linux-kernel - Re: [PATCH v8 12/28] x86/insn-eval: Add utility functions to get segment selector

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Message-ID: <20170929115611.ldpldjr7z7ygdgph@pd.tnic>
Date:   Fri, 29 Sep 2017 13:56:11 +0200
From:   Borislav Petkov <bp@...e.de>
To:     Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
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>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Shuah Khan <shuah@...nel.org>, linux-kernel@...r.kernel.org,
        x86@...nel.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: [PATCH v8 12/28] x86/insn-eval: Add utility functions to get
 segment selector

On Thu, Sep 28, 2017 at 11:06:42PM -0700, Ricardo Neri wrote:
> I agree. In fact, insn_get_seg_base() does not need insn at all. All it needs is
> a INAT_SEG_REG_* index. This would make things clear. UMIP (and callers that
> need to copy_from_user code can do insn_get_seg_base(regs, INAT_SEG_REG_CS). No
> insn needed.

Yap.

> In fact, it is only the insn_get_addr_ref_xx() family of functions that does

I think you mean get_addr_ref_xx() here.

> Do you think the pseudocode above addresses your concerns?
> 
> *insn_get_seg_base() will take a INAT_SEG_REG_* index
> *insn_get_ref_xx() receives an initialized insn that can check for NULL value.
> *a reworked resolve_seg_reg_idx will clearly check if it can use segment
> override prefixes and obtain them. If not, it will use default values.

Makes sense, but send me the final version to take a look at it too.

Thanks.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
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