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=-13.6 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,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 8C870C4321A for ; Tue, 11 Jun 2019 17:21:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5F7952089E for ; Tue, 11 Jun 2019 17:21:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="p6M2O8JB" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2405985AbfFKRVQ (ORCPT ); Tue, 11 Jun 2019 13:21:16 -0400 Received: from mail-ed1-f67.google.com ([209.85.208.67]:42911 "EHLO mail-ed1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2405263AbfFKRVQ (ORCPT ); Tue, 11 Jun 2019 13:21:16 -0400 Received: by mail-ed1-f67.google.com with SMTP id z25so21229285edq.9 for ; Tue, 11 Jun 2019 10:21:15 -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=oLZoCH+w0vEsUh5B0jjb151kNbWDekY9Hx2peXKMbk4=; b=p6M2O8JBT2y4hXNXJ+k4giMVUWIS/Vosq/FvvB5BUcx5CPLUCVhxMVpiKnBWJjmM+j bpuaGCRGv3v0FS4vVfk6v3U5vqxLynpHPLlsCXUykwcn1Ztl5JH+vHVIe7GMg0z+CPBr LzbhW4T+KhsMjCaPYzE5s6M5K9kOVr3z2uwec/+WMTXMQ3ppTHziHNvlDaySYajKXhpd FQvVjnanOlnC/2R6c/9V1sx0kbvm5T7fxtOXsSmsRjSSLd2u4doQFURIdkmck2CsNZu5 BLGgTvnkcl0ZS2Pst76joa7hhkGeR5KfgWZin00PDYtmQZsnEHwmJNw7N1jq6PrmoVG4 vh9w== 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=oLZoCH+w0vEsUh5B0jjb151kNbWDekY9Hx2peXKMbk4=; b=B46W7NGJplufibTibnHtGHT8YkKVUTzNHLtQFCScdPHJqOudbNyalTT7S/AZC43Kcd 8zIT82XbT1fJNdYYfAg6XxDXLT8KG8bdCaH4cDMdDszAm8ZBJMMTD7sWAgLUAzkkQfQQ PqvPvbkkEzZ7vcRRl3GqczXotmshrOVGNWozkOadW8pGs46APMyq9ZWR+80hA10ik+P4 Ow1TXV1SjMpaCdK7XKS7V5onmTr59u6msCJdRX5IdnqwROVJPQIU7unGnrDjGAhsMZS8 COTFIcVTGezIJ6ZkJOQXsZ1Ut87yocu2bvoOjfasLMe77eEwVEBYdzNGLTA/n0R7o0sX 3nJQ== X-Gm-Message-State: APjAAAXmhkx7CJYH1ZS7D8fnvy/jroSKgjNhl0ngceBYEpnD1lJVFf3w mOqJ4LX0qlWVxYPMj+n8RV8= X-Google-Smtp-Source: APXvYqyFh8CR41gRS/XNKx0eEHFjObJh4Rmr0MyxvtAXn6PhWqRAH/Y2ng7P1x+vtBW7ACiKuHvkyw== X-Received: by 2002:a17:906:d6a:: with SMTP id s10mr29877187ejh.180.1560273674134; Tue, 11 Jun 2019 10:21:14 -0700 (PDT) Received: from localhost.localdomain ([2a01:4f9:2b:2b15::2]) by smtp.gmail.com with ESMTPSA id k9sm2403111eja.72.2019.06.11.10.21.12 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Tue, 11 Jun 2019 10:21:13 -0700 (PDT) From: Nathan Chancellor To: Catalin Marinas , Will Deacon Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com, Nathan Chancellor , Qian Cai , Dave Martin , Nick Desaulniers Subject: [PATCH v2] arm64: Don't unconditionally add -Wno-psabi to KBUILD_CFLAGS Date: Tue, 11 Jun 2019 10:19:32 -0700 Message-Id: <20190611171931.99705-1-natechancellor@gmail.com> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190607161201.73430-1-natechancellor@gmail.com> References: <20190607161201.73430-1-natechancellor@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-Patchwork-Bot: notify Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is a GCC only option, which warns about ABI changes within GCC, so unconditionally adding it breaks Clang with tons of: warning: unknown warning option '-Wno-psabi' [-Wunknown-warning-option] and link time failures: ld.lld: error: undefined symbol: __efistub___stack_chk_guard >>> referenced by arm-stub.c:73 (/home/nathan/cbl/linux/drivers/firmware/efi/libstub/arm-stub.c:73) >>> arm-stub.stub.o:(__efistub_install_memreserve_table) in archive ./drivers/firmware/efi/libstub/lib.a These failures come from the lack of -fno-stack-protector, which is added via cc-option in drivers/firmware/efi/libstub/Makefile. When an unknown flag is added to KBUILD_CFLAGS, clang will noisily warn that it is ignoring the option like above, unlike gcc, who will just error. $ echo "int main() { return 0; }" > tmp.c $ clang -Wno-psabi tmp.c; echo $? warning: unknown warning option '-Wno-psabi' [-Wunknown-warning-option] 1 warning generated. 0 $ gcc -Wsometimes-uninitialized tmp.c; echo $? gcc: error: unrecognized command line option ‘-Wsometimes-uninitialized’; did you mean ‘-Wmaybe-uninitialized’? 1 For cc-option to work properly with clang and behave like gcc, -Werror is needed, which was done in commit c3f0d0bc5b01 ("kbuild, LLVMLinux: Add -Werror to cc-option to support clang"). $ clang -Werror -Wno-psabi tmp.c; echo $? error: unknown warning option '-Wno-psabi' [-Werror,-Wunknown-warning-option] 1 As a consequence of this, when an unknown flag is unconditionally added to KBUILD_CFLAGS, it will cause cc-option to always fail and those flags will never get added: $ clang -Werror -Wno-psabi -fno-stack-protector tmp.c; echo $? error: unknown warning option '-Wno-psabi' [-Werror,-Wunknown-warning-option] 1 This can be seen when compiling the whole kernel as some warnings that are normally disabled (see below) show up. The full list of flags missing from drivers/firmware/efi/libstub are the following (gathered from diffing .arm64-stub.o.cmd): -fno-delete-null-pointer-checks -Wno-address-of-packed-member -Wframe-larger-than=2048 -Wno-unused-const-variable -fno-strict-overflow -fno-merge-all-constants -fno-stack-check -Werror=date-time -Werror=incompatible-pointer-types -ffreestanding -fno-stack-protector Use cc-disable-warning so that it gets disabled for GCC and does nothing for Clang. Fixes: ebcc5928c5d9 ("arm64: Silence gcc warnings about arch ABI drift") Link: https://github.com/ClangBuiltLinux/linux/issues/511 Reported-by: Qian Cai Acked-by: Dave Martin Reviewed-by: Nick Desaulniers Signed-off-by: Nathan Chancellor --- v1 -> v2: * Improve commit message explanation, I wasn't entirely happy with the first one; let me know if there are any issues/questions. * Carry forward Dave's ack and Nick's review (let me know if you disagree with the commit messasge rewording). arch/arm64/Makefile | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index 8fbd583b18e1..e9d2e578cbe6 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile @@ -51,7 +51,7 @@ endif KBUILD_CFLAGS += -mgeneral-regs-only $(lseinstr) $(brokengasinst) KBUILD_CFLAGS += -fno-asynchronous-unwind-tables -KBUILD_CFLAGS += -Wno-psabi +KBUILD_CFLAGS += $(call cc-disable-warning, psabi) KBUILD_AFLAGS += $(lseinstr) $(brokengasinst) KBUILD_CFLAGS += $(call cc-option,-mabi=lp64) -- 2.22.0