From patchwork Sun Jun 9 16:41:46 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 166230 Delivered-To: patch@linaro.org Received: by 2002:a92:4782:0:0:0:0:0 with SMTP id e2csp52555ilk; Sun, 9 Jun 2019 09:47:19 -0700 (PDT) X-Google-Smtp-Source: APXvYqyIDwMXssFMbqueIFa+GhDRs1B9j8nQ9C4Pz5XsPCU990Q6/oFST/w3HFnn7/LcwB1GXCNl X-Received: by 2002:a63:fd50:: with SMTP id m16mr12064313pgj.192.1560098838844; Sun, 09 Jun 2019 09:47:18 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1560098838; cv=none; d=google.com; s=arc-20160816; b=MHM6X51lhww4ICB1j03dKabQJiuzuWrUB3jhenD/xDILtf9a+2rsyy6kXGd9fa1gyM 0xLmh1hXvUObVUN7CkoIbg0pAyH/IFBp1oCbGB3iPlkj6pG/D/LJX1+pJU7+z/qlUuHA Fy/NB1Ls1mED2eHxPgO7lBXhBnvdEviYnYP6Lr+lz/e4E2x54P6Q710WTRr2tBOG00qL M1sTMDQkC9KhWpUqXJYUO+FgjuWyZ3+9/x8cqJudYwCB6waKNc+u3/jnF5BSDi8KP8F7 L6Bpu1SnJVT9saivO/ojgOp95IJh73oU5e4hVueeN4CpaQj4VX4XEVVWXjXiWPLBeefa n5Ow== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:content-transfer-encoding:mime-version :user-agent:references:in-reply-to:message-id:date:subject:cc:to :from:dkim-signature; bh=WbH+BOTq4tf+hSE8P3Gkgvg2oACBXUBp3F52kYhSJfg=; b=tVFdXg2kYhfCc+c5ACRu+aHsZ7QnQtgaj2xhDJphNX8GY8beGKQY705J+ICe8f0idQ J5hrrmaXcqOPRHmq/REyT8w87eEd8rOsmmwZukGGo8Jj+k50+aaJRoEk0FW20joNTfa0 79D8C0/4I4dmcoubhSujZl776fAJdpeNfHZOnsW0Ilqmf5XdXAJ7VXFfwtpyL3m6vAzO mcscuNIE2qaR/2+UrBIioOTscPubbxmAW25fYdD+iQrpI0hZ2GtUB1t17WXJJTvXf9YI v2G1+RJ3pdomc5vnx1I5S+4bf3jaua2UcZYqIq49rCrByVWUe5Wa0yQ/URqjIuasOI33 I7Uw== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=cgaJ5nNe; spf=pass (google.com: best guess record for domain of stable-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=stable-owner@vger.kernel.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id j14si7689156pfh.232.2019.06.09.09.47.18; Sun, 09 Jun 2019 09:47:18 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of stable-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=cgaJ5nNe; spf=pass (google.com: best guess record for domain of stable-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=stable-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729868AbfFIQrR (ORCPT + 14 others); Sun, 9 Jun 2019 12:47:17 -0400 Received: from mail.kernel.org ([198.145.29.99]:45844 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730798AbfFIQrQ (ORCPT ); Sun, 9 Jun 2019 12:47:16 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id EABA12081C; Sun, 9 Jun 2019 16:47:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1560098835; bh=1UTgMr9SJoHnfT0WfOenI8NDzCMDHeZtBSXR4xaotXc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=cgaJ5nNeQ6W5iaLKpk1sNxQ5YJn2jn7BeadR/m09lgsqLoGXQ7gmsFfTwjhe5SYtS 8LDEvr6QWLNzm48lHswaFN7eCEQVNx/yq1ti8Z8itXQS6U+epyujdS3S0nnPVJ+Lh2 O0NaEBLyJBKtB+8cxHNSpnYHpdsBOV1ty8qS/b5M= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Alexey Brodkin , Masahiro Yamada Subject: [PATCH 5.1 35/70] kbuild: use more portable command -v for cc-cross-prefix Date: Sun, 9 Jun 2019 18:41:46 +0200 Message-Id: <20190609164130.078925185@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190609164127.541128197@linuxfoundation.org> References: <20190609164127.541128197@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Masahiro Yamada commit 913ab9780fc021298949cc5514d6255a008e69f9 upstream. To print the pathname that will be used by shell in the current environment, 'command -v' is a standardized way. [1] 'which' is also often used in scripts, but it is less portable. When I worked on commit bd55f96fa9fc ("kbuild: refactor cc-cross-prefix implementation"), I was eager to use 'command -v' but it did not work. (The reason is explained below.) I kept 'which' as before but got rid of '> /dev/null 