linux/tools/perf/util/cgroup.c

// SPDX-License-Identifier: GPL-2.0
#include <subcmd/parse-options.h>
#include "evsel.h"
#include "cgroup.h"
#include "evlist.h"
#include "rblist.h"
#include "metricgroup.h"
#include "stat.h"
#include <linux/zalloc.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/statfs.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <api/fs/fs.h>
#include <ftw.h>
#include <regex.h>

int nr_cgroups;
bool cgrp_event_expanded;

/* used to match cgroup name with patterns */
struct cgroup_name {
	struct list_head list;
	bool used;
	char name[];
};
static LIST_HEAD(cgroup_list);

static int open_cgroup(const char *name)
{
	char path[PATH_MAX + 1];
	char mnt[PATH_MAX + 1];
	int fd;


	if (cgroupfs_find_mountpoint(mnt, PATH_MAX + 1, "perf_event"))
		return -1;

	scnprintf(path, PATH_MAX, "%s/%s", mnt, name);

	fd = open(path, O_RDONLY);
	if (fd == -1)
		fprintf(stderr, "no access to cgroup %s\n", path);

	return fd;
}

#ifdef HAVE_FILE_HANDLE
static u64 __read_cgroup_id(const char *path)
{
	struct {
		struct file_handle fh;
		uint64_t cgroup_id;
	} handle;
	int mount_id;

	handle.fh.handle_bytes = sizeof(handle.cgroup_id);
	if (name_to_handle_at(AT_FDCWD, path, &handle.fh, &mount_id, 0) < 0)
		return -1ULL;

	return handle.cgroup_id;
}

int read_cgroup_id(struct cgroup *cgrp)
{
	char path[PATH_MAX + 1];
	char mnt[PATH_MAX + 1];

	if (cgroupfs_find_mountpoint(mnt, PATH_MAX + 1, "perf_event"))
		return -1;

	scnprintf(path, PATH_MAX, "%s/%s", mnt, cgrp->name);

	cgrp->id = __read_cgroup_id(path);
	return 0;
}
#else
static inline u64 __read_cgroup_id(const char *path __maybe_unused) { return -1ULL; }
#endif  /* HAVE_FILE_HANDLE */

#ifndef CGROUP2_SUPER_MAGIC
#define CGROUP2_SUPER_MAGIC  0x63677270
#endif

int cgroup_is_v2(const char *subsys)
{
	char mnt[PATH_MAX + 1];
	struct statfs stbuf;

	if (cgroupfs_find_mountpoint(mnt, PATH_MAX + 1, subsys))
		return -1;

	if (statfs(mnt, &stbuf) < 0)
		return -1;

	return (stbuf.f_type == CGROUP2_SUPER_MAGIC);
}

static struct cgroup *evlist__find_cgroup(struct evlist *evlist, const char *str)
{
	struct evsel *counter;
	/*
	 * check if cgrp is already defined, if so we reuse it
	 */
	evlist__for_each_entry(evlist, counter) {
		if (!counter->cgrp)
			continue;
		if (!strcmp(counter->cgrp->name, str))
			return cgroup__get(counter->cgrp);
	}

	return NULL;
}

struct cgroup *cgroup__new(const char *name, bool do_open)
{
	struct cgroup *cgroup = zalloc(sizeof(*cgroup));

	if (cgroup != NULL) {
		refcount_set(&cgroup->refcnt, 1);

		cgroup->name = strdup(name);
		if (!cgroup->name)
			goto out_err;

		if (do_open) {
			cgroup->fd = open_cgroup(name);
			if (cgroup->fd == -1)
				goto out_free_name;
		} else {
			cgroup->fd = -1;
		}
	}

	return cgroup;

out_free_name:
	zfree(&cgroup->name);
out_err:
	free(cgroup);
	return NULL;
}

struct cgroup *evlist__findnew_cgroup(struct evlist *evlist, const char *name)
{
	struct cgroup *cgroup = evlist__find_cgroup(evlist, name);

	return cgroup ?: cgroup__new(name, true);
}

static int add_cgroup(struct evlist *evlist, const char *str)
{
	struct evsel *counter;
	struct cgroup *cgrp = evlist__findnew_cgroup(evlist, str);
	int n;

