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#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#include <sys/vfs.h>
#include <sys/mount.h>
#include <linux/kernel.h>
#include "tracefs.h"
#ifndef TRACEFS_DEFAULT_PATH
#define TRACEFS_DEFAULT_PATH "/sys/kernel/tracing"
#endif
char tracefs_mountpoint[PATH_MAX + 1] = TRACEFS_DEFAULT_PATH;
static const char * const tracefs_known_mountpoints[] = {
TRACEFS_DEFAULT_PATH,
"/sys/kernel/debug/tracing",
"/tracing",
"/trace",
0,
};
static bool tracefs_found;
/* find the path to the mounted tracefs */
const char *tracefs_find_mountpoint(void)
{
const char *ret;
if (tracefs_found)
return (const char *)tracefs_mountpoint;
ret = find_mountpoint("tracefs", (long) TRACEFS_MAGIC,
tracefs_mountpoint, PATH_MAX + 1,
tracefs_known_mountpoints);
if (ret)
tracefs_found = true;
return ret;
}
/* mount the tracefs somewhere if it's not mounted */
char *tracefs_mount(const char *mountpoint)
{
/* see if it's already mounted */
if (tracefs_find_mountpoint())
goto out;
/* if not mounted and no argument */
if (mountpoint == NULL) {
/* see if environment variable set */
mountpoint = getenv(PERF_TRACEFS_ENVIRONMENT);
/* if no environment variable, use default */
if (mountpoint == NULL)
mountpoint = TRACEFS_DEFAULT_PATH;
}
if (mount(NULL, mountpoint, "tracefs", 0, NULL) < 0)
return NULL;
/* save the mountpoint */
tracefs_found = true;
strncpy(tracefs_mountpoint, mountpoint, sizeof(tracefs_mountpoint));
out:
return tracefs_mountpoint;
}
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