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 	bool			 checked;
94 	long			 magic;
95 };
96 
97 enum {
98 	FS__SYSFS   = 0,
99 	FS__PROCFS  = 1,
100 	FS__DEBUGFS = 2,
101 	FS__TRACEFS = 3,
102 	FS__HUGETLBFS = 4,
103 	FS__BPF_FS = 5,
104 };
105 
106 #ifndef TRACEFS_MAGIC
107 #define TRACEFS_MAGIC 0x74726163
108 #endif
109 
110 static struct fs fs__entries[] = {
111 	[FS__SYSFS] = {
112 		.name	= "sysfs",
113 		.mounts	= sysfs__fs_known_mountpoints,
114 		.magic	= SYSFS_MAGIC,
115 		.checked = false,
116 	},
117 	[FS__PROCFS] = {
118 		.name	= "proc",
119 		.mounts	= procfs__known_mountpoints,
120 		.magic	= PROC_SUPER_MAGIC,
121 		.checked = false,
122 	},
123 	[FS__DEBUGFS] = {
124 		.name	= "debugfs",
125 		.mounts	= debugfs__known_mountpoints,
126 		.magic	= DEBUGFS_MAGIC,
127 		.checked = false,
128 	},
129 	[FS__TRACEFS] = {
130 		.name	= "tracefs",
131 		.mounts	= tracefs__known_mountpoints,
132 		.magic	= TRACEFS_MAGIC,
133 		.checked = false,
134 	},
135 	[FS__HUGETLBFS] = {
136 		.name	= "hugetlbfs",
137 		.mounts = hugetlbfs__known_mountpoints,
138 		.magic	= HUGETLBFS_MAGIC,
139 		.checked = false,
140 	},
141 	[FS__BPF_FS] = {
142 		.name	= "bpf",
143 		.mounts = bpf_fs__known_mountpoints,
144 		.magic	= BPF_FS_MAGIC,
145 		.checked = false,
146 	},
147 };
148 
fs__read_mounts(struct fs * fs)149 static bool fs__read_mounts(struct fs *fs)
150 {
151 	bool found = false;
152 	char type[100];
153 	FILE *fp;
154 
155 	fp = fopen("/proc/mounts", "r");
156 	if (fp == NULL)
157 		return NULL;
158 
159 	while (!found &&
160 	       fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
161 		      fs->path, type) == 2) {
162 
163 		if (strcmp(type, fs->name) == 0)
164 			found = true;
165 	}
166 
167 	fclose(fp);
168 	fs->checked = true;
169 	return fs->found = found;
170 }
171 
fs__valid_mount(const char * fs,long magic)172 static int fs__valid_mount(const char *fs, long magic)
173 {
174 	struct statfs st_fs;
175 
176 	if (statfs(fs, &st_fs) < 0)
177 		return -ENOENT;
178 	else if ((long)st_fs.f_type != magic)
179 		return -ENOENT;
180 
181 	return 0;
182 }
183 
fs__check_mounts(struct fs * fs)184 static bool fs__check_mounts(struct fs *fs)
185 {
186 	const char * const *ptr;
187 
188 	ptr = fs->mounts;
189 	while (*ptr) {
190 		if (fs__valid_mount(*ptr, fs->magic) == 0) {
191 			fs->found = true;
192 			strcpy(fs->path, *ptr);
193 			return true;
194 		}
195 		ptr++;
196 	}
197 
198 	return false;
199 }
200 
mem_toupper(char * f,size_t len)201 static void mem_toupper(char *f, size_t len)
202 {
203 	while (len) {
204 		*f = toupper(*f);
205 		f++;
206 		len--;
207 	}
208 }
209 
210 /*
211  * Check for "NAME_PATH" environment variable to override fs location (for
212  * testing). This matches the recommendation in Documentation/admin-guide/sysfs-rules.rst
213  * for SYSFS_PATH.
214  */
fs__env_override(struct fs * fs)215 static bool fs__env_override(struct fs *fs)
216 {
217 	char *override_path;
218 	size_t name_len = strlen(fs->name);
219 	/* name + "_PATH" + '\0' */
220 	char upper_name[name_len + 5 + 1];
221 
222 	memcpy(upper_name, fs->name, name_len);
223 	mem_toupper(upper_name, name_len);
224 	strcpy(&upper_name[name_len], "_PATH");
225 
226 	override_path = getenv(upper_name);
227 	if (!override_path)
228 		return false;
229 
230 	fs->found = true;
231 	fs->checked = true;
232 	strncpy(fs->path, override_path, sizeof(fs->path) - 1);
233 	fs->path[sizeof(fs->path) - 1] = '\0';
234 	return true;
235 }
236 
fs__get_mountpoint(struct fs * fs)237 static const char *fs__get_mountpoint(struct fs *fs)
238 {
239 	if (fs__env_override(fs))
240 		return fs->path;
241 
242 	if (fs__check_mounts(fs))
243 		return fs->path;
244 
245 	if (fs__read_mounts(fs))
246 		return fs->path;
247 
248 	return NULL;
249 }
250 
fs__mountpoint(int idx)251 static const char *fs__mountpoint(int idx)
252 {
253 	struct fs *fs = &fs__entries[idx];
254 
255 	if (fs->found)
256 		return (const char *)fs->path;
257 
258 	/* the mount point was already checked for the mount point
259 	 * but and did not exist, so return NULL to avoid scanning again.
