Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S937996AbdD0BHn (ORCPT ); Wed, 26 Apr 2017 21:07:43 -0400 Received: from mga01.intel.com ([192.55.52.88]:19124 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754310AbdD0BHl (ORCPT ); Wed, 26 Apr 2017 21:07:41 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.37,256,1488873600"; d="scan'208";a="1161467652" Message-ID: <1493255260.36058.80.camel@ranerica-desktop> Subject: Re: [v6 PATCH 09/21] x86/insn-eval: Add functions to get default operand and address sizes 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: Wed, 26 Apr 2017 18:07:40 -0700 In-Reply-To: <20170420130649.ezudk44ckddznadu@pd.tnic> References: <20170308003254.27833-1-ricardo.neri-calderon@linux.intel.com> <20170308003254.27833-10-ricardo.neri-calderon@linux.intel.com> <20170420130649.ezudk44ckddznadu@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 Content-Length: 5150 Lines: 126 On Thu, 2017-04-20 at 15:06 +0200, Borislav Petkov wrote: > On Tue, Mar 07, 2017 at 04:32:42PM -0800, Ricardo Neri wrote: > > These functions read the default values of the address and operand sizes > > as specified in the segment descriptor. This information is determined > > from the D and L bits. Hence, it can be used for both IA-32e 64-bit and > > 32-bit legacy modes. For virtual-8086 mode, the default address and > > operand sizes are always 2 bytes. > > Yeah, we tend to call that customarily 16-bit :) I will call it like this. > > > The D bit is only meaningful for code segments. Thus, these functions > > always use the code segment selector contained in regs. > > > > 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/include/asm/insn-eval.h | 2 + > > arch/x86/lib/insn-eval.c | 80 ++++++++++++++++++++++++++++++++++++++++ > > 2 files changed, 82 insertions(+) > > > > diff --git a/arch/x86/include/asm/insn-eval.h b/arch/x86/include/asm/insn-eval.h > > index b201742..a0d81fc 100644 > > --- a/arch/x86/include/asm/insn-eval.h > > +++ b/arch/x86/include/asm/insn-eval.h > > @@ -15,6 +15,8 @@ void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs); > > int insn_get_reg_offset_modrm_rm(struct insn *insn, struct pt_regs *regs); > > int insn_get_reg_offset_sib_base(struct insn *insn, struct pt_regs *regs); > > int insn_get_reg_offset_sib_base(struct insn *insn, struct pt_regs *regs); > > +unsigned char insn_get_seg_default_address_bytes(struct pt_regs *regs); > > +unsigned char insn_get_seg_default_operand_bytes(struct pt_regs *regs); > > unsigned long insn_get_seg_base(struct pt_regs *regs, struct insn *insn, > > int regoff, bool use_default_seg); > > > > diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c > > index 383ca83..cda6c71 100644 > > --- a/arch/x86/lib/insn-eval.c > > +++ b/arch/x86/lib/insn-eval.c > > @@ -421,6 +421,86 @@ unsigned long insn_get_seg_base(struct pt_regs *regs, struct insn *insn, > > } > > > > /** > > + * insn_get_seg_default_address_bytes - Obtain default address size of segment > > + * @regs: Set of registers containing the segment selector > > + * > > + * Obtain the default address size as indicated in the segment descriptor > > + * selected in regs' code segment selector. In protected mode, the default > > + * address is determined by inspecting the L and D bits of the segment > > + * descriptor. In virtual-8086 mode, the default is always two bytes. > > + * > > + * Return: Default address size of segment > > 0 on error. > > > + */ > > +unsigned char insn_get_seg_default_address_bytes(struct pt_regs *regs) > > +{ > > + struct desc_struct *desc; > > + unsigned short seg; > > + int ret; > > + > > + if (v8086_mode(regs)) > > + return 2; > > + > > + seg = (unsigned short)regs->cs; > > + > > + ret = get_desc(seg, &desc); > > + if (ret) > > + return 0; > > + > > + switch ((desc->l << 1) | desc->d) { > > + case 0: /* Legacy mode. 16-bit addresses. CS.L=0, CS.D=0 */ > > + return 2; > > + case 1: /* Legacy mode. 32-bit addresses. CS.L=0, CS.D=1 */ > > + return 4; > > + case 2: /* IA-32e 64-bit mode. 64-bit addresses. CS.L=1, CS.D=0 */ > > + return 8; > > + case 3: /* Invalid setting. CS.L=1, CS.D=1 */ > > + /* fall through */ > > + default: > > + return 0; > > + } > > +} > > + > > +/** > > + * insn_get_seg_default_operand_bytes - Obtain default operand size of segment > > + * @regs: Set of registers containing the segment selector > > + * > > + * Obtain the default operand size as indicated in the segment descriptor > > + * selected in regs' code segment selector. In protected mode, the default > > + * operand size is determined by inspecting the L and D bits of the segment > > + * descriptor. In virtual-8086 mode, the default is always two bytes. > > + * > > + * Return: Default operand size of segment > > + */ > > +unsigned char insn_get_seg_default_operand_bytes(struct pt_regs *regs) > > Right, so default address and operand size always go together so I don't > think you need two separate functions. > > So what I'd suggest - provided this pans out (I still haven't reviewed > the whole thing) - is to determine the operating mode of the segment: > long, legacy, etc and then return both address and operand sizes. Patch > 17/21 needs them both at the same time AFAICT. It makes sense to me. So far these two functions are used in the same place. Thanks and BR, Ricardo