Subject: Re: linux-next: x86: Unalbe to run x32 processes on the x86_64 kernel
To: Thomas Gleixner <tglx@linutronix.de>,
        Adam Borowski <kilobyte@angband.pl>
References: <CANaxB-yGu9yWuFyeuZGyKP-0KGDamfoxpiVYo2fSoi3p4qSULw@mail.gmail.com>
 <CANaxB-xWX+e9VdO4wJfC3Mr=spLNmd2Gyc7qTH6_L5PfY-qHRQ@mail.gmail.com>
 <20170321064539.GB30094@gmail.com>
 <20170321075934.o4sccpawzn4rmtvh@angband.pl>
 <alpine.DEB.2.20.1703211339200.3617@nanos>
CC: Ingo Molnar <mingo@kernel.org>, Andrei Vagin <avagin@gmail.com>,
        Ingo Molnar <mingo@redhat.com>, LKML <linux-kernel@vger.kernel.org>,
        Cyrill Gorcunov <gorcunov@openvz.org>,
        Andy Lutomirski <luto@kernel.org>,
        Thomas Garnier <thgarnie@google.com>, "H. Peter Anvin" <hpa@zytor.com>
From: Dmitry Safonov <dsafonov@virtuozzo.com>
Message-ID: <5b3938fb-ee84-c78d-be9b-e3ba6656065d@virtuozzo.com>
Date: Tue, 21 Mar 2017 15:50:11 +0300
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101
 Thunderbird/45.7.1
MIME-Version: 1.0
In-Reply-To: <alpine.DEB.2.20.1703211339200.3617@nanos>
Content-Type: text/plain; charset="windows-1252"; format=flowed
Content-Transfer-Encoding: 7bit
SpamDiagnosticOutput: 1:99
SpamDiagnosticMetadata: NSPM
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 21 Mar 2017 12:53:50.5692 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM5PR0801MB1729
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 1127
Lines: 33

On 03/21/2017 03:49 PM, Thomas Gleixner wrote:
> On Tue, 21 Mar 2017, Adam Borowski wrote:
>> On Tue, Mar 21, 2017 at 07:45:39AM +0100, Ingo Molnar wrote:
>>> * Andrei Vagin <avagin@gmail.com> wrote:
>>>
>>>> # first bad commit: [45fc8757d1d2128e342b4e7ef39adedf7752faac] x86:
>>>> Make the GDT remapping read-only on 64-bit
>>>
>>> Just wondering, does the following commit fix it:
>>>
>>>   5b781c7e317f x86/tls: Forcibly set the accessed bit in TLS segments
>>
>> It does fix i386 but not x32.
>>
>> By "x32" I mean CONFIG_X86_X32, by "i386" CONFIG_IA32_EMULATION, contrary to
>> Andrei's first report.  The naming of the new ABI wasn't too fortunate...
>
> The X32 issue is unrelated to the GDT mapping.
>
> What happens is that the mmap rework from Dmitry switched X32 to use 64bit
> mappings, which is wrong. X32 has 64bit instructions and syscalls and 32bit
> address space.

Hmm, in_compat_syscall() checks x32 syscall bit.
I'll take a look, what happens there.

> Dmitry, can you please have a look and fix that up? For reproduction just
> compile helloworld.c with gcc -mx32.

Sure, thanks.

-- 
              Dmitry