Information-flow control on ARM and POWER multicore processors

Weak memory models implemented on modern multicore processors are known to affect the correctness of concurrent code. They can also affect whether or not the concurrent code is secure. This is particularly the case in programs where the security levels of variables are value-dependent, i.e., depend on the values of other variables. In this paper, we illustrate how instruction reordering allowed by ARM and POWER multicore processors leads to vulnerabilities in such programs, and present a compositional, flow-sensitive information-flow logic which can be used to detect such vulnerabilities. The logic allows step-local reasoning (one instruction at a time) about a thread’s security by tracking information about dependencies between instructions which guarantee their order of occurrence. Program security can then be established from individual thread security using rely/guarantee reasoning. The logic has been proved sound with respect to existing operational semantics using Isabelle/HOL, and implemented in an automatic symbolic execution tool.