linux-kernel - Re: ppc elf_map breakage with MAP_FIXED

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Message-Id: <7a44f42e-39d0-1c4b-19e0-7df1b0842c18@linux.vnet.ibm.com>
Date:   Mon, 8 Jan 2018 08:32:03 +0530
From:   Anshuman Khandual <khandual@...ux.vnet.ibm.com>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Michal Hocko <mhocko@...nel.org>,
        Anshuman Khandual <khandual@...ux.vnet.ibm.com>
Cc:     akpm@...ux-foundation.org, mm-commits@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, linux-next@...r.kernel.org,
        sfr@...b.auug.org.au, broonie@...nel.org
Subject: Re: ppc elf_map breakage with MAP_FIXED_NOREPLACE

On 01/07/2018 04:56 PM, Michael Ellerman wrote:
> Michal Hocko <mhocko@...nel.org> writes:
> 
>> On Sun 07-01-18 12:19:32, Anshuman Khandual wrote:
>>> On 01/05/2018 02:16 PM, Michal Hocko wrote:
>> [...]
>>>> Could you give us more information about the failure please. Debugging
>>>> patch from http://lkml.kernel.org/r/20171218091302.GL16951@dhcp22.suse.cz
>>>> should help to see what is the clashing VMA.
>>> Seems like its re-requesting the same mapping again.
>> It always seems to be the same mapping which is a bit strange as we
>> have multiple binaries here. Are these binaries any special? Does this
>> happen to all bianries (except for init which has obviously started
>> successfully)? Could you add an additional debugging (at the do_mmap
>> layer) to see who is requesting the mapping for the first time?
>>
>>> [   23.423642] 9148 (sed): Uhuuh, elf segment at 0000000010030000 requested but the memory is mapped already
>>> [   23.423706] requested [10030000, 10040000] mapped [10030000, 10040000] 100073 anon
>> I also find it a bit unexpected that this is an anonymous mapping
>> because the elf loader should always map a file backed one.
> Anshuman what machine is this on, and what distro and toolchain is it running?
> 
> I don't see this on any of my machines, so I wonder if this is
> toolchain/distro specific.

POWER9, RHEL 7.4, gcc (GCC) 4.8.5 20150623, GNU Make 3.82 etc.