From patchwork Tue Sep 29 21:46:16 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sami Tolvanen X-Patchwork-Id: 11807163 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 4001413B2 for ; Tue, 29 Sep 2020 21:49:04 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 81D3A20774 for ; Tue, 29 Sep 2020 21:49:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="VsL4ntl5" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 81D3A20774 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-20044-patchwork-kernel-hardening=patchwork.kernel.org@lists.openwall.com Received: (qmail 30554 invoked by uid 550); 29 Sep 2020 21:47:18 -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 30424 invoked from network); 29 Sep 2020 21:47:16 -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=3CV3/71SvI9Aae4EB6SuVg1gWevq6V3dKGQQ0SLCSxM=; b=VsL4ntl5+hY0sK9YbHIOCU/8xkMTUwfbSaQJDJE3/xjI5F6RvBhZ95rjnSx9qzKP19 c8dtjWQ9X1ycYC5cQdhz1pOUlwobIqAkhxQS/79ifUywIFe8vgvwUcWjLeboFlrrbcYK f+yGk+07cGJpo17CclConQX5GRnPs77eYx1X4Y/VF+Ljh28bTgeQSAfYO28SLdB3x+Y9 NGL1RCxovqI1uJnDovNqoqdjqzucm59FJTBc3enczCyNqTlCQDgreBEoQ6ZIkYl4frgU j3XEkn1c1qgjUZRuJJnggDEhbR6LNJUg+9sOgKjHf5cebOSVhsYP16Et9tjoyV5Q4Nqx WMXQ== 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=3CV3/71SvI9Aae4EB6SuVg1gWevq6V3dKGQQ0SLCSxM=; b=nGc566vtQz6fHGy9xzlNgOL93DroeJOnlcxDkTA1xuEPtqODrLBwfgtYIM1DHmbaPv tk7KEh48uU0Y7oz1cNlb9SuRLzbd1kgeAQYzkUu/BUxayA9q760syjL/HVwWNuP4UwfR nSfI/ldAeU3nh9CEnH7D0EdoZbrGmvsEFhgIzF0Zx8kgQRH8sBofuWLbLt02PXetJ2Tc POYrDc8g/3FthzsN2t3chw4ReUHwfEcXye+nTVeikIy6j6wvHALpJi8wj3tP3h0SGSE1 PiJ/DzcRh6jfcpUg5fui75HcZLaI+VSSYeTURxFJ07ISpYTI9/a0tqNBGuSnQmtVEqQ9 byVQ== X-Gm-Message-State: AOAM532xjEmM2XuM9kp23L/tTctrhnAgKyuxv6d+kZGw9fPUMOu4I7Rr GG/3xtMK58nfl98rEFFeSYPzdRUNCu2Ln/b4/sA= X-Google-Smtp-Source: ABdhPJw1rbXd3Wm2I/qDL+pij6pWpBrSY8S/UcyV+ktSoutrbImixV21BdVnAU852tswQtkkdWHRxrar/pvIuY7K2Z8= 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:ad4:58c7:: with SMTP id dh7mr6716071qvb.20.1601416024173; Tue, 29 Sep 2020 14:47:04 -0700 (PDT) Date: Tue, 29 Sep 2020 14:46:16 -0700 In-Reply-To: <20200929214631.3516445-1-samitolvanen@google.com> Message-Id: <20200929214631.3516445-15-samitolvanen@google.com> Mime-Version: 1.0 References: <20200929214631.3516445-1-samitolvanen@google.com> X-Mailer: git-send-email 2.28.0.709.gb0816b6eb0-goog Subject: [PATCH v4 14/29] 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 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 23cdb475c445..d6510ee99ffc 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