Brooks Davis

CHERI is a portable architectural extension providing spatial, referential, and temporal memory safety along with strong, light-weight compartmentalization. CheriBSD is a port of FreeBSD supporting CHERI on Arm Morello, MIPS, and RISC-V. CheriBSD is the reference POSIX OS implementation for CHERI.

CheriBSD supports unmodified binaries from the native architecture plus CheriABI programs which have strong spatial, referential, and temporal safety guarantees. I will discuss our implementation of CheriBSD with a focus on CheriABI.

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).

The FreeBSD Project has been actively working to incorporate tools from the LLVM project into our base system including clang, libc++, and possibly lldb. This talk will cover our efforts so far including our plans to ship FreeBSD 9.0 with clang in the base system. I will cover both our current work to replace GPL licensed components with BSD(ish) licensed components and future or experimental work to incorporate new technologies made possible by LLVM.