/* vi: set sw=4 ts=4: */
/*
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */

/*
        devfsd implementation for busybox

        Copyright (C) 2003 by Tito Ragusa <farmatito@tiscali.it>

        Busybox version is based on some previous work and ideas
        Copyright (C) [2003] by [Matteo Croce] <3297627799@wind.it>

        devfsd.c

        Main file for  devfsd  (devfs daemon for Linux).

    Copyright (C) 1998-2002  Richard Gooch

        devfsd.h

    Header file for  devfsd  (devfs daemon for Linux).

    Copyright (C) 1998-2000  Richard Gooch

        compat_name.c

    Compatibility name file for  devfsd  (build compatibility names).

    Copyright (C) 1998-2002  Richard Gooch

        expression.c

    This code provides Borne Shell-like expression expansion.

    Copyright (C) 1997-1999  Richard Gooch

        This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

    Richard Gooch may be reached by email at  rgooch@atnf.csiro.au
    The postal address is:
      Richard Gooch, c/o ATNF, P. O. Box 76, Epping, N.S.W., 2121, Australia.
*/

//usage:#define devfsd_trivial_usage
//usage:       "mntpnt [-v]" IF_DEVFSD_FG_NP("[-fg][-np]")
//usage:#define devfsd_full_usage "\n\n"
//usage:       "Manage devfs permissions and old device name symlinks\n"
//usage:     "\n        mntpnt  The mount point where devfs is mounted"
//usage:     "\n        -v      Print the protocol version numbers for devfsd"
//usage:     "\n                and the kernel-side protocol version and exit"
//usage:        IF_DEVFSD_FG_NP(
//usage:     "\n        -fg     Run in foreground"
//usage:     "\n        -np     Exit after parsing the configuration file"
//usage:     "\n                and processing synthetic REGISTER events,"
//usage:     "\n                don't poll for events"
//usage:        )

#include "libbb.h"
#include "xregex.h"
#include <syslog.h>

#include <sys/un.h>
#include <sys/sysmacros.h>

/* Various defines taken from linux/major.h */
#define IDE0_MAJOR      3
#define IDE1_MAJOR      22
#define IDE2_MAJOR      33
#define IDE3_MAJOR      34
#define IDE4_MAJOR      56
#define IDE5_MAJOR      57
#define IDE6_MAJOR      88
#define IDE7_MAJOR      89
#define IDE8_MAJOR      90
#define IDE9_MAJOR      91


/* Various defines taken from linux/devfs_fs.h */
#define DEVFSD_PROTOCOL_REVISION_KERNEL  5
#define DEVFSD_IOCTL_BASE       'd'
/*  These are the various ioctls  */
#define DEVFSDIOC_GET_PROTO_REV         _IOR(DEVFSD_IOCTL_BASE, 0, int)
#define DEVFSDIOC_SET_EVENT_MASK        _IOW(DEVFSD_IOCTL_BASE, 2, int)
#define DEVFSDIOC_RELEASE_EVENT_QUEUE   _IOW(DEVFSD_IOCTL_BASE, 3, int)
#define DEVFSDIOC_SET_CONFIG_DEBUG_MASK _IOW(DEVFSD_IOCTL_BASE, 4, int)
#define DEVFSD_NOTIFY_REGISTERED    0
#define DEVFSD_NOTIFY_UNREGISTERED  1
#define DEVFSD_NOTIFY_ASYNC_OPEN    2
#define DEVFSD_NOTIFY_CLOSE         3
#define DEVFSD_NOTIFY_LOOKUP        4
#define DEVFSD_NOTIFY_CHANGE        5
#define DEVFSD_NOTIFY_CREATE        6
#define DEVFSD_NOTIFY_DELETE        7
#define DEVFS_PATHLEN               1024
/*  Never change this otherwise the binary interface will change   */

struct devfsd_notify_struct {
        /*  Use native C types to ensure same types in kernel and user space     */
        unsigned int type;           /*  DEVFSD_NOTIFY_* value                   */
        unsigned int mode;           /*  Mode of the inode or device entry       */
        unsigned int major;          /*  Major number of device entry            */
        unsigned int minor;          /*  Minor number of device entry            */
        unsigned int uid;            /*  Uid of process, inode or device entry   */
        unsigned int gid;            /*  Gid of process, inode or device entry   */
        unsigned int overrun_count;  /*  Number of lost events                   */
        unsigned int namelen;        /*  Number of characters not including '\0' */
        /*  The device name MUST come last                                       */
        char devname[DEVFS_PATHLEN]; /*  This will be '\0' terminated            */
};

#define BUFFER_SIZE 16384
#define DEVFSD_VERSION "1.3.25"
#define CONFIG_FILE  "/etc/devfsd.conf"
#define MODPROBE                "/sbin/modprobe"
#define MODPROBE_SWITCH_1 "-k"
#define MODPROBE_SWITCH_2 "-C"
#define CONFIG_MODULES_DEVFS "/etc/modules.devfs"
#define MAX_ARGS     (6 + 1)
#define MAX_SUBEXPR  10
#define STRING_LENGTH 255

/* for get_uid_gid() */
#define UID                     0
#define GID                     1

/* fork_and_execute() */
# define DIE                    1
# define NO_DIE                 0

/* for dir_operation() */
#define RESTORE         0
#define SERVICE         1
#define READ_CONFIG 2

/*  Update only after changing code to reflect new protocol  */
#define DEVFSD_PROTOCOL_REVISION_DAEMON  5

/*  Compile-time check  */
#if DEVFSD_PROTOCOL_REVISION_KERNEL != DEVFSD_PROTOCOL_REVISION_DAEMON
#error protocol version mismatch. Update your kernel headers
#endif

#define AC_PERMISSIONS                          0
#define AC_MODLOAD                                      1
#define AC_EXECUTE                                      2
#define AC_MFUNCTION                            3       /* not supported by busybox */
#define AC_CFUNCTION                            4       /* not supported by busybox */
#define AC_COPY                                         5
#define AC_IGNORE                                       6
#define AC_MKOLDCOMPAT                          7
#define AC_MKNEWCOMPAT                          8
#define AC_RMOLDCOMPAT                          9
#define AC_RMNEWCOMPAT                          10
#define AC_RESTORE                                      11

struct permissions_type {
        mode_t mode;
        uid_t uid;
        gid_t gid;
};

struct execute_type {
        char *argv[MAX_ARGS + 1];  /*  argv[0] must always be the programme  */
};

struct copy_type {
        const char *source;
        const char *destination;
};

struct action_type {
        unsigned int what;
        unsigned int when;
};

struct config_entry_struct {
        struct action_type action;
        regex_t preg;
        union
        {
        struct permissions_type permissions;
        struct execute_type execute;
        struct copy_type copy;
        }
        u;
        struct config_entry_struct *next;
};

struct get_variable_info {
        const struct devfsd_notify_struct *info;
        const char *devname;
        char devpath[STRING_LENGTH];
};

static void dir_operation(int , const char * , int,  unsigned long*);
static void service(struct stat statbuf, char *path);
static int st_expr_expand(char *, unsigned, const char *, const char *(*)(const char *, void *), void *);
static const char *get_old_name(const char *, unsigned, char *, unsigned, unsigned);
static int mksymlink(const char *oldpath, const char *newpath);
static void read_config_file(char *path, int optional, unsigned long *event_mask);
static void process_config_line(const char *, unsigned long *);
static int  do_servicing(int, unsigned long);
static void service_name(const struct devfsd_notify_struct *);
static void action_permissions(const struct devfsd_notify_struct *, const struct config_entry_struct *);
static void action_execute(const struct devfsd_notify_struct *, const struct config_entry_struct *,
                                                        const regmatch_t *, unsigned);
static void action_modload(const struct devfsd_notify_struct *info, const struct config_entry_struct *entry);
static void action_copy(const struct devfsd_notify_struct *, const struct config_entry_struct *,
                                                const regmatch_t *, unsigned);
static void action_compat(const struct devfsd_notify_struct *, unsigned);
static void free_config(void);
static void restore(char *spath, struct stat source_stat, int rootlen);
static int copy_inode(const char *, const struct stat *, mode_t, const char *, const struct stat *);
static mode_t get_mode(const char *);
static void signal_handler(int);
static const char *get_variable(const char *, void *);
static int make_dir_tree(const char *);
static int expand_expression(char *, unsigned, const char *, const char *(*)(const char *, void *), void *,
                                                        const char *, const regmatch_t *, unsigned);
static void expand_regexp(char *, size_t, const char *, const char *, const regmatch_t *, unsigned);
static const char *expand_variable(     char *, unsigned, unsigned *, const char *,
                                                                        const char *(*)(const char *, void *), void *);
static const char *get_variable_v2(const char *, const char *(*)(const char *, void *), void *);
static char get_old_ide_name(unsigned, unsigned);
static char *write_old_sd_name(char *, unsigned, unsigned, const char *);

