From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BAFC7EB64D8 for ; Wed, 14 Jun 2023 18:43:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233251AbjFNSm6 (ORCPT ); Wed, 14 Jun 2023 14:42:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58034 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235103AbjFNSmx (ORCPT ); Wed, 14 Jun 2023 14:42:53 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A357D1BEC; Wed, 14 Jun 2023 11:42:51 -0700 (PDT) Date: Wed, 14 Jun 2023 18:42:49 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1686768170; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=S12bjusbzZwPYFboksUHkPk1TprVMLPd+OX6SytDRkA=; b=2tGI5YkpLcHel75sR9lbWFlr8DCyWREGx8jGZRAxeIbrIjDJDkamqzmRWm61dAgsftlYkF KA4batutX12rfWiZUE8H4zOnbKhOA5MMczTEaudFSlHatoW8nlklf4djLMV3N7dfQhHkFP Ogel6rOmN42A+/6nxFORM7FgmtGo5WW9IJV6X1JTV5Knen3fxfn25jWXlvYviNmMu2P2n4 v8mfwYDt0ES8n+9nKesmAApddIIYr9FP60CzrhWJhTVLRENCW5ZyRVZgFMI4kWjBhDHZP7 qQErYU020Lk7rPJ8AN4fVjopJODNBmbcsUNAwaAzOmcRmsTWAAJiJyt2mkSyVQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1686768170; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=S12bjusbzZwPYFboksUHkPk1TprVMLPd+OX6SytDRkA=; b=ETrv5BO+CCr0lNxEPwzSSUOG2oKsPp3jFZxtioDSPQS199Xc/Wss3WgsEsgrMoEulVLhx6 4V37zxeZ2h3Rl6Cw== From: "tip-bot2 for Petr Pavlu" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: x86/build] x86/build: Avoid relocation information in final vmlinux Cc: Petr Pavlu , "Borislav Petkov (AMD)" , Nick Desaulniers , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20220927084632.14531-1-petr.pavlu@suse.com> References: <20220927084632.14531-1-petr.pavlu@suse.com> MIME-Version: 1.0 Message-ID: <168676816939.404.11506682535615735950.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the x86/build branch of tip: Commit-ID: 9d9173e9ceb63660ccad80f41373fd7eb48ff4ac Gitweb: https://git.kernel.org/tip/9d9173e9ceb63660ccad80f41373fd7eb48ff4ac Author: Petr Pavlu AuthorDate: Mon, 27 Mar 2023 11:54:06 +02:00 Committer: Borislav Petkov (AMD) CommitterDate: Wed, 14 Jun 2023 19:54:40 +02:00 x86/build: Avoid relocation information in final vmlinux The Linux build process on x86 roughly consists of compiling all input files, statically linking them into a vmlinux ELF file, and then taking and turning this file into an actual bzImage bootable file. vmlinux has in this process two main purposes: 1) It is an intermediate build target on the way to produce the final bootable image. 2) It is a file that is expected to be used by debuggers and standard ELF tooling to work with the built kernel. For the second purpose, a vmlinux file is typically collected by various package build recipes, such as distribution spec files, including the kernel's own tar-pkg target. When building a kernel supporting KASLR with CONFIG_X86_NEED_RELOCS, vmlinux contains also relocation information produced by using the --emit-relocs linker option. This is utilized by subsequent build steps to create vmlinux.relocs and produce a relocatable image. However, the information is not needed by debuggers and other standard ELF tooling. The issue is then that the collected vmlinux file and hence distribution packages end up unnecessarily large because of this extra data. The following is a size comparison of vmlinux v6.0 with and without the relocation information: | Configuration | With relocs | Stripped relocs | | x86_64_defconfig | 70 MB | 43 MB | | +CONFIG_DEBUG_INFO | 818 MB | 367 MB | Optimize a resulting vmlinux by adding a postlink step that splits the relocation information into vmlinux.relocs and then strips it from the vmlinux binary. Signed-off-by: Petr Pavlu Signed-off-by: Borislav Petkov (AMD) Tested-by: Nick Desaulniers Link: https://lore.kernel.org/r/20220927084632.14531-1-petr.pavlu@suse.com --- arch/x86/Makefile.postlink | 47 ++++++++++++++++++++++++++++++- arch/x86/boot/compressed/Makefile | 8 +---- 2 files changed, 50 insertions(+), 5 deletions(-) create mode 100644 arch/x86/Makefile.postlink diff --git a/arch/x86/Makefile.postlink b/arch/x86/Makefile.postlink new file mode 100644 index 0000000..936093d --- /dev/null +++ b/arch/x86/Makefile.postlink @@ -0,0 +1,47 @@ +# SPDX-License-Identifier: GPL-2.0 +# =========================================================================== +# Post-link x86 pass +# =========================================================================== +# +# 1. Separate relocations from vmlinux into vmlinux.relocs. +# 2. Strip relocations from vmlinux. + +PHONY := __archpost +__archpost: + +-include include/config/auto.conf +include $(srctree)/scripts/Kbuild.include + +CMD_RELOCS = arch/x86/tools/relocs +OUT_RELOCS = arch/x86/boot/compressed +quiet_cmd_relocs = RELOCS $(OUT_RELOCS)/$@.relocs + cmd_relocs = \ + mkdir -p $(OUT_RELOCS); \ + $(CMD_RELOCS) $@ > $(OUT_RELOCS)/$@.relocs; \ + $(CMD_RELOCS) --abs-relocs $@ + +quiet_cmd_strip_relocs = RSTRIP $@ + cmd_strip_relocs = \ + $(OBJCOPY) --remove-section='.rel.*' --remove-section='.rel__*' \ + --remove-section='.rela.*' --remove-section='.rela__*' $@ + +# `@true` prevents complaint when there is nothing to be done + +vmlinux: FORCE + @true +ifeq ($(CONFIG_X86_NEED_RELOCS),y) + $(call cmd,relocs) + $(call cmd,strip_relocs) +endif + +%.ko: FORCE + @true + +clean: + @rm -f $(OUT_RELOCS)/vmlinux.relocs + +PHONY += FORCE clean + +FORCE: + +.PHONY: $(PHONY) diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile index 6b6cfe6..0f78dbb 100644 --- a/arch/x86/boot/compressed/Makefile +++ b/arch/x86/boot/compressed/Makefile @@ -121,11 +121,9 @@ $(obj)/vmlinux.bin: vmlinux FORCE targets += $(patsubst $(obj)/%,%,$(vmlinux-objs-y)) vmlinux.bin.all vmlinux.relocs -CMD_RELOCS = arch/x86/tools/relocs -quiet_cmd_relocs = RELOCS $@ - cmd_relocs = $(CMD_RELOCS) $< > $@;$(CMD_RELOCS) --abs-relocs $< -$(obj)/vmlinux.relocs: vmlinux FORCE - $(call if_changed,relocs) +# vmlinux.relocs is created by the vmlinux postlink step. +$(obj)/vmlinux.relocs: vmlinux + @true vmlinux.bin.all-y := $(obj)/vmlinux.bin vmlinux.bin.all-$(CONFIG_X86_NEED_RELOCS) += $(obj)/vmlinux.relocs