[PATCH bpf-next v3 7/8] selftests/bpf: extend cgroup helpers

Yosry Ahmed
2022-07-09T00:05:56Z

This patch extends bpf selftests cgroup helpers in various ways:
- Add enable_controllers() that allows tests to enable all or a
subset of controllers for a specific cgroup.
- Add join_cgroup_parent(). The cgroup workdir is based on the pid,
therefore a spawned child cannot join the same cgroup hierarchy of the
test through join_cgroup(). join_cgroup_parent() is used in child
processes to join a cgroup under the parent's workdir.
- Add write_cgroup_file() and write_cgroup_file_parent() (similar to
join_cgroup_parent() above).
- Add get_root_cgroup() for tests that need to do checks on root cgroup.
- Distinguish relative and absolute cgroup paths in function arguments.
Now relative paths are called relative_path, and absolute paths are
called cgroup_path.

Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
---
tools/testing/selftests/bpf/cgroup_helpers.c | 201 +++++++++++++++----
tools/testing/selftests/bpf/cgroup_helpers.h | 19 +-
2 files changed, 173 insertions(+), 47 deletions(-)

diff --git a/tools/testing/selftests/bpf/cgroup_helpers.c b/tools/testing/selftests/bpf/cgroup_helpers.c
index 9d59c3990ca8d..f06a5a255e195 100644
--- a/tools/testing/selftests/bpf/cgroup_helpers.c
+++ b/tools/testing/selftests/bpf/cgroup_helpers.c
@@ -33,49 +33,51 @@
#define CGROUP_MOUNT_DFLT "/sys/fs/cgroup"
#define NETCLS_MOUNT_PATH CGROUP_MOUNT_DFLT "/net_cls"
#define CGROUP_WORK_DIR "/cgroup-test-work-dir"
-#define format_cgroup_path(buf, path) \
+
+#define format_cgroup_path_pid(buf, path, pid) \
snprintf(buf, sizeof(buf), "%s%s%d%s", CGROUP_MOUNT_PATH, \
- CGROUP_WORK_DIR, getpid(), path)
+ CGROUP_WORK_DIR, pid, path)
+
+#define format_cgroup_path(buf, path) \
+ format_cgroup_path_pid(buf, path, getpid())
+
+#define format_parent_cgroup_path(buf, path) \
+ format_cgroup_path_pid(buf, path, getppid())

#define format_classid_path(buf) \
snprintf(buf, sizeof(buf), "%s%s", NETCLS_MOUNT_PATH, \
CGROUP_WORK_DIR)

-/**
- * enable_all_controllers() - Enable all available cgroup v2 controllers
- *
- * Enable all available cgroup v2 controllers in order to increase
- * the code coverage.
- *
- * If successful, 0 is returned.
- */
-static int enable_all_controllers(char *cgroup_path)
+
+static int __enable_controllers(const char *cgroup_path, const char *controllers)
{
char path[PATH_MAX + 1];
- char buf[PATH_MAX];
+ char enable[PATH_MAX + 1];
char *c, *c2;
int fd, cfd;
ssize_t len;

- snprintf(path, sizeof(path), "%s/cgroup.controllers", cgroup_path);
- fd = open(path, O_RDONLY);
- if (fd < 0) {
- log_err("Opening cgroup.controllers: %s", path);
- return 1;
- }
+ /* If not controllers are passed, enable all available controllers */
+ if (!controllers) {
+ snprintf(path, sizeof(path), "%s/cgroup.controllers",
+ cgroup_path);
+ fd = open(path, O_RDONLY);
+ if (fd < 0) {
+ log_err("Opening cgroup.controllers: %s", path);
+ return 1;
+ }

- len = read(fd, buf, sizeof(buf) - 1);
- if (len < 0) {
+ len = read(fd, enable, sizeof(enable) - 1);
+ if (len < 0) {
+ close(fd);
+ log_err("Reading cgroup.controllers: %s", path);
+ return 1;
+ } else if (len == 0) /* No controllers to enable */
+ return 0;
+ enable[len] = 0;
close(fd);
- log_err("Reading cgroup.controllers: %s", path);
- return 1;
- }
- buf[len] = 0;
- close(fd);
-
- /* No controllers available? We're probably on cgroup v1. */
- if (len == 0)
- return 0;
+ } else
+ strncpy(enable, controllers, sizeof(enable));

snprintf(path, sizeof(path), "%s/cgroup.subtree_control", cgroup_path);
cfd = open(path, O_RDWR);
@@ -84,7 +86,7 @@ static int enable_all_controllers(char *cgroup_path)
return 1;
}

