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[Ubuntu Foundations Team Bug Bot <1413646@xxxxxxxxxxxxxxxxxx>]

** Tags added: patch

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Title:
  15.04: incomplete debug symbols package - please disable
  CONFIG_DEBUG_INFO_SPLIT or package the .dwo files

Status in linux package in Ubuntu:
  Confirmed

Bug description:
  The kernel option CONFIG_DEBUG_INFO_SPLIT has been enabled in vivid
  (commit bb5f2d940954fb389f16a0f7ad05b5a53a7e5227).

  It moves debuginfo to .dwo files, using gcc -split-dwarf.  
  The kernel packaging received no updates to include the .dwo files, AFAICT.

  This results in  gdb/crash not unable to find/read the kernel debug
  symbols, because the .dwo files are not present.

  Possible solutions include:
  1) Disable CONFIG_DEBUG_INFO_SPLIT
  2) Update the packaging to include .dwo files.

  Options #1 (patch attached) tested, and it worked.

  
  Before:
  ----------

  	# grep CONFIG_DEBUG_INFO_SPLIT /boot/config-3.18.0-9-generic 
  	CONFIG_DEBUG_INFO_SPLIT=y

  gdb:

  	(gdb) symbol-file /usr/lib/debug/boot/vmlinux-3.18.0-9-generic
  	Reading symbols from /usr/lib/debug/boot/vmlinux-3.18.0-9-generic...
  	warning: Could not find DWO CU arch/powerpc/kernel/.tmp_prom_init.dwo(0xa3396d7f33b2feee) referenced by CU at offset 0x24c [in module /usr/lib/debug/boot/vmlinux-3.18.0-9-generic]
  	<and many other .dwo files>

  crash:

  	gdb called without error_hook: Dwarf Error: CU at offset 0x24c references unknown DWO with ID 51757104ad7ccc06 [in module /usr/lib/debug/boot/vmlinux-3.18.0-8-generic]
  	Dwarf Error: CU at offset 0x24c references unknown DWO with ID 51757104ad7ccc06 [in module /usr/lib/debug/boot/vmlinux-3.18.0-8-generic]

          crash: /usr/lib/debug/boot/vmlinux-3.18.0-8-generic: no
  debugging data available

  
  After:
  --------

  	# grep CONFIG_DEBUG_INFO_SPLIT /boot/config-3.18.0-9-generic 
  	# CONFIG_DEBUG_INFO_SPLIT is not set

  gdb:

  	(gdb) symbol-file /usr/lib/debug/boot/vmlinux-3.18.0-9-generic 
  	Reading symbols from /usr/lib/debug/boot/vmlinux-3.18.0-9-generic...done.

  crash:

  	# crash /usr/lib/debug/boot/vmlinux-3.18.0-9-generic /var/crash/201501221026/dump.201501221026
  	<...>
  	      KERNEL: /usr/lib/debug/boot/vmlinux-3.18.0-9-generic
  	    DUMPFILE: /var/crash/201501221026/dump.201501221026  [PARTIAL DUMP]
  	<...>
  	crash>

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