Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752570AbdHSAdM (ORCPT ); Fri, 18 Aug 2017 20:33:12 -0400 Received: from mga07.intel.com ([134.134.136.100]:43538 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750847AbdHSA2q (ORCPT ); Fri, 18 Aug 2017 20:28:46 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.41,394,1498546800"; d="scan'208";a="1164119697" From: Ricardo Neri To: Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , Andy Lutomirski , Borislav Petkov Cc: Peter Zijlstra , Andrew Morton , Brian Gerst , Chris Metcalf , Dave Hansen , Paolo Bonzini , Liang Z Li , 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, Ricardo Neri , Adam Buchbinder , Colin Ian King , Lorenzo Stoakes , Qiaowei Ren , Arnaldo Carvalho de Melo , Adrian Hunter , Kees Cook , Thomas Garnier , Dmitry Vyukov Subject: [PATCH v8 15/28] x86/insn-eval: Add function to get default params of code segment Date: Fri, 18 Aug 2017 17:27:56 -0700 Message-Id: <20170819002809.111312-16-ricardo.neri-calderon@linux.intel.com> X-Mailer: git-send-email 2.13.0 In-Reply-To: <20170819002809.111312-1-ricardo.neri-calderon@linux.intel.com> References: <20170819002809.111312-1-ricardo.neri-calderon@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4347 Lines: 121 Obtain the default values of the address and operand sizes as specified in the D and L bits of the the segment descriptor selected by the register CS. The function can be used for both protected and long modes. For virtual-8086 mode, the default address and operand sizes are always 2 bytes. The returned parameters are encoded in a signed 8-bit data type. Auxiliar macros are provided to encode and decode such values. 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 | 5 ++++ arch/x86/lib/insn-eval.c | 59 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 64 insertions(+) diff --git a/arch/x86/include/asm/insn-eval.h b/arch/x86/include/asm/insn-eval.h index 7f3c7fe72cd0..e8c3e7cd1673 100644 --- a/arch/x86/include/asm/insn-eval.h +++ b/arch/x86/include/asm/insn-eval.h @@ -11,9 +11,14 @@ #include #include +#define INSN_CODE_SEG_ADDR_SZ(params) ((params >> 4) & 0xf) +#define INSN_CODE_SEG_OPND_SZ(params) (params & 0xf) +#define INSN_CODE_SEG_PARAMS(oper_sz, addr_sz) (oper_sz | (addr_sz << 4)) + 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); +char 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 2c5e7081957d..a8e12bd0aecd 100644 --- a/arch/x86/lib/insn-eval.c +++ b/arch/x86/lib/insn-eval.c @@ -584,6 +584,65 @@ 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 signed 8-bit value containing the default parameters on success and + * -EINVAL on error. + */ +char insn_get_code_seg_defaults(struct pt_regs *regs) +{ + struct desc_struct *desc; + unsigned short sel; + + if (v8086_mode(regs)) + /* Address and operand size are both 16-bit. */ + return INSN_CODE_SEG_PARAMS(2, 2); + + sel = (unsigned short)regs->cs; + + desc = get_desc(sel); + if (!desc) + return -EINVAL; + + /* + * The most significant byte of the Type field of the segment descriptor + * determines whether a segment contains data or code. If this is a data + * segment, return error. + */ + if (!(desc->type & BIT(3))) + return -EINVAL; + + switch ((desc->l << 1) | desc->d) { + case 0: /* + * Legacy mode. CS.L=0, CS.D=0. Address and operand size are + * both 16-bit. + */ + return INSN_CODE_SEG_PARAMS(2, 2); + case 1: /* + * Legacy mode. CS.L=0, CS.D=1. Address and operand size are + * both 32-bit. + */ + return INSN_CODE_SEG_PARAMS(4, 4); + case 2: /* + * IA-32e 64-bit mode. CS.L=1, CS.D=0. Address size is 64-bit; + * operand size is 32-bit. + */ + return INSN_CODE_SEG_PARAMS(4, 8); + case 3: /* Invalid setting. CS.L=1, CS.D=1 */ + /* fall through */ + default: + return -EINVAL; + } +} + +/** * insn_get_modrm_rm_off() - Obtain register in r/m part of ModRM byte * @insn: Instruction structure containing the ModRM byte * @regs: Structure with register values as seen when entering kernel mode -- 2.13.0