- for (c = strtok_r(buf, " ", &c2); c; c = strtok_r(NULL, " ", &c2)) {
+ for (c = strtok_r(enable, " ", &c2); c; c = strtok_r(NULL, " ", &c2)) {
if (dprintf(cfd, "+%s\n", c) <= 0) {
log_err("Enabling controller %s: %s", c, path);
close(cfd);
@@ -95,6 +97,87 @@ static int enable_all_controllers(char *cgroup_path)
return 0;
}

+/**
+ * enable_controllers() - Enable cgroup v2 controllers
+ * @relative_path: The cgroup path, relative to the workdir
+ * @controllers: List of controllers to enable in cgroup.controllers format
+ *
+ *
+ * Enable given cgroup v2 controllers, if @controllers is NULL, enable all
+ * available controllers.
+ *
+ * If successful, 0 is returned.
+ */
+int enable_controllers(const char *relative_path, const char *controllers)
+{
+ char cgroup_path[PATH_MAX + 1];
+
+ format_cgroup_path(cgroup_path, relative_path);
+ return __enable_controllers(cgroup_path, controllers);
+}
+
+static int __write_cgroup_file(const char *cgroup_path, const char *file,
+ const char *buf)
+{
+ char file_path[PATH_MAX + 1];
+ int fd;
+
+ snprintf(file_path, sizeof(file_path), "%s/%s", cgroup_path, file);
+ fd = open(file_path, O_RDWR);
+ if (fd < 0) {
+ log_err("Opening %s", file_path);
+ return 1;
+ }
+
+ if (dprintf(fd, "%s", buf) <= 0) {
+ log_err("Writing to %s", file_path);
+ close(fd);
+ return 1;
+ }
+ close(fd);
+ return 0;
+}
+
+/**
+ * write_cgroup_file() - Write to a cgroup file
+ * @relative_path: The cgroup path, relative to the workdir
+ * @file: The name of the file in cgroupfs to write to
+ * @buf: Buffer to write to the file
+ *
+ * Write to a file in the given cgroup's directory.
+ *
+ * If successful, 0 is returned.
+ */
+int write_cgroup_file(const char *relative_path, const char *file,
+ const char *buf)
+{
+ char cgroup_path[PATH_MAX - 24];
+
+ format_cgroup_path(cgroup_path, relative_path);
+ return __write_cgroup_file(cgroup_path, file, buf);
+}
+
+/**
+ * write_cgroup_file_parent() - Write to a cgroup file in the parent process
+ * workdir
+ * @relative_path: The cgroup path, relative to the parent process workdir
+ * @file: The name of the file in cgroupfs to write to
+ * @buf: Buffer to write to the file
+ *
+ * Write to a file in the given cgroup's directory under the parent process
+ * workdir.
+ *
+ * If successful, 0 is returned.
+ */
+int write_cgroup_file_parent(const char *relative_path, const char *file,
+ const char *buf)
+{
+ char cgroup_path[PATH_MAX - 24];
+
+ format_parent_cgroup_path(cgroup_path, relative_path);
+ return __write_cgroup_file(cgroup_path, file, buf);
+}
+
/**
* setup_cgroup_environment() - Setup the cgroup environment
*
@@ -133,7 +216,9 @@ int setup_cgroup_environment(void)
return 1;
}

- if (enable_all_controllers(cgroup_workdir))
+ /* Enable all available controllers to increase test coverage */
+ if (__enable_controllers(CGROUP_MOUNT_PATH, NULL) ||
+ __enable_controllers(cgroup_workdir, NULL))
return 1;

return 0;
@@ -173,7 +258,7 @@ static int join_cgroup_from_top(const char *cgroup_path)

/**
* join_cgroup() - Join a cgroup
- * @path: The cgroup path, relative to the workdir, to join
+ * @relative_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
@@ -182,11 +267,27 @@ static int join_cgroup_from_top(const char *cgroup_path)
*
* On success, it returns 0, otherwise on failure it returns 1.
*/
-int join_cgroup(const char *path)
+int join_cgroup(const char *relative_path)
+{
+ char cgroup_path[PATH_MAX + 1];
+
+ format_cgroup_path(cgroup_path, relative_path);
+ return join_cgroup_from_top(cgroup_path);
+}
+
+/**
+ * join_parent_cgroup() - Join a cgroup in the parent process workdir
+ * @relative_path: The cgroup path, relative to parent process workdir, to join
+ *
+ * See join_cgroup().
+ *
+ * On success, it returns 0, otherwise on failure it returns 1.
+ */
+int join_parent_cgroup(const char *relative_path)
{
char cgroup_path[PATH_MAX + 1];

