[Bug bpf/24759] New: stapbpf-next housekeeping: need version checking between stap translator and stapbpf

[me at serhei dot io]

https://sourceware.org/bugzilla/show_bug.cgi?id=24759

            Bug ID: 24759
           Summary: stapbpf-next housekeeping: need version checking
                    between stap translator and stapbpf
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: bpf
          Assignee: systemtap at sourceware dot org
          Reporter: me at serhei dot io
  Target Milestone: ---

Currently you can generate a .bo module with one version of the systemtap
translator and feed it to a different version of stapbpf, which will dutifully
try to interpret it.

Because a lot of stapbpf feature work requires tweaks to the ELF format
(changing the ABI of stapbpf modules), this can result in nonsense behaviour.
For example, pr23858 work will require changing the ABI of the
bpf_map_get_next_key helper.

We should write the stap version in a new section of the .bo file and have
stapbpf check it. By default, stapbpf should output an error (or warning) if
the versions do not match.

In future, we can look at what's required to safely enable compatibility
between different stap translator and stapbpf versions. For example, we may
want a newer translator (deployed locally, easy to update) to be able to
generate code for an older (deployed elsewhere, hard to update) stapbpf
version.

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