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_warning("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