tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1#define _GNU_SOURCE
2#include <sched.h>
3#include <sys/mount.h>
4#include <sys/stat.h>
5#include <sys/types.h>
6#include <linux/limits.h>
7#include <stdio.h>
8#include <linux/sched.h>
9#include <fcntl.h>
10#include <unistd.h>
11#include <ftw.h>
12
13
14#include "cgroup_helpers.h"
15
16/*
17 * To avoid relying on the system setup, when setup_cgroup_env is called
18 * we create a new mount namespace, and cgroup namespace. The cgroup2
19 * root is mounted at CGROUP_MOUNT_PATH
20 *
21 * Unfortunately, most people don't have cgroupv2 enabled at this point in time.
22 * It's easier to create our own mount namespace and manage it ourselves.
23 *
24 * We assume /mnt exists.
25 */
26
27#define WALK_FD_LIMIT 16
28#define CGROUP_MOUNT_PATH "/mnt"
29#define CGROUP_WORK_DIR "/cgroup-test-work-dir"
30#define format_cgroup_path(buf, path) \
31 snprintf(buf, sizeof(buf), "%s%s%s", CGROUP_MOUNT_PATH, \
32 CGROUP_WORK_DIR, path)
33
34/**
35 * setup_cgroup_environment() - Setup the cgroup environment
36 *
37 * After calling this function, cleanup_cgroup_environment should be called
38 * once testing is complete.
39 *
40 * This function will print an error to stderr and return 1 if it is unable
41 * to setup the cgroup environment. If setup is successful, 0 is returned.
42 */
43int setup_cgroup_environment(void)
44{
45 char cgroup_workdir[PATH_MAX + 1];
46
47 format_cgroup_path(cgroup_workdir, "");
48
49 if (unshare(CLONE_NEWNS)) {
50 log_err("unshare");
51 return 1;
52 }
53
54 if (mount("none", "/", NULL, MS_REC | MS_PRIVATE, NULL)) {
55 log_err("mount fakeroot");
56 return 1;
57 }
58
59 if (mount("none", CGROUP_MOUNT_PATH, "cgroup2", 0, NULL)) {
60 log_err("mount cgroup2");
61 return 1;
62 }
63
64 /* Cleanup existing failed runs, now that the environment is setup */
65 cleanup_cgroup_environment();
66
67 if (mkdir(cgroup_workdir, 0777) && errno != EEXIST) {
68 log_err("mkdir cgroup work dir");
69 return 1;
70 }
71
72 return 0;
73}
74
75static int nftwfunc(const char *filename, const struct stat *statptr,
76 int fileflags, struct FTW *pfwt)
77{
78 if ((fileflags & FTW_D) && rmdir(filename))
79 log_err("Removing cgroup: %s", filename);
80 return 0;
81}
82
83
84static int join_cgroup_from_top(char *cgroup_path)
85{
86 char cgroup_procs_path[PATH_MAX + 1];
87 pid_t pid = getpid();
88 int fd, rc = 0;
89
90 snprintf(cgroup_procs_path, sizeof(cgroup_procs_path),
91 "%s/cgroup.procs", cgroup_path);
92
93 fd = open(cgroup_procs_path, O_WRONLY);
94 if (fd < 0) {
95 log_err("Opening Cgroup Procs: %s", cgroup_procs_path);
96 return 1;
97 }
98
99 if (dprintf(fd, "%d\n", pid) < 0) {
100 log_err("Joining Cgroup");
101 rc = 1;
102 }
103
104 close(fd);
105 return rc;
106}
107
108/**
109 * join_cgroup() - Join a cgroup
110 * @path: The cgroup path, relative to the workdir, to join
111 *
112 * This function expects a cgroup to already be created, relative to the cgroup
113 * work dir, and it joins it. For example, passing "/my-cgroup" as the path
114 * would actually put the calling process into the cgroup
115 * "/cgroup-test-work-dir/my-cgroup"
116 *
117 * On success, it returns 0, otherwise on failure it returns 1.
118 */
119int join_cgroup(char *path)
120{
121 char cgroup_path[PATH_MAX + 1];
122
123 format_cgroup_path(cgroup_path, path);
124 return join_cgroup_from_top(cgroup_path);
125}
126
127/**
128 * cleanup_cgroup_environment() - Cleanup Cgroup Testing Environment
129 *
130 * This is an idempotent function to delete all temporary cgroups that
131 * have been created during the test, including the cgroup testing work
132 * directory.
133 *
134 * At call time, it moves the calling process to the root cgroup, and then
135 * runs the deletion process. It is idempotent, and should not fail, unless
136 * a process is lingering.
137 *
138 * On failure, it will print an error to stderr, and try to continue.
139 */
140void cleanup_cgroup_environment(void)
141{
142 char cgroup_workdir[PATH_MAX + 1];
143
144 format_cgroup_path(cgroup_workdir, "");
145 join_cgroup_from_top(CGROUP_MOUNT_PATH);
146 nftw(cgroup_workdir, nftwfunc, WALK_FD_LIMIT, FTW_DEPTH | FTW_MOUNT);
147}
148
149/**
150 * create_and_get_cgroup() - Create a cgroup, relative to workdir, and get the FD
151 * @path: The cgroup path, relative to the workdir, to join
152 *
153 * This function creates a cgroup under the top level workdir and returns the
154 * file descriptor. It is idempotent.
155 *
156 * On success, it returns the file descriptor. On failure it returns 0.
157 * If there is a failure, it prints the error to stderr.
158 */
159int create_and_get_cgroup(char *path)
160{
161 char cgroup_path[PATH_MAX + 1];
162 int fd;
163
164 format_cgroup_path(cgroup_path, path);
165 if (mkdir(cgroup_path, 0777) && errno != EEXIST) {
166 log_err("mkdiring cgroup");
167 return 0;
168 }
169
170 fd = open(cgroup_path, O_RDONLY);
171 if (fd < 0) {
172 log_err("Opening Cgroup");
173 return 0;
174 }
175
176 return fd;
177}