[Bug 1908756] Re: Ubuntu 20.10 - elfutils unwinding broken for s390 compat

[Frank Heimes]

** Also affects: elfutils (Ubuntu Hirsute)
   Importance: Undecided
     Assignee: Skipper Bug Screeners (skipper-screen-team)
       Status: New

** Also affects: elfutils (Ubuntu Groovy)
   Importance: Undecided
       Status: New

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Title:
  Ubuntu 20.10 - elfutils unwinding broken for s390 compat

Status in Ubuntu on IBM z Systems:
  New
Status in elfutils package in Ubuntu:
  New
Status in elfutils source package in Groovy:
  New
Status in elfutils source package in Hirsute:
  New

Bug description:
  ---Problem Description---
  libdw unwinding fails for 32 bit binaries.
   
  Elfutils biarch test currently fails on s390x doing unwinding for a 32 bit process.

  FAIL: run-backtrace-native-biarch.sh
  ====================================

  0x557e7000      0x557eb000      /root/elfutils/tests/backtrace-child-biarch
  0x7dba4000      0x7dd51000      /usr/lib/libc-2.32.so
  0x7dd53000      0x7dd70000      /usr/lib/libpthread-2.32.so
  0x7dd7f000      0x7dda6000      /usr/lib/ld-2.32.so
  TID 376858:
  # 0 0x7dd6668a          raise
  # 1 0x7fd0ef60 - 1      <null>
  /root/elfutils/tests/backtrace: dwfl_thread_getframes: No DWARF information found
  backtrace: backtrace.c:114: callback_verify: Assertion `symname != NULL && strcmp (symname, "sigusr2") == 0' failed.
  ./test-subr.sh: line 84: 376822 Aborted                 (core dumped) LD_LIBRARY_PATH="${built_library_path}${LD_LIBRARY_PATH:+:}$LD_LIBRARY_PATH" $VALGRIND_CMD "$@"
  backtrace-child-biarch: no main
  FAIL run-backtrace-native-biarch.sh (exit status: 1)

  Patch has already been posted and upstream committed:
  https://sourceware.org/pipermail/elfutils-devel/2020q4/003149.html

  Please pick up the following commit for the next release:
  commit e4d985a3c1c873f77d20fa0cd421458cc2824996
  Author: Andreas Krebbel <krebbel at linux.ibm.com>
  Date:   Thu Nov 19 20:32:24 2020 +0100

      IBM Z: Fix endianess problem in pid_memory_read
      
      The cached reads lack the big endian adjustments done in the fallback
      path.
      
      Signed-off-by: Andreas Krebbel <krebbel at linux.ibm.com>

  
  The patch applies cleanly ontop of elfutils_0.181-1.

  ====
  strace right now is not built with unwinding support for IBM Z although both variants should work - libdw and libunwind.

  Other distros use libdw from elfutils while Ubuntu on x86 appears to
  use libunwind. libdw and libunwind do support IBM Z.

  It would be good to build strace with unwinding support for Z.

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