tools/lib/api/fs/debugfs.c

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