/* busybox functions */
static int get_uid_gid(int flag, const char *string);
static void safe_memcpy(char * dest, const char * src, int len);
static unsigned int scan_dev_name_common(const char *d, unsigned int n, int addendum, const char *ptr);
static unsigned int scan_dev_name(const char *d, unsigned int n, const char *ptr);

/* Structs and vars */
static struct config_entry_struct *first_config = NULL;
static struct config_entry_struct *last_config = NULL;
static char *mount_point = NULL;
static volatile int caught_signal = FALSE;
static volatile int caught_sighup = FALSE;
static struct initial_symlink_struct {
        const char *dest;
        const char *name;
} initial_symlinks[] = {
        {"/proc/self/fd", "fd"},
        {"fd/0", "stdin"},
        {"fd/1", "stdout"},
        {"fd/2", "stderr"},
        {NULL, NULL},
};

static struct event_type {
        unsigned int type;        /*  The DEVFSD_NOTIFY_* value                  */
        const char *config_name;  /*  The name used in the config file           */
} event_types[] = {
        {DEVFSD_NOTIFY_REGISTERED,   "REGISTER"},
        {DEVFSD_NOTIFY_UNREGISTERED, "UNREGISTER"},
        {DEVFSD_NOTIFY_ASYNC_OPEN,   "ASYNC_OPEN"},
        {DEVFSD_NOTIFY_CLOSE,        "CLOSE"},
        {DEVFSD_NOTIFY_LOOKUP,       "LOOKUP"},
        {DEVFSD_NOTIFY_CHANGE,       "CHANGE"},
        {DEVFSD_NOTIFY_CREATE,       "CREATE"},
        {DEVFSD_NOTIFY_DELETE,       "DELETE"},
        {0xffffffff,                 NULL}
};

/* Busybox messages */

static const char bb_msg_proto_rev[] ALIGN1          = "protocol revision";
static const char bb_msg_bad_config[] ALIGN1         = "bad %s config file: %s";
static const char bb_msg_small_buffer[] ALIGN1       = "buffer too small";
static const char bb_msg_variable_not_found[] ALIGN1 = "variable: %s not found";

/* Busybox stuff */
#if ENABLE_DEVFSD_VERBOSE || ENABLE_DEBUG
#define info_logger(p, fmt, args...)                 bb_info_msg(fmt, ## args)
#define msg_logger(p, fmt, args...)                  bb_error_msg(fmt, ## args)
#define msg_logger_and_die(p, fmt, args...)          bb_error_msg_and_die(fmt, ## args)
#define error_logger(p, fmt, args...)                bb_perror_msg(fmt, ## args)
#define error_logger_and_die(p, fmt, args...)        bb_perror_msg_and_die(fmt, ## args)
#else
#define info_logger(p, fmt, args...)
#define msg_logger(p, fmt, args...)
#define msg_logger_and_die(p, fmt, args...)           exit(EXIT_FAILURE)
#define error_logger(p, fmt, args...)
#define error_logger_and_die(p, fmt, args...)         exit(EXIT_FAILURE)
#endif

static void safe_memcpy(char *dest, const char *src, int len)
{
        memcpy(dest , src, len);
        dest[len] = '\0';
}

static unsigned int scan_dev_name_common(const char *d, unsigned int n, int addendum, const char *ptr)
{
        if (d[n - 4] == 'd' && d[n - 3] == 'i' && d[n - 2] == 's' && d[n - 1] == 'c')
                return 2 + addendum;
        if (d[n - 2] == 'c' && d[n - 1] == 'd')
                return 3 + addendum;
        if (ptr[0] == 'p' && ptr[1] == 'a' && ptr[2] == 'r' && ptr[3] == 't')
                return 4 + addendum;
        if (ptr[n - 2] == 'm' && ptr[n - 1] == 't')
                return 5 + addendum;
        return 0;
}

static unsigned int scan_dev_name(const char *d, unsigned int n, const char *ptr)
{
        if (d[0] == 's' && d[1] == 'c' && d[2] == 's' && d[3] == 'i' && d[4] == '/') {
                if (d[n - 7] == 'g' && d[n - 6] == 'e' && d[n - 5] == 'n'
                        && d[n - 4] == 'e' && d[n - 3] == 'r' && d[n - 2] == 'i' && d[n - 1] == 'c'
                )
                        return 1;
                return scan_dev_name_common(d, n, 0, ptr);
        }
        if (d[0] == 'i' && d[1] == 'd' && d[2] == 'e' && d[3] == '/'
                && d[4] == 'h' && d[5] == 'o' && d[6] == 's' && d[7] == 't'
        )
                return scan_dev_name_common(d, n, 4, ptr);
        if (d[0] == 's' && d[1] == 'b' && d[2] == 'p' && d[3] == '/')
                return 10;
        if (d[0] == 'v' && d[1] == 'c' && d[2] == 'c' && d[3] == '/')
                return 11;
        if (d[0] == 'p' && d[1] == 't' && d[2] == 'y' && d[3] == '/')
                return 12;
        return 0;
}

/*  Public functions follow  */

int devfsd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int devfsd_main(int argc, char **argv)
{
        int print_version = FALSE;
        int do_daemon = TRUE;
        int no_polling = FALSE;
        int do_scan;
        int fd, proto_rev, count;
        unsigned long event_mask = 0;
        struct sigaction new_action;
        struct initial_symlink_struct *curr;

        if (argc < 2)
                bb_show_usage();

        for (count = 2; count < argc; ++count) {
                if (argv[count][0] == '-') {
                        if (argv[count][1] == 'v' && !argv[count][2]) /* -v */
                                print_version = TRUE;
                        else if (ENABLE_DEVFSD_FG_NP && argv[count][1] == 'f'
                         && argv[count][2] == 'g' && !argv[count][3]) /* -fg */
                                do_daemon = FALSE;
                        else if (ENABLE_DEVFSD_FG_NP && argv[count][1] == 'n'
                         && argv[count][2] == 'p' && !argv[count][3]) /* -np */
                                no_polling = TRUE;
                        else
                                bb_show_usage();
                }
        }

        mount_point = bb_simplify_path(argv[1]);

        xchdir(mount_point);

        fd = xopen(".devfsd", O_RDONLY);
        close_on_exec_on(fd);
        xioctl(fd, DEVFSDIOC_GET_PROTO_REV, &proto_rev);

        /*setup initial entries */
        for (curr = initial_symlinks; curr->dest != NULL; ++curr)
                symlink(curr->dest, curr->name);

        /* NB: The check for CONFIG_FILE is done in read_config_file() */

        if (print_version || (DEVFSD_PROTOCOL_REVISION_DAEMON != proto_rev)) {
                printf("%s v%s\nDaemon %s:\t%d\nKernel-side %s:\t%d\n",
                                applet_name, DEVFSD_VERSION, bb_msg_proto_rev,
                                DEVFSD_PROTOCOL_REVISION_DAEMON, bb_msg_proto_rev, proto_rev);
                if (DEVFSD_PROTOCOL_REVISION_DAEMON != proto_rev)
                        bb_error_msg_and_die("%s mismatch!", bb_msg_proto_rev);
                exit(EXIT_SUCCESS); /* -v */
        }
        /*  Tell kernel we are special(i.e. we get to see hidden entries)  */
        xioctl(fd, DEVFSDIOC_SET_EVENT_MASK, 0);

        /*  Set up SIGHUP and SIGUSR1 handlers  */
        sigemptyset(&new_action.sa_mask);
        new_action.sa_flags = 0;
        new_action.sa_handler = signal_handler;
        sigaction_set(SIGHUP, &new_action);
        sigaction_set(SIGUSR1, &new_action);

        printf("%s v%s started for %s\n", applet_name, DEVFSD_VERSION, mount_point);

