The first milliseconds...

What happens when I run my application

Transcript

1. The first milliseconds Or what happens before the ‘hello world’
2. I promise unicorns and cats
3. Who am I? Cristian Prieto (@cprieto)
4. Why? What is all about?
6. You will see… • Lot’s of unrelated cat pictures (and maybe unicorns) • Hexadecimal notation • Debugger commands • A little of .NET code • ASSEMBLER!!!
7. It is simple…
8. The “classic” ‘Hello World’
9. We can compile this with GCC (the compiler)
10. Yay! we now have an executable!
11. So… the compiler generates executable code, right?
12. Not exactly
13. • Compiler: Compiles the code into assembler code • Assembler: assemble the code into object format • Linker: Links the code with libraries • Loader: Loads the program for execution
15. • Compiler/assembler produce an object file • Object files are consumed by the linker • The linker produces image files • An image file can be an executable, a static library or a shared (dynamic) library • The loader consumes image files
16. A 64 bit ELF Executable
17. What?! an ELF?!
18. Every OS has their own binary file format.
19. • Windows uses PE+ (which is a variant of COFF) • MacOSX and iOS use Mach-O • Almost everything else (Linux, BSDs, Android, blah blah blah) use ELF
20. We will concentrate in “Windows” now
21. Time for history…
22. We had DOS…
23. Fitting memory…
24. The big jump…
25. PE was released for Windows NT
27. This program cannot be run in DOS mode
28. What about real Windows apps?
29. I thought this talk was about .NET
30. As part of the IL standard we generate PE files