From 9762dc1432e10d5571c1ae746c41469504360c2a Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Fri, 11 Jan 2019 14:41:00 +0100 Subject: [PATCH] samples: add binderfs sample program This adds a simple sample program mounting binderfs and adding, then removing a binder device. Hopefully, it will be helpful to users who want to know how binderfs is supposed to be used. Signed-off-by: Christian Brauner Signed-off-by: Jonathan Corbet --- samples/Kconfig | 7 +++ samples/Makefile | 2 +- samples/binderfs/Makefile | 1 + samples/binderfs/binderfs_example.c | 83 +++++++++++++++++++++++++++++ 4 files changed, 92 insertions(+), 1 deletion(-) create mode 100644 samples/binderfs/Makefile create mode 100644 samples/binderfs/binderfs_example.c diff --git a/samples/Kconfig b/samples/Kconfig index ad1ec7016d4c..d19754ccad08 100644 --- a/samples/Kconfig +++ b/samples/Kconfig @@ -147,6 +147,13 @@ config SAMPLE_VFIO_MDEV_MBOCHS Specifically it does *not* include any legacy vga stuff. Device looks a lot like "qemu -device secondary-vga". +config SAMPLE_ANDROID_BINDERFS + bool "Build Android binderfs example" + depends on CONFIG_ANDROID_BINDERFS + help + Builds a sample program to illustrate the use of the Android binderfs + filesystem. + config SAMPLE_STATX bool "Build example extended-stat using code" depends on BROKEN diff --git a/samples/Makefile b/samples/Makefile index bd601c038b86..b1142a958811 100644 --- a/samples/Makefile +++ b/samples/Makefile @@ -3,4 +3,4 @@ obj-$(CONFIG_SAMPLES) += kobject/ kprobes/ trace_events/ livepatch/ \ hw_breakpoint/ kfifo/ kdb/ hidraw/ rpmsg/ seccomp/ \ configfs/ connector/ v4l/ trace_printk/ \ - vfio-mdev/ statx/ qmi/ + vfio-mdev/ statx/ qmi/ binderfs/ diff --git a/samples/binderfs/Makefile b/samples/binderfs/Makefile new file mode 100644 index 000000000000..01ca9f2529a7 --- /dev/null +++ b/samples/binderfs/Makefile @@ -0,0 +1 @@ +obj-$(CONFIG_SAMPLE_ANDROID_BINDERFS) += binderfs_example.o diff --git a/samples/binderfs/binderfs_example.c b/samples/binderfs/binderfs_example.c new file mode 100644 index 000000000000..5bbd2ebc0aea --- /dev/null +++ b/samples/binderfs/binderfs_example.c @@ -0,0 +1,83 @@ +// SPDX-License-Identifier: GPL-2.0 + +#define _GNU_SOURCE +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +int main(int argc, char *argv[]) +{ + int fd, ret, saved_errno; + size_t len; + struct binderfs_device device = { 0 }; + + ret = unshare(CLONE_NEWNS); + if (ret < 0) { + fprintf(stderr, "%s - Failed to unshare mount namespace\n", + strerror(errno)); + exit(EXIT_FAILURE); + } + + ret = mount(NULL, "/", NULL, MS_REC | MS_PRIVATE, 0); + if (ret < 0) { + fprintf(stderr, "%s - Failed to mount / as private\n", + strerror(errno)); + exit(EXIT_FAILURE); + } + + ret = mkdir("/dev/binderfs", 0755); + if (ret < 0 && errno != EEXIST) { + fprintf(stderr, "%s - Failed to create binderfs mountpoint\n", + strerror(errno)); + exit(EXIT_FAILURE); + } + + ret = mount(NULL, "/dev/binderfs", "binder", 0, 0); + if (ret < 0) { + fprintf(stderr, "%s - Failed to mount binderfs\n", + strerror(errno)); + exit(EXIT_FAILURE); + } + + memcpy(device.name, "my-binder", strlen("my-binder")); + + fd = open("/dev/binderfs/binder-control", O_RDONLY | O_CLOEXEC); + if (fd < 0) { + fprintf(stderr, "%s - Failed to open binder-control device\n", + strerror(errno)); + exit(EXIT_FAILURE); + } + + ret = ioctl(fd, BINDER_CTL_ADD, &device); + saved_errno = errno; + close(fd); + errno = saved_errno; + if (ret < 0) { + fprintf(stderr, "%s - Failed to allocate new binder device\n", + strerror(errno)); + exit(EXIT_FAILURE); + } + + printf("Allocated new binder device with major %d, minor %d, and name %s\n", + device.major, device.minor, device.name); + + ret = unlink("/dev/binderfs/my-binder"); + if (ret < 0) { + fprintf(stderr, "%s - Failed to delete binder device\n", + strerror(errno)); + exit(EXIT_FAILURE); + } + + /* Cleanup happens when the mount namespace dies. */ + exit(EXIT_SUCCESS); +}