } while (NextEntryOffset = pspi->NextEntryOffset);
            }
            ExFreePool(buf);
        }

    } while (status == STATUS_INFO_LENGTH_MISMATCH);

    return status;
}

// Usage:

HANDLE hCsrssPid = (HANDLE)0;
GetCsrssPid(&hCsrssPid);
DbgPrint("%x\n", hCsrssPid);