	if (!cgrp)
		return -1;
	/*
	 * find corresponding event
	 * if add cgroup N, then need to find event N
	 */
	n = 0;
	evlist__for_each_entry(evlist, counter) {
		if (n == nr_cgroups)
			goto found;
		n++;
	}

	cgroup__put(cgrp);
	return -1;
found:
	counter->cgrp = cgrp;
	return 0;
}

static void cgroup__delete(struct cgroup *cgroup)
{
	if (cgroup->fd >= 0)
		close(cgroup->fd);
	zfree(&cgroup->name);
	free(cgroup);
}

void cgroup__put(struct cgroup *cgrp)
{
	if (cgrp && refcount_dec_and_test(&cgrp->refcnt)) {
		cgroup__delete(cgrp);
	}
}

struct cgroup *cgroup__get(struct cgroup *cgroup)
{
       if (cgroup)
		refcount_inc(&cgroup->refcnt);
       return cgroup;
}

static void evsel__set_default_cgroup(struct evsel *evsel, struct cgroup *cgroup)
{
	if (evsel->cgrp == NULL)
		evsel->cgrp = cgroup__get(cgroup);
}

void evlist__set_default_cgroup(struct evlist *evlist, struct cgroup *cgroup)
{
	struct evsel *evsel;

	evlist__for_each_entry(evlist, evsel)
		evsel__set_default_cgroup(evsel, cgroup);
}

/* helper function for ftw() in match_cgroups and list_cgroups */
static int add_cgroup_name(const char *fpath, const struct stat *sb __maybe_unused,
			   int typeflag, struct FTW *ftwbuf __maybe_unused)
{
	struct cgroup_name *cn;

	if (typeflag != FTW_D)
		return 0;

	cn = malloc(sizeof(*cn) + strlen(fpath) + 1);
	if (cn == NULL)
		return -1;

	cn->used = false;
	strcpy(cn->name, fpath);

	list_add_tail(&cn->list, &cgroup_list);
	return 0;
}

static int check_and_add_cgroup_name(const char *fpath)
{
	struct cgroup_name *cn;

	list_for_each_entry(cn, &cgroup_list, list) {
		if (!strcmp(cn->name, fpath))
			return 0;
	}

	/* pretend if it's added by ftw() */
	return add_cgroup_name(fpath, NULL, FTW_D, NULL);
}

static void release_cgroup_list(void)
{
	struct cgroup_name *cn;

	while (!list_empty(&cgroup_list)) {
		cn = list_first_entry(&cgroup_list, struct cgroup_name, list);
		list_del(&cn->list);
		free(cn);
	}
}

/* collect given cgroups only */
static int list_cgroups(const char *str)
{
	const char *p, *e, *eos = str + strlen(str);
	struct cgroup_name *cn;
	char *s;

	/* use given name as is when no regex is given */
	for (;;) {
		p = strchr(str, ',');
		e = p ? p : eos;

		if (e - str) {
			int ret;

			s = strndup(str, e - str);
			if (!s)
				return -1;

			ret = check_and_add_cgroup_name(s);
			free(s);
			if (ret < 0)
				return -1;
		} else {
			if (check_and_add_cgroup_name("/") < 0)
				return -1;
		}

		if (!p)
			break;
		str = p+1;
	}

	/* these groups will be used */
	list_for_each_entry(cn, &cgroup_list, list)
		cn->used = true;

	return 0;
}

/* collect all cgroups first and then match with the pattern */
static int match_cgroups(const char *str)
{
	char mnt[PATH_MAX];
	const char *p, *e, *eos = str + strlen(str);
	struct cgroup_name *cn;
	regex_t reg;
	int prefix_len;
	char *s;

	if (cgroupfs_find_mountpoint(mnt, sizeof(mnt), "perf_event"))
		return -1;

	/* cgroup_name will have a full path, skip the root directory */
	prefix_len = strlen(mnt);

	/* collect all cgroups in the cgroup_list */
	if (nftw(mnt, add_cgroup_name, 20, 0) < 0)
		return -1;

	for (;;) {
		p = strchr(str, ',');
		e = p ? p : eos;

