Memory overflow protection for embedded systems using run-time checks, reuse and compression

Abstract

Out-of-memory errors are a serious source of unreliability in most embedded systems. Applications run out of main memory because of the frequent difficulty of estimating the memory requirement before deployment, either because it depends on input data, or because certain language features prevent estimation. The typical lack of disks and virtual memory in embedded systems has two serious consequences when an out-of-memory error occurs. First, there is no swap space for the application to grow into, and the system crashes. Second, since protection from virtual memory is usually absent, the fact that a segment has exceeded its bounds is not even detected and hence no pre-crash remedial action is possible.This work improves system reliability in two ways. First it proposes a low-overhead system of run-time checks by which the outof-memory errors are detected just before they will happen, by using carefully optimized compiler-inserted run-time check code. Such error detection enables the designer to incorporate systemspecific remedial action, such as transfer to manual control, shutting down of non-critical tasks, or other actions. Second, this work proposes five related techniques that can grow the stack or heap segment after it is out of memory, into previously un-utilized space such as dead variables and space freed by compressed live variables. These techniques can avoid the out-of-memory error if the extra space recovered is enough to complete execution.Results from our benchmarks show that the overheads from the system of run-time checks for detecting memory overflow are extremely low: the run-time and code-size overheads are 1.1% and 0.09% on average. When the reuse functionality is included, the run-time and code-size overheads increase to only 3.2% and 2.33%, but the method is able to grow the stack or heap beyond its overflow by an amount that ranges from 0.7% to 93.5% of the combined stack and heap size.

MemSafe: Ensuring the Spatial and Temporal Memory Safety of C at Runtime

“…Like paging, segmented virtual memory is a common approach for providing coarse-grained memory protection. In another method, Biswas et al [54] developed a technique for avoiding out-of-memory errors with compilerinserted runtime checks, memory reuse, and the compression of unused data. Finally, Middha et al [55] developed a similar method for avoiding out-of-memory errors in embedded systems by sharing stack space among the executing tasks of multitasking workloads.…”

Eliminating the call stack to save RAM

“…Like function inlining [Cooper et al 1991] and cloning [Cooper et al 1993], flattening copies code and alters control flow in simple ways, with the goal of enabling subsequent optimizations to do a better job. Biswas et al [2004] and Middha et al [2005] use compilerdriven techniques to blur the lines between different storage regions. This permits, for example, stacks to overflow into unused parts of the heap, globals, or other stacks.…”

Safe and Structured Use of Interrupts in Real-Time and Embedded Software

“…The only tools that we know of that analyze stack depth in the presence of interrupts are ours [16] and Brylow et al's [5]. In related work, Barua et al [3] investigate an approach that, upon detecting stack overflow, spills the stack data into an unused region of RAM, if one is available.…”