        /*  Set umask so that mknod(2), open(2) and mkdir(2) have complete control over permissions  */
        umask(0);
        read_config_file((char*)CONFIG_FILE, FALSE, &event_mask);
        /*  Do the scan before forking, so that boot scripts see the finished product  */
        dir_operation(SERVICE, mount_point, 0, NULL);

        if (ENABLE_DEVFSD_FG_NP && no_polling)
                exit(EXIT_SUCCESS);

        if (ENABLE_DEVFSD_VERBOSE || ENABLE_DEBUG)
                logmode = LOGMODE_BOTH;
        else if (do_daemon == TRUE)
                logmode = LOGMODE_SYSLOG;
        /* This is the default */
        /*else
                logmode = LOGMODE_STDIO; */

        if (do_daemon) {
                /*  Release so that the child can grab it  */
                xioctl(fd, DEVFSDIOC_RELEASE_EVENT_QUEUE, 0);
                bb_daemonize_or_rexec(0, argv);
        } else if (ENABLE_DEVFSD_FG_NP) {
                setpgid(0, 0);  /*  Become process group leader                    */
        }

        while (TRUE) {
                do_scan = do_servicing(fd, event_mask);

                free_config();
                read_config_file((char*)CONFIG_FILE, FALSE, &event_mask);
                if (do_scan)
                        dir_operation(SERVICE, mount_point, 0, NULL);
        }
        if (ENABLE_FEATURE_CLEAN_UP) free(mount_point);
}   /*  End Function main  */


/*  Private functions follow  */

static void read_config_file(char *path, int optional, unsigned long *event_mask)
/*  [SUMMARY] Read a configuration database.
    <path> The path to read the database from. If this is a directory, all
    entries in that directory will be read(except hidden entries).
    <optional> If TRUE, the routine will silently ignore a missing config file.
    <event_mask> The event mask is written here. This is not initialised.
    [RETURNS] Nothing.
*/
{
        struct stat statbuf;
        FILE *fp;
        char buf[STRING_LENGTH];
        char *line = NULL;
        char *p;

        if (stat(path, &statbuf) == 0) {
                /* Don't read 0 length files: ignored */
                /*if (statbuf.st_size == 0)
                                return;*/
                if (S_ISDIR(statbuf.st_mode)) {
                        p = bb_simplify_path(path);
                        dir_operation(READ_CONFIG, p, 0, event_mask);
                        free(p);
                        return;
                }
                fp = fopen_for_read(path);
                if (fp != NULL) {
                        while (fgets(buf, STRING_LENGTH, fp) != NULL) {
                                /*  Skip whitespace  */
                                line = buf;
                                line = skip_whitespace(line);
                                if (line[0] == '\0' || line[0] == '#')
                                        continue;
                                process_config_line(line, event_mask);
                        }
                        fclose(fp);
                } else {
                        goto read_config_file_err;
                }
        } else {
read_config_file_err:
                if (optional == 0 && errno == ENOENT)
                        error_logger_and_die(LOG_ERR, "read config file: %s", path);
        }
}   /*  End Function read_config_file   */

static void process_config_line(const char *line, unsigned long *event_mask)
/*  [SUMMARY] Process a line from a configuration file.
    <line> The configuration line.
    <event_mask> The event mask is written here. This is not initialised.
    [RETURNS] Nothing.
*/
{
        int  num_args, count;
        struct config_entry_struct *new;
        char p[MAX_ARGS][STRING_LENGTH];
        char when[STRING_LENGTH], what[STRING_LENGTH];
        char name[STRING_LENGTH];
        const char *msg = "";
        char *ptr;
        int i;

        /* !!!! Only Uppercase Keywords in devsfd.conf */
        static const char options[] ALIGN1 =
                "CLEAR_CONFIG\0""INCLUDE\0""OPTIONAL_INCLUDE\0"
                "RESTORE\0""PERMISSIONS\0""MODLOAD\0""EXECUTE\0"
                "COPY\0""IGNORE\0""MKOLDCOMPAT\0""MKNEWCOMPAT\0"
                "RMOLDCOMPAT\0""RMNEWCOMPAT\0";

        for (count = 0; count < MAX_ARGS; ++count)
                p[count][0] = '\0';
        num_args = sscanf(line, "%s %s %s %s %s %s %s %s %s %s",
                        when, name, what,
                        p[0], p[1], p[2], p[3], p[4], p[5], p[6]);

        i = index_in_strings(options, when);

        /* "CLEAR_CONFIG" */
        if (i == 0) {
                free_config();
                *event_mask = 0;
                return;
        }

        if (num_args < 2)
                goto process_config_line_err;

        /* "INCLUDE" & "OPTIONAL_INCLUDE" */
        if (i == 1 || i == 2) {
                st_expr_expand(name, STRING_LENGTH, name, get_variable, NULL);
                info_logger(LOG_INFO, "%sinclude: %s", (toupper(when[0]) == 'I') ? "": "optional_", name);
                read_config_file(name, (toupper(when[0]) == 'I') ? FALSE : TRUE, event_mask);
                return;
        }
        /* "RESTORE" */
        if (i == 3) {
                dir_operation(RESTORE, name, strlen(name),NULL);
                return;
        }
        if (num_args < 3)
                goto process_config_line_err;

        new = xzalloc(sizeof *new);

        for (count = 0; event_types[count].config_name != NULL; ++count) {
                if (strcasecmp(when, event_types[count].config_name) != 0)
                        continue;
                new->action.when = event_types[count].type;
                break;
        }
        if (event_types[count].config_name == NULL) {
                msg = "WHEN in";
                goto process_config_line_err;
        }

        i = index_in_strings(options, what);

        switch (i) {
                case 4: /* "PERMISSIONS" */
                        new->action.what = AC_PERMISSIONS;
                        /*  Get user and group  */
                        ptr = strchr(p[0], '.');
                        if (ptr == NULL) {
                                msg = "UID.GID";
                                goto process_config_line_err; /*"missing '.' in UID.GID"*/
                        }

                        *ptr++ = '\0';
                        new->u.permissions.uid = get_uid_gid(UID, p[0]);
                        new->u.permissions.gid = get_uid_gid(GID, ptr);
                        /*  Get mode  */
                        new->u.permissions.mode = get_mode(p[1]);
                        break;
                case 5: /*  MODLOAD */
                        /*This  action will pass "/dev/$devname"(i.e. "/dev/" prefixed to
                        the device name) to the module loading  facility.  In  addition,
                        the /etc/modules.devfs configuration file is used.*/
                        if (ENABLE_DEVFSD_MODLOAD)
                                new->action.what = AC_MODLOAD;
                        break;
                case 6: /* EXECUTE */
                        new->action.what = AC_EXECUTE;
                        num_args -= 3;

                        for (count = 0; count < num_args; ++count)
                                new->u.execute.argv[count] = xstrdup(p[count]);

                        new->u.execute.argv[num_args] = NULL;
                        break;
                case 7: /* COPY */
                        new->action.what = AC_COPY;
                        num_args -= 3;
                        if (num_args != 2)
                                goto process_config_line_err; /* missing path and function in line */

                        new->u.copy.source = xstrdup(p[0]);
                        new->u.copy.destination = xstrdup(p[1]);
                        break;
                case 8: /* IGNORE */
                /* FALLTROUGH */
                case 9: /* MKOLDCOMPAT */
                /* FALLTROUGH */
                case 10: /* MKNEWCOMPAT */
                /* FALLTROUGH */
                case 11:/* RMOLDCOMPAT */
                /* FALLTROUGH */
                case 12: /* RMNEWCOMPAT */
                /*      AC_IGNORE                                       6
                        AC_MKOLDCOMPAT                          7
                        AC_MKNEWCOMPAT                          8
                        AC_RMOLDCOMPAT                          9
                        AC_RMNEWCOMPAT                          10*/
                        new->action.what = i - 2;
                        break;
                default:
                        msg = "WHAT in";
                        goto process_config_line_err;
                /*esac*/
        } /* switch (i) */

        xregcomp(&new->preg, name, REG_EXTENDED);

        *event_mask |= 1 << new->action.when;
        new->next = NULL;
        if (first_config == NULL)
                first_config = new;
        else
                last_config->next = new;
        last_config = new;
        return;

 process_config_line_err:
        msg_logger_and_die(LOG_ERR, bb_msg_bad_config, msg , line);
}  /*  End Function process_config_line   */

static int do_servicing(int fd, unsigned long event_mask)
/*  [SUMMARY] Service devfs changes until a signal is received.
    <fd> The open control file.
    <event_mask> The event mask.
    [RETURNS] TRUE if SIGHUP was caught, else FALSE.
*/
{
        ssize_t bytes;
        struct devfsd_notify_struct info;

