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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
49static const char * const sysfs__known_mountpoints[] = {
50 "/sys",
51 0,
52};
53
54static 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
63static 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
74static const char * const tracefs__known_mountpoints[] = {
75 TRACEFS_DEFAULT_PATH,
76 "/sys/kernel/debug/tracing",
77 "/tracing",
78 "/trace",
79 0,
80};
81
82static const char * const hugetlbfs__known_mountpoints[] = {
83 0,
84};
85
86static const char * const bpf_fs__known_mountpoints[] = {
87 "/sys/fs/bpf",
88 0,
89};
90
91struct 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
103static void fs__init_once(struct fs *fs);
104static const char *fs__mountpoint(const struct fs *fs);
105static const char *fs__mount(struct fs *fs);
106
107#define FS(lower_name, fs_name, upper_name) \
108static 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 \
115static void lower_name##_init_once(void) \
116{ \
117 struct fs *fs = &fs__##lower_name; \
118 \
119 fs__init_once(fs); \
120} \
121 \
122const 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 \
131const 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 \
142bool lower_name##__configured(void) \
143{ \
144 return lower_name##__mountpoint() != NULL; \
145}
146
147FS(sysfs, sysfs, SYSFS);
148FS(procfs, procfs, PROC_SUPER);
149FS(debugfs, debugfs, DEBUGFS);
150FS(tracefs, tracefs, TRACEFS);
151FS(hugetlbfs, hugetlbfs, HUGETLBFS);
152FS(bpf_fs, bpf, BPF_FS);
153
154static 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
177static 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
189static 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
207static 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 */
221static 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
242static 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
253static const char *fs__mountpoint(const struct fs *fs)
254{
255 return fs->path;
256}
257
258static 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, sizeof(upper_name), "PERF_%s_ENVIRONMENT", fs->name);
265 mem_toupper(upper_name, strlen(upper_name));
266
267 return getenv(upper_name) ?: *fs->mounts;
268}
269
270static 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 }
288out:
289 pthread_mutex_unlock(&fs->mount_mutex);
290 return mountpoint;
291}
292
293int filename__read_int(const char *filename, int *value)
294{
295 char line[64];
296 int fd = open(filename, O_RDONLY), err = -1;
297 ssize_t n;
298
299 if (fd < 0)
300 return -errno;
301
302 n = read(fd, line, sizeof(line) - 1);
303 if (n > 0) {
304 line[n] = '\0';
305 *value = atoi(line);
306 err = 0;
307 }
308
309 close(fd);
310 return err;
311}
312
313static int filename__read_ull_base(const char *filename,
314 unsigned long long *value, int base)
315{
316 char line[64];
317 int fd = open(filename, O_RDONLY), err = -1;
318 ssize_t n;
319
320 if (fd < 0)
321 return -errno;
322
323 n = read(fd, line, sizeof(line) - 1);
324 if (n > 0) {
325 line[n] = '\0';
326 *value = strtoull(line, NULL, base);
327 if (*value != ULLONG_MAX)
328 err = 0;
329 }
330
331 close(fd);
332 return err;
333}
334
335/*
336 * Parses @value out of @filename with strtoull.
337 * By using 16 for base to treat the number as hex.
338 */
339int filename__read_xll(const char *filename, unsigned long long *value)
340{
341 return filename__read_ull_base(filename, value, 16);
342}
343
344/*
345 * Parses @value out of @filename with strtoull.
346 * By using 0 for base, the strtoull detects the
347 * base automatically (see man strtoull).
