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