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 13C98C04AAF for ; Thu, 16 May 2019 16:04:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E3B3320815 for ; Thu, 16 May 2019 16:04:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726460AbfEPQEr (ORCPT ); Thu, 16 May 2019 12:04:47 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:42438 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726665AbfEPP6l (ORCPT ); Thu, 16 May 2019 11:58:41 -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 1hRImD-0006yv-Dt; Thu, 16 May 2019 16:58:37 +0100 Received: from ben by deadeye with local (Exim 4.92) (envelope-from ) id 1hRImC-0001Nh-Sx; 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 , "Peter Zijlstra" , "Thomas Gleixner" , "Boris Ostrovsky" , "Ingo Molnar" , "Linus Torvalds" , "H. Peter Anvin" Date: Thu, 16 May 2019 16:55:33 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 17/86] jump_label/x86: Work around asm build bug on older/backported GCCs 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: Peter Zijlstra commit d420acd816c07c7be31bd19d09cbcb16e5572fa6 upstream. Boris reported that gcc version 4.4.4 20100503 (Red Hat 4.4.4-2) fails to build linux-next kernels that have this fresh commit via the locking tree: 11276d5306b8 ("locking/static_keys: Add a new static_key interface") The problem appears to be that even though @key and @branch are compile time constants, it doesn't see the following expression as an immediate value: &((char *)key)[branch] More recent GCCs don't appear to have this problem. In particular, Red Hat backported the 'asm goto' feature into 4.4, 'normal' 4.4 compilers will not have this feature and thus not run into this asm. The workaround is to supply both values to the asm as immediates and do the addition in asm. Suggested-by: H. Peter Anvin Reported-by: Boris Ostrovsky Tested-by: Boris Ostrovsky Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar Signed-off-by: Ben Hutchings --- arch/x86/include/asm/jump_label.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) --- a/arch/x86/include/asm/jump_label.h +++ b/arch/x86/include/asm/jump_label.h @@ -22,9 +22,9 @@ static __always_inline bool arch_static_ ".byte " __stringify(STATIC_KEY_INIT_NOP) "\n\t" ".pushsection __jump_table, \"aw\" \n\t" _ASM_ALIGN "\n\t" - _ASM_PTR "1b, %l[l_yes], %c0 \n\t" + _ASM_PTR "1b, %l[l_yes], %c0 + %c1 \n\t" ".popsection \n\t" - : : "i" (&((char *)key)[branch]) : : l_yes); + : : "i" (key), "i" (branch) : : l_yes); return false; l_yes: @@ -38,9 +38,9 @@ static __always_inline bool arch_static_ "2:\n\t" ".pushsection __jump_table, \"aw\" \n\t" _ASM_ALIGN "\n\t" - _ASM_PTR "1b, %l[l_yes], %c0 \n\t" + _ASM_PTR "1b, %l[l_yes], %c0 + %c1 \n\t" ".popsection \n\t" - : : "i" (&((char *)key)[branch]) : : l_yes); + : : "i" (key), "i" (branch) : : l_yes); return false; l_yes: