samples: add binderfs sample program (9762dc14) · Commits · 戴 / test

samples/Kconfig

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		@@ -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

samples/Makefile

+1 −1

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		@@ -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/

samples/binderfs/Makefile

0 → 100644

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		obj-$(CONFIG_SAMPLE_ANDROID_BINDERFS) += binderfs_example.o

samples/binderfs/binderfs_example.c

0 → 100644

+83 −0

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		// SPDX-License-Identifier: GPL-2.0

		#define _GNU_SOURCE
		#include <errno.h>
		#include <fcntl.h>
		#include <sched.h>
		#include <stdio.h>
		#include <stdlib.h>
		#include <string.h>
		#include <sys/ioctl.h>
		#include <sys/mount.h>
		#include <sys/stat.h>
		#include <sys/types.h>
		#include <unistd.h>
		#include <linux/android/binder.h>
		#include <linux/android/binderfs.h>

		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);
		}

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