linux-kernel - Re: [PATCH v3 2/5] x86/entry: Rename ignore

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Date:   Mon, 19 Jun 2023 16:30:40 +0300
From:   Nikolay Borisov <nik.borisov@...e.com>
To:     Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, mhocko@...e.com, jslaby@...e.cz
Subject: Re: [PATCH v3 2/5] x86/entry: Rename ignore_sysret



On 18.06.23 г. 23:51 ч., Thomas Gleixner wrote:
> On Fri, Jun 16 2023 at 15:57, Nikolay Borisov wrote:
> 
>> Give ignore_sysret() a more descriptive name as it's actually used to make
>> 32bit syscalls return ENOSYS, rather than doing anything specific with
> 
> That's not really correct. This is not about 32bit syscalls in general.
> 
> It's specifically about the SYSCALL entry point on 32bit, right?
> 
> The reason why this is required is because 32bit SYSCALL cannot be
> disabled in hardware.

How about:

"SYSCALL instruction cannot really be disabled in compatibility mode. 
The best that can be done is to configure the CSTAR msr with a minimal 
handler that returns directly some error value.

ignore_sysret is this minimal handler in the Linux kernel. Rename it by 
giving it a more descriptive name."

> 
> Thanks,
> 
>          tglx
> 
>