        /* (void*) cast is only in order to match prototype */
        xioctl(fd, DEVFSDIOC_SET_EVENT_MASK, (void*)event_mask);
        while (!caught_signal) {
                errno = 0;
                bytes = read(fd, (char *) &info, sizeof info);
                if (caught_signal)
                        break;      /*  Must test for this first     */
                if (errno == EINTR)
                        continue;  /*  Yes, the order is important  */
                if (bytes < 1)
                        break;
                service_name(&info);
        }
        if (caught_signal) {
                int c_sighup = caught_sighup;

                caught_signal = FALSE;
                caught_sighup = FALSE;
                return c_sighup;
        }
        msg_logger_and_die(LOG_ERR, "read error on control file");
}   /*  End Function do_servicing  */

static void service_name(const struct devfsd_notify_struct *info)
/*  [SUMMARY] Service a single devfs change.
    <info> The devfs change.
    [RETURNS] Nothing.
*/
{
        unsigned int n;
        regmatch_t mbuf[MAX_SUBEXPR];
        struct config_entry_struct *entry;

        if (ENABLE_DEBUG && info->overrun_count > 0)
                msg_logger(LOG_ERR, "lost %u events", info->overrun_count);

        /*  Discard lookups on "/dev/log" and "/dev/initctl"  */
        if (info->type == DEVFSD_NOTIFY_LOOKUP
                && ((info->devname[0] == 'l' && info->devname[1] == 'o'
                && info->devname[2] == 'g' && !info->devname[3])
                || (info->devname[0] == 'i' && info->devname[1] == 'n'
                && info->devname[2] == 'i' && info->devname[3] == 't'
                && info->devname[4] == 'c' && info->devname[5] == 't'
                && info->devname[6] == 'l' && !info->devname[7]))
        )
                return;

        for (entry = first_config; entry != NULL; entry = entry->next) {
                /*  First check if action matches the type, then check if name matches */
                if (info->type != entry->action.when
                || regexec(&entry->preg, info->devname, MAX_SUBEXPR, mbuf, 0) != 0)
                        continue;
                for (n = 0;(n < MAX_SUBEXPR) && (mbuf[n].rm_so != -1); ++n)
                        /* VOID */;

                switch (entry->action.what) {
                        case AC_PERMISSIONS:
                                action_permissions(info, entry);
                                break;
                        case AC_MODLOAD:
                                if (ENABLE_DEVFSD_MODLOAD)
                                        action_modload(info, entry);
                                break;
                        case AC_EXECUTE:
                                action_execute(info, entry, mbuf, n);
                                break;
                        case AC_COPY:
                                action_copy(info, entry, mbuf, n);
                                break;
                        case AC_IGNORE:
                                return;
                                /*break;*/
                        case AC_MKOLDCOMPAT:
                        case AC_MKNEWCOMPAT:
                        case AC_RMOLDCOMPAT:
                        case AC_RMNEWCOMPAT:
                                action_compat(info, entry->action.what);
                                break;
                        default:
                                msg_logger_and_die(LOG_ERR, "Unknown action");
                }
        }
}   /*  End Function service_name  */

static void action_permissions(const struct devfsd_notify_struct *info,
                                const struct config_entry_struct *entry)
/*  [SUMMARY] Update permissions for a device entry.
    <info> The devfs change.
    <entry> The config file entry.
    [RETURNS] Nothing.
*/
{
        struct stat statbuf;

        if (stat(info->devname, &statbuf) != 0
         || chmod(info->devname, (statbuf.st_mode & S_IFMT) | (entry->u.permissions.mode & ~S_IFMT)) != 0
         || chown(info->devname, entry->u.permissions.uid, entry->u.permissions.gid) != 0
        )
                error_logger(LOG_ERR, "Can't chmod or chown: %s", info->devname);
}   /*  End Function action_permissions  */

static void action_modload(const struct devfsd_notify_struct *info,
                        const struct config_entry_struct *entry UNUSED_PARAM)
/*  [SUMMARY] Load a module.
    <info> The devfs change.
    <entry> The config file entry.
    [RETURNS] Nothing.
*/
{
        char *argv[6];

        argv[0] = (char*)MODPROBE;
        argv[1] = (char*)MODPROBE_SWITCH_1; /* "-k" */
        argv[2] = (char*)MODPROBE_SWITCH_2; /* "-C" */
        argv[3] = (char*)CONFIG_MODULES_DEVFS;
        argv[4] = concat_path_file("/dev", info->devname); /* device */
        argv[5] = NULL;

        spawn_and_wait(argv);
        free(argv[4]);
}  /*  End Function action_modload  */

static void action_execute(const struct devfsd_notify_struct *info,
                        const struct config_entry_struct *entry,
                        const regmatch_t *regexpr, unsigned int numexpr)
/*  [SUMMARY] Execute a programme.
    <info> The devfs change.
    <entry> The config file entry.
    <regexpr> The number of subexpression(start, end) offsets within the
    device name.
    <numexpr> The number of elements within <<regexpr>>.
    [RETURNS] Nothing.
*/
{
        unsigned int count;
        struct get_variable_info gv_info;
        char *argv[MAX_ARGS + 1];
        char largv[MAX_ARGS + 1][STRING_LENGTH];

        gv_info.info = info;
        gv_info.devname = info->devname;
        snprintf(gv_info.devpath, sizeof(gv_info.devpath), "%s/%s", mount_point, info->devname);
        for (count = 0; entry->u.execute.argv[count] != NULL; ++count) {
                expand_expression(largv[count], STRING_LENGTH,
                                entry->u.execute.argv[count],
                                get_variable, &gv_info,
                                gv_info.devname, regexpr, numexpr);
                argv[count] = largv[count];
        }
        argv[count] = NULL;
        spawn_and_wait(argv);
}   /*  End Function action_execute  */


static void action_copy(const struct devfsd_notify_struct *info,
                        const struct config_entry_struct *entry,
                        const regmatch_t *regexpr, unsigned int numexpr)
/*  [SUMMARY] Copy permissions.
    <info> The devfs change.
    <entry> The config file entry.
    <regexpr> This list of subexpression(start, end) offsets within the
    device name.
    <numexpr> The number of elements in <<regexpr>>.
    [RETURNS] Nothing.
*/
{
        mode_t new_mode;
        struct get_variable_info gv_info;
        struct stat source_stat, dest_stat;
        char source[STRING_LENGTH], destination[STRING_LENGTH];
        int ret = 0;

        dest_stat.st_mode = 0;

        if ((info->type == DEVFSD_NOTIFY_CHANGE) && S_ISLNK(info->mode))
                return;
        gv_info.info = info;
        gv_info.devname = info->devname;

        snprintf(gv_info.devpath, sizeof(gv_info.devpath), "%s/%s", mount_point, info->devname);
        expand_expression(source, STRING_LENGTH, entry->u.copy.source,
                                get_variable, &gv_info, gv_info.devname,
                                regexpr, numexpr);

        expand_expression(destination, STRING_LENGTH, entry->u.copy.destination,
                                get_variable, &gv_info, gv_info.devname,
                                regexpr, numexpr);

        if (!make_dir_tree(destination) || lstat(source, &source_stat) != 0)
                        return;
        lstat(destination, &dest_stat);
        new_mode = source_stat.st_mode & ~S_ISVTX;
        if (info->type == DEVFSD_NOTIFY_CREATE)
                new_mode |= S_ISVTX;
        else if ((info->type == DEVFSD_NOTIFY_CHANGE) &&(dest_stat.st_mode & S_ISVTX))
                new_mode |= S_ISVTX;
        ret = copy_inode(destination, &dest_stat, new_mode, source, &source_stat);
        if (ENABLE_DEBUG && ret && (errno != EEXIST))
                error_logger(LOG_ERR, "copy_inode: %s to %s", source, destination);
}   /*  End Function action_copy  */

static void action_compat(const struct devfsd_notify_struct *info, unsigned int action)
/*  [SUMMARY] Process a compatibility request.
    <info> The devfs change.
    <action> The action to take.
    [RETURNS] Nothing.
*/
{
        int ret;
        const char *compat_name = NULL;
        const char *dest_name = info->devname;
        const char *ptr;
        char compat_buf[STRING_LENGTH], dest_buf[STRING_LENGTH];
        int mode, host, bus, target, lun;
        unsigned int i;
        char rewind_;
        /* 1 to 5  "scsi/" , 6 to 9 "ide/host" */
        static const char *const fmt[] = {
                NULL ,
                "sg/c%db%dt%du%d",              /* scsi/generic */
                "sd/c%db%dt%du%d",              /* scsi/disc */
                "sr/c%db%dt%du%d",              /* scsi/cd */
                "sd/c%db%dt%du%dp%d",           /* scsi/part */
                "st/c%db%dt%du%dm%d%c",         /* scsi/mt */
                "ide/hd/c%db%dt%du%d",          /* ide/host/disc */
                "ide/cd/c%db%dt%du%d",          /* ide/host/cd */
                "ide/hd/c%db%dt%du%dp%d",       /* ide/host/part */
                "ide/mt/c%db%dt%du%d%s",        /* ide/host/mt */
                NULL
        };

