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