1 #include <errno.h>
2 #include <stdio.h>
3 #include <stdlib.h>
4 #include <string.h>
5 #include <unistd.h>
6 #include <stdbool.h>
7 #include <sys/vfs.h>
8 #include <sys/types.h>
9 #include <sys/stat.h>
10 #include <sys/mount.h>
11 #include <linux/kernel.h>
12
13 #include "tracefs.h"
14
15 #ifndef TRACEFS_DEFAULT_PATH
16 #define TRACEFS_DEFAULT_PATH "/sys/kernel/tracing"
17 #endif
18
19 char tracefs_mountpoint[PATH_MAX + 1] = TRACEFS_DEFAULT_PATH;
20
21 static const char * const tracefs_known_mountpoints[] = {
22 TRACEFS_DEFAULT_PATH,
23 "/sys/kernel/debug/tracing",
24 "/tracing",
25 "/trace",
26 0,
27 };
28
29 static bool tracefs_found;
30
tracefs_configured(void)31 bool tracefs_configured(void)
32 {
33 return tracefs_find_mountpoint() != NULL;
34 }
35
36 /* find the path to the mounted tracefs */
tracefs_find_mountpoint(void)37 const char *tracefs_find_mountpoint(void)
38 {
39 const char *ret;
40
41 if (tracefs_found)
42 return (const char *)tracefs_mountpoint;
43
44 ret = find_mountpoint("tracefs", (long) TRACEFS_MAGIC,
45 tracefs_mountpoint, PATH_MAX + 1,
46 tracefs_known_mountpoints);
47
48 if (ret)
49 tracefs_found = true;
50
51 return ret;
52 }
53
54 /* mount the tracefs somewhere if it's not mounted */
tracefs_mount(const char * mountpoint)55 char *tracefs_mount(const char *mountpoint)
56 {
57 /* see if it's already mounted */
58 if (tracefs_find_mountpoint())
59 goto out;
60
61 /* if not mounted and no argument */
62 if (mountpoint == NULL) {
63 /* see if environment variable set */
64 mountpoint = getenv(PERF_TRACEFS_ENVIRONMENT);
65 /* if no environment variable, use default */
66 if (mountpoint == NULL)
67 mountpoint = TRACEFS_DEFAULT_PATH;
68 }
69
70 if (mount(NULL, mountpoint, "tracefs", 0, NULL) < 0)
71 return NULL;
72
73 /* save the mountpoint */
74 tracefs_found = true;
75 strncpy(tracefs_mountpoint, mountpoint, sizeof(tracefs_mountpoint));
76 out:
77 return tracefs_mountpoint;
78 }
79