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#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);
}
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