linux-kernel - Re: [v6 PATCH 12/21] x86/insn: Support both signed 32-bit and 64-bit effective addresses

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Date:   Thu, 11 May 2017 18:55:54 -0700
From:   Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
To:     Borislav Petkov <bp@...e.de>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Brian Gerst <brgerst@...il.com>,
        Chris Metcalf <cmetcalf@...lanox.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Huang Rui <ray.huang@....com>, Jiri Slaby <jslaby@...e.cz>,
        Jonathan Corbet <corbet@....net>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Chen Yucong <slaoub@...il.com>,
        Alexandre Julliard <julliard@...ehq.org>,
        Stas Sergeev <stsp@...t.ru>, Fenghua Yu <fenghua.yu@...el.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Shuah Khan <shuah@...nel.org>, linux-kernel@...r.kernel.org,
        x86@...nel.org, linux-msdos@...r.kernel.org, wine-devel@...ehq.org,
        Adam Buchbinder <adam.buchbinder@...il.com>,
        Colin Ian King <colin.king@...onical.com>,
        Lorenzo Stoakes <lstoakes@...il.com>,
        Qiaowei Ren <qiaowei.ren@...el.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Kees Cook <keescook@...omium.org>,
        Thomas Garnier <thgarnie@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [v6 PATCH 12/21] x86/insn: Support both signed 32-bit and
 64-bit effective addresses

On Mon, 2017-05-08 at 13:42 +0200, Borislav Petkov wrote:
> On Wed, Apr 26, 2017 at 08:33:46PM -0700, Ricardo Neri wrote:
> > This is the reason I check the value of long_bytes. If long_bytes is not
> > 4, being the only other possible value 8 (perhaps I need to issue an
> > error when the value is not any of these values),
> 
> Well, maybe I'm a bit too paranoid. Bottom line is, we should do the
> address computations exactly like the hardware does them so that there
> are no surprises. Doing them with longs looks ok to me.

Using long is exactly what I intend to do. The problem that I am trying
to resolve is to sign-extend signed memory offsets of 32-bit programs
running on 64-bit kernels. For 64-bit programs running on 64-bit kernels
I can simply use longs. I added error checking in my v7 of this series
[1].

Thanks and BR,
Ricardo

[1]. https://lkml.org/lkml/2017/5/5/407