Increasingly many systems have to run all the time with no downtime allowed. Consider, for example, systems controlling electric power plants and e-banking servers. Nevertheless, security patches and a constant stream of new operating system versions need to be deployed without stopping running programs. These factors naturally lead to a pressing demand for live update---upgrading all or parts of the operating system without rebooting. Unfortunately, existing solutions require significant manual intervention and thus work reliably only for small operating system patches.

Fault injection is a pivotal technique in dependability benchmarking. Unfortunately, existing general-purpose fault injection tools either inject faults in predetermined memory locations or resort to random injection, approaches that generally result in poor fault coverage and controllability guarantees. This makes it difficult to reproduce or compare experiments across different systems or workloads. This paper presents EDFI, a new tool for dependable general-purpose fault injection experiments. EDFI combines static and dynamic program instrumentation to perform execution-driven fault injection, a technique which allows realistic software faults to be injected in a controlled way as the target system executes. Our instrumentation strategy guarantees a predetermined fault load distribution during the entirety of the experiment, independently of the particular system or workload considered. Our evaluation confirms that EDFI significantly improves the precision and controllability of prior tools, at the cost of only modest memory and performance overhead during fault-free execution.