> How is your system configured?
4k pages with 3-level PTE
I did not backport any of the support for deeper level PTE's or larger page sizes

>You might even be able to get to a crash> prompt by running:
> $ crash /proc/kcore --no_modules

no_modules works like a champ

root@odroid64-pre:~/crash-7.1.4# ./crash /proc/kcore --no_modules
crash 7.1.4
Copyright (C) 2002-2015  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"...

WARNING: no kernel module access

      KERNEL: /lib/modules/3.14.29+/build/vmlinux
    DUMPFILE: /proc/kcore
        CPUS: 4
        DATE: Tue Mar  8 15:15:26 2016
      UPTIME: 05:23:46
LOAD AVERAGE: 0.67, 0.36, 0.19
       TASKS: 207
    NODENAME: odroid64-pre
     RELEASE: 3.14.29+
     VERSION: #1 SMP PREEMPT Tue Mar 8 01:06:35 CST 2016
     MACHINE: aarch64  (unknown Mhz)
      MEMORY: 1.9 GB
         PID: 8000
     COMMAND: "crash"
        TASK: ffffffc05c298c00  [THREAD_INFO: ffffffc05857c000]
         CPU: 1
       STATE: TASK_RUNNING (ACTIVE)

crash>

root@odroid64-pre:~/crash-7.1.4# ./crash /proc/kcore -d8

crash 7.1.4
find_booted_kernel: check: /lib/modules/3.14.29+/build/vmlinux
find_booted_kernel: found: /lib/modules/3.14.29+/build/vmlinux
get_live_memory_source: /proc/kcore
proc_kcore_data:
       flags: 0 (KCORE_LOCAL|KCORE_ELF64)
    segments: 6
  elf_header: c71bb0
       elf64: c71bb0
      load64: c71c28
       elf32: 0
      load32: 0
... continues like this a while ...
/proc/version:
Linux version 3.14.29+ (root@odroid64-pre) (gcc version 5.3.1 20160225 (Ubuntu/Linaro 5.3.1-10ubuntu2) ) #1 SMP PREEMPT Tue Mar 8 01:06:35 CST 2016
/lib/modules/3.14.29+/build/vmlinux:
Linux version 3.14.29+ (root@odroid64-pre) (gcc version 5.3.1 20160225 (Ubuntu/Linaro 5.3.1-10ubuntu2) ) #1 SMP PREEMPT Tue Mar 8 01:06:35 CST 2016
readmem: read_proc_kcore() -> /proc/kcore
VA_BITS: 39
using 1000000 as phys_offset
gdb /lib/modules/3.14.29+/build/vmlinux
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"...
GETBUF(248 -> 0)
  GETBUF(1500 -> 1)

