kexec April 2019

kexec@lists.fedoraproject.org

5 participants
12 discussions

[PATCH] kexec-kdump-howto: Add note on setting correct value of kptr_restrict
by Baoquan He 19 Apr '19

19 Apr '19

kdumpctl fails to load a crash kernel if KASLR is enabled. The incorrect configuration of the kptr_restrict parameter causes that the kdumpctl fails to load a crash kernel. The problem occurs when the Kernel Address Space Layout Randomization (KASLR) mechanism is enabled. The value of kptr_restrict decides how to expose the content of /proc files. Inappropriate setting will cause that the /proc/kcore file is being printed as all zeros. This configuration will break the kdump loading process since it needs access to the conntent of /proc/kcore if KASLR is enabled. Set kptr_restrict to 1 to avoid the problem described above. Signed-off-by: Baoquan He <bhe(a)redhat.com> --- kexec-kdump-howto.txt | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/kexec-kdump-howto.txt b/kexec-kdump-howto.txt index 011a19f..193b4a9 100644 --- a/kexec-kdump-howto.txt +++ b/kexec-kdump-howto.txt @@ -91,6 +91,11 @@ This line tells kexec to reserve 64M of ram if the system contains between 512M and 2G of physical memory. If the system contains 2G or more of physical memory, 128M should be reserved. +Besides, since kdump needs to access /proc/kcore during a kernel loading +if KASLR is enabled, check /proc/sys/kernel/kptr_restrict to make sure +that the content of /proc/kcore is exposed correctly. We recommend to +set the value of kptr_restrict to '1'. + After making said changes, reboot your system, so that the X MB of memory is left untouched by the normal system, reserved for the capture kernel. Take note that the output of 'free -m' will show X MB less memory than without this -- 2.17.2

2 2

[PATCH v3 0/2] Add rebuild support and doc reload command
by Kairui Song 04 Apr '19

04 Apr '19

Update from V2: - Remove an error check in setup_initrd that is no longer required. Update from V1: - merge fadump related initramfs backup/restore into setup_initrd as suggested by Dave and Hari, also only do permission only when actually trying to rebuild the image. Kairui Song (2): kdumpctl: add rebuild support Update man page for new kdumpctl command: reload / rebuild kdumpctl | 55 ++++++++++++++++++++++++++++-------------------------- kdumpctl.8 | 6 ++++++ 2 files changed, 35 insertions(+), 26 deletions(-) -- 2.20.1

3 5

2024

2023

2022

2021

2020

2019

2018

2017

2016

2015

2014

2013

kexec April 2019