xref: /openbmc/linux/tools/lib/api/fs/fs.c (revision ddc141e5)
1 // SPDX-License-Identifier: GPL-2.0
2 #include <ctype.h>
3 #include <errno.h>
4 #include <limits.h>
5 #include <stdbool.h>
6 #include <stdio.h>
7 #include <stdlib.h>
8 #include <string.h>
9 #include <sys/vfs.h>
10 #include <sys/types.h>
11 #include <sys/stat.h>
12 #include <fcntl.h>
13 #include <unistd.h>
14 #include <sys/mount.h>
15 
16 #include "fs.h"
17 #include "debug-internal.h"
18 
19 #define _STR(x) #x
20 #define STR(x) _STR(x)
21 
22 #ifndef SYSFS_MAGIC
23 #define SYSFS_MAGIC            0x62656572
24 #endif
25 
26 #ifndef PROC_SUPER_MAGIC
27 #define PROC_SUPER_MAGIC       0x9fa0
28 #endif
29 
30 #ifndef DEBUGFS_MAGIC
31 #define DEBUGFS_MAGIC          0x64626720
32 #endif
33 
34 #ifndef TRACEFS_MAGIC
35 #define TRACEFS_MAGIC          0x74726163
36 #endif
37 
38 #ifndef HUGETLBFS_MAGIC
39 #define HUGETLBFS_MAGIC        0x958458f6
40 #endif
41 
42 #ifndef BPF_FS_MAGIC
43 #define BPF_FS_MAGIC           0xcafe4a11
44 #endif
45 
46 static const char * const sysfs__fs_known_mountpoints[] = {
47 	"/sys",
48 	0,
49 };
50 
51 static const char * const procfs__known_mountpoints[] = {
52 	"/proc",
53 	0,
54 };
55 
56 #ifndef DEBUGFS_DEFAULT_PATH
57 #define DEBUGFS_DEFAULT_PATH "/sys/kernel/debug"
58 #endif
59 
60 static const char * const debugfs__known_mountpoints[] = {
61 	DEBUGFS_DEFAULT_PATH,
62 	"/debug",
63 	0,
64 };
65 
66 
67 #ifndef TRACEFS_DEFAULT_PATH
68 #define TRACEFS_DEFAULT_PATH "/sys/kernel/tracing"
69 #endif
70 
71 static const char * const tracefs__known_mountpoints[] = {
72 	TRACEFS_DEFAULT_PATH,
73 	"/sys/kernel/debug/tracing",
74 	"/tracing",
75 	"/trace",
76 	0,
77 };
78 
79 static const char * const hugetlbfs__known_mountpoints[] = {
80 	0,
81 };
82 
83 static const char * const bpf_fs__known_mountpoints[] = {
84 	"/sys/fs/bpf",
85 	0,
86 };
87 
88 struct fs {
89 	const char		*name;
90 	const char * const	*mounts;
91 	char			 path[PATH_MAX];
92 	bool			 found;
93 	long			 magic;
94 };
95 
96 enum {
97 	FS__SYSFS   = 0,
98 	FS__PROCFS  = 1,
99 	FS__DEBUGFS = 2,
100 	FS__TRACEFS = 3,
101 	FS__HUGETLBFS = 4,
102 	FS__BPF_FS = 5,
103 };
104 
105 #ifndef TRACEFS_MAGIC
106 #define TRACEFS_MAGIC 0x74726163
107 #endif
108 
109 static struct fs fs__entries[] = {
110 	[FS__SYSFS] = {
111 		.name	= "sysfs",
112 		.mounts	= sysfs__fs_known_mountpoints,
113 		.magic	= SYSFS_MAGIC,
114 	},
115 	[FS__PROCFS] = {
116 		.name	= "proc",
117 		.mounts	= procfs__known_mountpoints,
118 		.magic	= PROC_SUPER_MAGIC,
119 	},
120 	[FS__DEBUGFS] = {
121 		.name	= "debugfs",
122 		.mounts	= debugfs__known_mountpoints,
123 		.magic	= DEBUGFS_MAGIC,
124 	},
125 	[FS__TRACEFS] = {
126 		.name	= "tracefs",
127 		.mounts	= tracefs__known_mountpoints,
128 		.magic	= TRACEFS_MAGIC,
129 	},
130 	[FS__HUGETLBFS] = {
131 		.name	= "hugetlbfs",
132 		.mounts = hugetlbfs__known_mountpoints,
133 		.magic	= HUGETLBFS_MAGIC,
134 	},
135 	[FS__BPF_FS] = {
136 		.name	= "bpf",
137 		.mounts = bpf_fs__known_mountpoints,
138 		.magic	= BPF_FS_MAGIC,
139 	},
140 };
141 
142 static bool fs__read_mounts(struct fs *fs)
143 {
144 	bool found = false;
145 	char type[100];
146 	FILE *fp;
147 
148 	fp = fopen("/proc/mounts", "r");
149 	if (fp == NULL)
150 		return NULL;
151 
152 	while (!found &&
153 	       fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
154 		      fs->path, type) == 2) {
155 
156 		if (strcmp(type, fs->name) == 0)
157 			found = true;
158 	}
159 
160 	fclose(fp);
161 	return fs->found = found;
162 }
163 
164 static int fs__valid_mount(const char *fs, long magic)
165 {
166 	struct statfs st_fs;
167 
168 	if (statfs(fs, &st_fs) < 0)
169 		return -ENOENT;
170 	else if ((long)st_fs.f_type != magic)
171 		return -ENOENT;
172 
173 	return 0;
174 }
175 
176 static bool fs__check_mounts(struct fs *fs)
177 {
178 	const char * const *ptr;
179 
180 	ptr = fs->mounts;
181 	while (*ptr) {
182 		if (fs__valid_mount(*ptr, fs->magic) == 0) {
183 			fs->found = true;
184 			strcpy(fs->path, *ptr);
185 			return true;
186 		}
187 		ptr++;
188 	}
189 
190 	return false;
191 }
192 
193 static void mem_toupper(char *f, size_t len)
194 {
195 	while (len) {
196 		*f = toupper(*f);
197 		f++;
198 		len--;
199 	}
200 }
201 
202 /*
203  * Check for "NAME_PATH" environment variable to override fs location (for
204  * testing). This matches the recommendation in Documentation/sysfs-rules.txt
205  * for SYSFS_PATH.