348 */
349int filename__read_ull(const char *filename, unsigned long long *value)
350{
351 return filename__read_ull_base(filename, value, 0);
352}
353
354int filename__read_str(const char *filename, char **buf, size_t *sizep)
355{
356 struct io io;
357 char bf[128];
358 int err;
359
360 io.fd = open(filename, O_RDONLY);
361 if (io.fd < 0)
362 return -errno;
363 io__init(&io, io.fd, bf, sizeof(bf));
364 *buf = NULL;
365 err = io__getdelim(&io, buf, sizep, /*delim=*/-1);
366 if (err < 0) {
367 free(*buf);
368 *buf = NULL;
369 } else
370 err = 0;
371 close(io.fd);
372 return err;
373}
374
375int filename__write_int(const char *filename, int value)
376{
377 int fd = open(filename, O_WRONLY), err = -1;
378 char buf[64];
379 int len;
380
381 if (fd < 0)
382 return -errno;
383
384 len = sprintf(buf, "%d", value);
385 if (write(fd, buf, len) == len)
386 err = 0;
387
388 close(fd);
389 return err;
390}
391
392int procfs__read_str(const char *entry, char **buf, size_t *sizep)
393{
394 char path[PATH_MAX];
395 const char *procfs = procfs__mountpoint();
396
397 if (!procfs)
398 return -1;
399
400 snprintf(path, sizeof(path), "%s/%s", procfs, entry);
401
402 return filename__read_str(path, buf, sizep);
403}
404
405static int sysfs__read_ull_base(const char *entry,
406 unsigned long long *value, int base)
407{
408 char path[PATH_MAX];
409 const char *sysfs = sysfs__mountpoint();
410
411 if (!sysfs)
412 return -1;
413
414 snprintf(path, sizeof(path), "%s/%s", sysfs, entry);
415
416 return filename__read_ull_base(path, value, base);
417}
418
419int sysfs__read_xll(const char *entry, unsigned long long *value)
420{
421 return sysfs__read_ull_base(entry, value, 16);
422}
423
424int sysfs__read_ull(const char *entry, unsigned long long *value)
425{
426 return sysfs__read_ull_base(entry, value, 0);
427}
428
429int sysfs__read_int(const char *entry, int *value)
430{
431 char path[PATH_MAX];
432 const char *sysfs = sysfs__mountpoint();
433
434 if (!sysfs)
435 return -1;
436
437 snprintf(path, sizeof(path), "%s/%s", sysfs, entry);
438
439 return filename__read_int(path, value);
440}
441
442int sysfs__read_str(const char *entry, char **buf, size_t *sizep)
443{
444 char path[PATH_MAX];
445 const char *sysfs = sysfs__mountpoint();
446
447 if (!sysfs)
448 return -1;
449
450 snprintf(path, sizeof(path), "%s/%s", sysfs, entry);
451
452 return filename__read_str(path, buf, sizep);
453}
454
455int sysfs__read_bool(const char *entry, bool *value)
456{
457 struct io io;
458 char bf[16];
459 int ret = 0;
460 char path[PATH_MAX];
461 const char *sysfs = sysfs__mountpoint();
462
463 if (!sysfs)
464 return -1;
465
466 snprintf(path, sizeof(path), "%s/%s", sysfs, entry);
467 io.fd = open(path, O_RDONLY);
468 if (io.fd < 0)
469 return -errno;
470
471 io__init(&io, io.fd, bf, sizeof(bf));
472 switch (io__get_char(&io)) {
473 case '1':
474 case 'y':
475 case 'Y':
476 *value = true;
477 break;
478 case '0':
479 case 'n':
480 case 'N':
481 *value = false;
482 break;
483 default:
484 ret = -1;
485 }
486 close(io.fd);
487
488 return ret;
489}
490int sysctl__read_int(const char *sysctl, int *value)
491{
492 char path[PATH_MAX];
493 const char *procfs = procfs__mountpoint();
494
495 if (!procfs)
496 return -1;
497
498 snprintf(path, sizeof(path), "%s/sys/%s", procfs, sysctl);
499
500 return filename__read_int(path, value);
501}
502
503int sysfs__write_int(const char *entry, int value)
504{
505 char path[PATH_MAX];
506 const char *sysfs = sysfs__mountpoint();
507
508 if (!sysfs)
509 return -1;
510
511 if (snprintf(path, sizeof(path), "%s/%s", sysfs, entry) >= PATH_MAX)
512 return -1;
513
514 return filename__write_int(path, value);
515}