  FREEBUF(1)
FREEBUF(0)
<readmem: ffffffc001874510, KVADDR, "kernel_config_data", 32768, (ROE), 17e0a60>
<read_proc_kcore: addr: ffffffc001874510 paddr: 2874510 cnt: 2800>
<read_proc_kcore: addr: ffffffc001875000 paddr: 2875000 cnt: 4096>
<read_proc_kcore: addr: ffffffc001876000 paddr: 2876000 cnt: 4096>
<read_proc_kcore: addr: ffffffc001877000 paddr: 2877000 cnt: 4096>
<read_proc_kcore: addr: ffffffc001878000 paddr: 2878000 cnt: 4096>
<read_proc_kcore: addr: ffffffc001879000 paddr: 2879000 cnt: 4096>
<read_proc_kcore: addr: ffffffc00187a000 paddr: 287a000 cnt: 4096>
<read_proc_kcore: addr: ffffffc00187b000 paddr: 287b000 cnt: 4096>
<read_proc_kcore: addr: ffffffc00187c000 paddr: 287c000 cnt: 1296>
#
# Automatically generated file; DO NOT EDIT.
# Linux/arm64 3.14.29 Kernel Configuration
... skip kernel config ...
GETBUF(248 -> 0)
FREEBUF(0)
GETBUF(8 -> 0)
<readmem: ffffffc00186fd80, KVADDR, "cpu_possible_mask", 8, (FOE), 7ffced02f0>
<read_proc_kcore: addr: ffffffc00186fd80 paddr: 286fd80 cnt: 8>
<readmem: ffffffc001cd9988, KVADDR, "possible", 8, (ROE), c14b08>
<read_proc_kcore: addr: ffffffc001cd9988 paddr: 2cd9988 cnt: 8>
cpu_possible_mask: cpus: 0 1 2 3
<readmem: ffffffc00186fd70, KVADDR, "cpu_present_mask", 8, (FOE), 7ffced02f0>
<read_proc_kcore: addr: ffffffc00186fd70 paddr: 286fd70 cnt: 8>
<readmem: ffffffc001cd9980, KVADDR, "present", 8, (ROE), c14b08>
<read_proc_kcore: addr: ffffffc001cd9980 paddr: 2cd9980 cnt: 8>
 cpu_present_mask: cpus: 0 1 2 3
<readmem: ffffffc00186fd78, KVADDR, "cpu_online_mask", 8, (FOE), 7ffced02f0>
<read_proc_kcore: addr: ffffffc00186fd78 paddr: 286fd78 cnt: 8>
<readmem: ffffffc001cd9978, KVADDR, "online", 8, (ROE), c14b08>
<read_proc_kcore: addr: ffffffc001cd9978 paddr: 2cd9978 cnt: 8>
  cpu_online_mask: cpus: 0 1 2 3
<readmem: ffffffc00186fd68, KVADDR, "cpu_active_mask", 8, (FOE), 7ffced02f0>
<read_proc_kcore: addr: ffffffc00186fd68 paddr: 286fd68 cnt: 8>
<readmem: ffffffc001cd9998, KVADDR, "active", 8, (ROE), c14b08>
<read_proc_kcore: addr: ffffffc001cd9998 paddr: 2cd9998 cnt: 8>
  cpu_active_mask: cpus: 0 1 2 3
..... skip
<readmem: ffffffc001d61238, KVADDR, "timekeeper xtime_sec", 8, (ROE), 7ffced03b8>
<read_proc_kcore: addr: ffffffc001d61238 paddr: 2d61238 cnt: 8>
xtime timespec.tv_sec: 56df41b3: Tue Mar  8 15:18:43 2016
<readmem: ffffffc001c0dbac, KVADDR, "init_uts_ns", 390, (ROE), bb208c>
<read_proc_kcore: addr: ffffffc001c0dbac paddr: 2c0dbac cnt: 390>
utsname:
     sysname: Linux
    nodename: odroid64-pre
     release: 3.14.29+
     version: #1 SMP PREEMPT Tue Mar 8 01:06:35 CST 2016
     machine: aarch64
  domainname: (none)
base kernel version: 3.14.29
<readmem: ffffffc00186a090, KVADDR, "accessible check", 8, (ROE|Q), 7ffcecfa70>
<read_proc_kcore: addr: ffffffc00186a090 paddr: 286a090 cnt: 8>
<readmem: ffffffc00186a090, KVADDR, "read_string characters", 1499, (ROE|Q), 7ffcecfde8>
<read_proc_kcore: addr: ffffffc00186a090 paddr: 286a090 cnt: 1499>
linux_banner:
Linux version 3.14.29+ (root@odroid64-pre) (gcc version 5.3.1 20160225 (Ubuntu/Linaro 5.3.1-10ubuntu2) ) #1 SMP PREEMPT Tue Mar 8 01:06:35 CST 2016

verify_namelist:
live memory /proc/version:
Linux version 3.14.29+ (root@odroid64-pre) (gcc version 5.3.1 20160225 (Ubuntu/Linaro 5.3.1-10ubuntu2) ) #1 SMP PREEMPT Tue Mar 8 01:06:35 CST 2016
/lib/modules/3.14.29+/build/vmlinux:
Linux version 3.14.29+ (root@odroid64-pre) (gcc version 5.3.1 20160225 (Ubuntu/Linaro 5.3.1-10ubuntu2) ) #1 SMP PREEMPT Tue Mar 8 01:06:35 CST 2016

