Virtual machines (VM) are widely used to host and isolate software modules. However, extremely small memory and low-energy budgets have so far prevented wide use of VMs on typical microcontroller-based IoT devices. In this paper, we explore the potential of two minimal VM approaches on such low-power hardware. We design rBPF, a register-based VM based on extended Berkeley Packet Filters (eBPF). We compare it with a stack-based VM based on WebAssembly (Wasm) adapted for embedded systems. We implement prototypes of each VM, hosted in the IoT operating system RIOT. We perform measurements on commercial off-the-shelf IoT hardware. Unsurprisingly, we observe that both Wasm and rBPF virtual machines yield execution time and memory overhead, compared to not using a VM. We show however that this execution time overhead is tolerable for low-throughput, low-energy IoT devices. We further show that, while using a VM based on Wasm entails doubling the memory budget for a simple networked IoT application using a 6LoWPAN/CoAP stack, using a VM based on rBPF requires only negligible memory overhead (less than 10% more memory). rBPF is thus a promising approach to host small software modules, isolated from OS software, and updatable on-demand, over low-power networks.

中文翻译：

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物联网微控制器上的最小虚拟机：带有rBPF的Berkeley数据包过滤器的案例

虚拟机（VM）被广泛用于承载和隔离软件模块。但是，迄今为止，极小的内存和低能耗的预算阻止了VM在典型的基于微控制器的IoT设备上的广泛使用。在本文中，我们探讨了在这种低功耗硬件上使用两种最小VM方法的潜力。我们设计了rBPF，这是一个基于寄存器的VM，基于扩展的Berkeley数据包过滤器（eBPF）。我们将其与适用于嵌入式系统的基于WebAssembly（Wasm）的基于堆栈的VM进行比较。我们实现了在IoT操作系统RIOT中托管的每个VM的原型。我们在商用现成的IoT硬件上执行测量。毫不奇怪，我们观察到，与不使用VM相比，Wasm和rBPF虚拟机都产生执行时间和内存开销。但是，我们证明了这种执行时间开销对于低吞吐量是可以容忍的，低能耗物联网设备。我们进一步表明，虽然使用基于Wasm的VM会使使用6LoWPAN / CoAP堆栈的简单联网IoT应用程序的内存预算增加一倍，但使用基于rBPF的VM仅需要微不足道的内存开销（内存少于10％）。因此，rBPF是一种托管小型软件模块的有前途的方法，这些软件模块与OS软件隔离，并且可以通过低功耗网络按需更新。