From a7a40dfa65cd2df35cb0f635983495150fe23f24 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Sun, 7 Jun 2020 12:20:53 +0900 Subject: [PATCH] samples: binderfs: really compile this sample and fix build issues Even after commit 2572af5653a0 ("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 38feedc1a3f2 ("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 having 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 search path. I added 'depends on HEADERS_INSTALL' in Kconfig, and '-I usr/include' compiler flag in Makefile. [2] compile the sample for target architecture Because headers_install works for the target architecture, only the native compiler was able to build sample code that requires '-I usr/include'. Commit d7bc305eb24a ("kbuild: add infrastructure to build userspace programs") added the new syntax 'userprogs' to compile user-space programs for the target architecture. Use it, and then 'ifndef CROSS_COMPILE' will go away. I added 'depends on CC_CAN_LINK' because $(CC) is not necessarily capable of linking user-space programs. [3] use subdir-y to descend into samples/binderfs Since this directory does not contain any kernel-space code, it has no point in generating built-in.a or modules.order. Replace obj-$(CONFIG_...) with subdir-$(CONFIG_...). [4] -Wunused-variable warning If I compile this, I see the following warning. samples/binderfs/binderfs_example.c: In function 'main': samples/binderfs/binderfs_example.c:21:9: warning: unused variable 'len' [-Wunused-variable] 21 | size_t len; | ^~~ I removed the unused 'len'. [5] CONFIG_ANDROID_BINDERFS is not required Since this is a user-space standalone program, it is independent of the kernel configuration. Remove 'depends on ANDROID_BINDERFS'. Fixes: 1dcf16731796 ("samples: add binderfs sample program") Fixes: 2572af5653a0 ("samples: fix binderfs sample") Signed-off-by: Masahiro Yamada Acked-by: Christian Brauner --- samples/Kconfig | 2 +- samples/Makefile | 2 +- samples/binderfs/Makefile | 9 ++++----- samples/binderfs/binderfs_example.c | 1 - 4 files changed, 6 insertions(+), 8 deletions(-) diff --git a/samples/Kconfig b/samples/Kconfig index 0cbb6146f3cf9..953abbdebf7b2 100644 --- a/samples/Kconfig +++ b/samples/Kconfig @@ -185,7 +185,7 @@ config SAMPLE_VFIO_MDEV_MBOCHS config SAMPLE_ANDROID_BINDERFS bool "Build Android binderfs example" - depends on ANDROID_BINDERFS + depends on CC_CAN_LINK && HEADERS_INSTALL help Builds a sample program to illustrate the use of the Android binderfs filesystem. diff --git a/samples/Makefile b/samples/Makefile index 29c66aadd954a..4029d207cebb3 100644 --- a/samples/Makefile +++ b/samples/Makefile @@ -2,7 +2,7 @@ # Makefile for Linux samples code subdir-$(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 a3ac5476338a4..989e4badaee2d 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 5bbd2ebc0aea3..0fd92cdda460b 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); -- 2.39.5