Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752650AbdCCVqr (ORCPT ); Fri, 3 Mar 2017 16:46:47 -0500 Received: from mga01.intel.com ([192.55.52.88]:28918 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752093AbdCCVnL (ORCPT ); Fri, 3 Mar 2017 16:43:11 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.35,238,1484035200"; d="scan'208";a="64033557" 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 , 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, Ricardo Neri , Adam Buchbinder , Colin Ian King , Lorenzo Stoakes , Qiaowei Ren , Arnaldo Carvalho de Melo , Adrian Hunter , Kees Cook , Thomas Garnier , Dmitry Vyukov Subject: [v5 07/20] x86/insn-eval: Add utility function to get segment descriptor Date: Fri, 3 Mar 2017 13:41:19 -0800 Message-Id: <20170303214132.77244-8-ricardo.neri-calderon@linux.intel.com> X-Mailer: git-send-email 2.9.3 In-Reply-To: <20170303214132.77244-1-ricardo.neri-calderon@linux.intel.com> References: <20170303214132.77244-1-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: 3794 Lines: 117 The segment descriptor contains information that is relevant to how linear address need to be computed. It contains the default size of addresses as well as the base address of the segment. Thus, given a segment selector, we ought look at segment descriptor to correctly calculate the linear address. In protected mode, the segment selector might indicate a segment descriptor from either the global descriptor table or a local descriptor table. Both cases are considered in this function. This function is the initial implementation for subsequent functions that will obtain the aforementioned attributes of the segment descriptor. 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 | 61 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 61 insertions(+) diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c index 8d45df8..8608adf 100644 --- a/arch/x86/lib/insn-eval.c +++ b/arch/x86/lib/insn-eval.c @@ -5,9 +5,13 @@ */ #include #include +#include +#include #include #include #include +#include +#include #include enum reg_type { @@ -294,6 +298,63 @@ static int get_reg_offset(struct insn *insn, struct pt_regs *regs, } /** + * get_desc() - Obtain address of segment descriptor + * @seg: Segment selector + * @desc: Pointer to the selected segment descriptor + * + * Given a segment selector, obtain a memory pointer to the segment + * descriptor. Both global and local descriptor tables are supported. + * desc will contain the address of the descriptor. + * + * Return: 0 if success, -EINVAL if failure + */ +static int get_desc(unsigned short seg, struct desc_struct **desc) +{ + struct desc_ptr gdt_desc = {0, 0}; + unsigned long desc_base; + + if (!desc) + return -EINVAL; + + desc_base = seg & ~(SEGMENT_RPL_MASK | SEGMENT_TI_MASK); + +#ifdef CONFIG_MODIFY_LDT_SYSCALL + if ((seg & SEGMENT_TI_MASK) == SEGMENT_LDT) { + seg >>= 3; + + mutex_lock(¤t->active_mm->context.lock); + if (unlikely(!current->active_mm->context.ldt || + seg >= current->active_mm->context.ldt->size)) { + *desc = NULL; + mutex_unlock(¤t->active_mm->context.lock); + return -EINVAL; + } + + *desc = ¤t->active_mm->context.ldt->entries[seg]; + mutex_unlock(¤t->active_mm->context.lock); + return 0; + } +#endif + native_store_gdt(&gdt_desc); + + /* + * Bits [15:3] of the segment selector contain the index. Such + * index needs to be multiplied by 8. However, as the index + * least significant bit is already in bit 3, we don't have + * to perform the multiplication. + */ + desc_base = seg & ~(SEGMENT_RPL_MASK | SEGMENT_TI_MASK); + + if (desc_base > gdt_desc.size) { + *desc = NULL; + return -EINVAL; + } + + *desc = (struct desc_struct *)(gdt_desc.address + desc_base); + return 0; +} + +/** * insn_get_reg_offset_modrm_rm - Obtain register in r/m part of ModRM byte * @insn: Instruction structure containing the ModRM byte * @regs: Set of registers indicated by the ModRM byte -- 2.9.3