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selftests/bpf: extend cgroup helpers
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This patch extends bpf selft cgroup_helpers [ID] n 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>
Signed-off-by: Hao Luo <haoluo@google.com>
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@yosrym93
yosrym93 authored and Kernel Patches Daemon committed Aug 8, 2022
1 parent cbd2a95 commit d6cd4f7
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Showing 2 changed files with 174 additions and 47 deletions.
202 changes: 161 additions & 41 deletions tools/testing/selftests/bpf/cgroup_helpers.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -33,49 +33,52 @@
#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;
}

len = read(fd, buf, sizeof(buf) - 1);
if (len < 0) {
/* 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, 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 */
close(fd);
return 0;
}
enable[len] = 0;
close(fd);
log_err("Reading cgroup.controllers: %s", path);
return 1;
} else {
strncpy(enable, controllers, sizeof(enable));
}
buf[len] = 0;
close(fd);

/* No controllers available? We're probably on cgroup v1. */
if (len == 0)
return 0;

snprintf(path, sizeof(path), "%s/cgroup.subtree_control", cgroup_path);
cfd = open(path, O_RDWR);
Expand All @@ -84,7 +87,7 @@ 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);
Expand All @@ -95,6 +98,87 @@ 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
*
Expand Down Expand Up @@ -133,7 +217,9 @@ 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;
Expand Down Expand Up @@ -173,7 +259,7 @@ 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
Expand All @@ -182,11 +268,27 @@ 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);
}

Expand All @@ -212,24 +314,42 @@ 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.
*
* 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;
}

Expand All @@ -244,13 +364,13 @@ 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 {
Expand All @@ -261,7 +381,7 @@ 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;
Expand Down
19 changes: 13 additions & 6 deletions tools/testing/selftests/bpf/cgroup_helpers.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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);
Expand All @@ -26,4 +33,4 @@ int join_classid(void);
int setup_classid_environment(void);
void cleanup_classid_environment(void);

#endif /* __CGROUP_HELPERS_H */
#endif /* __CGROUP_HELPERS_H */

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