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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=INO1oAW4O18ZRkPSAuvWGcuaA7PwFB8WVP+h12U+F1bHVoiHHVP6wBGIwulRvUv3kq pB0SDXfpOKvMMl996eALbcwGYy5bw/EE68CK5z1btTYh2CMuD2AvYinkU1zzaUTsBwYp y6nDieb4Fd1WXY8uQHENUJK//2flB5+Jk6oUynO7Dkjk/tzRRHXAWvKeTzwMIabnjhsI O25n6x6bdjqXfHa6UDsZlmOEdLvGmkEqcY7ELli7voSdVQAH4YAQlIEXi8+CiaOj2a5m ZTMBrcOC9wyGxv8ooX0bAYx1A+Sq8HUhNYZz8ycIxw5LJ/e1E2bsB17R1vTt1WATXU7a gUBA== X-Gm-Message-State: AOAM533L42tm6qPRgU7sYNNAPblBrDOUPP0qp3m2VcOChpX+xRSjgIsN S+yx6LjvpENGZCNmdoujcGfCiBh9HZQ9YaqPQIg= X-Google-Smtp-Source: ABdhPJw1rbXd3Wm2I/qDL+pij6pWpBrSY8S/UcyV+ktSoutrbImixV21BdVnAU852tswQtkkdWHRxrar/pvIuY7K2Z8= 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 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200929_174708_169617_687E9192 X-CRM114-Status: GOOD ( 12.50 ) X-Spam-Score: -8.2 (--------) X-Spam-Report: SpamAssassin version 3.4.4 on merlin.infradead.org summary: Content analysis details: (-8.2 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at https://www.dnswl.org/, no trust [2607:f8b0:4864:20:0:0:0:849 listed in] [list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record -7.5 USER_IN_DEF_DKIM_WL From: address is in the default DKIM white-list 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from envelope-from domain -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature -0.5 DKIMWL_WL_MED DKIMwl.org - Medium trust sender X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, x86@kernel.org, Kees Cook , "Paul E. McKenney" , kernel-hardening@lists.openwall.com, Peter Zijlstra , Greg Kroah-Hartman , linux-kbuild@vger.kernel.org, Nick Desaulniers , linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com, Sami Tolvanen , linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.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 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