tools/lib/lk/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/magic.h>
   9 #include <linux/kernel.h>
  10
  11 #include "debugfs.h"
  12
  13 char debugfs_mountpoint[PATH_MAX + 1] = "/sys/kernel/debug";
  14 char tracing_events_path[PATH_MAX + 1] = "/sys/kernel/debug/tracing/events";
  15
  16 static const char * const debugfs_known_mountpoints[] = {
  17         "/sys/kernel/debug/",
  18         "/debug/",
  19         0,
  20 };
  21
  22 static bool debugfs_found;
  23
  24 /* find the path to the mounted debugfs */
  25 const char *debugfs_find_mountpoint(void)
  26 {
  27         const char * const *ptr;
  28         char type[100];
  29         FILE *fp;
  30
  31         if (debugfs_found)
  32                 return (const char *)debugfs_mountpoint;
  33
  34         ptr = debugfs_known_mountpoints;
  35         while (*ptr) {
  36                 if (debugfs_valid_mountpoint(*ptr) == 0) {
  37                         debugfs_found = true;
  38                         strcpy(debugfs_mountpoint, *ptr);
  39                         return debugfs_mountpoint;
  40                 }
  41                 ptr++;
  42         }
  43
  44         /* give up and parse /proc/mounts */
  45         fp = fopen("/proc/mounts", "r");
  46         if (fp == NULL)
  47                 return NULL;
  48
  49         while (fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
  50                       debugfs_mountpoint, type) == 2) {
  51                 if (strcmp(type, "debugfs") == 0)
  52                         break;
  53         }
  54         fclose(fp);
  55
  56         if (strcmp(type, "debugfs") != 0)
  57                 return NULL;
  58
  59         debugfs_found = true;
  60
  61         return debugfs_mountpoint;
  62 }
  63
  64 /* verify that a mountpoint is actually a debugfs instance */
  65
  66 int debugfs_valid_mountpoint(const char *debugfs)
  67 {
  68         struct statfs st_fs;
  69
  70         if (statfs(debugfs, &st_fs) < 0)
  71                 return -ENOENT;
  72         else if (st_fs.f_type != (long) DEBUGFS_MAGIC)
  73                 return -ENOENT;
  74
  75         return 0;
  76 }
  77
  78 static void debugfs_set_tracing_events_path(const char *mountpoint)
  79 {
  80         snprintf(tracing_events_path, sizeof(tracing_events_path), "%s/%s",
  81                  mountpoint, "tracing/events");
  82 }
  83
  84 /* mount the debugfs somewhere if it's not mounted */
  85
  86 char *debugfs_mount(const char *mountpoint)
  87 {
  88         /* see if it's already mounted */
  89         if (debugfs_find_mountpoint())
  90                 goto out;
  91
  92         /* if not mounted and no argument */
  93         if (mountpoint == NULL) {
  94                 /* see if environment variable set */
  95                 mountpoint = getenv(PERF_DEBUGFS_ENVIRONMENT);
  96                 /* if no environment variable, use default */
  97                 if (mountpoint == NULL)
  98                         mountpoint = "/sys/kernel/debug";
  99         }
 100
 101         if (mount(NULL, mountpoint, "debugfs", 0, NULL) < 0)
 102                 return NULL;
 103
 104         /* save the mountpoint */
 105         debugfs_found = true;
 106         strncpy(debugfs_mountpoint, mountpoint, sizeof(debugfs_mountpoint));
 107 out:
 108         debugfs_set_tracing_events_path(debugfs_mountpoint);
 109         return debugfs_mountpoint;
 110 }
 111
 112 void debugfs_set_path(const char *mountpoint)
 113 {
 114         snprintf(debugfs_mountpoint, sizeof(debugfs_mountpoint), "%s", mountpoint);
 115         debugfs_set_tracing_events_path(mountpoint);
 116 }