- format_cgroup_path(cgroup_path, path);
+ format_parent_cgroup_path(cgroup_path, relative_path);
return join_cgroup_from_top(cgroup_path);
}

@@ -212,9 +313,27 @@ void cleanup_cgroup_environment(void)
nftw(cgroup_workdir, nftwfunc, WALK_FD_LIMIT, FTW_DEPTH | FTW_MOUNT);
}

+/**
+ * get_root_cgroup() - Get the FD of the root cgroup
+ *
+ * On success, it returns the file descriptor. On failure, it returns -1.
+ * If there is a failure, it prints the error to stderr.
+ */
+int get_root_cgroup(void)
+{
+ int fd;
+
+ fd = open(CGROUP_MOUNT_PATH, O_RDONLY);
+ if (fd < 0) {
+ log_err("Opening root cgroup");
+ return -1;
+ }
+ return fd;
+}
+
/**
* create_and_get_cgroup() - Create a cgroup, relative to workdir, and get the FD
- * @path: The cgroup path, relative to the workdir, to join
+ * @relative_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.
@@ -222,14 +341,14 @@ void cleanup_cgroup_environment(void)
* On success, it returns the file descriptor. On failure it returns -1.
* If there is a failure, it prints the error to stderr.
*/
-int create_and_get_cgroup(const char *path)
+int create_and_get_cgroup(const char *relative_path)
{
char cgroup_path[PATH_MAX + 1];
int fd;

- format_cgroup_path(cgroup_path, path);
+ format_cgroup_path(cgroup_path, relative_path);
if (mkdir(cgroup_path, 0777) && errno != EEXIST) {
- log_err("mkdiring cgroup %s .. %s", path, cgroup_path);
+ log_err("mkdiring cgroup %s .. %s", relative_path, cgroup_path);
return -1;
}

@@ -244,13 +363,13 @@ int create_and_get_cgroup(const char *path)

/**
* get_cgroup_id() - Get cgroup id for a particular cgroup path
- * @path: The cgroup path, relative to the workdir, to join
+ * @relative_path: The cgroup path, relative to the workdir, to join
*
* On success, it returns the cgroup id. On failure it returns 0,
* which is an invalid cgroup id.
* If there is a failure, it prints the error to stderr.
*/
-unsigned long long get_cgroup_id(const char *path)
+unsigned long long get_cgroup_id(const char *relative_path)
{
int dirfd, err, flags, mount_id, fhsize;
union {
@@ -261,7 +380,7 @@ unsigned long long get_cgroup_id(const char *path)
struct file_handle *fhp, *fhp2;
unsigned long long ret = 0;

- format_cgroup_path(cgroup_workdir, path);
+ format_cgroup_path(cgroup_workdir, relative_path);

dirfd = AT_FDCWD;
flags = 0;
diff --git a/tools/testing/selftests/bpf/cgroup_helpers.h b/tools/testing/selftests/bpf/cgroup_helpers.h
index fcc9cb91b2111..3358734356ab7 100644
--- a/tools/testing/selftests/bpf/cgroup_helpers.h
+++ b/tools/testing/selftests/bpf/cgroup_helpers.h
@@ -10,11 +10,18 @@
__FILE__, __LINE__, clean_errno(), ##__VA_ARGS__)

/* cgroupv2 related */
-int cgroup_setup_and_join(const char *path);
-int create_and_get_cgroup(const char *path);
-unsigned long long get_cgroup_id(const char *path);
-
-int join_cgroup(const char *path);
+int enable_controllers(const char *relative_path, const char *controllers);
+int write_cgroup_file(const char *relative_path, const char *file,
+ const char *buf);
+int write_cgroup_file_parent(const char *relative_path, const char *file,
+ const char *buf);
+int cgroup_setup_and_join(const char *relative_path);
+int get_root_cgroup(void);
+int create_and_get_cgroup(const char *relative_path);
+unsigned long long get_cgroup_id(const char *relative_path);
+
+int join_cgroup(const char *relative_path);
+int join_parent_cgroup(const char *relative_path);

int setup_cgroup_environment(void);
void cleanup_cgroup_environment(void);
@@ -26,4 +33,4 @@ int join_classid(void);
int setup_classid_environment(void);
void cleanup_classid_environment(void);

-#endif /* __CGROUP_HELPERS_H */
\ No newline at end of file
+#endif /* __CGROUP_HELPERS_H */
--
2.37.0.rc0.161.g10f37bed90-goog