From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DD704C282CF for ; Tue, 29 Jan 2019 00:41:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B698B217F5 for ; Tue, 29 Jan 2019 00:41:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728351AbfA2Akl (ORCPT ); Mon, 28 Jan 2019 19:40:41 -0500 Received: from mga06.intel.com ([134.134.136.31]:5081 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727509AbfA2AjR (ORCPT ); Mon, 28 Jan 2019 19:39:17 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga104.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 28 Jan 2019 16:39:11 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,535,1539673200"; d="scan'208";a="133921904" Received: from rpedgeco-desk5.jf.intel.com ([10.54.75.79]) by orsmga001.jf.intel.com with ESMTP; 28 Jan 2019 16:39:11 -0800 From: Rick Edgecombe To: Andy Lutomirski , Ingo Molnar Cc: linux-kernel@vger.kernel.org, x86@kernel.org, hpa@zytor.com, Thomas Gleixner , Borislav Petkov , Nadav Amit , Dave Hansen , Peter Zijlstra , linux_dti@icloud.com, linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, akpm@linux-foundation.org, kernel-hardening@lists.openwall.com, linux-mm@kvack.org, will.deacon@arm.com, ard.biesheuvel@linaro.org, kristen@linux.intel.com, deneen.t.dock@intel.com, Nadav Amit , Rick Edgecombe Subject: [PATCH v2 07/20] x86/kgdb: avoid redundant comparison of patched code Date: Mon, 28 Jan 2019 16:34:09 -0800 Message-Id: <20190129003422.9328-8-rick.p.edgecombe@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190129003422.9328-1-rick.p.edgecombe@intel.com> References: <20190129003422.9328-1-rick.p.edgecombe@intel.com> Sender: linux-integrity-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org From: Nadav Amit text_poke() already ensures that the written value is the correct one and fails if that is not the case. There is no need for an additional comparison. Remove it. Acked-by: Peter Zijlstra (Intel) Signed-off-by: Nadav Amit Signed-off-by: Rick Edgecombe --- arch/x86/kernel/kgdb.c | 14 +------------- 1 file changed, 1 insertion(+), 13 deletions(-) diff --git a/arch/x86/kernel/kgdb.c b/arch/x86/kernel/kgdb.c index 1461544cba8b..057af9187a04 100644 --- a/arch/x86/kernel/kgdb.c +++ b/arch/x86/kernel/kgdb.c @@ -746,7 +746,6 @@ void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long ip) int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt) { int err; - char opc[BREAK_INSTR_SIZE]; bpt->type = BP_BREAKPOINT; err = probe_kernel_read(bpt->saved_instr, (char *)bpt->bpt_addr, @@ -765,11 +764,6 @@ int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt) return -EBUSY; text_poke_kgdb((void *)bpt->bpt_addr, arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE); - err = probe_kernel_read(opc, (char *)bpt->bpt_addr, BREAK_INSTR_SIZE); - if (err) - return err; - if (memcmp(opc, arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE)) - return -EINVAL; bpt->type = BP_POKE_BREAKPOINT; return err; @@ -777,9 +771,6 @@ int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt) int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt) { - int err; - char opc[BREAK_INSTR_SIZE]; - if (bpt->type != BP_POKE_BREAKPOINT) goto knl_write; /* @@ -790,10 +781,7 @@ int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt) goto knl_write; text_poke_kgdb((void *)bpt->bpt_addr, bpt->saved_instr, BREAK_INSTR_SIZE); - err = probe_kernel_read(opc, (char *)bpt->bpt_addr, BREAK_INSTR_SIZE); - if (err || memcmp(opc, bpt->saved_instr, BREAK_INSTR_SIZE)) - goto knl_write; - return err; + return 0; knl_write: return probe_kernel_write((char *)bpt->bpt_addr, -- 2.17.1