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
 12char debugfs_mountpoint[PATH_MAX + 1] = "/sys/kernel/debug";
 13
 14static const char * const debugfs_known_mountpoints[] = {
 15	"/sys/kernel/debug",
 16	"/debug",
 17	0,
 18};
 19
 20static bool debugfs_found;
 21
 22/* find the path to the mounted debugfs */
 23const 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
 64int 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 */
 77char *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));
 98out:
 99	return debugfs_mountpoint;
100}