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 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;
  34                         strcpy(debugfs_mountpoint, *ptr);
  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 {
  76         snprintf(tracing_events_path, sizeof(tracing_events_path), "%s/%s",
  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 */
  85         if (debugfs_find_mountpoint()) {
  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 }