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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 DB342C04AB4 for ; Thu, 16 May 2019 15:58:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B7FF22087E for ; Thu, 16 May 2019 15:58:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727143AbfEPP6t (ORCPT ); Thu, 16 May 2019 11:58:49 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:42338 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726441AbfEPP6k (ORCPT ); Thu, 16 May 2019 11:58:40 -0400 Received: from [167.98.27.226] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1hRImC-0006ym-Uw; Thu, 16 May 2019 16:58:37 +0100 Received: from ben by deadeye with local (Exim 4.92) (envelope-from ) id 1hRImC-0001Ms-Gm; Thu, 16 May 2019 16:58:36 +0100 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, Denis Kirjanov , "Martin Schwidefsky" , "Heiko Carstens" Date: Thu, 16 May 2019 16:55:32 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 07/86] s390/jump label: use different nop instruction In-Reply-To: X-SA-Exim-Connect-IP: 167.98.27.226 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.68-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Heiko Carstens commit d5caa4dbf9bd2ad8cd7f6be0ca76722be947182b upstream. Use a brcl 0,2 instruction for jump label nops during compile time, so we don't mix up the different nops during mcount/hotpatch call site detection. The initial jump label code instruction replacement will exchange these instructions with either a branch or a brcl 0,0 instruction. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky Signed-off-by: Ben Hutchings --- arch/s390/include/asm/jump_label.h | 7 ++++++- arch/s390/kernel/jump_label.c | 19 +++++++++++++------ 2 files changed, 19 insertions(+), 7 deletions(-) --- a/arch/s390/include/asm/jump_label.h +++ b/arch/s390/include/asm/jump_label.h @@ -4,6 +4,7 @@ #include #define JUMP_LABEL_NOP_SIZE 6 +#define JUMP_LABEL_NOP_OFFSET 2 #ifdef CONFIG_64BIT #define ASM_PTR ".quad" @@ -13,9 +14,13 @@ #define ASM_ALIGN ".balign 4" #endif +/* + * We use a brcl 0,2 instruction for jump labels at compile time so it + * can be easily distinguished from a hotpatch generated instruction. + */ static __always_inline bool arch_static_branch(struct static_key *key) { - asm_volatile_goto("0: brcl 0,0\n" + asm_volatile_goto("0: brcl 0,"__stringify(JUMP_LABEL_NOP_OFFSET)"\n" ".pushsection __jump_table, \"aw\"\n" ASM_ALIGN "\n" ASM_PTR " 0b, %l[label], %0\n" --- a/arch/s390/kernel/jump_label.c +++ b/arch/s390/kernel/jump_label.c @@ -49,6 +49,11 @@ static void jump_label_bug(struct jump_e panic("Corrupted kernel text"); } +static struct insn orignop = { + .opcode = 0xc004, + .offset = JUMP_LABEL_NOP_OFFSET >> 1, +}; + static void __jump_label_transform(struct jump_entry *entry, enum jump_label_type type, int init) @@ -59,14 +64,16 @@ static void __jump_label_transform(struc jump_label_make_nop(entry, &old); jump_label_make_branch(entry, &new); } else { - if (init) - jump_label_make_nop(entry, &old); - else - jump_label_make_branch(entry, &old); + jump_label_make_branch(entry, &old); jump_label_make_nop(entry, &new); } - if (memcmp((void *)entry->code, &old, sizeof(old))) - jump_label_bug(entry, &old); + if (init) { + if (memcmp((void *)entry->code, &orignop, sizeof(orignop))) + jump_label_bug(entry, &old); + } else { + if (memcmp((void *)entry->code, &old, sizeof(old))) + jump_label_bug(entry, &old); + } probe_kernel_write((void *)entry->code, &new, sizeof(new)); }