From patchwork Sun Jan 8 19:23:17 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Masahiro Yamada X-Patchwork-Id: 13092656 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 725FDC54EBE for ; Sun, 8 Jan 2023 19:23:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229503AbjAHTXa (ORCPT ); Sun, 8 Jan 2023 14:23:30 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45354 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229520AbjAHTX3 (ORCPT ); Sun, 8 Jan 2023 14:23:29 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9A39E32B; Sun, 8 Jan 2023 11:23:25 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 30BC460DBC; Sun, 8 Jan 2023 19:23:25 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0DF40C433D2; Sun, 8 Jan 2023 19:23:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1673205804; bh=S/YzwT6FzIsQ1JpAEmE6HfkP5R0JUwVaQei8ou4tv+M=; h=From:To:Cc:Subject:Date:From; b=Z3QiAklDzI1EDoAzW7fLQ7NRxP8k9spAbJ8CCydGYBEMUNoU8SwLRzfrhikdSiUDV NWN66hRvCe8RLoMDjzNpj16V3uCAm3dYsN7rcOD0gkoB8JTrDFc39HWsZVrmYMAfRl HOV6QGHd0CJ+1D8ITeVrFHxGZqJaedS3qzgePFDqpReJ1yYr77AdrqqxkAV5anClyB tTxj+XezTchSjwk1pQqL8EB8E1vknFSkOU1SwXsiDNZFTEXV4c5aljfNohER13pM8a Ql5p183McoySRfbCLzA3DQ7mCwa9L/wnV0AggCXzJDJlU1RC0Qr2/OfJTBsiH51a1y nzuAgjK5lPxpQ== From: Masahiro Yamada To: linux-kbuild@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Masahiro Yamada , Nathan Chancellor , Nicolas Schier , Nick Desaulniers Subject: [PATCH v3] kbuild: export top-level LDFLAGS_vmlinux only to scripts/Makefile.vmlinux Date: Mon, 9 Jan 2023 04:23:17 +0900 Message-Id: <20230108192317.2988108-1-masahiroy@kernel.org> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kbuild@vger.kernel.org Nathan Chancellor reports that $(NM) emits an error message when GNU Make 4.4 is used to build the ARM zImage. $ make-4.4 ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- O=build defconfig zImage [snip] LD vmlinux NM System.map SORTTAB vmlinux OBJCOPY arch/arm/boot/Image Kernel: arch/arm/boot/Image is ready arm-linux-gnueabi-nm: 'arch/arm/boot/compressed/../../../../vmlinux': No such file /bin/sh: 1: arithmetic expression: expecting primary: " " LDS arch/arm/boot/compressed/vmlinux.lds AS arch/arm/boot/compressed/head.o GZIP arch/arm/boot/compressed/piggy_data AS arch/arm/boot/compressed/piggy.o CC arch/arm/boot/compressed/misc.o This occurs since GNU Make commit 98da874c4303 ("[SV 10593] Export variables to $(shell ...) commands"), and the O= option is needed to reproduce it. The generated zImage is correct despite the error message. As the commit description of 98da874c4303 [1] says, exported variables are passed down to $(shell ) functions, which means exported recursive variables might be expanded earlier than before, in the parse stage. The following test code demonstrates the change for GNU Make 4.4. [Test Makefile] $(shell echo hello > foo) export foo = $(shell cat bar/../foo) $(shell mkdir bar) all: @echo $(foo) [GNU Make 4.3] $ rm -rf bar; make-4.3 hello [GNU Make 4.4] $ rm -rf bar; make-4.4 cat: bar/../foo: No such file or directory hello The 'foo' is a resursively expanded (i.e. lazily expanded) variable. GNU Make 4.3 expands 'foo' just before running the recipe '@echo $(foo)', at this point, the directory 'bar' exists. GNU Make 4.4 expands 'foo' to evaluate $(shell mkdir bar) because it is exported. At this point, the directory 'bar' does not exit yet. The cat command cannot resolve the bar/../foo path, hence the error message. Let's get back to the kernel Makefile. In arch/arm/boot/compressed/Makefile, KBSS_SZ is referenced by LDFLAGS_vmlinux, which is recursive and also exported by the top Makefile. GNU Make 4.3 expands KBSS_SZ just before running the recipes, so no error message. GNU Make 4.4 expands KBSS_SZ in the parse stage, where the directory arm/arm/boot/compressed does not exit yet. When compiled with O=, the output directory is created by $(shell mkdir -p $(obj-dirs)) in scripts/Makefile.build. There are two ways to fix this particular issue: - change "$(obj)/../../../../vmlinux" in KBSS_SZ to "vmlinux" - unexport LDFLAGS_vmlinux This commit takes the latter course because it is what I originally intended. Commit 3ec8a5b33dea ("kbuild: do not export LDFLAGS_vmlinux") unexported LDFLAGS_vmlinux. Commit 5d4aeffbf709 ("kbuild: rebuild .vmlinux.export.o when its prerequisite is updated") accidentally exported it again. We can clean up arch/arm/boot/compressed/Makefile later. [1]: https://git.savannah.gnu.org/cgit/make.git/commit/?id=98da874c43035a490cdca81331724f233a3d0c9a Link: https://lore.kernel.org/all/Y7i8+EjwdnhHtlrr@dev-arch.thelio-3990X/ Fixes: 5d4aeffbf709 ("kbuild: rebuild .vmlinux.export.o when its prerequisite is updated") Reported-by: Nathan Chancellor Signed-off-by: Masahiro Yamada Reviewed-by: Nicolas Schier Tested-by: Nathan Chancellor --- Changes in v3: - Minimize the scope of exporting. LDFLAGS_vmlinux is only exported to scripts/Makefile.vmlinux Changes in v2: - Postpone the change for arch/arm/boot/compressed/Makefile - Update the commit description Makefile | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/Makefile b/Makefile index dfba294ae790..9eed3e9b3657 100644 --- a/Makefile +++ b/Makefile @@ -549,7 +549,7 @@ LDFLAGS_MODULE = CFLAGS_KERNEL = RUSTFLAGS_KERNEL = AFLAGS_KERNEL = -export LDFLAGS_vmlinux = +LDFLAGS_vmlinux = # Use USERINCLUDE when you must reference the UAPI directories only. USERINCLUDE := \ @@ -1248,6 +1248,18 @@ vmlinux.o modules.builtin.modinfo modules.builtin: vmlinux_o @: PHONY += vmlinux +# LDFLAGS_vmlinux in the top Makefile defines linker flags for the top vmlinux, +# not for decompressors. LDFLAGS_vmlinux in arch/*/boot/compressed/Makefile is +# unrelated; the decompressors just happen to have the same base name, +# arch/*/boot/compressed/vmlinux. +# Export LDFLAGS_vmlinux only to scripts/Makefile.vmlinux. +# +# _LDFLAGS_vmlinux is an indirection to work around the bug: +# https://savannah.gnu.org/bugs/?61463 +# For Make > 4.4, the following simple code will work: +# vmlinux: private export LDFLAGS_vmlinux := $(LDFLAGS_vmlinux) +vmlinux: private _LDFLAGS_vmlinux := $(LDFLAGS_vmlinux) +vmlinux: export LDFLAGS_vmlinux = $(_LDFLAGS_vmlinux) vmlinux: vmlinux.o $(KBUILD_LDS) modpost $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.vmlinux