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 X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2F51EC433E0 for ; Tue, 9 Jun 2020 07:45:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0CDCD207F9 for ; Tue, 9 Jun 2020 07:45:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728079AbgFIHpX (ORCPT ); Tue, 9 Jun 2020 03:45:23 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:60814 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726404AbgFIHpV (ORCPT ); Tue, 9 Jun 2020 03:45:21 -0400 Received: from ip5f5af183.dynamic.kabel-deutschland.de ([95.90.241.131] helo=wittgenstein) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1jiYwa-00061m-MX; Tue, 09 Jun 2020 07:45:12 +0000 Date: Tue, 9 Jun 2020 09:45:12 +0200 From: Christian Brauner To: Masahiro Yamada Cc: linux-kbuild@vger.kernel.org, Arnd Bergmann , Christian Brauner , Jonathan Corbet , linux-kernel@vger.kernel.org Subject: Re: [PATCH] samples: binderfs: really compile this sample and fix build issues Message-ID: <20200609074512.4uh7gs5gg6tewmj5@wittgenstein> References: <20200607032053.145302-1-masahiroy@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200607032053.145302-1-masahiroy@kernel.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Jun 07, 2020 at 12:20:53PM +0900, Masahiro Yamada wrote: > Even after commit c624adc9cb6e ("samples: fix binderfs sample"), this > sample is never compiled. > > 'hostprogs' teaches Kbuild that this is a host program, but not enough > to order to compile it. You must add it to 'always-y' to really compile > it. > > Since this sample has never been compiled in upstream, various issues > are left unnoticed. > > [1] compilers without are still widely used > > is only available since commit c13295ad219d > ("binderfs: rename header to binderfs.h"), i.e., Linux 5.0 > > If your compiler is based on UAPI headers older than Linux 5.0, you > will see the following error: > > samples/binderfs/binderfs_example.c:16:10: fatal error: linux/android/binderfs.h: No such file or directory > #include > ^~~~~~~~~~~~~~~~~~~~~~~~~~ > compilation terminated. > > You cannot rely on compilers to have such a new header. > > The common approach is to install UAPI headers of this kernel into > usr/include, and then add it to the header include path. > > I added 'depends on HEADERS_INSTALL' in Kconfig, and '-I usr/include' > compiler flag in Makefile. > > [2] compile the sample for target architecture > > Since headers_install works for the target architecture, only the native > build was able to build sample code that requires '-I usr/include'. > > Commit 7f3a59db274c ("kbuild: add infrastructure to build userspace > programs") added the new syntax 'userprogs' to compile user-space > programs for the target architecture. > > Use it, and 'ifndef CROSS_COMPILE' will go away. > > I added 'depends on CC_CAN_LINK' because $(CC) is not necessarily capable > of linking user-space programs. > > [3] use subdir-y to descend into samples/binderfs/ > > Since this directory does not contain any kernel-space code, it has no > point to generate built-in.a or modules.order. > > Replace obj-$(CONFIG_...) with subdir-$(CONFIG_...). > > [4] -Wunused-variable warning > > If I compile this, I see the following warning. > > samples/binderfs/binderfs_example.c: In function 'main': > samples/binderfs/binderfs_example.c:21:9: warning: unused variable 'len' [-Wunused-variable] > 21 | size_t len; > | ^~~ > > I removed the unused 'len'. > > [5] CONFIG_ANDROID_BINDERFS is not required > > Since this is a user-space standalone program, it is independent of > the kernel configuration. > > Remove 'depends on ANDROID_BINDERFS'. > > Fixes: 9762dc1432e1 ("samples: add binderfs sample program") > Fixes: c624adc9cb6e ("samples: fix binderfs sample") > Signed-off-by: Masahiro Yamada Sorry, I missed this: Acked-by: Christian Brauner Thanks! Christian > --- > > samples/Kconfig | 2 +- > samples/Makefile | 2 +- > samples/binderfs/Makefile | 9 ++++----- > samples/binderfs/binderfs_example.c | 1 - > 4 files changed, 6 insertions(+), 8 deletions(-) > > diff --git a/samples/Kconfig b/samples/Kconfig > index 0cbb6146f3cf..953abbdebf7b 100644 > --- a/samples/Kconfig > +++ b/samples/Kconfig > @@ -185,7 +185,7 @@ config SAMPLE_VFIO_MDEV_MBOCHS > > config SAMPLE_ANDROID_BINDERFS > bool "Build Android binderfs example" > - depends on ANDROID_BINDERFS > + depends on CC_CAN_LINK && HEADERS_INSTALL > help > Builds a sample program to illustrate the use of the Android binderfs > filesystem. > diff --git a/samples/Makefile b/samples/Makefile > index 29c66aadd954..4029d207cebb 100644 > --- a/samples/Makefile > +++ b/samples/Makefile > @@ -2,7 +2,7 @@ > # Makefile for Linux samples code > > subdir-$(CONFIG_SAMPLE_AUXDISPLAY) += auxdisplay > -obj-$(CONFIG_SAMPLE_ANDROID_BINDERFS) += binderfs/ > +subdir-$(CONFIG_SAMPLE_ANDROID_BINDERFS) += binderfs > obj-$(CONFIG_SAMPLE_CONFIGFS) += configfs/ > obj-$(CONFIG_SAMPLE_CONNECTOR) += connector/ > subdir-$(CONFIG_SAMPLE_HIDRAW) += hidraw > diff --git a/samples/binderfs/Makefile b/samples/binderfs/Makefile > index a3ac5476338a..989e4badaee2 100644 > --- a/samples/binderfs/Makefile > +++ b/samples/binderfs/Makefile > @@ -1,6 +1,5 @@ > # SPDX-License-Identifier: GPL-2.0-only > -ifndef CROSS_COMPILE > -ifdef CONFIG_SAMPLE_ANDROID_BINDERFS > -hostprogs := binderfs_example > -endif > -endif > +userprogs := binderfs_example > +always-y := $(userprogs) > + > +userccflags += -I usr/include > diff --git a/samples/binderfs/binderfs_example.c b/samples/binderfs/binderfs_example.c > index 5bbd2ebc0aea..0fd92cdda460 100644 > --- a/samples/binderfs/binderfs_example.c > +++ b/samples/binderfs/binderfs_example.c > @@ -18,7 +18,6 @@ > int main(int argc, char *argv[]) > { > int fd, ret, saved_errno; > - size_t len; > struct binderfs_device device = { 0 }; > > ret = unshare(CLONE_NEWNS); > -- > 2.25.1 >