| 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 <linux/sched.h> |
| 10 | #include <fcntl.h> |
| 11 | #include <unistd.h> |
| 12 | #include <ftw.h> |
| 13 | |
| 14 | |
| 15 | #include "cgroup_helpers.h" |
| 16 | |
| 17 | /* |
| 18 | * To avoid relying on the system setup, when setup_cgroup_env is called |
| 19 | * we create a new mount namespace, and cgroup namespace. The cgroup2 |
| 20 | * root is mounted at CGROUP_MOUNT_PATH |
| 21 | * |
| 22 | * Unfortunately, most people don't have cgroupv2 enabled at this point in time. |
| 23 | * It's easier to create our own mount namespace and manage it ourselves. |
| 24 | * |
| 25 | * We assume /mnt exists. |
| 26 | */ |
| 27 | |
| 28 | #define WALK_FD_LIMIT 16 |
| 29 | #define CGROUP_MOUNT_PATH "/mnt" |
| 30 | #define CGROUP_WORK_DIR "/cgroup-test-work-dir" |
| 31 | #define format_cgroup_path(buf, path) \ |
| 32 | snprintf(buf, sizeof(buf), "%s%s%s", CGROUP_MOUNT_PATH, \ |
| 33 | CGROUP_WORK_DIR, path) |
| 34 | |
| 35 | /** |
| 36 | * setup_cgroup_environment() - Setup the cgroup environment |
| 37 | * |
| 38 | * After calling this function, cleanup_cgroup_environment should be called |
| 39 | * once testing is complete. |
| 40 | * |
| 41 | * This function will print an error to stderr and return 1 if it is unable |
| 42 | * to setup the cgroup environment. If setup is successful, 0 is returned. |
| 43 | */ |
| 44 | int setup_cgroup_environment(void) |
| 45 | { |
| 46 | char cgroup_workdir[PATH_MAX + 1]; |
| 47 | |
| 48 | format_cgroup_path(cgroup_workdir, ""); |
| 49 | |
| 50 | if (unshare(CLONE_NEWNS)) { |
| 51 | log_err("unshare"); |
| 52 | return 1; |
| 53 | } |
| 54 | |
| 55 | if (mount("none", "/", NULL, MS_REC | MS_PRIVATE, NULL)) { |
| 56 | log_err("mount fakeroot"); |
| 57 | return 1; |
| 58 | } |
| 59 | |
| 60 | if (mount("none", CGROUP_MOUNT_PATH, "cgroup2", 0, NULL) && errno != EBUSY) { |
| 61 | log_err("mount cgroup2"); |
| 62 | return 1; |
| 63 | } |
| 64 | |
| 65 | /* Cleanup existing failed runs, now that the environment is setup */ |
| 66 | cleanup_cgroup_environment(); |
| 67 | |
| 68 | if (mkdir(cgroup_workdir, 0777) && errno != EEXIST) { |
| 69 | log_err("mkdir cgroup work dir"); |
| 70 | return 1; |
| 71 | } |
| 72 | |
| 73 | return 0; |
| 74 | } |
| 75 | |
| 76 | static int nftwfunc(const char *filename, const struct stat *statptr, |
| 77 | int fileflags, struct FTW *pfwt) |
| 78 | { |
| 79 | if ((fileflags & FTW_D) && rmdir(filename)) |
| 80 | log_err("Removing cgroup: %s", filename); |
| 81 | return 0; |
| 82 | } |
| 83 | |
| 84 | |
| 85 | static int join_cgroup_from_top(char *cgroup_path) |
| 86 | { |
| 87 | char cgroup_procs_path[PATH_MAX + 1]; |
| 88 | pid_t pid = getpid(); |
| 89 | int fd, rc = 0; |
| 90 | |
| 91 | snprintf(cgroup_procs_path, sizeof(cgroup_procs_path), |
| 92 | "%s/cgroup.procs", cgroup_path); |
| 93 | |
| 94 | fd = open(cgroup_procs_path, O_WRONLY); |
| 95 | if (fd < 0) { |
