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=-20.4 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 2B24FC433E7 for ; Fri, 9 Oct 2020 16:14:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E6237222EA for ; Fri, 9 Oct 2020 16:14:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="ZNNTphyu" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389776AbgJIQOV (ORCPT ); Fri, 9 Oct 2020 12:14:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41546 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389720AbgJIQOI (ORCPT ); Fri, 9 Oct 2020 12:14:08 -0400 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 34999C0613B8 for ; Fri, 9 Oct 2020 09:14:06 -0700 (PDT) Received: by mail-yb1-xb49.google.com with SMTP id p187so9500800ybg.14 for ; Fri, 09 Oct 2020 09:14:06 -0700 (PDT) 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=4HzvBRrh7y77qbzNEjVJ7UvC0hGlxJRwsbNcMQwghFk=; b=ZNNTphyuqijkRLPow6CC/aXgGKsYBRFzq/yKSKcyxkgD/lkmYvVzPyhTAXclZndZdh L3lGMAoJTnYIv0JKMzOqbYFxS0Z/IXLeipSXzl8ZMqk57oa/VznHrTFfgXFW0/IfZcD5 RqYTIdP+HiFz81jIb/NfQ1D9Haxc/uPLhTJVMZahC+e46ULJHAo2s4sjJ9UcS9BRTN/f US6FT8LeKQoMEj/HEtVefzXtpmZ2ndjtN2ZYgQYJ/yL6MsN+9+7BEiRxGDQkpU/Prblz jXweMCv47z7uMWgqx10kSVje4u+fTnnhzw09XocxwMtFtHquTcS5T3ofegl5oYhmmSKN kLnQ== 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=4HzvBRrh7y77qbzNEjVJ7UvC0hGlxJRwsbNcMQwghFk=; b=ks0VESClT7QPUgR276GJC5jevqPoSo5HCjmz2h+k6nGFkrP9peg5bCsaSkRT2ugrX5 m14gpyUt8b3JnC2QskWk+RsTG/uIw0xJ72sA37SMcknYXCZRBTu0JhdCTa7ORkw7bVKN BHEGhJflmibKmxHW124F13yu0WS2CTc2NowM5zMr2DwWx/Ir4Ii7kFL14kM8SnA5fWH/ k6ShGHq2c4QXHTa5o4dkWbRGt64W6/iEC0q5p92i2eHKr29n3OW0MgTjCq0DWvl3SRii P6hRXngyt1p+ljuYaevO8dCjri0l2duw6kUpBcjKsY4OuCWzGj7QWCIqgUtD5L2eMQ0U Xxcg== X-Gm-Message-State: AOAM530gJWiDPywMnrqcY1boS2IC/ebPZLU+BSmt2+OkT7Q/qjPR0CTT mCz/3O0whZTBIdvtulAcQ33p6lC3xs7/Qk9A7eA= X-Google-Smtp-Source: ABdhPJw9ZF97isedllPPEidWjLehS6Y9RG+YGmBbMiJNYvcjDkRjrFEYfvutxmTQNPM4Efl/aY3oqUISefUn5+QvCQY= 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:af90:: with SMTP id g16mr17666057ybh.259.1602260045402; Fri, 09 Oct 2020 09:14:05 -0700 (PDT) Date: Fri, 9 Oct 2020 09:13:21 -0700 In-Reply-To: <20201009161338.657380-1-samitolvanen@google.com> Message-Id: <20201009161338.657380-13-samitolvanen@google.com> Mime-Version: 1.0 References: <20201009161338.657380-1-samitolvanen@google.com> X-Mailer: git-send-email 2.28.0.1011.ga647a8990f-goog Subject: [PATCH v5 12/29] kbuild: lto: limit inlining From: Sami Tolvanen To: Masahiro Yamada , Will Deacon , Steven Rostedt Cc: 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, x86@kernel.org, Sami Tolvanen Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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 6d31a78d79ce..3fe2dca17261 100644 --- a/Makefile +++ b/Makefile @@ -894,6 +894,9 @@ 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 -- 2.28.0.1011.ga647a8990f-goog