        /*  First construct compatibility name  */
        switch (action) {
                case AC_MKOLDCOMPAT:
                case AC_RMOLDCOMPAT:
                        compat_name = get_old_name(info->devname, info->namelen, compat_buf, info->major, info->minor);
                        break;
                case AC_MKNEWCOMPAT:
                case AC_RMNEWCOMPAT:
                        ptr = bb_basename(info->devname);
                        i = scan_dev_name(info->devname, info->namelen, ptr);

                        /* nothing found */
                        if (i == 0 || i > 9)
                                return;

                        sscanf(info->devname + ((i < 6) ? 5 : 4), "host%d/bus%d/target%d/lun%d/", &host, &bus, &target, &lun);
                        snprintf(dest_buf, sizeof(dest_buf), "../%s", info->devname + (( i > 5) ? 4 : 0));
                        dest_name = dest_buf;
                        compat_name = compat_buf;


                        /* 1 == scsi/generic  2 == scsi/disc 3 == scsi/cd 6 == ide/host/disc 7 == ide/host/cd */
                        if (i == 1 || i == 2 || i == 3 || i == 6 || i ==7)
                                sprintf(compat_buf, fmt[i], host, bus, target, lun);

                        /* 4 == scsi/part 8 == ide/host/part */
                        if (i == 4 || i == 8)
                                sprintf(compat_buf, fmt[i], host, bus, target, lun, atoi(ptr + 4));

                        /* 5 == scsi/mt */
                        if (i == 5) {
                                rewind_ = info->devname[info->namelen - 1];
                                if (rewind_ != 'n')
                                        rewind_ = '\0';
                                mode=0;
                                if (ptr[2] ==  'l' /*108*/ || ptr[2] == 'm'/*109*/)
                                        mode = ptr[2] - 107; /* 1 or 2 */
                                if (ptr[2] ==  'a')
                                        mode = 3;
                                sprintf(compat_buf, fmt[i], host, bus, target, lun, mode, rewind_);
                        }

                        /* 9 == ide/host/mt */
                        if (i ==  9)
                                snprintf(compat_buf, sizeof(compat_buf), fmt[i], host, bus, target, lun, ptr + 2);
                /* esac */
        } /* switch (action) */

        if (compat_name == NULL)
                return;

        /*  Now decide what to do with it  */
        switch (action) {
                case AC_MKOLDCOMPAT:
                case AC_MKNEWCOMPAT:
                        mksymlink(dest_name, compat_name);
                        break;
                case AC_RMOLDCOMPAT:
                case AC_RMNEWCOMPAT:
                        ret = unlink(compat_name);
                        if (ENABLE_DEBUG && ret)
                                error_logger(LOG_ERR, "unlink: %s", compat_name);
                        break;
                /*esac*/
        } /* switch (action) */
}   /*  End Function action_compat  */

static void restore(char *spath, struct stat source_stat, int rootlen)
{
        char *dpath;
        struct stat dest_stat;

        dest_stat.st_mode = 0;
        dpath = concat_path_file(mount_point, spath + rootlen);
        lstat(dpath, &dest_stat);
        free(dpath);
        if (S_ISLNK(source_stat.st_mode) || (source_stat.st_mode & S_ISVTX))
                copy_inode(dpath, &dest_stat, (source_stat.st_mode & ~S_ISVTX), spath, &source_stat);

        if (S_ISDIR(source_stat.st_mode))
                dir_operation(RESTORE, spath, rootlen, NULL);
}


static int copy_inode(const char *destpath, const struct stat *dest_stat,
                        mode_t new_mode,
                        const char *sourcepath, const struct stat *source_stat)
/*  [SUMMARY] Copy an inode.
    <destpath> The destination path. An existing inode may be deleted.
    <dest_stat> The destination stat(2) information.
    <new_mode> The desired new mode for the destination.
    <sourcepath> The source path.
    <source_stat> The source stat(2) information.
    [RETURNS] TRUE on success, else FALSE.
*/
{
        int source_len, dest_len;
        char source_link[STRING_LENGTH], dest_link[STRING_LENGTH];
        int fd, val;
        struct sockaddr_un un_addr;
        char symlink_val[STRING_LENGTH];

        if ((source_stat->st_mode & S_IFMT) ==(dest_stat->st_mode & S_IFMT)) {
                /*  Same type  */
                if (S_ISLNK(source_stat->st_mode)) {
                        source_len = readlink(sourcepath, source_link, STRING_LENGTH - 1);
                        if ((source_len < 0)
                         || (dest_len = readlink(destpath, dest_link, STRING_LENGTH - 1)) < 0
                        )
                                return FALSE;
                        source_link[source_len] = '\0';
                        dest_link[dest_len]     = '\0';
                        if ((source_len != dest_len) || (strcmp(source_link, dest_link) != 0)) {
                                unlink(destpath);
                                symlink(source_link, destpath);
                        }
                        return TRUE;
                }   /*  Else not a symlink  */
                chmod(destpath, new_mode & ~S_IFMT);

                chown(destpath, source_stat->st_uid, source_stat->st_gid);
                return TRUE;
        }
        /*  Different types: unlink and create  */
        unlink(destpath);
        switch (source_stat->st_mode & S_IFMT) {
                case S_IFSOCK:
                        fd = socket(AF_UNIX, SOCK_STREAM, 0);
                        if (fd < 0)
                                break;
                        un_addr.sun_family = AF_UNIX;
                        snprintf(un_addr.sun_path, sizeof(un_addr.sun_path), "%s", destpath);
                        val = bind(fd, (struct sockaddr *) &un_addr, (int) sizeof un_addr);
                        close(fd);
                        if (val != 0 || chmod(destpath, new_mode & ~S_IFMT) != 0)
                                break;
                        goto do_chown;
                case S_IFLNK:
                        val = readlink(sourcepath, symlink_val, STRING_LENGTH - 1);
                        if (val < 0)
                                break;
                        symlink_val[val] = '\0';
                        if (symlink(symlink_val, destpath) == 0)
                                return TRUE;
                        break;
                case S_IFREG:
                        fd = open(destpath, O_RDONLY | O_CREAT, new_mode & ~S_IFMT);
                        if (fd < 0)
                                break;
                        close(fd);
                        if (chmod(destpath, new_mode & ~S_IFMT) != 0)
                                break;
                        goto do_chown;
                case S_IFBLK:
                case S_IFCHR:
                case S_IFIFO:
                        if (mknod(destpath, new_mode, source_stat->st_rdev) != 0)
                                break;
                        goto do_chown;
                case S_IFDIR:
                        if (mkdir(destpath, new_mode & ~S_IFMT) != 0)
                                break;
do_chown:
                        if (chown(destpath, source_stat->st_uid, source_stat->st_gid) == 0)
                                return TRUE;
                /*break;*/
        }
        return FALSE;
}   /*  End Function copy_inode  */

static void free_config(void)
/*  [SUMMARY] Free the configuration information.
    [RETURNS] Nothing.
*/
{
        struct config_entry_struct *c_entry;
        void *next;

        for (c_entry = first_config; c_entry != NULL; c_entry = next) {
                unsigned int count;

                next = c_entry->next;
                regfree(&c_entry->preg);
                if (c_entry->action.what == AC_EXECUTE) {
                        for (count = 0; count < MAX_ARGS; ++count) {
                                if (c_entry->u.execute.argv[count] == NULL)
                                        break;
                                free(c_entry->u.execute.argv[count]);
                        }
                }
                free(c_entry);
        }
        first_config = NULL;
        last_config = NULL;
}   /*  End Function free_config  */

