[Bug 2062118] Re: autopkgtests fail on s390x (segfault)

[Pragyansh Chaturvedi]

I thought that a separate SRU bug is needed for an SRU, so I created that.
SRU info:
[ Impact ]

 * The failures on s390x are primarily because tep_alloc sets file
   endianness to LITTLE_ENDIAN by default (with no checks)

 * The changes are already accepted into plucky and upstream:
   https://code.launchpad.net/~r41k0u/ubuntu/+source/libtraceevent/+git/libtraceevent/+merge/477042

 * This will fix autopkgtest segfaults of libtracefs on oracular and
noble for s390x.

[ Test Plan ]

 * Clone libtracefs (oracular-devel or noble-devel), compile it and the tests (make && make test),
   then run the tests as root (utest/trace-utest), on an s390x machine (running oracular or noble)

 * You can test the fix by installing the patched version of libtraceevent for the release you are
   testing and trying the libtracefs tests again.

[ Where problems could occur ]

 * This is not likely to break anything, as we can make a safe assumption
   to set file_bigendian to the same value as host_bigendian by default.
   If these are different, the user can set it using event-parse-api

 * In any case, this change seems logical. This does not affect any other
   little-endian architectures, and I think this won't be breaking any workarounds
   people did around this problem.

 * But in case we have some regressions as a result of this change, then there surely would
   be some workaround to this in a patch, which can then be reverted.

[ Other Info ]

 * This does not fix anything in libtraceevent but does fix the tests for libtracefs on s390x.
   But I have opened this bug against libtraceevent.

 * I see a workaround around this problem in the last patch in d/p/series, but this change does not affect
   it

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https://bugs.launchpad.net/bugs/2062118

Title:
  autopkgtests fail on s390x (segfault)

Status in Ubuntu on IBM z Systems:
  Triaged
Status in libtraceevent package in Ubuntu:
  Fix Released
Status in libtracefs package in Ubuntu:
  Fix Released
Status in libtraceevent source package in Noble:
  New
Status in libtracefs source package in Noble:
  New
Status in libtraceevent source package in Oracular:
  New
Status in libtracefs source package in Oracular:
  New
Status in libtraceevent source package in Plucky:
  Fix Released
Status in libtracefs source package in Plucky:
  Fix Released

Bug description:
  As part of the added QA to libtracefs it was found that it triggers a segfault on s390x.
  This isn't just a test failing, it seems this is still deeply broken on s390x.

  Either way, while in the time pressure of the noble release the
  decision was simplified like "The tests didn't make it worse, just now
  we know" and continued (To not leave these platforms behind later
  unable to add it, albeit knowing it is still incomplete for now).

  It does not mean that we can ignore them for too long and certainly
  need to work on completing that into being fully functional in tests
  and real usage. Hence we create this spin off bug from the MIR work in
  bug 2051925 for tracking the further efforts.

  Example test log:
  https://autopkgtest.ubuntu.com/results/autopkgtest-noble/noble/s390x/libt/libtracefs/20240417_184123_8ab96@/log.gz

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