Collaborative Working Sessions - Embedded systems

What are embedded systems:

• All systems which is not a PC, Software in a device.
• Industrial control (PLC = programmable logic control)
• Software in a toaster or dishwasher
• Small and powerful systems given:
• Small: TMS430 Series, 32 kByte ROM, 512 Byte RAM,
• Powerful: Raspi as controller
• => Focus to small systems, because powerful have often a Linux Kernel,
• Using a specific Real time operation system or not, no difference
• (If RTOS is used, it should be also reproducible)

Challenges

• Different Target systems, different compilers from diff. vendors, more variablility.
• comprehensibility process how the binary is built
• traceability of build process.
• Reprod. Build should be a part of the approval procedure for a device.

Solutions:

• All solutions known for gcc should be also applied to all known compiler,
• Is it done or in focus? Responsibility from the compiler vendors for this topic

Notes during session

• Reproducible required: Gambling industry requires it. restrict regulation.
• look for gcc link time optimization.

Look for:

• Debugging information in the object:
• 1) with the same path, different machines.
• 2) diff. path on diff machines
• If the path is a symbolic link (or Junction in Windows), the Compiler should not resolve the symbolic linked path, then the path is able to make unique.
• Use Option remove debug symbols.

• Always use the same compiler version.

• Build info file is not very well standardized? Look for https://wiki.debian.org/ReproducibleBuilds/BuildinfoFiles
• Have a script for all stuff of build inputs
• Language for sorting its a topic to the build system. (for linker), use always US-ASCII-sorting
• Optimizations should not randomized or have start seed. SDE Source date epoch as seed.
• Parallel compilation makes problems? Order of files.

gcc is reproducible by default. with the same source path. Or have not debug symbols. build-id.

Changing and testing: Test effort.

What about changing sources in a small way, reprod. build gives only small changes, test only the differences:

• Have to be more as one binary for the solutions. using dll libs ?
• Use static link, compare object files. Look from where comes the difference