Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
1#include "util.h"
2#include "debugfs.h"
3#include "cache.h"
4
5#include <linux/kernel.h>
6#include <sys/mount.h>
7
8static int debugfs_premounted;
9char debugfs_mountpoint[PATH_MAX + 1] = "/sys/kernel/debug";
10char tracing_events_path[PATH_MAX + 1] = "/sys/kernel/debug/tracing/events";
11
12static const char *debugfs_known_mountpoints[] = {
13 "/sys/kernel/debug/",
14 "/debug/",
15 0,
16};
17
18/* use this to force a umount */
19void debugfs_force_cleanup(void)
20{
21 debugfs_find_mountpoint();
22 debugfs_premounted = 0;
23 debugfs_umount();
24}
25
26/* construct a full path to a debugfs element */
27int debugfs_make_path(const char *element, char *buffer, int size)
28{
29 int len;
30
31 if (strlen(debugfs_mountpoint) == 0) {
32 buffer[0] = '\0';
33 return -1;
34 }
35
36 len = strlen(debugfs_mountpoint) + strlen(element) + 1;
37 if (len >= size)
38 return len+1;
39
40 snprintf(buffer, size-1, "%s/%s", debugfs_mountpoint, element);
41 return 0;
42}
43
44static int debugfs_found;
45
46/* find the path to the mounted debugfs */
47const char *debugfs_find_mountpoint(void)
48{
49 const char **ptr;
50 char type[100];
51 FILE *fp;
52
53 if (debugfs_found)
54 return (const char *) debugfs_mountpoint;
55
56 ptr = debugfs_known_mountpoints;
57 while (*ptr) {
58 if (debugfs_valid_mountpoint(*ptr) == 0) {
59 debugfs_found = 1;
60 strcpy(debugfs_mountpoint, *ptr);
61 return debugfs_mountpoint;
62 }
63 ptr++;
64 }
65
66 /* give up and parse /proc/mounts */
67 fp = fopen("/proc/mounts", "r");
68 if (fp == NULL)
69 return NULL;
70
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)
74 break;
75 }
76 fclose(fp);
77
78 if (strcmp(type, "debugfs") != 0)
79 return NULL;
80
81 debugfs_found = 1;
82
83 return debugfs_mountpoint;
84}
85
86/* verify that a mountpoint is actually a debugfs instance */
87
88int debugfs_valid_mountpoint(const char *debugfs)
89{
90 struct statfs st_fs;
91
92 if (statfs(debugfs, &st_fs) < 0)
93 return -ENOENT;
94 else if (st_fs.f_type != (long) DEBUGFS_MAGIC)
95 return -ENOENT;
96
97 return 0;
98}
99
100
101int debugfs_valid_entry(const char *path)
102{
103 struct stat st;
104
105 if (stat(path, &st))
106 return -errno;
107
108 return 0;
109}
110
111static void debugfs_set_tracing_events_path(const char *mountpoint)
112{
113 snprintf(tracing_events_path, sizeof(tracing_events_path), "%s/%s",
114 mountpoint, "tracing/events");
115}
116
117/* mount the debugfs somewhere if it's not mounted */
118
119char *debugfs_mount(const char *mountpoint)
120{
121 /* see if it's already mounted */
122 if (debugfs_find_mountpoint()) {
123 debugfs_premounted = 1;
124 goto out;
125 }
126
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";
134 }
135
136 if (mount(NULL, mountpoint, "debugfs", 0, NULL) < 0)
137 return NULL;
138
139 /* save the mountpoint */
140 debugfs_found = 1;
141 strncpy(debugfs_mountpoint, mountpoint, sizeof(debugfs_mountpoint));
142out:
143 debugfs_set_tracing_events_path(debugfs_mountpoint);
144 return debugfs_mountpoint;
145}
146
147void debugfs_set_path(const char *mountpoint)
148{
149 snprintf(debugfs_mountpoint, sizeof(debugfs_mountpoint), "%s", mountpoint);
150 debugfs_set_tracing_events_path(mountpoint);
151}
152
153/* umount the debugfs */
154
155int debugfs_umount(void)
156{
157 char umountcmd[128];
158 int ret;
159
160 /* if it was already mounted, leave it */
161 if (debugfs_premounted)
162 return 0;
163
164 /* make sure it's a valid mount point */
165 ret = debugfs_valid_mountpoint(debugfs_mountpoint);
166 if (ret)
167 return ret;
168
169 snprintf(umountcmd, sizeof(umountcmd),
170 "/bin/umount %s", debugfs_mountpoint);
171 return system(umountcmd);
172}
173
174int debugfs_write(const char *entry, const char *value)
175{
176 char path[PATH_MAX + 1];
177 int ret, count;
178 int fd;
179
180 /* construct the path */
181 snprintf(path, sizeof(path), "%s/%s", debugfs_mountpoint, entry);
182
183 /* verify that it exists */
184 ret = debugfs_valid_entry(path);
185 if (ret)
186 return ret;
187
188 /* get how many chars we're going to write */
189 count = strlen(value);
190
191 /* open the debugfs entry */
192 fd = open(path, O_RDWR);
193 if (fd < 0)
194 return -errno;
195
196 while (count > 0) {
197 /* write it */
198 ret = write(fd, value, count);
199 if (ret <= 0) {
200 if (ret == EAGAIN)
201 continue;
202 close(fd);
203 return -errno;
204 }
205 count -= ret;
206 }
207
208 /* close it */
209 close(fd);
210
211 /* return success */
212 return 0;
213}
214
215/*
216 * read a debugfs entry
217 * returns the number of chars read or a negative errno
218 */
219int debugfs_read(const char *entry, char *buffer, size_t size)
220{
221 char path[PATH_MAX + 1];
222 int ret;
223 int fd;
224
225 /* construct the path */
226 snprintf(path, sizeof(path), "%s/%s", debugfs_mountpoint, entry);
227
228 /* verify that it exists */
229 ret = debugfs_valid_entry(path);
230 if (ret)
231 return ret;
232
233 /* open the debugfs entry */
234 fd = open(path, O_RDONLY);
235 if (fd < 0)
236 return -errno;
237
238 do {
239 /* read it */
240 ret = read(fd, buffer, size);
241 if (ret == 0) {
242 close(fd);
243 return EOF;
244 }
245 } while (ret < 0 && errno == EAGAIN);
246
247 /* close it */
248 close(fd);
249
250 /* make *sure* there's a null character at the end */
251 buffer[ret] = '\0';
252
253 /* return the number of chars read */
254 return ret;
255}