Description of problem:
Crash can't open vmcore captured by kdump so that we can't perform debugging operations after a successful kdump.
Version-Release number of selected component (if applicable):
kernel-core-4.8.0-0.rc7.git0.1.fc26.x86_64 (patched to make kdump work)
Steps to Reproduce:
1. Run 'echo c > /proc/sysrq-trigger' to get a kdump vmcore
2. crash /path/to/vmlinux /path/to/vmcore
crash: page excluded: kernel virtual address: ffffffff81fdc940 type: "possible"
WARNING: cannot read cpu_possible_map
crash: page excluded: kernel virtual address: ffffffff81fdc140 type: "present"
WARNING: cannot read cpu_present_map
crash: page excluded: kernel virtual address: ffffffff81fdc540 type: "online"
WARNING: cannot read cpu_online_map
crash: page excluded: kernel virtual address: ffffffff81fdbd40 type: "active"
WARNING: cannot read cpu_active_map
crash: page excluded: kernel virtual address: ffffffff81e24090 type: "pv_init_ops"
crash: page excluded: kernel virtual address: ffffffff83195df0 type: "shadow_timekeeper xtime_sec"
crash: page excluded: kernel virtual address: ffffffff81e0d304 type: "init_uts_ns"
crash: /usr/lib/debug/lib/modules/4.8.0-0.rc7.git2.1.fc26.x86_64/vmlinux and /var/crash/127.0.0.1-2016-09-23-10:42:18/vmcore do not match!
crash loads vmcore without error and give out a debug shell.
Building crash from master branch on github can solve this problem. https://github.com/crash-utility/crash
I'm hoping to do a Rawhide rebase in the next couple of weeks.
The issue you're seeing is a due to the new CONFIG_RANDOMIZE_MEMORY
configuration, which I fixed in the upstream crash repo last Wednesday:
Author: Dave Anderson <email@example.com>
Date: Wed Sep 21 15:58:22 2016 -0400
Fix to recognize and support x86_64 Linux 4.8-rc1 and later kernels
that are configured with CONFIG_RANDOMIZE_MEMORY, which randomizes
the base addresses of the kernel's unity-map address (PAGE_OFFSET),
and the vmalloc region. Without the patch, the crash utility fails
with a segmentation violation during session initialization.
Also, Fedora's 4.8.0 kernel also introduced CONFIG_HARDENED_USERCOPY,
which will prevent crash from working on a live system. However, that
will require a kernel patch to the /dev/crash driver to fix it. I have
forwarded a patch to Josh Boyer (the Fedora kernel maintainer) last
Thursday (?), and it should appear in Fedora kernels in the near future.
- Fedora Rawhide build: crash-7.1.6-1.fc26 (10/14/16)