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 * setup_cgroup_environment() - Setup the cgroup environment
38 *
39 * After calling this function, cleanup_cgroup_environment should be called
40 * once testing is complete.
41 *
42 * This function will print an error to stderr and return 1 if it is unable
43 * to setup the cgroup environment. If setup is successful, 0 is returned.
44 */
setup_cgroup_environment(void)45 int setup_cgroup_environment(void)
46 {
47 char cgroup_workdir[PATH_MAX + 1];
48
49 format_cgroup_path(cgroup_workdir, "");
50
51 if (unshare(CLONE_NEWNS)) {
52 log_err("unshare");
53 return 1;
54 }
55
56 if (mount("none", "/", NULL, MS_REC | MS_PRIVATE, NULL)) {
57 log_err("mount fakeroot");
58 return 1;
59 }
60
61 if (mount("none", CGROUP_MOUNT_PATH, "cgroup2", 0, NULL) && errno != EBUSY) {
62 log_err("mount cgroup2");
63 return 1;
64 }
65
66 /* Cleanup existing failed runs, now that the environment is setup */
67 cleanup_cgroup_environment();
68
69 if (mkdir(cgroup_workdir, 0777) && errno != EEXIST) {
70 log_err("mkdir cgroup work dir");
71 return 1;
72 }
73
74 return 0;
75 }
76
nftwfunc(const char * filename,const struct stat * statptr,int fileflags,struct FTW * pfwt)77 static int nftwfunc(const char *filename, const struct stat *statptr,
78 int fileflags, struct FTW *pfwt)
79 {
80 if ((fileflags & FTW_D) && rmdir(filename))
81 log_err("Removing cgroup: %s", filename);
82 return 0;
83 }
84
85
join_cgroup_from_top(char * cgroup_path)86 static int join_cgroup_from_top(char *cgroup_path)
87 {
88 char cgroup_procs_path[PATH_MAX + 1];
89 pid_t pid = getpid();
90 int fd, rc = 0;
91
92 snprintf(cgroup_procs_path, sizeof(cgroup_procs_path),
93 "%s/cgroup.procs", cgroup_path);
94
95 fd = open(cgroup_procs_path, O_WRONLY);
96 if (fd < 0) {
97 log_err("Opening Cgroup Procs: %s", cgroup_procs_path);
98 return 1;
99 }
100
101 if (dprintf(fd, "%d\n", pid) < 0) {
102 log_err("Joining Cgroup");
103 rc = 1;
104 }
105
106 close(fd);
107 return rc;
108 }
109
110 /**
111 * join_cgroup() - Join a cgroup
112 * @path: The cgroup path, relative to the workdir, to join
113 *
114 * This function expects a cgroup to already be created, relative to the cgroup
115 * work dir, and it joins it. For example, passing "/my-cgroup" as the path
116 * would actually put the calling process into the cgroup
117 * "/cgroup-test-work-dir/my-cgroup"
118 *
119 * On success, it returns 0, otherwise on failure it returns 1.
120 */
join_cgroup(const char * path)121 int join_cgroup(const char *path)
122 {
123 char cgroup_path[PATH_MAX + 1];
124
125 format_cgroup_path(cgroup_path, path);
126 return join_cgroup_from_top(cgroup_path);
127 }
128
129 /**
130 * cleanup_cgroup_environment() - Cleanup Cgroup Testing Environment
131 *
132 * This is an idempotent function to delete all temporary cgroups that
133 * have been created during the test, including the cgroup testing work
134 * directory.
135 *
136 * At call time, it moves the calling process to the root cgroup, and then
137 * runs the deletion process. It is idempotent, and should not fail, unless
138 * a process is lingering.
139 *
140 * On failure, it will print an error to stderr, and try to continue.
141 */
cleanup_cgroup_environment(void)142 void cleanup_cgroup_environment(void)
143 {
144 char cgroup_workdir[PATH_MAX + 1];
145
146 format_cgroup_path(cgroup_workdir, "");
147 join_cgroup_from_top(CGROUP_MOUNT_PATH);
148 nftw(cgroup_workdir, nftwfunc, WALK_FD_LIMIT, FTW_DEPTH | FTW_MOUNT);
149 }
150
151 /**
152 * create_and_get_cgroup() - Create a cgroup, relative to workdir, and get the FD
153 * @path: The cgroup path, relative to the workdir, to join
154 *
155 * This function creates a cgroup under the top level workdir and returns the
156 * file descriptor. It is idempotent.
157 *
158 * On success, it returns the file descriptor. On failure it returns 0.
159 * If there is a failure, it prints the error to stderr.
160 */
create_and_get_cgroup(const char * path)161 int create_and_get_cgroup(const char *path)
162 {
163 char cgroup_path[PATH_MAX + 1];
164 int fd;
165
166 format_cgroup_path(cgroup_path, path);
167 if (mkdir(cgroup_path, 0777) && errno != EEXIST) {
168 log_err("mkdiring cgroup %s .. %s", path, cgroup_path);
169 return 0;
170 }
171
172 fd = open(cgroup_path, O_RDONLY);
173 if (fd < 0) {
174 log_err("Opening Cgroup");
175 return 0;
176 }
177
178 return fd;
179 }
180
181 /**
182 * get_cgroup_id() - Get cgroup id for a particular cgroup path
183 * @path: The cgroup path, relative to the workdir, to join
184 *
185 * On success, it returns the cgroup id. On failure it returns 0,
186 * which is an invalid cgroup id.
187 * If there is a failure, it prints the error to stderr.
188 */
get_cgroup_id(const char * path)189 unsigned long long get_cgroup_id(const char *path)
190 {
191 int dirfd, err, flags, mount_id, fhsize;
192 union {
193 unsigned long long cgid;
194 unsigned char raw_bytes[8];
195 } id;
196 char cgroup_workdir[PATH_MAX + 1];
197 struct file_handle *fhp, *fhp2;
198 unsigned long long ret = 0;
199
200 format_cgroup_path(cgroup_workdir, path);
201
202 dirfd = AT_FDCWD;
203 flags = 0;
204 fhsize = sizeof(*fhp);
205 fhp = calloc(1, fhsize);
206 if (!fhp) {
207 log_err("calloc");
208 return 0;
209 }
210 err = name_to_handle_at(dirfd, cgroup_workdir, fhp, &mount_id, flags);
211 if (err >= 0 || fhp->handle_bytes != 8) {
212 log_err("name_to_handle_at");
213 goto free_mem;
214 }
215
216 fhsize = sizeof(struct file_handle) + fhp->handle_bytes;
217 fhp2 = realloc(fhp, fhsize);
218 if (!fhp2) {
219 log_err("realloc");
220 goto free_mem;
221 }
222 err = name_to_handle_at(dirfd, cgroup_workdir, fhp2, &mount_id, flags);
223 fhp = fhp2;
224 if (err < 0) {
225 log_err("name_to_handle_at");
226 goto free_mem;
227 }
228
229 memcpy(id.raw_bytes, fhp->f_handle, 8);
230 ret = id.cgid;
231
232 free_mem:
233 free(fhp);
234 return ret;
235 }
236