Virtual machines and Software Frameworks are an initial part of our digital life. There are complex VM and simple Software Frameworks. I did my best to describe the way VM code may interact with native code and the Operating System, however, the backwards interaction is still left unexplained. This article is going to fix this omission.

These days we are simply surrounded by different software frameworks. Just to name a few: Java, .Net and, actually, many more. Have you ever wondered how those work or have you ever wanted or needed to implement one? In this article, I will cover a simple or even trivial runtime framework.

One of the aspects of software anti RE (reverse engineering) protection is the need to protect sensitive data (for example decryption or license keys, etc.) There is quite a common practice of storing such data in encrypted form and using it by passing to a certain routine for decryption. I am not going to say, that this is not a good idea, but the problem with such approach is - vendors (in most cases) only rely on the complexity of the encryption algorithm, which is not as protective as it is thought to be and too often is placed in a single function (which, potentially, may be ripped and used with malicious intent).

Sometimes, a need may rise to start a thread in a separate process and the need is not necessarily malicious. For example, one may want to replace library functions or to place some code between the executable and a library function. However, Linux does not provide a system call that would do anything similar to CreateRemoteThread Windows API despite the fact that I see people searching for such functionality.

Threads are everywhere. Even now, when you browse this page, threads are involved in the process. Most likely, you have more than one tab opened in the browser and each one has at least one thread associated with it. The server supplying this page runs several threads in order to serve multiple connections simultaneously. There may be unnumbered examples for threads, but let us concentrate on one specific implementation thereof. Namely, Linux implementation of threads.