From patchwork Thu Sep 3 20:30:37 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sami Tolvanen X-Patchwork-Id: 11754765 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 8657A13B1 for ; Thu, 3 Sep 2020 20:33:21 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id DE7E820722 for ; Thu, 3 Sep 2020 20:33:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="d3WTta76" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DE7E820722 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-19731-patchwork-kernel-hardening=patchwork.kernel.org@lists.openwall.com Received: (qmail 21810 invoked by uid 550); 3 Sep 2020 20:31:31 -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: Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 21724 invoked from network); 3 Sep 2020 20:31:30 -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=v4aEDtr6bLZLPmR/ra6D5NVXgPqHTR+q2+p+53rP8YU=; b=d3WTta769MJh+Bo0VzFx1dIubRn1F3/0OsgdvpRIABs/0F8aoQ0QxN6GC6ogiN8YAt 1n2fy7ycG6neE8i4JP6mcoL5+gOWppxCnH2U8kbhGmk3Ke0U/7qP7lute7a6H0uDoYhQ dWVIqp9Xjw2Q1WEklB8eqrGPTTy0VYDaAb7Vj5vkDxGtzwmgFWOj15UwJBAbJ05tl1sN Q4rZl0DzGVRAuAw5PJyrACjWBxr1NbGCE0oN5TR+pUi+Dq3TH5paoF63RYX5l7QEOrpB +a+BflxQgXchm/xsTBNIInkXUZW2NMgvFiHC7w8tScjlytwkaK3yal7TbaDvFzX+VZKt 2LRg== 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=v4aEDtr6bLZLPmR/ra6D5NVXgPqHTR+q2+p+53rP8YU=; b=ZDrmgiPyijVA+h2G/75YxbkiGqOAKV69CwpsmOLqpzJ0s/N3uXiAFKsWtZsrdwaaxd Ixcckl5aTLV0qPLH4ctUWpgG1OPbRzbUJjxJNp6gMMZRQskYwuh7HkvhcEwG5J9hzifo V879hW4Yur9ugaAKcTFEWUgNmRaEC/lWmCZe+I1btUeXVmx4CdOLu2KSk7gp6VsJe6Qo QBRiLtdOS4zkWidhKNVLG0GBB+cFtWOHgyzU91DfcC3cxGb8y0wPUPCnvRIi8PIrrFeL my9Gm9mLfpBodR4HrBysMqb72GB9u040E0ethzIXc2WVmju2w4mbvPipPPR3xVpwv0Yj nEuA== X-Gm-Message-State: AOAM532FCJSSh/4LaTnjRZQi69MRs6+HJF0IbrBBjzZ5AI0rMtAdpDLP IXmeWJSoirpy3wsyPvTm489PNnpaTxLV/W2P+R0= X-Google-Smtp-Source: ABdhPJxLcteMiXx6yxIAtF7C6LDsd43v+S+v/BljrbTvv0EuuMtNnvGzhvJa2qGTBh5Tw0uOlOWuvZqeImKd2fr7SwI= 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:a366:: with SMTP id d93mr5081717ybi.415.1599165079173; Thu, 03 Sep 2020 13:31:19 -0700 (PDT) Date: Thu, 3 Sep 2020 13:30:37 -0700 In-Reply-To: <20200903203053.3411268-1-samitolvanen@google.com> Message-Id: <20200903203053.3411268-13-samitolvanen@google.com> Mime-Version: 1.0 References: <20200624203200.78870-1-samitolvanen@google.com> <20200903203053.3411268-1-samitolvanen@google.com> X-Mailer: git-send-email 2.28.0.526.ge36021eeef-goog Subject: [PATCH v2 12/28] kbuild: lto: limit inlining From: Sami Tolvanen To: Masahiro Yamada , Will Deacon Cc: Peter Zijlstra , Steven Rostedt , 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 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 | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/Makefile b/Makefile index 2752be67b460..c69e07bd506a 100644 --- a/Makefile +++ b/Makefile @@ -917,6 +917,10 @@ else CC_FLAGS_LTO_CLANG := -flto endif CC_FLAGS_LTO_CLANG += -fvisibility=default + +# Limit inlining across translation units to reduce binary size +LD_FLAGS_LTO_CLANG := -mllvm -import-instr-limit=5 +KBUILD_LDFLAGS += $(LD_FLAGS_LTO_CLANG) endif ifdef CONFIG_LTO