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

[Atsushi Kumagai]

>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 ?

Thanks for your report, but I'm afraid that I'm going on
vacation till Oct 2.
I hope someone helps you until I'm back.


Regards,
Atsushi Kumagai

>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
>
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