linux-kernel - Re: [PATCH 3/3] x86: Disable running 32bit processes if ia32

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Date:   Thu, 8 Jun 2023 08:36:20 +0200
From:   Jiri Slaby <jirislaby@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Andrew Cooper <andrew.cooper3@...rix.com>,
        Nikolay Borisov <nik.borisov@...e.com>, x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, mhocko@...e.com
Subject: Re: [PATCH 3/3] x86: Disable running 32bit processes if ia32_disabled
 is passed

On 08. 06. 23, 8:16, Jiri Slaby wrote:
> On 08. 06. 23, 2:25, Thomas Gleixner wrote:
>> I really wish that we could disable syscall32 reliably on AMD and make
>> it raise #UD as it does on Intal.
> 
> Sorry, I am likely missing something, but why is not #GP enough when we 
> set CSTAR = 0?

Or rather to some hole (to avoid mappings when mmap_min_addr=0) or to 
something like entry_SYSCALL32_kill which you suggested elsewhere.

But that is maybe what you consider not being "reliable".

>  It's of course not as good as Intel's *defined* #UD, but 
> why is not the above sufficient/reliable?
> 
> thanks,

-- 
js
suse labs