<readmem: ffffffc001db2da8, KVADDR, "__per_cpu_offset", 32, (FOE), bb2238>
<read_proc_kcore: addr: ffffffc001db2da8 paddr: 2db2da8 cnt: 32>
GETBUF(248 -> 0)
FREEBUF(0)
GETBUF(248 -> 0)
GNU_GET_DATATYPE[runqueue]: returned via gdb_error_hook (1 buffer in use)
FREEBUF(0)
GETBUF(248 -> 0)
FREEBUF(0)
GETBUF(248 -> 0)
FREEBUF(0)
GETBUF(248 -> 0)
FREEBUF(0)
GETBUF(248 -> 0)
GNU_GET_DATATYPE[runqueue]: returned via gdb_error_hook (1 buffer in use)
FREEBUF(0)
GETBUF(248 -> 0)
FREEBUF(0)
^^^^ now repeats gdb_error_hook (1 buffer in use) for quite a while
kernel NR_CPUS: 4
<readmem: ffffffc001c33208, KVADDR, "init_mm.pgd", 8, (ROE), 7ffced83d0>
<read_proc_kcore: addr: ffffffc001c33208 paddr: 2c33208 cnt: 8>
<readmem: ffffffc001db2e78, KVADDR, "high_memory", 8, (FOE), bc6368>
<read_proc_kcore: addr: ffffffc001db2e78 paddr: 2db2e78 cnt: 8>
GETBUF(248 -> 0)
FREEBUF(0)
GETBUF(248 -> 0)
FREEBUF(0)
PAGESIZE=4096
mem_section_size = 32
NR_SECTION_ROOTS = 4
NR_MEM_SECTIONS = 1024
SECTIONS_PER_ROOT = 256
SECTION_ROOT_MASK = 0xff
PAGES_PER_SECTION = 262144
<readmem: ffffffc001db4a80, KVADDR, "memory section root table", 32, (FOE), 2ff3390>
<read_proc_kcore: addr: ffffffc001db4a80 paddr: 2db4a80 cnt: 32>
<readmem: ffffffc001db2bc8, KVADDR, "totalram_pages", 8, (FOE), bc6388>
<read_proc_kcore: addr: ffffffc001db2bc8 paddr: 2db2bc8 cnt: 8>
<readmem: ffffffc001db2e88, KVADDR, "max_mapnr", 8, (FOE), bc63a0>
<read_proc_kcore: addr: ffffffc001db2e88 paddr: 2db2e88 cnt: 8>
<readmem: ffffffc001db47f4, KVADDR, "nr_swapfiles", 4, (FOE), bc6430>
<read_proc_kcore: addr: ffffffc001db47f4 paddr: 2db47f4 cnt: 4>
GETBUF(248 -> 0)
FREEBUF(0)
GETBUF(248 -> 0)
FREEBUF(0)
GETBUF(248 -> 0)
GNU_GET_DATATYPE[free_area_struct]: returned via gdb_error_hook (1 buffer in use)
.... skip repeats
<readmem: ffffffc001c2f548, KVADDR, "node_online_map", 8, (ROE|Q), 41eede0>
<read_proc_kcore: addr: ffffffc001c2f548 paddr: 2c2f548 cnt: 8>
node_online_map: [1] -> nodes online: 1
.... skip repeats
<readmem: ffffffc001cd03d8, KVADDR, "pglist node_id", 4, (FOE), 7ffced6568>
<read_proc_kcore: addr: ffffffc001cd03d8 paddr: 2cd03d8 cnt: 4>
<readmem: ffffffc001cd03c0, KVADDR, "pglist node_start_pfn", 8, (FOE), 7ffced65a0>
<read_proc_kcore: addr: ffffffc001cd03c0 paddr: 2cd03c0 cnt: 8>
<readmem: ffffffc0741fe000, KVADDR, "memory section", 16, (FOE), 11e6810>
<read_proc_kcore: addr: ffffffc0741fe000 paddr: 751fe000 cnt: 16>
<readmem: ffffffc0741fe000, KVADDR, "memory section", 16, (FOE), 11e6810>
<read_proc_kcore: addr: ffffffc0741fe000 paddr: 751fe000 cnt: 16>
<readmem: ffffffc0741fe000, KVADDR, "memory section", 16, (FOE), 11e6810>
<read_proc_kcore: addr: ffffffc0741fe000 paddr: 751fe000 cnt: 16>
<readmem: ffffffc001cd03d0, KVADDR, "pglist node_spanned_pages", 8, (FOE), 7ffced65b0>
<read_proc_kcore: addr: ffffffc001cd03d0 paddr: 2cd03d0 cnt: 8>
<readmem: ffffffc001cd03c8, KVADDR, "pglist node_present_pages", 8, (FOE), 7ffced65b8>
<read_proc_kcore: addr: ffffffc001cd03c8 paddr: 2cd03c8 cnt: 8>
node_table[0]:
             id: 0
          pgdat: ffffffc001ccf280
           size: 487424
        present: 486912
        mem_map: ffffff8040058000
    start_paddr: 1000000
    start_mapnr: 4096
zone 0 at ffffffc001ccf280
