Single-address-space operating systems have well-known lightweightness benefits that result from their central design idea: the kernel and applications share a unique address space. This model makes these operating systems (OSes) incompatible by design with a large class of software: multiprocess POSIX applications. Indeed, the semantics of the primitive used to create POSIX processes, fork, are inextricably tied to the existence of multiple address spaces.

Dynamic Binary Modification (DBM) is an important technique used in computer architecture simulators, virtualization, and program analysis, to name a few examples. The software ecosystem of RISC-V is maturing at pace, but is still missing a high-performance, optimized DBM. Addressing this requirement is key to improving the overall software ecosystem. This paper presents a comprehensive performance evaluation study for a DBM (MAMBO) which has been ported and optimized for 64-bit RISC-V. The main optimizations for DBM on RISC architectures have been implemented and tuned for RISC-V to address specific architectural features. For example, jump trampolines have been specifically developed to address the short direct branch range specified by the RISC-V ISA. The evaluation shows that for SPEC CPU2006 the geometric mean overhead is of 14.5%, with SPECint having the largest contribution with a geometric mean of 28.5%, while SPECfp has only an overhead of 5.6%. Concretely, this results in a reduction in runtime for h264ref from over 75 hours using the baseline DBM, to 2.2 hours with optimizations applied.

Compartmentalization is a form of defensive software design in which an application is broken down into isolated but communicating components. Retrofitting compartmentalization into existing applications is often thought to be expensive from the engineering effort and performance overhead points of view. Still, recent years have seen proposals of compartmentalization methods with promises of low engineering efforts and reduced performance impact. ARM Morello combines a modern ARM processor with an implementation of Capability Hardware Enhanced RISC Instructions (CHERI) aiming to provide efficient and secure compartmentalization. Past works exploring CHERI-based compartmentalization were restricted to emulated/FPGA prototypes.