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 #include "tracefs.h"
  16
  17 #ifndef DEBUGFS_DEFAULT_PATH
  18 #define DEBUGFS_DEFAULT_PATH            "/sys/kernel/debug"
  19 #endif
  20
  21 char debugfs_mountpoint[PATH_MAX + 1] = DEBUGFS_DEFAULT_PATH;
  22
  23 static const char * const debugfs_known_mountpoints[] = {
  24         DEBUGFS_DEFAULT_PATH,
  25         "/debug",
  26         0,
  27 };
  28
  29 static bool debugfs_found;
  30
  31 bool debugfs_configured(void)
  32 {
  33         return debugfs_find_mountpoint() != NULL;
  34 }
  35
  36 /* find the path to the mounted debugfs */
  37 const char *debugfs_find_mountpoint(void)
  38 {
  39         const char *ret;
  40
  41         if (debugfs_found)
  42                 return (const char *)debugfs_mountpoint;
  43
  44         ret = find_mountpoint("debugfs", (long) DEBUGFS_MAGIC,
  45                               debugfs_mountpoint, PATH_MAX + 1,
  46                               debugfs_known_mountpoints);
  47         if (ret)
  48                 debugfs_found = true;
  49
  50         return ret;
  51 }
  52
  53 /* mount the debugfs somewhere if it's not mounted */
  54 char *debugfs_mount(const char *mountpoint)
  55 {
  56         /* see if it's already mounted */
  57         if (debugfs_find_mountpoint())
  58                 goto out;
  59
  60         /* if not mounted and no argument */
  61         if (mountpoint == NULL) {
  62                 /* see if environment variable set */
  63                 mountpoint = getenv(PERF_DEBUGFS_ENVIRONMENT);
  64                 /* if no environment variable, use default */
  65                 if (mountpoint == NULL)
  66                         mountpoint = DEBUGFS_DEFAULT_PATH;
  67         }
  68
  69         if (mount(NULL, mountpoint, "debugfs", 0, NULL) < 0)
  70                 return NULL;
  71
  72         /* save the mountpoint */
  73         debugfs_found = true;
  74         strncpy(debugfs_mountpoint, mountpoint, sizeof(debugfs_mountpoint));
  75 out:
  76         return debugfs_mountpoint;
  77 }
  78
  79 int debugfs__strerror_open(int err, char *buf, size_t size, const char *filename)
  80 {
  81         char sbuf[128];
  82
  83         switch (err) {
  84         case ENOENT:
  85                 if (debugfs_found) {
  86                         snprintf(buf, size,
  87                                  "Error:\tFile %s/%s not found.\n"
  88                                  "Hint:\tPerhaps this kernel misses some CONFIG_ setting to enable this feature?.\n",
  89                                  debugfs_mountpoint, filename);
  90                         break;
  91                 }
  92                 snprintf(buf, size, "%s",
  93                          "Error:\tUnable to find debugfs\n"
  94                          "Hint:\tWas your kernel compiled with debugfs support?\n"
  95                          "Hint:\tIs the debugfs filesystem mounted?\n"
  96                          "Hint:\tTry 'sudo mount -t debugfs nodev /sys/kernel/debug'");
  97                 break;
  98         case EACCES: {
  99                 const char *mountpoint = debugfs_mountpoint;
 100
 101                 if (!access(debugfs_mountpoint, R_OK) && strncmp(filename, "tracing/", 8) == 0) {
 102                         const char *tracefs_mntpoint = tracefs_find_mountpoint();
 103
 104                         if (tracefs_mntpoint)
 105                                 mountpoint = tracefs_mntpoint;
 106                 }
 107
 108                 snprintf(buf, size,
 109                          "Error:\tNo permissions to read %s/%s\n"
 110                          "Hint:\tTry 'sudo mount -o remount,mode=755 %s'\n",
 111                          debugfs_mountpoint, filename, mountpoint);
 112         }
 113                 break;
 114         default:
 115                 snprintf(buf, size, "%s", strerror_r(err, sbuf, sizeof(sbuf)));
 116                 break;
 117         }
 118
 119         return 0;
 120 }
 121
 122 int debugfs__strerror_open_tp(int err, char *buf, size_t size, const char *sys, const char *name)
 123 {
 124         char path[PATH_MAX];
 125
 126         snprintf(path, PATH_MAX, "tracing/events/%s/%s", sys, name ?: "*");
 127
 128         return debugfs__strerror_open(err, buf, size, path);
 129 }