1#include <errno.h>
2#include <stdio.h>
3#include <stdlib.h>
4#include <string.h>
5#include <stdbool.h>
6#include <sys/vfs.h>
7#include <sys/mount.h>
8#include <linux/kernel.h>
9
10#include "debugfs.h"
11
12char debugfs_mountpoint[PATH_MAX + 1] = "/sys/kernel/debug";
13
14static const char * const debugfs_known_mountpoints[] = {
15	"/sys/kernel/debug/",
16	"/debug/",
17	0,
18};
19
20static bool debugfs_found;
21
22/* find the path to the mounted debugfs */
23const char *debugfs_find_mountpoint(void)
24{
25	const char * const *ptr;
26	char type[100];
27	FILE *fp;
28
29	if (debugfs_found)
30		return (const char *)debugfs_mountpoint;
31
32	ptr = debugfs_known_mountpoints;
33	while (*ptr) {
34		if (debugfs_valid_mountpoint(*ptr) == 0) {
35			debugfs_found = true;
36			strcpy(debugfs_mountpoint, *ptr);
37			return debugfs_mountpoint;
38		}
39		ptr++;
40	}
41
42	/* give up and parse /proc/mounts */
43	fp = fopen("/proc/mounts", "r");
44	if (fp == NULL)
45		return NULL;
46
47	while (fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
48		      debugfs_mountpoint, type) == 2) {
49		if (strcmp(type, "debugfs") == 0)
50			break;
51	}
52	fclose(fp);
53
54	if (strcmp(type, "debugfs") != 0)
55		return NULL;
56
57	debugfs_found = true;
58
59	return debugfs_mountpoint;
60}
61
62/* verify that a mountpoint is actually a debugfs instance */
63
64int debugfs_valid_mountpoint(const char *debugfs)
65{
66	struct statfs st_fs;
67
68	if (statfs(debugfs, &st_fs) < 0)
69		return -ENOENT;
70	else if (st_fs.f_type != (long) DEBUGFS_MAGIC)
71		return -ENOENT;
72
73	return 0;
74}
75
76/* mount the debugfs somewhere if it's not mounted */
77char *debugfs_mount(const char *mountpoint)
78{
79#ifdef __APPLE__
80	goto out;
81#else
82	/* see if it's already mounted */
83	if (debugfs_find_mountpoint())
84		goto out;
85
86	/* if not mounted and no argument */
87	if (mountpoint == NULL) {
88		/* see if environment variable set */
89		mountpoint = getenv(PERF_DEBUGFS_ENVIRONMENT);
90		/* if no environment variable, use default */
91		if (mountpoint == NULL)
92			mountpoint = "/sys/kernel/debug";
93	}
94
95	if (mount(NULL, mountpoint, "debugfs", 0, NULL) < 0)
96		return NULL;
97
98	/* save the mountpoint */
99	debugfs_found = true;
100	strncpy(debugfs_mountpoint, mountpoint, sizeof(debugfs_mountpoint));
101#endif
102out:
103	return debugfs_mountpoint;
104}
105