linux-kernel - Re: ppc elf_map breakage with MAP_FIXED

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Message-ID: <87tvvw80f2.fsf@concordia.ellerman.id.au>
Date:   Tue, 09 Jan 2018 09:12:49 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Anshuman Khandual <khandual@...ux.vnet.ibm.com>,
        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

Anshuman Khandual <khandual@...ux.vnet.ibm.com> writes:

> 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.

So what does readelf -a of /bin/sed look like?

cheers