linux-kernel - Re: [v6 PATCH 04/21] x86/mpx, x86/insn: Relocate insn util functions to a new insn-kernel

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Date:   Tue, 25 Apr 2017 19:05:53 -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 04/21] x86/mpx, x86/insn: Relocate insn util
 functions to a new insn-kernel

On Wed, 2017-04-12 at 12:03 +0200, Borislav Petkov wrote:
> > +              * If mod is 0 and register R/EBP (regno=5) is
> indicated in the
> > +              * base part of the SIB byte, the value of such
> register should
> > +              * not be used in the address computation. Also, a
> 32-bit
> > +              * displacement is expected in this case; the
> instruction
> > +              * decoder takes care of it. This is true for both R13
> and
> > +              * R/EBP as REX.B will not be decoded.
> > +              */
> > +             if (regno == 5 && X86_MODRM_MOD(insn->modrm.value) ==
> 0)
> > +                     return -EDOM;
> > +
> > +             if (X86_REX_B(insn->rex_prefix.value))
> > +                     regno += 8;
> > +             break;
> > +
> > +     default:
> > +             pr_err("invalid register type");
> > +             BUG();
> 
> WARNING: Avoid crashing the kernel - try using WARN_ON & recovery code
> rather than BUG() or BUG_ON()
> #211: FILE: arch/x86/lib/insn-eval.c:90:
> +               BUG();
> 
> And checkpatch is kinda right. We need to warn here, not explode. Oh
> and
> that function returns negative values on error...
> 
> Please change that with a patch ontop of the move.

Sure, I will change it.