static int get_uid_gid(int flag, const char *string)
/*  [SUMMARY] Convert a string to a UID or GID value.
        <flag> "UID" or "GID".
        <string> The string.
    [RETURNS] The UID or GID value.
*/
{
        struct passwd *pw_ent;
        struct group *grp_ent;
        const char *msg;

        if (isdigit(string[0]) || ((string[0] == '-') && isdigit(string[1])))
                return atoi(string);

        if (flag == UID && (pw_ent = getpwnam(string)) != NULL)
                return pw_ent->pw_uid;

        if (ENABLE_DEVFSD_VERBOSE)
                msg = "user";

        if (flag == GID) {
                if ((grp_ent = getgrnam(string)) != NULL)
                        return grp_ent->gr_gid;
                if (ENABLE_DEVFSD_VERBOSE)
                        msg = "group";
        }

        if (ENABLE_DEVFSD_VERBOSE)
                msg_logger(LOG_ERR, "unknown %s: %s, defaulting to %cid=0",  msg, string, msg[0]);
        return 0;
}/*  End Function get_uid_gid  */

static mode_t get_mode(const char *string)
/*  [SUMMARY] Convert a string to a mode value.
    <string> The string.
    [RETURNS] The mode value.
*/
{
        mode_t mode;
        int i;

        if (isdigit(string[0]))
                return strtoul(string, NULL, 8);
        if (strlen(string) != 9)
                msg_logger_and_die(LOG_ERR, "bad mode: %s", string);

        mode = 0;
        i = S_IRUSR;
        while (i > 0) {
                if (string[0] == 'r' || string[0] == 'w' || string[0] == 'x')
                        mode += i;
                i = i / 2;
                string++;
        }
        return mode;
}   /*  End Function get_mode  */

static void signal_handler(int sig)
{
        caught_signal = TRUE;
        if (sig == SIGHUP)
                caught_sighup = TRUE;

        info_logger(LOG_INFO, "Caught signal %d", sig);
}   /*  End Function signal_handler  */

static const char *get_variable(const char *variable, void *info)
{
        static char *hostname;

        struct get_variable_info *gv_info = info;
        const char *field_names[] = {
                        "hostname", "mntpt", "devpath", "devname", "uid", "gid", "mode",
                        NULL, mount_point, gv_info->devpath, gv_info->devname, NULL
        };
        int i;

        if (!hostname)
                hostname = safe_gethostname();
        field_names[7] = hostname;

        /* index_in_str_array returns i>=0  */
        i = index_in_str_array(field_names, variable);

        if (i > 6 || i < 0 || (i > 1 && gv_info == NULL))
                return NULL;
        if (i >= 0 && i <= 3)
                return field_names[i + 7];

        if (i == 4)
                return auto_string(xasprintf("%u", gv_info->info->uid));
        if (i == 5)
                return auto_string(xasprintf("%u", gv_info->info->gid));
        /* i == 6 */
        return auto_string(xasprintf("%o", gv_info->info->mode));
}   /*  End Function get_variable  */

static void service(struct stat statbuf, char *path)
{
        struct devfsd_notify_struct info;

        memset(&info, 0, sizeof info);
        info.type = DEVFSD_NOTIFY_REGISTERED;
        info.mode = statbuf.st_mode;
        info.major = major(statbuf.st_rdev);
        info.minor = minor(statbuf.st_rdev);
        info.uid = statbuf.st_uid;
        info.gid = statbuf.st_gid;
        snprintf(info.devname, sizeof(info.devname), "%s", path + strlen(mount_point) + 1);
        info.namelen = strlen(info.devname);
        service_name(&info);
        if (S_ISDIR(statbuf.st_mode))
                dir_operation(SERVICE, path, 0, NULL);
}

static void dir_operation(int type, const char * dir_name, int var, unsigned long *event_mask)
/*  [SUMMARY] Scan a directory tree and generate register events on leaf nodes.
        <flag> To choose which function to perform
        <dp> The directory pointer. This is closed upon completion.
    <dir_name> The name of the directory.
        <rootlen> string length parameter.
    [RETURNS] Nothing.
*/
{
        struct stat statbuf;
        DIR *dp;
        struct dirent *de;
        char *path;

        dp = warn_opendir(dir_name);
        if (dp == NULL)
                return;

        while ((de = readdir(dp)) != NULL) {

                if (de->d_name && DOT_OR_DOTDOT(de->d_name))
                        continue;
                path = concat_path_file(dir_name, de->d_name);
                if (lstat(path, &statbuf) == 0) {
                        switch (type) {
                                case SERVICE:
                                        service(statbuf, path);
                                        break;
                                case RESTORE:
                                        restore(path, statbuf, var);
                                        break;
                                case READ_CONFIG:
                                        read_config_file(path, var, event_mask);
                                        break;
                        }
                }
                free(path);
        }
        closedir(dp);
}   /*  End Function do_scan_and_service  */

static int mksymlink(const char *oldpath, const char *newpath)
/*  [SUMMARY] Create a symlink, creating intervening directories as required.
    <oldpath> The string contained in the symlink.
    <newpath> The name of the new symlink.
    [RETURNS] 0 on success, else -1.
*/
{
        if (!make_dir_tree(newpath))
                return -1;

        if (symlink(oldpath, newpath) != 0) {
                if (errno != EEXIST)
                        return -1;
        }
        return 0;
}   /*  End Function mksymlink  */


static int make_dir_tree(const char *path)
/*  [SUMMARY] Creating intervening directories for a path as required.
    <path> The full pathname(including the leaf node).
    [RETURNS] TRUE on success, else FALSE.
*/
{
        if (bb_make_directory(dirname((char *)path), -1, FILEUTILS_RECUR) == -1)
                return FALSE;
        return TRUE;
} /*  End Function make_dir_tree  */

static int expand_expression(char *output, unsigned int outsize,
                        const char *input,
                        const char *(*get_variable_func)(const char *variable, void *info),
                        void *info,
                        const char *devname,
                        const regmatch_t *ex, unsigned int numexp)
/*  [SUMMARY] Expand environment variables and regular subexpressions in string.
    <output> The output expanded expression is written here.
    <length> The size of the output buffer.
    <input> The input expression. This may equal <<output>>.
    <get_variable> A function which will be used to get variable values. If
    this returns NULL, the environment is searched instead. If this is NULL,
    only the environment is searched.
    <info> An arbitrary pointer passed to <<get_variable>>.
    <devname> Device name; specifically, this is the string that contains all
    of the regular subexpressions.
    <ex> Array of start / end offsets into info->devname for each subexpression
    <numexp> Number of regular subexpressions found in <<devname>>.
    [RETURNS] TRUE on success, else FALSE.
*/
{
        char temp[STRING_LENGTH];

        if (!st_expr_expand(temp, STRING_LENGTH, input, get_variable_func, info))
                return FALSE;
        expand_regexp(output, outsize, temp, devname, ex, numexp);
        return TRUE;
}   /*  End Function expand_expression  */

static void expand_regexp(char *output, size_t outsize, const char *input,
                        const char *devname,
                        const regmatch_t *ex, unsigned int numex)
/*  [SUMMARY] Expand all occurrences of the regular subexpressions \0 to \9.
    <output> The output expanded expression is written here.
    <outsize> The size of the output buffer.
    <input> The input expression. This may NOT equal <<output>>, because
    supporting that would require yet another string-copy. However, it's not
    hard to write a simple wrapper function to add this functionality for those
    few cases that need it.
    <devname> Device name; specifically, this is the string that contains all
    of the regular subexpressions.
    <ex> An array of start and end offsets into <<devname>>, one for each
    subexpression
    <numex> Number of subexpressions in the offset-array <<ex>>.
    [RETURNS] Nothing.
*/
{
        const char last_exp = '0' - 1 + numex;
        int c = -1;

        /*  Guarantee NULL termination by writing an explicit '\0' character into
        the very last byte  */
        if (outsize)
                output[--outsize] = '\0';
        /*  Copy the input string into the output buffer, replacing '\\' with '\'
        and '\0' .. '\9' with subexpressions 0 .. 9, if they exist. Other \x
        codes are deleted  */
        while ((c != '\0') && (outsize != 0)) {
                c = *input;
                ++input;
                if (c == '\\') {
                        c = *input;
                        ++input;
                        if (c != '\\') {
                                if ((c >= '0') && (c <= last_exp)) {
                                        const regmatch_t *subexp = ex + (c - '0');
                                        unsigned int sublen = subexp->rm_eo - subexp->rm_so;

