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Diffstat (limited to 'samples/bpf/cgroup_helpers.c')
| -rw-r--r-- | samples/bpf/cgroup_helpers.c | 177 |
1 files changed, 177 insertions, 0 deletions
diff --git a/samples/bpf/cgroup_helpers.c b/samples/bpf/cgroup_helpers.c new file mode 100644 index 000000000000..9d1be9426401 --- /dev/null +++ b/samples/bpf/cgroup_helpers.c @@ -0,0 +1,177 @@ +#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 <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) + +/** + * 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 + 1]; + + 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)) { + 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; + } + + 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(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 0. + * If there is a failure, it prints the error to stderr. + */ +int create_and_get_cgroup(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"); + return 0; + } + + fd = open(cgroup_path, O_RDONLY); + if (fd < 0) { + log_err("Opening Cgroup"); + return 0; + } + + return fd; +} |