Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <2a64981c-ee53-f146-32a4-e97d4c036259@kernel.org>
Date:   Thu, 8 Jun 2023 08:29:02 +0200
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.11.2
Subject: Re: [PATCH 3/3] x86: Disable running 32bit processes if ia32_disabled
 is passed
Content-Language: en-US
To:     Thomas Gleixner <tglx@linutronix.de>,
        Andrew Cooper <andrew.cooper3@citrix.com>,
        Nikolay Borisov <nik.borisov@suse.com>, x86@kernel.org
Cc:     linux-kernel@vger.kernel.org, mhocko@suse.com
References: <20230607072936.3766231-1-nik.borisov@suse.com>
 <20230607072936.3766231-4-nik.borisov@suse.com> <87legvjxat.ffs@tglx>
 <80f2045b-f276-e127-8e46-87fb6994fb41@suse.com> <87fs73juwa.ffs@tglx>
 <ba15bccd-9580-c20e-ae9c-b8d60f49fa07@suse.com> <87a5xbjpk2.ffs@tglx>
 <875d0ab7-4470-25e2-6c01-72e231aae515@citrix.com> <874jnjj5z2.ffs@tglx>
 <278d7231-ee27-602f-4ba7-45d45d6772b3@citrix.com> <871qimkdft.ffs@tglx>
From:   Jiri Slaby <jirislaby@kernel.org>
In-Reply-To: <871qimkdft.ffs@tglx>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 08. 06. 23, 2:25, Thomas Gleixner wrote:
>> For usecases where there ought not to be any 32bit code at all (and
>> there absolutely are), it would be lovely if this could be enforced,
>> rather than relying on blind hope that it doesn't happen.
> 
> I think it's rather clear what needs to be done here to achieve that,
> but that's completely orthogonal to the intent of the patch series in
> question which aims to make CONFIG_IA32_EMULATION a boot time decision.

Agreed. The original intent was only to disable the 32bit paths in the 
kernel. I.e. set CONFIG_IA32_EMULATION=n by a runtime switch.

Then we came up with idea to disallow loading 32bit binaries to WARN 
people as the bins won't (mostly) work anyway. (We are/were aware this 
doesn't forbid running 32bit code.)

But now, when we are doing that, I think we should disable 32 bits 
completely by the switch. I.e. don't provide 32bit segments and 
whatever. And make that clear and documented in the series. Because as 
it stands now, it's half-way. Agreed? This whole attempt served as a 
call for opinions which we got and which is perfect.

thanks,
-- 
js
suse labs