                                        /*  Range checking  */
                                        if (sublen > outsize)
                                                sublen = outsize;
                                        strncpy(output, devname + subexp->rm_so, sublen);
                                        output += sublen;
                                        outsize -= sublen;
                                }
                                continue;
                        }
                }
                *output = c;
                ++output;
                --outsize;
        } /* while */
}   /*  End Function expand_regexp  */


/* from compat_name.c */

struct translate_struct {
        const char *match;    /*  The string to match to(up to length)                */
        const char *format;   /*  Format of output, "%s" takes data past match string,
                        NULL is effectively "%s"(just more efficient)       */
};

static struct translate_struct translate_table[] =
{
        {"sound/",     NULL},
        {"printers/",  "lp%s"},
        {"v4l/",       NULL},
        {"parports/",  "parport%s"},
        {"fb/",        "fb%s"},
        {"netlink/",   NULL},
        {"loop/",      "loop%s"},
        {"floppy/",    "fd%s"},
        {"rd/",        "ram%s"},
        {"md/",        "md%s"},         /*  Meta-devices                         */
        {"vc/",        "tty%s"},
        {"misc/",      NULL},
        {"isdn/",      NULL},
        {"pg/",        "pg%s"},         /*  Parallel port generic ATAPI interface*/
        {"i2c/",       "i2c-%s"},
        {"staliomem/", "staliomem%s"},  /*  Stallion serial driver control       */
        {"tts/E",      "ttyE%s"},       /*  Stallion serial driver               */
        {"cua/E",      "cue%s"},        /*  Stallion serial driver callout       */
        {"tts/R",      "ttyR%s"},       /*  Rocketport serial driver             */
        {"cua/R",      "cur%s"},        /*  Rocketport serial driver callout     */
        {"ip2/",       "ip2%s"},        /*  Computone serial driver control      */
        {"tts/F",      "ttyF%s"},       /*  Computone serial driver              */
        {"cua/F",      "cuf%s"},        /*  Computone serial driver callout      */
        {"tts/C",      "ttyC%s"},       /*  Cyclades serial driver               */
        {"cua/C",      "cub%s"},        /*  Cyclades serial driver callout       */
        {"tts/",       "ttyS%s"},       /*  Generic serial: must be after others */
        {"cua/",       "cua%s"},        /*  Generic serial: must be after others */
        {"input/js",   "js%s"},         /*  Joystick driver                      */
        {NULL,         NULL}
};

const char *get_old_name(const char *devname, unsigned int namelen,
                        char *buffer, unsigned int major, unsigned int minor)
/*  [SUMMARY] Translate a kernel-supplied name into an old name.
    <devname> The device name provided by the kernel.
    <namelen> The length of the name.
    <buffer> A buffer that may be used. This should be at least 128 bytes long.
    <major> The major number for the device.
    <minor> The minor number for the device.
    [RETURNS] A pointer to the old name if known, else NULL.
*/
{
        const char *compat_name = NULL;
        const char *ptr;
        struct translate_struct *trans;
        unsigned int i;
        char mode;
        int indexx;
        const char *pty1;
        const char *pty2;
        /* 1 to 5  "scsi/" , 6 to 9 "ide/host", 10 sbp/, 11 vcc/, 12 pty/ */
        static const char *const fmt[] = {
                NULL ,
                "sg%u",                 /* scsi/generic */
                NULL,                   /* scsi/disc */
                "sr%u",                 /* scsi/cd */
                NULL,                   /* scsi/part */
                "nst%u%c",              /* scsi/mt */
                "hd%c"  ,               /* ide/host/disc */
                "hd%c"  ,               /* ide/host/cd */
                "hd%c%s",               /* ide/host/part */
                "%sht%d",               /* ide/host/mt */
                "sbpcd%u",              /* sbp/ */
                "vcs%s",                /* vcc/ */
                "%cty%c%c",             /* pty/ */
                NULL
        };

        for (trans = translate_table; trans->match != NULL; ++trans) {
                char *after_match = is_prefixed_with(devname, trans->match);
                if (after_match) {
                        if (trans->format == NULL)
                                return after_match;
                        sprintf(buffer, trans->format, after_match);
                        return buffer;
                }
        }

        ptr = bb_basename(devname);
        i = scan_dev_name(devname, namelen, ptr);

        if (i > 0 && i < 13)
                compat_name = buffer;
        else
                return NULL;

        /* 1 == scsi/generic, 3 == scsi/cd, 10 == sbp/ */
        if (i == 1 || i == 3 || i == 10)
                sprintf(buffer, fmt[i], minor);

        /* 2 ==scsi/disc, 4 == scsi/part */
        if (i == 2 || i == 4)
                compat_name = write_old_sd_name(buffer, major, minor, ((i == 2) ? "" : (ptr + 4)));

        /* 5 == scsi/mt */
        if (i == 5) {
                mode = ptr[2];
                if (mode == 'n')
                        mode = '\0';
                sprintf(buffer, fmt[i], minor & 0x1f, mode);
                if (devname[namelen - 1] != 'n')
                        ++compat_name;
        }
        /* 6 == ide/host/disc, 7 == ide/host/cd, 8 == ide/host/part */
        if (i == 6 || i == 7 || i == 8)
                /* last arg should be ignored for i == 6 or i== 7 */
                sprintf(buffer, fmt[i] , get_old_ide_name(major, minor), ptr + 4);

        /* 9 ==  ide/host/mt */
        if (i == 9)
                sprintf(buffer, fmt[i], ptr + 2, minor & 0x7f);

        /*  11 == vcc/ */
        if (i == 11) {
                sprintf(buffer, fmt[i], devname + 4);
                if (buffer[3] == '0')
                        buffer[3] = '\0';
        }
        /* 12 ==  pty/ */
        if (i == 12) {
                pty1 = "pqrstuvwxyzabcde";
                pty2 = "0123456789abcdef";
                indexx = atoi(devname + 5);
                sprintf(buffer, fmt[i], (devname[4] == 'm') ? 'p' : 't', pty1[indexx >> 4], pty2[indexx & 0x0f]);
        }
        return compat_name;
}   /*  End Function get_old_name  */

static char get_old_ide_name(unsigned int major, unsigned int minor)
/*  [SUMMARY] Get the old IDE name for a device.
    <major> The major number for the device.
    <minor> The minor number for the device.
    [RETURNS] The drive letter.
*/
{
        char letter = 'y';      /* 121 */
        char c = 'a';           /*  97 */
        int i = IDE0_MAJOR;

        /* I hope it works like the previous code as it saves a few bytes. Tito ;P */
        do {
                if (i == IDE0_MAJOR || i == IDE1_MAJOR || i == IDE2_MAJOR
                 || i == IDE3_MAJOR || i == IDE4_MAJOR || i == IDE5_MAJOR
                 || i == IDE6_MAJOR || i == IDE7_MAJOR || i == IDE8_MAJOR
                 || i == IDE9_MAJOR
                ) {
                        if ((unsigned int)i == major) {
                                letter = c;
                                break;
                        }
                        c += 2;
                }
                i++;
        } while (i <= IDE9_MAJOR);

        if (minor > 63)
                ++letter;
        return letter;
}   /*  End Function get_old_ide_name  */

static char *write_old_sd_name(char *buffer,
                                unsigned int major, unsigned int minor,
                                const char *part)
/*  [SUMMARY] Write the old SCSI disc name to a buffer.
    <buffer> The buffer to write to.
    <major> The major number for the device.
    <minor> The minor number for the device.
    <part> The partition string. Must be "" for a whole-disc entry.
    [RETURNS] A pointer to the buffer on success, else NULL.
*/
{
        unsigned int disc_index;

        if (major == 8) {
                sprintf(buffer, "sd%c%s", 'a' + (minor >> 4), part);
                return buffer;
        }
        if ((major > 64) && (major < 72)) {
                disc_index = ((major - 64) << 4) +(minor >> 4);
                if (disc_index < 26)
                        sprintf(buffer, "sd%c%s", 'a' + disc_index, part);
                else
                        sprintf(buffer, "sd%c%c%s", 'a' +(disc_index / 26) - 1, 'a' + disc_index % 26, part);
                return buffer;
        }
        return NULL;
}   /*  End Function write_old_sd_name  */


