From: Richard Weinberger <richard@nod.at>
Subject: Re: [uml-devel] fuzz tested 32 bit user mode linux image hangs in
 radix_tree_next_chunk()
Date: Sat, 09 Nov 2013 20:33:45 +0100
Message-ID: <527E8E19.9030802@nod.at>
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Cc: Konstantin Khlebnikov <koct9i@gmail.com>,
 Linux Kernel <linux-kernel@vger.kernel.org>,
 linux-fsdevel <linux-fsdevel@vger.kernel.org>,
 "linux-mm@kvack.org" <linux-mm@kvack.org>,
 UML devel <user-mode-linux-devel@lists.sourceforge.net>
To: =?UTF-8?B?VG9yYWxmIEbDtnJzdGVy?= <toralf.foerster@gmx.de>
Return-path: <owner-linux-mm@kvack.org>
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List-Id: linux-fsdevel.vger.kernel.org

Am 09.11.2013 20:07, schrieb Toralf F=C3=B6rster:
> On 11/06/2013 10:31 PM, Richard Weinberger wrote:
>> Am 06.11.2013 22:18, schrieb Toralf F=C3=B6rster:
>>> On 11/06/2013 05:06 PM, Konstantin Khlebnikov wrote:
>>>> In this case it must stop after scanning whole tree in line:
>>>> /* Overflow after ~0UL */
>>>> if (!index)
>>>>   return NULL;
>>>>
>>>
>>> A fresh current example with latest git tree shows that lines 769 and=
 770 do alternate :
>>
>> Can you please ask gdb for the value of offset?
>>
>> Thanks,
>> //richard
>>
>=20
> Still trying to get those values. One attempt to do that was to replace=
 -O2 with -O0 in the Makefile,
> but that resulted into this error :
>=20
>   LD      kernel/built-in.o
>   CC      mm/memory.o
> In function =E2=80=98zap_pmd_range=E2=80=99,
>     inlined from =E2=80=98zap_pud_range=E2=80=99 at mm/memory.c:1265:8,
>     inlined from =E2=80=98unmap_page_range=E2=80=99 at mm/memory.c:1290=
:8:
> mm/memory.c:1220:23: error: call to =E2=80=98__compiletime_assert_1220=E2=
=80=99 declared with attribute error: BUILD_BUG failed
> mm/memory.c: In function =E2=80=98follow_page_mask=E2=80=99:
> mm/memory.c:1530:18: error: call to =E2=80=98__compiletime_assert_1530=E2=
=80=99 declared with attribute error: BUILD_BUG failed
> make[1]: *** [mm/memory.o] Error 1
> make: *** [mm] Error 2
>=20
>=20
> With -O1 it compiled at least.

You cannot build Linux with -O1/O0.
Try printing the value using printk...

Thanks,
//richard

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