2>&1' as I thought it was no longer needed. Sorry, I was wrong. It works well on my Ubuntu machine, but Alexey Brodkin reports noisy warnings on CentOS7 when 'which' fails to find the given command in the PATH environment. $ which foo which: no foo in (/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin) Given that behavior of 'which' depends on system (and it may not be installed by default), I want to try 'command -v' once again. The specification [1] clearly describes the behavior of 'command -v' when the given command is not found: Otherwise, no output shall be written and the exit status shall reflect that the name was not found. However, we need a little magic to use 'command -v' from Make. $(shell ...) passes the argument to a subshell for execution, and returns the standard output of the command. Here is a trick. GNU Make may optimize this by executing the command directly instead of forking a subshell, if no shell special characters are found in the command and omitting the subshell will not change the behavior. In this case, no shell special character is used. So, Make will try to run it directly. However, 'command' is a shell-builtin command, then Make would fail to find it in the PATH environment: $ make ARCH=m68k defconfig make: command: Command not found make: command: Command not found make: command: Command not found In fact, Make has a table of shell-builtin commands because it must ask the shell to execute them. Until recently, 'command' was missing in the table. This issue was fixed by the following commit: | commit 1af314465e5dfe3e8baa839a32a72e83c04f26ef | Author: Paul Smith | Date: Sun Nov 12 18:10:28 2017 -0500 | | * job.c: Add "command" as a known shell built-in. | | This is not a POSIX shell built-in but it's common in UNIX shells. | Reported by Nick Bowler . Because the latest release is GNU Make 4.2.1 in 2016, this commit is not included in any released versions. (But some distributions may have back-ported it.) We need to trick Make to spawn a subshell. There are various ways to do so: 1) Use a shell special character '~' as dummy $(shell : ~; command -v $(c)gcc) 2) Use a variable reference that always expands to the empty string (suggested by David Laight) $(shell command$${x:+} -v $(c)gcc) 3) Use redirect $(shell command -v $(c)gcc 2>/dev/null) I chose 3) to not confuse people. The stderr would not be polluted anyway, but it will provide extra safety, and is easy to understand. Tested on Make 3.81, 3.82, 4.0, 4.1, 4.2, 4.2.1 [1] http://pubs.opengroup.org/onlinepubs/9699919799/utilities/command.html Fixes: bd55f96fa9fc ("kbuild: refactor cc-cross-prefix implementation") Cc: linux-stable # 5.1 Reported-by: Alexey Brodkin Signed-off-by: Masahiro Yamada Tested-by: Alexey Brodkin Signed-off-by: Greg Kroah-Hartman --- scripts/Kbuild.include | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) --- a/scripts/Kbuild.include +++ b/scripts/Kbuild.include @@ -73,8 +73,13 @@ endef # Usage: CROSS_COMPILE := $(call cc-cross-prefix, m68k-linux-gnu- m68k-linux-) # Return first where a gcc is found in PATH. # If no gcc found in PATH with listed prefixes return nothing +# +# Note: '2>/dev/null' is here to force Make to invoke a shell. Otherwise, it +# would try to directly execute the shell builtin 'command'. This workaround +# should be kept for a long time since this issue was fixed only after the +# GNU Make 4.2.1 release. cc-cross-prefix = $(firstword $(foreach c, $(filter-out -%, $(1)), \ - $(if $(shell which $(c)gcc), $(c)))) + $(if $(shell command -v $(c)gcc 2>/dev/null), $(c)))) # output directory for tests below TMPOUT := $(if $(KBUILD_EXTMOD),$(firstword $(KBUILD_EXTMOD))/)