| 96 | log_err("Opening Cgroup Procs: %s", cgroup_procs_path); |
| 97 | return 1; |
| 98 | } |
| 99 | |
| 100 | if (dprintf(fd, "%d\n", pid) < 0) { |
| 101 | log_err("Joining Cgroup"); |
| 102 | rc = 1; |
| 103 | } |
| 104 | |
| 105 | close(fd); |
| 106 | return rc; |
| 107 | } |
| 108 | |
| 109 | /** |
| 110 | * join_cgroup() - Join a cgroup |
| 111 | * @path: The cgroup path, relative to the workdir, to join |
| 112 | * |
| 113 | * This function expects a cgroup to already be created, relative to the cgroup |
| 114 | * work dir, and it joins it. For example, passing "/my-cgroup" as the path |
| 115 | * would actually put the calling process into the cgroup |
| 116 | * "/cgroup-test-work-dir/my-cgroup" |
| 117 | * |
| 118 | * On success, it returns 0, otherwise on failure it returns 1. |
| 119 | */ |
| 120 | int join_cgroup(char *path) |
| 121 | { |
| 122 | char cgroup_path[PATH_MAX + 1]; |
| 123 | |
| 124 | format_cgroup_path(cgroup_path, path); |
| 125 | return join_cgroup_from_top(cgroup_path); |
| 126 | } |
| 127 | |
| 128 | /** |
| 129 | * cleanup_cgroup_environment() - Cleanup Cgroup Testing Environment |
| 130 | * |
| 131 | * This is an idempotent function to delete all temporary cgroups that |
| 132 | * have been created during the test, including the cgroup testing work |
| 133 | * directory. |
| 134 | * |
| 135 | * At call time, it moves the calling process to the root cgroup, and then |
| 136 | * runs the deletion process. It is idempotent, and should not fail, unless |
| 137 | * a process is lingering. |
| 138 | * |
| 139 | * On failure, it will print an error to stderr, and try to continue. |
| 140 | */ |
| 141 | void cleanup_cgroup_environment(void) |
| 142 | { |
| 143 | char cgroup_workdir[PATH_MAX + 1]; |
| 144 | |
| 145 | format_cgroup_path(cgroup_workdir, ""); |
| 146 | join_cgroup_from_top(CGROUP_MOUNT_PATH); |
| 147 | nftw(cgroup_workdir, nftwfunc, WALK_FD_LIMIT, FTW_DEPTH | FTW_MOUNT); |
| 148 | } |
| 149 | |
| 150 | /** |
| 151 | * create_and_get_cgroup() - Create a cgroup, relative to workdir, and get the FD |
| 152 | * @path: The cgroup path, relative to the workdir, to join |
| 153 | * |
| 154 | * This function creates a cgroup under the top level workdir and returns the |
| 155 | * file descriptor. It is idempotent. |
| 156 | * |
| 157 | * On success, it returns the file descriptor. On failure it returns 0. |
| 158 | * If there is a failure, it prints the error to stderr. |
| 159 | */ |
| 160 | int create_and_get_cgroup(char *path) |
| 161 | { |
| 162 | char cgroup_path[PATH_MAX + 1]; |
| 163 | int fd; |
| 164 | |
| 165 | format_cgroup_path(cgroup_path, path); |
| 166 | if (mkdir(cgroup_path, 0777) && errno != EEXIST) { |
| 167 | log_err("mkdiring cgroup %s .. %s", path, cgroup_path); |
| 168 | return 0; |
| 169 | } |
| 170 | |
| 171 | fd = open(cgroup_path, O_RDONLY); |
| 172 | if (fd < 0) { |
| 173 | log_err("Opening Cgroup"); |
| 174 | return 0; |
| 175 | } |
| 176 | |
| 177 | return fd; |
| 178 | } |