CoreSight based execution monitoring for space applications 

CoreSight is a hardware technology present in many modern ARM based Systems-on-Chips (SoC) which enables tracing of program execution and system events in a non-invasive way – without additional hardware or instrumentation of the analysed software and with negligible performance penalty. The objectives of the project were to evaluate CoreSight feature availability on a selection of SoCs, develop embedded software to interface with the CoreSight hardware on the selected platform and demonstrate the capabilities and performance of the developed solution using a representative use-case based on PROBA3 payload Application Software (ASW).

CoreSight feature availability was researched and reported. Embedded Trace Software Modules (ETSM) were developed for Xilinx Zynq Ultrascale+ ZCU104 board running Linux, interfacing with CoreSight via perf subsystem, supporting the required functionality and exposing it via PUS 6 and a custom PUS service over ethernet. The development of ETSM required modifications of the Linux kernel subsystems related to perf and CoreSight support. PUS C Deployment tool suite, developed by N7 Space, was used to design the PUS C services and generate the corresponding ASN.1 and ACN data type definitions, from which the telecommand/telemetry transcoders were automatically derived. Test and Tracing Support Modules (TTSM) were developed to interface an in-house software validation facility with ETSM. PROBA3 payload ASW was modified to remove its dependencies on PROBA3 hardware and to run on Linux via a thin RTEMS API emulation layer. The following capabilities were successfully demonstrated:

Trace captured from an execution of non-instrumented code with artificially inserted bug. The trace lists the sequence of executed instructions which led to a crash, unlike a stack trace, which would show only the sequence of function calls.

Histogram of execution times of a block of code, captured without code instrumentation.

Plot of bus access events (correlated with cache misses) with respect to code execution times, in various configurations of an interfering program running concurrently on a different processor core.

The developed solution has the potential to facilitate performance measurements, behaviour analysis, testing and debugging of on-board software, both on-ground and in-flight. The performance measurements may be a valuable input to software verification and various analyses (e.g. schedulability and inter-core interference).

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Disclaimer: This work performed during this project was carried out under a programme of, and funded by, the European Space Agency. The views expressed here can in no way be taken to reflect the official opinion of the European Space Agency.