1 /* SPDX-License-Identifier: GPL-2.0 */
2 
3 #define _GNU_SOURCE
4 
5 #include <errno.h>
6 #include <fcntl.h>
7 #include <linux/limits.h>
8 #include <signal.h>
9 #include <stdio.h>
10 #include <stdlib.h>
11 #include <string.h>
12 #include <sys/stat.h>
13 #include <sys/types.h>
14 #include <sys/wait.h>
15 #include <unistd.h>
16 
17 #include "cgroup_util.h"
18 
19 static ssize_t read_text(const char *path, char *buf, size_t max_len)
20 {
21 	ssize_t len;
22 	int fd;
23 
24 	fd = open(path, O_RDONLY);
25 	if (fd < 0)
26 		return fd;
27 
28 	len = read(fd, buf, max_len - 1);
29 	if (len < 0)
30 		goto out;
31 
32 	buf[len] = 0;
33 out:
34 	close(fd);
35 	return len;
36 }
37 
38 static ssize_t write_text(const char *path, char *buf, ssize_t len)
39 {
40 	int fd;
41 
42 	fd = open(path, O_WRONLY | O_APPEND);
43 	if (fd < 0)
44 		return fd;
45 
46 	len = write(fd, buf, len);
47 	if (len < 0) {
48 		close(fd);
49 		return len;
50 	}
51 
52 	close(fd);
53 
54 	return len;
55 }
56 
57 char *cg_name(const char *root, const char *name)
58 {
59 	size_t len = strlen(root) + strlen(name) + 2;
60 	char *ret = malloc(len);
61 
62 	snprintf(ret, len, "%s/%s", root, name);
63 
64 	return ret;
65 }
66 
67 char *cg_name_indexed(const char *root, const char *name, int index)
68 {
69 	size_t len = strlen(root) + strlen(name) + 10;
70 	char *ret = malloc(len);
71 
72 	snprintf(ret, len, "%s/%s_%d", root, name, index);
73 
74 	return ret;
75 }
76 
77 char *cg_control(const char *cgroup, const char *control)
78 {
79 	size_t len = strlen(cgroup) + strlen(control) + 2;
80 	char *ret = malloc(len);
81 
82 	snprintf(ret, len, "%s/%s", cgroup, control);
83 
84 	return ret;
85 }
86 
87 int cg_read(const char *cgroup, const char *control, char *buf, size_t len)
88 {
89 	char path[PATH_MAX];
90 
91 	snprintf(path, sizeof(path), "%s/%s", cgroup, control);
92 
93 	if (read_text(path, buf, len) >= 0)
94 		return 0;
95 
96 	return -1;
97 }
98 
99 int cg_read_strcmp(const char *cgroup, const char *control,
100 		   const char *expected)
101 {
102 	size_t size;
103 	char *buf;
104 	int ret;
105 
106 	/* Handle the case of comparing against empty string */
107 	if (!expected)
108 		size = 32;
109 	else
110 		size = strlen(expected) + 1;
111 
112 	buf = malloc(size);
113 	if (!buf)
114 		return -1;
115 
116 	if (cg_read(cgroup, control, buf, size)) {
117 		free(buf);
118 		return -1;
119 	}
120 
121 	ret = strcmp(expected, buf);
122 	free(buf);
123 	return ret;
124 }
125 
126 int cg_read_strstr(const char *cgroup, const char *control, const char *needle)
127 {
128 	char buf[PAGE_SIZE];
129 
130 	if (cg_read(cgroup, control, buf, sizeof(buf)))
131 		return -1;
132 
133 	return strstr(buf, needle) ? 0 : -1;
134 }
135 
136 long cg_read_long(const char *cgroup, const char *control)
137 {
138 	char buf[128];
139 
140 	if (cg_read(cgroup, control, buf, sizeof(buf)))
141 		return -1;
142 
143 	return atol(buf);
144 }
145 
