1// SPDX-License-Identifier: GPL-2.0
  2#define _GNU_SOURCE
  3#include <sched.h>
  4#include <sys/mount.h>
  5#include <sys/stat.h>
  6#include <sys/types.h>
  7#include <linux/limits.h>
  8#include <stdio.h>
  9#include <stdlib.h>
 10#include <linux/sched.h>
 11#include <fcntl.h>
 12#include <unistd.h>
 13#include <ftw.h>
 14
 15
 16#include "cgroup_helpers.h"
 17
 18/*
 19 * To avoid relying on the system setup, when setup_cgroup_env is called
 20 * we create a new mount namespace, and cgroup namespace. The cgroup2
 21 * root is mounted at CGROUP_MOUNT_PATH
 22 *
 23 * Unfortunately, most people don't have cgroupv2 enabled at this point in time.
 24 * It's easier to create our own mount namespace and manage it ourselves.
 25 *
 26 * We assume /mnt exists.
 27 */
 28
 29#define WALK_FD_LIMIT			16
 30#define CGROUP_MOUNT_PATH		"/mnt"
 31#define CGROUP_WORK_DIR			"/cgroup-test-work-dir"
 32#define format_cgroup_path(buf, path) \
 33	snprintf(buf, sizeof(buf), "%s%s%s", CGROUP_MOUNT_PATH, \
 34		 CGROUP_WORK_DIR, path)
 35
 36/**
 37 * enable_all_controllers() - Enable all available cgroup v2 controllers
 38 *
 39 * Enable all available cgroup v2 controllers in order to increase
 40 * the code coverage.
 41 *
 42 * If successful, 0 is returned.
 43 */
 44static int enable_all_controllers(char *cgroup_path)
 45{
 46	char path[PATH_MAX + 1];
 47	char buf[PATH_MAX];
 48	char *c, *c2;
 49	int fd, cfd;
 50	ssize_t len;
 51
 52	snprintf(path, sizeof(path), "%s/cgroup.controllers", cgroup_path);
 53	fd = open(path, O_RDONLY);
 54	if (fd < 0) {
 55		log_err("Opening cgroup.controllers: %s", path);
 56		return 1;
 57	}
 58
 59	len = read(fd, buf, sizeof(buf) - 1);
 60	if (len < 0) {
 61		close(fd);
 62		log_err("Reading cgroup.controllers: %s", path);
 63		return 1;
 64	}
 65	buf[len] = 0;
 66	close(fd);
 67
 68	/* No controllers available? We're probably on cgroup v1. */
 69	if (len == 0)
 70		return 0;
 71
 72	snprintf(path, sizeof(path), "%s/cgroup.subtree_control", cgroup_path);
 73	cfd = open(path, O_RDWR);
 74	if (cfd < 0) {
 75		log_err("Opening cgroup.subtree_control: %s", path);
 76		return 1;
 77	}
 78
 79	for (c = strtok_r(buf, " ", &c2); c; c = strtok_r(NULL, " ", &c2)) {
 80		if (dprintf(cfd, "+%s\n", c) <= 0) {
 81			log_err("Enabling controller %s: %s", c, path);
 82			close(cfd);
 83			return 1;
 84		}
 85	}
 86	close(cfd);
 87	return 0;
 88}
 89
 90/**
 91 * setup_cgroup_environment() - Setup the cgroup environment
 92 *
 93 * After calling this function, cleanup_cgroup_environment should be called
 94 * once testing is complete.
 95 *
 96 * This function will print an error to stderr and return 1 if it is unable
 97 * to setup the cgroup environment. If setup is successful, 0 is returned.
 98 */
 99int setup_cgroup_environment(void)
100{
101	char cgroup_workdir[PATH_MAX - 24];
102
103	format_cgroup_path(cgroup_workdir, "");
104
105	if (unshare(CLONE_NEWNS)) {
106		log_err("unshare");
107		return 1;
108	}
109
110	if (mount("none", "/", NULL, MS_REC | MS_PRIVATE, NULL)) {
111		log_err("mount fakeroot");
112		return 1;
113	}
114
115	if (mount("none", CGROUP_MOUNT_PATH, "cgroup2", 0, NULL) && errno != EBUSY) {
116		log_err("mount cgroup2");
117		return 1;
118	}
119
120	/* Cleanup existing failed runs, now that the environment is setup */
121	cleanup_cgroup_environment();
122
123	if (mkdir(cgroup_workdir, 0777) && errno != EEXIST) {
124		log_err("mkdir cgroup work dir");
125		return 1;
126	}
127
128	if (enable_all_controllers(cgroup_workdir))
129		return 1;
130
131	return 0;
132}
133
134static int nftwfunc(const char *filename, const struct stat *statptr,
135		    int fileflags, struct FTW *pfwt)
136{
137	if ((fileflags & FTW_D) && rmdir(filename))
138		log_err("Removing cgroup: %s", filename);
139	return 0;
140}
141
142
143static int join_cgroup_from_top(char *cgroup_path)
144{
145	char cgroup_procs_path[PATH_MAX + 1];
146	pid_t pid = getpid();
147	int fd, rc = 0;
148
149	snprintf(cgroup_procs_path, sizeof(cgroup_procs_path),
150		 "%s/cgroup.procs", cgroup_path);
151
152	fd = open(cgroup_procs_path, O_WRONLY);
153	if (fd < 0) {
154		log_err("Opening Cgroup Procs: %s", cgroup_procs_path);
155		return 1;
156	}
157
158	if (dprintf(fd, "%d\n", pid) < 0) {
159		log_err("Joining Cgroup");
160		rc = 1;
161	}
162
163	close(fd);
164	return rc;
165}
166
167/**
168 * join_cgroup() - Join a cgroup
169 * @path: The cgroup path, relative to the workdir, to join
170 *
171 * This function expects a cgroup to already be created, relative to the cgroup
172 * work dir, and it joins it. For example, passing "/my-cgroup" as the path
173 * would actually put the calling process into the cgroup
174 * "/cgroup-test-work-dir/my-cgroup"
175 *
176 * On success, it returns 0, otherwise on failure it returns 1.