/*  expression.c */

/*EXPERIMENTAL_FUNCTION*/

int st_expr_expand(char *output, unsigned int length, const char *input,
                const char *(*get_variable_func)(const char *variable,
                                                void *info),
                void *info)
/*  [SUMMARY] Expand an expression using Borne Shell-like unquoted rules.
    <output> The output expanded expression is written here.
    <length> The size of the output buffer.
    <input> The input expression. This may equal <<output>>.
    <get_variable> A function which will be used to get variable values. If
    this returns NULL, the environment is searched instead. If this is NULL,
    only the environment is searched.
    <info> An arbitrary pointer passed to <<get_variable>>.
    [RETURNS] TRUE on success, else FALSE.
*/
{
        char ch;
        unsigned int len;
        unsigned int out_pos = 0;
        const char *env;
        const char *ptr;
        struct passwd *pwent;
        char buffer[BUFFER_SIZE], tmp[STRING_LENGTH];

        if (length > BUFFER_SIZE)
                length = BUFFER_SIZE;
        for (; TRUE; ++input) {
                switch (ch = *input) {
                        case '$':
                                /*  Variable expansion  */
                                input = expand_variable(buffer, length, &out_pos, ++input, get_variable_func, info);
                                if (input == NULL)
                                        return FALSE;
                                break;
                        case '~':
                                /*  Home directory expansion  */
                                ch = input[1];
                                if (isspace(ch) ||(ch == '/') ||(ch == '\0')) {
                                        /* User's own home directory: leave separator for next time */
                                        env = getenv("HOME");
                                        if (env == NULL) {
                                                info_logger(LOG_INFO, bb_msg_variable_not_found, "HOME");
                                                return FALSE;
                                        }
                                        len = strlen(env);
                                        if (len + out_pos >= length)
                                                goto st_expr_expand_out;
                                        memcpy(buffer + out_pos, env, len + 1);
                                        out_pos += len;
                                        continue;
                                }
                                /*  Someone else's home directory  */
                                for (ptr = ++input; !isspace(ch) && (ch != '/') && (ch != '\0'); ch = *++ptr)
                                        /* VOID */;
                                len = ptr - input;
                                if (len >= sizeof tmp)
                                        goto st_expr_expand_out;
                                safe_memcpy(tmp, input, len);
                                input = ptr - 1;
                                pwent = getpwnam(tmp);
                                if (pwent == NULL) {
                                        info_logger(LOG_INFO, "no pwent for: %s", tmp);
                                        return FALSE;
                                }
                                len = strlen(pwent->pw_dir);
                                if (len + out_pos >= length)
                                        goto st_expr_expand_out;
                                memcpy(buffer + out_pos, pwent->pw_dir, len + 1);
                                out_pos += len;
                                break;
                        case '\0':
                        /* Falltrough */
                        default:
                                if (out_pos >= length)
                                        goto st_expr_expand_out;
                                buffer[out_pos++] = ch;
                                if (ch == '\0') {
                                        memcpy(output, buffer, out_pos);
                                        return TRUE;
                                }
                                break;
                        /* esac */
                }
        }
        return FALSE;
st_expr_expand_out:
        info_logger(LOG_INFO, bb_msg_small_buffer);
        return FALSE;
}   /*  End Function st_expr_expand  */


/*  Private functions follow  */

static const char *expand_variable(char *buffer, unsigned int length,
                                unsigned int *out_pos, const char *input,
                                const char *(*func)(const char *variable,
                                                        void *info),
                                void *info)
/*  [SUMMARY] Expand a variable.
    <buffer> The buffer to write to.
    <length> The length of the output buffer.
    <out_pos> The current output position. This is updated.
    <input> A pointer to the input character pointer.
    <func> A function which will be used to get variable values. If this
    returns NULL, the environment is searched instead. If this is NULL, only
    the environment is searched.
    <info> An arbitrary pointer passed to <<func>>.
    <errfp> Diagnostic messages are written here.
    [RETURNS] A pointer to the end of this subexpression on success, else NULL.
*/
{
        char ch;
        int len;
        unsigned int open_braces;
        const char *env, *ptr;
        char tmp[STRING_LENGTH];

        ch = input[0];
        if (ch == '$') {
                /*  Special case for "$$": PID  */
                sprintf(tmp, "%d", (int) getpid());
                len = strlen(tmp);
                if (len + *out_pos >= length)
                        goto expand_variable_out;

                memcpy(buffer + *out_pos, tmp, len + 1);
                out_pos += len;
                return input;
        }
        /*  Ordinary variable expansion, possibly in braces  */
        if (ch != '{') {
                /*  Simple variable expansion  */
                for (ptr = input; isalnum(ch) || (ch == '_') || (ch == ':'); ch = *++ptr)
                        /* VOID */;
                len = ptr - input;
                if ((size_t)len >= sizeof tmp)
                        goto expand_variable_out;

                safe_memcpy(tmp, input, len);
                input = ptr - 1;
                env = get_variable_v2(tmp, func, info);
                if (env == NULL) {
                        info_logger(LOG_INFO, bb_msg_variable_not_found, tmp);
                        return NULL;
                }
                len = strlen(env);
                if (len + *out_pos >= length)
                        goto expand_variable_out;

                memcpy(buffer + *out_pos, env, len + 1);
                *out_pos += len;
                return input;
        }
        /*  Variable in braces: check for ':' tricks  */
        ch = *++input;
        for (ptr = input; isalnum(ch) || (ch == '_'); ch = *++ptr)
                /* VOID */;
        if (ch == '}') {
                /*  Must be simple variable expansion with "${var}"  */
                len = ptr - input;
                if ((size_t)len >= sizeof tmp)
                        goto expand_variable_out;

                safe_memcpy(tmp, input, len);
                ptr = expand_variable(buffer, length, out_pos, tmp, func, info);
                if (ptr == NULL)
                        return NULL;
                return input + len;
        }
        if (ch != ':' || ptr[1] != '-') {
                info_logger(LOG_INFO, "illegal char in var name");
                return NULL;
        }
        /*  It's that handy "${var:-word}" expression. Check if var is defined  */
        len = ptr - input;
        if ((size_t)len >= sizeof tmp)
                goto expand_variable_out;

        safe_memcpy(tmp, input, len);
        /*  Move input pointer to ':'  */
        input = ptr;
        /*  First skip to closing brace, taking note of nested expressions  */
        ptr += 2;
        ch = ptr[0];
        for (open_braces = 1; open_braces > 0; ch = *++ptr) {
                switch (ch) {
                        case '{':
                                ++open_braces;
                                break;
                        case '}':
                                --open_braces;
                                break;
                        case '\0':
                                info_logger(LOG_INFO, "\"}\" not found in: %s", input);
                                return NULL;
                        default:
                                break;
                }
        }
        --ptr;
        /*  At this point ptr should point to closing brace of "${var:-word}"  */
        env = get_variable_v2(tmp, func, info);
        if (env != NULL) {
                /*  Found environment variable, so skip the input to the closing brace
                        and return the variable  */
                input = ptr;
                len = strlen(env);
                if (len + *out_pos >= length)
                        goto expand_variable_out;

                memcpy(buffer + *out_pos, env, len + 1);
                *out_pos += len;
                return input;
        }
        /*  Environment variable was not found, so process word. Advance input
        pointer to start of word in "${var:-word}"  */
        input += 2;
        len = ptr - input;
        if ((size_t)len >= sizeof tmp)
                goto expand_variable_out;

        safe_memcpy(tmp, input, len);
        input = ptr;
        if (!st_expr_expand(tmp, STRING_LENGTH, tmp, func, info))
                return NULL;
        len = strlen(tmp);
        if (len + *out_pos >= length)
                goto expand_variable_out;

        memcpy(buffer + *out_pos, tmp, len + 1);
        *out_pos += len;
        return input;
expand_variable_out:
        info_logger(LOG_INFO, bb_msg_small_buffer);
        return NULL;
}   /*  End Function expand_variable  */


static const char *get_variable_v2(const char *variable,
                                const char *(*func)(const char *variable, void *info),
                                void *info)
/*  [SUMMARY] Get a variable from the environment or .
    <variable> The variable name.
    <func> A function which will be used to get the variable. If this returns
    NULL, the environment is searched instead. If this is NULL, only the
    environment is searched.
    [RETURNS] The value of the variable on success, else NULL.
*/
{
        const char *value;

        if (func != NULL) {
                value = (*func)(variable, info);
                if (value != NULL)
                        return value;
        }
        return getenv(variable);
}   /*  End Function get_variable  */

/* END OF CODE */