260 	 * This makes the found and not found paths cost equivalent
261 	 * in case of multiple calls.
262 	 */
263 	if (fs->checked)
264 		return NULL;
265 
266 	return fs__get_mountpoint(fs);
267 }
268 
mount_overload(struct fs * fs)269 static const char *mount_overload(struct fs *fs)
270 {
271 	size_t name_len = strlen(fs->name);
272 	/* "PERF_" + name + "_ENVIRONMENT" + '\0' */
273 	char upper_name[5 + name_len + 12 + 1];
274 
275 	snprintf(upper_name, name_len, "PERF_%s_ENVIRONMENT", fs->name);
276 	mem_toupper(upper_name, name_len);
277 
278 	return getenv(upper_name) ?: *fs->mounts;
279 }
280 
fs__mount(int idx)281 static const char *fs__mount(int idx)
282 {
283 	struct fs *fs = &fs__entries[idx];
284 	const char *mountpoint;
285 
286 	if (fs__mountpoint(idx))
287 		return (const char *)fs->path;
288 
289 	mountpoint = mount_overload(fs);
290 
291 	if (mount(NULL, mountpoint, fs->name, 0, NULL) < 0)
292 		return NULL;
293 
294 	return fs__check_mounts(fs) ? fs->path : NULL;
295 }
296 
297 #define FS(name, idx)				\
298 const char *name##__mountpoint(void)		\
299 {						\
300 	return fs__mountpoint(idx);		\
301 }						\
302 						\
303 const char *name##__mount(void)			\
304 {						\
305 	return fs__mount(idx);			\
306 }						\
307 						\
308 bool name##__configured(void)			\
309 {						\
310 	return name##__mountpoint() != NULL;	\
311 }
312 
313 FS(sysfs,   FS__SYSFS);
314 FS(procfs,  FS__PROCFS);
315 FS(debugfs, FS__DEBUGFS);
316 FS(tracefs, FS__TRACEFS);
317 FS(hugetlbfs, FS__HUGETLBFS);
318 FS(bpf_fs, FS__BPF_FS);
319 
filename__read_int(const char * filename,int * value)320 int filename__read_int(const char *filename, int *value)
321 {
322 	char line[64];
323 	int fd = open(filename, O_RDONLY), err = -1;
324 
325 	if (fd < 0)
326 		return -1;
327 
328 	if (read(fd, line, sizeof(line)) > 0) {
329 		*value = atoi(line);
330 		err = 0;
331 	}
332 
333 	close(fd);
334 	return err;
335 }
336 
filename__read_ull_base(const char * filename,unsigned long long * value,int base)337 static int filename__read_ull_base(const char *filename,
338 				   unsigned long long *value, int base)
339 {
340 	char line[64];
341 	int fd = open(filename, O_RDONLY), err = -1;
342 
343 	if (fd < 0)
344 		return -1;
345 
346 	if (read(fd, line, sizeof(line)) > 0) {
347 		*value = strtoull(line, NULL, base);
348 		if (*value != ULLONG_MAX)
349 			err = 0;
350 	}
351 
352 	close(fd);
353 	return err;
354 }
355 
356 /*
357  * Parses @value out of @filename with strtoull.
358  * By using 16 for base to treat the number as hex.
359  */
filename__read_xll(const char * filename,unsigned long long * value)360 int filename__read_xll(const char *filename, unsigned long long *value)
361 {
362 	return filename__read_ull_base(filename, value, 16);
363 }
364 
365 /*
366  * Parses @value out of @filename with strtoull.
367  * By using 0 for base, the strtoull detects the
368  * base automatically (see man strtoull).
