Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752527AbdHSA3F (ORCPT ); Fri, 18 Aug 2017 20:29:05 -0400 Received: from mga07.intel.com ([134.134.136.100]:26711 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752204AbdHSA2t (ORCPT ); Fri, 18 Aug 2017 20:28:49 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.41,394,1498546800"; d="scan'208";a="1164119708" 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 17/28] x86/insn-eval: Incorporate segment base in linear address computation Date: Fri, 18 Aug 2017 17:27:58 -0700 Message-Id: <20170819002809.111312-18-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: 3356 Lines: 93 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 | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c index 04f696c3793e..8ae110a273de 100644 --- a/arch/x86/lib/insn-eval.c +++ b/arch/x86/lib/insn-eval.c @@ -673,7 +673,7 @@ 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; + unsigned long linear_addr, seg_base_addr; long eff_addr, base, indx; insn_byte_t sib; @@ -687,6 +687,10 @@ void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs) goto out_err; eff_addr = regs_get_register(regs, addr_offset); + + seg_base_addr = insn_get_seg_base(regs, insn, addr_offset); + if (seg_base_addr == -1L) + goto out_err; } else { if (insn->sib.nbytes) { /* @@ -712,6 +716,11 @@ void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs) indx = regs_get_register(regs, indx_offset); eff_addr = base + indx * (1 << X86_SIB_SCALE(sib)); + + seg_base_addr = insn_get_seg_base(regs, insn, + base_offset); + if (seg_base_addr == -1L) + goto out_err; } else { addr_offset = get_reg_offset(insn, regs, REG_TYPE_RM); @@ -730,12 +739,17 @@ void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs) } else { eff_addr = regs_get_register(regs, addr_offset); } + + seg_base_addr = insn_get_seg_base(regs, insn, + addr_offset); + if (seg_base_addr == -1L) + goto out_err; } eff_addr += insn->displacement.value; } - linear_addr = (unsigned long)eff_addr; + linear_addr = (unsigned long)eff_addr + seg_base_addr; return (void __user *)linear_addr; out_err: -- 2.13.0