From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752621AbdJTSLq (ORCPT ); Fri, 20 Oct 2017 14:11:46 -0400 Received: from mga09.intel.com ([134.134.136.24]:33348 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752214AbdJTSLo (ORCPT ); Fri, 20 Oct 2017 14:11:44 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.43,408,1503385200"; d="scan'208";a="912008159" Date: Fri, 20 Oct 2017 11:10:51 -0700 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 , "Ravi V. Shankar" , Shuah Khan , linux-kernel@vger.kernel.org, x86@kernel.org, ricardo.neri@intel.com, Adam Buchbinder , Colin Ian King , Lorenzo Stoakes , Qiaowei Ren , Arnaldo Carvalho de Melo , Adrian Hunter , Kees Cook , Thomas Garnier , Dmitry Vyukov Subject: Re: [PATCH v9 18/29] x86/insn-eval: Incorporate segment base in linear address computation Message-ID: <20171020181051.GD12298@voyager> References: <1507089272-32733-1-git-send-email-ricardo.neri-calderon@linux.intel.com> <1507089272-32733-19-git-send-email-ricardo.neri-calderon@linux.intel.com> <20171020160833.mzzo5sqbczgp3uqo@pd.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171020160833.mzzo5sqbczgp3uqo@pd.tnic> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 20, 2017 at 06:08:41PM +0200, Borislav Petkov wrote: > On Tue, Oct 03, 2017 at 08:54:21PM -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 > > Cc: Adam Buchbinder > > Cc: Colin Ian King > > Cc: Lorenzo Stoakes > > Cc: Qiaowei Ren > > Cc: Arnaldo Carvalho de Melo > > Cc: Masami Hiramatsu > > Cc: Adrian Hunter > > Cc: Kees Cook > > Cc: Thomas Garnier > > Cc: Peter Zijlstra > > Cc: Borislav Petkov > > Cc: Dmitry Vyukov > > Cc: Ravi V. Shankar > > Cc: x86@kernel.org > > Signed-off-by: Ricardo Neri > > --- > > arch/x86/lib/insn-eval.c | 30 +++++++++++++++++++++++++++--- > > 1 file changed, 27 insertions(+), 3 deletions(-) > > > > diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c > > index dd84819..b3aa891 100644 > > --- a/arch/x86/lib/insn-eval.c > > +++ b/arch/x86/lib/insn-eval.c > > @@ -719,8 +719,8 @@ int insn_get_modrm_rm_off(struct insn *insn, struct pt_regs *regs) > > */ > > void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs) > > { > > - int addr_offset, base_offset, indx_offset; > > - unsigned long linear_addr = -1L; > > + int addr_offset, base_offset, indx_offset, seg_reg_indx; > > + unsigned long linear_addr = -1L, seg_base_addr; > > long eff_addr, base, indx; > > insn_byte_t sib; > > > > @@ -734,6 +734,14 @@ void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs) > > goto out; > > > > eff_addr = regs_get_register(regs, addr_offset); > > + > > + seg_reg_indx = resolve_seg_reg(insn, regs, addr_offset); > > + if (seg_reg_indx < 0) > > + goto out; > > + > > + seg_base_addr = insn_get_seg_base(regs, seg_reg_indx); > > + if (seg_base_addr == -1L) > > + goto out; > > Instead of replicating the same calls three times, add a > get_seg_base_addr() helper and call it where needed. I will add this function. Thanks and BR, Ricardo > --