Abstract

It is an established trend to develop low-level code—embedded software, device drivers, and operating systems—using high-level languages, especially functional languages with advanced facilities to abstract and generate code. To be reliable and secure, low-level code must correctly manage space, time, and other resources, so special type systems and verification tools arose to regulate resource access statically. However, a general-purpose functional language practical today can provide the same static assurances, also without run-time overhead. We substantiate this claim and promote the trend with two security kernels in the domain of device drivers: 1. one built around raw pointers, to track and arbitrate the size, alignment, write permission, and other properties of memory areas across indexing and casting; 2. the other built around a device register, to enforce protocol and timing requirements while reading from the register. Our style is convenient in Haskell thanks to custom kinds and predicates (as type classes); type-level numbers, functions, and records (using functional dependencies); and mixed type- and term-level programming (enabling partial type signatures). 1

Citations