369  */
filename__read_ull(const char * filename,unsigned long long * value)370 int filename__read_ull(const char *filename, unsigned long long *value)
371 {
372 	return filename__read_ull_base(filename, value, 0);
373 }
374 
375 #define STRERR_BUFSIZE  128     /* For the buffer size of strerror_r */
376 
filename__read_str(const char * filename,char ** buf,size_t * sizep)377 int filename__read_str(const char *filename, char **buf, size_t *sizep)
378 {
379 	size_t size = 0, alloc_size = 0;
380 	void *bf = NULL, *nbf;
381 	int fd, n, err = 0;
382 	char sbuf[STRERR_BUFSIZE];
383 
384 	fd = open(filename, O_RDONLY);
385 	if (fd < 0)
386 		return -errno;
387 
388 	do {
389 		if (size == alloc_size) {
390 			alloc_size += BUFSIZ;
391 			nbf = realloc(bf, alloc_size);
392 			if (!nbf) {
393 				err = -ENOMEM;
394 				break;
395 			}
396 
397 			bf = nbf;
398 		}
399 
400 		n = read(fd, bf + size, alloc_size - size);
401 		if (n < 0) {
402 			if (size) {
403 				pr_warn("read failed %d: %s\n", errno,
404 					strerror_r(errno, sbuf, sizeof(sbuf)));
405 				err = 0;
406 			} else
407 				err = -errno;
408 
409 			break;
410 		}
411 
412 		size += n;
413 	} while (n > 0);
414 
415 	if (!err) {
416 		*sizep = size;
417 		*buf   = bf;
418 	} else
419 		free(bf);
420 
421 	close(fd);
422 	return err;
423 }
424 
filename__write_int(const char * filename,int value)425 int filename__write_int(const char *filename, int value)
426 {
427 	int fd = open(filename, O_WRONLY), err = -1;
428 	char buf[64];
429 
430 	if (fd < 0)
431 		return err;
432 
433 	sprintf(buf, "%d", value);
434 	if (write(fd, buf, sizeof(buf)) == sizeof(buf))
435 		err = 0;
436 
437 	close(fd);
438 	return err;
439 }
440 
procfs__read_str(const char * entry,char ** buf,size_t * sizep)441 int procfs__read_str(const char *entry, char **buf, size_t *sizep)
442 {
443 	char path[PATH_MAX];
444 	const char *procfs = procfs__mountpoint();
445 
446 	if (!procfs)
447 		return -1;
448 
449 	snprintf(path, sizeof(path), "%s/%s", procfs, entry);
450 
451 	return filename__read_str(path, buf, sizep);
452 }
453 
sysfs__read_ull_base(const char * entry,unsigned long long * value,int base)454 static int sysfs__read_ull_base(const char *entry,
455 				unsigned long long *value, int base)
456 {
457 	char path[PATH_MAX];
458 	const char *sysfs = sysfs__mountpoint();
459 
460 	if (!sysfs)
461 		return -1;
462 
463 	snprintf(path, sizeof(path), "%s/%s", sysfs, entry);
464 
465 	return filename__read_ull_base(path, value, base);
466 }
467 
sysfs__read_xll(const char * entry,unsigned long long * value)468 int sysfs__read_xll(const char *entry, unsigned long long *value)
469 {
470 	return sysfs__read_ull_base(entry, value, 16);
471 }
472 
sysfs__read_ull(const char * entry,unsigned long long * value)473 int sysfs__read_ull(const char *entry, unsigned long long *value)
474 {
475 	return sysfs__read_ull_base(entry, value, 0);
476 }
477 
sysfs__read_int(const char * entry,int * value)478 int sysfs__read_int(const char *entry, int *value)
479 {
480 	char path[PATH_MAX];
481 	const char *sysfs = sysfs__mountpoint();
482 
483 	if (!sysfs)
484 		return -1;
485 
486 	snprintf(path, sizeof(path), "%s/%s", sysfs, entry);
487 
488 	return filename__read_int(path, value);
489 }
490 
sysfs__read_str(const char * entry,char ** buf,size_t * sizep)491 int sysfs__read_str(const char *entry, char **buf, size_t *sizep)
492 {
493 	char path[PATH_MAX];
494 	const char *sysfs = sysfs__mountpoint();
495 
496 	if (!sysfs)
497 		return -1;
498 
499 	snprintf(path, sizeof(path), "%s/%s", sysfs, entry);
500 
501 	return filename__read_str(path, buf, sizep);
502 }
503 
sysfs__read_bool(const char * entry,bool * value)504 int sysfs__read_bool(const char *entry, bool *value)
505 {
506 	char *buf;
507 	size_t size;
508 	int ret;
509 
510 	ret = sysfs__read_str(entry, &buf, &size);
511 	if (ret < 0)
512 		return ret;
513 
514 	switch (buf[0]) {
515 	case '1':
516 	case 'y':
517 	case 'Y':
518 		*value = true;
519 		break;
520 	case '0':
521 	case 'n':
522 	case 'N':
523 		*value = false;
524 		break;
525 	default:
526 		ret = -1;
527 	}
528 
529 	free(buf);
530 
531 	return ret;
532 }
sysctl__read_int(const char * sysctl,int * value)533 int sysctl__read_int(const char *sysctl, int *value)
534 {
535 	char path[PATH_MAX];
536 	const char *procfs = procfs__mountpoint();
537 
538 	if (!procfs)
539 		return -1;
540 
541 	snprintf(path, sizeof(path), "%s/sys/%s", procfs, sysctl);
542 
543 	return filename__read_int(path, value);
544 }
545 
sysfs__write_int(const char * entry,int value)546 int sysfs__write_int(const char *entry, int value)
547 {
548 	char path[PATH_MAX];
549 	const char *sysfs = sysfs__mountpoint();
550 
551 	if (!sysfs)
552 		return -1;
553 
554 	if (snprintf(path, sizeof(path), "%s/%s", sysfs, entry) >= PATH_MAX)
555 		return -1;
556 
557 	return filename__write_int(path, value);
558 }
559