[Bug 1830796] Re: [Bionic][ARM64]Failure debugging linux kernel

[Brian Murray]

Hello Manoj, or anyone else affected,

Accepted gdb into bionic-proposed. The package will build now and be
available at https://launchpad.net/ubuntu/+source/gdb/8.1-0ubuntu3.1 in
a few hours, and then in the -proposed repository.

Please help us by testing this new package.  See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how
to enable and use -proposed.  Your feedback will aid us getting this
update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug,
mentioning the version of the package you tested and change the tag from
verification-needed-bionic to verification-done-bionic. If it does not
fix the bug for you, please add a comment stating that, and change the
tag to verification-failed-bionic. In either case, without details of
your testing we will not be able to proceed.

Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification .  Thank you in
advance for helping!

N.B. The updated package will be released to -updates after the bug(s)
fixed by this package have been verified and the package has been in
-proposed for a minimum of 7 days.

** Changed in: gdb (Ubuntu Bionic)
       Status: In Progress => Fix Committed

** Tags added: verification-needed verification-needed-bionic

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https://bugs.launchpad.net/bugs/1830796

Title:
  [Bionic][ARM64]Failure debugging linux kernel

Status in gdb package in Ubuntu:
  Fix Released
Status in gdb source package in Bionic:
  Fix Committed

Bug description:
  [Impact]
  GDB fails to debug ARM64 vmlinux debug image with proc/kcore information. For example it is unable to print values of variables like 'jiffies_64'.

  [Test]
  # gdb /usr/lib/debug/boot/vmlinux-4.18.0-20-generic  /proc/kcore
  [New process 1]
  Core was generated by `BOOT_IMAGE=/boot/vmlinuz-4.18.0-20-generic root=UUID=edb5e5a7-8272-4e13-aa25-37'.
  #0  0x0000000000000000 in ?? ()
  (gdb) p jiffies_64
  Cannot access memory at address 0xffff000009616980
  (gdb)

  [Fix]
  This issue was fixed upstream (git://sourceware.org/git/binutils-gdb.git) by the following patch:
  8727de56b0  Fix tagged pointer support

  [Regression Potential]
  The risk of regression after applying this patch could be to architectures other than ARM64 due to changes to gdb/util.c. Please see comment #2 where I have tested the PPA package on a ppc64el system and found it does not introduce any regressions.

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