added some documentation

c/linux_loader_poc/README.md

@@ -1,8 +1,36 @@
-# Custom ELF interpreter under Linux
+# Proof-of-concept custom loaders in Linux
 
-This is proof-of-concept shows how to use a custom 
+This is a proof-of-concept to show different methods to load executables in the Linux kernel with our own loaders / linkers / interpreters.
 
+### Methods
 
-#### Credits
+#### 1. binfmt_misc
+
+We use a kernel module called binfmt_misc to register our own binary format in the Linux kernel.
+
+The loader will be called in userspace.
+
+See: https://www.kernel.org/doc/Documentation/binfmt_misc.txt
+
+See: `demo_binfmt_misc` in Makefile
+
+#### 2. ELF Interpreter section (INTERP)
+
+Every dynamically linked ELF executable contains a special section called `.interp`.
+
+In case the Linux kernel sees such a section, I will load the interpreter instead.
+Afterwards, it is the task of the interpreter (usually ld-linux.so) to load all dependencies and do the final relocation.
+
+See: `demo_interpreter` in the Makefile
+
+#### 3. Custom kernel module
+
+We use the binfmt subsystem of the Linux kernel to implement our own format.
+
+A good example is the loader for the script she-bangs (`#!/bin/bash` et al):
+
+https://github.com/torvalds/linux/blob/master/fs/binfmt_script.c
+
+### Credits
 
 Steffen Vogel <post@steffenvogel.de>