146 long cg_read_key_long(const char *cgroup, const char *control, const char *key)
147 {
148 	char buf[PAGE_SIZE];
149 	char *ptr;
150 
151 	if (cg_read(cgroup, control, buf, sizeof(buf)))
152 		return -1;
153 
154 	ptr = strstr(buf, key);
155 	if (!ptr)
156 		return -1;
157 
158 	return atol(ptr + strlen(key));
159 }
160 
161 int cg_write(const char *cgroup, const char *control, char *buf)
162 {
163 	char path[PATH_MAX];
164 	ssize_t len = strlen(buf);
165 
166 	snprintf(path, sizeof(path), "%s/%s", cgroup, control);
167 
168 	if (write_text(path, buf, len) == len)
169 		return 0;
170 
171 	return -1;
172 }
173 
174 int cg_find_unified_root(char *root, size_t len)
175 {
176 	char buf[10 * PAGE_SIZE];
177 	char *fs, *mount, *type;
178 	const char delim[] = "\n\t ";
179 
180 	if (read_text("/proc/self/mounts", buf, sizeof(buf)) <= 0)
181 		return -1;
182 
183 	/*
184 	 * Example:
185 	 * cgroup /sys/fs/cgroup cgroup2 rw,seclabel,noexec,relatime 0 0
186 	 */
187 	for (fs = strtok(buf, delim); fs; fs = strtok(NULL, delim)) {
188 		mount = strtok(NULL, delim);
189 		type = strtok(NULL, delim);
190 		strtok(NULL, delim);
191 		strtok(NULL, delim);
192 		strtok(NULL, delim);
193 
194 		if (strcmp(type, "cgroup2") == 0) {
195 			strncpy(root, mount, len);
196 			return 0;
197 		}
198 	}
199 
200 	return -1;
201 }
202 
203 int cg_create(const char *cgroup)
204 {
205 	return mkdir(cgroup, 0644);
206 }
207 
208 int cg_wait_for_proc_count(const char *cgroup, int count)
209 {
210 	char buf[10 * PAGE_SIZE] = {0};
211 	int attempts;
212 	char *ptr;
213 
214 	for (attempts = 10; attempts >= 0; attempts--) {
215 		int nr = 0;
216 
217 		if (cg_read(cgroup, "cgroup.procs", buf, sizeof(buf)))
218 			break;
219 
220 		for (ptr = buf; *ptr; ptr++)
221 			if (*ptr == '\n')
222 				nr++;
223 
224 		if (nr >= count)
225 			return 0;
226 
227 		usleep(100000);
228 	}
229 
230 	return -1;
231 }
232 
233 int cg_killall(const char *cgroup)
234 {
235 	char buf[PAGE_SIZE];
236 	char *ptr = buf;
237 
238 	if (cg_read(cgroup, "cgroup.procs", buf, sizeof(buf)))
239 		return -1;
240 
241 	while (ptr < buf + sizeof(buf)) {
242 		int pid = strtol(ptr, &ptr, 10);
243 
244 		if (pid == 0)
245 			break;
246 		if (*ptr)
247 			ptr++;
248 		else
249 			break;
250 		if (kill(pid, SIGKILL))
251 			return -1;
252 	}
253 
254 	return 0;
255 }
256 
257 int cg_destroy(const char *cgroup)
258 {
259 	int ret;
260 
261 retry:
262 	ret = rmdir(cgroup);
263 	if (ret && errno == EBUSY) {
264 		cg_killall(cgroup);
265 		usleep(100);
266 		goto retry;
267 	}
268 
269 	if (ret && errno == ENOENT)
270 		ret = 0;
271 
272 	return ret;
273 }
274 
275 int cg_enter(const char *cgroup, int pid)
276 {
277 	char pidbuf[64];
278 
279 	snprintf(pidbuf, sizeof(pidbuf), "%d", pid);
280 	return cg_write(cgroup, "cgroup.procs", pidbuf);
281 }
282 
283 int cg_enter_current(const char *cgroup)
284 {
285 	return cg_write(cgroup, "cgroup.procs", "0");
