sysfs.c

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#include "util.h"
#include "sysfs.h"

static const char * const sysfs_known_mountpoints[] = {
    "/sys",
    0,
};

static int sysfs_found;
char sysfs_mountpoint[PATH_MAX];

static int sysfs_valid_mountpoint(const char *sysfs)
{
    struct statfs st_fs;

    if (statfs(sysfs, &st_fs) < 0)
        return -ENOENT;
    else if (st_fs.f_type != (long) SYSFS_MAGIC)
        return -ENOENT;

    return 0;
}

const char *sysfs_find_mountpoint(void)
{
    const char * const *ptr;
    char type[100];
    FILE *fp;

    if (sysfs_found)
        return (const char *) sysfs_mountpoint;

    ptr = sysfs_known_mountpoints;
    while (*ptr) {
        if (sysfs_valid_mountpoint(*ptr) == 0) {
            sysfs_found = 1;
            strcpy(sysfs_mountpoint, *ptr);
            return sysfs_mountpoint;
        }
        ptr++;
    }

    /* give up and parse /proc/mounts */
    fp = fopen("/proc/mounts", "r");
    if (fp == NULL)
        return NULL;

    while (!sysfs_found &&
           fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
              sysfs_mountpoint, type) == 2) {

        if (strcmp(type, "sysfs") == 0)
            sysfs_found = 1;
    }

    fclose(fp);

    return sysfs_found ? sysfs_mountpoint : NULL;
}