From patchwork Fri Apr 26 00:11:28 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nadav Amit X-Patchwork-Id: 10918629 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id DA96492A for ; Fri, 26 Apr 2019 07:33:04 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id CAA8528DA2 for ; Fri, 26 Apr 2019 07:33:04 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id BE6AF28DA3; Fri, 26 Apr 2019 07:33:04 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.4 required=2.0 tests=BAYES_00,DATE_IN_PAST_06_12, RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 6F7C028DA7 for ; Fri, 26 Apr 2019 07:33:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726321AbfDZHb6 (ORCPT ); Fri, 26 Apr 2019 03:31:58 -0400 Received: from ex13-edg-ou-002.vmware.com ([208.91.0.190]:29121 "EHLO EX13-EDG-OU-002.vmware.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726309AbfDZHb6 (ORCPT ); Fri, 26 Apr 2019 03:31:58 -0400 Received: from sc9-mailhost3.vmware.com (10.113.161.73) by EX13-EDG-OU-002.vmware.com (10.113.208.156) with Microsoft SMTP Server id 15.0.1156.6; Fri, 26 Apr 2019 00:31:44 -0700 Received: from sc2-haas01-esx0118.eng.vmware.com (sc2-haas01-esx0118.eng.vmware.com [10.172.44.118]) by sc9-mailhost3.vmware.com (Postfix) with ESMTP id A1013412A3; Fri, 26 Apr 2019 00:31:45 -0700 (PDT) From: Nadav Amit To: Peter Zijlstra , Borislav Petkov , Andy Lutomirski , Ingo Molnar CC: , , , Thomas Gleixner , Nadav Amit , Dave Hansen , , , , , , , , , , , Rick Edgecombe , Nadav Amit Subject: [PATCH v5 08/23] x86/kgdb: Avoid redundant comparison of patched code Date: Thu, 25 Apr 2019 17:11:28 -0700 Message-ID: <20190426001143.4983-9-namit@vmware.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190426001143.4983-1-namit@vmware.com> References: <20190426001143.4983-1-namit@vmware.com> MIME-Version: 1.0 Received-SPF: None (EX13-EDG-OU-002.vmware.com: namit@vmware.com does not designate permitted sender hosts) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: X-Virus-Scanned: ClamAV using ClamSMTP 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 2b203ee5b879..13b13311b792 100644 --- a/arch/x86/kernel/kgdb.c +++ b/arch/x86/kernel/kgdb.c @@ -747,7 +747,6 @@ 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, @@ -766,11 +765,6 @@ 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; @@ -778,9 +772,6 @@ 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; /* @@ -791,10 +782,7 @@ 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,