aboutsummaryrefslogtreecommitdiff
path: root/tools/perf/util/debugfs.c
blob: a88fefc0cc0ada1afdbf8fc133cca9f8d49fe5a3 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
#include "util.h"
#include "debugfs.h"
#include "cache.h"

static int debugfs_premounted;
static char debugfs_mountpoint[MAX_PATH+1];

static const char *debugfs_known_mountpoints[] = {
	"/sys/kernel/debug/",
	"/debug/",
	0,
};

/* use this to force a umount */
void debugfs_force_cleanup(void)
{
	debugfs_find_mountpoint();
	debugfs_premounted = 0;
	debugfs_umount();
}

/* construct a full path to a debugfs element */
int debugfs_make_path(const char *element, char *buffer, int size)
{
	int len;

	if (strlen(debugfs_mountpoint) == 0) {
		buffer[0] = '\0';
		return -1;
	}

	len = strlen(debugfs_mountpoint) + strlen(element) + 1;
	if (len >= size)
		return len+1;

	snprintf(buffer, size-1, "%s/%s", debugfs_mountpoint, element);
	return 0;
}

static int debugfs_found;

/* find the path to the mounted debugfs */
const char *debugfs_find_mountpoint(void)
{
	const char **ptr;
	char type[100];
	FILE *fp;

	if (debugfs_found)
		return (const char *) debugfs_mountpoint;

	ptr = debugfs_known_mountpoints;
	while (*ptr) {
		if (debugfs_valid_mountpoint(*ptr) == 0) {
			debugfs_found = 1;
			strcpy(debugfs_mountpoint, *ptr);
			return debugfs_mountpoint;
		}
		ptr++;
	}

	/* give up and parse /proc/mounts */
	fp = fopen("/proc/mounts", "r");
	if (fp == NULL)
		die("Can't open /proc/mounts for read");

	while (fscanf(fp, "%*s %"
		      STR(MAX_PATH)
		      "s %99s %*s %*d %*d\n",
		      debugfs_mountpoint, type) == 2) {
		if (strcmp(type, "debugfs") == 0)
			break;
	}
	fclose(fp);

	if (strcmp(type, "debugfs") != 0)
		return NULL;

	debugfs_found = 1;

	return debugfs_mountpoint;
}

/* verify that a mountpoint is actually a debugfs instance */

int debugfs_valid_mountpoint(const char *debugfs)
{
	struct statfs st_fs;

	if (statfs(debugfs, &st_fs) < 0)
		return -ENOENT;
	else if (st_fs.f_type != (long) DEBUGFS_MAGIC)
		return -ENOENT;

	return 0;
}


int debugfs_valid_entry(const char *path)
{
	struct stat st;

	if (stat(path, &st))
		return -errno;

	return 0;
}

/* mount the debugfs somewhere if it's not mounted */

char *debugfs_mount(const char *mountpoint)
{
	/* see if it's already mounted */
	if (debugfs_find_mountpoint()) {
		debugfs_premounted = 1;
		return debugfs_mountpoint;
	}

	/* if not mounted and no argument */
	if (mountpoint == NULL) {
		/* see if environment variable set */
		mountpoint = getenv(PERF_DEBUGFS_ENVIRONMENT);
		/* if no environment variable, use default */
		if (mountpoint == NULL)
			mountpoint = "/sys/kernel/debug";
	}

	if (mount(NULL, mountpoint, "debugfs", 0, NULL) < 0)
		return NULL;

	/* save the mountpoint */
	strncpy(debugfs_mountpoint, mountpoint, sizeof(debugfs_mountpoint));
	debugfs_found = 1;

	return debugfs_mountpoint;
}

/* umount the debugfs */

int debugfs_umount(void)
{
	char umountcmd[128];
	int ret;

	/* if it was already mounted, leave it */
	if (debugfs_premounted)
		return 0;

	/* make sure it's a valid mount point */
	ret = debugfs_valid_mountpoint(debugfs_mountpoint);
	if (ret)
		return ret;

	snprintf(umountcmd, sizeof(umountcmd),
		 "/bin/umount %s", debugfs_mountpoint);
	return system(umountcmd);
}

int debugfs_write(const char *entry, const char *value)
{
	char path[MAX_PATH+1];
	int ret, count;
	int fd;

	/* construct the path */
	snprintf(path, sizeof(path), "%s/%s", debugfs_mountpoint, entry);

	/* verify that it exists */
	ret = debugfs_valid_entry(path);
	if (ret)
		return ret;

	/* get how many chars we're going to write */
	count = strlen(value);

	/* open the debugfs entry */
	fd = open(path, O_RDWR);
	if (fd < 0)
		return -errno;

	while (count > 0) {
		/* write it */
		ret = write(fd, value, count);
		if (ret <= 0) {
			if (ret == EAGAIN)
				continue;
			close(fd);
			return -errno;
		}
		count -= ret;
	}

	/* close it */
	close(fd);

	/* return success */
	return 0;
}

/*
 * read a debugfs entry
 * returns the number of chars read or a negative errno
 */
int debugfs_read(const char *entry, char *buffer, size_t size)
{
	char path[MAX_PATH+1];
	int ret;
	int fd;

	/* construct the path */
	snprintf(path, sizeof(path), "%s/%s", debugfs_mountpoint, entry);

	/* verify that it exists */
	ret = debugfs_valid_entry(path);
	if (ret)
		return ret;

	/* open the debugfs entry */
	fd = open(path, O_RDONLY);
	if (fd < 0)
		return -errno;

	do {
		/* read it */
		ret = read(fd, buffer, size);
		if (ret == 0) {
			close(fd);
			return EOF;
		}
	} while (ret < 0 && errno == EAGAIN);

	/* close it */
	close(fd);

	/* make *sure* there's a null character at the end */
	buffer[ret] = '\0';

	/* return the number of chars read */
	return ret;
}