Tag ELF files with platform specific section

[lmb]

Compiling against Windows eBPF headers produces object files which are not easily distinguishable from object files compiled against Linux headers. This is a problem for cross-platform tooling which wishes to inspect the contents of an ELF.

Emit a section .ebpf_for_windows with the contents 0x01 into ELFs compiled against the windows headers.

Updates #3956

[lmb]

This is not a foolproof solution unfortunately because a program might not include the header that contains the section definition. As far as I can tell there is a single file in the repo which has this problem, atomic_instructions_other.o but I can't figure out what the source for that is.

[dthaler]

I'll observe that this PR has no tests. https://github.com/microsoft/ebpf-for-windows/blob/main/CONTRIBUTING.md#contributing-code says:

For all new Pull Requests the following rules apply:

• Existing tests should continue to pass.
• Tests need to be provided for every bug/feature that is completed.
• Documentation needs to be provided for every feature that is end-user visible.

I would expect a test that (say) verifies that one or more sample programs have this section with the correct content. Can you add such a test as part of #3956?

[lmb]

Do you have existing tests which run the equivalent of a shell script? I’ll not have much time in the next weeks and will prioritise getting the names map and program changes in

[dthaler]

Do you have existing tests which run the equivalent of a shell script?

Yes. tests\bpftool_tests\bpftool_tests.cpp executes commands.

However, another way to do it is to have the test use elfio to check that the section is correct. libfuzzer\verifier_fuzzer\libfuzz_harness.cpp is an example of a test that uses ELFIO::elfio.