		/* allow empty cgroups, i.e., skip */
		if (e - str) {
			/* termination added */
			s = strndup(str, e - str);
			if (!s)
				return -1;
			if (regcomp(&reg, s, REG_NOSUB)) {
				free(s);
				return -1;
			}

			/* check cgroup name with the pattern */
			list_for_each_entry(cn, &cgroup_list, list) {
				char *name = cn->name + prefix_len;

				if (name[0] == '/' && name[1])
					name++;
				if (!regexec(&reg, name, 0, NULL, 0))
					cn->used = true;
			}
			regfree(&reg);
			free(s);
		} else {
			/* first entry to root cgroup */
			cn = list_first_entry(&cgroup_list, struct cgroup_name,
					      list);
			cn->used = true;
		}

		if (!p)
			break;
		str = p+1;
	}
	return prefix_len;
}

int parse_cgroups(const struct option *opt, const char *str,
		  int unset __maybe_unused)
{
	struct evlist *evlist = *(struct evlist **)opt->value;
	struct evsel *counter;
	struct cgroup *cgrp = NULL;
	const char *p, *e, *eos = str + strlen(str);
	char *s;
	int ret, i;

	if (list_empty(&evlist->core.entries)) {
		fprintf(stderr, "must define events before cgroups\n");
		return -1;
	}

	for (;;) {
		p = strchr(str, ',');
		e = p ? p : eos;

		/* allow empty cgroups, i.e., skip */
		if (e - str) {
			/* termination added */
			s = strndup(str, e - str);
			if (!s)
				return -1;
			ret = add_cgroup(evlist, s);
			free(s);
			if (ret)
				return -1;
		}
		/* nr_cgroups is increased een for empty cgroups */
		nr_cgroups++;
		if (!p)
			break;
		str = p+1;
	}
	/* for the case one cgroup combine to multiple events */
	i = 0;
	if (nr_cgroups == 1) {
		evlist__for_each_entry(evlist, counter) {
			if (i == 0)
				cgrp = counter->cgrp;
			else {
				counter->cgrp = cgrp;
				refcount_inc(&cgrp->refcnt);
			}
			i++;
		}
	}
	return 0;
}

static bool has_pattern_string(const char *str)
{
	return !!strpbrk(str, "{}[]()|*+?^$");
}

int evlist__expand_cgroup(struct evlist *evlist, const char *str, bool open_cgroup)
{
	struct evlist *orig_list, *tmp_list;
	struct evsel *pos, *evsel, *leader;
	struct rblist orig_metric_events;
	struct cgroup *cgrp = NULL;
	struct cgroup_name *cn;
	int ret = -1;
	int prefix_len;

	if (evlist->core.nr_entries == 0) {
		fprintf(stderr, "must define events before cgroups\n");
		return -EINVAL;
	}

	orig_list = evlist__new();
	tmp_list = evlist__new();
	if (orig_list == NULL || tmp_list == NULL) {
		fprintf(stderr, "memory allocation failed\n");
		return -ENOMEM;
	}

	/* save original events and init evlist */
	evlist__splice_list_tail(orig_list, &evlist->core.entries);
	evlist->core.nr_entries = 0;

	orig_metric_events = evlist->metric_events;
	metricgroup__rblist_init(&evlist->metric_events);

	if (has_pattern_string(str))
		prefix_len = match_cgroups(str);
	else
		prefix_len = list_cgroups(str);

	if (prefix_len < 0)
		goto out_err;

	list_for_each_entry(cn, &cgroup_list, list) {
		char *name;

		if (!cn->used)
			continue;

		/* cgroup_name might have a full path, skip the prefix */
		name = cn->name + prefix_len;
		if (name[0] == '/' && name[1])
			name++;

