1 files changed, 315 insertions, 0 deletions
diff --git a/tools/testing/selftests/bpf/cgroup_helpers.c b/tools/testing/selftests/bpf/cgroup_helpers.c
new file mode 100644
index 000000000..033051717
--- /dev/null
+++ b/tools/testing/selftests/bpf/cgroup_helpers.c
@@ -0,0 +1,315 @@
+// SPDX-License-Identifier: GPL-2.0
+#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 <stdlib.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)
+
+/**
+ * enable_all_controllers() - Enable all available cgroup v2 controllers
+ *
+ * Enable all available cgroup v2 controllers in order to increase
+ * the code coverage.
+ *
+ * If successful, 0 is returned.
+ */
+static int enable_all_controllers(char *cgroup_path)
+{
+	char path[PATH_MAX + 1];
+	char buf[PATH_MAX];
+	char *c, *c2;
+	int fd, cfd;
+	ssize_t len;
+
+	snprintf(path, sizeof(path), "%s/cgroup.controllers", cgroup_path);
+	fd = open(path, O_RDONLY);
+	if (fd < 0) {
+		log_err("Opening cgroup.controllers: %s", path);
+		return 1;
+	}
+
+	len = read(fd, buf, sizeof(buf) - 1);
+	if (len < 0) {
+		close(fd);
+		log_err("Reading cgroup.controllers: %s", path);
+		return 1;
+	}
+	buf[len] = 0;
+	close(fd);
+
+	/* No controllers available? We're probably on cgroup v1. */
+	if (len == 0)
+		return 0;
+
+	snprintf(path, sizeof(path), "%s/cgroup.subtree_control", cgroup_path);
+	cfd = open(path, O_RDWR);
+	if (cfd < 0) {
+		log_err("Opening cgroup.subtree_control: %s", path);
+		return 1;
+	}
+
+	for (c = strtok_r(buf, " ", &c2); c; c = strtok_r(NULL, " ", &c2)) {
+		if (dprintf(cfd, "+%s\n", c) <= 0) {
+			log_err("Enabling controller %s: %s", c, path);
+			close(cfd);
+			return 1;
+		}
+	}
+	close(cfd);
+	return 0;
+}
+
+/**
+ * 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 - 24];
+
+	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) && errno != EBUSY) {
+		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;
+	}
+
+	if (enable_all_controllers(cgroup_workdir))
+		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(const 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 -1.
+ * If there is a failure, it prints the error to stderr.
+ */
+int create_and_get_cgroup(const 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 %s .. %s", path, cgroup_path);
+		return -1;
+	}
+
+	fd = open(cgroup_path, O_RDONLY);
+	if (fd < 0) {
+		log_err("Opening Cgroup");
+		return -1;
+	}
+
+	return fd;
+}
+
+/**
+ * get_cgroup_id() - Get cgroup id for a particular cgroup path
+ * @path: The cgroup path, relative to the workdir, to join
+ *
+ * On success, it returns the cgroup id. On failure it returns 0,
+ * which is an invalid cgroup id.
+ * If there is a failure, it prints the error to stderr.
+ */
+unsigned long long get_cgroup_id(const char *path)
+{
+	int dirfd, err, flags, mount_id, fhsize;
+	union {
+		unsigned long long cgid;
+		unsigned char raw_bytes[8];
+	} id;
+	char cgroup_workdir[PATH_MAX + 1];
+	struct file_handle *fhp, *fhp2;
+	unsigned long long ret = 0;
+
+	format_cgroup_path(cgroup_workdir, path);
+
+	dirfd = AT_FDCWD;
+	flags = 0;
+	fhsize = sizeof(*fhp);
+	fhp = calloc(1, fhsize);
+	if (!fhp) {
+		log_err("calloc");
+		return 0;
+	}
+	err = name_to_handle_at(dirfd, cgroup_workdir, fhp, &mount_id, flags);
+	if (err >= 0 || fhp->handle_bytes != 8) {
+		log_err("name_to_handle_at");
+		goto free_mem;
+	}
+
+	fhsize = sizeof(struct file_handle) + fhp->handle_bytes;
+	fhp2 = realloc(fhp, fhsize);
+	if (!fhp2) {
+		log_err("realloc");
+		goto free_mem;
+	}
+	err = name_to_handle_at(dirfd, cgroup_workdir, fhp2, &mount_id, flags);
+	fhp = fhp2;
+	if (err < 0) {
+		log_err("name_to_handle_at");
+		goto free_mem;
+	}
+
+	memcpy(id.raw_bytes, fhp->f_handle, 8);
+	ret = id.cgid;
+
+free_mem:
+	free(fhp);
+	return ret;
+}
+
+int cgroup_setup_and_join(const char *path) {
+	int cg_fd;
+
+	if (setup_cgroup_environment()) {
+		fprintf(stderr, "Failed to setup cgroup environment\n");
+		return -EINVAL;
+	}
+
+	cg_fd = create_and_get_cgroup(path);
+	if (cg_fd < 0) {
+		fprintf(stderr, "Failed to create test cgroup\n");
+		cleanup_cgroup_environment();
+		return cg_fd;
+	}
+
+	if (join_cgroup(path)) {
+		fprintf(stderr, "Failed to join cgroup\n");
+		cleanup_cgroup_environment();
+		return -EINVAL;
+	}
+	return cg_fd;
+}