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 9178CC4363D for ; Fri, 9 Oct 2020 16:14:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 58840222BA for ; Fri, 9 Oct 2020 16:14:18 +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 S2389745AbgJIQOR (ORCPT ); Fri, 9 Oct 2020 12:14:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41562 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389701AbgJIQOH (ORCPT ); Fri, 9 Oct 2020 12:14:07 -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 3D44EC0613BB for ; Fri, 9 Oct 2020 09:14:06 -0700 (PDT) Received: by mail-yb1-xb49.google.com with SMTP id n13so9316590ybk.9 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=KT8nVSaJOb/2z+508Z4YF0bFs0hxW2TqYkqud7a9zV2svX5lbZISWhbscZ61wgTnda 2heb+m9WQ0mgIB5viiI+Btn+eqAPEAcKPfa0butspu7rjAFmNmyh17STkCrF0GfQehli U1OtDcysNF131Fqr4I1nstwR1CfqpaPMuLQ96EqB/OK6k99LOCnhKhACw8Nep6wBOmjA xCmn+rxQpoeSGCwc+EtbJ9QN1GzUPiNdKws8+3FQGsR467hMTWntA7nqz5BHMkMLd/2e lTgYeBPu8/umApENN1fPsSukrHMZu6Jn//MAzCodq/O29c78NYOFA8bs4bk8Tze9nFDy E0bg== X-Gm-Message-State: AOAM5327eFKUYACum5o6h2IWzFxItAeHUUf2gFh2V0zrqByku7fca3U0 X8OJo4pLazmbRsH4+454z0AdU0tARgNt4XziYcQ= 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-arch@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