samples, bpf: Refactor test_current_task_under_cgroup - separate out helpers

This patch modifies test_current_task_under_cgroup_user. The test has
several helpers around creating a temporary environment for cgroup
testing, and moving the current task around cgroups. This set of
helpers can then be used in other tests.

Signed-off-by: Sargun Dhillon <sargun@sargun.me>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 24 insertions, 84 deletions

diff --git a/samples/bpf/test_current_task_under_cgroup_user.c b/samples/bpf/test_current_task_under_cgroup_user.c
index 30b0bce884f9..95aaaa846130 100644
--- a/samples/bpf/test_current_task_under_cgroup_user.c
+++ b/samples/bpf/test_current_task_under_cgroup_user.c
@@ -11,50 +11,16 @@
 #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>
+#include "cgroup_helpers.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;
-}
+#define CGROUP_PATH             "/my-cgroup"
 
 int main(int argc, char **argv)
 {
-        char filename[256];
-        int cg2, idx = 0;
         pid_t remote_pid, local_pid = getpid();
+        int cg2, idx = 0, rc = 0;
+        char filename[256];
 
         snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
         if (load_bpf_file(filename)) {
@@ -62,47 +28,22 @@ int main(int argc, char **argv)
                 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 (setup_cgroup_environment())
+                goto err;
 
-        if (mkdir(CGROUP_PATH, 0777) && errno != EEXIST) {
-                log_err("mkdir cgroup");
-                return 1;
-        }
+        cg2 = create_and_get_cgroup(CGROUP_PATH);
 
-        cg2 = open(CGROUP_PATH, O_RDONLY);
-        if (cg2 < 0) {
-                log_err("opening target cgroup");
-                goto cleanup_cgroup_err;
-        }
+        if (!cg2)
+                goto 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;
+                goto err;
         }
 
+        if (join_cgroup(CGROUP_PATH))
+                goto err;
+
         /*
          * The installed helper program catched the sync call, and should
          * write it to the map.
@@ -115,12 +56,12 @@ int main(int argc, char **argv)
                 fprintf(stderr,
                         "BPF Helper didn't write correct PID to map, but: %d\n",
                         remote_pid);
-                goto leave_cgroup_err;
+                goto err;
         }
 
         /* Verify the negative scenario; leave the cgroup */
-        if (join_cgroup(CGROUP_MOUNT_PATH))
-                goto leave_cgroup_err;
+        if (join_cgroup("/"))
+                goto err;
 
         remote_pid = 0;
         bpf_update_elem(map_fd[1], &idx, &remote_pid, BPF_ANY);
@@ -130,16 +71,15 @@ int main(int argc, char **argv)
 
         if (local_pid == remote_pid) {
                 fprintf(stderr, "BPF cgroup negative test did not work\n");
-                goto cleanup_cgroup_err;
+                goto err;
         }
 
-        rmdir(CGROUP_PATH);
-        return 0;
+        goto out;
+err:
+        rc = 1;
 
-        /* Error condition, cleanup */
-leave_cgroup_err:
-        join_cgroup(CGROUP_MOUNT_PATH);
-cleanup_cgroup_err:
-        rmdir(CGROUP_PATH);
-        return 1;
+out:
+        close(cg2);
+        cleanup_cgroup_environment();
+        return rc;
 }