LXR linux/tools/lib/api/fs/tracefs.c

   1#include <errno.h>
   2#include <stdio.h>
   3#include <stdlib.h>
   4#include <string.h>
   5#include <unistd.h>
   6#include <stdbool.h>
   7#include <sys/vfs.h>
   8#include <sys/types.h>
   9#include <sys/stat.h>
  10#include <sys/mount.h>
  11#include <linux/kernel.h>
  12
  13#include "tracefs.h"
  14
  15#ifndef TRACEFS_DEFAULT_PATH
  16#define TRACEFS_DEFAULT_PATH            "/sys/kernel/tracing"
  17#endif
  18
  19char tracefs_mountpoint[PATH_MAX + 1] = TRACEFS_DEFAULT_PATH;
  20
  21static const char * const tracefs_known_mountpoints[] = {
  22        TRACEFS_DEFAULT_PATH,
  23        "/sys/kernel/debug/tracing",
  24        "/tracing",
  25        "/trace",
  26        0,
  27};
  28
  29static bool tracefs_found;
  30
  31bool tracefs_configured(void)
  32{
  33        return tracefs_find_mountpoint() != NULL;
  34}
  35
  36/* find the path to the mounted tracefs */
  37const char *tracefs_find_mountpoint(void)
  38{
  39        const char *ret;
  40
  41        if (tracefs_found)
  42                return (const char *)tracefs_mountpoint;
  43
  44        ret = find_mountpoint("tracefs", (long) TRACEFS_MAGIC,
  45                              tracefs_mountpoint, PATH_MAX + 1,
  46                              tracefs_known_mountpoints);
  47
  48        if (ret)
  49                tracefs_found = true;
  50
  51        return ret;
  52}
  53
  54/* mount the tracefs somewhere if it's not mounted */
  55char *tracefs_mount(const char *mountpoint)
  56{
  57        /* see if it's already mounted */
  58        if (tracefs_find_mountpoint())
  59                goto out;
  60
  61        /* if not mounted and no argument */
  62        if (mountpoint == NULL) {
  63                /* see if environment variable set */
  64                mountpoint = getenv(PERF_TRACEFS_ENVIRONMENT);
  65                /* if no environment variable, use default */
  66                if (mountpoint == NULL)
  67                        mountpoint = TRACEFS_DEFAULT_PATH;
  68        }
  69
  70        if (mount(NULL, mountpoint, "tracefs", 0, NULL) < 0)
  71                return NULL;
  72
  73        /* save the mountpoint */
  74        tracefs_found = true;
  75        strncpy(tracefs_mountpoint, mountpoint, sizeof(tracefs_mountpoint));
  76out:
  77        return tracefs_mountpoint;
  78}
  79