kernel/tools/lib/api/fs/debugfs.c

   1 #define _GNU_SOURCE
   2 #include <errno.h>
   3 #include <stdio.h>
   4 #include <stdlib.h>
   5 #include <string.h>
   6 #include <unistd.h>
   7 #include <stdbool.h>
   8 #include <sys/vfs.h>
   9 #include <sys/types.h>
  10 #include <sys/stat.h>
  11 #include <sys/mount.h>
  12 #include <linux/kernel.h>
  13
  14 #include "debugfs.h"
  15
  16 #ifndef DEBUGFS_DEFAULT_PATH
  17 #define DEBUGFS_DEFAULT_PATH            "/sys/kernel/debug"
  18 #endif
  19
  20 char debugfs_mountpoint[PATH_MAX + 1] = DEBUGFS_DEFAULT_PATH;
  21
  22 static const char * const debugfs_known_mountpoints[] = {
  23         DEBUGFS_DEFAULT_PATH,
  24         "/debug",
  25         0,
  26 };
  27
  28 static bool debugfs_found;
  29
  30 bool debugfs_configured(void)
  31 {
  32         return debugfs_find_mountpoint() != NULL;
  33 }
  34
  35 /* find the path to the mounted debugfs */
  36 const char *debugfs_find_mountpoint(void)
  37 {
  38         const char *ret;
  39
  40         if (debugfs_found)
  41                 return (const char *)debugfs_mountpoint;
  42
  43         ret = find_mountpoint("debugfs", (long) DEBUGFS_MAGIC,
  44                               debugfs_mountpoint, PATH_MAX + 1,
  45                               debugfs_known_mountpoints);
  46         if (ret)
  47                 debugfs_found = true;
  48
  49         return ret;
  50 }
  51
  52 /* mount the debugfs somewhere if it's not mounted */
  53 char *debugfs_mount(const char *mountpoint)
  54 {
  55         /* see if it's already mounted */
  56         if (debugfs_find_mountpoint())
  57                 goto out;
  58
  59         /* if not mounted and no argument */
  60         if (mountpoint == NULL) {
  61                 /* see if environment variable set */
  62                 mountpoint = getenv(PERF_DEBUGFS_ENVIRONMENT);
  63                 /* if no environment variable, use default */
  64                 if (mountpoint == NULL)
  65                         mountpoint = DEBUGFS_DEFAULT_PATH;
  66         }
  67
  68         if (mount(NULL, mountpoint, "debugfs", 0, NULL) < 0)
  69                 return NULL;
  70
  71         /* save the mountpoint */
  72         debugfs_found = true;
  73         strncpy(debugfs_mountpoint, mountpoint, sizeof(debugfs_mountpoint));
  74 out:
  75         return debugfs_mountpoint;
  76 }
  77
  78 int debugfs__strerror_open(int err, char *buf, size_t size, const char *filename)
  79 {
  80         char sbuf[128];
  81
  82         switch (err) {
  83         case ENOENT:
  84                 if (debugfs_found) {
  85                         snprintf(buf, size,
  86                                  "Error:\tFile %s/%s not found.\n"
  87                                  "Hint:\tPerhaps this kernel misses some CONFIG_ setting to enable this feature?.\n",
  88                                  debugfs_mountpoint, filename);
  89                         break;
  90                 }
  91                 snprintf(buf, size, "%s",
  92                          "Error:\tUnable to find debugfs\n"
  93                          "Hint:\tWas your kernel compiled with debugfs support?\n"
  94                          "Hint:\tIs the debugfs filesystem mounted?\n"
  95                          "Hint:\tTry 'sudo mount -t debugfs nodev /sys/kernel/debug'");
  96                 break;
  97         case EACCES:
  98                 snprintf(buf, size,
  99                          "Error:\tNo permissions to read %s/%s\n"
 100                          "Hint:\tTry 'sudo mount -o remount,mode=755 %s'\n",
 101                          debugfs_mountpoint, filename, debugfs_mountpoint);
 102                 break;
 103         default:
 104                 snprintf(buf, size, "%s", strerror_r(err, sbuf, sizeof(sbuf)));
 105                 break;
 106         }
 107
 108         return 0;
 109 }
 110
 111 int debugfs__strerror_open_tp(int err, char *buf, size_t size, const char *sys, const char *name)
 112 {
 113         char path[PATH_MAX];
 114
 115         snprintf(path, PATH_MAX, "tracing/events/%s/%s", sys, name ?: "*");
 116
 117         return debugfs__strerror_open(err, buf, size, path);
 118 }