Linux Kernel  3.7.1
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debugfs.c
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1 #include "util.h"
2 #include "debugfs.h"
3 #include "cache.h"
4 
5 #include <linux/kernel.h>
6 #include <sys/mount.h>
7 
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";
11 
12 static const char *debugfs_known_mountpoints[] = {
13  "/sys/kernel/debug/",
14  "/debug/",
15  0,
16 };
17 
18 static int debugfs_found;
19 
20 /* find the path to the mounted debugfs */
21 const char *debugfs_find_mountpoint(void)
22 {
23  const char **ptr;
24  char type[100];
25  FILE *fp;
26 
27  if (debugfs_found)
28  return (const char *) debugfs_mountpoint;
29 
30  ptr = debugfs_known_mountpoints;
31  while (*ptr) {
32  if (debugfs_valid_mountpoint(*ptr) == 0) {
33  debugfs_found = 1;
35  return debugfs_mountpoint;
36  }
37  ptr++;
38  }
39 
40  /* give up and parse /proc/mounts */
41  fp = fopen("/proc/mounts", "r");
42  if (fp == NULL)
43  return NULL;
44 
45  while (fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
46  debugfs_mountpoint, type) == 2) {
47  if (strcmp(type, "debugfs") == 0)
48  break;
49  }
50  fclose(fp);
51 
52  if (strcmp(type, "debugfs") != 0)
53  return NULL;
54 
55  debugfs_found = 1;
56 
57  return debugfs_mountpoint;
58 }
59 
60 /* verify that a mountpoint is actually a debugfs instance */
61 
62 int debugfs_valid_mountpoint(const char *debugfs)
63 {
64  struct statfs st_fs;
65 
66  if (statfs(debugfs, &st_fs) < 0)
67  return -ENOENT;
68  else if (st_fs.f_type != (long) DEBUGFS_MAGIC)
69  return -ENOENT;
70 
71  return 0;
72 }
73 
74 static void debugfs_set_tracing_events_path(const char *mountpoint)
75 {
77  mountpoint, "tracing/events");
78 }
79 
80 /* mount the debugfs somewhere if it's not mounted */
81 
82 char *debugfs_mount(const char *mountpoint)
83 {
84  /* see if it's already mounted */
86  debugfs_premounted = 1;
87  goto out;
88  }
89 
90  /* if not mounted and no argument */
91  if (mountpoint == NULL) {
92  /* see if environment variable set */
93  mountpoint = getenv(PERF_DEBUGFS_ENVIRONMENT);
94  /* if no environment variable, use default */
95  if (mountpoint == NULL)
96  mountpoint = "/sys/kernel/debug";
97  }
98 
99  if (mount(NULL, mountpoint, "debugfs", 0, NULL) < 0)
100  return NULL;
101 
102  /* save the mountpoint */
103  debugfs_found = 1;
104  strncpy(debugfs_mountpoint, mountpoint, sizeof(debugfs_mountpoint));
105 out:
106  debugfs_set_tracing_events_path(debugfs_mountpoint);
107  return debugfs_mountpoint;
108 }
109 
110 void debugfs_set_path(const char *mountpoint)
111 {
112  snprintf(debugfs_mountpoint, sizeof(debugfs_mountpoint), "%s", mountpoint);
113  debugfs_set_tracing_events_path(mountpoint);
114 }