From patchwork Tue Oct 13 00:31:50 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sami Tolvanen X-Patchwork-Id: 11834797 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id D5DC4175A for ; Tue, 13 Oct 2020 02:45:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BCEAD20678 for ; Tue, 13 Oct 2020 02:45:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="nfKwI9L0" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727242AbgJMAdY (ORCPT ); Mon, 12 Oct 2020 20:33:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47824 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727479AbgJMAcj (ORCPT ); Mon, 12 Oct 2020 20:32:39 -0400 Received: from mail-qt1-x84a.google.com (mail-qt1-x84a.google.com [IPv6:2607:f8b0:4864:20::84a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5EE83C0613D9 for ; Mon, 12 Oct 2020 17:32:31 -0700 (PDT) Received: by mail-qt1-x84a.google.com with SMTP id b12so13756502qte.11 for ; Mon, 12 Oct 2020 17:32:31 -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=VMCZDfrBZTgAeIay1rQ29+uk2lw3Iqw8lHEoyZvJXcw=; b=nfKwI9L0AIFN/q2chPmhJejzrBkYs0AxSEEy5fMqd20mS1osQThhU+ktBGNYJaYON2 MjqIs9Rl7hlo6AIxtQ8N9k1pcoq5ps0nN8zY2Xo536Oyj1gVgj/lQEyGB8wz3lEphQRn 2a1yV5HhbU2nGBMNwGgkGuol3VvcnDW+IkWtbFHZhCYQRfBcbMJubOSbajBBqU+1O5Lc vfXB9fY0pxR64gHEC1sLB+1X7ygPM6rsC8GT4gpvySGeXGx9VtbnLfGxKbpXvIJwD6/H 97AQwdvtwYTTmK+V2mtwsV3UBIBJzwfFWuK8t1tvV6xVdxIgGCV2JLCT63S6ODvptoz5 tFPg== 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=VMCZDfrBZTgAeIay1rQ29+uk2lw3Iqw8lHEoyZvJXcw=; b=POLojAOawAwq8QCqUt8Gzru9O1AviMcRvF7pM+VYQ5SMUBlrsaJLEp+u9FatNWnQxF 3jvGUaUAuuR3R/kwfixICEeuPs3mwt3lGnd04xAO4d+Kf+o9keTT7k68GVA/6BhimXu1 qTnxByF/tUB7nVczl3Y+J0aqbyppEEAulgKHuqjk5gejtOKnndViNKlJon+Ln4IBJluP XNvGqJIX5D6fqoBAiMAYCLmvR70ws36jYqH+vovI9q4LauCwAKZqZs1+S9RyB0GQ3/Or h3f7ecX8ZHPGHfRJDkMUJ0sct3HuptHvR/ezqdALVGaK3It2564aEBGoTju1U8TTqcDm 1Bwg== X-Gm-Message-State: AOAM533RWNhcP+/Rx9XXC4pLOoNdYe6iKPlgDheWgL8p/QrkTgLsMpjP L0S9tsbPykoDWBcB5X9jmWEQxAHr2Wpib32G7aA= X-Google-Smtp-Source: ABdhPJxSmGaKr8jvnZZWeZs3NgnMtwPC1onr9g3CEDlPD9ytqEe1Dbwb5OtBLL/kqlcnIZWLZSXhLwgEYzEWhabcOlM= 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:ad4:4b2a:: with SMTP id s10mr1226538qvw.54.1602549150461; Mon, 12 Oct 2020 17:32:30 -0700 (PDT) Date: Mon, 12 Oct 2020 17:31:50 -0700 In-Reply-To: <20201013003203.4168817-1-samitolvanen@google.com> Message-Id: <20201013003203.4168817-13-samitolvanen@google.com> Mime-Version: 1.0 References: <20201013003203.4168817-1-samitolvanen@google.com> X-Mailer: git-send-email 2.28.0.1011.ga647a8990f-goog Subject: [PATCH v6 12/25] kbuild: lto: limit inlining From: Sami Tolvanen To: Masahiro Yamada , Steven Rostedt Cc: Will Deacon , 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 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 91cd6caefa6e..41b01248d400 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