1 files changed, 145 insertions, 0 deletions
diff --git a/samples/bpf/test_current_task_under_cgroup_user.c b/samples/bpf/test_current_task_under_cgroup_user.c
new file mode 100644
index 000000000000..30b0bce884f9
--- /dev/null
+++ b/samples/bpf/test_current_task_under_cgroup_user.c
@@ -0,0 +1,145 @@
+/* Copyright (c) 2016 Sargun Dhillon <sargun@sargun.me>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ */
+
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <linux/bpf.h>
+#include <unistd.h>
+#include "libbpf.h"
+#include "bpf_load.h"
+#include <string.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <linux/bpf.h>
+#include <sched.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <linux/limits.h>
+
+#define CGROUP_MOUNT_PATH	"/mnt"
+#define CGROUP_PATH		"/mnt/my-cgroup"
+
+#define clean_errno() (errno == 0 ? "None" : strerror(errno))
+#define log_err(MSG, ...) fprintf(stderr, "(%s:%d: errno: %s) " MSG "\n", \
+	__FILE__, __LINE__, clean_errno(), ##__VA_ARGS__)
+
+static int join_cgroup(char *path)
+{
+	int fd, rc = 0;
+	pid_t pid = getpid();
+	char cgroup_path[PATH_MAX + 1];
+
+	snprintf(cgroup_path, sizeof(cgroup_path), "%s/cgroup.procs", path);
+
+	fd = open(cgroup_path, O_WRONLY);
+	if (fd < 0) {
+		log_err("Opening Cgroup");
+		return 1;
+	}
+
+	if (dprintf(fd, "%d\n", pid) < 0) {
+		log_err("Joining Cgroup");
+		rc = 1;
+	}
+	close(fd);
+	return rc;
+}
+
+int main(int argc, char **argv)
+{
+	char filename[256];
+	int cg2, idx = 0;
+	pid_t remote_pid, local_pid = getpid();
+
+	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
+	if (load_bpf_file(filename)) {
+		printf("%s", bpf_log_buf);
+		return 1;
+	}
+
+	/*
+	 * This is to avoid interfering with existing cgroups. Unfortunately,
+	 * most people don't have cgroupv2 enabled at this point in time.
+	 * It's easier to create our own mount namespace and manage it
+	 * ourselves.
+	 */
+	if (unshare(CLONE_NEWNS)) {
+		log_err("unshare");
+		return 1;
+	}
+
+	if (mount("none", "/", NULL, MS_REC | MS_PRIVATE, NULL)) {
+		log_err("mount fakeroot");
+		return 1;
+	}
+
+	if (mount("none", CGROUP_MOUNT_PATH, "cgroup2", 0, NULL)) {
+		log_err("mount cgroup2");
+		return 1;
+	}
+
+	if (mkdir(CGROUP_PATH, 0777) && errno != EEXIST) {
+		log_err("mkdir cgroup");
+		return 1;
+	}
+
+	cg2 = open(CGROUP_PATH, O_RDONLY);
+	if (cg2 < 0) {
+		log_err("opening target cgroup");
+		goto cleanup_cgroup_err;
+	}
+
+	if (bpf_update_elem(map_fd[0], &idx, &cg2, BPF_ANY)) {
+		log_err("Adding target cgroup to map");
+		goto cleanup_cgroup_err;
+	}
+	if (join_cgroup("/mnt/my-cgroup")) {
+		log_err("Leaving target cgroup");
+		goto cleanup_cgroup_err;
+	}
+
+	/*
+	 * The installed helper program catched the sync call, and should
+	 * write it to the map.
+	 */
+
+	sync();
+	bpf_lookup_elem(map_fd[1], &idx, &remote_pid);
+
+	if (local_pid != remote_pid) {
+		fprintf(stderr,
+			"BPF Helper didn't write correct PID to map, but: %d\n",
+			remote_pid);
+		goto leave_cgroup_err;
+	}
+
+	/* Verify the negative scenario; leave the cgroup */
+	if (join_cgroup(CGROUP_MOUNT_PATH))
+		goto leave_cgroup_err;
+
+	remote_pid = 0;
+	bpf_update_elem(map_fd[1], &idx, &remote_pid, BPF_ANY);
+
+	sync();
+	bpf_lookup_elem(map_fd[1], &idx, &remote_pid);
+
+	if (local_pid == remote_pid) {
+		fprintf(stderr, "BPF cgroup negative test did not work\n");
+		goto cleanup_cgroup_err;
+	}
+
+	rmdir(CGROUP_PATH);
+	return 0;
+
+	/* Error condition, cleanup */
+leave_cgroup_err:
+	join_cgroup(CGROUP_MOUNT_PATH);
+cleanup_cgroup_err:
+	rmdir(CGROUP_PATH);
+	return 1;
+}