From patchwork Tue Dec 1 21:36:55 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sami Tolvanen X-Patchwork-Id: 11943933 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=-26.2 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, 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,USER_IN_DEF_DKIM_WL 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 6BEF7C83016 for ; Tue, 1 Dec 2020 21:39:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0D4A120870 for ; Tue, 1 Dec 2020 21:39:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="WQCyqpyw" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389199AbgLAVjM (ORCPT ); Tue, 1 Dec 2020 16:39:12 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56458 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388655AbgLAVjL (ORCPT ); Tue, 1 Dec 2020 16:39:11 -0500 Received: from mail-yb1-xb49.google.com (mail-yb1-xb49.google.com [IPv6:2607:f8b0:4864:20::b49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B4C05C061A56 for ; Tue, 1 Dec 2020 13:37:20 -0800 (PST) Received: by mail-yb1-xb49.google.com with SMTP id c9so4009059ybs.8 for ; Tue, 01 Dec 2020 13:37:20 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=sender:date:in-reply-to:message-id:mime-version:references:subject :from:to:cc; bh=vhe2fhhubG0SMFTgpBNX4/KlbzQ2mtF+9llrSjbBo08=; b=WQCyqpywTb9sjhDQE0uOd7b+9m6ebi816QKf9yVHZCPLWaGBG+ipLHxcUm8kqWX+KJ kfKXPytExTkGVOe4NfXDntXrOaPJsp9DGA/e+Z5eC+AB1fjt5JjOY6moHYKtMdYABXlc pqwT9bceah0mNt1zUgNTQJmG7XZ4Nqu08tOaPOFkTunOluNW1v+MiVxaG85YN4/M5u+k HXPgLPzYDq4JSCLjbyTdrYr0q8bfH/+KpCl0SDkUgF3lejzLr/TISZQcZo011awEDOER hEKx1vs28+FQbBudhpM53qOZF9Lg00bdHxOHtQRU8na1jUSF06Ou0gmHopnqw5/ud94s 4QmQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=vhe2fhhubG0SMFTgpBNX4/KlbzQ2mtF+9llrSjbBo08=; b=gRGY43hCa8LkdjNvT39su52qexzJY8VRgSMNSSlQfeakHW9xU5WkCzQTw2YMV6teUo eoXyrGDI1YJ+bx9Mjkzc740GNzpxbUmwnUjOOCCUDdf3elU9rAmlh2Ngia/kvDE2XiBC /K+XV2rYmXN8KTA7a++fg//oNgMseoGVbeul6T7k+stcoSCeQmrAuCIUV+CoInmYia1L H7XD4FXyntEjz4LZ2biyzR/bXq93EIbGxBR7D02NjcytsQl+sZWAxhEpXr+WpiSL/HdQ mAkS+9jlF2xzV8pom46GBVHXiaWDhCBtRnzJos8/b0AtH2t65kgeE7L4f6e541VPVKhN T02Q== X-Gm-Message-State: AOAM533iW5VHK2edYdCzxpYLOzu84+ap7rPlunnzIh7M2lb4VP1tBPvp QupF7aDM3Ld4DjgmSfQ2fiUyDDe5NqsZBpvOuEc= X-Google-Smtp-Source: ABdhPJzj8ZnKlwOa7MfJuQkhiVpth6ScVKMd4AIpnLjVPcTB19+WZbXrany4DQG3oU9eJ5gCXDSYO/sX5i8KB6YTJcA= Sender: "samitolvanen via sendgmr" X-Received: from samitolvanen1.mtv.corp.google.com ([2620:15c:201:2:f693:9fff:fef4:1b6d]) (user=samitolvanen job=sendgmr) by 2002:a25:468a:: with SMTP id t132mr5364497yba.312.1606858639932; Tue, 01 Dec 2020 13:37:19 -0800 (PST) Date: Tue, 1 Dec 2020 13:36:55 -0800 In-Reply-To: <20201201213707.541432-1-samitolvanen@google.com> Message-Id: <20201201213707.541432-5-samitolvanen@google.com> Mime-Version: 1.0 References: <20201201213707.541432-1-samitolvanen@google.com> X-Mailer: git-send-email 2.29.2.576.ga3fc446d84-goog Subject: [PATCH v8 04/16] kbuild: lto: limit inlining From: Sami Tolvanen To: Masahiro Yamada , Steven Rostedt , Will Deacon Cc: Josh Poimboeuf , Peter Zijlstra , Greg Kroah-Hartman , "Paul E. McKenney" , Kees Cook , Nick Desaulniers , clang-built-linux@googlegroups.com, kernel-hardening@lists.openwall.com, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, Sami Tolvanen Precedence: bulk List-ID: X-Mailing-List: linux-kbuild@vger.kernel.org This change limits function inlining across translation unit boundaries in order to reduce the binary size with LTO. The -import-instr-limit flag defines a size limit, as the number of LLVM IR instructions, for importing functions from other TUs, defaulting to 100. Based on testing with arm64 defconfig, we found that a limit of 5 is a reasonable compromise between performance and binary size, reducing the size of a stripped vmlinux by 11%. Suggested-by: George Burgess IV Signed-off-by: Sami Tolvanen Reviewed-by: Kees Cook --- Makefile | 3 +++ 1 file changed, 3 insertions(+) diff --git a/Makefile b/Makefile index 222ae96d179d..ac836907d8b1 100644 --- a/Makefile +++ b/Makefile @@ -899,6 +899,9 @@ else CC_FLAGS_LTO += -flto endif CC_FLAGS_LTO += -fvisibility=default + +# Limit inlining across translation units to reduce binary size +KBUILD_LDFLAGS += -mllvm -import-instr-limit=5 endif ifdef CONFIG_LTO