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
12 char debugfs_mountpoint[PATH_MAX + 1] = "/sys/kernel/debug";
13
14 static const char * const debugfs_known_mountpoints[] = {
15 "/sys/kernel/debug/",
16 "/debug/",
17 0,
18 };
19
20 static bool debugfs_found;
21
22 /* find the path to the mounted debugfs */
debugfs_find_mountpoint(void)23 const 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
debugfs_valid_mountpoint(const char * debugfs)64 int 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 */
debugfs_mount(const char * mountpoint)77 char *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
102 out:
103 return debugfs_mountpoint;
104 }
105