[Bug 1233185] Re: gdb-multiarch cannot read ARM cores: "wrong size gregset struct in core file"

[Brian Murray]

This patch seems to have disappeared from the Ubuntu versions of gdb in
Saucy, Trusty and Utopic. I've actually no idea what happened to the
Saucy version of the package 7.6-5ubuntu3. I'll take care of fixing this
in Utopic and Trusty.  The test case in the description is still valid.

** Changed in: gdb (Ubuntu)
   Importance: Undecided => High

** Changed in: gdb (Ubuntu)
       Status: Fix Released => Triaged

** Also affects: gdb (Ubuntu Trusty)
   Importance: Undecided
       Status: New

** Changed in: gdb (Ubuntu)
     Assignee: (unassigned) => Brian Murray (brian-murray)

** Changed in: gdb (Ubuntu Trusty)
     Assignee: (unassigned) => Brian Murray (brian-murray)

** Changed in: gdb (Ubuntu Trusty)
   Importance: Undecided => High

** Changed in: gdb (Ubuntu Trusty)
       Status: New => Triaged

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https://bugs.launchpad.net/bugs/1233185

Title:
  gdb-multiarch cannot read ARM cores: "wrong size gregset struct in
  core file"

Status in “gdb” package in Ubuntu:
  In Progress
Status in “gdb” source package in Trusty:
  In Progress
Status in “gdb” package in Debian:
  Fix Released

Bug description:
  We are getting complaints that the Launchpad apport retracers cannot
  create proper symbolic stack traces for crashes on ARM. It seems gdb-
  multiarch does not get along with our core dumps on ARM any more.
  Reproducing the full apport-retrace environment is a bit complicated,
  so I reduced this to a very simple test case:

  Log into an ARM machine, like the Nexus G4, or porter-
  armhf.canonical.com (shedir), using "schroot -c saucy-armhf".

   1. create a core dump of bash:

       $ cd /tmp/
       $ bash -c 'ulimit -c unlimited; kill -SEGV $$'

    2. Run it with gdb:

      $ gdb --batch --ex 'file /bin/bash' --ex 'core-file core' --ex 'bt'
      Core was generated by `bash -c ulimit -c unlimited; kill -SEGV $$'.
      Program terminated with signal 11, Segmentation fault.
      #0  0x00007f2eae349257 in kill () at ../sysdeps/unix/syscall-template.S:8181
   	../sysdeps/unix/syscall-template.S: Datei oder Verzeichnis nicht gefunden.
      #0  0x00007f2eae349257 in kill () at ../sysdeps/unix/syscall-template.S:81
      #1  0x00000000004418a1 in kill_pid ()
      [...]

      There are not a lot of symbols as usually one doesn't have bash-
  dbgsym etc. installed, but it's clearly able to produce a stack trace.

    3. Run the same with gdb-multiarch:

       $ gdb-multiarch --batch --ex 'file /bin/bash' --ex 'core-file core' --ex 'bt'
      warning: wrong size gregset struct in core file
      Core was generated by `bash -c ulimit -c unlimited; kill -SEGV $$'.
      Program terminated with signal 11, Segmentation fault.
      warning: wrong size gregset struct in core file
      #0  <unavailable> in ?? ()
      #0  <unavailable> in ?? ()
      PC not available

  FTR, Apport uses gdb-multiarch on amd64, and --ex 'set architecture
  arm' --ex 'set gnutarget elf32-littlearm' to generate stack traces for
  ARM coredumps on x86 (using binaries/libaries/debug symbols for ARM
  that get unpacked into a temporary directory). The full invocation
  looks something like this:

    gdb-multiarch --ex 'set architecture arm' --ex 'set gnutarget
  elf32-littlearm' --ex 'set debug-file-directory /tmp/s/usr/lib/debug'
  --ex 'set solib-absolute-prefix /tmp/s' --ex 'file /tmp/s/bin/bash'
  --ex 'core-file CoreDump' --ex 'bt full' --batch

  But as gdb-multiarch does not even work on a native ARM machine for a
  native ARM core dump of the very same machine/OS, I guess it's
  something more fundamental which got broken there.

  The same test case on amd64 works fine BTW, i. e. gdb-multiarch can
  process amd64 binaries on amd64.

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