5 #include <linux/kernel.h>
8 static int debugfs_premounted;
9 char debugfs_mountpoint[PATH_MAX + 1] = "/sys/kernel/debug";
10 char tracing_events_path[PATH_MAX + 1] = "/sys/kernel/debug/tracing/events";
12 static const char *debugfs_known_mountpoints[] = {
18 /* use this to force a umount */
19 void debugfs_force_cleanup(void)
21 debugfs_find_mountpoint();
22 debugfs_premounted = 0;
26 /* construct a full path to a debugfs element */
27 int debugfs_make_path(const char *element, char *buffer, int size)
31 if (strlen(debugfs_mountpoint) == 0) {
36 len = strlen(debugfs_mountpoint) + strlen(element) + 1;
40 snprintf(buffer, size-1, "%s/%s", debugfs_mountpoint, element);
44 static int debugfs_found;
46 /* find the path to the mounted debugfs */
47 const char *debugfs_find_mountpoint(void)
54 return (const char *) debugfs_mountpoint;
56 ptr = debugfs_known_mountpoints;
58 if (debugfs_valid_mountpoint(*ptr) == 0) {
60 strcpy(debugfs_mountpoint, *ptr);
61 return debugfs_mountpoint;
66 /* give up and parse /proc/mounts */
67 fp = fopen("/proc/mounts", "r");
71 while (fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
72 debugfs_mountpoint, type) == 2) {
73 if (strcmp(type, "debugfs") == 0)
78 if (strcmp(type, "debugfs") != 0)
83 return debugfs_mountpoint;
86 /* verify that a mountpoint is actually a debugfs instance */
88 int debugfs_valid_mountpoint(const char *debugfs)
92 if (statfs(debugfs, &st_fs) < 0)
94 else if (st_fs.f_type != (long) DEBUGFS_MAGIC)
101 int debugfs_valid_entry(const char *path)
111 static void debugfs_set_tracing_events_path(const char *mountpoint)
113 snprintf(tracing_events_path, sizeof(tracing_events_path), "%s/%s",
114 mountpoint, "tracing/events");
117 /* mount the debugfs somewhere if it's not mounted */
119 char *debugfs_mount(const char *mountpoint)
121 /* see if it's already mounted */
122 if (debugfs_find_mountpoint()) {
123 debugfs_premounted = 1;
127 /* if not mounted and no argument */
128 if (mountpoint == NULL) {
129 /* see if environment variable set */
130 mountpoint = getenv(PERF_DEBUGFS_ENVIRONMENT);
131 /* if no environment variable, use default */
132 if (mountpoint == NULL)
133 mountpoint = "/sys/kernel/debug";
136 if (mount(NULL, mountpoint, "debugfs", 0, NULL) < 0)
139 /* save the mountpoint */
141 strncpy(debugfs_mountpoint, mountpoint, sizeof(debugfs_mountpoint));
143 debugfs_set_tracing_events_path(debugfs_mountpoint);
144 return debugfs_mountpoint;
147 void debugfs_set_path(const char *mountpoint)
149 snprintf(debugfs_mountpoint, sizeof(debugfs_mountpoint), "%s", mountpoint);
150 debugfs_set_tracing_events_path(mountpoint);
153 /* umount the debugfs */
155 int debugfs_umount(void)
160 /* if it was already mounted, leave it */
161 if (debugfs_premounted)
164 /* make sure it's a valid mount point */
165 ret = debugfs_valid_mountpoint(debugfs_mountpoint);
169 snprintf(umountcmd, sizeof(umountcmd),
170 "/bin/umount %s", debugfs_mountpoint);
171 return system(umountcmd);
174 int debugfs_write(const char *entry, const char *value)
176 char path[PATH_MAX + 1];
180 /* construct the path */
181 snprintf(path, sizeof(path), "%s/%s", debugfs_mountpoint, entry);
183 /* verify that it exists */
184 ret = debugfs_valid_entry(path);
188 /* get how many chars we're going to write */
189 count = strlen(value);
191 /* open the debugfs entry */
192 fd = open(path, O_RDWR);
198 ret = write(fd, value, count);
216 * read a debugfs entry
217 * returns the number of chars read or a negative errno
219 int debugfs_read(const char *entry, char *buffer, size_t size)
221 char path[PATH_MAX + 1];
225 /* construct the path */
226 snprintf(path, sizeof(path), "%s/%s", debugfs_mountpoint, entry);
228 /* verify that it exists */
229 ret = debugfs_valid_entry(path);
233 /* open the debugfs entry */
234 fd = open(path, O_RDONLY);
240 ret = read(fd, buffer, size);
245 } while (ret < 0 && errno == EAGAIN);
250 /* make *sure* there's a null character at the end */
253 /* return the number of chars read */