<readmem: ffffffc001ccfaa8, KVADDR, "zone spanned_pages", 8, (FOE), 7ffced65c8>
<read_proc_kcore: addr: ffffffc001ccfaa8 paddr: 2ccfaa8 cnt: 8>
<readmem: ffffffc001ccf8d8, KVADDR, "zone[_struct] free_pages", 8, (FOE), 7ffced65c0>
<read_proc_kcore: addr: ffffffc001ccf8d8 paddr: 2ccf8d8 cnt: 8>
<readmem: ffffffc001ccfac8, KVADDR, "zone[_struct] name", 8, (FOE), 7ffced6610>
<read_proc_kcore: addr: ffffffc001ccfac8 paddr: 2ccfac8 cnt: 8>
<readmem: ffffffc001a38168, KVADDR, "read_string characters", 1499, (ROE|Q), 7ffced6638>
<read_proc_kcore: addr: ffffffc001a38168 paddr: 2a38168 cnt: 1499>
<readmem: ffffffc001ccfaa0, KVADDR, "node_zones zone_start_pfn", 8, (FOE), 7ffced65f8>
<read_proc_kcore: addr: ffffffc001ccfaa0 paddr: 2ccfaa0 cnt: 8>
<readmem: ffffffc0741fe000, KVADDR, "memory section", 16, (FOE), 11e6810>
<read_proc_kcore: addr: ffffffc0741fe000 paddr: 751fe000 cnt: 16>
<readmem: ffffffc0741fe000, KVADDR, "memory section", 16, (FOE), 11e6810>
<read_proc_kcore: addr: ffffffc0741fe000 paddr: 751fe000 cnt: 16>
<readmem: ffffffc0741fe000, KVADDR, "memory section", 16, (FOE), 11e6810>
<read_proc_kcore: addr: ffffffc0741fe000 paddr: 751fe000 cnt: 16>
zone 1 at ffffffc001ccfb00
<readmem: ffffffc001cd0328, KVADDR, "zone spanned_pages", 8, (FOE), 7ffced65c8>
<read_proc_kcore: addr: ffffffc001cd0328 paddr: 2cd0328 cnt: 8>
<readmem: ffffffc001cd0158, KVADDR, "zone[_struct] free_pages", 8, (FOE), 7ffced65c0>
<read_proc_kcore: addr: ffffffc001cd0158 paddr: 2cd0158 cnt: 8>
<readmem: ffffffc001cd0348, KVADDR, "zone[_struct] name", 8, (FOE), 7ffced6610>
<read_proc_kcore: addr: ffffffc001cd0348 paddr: 2cd0348 cnt: 8>
<readmem: ffffffc001a38500, KVADDR, "read_string characters", 1499, (ROE|Q), 7ffced6638>
<read_proc_kcore: addr: ffffffc001a38500 paddr: 2a38500 cnt: 1499>
<readmem: ffffffc001cd0320, KVADDR, "node_zones zone_start_pfn", 8, (FOE), 7ffced65f8>
<read_proc_kcore: addr: ffffffc001cd0320 paddr: 2cd0320 cnt: 8>
<readmem: ffffffc001cd03d8, KVADDR, "pglist node_id", 4, (FOE), 7ffced6568>
<read_proc_kcore: addr: ffffffc001cd03d8 paddr: 2cd03d8 cnt: 4>
<readmem: ffffffc001cd03c0, KVADDR, "pglist node_start_pfn", 8, (FOE), 7ffced65a0>
<read_proc_kcore: addr: ffffffc001cd03c0 paddr: 2cd03c0 cnt: 8>
<readmem: ffffffc0741fe000, KVADDR, "memory section", 16, (FOE), 11e6810>
<read_proc_kcore: addr: ffffffc0741fe000 paddr: 751fe000 cnt: 16>
<readmem: ffffffc0741fe000, KVADDR, "memory section", 16, (FOE), 11e6810>
<read_proc_kcore: addr: ffffffc0741fe000 paddr: 751fe000 cnt: 16>
<readmem: ffffffc0741fe000, KVADDR, "memory section", 16, (FOE), 11e6810>
<read_proc_kcore: addr: ffffffc0741fe000 paddr: 751fe000 cnt: 16>
<readmem: ffffffc001cd03d0, KVADDR, "pglist node_spanned_pages", 8, (FOE), 7ffced65b0>
<read_proc_kcore: addr: ffffffc001cd03d0 paddr: 2cd03d0 cnt: 8>
<readmem: ffffffc001cd03c8, KVADDR, "pglist node_present_pages", 8, (FOE), 7ffced65b8>
<read_proc_kcore: addr: ffffffc001cd03c8 paddr: 2cd03c8 cnt: 8>
NODE    SIZE      PGLIST_DATA       BOOTMEM_DATA       NODE_ZONES
  0    487424   ffffffc001ccf280        ----        ffffffc001ccf280
                                                    ffffffc001ccfb00
    MEM_MAP          START_PADDR    START_MAPNR
ffffff8040058000       1000000          4096

