source: MondoRescue/branches/stable/mindi-busybox/util-linux/mdev.c@ 821

/* vi:set ts=4:
 *
 * mdev - Mini udev for busybox
 *
 * Copyright 2005 Rob Landley <rob@landley.net>
 * Copyright 2005 Frank Sorenson <frank@tuxrocks.com>
 *
 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
 */

#include "busybox.h"
#include <ctype.h>
#include <errno.h>
#include <sys/mman.h>
#include <sys/sysmacros.h>
#include "xregex.h"

#define DEV_PATH    "/dev"

struct mdev_globals
{
    int root_major, root_minor;
} mdev_globals;

#define bbg mdev_globals

/* mknod in /dev based on a path like "/sys/block/hda/hda1" */
static void make_device(char *path, int delete)
{
    char *device_name;
    int major, minor, type, len, fd;
    int mode = 0660;
    uid_t uid = 0;
    gid_t gid = 0;
    char *temp = path + strlen(path);
    char *command = NULL;

    /* Try to read major/minor string.  Note that the kernel puts \n after
     * the data, so we don't need to worry about null terminating the string
     * because sscanf() will stop at the first nondigit, which \n is.  We
     * also depend on path having writeable space after it. */

    strcat(path, "/dev");
    fd = open(path, O_RDONLY);
    len = read(fd, temp + 1, 64);
    *temp++ = 0;
    close(fd);
    if (len < 1) return;

    /* Determine device name, type, major and minor */

    device_name = strrchr(path, '/') + 1;
    type = path[5]=='c' ? S_IFCHR : S_IFBLK;
    if (sscanf(temp, "%d:%d", &major, &minor) != 2) return;

    /* If we have a config file, look up permissions for this device */

    if (ENABLE_FEATURE_MDEV_CONF) {
        char *conf, *pos, *end;

        /* mmap the config file */
        if (-1 != (fd=open("/etc/mdev.conf",O_RDONLY))) {
            len = lseek(fd, 0, SEEK_END);
            conf = mmap(NULL, len, PROT_READ, MAP_PRIVATE, fd, 0);
            if (conf) {
                int line = 0;

                /* Loop through lines in mmaped file*/
                for (pos=conf; pos-conf<len;) {
                    int field;
                    char *end2;

                    line++;
                    /* find end of this line */
                    for(end=pos; end-conf<len && *end!='\n'; end++)
                        ;

                    /* Three fields: regex, uid:gid, mode */
                    for (field=0; field < (3 + ENABLE_FEATURE_MDEV_EXEC);
                            field++)
                    {
                        /* Skip whitespace */
                        while (pos<end && isspace(*pos)) pos++;
                        if (pos==end || *pos=='#') break;
                        for (end2=pos;
                            end2<end && !isspace(*end2) && *end2!='#'; end2++)
                            ;

                        if (!field) {
                            /* Regex to match this device */

                            char *regex = strndupa(pos, end2-pos);
                            regex_t match;
                            regmatch_t off;
                            int result;

                            /* Is this it? */
                            xregcomp(&match,regex, REG_EXTENDED);
                            result = regexec(&match, device_name, 1, &off, 0);
                            regfree(&match);

                            /* If not this device, skip rest of line */
                            if (result || off.rm_so
                                    || off.rm_eo != strlen(device_name))
                                break;

                        } else if (field == 1) {
                            /* uid:gid */

                            char *s, *s2;

                            /* Find : */
                            for(s=pos; s<end2 && *s!=':'; s++)
                                ;
                            if (s == end2) break;

                            /* Parse UID */
                            uid = strtoul(pos,&s2,10);
                            if (s != s2) {
                                struct passwd *pass;
                                pass = getpwnam(strndupa(pos, s-pos));
                                if (!pass) break;
                                uid = pass->pw_uid;
                            }
                            s++;
                            /* parse GID */
                            gid = strtoul(s, &s2, 10);
                            if (end2 != s2) {
                                struct group *grp;
                                grp = getgrnam(strndupa(s, end2-s));
                                if (!grp) break;
                                gid = grp->gr_gid;
                            }
                        } else if (field == 2) {
                            /* mode */

