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(fs, "cgroup") == 0 &&
195 		    strcmp(type, "cgroup2") == 0) {
196 			strncpy(root, mount, len);
197 			return 0;
198 		}
199 	}
200 
201 	return -1;
202 }
203 
204 int cg_create(const char *cgroup)
205 {
206 	return mkdir(cgroup, 0644);
207 }
208 
209 int cg_wait_for_proc_count(const char *cgroup, int count)
210 {
211 	char buf[10 * PAGE_SIZE] = {0};
212 	int attempts;
213 	char *ptr;
214 
215 	for (attempts = 10; attempts >= 0; attempts--) {
216 		int nr = 0;
217 
218 		if (cg_read(cgroup, "cgroup.procs", buf, sizeof(buf)))
219 			break;
220 
221 		for (ptr = buf; *ptr; ptr++)
222 			if (*ptr == '\n')
223 				nr++;
224 
225 		if (nr >= count)
226 			return 0;
227 
228 		usleep(100000);
229 	}
230 
231 	return -1;
232 }
233 
234 int cg_killall(const char *cgroup)
235 {
236 	char buf[PAGE_SIZE];
237 	char *ptr = buf;
238 
239 	if (cg_read(cgroup, "cgroup.procs", buf, sizeof(buf)))
240 		return -1;
241 
242 	while (ptr < buf + sizeof(buf)) {
243 		int pid = strtol(ptr, &ptr, 10);
244 
245 		if (pid == 0)
246 			break;
247 		if (*ptr)
248 			ptr++;
249 		else
250 			break;
251 		if (kill(pid, SIGKILL))
252 			return -1;
253 	}
254 
255 	return 0;
256 }
257 
258 int cg_destroy(const char *cgroup)
259 {
260 	int ret;
261 
262 retry:
263 	ret = rmdir(cgroup);
264 	if (ret && errno == EBUSY) {
265 		cg_killall(cgroup);
266 		usleep(100);
267 		goto retry;
268 	}
269 
270 	if (ret && errno == ENOENT)
271 		ret = 0;
272 
273 	return ret;
274 }
275 
276 int cg_enter(const char *cgroup, int pid)
277 {
278 	char pidbuf[64];
279 
280 	snprintf(pidbuf, sizeof(pidbuf), "%d", pid);
281 	return cg_write(cgroup, "cgroup.procs", pidbuf);
282 }
283 
284 int cg_enter_current(const char *cgroup)
285 {
286 	char pidbuf[64];
287 
288 	snprintf(pidbuf, sizeof(pidbuf), "%d", getpid());
289 	return cg_write(cgroup, "cgroup.procs", pidbuf);
290 }
291 
292 int cg_run(const char *cgroup,
293 	   int (*fn)(const char *cgroup, void *arg),
294 	   void *arg)
295 {
296 	int pid, retcode;
297 
298 	pid = fork();
299 	if (pid < 0) {
300 		return pid;
301 	} else if (pid == 0) {
302 		char buf[64];
303 
304 		snprintf(buf, sizeof(buf), "%d", getpid());
305 		if (cg_write(cgroup, "cgroup.procs", buf))
306 			exit(EXIT_FAILURE);
307 		exit(fn(cgroup, arg));
308 	} else {
309 		waitpid(pid, &retcode, 0);
310 		if (WIFEXITED(retcode))
311 			return WEXITSTATUS(retcode);
312 		else
313 			return -1;
314 	}
315 }
316 
317 int cg_run_nowait(const char *cgroup,
318 		  int (*fn)(const char *cgroup, void *arg),
319 		  void *arg)
320 {
321 	int pid;
322 
323 	pid = fork();
324 	if (pid == 0) {
325 		char buf[64];
326 
327 		snprintf(buf, sizeof(buf), "%d", getpid());
328 		if (cg_write(cgroup, "cgroup.procs", buf))
329 			exit(EXIT_FAILURE);
330 		exit(fn(cgroup, arg));
331 	}
332 
333 	return pid;
334 }
335 
336 int get_temp_fd(void)
337 {
338 	return open(".", O_TMPFILE | O_RDWR | O_EXCL);
339 }
340 
341 int alloc_pagecache(int fd, size_t size)
342 {
343 	char buf[PAGE_SIZE];
344 	struct stat st;
345 	int i;
346 
347 	if (fstat(fd, &st))
348 		goto cleanup;
349 
350 	size += st.st_size;
351 
352 	if (ftruncate(fd, size))
353 		goto cleanup;
354 
355 	for (i = 0; i < size; i += sizeof(buf))
356 		read(fd, buf, sizeof(buf));
357 
358 	return 0;
359 
360 cleanup:
361 	return -1;
362 }
363 
364 int alloc_anon(const char *cgroup, void *arg)
365 {
366 	size_t size = (unsigned long)arg;
367 	char *buf, *ptr;
368 
369 	buf = malloc(size);
370 	for (ptr = buf; ptr < buf + size; ptr += PAGE_SIZE)
371 		*ptr = 0;
372 
373 	free(buf);
374 	return 0;
375 }
376 
377 int is_swap_enabled(void)
378 {
379 	char buf[PAGE_SIZE];
380 	const char delim[] = "\n";
381 	int cnt = 0;
382 	char *line;
383 
384 	if (read_text("/proc/swaps", buf, sizeof(buf)) <= 0)
385 		return -1;
386 
387 	for (line = strtok(buf, delim); line; line = strtok(NULL, delim))
388 		cnt++;
389 
390 	return cnt > 1;
391 }
392 
393 int set_oom_adj_score(int pid, int score)
394 {
395 	char path[PATH_MAX];
396 	int fd, len;
397 
398 	sprintf(path, "/proc/%d/oom_score_adj", pid);
399 
400 	fd = open(path, O_WRONLY | O_APPEND);
401 	if (fd < 0)
402 		return fd;
403 
404 	len = dprintf(fd, "%d", score);
405 	if (len < 0) {
406 		close(fd);
407 		return len;
408 	}
409 
410 	close(fd);
411 	return 0;
412 }
413 
414 char proc_read_text(int pid, const char *item, char *buf, size_t size)
415 {
416 	char path[PATH_MAX];
417 
418 	snprintf(path, sizeof(path), "/proc/%d/%s", pid, item);
419 
420 	return read_text(path, buf, size);
421 }
422