ZONE  NAME         SIZE       MEM_MAP      START_PADDR  START_MAPNR
zone 0 at ffffffc001ccf280
<readmem: ffffffc001ccfaa8, KVADDR, "zone spanned_pages", 8, (FOE), 7ffced65c8>
<read_proc_kcore: addr: ffffffc001ccfaa8 paddr: 2ccfaa8 cnt: 8>
<readmem: ffffffc001ccf8d8, KVADDR, "zone[_struct] free_pages", 8, (FOE), 7ffced65c0>
<read_proc_kcore: addr: ffffffc001ccf8d8 paddr: 2ccf8d8 cnt: 8>
<readmem: ffffffc001ccfac8, KVADDR, "zone[_struct] name", 8, (FOE), 7ffced6610>
<read_proc_kcore: addr: ffffffc001ccfac8 paddr: 2ccfac8 cnt: 8>
<readmem: ffffffc001a38168, KVADDR, "read_string characters", 1499, (ROE|Q), 7ffced6638>
<read_proc_kcore: addr: ffffffc001a38168 paddr: 2a38168 cnt: 1499>
<readmem: ffffffc001ccfaa0, KVADDR, "node_zones zone_start_pfn", 8, (FOE), 7ffced65f8>
<read_proc_kcore: addr: ffffffc001ccfaa0 paddr: 2ccfaa0 cnt: 8>
<readmem: ffffffc0741fe000, KVADDR, "memory section", 16, (FOE), 11e6810>
<read_proc_kcore: addr: ffffffc0741fe000 paddr: 751fe000 cnt: 16>
<readmem: ffffffc0741fe000, KVADDR, "memory section", 16, (FOE), 11e6810>
<read_proc_kcore: addr: ffffffc0741fe000 paddr: 751fe000 cnt: 16>
<readmem: ffffffc0741fe000, KVADDR, "memory section", 16, (FOE), 11e6810>
<read_proc_kcore: addr: ffffffc0741fe000 paddr: 751fe000 cnt: 16>
  0   Normal     487424  ffffff8040058000      1000000         4096
zone 1 at ffffffc001ccfb00
<readmem: ffffffc001cd0328, KVADDR, "zone spanned_pages", 8, (FOE), 7ffced65c8>
<read_proc_kcore: addr: ffffffc001cd0328 paddr: 2cd0328 cnt: 8>
<readmem: ffffffc001cd0158, KVADDR, "zone[_struct] free_pages", 8, (FOE), 7ffced65c0>
<read_proc_kcore: addr: ffffffc001cd0158 paddr: 2cd0158 cnt: 8>
<readmem: ffffffc001cd0348, KVADDR, "zone[_struct] name", 8, (FOE), 7ffced6610>
<read_proc_kcore: addr: ffffffc001cd0348 paddr: 2cd0348 cnt: 8>
<readmem: ffffffc001a38500, KVADDR, "read_string characters", 1499, (ROE|Q), 7ffced6638>
<read_proc_kcore: addr: ffffffc001a38500 paddr: 2a38500 cnt: 1499>
<readmem: ffffffc001cd0320, KVADDR, "node_zones zone_start_pfn", 8, (FOE), 7ffced65f8>
<read_proc_kcore: addr: ffffffc001cd0320 paddr: 2cd0320 cnt: 8>
  1   Movable         0                 0            0            0

