makedumpfile issues many readpage_elf: Attempt to read non-existent page

[Louis Bouchard]

Hello,

I am investigating an issue with makedumpfile and kernel 4.8 where makedumpfile
(1.6.0) exits on error with the following message :

  get_mem_map: Can't distinguish the memory type.

I found commit 2c21d4656e8d3c2af2b1e14809d076941ae69e96 in the upstream
development branch that is supposed to fix this :

[PATCH v2] Support _count -> _refcount rename in struct page

    _count member was renamed to _refcount in linux commit 0139aa7b7fa12
    ("mm: rename _count, field of the struct page, to _refcount") and this
    broke makedumpfile. The reason for making the change was to find all users
    accessing it directly and not through the recommended API. I tried
    suggesting to revert the change but failed, I see no other choice than to
    start supporting both _count and _refcount in makedumpfile.

Though, when I apply the patch and test on either Ubuntu's 4.8.0-11 kernel, or
kernel.org's mainline 4.8.0-040800rc7 kernel, I get the following repeated
multiple times :

> makedumpfile -c -d 31 /proc/vmcore /var/crash/201609221517/dump-incomplete
> [    7.513337] kdump-tools[715]: readpage_elf: Attempt to read non-existent page at 0x134dfff78000.
> [    7.524186] kdump-tools[715]: readmem: type_addr: 0, addr:ffff9b4dfff78000, size:16
> [    7.528440] kdump-tools[715]: section_mem_map_addr: Can't get a struct mem_section(ffff9b4dfff78000).
> [    7.536562] kdump-tools[715]: readpage_elf: Attempt to read non-existent page at 0x134dfff78000.
> [    7.544356] kdump-tools[715]: readmem: type_addr: 0, addr:ffff9b4dfff78010, size:16
> [    7.552422] kdump-tools[715]: section_mem_map_addr: Can't get a struct mem_section(ffff9b4dfff78010).
> [    7.560317] kdump-tools[715]: readpage_elf: Attempt to read non-existent page at 0x134dfff78000.
> [    7.568422] kdump-tools[715]: readmem: type_addr: 0, addr:ffff9b4dfff78020, size:16
> [    7.572296] kdump-tools[715]: section_mem_map_addr: Can't get a struct mem_section(ffff9b4dfff78020).

I also tested with all the commits in the upstream/development branch with no
luck, I still get the same behavior.

Does someone have an idea of where this could come from ?

TIA,

Louis
-- 
Louis Bouchard
Software engineer, Cloud & Sustaining eng.
Canonical Ltd
Ubuntu developer                       Debian Maintainer
GPG : 429D 7A3B DD05 B6F8 AF63  B9C4 8B3D 867C 823E 7A61