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-rw-r--r--samples/bpf/cgroup_helpers.c177
1 files changed, 177 insertions, 0 deletions
diff --git a/samples/bpf/cgroup_helpers.c b/samples/bpf/cgroup_helpers.c
new file mode 100644
index 000000000000..9d1be9426401
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+++ b/samples/bpf/cgroup_helpers.c
@@ -0,0 +1,177 @@
+#define _GNU_SOURCE
+#include <sched.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <linux/limits.h>
+#include <stdio.h>
+#include <linux/sched.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <ftw.h>
+
+
+#include "cgroup_helpers.h"
+
+/*
+ * To avoid relying on the system setup, when setup_cgroup_env is called
+ * we create a new mount namespace, and cgroup namespace. The cgroup2
+ * root is mounted at CGROUP_MOUNT_PATH
+ *
+ * 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.
+ *
+ * We assume /mnt exists.
+ */
+
+#define WALK_FD_LIMIT 16
+#define CGROUP_MOUNT_PATH "/mnt"
+#define CGROUP_WORK_DIR "/cgroup-test-work-dir"
+#define format_cgroup_path(buf, path) \
+ snprintf(buf, sizeof(buf), "%s%s%s", CGROUP_MOUNT_PATH, \
+ CGROUP_WORK_DIR, path)
+
+/**
+ * setup_cgroup_environment() - Setup the cgroup environment
+ *
+ * After calling this function, cleanup_cgroup_environment should be called
+ * once testing is complete.
+ *
+ * This function will print an error to stderr and return 1 if it is unable
+ * to setup the cgroup environment. If setup is successful, 0 is returned.
+ */
+int setup_cgroup_environment(void)
+{
+ char cgroup_workdir[PATH_MAX + 1];
+
+ format_cgroup_path(cgroup_workdir, "");
+
+ 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;
+ }
+
+ /* Cleanup existing failed runs, now that the environment is setup */
+ cleanup_cgroup_environment();
+
+ if (mkdir(cgroup_workdir, 0777) && errno != EEXIST) {
+ log_err("mkdir cgroup work dir");
+ return 1;
+ }
+
+ return 0;
+}
+
+static int nftwfunc(const char *filename, const struct stat *statptr,
+ int fileflags, struct FTW *pfwt)
+{
+ if ((fileflags & FTW_D) && rmdir(filename))
+ log_err("Removing cgroup: %s", filename);
+ return 0;
+}
+
+
+static int join_cgroup_from_top(char *cgroup_path)
+{
+ char cgroup_procs_path[PATH_MAX + 1];
+ pid_t pid = getpid();
+ int fd, rc = 0;
+
+ snprintf(cgroup_procs_path, sizeof(cgroup_procs_path),
+ "%s/cgroup.procs", cgroup_path);
+
+ fd = open(cgroup_procs_path, O_WRONLY);
+ if (fd < 0) {
+ log_err("Opening Cgroup Procs: %s", cgroup_procs_path);
+ return 1;
+ }
+
+ if (dprintf(fd, "%d\n", pid) < 0) {
+ log_err("Joining Cgroup");
+ rc = 1;
+ }
+
+ close(fd);
+ return rc;
+}
+
+/**
+ * join_cgroup() - Join a cgroup
+ * @path: The cgroup path, relative to the workdir, to join
+ *
+ * This function expects a cgroup to already be created, relative to the cgroup
+ * work dir, and it joins it. For example, passing "/my-cgroup" as the path
+ * would actually put the calling process into the cgroup
+ * "/cgroup-test-work-dir/my-cgroup"
+ *
+ * On success, it returns 0, otherwise on failure it returns 1.
+ */
+int join_cgroup(char *path)
+{
+ char cgroup_path[PATH_MAX + 1];
+
+ format_cgroup_path(cgroup_path, path);
+ return join_cgroup_from_top(cgroup_path);
+}
+
+/**
+ * cleanup_cgroup_environment() - Cleanup Cgroup Testing Environment
+ *
+ * This is an idempotent function to delete all temporary cgroups that
+ * have been created during the test, including the cgroup testing work
+ * directory.
+ *
+ * At call time, it moves the calling process to the root cgroup, and then
+ * runs the deletion process. It is idempotent, and should not fail, unless
+ * a process is lingering.
+ *
+ * On failure, it will print an error to stderr, and try to continue.
+ */
+void cleanup_cgroup_environment(void)
+{
+ char cgroup_workdir[PATH_MAX + 1];
+
+ format_cgroup_path(cgroup_workdir, "");
+ join_cgroup_from_top(CGROUP_MOUNT_PATH);
+ nftw(cgroup_workdir, nftwfunc, WALK_FD_LIMIT, FTW_DEPTH | FTW_MOUNT);
+}
+
+/**
+ * create_and_get_cgroup() - Create a cgroup, relative to workdir, and get the FD
+ * @path: The cgroup path, relative to the workdir, to join
+ *
+ * This function creates a cgroup under the top level workdir and returns the
+ * file descriptor. It is idempotent.
+ *
+ * On success, it returns the file descriptor. On failure it returns 0.
+ * If there is a failure, it prints the error to stderr.
+ */
+int create_and_get_cgroup(char *path)
+{
+ char cgroup_path[PATH_MAX + 1];
+ int fd;
+
+ format_cgroup_path(cgroup_path, path);
+ if (mkdir(cgroup_path, 0777) && errno != EEXIST) {
+ log_err("mkdiring cgroup");
+ return 0;
+ }
+
+ fd = open(cgroup_path, O_RDONLY);
+ if (fd < 0) {
+ log_err("Opening Cgroup");
+ return 0;
+ }
+
+ return fd;
+}