linux-kernel - Re: [PATCH v28 04/10] x86/cet/ibt: Disable IBT for ia32

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Date:   Tue, 10 Aug 2021 09:07:49 -0700
From:   "Yu, Yu-cheng" <yu-cheng.yu@...el.com>
To:     Andy Lutomirski <luto@...nel.org>, <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, <linux-kernel@...r.kernel.org>,
        <linux-doc@...r.kernel.org>, <linux-mm@...ck.org>,
        <linux-arch@...r.kernel.org>, <linux-api@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Balbir Singh <bsingharora@...il.com>,
        Borislav Petkov <bp@...en8.de>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Eugene Syromiatnikov <esyr@...hat.com>,
        Florian Weimer <fweimer@...hat.com>,
        "H.J. Lu" <hjl.tools@...il.com>, "Jann Horn" <jannh@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>,
        Peter Zijlstra <peterz@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        "Dave Martin" <Dave.Martin@....com>,
        Weijiang Yang <weijiang.yang@...el.com>,
        Pengfei Xu <pengfei.xu@...el.com>,
        Haitao Huang <haitao.huang@...el.com>,
        Rick P Edgecombe <rick.p.edgecombe@...el.com>
Subject: Re: [PATCH v28 04/10] x86/cet/ibt: Disable IBT for ia32

On 8/9/2021 4:04 PM, Andy Lutomirski wrote:
> On 7/22/21 1:57 PM, Yu-cheng Yu wrote:
>> In a signal, a task's IBT status needs to be saved to the signal frame, and
>> later restored in sigreturn.  For the purpose, previous versions of the
>> series add a new struct to the signal frame.  However, a new signal frame
>> format (or re-using a reserved space) introduces complex compatibility
>> issues.
>>
>> In the discussion (see link below), Andy Lutomirski proposed using a
>> ucontext flag.  The approach is clean and eliminates most compatibility
>> issues.
>>
>> However, a legacy IA32 signal frame does not have ucontext and cannot
>> support a uc flag.  Thus,
>>
>> - Disable IBT for ia32.
>> - In ia32 sigreturn, verify ibt is disabled.
> 
> Acked-by: Andy Lutomirski <luto@...nel.org>
> 

Thanks!