-------------------------------------------------------------------

NR      SECTION        CODED_MEM_MAP        MEM_MAP       PFN
<readmem: ffffffc0741fe000, KVADDR, "memory section", 16, (FOE), 11e6810>
<read_proc_kcore: addr: ffffffc0741fe000 paddr: 751fe000 cnt: 16>
<readmem: ffffffc0741fe000, KVADDR, "memory section", 16, (FOE), 11e6810>
<read_proc_kcore: addr: ffffffc0741fe000 paddr: 751fe000 cnt: 16>
 0  ffffffc0741fe000  ffffff8040010000  ffffff8040010000  0
<readmem: ffffffc0741fe010, KVADDR, "memory section", 16, (FOE), 11e6810>
<read_proc_kcore: addr: ffffffc0741fe010 paddr: 751fe010 cnt: 16>
.... continues on this way a while
GETBUF(248 -> 0)
FREEBUF(0)
<readmem: ffffffc001c27f58, KVADDR, "modules", 8, (FOE), bb1a88>
<read_proc_kcore: addr: ffffffc001c27f58 paddr: 2c27f58 cnt: 8>
GETBUF(528 -> 0)
module: ffffffbffc081ad0
<readmem: ffffffbffc081ad0, KVADDR, "module struct", 528, (ROE|Q), c14b08>
<readmem: ffffffc001ffc000, KVADDR, "pgd page", 4096, (FOE), f41e90>
<read_proc_kcore: addr: ffffffc001ffc000 paddr: 2ffc000 cnt: 4096>
<readmem: ffffffc000ffe000, KVADDR, "pmd page", 4096, (FOE), f42ea0>
<read_proc_kcore: addr: ffffffc000ffe000 paddr: 1ffe000 cnt: 4096>
crash: seek error: kernel virtual address: ffffffc000ffe000  type: "pmd page"
root@odroid64-pre:~/crash-7.1.4#


On Tue, Mar 8, 2016 at 3:02 PM, Dave Anderson <anderson@redhat.com> wrote:


----- Original Message -----
> root@odroid64-pre:~/crash-7.1.4# ./crash /proc/kcore
>
> crash 7.1.4
> Copyright (C) 2002-2015 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"...
>
> crash: seek error: kernel virtual address: ffffffc000ffe000 type: "pmd page"

So if you did a "crash -d8", you would see that you got significantly
farther than you did with /dev/mem, and where I think from the seek error
type above, perhaps as far as getting into the module initialization phase.
Although, if I run with -d8, I never see the "pmd page" type being read,
so I'm not sure where that's coming from.

Anyway, try -d8, and you should see legitimate stuff read from "linux_banner"
and the utsname structure, and you should see how far you got.

You might even be able to get to a crash> prompt by running:

 $ crash /proc/kcore --no_modules

which would avoid doing any kind of PTE-requiring address translation.

In any case, there's something about the /dev/mem driver that I'm not aware
of.  I'm pretty sure that that when I did the initial arm64 port for crash,
that I *did* use /dev/mem at first, because Red Hat hadn't gotten around to
restricting it yet.

Anyway, if you're at the module initialization stage, then the PTE
stuff comes into play.  Note that crash currently only supports ARM64
systems configured with 64k pages with 2-level PTEs  or 4k pages with
3-level PTEs.  How is your system configured?

Dave





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