From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751550AbdFGM7x (ORCPT ); Wed, 7 Jun 2017 08:59:53 -0400 Received: from mx2.suse.de ([195.135.220.15]:44061 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751203AbdFGM7w (ORCPT ); Wed, 7 Jun 2017 08:59:52 -0400 Date: Wed, 7 Jun 2017 14:59:34 +0200 From: Borislav Petkov To: Ricardo Neri 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 Subject: Re: [PATCH v7 13/26] x86/insn-eval: Add function to get default params of code segment Message-ID: <20170607125934.27jiyy636wgjrmck@pd.tnic> References: <20170505181724.55000-1-ricardo.neri-calderon@linux.intel.com> <20170505181724.55000-14-ricardo.neri-calderon@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20170505181724.55000-14-ricardo.neri-calderon@linux.intel.com> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 05, 2017 at 11:17:11AM -0700, Ricardo Neri wrote: > This function returns 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. > > 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 | 6 ++++ > arch/x86/lib/insn-eval.c | 65 ++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 71 insertions(+) > > diff --git a/arch/x86/include/asm/insn-eval.h b/arch/x86/include/asm/insn-eval.h > index 7f3c7fe..9ed1c88 100644 > --- a/arch/x86/include/asm/insn-eval.h > +++ b/arch/x86/include/asm/insn-eval.h > @@ -11,9 +11,15 @@ > #include > #include > > +struct insn_code_seg_defaults { A whole struct for a function which gets called only once? Bah, that's a bit too much, if you ask me. So you're returning two small unsigned integers - i.e., you can just as well return a single u8 and put address and operand sizes in there: ret = oper_sz | addr_sz << 4; No need for special structs for that. > + unsigned char address_bytes; > + unsigned char operand_bytes; > +}; > + > void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs); > int insn_get_modrm_rm_off(struct insn *insn, struct pt_regs *regs); > unsigned long insn_get_seg_base(struct pt_regs *regs, struct insn *insn, > int regoff); > +struct insn_code_seg_defaults insn_get_code_seg_defaults(struct pt_regs *regs); > > #endif /* _ASM_X86_INSN_EVAL_H */ > diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c > index c77ed80..693e5a8 100644 > --- a/arch/x86/lib/insn-eval.c > +++ b/arch/x86/lib/insn-eval.c > @@ -603,6 +603,71 @@ static unsigned long get_seg_limit(struct pt_regs *regs, struct insn *insn, > } > > /** > + * insn_get_code_seg_defaults() - Obtain code segment default parameters > + * @regs: Structure with register values as seen when entering kernel mode > + * > + * Obtain the default parameters of the code segment: address and operand sizes. > + * The code segment is obtained from the selector contained in the CS register > + * in regs. 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 for both address and operand sizes. > + * > + * Return: A populated insn_code_seg_defaults structure on success. The > + * structure contains only zeros on failure. s/failure/error/ > + */ > +struct insn_code_seg_defaults insn_get_code_seg_defaults(struct pt_regs *regs) > +{ > + struct desc_struct *desc; > + struct insn_code_seg_defaults defs; > + unsigned short sel; > + /* > + * The most significant byte of AR_TYPE_MASK determines whether a > + * segment contains data or code. > + */ > + unsigned int type_mask = AR_TYPE_MASK & (1 << 11); > + > + memset(&defs, 0, sizeof(defs)); > + > + if (v8086_mode(regs)) { > + defs.address_bytes = 2; > + defs.operand_bytes = 2; > + return defs; > + } > + > + sel = (unsigned short)regs->cs; > + > + desc = get_desc(sel); > + if (!desc) > + return defs; > + > + /* if data segment, return */ > + if (!(desc->b & type_mask)) > + return defs; So you can simplify that into: /* A code segment? */ if (!(desc->b & BIT(11))) return defs; and remove that type_mask thing. -- Regards/Gruss, Boris. SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) --