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=-18.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 1510EC2B9F4 for ; Mon, 14 Jun 2021 11:23:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F271061004 for ; Mon, 14 Jun 2021 11:23:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234609AbhFNLZd (ORCPT ); Mon, 14 Jun 2021 07:25:33 -0400 Received: from mail.kernel.org ([198.145.29.99]:42526 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234717AbhFNLLz (ORCPT ); Mon, 14 Jun 2021 07:11:55 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 0FCDA61951; Mon, 14 Jun 2021 10:48:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1623667684; bh=ROxKfwcxodE0zhvauAbH2Wq6lyAIhtvHimFSA8eXLvA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=JRi6odW9pNYr0QBFWAg7XPnCLruJIsJf04TkL+vKmZZcgScMKp1iJBXV3U28aIy9e G9tWyYVq7AFLK81jslNy4zTxp4B5MoIZOysOJun9hcgWo4ZVCoxlXArx09AwDzeYmh uoAGf6Q6Ahx+b+1bsAN5IJxrfwpiFGFDuVSaTtYw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Sami Tolvanen , Candle Sun , Fangrui Song , Nick Desaulniers , Kees Cook , Sasha Levin Subject: [PATCH 5.12 035/173] Makefile: LTO: have linker check -Wframe-larger-than Date: Mon, 14 Jun 2021 12:26:07 +0200 Message-Id: <20210614102659.317088098@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210614102658.137943264@linuxfoundation.org> References: <20210614102658.137943264@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Nick Desaulniers [ Upstream commit 24845dcb170e16b3100bd49743687648c71387ae ] -Wframe-larger-than= requires stack frame information, which the frontend cannot provide. This diagnostic is emitted late during compilation once stack frame size is available. When building with LTO, the frontend simply lowers C to LLVM IR and does not have stack frame information, so it cannot emit this diagnostic. When the linker drives LTO, it restarts optimizations and lowers LLVM IR to object code. At that point, it has stack frame information but doesn't know to check for a specific max stack frame size. I consider this a bug in LLVM that we need to fix. There are some details we're working out related to LTO such as which value to use when there are multiple different values specified per TU, or how to propagate these to compiler synthesized routines properly, if at all. Until it's fixed, ensure we don't miss these. At that point we can wrap this in a compiler version guard or revert this based on the minimum support version of Clang. The error message is not generated during link: LTO vmlinux.o ld.lld: warning: stack size limit exceeded (8224) in foobarbaz Cc: Sami Tolvanen Reported-by: Candle Sun Suggested-by: Fangrui Song Signed-off-by: Nick Desaulniers Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20210312010942.1546679-1-ndesaulniers@google.com Signed-off-by: Sasha Levin --- Makefile | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/Makefile b/Makefile index ebc02c56db03..358a2b103de9 100644 --- a/Makefile +++ b/Makefile @@ -912,6 +912,11 @@ CC_FLAGS_LTO += -fvisibility=hidden # Limit inlining across translation units to reduce binary size KBUILD_LDFLAGS += -mllvm -import-instr-limit=5 + +# Check for frame size exceeding threshold during prolog/epilog insertion. +ifneq ($(CONFIG_FRAME_WARN),0) +KBUILD_LDFLAGS += -plugin-opt=-warn-stack-size=$(CONFIG_FRAME_WARN) +endif endif ifdef CONFIG_LTO -- 2.30.2