1#include "util.h"
  2#include "debugfs.h"
  3#include "cache.h"
  4
  5static int debugfs_premounted;
  6static char debugfs_mountpoint[MAX_PATH+1];
  7
  8static const char *debugfs_known_mountpoints[] = {
  9	"/sys/kernel/debug/",
 10	"/debug/",
 11	0,
 12};
 13
 14/* use this to force a umount */
 15void debugfs_force_cleanup(void)
 16{
 17	debugfs_find_mountpoint();
 18	debugfs_premounted = 0;
 19	debugfs_umount();
 20}
 21
 22/* construct a full path to a debugfs element */
 23int debugfs_make_path(const char *element, char *buffer, int size)
 24{
 25	int len;
 26
 27	if (strlen(debugfs_mountpoint) == 0) {
 28		buffer[0] = '\0';
 29		return -1;
 30	}
 31
 32	len = strlen(debugfs_mountpoint) + strlen(element) + 1;
 33	if (len >= size)
 34		return len+1;
 35
 36	snprintf(buffer, size-1, "%s/%s", debugfs_mountpoint, element);
 37	return 0;
 38}
 39
 40static int debugfs_found;
 41
 42/* find the path to the mounted debugfs */
 43const char *debugfs_find_mountpoint(void)
 44{
 45	const char **ptr;
 46	char type[100];
 47	FILE *fp;
 48
 49	if (debugfs_found)
 50		return (const char *) debugfs_mountpoint;
 51
 52	ptr = debugfs_known_mountpoints;
 53	while (*ptr) {
 54		if (debugfs_valid_mountpoint(*ptr) == 0) {
 55			debugfs_found = 1;
 56			strcpy(debugfs_mountpoint, *ptr);
 57			return debugfs_mountpoint;
 58		}
 59		ptr++;
 60	}
 61
 62	/* give up and parse /proc/mounts */
 63	fp = fopen("/proc/mounts", "r");
 64	if (fp == NULL)
 65		die("Can't open /proc/mounts for read");
 66
 67	while (fscanf(fp, "%*s %"
 68		      STR(MAX_PATH)
 69		      "s %99s %*s %*d %*d\n",
 70		      debugfs_mountpoint, type) == 2) {
 71		if (strcmp(type, "debugfs") == 0)
 72			break;
 73	}
 74	fclose(fp);
 75
 76	if (strcmp(type, "debugfs") != 0)
 77		return NULL;
 78
 79	debugfs_found = 1;
 80
 81	return debugfs_mountpoint;
 82}
 83
 84/* verify that a mountpoint is actually a debugfs instance */
 85
 86int debugfs_valid_mountpoint(const char *debugfs)
 87{
 88	struct statfs st_fs;
 89
 90	if (statfs(debugfs, &st_fs) < 0)
 91		return -ENOENT;
 92	else if (st_fs.f_type != (long) DEBUGFS_MAGIC)
 93		return -ENOENT;
 94
 95	return 0;
 96}
 97
 98
 99int debugfs_valid_entry(const char *path)
100{
101	struct stat st;
102
103	if (stat(path, &st))
104		return -errno;
105
106	return 0;
107}
108
109/* mount the debugfs somewhere if it's not mounted */
110
111char *debugfs_mount(const char *mountpoint)
112{
113	/* see if it's already mounted */
114	if (debugfs_find_mountpoint()) {
115		debugfs_premounted = 1;
116		return debugfs_mountpoint;
117	}
118
119	/* if not mounted and no argument */
120	if (mountpoint == NULL) {
121		/* see if environment variable set */
122		mountpoint = getenv(PERF_DEBUGFS_ENVIRONMENT);
123		/* if no environment variable, use default */
124		if (mountpoint == NULL)
125			mountpoint = "/sys/kernel/debug";
126	}
127
128	if (mount(NULL, mountpoint, "debugfs", 0, NULL) < 0)
129		return NULL;
130
131	/* save the mountpoint */
132	strncpy(debugfs_mountpoint, mountpoint, sizeof(debugfs_mountpoint));
133	debugfs_found = 1;
134
135	return debugfs_mountpoint;
136}
137
138/* umount the debugfs */
139
140int debugfs_umount(void)
141{
142	char umountcmd[128];
143	int ret;
144
145	/* if it was already mounted, leave it */
146	if (debugfs_premounted)
147		return 0;
148
149	/* make sure it's a valid mount point */
150	ret = debugfs_valid_mountpoint(debugfs_mountpoint);
151	if (ret)
152		return ret;
153
154	snprintf(umountcmd, sizeof(umountcmd),
155		 "/bin/umount %s", debugfs_mountpoint);
156	return system(umountcmd);
157}
158
159int debugfs_write(const char *entry, const char *value)
160{
161	char path[MAX_PATH+1];
162	int ret, count;
163	int fd;
164
165	/* construct the path */
166	snprintf(path, sizeof(path), "%s/%s", debugfs_mountpoint, entry);
167
168	/* verify that it exists */
169	ret = debugfs_valid_entry(path);
170	if (ret)
171		return ret;
172
173	/* get how many chars we're going to write */
174	count = strlen(value);
175
176	/* open the debugfs entry */
177	fd = open(path, O_RDWR);
178	if (fd < 0)
179		return -errno;
180
181	while (count > 0) {
182		/* write it */
183		ret = write(fd, value, count);
184		if (ret <= 0) {
185			if (ret == EAGAIN)
186				continue;
187			close(fd);
188			return -errno;
189		}
190		count -= ret;
191	}
192
193	/* close it */
194	close(fd);
195
196	/* return success */
197	return 0;
198}
199
200/*
201 * read a debugfs entry
202 * returns the number of chars read or a negative errno
203 */
204int debugfs_read(const char *entry, char *buffer, size_t size)
205{
206	char path[MAX_PATH+1];
207	int ret;
208	int fd;
209
210	/* construct the path */
211	snprintf(path, sizeof(path), "%s/%s", debugfs_mountpoint, entry);
212
213	/* verify that it exists */
214	ret = debugfs_valid_entry(path);
215	if (ret)
216		return ret;
217
218	/* open the debugfs entry */
219	fd = open(path, O_RDONLY);
220	if (fd < 0)
221		return -errno;
222
223	do {
224		/* read it */
225		ret = read(fd, buffer, size);
226		if (ret == 0) {
227			close(fd);
228			return EOF;
229		}
230	} while (ret < 0 && errno == EAGAIN);
231
232	/* close it */
233	close(fd);
234
235	/* make *sure* there's a null character at the end */
236	buffer[ret] = '\0';
237
238	/* return the number of chars read */
239	return ret;
240}