While PIC is standard for Linux and host development, it is far less known to the embedded world. But with the growing usage of bootloaders and loadable ‘applets’ especially in the ‘IoT’ world, PIC could be an interesting solution. Instead I want you to give the insights so you can pick and choose your own implementation.įor most applications running on ARM Cortex-M, PIC is not needed or even might be the wrong solution, because usually there is no dynamic loading of code involved. So I’m not going to address any of them in this article directly.
There can be certainly an unlimited number of use cases. With using PIC the data amount for firmware updates over low bandwidth network connections like LoRa could be minimized too. In essence: a library shall be using position-independent-code (PIC) so it can be placed and run at different addresses on a device.
from a memory device/SD card and then run anywhere in the memory Support a loading mechanism to load code e.g.Provide the a library to many devices in the field, and each device can load or have that library in different memory ranges, e.g.Build application image position independent to minimize future update size.Execute a loadable task anywhere in the memory.Build a library which can be loaded by different applications at runtime.Copy code from slower FLASH to faster SRAM for execution.Basically it means that the code can run ‘anywhere’.
Position-Independent code (or PIC) is what is suitable for shared library code or if you want to use a loader to load and execute code anywhere in your address space. Let’s find out! Let’s start a journey through the wonderland… Outline Leading to the central question: how is position-independent code going to work with an embedded application on an ARM Cortex-M? Something you might not have been aware of what could be possible with the tools you have at hand today. That option opened up a ‘rabbit hole’ with lots of wonderful, powerful and strange things. It sounds simple: just add -fPIC to the compiler settings and you are done. Welcome to ‘ Alice in Wonderland‘! For a university research project using an ARM Cortex-M33 we are evaluating position-independent code as way to load applications or part of it with a bootloader.
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