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=-14.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT 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 B5363C4360C for ; Mon, 14 Oct 2019 02:51:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8A9492083B for ; Mon, 14 Oct 2019 02:51:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="DAHcZpcH" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729917AbfJNCv2 (ORCPT ); Sun, 13 Oct 2019 22:51:28 -0400 Received: from mail-oi1-f193.google.com ([209.85.167.193]:46216 "EHLO mail-oi1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729901AbfJNCv0 (ORCPT ); Sun, 13 Oct 2019 22:51:26 -0400 Received: by mail-oi1-f193.google.com with SMTP id k25so12526927oiw.13 for ; Sun, 13 Oct 2019 19:51:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=ELg5bkMi+FoappyTCFIUx1Rg8zAW2tMRA+teB43Z1gY=; b=DAHcZpcHRxIEH+BjxCNkrpahqtOtpNE8Wov9Ku5GbbLrWCYS6wZZY8TxY5xsTvnRcI cx/tv3jnL40q4qAna6T/lHY6gVi2sQk9AMYAbtRLOt5DOGVB8MDmRowbngBngLe11bHw /W3qsCzLy6Q5QynUELtKB6qPYh4pb3q2CS7qxjMfjBbr+Swzlgc9B7GtkNilk3l/rIrG CxPEjXn8sulp19LAonhdDj+koKA2aU0diP1aofLiHm7E7SZqb/sbIiAn4xY29E7fVKWP 6xnU+o2lELxjR137GkPGzDjV3Uwef9cz96XbN9OUWi8VAZrm2GCQrCRjkd2h99eFgc5h Cs3g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=ELg5bkMi+FoappyTCFIUx1Rg8zAW2tMRA+teB43Z1gY=; b=KNfPDNHfnTMCLRUkrusOkQSedp4oU9XsF5Xx9a5LJg6Gdhaz+fovY2ppTQs4SfI1WT nq8cOsSkCn9yeVVP3CLG8/zBNz2a9WOGpE0nAmcLyIpTZa1ur/lS9l+n41i/2ArmE/47 DKOfMxXYb3o65PB7CVKBCIegFcAcjsM/xWIENak1ZQlGPVdOyckoNVxxKsWLoEc3CJ/r Ykfi3TwVZsxDg0UxLmHfFdP3X+I6XjSyrqaMUkyudiHDs22wt1MWzJr04LtoAlKqqOW8 GtwIM9sWgPed/Qdzcy8hcnKSCEiu6nL1SDsf9kuJOSkTOn+bbee0wL9Z2LyoGfAOylv0 BfAg== X-Gm-Message-State: APjAAAWOffPhOSTQjckv1b5afUx+HIJnAYbiJ6XE6PCZGCdAkONfMInQ 988TY191xOEJKDzOUQvs4Uo= X-Google-Smtp-Source: APXvYqxidzN5tutwxdHg98hmZURUZDkArUJX8YnsN19/vfIrWs3pMFVf3dOO84FGEF13ujyo5Vsozg== X-Received: by 2002:a54:418c:: with SMTP id 12mr22608906oiy.154.1571021484434; Sun, 13 Oct 2019 19:51:24 -0700 (PDT) Received: from localhost.localdomain ([2604:1380:4111:8b00::1]) by smtp.gmail.com with ESMTPSA id 11sm5612491otg.62.2019.10.13.19.51.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 13 Oct 2019 19:51:23 -0700 (PDT) From: Nathan Chancellor To: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com, Nick Desaulniers , Nathan Chancellor Subject: [PATCH v4 3/3] powerpc/prom_init: Use -ffreestanding to avoid a reference to bcmp Date: Sun, 13 Oct 2019 19:51:01 -0700 Message-Id: <20191014025101.18567-4-natechancellor@gmail.com> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20191014025101.18567-1-natechancellor@gmail.com> References: <20190911182049.77853-1-natechancellor@gmail.com> <20191014025101.18567-1-natechancellor@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org r374662 gives LLVM the ability to convert certain loops into a reference to bcmp as an optimization; this breaks prom_init_check.sh: CALL arch/powerpc/kernel/prom_init_check.sh Error: External symbol 'bcmp' referenced from prom_init.c make[2]: *** [arch/powerpc/kernel/Makefile:196: prom_init_check] Error 1 bcmp is defined in lib/string.c as a wrapper for memcmp so this could be added to the whitelist. However, commit 450e7dd4001f ("powerpc/prom_init: don't use string functions from lib/") copied memcmp as prom_memcmp to avoid KASAN instrumentation so having bcmp be resolved to regular memcmp would break that assumption. Furthermore, because the compiler is the one that inserted bcmp, we cannot provide something like prom_bcmp. To prevent LLVM from being clever with optimizations like this, use -ffreestanding to tell LLVM we are not hosted so it is not free to make transformations like this. Link: https://github.com/ClangBuiltLinux/linux/issues/647 Link: https://github.com/llvm/llvm-project/commit/76cdcf25b883751d83402baea6316772aa73865c Reviewed-by: Nick Desaulneris Signed-off-by: Nathan Chancellor --- v1 -> v3: * New patch in the series v3 -> v4: * Rebase on v5.4-rc3. * Add Nick's reviewed-by tag. * Update the LLVM commit reference to the latest applied version (r374662) as it was originally committed as r370454, reverted in r370788, and reapplied as r374662. arch/powerpc/kernel/Makefile | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile index f1f362146135..7f0ee465dfb6 100644 --- a/arch/powerpc/kernel/Makefile +++ b/arch/powerpc/kernel/Makefile @@ -21,7 +21,7 @@ CFLAGS_prom_init.o += $(DISABLE_LATENT_ENTROPY_PLUGIN) CFLAGS_btext.o += $(DISABLE_LATENT_ENTROPY_PLUGIN) CFLAGS_prom.o += $(DISABLE_LATENT_ENTROPY_PLUGIN) -CFLAGS_prom_init.o += $(call cc-option, -fno-stack-protector) +CFLAGS_prom_init.o += $(call cc-option, -fno-stack-protector) -ffreestanding ifdef CONFIG_FUNCTION_TRACER # Do not trace early boot code -- 2.23.0