177 */
178int join_cgroup(const char *path)
179{
180	char cgroup_path[PATH_MAX + 1];
181
182	format_cgroup_path(cgroup_path, path);
183	return join_cgroup_from_top(cgroup_path);
184}
185
186/**
187 * cleanup_cgroup_environment() - Cleanup Cgroup Testing Environment
188 *
189 * This is an idempotent function to delete all temporary cgroups that
190 * have been created during the test, including the cgroup testing work
191 * directory.
192 *
193 * At call time, it moves the calling process to the root cgroup, and then
194 * runs the deletion process. It is idempotent, and should not fail, unless
195 * a process is lingering.
196 *
197 * On failure, it will print an error to stderr, and try to continue.
198 */
199void cleanup_cgroup_environment(void)
200{
201	char cgroup_workdir[PATH_MAX + 1];
202
203	format_cgroup_path(cgroup_workdir, "");
204	join_cgroup_from_top(CGROUP_MOUNT_PATH);
205	nftw(cgroup_workdir, nftwfunc, WALK_FD_LIMIT, FTW_DEPTH | FTW_MOUNT);
206}
207
208/**
209 * create_and_get_cgroup() - Create a cgroup, relative to workdir, and get the FD
210 * @path: The cgroup path, relative to the workdir, to join
211 *
212 * This function creates a cgroup under the top level workdir and returns the
213 * file descriptor. It is idempotent.
214 *
215 * On success, it returns the file descriptor. On failure it returns -1.
216 * If there is a failure, it prints the error to stderr.
217 */
218int create_and_get_cgroup(const char *path)
219{
220	char cgroup_path[PATH_MAX + 1];
221	int fd;
222
223	format_cgroup_path(cgroup_path, path);
224	if (mkdir(cgroup_path, 0777) && errno != EEXIST) {
225		log_err("mkdiring cgroup %s .. %s", path, cgroup_path);
226		return -1;
227	}
228
229	fd = open(cgroup_path, O_RDONLY);
230	if (fd < 0) {
231		log_err("Opening Cgroup");
232		return -1;
233	}
234
235	return fd;
236}
237
238/**
239 * get_cgroup_id() - Get cgroup id for a particular cgroup path
240 * @path: The cgroup path, relative to the workdir, to join
241 *
242 * On success, it returns the cgroup id. On failure it returns 0,
243 * which is an invalid cgroup id.
244 * If there is a failure, it prints the error to stderr.
245 */
246unsigned long long get_cgroup_id(const char *path)
247{
248	int dirfd, err, flags, mount_id, fhsize;
249	union {
250		unsigned long long cgid;
251		unsigned char raw_bytes[8];
252	} id;
253	char cgroup_workdir[PATH_MAX + 1];
254	struct file_handle *fhp, *fhp2;
255	unsigned long long ret = 0;
256
257	format_cgroup_path(cgroup_workdir, path);
258
259	dirfd = AT_FDCWD;
260	flags = 0;
261	fhsize = sizeof(*fhp);
262	fhp = calloc(1, fhsize);
263	if (!fhp) {
264		log_err("calloc");
265		return 0;
266	}
267	err = name_to_handle_at(dirfd, cgroup_workdir, fhp, &mount_id, flags);
268	if (err >= 0 || fhp->handle_bytes != 8) {
269		log_err("name_to_handle_at");
270		goto free_mem;
271	}
272
273	fhsize = sizeof(struct file_handle) + fhp->handle_bytes;
274	fhp2 = realloc(fhp, fhsize);
275	if (!fhp2) {
276		log_err("realloc");
277		goto free_mem;
278	}
279	err = name_to_handle_at(dirfd, cgroup_workdir, fhp2, &mount_id, flags);
280	fhp = fhp2;
281	if (err < 0) {
282		log_err("name_to_handle_at");
283		goto free_mem;
284	}
285
286	memcpy(id.raw_bytes, fhp->f_handle, 8);
287	ret = id.cgid;
288
289free_mem:
290	free(fhp);
291	return ret;
292}
293
294int cgroup_setup_and_join(const char *path) {
295	int cg_fd;
296
297	if (setup_cgroup_environment()) {
298		fprintf(stderr, "Failed to setup cgroup environment\n");
299		return -EINVAL;
300	}
301
302	cg_fd = create_and_get_cgroup(path);
303	if (cg_fd < 0) {
304		fprintf(stderr, "Failed to create test cgroup\n");
305		cleanup_cgroup_environment();
306		return cg_fd;
307	}
308
309	if (join_cgroup(path)) {
310		fprintf(stderr, "Failed to join cgroup\n");
311		cleanup_cgroup_environment();
312		return -EINVAL;
313	}
314	return cg_fd;
315}