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, name_len, "PERF_%s_ENVIRONMENT", fs->name);
265	mem_toupper(upper_name, name_len);
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
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
310static 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 */
333int 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 */
343int filename__read_ull(const char *filename, unsigned long long *value)
344{
345	return filename__read_ull_base(filename, value, 0);
346}
347
348int 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
369int 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
385int 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
398static 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
412int sysfs__read_xll(const char *entry, unsigned long long *value)
413{
414	return sysfs__read_ull_base(entry, value, 16);
415}
416
417int sysfs__read_ull(const char *entry, unsigned long long *value)
418{
419	return sysfs__read_ull_base(entry, value, 0);
420}
421
422int 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
435int 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
448int 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 '0':
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}
483int 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
496int 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