tools/perf/util/debugfs.c

   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 char debugfs_mountpoint[PATH_MAX + 1] = "/sys/kernel/debug";
   9 char tracing_events_path[PATH_MAX + 1] = "/sys/kernel/debug/tracing/events";
  10
  11 static const char *debugfs_known_mountpoints[] = {
  12         "/sys/kernel/debug/",
  13         "/debug/",
  14         0,
  15 };
  16
  17 static bool debugfs_found;
  18
  19 /* find the path to the mounted debugfs */
  20 const char *debugfs_find_mountpoint(void)
  21 {
  22         const char **ptr;
  23         char type[100];
  24         FILE *fp;
  25
  26         if (debugfs_found)
  27                 return (const char *) debugfs_mountpoint;
  28
  29         ptr = debugfs_known_mountpoints;
  30         while (*ptr) {
  31                 if (debugfs_valid_mountpoint(*ptr) == 0) {
  32                         debugfs_found = true;
  33                         strcpy(debugfs_mountpoint, *ptr);
  34                         return debugfs_mountpoint;
  35                 }
  36                 ptr++;
  37         }
  38
  39         /* give up and parse /proc/mounts */
  40         fp = fopen("/proc/mounts", "r");
  41         if (fp == NULL)
  42                 return NULL;
  43
  44         while (fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
  45                       debugfs_mountpoint, type) == 2) {
  46                 if (strcmp(type, "debugfs") == 0)
  47                         break;
  48         }
  49         fclose(fp);
  50
  51         if (strcmp(type, "debugfs") != 0)
  52                 return NULL;
  53
  54         debugfs_found = true;
  55
  56         return debugfs_mountpoint;
  57 }
  58
  59 /* verify that a mountpoint is actually a debugfs instance */
  60
  61 int debugfs_valid_mountpoint(const char *debugfs)
  62 {
  63         struct statfs st_fs;
  64
  65         if (statfs(debugfs, &st_fs) < 0)
  66                 return -ENOENT;
  67         else if (st_fs.f_type != (long) DEBUGFS_MAGIC)
  68                 return -ENOENT;
  69
  70         return 0;
  71 }
  72
  73 static void debugfs_set_tracing_events_path(const char *mountpoint)
  74 {
  75         snprintf(tracing_events_path, sizeof(tracing_events_path), "%s/%s",
  76                  mountpoint, "tracing/events");
  77 }
  78
  79 /* mount the debugfs somewhere if it's not mounted */
  80
  81 char *debugfs_mount(const char *mountpoint)
  82 {
  83         /* see if it's already mounted */
  84         if (debugfs_find_mountpoint())
  85                 goto out;
  86
  87         /* if not mounted and no argument */
  88         if (mountpoint == NULL) {
  89                 /* see if environment variable set */
  90                 mountpoint = getenv(PERF_DEBUGFS_ENVIRONMENT);
  91                 /* if no environment variable, use default */
  92                 if (mountpoint == NULL)
  93                         mountpoint = "/sys/kernel/debug";
  94         }
  95
  96         if (mount(NULL, mountpoint, "debugfs", 0, NULL) < 0)
  97                 return NULL;
  98
  99         /* save the mountpoint */
 100         debugfs_found = true;
 101         strncpy(debugfs_mountpoint, mountpoint, sizeof(debugfs_mountpoint));
 102 out:
 103         debugfs_set_tracing_events_path(debugfs_mountpoint);
 104         return debugfs_mountpoint;
 105 }
 106
 107 void debugfs_set_path(const char *mountpoint)
 108 {
 109         snprintf(debugfs_mountpoint, sizeof(debugfs_mountpoint), "%s", mountpoint);
 110         debugfs_set_tracing_events_path(mountpoint);
 111 }