286 }
287 
288 int cg_enter_current_thread(const char *cgroup)
289 {
290 	return cg_write(cgroup, "cgroup.threads", "0");
291 }
292 
293 int cg_run(const char *cgroup,
294 	   int (*fn)(const char *cgroup, void *arg),
295 	   void *arg)
296 {
297 	int pid, retcode;
298 
299 	pid = fork();
300 	if (pid < 0) {
301 		return pid;
302 	} else if (pid == 0) {
303 		char buf[64];
304 
305 		snprintf(buf, sizeof(buf), "%d", getpid());
306 		if (cg_write(cgroup, "cgroup.procs", buf))
307 			exit(EXIT_FAILURE);
308 		exit(fn(cgroup, arg));
309 	} else {
310 		waitpid(pid, &retcode, 0);
311 		if (WIFEXITED(retcode))
312 			return WEXITSTATUS(retcode);
313 		else
314 			return -1;
315 	}
316 }
317 
318 int cg_run_nowait(const char *cgroup,
319 		  int (*fn)(const char *cgroup, void *arg),
320 		  void *arg)
321 {
322 	int pid;
323 
324 	pid = fork();
325 	if (pid == 0) {
326 		char buf[64];
327 
328 		snprintf(buf, sizeof(buf), "%d", getpid());
329 		if (cg_write(cgroup, "cgroup.procs", buf))
330 			exit(EXIT_FAILURE);
331 		exit(fn(cgroup, arg));
332 	}
333 
334 	return pid;
335 }
336 
337 int get_temp_fd(void)
338 {
339 	return open(".", O_TMPFILE | O_RDWR | O_EXCL);
340 }
341 
342 int alloc_pagecache(int fd, size_t size)
343 {
344 	char buf[PAGE_SIZE];
345 	struct stat st;
346 	int i;
347 
348 	if (fstat(fd, &st))
349 		goto cleanup;
350 
351 	size += st.st_size;
352 
353 	if (ftruncate(fd, size))
354 		goto cleanup;
355 
356 	for (i = 0; i < size; i += sizeof(buf))
357 		read(fd, buf, sizeof(buf));
358 
359 	return 0;
360 
361 cleanup:
362 	return -1;
363 }
364 
365 int alloc_anon(const char *cgroup, void *arg)
366 {
367 	size_t size = (unsigned long)arg;
368 	char *buf, *ptr;
369 
370 	buf = malloc(size);
371 	for (ptr = buf; ptr < buf + size; ptr += PAGE_SIZE)
372 		*ptr = 0;
373 
374 	free(buf);
375 	return 0;
376 }
377 
378 int is_swap_enabled(void)
379 {
380 	char buf[PAGE_SIZE];
381 	const char delim[] = "\n";
382 	int cnt = 0;
383 	char *line;
384 
385 	if (read_text("/proc/swaps", buf, sizeof(buf)) <= 0)
386 		return -1;
387 
388 	for (line = strtok(buf, delim); line; line = strtok(NULL, delim))
389 		cnt++;
390 
391 	return cnt > 1;
392 }
393 
394 int set_oom_adj_score(int pid, int score)
395 {
396 	char path[PATH_MAX];
397 	int fd, len;
398 
399 	sprintf(path, "/proc/%d/oom_score_adj", pid);
400 
401 	fd = open(path, O_WRONLY | O_APPEND);
402 	if (fd < 0)
403 		return fd;
404 
405 	len = dprintf(fd, "%d", score);
406 	if (len < 0) {
407 		close(fd);
408 		return len;
409 	}
410 
411 	close(fd);
412 	return 0;
413 }
414 
415 ssize_t proc_read_text(int pid, bool thread, const char *item, char *buf, size_t size)
416 {
417 	char path[PATH_MAX];
418 
419 	if (!pid)
420 		snprintf(path, sizeof(path), "/proc/%s/%s",
421 			 thread ? "thread-self" : "self", item);
422 	else
423 		snprintf(path, sizeof(path), "/proc/%d/%s", pid, item);
424 
425 	return read_text(path, buf, size);
426 }
427