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: 11943967 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=ham 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 64447C64E7A for ; Tue, 1 Dec 2020 21:38:08 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 70BFC2086A for ; Tue, 1 Dec 2020 21:38:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="WQCyqpyw" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 70BFC2086A Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-20492-kernel-hardening=archiver.kernel.org@lists.openwall.com Received: (qmail 15513 invoked by uid 550); 1 Dec 2020 21:37:32 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Received: (qmail 15455 invoked from network); 1 Dec 2020 21:37:31 -0000 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=k0qxFsxDH6rE8uAqlfS0tzc3LpxtM/MlDGgX0UgnHlO4NH2DB3wNo5v66ZjdzK0LVB KgJ1wAbiDu4aDpdIEt2sfrf45P06E54TupmIBNSBXSZ1jWCTLSDEFRC0obvOBs+rPobV W++TxZ9l8QamyV/0rQgsB6Hr88wtEX/E8IS5L8fvNmeKQoMmGwfXSyoMsxXahoiYXSn2 vxq1VhxGPx87Kt27TrUeD5m/UNFQpi/Hl5NNaugsoChq5OyhzONzUa1suPRsmtxbwGO6 RbNnfd/zfMwXA+P1BxkXFJjN9xV++I4aFn63fBn819HKnf54mVwoP/QTMmBthxPgrqLT pLNw== X-Gm-Message-State: AOAM5326GaRIA0lNLYbmbFbMIN3NtETVmxsnGkJ+VvaQwJvv7JPBJyQu 3sU3Tcu7EwKYivEBZCaOJCr8xjlKsMm+pwGawvs= 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 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