#define _GNU_SOURCE#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 "debugfs.h" char debugfs_mountpoint[PATH_MAX + 1] = "/sys/kernel/debug"; static const char * const debugfs_known_mountpoints[] = {	"/sys/kernel/debug",	"/debug",	0,}; static bool debugfs_found; /* find the path to the mounted debugfs */const char *debugfs_find_mountpoint(void){	const char * const *ptr;	char type[100];	FILE *fp; 	if (debugfs_found)		return (const char *)debugfs_mountpoint; 	ptr = debugfs_known_mountpoints;	while (*ptr) {		if (debugfs_valid_mountpoint(*ptr) == 0) {			debugfs_found = true;			strcpy(debugfs_mountpoint, *ptr);			return debugfs_mountpoint;		}		ptr++;	} 	/* give up and parse /proc/mounts */	fp = fopen("/proc/mounts", "r");	if (fp == NULL)		return NULL; 	while (fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",		      debugfs_mountpoint, type) == 2) {		if (strcmp(type, "debugfs") == 0)			break;	}	fclose(fp); 	if (strcmp(type, "debugfs") != 0)		return NULL; 	debugfs_found = true; 	return debugfs_mountpoint;} /* verify that a mountpoint is actually a debugfs instance */ int debugfs_valid_mountpoint(const char *debugfs){	struct statfs st_fs; 	if (statfs(debugfs, &st_fs) < 0)		return -ENOENT;	else if ((long)st_fs.f_type != (long)DEBUGFS_MAGIC)		return -ENOENT; 	return 0;} /* mount the debugfs somewhere if it's not mounted */char *debugfs_mount(const char *mountpoint){	/* see if it's already mounted */	if (debugfs_find_mountpoint())		goto out; 	/* if not mounted and no argument */	if (mountpoint == NULL) {		/* see if environment variable set */		mountpoint = getenv(PERF_DEBUGFS_ENVIRONMENT);		/* if no environment variable, use default */		if (mountpoint == NULL)			mountpoint = "/sys/kernel/debug";	} 	if (mount(NULL, mountpoint, "debugfs", 0, NULL) < 0)		return NULL; 	/* save the mountpoint */	debugfs_found = true;	strncpy(debugfs_mountpoint, mountpoint, sizeof(debugfs_mountpoint));out:	return debugfs_mountpoint;} int debugfs__strerror_open(int err, char *buf, size_t size, const char *filename){	char sbuf[128]; 	switch (err) {	case ENOENT:		if (debugfs_found) {			snprintf(buf, size,				 "Error:\tFile %s/%s not found.\n"				 "Hint:\tPerhaps this kernel misses some CONFIG_ setting to enable this feature?.\n",				 debugfs_mountpoint, filename);			break;		}		snprintf(buf, size, "%s",			 "Error:\tUnable to find debugfs\n"			 "Hint:\tWas your kernel compiled with debugfs support?\n"			 "Hint:\tIs the debugfs filesystem mounted?\n"			 "Hint:\tTry 'sudo mount -t debugfs nodev /sys/kernel/debug'");		break;	case EACCES:		snprintf(buf, size,			 "Error:\tNo permissions to read %s/%s\n"			 "Hint:\tTry 'sudo mount -o remount,mode=755 %s'\n",			 debugfs_mountpoint, filename, debugfs_mountpoint);		break;	default:		snprintf(buf, size, "%s", strerror_r(err, sbuf, sizeof(sbuf)));		break;	} 	return 0;} int debugfs__strerror_open_tp(int err, char *buf, size_t size, const char *sys, const char *name){	char path[PATH_MAX]; 	snprintf(path, PATH_MAX, "tracing/events/%s/%s", sys, name ?: "*"); 	return debugfs__strerror_open(err, buf, size, path);}