kdump service fails to start on Power8

[SRU justification]
Needed to avoid load failure on Power8

[Impact]
Without this fix, kexec will not load on Power8

[Fix]
Apply upstream fix present in Dev release

[Test Case]
1) sudo apt-get install linux-crashdump
2) reboot server
3) kdump-config load

As outlined in the initial description, kdump will fail to load without the fix.

[Regression]
None expected, fix is already present in the development version (Wily)

[Original description of the problem]
== Comment: #0 - SACHIN P. SANT <email address hidden> - 2015-06-01 06:39:56 ==
---Problem Description---
kdump service fails to start

Contact Information = Sachin Sant / <email address hidden>

---uname output---
3.19.0-18-generic

Machine Type = POWER8

---Debugger---
A debugger is not configured

---Steps to Reproduce---
 1) Using latest daily ISO install 14.04.02 as a Power VM guest
2) Upgrade the kernel to 3.19 level (3.19.0-18-generic)
3) Configure kdump

kdump-config load command fails with following error:

root@alp9:~# cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinux-3.19.0-18-generic root=UUID=3ea23bcf-7269-432f-bacc-f82c6cdd774e ro splash crashkernel=2G-4G:320M,4G-32G:512M,32G-64G:1024M,64G-128G:2048M,128G-:4096M vt.handoff=7
root@alp9:~# kdump-config show
USE_KDUMP: 1
KDUMP_SYSCTL: kernel.panic_on_oops=1
KDUMP_COREDIR: /var/crash
crashkernel addr:
current state: Not ready to kdump

kexec command:
  no kexec command recorded
root@alp9:~# kdump-config load
unrecoverable error: short read from"/proc/device-tree//ibm,drc-names"
 * failed to load kdump kernel
root@alp9:~#

Userspace tool common name: kexec-tools

The userspace tool has the following bit modes: 64-bit

Userspace rpm: kdump-tools(1.5.5-2ubuntu1.2)

Userspace tool obtained from project website: na

*Additional Instructions for Sachin Sant / <email address hidden>:
-Post a private note with access information to the machine that the bug is occuring on.
-Attach ltrace and strace of userspace application.

== Comment: #2 - MAMATHA INAMDAR <email address hidden> - 2015-06-02 02:23:51 ==
root@alp9:~# /etc/init.d/kdump-tools start
Starting kdump-tools: unrecoverable error: short read from"/proc/device-tree//ibm,drc-names"
 * failed to load kdump kernel

root@alp9:~# dpkg -l | grep kexec
ii kexec-tools 1:2.0.6-0ubuntu2.1 ppc64el tools to support fast kexec reboots

root@alp9:~# dpkg -l | grep kdump
ii kdump-tools 1.5.5-2ubuntu1.2 all scripts and tools for automating kdump (Linux crash dumps)

root@alp9:~# cat /sys/kernel/kexec_crash_loaded
0
root@alp9:~# kdump-config status
current state : Not ready to kdump

root@alp9:~# dmesg | grep -i crash
[ 0.000000] Reserving 2048MB of memory at 128MB for crashkernel (System RAM: 102400MB)
[ 0.000000] Kernel command line: BOOT_IMAGE=/boot/vmlinux-3.19.0-18-generic root=UUID=3ea23bcf-7269-432f-bacc-f82c6cdd774e ro splash crashkernel=2G-4G:320M,4G-32G:512M,32G-64G:1024M,64G-128G:2048M,128G-:4096M vt.handoff=7
root@alp9:~#

== Comment: #3 - Hari Krishna Bathini <email address hidden> - 2015-06-02 07:29:23 ==
The following upstream commit fixes this issue:

---
commit d1932cd592e2a6aaf50ed22cfa2d7562b583854a
Author: Anton Blanchard <email address hidden>
Date: Tue Dec 2 10:59:40 2014 +1100

    kexec/fs2dt: Use slurp_file_len to avoid partial read of files

    The OPAL firmware is going to embed its symbol map in the device tree.
    The size is large enough to be more than a page, and it takes
    multiple reads to get the whole file. This is because sysfs uses
    the seq_file helpers which do a page at a time.

    Unfortunately fs2dt has no handling for short reads and we die with:

    unrecoverable error: short read from"/proc/device-tree//ibm,opal/firmware/symbol-map"

    This patch uses the slurp_file_len helper which does the right thing.
    It moves the explicit open of the file further down for
    add_usable_mem_property and add_dyn_reconf_usable_mem_property.
    We should convert both of these to use the buffer provided by
    slurp_file_len at some stage.

    Signed-off-by: Anton Blanchard <email address hidden>
    Signed-off-by: Simon Horman <email address hidden>
---

This patch applies cleanly on the kexec-tools version 1:2.0.6-0ubuntu2.1 on Ubuntu 14.04.2.

Thanks
Hari