samples/bpf: Add test_current_task_under_cgroup test

[cascardo/linux.git] / samples / bpf / test_current_task_under_cgroup_user.c

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 (file)
index 0000000..30b0bce
--- /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;
+}