206  */
207 static bool fs__env_override(struct fs *fs)
208 {
209 	char *override_path;
210 	size_t name_len = strlen(fs->name);
211 	/* name + "_PATH" + '\0' */
212 	char upper_name[name_len + 5 + 1];
213 	memcpy(upper_name, fs->name, name_len);
214 	mem_toupper(upper_name, name_len);
215 	strcpy(&upper_name[name_len], "_PATH");
216 
217 	override_path = getenv(upper_name);
218 	if (!override_path)
219 		return false;
220 
221 	fs->found = true;
222 	strncpy(fs->path, override_path, sizeof(fs->path));
223 	return true;
224 }
225 
226 static const char *fs__get_mountpoint(struct fs *fs)
227 {
228 	if (fs__env_override(fs))
229 		return fs->path;
230 
231 	if (fs__check_mounts(fs))
232 		return fs->path;
233 
234 	if (fs__read_mounts(fs))
235 		return fs->path;
236 
237 	return NULL;
238 }
239 
240 static const char *fs__mountpoint(int idx)
241 {
242 	struct fs *fs = &fs__entries[idx];
243 
244 	if (fs->found)
245 		return (const char *)fs->path;
246 
247 	return fs__get_mountpoint(fs);
248 }
249 
250 static const char *mount_overload(struct fs *fs)
251 {
252 	size_t name_len = strlen(fs->name);
253 	/* "PERF_" + name + "_ENVIRONMENT" + '\0' */
254 	char upper_name[5 + name_len + 12 + 1];
255 
256 	snprintf(upper_name, name_len, "PERF_%s_ENVIRONMENT", fs->name);
257 	mem_toupper(upper_name, name_len);
258 
259 	return getenv(upper_name) ?: *fs->mounts;
260 }
261 
262 static const char *fs__mount(int idx)
263 {
264 	struct fs *fs = &fs__entries[idx];
265 	const char *mountpoint;
266 
267 	if (fs__mountpoint(idx))
268 		return (const char *)fs->path;
269 
270 	mountpoint = mount_overload(fs);
271 
272 	if (mount(NULL, mountpoint, fs->name, 0, NULL) < 0)
273 		return NULL;
274 
275 	return fs__check_mounts(fs) ? fs->path : NULL;
276 }
277 
278 #define FS(name, idx)				\
279 const char *name##__mountpoint(void)		\
280 {						\
281 	return fs__mountpoint(idx);		\
282 }						\
283 						\
284 const char *name##__mount(void)			\
285 {						\
286 	return fs__mount(idx);			\
287 }						\
288 						\
289 bool name##__configured(void)			\
290 {						\
291 	return name##__mountpoint() != NULL;	\
292 }
293 
294 FS(sysfs,   FS__SYSFS);
295 FS(procfs,  FS__PROCFS);
296 FS(debugfs, FS__DEBUGFS);
297 FS(tracefs, FS__TRACEFS);
298 FS(hugetlbfs, FS__HUGETLBFS);
299 FS(bpf_fs, FS__BPF_FS);
300 
301 int filename__read_int(const char *filename, int *value)
302 {
303 	char line[64];
304 	int fd = open(filename, O_RDONLY), err = -1;
305 
306 	if (fd < 0)
307 		return -1;
308 
309 	if (read(fd, line, sizeof(line)) > 0) {
310 		*value = atoi(line);
311 		err = 0;
312 	}
313 
314 	close(fd);
315 	return err;
316 }
317 
318 /*
319  * Parses @value out of @filename with strtoull.
320  * By using 0 for base, the strtoull detects the
321  * base automatically (see man strtoull).
