Apologies if this the wrong place to ask this question. If in fact this is the wrong alias to post this question, appreciate a pointer in the right direction. We have been trying to get crash working on a live kernel (aarch64) but have not been able to.

Based on the crash help text:

--machdep option=value
    Pass an option and value pair to machine-dependent code.  These
    architecture-specific option/pairs should only be required in
    very rare circumstances:

    ARM64:
      phys_offset=<physical-address>
      kimage_voffset=<kimage_voffset-value>
      max_physmem_bits=<value>
      vabits_actual=<value>

We probably need to specify the proper values for phys_offset and kimage_voffset. kimage_offset is in /proc/kallsyms, but not phys_offset. It is just not clear where the values should come from. I did try using the value of kimage_offset  found in /proc/kallsyms but that did not help. It is not clear where one needs to get the values from (and in fact a casual reading of the crash source seems to try to compute the values automatically)

Here is some additional information:

# uname -a
Linux bringup 5.1.0 #1 SMP Fri Oct 11 17:01:55 UTC 2019 aarch64 GNU/Linux

# crash -s
crash: /proc/kcore: No such file or directory
WARNING: could not find MAGIC_START!
WARNING: cannot read linux_banner string
crash: /boot/vmlinux-5.1.0 and /dev/mem do not match!

This is with additional debugging turned on:

# ./crash --version

crash 7.2.8++
Copyright (C) 2002-2020  Red Hat, Inc.
Copyright (C) 2004, 2005, 2006, 2010  IBM Corporation
Copyright (C) 1999-2006  Hewlett-Packard Co
Copyright (C) 2005, 2006, 2011, 2012  Fujitsu Limited
Copyright (C) 2006, 2007  VA Linux Systems Japan K.K.
Copyright (C) 2005, 2011  NEC Corporation
Copyright (C) 1999, 2002, 2007  Silicon Graphics, Inc.
Copyright (C) 1999, 2000, 2001, 2002  Mission Critical Linux, Inc.
This program is free software, covered by the GNU General Public License,
and you are welcome to change it and/or distribute copies of it under
certain conditions.  Enter "help copying" to see the conditions.
This program has absolutely no warranty.  Enter "help warranty" for details.
 
GNU gdb (GDB) 7.6
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "aarch64-unknown-linux-gnu".

Here is crash running with -d flag:

find_booted_kernel: check: /boot/vmlinux-5.1.0
find_booted_kernel: found: /boot/vmlinux-5.1.0
get_live_memory_source: /dev/mem
/proc/version:
Linux version 5.1.0 (oe-user@oe-host) (gcc version 7.3.0 (GCC)) #1 SMP Fri Oct 11 17:01:55 UTC 2019
/boot/vmlinux-5.1.0:
Linux version 5.1.0 (oe-user@oe-host) (gcc version 7.3.0 (GCC)) #1 SMP Fri Oct 11 17:01:55 UTC 2019
crash: /proc/kcore: No such file or directory
readmem: read_dev_mem() -> /dev/mem
VA_BITS: 48
kimage_voffset: fffeffff88000000
phys_offset: 0
physvirt_offset: 800000000000
gdb --quiet /boot/vmlinux-5.1.0
GETBUF(328 -> 0)
  GETBUF(1500 -> 1)
  FREEBUF(1)
FREEBUF(0)
<readmem: ffff0000109c63b8, KVADDR, "kernel_config_data", 32768, (ROE), aaaad82d4630>
<read_dev_mem: addr: ffff0000109c63b8 paddr: 889c63b8 cnt: 3144>
<read_dev_mem: addr: ffff0000109c7000 paddr: 889c7000 cnt: 4096>
<read_dev_mem: addr: ffff0000109c8000 paddr: 889c8000 cnt: 4096>
<read_dev_mem: addr: ffff0000109c9000 paddr: 889c9000 cnt: 4096>
<read_dev_mem: addr: ffff0000109ca000 paddr: 889ca000 cnt: 4096>
<read_dev_mem: addr: ffff0000109cb000 paddr: 889cb000 cnt: 4096>
<read_dev_mem: addr: ffff0000109cc000 paddr: 889cc000 cnt: 4096>
<read_dev_mem: addr: ffff0000109cd000 paddr: 889cd000 cnt: 4096>
<read_dev_mem: addr: ffff0000109ce000 paddr: 889ce000 cnt: 952>
<readmem: ffff0000109c63b0, KVADDR, "kernel_config_data MAGIC_START", 8, (ROE), ffffe6a6d5a0>
<read_dev_mem: addr: ffff0000109c63b0 paddr: 889c63b0 cnt: 8>
WARNING: could not find MAGIC_START!
GETBUF(328 -> 0)
FREEBUF(0)
GETBUF(8 -> 0)
<readmem: ffff000010e1c6d8, KVADDR, "possible", 8, (ROE|Q), aaaacd15f258>
<read_dev_mem: addr: ffff000010e1c6d8 paddr: 88e1c6d8 cnt: 8>
cpu_possible_mask: cpus: (none)
<readmem: ffff000010e1c6d0, KVADDR, "present", 8, (ROE|Q), aaaacd15f258>
<read_dev_mem: addr: ffff000010e1c6d0 paddr: 88e1c6d0 cnt: 8>
 cpu_present_mask: cpus: (none)
<readmem: ffff000010e1c6c8, KVADDR, "online", 8, (ROE|Q), aaaacd15f258>
<read_dev_mem: addr: ffff000010e1c6c8 paddr: 88e1c6c8 cnt: 8>
  cpu_online_mask: cpus: (none)
<readmem: ffff000010e1c6e0, KVADDR, "active", 8, (ROE|Q), aaaacd15f258>
<read_dev_mem: addr: ffff000010e1c6e0 paddr: 88e1c6e0 cnt: 8>
  cpu_active_mask: cpus: (none)
FREEBUF(0)
GETBUF(328 -> 0)
FREEBUF(0)
GETBUF(328 -> 0)
FREEBUF(0)
GETBUF(328 -> 0)
FREEBUF(0)
<readmem: ffff000010ef8150, KVADDR, "shadow_timekeeper xtime_sec", 8, (ROE), ffffe6a650b8>
<read_dev_mem: addr: ffff000010ef8150 paddr: 88ef8150 cnt: 8>
xtime timespec.tv_sec: 0: Wed Dec 31 16:00:00 1969
<readmem: ffff000010e2533c, KVADDR, "init_uts_ns", 390, (ROE), aaaacd0fd194>
<read_dev_mem: addr: ffff000010e2533c paddr: 88e2533c cnt: 390>
utsname:
     sysname:
    nodename:
     release:
     version:
     machine:
  domainname:
base kernel version: 0.0.0
<readmem: ffff0000109b0098, KVADDR, "accessible check", 8, (ROE|Q), ffffe6a64770>
<read_dev_mem: addr: ffff0000109b0098 paddr: 889b0098 cnt: 8>
<readmem: ffff0000109b0098, KVADDR, "read_string characters", 1499, (ROE|Q), ffffe6a64ae8>
<read_dev_mem: addr: ffff0000109b0098 paddr: 889b0098 cnt: 1499>
WARNING: cannot read linux_banner string
/proc/version:
Linux version 5.1.0 (oe-user@oe-host) (gcc version 7.3.0 (GCC)) #1 SMP Fri Oct 11 17:01:55 UTC 2019
linux_banner:

crash: /boot/vmlinux-5.1.0 and /dev/mem do not match!