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Date: Wed, 1 Nov 2017 18:56:42 +0100
From: Borislav Petkov <bp@suse.de>
To: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>, Thomas Gleixner <tglx@linutronix.de>,
        "H. Peter Anvin" <hpa@zytor.com>, Andy Lutomirski <luto@kernel.org>,
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        "Ravi V. Shankar" <ravi.v.shankar@intel.com>,
        Shuah Khan <shuah@kernel.org>, linux-kernel@vger.kernel.org,
        x86@kernel.org, ricardo.neri@intel.com,
        Adam Buchbinder <adam.buchbinder@gmail.com>,
        Colin Ian King <colin.king@canonical.com>,
        Lorenzo Stoakes <lstoakes@gmail.com>,
        Qiaowei Ren <qiaowei.ren@intel.com>,
        Arnaldo Carvalho de Melo <acme@redhat.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Kees Cook <keescook@chromium.org>,
        Thomas Garnier <thgarnie@google.com>,
        Dmitry Vyukov <dvyukov@google.com>
Subject: Re: [PATCH v10 18/18] x86/insn-eval: Incorporate segment base in
 linear address computation
Message-ID: <20171101175642.ep7ijnvzi6o37u5w@pd.tnic>
References: <1509135945-13762-1-git-send-email-ricardo.neri-calderon@linux.intel.com>
 <1509135945-13762-19-git-send-email-ricardo.neri-calderon@linux.intel.com>
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On Fri, Oct 27, 2017 at 01:25:45PM -0700, Ricardo Neri wrote:
> insn_get_addr_ref() returns the effective address as defined by the
> section 3.7.5.1 Vol 1 of the Intel 64 and IA-32 Architectures Software
> Developer's Manual. In order to compute the linear address, we must add
> to the effective address the segment base address as set in the segment
> descriptor. The segment descriptor to use depends on the register used as
> operand and segment override prefixes, if any.
> 
> In most cases, the segment base address will be 0 if the USER_DS/USER32_DS
> segment is used or if segmentation is not used. However, the base address
> is not necessarily zero if a user programs defines its own segments. This
> is possible by using a local descriptor table.
> 
> Since the effective address is a signed quantity, the unsigned segment
> base address is saved in a separate variable and added to the final,
> unsigned, effective address.
> 
> Cc: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: Adam Buchbinder <adam.buchbinder@gmail.com>
> Cc: Colin Ian King <colin.king@canonical.com>
> Cc: Lorenzo Stoakes <lstoakes@gmail.com>
> Cc: Qiaowei Ren <qiaowei.ren@intel.com>
> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> Cc: Masami Hiramatsu <mhiramat@kernel.org>
> Cc: Adrian Hunter <adrian.hunter@intel.com>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Thomas Garnier <thgarnie@google.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: Dmitry Vyukov <dvyukov@google.com>
> Cc: Ravi V. Shankar <ravi.v.shankar@intel.com>
> Cc: x86@kernel.org
> Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
> ---
>  arch/x86/lib/insn-eval.c | 55 +++++++++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 52 insertions(+), 3 deletions(-)

Reviewed-by: Borislav Petkov <bp@suse.de>

-- 
Regards/Gruss,
    Boris.

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