1 #define _GNU_SOURCE
2 #include <errno.h>
3 #include <stdio.h>
4 #include <stdlib.h>
5 #include <string.h>
6 #include <stdbool.h>
7 #include <sys/vfs.h>
8 #include <sys/mount.h>
9 #include <linux/kernel.h>
10
11 #include "debugfs.h"
12
13 char debugfs_mountpoint[PATH_MAX + 1] = "/sys/kernel/debug";
14
15 static const char * const debugfs_known_mountpoints[] = {
16 "/sys/kernel/debug",
17 "/debug",
18 0,
19 };
20
21 static bool debugfs_found;
22
23 /* find the path to the mounted debugfs */
24 const char *debugfs_find_mountpoint(void)
25 {
26 const char * const *ptr;
27 char type[100];
28 FILE *fp;
29
30 if (debugfs_found)
31 return (const char *)debugfs_mountpoint;
32
33 ptr = debugfs_known_mountpoints;
34 while (*ptr) {
35 if (debugfs_valid_mountpoint(*ptr) == 0) {
36 debugfs_found = true;
37 strcpy(debugfs_mountpoint, *ptr);
38 return debugfs_mountpoint;
39 }
40 ptr++;
41 }
42
43 /* give up and parse /proc/mounts */
44 fp = fopen("/proc/mounts", "r");
45 if (fp == NULL)
46 return NULL;
47
48 while (fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
49 debugfs_mountpoint, type) == 2) {
50 if (strcmp(type, "debugfs") == 0)
51 break;
52 }
53 fclose(fp);
54
55 if (strcmp(type, "debugfs") != 0)
56 return NULL;
57
58 debugfs_found = true;
59
60 return debugfs_mountpoint;
61 }
62
63 /* verify that a mountpoint is actually a debugfs instance */
64
65 int debugfs_valid_mountpoint(const char *debugfs)
66 {
67 struct statfs st_fs;
68
69 if (statfs(debugfs, &st_fs) < 0)
70 return -ENOENT;
71 else if ((long)st_fs.f_type != (long)DEBUGFS_MAGIC)
72 return -ENOENT;
73
74 return 0;
75 }
76
77 /* mount the debugfs somewhere if it's not mounted */
78 char *debugfs_mount(const char *mountpoint)
79 {
80 /* see if it's already mounted */
81 if (debugfs_find_mountpoint())
82 goto out;
83
84 /* if not mounted and no argument */
85 if (mountpoint == NULL) {
86 /* see if environment variable set */
87 mountpoint = getenv(PERF_DEBUGFS_ENVIRONMENT);
88 /* if no environment variable, use default */
89 if (mountpoint == NULL)
90 mountpoint = "/sys/kernel/debug";
91 }
92
93 if (mount(NULL, mountpoint, "debugfs", 0, NULL) < 0)
94 return NULL;
95
96 /* save the mountpoint */
97 debugfs_found = true;
98 strncpy(debugfs_mountpoint, mountpoint, sizeof(debugfs_mountpoint));
99 out:
100 return debugfs_mountpoint;
101 }
102
103 int debugfs__strerror_open(int err, char *buf, size_t size, const char *filename)
104 {
105 char sbuf[128];
106
107 switch (err) {
108 case ENOENT:
109 if (debugfs_found) {
110 snprintf(buf, size,
111 "Error:\tFile %s/%s not found.\n"
112 "Hint:\tPerhaps this kernel misses some CONFIG_ setting to enable this feature?.\n",
113 debugfs_mountpoint, filename);
114 break;
115 }
116 snprintf(buf, size, "%s",
117 "Error:\tUnable to find debugfs\n"
118 "Hint:\tWas your kernel compiled with debugfs support?\n"
119 "Hint:\tIs the debugfs filesystem mounted?\n"
120 "Hint:\tTry 'sudo mount -t debugfs nodev /sys/kernel/debug'");
121 break;
122 case EACCES:
123 snprintf(buf, size,
124 "Error:\tNo permissions to read %s/%s\n"
125 "Hint:\tTry 'sudo mount -o remount,mode=755 %s'\n",
126 debugfs_mountpoint, filename, debugfs_mountpoint);
127 break;
128 default:
129 snprintf(buf, size, "%s", strerror_r(err, sbuf, sizeof(sbuf)));
130 break;
131 }
132
133 return 0;
134 }
135
136 int debugfs__strerror_open_tp(int err, char *buf, size_t size, const char *sys, const char *name)
137 {
138 char path[PATH_MAX];
139
140 snprintf(path, PATH_MAX, "tracing/events/%s/%s", sys, name ?: "*");
141
142 return debugfs__strerror_open(err, buf, size, path);
143 }
144
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