[systemd-devel] Storing package metadata in ELF objects

[Luca Boccassi]

On Fri, 2021-04-30 at 19:57 +0200, Mark Wielaard wrote:
> Hi,
> 
> On Sat, 2021-04-10 at 18:44 +0000, Zbigniew Jędrzejewski-Szmek wrote:
> > [I'm forwarding the mail from Luca who is not subscribed to fedora-
> > devel]
> > On Sat, Apr 10, 2021 at 01:38:31PM +0100, Luca Boccassi wrote:
> > Cross-posting to the mailing lists of a few relevant projects.
> 
> Note that in this version of the email the [N] references in your email
> don't seem to point anywhere. I found an older variant of the same
> email which contained:
> 
> [0] https://github.com/systemd/systemd/issues/18433
> [1] https://systemd.io/COREDUMP_PACKAGE_METADATA/
> [2] https://fedoraproject.org/wiki/Changes/Package_information_on_ELF_objects
> [3] https://github.com/systemd/package-notes

Sorry about that! Must have messed up the copy&paste.

> > After an initial discussion [0], recently we have been working on a new
> > specification [0] to encode rich package-level metadata inside ELF
> > objects, so that it can be included automatically in generated coredump
> > files. The prototype to parse this in systemd-coredump and store the
> > information in systemd-journal is ready for testing and merged
> > upstream. We are now seeking further comments/opinions/suggestions, as
> > we have a few months before the next release and thus there's plenty of
> > time to make incompatible changes to the format and implementation, if
> > required.
> > 
> > A proposal to use this by default for all packages built in Fedora 35
> > has been submitted [1].
> > 
> > The Fedora Wiki and the systemd.io document have more details, but to
> > make a long story short, a new .notes.package section with a JSON
> > payload will be included in ELF objects, encoding various package-
> > build-time information like distro name&version, package
> > name&version,
> > etc.
> 
> Is there a list of default keys (and their canonical spelling, upper-
> lower-Camel_Case, etc.)? If there is, could we have a "debuginfod" key
> with as value an URL pointing to the debuginfod server URL where the
> embedded build-id executable, debuginfo and sources can be found?
> https://sourceware.org/elfutils/Debuginfod.html

The "Implementation" section of the spec lists the "main" fields:

https://systemd.io/COREDUMP_PACKAGE_METADATA/

(source for that is https://github.com/systemd/systemd/blob/main/docs/COREDUMP_PACKAGE_METADATA.md )

Would you like to send a PR to update it and add that field?

> > To summarize from the discussion, the main reasons why we believe this
> > is useful are as following:
> > 
> > 1) minimal containers: the rpm database is not installed in the
> > containers. The information about build-ids needs to be stored
> > externally, so package name information is not available immediately,
> > but only after offline processing. The new note doesn't depend on the
> > rpm db in any way.
> > 
> > 2) handling of a core from a container, where the container and host
> > have different distros
> > 
> > 3) self-built and external packages: unless a lot of care is taken to
> > keep access to the debuginfo packages, this information may be lost.
> > The new note is available even if the repository metadata gets lost.
> > Users can easily provide equivalent information in a format that makes
> > sense in their own environment. It should work even when rpms and debs
> > and other formats are mixed, e.g. during container image creation.
> > 
> > Other than in Fedora, we are already making the required code changes
> > at Microsoft to use the same format&specification for internally-built
> > binaries, and for tools that parse core files and logs.
> > 
> > Tools for RPM and DEB (debhelper) integration are also available [3].
> > 
> > > -- 
> > > Kind regards,
> > > Luca Boccassi

-- 
Kind regards,
Luca Boccassi
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