From patchwork Wed Nov 18 22:07:18 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sami Tolvanen X-Patchwork-Id: 11916025 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 26E66C64E7C for ; Wed, 18 Nov 2020 22:08:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BAFE4246DD for ; Wed, 18 Nov 2020 22:08:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="OOlRBBd1" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727251AbgKRWHo (ORCPT ); Wed, 18 Nov 2020 17:07:44 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53776 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727252AbgKRWHl (ORCPT ); Wed, 18 Nov 2020 17:07:41 -0500 Received: from mail-pf1-x449.google.com (mail-pf1-x449.google.com [IPv6:2607:f8b0:4864:20::449]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BF7E3C061A4F for ; Wed, 18 Nov 2020 14:07:41 -0800 (PST) Received: by mail-pf1-x449.google.com with SMTP id z28so2089029pfr.12 for ; Wed, 18 Nov 2020 14:07:41 -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=OmvLBVHrXYJgk90zzJ7qPiL6Oqy/f8wdr2oL1+M7ruk=; b=OOlRBBd15lFDmzj+eQqhl6JOtOXoAglrgb4iMn+oJHxK0ENZkBjJjpLRPk8q5A7SFY ZxOzbIi6eI8fOpXWY6S1PtuFb9wg3TX+Bl/FrS4kXMHRbAe+z1Spr6ZgEqWyaJ5aKKGh CYZOPt70DGmhjLkIIlNFkUn5wAZcqd9p24/TP07dxXRKEgV6/xSmfaZiGowvpnrChr3h oRO+CqR4Ru8/QzOnLXn22YARn7ZtJna8chF9gED7FTMLvJ5bG1fnbkKMtM2vVSGmCzM9 01mn+DFFeos8A/Ej3OQuxmZxuUaqeCTk5sVd6ATqwCmTjVTPWyZ/EVXTwx/DNAKAAf5i Lm3g== 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=OmvLBVHrXYJgk90zzJ7qPiL6Oqy/f8wdr2oL1+M7ruk=; b=d1T3hT+51Bri3Fc6gOfT2Lz2aajK/FUARRvVUs4ydAUSpqq8128pJjqyA7gkmxkARY g60QrAYmhohDZs0YtiZgOpPOqQ1a1udUtLdNkNd/E56cPK01OMYhkH+Th4i8KVrvKcNM oRgtUipwz7Ujy1qHnBXtR3jZKARDttMK7d55Tqy6SsfL0uPSNi3JftZZBV87T0UlmkSq 95NTXviQ61+SPKyRkagNppZW+mUnmfr7fmkvUaG1pPzG6HcUCssjDwVLDm+nr4wCpxWf FE3s/lrgKKo0/4pfxDgIrHtIClCJxpyT4OEhdZ7irIXEk4KSQVGcvbo3A878glUmYRyY xG/A== X-Gm-Message-State: AOAM533lNsKNYrs2aolJNfWirKAeh3LNxivQx0HxeiylB/DJVwoZyuX6 f/ysY3FfQPC33zpvVhnWjUmIilIsxyJ6MeCcczE= X-Google-Smtp-Source: ABdhPJzDNOiTYuvtSCpROfZDlglre2puYkkaLcBNYl9GE1qztV2AAXOG3khM8OqSsFXToIMyXQUc4gcbg+Ue1s/szjs= 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:a63:550d:: with SMTP id j13mr10510189pgb.365.1605737261156; Wed, 18 Nov 2020 14:07:41 -0800 (PST) Date: Wed, 18 Nov 2020 14:07:18 -0800 In-Reply-To: <20201118220731.925424-1-samitolvanen@google.com> Message-Id: <20201118220731.925424-5-samitolvanen@google.com> Mime-Version: 1.0 References: <20201118220731.925424-1-samitolvanen@google.com> X-Mailer: git-send-email 2.29.2.454.gaff20da3a2-goog Subject: [PATCH v7 04/17] 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 f27c0da5d05a..bee378f9fd50 100644 --- a/Makefile +++ b/Makefile @@ -901,6 +901,9 @@ 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