linux-kernel - Re: ppc elf_map breakage with MAP_FIXED_NOREPLACE (was: Re: mmotm 2018-01-04-16-19 uploaded)

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Date:   Sun, 07 Jan 2018 22:26:57 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     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 (was: Re: mmotm 2018-01-04-16-19 uploaded)

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.

cheers