                            mode = strtoul(pos, &pos, 8);
                            if (pos != end2) break;
                        } else if (ENABLE_FEATURE_MDEV_EXEC && field == 3) {
                            // Command to run
                            char *s = "@$*", *s2;
                            if (!(s2 = strchr(s, *pos++))) {
                                // Force error
                                field = 1;
                                break;
                            }
                            if ((s2-s+1) & (1<<delete))
                                command = bb_xstrndup(pos, end-pos);
                        }

                        pos = end2;
                    }

                    /* Did everything parse happily? */

                    if (field > 2) break;
                    if (field) bb_error_msg_and_die("Bad line %d",line);

                    /* Next line */
                    pos = ++end;
                }
                munmap(conf, len);
            }
            close(fd);
        }
    }

    umask(0);
    if (!delete) {
        if (mknod(device_name, mode | type, makedev(major, minor)) && errno != EEXIST)
            bb_perror_msg_and_die("mknod %s failed", device_name);

        if (major == bbg.root_major && minor == bbg.root_minor)
            symlink(device_name, "root");
    
        if (ENABLE_FEATURE_MDEV_CONF) chown(device_name, uid, gid);
    }
    if (command) {
        int rc;
        char *s;
        
        s=bb_xasprintf("MDEV=%s",device_name);
        putenv(s);
        rc = system(command);
        s[4]=0;
        putenv(s);
        free(s);
        free(command);
        if (rc == -1) bb_perror_msg_and_die("Couldn't run %s", command);
    }
    if (delete) unlink(device_name);
}

/* Recursive search of /sys/block or /sys/class.  path must be a writeable
 * buffer of size PATH_MAX containing the directory string to start at. */

static void find_dev(char *path)
{
    DIR *dir;
    size_t len = strlen(path);
    struct dirent *entry;

    if ((dir = opendir(path)) == NULL)
        return;

    while ((entry = readdir(dir)) != NULL) {
        struct stat st;

        /* Skip "." and ".." (also skips hidden files, which is ok) */

        if (entry->d_name[0] == '.')
            continue;

        // uClibc doesn't fill out entry->d_type reliably. so we use lstat().

        snprintf(path+len, PATH_MAX-len, "/%s", entry->d_name);
        if (!lstat(path, &st) && S_ISDIR(st.st_mode)) find_dev(path);
        path[len] = 0;

        /* If there's a dev entry, mknod it */

        if (!strcmp(entry->d_name, "dev")) make_device(path, 0);
    }

    closedir(dir);
}

int mdev_main(int argc, char *argv[])
{
    char *action;
    char *env_path;
    RESERVE_CONFIG_BUFFER(temp,PATH_MAX);

    bb_xchdir(DEV_PATH);

    /* Scan */

    if (argc == 2 && !strcmp(argv[1],"-s")) {
        struct stat st;

        stat("/", &st);  // If this fails, we have bigger problems.
        bbg.root_major=major(st.st_dev);
        bbg.root_minor=minor(st.st_dev);
        strcpy(temp,"/sys/block");
        find_dev(temp);
        strcpy(temp,"/sys/class");
        find_dev(temp);

    /* Hotplug */

    } else {
        action = getenv("ACTION");
        env_path = getenv("DEVPATH");
        if (!action || !env_path)
            bb_show_usage();

        sprintf(temp, "/sys%s", env_path);
        if (!strcmp(action, "add")) make_device(temp,0);
        else if (!strcmp(action, "remove")) make_device(temp,1);
    }

    if (ENABLE_FEATURE_CLEAN_UP) RELEASE_CONFIG_BUFFER(temp);
    return 0;
}