		/* the cgroup can go away in the meantime */
		cgrp = cgroup__new(name, open_cgroup);
		if (cgrp == NULL)
			continue;

		leader = NULL;
		evlist__for_each_entry(orig_list, pos) {
			evsel = evsel__clone(/*dest=*/NULL, pos);
			if (evsel == NULL)
				goto out_err;

			cgroup__put(evsel->cgrp);
			evsel->cgrp = cgroup__get(cgrp);

			if (evsel__is_group_leader(pos))
				leader = evsel;
			evsel__set_leader(evsel, leader);

			evlist__add(tmp_list, evsel);
		}
		/* cgroup__new() has a refcount, release it here */
		cgroup__put(cgrp);
		nr_cgroups++;

		if (metricgroup__copy_metric_events(tmp_list, cgrp,
						    &evlist->metric_events,
						    &orig_metric_events) < 0)
			goto out_err;

		evlist__splice_list_tail(evlist, &tmp_list->core.entries);
		tmp_list->core.nr_entries = 0;
	}

	if (list_empty(&evlist->core.entries)) {
		fprintf(stderr, "no cgroup matched: %s\n", str);
		goto out_err;
	}

	ret = 0;
	cgrp_event_expanded = true;

out_err:
	evlist__delete(orig_list);
	evlist__delete(tmp_list);
	metricgroup__rblist_exit(&orig_metric_events);
	release_cgroup_list();

	return ret;
}

static struct cgroup *__cgroup__findnew(struct rb_root *root, uint64_t id,
					bool create, const char *path)
{
	struct rb_node **p = &root->rb_node;
	struct rb_node *parent = NULL;
	struct cgroup *cgrp;

	while (*p != NULL) {
		parent = *p;
		cgrp = rb_entry(parent, struct cgroup, node);

		if (cgrp->id == id)
			return cgrp;

		if (cgrp->id < id)
			p = &(*p)->rb_left;
		else
			p = &(*p)->rb_right;
	}

	if (!create)
		return NULL;

	cgrp = malloc(sizeof(*cgrp));
	if (cgrp == NULL)
		return NULL;

	cgrp->name = strdup(path);
	if (cgrp->name == NULL) {
		free(cgrp);
		return NULL;
	}

	cgrp->fd = -1;
	cgrp->id = id;
	refcount_set(&cgrp->refcnt, 1);

	rb_link_node(&cgrp->node, parent, p);
	rb_insert_color(&cgrp->node, root);

	return cgrp;
}

struct cgroup *cgroup__findnew(struct perf_env *env, uint64_t id,
			       const char *path)
{
	struct cgroup *cgrp;

	down_write(&env->cgroups.lock);
	cgrp = __cgroup__findnew(&env->cgroups.tree, id, true, path);
	up_write(&env->cgroups.lock);
	return cgrp;
}

struct cgroup *__cgroup__find(struct rb_root *root, uint64_t id)
{
	return __cgroup__findnew(root, id, /*create=*/false, /*path=*/NULL);
}

struct cgroup *cgroup__find(struct perf_env *env, uint64_t id)
{
	struct cgroup *cgrp;

	down_read(&env->cgroups.lock);
	cgrp = __cgroup__findnew(&env->cgroups.tree, id, false, NULL);
	up_read(&env->cgroups.lock);
	return cgrp;
}

void perf_env__purge_cgroups(struct perf_env *env)
{
	struct rb_node *node;
	struct cgroup *cgrp;

	down_write(&env->cgroups.lock);
	while (!RB_EMPTY_ROOT(&env->cgroups.tree)) {
		node = rb_first(&env->cgroups.tree);
		cgrp = rb_entry(node, struct cgroup, node);

		rb_erase(node, &env->cgroups.tree);
		cgroup__put(cgrp);
	}
	up_write(&env->cgroups.lock);
}

void read_all_cgroups(struct rb_root *root)
{
	char mnt[PATH_MAX];
	struct cgroup_name *cn;
	int prefix_len;

	if (cgroupfs_find_mountpoint(mnt, sizeof(mnt), "perf_event"))
		return;

	/* cgroup_name will have a full path, skip the root directory */
	prefix_len = strlen(mnt);

	/* collect all cgroups in the cgroup_list */
	if (nftw(mnt, add_cgroup_name, 20, 0) < 0)
		return;

	list_for_each_entry(cn, &cgroup_list, list) {
		const char *name;
		u64 cgrp_id;

		/* cgroup_name might have a full path, skip the prefix */
		name = cn->name + prefix_len;
		if (name[0] == '\0')
			name = "/";

		cgrp_id = __read_cgroup_id(cn->name);
		__cgroup__findnew(root, cgrp_id, /*create=*/true, name);
	}

	release_cgroup_list();
}