Brussels / 4 & 5 February 2017


Everything You Always Wanted to Know About "Hello, World"*

(*But Were Afraid To Ask)

I've been working on a new system call ABI and the required runtime support for a C variant with spacial memory safety. Along the way I've encountered lots of interesting bits and pieces required to implement a simple C "Hello, World" program. I found the process fascinating so this talk brings all that knowledge together in one place.

The first example in the classic "The C Programming Language" by Kernighan and Ritchie is in fact a remarkably complete test of the C programming language. This talk provides a guided tour a slightly more complex program where printf() is called with multiple arguments. Along the way from the initial processes' call to exec() to the final _exit(), we'll tour the program loading code in the kernel and the dynamic linker, the basics of system call implementation, the implementation of the memory allocator, and of course printf(). We'll also touch on localization and a little on threading support. Where appropriate, I'll discuss portions of the system that need changing to accommodate memory safe versions of C like the version we are developing for our CHERI CPU.

This talk will assume some knowledge of a language with C-like syntax (C, C++, Java, and PHP should all be fine).


Brooks Davis