322  */
323 int filename__read_ull(const char *filename, unsigned long long *value)
324 {
325 	char line[64];
326 	int fd = open(filename, O_RDONLY), err = -1;
327 
328 	if (fd < 0)
329 		return -1;
330 
331 	if (read(fd, line, sizeof(line)) > 0) {
332 		*value = strtoull(line, NULL, 0);
333 		if (*value != ULLONG_MAX)
334 			err = 0;
335 	}
336 
337 	close(fd);
338 	return err;
339 }
340 
341 #define STRERR_BUFSIZE  128     /* For the buffer size of strerror_r */
342 
343 int filename__read_str(const char *filename, char **buf, size_t *sizep)
344 {
345 	size_t size = 0, alloc_size = 0;
346 	void *bf = NULL, *nbf;
347 	int fd, n, err = 0;
348 	char sbuf[STRERR_BUFSIZE];
349 
350 	fd = open(filename, O_RDONLY);
351 	if (fd < 0)
352 		return -errno;
353 
354 	do {
355 		if (size == alloc_size) {
356 			alloc_size += BUFSIZ;
357 			nbf = realloc(bf, alloc_size);
358 			if (!nbf) {
359 				err = -ENOMEM;
360 				break;
361 			}
362 
363 			bf = nbf;
364 		}
365 
366 		n = read(fd, bf + size, alloc_size - size);
367 		if (n < 0) {
368 			if (size) {
369 				pr_warning("read failed %d: %s\n", errno,
370 					 strerror_r(errno, sbuf, sizeof(sbuf)));
371 				err = 0;
372 			} else
373 				err = -errno;
374 
375 			break;
376 		}
377 
378 		size += n;
379 	} while (n > 0);
380 
381 	if (!err) {
382 		*sizep = size;
383 		*buf   = bf;
384 	} else
385 		free(bf);
386 
387 	close(fd);
388 	return err;
389 }
390 
391 int filename__write_int(const char *filename, int value)
392 {
393 	int fd = open(filename, O_WRONLY), err = -1;
394 	char buf[64];
395 
396 	if (fd < 0)
397 		return err;
398 
399 	sprintf(buf, "%d", value);
400 	if (write(fd, buf, sizeof(buf)) == sizeof(buf))
401 		err = 0;
402 
403 	close(fd);
404 	return err;
405 }
406 
407 int procfs__read_str(const char *entry, char **buf, size_t *sizep)
408 {
409 	char path[PATH_MAX];
410 	const char *procfs = procfs__mountpoint();
411 
412 	if (!procfs)
413 		return -1;
414 
415 	snprintf(path, sizeof(path), "%s/%s", procfs, entry);
416 
417 	return filename__read_str(path, buf, sizep);
418 }
419 
420 int sysfs__read_ull(const char *entry, unsigned long long *value)
421 {
422 	char path[PATH_MAX];
423 	const char *sysfs = sysfs__mountpoint();
424 
425 	if (!sysfs)
426 		return -1;
427 
428 	snprintf(path, sizeof(path), "%s/%s", sysfs, entry);
429 
430 	return filename__read_ull(path, value);
431 }
432 
433 int sysfs__read_int(const char *entry, int *value)
434 {
435 	char path[PATH_MAX];
436 	const char *sysfs = sysfs__mountpoint();
437 
438 	if (!sysfs)
439 		return -1;
440 
441 	snprintf(path, sizeof(path), "%s/%s", sysfs, entry);
442 
443 	return filename__read_int(path, value);
444 }
445 
446 int sysfs__read_str(const char *entry, char **buf, size_t *sizep)
447 {
448 	char path[PATH_MAX];
449 	const char *sysfs = sysfs__mountpoint();
450 
451 	if (!sysfs)
452 		return -1;
453 
454 	snprintf(path, sizeof(path), "%s/%s", sysfs, entry);
455 
456 	return filename__read_str(path, buf, sizep);
457 }
458 
459 int sysfs__read_bool(const char *entry, bool *value)
460 {
461 	char *buf;
462 	size_t size;
463 	int ret;
464 
465 	ret = sysfs__read_str(entry, &buf, &size);
466 	if (ret < 0)
467 		return ret;
468 
469 	switch (buf[0]) {
470 	case '1':
471 	case 'y':
472 	case 'Y':
473 		*value = true;
474 		break;
475 	case '0':
476 	case 'n':
477 	case 'N':
478 		*value = false;
479 		break;
480 	default:
481 		ret = -1;
482 	}
483 
484 	free(buf);
485 
486 	return ret;
487 }
488 int sysctl__read_int(const char *sysctl, int *value)
489 {
490 	char path[PATH_MAX];
491 	const char *procfs = procfs__mountpoint();
492 
493 	if (!procfs)
494 		return -1;
495 
496 	snprintf(path, sizeof(path), "%s/sys/%s", procfs, sysctl);
497 
498 	return filename__read_int(path, value);
499 }
500 
501 int sysfs__write_int(const char *entry, int value)
502 {
503 	char path[PATH_MAX];
504 	const char *sysfs = sysfs__mountpoint();
505 
506 	if (!sysfs)
507 		return -1;
508 
509 	if (snprintf(path, sizeof(path), "%s/%s", sysfs, entry) >= PATH_MAX)
510 		return -1;
511 
512 	return filename__write_int(path, value);
513 }
514