From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751888AbdFOTgJ (ORCPT ); Thu, 15 Jun 2017 15:36:09 -0400 Received: from mga04.intel.com ([192.55.52.120]:22984 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751757AbdFOTgH (ORCPT ); Thu, 15 Jun 2017 15:36:07 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.39,344,1493708400"; d="scan'208";a="274802957" Message-ID: <1497555366.133434.4.camel@ranerica-desktop> Subject: Re: [PATCH v7 14/26] x86/insn-eval: Indicate a 32-bit displacement if ModRM.mod is 0 and ModRM.rm is 5 From: Ricardo Neri To: Borislav Petkov Cc: Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Andrew Morton , Brian Gerst , Chris Metcalf , Dave Hansen , Paolo Bonzini , Masami Hiramatsu , Huang Rui , Jiri Slaby , Jonathan Corbet , "Michael S. Tsirkin" , Paul Gortmaker , Vlastimil Babka , Chen Yucong , Alexandre Julliard , Stas Sergeev , Fenghua Yu , "Ravi V. Shankar" , Shuah Khan , linux-kernel@vger.kernel.org, x86@kernel.org, linux-msdos@vger.kernel.org, wine-devel@winehq.org, Adam Buchbinder , Colin Ian King , Lorenzo Stoakes , Qiaowei Ren , Arnaldo Carvalho de Melo , Adrian Hunter , Kees Cook , Thomas Garnier , Dmitry Vyukov Date: Thu, 15 Jun 2017 12:36:06 -0700 In-Reply-To: <20170607131550.y6zpkaggfsbinjo2@pd.tnic> References: <20170505181724.55000-1-ricardo.neri-calderon@linux.intel.com> <20170505181724.55000-15-ricardo.neri-calderon@linux.intel.com> <20170607131550.y6zpkaggfsbinjo2@pd.tnic> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.10.4-0ubuntu2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2017-06-07 at 15:15 +0200, Borislav Petkov wrote: > On Fri, May 05, 2017 at 11:17:12AM -0700, Ricardo Neri wrote: > > Section 2.2.1.3 of the Intel 64 and IA-32 Architectures Software > > Developer's Manual volume 2A states that when ModRM.mod is zero and > > ModRM.rm is 101b, a 32-bit displacement follows the ModRM byte. This means > > that none of the registers are used in the computation of the effective > > address. A return value of -EDOM signals callers that they should not use > > the value of registers when computing the effective address for the > > instruction. > > > > In IA-32e 64-bit mode (long mode), the effective address is given by the > > 32-bit displacement plus the value of RIP of the next instruction. > > In IA-32e compatibility mode (protected mode), only the displacement is > > used. > > > > The instruction decoder takes care of obtaining the displacement. > > ... > > > diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c > > index 693e5a8..4f600de 100644 > > --- a/arch/x86/lib/insn-eval.c > > +++ b/arch/x86/lib/insn-eval.c > > @@ -379,6 +379,12 @@ static int get_reg_offset(struct insn *insn, struct pt_regs *regs, > > switch (type) { > > case REG_TYPE_RM: > > regno = X86_MODRM_RM(insn->modrm.value); > > > <---- newline here. Will add the new line. > > > + /* > > + * ModRM.mod == 0 and ModRM.rm == 5 means a 32-bit displacement > > + * follows the ModRM byte. > > + */ > > + if (!X86_MODRM_MOD(insn->modrm.value) && regno == 5) > > + return -EDOM; > > if (X86_REX_B(insn->rex_prefix.value)) > > regno += 8; > > break; > > @@ -730,9 +736,21 @@ void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs) > > eff_addr = base + indx * (1 << X86_SIB_SCALE(sib)); > > } else { > > addr_offset = get_reg_offset(insn, regs, REG_TYPE_RM); > > - if (addr_offset < 0) > > ditto. Will add the new line. > > > + /* > > + * -EDOM means that we must ignore the address_offset. > > + * In such a case, in 64-bit mode the effective address > > + * relative to the RIP of the following instruction. > > + */ > > + if (addr_offset == -EDOM) { > > + eff_addr = 0; > > + if (user_64bit_mode(regs)) > > + eff_addr = (long)regs->ip + > > + insn->length; > > Let that line stick out and write it balanced: > > if (addr_offset == -EDOM) { > if (user_64bit_mode(regs)) > eff_addr = (long)regs->ip + insn->length; > else > eff_addr = 0; > > should be easier parseable this way. Will rewrite as you suggest. Thanks and BR, Ricardo