set reasonable default cmdlines for arm64

[dann frazier]

[Impact]
Crash dump support doesn't work by default on any known arm64 platform. Users have to figure out working incantations for the crashkernel= parameter and the parameters passed to the crash-dump kernel themselves and manual edit 2 different config files.

*NOTE* one of these config files moved from kexec-tools to kdump-tools between xenial & artful - that's why kexec-tools is only updated for xenial.

*NOTE* the debdiffs here are large because a few files have been renamed to "*.in" so they can be used as templates for generating per-architecture files at build time.

[Test Case]
Using either a Centriq 2400 or a Cavium ThunderX CRB (these platforms are known to support crashdump), and with a kernel >= 4.13 (xenial-ga did not support crashdump on arm64):

sudo apt install kdump-tools
(reboot, so crashkernel= is added to the kernel commandline)
echo c | sudo tee /proc/sysrq-trigger

Without having to edit any config files, crash dump should occur, with artifacts collected in /var/crash.

If you want to verify that the dump is usable, install the corresponding linux-image-<ver>-dbgsym package and run:

sudo crash /usr/lib/debug/boot/vmlinux-<ver> /var/crash/<crash>/dump.<crash>

crash should successfully load, placing you at a "crash>" prompt. At that prompt, you can issue the 'bt' command to see a backtrace.
Note: you need crash from zesty (7.1.8-1ubuntu1) or later.

[Regression Risk]
The biggest regression risk I see here is that we're introducing build-time mechanisms for generating config files per-architecture, and bugs in that implementation could lead to incorrect settings for non-arm64 architectures. To validate that, I've staged these update in a PPA (ppa:dannf/arm64-kdump), and I extracted those debs in a directory next to the current debs and diff'd the two trees[1]. Ignoring binary files, diff shows that only config files in the arm64 build are different, as intended. Note that, while this config file generation also exists in bionic, I modified it for these backports so that it retains the parameter order from the previous xenial/artful builds. This is so that the config files for non-arm64 architectures will be identical to the previous builds, and dpkg won't unnecessarily prompt admins to resolve conflicts if they've customized them.

[1]
$ for arch in amd64 arm64 armhf i386 ppc64el s390x; do
    diff -u0 -rpN ${arch}-cur ${arch}-new | grep -v ^Binary
  done

[Łukasz Zemczak (sil2100)]

Hello dann, or anyone else affected,

Accepted makedumpfile into artful-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/makedumpfile/1:1.6.1-2ubuntu0.2 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-artful to verification-done-artful. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-artful. 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!

[Łukasz Zemczak (sil2100)]

Hello dann, or anyone else affected,

Accepted makedumpfile into xenial-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/makedumpfile/1:1.5.9-5ubuntu0.7 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-xenial to verification-done-xenial. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-xenial. 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!

[Łukasz Zemczak (sil2100)]

Hello dann, or anyone else affected,

Accepted kexec-tools into xenial-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/kexec-tools/1:2.0.10-1ubuntu2.5 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-xenial to verification-done-xenial. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-xenial. 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!

[dann frazier (dannf)]

For xenial and artful, I have verified by:

1) Deploying an arm64 system (Cavium ThunderX CRB1S), enabling proposed, installing kdump-tools, rebooting, then triggering a dump.
2) Regression/upgrade tested on x86 by launching a guest, installing kdump-tools, rebooting, then trigger a dump. Next, enabled proposed, dist-upgraded, rebooted, then triggering another dump.

Everything worked as expected.

[Launchpad Janitor (janitor)]

This bug was fixed in the package makedumpfile - 1:1.6.1-2ubuntu0.2

---------------
makedumpfile (1:1.6.1-2ubuntu0.2) artful; urgency=medium

  * kdump-tools: Add reasonable default 'crashkernel' parameter and kdump
    kernel cmdline for arm64. The files that contain the default kernel
    cmdline are now generated per-architecture at build-time. (LP: #1763532).

 -- dann frazier <email address hidden> Fri, 13 Apr 2018 17:49:36 -0600

[Łukasz Zemczak (sil2100)]

The verification of the Stable Release Update for makedumpfile has completed successfully and the package has now been released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.

[Launchpad Janitor (janitor)]

This bug was fixed in the package makedumpfile - 1:1.5.9-5ubuntu0.7

---------------
makedumpfile (1:1.5.9-5ubuntu0.7) xenial; urgency=medium

  * kdump-tools: Add reasonable default kdump kernel cmdline for arm64.
    The files that contain the default kernel cmdline are now generated
    per-architecture at build-time. Consequently, kdump-tools is no
    longer Architecture: all. (LP: #1763532).

 -- dann frazier <email address hidden> Fri, 13 Apr 2018 17:50:04 -0600

[Launchpad Janitor (janitor)]

This bug was fixed in the package kexec-tools - 1:2.0.10-1ubuntu2.5

---------------
kexec-tools (1:2.0.10-1ubuntu2.5) xenial; urgency=medium

  * The default crashkernel parameter didn't work on any known arm64
    systems, set a reasonable default instead (LP: #1763532).

 -- dann frazier <email address hidden> Fri, 13 Apr 2018 17:50:27 -0600